UNEP Cleaner Production~ Energy Efficiency MANUAL United Nations Environment Programme Division of Technology, Industry and Economics Guidelines for the Integration of Cleaner Production and Energy Efficiency Contents listing About the CP-EE Manual Part 1 CP-EE methodology Part 2 Technical modules Part 3 Tools and resources
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UNEP
Cleaner Production~
Energy Efficiency
MANUAL
United Nations Environment ProgrammeDivision of Technology, Industry and Economics
Guidelines for the Integration of Cleaner Production and Energy Efficiency
Contents listing
About the CP-EE Manual
Part 1 CP-EE methodology
Part 2 Technical modules
Part 3 Tools and resources
Cleaner Production – Energy Efficiency Manual page b
This publication may be reproduced in whole or in part and in anyform for educational or non-profit purposes without special permissionfrom the copyright holder, provided acknowledgement of the sourceis made. UNEP would appreciate receiving a copy of any publicationthat uses this publication as a source.
No use of this publication may be made for resale or for any othercommercial purpose whatsoever without prior permission in writingfrom UNEP.
First edition 2004
The designations employed and the presentation of the material in thispublication do not imply the expression of any opinion whatsoever onthe part of the United Nations Environment Programme concerningthe legal status of any country, territory, city or area or of itsauthorities, or concerning delimitation of its frontiers or boundaries.Moreover, the views expressed do not necessarily represent thedecision or the stated policy of the United Nations EnvironmentProgramme, nor does citing of individual companies, trade names orcommercial processes constitute endorsement.
UNITED NATIONS PUBLICATIONISBN: 92-807-2444-4
Designed and produced by Words and Publications, Oxford, UK
Cover photographs courtesy of Photodisc Inc.
These Guidelines for the Integration of Cleaner Production and Energy Efficiency are part of a UNEP
effort to link the professional disciplines of Cleaner Production and Energy Efficiency in a more
systematic manner. They were developed during a project that saw National Cleaner Production
Centres (NCPCs) in six countries pull energy management principles into the resource efficiency
approach that lies at the heart of Cleaner Production.
The National Productivity Council of India prepared the draft manual, which was then used by NCPC
staff in China, the Czech Republic, Hungary, India, the Slovak Republic and Vietnam. Together these
NCPCs then tested the Cleaner Production–Energy Efficiency methodology in almost 100 companies.
Their experiences in applying the Guidelines helped improve the working draft, as did the editorial
skill of Geoffrey Bird.
The manual has also benefited from comments and suggestions provided by external reviewers, most
notably Thomas Bürki.
Preparation of the manual was coordinated at UNEP by Amr Abdel Hai. Surya Chandak and Mark
Radka also contributed to the effort, which was conducted as a joint activity between UNEP’s Cleaner
Production and Energy programmes.
Cleaner Production – Energy Efficiency Manual page i
Preface
Objectives of the ManualThis electronic manual is part of UNEP DTIE's broad effort to strengthen the energy component of
Cleaner Production (CP) assessments carried out by National Cleaner Production Centres (NCPC).
The Manual presents an integrated Cleaner Production–Energy Efficiency (CP-EE) methodology
based on the proven CP methodology and combines this with factual information, technical data,
worksheets, and tools and resources that will allow both technical specialists and managers to take
direct and effective action.
The guidance provided in the manual can be used by facility personnel conducting in-house
assessments and by consultants interested in providing industrial assessments. CP professionals (who
are not energy specialists) will find guidance on how to better incorporate energy issues into their CP
assessments at industrial or other facilities. Managers will gain insight into the role they can play in
instigating and supporting an ongoing, cost-effective process that has both economic and
environmental advantages.
Structure of the ManualThe CP-EE Manual makes full use of the advantages of its electronic format, providing readers with
‘hyperlinks’ to the sections that are most relevant to their needs. This aspect is explained further in
‘Navigating the Manual’ on the following page.
The first two chapters lay the foundations of the CP-EE assessment methodology for all readers.
Chapter 1 introduces the benefits of integrating CP and EE and of producing a CP-EE methodology.
This is followed, in Chapter 2, by a full explanation of the five steps that make up the methodology.
Readers are then ‘walked through’ the tasks that comprise each step. These simple and easy to follow
explanations are accompanied by a ‘Running Example’ in the form of Completed Worksheets taken
from the actual CP-EE assessment of a textile processing house in India.
Worksheets are an important tool for CP-EE assessment and blank versions of those used for the
Running Example are provided on the CP-EE CD-ROM in editable, printable form, allowing users to
adapt them to their own purposes (see Navigating the Manual on the following page).
The third and final chapter of Part 1 presents the full Case Study of the textile firm used for the
Running Example in Chapter 2.
Cleaner Production – Energy Efficiency Manual page ii
About the CP-EE Manual
Part 1 CP-EE methodology
Cleaner Production – Energy Efficiency Manual page iii
… About the CP-EE Manual (continued)
Module 1 provides background information on different energy-using systems (thermal and
electrical), information that will be helpful in identifying areas of focus for CP-EE assessments.
Module 2 presents Energy Efficient Technologies. Module 1 includes further worksheets that can be
used during assessment.
Part 3 provides tools and resources for everyday use, including: checklists (of procedures that improve
energy efficiency and safety in energy-using equipment); thumb rules (for rapid assessment of the
efficiency of major energy systems); a summary of different types of measuring instruments; links to
sources of information on the Internet; conversion tables (equating SI, metric and other units); and a
summary of acronyms and abbreviations used throughout the Manual.
An additional feature of Part 3 is UNEP’s ‘GHG Indicator’—a spreadsheet based calculator that
allows users to compute the greenhouse gas (GHG) emissions from their facilities. Hyperlinks provide
access to the GHG Indicator either on UNEP’s website or on the CP-EE CD-ROM.
Navigating the ManualHyperlinks are provided throughout the three Parts of the Manual, allowing readers to navigate within
the document and to access Internet based and additional resources with ease. For example:
• Hyperlinks in the contents pages and at the beginning of each main Part enable readers to jump
directly to the topics of their choice.
• Blank versions of the sample Worksheets presented in Parts 1 and 2 are included on the CP-EE CD-ROM
in editable (Microsoft® Word™) format. These can be opened individually by clicking on the
‘Open File’ button at the top right hand corner of the Worksheets displayed in the Manual.
• UNEP’s GHG Indicator is included on the CD-ROM and can be opened directly via the hyperlinks
on the contents page and in Part 3 of the Manual.
• Part 3 includes a comprehensive list of information resources on the Internet. Hyperlinks are
included to provide the reader with direct access to the Internet sites listed. (Note: please read
the disclaimer at the beginning of this section of the Manual before using these resources).
Part 2 Technical modules
Part 3 Tools and resources
Cleaner Production – Energy Efficiency Manual page iv
Cleaner Production ~ Energy Efficiency (CP-EE)Guidelines for the Integration of Cleaner Production and Energy Efficiency
MANUAL
Contents
Preface i
About the CP-EE manual ii
Part 1 CP-EE methodology 1
Chapter 1: Introduction 2
1.0 Building on established strategies 2
1.1 Cleaner Production (CP)—a focus on material flows 2
1.2 Energy Efficiency (EE)—a focus on cost reduction 2
1.3 Integrating CP and EE 3
1.4 Areas requiring particular attention when integrating CP-EE 4
Chapter 2: CP-EE assessment methodology 7
2.1 Introduction 7
2.2 CP assessment—an established methodology 8
2.3 EE assessment—towards a methodology 10
2.4 Integrated CP-EE assessment methodology—combining for synergy 10
2.5 Description of a CP-EE methodology 12
2.6 The CP-EE process (incorporating the Running Example) 14
2.7 Worksheets for a CP-EE assessment methodology 61
Chapter 3: Case study 87
3.1 About the company 87
3.2 Process description and process flow chart 88
3.3 Baseline information 91
3.4 Identification of waste streams, cause analysis and CP-EE opportunities 95
3.5 Feasibility analysis of CP-EE options 98
3.6 Benefits and achievements 105
3.7 CP-EE assessment barriers 108
3.8 Conclusions 109
… Contents (continued)
Cleaner Production – Energy Efficiency Manual page v
Part 2 Technical modules 111
Module 1: Energy use in industrial production 112
Thermal systems 112
M1.1 Fuels—storage, preparation and handling 112
M1.2 Combustion 116
M1.3 Boilers 121
M1.4 Thermic fluid heaters 135
M1.5 Steam distribution and utilization 137
M1.6 Furnaces 154
M1.7 Waste heat recovery 163
Electrical systems 176
M1.8 Electricity management systems 176
M1.9 Electric drives and electrical end-use equipment 189
M1.10 Cooling towers 222
M1.11 Refrigeration and air-conditioning 227
M1.12 Lighting systems basics 234
Module 2: Energy efficient technologies 240
M2.1 New electrical technologies 240
M2.2 Boiler and furnace technologies 242
M2.3 Heat upgrading systems 244
M2.4 Other utilities 245
Part 3 Tools and resources 247
A: Checklists for enhancing efficiency and safety 248
B: Thumb rules for quick efficiency assessment 260
C: List of energy measuring instruments 262
D: Greenhouse Gas Emissions Indicator 267
E: Information resources 276
F: Conversion tables 287
G: Acronyms and abbreviations 293
Cleaner Production – Energy Efficiency Manual page vi
ENERGYEFFICIENCY
Cleaner Production – Energy Efficiency Manual page 1
Contents listing
Part 2 Technical modules
Part 3 Tools and resources
Part 1 CP-EE methodology
Cleaner Production (CP) and Energy Efficiency (EE)
are established and powerful strategies that reduce costs
and generate profits by reducing waste. Their integration
can provide synergies that broaden the scope of their
application and give more effective results—both
environmental and economic. Integration of these two
powerful strategies is the subject of this manual.
1.0 Building on established strategiesBoth Cleaner Production (CP) and Energy Efficiency (EE) are established and powerful
strategies that reduce costs and generate profits by reducing waste. They are, however,
generally practiced separately, with little or no search for common ground. This is
unfortunate, since CP and EE are often highly complementary and their integration can
provide synergies that broaden the scope of their application and give more effective
results—both environmental and economic. Integration of these two powerful
strategies is the subject of this manual.
1.1 Cleaner Production—a focus on material flowsCP was developed as a preventive strategy to reduce environmental pollution and
simultaneously reduce consumption of material resources. Its main focus is on
processes and on reduction of the resources they use. CP is a new and creative way of
thinking about products and processes that implies continuous application of strategies
to prevent and/or reduce the occurrence of waste. Practitioners of CP call on an
established CP methodology to identify and implement solutions.
As the example below right illustrates, the CP concept can combine real opportunities
for growth with maximum efficiency in use of materials. However, because CP evolved
from environmental concerns about physical pollution arising from material waste
streams and emissions, its proponents and practitioners have focused on material
resource conservation. CP does not, generally, address issues of total resource
productivity holistically, and other avenues of productivity—such as energy
conservation, industrial engineering, value engineering, etc.—have not been well
integrated into the concept. In addition, CP—by definition—does not cover ‘end-of-
pipe’ solutions.
1.2 Energy Efficiency—a focus on cost reduction Efforts to improve energy efficiency in industry began in the early 1970s, driven
primarily by the need to reduce production costs. Although energy is a vital input to
many processes, it is not necessarily a critical cost component. This may explain why
EE practitioners have tended to focus on energy conversion equipment (involving less
risk in terms of process disruption) and have avoided process-related EE options (a
riskier proposition).
There is no universal, systematic methodology characterizing an EE approach and to
which EE practitioners can refer. Individual countries have accordingly adopted their
own strategies to address energy efficiency and energy input costs. Currently, EE is
Cleaner Production – Energy Efficiency Manual page 2
Part 1 CP-EE methodology
Chapter 1: Introduction
snapshot
CP-EE
A small-scale textile-processing unit used
winches (heated by directfiring of solid fuel) for
bleaching and dyeing ofcotton fabric. A CP studyrevealed that the unit waswasting large amounts of
water, dyes and otherchemicals. CP solutions,including reducing thematerial-to-liquor ratiofrom 1:20 to 1:15 and
optimizing the chemicalsand dyes, reduced the
consumption of water andchemicals used and
resulted in annual savingsof US$3 600.
A seasoned CP practitioner,was asked to look into a
large educational institution’spumping system to improvewater use. Having recently
acquired EE skills, he was notonly able to reduce wastefulwater consumption by 30per cent but also to reduce
the energy used forpumping by 37 per cent(through reduced use,
optimum pipe size,simplified distribution
network and reduced headrequirements).
snapshot
CP-EE
Cleaner Production – Energy Efficiency Manual page 3
Part 1 CP-EE methodology Chapter 1: Introduction
viewed as being highly compartmentalized and, in the absence of an established
methodology, is generally prescriptive and sporadic.
Very few EE practitioners are concerned about the environmental results of
implementation of EE and—even though a fair proportion of EE options lead to benefits
for the environment—these are almost never highlighted. For EE practitioners, cost
reduction is the overriding concern and they will favour economically attractive options
even when these may have negative environmental impacts.
1.3 Integrating CP and EE 1.3.1 Benefits of integrating CP and EE
The numerous, tangible benefits of an integrated CP-EE approach, illustrated succinctly
by the snapshots, are outlined below. Once the benefits have been described, some
consideration is given to important aspects of integration, highlighting differences in
assessing material and energy flows and identifying skills needed for successful CP-EE
integration.
An integrated CP-EE approach offers the following benefits:
I. Expanded service package with greater benefits (synergy)
When resources are low priced (or perhaps subsidized) and/or environmental issues are
not considered significant, a CP solution alone may not be attractive. By combining it
with EE benefits, a more attractive package can be proposed. Similarly, the
attractiveness of reduced energy consumption in a situation where energy prices are
not significant may be enhanced by combining it with CP. An integrated CP-EE
approach draws from a much wider repertoire of best practices, yielding
comprehensive business solutions and more attractive cost benefits.
II. Greater market share for products
CP-EE can lead to products that can genuinely be described as ‘eco-friendly’. ‘Green’
products that warrant both eco and energy rating labels have an additional
competitive edge—they can gain a better market share.
III. Integration ensures sustainability of EE options
To date, the prevailing approach to EE has been task oriented and prescriptive in nature
and EE has not been viewed as part of day-to-day management. EE improvement
programmes have therefore often ended as soon as advisors have left the plants,
resulting in programmes that are sporadic and short-lived.
snapshot
EE
A small-scale textile-processing unit used an
open winch for bleachingand dyeing of cottonfabric. The winch was
heated by direct firing ofsolid fuel under the tank.An energy audit indicatedinefficiency in the heatingsystem resulting in heavyfuel consumption and less
than optimum bathtemperatures. When, on
the EE professional's advice,changes were made to thedesign of the furnace, the
bath temperature wasincreased from 55 °C to
60 °C, and fuelconsumption was reduced.
This brought an annualsaving of US$1 200.
An acclaimed EE expert,was asked by the managersof a Vietnamese steel plantto help reduce energy bills.
Using integrated CP-EEtechniques, he not only
brought down oilconsumption and costs by20 per cent (by fine tuningexcess air in burners of heattreatment furnaces) but alsoreduced scale losses (due tooxidation) from 3 per centto less than 0.5 per cent—equivalent to an additional10 per cent of oil savings.
snapshot
CP-EE
Cleaner Production – Energy Efficiency Manual page 4
Part 1 CP-EE methodology Chapter 1: Introduction
Conversely, continuous application is a key aspect of CP. When CP and EE are
integrated, the notion of continuity becomes extended to EE thereby ensuring its long
term sustainability.
IV. Facilitating implementation of global agreements and protocols
In recent years a number of global and regional agreements and protocols have been
developed covering both environmental and energy issues.
CP-EE can help to mainstream these more easily than CP or EE alone. Some countries
have introduced laws on CP others on EE; a combination of both can help to enforce
material and energy conservation measures simultaneously. A CP-EE group could play
a pivotal role in helping a country’s government towards this end.
V. Less duplication of tasks and synergy between CP and EE objectives
CP and EE professionals spend a lot of time collecting and analysing data separately,
and then generating material and energy savings options, once again separately. An
integrated and simultaneous effort would save a lot of collection and analysis time and
would also lead to simpler ways of addressing interdependent issues of material and
energy waste.
VI. Improving access to a wider range of funding sources
There are global and regional sources of funds available exclusively for CP or exclusively
for EE. These could be accessed jointly by CP-EE.
VII. CP-EE paves the way for implementation of Environmental Management Systems (EMS)
An integrated CP-EE approach, by virtue of its methodology, makes it easier to implement
and sustain a more comprehensive Environmental Management System (EMS).
1.4 Areas requiring particular attention when integratingCP-EE: hidden wastes and inefficiencies in energy systemsBecause CP is generally applied to visible (i.e. material) resource wastes, it leaves little to
chance. Material inputs to a given operation can generally be traced through to
perceivable and quantifiable outputs. This is not always the case when considering
energy streams. While the same basic rule must hold true for energy inputs (i.e. amount
of energy ‘in’ must, ultimately, be equal to the amount of energy ‘out’) output energy
streams are often less easy to perceive than material ones. Identification and evaluation
of hidden waste streams and inefficiencies can therefore be a difficult proposition.
Cleaner Production – Energy Efficiency Manual page 5
Part 1 CP-EE methodology Chapter 1: Introduction
This is particularly true for electrically driven equipment such as pumps, fans, air
compressors, etc. where input energy, in the form of electricity, is easily measurable but
the degree to which this is efficiently converted into useful output (e.g. pumped water,
compressed air, etc.) is not directly quantifiable.
The following are examples of typical situations where only looking for visible/perceivable
energy streams can lead to overlooking of energy loss in output streams:
• Loss due to part load operation of energy-using equipment.
• Loss due to (low-efficiency) banking/idling operations of energy using equipment.
• Losses due to resistance to flow (high but avoidable resistance in electricity
conductors and fluid pipelines).
• Loss due to equipment degradation (pump impellers, pump bearings, etc.)
leading to increased losses.
1.4.1 Additional parameters and skills
In order to ascertain the outputs (both perceivable and non-perceivable) from energy
systems, some EE parameters have to be measured/monitored during a CP assessment
in addition to the essential ones—such as temperature, flow, humidity, concentration,
percentage compositions, etc.—already measured as part of CP.
Additional EE parameters that need to be measured/monitored could include:
kW (kilowatt power input); kV (kilovolts—impressed voltage); I (amperes—electrical
current); PF (power factor of induction electric equipment); Hz (frequency of
alternating current); N (rpm or speed of rotating equipment); P (pressure of
liquid/gaseous streams); DP (pressure drops in input/output liquid and gaseous
streams); Lux (light intensity); GCV, NCV (gross and net calorific value of fuels); etc.
CP professionals will need some additional skills to be able to integrate EE during
assessments effectively. They should:
• have a basic understanding of electrical circuits, to be able to measure input
power to motor drives correctly;
• be able to evaluate enthalpy (heat content) in each stream by measuring
temperature, pressure and flow;
• be able to quantify non-perceivable (invisible) streams using known streams. For
example, given pump output parameters (such as pressure developed, flow and
density) they should be able to evaluate work done and thus estimate energy output;
Cleaner Production – Energy Efficiency Manual page 6
Part 1 CP-EE methodology Chapter 1: Introduction
• be familiar with and able to convert between various energy, pressure and heat
content units;
• be able to control waste energy streams and learn to correlate the effect of
control measures with conversion efficiency of equipment.
Differences between material and energy flows are considered further when the
methodology for carrying out a CP-EE assessment is presented in Chapter 2.
1.4.2 Possible contradictions
CP and EE are highly complementary, with synergies between the individual benefits
of each delivering a more effective overall outcome. However, there are some situations
where the beneficial results of one methodology (say CP) can be perceived as being in
contradiction with the other methodology (EE). A few simple examples will illustrate
this:
• Recycling is a very profitable CP technique, but recycling of oils, and lubricants,
and reuse of reconditioned bearings or rewinding of burned out motors
(especially when not done properly) often lead to higher energy consumption.
• Refrigeration by vapour absorption is an eco friendly and pro-CP option in
comparison with the prevalent vapour compression machines. However, in terms
of energy use, vapour absorption systems are less efficient.
• Slim fluorescent tube lights are far more energy efficient than incandescent lamps,
but from the environmental (CP) point of view, their mercury coating makes them
less eco-friendly.
snapshot
CP-EE
‘EA’, a medium scale edibleoil processing unit in India,
was experiencing highhexane losses of 4.93 litresper ton of seeds processed.CP-EE studies in the plantrevealed that the losseswere primarily due to
inadequate steam supply atthe desired pressure,
inadequate heating surfacearea of the reactor vessel,
low vacuum, andinadequate condenser size.Further detailed studies ofthe boiler revealed that itdid not have the capacity
to supply the requiredquantity of steam at
optimum pressure. Thecompany changed the
boiler and—after necessarymodification of the reactor
vessel to increase theheating surface area—
reduced hexane losses by12.2 per cent. Besides
improving itsenvironmental
performance, the companyimproved the quality of the
de-oiled cake. A totalinvestment of US$255 500resulted in annual savings
of US$270 000.
Cleaner Production – Energy Efficiency Manual page 7
Part 1 CP-EE methodology
Chapter 2:
CP-EE assessment methodology
2.1 IntroductionFrom the arguments presented in Chapter 1, the benefits, and the possible
importance, of integrating CP and EE should now be clear. This second section looks
at methodology, and shows how the proven method of carrying out a CP assessment
can be expanded to ensure a systematic approach to EE.
Traditionally, EE assessments have been driven by a need for quick solutions, to be
implemented quickly, and for quick profits. EE assessments and projects have therefore
tended to be needs-based, arising from situational demands, and have generally relied
on external EE expertise. There has been no perceived need to develop in-house
capacities to foster continuous improvement programmes. As a consequence, EE
assessments and implementation of the resulting projects have tended to be ad hoc,
piecemeal, and less logically structured than CP assessments.
If CP-EE coverage is to be comprehensive, a CP-EE assessment—like a CP assessment—
must be conducted systematically. A structured approach is essential to get the best
results and to ensure that the outcomes are consistent with those identified in the
enterprise's broader planning process. A step-by-step procedure based on a sound
methodology will ensure maximum benefit from CP-EE opportunities.
The assessment method should be flexible enough to accommodate unforeseen
circumstances and problems, and to allow solutions to be identified. How formal the
method needs to be will depend on the size and composition of the company, on its
material and energy use, and on specific aspects of its waste production.
The CP-EE assessment method should also ensure better use of available resources
(manpower, machinery, material, money) and should foster logical and sequential
thinking.
A CP-EE assessment is an excellent way of building a waste avoidance culture and of
creating competence within the company that is crucial for long-term sustainability.
And finally, if the CP-EE programme is to be effective and continuous, it is essential to
involve people from the different sectors of the company in its implementation.
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
2.2 CP assessment—an established methodologyAssessment, involving analysis of the material and energy flows entering and leaving a
process, is a central element of CP. Conducting a CP style assessment relies on a logical
and methodical approach that makes it possible to identify opportunities for CP, to
solve waste and emission problems at source, and to ensure continuity of CP activities
in a company. This analytical assessment approach is embedded in the CP
methodology, shown in Figure 1.1.
The basic CP methodology consists of the following principal elements:
• Planning and Organization
• Pre-assessment
• Assessment
• Feasibility Analysis
• Implementation and Continuation.
Cleaner Production – Energy Efficiency Manual page 8
Planning andOrganization
obtain commitment of top management
involve employees
organize a team
identify barriers and solutions to the CPA process
decide the focus of the CPA
compile and prepare basic information
conduct a walkthrough
prepare an eco-mapprepare a preliminary material and energy balance
prepare a detailed materialand energy balance
conduct cause diagnosis
generate options
screen options
conduct economic andenvironmental evaluation
select feasible options
prepare a cleaner production implementation plan sustain cleaner production assessments
Pre-assessment
Assessment
FeasibilityAnalysis
Implementationand Continuation
compile existing basic information
Figure 1.1 CP methodology
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Figure 1.1 shows the generic CP methodology. However, in practice, different
institutions and practitioners have expanded and/or modified the steps in this basic
methodology and have developed specific tasks at each step that suit local conditions
and specific requirements. A typical empirical CP methodology is presented in Figure
1.2. This is used later (in Section 2.5) to develop a CP-EE assessment methodology that
adheres strictly to the steps presented here but also includes specific features that need
to be covered to integrate energy efficiency aspects.
Cleaner Production – Energy Efficiency Manual page 9
STEP 1: Planning and Organization
Task 1: Obtaining commitment and involvement of top managementTask 2: Involving employeesTask 3: Organizing a CP teamTask 4: Compiling existing basic informationTask 5: Identifying barriers and solutions to the CP assessment processTask 6: Deciding the focus of the CP assessment
Task 7: Preparing a process flow diagramTask 8: Conducting a walkthroughTask 9: Preparing material input-output quantification and characterizationTask 10: Generating and finalizing base data
Task 11: Preparing a detailed material balance with lossesTask 12: Conducting cause diagnosisTask 13: Generating optionsTask 14: Screening options
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
2.3 EE assessment—towards a methodologyFor most companies, it is the absence or disruption of energy supply that is perceived
as having a dramatic impact on the process, not day-to-day energy consumption.
Energy is viewed as a crucial input but not always as an important cost intensive one.
There has therefore been little motivation and incentive to develop riskier but more
rewarding energy reduction initiatives in manufacturing process.
EE improvements have generally been made to standard energy converting
equipment—such as boilers, furnaces, heaters, dryers, ovens and kilns, and electrically
driven equipment such as pumps, fans, air compressors, refrigeration compressors,
etc.—with little effort on process and production related equipment and technology.
All industrial and commercial facilities have some energy conversion equipment, and
nearly all of this has well standardized performance assessment procedures and
reference performance indicators. The existence of these procedures and indicators is
seen as making a logical, structured and comprehensive methodology unnecessary and
gives little incentive for innovation and creativity in approach and methodology.
Over a period of time, this has led to development of very mature, proven, cost-
effective and standardized prescriptive solutions, with very little effort going into the
development of creative alternatives.
2.4 Integrated CP-EE assessment methodology—combining for synergySection 1.4 outlined important differences between CP and EE assessments,
underscoring the differences between material and energy flows and some of the
difficulties of quantifying the latter. The material below builds on that information,
going into greater detail on how energy flows can be quantified.
a) In a CP assessment, material streams are identifiable and quantifiable at both input
and output stages, since the material streams do not generally change form. In a
CP-EE assessment, however, care must be exercised when accounting for energy,
since energy is largely invisible at input and changes form within the process.
Electricity, for example, is used to drive motors but also to compress air as well as
for lighting, heating, etc. It may be identifiable and quantifiable at the input stage,
but it is much more difficult to identify and quantify at output.
Cleaner Production – Energy Efficiency Manual page 10
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
b) Whenever energy changes form there are some inevitable losses. For CP, these
losses are not considered as important because they do not have a significant direct
impact on the environment. For EE, on the other hand, identification of the areas
where these losses occur is of great importance.
c) To identify losses, CP-EE studies have to include measurement of parameters not
measured for CP (e.g. temperature, tension in belts, lumens for lighting, etc.).
There are also parameters such as friction, surface tension, etc. which cannot be
perceived directly and which cannot therefore be measured directly. In these
cases estimates have to be made using empirical equations.
d) CP does not identify waste streams unless they are in the form of material waste.
For instance, in a combustion process, a CP study will measure the airflow before
and after combustion (in stack). If the quantities match, little or no further
attention will be paid to this stream. For EE studies, however, excess air levels in
the flue gas (in stack) are of great importance. Similarly a stream of hot
wastewater is a material waste for CP, for EE it is a heat loss.
e) In a CP assessment it is relatively easy to produce a material and mass balance for
a process because, as already explained, material streams do not generally change form1.
It is more difficult for a CP-EE assessment to produce an exact energy balance right across
a process since energy is invisible and changes its form. Even perceivable losses, such
as iron or copper losses, eddy current loss in motors, friction losses etc., are difficult to
measure and quantify. A different approach has to be adopted to obtain energy balances.
Some options for producing an energy balance are:
i) System efficiency based on measurable energy input and work output
For example, fan delivery air can be measured (in m3) against power consumed (in
kW), giving an indication of efficiency as kW/m3. A similar indication could be given for
a refrigeration system, as kW/TR.
ii) Measurement of major loss only
Sometimes input and output energy streams are difficult to measure. This would be the
case, for example, for steam flowing in a pipeline over a long distance and where it is
possible to measure neither input steam, owing to lack of flow meters, nor output heat
effect, because of the very narrow temperature difference. However, parameters such
as surface losses or radiation losses can be measured.
Cleaner Production – Energy Efficiency Manual page 11
1 Even when some of the materials do change form (e.g. vapour loss from water duringheating) the changes are usually very small.
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
iii) Single parameter measurement and benchmark comparison
For systems like agitators, where even measuring of losses is not practicable,
comparative efficiency levels can be obtained by measuring the electricity input and
comparing it with input for similar systems elsewhere.
The causes of energy waste are well known, relatively uniform and standard and, at
times, making an exhaustive cause analysis may seem superfluous (e.g. Waste = excess
air in flue gas. Cause = air fan supplying too much air or air ingress). However, until the
CP-EE team becomes fully conversant with the normal/standard causes, it may still be
advisable to conduct an exhaustive cause analysis, to avoid overlooking possible causes.
2.5 Description of a CP-EE methodologyThe CP-EE methodology (shown in Figure 1.3) follows the same generic, systematic
and step-by-step approach as the CP methodology, and is characterized by the same
five steps. For a CP practitioner, the basic assessment methodology remains the same,
the difference lying in some of the specific tasks, in particular those in Step 2, and in
the details of the material and energy balance, in Step 3.
Cleaner Production – Energy Efficiency Manual page 12
Planning andOrganization
STEP 1
Pre-assessmentSTEP 2
AssessmentSTEP 3
Implementationand Continuation
STEP 5
FeasibilityAnalysisSTEP 4
START HERE
Figure 1.3 CP-EE methodology
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
STEP 1: Planning and Organization
Task 1: Obtaining commitment and involvement of top managementTask 2: Involving employeesTask 3: Organizing a CP-EE teamTask 4: Compiling existing basic informationTask 5: Identifying barriers and solutions to the CP-EE assessment processTask 6: Deciding the focus of the CP-EE assessment
Task 7: Preparing a process flow diagramTask 8: Conducting a walkthroughTask 9: Preparing material and energy input-output quantification
and characterizationTask 10: Generating and finalizing base data
Task 11: Preparing a detailed material and energy balance with lossesTask 12: Conducting cause diagnosisTask 13: Generating optionsTask 14: Screening options
Cleaner Production – Energy Efficiency Manual page 13
Figure 1.4 CP-EE assessment methodology
Note: the next to the
Tasks in Figure 1.4 indicate
Tasks which require additional
skills, expertise, data
collection and work; these
Tasks are similarly indicated
where they occur in the text.
!
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
2.6 The CP-EE process
Introduction
This section describes the CP-EE process. It gives detailed comments on each of the 18
tasks that make up the 5 steps of the process, and presents a set of Worksheets—the
tools for conducting an assessment—at the end of the section*.
To better illustrate the steps of the CP-EE assessment methodology, a ‘Running
Example’ is presented in this section of the manual. It is described as a ‘running’
example because it recurs throughout the section presenting relevant data and values,
in the form of Completed Worksheets, as each task of the five steps of the CP-EE
methodology is explained.
The data and values used in the Completed Worksheets are taken from an actual CP-EE
assessment carried out in 2002 at M/s Luthra Dyeing and Printing Mills (LDPM), Surat,
India. LDPM is a well-equipped textile processing house that is representative of the
synthetic fabric processing sector in India. A full description of the step by step CP-EE
assessment of LDPM is presented as a ‘Case Study’ contained in Chapter 3.
STEP 1 Planning and Organization
The planning and organization step is one of the most important for a successful CP-EE
assessment. It consists of the following six tasks:
• Obtaining commitment and involvement of top management
• Involving employees
• Organizing a CP-EE team
• Compiling existing basic information
• Identifying barriers and solutions to the CP-EE assessment process
• Deciding the focus of the CP-EE assessment.
Planning can begin once the members of the CP-EE team are identified and once the
interest of management in CP-EE has been obtained—often as a result of awareness
raising. However, a CP-EE assessment can only be initiated after a decision has been
made by the management to take action.
Cleaner Production – Energy Efficiency Manual page 14
* The Worksheets
presented in Section 2.7
are included on the
CD-ROM in Microsoft®
Word™ format. These
editable files can be
opened by clicking on the
‘Open File’ button in the
top right corner of each
Worksheet displayed in the
Manual.
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Cleaner Production – Energy Efficiency Manual page 15
The CP-EE assessment may be conducted by an internal company team or by hiring
external CP-EE professionals.
Task 1 Obtaining commitment and involvement
of top management
If the company decides to involve external CP-EE professionals (consultants) a
meeting is generally organized between the consultants and top management
to formalize this decision.
Typically, a memorandum of understanding (MoU) is drawn up between the
consultants and the company to define the CP-EE objectives; establish a work
plan that will indicate a time frame, sharing of responsibilities and outcomes;
and to set fees.
The management of the company has to set the stage for the CP-EE assessment
in order to ensure cooperation and participation of the staff members. In addition
to signing the MoU, top management's commitment should take the form of:
• management of formation of a CP-EE team;
• ensuring availability of required resources;
• provision of necessary training, awareness-raising meetings for employees;
and
• responsiveness to the CP-EE results.
It is also important to assess the following:
• Where does the company stand in relation to environmental and energy
policies and to what extent have these been implemented?
• What is the status of environmental and energy management in the
company?
• What is the status of internal communications at different levels in the
company, of information flow, and of initiatives to raise awareness of energy
and environmental management issues amongst employees?
The Completed Worksheet 1 in the Running Example on the following page
shows how a matrix can facilitate assessment of managerial aspects.
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Cleaner Production – Energy Efficiency Manual page 16
Running Example: Task 1
Obtaining commitment and involvement of top management
CP-EE is not just a matter of finding technical solutions, numerous other factors influence
energy management and the identification and implementation of CP-EE options both
directly and indirectly. Commitment and involvement of a firm's top management are
therefore essential—CP-EE can only be initiated after management has made the
decision to act.
An Environmental Management Matrix like the one shown below2 (as the first
Completed Worksheet) can be used to foster management involvement and assist in
making decisions and identifying potential CP-EE solutions. Completing the matrix
indicates where the company stands in relation to six energy/environmental
management areas: policy and systems, organization, motivation, information systems,
awareness and investment.
The matrix presented below is the one used at M/s Luthra Dyeing and Printing Mills
(LDPM), Surat, India, the information being based on interviews with management and
presentations during an initial meeting on energy and environmental management
activities.
Based on interview outcomes, bullet points are inserted in the matrix, and these are
connected to give a curve (as shown in the matrix below). The peaks indicate where
current efforts are most advanced; the troughs indicate where the company is least
advanced. It is not unusual for the 'curve' to be uneven, this is the case for most
organizations.
The matrix helps to identify aspects where further attention is required to ensure energy
and environmental management is developed in a rounded and effective way. It will also
assist in organizing an energy and environmental management system.
How to use the matrix• Senior management staff and the CP-EE Team Leader are given a blank version of
the matrix. Ask them to indicate on it what they believe to be their company’spresent situation. A score of ‘4’ for a specific category means that all initiativesmentioned in categories 0 to 4 must be present.
• Hold a 1-hour interview with senior management to check the real position.• Based on interview outcomes, insert the bullets in the matrix and connect them up.
2 Modified from the Energy Management Matrix provided by the Sustainable Energy Authorityof Victoria, Australia, www.seav.vic.gov.au
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Cleaner Production – Energy Efficiency Manual page 17
Motivation
Formal and informalchannels ofcommunicationregularly used byenergy/environmentalmanager and staff at alllevels
Energy/environmentcommittee used asmain channel togetherwith direct contact withmajor users
Contact with majorusers through ad hoccommittee chaired bysenior departmentalmanager
Informal contactsbetween engineer anda few users
No contact with users
Organization
Energy/environmentalmanagement fullyintegrated intomanagement structure.Clear delegation ofresponsibility for energyuse
Energy/environmentalmanager accountableto energy committee,chaired by a member ofthe management board
Energy/environmentalmanager in postreporting to ad hoccommittee but linemanagement andauthority unclear
Energy and environmentalmanagement are part-time responsibility ofsomeone with onlylimited influence or authority
No energy/env.manager or formaldelegation ofresponsibility forenv./energy use
Policy and systems
Formal energy/environmental policyand managementsystem, action plan andregular review withcommitment of seniormanagement or part ofcorporate strategy
Formal energy/environmental policybut no formalmanagement system,and with no activecommitment from topmanagement
Unadopted/informalenergy/environmentalpolicy set byenergy/environmentalmanager
Unwritten guidelines
No explicit policy
Information systems
Comprehensive systemsets targets; monitorsmaterials and energyconsumption, wastesand emissions;identifies faults;quantifies costs andsavings; and providesbudget tracking
Monitoring andtargeting reports forindividual premisesbased on sub-metering/monitoring,but savings not reportedeffectively to users
Monitoring andtargeting reports basedon supplymeter/measurementdata and invoices.Env./energy staff havead hoc involvement inbudget setting
Cost reporting basedon invoice data.Engineer compilesreports for internal usewithin technicaldepartment
No information system.No accounting formaterials and energyconsumption and waste
Awareness
Marketing the value ofmaterial and energyefficiency and theperformance ofenergy/environmentalmanagement
Programme of staffawareness and training
Some ad hoc staffawareness and training
Informal contacts usedto promote energyefficiency and resourceconservation
No promotion ofenergy efficiency andresource conservation
Investment
Positive discriminationin favour of energy/environmental savingschemes with detailedinvestment appraisalof all new buildingand plantimprovementopportunities
Same pay-back criteriaas for all otherinvestments. Cursoryappraisal of newbuilding and plantimprovementopportunities.
Investment usingmostly short-termpay-back critera
Only low-costmeasures taken
No investment inincreasingenvironmental/energyefficiency in premises
Level
4
3
2
1
0
Completed Worksheet 1
… Running Example: Task 1 (continued)
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
!
Cleaner Production – Energy Efficiency Manual page 18
Task 2 Involving employees
Success of a CP-EE assessment depends heavily on staff involvement. It isimportant to remember that successful CP-EE assessments are not carried outby people external to the company, such as consultants, but by the staff of thecompany itself supported, if and where necessary, by people from outside.
Staff in this context means everyone, from senior management to employees onthe shop-floor. In fact, shop-floor staff often have a better understanding ofprocesses and are able to suggest improvements. Other departments such aspurchasing, marketing, finance, and administration can also play an important role.
Staff members provide useful data, especially on process ‘inputs’ and ‘outputs’, andassist with assessment of the economic and financial feasibility of CP-EE options.Group meetings should be organized to involve them. Well managed meetings willgain the goodwill and confidence of employees and also inform them about thebenefits of a CP-EE assessment. This rapport with employees will help to motivatethem and ensure their involvement in the studies. Completed Worksheet 2 showsa checklist of various activities that can be undertaken to involve employees.
Task 3 Organizing a CP-EE Team
Setting up one or more CP-EE teams is an important aspect of the initiation,coordination and supervision of the CP-EE studies. Teams should consist of companystaff supported and assisted where necessary by CP-EE professionals. Getting theright mix of team members is crucial, otherwise teams may face hindrance fromwithin (e.g. from other company staff members) as well as from outside.
For large organizations, teams could comprise a core group ensuring afavourable response to CP-EE options (made up of representatives of differentdepartments, especially finance/accounts and projects departments) and sub-groups addressing specific tasks.
For small and medium size firms, a single team comprising the owner or proprietorand supervisors or managers overseeing day-to-day operations may well besufficient. To be effective, the team should have enough collective knowledge toanalyse and review current production practices and energy systems and toexplore, develop and evaluate CP-EE measures. (See Completed Worksheet 3).
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Cleaner Production – Energy Efficiency Manual page 19
No ✗
✗
✗
✗
✗
✗
✗
Yes ✓
✓
✓
✓
✓
✓
✓
Tasks
CP-EE introduction
Workshop
• Middle manager
• Shop floor workers
• Utilities workers
• Administration staff
Group meetings
• Administration staff
• Various sections in the process house
• Utilities staff
• Maintenance staff
• Purchase department staff
Display of CP-EE posters
Showing of short films on CP-EE success stories
Organizing of slogan campaign on environmental and energy themes
Section no.
1)
2)
3)
4)
5)
Completed Worksheet 2
LDPM employees were given formal training and were informed about CP-EE
Running Example: Task 2
Designation
Director
Operation In-charge
Maintenance Engineer
Dyeing In-charge
External Consultant
Department
Overall
Equipment and utilities
Plant maintenance
Dyeing section
–
Role
Team leader
Team member
Team member
Team member
Team member
Name
Girish Luthra
Bimal Kumar
Nikun Nanavati
Dadaram Gohdsware
Rajiv Garg
Section no.
1)
2)
3)
4)
5)
Completed Worksheet 3
A CP-EE Team was organized in consultation with the management
Running Example: Task 3
!Task 4 Compiling existing basic information
In this task, the CP-EE team generates four important outputs:
General company information
This involves obtaining general details about the company including details of
key contact people, main products, turnover, employees, working hours and
production days in a year. (See Completed Worksheet 4a).
General production flow chart
A general production flow chart includes major energy conversion equipment
supplying utilities such as steam (boilers), compressed air (air compressors),
chilled water (refrigeration compressors), etc. (See Completed Worksheet 4b).
Data on consumption and cost of input raw materials, chemicals and energy
resources (electricity and fuels) must be collected and compiled, together with
data on consumption by utilities and details of production for both the entire
plant and for each process department. These data should be compiled in three
forms, namely: daily or batch average; monthly average (daily data over a
period of three to four representative months); and yearly average (twelve-
month data for preceding three years) (see Completed Worksheets 4c and 4d).
Graphical representation of the data will help the team to analyse work
practices and trends within the facility and may also highlight unusual practices
that are worthy of investigation.
Details of technical specifications
Details of technical specifications for equipment used in the production process and
supply of process utilities must also be collected. (See Completed Worksheet 4e).
A status list of readily available information
A status list of readily available information about the plant should be made. This
will include process flow diagrams, plant layouts, inventory and dispatch data
sheets, raw material consumption and cost data, production data, production
log sheets, material balance, water balance and conservation details, energy
General information about the company was collected, presented in Completed Worksheets 4a to 4f
Completed Worksheet 4b: General production flowchart
coal
fines
waste gases
blowdown
steam
water
chemicals
coal yard
crusherhouse
boilerhouse
pre-treatment
bleachingand dyeing
product
grey cloth
wastewater
wastewater
wastewater
emissions
watersteam
chemicals
Utilities• DG sets• gas storage and handling
treated waterto drain + recycling
ETP
sludge
fines
watersteam
chemicals
printing
watersteam
chemicals
finishing
gassteam
chemicals
Completed Worksheet 4c: Monthly variation
cloth dyed (tons)
cloth printed (tons)
total dyed + printed (tons)
total cloth normalized (tons)
0
50
100
150
200
250
300
month
prod
ucti
on
1 2 3 4 5 6 7 8 9 10 11 12
51 30 65 48 62 44 42 63 80 126 83 104
87 108 112 155 157 92 148 168 162 148 101 151
138 138 177 203 219 136 191 231 242 274 184 256
112 123 145 179 188 114 170 199 202 211 143 203
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Cleaner Production – Energy Efficiency Manual page 22
MonthsUnit
1
115
201
3
772
698
247
827
1 525
61
82
2
122
208
846
663
256
858
1 521
65.4
80
3
136
222
4
697
345
363
1 216
1 561
60.5
88
4
148
234
4
625
1 587
0
0
1 587
65.1
93
5
136
222
3
611
234
608
2 037
2 272
60.1
85
6
172
258
3
804
294
417
1 395
1 690
74.2
110
7
143
229
4
629
225
421
1 410
1 636
61
100
8
133
219
4
656
234
366
1 227
1 461
61.4
93
9
123
209
4
582
208
361
1 209
1 417
61.8
87
10
136
222
4
576
1 469
0
0
1 469
61.3
90
11
135
221
4
623
1 641
0
0
1 641
64
99
12
125
211
3
553
1 356
0
0
1 356
63.5
85
Total average
135
221
3
664
746
253
848
1 595
63.2
91
Resources
Purchased water
Total water
Coal
Gas
Grid electricity
Diesel
Eqivalentelectricityfrom diesel
Total kWhelectricity
Dyes
Gums
m3/ton cloth
m3/ton cloth
t/ton cloth
m3/ton cloth
kWh/ton cloth
litre/ton cloth
kWh/ton cloth
kWh/ton cloth
kgs/ton cloth
kWh/ton cloth
Completed Worksheet 4d: Resource consumption
… Running Example: Task 4 (continued)
On average, the unit processes 8.0 tons of cloth per day. As is typical of textile processing units, the process requires steam, water,gas, compressed air, dyes and printing chemicals, etc. Consumption of major resources per ton of cloth processed in the year 2002 istabulated below.
Name of utility Capacity Quantity Specifications
6 t/hr
-
380 kVA125 kVA
>50 HP50 – 10
<10
3 280 m3/hr
5 m3/hr
1
2
21
81636
11
2
Make
IBL
-
KirloskarCummins
several
--
-
Type
Smoke tube
Screw compressor
3-phase
IDFD
Specific design parameters
6 t/hr, 10.98 kg/cm2,at 75% eff.
250 cfm at 6 kg/cm2
3 280 m3 hr at 600 mm WC
4 kg/cm2 at 30°, 5 m3/hr
Section no.
1)
2)
3)
4)
5)
6)
Boiler
Compressed air system
DG set
Motors
Fans
Pumps
Completed Worksheet 4e: Existing utilities and energy-intensive equipment
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Cleaner Production – Energy Efficiency Manual page 23
Completed Worksheet 4f: Information available within the unit
… Running Example: Task 4 (continued)
Section no. Information required Available Not available Remarks
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
_
_
_
_
_
_
_
_
_
_
_
_
_
Partially
Partially
Partially
Partially
Partially
Layout
• Factory
• Steam and condensate distribution network
• Compressed air distribution network
Production details
Process flow diagram
Material balance
Energy balance
Design specification of utilities
Raw material consumption and cost
Energy, water consumption and cost
Waste generation and disposal records
Waste treatment records
Maintenance records
Task 5 Identifying barriers and solutions to the CP-EE
assessment process
In order to develop workable solutions, the CP-EE team must identify
impediments to the CP-EE process—for example difficulties in obtaining
information from certain departments. The team should highlight such
difficulties right away, so that corrective measures can be taken by
management to resolve the issue before the start of the CP-EE assessment itself.
Lack of measuring instruments and lack of provision for measurements could
also be a major barrier. Adequate steps must be taken to overcome such
barriers (e.g. purchasing or hiring of measuring equipment and making of
provision for measurement).
Lack of awareness of CP-EE on the part of staff and lack of relevant skills are
further possible barriers. These barriers are typically overcome by conducting
in-plant awareness-raising sessions, through training activities or through
provision and explanation of relevant case studies and similar measures. (See
Completed Worksheet 5).
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Cleaner Production – Energy Efficiency Manual page 24
Running Example: Task 5
Barrier Enabling measures suggestedNo.
1
2
3
4
5
6
Attitude barriers
Lack of awareness of energy and environmental issues
Emphasis on maximum production rather thanproductivity
Complacent attitude towards existingprocess/production conditions
Hesitant about risks involved
Low participation of workers in CP-EE programme
Belief that ‘I am doing the best’
Organizational barriers
One man show; middle (supervisory) level missing
Loose management structure
Production on ad-hoc basis
Labour intensive: workers employed on contract basis
Inadequate documentation of inventory andproduction data
Relevant technical literature not readily available
Highly water-intensive process steps
Technology developed abroad not applicable in Indian conditions
Economic barriers
Adequate funds not available
Low financial returns on certain CP-EE measures
Availability of cheap un-skilled labour, makingautomation less attractive
Changing excise and tax liabilities
Other barriers
Abundant supply of resources such as water, makingwater conservation less financially attractive
Lack of available space
Lack of regulation on environmental and energymanagement systems
Increase awareness
Involve workers in decision making
Acknowledge workers’ efforts
Formulate incentive schemes for workers
Encourage experimentation for CP-EE options
Review CP-EE measures on regular basis using simple indicators
Increase interaction among similar kinds of industries
Delegation of authority
Induction of technically sound person
Right wage for the right person
Recruitment of permanent skilled workforce
Setting up of integrated plants
Ensuring good quality of raw materials from supplier
Standardization of product
Promotion of marketing in the international market
Training and awareness workshops on CP-EE
Setting up of laboratory with basic facilities
Provision of regular power supply through captivepower generation
Promotion of relevant technical literature through in-house circulation
Development of indigenous CP-EE measures
Encouraging waste exchange among industrial units
Soft loans
Planned investment
Incentive schemes for industries going in for CP-EE
Training of workforce for specific job and formulation oflong-term industrial policy
Imposition of water levy on industries to restrict wateruse and encouraging of modernization of existing plants
Completed Worksheet 5: Barriers and solutions
No ✗Yes ✓ No ✗Yes ✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✗
✗
✗
✗
✗
✗
✗
✗
✗
✗
✗
✗
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
!Task 6 Deciding the focus of the CP-EE assessment
Deciding the focus of the CP-EE involves making decisions in two areas:
• scope: deciding whether to include the entire plant or limit CP-EE to certain
units/departments/processes; and
• emphasis: deciding which materials and energy resources to include (e.g.
raw material, products, fuel, electricity, steam, compressed air and
refrigeration, etc.).
The focus of the CP-EE assessment can be decided by using a set of weighted
criteria applied to the different sections and allocating a score to those sections
of a plant or facility that could be the focus of assessment. An example is given
in Completed Worksheet 6. The weight given to any particular criterion
depends on many factors and will probably need to be adapted to suit the
nature of the particular industry, location, etc.
Cleaner Production – Energy Efficiency Manual page 25
In the textile industry, thegarment section is oftenoverlooked, as it is not a
major consumer ofresources or generator ofwastes or emissions. Inthe cement industry,
water is not given muchemphasis for CP-EE, asthe focus is on energy
and materials.Focus areas need to be
fixed on the basis ofinformation on
departments, utilitiesand/or sections, takingaccount of barriers and
the solutions toovercome them.
snapshot
CP-EE
Weight Scores obtainedCriteriaSection no.
1
2
3
4
5
6
7
10
5
5
5
5
10
10
7
2
2
3
3
8
8
4
3
1
3
1
3
4
5
3
2
3
3
5
6
5
4
1
2
2
4
5
Probability of pay-back for CP-EE options from section
Section/area consuming maximum resources
Multiplier effects
Increase in product quality/production rate
Barriers
Management preference
External pressure (govt. NGO, etc.)
SECTION Boiler house Dye house Printing Pre-treatment
Completed Worksheet 6: Audit focus for detailed CP-EE assessment
Different sections of the plant were analysed in accordance with the matrix and the boiler house was chosen asan audit focus for detailed CP-EE assessment.
Running Example: Task 6
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
!
STEP 2 Pre-assessment
Pre-assessment, Step 2 in the CP-EE assessment methodology, gives the CP-EE
practitioner an initial ‘hands on’ feel for the company’s operations. It consists of the
following four important tasks:
• Preparing process flow diagrams of CP-EE focus areas, using available information
and data
• Conducting a walkthrough
• Preparing material and energy input and output quantification and
characterization
• Generating and finalizing baseline data
Task 7 Preparing process flow diagrams
Preparing a process flow diagram (PFD) is an important step in the CP-EE
assessment. PFDs are prepared on the basis of discussions with plant personnel,
using readily available data, and for the audit focus areas only.
The best way for the CP-EE team to start is by listing the important process/unit
operations and the associated utility supply equipment/systems. At each
operation the team should list: (a) major input resources i.e. energy (electricity,
fuels, etc.), raw materials and chemicals, and utilities (water, steam, etc.); (b)
intermediate and final products; and (c) waste streams (wastewater, exhaust
and improved working conditions. An example of raw material substitution is
the replacement of chemical dyes with natural ones. Where energy is
concerned, it may be useful to evaluate the use of cleaner/renewable sources.
Use of renewable or non conventional energy sources is beneficial because it
has the global benefit of reducing greenhouse gas (GHG) emissions.
• New product design: changing product design can have impacts on both
the ‘upstream’ and ‘downstream’ sides of the product life-cycle. For
Cleaner Production – Energy Efficiency Manual page 45
snapshot
CP-EE
A simple example of goodhousekeeping in a dyeingoperation is to clean thefloors and machines ofdirt, grease, rust, etc.
regularly. This will reducethe possibility of
accidentally soiling thefabric, and thus minimize
the need for extrawashing.
snapshot
CP-EE
In the case of a textiledyeing unit, instead of
draining off the last coldwashes, they can be
collected in anunderground tank,
adjusted for pH, and thenfiltered prior to reuse in
subsequent washingoperations. These options
are typically low tomedium cost and can
provide moderate to highbenefits.
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
example, re-designing a product may reduce the quantity or toxicity of
materials in the product; reduce the use of energy, water and other
materials consumed during the product's use; reduce packaging
requirements; or increase the ‘recyclability’ of used components. Benefits of
this can include reduced consumption of natural resources, increased
productivity, and reduced environmental risks. Product re-design can also
help to establish new markets or expand existing ones. It is, however, a
major business strategy decision, and may require feasibility studies and
market surveys, especially if the supply-chain for the product is already
established and is complex.
• Recovery of useful by-products, materials and energy: this category of CP-
EE option entails recovery of wastes (in the form of by-products from the
process or from resources) which may have useful applications within the
industry itself or outside of it. As the wastes or by-products are produced
anyway, this type of option can generate additional revenue with little or no
extra effort.
• On-site recycling and reuse: on-site recycling and reuse involves returning
of waste energy or material to the original process or using these as inputs
to another process. It should, however, be borne in mind that it is better not
to generate waste in the first place, rather than to generate it and then
recycle, recover or reuse it. The team should therefore only consider the
latter type of options once all options that could prevent generation of
waste have been examined. It is also important to remember that some of
the chosen options may require major changes in the processes or
equipment or product. While these may well dramatically reduce waste
generation or increase productivity, they also often imply considerable
investment.
Finally, it is important to bear in mind that certain options may require
laboratory, bench-scale or pilot studies to ensure that product quality is not lost
as a result of their application, and that they are acceptable to the market.
We round off this section by combining our example of cause diagnosis using
the fishbone diagram with the identification of possible options for cleaner
production. This is presented in Table 1.1.
Cleaner Production – Energy Efficiency Manual page 46
A textile-processing unit inThailand used sodiumsulphide and acidifieddichromate as auxiliaryagents in the sulphurblack, textile dyeing
process. However, both ofthese agents are toxic andhazardous to handle andtheir use leaves harmfulresidues in the finishedfabric and generates
effluents that are difficultto treat and damaging to
the environment. CP-EE studies conducted at
the unit indicated thatboth of these agents couldsafely be replaced with noloss of fabric quality, thuseliminating adverse health
and environmentalimpacts. Glucose or
dextrose can be substitutedfor sodium sulphide andacidified dichromate canbe replaced by sodium
perborate or ammoniumpersulphate.
snapshot
CP-EE
snapshot
CP-EE
A common example ofrecovery from a waste
stream for many industriesis heat recovery through
the use of heatexchangers. Such optionsare typically medium costand can provide moderate
to high benefits.
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Cleaner Production – Energy Efficiency Manual page 47
Wastestream
CP-EE OptionsOptionref. no.
RMSPOOPGHK
Coal yard
ID and FDfan motors
Boiler
Steamdistribution
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Store the coal on a concrete/brick lined level floor
Optimize the stack height and width of coalheaps
Use FIFO basis for coal usage
Construction of shed for coal storage
Optimize the use of water by installingefficient showers/sprinklers/spray/nozzles
Procure better quality coal from differentsources
Install mechanical coal crusher
Installation of variable speed drives in ID andFD fan motors
Installation of damper to control air flow
Install on-line O2 measuring sensor
Install economizer for recovery of waste heat
Install air heater for recovery of waste heat
Plug all the air leakages into boiler furnace
Conversion of existing boiler to FBC boiler
Replace existing boiler with FBC Boiler
Optimize coal sizing by proper crushing andsieving
Modify existing grate by reducing gapsbetween rods
Optimize the firing rate by use of stokerfiring
Install water treatment system (RO) plant
Change the water used in the boiler fromtanker water to municipal supply water
Install conductivity meter to check boilerdrum water quality and therefore optimizeblow down rate
Recover flash steam from boiler blow down
Re-circulate condensate from steamseparator wherever possible
Insulate all the bare and damaged portions
Insulate flanges (125 flanges)
Installation of steam traps (thermodynamictraps) of rated capacity to be provided inthe steam main pipe within a gap of 25 m
Loss of coal
Electricalenergy loss
Heat loss dueto flue gas
Heat loss dueto flue gas
Unburnt in ash
Blow down loss
Radiation loss
Radiation loss
Completed Worksheet 13: CP-EE options
Running Example: Task 13
EMORRNPDNT
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
Section
GHK: Good House Keeping OP: Operational Practices PO: Process Optimization RMS: Raw Material Substitution NT: New Technology NPD: New Product Design ORR: On-site Recycle & Reuse EM: Equipment Modification
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Cleaner Production – Energy Efficiency Manual page 48
Primary causes Secondary causes Possible CP-EE options Category of CP-EE option
Man
Method
Material
Energy and energyequipment
Lack ofsupervision
Dyeing operation notcarried outproperly
Input materialsare of poorquality
Poor process control resulting ininconsistentperformance
Absence of clear workinstructions
Lack of training
Excessive use of salt indosing
Incorrect procedurewhile dosing chemicals
High impurities in dyes
Shelf-life of auxiliariesexceeded
Improper storage of fabric
Poor water quality
Optimumtemperature notmaintained in the dyebath liquor
Poor contact betweenfabric and dye liquor
Management and personnelpractices
Management and personnelpractices
Management and personnelpractices, process optimization,raw material substitution
Management and personnelpractices
Raw material substitution
Management and personnelpractices
Management and personnelpractices, housekeeping
Raw material substitution
Process optimization, newtechnology
New equipment
Develop work instructions as Standard OperatingPractices (SOPs). Have the SOPs reviewed by externalexperts. Closely monitor improvements or identifyproblems faced, if any, in the implementation of theSOPs. Build a record keeping system to monitor SOPrelated compliance.
Organize shop floor based training programmes forworkers and supervisors.
Improve worker instruction and supervision.Redesign the dyeing recipe by changingcomposition and materials e.g. use of low salt dyes.
Improve worker instruction and supervision.
Have the dye purity checked by independentinstitutions over a number of samples and acrosscommonly used shades; change the supplier ifnecessary.
Improve the inspection at the receiving unit. Checkthe container labelling, storage and supply systems.
Ensure proper storage of scoured/bleached materialse.g. on wooden blocks, wrapping to avoid soiling
Analyse the water for hardness, total dissolvedsolids, pH and iron/manganese content, etc. andcompare the measured levels with recommendedstandards. Treat water to ensure that theparameters are within the recommended standards.
Check the steam inlet position and steam pressureto ensure that heating is optimum. Take readings oftemperature of the liquor before and after requisitemodifications.
Explore changing from a winch to a jet dyeingmachine that is enclosed, operates under pressureand gives better contact between fabric and dyeliquor.
Table 1.1: Matching the problems diagnosed using the fishbone diagram with possible CP–EE options
Categories
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Task 14 Screening options
Preliminary screening of options
Once brainstorming has helped to identify CP-EE options, preliminary and
rapid screening should be carried out to decide on implementation priorities.
This screening exercise will place options in two categories:
• Options that can be implemented directly Simple and obvious options can be implemented straightaway. In general,
housekeeping (e.g. plugging leaks and avoiding spills) or simple process
optimization (e.g. control of excess air in combustion systems) options fall into
this category. No further detailed feasibility analysis is required for these
options. Moreover, their immediate implementation results in real and tangible
benefits in a short period, increasing management’s confidence in the CP-EE
assessment process.
• Options requiring further analysisSome options are technically and/or economically more complex and a
decision to implement them would require examination of their techno-
economic and environmental feasibility. Most management improvement, raw
material substitution, and equipment or technology change options fall into
this category.
Decision on options that require much more information collection or are
difficult to implement (e.g. for reasons of very high costs or lack of technology)
can be considered at a later time. Completed Worksheet 14 on the following
page shows how this works in practice.
Cleaner Production – Energy Efficiency Manual page 49
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Cleaner Production – Energy Efficiency Manual page 50
Completed Worksheet 14: Screeening of CP-EE options
Running Example: Task 14
CP-EE optionref. no.
Directlyimplementable
Require furtheranalysis
Pending laterconsideration
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
STEP 4 Feasibility analysis
• Technical, economic and environmental evaluation• Selecting feasible options
Task 15 Technical, economic and environmental evaluation
Detailed screening of options
The team can now undertake detailed screening of those options that require
further analysis, to determine which options are technically feasible and
ascertain both the economic and environmental benefits of their
implementation. These aspects are described below.
Technical evaluation
Technical evaluation should cover the following aspects (see also Completed
Worksheet 15a):
• Consumption of materials and energy: it is important to establish M&E
balances for each option before and after implementation conditions, in
order to quantify the materials and energy savings that would result.
• Product/by-product quality: quality of the product should be assessed before
and after implementation of the option.
• Right First Time (RFT): estimate must be made of the possible improvement
in RFT that would result from implementation of the option.
It is important to examine the following aspects when considering implementation:
• Human resources required: a decision must be made as to whether the option
can be implemented by in-house staff or whether external expertise or
collaboration with partner organization is required.
• Risks in implementing the option: some options may not be fully proven and
may require laboratory-scale experiments or pilot studies to assess their
outcomes before full-scale implementation. When options affect key
production processes or product features, the potential impact on business
if they do not work as planned can be very high.
• Ease of implementation: the ease with which an option can be implemented
will depend on such things as the layout of the production processes and of
the auxiliary services (e.g. steam lines, water lines, inert gas lines, etc.); the
Cleaner Production – Energy Efficiency Manual page 51
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
physical space available; the maintenance requirements; training
requirements; etc. In addition, when options require work on key production
processes, the timing of their implementation becomes critical. If major
changes or interruptions to production patterns are required, any loss in
production needs to be factored into the economic analysis of the option.
• Time required for implementation: the time which implementation of an
option may require for procurement, installation or commissioning of
equipment or material must be considered. This must include consideration
of any shut-down time necessary for implementation.
• Cross-linkages with other options: a particular option may be linked to
implementation of other options; the decision must be made as to whether
it should be implemented on its own or with other options.
Environmental evaluation
Whenever practically possible, the environmental evaluation of an option
should take account of its impacts throughout the entire life cycle of a product
or service. In practice, however, evaluation is often restricted to on-site and off-
site (neighbourhood) environmental improvements.
The environmental evaluation should include estimates of the following
benefits that each option may bring about (where relevant):
• Likely reduction in the quantity of waste or emissions generated (expressed
as mass).
• Likely reduction in GHG emissions.
• Likely reduction in the release of hazardous, toxic, or non-biodegradable
wastes or emissions (expressed as mass).
• Likely reduction in consumption of non-renewable natural resources, e.g.
fossil fuels consumed (expressed as mass).
• Likely reduction in noise levels.
• Likely reduction in odour nuisance (by elimination of a substance causing
odour).
• Likely reduction in on-site risk levels (from the point of view of process
safety).
• Likely reduction in release of globally important pollutants, e.g. ozone-
depleting substances, persistent pollutants, etc.
Completed Worksheet 15b gives an example of environmental evaluation in practice.
Cleaner Production – Energy Efficiency Manual page 52
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Cleaner Production – Energy Efficiency Manual page 53
Cleaner Production – Energy Efficiency Manual page 85
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Worksheet 16: Selection of CP-EE measures for implementation
Options Options Technical Environmental Economic Total Rank
ref. no. feasibility impact feasibility
Weighting (%) 30 25 45 10
OPEN FILE
Cleaner Production – Energy Efficiency Manual page 86
Part 1 CP-EE methodology Chapter 2: CP-EE assessment methodology
Worksheet 17: Implementation plan for CP-EE measures
Opt
ion
Sele
cted
Cla
ssifi
cati
onD
ate
Pers
onRe
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no.
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OPEN FILE
3.1 About the companyM/s Luthra Dyeing and Printing Mills (LDPM)—located in Surat, a city which accounts
for 40 per cent of textile dyeing and processing houses in India—is a leading and well
equipped textile processing house. The company started operations in 1980 and has
grown continuously since. It processes various types of synthetic polyester cloths from
grey to finished stage, with an installed processing capacity of around 3 200 tons of
fabric per year. By 2002, the company was processing around 2 400 tons of fabric per
year with a workforce of around 550 people. LDPM operates around 300 days per year,
on three shifts a day.
The company has recently acquired ISO 14001 certification. In order to continue on its
path to excellence in resource and energy conservation, it volunteered to undertake
CP-EE studies implemented by India's National Cleaner Production Centre. LDPM was
also selected for CP-EE studies for the following reasons:
• It is representative of the synthetic fabric processing sector in India.
• It has significant potential for CP-EE interventions, especially regarding water and
energy conservation.
• There is potential for technology upgrade.
• There is a possible multiplier effect.
• Management was committed to CP-EE studies and ready to cooperate.
Cleaner Production – Energy Efficiency Manual page 87
Part 1 CP-EE methodology
Chapter 3: Case study
Cleaner Production and Energy Efficiency Assessment
at
Luthra Dyeing and Printing Mills
Gidc, Pandesera, Surat, India (July 2002)
Cleaner Production – Energy Efficiency Manual page 88
Part 1 CP-EE methodology Chapter 3: Case study
3.2 Process description and process flow chartAs for any typical textile firm, the demand for fabric processing at LDPM is largely
dependent on customer requirements which are basically governed by existing market
trends and fashion. There are variations in the use of chemicals, in process operating
sequences and even in the equipment used for processing. A general description of the
process is given below, and the process is summarized in Figures 1.10 and 1.11.
The main activities carried out at LDPM for textile processing are as follows:
• Pre-treatment, which comprises drumming and scouring, weight reduction
and bleaching
• Dyeing• Printing• Finishing• Ageing• Washing (washing is carried out after every operation)
Pre-treatment
The pre-treatment process prepares the textile material for subsequent processing.
a) Drumming
The grey fabric received is treated in the drumming machine to obtain the desired grain
texture. The cloth is wetted and rotated in drums, both clockwise and anti-clockwise.
The operation is done four times—with plain water, then with swelling chemicals,
followed by two washes. The drummed fabric is dewatered in a hydro extractor.
b) Scouring, weight reduction and bleaching
Scouring is the main operation carried out to remove foreign substances such as oils,
fats and other impurities. It is an alkaline extraction process involving heat (80–130 °C)
and pressure (2–3 kg/cm2). Additional swelling of fibres takes place during scouring,
improving the dye-uptake rate.
If necessary, the fabric is treated in the same bath to reduce its weight to give it a light
feel. Whiteness of the fabric needs to be improved and bleaching is also carried out in
this bath (by oxidative or reductive decomposition).
The scoured fabric is subjected to hot wash, followed by neutralization of residual alkali.
Cleaner Production – Energy Efficiency Manual page 89
Part 1 CP-EE methodology Chapter 3: Case study
Dyeing
Fabric is dyed to give it its desired colour. The fabric to be dyed is treated with dyes
and auxiliary chemicals at 120–130 °C and under pressure. Polyester fibre is usually
dyed by an exhaustion process. A dispersing agent is added and the pH is adjusted.
Accelerants and other auxiliaries (wetting agents, levelling agent, etc.) are also added
as required. Vat dyes are also occasionally used for dyeing.
In the post-dyeing stage, the material is rinsed thoroughly or soaped. For dark finishes,
the fabric is subjected to reductive alkaline cleaning after dyeing. It is then subjected
to pH balance and, if no printing is required, is subjected to a heat setting operation.
Figure 1.10: Process sequence
GREY FABRIC
DYED FINISHED FABRIC PRINTED FINISHED FABRIC
hydro extraction
cold washing
chemical treatment
wetting (in drums)
washings
neutralization
scouring
stentoring
cold washing
hot washing
dyeing
reduction clearing
washings
dyeing
printing
colour developing
drying
stentoring
shrinking
• Operations in the
orange shaded area are
carried out in drums.
• Operations in the blue
area are carried out in
jet dyeing machines.
Cleaner Production – Energy Efficiency Manual page 90
Part 1 CP-EE methodology Chapter 3: Case study
Figure 1.11: Pretreatment operations—inputs and outputs
GREY OR DRUM TREATED FABRIC
PRE-TREATED FABRIC
hot washing
heat setting
caustic washing
washing
scouring
washing
neutralization
water
watersoda
watersteam
scouring chemicals
watersteam
waterHCI
water
heat by steam
wastewater
wastewater
wastewater
wastewater
wastewater
wastewater
fumes
Printing
Printing is the process by which coloured patterns are produced on the fabric. The fabric
is printed on programmed, flat-bed or rotary screen-printing machines. It is then passed
through an attached dryer to remove moisture. Temperature in the dryer is varied
depending on the nature of fabric processed and the types of dyes used for printing. For
pigment printing, the temperature is maintained in the 160–170 °C range.
After printing, the printing screens are washed with water.
Finishing
Finishing comprises the final processes that make the fabric into an end-product. It
improves the feel and volume of the fabric.
Ageing
After printing the colours are not permanently fixed in the fabric. The ageing treatment
fixes the colour in the fabric permanently. This treatment is done in a Steam Ager or a
Loop Ager machine, at a temperature of 180–190 °C.
Washing
The fabric is washed to remove excess chemicals and dyes after every operation, or as
required. It is washed in several cold and hot washes, either in machines or in a series
of baths called washing ‘kundis’ (tanks). Excess wash water is removed by centrifuging.
Cleaner Production – Energy Efficiency Manual page 91
Part 1 CP-EE methodology Chapter 3: Case study
3.3 Baseline informationThe CP-EE team observed wide variations in the production process and the product
at LDPM. Initially, it was planned to study one complete batch to provide the basis for
a detailed material and energy balance, and to extrapolate from this to obtain an
overall scenario for the year. However, when values were compared it was found that,
for this type of industry, using just one batch as a unit is neither representative nor
useful in obtaining the desired information for a CP-EE assessment.
Data was collected for the year 2002, which was then considered as the baseline for
further comparison.
Production
The unit's products divide easily into two categories: dyed cloth and printed cloth, with
printed cloth being initially dyed or whitened. The total production is normalized in
terms of the total cloth produced on the basis of the resources used during the
production of the cloth. As inferred from production data (see Figure 1.12), the total
output from the unit is equal to the total cloth printed plus half of the total dyed
production. On average, the unit produces 100–210 tons of cloth per month
(normalized basis), depending on orders and market situation.
Figure 1.12: Production data
cloth dyed (tons)
cloth printed (tons)
total dyed + printed (tons)
total cloth normalized (tons)
0
50
100
150
200
250
300
month
prod
ucti
on
1 2 3 4 5 6 7 8 9 10 11 12
51 30 65 48 62 44 42 63 80 126 83 104
87 108 112 155 157 92 148 168 162 148 101 151
138 138 177 203 219 136 191 231 242 274 184 256
112 123 145 179 188 114 170 199 202 211 143 203
Quantifying and characterizing wastewater
Monitoring in order to quantify and characterize wastewater in pre-treatment and
dyeing operations was carried out for a single batch of 2 400 metres of polyester fabric,
equivalent to 168 kg of fabric. Values were extrapolated for the day, assuming 48
batches per day, equivalent to 8.0 tons of cloth processed per day. For printing and
post-printing operations, monitoring was carried out for a 24-hour cycle.
The composite wastewater sample collected during the monitoring gave the results
shown in Table 1.3.
Cleaner Production – Energy Efficiency Manual page 92
Part 1 CP-EE methodology Chapter 3: Case study
Resource consumption
On average, the unit processes 8.0 tons of cloth per day. Like any textile processing
unit, the process requires steam, water, gas, compressed air, dyes and printing
chemicals, etc. The consumption of major resources for the year 2002 per ton of cloth
processed is shown in Table 1.2
Unit/ton fabric
Months
Average
Purchasedwater(tanker ormunicipalsupply)
Bore wellwater
Recycledwater(from ETP)
Total water
Coal (lignite)
Gas
Gridelectricity
Diesel
Equivalentelectricityfrom diesel
Total kWhelectricity
Dyes
Gums
m3
m3
m3
m3
ton
m3
kWh
litre
kWh
kWh
kg
kg
115
36
50
201
3
772
698
247
827
1 525
61
82
122
30
56
208
4
846
663
256
858
1 521
65.4
80
136
2 4
62
222
4
697
345
363
1 216
1 561
60.5
88
148
20
66
234
4
625
1 587
0
0
1 587
65.1
93
136
40
46
222
3
611
234
608
2 037
2 272
60.1
85
172
48
38
258
3
804
294
417
1 395
1 690
74.2
110
143
42
44
229
4
629
225
421
1 410
1 636
61
100
133
50
36
219
4
656
234
366
1 227
1 461
61.4
93
123
46
40
209
4
582
208
361
1 209
1 417
61.8
87
136
30
56
222
4
576
1 469
0
0
1 469
61.3
90
135
34
52
221
4
623
1 641
0
0
1 641
64
99
125
32
54
211
3
553
1 356
0
0
1 356
63.5
85
135
36
50
221
3
664
746
253
848
1 595
63.2
91
Table 1.2: Major resource consumption at LDPM in 2002
Resources
Cleaner Production – Energy Efficiency Manual page 93
Part 1 CP-EE methodology Chapter 3: Case study
Waste stream Quantity(litres/batch)
Quantity (litres/day)
pH TS (mg/l) COD (mg/l) BOD (mg/l)
Characteristics
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Wastewater from drum wash
Wastewater from washing of grey fabric
Wastewater from scouring
Wastewater after cold wash of scouring
Wastewater from bleaching(bleaching liquor)
Wastewater from cold wash of bleaching
Wastewater from dyeing only(exhausted dye bath).
Wastewater from dyeing wash
Wastewater from neutralization
Wastewater from neutralization wash
Wastewater from washing of stirrerblades in print paste cooking
Wastewater from washing of bucketsand drums used for print pastepreparation and storage
Wastewater from screen washing
Wastewater from squeeze wash
Wastewater from screen preparation
Wastewater from print blanket washing
Wastewater from washing of printedfabric
Steam condensate from dyeing
Cooling water (not to ETP)
800
700
700
900
700
720
800
770
720
720
30 kl/d
715 kl/d
1.1 l/s
3.0 kl/d
94 kl/d
100 kl/d
600
38 400
33 600
33 600
43 200
33 600
34 560
38 400
36 960
34 560
34 560
30 000
71 500
31 680
3 000
94 000
100 000
28 800
150 000
8.11
7.7
9.5
7.12
7.27
8.35
4
8.85
7.59
-
-
-
5.81
-
5.69
8.48
20 608
14 923
13 856
4 500
6 500
4 300
4 480
4 350
4 840
4 800
8 000
8 500
27 048
8 000
25 688
11 712
1 362
1 515
2 210
1 532
1 224
890
2 020
800
1 510
980
1 600
770
1 980
1 700
745
1 750
654
353
380
243
308
150
1 216
250
389
316
450
230
204
170
238
360
0
Table 1.4: Wastewater quantification and characterization for individual streams
Section no.
Parameter Range of values
1
2
3
4
5
Volume
pH
Total solids (TS)*
COD
BOD
130 m3/d to 140 m3/d
6.75–8.5
9 000–11 500 mg/l
900–1 200 mg/l
275–325 mg/l
Table 1.3: Composite wastewater characteristics
Section no.
* TS values are relativelyhigh in relation to thosefor typical textileprocessing companiesbecause the groundwater(bore well) used forprocessing had a veryhigh total dissolved solidsconcentration.
Table 1.4 shows quantification and characterization data for individual wastewater
streams.
Cleaner Production – Energy Efficiency Manual page 94
Part 1 CP-EE methodology Chapter 3: Case study
CP-EE potential, targets and selection of audit focus
Based on the resource consumption and waste water generation data, it was surmised
that there was wide scope for resource reduction at LDPM, including energy and water.
Table 1.5 indicates the existing conditions, the potential for improvements and
probable targets to be achieved in the future.
Audit focus
It can be seen from Table 1.5, that the company has great potential for reduction of all
resources used. After discussions between the CP-EE team and management, it was
decided that the CP-EE studies should cover the entire plant and utilities. The aim was
to minimize resource wastage as far as possible so as to maximize reductions in GHG
Table 1.5: Potential for resource reduction at LDPM
Section no.
Cleaner Production – Energy Efficiency Manual page 95
Part 1 CP-EE methodology Chapter 3: Case study
3.4 Identification of waste streams, cause analysis and CP-EE opportunitiesBased on the information collected and compiled by the CP-EE team, a detailed cause
analysis was made of the various waste streams. Cause analysis and the observations
made during company visits were used as a basis to identify CP-EE options to reduce
resource consumption. Some of the major CP-EE options are given in Table 1.6.
Probable cause CP-EE options
Wastewater from washingof grey cloth in drumsbefore pre-treatmentoperations
Low power factor in drummotors
Wastewater from scouringand weight reductionoperations andsubsequent washings
• Presence of foreign material (e.g. dust sticking tofabric, inks, markings, etc.)
• Removal of sizing material, oils and additionalimpurities, etc. used during weaving operations
• Use of excess water for drum soaking and washingdue to less than optimum capacity utilization
• Use of large quantities of water for direct cooling ofthe fabric (when the drum is opened, the fabric iscooled before removal; this is done by placing ahose into the drum and allowing the excess water toflow out continuously)
• Use of swelling agents during drum washingoperations
• Variable loading of drums and sudden load duringstart up operations
• Use of excess scouring chemicals (caustic) in theoperation
• Numerous steps for every small operation, withwashing after every operation.
• Use of high cloth to liquor ratio• Unexhausted dyes in the wastewater• Use of direct steam injection in jet machine to
maintain temperature and increase production rate• Small batches for dyeing in large jet dyeing machine
(i.e. unoptimized capacity utilization)
1 Optimization of cloth to liquor ratio from 1:6 to1:4, by installation of water measurement deviceor drum calibration and proper worker training
2 Installation of large capacity drum washer withindirect cooling mechanism for improvedproductivity and quality
3 Optimization of production planning for highercapacity utilization of the existing drum washers
4 Installation of soft starter and variablespeed/frequency drives in motors
5 Reuse of wastewater from scouring by addingmake up chemicals
6 Recovery of caustic by installing caustic recoverysystem
7 Combining weight reduction, scouring andwhitening operations into a single operation
8 Markings on the jet machine so as to ensureproper cloth to liquor ratio
9 Reduction in dye consumption from 5.5% to4.25% by change in process parameters, e.g.temperature from 130 °C to 135 °C andretention time from 30 minutes to 60 minutes
Table 1.6: Cause analysis and generating CP-EE options
Waste streams
continued …
Cleaner Production – Energy Efficiency Manual page 96
Wastewater from washingof stirrer blades aftercooking, print pastepreparation buckets anddrums
Wastewater from washingof screens after printing
Wastewater and solventwaste from blanket of flatbed printing machine
• Use of organic acids causing high COD load
• Variable load pattern due to different batch sizesand weight of cloth
• Increase in peak demand • Improper removal of dyeing chemicals in washing
after dyeing
• Excess print paste sticking to the stirrer blades,buckets and drums
• Excess print paste sticking to the screens and on theedges of the screen frames
• Excess print paste seeping from screen throughcloth and onto the blanket
• Printing on portions of blanket not covered by cloth
10 Use of indirect steam instead of direct steam forheating and recovery of condensate for reuse asboiler feed water
11 Optimizing capacity utilization of jet dyeingmachine by production planning andprocurement of new, small jet dyeing machine
12 Replace acetic acid by tartaric acid13 Eliminate usage of Citric W14 Reduce usage of levelling agents by 10%15 Use inorganic mineral acids in place of organic
acids16 Replace the bottom basket in jet dyeing machine
by Teflon rods so as to increase the area andenhance the capacity of the machine by 70 kg
17 Enhance capacity of the jet machines byincreasing the height of the machine
18 Use of spent dye bath from polyester dyeingby adding make-up chemicals
19 Replacing ordinary water used for dyeing byRO/DM water for higher dye exhaustion rate
21 Optimizing the washing operations after dyeing22 Reuse of neutralization waste liquor after adding
make up chemicals
23 Scraping of print paste before washing24 Use of dedicated buckets/drums and stirrer for
print paste preparation25 Wiping of print paste from buckets with waste
tissue paper, rags, etc. before washing
26 Scraping and reuse of print paste from thescreens before washing
27 Washing of screens by high pressure, manuallyactuated showers
28 Dipping of screens in a tank full of water beforefinal washing with fresh water
29 Reduce mesh size of the printing screens30 Cover un-used side strip of blanket by waste
cloth strip31 Provision of scraping mechanism using doctor
blade and squeeze end brush half dipped inwater to recover and reuse print paste from theblanket
32 Recovery of solvent used for blanket washing byinstalling solvent recovery plant
33 Use of non-organic liquid in place of solvent
Table 1.6: Cause analysis and generating CP-EE options (continued)
Waste streams
continued …
Cleaner Production – Energy Efficiency Manual page 97
Part 1 CP-EE methodology Chapter 3: Case study
Probable cause CP-EE options
Waste thermal energy(gas) in printing machine
Waste thermal energy(gas) in padding mangle
Wastewater from postprint washing in tanks(kundi)
Wastewater from cookingpan, ageing machine andzero-zero machine
Electrical and thermalenergy loss in loop agermachine
Thermal energy loss insanforizing drum
Thermal energy loss inexisting boiler
Thermal energy losses insteam distribution system
Electrical energy loss incompressed air supplysystem
Electrical energy loss inmotors
Energy loss in electricallighting system
• Idle running of burner on printing machine
• Idle running of dryer even if there is no fabric
• Unoptimized water usage in washing
• Condensate from steam drained to ETP
• Low efficiency of heat transfer from steam heatedtubes in loop ager machine
• Feeding of single layer of cloth in loop ager even forlighter quality of cloth
• Inefficient heat transfer from steam to the drum
• No Excess air control• No waste heat recovery system from the boiler flue
gases• Higher blow down from boiler drum due to high
TDS in feed water• High level of unburnts in ash• Old and obsolete technology with efficiency of
around 65%
• Uninsulated flanges• Condensation of steam forming pools of water in
the steam carrying pipes
• Leakages in the compressed air supply lines• Compressed air used at a higher pressure than
required
• Unoptimized motor loading
• Use of old, energy-inefficient lighting fixtures
34 Operating the machine on continuous drive byinstalling auto cut off photovoltaic cell
35 Installing photovoltaic cut off switch in paddingmangle
36 Use of counter-current washing technique37 Passing the cloth through roller squeezes
between each wash
38 Reuse condensate to boiler
39 REPLACEMENT OF EXISTING LOOP AGER WITHDIRECT GAS FIRED LOOP AGER SYSTEM (ANINNOVATIVE SYSTEM DEVELOPED AT THEPLANT AND NOW PATENTED)
40 Two end overlapped feeding of cloth to the loopager for light weight fabric
41 Direct gas firing in sanforizing drum by slit typeburner
42 Installation of damper and variable speed drivesfor ID and FD fans
43 Preheat the feed water to boiler by exit flue gases44 Use low TDS municipal water in place of tanker
water45 Reduce the coal size (lower mesh size) to be
used in boiler46 Replace existing boiler system with a new FBC
boiler of 32 kg/cm2 pressure, coupled with backpressure turbine for cogeneration of 2 MWelectrical power
47 Insulate all 125 existing flanges48 Install thermodynamic steam traps in the main
header with a gap of 25 metres
49 Conduct regular air leak detection tests50 Reduce the air pressure to optimum limit
51 Conduct load analysis on motors andreshuffle/replace optimum rating motors
52 Replace 40 W tube light fixtures with energyefficient 30 W fixtures
53 Provision of skylight windows overhead toreduce lighting required during day time
Table 1.6: Cause analysis and generating CP-EE options (continued)
Waste streams
Cleaner Production – Energy Efficiency Manual page 98
Part 1 CP-EE methodology Chapter 3: Case study
3.5 Feasibility analysis of CP-EE options To decide on implementation priorities, the CP-EE options developed were divided, by
preliminary screening, into ‘Directly Implementable’, ‘Requiring Further Analysis’ and
‘Pending, for Later Consideration’. Table 1.7 gives the detailed analysis.
CP-EE options Requiringfurther analysis
Directlyimplementable
1
2
3
4
5
6
7
8
9
Optimization of cloth to liquor ratio from 1:6 to1:4, by installation of water measurement deviceor drum calibration and proper worker training
Installation of large capacity drum washer withindirect cooling mechanism for improvedproductivity and quality
Optimization of production planning forcapacity utilization of the existing drum washers
Installation of soft starter and variablespeed/frequency drives in motors
Reuse of wastewater from scouring by addingmake-up chemicals
Recovery of caustic by installing caustic recoverysystem
Combining weight reduction, scouring andwhitening operations into a single operation
Markings on the jet machine so as to ensureproper cloth to liquor ratio
Reduction in dye consumption from 5.5% to4.25% by change in process parameters (e.g.temperature from 130 °C to 135 °C andretention time from 30 minutes to 60 minutes)
✓
✓
✓
✓
✓
✓
✓
✓
✓
Change in operatingpractice—workers fill drumsbased on their experience,and generally overfill them
Discharged wastewater withvery high impurities, hencecannot be reused
Change in operatingpractice—workers fill drumsbased on their experience,and generally overfill them
Table 1.7: Prioritizing CP-EE options
CP-EEoption no.
continued …
Pending, for laterconsideration
Remarks
Cleaner Production – Energy Efficiency Manual page 99
Part 1 CP-EE methodology Chapter 3: Case study
CP-EE options Requiringfurther analysis
Directlyimplementable
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Use of indirect steam to direct steam for heatingand recovery of condensate for reuse as boilerfeed water
Optimizing the capacity utilization of jet dyeingmachine by production planning andprocurement of new, small jet dyeing machine
Replace acetic acid by tartaric acid
Eliminate usage of Citric W
Reduce usage of levelling agents by 10%
Use inorganic mineral acids in place of organicacids
Replace the bottom basket in jet dyeingmachine by Teflon rods so as to increase thearea and enhance the capacity of the machineby 70 kg
Enhance capacity of the jet machines byincreasing the height of the machine
Use of spent dye bath from polyester dyeing byadding make-up chemicals
Replacing ordinary water used for dyeing byRO/ DM water for increase dye exhaustion rate
Install soft starters and variable speed drives onjet machine motors
Optimizing the washing operations after dyeing
Reuse of neutralization waste liquor after addingmake up chemicals
Scraping of print paste from buckets /drumsbefore washing
Use of dedicated buckets/drums and stirrer forprint paste preparation
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
Will cause quality problemswith the fabric and is difficultto handle and use in smallquantities
Will effect the quality of thefabric as the dischargedwastewater will be coloured
Change in operating practiceleading to recovery of printpaste
Number of variations andkeeping dedicated bucketsetc. is not feasible
Table 1.7: Prioritizing CP-EE options (continued)
CP-EEoption no.
continued …
Pending, for laterconsideration
Remarks
Cleaner Production – Energy Efficiency Manual page 100
Part 1 CP-EE methodology Chapter 3: Case study
CP-EE options Requiresfurther analysis
Directlyimplementable
25
26
27
28
29
30
31
32
33
34
35
36
37
38
Wiping of print paste from buckets with wastetissue paper, rags etc before washing
Scraping and reuse of print paste from thescreens before washing
Washing of screens by high pressure, manuallyactuated showers
Dipping of screens in a tank full of water beforefinal washing with fresh water
Reduce mesh size of the printing screens
Cover unused side strip of blanket by wastecloth strip
Provision for scraping mechanism using doctorblade and squeeze end brush half dipped inwater to recover and reuse print paste from theblanket
Recovery of solvent used for blanket washing byinstalling solvent recovery plant
Use of non-organic liquid in place of solvent
Operating the machine on continuous drive byinstalling auto cut off photovoltaic cell
Installing photovoltaic cut off switch in paddingmangle
Use of counter-current washing technique
Passing the cloth through roller squeezesbetween each wash
Reuse condensate to boiler
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
Will lead to increase ofsolid/hazardous waste
Change in operating practiceleading to recovery of printpaste
Very low-investment solutionleading to water savings andincreased washing efficiency
Change in operating practicewith very small investment
Reducing mesh size meansthat consistency of the printpaste will have to bereduced, making dyes spreadon the cloth
Small investment resulting insavings of print paste
Small investment leading tovery high recovery of printpaste
The quantity of solvent is toosmall to be recovered
Blanket washing efficiencywill reduce and may lead tocolour sticking on theblanket causing problems forfurther printing of fabric
Obvious option resulting invery high energy savings
Table 1.7: Prioritizing CP-EE options (continued)
CP-EEoption no.
continued …
Pending, for laterconsideration
Remarks
Cleaner Production – Energy Efficiency Manual page 101
Part 1 CP-EE methodology Chapter 3: Case study
CP-EE options Requiresfurther analysis
Directlyimplementable
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
REPLACEMENT OF EXISTING LOOP AGER WITHDIRECT GAS FIRED LOOP AGER SYSTEM (ANINNOVATIVE SYSTEM DEVELOPED AT THEPLANT ITSELF AND NOW PATENTED)
Two end overlapped feeding of cloth to theloop ager for light weight fabric
Direct gas firing in sanforizing drum by slit typeof burner
Installation of damper and variable speed drivesfor ID and FD fans
Preheat the feed water to boiler by exit flue gases
Use low TDS municipal water in place of tankerwater
Reduce the coal size (lower mesh size) to beused in boiler
Replace existing boiler system with a new FBCboiler of 32 kg/cm2 pressure coupled with backpressure turbine for cogeneration of 2 MWelectrical power
Insulate all 125 existing flanges
Install thermodynamic steam traps in the mainheader with a gap of 25 metres
Conduct regular air leak detection tests
Reduce the air pressure to optimum limit
Conduct load analysis on motors andreshuffle/replace optimum rating motors
Replace 40 W tube light fixtures with energy-efficient 30 W fixtures
Provision of skylight windows overhead toreduce lighting required during day time
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
Change in operating practicefor lighter fabric resulting inenergy savings
Obvious solution leading toenergy savings and betterquality of steam to besupplied at the user end
Obvious solution leading toenergy savings and betterquality of steam to besupplied at the user end
Good operation andmanagement practiceleading to energy savings
Change in operating practiceleading to energy savings
Obvious solution leading toelectrical energy savings
Obvious solution leading toelectrical energy savings
Table 1.7: Prioritizing CP-EE options (continued)
CP-EEoption no.
Pending, for laterconsideration
Remarks
Cleaner Production – Energy Efficiency Manual page 102
Part 1 CP-EE methodology Chapter 3: Case study
Techno-economic and environmental analysis
Before implementing CP-EE options it is necessary to verify their techno-economic and
environmental feasibility. This provides a basis to prioritize implementation of the
options. The team identified 53 CP-EE options at LDPM. Of the 53 options, 8 (15%)
were rejected at the outset as they were evidently unfeasible. Sixteen options were
considered for direct implementation, as their financial and technical implications were
fairly minor and quite evident. The remaining 29 options were subjected to testing of
their technical feasibility and the viability of those found to be technically feasible was
then subjected to environmental and economic analysis. Table 1.8 summarizes the
results of the analyses.
CP-EE options Technical feasibility
Technologyavailability
Spaceavailability
Productionquality*(+/0/-)
2
3
4
6
7
9
Installation of large capacitydrum washer with indirectcooling mechanism for improvedproductivity and quality
Optimization of productionplanning for capacity utilizationof the existing drum washers
Installation of soft starter andvariable speed/frequency drivesin drum motors
Recovery of caustic by installingcaustic recovery system
Combining weight reduction,scouring and whiteningoperations into a single operation
Reduction in dye consumptionfrom 5.5% to 4.25% by changein process parameters (e.g.temperature from 130 ° to135 ° and retention time from30 minutes to 60 minutes)
Yes
Yes
Yes
Notavailable(reject)
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
+
+
+
+
+
+
Reducedwastewater volumeand pollution load
Reducedwastewater volumeand pollution load
Increase powerfactor and reducedGHG emission(accounted for inoption 42)
Reduced wastewater volume andpollution load
Reduction in dyeconsumption andpollution load
1 1361
NQ
909 permachine
NIL
NIL
NQ
NQ
682
NQ
NQ
NQ
NQ
18 months
Immediate
NQ
Table 1.8: Techno-economic and environmental feasibility of CP-EE options
CP-EEoption
no.
continued …
Environmentalbenefits
Investment(US$)
Annualsaving(US$)
Paybackperiod
Cleaner Production – Energy Efficiency Manual page 103
Part 1 CP-EE methodology Chapter 3: Case study
CP-EE options Technical feasibility
Technologyavailability
Spaceavailability
Productionquality*(+/0/-)
10
11
12
13
14
16
17
18
19
20
21
Use of indirect steam to directsteam for heating and recoveryof condensate for reuse asboiler feed water
Optimizing capacity utilizationof jet dyeing machine byproduction planning andprocurement of new small jetdyeing machine
Replace acetic acid by tartaricacid
Eliminate usage of Citric W
Reduce usage of levellingagents by 10%
Replace the bottom basket injet dyeing machine by Teflonrods so as to increase the areaand enhance the capacity ofthe machine by 70 kg
Enhance capacity of the jetmachines by increasing theheight of the machine
Use of spent dye bath frompolyester dyeing by addingmake-up chemicals
Replacing ordinary water usedfor dyeing by RO/ DM waterfor high dye exhaustion rate
Install soft starters and variablespeed drives on jet machinemotors
Reduced pollutionload (dyeexhaustionincreased by 8% intrials)
Reduced GHGemissions
Lower wastewaterand GHG emissions
795
13 633
Nil
Nil
Nil
23 permachine
909
2 272
909 per machine
NQ
5 453
NQ
NQ
NQ
NQ
NQ
NQ
1 818
568 per machine
NQ
15 months
NQ
NQ
Immediate
Immediate
Less than 3months
NQ
14 months
20 months
Immediate
Table 1.8: Techno-economic and environmental feasibility of CP-EE options (continued)
CP-EEoption
no.
continued …
Environmentalbenefits
Investment(US$)
Annualsaving(US$)
Paybackperiod
Cleaner Production – Energy Efficiency Manual page 104
Part 1 CP-EE methodology Chapter 3: Case study
CP-EE options Technical feasibility
Technologyavailability
Spaceavailability
Productionquality*(+/0/-)
34
35
36
37
39
41
42
43
44
45
Operating the machine oncontinuous drive by installingauto cut off photovoltaic cell
Installing photovoltaic cut offswitch in padding mangle
Use of counter-current washingtechnique
Passing the cloth through rollersqueezes between each wash
REPLACEMENT OF EXISTINGLOOP AGER WITH DIRECT GASFIRED LOOP AGER SYSTEM(INNOVATIVE SYSTEMDEVELOPED AT THE PLANTAND NOW PATENTED)
Direct gas firing in sanforizingdrum by slit type of burner
Installation of damper andvariable speed drives for ID andFD fans
Preheat the feed water to boilerby exit flue gases
Use low TDS municipal water inplace of tanker water
Reduce the coal size (lowermesh size) to be used in boiler
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Space notavailable(reject)
Yes
Yes
Yes
Yes
Yes
Yes
Yes
0
0
0
Trial failed(reject)
+
+
0
0
0
0
Reduced GHGemission due tosavings of 6 300m3 gas/ year
Reduced GHGemission due tosavings of 6 000m3 gas/ year
Reduced GHG by2 300 t/yearthrough gassavings of 108 000m3/yr and coal1 270 t/yr
Reduced GHGemissions by fuelsavings of 7 tonslignite
Reduced GHGemission due toelectrical savings of75 000 kWh (allelectrical options)
Reduced GHGemissions due tolignite savings of784 t/yr
Reduced GHGemissions due tolignite savings of337 t/yr
Reduced GHGemissions
227
227
45 445
1 136
7 953
2 272
NIL
1 432
1 363
73 598
3 749
6 817
28 403
12 270
6 months
6 months
7 months
3 months
10 months
2 months
Immediate
Table 1.8: Techno-economic and environmental feasibility of CP-EE options (continued)
CP-EEoption
no.
continued …
Environmentalbenefits
Investment(US$)
Annualsaving(US$)
Paybackperiod
Combined with option 43
Cleaner Production – Energy Efficiency Manual page 105
Part 1 CP-EE methodology Chapter 3: Case study
CP-EE options Technical feasibility
Technologyavailability
Spaceavailability
Productionquality*(+/0/-)
46
51
Replace existing boiler systemwith a new FBC boiler of32 kg/cm2 pressure coupledwith back pressure turbine forcogeneration of 2 MWelectrical power
Conduct load analysis onmotors and reshuffle/replaceoptimum rating motors
Yes
Yes
Yes
Yes
0
0
Reduced GHGemissions (about3 200 t/yr)
Reduced GHGemissions
181 779
NQ
153 149
NQ NQ
Table 1.8: Techno-economic and environmental feasibility of CP-EE options (continued)
CP-EEoption
no.
Environmentalbenefits
Investment(US$)
Annualsaving(US$)
Paybackperiod
* Production quality: 0 = no effect + = positive - = negative effect
Values marked ‘NQ’ cannot be quantified at present because data were missing; they would be quantified after implementation ofthe CP-EE solution.
Three CP-EE options were rejected on the basis of their technical feasibility analysis—one
because of non-availability of space in the company, another because trials were not
successful, and a third because of non-availability of proven technology at small scale.
The company has already implemented a number of low-cost options and has also
invested in at least one large, capital-intensive CP-EE option: conversion of the loop
ager system to combined direct gas firing and steam. Since implementation of this
system, the company has obtained a patent for it. Demonstration of the system at
LDPM's premises could persuade other companies to adopt this technology.
3.6 Benefits and achievementsThe LDPM unit has already implemented 27 CP-EE options fully and 12 more options
have either been partially implemented or are in the advanced stages of planning. No
consensus was arrived at for three options, which were left to be followed up later.
Since one of the objectives of the project is to reduce GHG emissions, special emphasis
was given to the GHG emission reduction potential of the CP-EE options. Table 1.9
indicates the GHG saving from various CP-EE options
Cleaner Production – Energy Efficiency Manual page 106
Part 1 CP-EE methodology Chapter 3: Case study
CP-EE options Savings(coal/gas/electricity)
4
10
20
34
35
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
Installation of soft starter and variable speed/frequency drivesin drum motors
Use of indirect steam to direct steam for heating and recoveryof condensate for reuse as boiler feed water
Install soft starters and variable speed drives on jet machine motors
Operating the machine on continuous drive by installing autocut off photovoltaic cell
Installing photovoltaic cut off switch in padding mangle
Reuse the condensate (from cooking pan) to boiler
REPLACEMENT OF EXISTING LOOP AGER WITH DIRECT GASFIRED LOOP AGER (AN INNOVATIVE SYSTEM DEVELOPED ATTHE PLANT AND NOW PATENTED)
Two end overlapped feeding of cloth to the loop ager forlight weight fabric
Direct gas firing in sanforizing drum by slit type burner
Installation of damper and variable speed drives for ID and FD fans
Preheat the feed water to boiler by exit flue gases
Use low TDS municipal water in place of tanker water
Reduce the coal size (lower mesh size) to be used in boiler
Replace existing boiler system with a new FBC boiler of32 kg/cm2 pressure coupled with back pressure turbine forcogeneration of 2 MW electrical power
Insulate all 125 existing flanges
Install thermodynamic steam traps in the main header withgap of 25 metres
Conduct regular air leak detection tests
Reduce compressed air pressure to optimum limit
Reshuffle and replace optimum rating motors
Replace 40W tube light fixtures with energy efficient 30W fixtures
Provision of skylight windows overhead to reduce lightingrequired during day time
Increase power factor and reduced GHGemission (accounted for in option 42)
150 t/yr coal
Reduced GHG emissions
Reduced GHG emission due to savings of6 300 m3 gas/ year
Reduced GHG emission due to savings of6 000 m3 gas/ year
Reduced GHG emissions
Reduced GHG by 2 206 t/year through gassavings of 108 000 m3/yr and coal 1 270 t/yr
Reduced GHG emissions
Reduced GHG emissions by fuel savings of7 tons lignite
Reduced GHG emission due to electricalsavings of 75 000 kWh (all electrical options)
Reduced GHG emissions due to lignitesavings of 784 t/yr
Reduced GHG emissions due to lignitesavings of 337 t/yr
Reduced GHG emissions
Reduced GHG emissions by about 3 200 t/yr
Reduced GHG emissions due to savings of30 t lignite/yr
Reduced GHG emissions
Reduced GHG emissions
Reduced GHG emissions due to savings of8 125 kWh/yr electrical power
Reduced GHG emissions
Reduced GHG emissions by electrical powersavings of 70 664 kWh/year
Reduced GHG emissions
TOTAL
-
230
NQ
15
15
NQ
2 206
NQ
10.7
67
1 200
516
NQ
3 200
46
NQ
NQ
7.2
NQ
63
NQ
7 756 t/yr
Table 1.9: GHG savings potential of CP-EE options
CP-EEoption no.
GHG reduction(tons/year)
Cleaner Production – Energy Efficiency Manual page 107
Part 1 CP-EE methodology Chapter 3: Case study
The CP-EE team collected the data from the unit for the month of April 2003 and
compared this with the baseline data (i.e. before implementation of the CP-EE options).
Table 1.10 shows the comparison of various parameters before and after the
implementation of CP-EE options.
1 Original figures were given in Indian rupees, slight discrepancies between savings per unit price and total savings are due torounding after conversion to dollars. The figures indicate the magnitude of possible savings.
2 The reduction in dyes used cannot be attributed wholly to the improvement due to implementation of CP-EE solutions. Changesin market conditions, prevalent fashion requiring lighter shade, etc. would also result in reduction in dyes used.
Parameters Values before CP-EE
monthly average 2002
Value after CP-EE
implementation
monthly average 2002
1
2
3
4
5
6
Production
(tons of fabric)
Normalized
Water (m3/t fabric)
Purchased
Bore well
Recycled
Total
Electrical power
(kWh/t fabric)
Thermal
Lignite (t/t fabric)
Natural gas (m3/t fabric)
Chemicals
Dyes (kg/t fabric)
Gum (kg/t fabric)
Pollution load
COD (kg/t fabric)
GHG (t/t fabric)
Wastewater (m3/t fabric)
153.4
135
36
50
221
1 595
3.0
664
63.2
91
150
7.6
161
145
102
36
30
168
1 268
2.15
482
43
70
140
5.6
130
24.4
0
40
24
20.5
28.3
9.9
32.02
23.1
6.7
22.8
19.3
0.46/m3
0.017/m3
0.11/kWh
36/t
0.20/m3
9.18/kg
0.42/kg
364 240
85 595
73 552
31 879
21 232
NQ, reduced
O&M cost
of ETP
Table 1.10: LDPM before and after CP-EE
Section no.
averagechange
(%)
Remarks Average cost1
(US$)
Annual economicbenefit (basis =
2 400 tonsproduction/year)1
(US$)
Cleaner Production – Energy Efficiency Manual page 108
Part 1 CP-EE methodology Chapter 3: Case study
3.7 CP-EE assessment barriersProject progress was hampered by barriers from the CP-EE assessment phase through
to the implementation phase. CP-EE implementation started very well but suffered
later, particularly because of market conditions and increasing competition.
Table 1.11 shows the major constraints encountered and indicates actions taken to
overcome them.
Barrier Consequences Actions undertaken to overcome barriers
Status of fittingsOK/not OK, for: sight glass;bypass valve; filter.
RemarksEstimate of steam loss,suggestions, etc.
OPEN FILE
M1.5.2 Steam leakage
Leakage from steam lines not only wastes heat, it also causes pressure drop in the lines.
The quantity of steam leaked depends on the size of the leak and on steam pressure.
If visibly evident steam leakage is observed, it must be stopped. Table M.13 gives an
indication of steam losses at different steam pressures and leak diameters.
Cleaner Production – Energy Efficiency Manual page 140
Part 2 Technical modules Module 1: Energy use in industrial production
1
2
3
4
1.5
3.0
4.5
6.0
29.0
116.0
232.0
465.0
667
2 668
5 336
10 695
47.0
193.0
433.0
767.0
1 081
4 439
9 959
17 641
Sectionno.
Diameterof leak(mm)
Annual steam loss
at 7 kg/cm2at 3.5 kg/cm2
tons US$ tons US$
Table M.13: Steam loss vs. leak diameter
M1.5.3 Removal of air from steam installations
Air and other non-condensable gases such as oxygen and carbon dioxide are a natural
hazard in any steam-using plant. They can slow down the rate of steam distribution,
create cold spots on the heating surface, cause distortion and stressing of the plant and
can be the root cause of corrosion related problems. However, it is perhaps their overall
effect on heat transfer that is most important from the production point of view.
Some practical examples:
• The presence of air in a jacketed boiling pan increased cooking time from 12.5
minutes to 20 minutes. Sixty per cent air in the steam going to a unit heater
reduced output by as much as 30 per cent.
• Dry saturated steam at 40 psi will have a temperature of 287 °C. If there is 90 per
cent steam and 10 per cent air, the temperature will be only 280 °C. With 25 per
cent air the temperature would drop to 270 °C. In all of these cases the pressure
gauge would remain at 40 psi.
In relative terms, the thermal conductivity of air is 0.2 compared to 5 for water,
340 for iron and 2 620 for copper. Which means that a film of air only one
1/1000 inch (0.025 mm) thick will offer the same resistance to heat flow as a wall
of copper 13 inches (32.5 cm) thick.
The removal of air is essential and can be carried out by either manual or
automatic venting. Manual air venting has the disadvantage of relying on the
human element (i.e. a staff member) knowing just when and how often the cock
should be opened. The best alternative is obviously an automatic air vent.
M1.5.4 Thermal insulation
The need for efficient thermal insulation has become more important as both
operating temperatures and energy costs have increased. The production, distribution
and use of steam require thermal insulation to ensure that process requirements are
satisfied. The first consideration is to ensure that steam generated at the boiler can be
delivered to the point of use at the correct temperature and pressure. To ensure that
energy loss remains within design tolerance it is essential to make the correct choice of
thermal insulation system.
Types and forms of insulation materialThermal insulation materials can be divided into four types: granular, fibrous, cellular
and reflective. Typical thermal insulation materials for use in the 50–1 000 °C
temperature range are given in Table M.14.
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Part 2 Technical modules Module 1: Energy use in industrial production
1
2
3
4
5
6
7
8
9
10
11
12
Cellular glass
Glass fibre
Rockwool andSlagwool
Calcium silicate
Magnesia
Diatomaceous
Silica
Alumino silicate
Alumino silicate
Aluminium
Stainless steel
Vermiculite
Cellular
Fibrous
Fibrous
Granular
Granular
Granular
Fibrous
Fibrous
Granular
Reflective
Reflective
Granular
a b
a b d e f
a b d e g
a b c
a b c
a b c j
d e f
d e f g
j
h
h
a b c d g j
150
10–150
20–250
200–260
200
250–500
50–150
50–250
500–800
10–30
300–600
50–500
450
550
850
850
300
1 000
1 000
1 200
1 200
500
800
1 100
Sectionno.
Insulation Type Approx. limitingtemperature (°C)
Availability* Density(kg/m3)
Table M.14: Typical insulation materials for the 50–1 000 °C temperature range
* Notes:
a = slabs
b = sections
c = plastics
d = loose-fill
e = mattress
f = textile
g = sprayable
h = reflective
j = insulating bricks
Economic thickness of insulation The effectiveness of insulation follows a law of diminishing returns. Hence, there is a
definite economic limit to the amount of insulation that is justified. Beyond a certain
level, increased thickness is not viable in terms of cost as this cannot be recovered
through small heat savings. This limiting value is termed the economic thickness of
insulation (ETI). Firms have different fuel costs and boiler efficiencies and these factors
can be brought together to calculate ETI. In other words, for a given set of
circumstances, a certain thickness results in the lowest overall cost of insulation and
heat loss over a given period of time. Figure M.9 illustrates the principle of ETI.
Cleaner Production – Energy Efficiency Manual page 142
Part 2 Technical modules Module 1: Energy use in industrial production
Figure M.9 Determining ETI
I + H
insulation thickness
I
H
M
cost
I = cost of insulation
H = cost of heat loss
I + H = total cost
M = economic thickness
Determining ETI requires attention to the following factors:
• Fuel cost
• Annual hours of operation
• Heat content of fuel
• Boiler efficiency
• Operating surface temperature
• Pipe diameter/thickness of surface
• Estimated cost of insulation
• Average exposure at ambient still air temperature
Heat savings and application criteriaA variety of charts, graphs and references are available for heat loss calculation. As this
manual is intended for CP practitioners, the more complex procedures for working out
heat losses are not considered. Surface heat loss can be calculated with the help of the
simple equation for energy loss shown below. This can be used for surface
temperatures up to 200 °C. Factors such as wind velocity or conductivity of insulating
material have not been considered.
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Part 2 Technical modules Module 1: Energy use in industrial production
S = 10 + (Ts – Ta) / 20 x (Ts – Ta)
Where:
S = Surface heat loss (kcal/hr/m2)
Ts = Hot surface temperature (°C)
Ta = Ambient temperature (°C)
Total heat loss/hr (Hs) = S x A
Where A is the surface area in m2.
Based on the cost of heat energy, the value of heat loss in US$ can be worked
out as follows:
Equivalent fuel loss (Hf)(kg/yr) =Hs x hours of operation per year
GCV x ηb
Annual heat loss in monetary terms ($) = Hf x Fuel cost (US$/kg)
Where:
GCV = Gross calorific value of fuel (kcal/kg)
ηb = Boiler efficiency (as %)
Example calculation follows …
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Part 2 Technical modules Module 1: Energy use in industrial production
Calculate the fuel savings when a steam pipe with a diameter of 100 mm, supplying steam at10 kg/cm2 to equipment, and un-insulated over 100 m of its length, is properly insulated with65 mm of insulating material.
Assumptions:
• Boiler efficiency: 80 %• Fuel oil cost: US$300/ton• Surface temperature without insulation: 170 °C• Surface temperature after insulation: 65 °C• Ambient temperature: 25 °C
Existing heat loss:
S = [10 + (Ts – Ta) / 20] x (Ts – Ta)Ts = 170 °CTa = 25 °CS = [10 + (170 – 25)/20] x (170 – 25)
= 2 500 kcal/hr m2
S1 = S = Existing heat loss (2 500 kcal/hr m2 )
Modified System:
After insulating with 65 mm of glass wool with aluminium cladding, the hot face temperature willbe 65 °C
Ts = 65 °CTa = 25 °C
Substituting these values:
S = [10 + (65 – 25) / 20] x (65 – 20)= 480 kcal/hr m2
S2 = S = Existing heat loss (480 kcal/hr m2)
Table M.15 illustrates this further.
Example 4
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Part 2 Technical modules Module 1: Energy use in industrial production
Pipe dimension
Surface area (existing) (A1)
Surface area after insulation (A2)
Total heat loss in existing system (S1 x A1)
Total heat loss in modified system (S2 x A2)
Reduction in heat loss
No. of hours operation in a year
Total heat loss (kcal/y)
Calorific value of fuel oil
Boiler efficiency
Price of fuel oil
Yearly fuel oil savings
Monetary savings
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
100 mm φand 100 m length
3.14 x 0.1 x 100
31.4 m2
3.14 x 0.23 x 100
72.2 m2
2 500 x 31.42
78 850 kcal/hr
480 x 72.2
34 656 kcal/hr
78 860 – 34 656
44 194 kcal/hr
8 400
44 194 x 8 400
371 229 600
10 300 kcal/kg
80 %
US$300/ton
371 229 600/10 300 x 0.8
45 052.136 kg/year
45.052 x 300
US$13 515.64
Table M.15: Calculating fuel savings
Table M.16 can be used as a guide for insulation schemes for steam and condensate
lines, and for hot surfaces.
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Part 2 Technical modules Module 1: Energy use in industrial production
Less than 100 °C
100–150 °C
150–200 °C
200–250 °C
250–300 °C
25 mm
25 mm
25 mm
25 mm
25 mm
25 mm
25 mm
40 mm
50 mm
50 mm
50 mm
50 mm
50 mm
50 mm
50 mm
50 mm
50 mm
65 mm
65 mm
75 mm
65 mm
65 mm
75 mm
75 mm
90 mm
50 mm
75 mm
90 mm
90 mm
100 mm
Temperature Flat surfaces
Pipe diameter
25 mm 50 mm 75 mm 100 mm 150 mm
Table M.16: Guide to insulation schemes
Worksheet: Insulation losses
Sect
ion
no.
Loca
tion
Equi
pmen
t re
fere
nce
Exis
ting
out
erdi
amet
er
Exis
ting
sur
face
tem
pera
ture
Exis
ting
insu
lati
onth
ickn
ess
(if
any)
Thermal insulation can be justified by balancing the cost of different heat losses or heat savingsagainst the cost of insulation.
OPEN FILE
M1.5.5 Condensate recovery
Steam is used very extensively as a heating medium in various types of plants—efficient
use of steam is therefore the key to energy conservation. The heat energy contained in
steam consists of sensible heat and latent heat, the latter only being used in most types
of steam-using equipment. When steam gives off its latent heat, it condenses back to
water at the saturation point. The sensible heat contained in the condensate amounts
to as much as 20–30 per cent of the total heat of the steam (see Figure M.10).
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Part 2 Technical modules Module 1: Energy use in industrial production
Figure M.10 Total enthalpy of saturated steam at 10 kg/cm2
To maintain maximum efficiency of steam equipment, condensate forming in the
equipment should be discharged via steam traps as quickly as possible. In other words,
the higher the temperature of discharged condensate, the higher the efficiency of the
equipment, resulting in the most efficient use of steam.
In this case, the discharged condensate has the highest ‘quality’ of heat it can have, and
this heat can be used for other processes. In addition, the condensate itself can be used
as make-up water for the boiler. Figure M.11 shows the benefits of condensate recovery.
fuelinput steam
output
fresh water
totallosses
steamconsumer
dischargedcondensate
fuelinput steam
output
totallosses
steamconsumer
recovered condensate
Condensate recovery has numerous advantages, the most important of these are given
below:
A. Heat recovery• Boiler fuel is saved.
• Boiler efficiency is improved.
B. Water recovery• Water for industrial use is saved.
• Water treatment cost (and chemicals) are saved.
• Blow down is reduced.
C. Additional advantages• Air pollution is lessened by reduction in fuel consumption in boiler.
• No steam trap operating noise.
• No screening of moisture caused by flashing of condensate discharged
through steam traps.
Sizing the condensate return lineTable M.17 and Figure M.12 can be used to size the condensate return line, as
explained below.
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Part 2 Technical modules Module 1: Energy use in industrial production
EVERY 6 °C INCREASE IN BOILER FEED WATER TEMPERATURE
CAN SAVE 1 PER CENT BOILER FUEL
15
20
25
32
40
50
65
80
100
160
370
700
1 500
2 300
4 500
8 000
14 000
29 000
Pipe size (mm) Maximum capacity – starting load (kg/hr)
Table M.17: Sizing the condensate return line
From Table M.17, it is now possible to determine size, as indicated in Figure M.12,
below.
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Part 2 Technical modules Module 1: Energy use in industrial production
Figure M.12 Example of condensate return line sizing
R-450 kg
S-900 kg
R-250 kg
S-500 kg
R-110 kg
S-220 kg
R-400 kg
S-800 kg
900 kg/hr 1120 kg/hr 1620 kg/hr 2420 kg/hr
A B C D E
S = starting load/hr
R = running load/hr
Table M.17 can now be used to determine the sizes as follows:
• A to B carries 900 kg/hr—size required is therefore 32 mm.
• B to C carries 1 120 kg/hr—size required is therefore 32 mm.
• C to D carries 1 620 kg/hr—size required is therefore 40 mm.
• D to E carries 2 420 kg/hr—size required is therefore 50 mm.
Lifting the condensateThe steam pressure at the steam trap does the lifting, but this may lead to back
pressure on the trap and, by doing so, reduce the pressure differential across the trap.
To avoid the problem of back pressure, there must always be sufficient steam pressure
at the trap to overcome the back pressure. Lifting condensate directly to the
condensate return line without considering the above facts has the followings
disadvantages.
• Back pressure in the equipment from which condensate is lifted.
• ‘Chattering’ in the equipment, resulting in leakages at joints.
• Reduced equipment output capacity, and hence an increase in energy
consumption.
• Effects on product quality, especially in paper/textile dryers, as condensate
accumulates.
It is advisable to avoid lifting condensate because, even under the most favourable
conditions, lifting can be a hindrance to start-up because it causes back pressure which
slows down clearance of condensate at precisely the time this is least desirable. All of
this can be avoided by draining the condensate to a receiver by natural fall, and then
sending it to the boiler house by an independent pump.
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In a process house 3t/hr of steam at a pressure of 2.5 kg/cm2 are used indirectly in the equipment.There is no condensate recovery system. The boiler feed water temperature is 25 °C.
Example 5
Feed water temperature = 25 °C Feed water temperature = 65 °C
Before adjustment After adjustment
Condensatereturn = nil
Condensatereturn = 3 t/hr
Savings = US$37 830
The procedure for calculating the savings that can be achieved by condensate recovery
is illustrated in Figure M.13 on the following page.
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Figure M.13 Fuel savings from condensate recovery
hourly condensate recovered:
x hours per year:
Coal
3 000
8 400
kg/hr
= annual condensate recovered: 25 200 000 kg/yr
x heat content increase,
feed water temperature = 40 °C(25 °C to 65 °C)
40 kcal/kg
= heat recovered: 1 008 x 106 kcal/yr
÷ boiler efficiency = 85%:
÷ boiler efficiency = 80%:
÷ boiler efficiency = 75%:
÷ boiler efficiency = 70%:
1.18
1.25
1.33
1.43
✓ ✓
= heat saved: 1 260 x 106 kcal/yr
Oil Gas
÷ calorific value of fuel
=
÷
= fuel saved
x
= annual savings
kcal/kg
kg/yr
kg/ton
tons/yr
price/ton
1 000
kcal/kg
kg/yr
kg/l
heavy
medium
light
litres/yr
price/kl
kcal/m3
m3/yr
m3/yr
price/m3
10 300
122 330
0.97
0.95
0.935
126 113
US$ 300
US$ 37 830
Factors to be considered in incorporating a condensate recovery system
• A high condensate temperature necessitates a review of the available net positive
suction head, to avoid vapour locking and cavitation problems of feed water
pumps. Table M.18 provides guidelines.
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Part 2 Technical modules Module 1: Energy use in industrial production
86
90
95
100
1.5
2.1
3.5
5.2
Feed water temperature (°C) Suction feed (m)
Table M.18: Feed water temperature vs. suction feed
• In cases where increased feed water temperature gives rise to steaming problems,
as in economizers, some of the return condensate can be diverted for process
applications.
• Overflowing of condensate in collection tanks is a common occurrence. This
should be avoided by use of a simple control system with float switch.
• Thermal insulation is often ignored for condensate recovery. It is worthwhile
insulating condensate lines to save heat.
M1.5.6 Flash steam recovery
Flash steam is produced when condensate at a high pressure is released at a lower
pressure. The recovery of flash steam from high pressure condensate constitutes an
important area of heat saving.
The graph in Figure M.14 illustrates the percentage of flash steam generated under
different operating conditions.
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Consider the case of a machine where 1 000 kg of condensate at 7 kg/cm2 is flashed toatmospheric pressure.
From Figure M.14, flash quantity (kg/kg) from condensate is 14.0 per cent.
The flash steam generated per hour per 1 000 kg is therefore 140 kg/hr.
With an evaporation ratio (see Section M1.3) of 13 (i.e. 1 kg of oil burned in the boiler canproduce 13 kg of steam), the equivalent fuel oil saving (kg) by flash heat recovery is 140 ÷ 13 = 10.76 kg of oil per hour.
The annual fuel oil saving for 6 000 working hours would be:= (10.76 x 6000) / 1000 = 64.6 t/year
Assuming a fuel oil price of US$300/ton, monetary savings would be:= 64.6t x US$300 = US$19 385 /year
Example 6
The following example may prove helpful:
Flash steam generated is recovered by incorporating a flash vessel. The guidelines in
Table M.19 illustrate some essentials of flash vessel design.
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The flash vessel should be designed so that there is a considerabledrop in velocity. This allows condensate to fall to the bottom and bedrained out by the steam trap.
The height of the vessel should be such that as little water as possibleis entrained along with the flash steam. A minimum height of 1 metreand exit steam velocity of not more than 15 metres/second should beaimed for.
Table M.19: Guidelines for flash vessel design
In a flash steam recovery system—in the form of a small column—flashing vapours are
cooled by a spray. In this system, the vapours move up and lose their heat to the falling
water spray. Perforated baffles in the flow path help to provide intimate contact for
better heat transfer.
M1.6 FurnacesThe primary functions of an industrial furnace are to heat/melt/soak and generally treat
materials at given temperatures. Furnaces can be classified according to their method
of operation, their use and their method of utilizing fuel, as shown in Figure M.15.
M1.6.1 Types of furnace
Specific aspects of different types of furnaces are explained below and parameters of
various types are shown in Table M.20.
Forging furnaceForging furnaces are used to preheat billets and ingots to forge temperature. The furnace
temperature is maintained at around 1 200 to 1 250 °C (depending on the carbon
content of the steel). Normally, large pieces are soaked for 4 to 6 hours in the furnace to
attain a uniform temperature throughout the material. Actual soaking times vary with the
type and thickness of the material. Bigger pieces, weighing between 1 and 2 tons, may
be reheated several times. Charging and discharging of the material is done manually
and this results in significant heat loss during the forging operation. Forging furnaces use
an open fireplace system with most of the heat being transmitted by radiation.
Assessment of specific fuel consumption in this type of furnace is rather difficult
because it depends on the type of material and number of reheats required. On
average, the figure is between 0.65 to 0.85 tons of coal per ton of forging.
End fired (box type) furnaceThe ‘end fired’ box type furnace is used for batch type re-rolling mills. It is preferred to
the pusher type furnace (see below) when there is a wider variety of size and weight
of ‘material’ to be heated. End fired box type furnaces are used, usually, to heat scrap,
small ingots and billets weighing from 2 to 20 kg, for re-rolling. Charging and
discharging is manual, and the final product is in the form of rods, strips, etc.
Re-rolling (batch) furnaceRe-rolling (batch) furnaces operate 8 to 10 hours per day with an average output of
1 to 1.5 t/hr. The charge is loaded before firing, and nearly 1.5 hours of heat-up time
is required to attain a temperature of 1 200 °C. The total cycle time can be broken
down into heat-up time and re-rolling time. During heat-up time the material is heated
to the required temperature and is then removed manually for re-rolling. After
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Figure M.15: Classification of furnaces
Furnaceclassification
According tomode of
heat transfer
According tomode ofcharging
Mode ofheat reovery
Open fireplace furnace
Heated through liquid
Periodical
Continuous
Forging
Recuperative
Regenerative
Re-rolling(batch/continuous pusher)
Pot
Glass tank melting(regenerative/recuperative
completing first re-rolling, which takes around 3.5 to 4 hours, the furnace is loaded
with fresh ‘material’, which takes only 30 minutes to heat-up for re-rolling.
Average output from these furnaces varies from 10 to 15 tons/day and the specific fuel
consumption varies from 180 to 280 kg of coal per ton of heated material. Specific coal
consumption varies with the weight of the material being heated for re-rolling and with
operating efficiency of the furnace.
Continuous pusher type furnaceContinuous pusher type furnaces have a distinct advantage over batch type furnaces.
Although the process flow diagram and operating cycles are the same as those of the
batch furnace, the cross-sectional area of the billet or ingot that can be fed into the
pusher furnace is 65 to 100 mm2 (45 to 90 kg weight/piece). These furnaces generally
operate 8 to 10 hours with an output of 20 to 25 tons per day; their normal rating is
around 4 to 6 tons/hour at peak load.
Since the length of a pusher furnace is generally between 13.7 and 15.25 metres, the
material itself can recover a part of the heat from flue gases as it moves down the
length of the furnace. Heat absorption by the material in the furnace is slow and steady
and uniform throughout the cross-section.
The material pushed into the furnace takes 2 to 2.5 hours to reach the soaking zone,
where the temperature is maintained at around 1 200 to 1 250 °C. After sufficient
soaking, which depends on cross-section, the material is removed manually for re-
rolling. Specific fuel consumption varies from 180 to 250 kg of coal per ton of heated
material. Inefficient furnace operation is one of the major reasons for wide variations in
specific fuel consumption.
Pot furnacesPot furnaces are usually used when the final product is small glassware, shells,
laboratory instruments, bangles, etc. or wherever a ‘batch’ is melted intermittently.
Coal is burned on a fixed grate with natural draught.
In pot furnaces the flue gas temperature just after the furnace is in the range of 1 200
to 1 250 °C. Specific fuel consumption is 1.2 to 1.5 tons of coal per ton of glass drawn.
This varies from unit to unit, depending on the type of product and coal quality.
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Glass furnace: a typical glass furnace consists of 10 to 12 pots, each with a capacity of
200 kg of molten glass. The furnace temperature is maintained at around 1 350 to
1 400 °C. Around 14 to 18 hours are needed for complete melting and refining of a
batch of glass. Drawing of molten glass from the pots requires another 6 to 8 hours.
In the glass tank regenerative furnace, batch charging and glass drawing is continuous.
Normally, the quantity of glass drawn ranges from 10 to 20 tons per day in such
furnaces. A tank furnace consists of a bath, the bottom and sides of which are usually
made of refractory blocks. Ports are provided for mixing of fuel and air above the
melting level.
The coal is not burned directly in the glass tank furnace. Instead, it is used as a raw
material to first generate product gas which, in turn, is cross-flow-fired to heat the tank
across the width of the furnace.
The mixed batch, comprising sand, limestone, soda ash and cullet, is shovelled into the
furnace manually. Melting of the glass in tanks occurs in the following stages:
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Design parameters
Length (mm)
Width (mm)
Height (mm)
Grate width (mm)
Grate length (mm)
Operating parameters
Furnace temperature (°C)
Flue gas temperature (°C)
CO2% in flue gas
Specific fuel consumption
Tons of coal/ton ofmaterial heated
3 000
1 850
900
900
1 850
1 200–1 250
1 100
3–10
0.6–0.8
6 000
2 000
1 100 (front end)
900 (rear end)
900
1 850
1 150–1 200
700–750
4–12
0.18–0.28
13 700/152 250
1 800
1 050 (front end)
400 (rear end)
900
1 850
1 200–1 250
550–600
4–12
0.18–0.25
Average weightof molten glass200 kg per pot
1 350–1 400
1 200–1 250
4–8(O2)
1.2–1.5
Depends on the capacity of the furnace
Static producer
1 400–1 450
200–350 (just after regeneration)
2–6 (O2)
0.55–1.0
Furnace Pot Glass tank melting (regenerative or
recuperative)
Forging(open
fireplace)
Re-rolling
Batch Continuous pusher
Table M.20: Furnace parameters
1. The batch is pushed into the furnace where it floats on the top of molten glass
and melts to a frothy state.
2. Temperature is held sufficiently high to remove gas bubbles and homogenize the
bath, refining the glass.
3. Glass then flows to the cooler working end for drawing at a carefully controlled
rate/temperature.
Molten glass is supplied from the working end to one or more operating units. The
forming of glassware may be carried out either by hand or by machine. The glassware
is then taken to an annealing furnace. Annealing avoids stresses being set up in the
glass by too rapid or uneven cooling, as this may increase its tendency to fracture.
Rejected articles, known as ‘cullet’, are recycled in the fresh batch.
M1.6.2 Fuel consumption and heat economy
For an industrial furnace, the term ‘efficiency’, when used in the true sense, refers to
the quantity of fuel expended to heat a unit weight of stock. While efficiency for boilers
ranges from 60 to 85 per cent, the efficiency of furnaces is sometimes as low as 5
per cent. One reason for the difference in efficiency between boilers and industrial
furnaces is in the final temperature of the material being heated. Gases can give up
heat to the charge only as long as they are hotter than the charge. Consequently, flue
gases leave industrial furnaces at a very high temperature. This factor is responsible for
low furnace efficiencies.
Examination of Figure M.16 will give a clear understanding of the distribution of heat
in a simple furnace.
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Figure M.16 Flow of heat in a furnace
1
2
3
3
2
7
2
4
6
4
5
1
1 = stock
2 = ground and surroundings
5 = door
6 = protruding stock
3 = hearth
4 = cracks and openings
7 = stack
Heat flow in a furnaceIt is desirable for most of the heat liberated by the fuel to be imparted to the stock.
However, as shown in Figure M.16, some of the heat in a furnace passes into the
furnace walls and hearth, and some is lost to the surroundings by radiation and
convection from the outer surface of the walls or by conduction into the ground. Heat
is also radiated through cracks or other openings and furnace gases pass out around
the door, often burning in the open air and carrying off heat. Heat is also lost every
time the door is opened or can be dissipated if stock protrudes beyond the furnace
enclosure. Finally, most of the heat lost passes out along with the products of
combustion, either in the form of sensible heat or as incomplete combustion. Fuel
economy demands that the fraction of total heat that passes into the stock be as large
as possible and that all losses be minimized.
1.6.3 Factors affecting fuel economy
Complete combustion with minimum excess airTo achieve complete combustion of fuel with minimum excess air, a number of factors
(such as proper selection and maintenance of control, excess air monitoring, air
infiltration, pressure of combustion air) are to be considered. In addition to an
abnormal increase in stack losses, the ingress of too much excess air lowers flame
temperature, reducing furnace temperature and heating rate. If too little excess air is
used, combustion is incomplete and chimney gases will carry away unused fuel
potential in the form of unburned combustible gases such as carbon monoxide and
hydrogen, and unburned hydrocarbons which would otherwise have burned usefully
in the combustion chamber.
Proper heat distributionIdeally, a furnace should be designed so that, in a given time, as much material as
possible is heated to as uniform a temperature as possible, with the minimum fuel firing
rate. To achieve this, the following points should be considered.
i) The flame should not touch the stock and should propagate clear of any solid
object. Any obstruction whatsoever de-atomizes the fuel particles, affecting
combustion and creating black smoke. If the flame touches the stock, the scale of
losses is greatly increased.
ii) Refractories are leached if the flames touch any part of the furnace, as the
products of incomplete combustion can react with some of the refractory
constituents at high flame temperatures.
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iii) The flames from burners in the combustion space should also remain clear of oneanother. If flames interact, inefficient combustion will occur. This can becontrolled by staggering the burners on opposite walls.
iv) The flame has a tendency to travel freely in the combustion space just above thematerial. In small reheating furnaces, the burner axis is never parallel to thehearth but always at an upward angle. Every precaution should be taken toensure that the flame never impinges on the roof.
v) A larger burner produces a long flame which may be difficult to contain within thefurnace walls. More burners of less capacity give better distribution of heat in thefurnace, and also reduce scale losses while increasing furnace life, as shown inFigure M.17.
vi) For uniform heating in smaller reheating furnaces it is advisable to maintain a longflame with a golden yellow colour when firing furnace oil. The flame should not beallowed to become so long that it enters the chimney and comes out at the top orthrough doors, as occurs when excessive oil is fired. This operational practice issometimes employed to increase production rate, in reality it helps only marginally.
vii) It is also desirable to provide a combustion volume that is adequate to the heatrelease rate.
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stockflame stockflame
incorrect correct incorrect correct
flameflame
flame
Figure M.17 Heat distribution in furnaces
Operating at the desired temperatureThere is an optimum temperature for furnace operation for any given industrial heatingor melting operation. Table M.21 shows operating temperatures for different furnaces.
Operating at too high a temperature will not only mean unnecessary waste of fuel andheat, it will also cause overheating of the stock, its spoilage or excessive oxidation anddecarburization, as well as over-stressing of refractories. To avoid this, provision shouldbe made for temperature control instruments.
In the ‘off’ condition, only the atomizing air enters the furnace, bringing itstemperature down rapidly so that when the oil firing process recommences, the
amount of oil supplied to the furnace to raise the temperature is far greater than wouldbe necessary had the furnace been operated on ‘proportional control’.
Reducing heat losses from furnace openingsIn oil fired furnaces, substantial heat losses occur through furnace openings. For every
large opening, heat loss may be calculated by multiplying black body radiation at
furnace temperature by the emissivity (usually 0.8 for furnace brick work) and the factor
for radiation through openings. Black body radiation losses and radiation factors can be
obtained directly from curves and nomograms such as those shown in Figure M.18.
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Figure M.18 Using black body radiation to calculate heat loss
Slab reheating furnaces
Rolling mill furnace
Bar furnace for sheet mill
Bogey type annealing furnace
Bogey type roll annealing furnace
Small forging furnace
Rotary iron melting furnace
Enamelling furnace
1 200 °C
1 180 °C
850 °C
659–750 °C
1 000 °C
1 150 °C
1 550 °C
820–860 °C
Table M.21: Furnace operating temperatures
0325
1 000blac
k bo
dy r
adia
tion
(kc
al/c
m2 /
hr)
temperature (°C)
2 000
3 000
4 000
5 000
6 000
500 750 1 000 1 250 1 500 1 650
tota
l rad
iati
on f
acto
r
0
1.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0.2 0.4 0.6 0.8 1.0 2 3 4 5 60
a) Black body radiation b) Radiation through openings of various shapes
ratio =diameter or least width
thickness of wall=
Dx
x
Dvery long slot
2:1 rectangular opening
square opening
round (cylindrical) opening
Minimizing wall lossesIn intermittent or continuous furnaces, heat losses generally account for around 30–40
per cent of the fuel input to the furnace. The appropriate choice of refractory and
insulation materials goes a long way towards achieving fairly high fuel savings in
industrial furnaces.
In industrial furnaces, fuel consumption can be substantially reduced by judicious
application of external insulation. Several materials with different combinations of heat
insulation and thermal inertia should be considered to minimize heat losses through
furnace walls. For intermittent furnaces, the use of insulating refractories of appropriate
quality and thickness can cut down heat storage capacity of walls and the time
required to bring the furnace to operating temperature by as much as 60–70 per cent.
Control of furnace draughtIngress of uncontrolled free air must be prevented in any furnace. It is better to maintain
a slight excess pressure inside the furnace to avoid air infiltration. If negative pressures
exist in the furnace, air infiltration is liable to occur through the cracks and openings,
thereby affecting air/fuel ratio control. Neglecting furnace pressure could mean problems
of cold metal and non-uniform metal temperatures, which could affect subsequent
operations such as forging and rolling and could result in increased fuel consumption.
Furnace loadingOne of the most vital factors affecting efficiency is loading. There is a particular loading
at which the furnace will operate at maximum thermal efficiency. If the furnace is
under-loaded, a smaller fraction of the available heat in the working chamber will be
taken up by the load and the efficiency will accordingly be low. The best method of
loading is generally obtained by trial, noting the weight of material put in at each
charge, the time it takes to reach a given temperature and the amount of fuel used.
Care should be taken to load a furnace at the rate associated with optimum efficiency,
although it must be realized that limitations in achieving this are sometimes imposed
by availability of work or other factors beyond operational control.
Placing of stockThe load should be placed on the furnace hearth in such a way that:
• It receives maximum radiation from the hot surfaces of the heating chamber and
the flames.
• The hot gases circulate efficiently around the heat receiving surfaces.
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• There is adequate spacing between the billets. Overlapping of materials results in
non-uniformity of temperature and should be avoided.
Stock should not be placed in the following positions:
• In the direct path of the burners or where the flame is likely to impinge.
• In an area which is likely to cause a blockage or restriction of the flue system of
the furnace.
• Close to any door or opening where cold spots are likely to develop.
Load residence timeIn the interest of fuel economy and work quality, the materials comprising the load
should remain in the furnace for the minimum stipulated time to obtain the required
physical and metallurgical requirements. When the materials attain these properties
they should be removed from the furnace to avoid damage and fuel wastage.
M1.7 Waste heat recovery
M1.7.1 What is waste heat?
Boilers, kilns, ovens and furnaces generate large quantities of hot flue gases. If some of
this waste heat can be recovered, a considerable amount of primary fuel can be saved.
Not all of the energy lost in waste gases can be recovered. However, much of the heat
can be recovered and losses can be minimized by adopting the measures described
below.
M1.7.2 Sources of waste heat
When considering the potential for heat recovery, it is useful to note all of the
possibilities, and to grade the waste heat in terms of potential value, as shown in
Table M.22.
M1.7.3 Waste heat recovery from flue gases
After identifying sources of waste heat and possible uses, the next step is to select
suitable heat recovery systems and equipment to recover and use the heat.
Considerable fuel savings can be made by preheating combustion air. The heat saving
devices used for this purpose are the recuperator and the regenerator.
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RecuperatorIn a recuperator, heat exchange takes place between the flue gases and the air via
metallic or ceramic walls. Ducts or tubes carry the combustion air that is to be pre-
heated, the other side of the exchanger carries the waste heat stream.
Ceramic recuperators are bulky and offer considerable resistance to transfer of heat
because of low conductivity; they also have a greater tendency to leak. Metallic
recuperators are less prone to leaks and thermal expansion and can be controlled.
Metallic recuperators are easier to maintain and install and involve less initial cost. For
the reasons outlined above, ceramic recuperators are not widely used. Some of the
common flow arrangements used in recuperators are shown in Figures M.19–M.21.
Metallic recuperators can be of three basic types, depending on the method of heat
transfer: i.e. radiation, convection, or combined convection and radiation.
Ceramic recuperator
Ceramic tube recuperators have been developed to overcome the temperature limit of
metallic recuperators (around 1 000 °C on the gas side). The materials used for ceramic
recuperators allow gas side temperatures of up to 1 300 °C and temperatures up to
850 °C on the preheated air side.
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1
2
3
4
5
6
7
Heat in flue gases
Heat in vapour streams
Convective and radiant heat lostfrom exterior of equipment
Heat losses in cooling water
Heat losses in providing chilledwater or in the disposal of chilledwater
Heat stored in products leaving theprocess
Heat in gaseous and liquid effluentsleaving process
The higher the temperature, the greaterthe potential value for heat recovery.
As above but when condensed, latentheat also recoverable.
Low grade—if collected may be used forspace heating or air preheats.
Low grade—useful gains if heat isexchanged with incoming fresh water.
a) High grade if it can be utilized toreduce demand for refrigeration.
b) Low grade if refrigeration unit used asa form of heat pump.
Quality depends on temperature.
Poor if heavily contaminated, thusrequiring alloy heat exchanger.
Section no. QualitySource
Table M.22: Sources of waste heat
The classification of recuperators based on their type of flow is given in Figure M.21.
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Table M.23 summarizes the applications and advantages of the different types of
recuperator.
Radiation type recuperators
(30% efficiency)
Convective recuperative system
(50–60% efficiency)
Advanced designs
(self-recuperative burners, up to
70% efficiency)
Steel industry (furnaces, soaking pots,
chimneys and flues)
Low temperature applications (food,
textiles, brewing, pulp and paper)
High temperature applications (flue
gases from kilns, metal processing
and glass melting furnaces, etc.)
Can handle very dirty,
abrasive dust-laden gases
Table M.23: Furnace operating temperatures
Energy performance Applications Advantages
Cooled waste gas
Hot air to process
Coldair
inletRadi
atio
n se
ctio
nC
onve
ctio
n se
ctio
n
Regenerator In a regenerator (see Figure M.23), the flue gases and the air to be heated are passed
alternately through a heat-storing medium, thereby resulting in transfer of heat. Long
periods of reversal result in lower average temperature of preheat and consequently
reduce fuel economy.
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Figure M.23 Regenerator
Figure M.24 Economizer
EconomizerFor a boiler system, an economizer (see Figure M.24) can be provided utilizing the flue
gas heat to pre-heat the boiler feed water. In an air pre-heater, the waste heat is used
to heat combustion air. In both cases, there is a corresponding reduction in the fuel
requirements of the boiler.
Gas
Chimney
Air regeneratorGas regenerator
Flue gas outlet
Flue gas intlet
Water outlet
Water inlet
Economizer cells
Air
M1.7.4 Plate type heat exchangers
The cost of heat exchange surfaces is a major cost factor when temperature differences
are not large. One way of solving this problem is the plate type heat exchanger (see
Figure M.25), which consists of a series of separate parallel plates forming narrow flow
passages. Plates are separated by gaskets and the hot stream passes in parallel through
alternating plates while the counter-flow of liquid to be heated passes in parallel
between the hot plates. Plates are corrugated to improve heat transfer. Plate type
exchangers are summarized in Table M.24.
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Figure M.25 Plate type heat exchanger
Plain form, cooling fluids flow
A series of separate,parallel plates formnarrow passages throughwhich the heating andcooling fluids flow
Temperature range 25–170 °C,(special design up to 200 °C). Easy toclean, replace parts and increasecapacity. Liquid-to-liquid systemsrecover up to 80–90% of availableheat. Widely used in brewing, dairyand chemical process industries; inregenerative recovery, and as acondenser for product heating.
Table M.24: Characteristics of plate heat exchangers
Type of plate heat exchanger Construction Comments
M1.7.5 Heat pipe
The heat pipe is a device that uses an evaporation-condensation cycle to transfer up to
100 times more thermal energy than copper, the best known conductor. It is a simple
device that absorbs and transfers thermal energy with no moving parts, and hence
minimum maintenance.
The heat pipe comprises three main elements: a sealed container; a working fluid; and
a capillary wick structure, (see Figure M.26).
The container encloses the working fluid which, because the container is sealed, is at
its own pressure equilibrium. Thermal energy applied to the outer surface of the heat
pipe causes the working fluid near the surface to evaporate instantaneously, picking up
the latent heat of evaporation. This region of the heat pipe is the ‘evaporator’. The
vapour, which now has a higher pressure, moves to the other, cooler, end of the pipe
where it condenses, giving up the latent heat of evaporation as it does so. This region
of the pipe forms the ‘condenser’. The capillary wick—fabricated as an integral part of
the inner surface of the evacuated container tube—provides a return path for the
working fluid, allowing the cycle to restart.
Performance and advantagesThe heat pipe heat exchanger (HPHE) is a lightweight compact heat recovery system.
It requires no input power for its operation and is free from cooling water and
lubrication systems. It also lowers fan horsepower requirement and increases overall
thermal efficiency of the system. HPHE recovery systems are capable of operating at
315 °C with 60–80 per cent heat recovery capability.
Typical applicationHeat pipes are used in following industrial applications:
a) Process to space heating: The HPHE transfers thermal energy from the process
exhaust for use in building heating. Preheated air can be blended if required. The
requirement for additional heating equipment to deliver heated make up air is
drastically reduced or eliminated.
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Figure M.26 Heat pipe
Vapourized fluid condensesand gives up heat
Metal mesh wick actsas return path for
liquid working fluid
Heat evaporatesworking fluid
Heat in
Vapour
Liquid
Heat out
b) Process to process: Heat pipe heat exchangers recover waste thermal energy from
the process exhaust and transfer this energy to the incoming process air. The
warmed incoming air can be used for the same process or other processes, thus
reducing process energy consumption.
c) HVAC Applications:
Cooling: a HPHE can precool building make up air in summer, thus reducing the total
tons of refrigeration as well as providing savings in operation of the cooling system.
Heating: the process described above is reversed during winter to preheat the make
up air.
Other industrial applications are:
• Preheating of steam boiler combustion air.
• Recovery of waste heat from furnaces.
• Reheating of fresh air for hot air driers.
• Recovery of waste heat from catalytic deodorizing equipment.
• Recovery of furnace waste heat as heat source for other ovens.
• Pre cooling of cold air.
• Heat source for air conditioning.
• Cooling of closed rooms with outside air.
• Preheating of boiler feed water by waste heat recovery from flue gases in the heat
pipe economizers.
M1.7.6 Heat pumps
Heat pumps have the ability to upgrade heat from a source to a value more than twice
that of the energy required to operate the device. The potential for application of heat
pumps is growing and numerous industries have benefited by recovering low grade
waste heat, upgrading it and using it in main process streams.
Basically, a heat pump system comprises a compressor, condenser, expansion valve,
evaporator and a working fluid. It extracts heat from air, water or a process liquid
stream and supplies it, via an exchanger, at a higher temperature to a liquid or gas
stream. The heat pump employs the same basic principle as the common refrigerator,
and the cycle can also be used for cooling. The principle of operation is presented in
Figure M.27.
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Heat pump applications (see Table M.25) are most promising when both the heating
and cooling capabilities can be used in combination. One example of this is a plastics
factory where chilled water from a heat is used to cool injection-moulding machines
whilst the heat output from the heat pump is used to provide factory or office heating.
Other examples of heat pump use include product drying, maintaining dry
atmosphere for storage and drying compressed air.
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Part 2 Technical modules Module 1: Energy use in industrial production
Figure M.27 Heat pump—operating principle
Heat drawn from warmexhaust can achieve COPs of 5 or 6
Maximum operatingtemperature can vary (40 °C,60 °C or 100 °C depending onchoice of working fluid)
Timber and woodproducts; ceramics andpottery; brickmanufacture and foodproducts
Reclaims heat at ambienttemperatures
Table M.25: Heat pump applications and advantages
Energy performance Applications Advantages
Working fluid expansionvalve converts hot liquid to
low-pressure coldliquid/vapour mixture
Heat energy extracted from wasteair is absorbed by the working fluidin cooling coil
Heat absorbed by cold liquidconverts it to cold gas
Heat pump compresses cold gas tohigh pressure hot gas
Heating coil adding heat to supplyair from hot gas condensing to hotliquid under pressure
M1.7.7 Heat (thermal) wheels
A variation on the basic methods of heat transfer is the rotary regenerator which uses
a cylinder rotating through waste gas and air streams (see Figure M.28). The ‘heat’ or
‘energy recovery’ wheel is a rotary gas heat regenerator that transfers heat from an
exhaust stream to cooler incoming gases. Its main area of application is when there is
a requirement for heat exchange between large masses of air with small temperature
differences. Heating and ventilation systems and recovery of heat from dryer exhaust
air are typical applications.
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Figure M.28 The heat wheel
The wheel rotor—which consists of sectors of either steel mesh or inorganic fibrous
materials with a hygroscopic coating of glass ceramic—offers a large surface area to the
air or gas flows. The wheel absorbs heat from the hot exhaust gases and, as the rotor
revolves, transfers heat to the cooler incoming stream. The speed of rotation of the
rotor is usually about 10–20 revolutions per minute. A purge bleed between the clean
and dirty gas streams is incorporated to avoid contamination between the two streams.
Efficiencies of over 80 per cent are claimed for this device, but they vary depending on
the individual case (see Table M.26).
Supply air ducting Rotating regenerator
Warmed air to room
Warm room exhaust air
Exhaust air ductingDirection of rotation
Cooled exhaust air
Cold outside air
M1.7.8 Self recuperative burner
In self-recuperative burners (see Figure M.29), the recuperator is an integral part of the
burner, saving costs and making it easier to retrofit to existing furnaces. Recuperator
burners are operated in pairs. While one burner is used to burn the fuel, the other
burner uses a porous ceramic bed to store heat. After a short period (minutes), the
process is reversed and heat stored in the ceramic bed is used to preheat the
combustion air.
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Waste heat recovery: 65% or more of available heatcan be recovered
Cost-effective infurnaces, ovens, printingmachinery, paper dryingand HVAC systems,metal melting furnaces
Reclaims heat at ambienttemperatures
More compact, lighter, and highertemperatures than comparablerecuperators
Lower gas exit temperatures aretherefore possible
Table M.26: The rotary wheel—applications and advantages
Energy performance Applications Advantages
Figure M.29 Self-recuperative burner
Natural gas
Combustion airHot
combustionproducts
Combustion products
Hot combustionproducts
Waste gas outlet
M1.7.9 Waste heat recovery system for diesel generation sets
Exhaust gases from diesel generation (DG) sets are at high temperatures, ranging from
330 to 550 °C depending on the type or make of the engine and the fuel used. The
energy in the hot exhaust gases can be recovered usefully for steam, hot water, thermic
fluid heating and hot air generation (see Figure M.30).
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Figure M.30: Hot water generation from DG exhaust
M1.7.10 Applicability of heat exchanger systems
Heat exchangers exist for nearly every possible combination of heat source and use.
Table M.27 indicates how common types are generally applied.
Thermic fluid pump
Thermic fluid in
350 °C
DG exhaust
To exhaust
Thermic fluid out
Typical processhot water bath
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Radiation recuperator
Convective recuperator
Furnace regenerator
Metallic heat wheel
Ceramic heat wheel
Finned tube regenerator
Shell and tuberegenerator
Heat pipes
Waste heat boiler
High
Medium to high
High
Low tomedium
Medium to high
Low tomedium
Low
Low tomedium
Medium tohigh
Incinerator or boiler exhaust
Soaking or annealingovens, melting furnaces,afterburners, gasincinerators, radiant tubeburners, reheat furnaces
Glass and steel meltingfurnaces
Curing and drying ovens,boiler exhaust
Large boiler or Incineratorexhaust
Boiler exhaust
Refrigeration condensates,waste steam, distillationcondensates, coolants fromengines, air compressors,bearings and lubricants
Drying, curing and bakingovens, waste steam, airdryers, kilns andreverberatory furnaces
Exhaust from gas turbines,reciprocating engines,incinerators and furnaces
Combustion air preheat
Combustion air preheat
Combustion air preheat
Combustion air preheat,space preheat
Combustion air preheat
Boiler make up water preheat
Liquid flows requiringheating
Combustion air preheat,boiler make up water preheat,steam generation, domestichot water, space heat
Hot water or steamgeneration
Table M.27: matrix of waste heat recovery devices and applications
Heat recoverydevice
Temperature range
Typical sources Typical uses
Electrical systems
M1.8 Electricity management systems
M1.8.1 Electricity cost
Electricity costs for an enterprise consist of the following:
• Energy costs in the true sense (i.e. the cost of the kWh consumed).
• Costs of power demand (i.e. the cost of the peak electrical power requirement).
Energy costs can be reduced primarily by reducing electricity consumption (i.e. by
increasing energy efficiency), while power demand costs can be reduced by other
means—by reducing peaks of power consumption. Reducing power peaks can lead to
reduced consumption of electrical energy, but this is not an inevitable consequence.
Both increasing energy efficiency and reducing maximum electrical load must be
preceded by analysis of the processes that consume electrical energy. Very precise
knowledge of the processes is necessary to define measures to increase energy
efficiency in an effective and economical way, and to be able cut off consumers during
(short) periods of time to reduce peak load.
M1.8.2 Electric load management and maximum demand control
IntroductionIf processes are not to be interrupted, electricity demand and supply must match
instantaneously. This requires reserve capacity to meet peak demands, and the costs of
meeting such demands—normally referred to as demand charges—are relatively high.
Managing electricity supply costs therefore requires integrated load management that
includes control of maximum demand and scheduling of its occurrence during peak/off-
peak periods. Figure M.31 gives an example of the load curve for an enterprise. How
such a curve can be plotted is explained in Example 7 (page 178).
Basically, there are two ways to reduce maximum load for an enterprise (see
Figure M.32):
a) cut off the peaks; or
b) reduce base load.
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Before considering methods of load prediction, some terms used in connection with
power supply need to be defined.
• Connected load—the nameplate rating (in kW or kVA) of the apparatus installed
at a consumer’s premises.
• Maximum demand—the maximum load that a consumer uses at any time.
• Demand factor—the ratio of maximum demand to connected load.
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A consumer has ten 40 kW electrical loads connected at a facility; the connected load is thus400 kW. However, the maximum number of loads actually used may be only nine—all ten maynever be used at once. Maximum demand is, therefore, 9 x 40 = 360 kW, and the demand factorof this load is 360/400 or 90 per cent. A consumer of electrical power will naturally use power asand when required and the load will therefore be constantly changing. As shown in Figure M.31,this can be represented by a graph known as a load curve that shows the consumer's loaddemand against time at different hours of the day.
When plotted for the 24 hours of a single day, the graph is known as a daily load curve. If it ispotted for a whole year, it is known as an annual load curve. This type of curve is useful inpredicting annual energy requirements, occurrence of loads at different hours and days in the year,and for power supply economics. As load is variable, it will only be at maximum for a certain timeand will be lower at other times. The average load during a 24 hour period, or other periodconsidered for the load curve, will be less than the maximum load. The ratio of average load tomaximum load is called the load factor.
The load factor can also be defined as the ratio of energy consumed during a given period to theenergy that would have been used if maximum demand had been maintained throughout thatperiod.
Example 7: Plotting a load curve
Load factor =Average load
Maximum load
Load factor =Energy consumed during 24 hours
Maximum recorded load x 24 hours
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A residential consumer has ten 60 W lamps connected. Demand is as follows:
From 12 midnight to 5 a.m.: 60 WFrom 5 a.m. to 6 p.m.: NilFrom 6 p.m. to 7 p.m.: 480 WFrom 7 p.m. to 9 p.m.: 540 WFrom 9 p.m. to 12 midnight: 240 W
The average load, maximum load, load factor and electrical energy consumption during the daycan be calculated as follows:
i) Maximum load is 540 W for 2 hours of the day, from 7 p.m. to 9 p.m.
ii) Energy consumption during 24 hours of the day is:
(5 x 60) + (480 x 1) + (540 x 2) + (240 x 3) = 2 580 Wh
= 2.58 kWh/day
iii) % Load factor =
=
= 19.9%
iv) Average Load =
= 107.5 kW
Example 8: Calculating the average load
Energy consumed during 24 hours x 100%
540 W x 24 hours
2580 x 100%
540 W x 24 hours
2 580 kWh
24 hours
spotlightCP-EE
In a wire drawing unit,three items of preliminarywire drawing equipmentwith loads of 50 HP per
wire were usedsimultaneously during the
day shift. Thesimultaneous maximumdemand for the overall
plant was about 450 kVA.Operation of the threeitems of wire drawing
equipment wasrescheduled to the 3rdshift, when only a few
items of equipment wereoperating. With
rescheduling, maximumdemand was reduced by
150 kVA, resulting insavings of about
US$2 000 per year indemand charges, as well
as flattening the loadcurve considerably.
Rescheduling of loads
To minimize simultaneous maximum demands, running of units or carrying out of
operations that demand a lot of power can be rescheduled to different shifts. To do
this, it is advisable to prepare an operation flow chart and a process run chart.
Analysing these charts and adopting an integrated approach make it possible to
reschedule the operations and to run heavy equipment in such a way as to reduce
maximum demand and improve the load factor (see Figure M.33).
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Part 2 Technical modules Module 1: Energy use in industrial production
require an electromagnetic field to operate and they therefore draw additional
‘reactive’ power (kVAR) to provide for this magnetizing component. Figure M.34
illustrates this situation—KW, the active power (shaft power or true power required)
and the reactive power (kVAR) are 90° out of phase, with reactive power (kVAR) lagging
the active power (kW). (As will be seen below, the ‘lag’ has significance for power factor
correction). The vector sum of kW and kVAR, is the apparent power, termed kVA. It is
kVA that represents the actual electrical load on the distribution system.
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Figure M.34
kW
kVAR
φ
kVA
From Figure M.34, it can be seen that if reactive power is zero (i.e. no inductive kVAR
needed) kVA and kW will be equal but if the inductive kVAR requirement increases, the
kVA required to provide the same active power (kW) also increases. In other words, the
ratio of kW to kVA varies with the reactive power drawn. This ratio is called the power
factor. It is always equal to or less than unity.
If all loads to which electricity utilities supply power had unity power factor, maximum
power would be transferred for the same distribution system capacity. In reality,
however, loads have power factors ranging from 0.2 to 0.9, and the lower power
factors place additional stress on the electrical distribution network. Low power factors
result largely from part load operation of motors and other equipment.
The effects of low power factors are:
• Maximum kVA demand for a given kW load increases.
• Line I2R losses increase considerably.
• On-line voltage drops are higher.
• Gross power consumption increases.
• Distribution system (transformers, cables) bear an increased load.
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The table below shows the kVA requirements (demand) and current drawn at various power factorsby an industrial installation with a 150 kW load requirement.
Example 9: The effects of power factors
Notes:kW = kVA x P.F.Line current = kVA ÷ √3 x voltage in kilovolts
It can be seen that, for the same kilowatt load, line current varies with power factor from208.7 amps to as much as 347.8 amps, i.e. an increase of 66.7 per cent, with acorresponding increase in load on the distribution system, and increase in distribution lossesto 278 per cent.
kVA and current vs power factor (P.F.) for a 150 kW load
Load (kW) P.F. kVA drawn Line current at 415 volts
150
150
150
150
150
0.60
0.70
0.80
0.90
Unity
250
214.3
187.5
166.67
150
347.8
298.1
260.9
231.9
208.7
Electricity suppliers impose penalties on users with low power factors, as these place a
heavy burden on distribution system capacity. There is therefore good reason to
compensate for reactive power.
Compensating for reactive power A very effective and well-established method of improving power factor is to
incorporate capacitors. The capacitor is a device which stores energy in an electric field
and has the characteristic of drawing leading reactive power. In other words, current
in a capacitor leads voltage by 90° and the reactive kVAR is therefore in exact
opposition to inductive kVAR. It therefore tends to nullify the reactive power drawn, as
illustrated below in Figure M.35.
By connecting an appropriately sized capacitor across an inductive load, the effects of
a low power factor can be nullified.
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kW
kVAR
without capacitor
kW
kVAR
with capacitor
kW = kVA
balancingcapacitivekVAR
The reactive power demand at plant level can be reduced to a considerable extent by
using capacitor banks. Maximum demand can also be reduced by maintaining
optimum power factor at the main incoming bus.
High-voltage capacitor banks (suitable for voltages of 11 kV and above) are available
with microprocessor-based control systems. These systems switch the capacitor banks
on and off in accordance with load power factors.
Figure M.35 Balancing inductive and capacitive kVAR
Selecting capacitorsThe figures given in Table M.28 are factors to be multiplied with the input power (kW)
to give the kVAR of capacitance required to change from one power factor to another.
Cleaner Production – Energy Efficiency Manual page 185
Part 2 Technical modules Module 1: Energy use in industrial production
• Type of industry: Food processing (pulverizing and grinding)• Total connected load: 247.5 HP• Maximum demand: 103 kVA• Instantaneous P.F.: 0.85• Existing capacitor banks: 4 x 20 kVAR
It was proposed to provide additional capacitors to improve the instantaneous power factor of highunit loads.
Additional requirement of capacitors to improve the instantaneous P.F. to 0.96 = 30 kVAR
Expected reduction in M.D. = 12 kVA
Savings in demand charges at US$3.0 per kVA M.D. = US$432
Estimated cost of installation = US$200
Simple payback period = Less than 0.5 years
Example 10: Using capacitor banks to reduce power demand
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.518
1.333
1.169
1.020
0.882
0.750
0.484
0.328
0.620
1.189
1.004
0.840
0.691
0.553
0.421
0.291
0.155
1.034
0.849
0.685
0.536
0.398
0.266
0.136
0.899
0.714
0.549
0.400
0.262
0.130
0.763
0.583
0.419
0.270
0.132
Table M.28: Factors for capacitive kVAR
Original P.F. Desired P.F.
1.0 0.95 0.90 0.85 0.80
Cleaner Production – Energy Efficiency Manual page 186
Part 2 Technical modules Module 1: Energy use in industrial production
The power factor for a 30 kW load is to be improved from 0.80 to 0.95. This is obtained as follows:
Size of the capacitor = kW x multiplication factor= 30 x 0.421= 12.63 (or) 13 kVAR
Example 11: Sizing the capacitor
Knowing the existing power factor, Table M.28 can be used to find the factor to raise
the power factor from its present value to a desired value.
For induction motors with different ratings and speeds, to improve power factor to
0.95 and above, the rating of the capacitor (in kVAR) for direct connection to induction
motor or a particular speed can be selected from Table M.29.
1.0
2.0
3.0
4.0
4.5
5.0
5.5
6.0
6.5
7.0
1.5
2.5
3.5
4.5
5.0
6.0
6.5
7.0
8.0
9.0
2.0
3.5
4.5
5.5
6.5
7.5
8.0
9.0
10.0
10.5
2.5
4.0
5.0
6.0
7.5
8.5
10.0
11.0
12.0
13.0
2.5
4.0
5.5
6.5
8.0
9.0
10.5
12.0
13.0
14.5
2.5
5.0
7.5
10.0
12.5
15.0
17.5
20.0
22.5
25.0
1.0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Table M.29: Recommended capacitor rating for direct connection to inductionmotors (in kVAR) (to improve power factor to 0.95 or more)
Motor H.P. Motor speed (rpm)
3000 1500 1000 750 600 500
The rated voltage of the capacitor should be equal to the rated voltage of the system,
provided voltage variation is not more than 10 per cent. If the voltage variation is
more, say 15 percent, the capacitor rating must be higher, so that the maximum
permissible voltage of the capacitor bank is equal to or slightly higher than the
maximum system voltage. For such capacitors, the actual capacity at normal operating
conditions is given by:
Actual kVAR = Rated kVAR x
2Operating voltage
Rated voltage
Location of capacitorsLocation of capacitors is an important factor. For the benefit of electricity boards,connection of capacitors on the H.T. side is good enough. Although the cost of H.T.capacitor per kVAR is low, the cost of the associated switchgear is quite high. Apartfrom this, plant operations may be affected significantly from time to time because ofcapacitor problems. There is also a possibility that all of the reactive current will flowthrough the L.T. cable and transformers, leading to higher losses.
Alternatively, the capacitors can be connected on the L.T. side of the main substation,although this does not help in reducing distribution losses. The best solution forlocation of capacitors is to connect at load centres, e.g. connecting capacitors directlyto motors or group of motors at motor control centres. Operation of capacitorswithout load is not a significant problem as the plant will be operated under leadingP.F. and voltage may rise to a small extent. Automatic P.F. correction control is alsoavailable and is required only in special cases.
Correction of P.F. at motors has a number of advantages, since induction motors arethe main source of reactive currents in every industrial plant. Advantages include:absence of additional switchgear; no separate control of capacitor required forswitching on and off; reduced effect of motor inrush; etc.
On the other hand, there are common problems associated with direct connection:excess voltage due to self-excitation after switching off; and large transient torque afterfast reclosure. Generally, compensation at motor terminals is restricted to correctingthe no load current so that the P.F. at full load is corrected to 0.9–0.95 and, at partialload, the P.F. is near to unity. Table M.30 gives typical values of capacitors to beconnected directly with induction motors.
Other types of load requiring use of capacitors include induction furnaces, inductionheaters, arc welding transformers, etc. The capacitors are normally supplied withcontrol gear for use with induction furnaces and induction heating applications, asfrequency is often different and, essentially, load characteristics change during meltingor heating cycles. P.F.s for arc furnaces vary widely over the melting cycle, changingfrom 0.7 at the start to 0.9 at the end of the cycle.
Power factors for arc welders and resistance welders are corrected by connectingcapacitors across the primary winding of the transformers, without which their P.F.would be around 0.35. The recommended capacitor ratings for various sizes of weldingtransformers are given in Table M.31.
Cleaner Production – Energy Efficiency Manual page 187
Part 2 Technical modules Module 1: Energy use in industrial production
Cleaner Production – Energy Efficiency Manual page 188
Part 2 Technical modules Module 1: Energy use in industrial production
2
4
5
7
12.5
23
33
42
50
2.5
4.5
6
9
16
26
36
45
53
3.5
5.5
7.5
10.5
18
28
38
47
55
5
10
15
25
50
100
150
200
250
2
3
4
6
11
21
31
40
48
Table M.30: Capacitors for induction motors (kVAR)
Motor H.P. Motor speed (rpm)
3 000 1 500 1 000 750
9
12
18
24
30
4
6
8
12
18
Table M.31: Recommended capacitor ratings for welding transformers
Welding transformer rating (kVA)
Single-phase
57
95
128
160
16.5
30
45
60
Three-phase
Capacitor rating (kVAR)
M1.9 Electric drives and electrical end-use equipment
M1.9.1 Electric motors
More than 85 per cent of electricity consumed by industry passes through electric
motors. However, motors constitute only an interim stage in energy conversion, as the
motor shaft power is used to drive equipment of which the efficiency is also vital if
overall electricity consumption is to be optimized. The simple example in Figure M.36
illustrates the point.
Cleaner Production – Energy Efficiency Manual page 189
Part 2 Technical modules Module 1: Energy use in industrial production
Figure M.36 Comparison of efficiency effects
Input = 50 kW
Case 1: Existing
Case 2: Motor replaced for efficiency
Case 3: Pump replaced for efficiency
Input = 48.30 kW
Input = 37.95 kW
Motor
Efficiency = 85%
Motor
Efficiency = 88%
Motor
Efficiency = 88%
Output = 42.5 kW
Output = 42.5 kW
Output = 33.39 kW
Pump
Efficiency = 55%
Pump
Efficiency = 55%
Pump
Efficiency = 70%
Delivery = 23.375 kW
Delivery = 23.375 kW
Delivery = 23.375 kW
Electric motors are intrinsically highly efficient and the margins for savings from their
replacement or improvement are low in comparison to those for driven equipment,
where much higher savings can be obtained.
Squirrel cage induction motors, the mainstay in industry, have operational efficiency of
85–95 per cent, depending on the HP rating, rpm, age, and extent of loading.
Given the increasing costs of electricity, replacement of old and rewound motors by
energy-efficient ones can be advantageous, especially if the motors run for long hours.
The margin for kW savings is given by the following equation:
Cleaner Production – Energy Efficiency Manual page 190
Part 2 Technical modules Module 1: Energy use in industrial production
% kW savings =(New efficiency – Old efficiency) x 100
New efficiency
It should also to be appreciated that, at today’s electricity costs, the running cost of a
motor is 8 to 10 times its investment cost. It is therefore highly advisable to select
higher efficiency motors in the first place.
Recent technologies that improve motor operation and energy efficiency are:
• Electronic soft starters, to optimize inrush starting currents and increase life.
• Variable speed drives, to optimize energy needs in cases where capacity control is
needed.
Recommended good operational practices are:• Operating motor with correct, balanced voltage, giving 3–5 per cent savings and
longer life.
• Proper lubrication, to maintain efficiency and reduce failures.
• Proper ventilation and heat evacuation, to reduce failures and enhance life.
• Power factor correction at motor terminals is recommended, especially in cases
where H.P. ratings are over 50 and where running periods are long.
• Regular check on motor loading (amps) is recommended, to monitor variations.
• Alignment, bearings, cable terminations, lubrication and V-belt tension (in case of
belt drives) are points that warrant regular attention for safe/smooth operation.
Variable speed drivesBy design, common squirrel cage induction motors run at nearly constant speed.
Conversely, pumps, fans, compressors, conveyors, rolling mills, crushers, extruders and
many other motor applications are subject to load variation and require capacity
control. Some traditional forms of control, such as throttling, valves, damper
operations, bypass operations, have very poor energy efficiency.
A variety of variable speed drive alternatives are available to help improve energy
efficiency, offering a much more elegant method of speed and capacity control for
driven machines. Table M.32 presents a menu of advantages and disadvantages.
Cleaner Production – Energy Efficiency Manual page 191
Part 2 Technical modules Module 1: Energy use in industrial production
Variable pulley sheaves
Gears
Chains
Friction drives
Multi-speed motors
Eddy-current drives
Max. speed ratio 10:1
Fluid coupling drives
Max. speed ratio 5:1
Low cost
Low cost
Low cost
Low cost
Operation at 2 or 4 fixed speeds
Simple, relatively low cost,
stepless speed control
Simple, relatively low cost,
stepless speed control
Low efficiency
High maintenance costs
Low efficiency
High maintenance costs
Low efficiency
High maintenance costs
Low efficiency
High maintenance costs
Stepped speed control, lower
efficiency than single-speed motors
Low efficiency at less than 50%
rated speed
Low efficiency at less than 50%
rated speed
Voltage control
<25 kW, 20–100%
Voltage source inverter
(VSI) <750 kW, 100:1
Current source inverter
(CSI) <25 kW, 10–150%
Pulse width modulation
(PWM) < 750 kW, 100:1
Simple, low cost
Good efficiency, simple
circuit design
Regenerative braking, simple
circuit design
Good power factor,
low distortion
Harmonics, low torque, low efficiency,
limited speed range
No regenerative braking, problems at
low speed (< 10%)
Poor power factor, poor performance
at low speed
No regenerative braking, slightly less
efficient than VSI
Table M.32: Speed control alternatives for AC induction motors
VSD Type
Electro-mechanical control methods
Solid-state electronic control methods
Advantages Disadvantages
Example follows …
The table below shows measurements before and after installation of a PWM inverter variablespeed drive on a 45-kW, 4-pole blower fan motor in a yarn quenching application in a textile mill,indicating potential savings.
Example 12: Comparison before and after a variable speed drive installation
Cleaner Production – Energy Efficiency Manual page 192
Part 2 Technical modules Module 1: Energy use in industrial production
Note:Savings high at part loads, i.e. at low damper openings
Data before and after variable speed drive installation
Discharge pressure Damper opening (%)
With damper control
With speed control
Input power (kW)
3.6
4.8
5.4
6.8
3.0
3.4
4.8
5.6
6.8
30
40
60
70
100
100
100
100
100
34.83
37.71
38.33
42.52
15.40
17.44
21.71
26.32
32.25
Cleaner Production – Energy Efficiency Manual page 193
Part 2 Technical modules Module 1: Energy use in industrial production
Worksheet: Electric motor rated specifications
Seri
al n
o.
Mot
or d
rive
ref
.
Type
Pow
er in
put
(kW
)
Volt
age
(kV
)
Full
load
cur
rent
(Am
ps)
Pow
er f
acto
r(P
.F.)
Spee
d (r
pm)
Freq
uenc
y (H
z)
Effic
ienm
cy (
%)
Worksheet: Electric motor load survey
Seri
al n
o.
Mot
or d
rive
ref
.
Rate
d po
wer
(kW
)
Volt
age
(kV
)
Cur
rent
(Am
ps)
Pow
er f
acto
r(P
.F.)
Act
ual i
nput
pow
er (
kW)
Act
ual o
utpu
tpo
wer
(kW
)
% m
otor
lo
adin
g(w
.r.t.
rat
ed)
Actual measured electrical parameters
Note: ‘Type’ could include: induction motor, direct current (DC); synchronous motor
Notes:Actual output power = Actual measured motor input power x Rated motor efficiency factor
% motor loading = Actual measured output power
Rated motor power
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M1.9.2 Transformers
A transformer is a device that transfers energy from one AC system to another.
Transformers receive energy at one voltage and deliver it at another. This allows
electrical energy to be generated at relatively low voltages; to be transmitted at high
voltages and low currents (reducing line losses); and to be used at safe voltages.
Transformers consist of two or more coils that are electrically insulated, but
magnetically linked. The primary coil is connected to the power source; the secondary
coil connects to the load. The turns ratio is the ratio of the number of turns in the
primary coil to the number of turns on the secondary. The secondary voltage is equal
to the primary voltage multiplied by the turns ratio. Ampere-turns are calculated by
multiplying the current in the coil by the number of turns. Primary ampere-turns are
equal to secondary ampere-turns. Voltage regulation of a transformer is the percentage
increase in voltage from full load to no load.
Losses and efficiency
• Transformers are inherently very efficient, by design.
• Efficiency varies from 96 per cent to 99 per cent.
However, transformer efficiency depends on load (% loading), making efficiency
dependent not only design but also on the effective operating load.
Transformer losses are of two types:
1. No-load loss, also referred to as ‘core loss’—the power consumed to sustain the
magnetic field in the transformer's core.
2. Load loss—associated with full-load current flow in the transformer windings and
due, primarily, to the resistance of the winding material. Because transformers
traditionally used copper windings, load loss is also referred to as ‘copper loss’.
From Ohm’s Law for power in a resistor (P=I2R), copper loss varies with the square
of the load current.
3. For a given transformer:
PTOTAL = PNO-LOAD + (% Load/100)2 x PLOAD
where % load = (actual load of transformer / rated power of transformer).
Cleaner Production – Energy Efficiency Manual page 194
Part 2 Technical modules Module 1: Energy use in industrial production
Reducing transformer losses
A. Proper transformer sizing
Greatly oversized transformers can contribute to inefficiency. When transformers are
matched to their loads, efficiency increases (see Table M.33).
Cleaner Production – Energy Efficiency Manual page 195
Part 2 Technical modules Module 1: Energy use in industrial production
100
125
160
200
250
315
400
500
630
800
1 000
500
570
670
800
950
1 150
1 380
1 660
1 980
2 400
2 800
2 000
2 350
2 840
3 400
4 000
4 770
5 700
6 920
8 260
9 980
11 880
97.5
97.66
97.81
97.90
98.02
98.15
98.23
98.28
98.37
98.45
98.54
kVA No-load loss (W) Full-load loss Efficiency
Table M.33: Losses in distribution transformers
100
160
200
250
315
500
630
750
1 000
60
90
110
160
180
240
300
360
430
1 635
2 000
3 000
3 280
4 000
5 600
6 300
7 200
9 000
Transformer kVA No-load loss (W) Full-load loss copper loss (W)
Table M.34: Amorphous core transformer losses
B. Energy efficient amorphous transformers
Amorphous iron is expensive but reduces core loss to less than 30 per cent of
conventional steel core losses. An alternative, less expensive core material is silicone
steel which has higher losses than amorphous iron but lower than standard carbon
steel (see Table M.34).
Cleaner Production – Energy Efficiency Manual page 196
Part 2 Technical modules Module 1: Energy use in industrial production
Worksheet: Transformer rated specifications
Sectionno.
Parameterreference
Units Transformer reference
1 2 3 4
1
2
3
4
5
6
7
8
9
10
Power rating
Primary voltage(high voltage)
Secondary voltage(low voltage)
Voltage ratio(HV/KV)
Primary current
Secondary current
Impedance
Power factor
No-load losses
Full-load losses
kVA
kV
kV
–
Amps
Amps
Ohms
–
kW
kW
Worksheet: Transformer operational parameters
Sectionno.
Parameterreference
Units Transformer reference
1 2 3 4
1
2
3
4
5
Power rating
Primary (average values)
a) Voltage
b) Current
c) Power Factor
d) Power Input
Secondary (average values)
a) Voltage
b) Current
c) Power Factor
d) Power Output
Efficiency
3d x 100
2d
% Loading
kVA
Volts
Amps
–
kVA kW
Volts
Amps
–
kVA kW
%
%
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Cleaner Production – Energy Efficiency Manual page 197
Part 2 Technical modules Module 1: Energy use in industrial production
M1.9.3 Pump systems
Pumps are only one component of pumping systems which also include motors, drives,
piping and valves. Typically, much less than half the electricity input to a pumping
system is converted into useful movement of fluid. The rest is dissipated in the various
components that make up the system. Energy losses are even greater when the system
is not operating at its design point. There is, therefore, a considerable potential for
saving electricity, by both improving component efficiencies and through better
system design.
Centrifugal pumpsCentrifugal pumps are used for the vast majority of pump applications in industry.
Centrifugal pumps impart energy to the fluid by centrifugal action. They rely on the
flow of fluid to create a seal to prevent fluid flowing backward through the pump. The
volute type (see Figure M.37) is the most common centrifugal design. The impeller
vanes generally curve backwards, but radial and forward vanes are also used. The
velocity head of the fluid is converted into pressure head.
Figure M.37 Volute centrifugal pump casing design
Discharge
Impeller
Impeller vanes
Suction
Volute casing
Casing drain
Need for careful selection of pumpsThe characteristic curve of a centrifugal pump is shown in Figure M.38. Pumps have to
be selected so that they operate at their best efficiency point. Oversizing of flow during
initial selection can lead to shifting of the efficiency point, resulting in reduced
operational efficiency. An oversized pump also needs to be throttled for reduced flow
conditions.
The relationship between head, capacity and power is given by the following equation:
Cleaner Production – Energy Efficiency Manual page 198
Part 2 Technical modules Module 1: Energy use in industrial production
Figure M.38 Characteristic curve of a centrifugal pump
Head
capacity
300 gpm68 m3/h
250 ft.76 m
156 ft.47 m
A
B
C
D
E
55% 60%50%
Best efficiency point
Head (metres) x capacity (m3/h)
360= kW
The following example shows how the most appropriate size of pump can be selected
in practice.
Cleaner Production – Energy Efficiency Manual page 199
Part 2 Technical modules Module 1: Energy use in industrial production
A facility needed to pump 68 m3/hr to a 47 metre head with a pump that is 60 per cent efficientat that point.
Liquid power: 68 x 47 / 360 = 8.9 kW (Where ‘360’ is a constant)Shaft power: 8.9 / 0.60 = 14.8 kW (Where 0.6 is the efficiency at that point)Motor power: 14.8 / 0.9 = 16.4 kW (Where 0.9 is the motor efficiency)
As shown in Figure M.38, impeller ‘E’ is the one that should be used to do this, but the pump isoversized, so the larger impeller ‘A’ is used with the pump discharge valve throttled back to68 m3/hr, giving an actual head of 76 metres.
The kilowatts now look like this: 68 x 76 / 360 = 14.3 kW being produced by the pump, and 14.3 / 0.50 = 28.6 kW required todo this. Subtracting the amount of kilowatts that should have been used gives: 28.6 – 14.8 = 13.8 extra kilowatts being used to pump against the throttled discharge valve.
Extra energy used = 8 760 hrs (i.e.1 yr) x 13.8 = 120 880 kW.
For the facility in question, that meant a saving of US$10 000/year.
In this example the extra cost of the electricity could almost equal the cost of purchasing two orthree pumps.
NOTE: Why the oversized pump?
• Safety margins were added to the original calculations.
• Several people were involved in the pump buying decision, and each of them was afraid ofrecommending a pump that would prove to be too small for the job.
• It was anticipated that a larger pump would be needed in the future, so it was purchased nowto save buying the larger one later on.
• It was the only pump the dealer had in stock and a pump was needed badly. The dealer mayhave proposed a ‘special deal’ on the larger size.
• The pump was taken out of the spare parts inventory. Capital equipment money is scarce so thelarger pump appeared to be the only choice.
Example 13: Pump selection
Affinity laws for pumpsThe basic laws governing a pump are:
Cleaner Production – Energy Efficiency Manual page 200
Part 2 Technical modules Module 1: Energy use in industrial production
Q1 / Q2 = N1 / N2,
e.g.: 100 / Q2 = 1750/3500,
Q2 = 200 GPM
H1/H2 = (N12) / (N22)
e.g.: 100 / H2 = 1750 2 / 3500 2
H2 = 400 Ft
P1 / P2 = (N13) / (N23)
e.g.: 5/P2 = 17503/ 35003
P2 = 40
Where: Q = discharge head
H = head
N = rpm
P = power
Flow control strategiesVarying flow requirements can be met by conventional and low cost options such as
by pass control or throttle control, but both of these methods are highly energy
inefficient. There are occasions when permanent change in the amount of fluid
pumped or a change in the discharge head of a centrifugal pump may be desirable.
This can be achieved economically by trimming the impeller or replacing it with a
reduced size impeller or, at the worst, replacing the pump itself.
The most efficient way to deal with varying flows is by means of a variable speed drive.
This ensures that the pump always operates at the best efficiency point and eliminates
the need for any throttling. The virtue of this method is that it reduces the energy input
to the system instead of dumping the excess. With decreasing costs in power
electronics, variable speed drives are becoming more popular today.
Variable flow requirements can also be met by multiple pump operation, with pumps
switching on and off as required.
Cleaner Production – Energy Efficiency Manual page 201
Part 2 Technical modules Module 1: Energy use in industrial production
Figure M.39: Rated pressure vs. rated flow
00
per
cent
rat
ed p
ress
ure
per cent rated flow
20
40
60
80
100
20 40 60 80 100 120
100%
80%
60%
40%
20%
Plm
Ppm
Worksheet: Pump rated specifications
Sectionno.
Parameter reference Units Pump reference
1 2 3 4
1
2
3
4
5
6
7
8
9
10
11
Make
Type (reciprocating/centrifugal)
Discharge capacity (flow)
Head developed
Density of fluid handled
Temperature of fluid handled
Pump input power
Pump speed
Pump efficiency
Specific power consumption
Pump motor:
Power
Full-load current
Voltage
Power factor
Speed
Frequency
Efficiency
m3/hr
mwc
kg/m3
°C
kW
rpm
%
kW/(m3/hr)
kW
Amps
Volts
PF
rpm
Hz
%
OPEN FILE
Cleaner Production – Energy Efficiency Manual page 202
Part 2 Technical modules Module 1: Energy use in industrial production
Worksheet: Pump performance evaluation
Sectionno.
Parameter reference Units Pump reference
1 2 3 4
1
2
3
4
5
6
7
8
9
10
11
12
13
Fluid flow measured or estimated (Q)
Suction pressure (include head correctiondue to pressure gauge location)
Discharge pressure (include headcorrection due to pressure gauge location)
Total dynamic head (3–2) (TDH)
Density of the fluid (γ)
Motor input power (P)
Frequency
Combined efficiency (pump + motor)(Q x γ ) x 9.81 x (TDH/γ) x 100
P
Pump efficiency =Combined efficiency x 100
motor efficiency
Specific power consumption
% Motor loadingw.r.t rated power
% Pump loadingw.r.t rated capacity
% Pump loadingw.r.t design TDH
m3/sec
mwc
mwc
mwc
kg/m3
kW
Hz
%
%
kW/(m3/hr)
%
%
%
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M.1.9.4 Fan systems
IntroductionFans and blowers provide air for ventilation and industrial process requirements. They
are distinguished by the method used to move the air, and by the system pressure at
which they must operate. As a general rule, fans operate at pressures up to around 2 psi,
blowers at between 2 psi and 20 psi, although custom-designed fans and blowers may
operate well above these ranges. Air compressors are used for systems requiring more
than 20 psi. Figure M.40 shows the components of a centrifugal fan, one of the most
widely used air movers. The role of the components is explained below.
Cleaner Production – Energy Efficiency Manual page 203
Part 2 Technical modules Module 1: Energy use in industrial production
• Air inlet—air enters the turning impeller wheel.
• Impeller wheel—imparts energy to the air in the form of motion and pressure. As
the wheel turns, air between the blades is moved in the direction of the blade
and accelerated outward by centrifugal force.
• Shaft—turned by a motor coupled either directly to the shaft or via V-belts and
pulleys.
• Scroll housing—directs air from the impeller wheel to the fan outlet efficiently.
• Outlet—typically connected to a duct distributing the air to where it is needed.
Fans generate a pressure to move air (or other gases) against a resistance caused by
ducts, dampers, or other system components. The fan rotor receives energy from a
rotating shaft and transmits it to the air. The energy appears in the air, downstream of
the fan, partly as velocity pressure and partly as static pressure. The ratio of static to
velocity pressure varies for different fan designs. Fans are typically characterized by the
algebraic sum of the two pressures, known as total pressure. Parts of the fan other than
the rotor (such as the housing, straightening vanes, and diffusers) influence the ratio
of velocity and static pressure at the outlet, but do not add energy to the airflow.
Figure M.40 Fan system components
Air outlet Impeller wheel
Shaft
Air inlet
Scroll housing
Typical applications and efficienciesFan and blower selection depends on the volume flow rate, pressure, type of material
handled, space limitations, and efficiency. Fan efficiencies differ from design to design
and also between types. A range of fan efficiencies is shown in Table M.35. Table M.36
lists a few of the many applications and the type of equipment typically used.
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Figure M.43 variable speed drives for fans and pumps
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Worksheet: Operating parameters and performance
Sectionno.
Parameter reference Units Fan reference
1 2 3 4
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Fluid (medium) flow (Q)(measured using pitot tube at fandischarge)
For suction pressure (measured at fan inlet using U-tubemanometer)
For discharge pressure (measured at fan discharge usingU-tube manometer)
Total head developed (TDH)[3–4/1000]
Temperature of fluid medium (measured at fan inlet using athermometer)
Density of fluid medium handled (r)(taken from standard data andcorrected to operatingtemperature/pressure conditions)
Motor input power (P) measured atmotor terminals or switchgear usingpanel or portable energymeter/power analyser
Frequency
Combined efficiency ( fan + motor)(Q x r) (9.81) (TDH/r) x 100
P x 1000
Fan efficiency =Combined efficiency x 100
Motor efficiency
% Motor loading w.r.t rated power
% Motor loading w.r.t rated capacity
% Motor loading w.r.t rated head
Specific power consumption
m3/sec
mmWC
mmWC
mWC
°C
kg/m3
kW
Hz
%
%
%
%
%
kW/(m3/h)
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M1.9.4 Compressed air systems
Compressed air is used in almost all types of industries and accounts for a major share
of the electricity used in some plants. It is used for a variety of end-uses such as
pneumatic tools and equipment, instrumentation, conveying, etc. and is preferred in
industry because it is convenient clean, readily available and safe. Compressed air is
probably the most expensive form of energy available in a plant, yet it is still often
chosen for applications for which other energy sources would be more economical—
for example, pneumatic grinders are chosen rather than electric ones.
As a general rule, compressed air should only be used if safety improvement, significant
productivity gains, or labour reductions will result. Typical overall efficiency is around
10 per cent.
Depending on requirements, compressed air systems consist of a number of
components: compressors, receiver, filters, air dryers, inter-stage coolers, oil separators,
valves, nozzles and piping. Figure M.44 shows a system layout.
The compressor is the main system component—it must therefore be selected
carefully. The most commonly used compressors in industry are reciprocating and
screw types. Centrifugals are also used where very large volumes are required.
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Figure M.44 Layout of a compressed air system
Reciprocating compressorsA reciprocating compressor (see Figure M.45) is a positive displacement machine that
uses a piston moving inside a cylinder to produce compression. The piston moves
through the cylinder, sucking in atmospheric air at one
end of its stroke and compressing it at the other.
Reciprocating compressors are available as ‘oil-free’ or ‘lubricated’ types. The reciprocating
compressor probably accounts for most of the compressors used worldwide.
Screw compressorsA screw compressor (see Figure M.46) is a positive displacement machine that uses a
pair of intermeshing rotors instead of a piston to produce compression. The rotors
comprise helical lobes fixed to a shaft.
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Figure M.45 A reciprocating compressor
First stage
Second stage
Baseplate Crankcase (frame)Drive motor
Figure M.46 A screw compressor
One rotor, called the male rotor, will typically have four bulbous lobes. The other,female, rotor has valleys machined into it that match the curvature of the male lobes.Typically, female rotors have six valleys meaning that for one revolution of the malerotor, the female rotor only turns through 240°. For the female rotor to complete onecycle, the male rotor has to rotate 1.5 times. Screw compressors are available as oil-freemachines, oil-lubricated machines and, more recently, as water lubricated machines.
CP-EE options in compressed air systemsA comprehensive compressed air system audit should include an examination of both airsupply and usage and the interaction between supply and demand. An audit determinesthe output (flow) of a compressed air system, energy consumption in kilowatt-hours,annual cost of operating the system and total air losses due to leaks. All components of thecompressed air system are inspected individually and problem areas are identified. Lossesand poor performance due to system leaks, inappropriate use, demand events, poor systemdesign, system misuse, and total system dynamics are evaluated and CP-EE measures arederived. Important aspects of a basic compressed air system audit are discussed below.
Pressure dropA properly designed system should have a pressure loss of much less than 10 per centof the compressor's discharge pressure, measured between the receiver tank outputand the point of use. Excessive pressure drop will result in poor system performanceand excessive energy consumption.
LeaksAs illustrated by Figure M.47, leaks can be a significant source of wasted energy in anindustrial compressed air system, sometimes wasting 25–50 per cent of a compressor'soutput. Proactive leak detection and repair can reduce leaks to less than 10 per cent ofcompressor output.
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Size Cost per year
1/16" US$523
1/8" US$2 095
1/4" US$8 382
Figure M.47 Leaks and losses
Cost calculated using electricity rate of US$0.05 per kWh,assuming constant operation and an efficient compressor.
In addition to being a source of wasted energy, leaks can also contribute to other
operating losses. Leaks cause a drop in system pressure, which can make air tools
function less efficiently, adversely affecting production. In addition, by forcing the
equipment to cycle more frequently, leaks shorten the life of almost all system
equipment (including the compressor package itself). Increased running time can also
lead to additional maintenance requirements and increased unscheduled downtime.
Finally, leaks can lead to addition of unnecessary compressor capacity.
Leakage can come from any part of the system, but the most common problem areas
are couplings, hoses, tubes, and fittings, pressure regulators, open condensate traps
and shut-off valves and pipe joints, disconnects, and thread sealants.
Estimating amount of leakage For compressors that use start/stop controls, there is an easy way to estimate the
amount of leakage in the system. This involves starting the compressor when there are
no demands on the system (i.e. when all the air-operated end-use equipment is turned
off). A number of measurements are taken to determine the average time it takes to
load and unload the compressor. The compressor will load and unload because the air
leaks will cause it to cycle on and off as the pressure drops from air escaping through
the leaks. Total leakage (percentage) can be calculated as follows:
where: T = on-load time (minutes)
t = off-load time (minutes)
Leakage will be expressed in terms of the percentage of compressor capacity lost. The
percentage lost to leakage should be less than 10 per cent in a well-maintained system.
Poorly maintained systems can have losses as high as 20–30 per cent of air capacity
and power. These tests should be carried out quarterly, as part of a regular leak
detection and repair programme.
Leak detection Since air leaks are almost impossible to see, other methods must be used to locate
them. The best way to detect leaks is to use an ultrasonic acoustic detector that
recognizes the high frequency hissing sounds associated with air leaks. These portable
units consist of directional microphones, amplifiers, and audio filters, and usually have
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Leakage (%) = (T x 100)
(T + t)
either visual indicators or earphones to detect leaks. A simpler method is to apply
soapy water with a paintbrush to suspect areas. Although reliable, this method can be
time consuming.
How to fix leaks Leaks occur most often at joints and connections. Stopping leaks can be as simple as
tightening a connection or as complex as replacing faulty equipment such as
couplings, fittings, pipe sections, hoses, joints, drains, and traps. In many cases leaks
are caused by bad or improperly applied thread sealant. Select high quality fittings,
disconnects, hoses, tubing, and install them properly with appropriate thread sealant.
Non-operating equipment can be an additional source of leaks. Equipment no longer
in use should be isolated by a valve in the distribution system. Once leaks have been
repaired, the compressor control system should be re-evaluated to ascertain the total
savings potential
A leak prevention programmeA good leak prevention programme will include the following components: identification
(including tagging), tracking, repair, verification, and employee involvement. All facilities
with compressed air systems should establish an aggressive leak prevention programme.
A cross-cutting team involving decision-making representatives from production should be
formed. The leak prevention programme should be part of an overall programme aimed
at improving the performance of compressed air systems. Once leaks are found and
repaired, the system should be re-evaluated.
Rationalization of compressed air useThe need for compressed air should be questioned at every usage point. In some
instances, the volume of air may be more important than pressure. Under such
circumstances alternative options like centrifugal blowers or roots blowers can be
considered. Misuse of compressed air for cleaning should be avoided.
Using lower pressureCompressor discharge pressure should be closely matched with the requirement
(allowing for pressure drops in the distribution system). Higher than necessary
discharge pressure is detrimental to performance since it increases the compression
ratio and hence the power consumption.
Table M.39 illustrates the effect of increased discharge pressure on specific power
consumption of reciprocating compressors.
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Heat recoveryAs much as 80–93 per cent of the electrical energy used by an industrial air compressor
is converted into heat. In many cases, a properly designed heat recovery unit can
recover anywhere from 50–90 per cent of this available thermal energy and put it to
use heating air or water.
Typical uses for recovered heat include additional space heating, industrial process
heating, water heating, make up air heating, and boiler make up water preheating.
Recoverable heat from a compressed air system is not, however, normally hot enough
to be used to produce steam directly.
Use of multiple compressorsWhen the demand on a compressed air system is variable in nature, and exhibits well
defined peak and slack demand periods, use of a single compressor designed to meet
peak demand would lead to under-loading of the compressor and increased duration
of the no-load cycle. Unloading power is 30 per cent of full load power. In this
situation, energy savings can be realized by using multiple compressors. The number
of compressors in operation is adjusted to the compressed air demand, thereby
avoiding under-loading of compressors.
Replacement/de-rating of oversized compressors In the case of oversized compressors, the power wastage during unloading can be
reduced by either replacing the compressor in the case of oversized machines, or by
de-rating. De-rating can be achieved by running the compressor at a lower speed.
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1
2
3
4
7
8
10
15
Single
Single
Single
Single
Double
Double
Double
Double
21.1
20.3
19.3
18.0
19.0
18.9
19.5
19.2
2.22
3.40
4.60
5.14
6.47
6.76
7.67
9.25
Pressure (bar) No. of stages Volume flow(m3/min)
Specific power(kW/m3/min)
Table M.39: Effect of increased discharge pressure on specific power consumption
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Empirical relationsSome useful empirical relationships for compressors are given below:
Leakage (Nm3/min) =
x (Compressor capacity Nm3/min)
Compressor Capacity (FAD) Nm3/hr =
Specific power consumption =
Load time
Unload time + Load time( )
Initial receive pressure kg/cm2.a – final receiver pressure kg/cm2.a
Atmosphere pressure kg/cm2.a( ) x
xVolume of receiver + volume of line between compressor and receiver in m3
Time taken to fill receiver from initial pressure to fonal pressure in minutes( )273
273 + reciever temperature °C( )
Actual motor power input
FAD (Nm3/m)( ) x 100
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Worksheet: Compressor rated specification
Air compressor reference Units Compressor reference
1 2 3 4
Make
Type
No. of stages
Discharge capacity
Discharge pressure
Speed
Receiver capacity
Motor rating
Power
Full load current
Voltage
Power factor
Speed
Frequency
Specific power consumption
–
–
–
Nm3/min
kg/cm2.g
rpm
m3
kW
Amps
Volts
P.F.
rpm
Hz
kW/m3/min
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Worksheet: Capacity testing
Air compressor reference Units Compressor reference
1 2 3 4
Receiver volume plus volumeof pipeline between receiverand the air compressor
Receiver temperature
Initial receiver pressure (P1)
Final receiver pressure (P2)
Time taken to fill receiverfrom P1 to P2 (t)
Atmospheric pressure (Po)
Air compressor capacity (free air delivery) Q
m3
°C
kg/cm2.a
kg/cm2.a
mins.
kg/cm2.a
Nm3/min
Note: Each compressor must have its own receiver.
Procedure:
1) The air compressor being tested for capacity is first isolated from the rest of thesystem, by operating the isolating non-return valve.
2) The compressor drive motor is shut-off.
3) The receiver connected to this air compressor is emptied.
4) The motor is re-started.
5) The pressure in the receiver begins to rise. Initial pressure, say 2 kg/cm2 , is noted. The stopwatch is started at this moment.
6) The stopwatch is stopped when receiver pressure has risen to, say, 9 kg/cm2.
7) Time elapsed is noted.
8) Compressor capacity is evaluated as:
(Nm3/min) = x xP2 – P1
P0 )( 273
273 + T)(Vr
t )(
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Worksheet: Leakage testing
Compressor in operation Units Names of section of factory
Compressed air users
Load time (t1)
Unload time (t2)
Capacity of compressor
Leakage
Leakage cfm
x (Capacity of compressor)
--
Seconds
Seconds
Nm3/min
%
Two (assumed)
(Measured)
(Measured)
(Given)
(Evaluated)
(Evaluated)
Note:
1) Per cent or Nm3/min of compressed air leakage is evaluated, and the energy cost ofcompressed air is determined.
2) Plant survey is undertaken to physically identify obvious compressed air leakages. Noinstruments are really necessary. However, an ultra-sonic leak detector may be used,optionally.
3) Elimination of leakage sources leads to direct and immediate compressed air andelectricity cost savings.
Procedure:
1) Leakage test is conducted when entire plant is shut-down or when all compressed airusers are not working. It would be advantageous if separate sections could be isolatedfrom one another by isolating valves.
2) A dedicated compressor is switched on to fill the system network with compressed air.
3) Since there are no compressed air users, the air compressor will unload the momentthe system pressure reaches the set point (say, 8 kg/cm2.g).
4) If the system has no leaks, the air compressor will remain unloaded indefinitely.
5) However, since there are bound to be system leaks, the receiver pressure graduallybegins to drop, until the lower set point is reached, at which point the air compressoris loaded again and begins to generate compressed air.
6) Load and unload times are measured using a stopwatch over 5–6 cycles, and averageload and unload times are worked out.
7) Compressed air leakage (%) and quantity are then evaluated.
t1
t1 + t2x 100)(
Leakage %
100 )(
spotlightCP-EE
• Leakage will beexpressed in terms ofthe percentage ofcompressor capacity lost.
• The percentage lost toleakage should be lessthan 10 per cent in awell-maintained system.
• Poorly maintainedsystems can have lossesas high as 20–30 percent of air capacity.
OPEN FILE
M1.10 Cooling towers
M1.10.1 Basics of cooling towers
Heat removed from a process or building must be disposed of. In many cases, this heat
is transferred to water at a lower temperature via a heat exchanger. It is then
transferred to a heat sink.
Billions of gallons of water are used every day for air conditioning/refrigeration systems
and for industrial process cooling in, for example, paper mills, chemical plants, food
processing, etc. To reduce both water costs
and pressure on water supplies, much of
this cooling water is re-circulated. Final
exchange of heat from a building or
process to a heat sink is often by means of
a water-to-air heat exchanger, with the
atmosphere being the heat sink.
These water-to-air devices are called
cooling towers. They play a vital role in
water conservation, typically reducing
water consumption by 95 per cent or
more, depending on whether an
evaporative or dry tower is used.
From the thermodynamic point of view, there are three basic types of cooling tower.
Wet or evaporative towers are ones in which the water to be cooled comes in contact
with the outdoor air. Both latent and sensible cooling occurs. These towers have the
highest thermal efficiency. They also consume more water than the other two types
(see below), but a 95 per cent saving is still significant.
A dry tower is one in which the water to be cooled flows within an extended heat
transfer surface—a finned tube coil—over which atmospheric air is blown.
The third type of tower is the wet-dry type, which combines the functions of the two
previous types. Table M.40 includes some terminology to aid understanding. The
discussion thereafter focuses on wet towers.
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Air flow
Approach
Capacity controldampers
Casing
Cavitation
Cold water basin
Composite
Concentrationratio
Conductivitymonitor
Cooling range
Cooling tower ton
Counter flow
Cross flow
Cycles ofconcentration
Discharge hood
Drift loss
Dry bulb
Total quantity of air including the associated water vapour flowing through thetower.
Difference between re-cooled water temperature and the inlet air wet bulbtemperature.
Airfoil blades placed at the discharge of a centrifugal fan that change positionso as to regulate airflow.
The part of a cooling tower enclosing the wet deck fill.
The phenomenon that occurs in a water pump when the pressure becomessufficiently low to allow vaporization of the fluid followed by a sudden collapseof the vapour ‘bubble’ as it passes to the high pressure area of the pump.
The collection point near the bottom of a cooling tower for the collection ofcooled water.
Construction material utilizing high strength glass materials held in place bycured epoxy resins in a precise order so as to maximize strength.
Ratio of the total mass of impurities in the circulating water to thecorresponding total mass in the make up water.
A device that measures the ease with which electricity passes through coolingsystem water. Conductivity is directly proportional to the amount of dissolvedsolids in the water and is used to initiate bleeding, feeding chemicals, etc.
Difference between the hot water temperature and the re-cooled watertemperature.
15 000 Btu/hr.
A cooling tower configuration where the air and water flow in oppositedirections.
A cooling tower configuration where the air and water flow at right angles toone another.
The number of times the solids content of water has been increased. Two fold = 2 cycles; three fold = 3 cycles, etc.
A discharge duct with sides that gently taper reducing the cross sectional areathereby accelerating the discharge air. Used to ‘blast’ discharge air from anenclosure to reduce recirculation potential. Note: suitable for centrifugal fantowers only.
Water loss caused by liquid drops carried away by the outlet air stream.
Temperature of air measured with a conventional thermometer with a dry bulb.
Table M.40: Table of cooling tower terminology
continued …
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Eliminator
Equalizer line
Fan deck
Fill
Hot water basin
Latent heat
Louvers
Make up
Psychrometricchart
Purge
Range
Re-circulation
Sensible heat
Ton
Turn down
Velocity recoverystack
Wet bulb
A device placed in the discharge airstream of a cooling tower that attempts to‘eliminate’ entrained water droplets. It works by rapidly changing the directionof airflow causing the heavier water particles to collide with the eliminatorsurface and fall back inside the tower.
A pipe connected between the cold water basins of multiple cooling towers. Itspurpose is to force ‘equalization’ of water levels.
The upper horizontal surface surrounding the fan stacks of a draw-through,propeller fan cooling tower.
Material added to a cooling tower to enhance evaporation.
Water collection area at the top of a crossflow cooling tower the bottom ofwhich is perforated to distribute water over the wet deck fill.
Heat which changes the properties of a material without changing itstemperature.
Horizontal blades placed at the air inlet of some cooling towers to preventwater from splashing out.
Water added to the circulating water system to replace leakage, evaporation,drift loss and purge.
A graphical representation of the physical characteristics of air.
Water deliberately discharged from the system in order to reduce theconcentration of salts and other impurities in the circulating water.
A cooling tower’s inlet water temperature minus its outlet water temperature.
The proportion of outlet air which re-enters the tower.
Heat that increases the temperature of a body to which it is added.
The rate of heat transfer represented by 2 000 tons of ice melting in a 24 hourperiod (12 000 Btu/hr).
The allowable percentage reduction of inlet water flow to a cooling tower.
A hyperbolic discharge plenum at the top of a draw-through, prop. fan coolingtower. The shape increases the efficiency of the fan by converting some of thevelocity pressure to static pressure for increased air flow.
The temperature read from the wet bulb of a thermometer placed in a movingair stream.
… Table M.40: Table of cooling tower terminology (continued)
spotlightCP-EE
Inefficient operation of atower with a cold water
temperature around1.5 °C higher than it
should be can increaseprocess plant energy
consumption by10 per cent or more.
M1.10.2 Energy audit of cooling towers
Cooling towers are energy audited to assess present levels of approach and range
against their design values; to identify areas of energy wastage; and to suggest
improvements. During an energy audit, parameters such as those listed below are
measured, using portable instruments:
• Wet bulb temperature of air
• Dry bulb temperature of air
• Cooling tower inlet water temperature
• Cooling tower outlet water temperature
• Exhaust air temperature
• Electrical readings of pump and fan motors
• Water flow rate
• Air flow rate
The instruments used and the corresponding parameters measured are listed in
Table M.41.
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Various electrical parameters such as kW, kVA, P.F., voltage, current and frequency are
measured using the power analyser. Knowing the percentage loading and power factor
of a motor, it is possible to estimate its operating efficiency from motor characteristic
curves. If efficiency is low, the possibility of replacing it with a new motor may have to
be considered.
Sling hygrometer
Temperature indicator withthermocouple
Flow meter
Anemometer
Power analyser
Wet bulb and dry bulb air temperature
Water temperature
Water flow rate
Air flow rate
Pump and fan electrical parameters
Parameters measuredInstrument used
Table M.41: Instruments and the parameters measured
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Worksheet: Cooling tower performance
Sectionno.
Parameter reference Units Cooling tower reference
1 2
1
2
3
4
5
6
7
8
9
10
11
12
Dry bulb temperature
Wet bulb temperature
CT inlet temperature
CT outlet temperature
Range
Approach
CT effectiveness
Average water flow
Average air quantity
Liquid gas (L/G) ratio
Evaporation loss
CT heat loading
°C
°C
°C
°C
°C
°C
%
kg/hr
kg/hr
kg water/kg air
m3/hr
kcal/hr
Basic equations used
a) CT Range (°C) = [CW inlet temp (°C) – CW outlet temp (°C)]
c) CT Effectiveness (%) = 100 x (CW temp – CW out temp) / (CW in temp – WB temp)
d) L/G Ratio (kg/water/kg air) = Total CW water flow in CT (kg/hr) / Total air flow in CT (kg/hr)
e) CT heat loading (kcal/hr) = CW flow (m3/hr) x ∆T (°C) x density of water (kg/m3)
f) CT evaporation loss (CMH) = CW circulation (CMH) x CW Temp. difference across CT in °C rate / 675
g) % Evaporation loss in cooling tower = Evaporation loss in CMH x 100 / CW circulation rate CMH
OPEN FILE
M1.11 Refrigeration and air-conditioning
Refrigeration is the process of lowering the temperature of a substance below that of
its surroundings. Process industries are the major users of refrigeration facilities.
Refrigeration is used to remove the heat of chemical reactions; to liquefy gases; to
separate gases by evaporation and condensation; and to purify products by preferential
freeze-out of one component from a liquid mixture. It is also extensively used in air-
conditioning of plant areas for comfort, process and thermal environment uses, as well
as in hotels, hospitals and office buildings, etc.
M1.11.1 Unit of refrigeration
Refrigeration capacity is normally expressed in tons of refrigeration (TR).
One ton of refrigeration is the amount of heat extracted to produce one ton of ice at
0 °C from water at 0 °C in 24 hours:
1 TR = 210 kJ/min = 50 kcal/min
M1.11.2 Types of refrigeration
There are two popular types of refrigeration system used in industry: vapour
compression and vapour absorption.
Vapour compression refrigeration systemsFigure M.48 shows the vapour compression refrigeration cycle. The refrigerant enters
a compressor at low pressure and at a temperature a few degrees higher than its
boiling point at that pressure. In the compressor, both the temperature and the
pressure of the refrigerant gas rise. The types of compressors normally employed are:
reciprocating, rotary vane, twin screw, single screw, centrifugal, and scroll.
The hot gas from the compressor then goes into the condenser. The gas first cools
from the compressor discharge temperature to the condensing saturation temperature,
giving up its sensible heat. Most of the heat transfer in the condenser (latent heat)
occurs when the refrigerant changes from a gas to a liquid. The types of condensers
used are: water-cooled shell and tube, air-cooled, and evaporative.
The liquid refrigerant then passes to an expansion valve, where its pressure is reduced,
during which some of the liquid flashes off, forming a mixture of low temperature
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liquid and low temperature vapour. Various types of valves are used: high-pressure float
valves, low-pressure float valves, and thermostatic expansion valves.
The liquid refrigerant passes to the evaporator where it is vaporized at constant
temperature. The refrigerant vapour is then returned to the compressor suction line
and the circuit is complete. Types of evaporators are: direct expansion, flooded shell
and tube, and re-circulation.
Vapour absorption refrigerationVapour absorption systems use a heat source instead of the compressor. This is an
economically attractive proposition where waste heat is available. The working
principle is described in Figure M.49 and important facts are listed below:
• The common commercial absorbent/ refrigerant pair is lithium bromide
(L-Br)/water.
• The refrigerant travels from the evaporator to the absorber as a vapour.
• The absorbent has a strong affinity for the refrigerant and absorbs it, creating a
vacuum (–0.2 psia in a L-Br system); the heat is removed by cooling water.
• The refrigerant–absorbent solution is then pumped towards the condenser,
passing through the generator.
• Heat applied to the generator causes the refrigerant to vaporize, leaving behind
the absorbent liquid.
• The refrigerant vapour, now separated from the liquid absorbent, travels to the
condenser.
• The liquid absorbent is re-circulated to the absorber through the regulating valve,
bringing it down to the evaporator pressure.
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Figure M.48 The vapour compression cycle
high pressure liquid
low pressure liquidand flash gas
expansion valve
CONDENSER
EVAPORATOR
lowpressuregas
highpressuregas
suction
discharge
compressor
M1.11.3 Energy efficiency evaluation
Once a refrigeration system has been installed, its operating efficiency and overall
running costs will be largely determined by the effectiveness of day-to-day monitoring.
The commonly used figures for comparison of refrigeration systems are: the Coefficient
of Performance (COP), Energy Efficiency Ratio (EER), and Specific Power Consumption
(SPC).
If both the refrigeration effect (heat removed from evaporator) and the work done by
the compressor (or the input power) are in the same units (TR or kcal/hr or kW or
Btu/hr), the ratio is:
If the refrigeration effect is expressed in kcal/hr and the work done in watts, the ratio is:
The other commonly used and easily understood useful figure is Specific Power
Consumption (SPC):
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Figure M.49 The vapour absorption cycle
COP = Refrigeration effect
Power supplied
EER = Refrigeration effect (Btu/hr)
Power supplied (Watts)
weaksolution
GENERATOR
ABSORBER
regulatingvalve
strongsolution
condenser
evaporator
throttlingvalve
cooling water
pump
waste heat/direct fired
SPC = Power consumption(kW)
Refrigeration effect (TR)
M1.11.4 Estimation of capacity of refrigeration system and
air-conditioning systems
The capacity of the liquid chilling system can be estimated if water/brine flows and
chiller inlet/outlet temperatures are known:
Where: Q = flow (m3/hr)
d = density (kg/m3)
s = specific heat (kcal/kg/°C)
Tin = temperature at inlet (°C)
Tout = temperature at outlet (°C)
Method of capacity estimation for systems having hot wells and cold wells tobalance primary and secondary refrigerantsFor this method of estimation of refrigeration capacity, the secondary pump (process
side) should be switched off for about 30 to 60 minutes. The compressor and primary
pumps should then be operated and the time to drop the temperature of the
secondary refrigerant in the hot and cold well by about 5 °C should be noted.
Where: V = volume of the secondary refrigerant in the hot and cold well (m3)
d = density of the secondary refrigerant (kg/m3)
∆T = drop in temperature (°C)
t = time taken (hours)
s = specific heat of the secondary refrigerant (kcal/kg/°C)
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Part 2 Technical modules Module 1: Energy use in industrial production
Heat load (TR) = Q x d x s x (Tin – Tout)
3023
Cooling capacity = +V x d x s x dT
(3023 x t)
Primary power pump (kWt)
3.51
M1.11.5 Heat load calculation for centralized air-conditioning systems
Where: Q = flow, m3/hr (can be measured with an anemometer)
D = density, kg/m3 (1.2 kg/m3 approx.)
hin = enthalpy at AHU inlet, kJ/kg
hout = enthalpy at AHU outlet, kJ/kg
(Dry bulb and wet bulb temperatures can be measured at the air-handling unit (AHU)
inlet and outlet; this data can be used with a psychrometric chart to determine the
enthalpy of air at the AHU inlet and outlet.)
The power consumption for these systems can be measured using a portable power
meter or an energy meter—specific power consumption can then be calculated.
Cleaner Production – Energy Efficiency Manual page 231
Part 2 Technical modules Module 1: Energy use in industrial production
Heat load (TR) = Q x d x (hin – hout)
4.18 x 3023
Cleaner Production – Energy Efficiency Manual page 232
Part 2 Technical modules Module 1: Energy use in industrial production
Worksheet: Refrigeration and AC system rated specifications
Sectionno.
Refrigeration compressor Units Machines reference
1 2 3 4
1
2
3
4
5
6
7
Make
Type
Capacity (of cooling)
Chiller:
a) No. of tubes
b) Diameter of tubes
c) Total heat transfer area
d) Chilled water flow
e) Chilled water temp. difference
Condenser:
a) No. of tubes
b) Diameter of tubes
c) Total heat transfer area
d) Condenser water flow
e) Condenser water temp. diff.
Chilled water pump:
a) Nos.
b) Capacity
c) Head developed
d) Rated power
e) Rated efficiency
Condenser water pump:
a) Nos.
b) Capacity
c) Head developed
d) Rated power
e) Rated efficiency
TR
–
m
m2
m3/hr
°C
m
m3/hr
°C
–
m3/hr
mWC
kW
%
–
m3/hr
mWC
kW
%
OPEN FILE
Cleaner Production – Energy Efficiency Manual page 233
Part 2 Technical modules Module 1: Energy use in industrial production
Worksheet: Operating parameters
Sectionno.
Parameter reference Units Refrigeration compressor reference
1 2 3 4
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Chilled water flow (using a flow meter orassessed by level difference)
Overall system specific powerconsumption [(2+17+19+20)/15]
m3/hr
kW
kg/cm2g
kg/cm2g
°C
°C
°C
kg/cm2
kg/cm2
°C
°C
kg/cm2 (or psig)
°C
kg/cm2 (or psig)
TR
–
kW
kW/TR
kW
kW
kW
kW/TR
OPEN FILE
M1.12 Lighting systems basicsA lighting system comprises all of the components necessary to deliver a desired level
of space illumination. It includes components such as switches to control power,
wiring, voltage stabilizers, lighting luminaires, fixtures, control gear, shade of walls,
shape of room, etc. A lighting system is shown in Figure M.50.
Cleaner Production – Energy Efficiency Manual page 234
Part 2 Technical modules Module 1: Energy use in industrial production
Periodic maintenance of the lighting system installed on the shop floor has a profound
impact on the energy consumed. In many industrial lighting systems, the fittings act
as dust traps. If they are not cleaned periodically, they will collect more dust resulting
in lower illumination.
Efficient lamps and luminaires can not only reduce maintenance costs, they can even
lower power consumption. For instance, use of twin-lamp fluorescent fittings with
polystyrene diffusers can provide the same degree of lighting with lower wattage
consumption. Similarly, high pressure sodium lamps provide energy savings of up to
80 per cent compared to high wattage tungsten filament lamps.
Figure M.50 A lighting system
ceiling
wiring
lightingcontrols
switch
electricity in
wall
floor
work surface
fixture
lens or diffuser
wall
desired area of illumination
In some systems, electronic control can provide energy conservation of around 25 per
cent at near unity power factor. Automatic switch off of lights can be provided when
they are not required. Solar or mechanical timer switches can be used to turn off
artificial lighting as soon as the optimum light level is reached.
M1.12.1 Choice of lighting
The following guidelines will help in choosing lighting:
Choose the right light
which is positioned where it is needed
used only when it is needed
for as long as it is need
and at the illumination level needed.
Search for savingsWith so many different types of lighting on the market, levels of efficiency and
performance must be known if the best choice is to be made. Table M.42 gives the
luminous efficiency of various lamp sources.
Cleaner Production – Energy Efficiency Manual page 235
Part 2 Technical modules Module 1: Energy use in industrial production
1
2
3
4
5
6
7
8
Incandescent lamps
Cool daylight fluorescent tubes
White fluorescent tubes
High pressure mercury vapour lamps
80 W
125 W
400 W
High pressure sodium lamps
70 W
250 W
400 W
Low pressure sodium lamps
10 W
18 W
Tungsten halogen
Metal halide
15
50–60
60–85
36
41
52
82
100
117
100
175
25
60–85
1 000
5 000
5 000
5 000
5 000
5 000
10 000
10 000
10 000
10 000
10 000
5 000
5 000
Section no. Efficiency (lumens/watt)
Average workinglife (hours)
Light sources
Table M.42: Luminous efficiencies
The table shows ranges of efficiency and lamp-life. As can be seen, the lighting
efficiency (lumens per watt) of a low-pressure sodium lamp is many times
(10–17 times) greater than that of an incandescent (tungsten-filament) lamp. It should
also be noted that, in general, the efficiency of a specific lamp type is higher for higher
power lamps.
Fittings should always be suitable for the maximum wattage of lamp with which they
are used. Higher wattage of lamps will produce more heat and could damage the
fittings or shade and may even cause a fire.
Fluorescent tube lights are preferred to general lighting service (GLS) lamps because,
for the same amount of electricity consumption, they produce four times the amount
of light obtainable from GLS lamps. The tubes last much longer, as they have a life
of 6 000 to 7 000 hours, although frequent switching on and off shortens this
substantially.
Today, so-called ‘electricity saving’ bulbs can be used as a substitute for tungsten
filament bulbs. These are compact fluorescent tubes which can be screwed into the
existing conventional bulb socket. These compact fluorescent bulbs consume about 80
per cent less electricity than a conventional bulb while producing the same amount of
light. They also have a life about 6 to 8 times longer.
Table M.43 shows norms of illuminance required for various work stations.
M1.12.2 Control of lighting
Even with efficient lamps and luminaires, energy used for lighting can be wasted in
several ways. In general, people usually turn lighting on only when they need it, but
cannot be relied upon to turn it off when daylight would provide adequate light, or
when rooms are unoccupied. The ideal solution would be to provide a manual switch
and some form of control for switching off.
A further source of unnecessary use results from the common practice of controlling
large areas of lighting with small numbers of switches, or by having confusing
switch layouts so that individual requirements can only be met by turning on many
luminaires. Controls are a very effective way of reducing lighting costs, but before
incurring significant capital costs, it is suggested that occupancy patterns and
behaviour be studied.
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Part 2 Technical modules Module 1: Energy use in industrial production
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Part 2 Technical modules Module 1: Energy use in industrial production
General lightingfor rooms andareas usedinfrequentlyand/or casuallyor for simplevisual tasks.
General lightingfor Interiors
20
30
50
75
100
150
200
300
500
750
1 000
1 500
2 000
Minimum service illuminance in exterior circulation areas
Outdoor stores and stockyards
Exterior walkways and platforms, indoor tasks, car parks
Docks and quays
Theatres and concert halls, hotel bedrooms, bathroomsand corridors
Circulation areas in industry, stores and stock rooms
Minimum service illuminance for a task (visual tasks notrequiring any perception of detail)
Rough bench and machine, motor vehicle assembly, printingmachine rooms, general offices, shops and stores, retail salesareas
Medium bench and machine, motor vehicle assembly,printing machine rooms, general offices, shops and stores,retail sales areas
Proofreading, general drawing office, offices with businessmachines
Fine bench and machine work, office machine assembly,colour work and critical drawing tasks
Very fine bench and machine work, instrument and smallprecision mechanism assembly, electronic componentsgauging and inspection of small intricate parts; may bepartly provided by local lighting
Minutely detailed and precise work, e.g. very small parts ofinstruments, watch making and engraving, operating areain operating theatres—2 000 lux minimum
Lighting systems Illuminance (lux)
Table M.43: Luminous efficiencies
Manual controlsSwitch arrangements should at least permit individual rows of luminaires parallel and
nearest to window walls to be controlled separately.
Switches should be as near as possible to the luminaires which they control. One simple
method which has been used effectively is the pull-cord operating ceiling switches
adjacent to each luminaire, or pull-chord switches with timer controls so that the lamp
automatically switches off after a pre-set period.
Automatic controlsa) Photo-electric controls
Photo-electric control of lighting can ensure that lighting is turned off when
daylight alone provides the required illuminance. For example, a photo-electric
sensor could respond to the exterior illuminance at the work place.
b) Time controls
If the occupation of a building effectively ceases at a fixed hour every working
day, it may be worth installing a time switch so that most of the lighting is
switched off at that time.
c) Mixed control systems
Switch control can give considerable energy savings. For instance, a time control
system can switch off all selected lights for fixed period in the day, but personal,
local override (switch on) controls can be provided.
This general principle is well suited to multi-occupant spaces such as group offices.
An idea of wastage of electrical energy due to unnecessary lighting can be obtained
from Table M.44.
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Part 2 Technical modules Module 1: Energy use in industrial production
Cleaner Production – Energy Efficiency Manual page 239
Part 2 Technical modules Module 1: Energy use in industrial production
40 W Tube light
60 W Ceiling fan
100 W Bulb
250 W Air cooler
450 W HPMV lamp
500 W Incandescent lamp
1 HP Electric motor
1 ton Window A.C.
1.5 ton Window A.C.
1 ton Water cooler
15
22
37
91
146
183
137
445
602
308
0.88
1.26
2.14
5.30
8.51
10.03
7.95
25.86
35.03
17.91
Item Consumption (in kWh) Value* (US$)
Table M.44: Loss in electrical energy as a result of misuse or wastage and its value per year
* Cost of electricity is considered as US$0.055 per kWh
Efficient use of energy is an on-going process. Research and development (R&D)
around the world is constantly leading to development of new processes and devices.
The basic objective of major R&D efforts on energy systems is to cut down on waste,
whether in the form of flue gases; heat lost through conduction, convection or
radiation; or to improve efficient use of electrical energy. This chapter presents some
generic examples—most of them well proven—to increase readers’ awareness of
energy systems already available or likely to be so in the future.
M2.1 New electrical technologies
● HVDC transmission system
Reduces distribution losses from 18–22 per cent to 8–10 per cent. Relevant to
The primary fuel requirement to meet heat and power demand is substantially
reduced. Relevant to large process industries such as sugar, pulp and paper,
chemical and petrochemicals, etc.
● Combined cycle based cogeneration plants for industries
Higher system efficiency: 70–80 per cent in the cogeneration mode, compared to
25–36 per cent for conventional thermal stations. Obtained by integration of
thermal and electrical energy from the same source. Relevant to natural gas
consuming process industries with steam demand above 10 TPH.
● Energy efficient DG sets
Lower rpm and higher efficiency than conventional DG sets.
● High efficiency fans and pumps
High efficiency centrifugal pumps and fans are now available from most leading
pump and fan manufacturers. Efficiency range: 75–83 per cent. Relevant to
almost all industrial units.
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Part 2 Technical modules
Module 2:
Energy efficient technologies
● Maximum demand controllers
Load factor improvement and peak demand reduction. Relevant to
industrial/commercial establishments/utilities.
● Automatic power factor controllers
Power factor improvement. Relevant to all industries.
● High efficiency motors
Motors with efficiencies of 92–96 per cent, often with a 10 year performance
guarantee, are available on the market from all leading motor manufacturers.
They are capable of working at temperatures as high as 80–100 °C.
● Static variable speed drives, frequency drives, inverters
Thyristor control systems where speed is controlled by varying the voltage and
frequency. Higher efficiency at partial loads. Relevant to medium and large
industries and power plants.
● Energy efficient fluorescent lighting system (fluorescent lamps, sodium
vapour lamps, compact fluorescent lamps)
Higher lumens per watt. Relevant to shop floor working bays, buildings, street
lights and yard lighting.
● Electronic regulators for fans
Reduction in energy loss during part load operation. Relevant to industrial offices,
technical buildings, domestic applications.
● Solid-state soft starters
Solid-state thyristor control systems. Applied voltage is varied with load on motor.
Higher efficiency at part loads. Relevant to conveyor belts, inching loads and
equipment operating frequently with part loads in medium and large industries.
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Part 2 Technical modules Module 2: Energy efficient technologies
M2.2 Boiler and furnace technologies
● Air preheater
Improvement in thermal efficiency by preheating the combustion air with waste
heat available in flue gases.
i) Metallic recuperator/regeneratorPreheat to 350 °C. Relevant to large boilers, small furnaces.
ii) Metallic recuperator (special steels)Preheat to 700 °C. Relevant to furnaces, rolling and soak pits, glass furnaces,
ceramic kilns.
iii) Ceramic recuperator/regeneratorPreheat to 1 000 °C. Relevant to integrated steel plants, glass tank furnaces.
● Film burners
Higher turn down to 7:1, reduced excess air level. Relevant to industrial boilers
and furnaces, reheating furnaces heat treatment furnaces, etc.
● Low excess air burners (0–5% x suction air)
Improvement in system efficiency. Relevant to industrial boilers, furnaces, kilns.
● Regenerative burners
Higher flame temperature and improved heat transfer. Relevant to industrial
furnaces and kilns.
● Fluidized bed boilers
Efficient combustion of inferior, high-ash-content coals and washery rejects.
● Waste heat boilers
Steam generation with waste heat available in flue. Relevant to sulphuric acid,
chemical, petrochemical, fertilizer and steel plants.
● Closed condensate recovery system
Efficient condensate recovery system. Relevant to all process and chemical
industries where indirect steam is used.
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Part 2 Technical modules Module 2: Energy efficient technologies
● High efficiency steam turbines
High efficiency impulse steam turbines of 5 MW and less have been developed
with efficiencies as high as 70 per cent. The back pressure class of turbines can be
used in designing cogeneration systems for industries. This would not only help in
reducing purchased energy but also in providing valuable power in cases of grid
power shortage.
● Innovation in cogeneration system
The steam based cogeneration system (bottoming cycle) may be suitable where
steam to power ratio is high. If steam to power ratio is low, gas turbine based
cogeneration systems (topping cycle or combined cycle) are more appropriate. The
latter system can absorb steam fluctuations to a certain level without sacrificing
overall system efficiency. A recent development is based on the ‘Cheng’ cycle where
any excess steam is superheated and injected back into the gas combustor. This
system allows maximum electric power generation with no or less process steam or
maximum power, as well as process steam generation simultaneously.
● On-line plugging of leaks
Leak prevention in steam and compressed air systems. Relevant to continuous
industries, power stations.
● Ceramic fibre
Reduction in heat storage and radiation losses, due to low thermal mass. Relevant
to furnaces, kilns, fired heaters, heaters, ovens, heat treatment furnaces, etc.
● Luminous wall furnace
High emissivity refractory coatings—a development of the US Space Programme—
prevent high temperature of refractory linings of furnaces. The results are 10–15 per
cent fuel savings; increased furnace structure radiation; improved temperature
uniformity; and increased working life of refractory and metallic components.
● Dynamic insulation
Air or other fluid is forced through the insulating material to oppose (contraflux)
or enhance (proflux) the transmission of heat, as required. It has additional
benefits, e.g. building insulation, pre-heated supply of filtered fresh air is readily
available. Can be used for boiler and furnace as pre-heated combustion air.
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Part 2 Technical modules Module 2: Energy efficient technologies
M2.3 Heat upgrading systems
● Organic rankine cycle
Utilizing low grade waste heat for generation of power in a turbine cycle
operating with organic liquids. Relevant to cement industry, large chemical and
petrochemical plants and refineries.
● Thermo compressor
Enables utilization of low grade energy by using thermal energy in higher
pressure steam in conjunction with vapours. Relevant to process industries such as
sugar, food processing, dairy, chemicals and petrochemicals.
● Vapour absorption refrigeration system
Steam powered or by tapping low grade waste streams (150–250 °C) provides
absorption cycle refrigeration using lithium bromide or ammonia. Relevant to
process and engineering industry.
● Mechanical vapour recompression system
The low grade steam from evaporators, driers, distillation columns is upgraded.
Relevant to food processing, chemical and petro-chemicals industries.
● Heat pipes
Waste heat recovery from process streams at lower and medium temperature
levels. Faster heat transfer rate, compact design. Relevant to process chemical
industries. The heat pipe acts like a super-heat-conductor: 1 000 times more
effective than a solid copper bar of the same size.
● Thermal energy wheels
Energy wheels are compact and are available not only for recovering heat from
centrally heated and cooled buildings but also for recovering heat from boiler and
furnaces at high temperature. With the use of glass ceramic materials, they can
now withstand temperatures as high as 1 250 °C.
● Heat pumps
Heat pumps enable heat to be upgraded and transferred to a point of use. They
cut down energy consumption and are a viable alternative to electrical resistance
heating, as their coefficient of performance is in the 3–5 range. Heat pumps also
Cleaner Production – Energy Efficiency Manual page 244
Part 2 Technical modules Module 2: Energy efficient technologies
utilize low temperature waste heat sources and upgrade them to temperature
levels at which they become useful.
● Condensing heat exchanger
Extracts not only sensible but also latent heat of water vapour in flue gases of
boilers and furnaces. Condensing heat exchangers comprise Teflon coated
heat exchanger surfaces resistant to acidic corrosion, thereby allowing the flue
gases to be cooled to very near ambient temperature, thus increasing the
efficiency of boilers substantially—to over 92 per cent in the case of oil and
gas firing systems.
● Special design heat exchanger
Heat transfer rate can be dramatically increased at sonic velocity. Based on this
principle, a special design of heat exchanger with much higher overall heat
transfer coefficients than those attainable in shell and tube type heat exchangers
has been developed. These devices are relatively maintenance free. Heat
exchangers with spherical matrices and helical inserts in the tubes have been
developed, reducing heat exchanger surfaces by 25–30 per cent.
● Microprocessor based system
More precise control of critical parameters. Relevant to boilers, furnaces, utilities,
distillation columns, process plants, power plants.
M2.4 Other utilities
● Air curtains
Reduction in air infiltration in air conditioning or space heating systems. Relevant
to textile and man-made fibres, cold storage plants, air conditioned buildings, etc.
● Flat belt
Modern flat belts have transmission efficiency of the order of 95–98 per cent as
compared to V-belt transmission efficiency of 80–85 per cent. Improved efficiency
is due to less friction losses between belt and pulley as well as absence of
wedging. Relevant to pulley driven drives.
Cleaner Production – Energy Efficiency Manual page 245
Part 2 Technical modules Module 2: Energy efficient technologies
● Industrial drying by electromagnetic radiation
Infrared, microwave, radio frequency and ultraviolet radiation are now being used
for drying purposes. Drying efficiencies increase by as much as 50–70 per cent.
All these techniques, are useful for particular types of product drying, e.g.
microwave for food processing; radio frequency for drying of paper, yarn
packages, etc.; infrared for curing of adhesives; ultraviolet for paint curing.
Cleaner Production – Energy Efficiency Manual page 246
Part 2 Technical modules Module 2: Energy efficient technologies
Cleaner Production – Energy Efficiency Manual page 247
Contents listing
Part 1 CP-EE methodology
Part 2 Technical modules
Part 3 Tools and resources
Part 3 provides the following tools and resources:
• Checklists of procedures that improve energy
efficiency and safety in energy-using equipment.
• Thumb Rules, for rapid assessment of the efficiency
of major energy systems.
• A list of Measuring Instruments that can be used
to quantify and monitor energy flows.
• Greenhouse Gas Emissions Indicator: a spreadsheet-
based calculator designed to help governments and
industry estimate greenhouse gas emissions.
• Information Resources to help in further
development of CP-EE and other energy-related
initiatives.
• Conversion Tables to provide a standardized
approach to energy measurements and calculations.
• A list of Acronyms and Abbreviations used.
A.1 Fuel oil checklists
● Daily checks
i. Oil temperature at the burner
ii. Oil/steam leakages
● Weekly tasks
i. Cleaning of all filters
ii. Draining of water from all tanks
● Yearly jobs
i. Cleaning of all tanks
● Troubleshooting hints
Oil not pumpable• Viscosity too high
• Blocked lines and filters
• Sludge in oil
• Leak in oil suction
• Vent pipe choked
Blocking of strainers• Sludge or wax in oil
• Heavy precipitated compounds in oil
• Rust or scale in tank
• Carbonization of oil due to excessive heating
Excess water in oil• Water delivered along with oil
• Leaking manhole
• Seepage from underground tank
• Ingress of moisture from vent pipe
• Leaking heater steam coils
Cleaner Production – Energy Efficiency Manual page 248
Part 3 Tools and resources
A: Checklists for enhancing efficiency
and safety of energy equipment
Remember!
Spilled oil is irretrievable.
Plug all leaks.
Impurities in furnace oil
affect combustion.
Filter oil in stages.
Oil has to be preheated
to obtain the right
viscosity for supply to
the burner. It is essential
to provide adequate
preheater capacity.
Pipeline plugged• Sludge in oil
• High viscosity oil
• Foreign materials such as rags, scale and wood splinters in line
• Carbonization of oil
A.2 Combustion checklists and troubleshooting
Step by step procedure for efficient operation of burners
● Start up
• Check for correct sized burner/nozzle.
• Establish air supply first (start blower). Ensure no vapour/gases are present
before light up.
• Ensure a flame from a torch or other source is placed in front of the nozzle.
• Turn ON the (preheated) oil supply (before start-up, drain off cold oil).
● Operations
• Check for correct temperature of oil at the burner tip (consult viscosity vs.
temperature chart).
• Check air pressure for LAP burners (63.5 cm to 76.2 cm w.c. air pressure is
commonly adopted).
• Check for oil drips near burner.
• Check for flame fading/flame pulsation.
• Check positioning of burner (ensure no flame impingement on refractory walls
or charge).
• Adjust flame length to suit the conditions (ensure flame does not extend
beyond the furnace).
● Load changes
• Operate both air and oil valves simultaneously (For self-proportioned burner,
operate the self-proportioning lever. Do not adjust valve only in oil line).
• Adjust burners and damper for a light brown (hazy) smoke from chimney and
at least 12 per cent CO2.
Cleaner Production – Energy Efficiency Manual page 249
Part 3 Tools and resources A: Checklists for enhancing efficiency and safety
Cleaner Production – Energy Efficiency Manual page 250
Part 3 Tools and resources A: Checklists for enhancing efficiency and safety
Causes and remedies
1. Starting difficult
2. Flame goes out or splutters
3. Flame flashesback
4 Smoke and soot
5. Clinker onrefractory
6. Cooking of fuelin burner
7. Excessive fueloil consumption
i. No oil in the tank.ii. Excess sludge and water in storage tanks.iii. Oil not flowing due to high viscosity/low temperature.iv. Choked burner tip.v. No air.vi. Strainers choked.
i. Sludge or water in oil.ii. Unsteady oil and air pressures.iii. Too high a pressure for atomizing medium which tends to blow out flame.iv. Presence of air in oil line. Look for leakages in suction line of pump.v. Broken burner block, or burner without block.
i. Oil supply left in ‘ON’ position after air supply cut off during earliershut off.
ii. Too high a positive pressure in combustion chamber.iii. Furnace too cold during starting to complete combustion (when
temperature rises, unburned oil particles burn).iv. Oil pressure too low.
i. Insufficient draft or blower of inadequate capacity.ii. Oil flow excessive.iii. Oil too heavy and not preheated to the required level.iv. Suction air holes in blower plugged.v. Chimney clogged with soot/damper closed.vi. Blower operating speed too low.
i. Flame hits refractory because combustion chamber is too small or burneris not correctly aligned.
ii. Oil dripping from nozzle.iii. Oil supply not ’cut off’ before the air supply during shut-offs.
i. Nozzle exposed to furnace radiation after shut-off.ii. Burner fed with atomizing air over 300 °C.iii. Burner block too short or too wide.iv. Oil not drained from nozzle after shut off.
i. Improper ratio of oil and air.ii. Burner nozzle oversized.iii. Excessive draft.iv. Improper oil/air mixing by burner.v. Air and oil pressure not correctvi. Oil not preheated properly.vii. Oil viscosity too low for the type of burner used.viii. Oil leaks in oil pipelines/preheater.ix Bad maintenance (too high or rising stack gas temperature).
Checklist 1: Troubleshooting chart for combustion
Complaint
● Shut down
• Close oil line first.
• Shut the blower after a few seconds (ensure gases are purged from
combustion chamber).
• Do not expose the burner nozzle to the radiant heat of the furnace. (When oil
is shut off, remove burner/nozzle or interpose a thin refractory between nozzle
and furnace).
A.3 Boilers
● Periodic tasks and checks outside of the boiler
• All access doors and platework should be maintained air tight with effective
gaskets.
• Flue systems should have all joints sealed effectively and be insulated where
appropriate.
• Boiler shells and sections should be effectively insulated. Is existing insulation
adequate? If insulation was applied to boilers, pipes and hot water cylinders
several years ago, it is almost certainly too thin even if it appears in good
condition. Remember, it was installed when fuel costs were much lower.
Increased thickness may well be justified.
• At the end of the heating season, boilers should be sealed thoroughly, internal
surfaces either ventilated naturally during the summer or very thoroughly
sealed with tray of desiccant inserted. (Only applicable to boilers that will
stand idle between heating seasons).
● Safety and monitoring
• Explosion relief doors should be located and/or guarded to prevent injury to
personnel.
• Safety valves should have self-draining discharge pipes terminating in a safe
location that can be easily observed.
• Installed instruments should be maintained in working order and positioned
where they can be seen easily.
• Provide test points with removable seal plugs in the flue from the boiler, to
enable flue gas combustion tests to be carried out.
• Do you check boiler combustion conditions periodically? CO2 or O2 readings
and exit temperatures can be obtained using relatively inexpensive portable
Cleaner Production – Energy Efficiency Manual page 251
Part 3 Tools and resources A: Checklists for enhancing efficiency and safety
Important!
Burners should be
dismantled and cleaned
periodically, preferably
once per shift
(always keep spare
burners ready).
equipment. Adjusting combustion by optimizing the fuel/air ratio costs
nothing and can make substantial savings.
• Do you monitor exit temperatures? There should be a steady rise between boiler
flue-duct cleaning intervals and this should not be allowed to exceed, say, 40 °C.
Try to clean based on temperature indications, rather than on the calendar.
• Some older sectional boilers and certain smoke tube type shell boilers can be
fitted with baffles or ‘retarders’ to improve heat transfer and therefore
efficiency. Have you checked whether this is possible on your boilers?
• Is there adequate ventilation to give sufficient combustion air for the boilers?
Insufficient ventilation can, at the least, lead to poor combustion and at worst
could enable dangerous gases to accumulate in the boiler house.
• Check the water side of the boiler periodically for corrosion or scale formation.
• Do you know the actual load on the boiler? A rough guide can be obtained from
oil or gas burners by timing the on/off periods, or the time on full flame for fully
modulating burners. With underfeed coal stokers, see what is the lowest speed
that will cope with demand, or put on full speed and time the on/off periods.
• If the boiler is oversized, either permanently or during part of the year, consider
whether it can be de-rated during those periods by adjusting burners or stokers
to operate only up to a top limit that is lower than full maximum output. Try to
keep the boiler operating for the highest possible percentage of time.
• Is there adequate boiler/burner control to match the load and prevent
excessive and unnecessary cycling?
• If you have more than one boiler, do you isolate boilers which are in excess of
load requirements? Automatic flue isolation should be used, if possible, to
prevent excessive purging by chimney draught during idle periods.
• In multi-boiler hot water installations, are the boilers hydraulically balanced to
ensure proper sharing of the load?
• Consider fitting heat exchangers/recuperators to flues; these can recover
5–7 per cent of energy available.
● Boilers: extra items for steam-raising and hot-water boilers
• Check regularly for build-up of scale or sludge in the boiler vessel or check
TDS of boiler water each shift, but not less than once per day. Impurities in
boiler water are concentrated in the boiler and the concentration has limits
that depend on type of boiler and load. Boiler blow down should be
minimized, but consistent with maintaining correct water density. Recover
heat from blow down water.
Cleaner Production – Energy Efficiency Manual page 252
Part 3 Tools and resources A: Checklists for enhancing efficiency and safety
• With steam boilers, is water treatment adequate to prevent foaming or priming
and consequent excessive carry over of water and chemicals into the steam
system?
• For steam boilers: are automatic water level controllers operational? The
presence of inter-connecting pipes can be extremely dangerous.
• Have checks been made regularly on air leakages round boiler inspection doors,
or between boiler and chimney? The former can reduce efficiency; the latter can
reduce draught availability and may encourage condensation, corrosion and
smutting.
• Combustion conditions should be checked using flue gas analysers at least
twice per season and the fuel/air ratio should be adjusted if required.
• Both detection and actual controls should be labelled effectively and checked
regularly.
• Safety lock-out features should have manual re-set and alarm features.
• Test points should be available, or permanent indicators should be fitted to oil
burners to give operating pressure/temperature conditions.
• With oil-fired or gas-fired boilers, if cables of fusible link systems for shutdown
due to fire or overheating run across any passageway accessible to personnel,
they should be fitted above head level.
• The emergency shut down facility is to be situated at exit door of the boiler
house.
• In order to reduce corrosion, steps should be taken to minimize the periods
when water return temperatures fall below dew point, particularly on oil and
coal fired boilers.
• Very large fuel users may have their own weighbridge and so can operate a
direct check on deliveries. If no weighbridge exists, do you occasionally ask
your supplier to run via a public weighbridge (or a friendly neighbour with a
weighbridge) just as a check? With liquid fuel deliveries do you check with the
vehicle’s dipsticks?
• With boiler plant, ensure that the fuel used is correct for the job. With solid
fuel, correct grading or size is important, and ash and moisture content should
be as the plant designer originally intended. With oil fuel, ensure that viscosity
is correct at the burner, and check fuel oil temperature.
• The monitoring of fuel usage should be as accurate as possible. Fuel stock
measurements must be realistic.
• With oil burners, examine parts and repairs. Burner nozzles should be changed
regularly and cleaned carefully to prevent damage to burner tip.
Cleaner Production – Energy Efficiency Manual page 253
Part 3 Tools and resources A: Checklists for enhancing efficiency and safety
• Maintenance and repair procedures should be reviewed especially for burner
equipment, controls and monitoring equipment.
• Regular cleaning of heat transfer surfaces maintains efficiency at the highest
possible level.
• Ensure that the boiler operators are conversant with the operational
procedures, especially any new control equipment.
• Have you investigated the possibility of heat recovery from boiler exit gases?
Modern heat exchangers/recuperators are available for most types and sizes of
boiler.
• Do you check feed and header tanks for leaking make up valves, correct
insulation or loss of water to drain?
• The boiler plant may have originally been provided with insulation by the
manufacturer. Is this still adequate with today’s fuel costs? Check on optimum
thickness.
• If the amount of steam produced is quite large, invest in a steam meter.
• Measure the output of steam and input of fuel. The ratio of steam to fuel is
the main measure of efficiency at the boiler.
• Use the monitoring system provided: this will expose any signs of
deterioration.
• Feed water should be checked regularly for both quantity and purity.
• Steam meters should be checked occasionally as they deteriorate with time
due to erosion of the metering orifice or pilot head. It should be noted that
steam meters only give correct readings at the calibrated steam pressure.
Recalibration may be required.
• Check all pipe work, connectors and steam traps for leaks, even in inaccessible
spaces.
• Pipes not in use should be isolated and redundant pipes disconnected.
• Is someone designated to operate and generally look after the installation?
This work should be included in their job specification.
• Are basic records available to that person in the form of drawings, operational
instructions and maintenance details?
• Is a log book kept to record details of maintenance carried out, actual
combustion flue gas readings taken, fuel consumption at weekly or monthly
intervals, and complaints made?
• Ensure that steam pressure is no higher than need be for the job. When night
load is materially less than day load, consider a pressure switch to allow
pressure to vary over a much wider band during night to reduce frequency of
burner cut-out, or limit the maximum firing rate of the burner.
Cleaner Production – Energy Efficiency Manual page 254
Part 3 Tools and resources A: Checklists for enhancing efficiency and safety
• Examine the need for maintaining boilers in standby conditions—this is
often an unjustified loss of heat. Standing boilers should be isolated on the
fluid and gas sides.
• Keep a proper log of boiler house activity so that performance can be
measured against targets. When checking combustion, etc. with portable
instruments, ensure that this is done regularly and that load conditions are
reported in the log: percentage of CO2 at full flame/half load, etc.
• Have the plant checked to ensure that severe load fluctuations are not caused
by incorrect operation of auxiliaries in the boiler house, for example, ON/OFF
feed control, defective modulating feed systems or incorrect header design.
• Have hot water heating systems been dosed with an anti-corrosion additive
and is this checked annually to see that concentration is still adequate? Make
sure that this additive is NOT put into the domestic hot water heater tank, it
will contaminate water going to taps at sinks and basins.
• Recover all condensate where practical and substantial savings are possible.
● Boiler rooms and plant rooms
• Ventilation openings should be kept free and clear at all times and the
opening area should be checked to ensure this is adequate.
• Plant rooms should not be used for storage, airing or drying purposes.
• Is maintenance of pumps and automatic valves in accordance with the
manufacturers’ instructions?
• Are run and standby pump units changed over approximately once per month?
• Are pump isolating valves provided?
• Are pressure/heat test points and/or indicators provided each side of the
pump?
• Are pump casings provided with air release facilities?
• Are moving parts (e.g. couplings) guarded?
• Ensure that accuracy of the instruments is checked regularly.
• Visually inspect all pipe work and valves for any leaks.
• Check that all safety devices operate efficiently.
• Check all electrical contacts to see that they are clean and secure.
• Ensure that all instrument covers and safety shields are in place.
• Inspect all sensors, make sure they are clean, unobstructed and not exposed to
unrepresentative conditions, for example temperature sensors must not be
exposed to direct sunlight nor be placed near to hot pipes or process plant.
• Ensure that only authorized personnel have access to control equipment.
Cleaner Production – Energy Efficiency Manual page 255
Part 3 Tools and resources A: Checklists for enhancing efficiency and safety
• Each section of the plant should operate when essential, and should preferably
be controlled automatically.
• Time controls should be incorporated and operation of the whole plant
should, preferably, be automatic.
• In multiple boiler installations, boilers not required to be available should be
isolated on the water side and—if safe and possible—on the gas side too.
Make sure boilers cannot be fired.
• Isolation of flue system (with protection) also reduces heat losses.
• In multiple boiler installations the lead/lag control should have a change round
facility.
• Where possible, any reduction in the system operating temperature should be
made by devices external to the boiler, the boiler plant operating in a normal
constant temperature range.
● Water and steam
• Water fed into the boilers must meet the specifications given by the
manufacturers. The water must be clear, colourless and free from suspended
impurities.
• Hardness nil. Max. 0.25 ppm CaCO3.
• pH of 8 to 10 retard forward action or corrosion. pH less than 7 speeds up
corrosion due to acidic action.
• Dissolved O2 less than 0.02 mg/l. Its presence with SO2 causes corrosion problems.
• CO2 level should be kept very low. Its presence with O2 causes corrosion,
especially in copper and copper bearing alloys.
• Water must be free from oil—it causes priming.
● Boiler water
• Water must be alkaline—within 150 ppm of CaCO3 and above 50 ppm of
CaCO3 at pH 8.3.
• Alkalinity number should be less than 120.
• Total solids should be maintained below the value at which contamination of
steam becomes excessive, in order to avoid cooling over and accompanying
danger of deposition on super heater, steam mains and prime movers.
• Phosphate should be no more than 25 ppm P2 O5.
• Make up feed water should not contain more than traces of silica. There must
be less than 40 ppm in boiler water and 0.02 ppm in steam, as SiO2. Greater
amounts may be carried to turbine blades.
Cleaner Production – Energy Efficiency Manual page 256
Part 3 Tools and resources A: Checklists for enhancing efficiency and safety
• Water treatment plants suitable for the application must be installed to ensure
water purity, and chemical dosing arrangement must be provided to further
control boiler water quality. Blow downs should be resorted to when
concentration increases beyond the permissible limits stipulated by the
manufacturers.
• Alkalinity not to exceed 20 per cent of total concentration. Boiler water level should
be correctly maintained. Normally, 2 gauge glasses are provided to ensure this.
• Operators should blow these down regularly in every shift, or at least once per
day where boilers are steamed less than 24 hours a day.
● Blow down (BD) procedure
A conventional and accepted procedure for blowing down gauge is as follows:
1. Close water lock
2. Open drain cock (note that steam escapes freely)
3. Close drain cock
4. Close steam cock
5. Open water cock
6. Open drain cock (note that water escapes freely)
7. Close drain cock
8. Open steam cock
9. Open and then close drain cock for final blow through.
The water that first appears is generally representative of the boiler water. If it is
discoloured, the reason should be ascertained.
Cleaner Production – Energy Efficiency Manual page 257
Part 3 Tools and resources A: Checklists for enhancing efficiency and safety
Maximum boiler water concentration (ppm)
0–20
20–30
30–40
40–50
50–60
60–70
70–100
3 500
3 000
2 500
2 000
1 500
1 250
1 000
Table A.1: Maximum boiler water concentrations recommendedby American Boiler Manufacturers Association
Boiler steam pressure (ata)
Cleaner Production – Energy Efficiency Manual page 258
Part 3 Tools and resources A: Checklists for enhancing efficiency and safety
Daily Weekly Monthly Annual
BD and watertreatment
Feed water system
Flue gases
Combustion airsupply
Burners
Boiler operatingcharacteristics
Relief valve
Steam pressure
Fuel system
Belts for glandpacking
Air leaks in waterside and fire sidesurfaces
Air leaks
Refractories onfuel side
Elec. system
Hydraulic andpneumatic valves
Check BD valves do notleak. BD is not excessive.
Check and correctunsteady water level.Ascertain cause of unsteadywater level, contaminantsover load, malfunction etc.
Check temp. at twodifferent points.
Check controls areoperating properly. Mayneed cleaning several timesa day.
Check for excess loadswhich will cause excessivevariation in pressure.
–
Condensate receiver,deaerator system pumps.
Same as weekly. Record references.
Same as weekly, clean andrecondition.
Remove and recondition.
Clean and reconditionsystem.
Clean surface as permanufacturer’srecommendation annually.
Check for leaks aroundaccess openings and flame.
Repair.
Clean, repair terminals andcontacts etc.
Repair all defects andcheck for proper operation.
Make sure solids do notbuild up.
Nil
Same as weekly. Comparewith previous readings.
Check adequate openingsexist in air inlet. Cleanpassages.
Same as weekly.
Check pumps, pressuregauges, transfer lines.Clean them.
Check for damages. Checkgland packing for leakagesand proper compression.
Inspect panels inside.
Clean equipment, oilspillages to be arrested andair leaks to be avoided.
–
Check controls by stoppingthe feed water pump andallow control to stop fuel.
Measure temp. andcompare composition atselected firings and adjustrecommended valves.
Clean burners, pilotassemblies, check conditionof spark gap of electrodeburners.
Observe flame failure andcharacteristics of the flame.
Check for leakages.
Clean panels outside.
Checklist 2: Boiler periodic checklist
System
Cleaner Production – Energy Efficiency Manual page 259
Part 3 Tools and resources A: Checklists for enhancing efficiency and safety
Don‘ts
1. Soot blowing regularly
2. Clean blow down gauge glass once a shift
3. Check safety valves once a week
4. Blow down in each shift, to requirement
5. Keep all furnace doors closed
6. Control furnace draughts
7. Clear, discharge ash hoppers every shift
8. Watch chimney smoke and control fires
9. Check auto controls on fuel by stoppingfeed water for short periods occasionally
10. Attend to leakages periodically
11. Check all valves, dampers etc. for correctoperation once a week
12. Lubricate all mechanisms for smoothworking
13. Keep switchboards neat and clean andindication systems in working order
14. Keep area clean, dust free
15. Keep fire fighting arrangements inreadiness always. Rehearsals to be carriedout once a month.
16. All log sheets must be truly filled
17. Trip FD fan if ID fan trips
18. CO2 or O2 recorder must be checked/calibrated once in three months
19. Traps should be checked and attended toperiodically
20. Quality of steam, water, should be checkedonce a day, or once a shift as applicable
21. Quality of fuel should be checked once aweek
22. Keep sub heater drain open during start up
23. Keep air cocks open during start and close
1. Don’t light up torches immediately after afireout (purge)
19. Don’t allow steam formation in economizer(watch temps.)
20. Don’t expose grate (spread evenly)
21. Don’t operate boiler with water tubeleaking
Checklist 3: Boiler dos and don’ts
Dos
B.1 Thermal energy
● Boilers
• 5 per cent reduction in excess air increases boiler efficiency by 1 per cent (or1 per cent reduction of residual oxygen in stack gas increases boiler efficiencyby 1 per cent).
• 22 °C reduction in flue gas temperature increases boiler efficiency by 1 per cent.• 6 °C rise in feed water temperature brought about by economizer/condensate
recovery corresponds to a 1 per cent saving in boiler fuel consumption. • 20 °C increase in combustion air temperature, pre-heated by waste heat
recovery, results in a 1 per cent fuel saving.• A 3 mm diameter hole in a pipe carrying 7 kg/cm2 steam would waste
32 650 litres of fuel oil per year.• 100 m of bare steam pipe with a diameter of 150 mm carrying saturated
steam at 8 kg/cm2 would waste 25 000 litres furnace oil in a year.• 70 per cent of heat losses can be reduced by floating a layer of 45 mm
diameter polypropylene (plastic) balls on the surface of a 90 °C hotliquid/condensate.
• A 0.25 mm thick air film offers the same resistance to heat transfer as a 330mm thick copper wall.
• A 3 mm thick soot deposit on a heat transfer surface can cause a 2.5 per centincrease in fuel consumption.
• A 1 mm thick scale deposit on the water side could increase fuel consumptionby 5 to 8 per cent.
B.2 Electrical energy
● Compressed air
• Every 5 °C reduction in intake air temperature would result in a 1 per centreduction in compressor power consumption.
• Compressed air leaking from a 1 mm hole at a pressure of 7 kg/cm2 meanspower loss equivalent to 0.5 kW.
• A reduction of 1 kg/cm2 in air pressure (8 kg/cm2 to 7 kg/cm2) would result ina 9 per cent saving in input power.
• A reduction of 1 kg/cm2 in line pressure (7 kg/cm2 to 6 kg/cm2) can reduce
the quantity leaking from a 1 mm hole by 10 per cent.
Cleaner Production – Energy Efficiency Manual page 260
Part 3 Tools and resources
B: Thumb rules for quick efficiency
assessment in major energy systems
● Refrigeration
• Refrigeration capacity reduces by 6 per cent for every 3.5 °C increase in
condensing temperature.
• Reducing condensing temperature by 5.5 °C results in a 20–25 per cent decrease
in compressor power consumption.
• A reduction of 0.55 °C in cooling water temperature at condenser inlet reduces
compressor power consumption by 3 per cent.
• 1 mm scale build-up on condenser tubes can increase energy consumption by
40 per cent.
• 5.5 °C increase in evaporator temperature reduces compressor power
consumption by 20–25 per cent.
● Electric motors
• High efficiency motors are 4–5 per cent more efficient than standard motors.
• Every 10 °C increase in motor operating temperature beyond the recommended
peak is estimated to halve the motor‘s life.
• If rewinding is not done properly, efficiency can be reduced by 5–8 per cent.
• Balanced voltage can reduce motor input power by 3–5 per cent.
• Variable speed drives can reduce input energy consumption by 5–15 per cent. As
much as 35 per cent of energy can be saved for some pump/fan applications.
• Soft starters/energy savers help to reduce power consumption by 3–7 per cent of
operating kW.
● Lighting
• Replacement of incandescent bulbs by CFL’s offer 75–80 per cent energy savings.
• Replacement of conventional tube lights by new energy-efficient tube light with
electronic ballast helps reduce power consumption by 40–50 per cent.
• 10 per cent increase in supply voltage will reduce bulb life by one-third.
• 10 per cent increase in supply voltage will increase lighting power consumption
by an equivalent 10 per cent.
● Buildings
• An increase in room temperature of 10 °C can increase the heating fuel
Table D.1: Emissions from fuel use—country-specific net calorific values (NCV) forcoal and CO2 emissions
Country
“What if my country is not listed in Table D.1 and I want to calculate GHG emissions?”
• If your country is not listed, you can use the default value (1.84 tons of CO2/ton
of coal) at the end of Table D.1.
“What if I use more than one fuel?”
• Refer to Worksheet D.1 which gives EF values for CO2 emissions from different
types of fuels. Multiply the respective EFs for the relevant fuels by the amounts
of those fuels your company uses to obtain the CO2 emissions.
• You can also total the respective CO2 emissions and divide by the total weight
of fuel to get an overall EF for your company.
Cleaner Production – Energy Efficiency Manual page 269
Part 3 Tools and resources D: Greenhouse Gas Emissions Indicator
Worksheet D.1: CO2 emissions from fuel use
Fuel types Basic Unit Emission Amount ofCO2 (t)
Coal
Petrol
Natural Gas
Gas/Diesel Oil
Residual Fuel Oil
LPG
Jet Kerosene
Shale Oil
Ethane
Naphtha
Bitumen
Lubricants
Petroleum Coke
Refinery Feedstock
Refinery Gas
Other Oil Products
Total
0.0059
0.0067
0.007
0.00222
0.00268
0.00300
0.00165
0.00258
0.00224
0.00263
0.00254
0.0003413
0.0002496
0.0002020
0.0002667
0.0002786
0.0002271
0.0002575
0.0002218
0.0002641
0.0002905
0.0002641
0.0003631
0.0002641
0.0002641
0.0002403
0.0002641
1.84
3.07
2.93
3.19
3.08
2.95
3.17
2.61
2.90
3.27
3.21
2.92
3.09
3.25
2.92
2.92
Therms Litres KWh Tons X tCO2 tCO2 tCO2 tCO2 =
“How do I calculate GHG emissions for the utility generated electricity consumed by mycompany? (My company consumes 100 000 kWh per year.)”
• A complete list of emission factors for electricity usage by country (using IEA
data) is given in Table D.2. First, find your country and determine its EF (e.g. for
Thailand, the emission factor is 0.000618). Multiply the EF by consumption (in
this example this gives: 100 000 x 0.000618 = 6.18 tons of CO2).
“My company exports power and steam for economic as well as social reasons. How do Icalculate in this case?”
• Your company should not be accountable for the associated emissions. Such
emissions should be accounted for by the user of the electricity or heat. The
emissions corresponding to the amount or heat exported should be calculated
and should then be deducted from your company’s emission total.
“My company imports electricity or heat generated by public CHP. How do I calculate?”
• If you import electricity from a public CHP plant, use the electricity factors given
in Table D.2 and then use Worksheet D.1 to calculate the CO2 emissions. The
electricity emission factors in Table D.2 incorporate public CHP schemes in the
energy mix.
Cleaner Production – Energy Efficiency Manual page 270
Part 3 Tools and resources D: Greenhouse Gas Emissions Indicator
A refinery consumes coal, refinery feedstock and petroleum coke. Its total CO2 emissions (in tons)and emission factor are calculated as shown below.
Fuel Annual fuel consumption (tons) EF tCO2
Coal 500 x 1.85 = 925
Refinery feedstock 3 502 x 3.25 = 11 382
Petroleum coke 45 x 3.09 = 139
Totals 4 047 12 446
Total fuel consumption = 4 047 tonsTotal CO2 emissions released = 12 446 tCO2CO2 Emission Factor for the refinery = Total CO2/total fuel input
= 12 446/4 047= 3.075 t CO2 per ton of fuel
Example: Calculating CO2 emissions for several fuels
Cleaner Production – Energy Efficiency Manual page 271
Part 3 Tools and resources D: Greenhouse Gas Emissions Indicator
1990 emission factor 1996 emission factor
Africa
Asia (excl. China)
Australia
Bangladesh
China
Egypt
Emirates
Europe
India
Iran
Iraq
Israel
Japan
Kazakhstan
Korea
Kuwait
Malaysia
Middle East
Nepal
New Zealand
Non-OECD:
Pakistan
Singapore
South Africa
Sri Lanka
Syria
Tajikistan
Thailand
Turkey
Turkmenistan
United Arab
Venezuela
0.00066
0.000658
0.000777
0.000604
0.00071
0.000546
0.000616
0.000496
0.000761
0.000541
0.000549
0.000814
0.000346
0.000000
0.000317
0.000591
0.000664
0.000632
0.000674
0.000103
0.00041
0.00089
0.000796
0.000003
0.000546
0.000000
0.000619
0.000492
0.000000
0.000237
0.000663
0.000724
0.000791
0.00054
0.000772
0.000561
0.000783
0.00042
0.00089
0.000534
0.000554
0.000801
0.000321
0.001312
0.000297
0.000512
0.000594
0.00065
0.000632
0.000099
0.000438
0.000622
0.00077
0.000205
0.00065
0.000068
0.000618
0.000461
0.000731
0.000176
Table D.2: Electricity emission factors for different countries (tCO2/kWh) for 1990 and 1996
Country
Sour
ce IE
A.
.
Worksheet D.2: Process-related greenhouse gas emissions
Trace Gas Basic Unit X Conversion values = CO2(GWP,100) equivalent
Carbon dioxide
CC1 4
CFC-11
CFC113
CFC 116
CFC12
CFC114
CFC115
Chloroform
HCFC 123
HCFC 124
HCFC 22
HFC 125
HFC 32
HFC
Methane
Methylene chloride
1
1300
3400
4500
6200
7100
7000
7000
4
90
430
1600
2800
650
150
21
9
“My company generates GHGs other than CO2 from its process. How do I account forGHG emissions?”
• Production of process-related GHGs is estimated (in tons) and converted to CO2
equivalents using the global warming potential (GWP) for a 100 year-time horizon
as a conversion factor. Worksheet D.2 can be used for process-related emissions.
Cleaner Production – Energy Efficiency Manual page 272
Part 3 Tools and resources D: Greenhouse Gas Emissions Indicator
Cleaner Production – Energy Efficiency Manual page 273
Part 3 Tools and resources D: Greenhouse Gas Emissions Indicator
“How do I account for my transport related emissions?”
• Emissions from transport are broken down by transport mode. The guidelines in
the GHG Indicator cover:
i) road vehicle transport;
ii) non-road transport.
• For road vehicle transport, first calculate the total fuel consumption for three
major transport fuels, and use Worksheet D.3 to calculate the CO2 emissions.
“My company rents transport for employees. How do I calculate GHG emissions in this case?”
• The nature of rented transport makes it difficult to calculate the consumption of
specific fuel types. Vehicle-kilometre calculations are used in this instance.
• Worksheet D.3 can be used to calculate CO2 emissions for rented transport and
non-road transport.
Worksheet D.3: Fuel emissions from transport
Transport Basic unit No. of CO2 E.F. CO2 E.F. CO2 emissions mode basic units X (tCO2/km) (tCO2/mile) = (tonnes)
Average petrol car
Average diesel car
HGV
Passenger air (short haul)
Passenger air (long haul)
Passenger train
Air freight (short haul)
Air freight (long haul)
Freight train
Inland shipping(freight)
Marine shipping(freight)
kilometre or mile
kilometre or mile
kilometre or mile
person.kilometre orperson.mile
person.kilometre orperson.mile
person.kilometre orperson.mile
tonne.kilometre ortonne.mile
tonne.kilometre ortonne.mile
tonne.kilometre ortonne.mile
tonne.kilometre ortonne.mile
tonne.kilometre ortonne.mile
0.000185
0.000156
0.000782
0.00018
0.00011
0.000034
0.000158
0.00057
0.000047
0.00003
0.000010
0.000299
0.000251
0.00126
0.00029
0.00018
0.000054
0.00025
0.00091
0.000075
0.000056
0.000016
“I have finally managed to calculate all energy and process emissions from my company.What do I do next?”
• Aggregate all the emissions and then normalize the data.
“What is aggregation?”
• Aggregation means summing of energy and transport related CO2 and process-
related emissions. See Table D.3 and the accompanying note.
“What is normalization?”
• Normalization is the process of dividing total CO2 emissions by turnover,
employees, added value and unit production. Table D.4 gives an example of
normalizing for a cement plant emitting 1 500 000 tCO2/year.
GHG source Tons of CO2 equivalent
1
2
3
4
5
6
Fuel; combustion
Electricity
CHP
Road transport
Unit. kilometre transport
Process-related GHG emissions
TOTAL CO2
Table D.3: Total global warming impact as CO2 equivalent aggregation Step 1Insert the relevant totals of CO2from the previous worksheetsfor each category.
Step 2Add the column and insert thetotal in box at the bottom.
Cleaner Production – Energy Efficiency Manual page 274
Part 3 Tools and resources D: Greenhouse Gas Emissions Indicator
Cleaner Production – Energy Efficiency Manual page 275
Part 3 Tools and resources D: Greenhouse Gas Emissions Indicator
Group consolidated figures(Column 1)
Normalized CO2 equivalents (tonnes per normalizing factor)
(Column 2)
Turnover
Added value
Employees
Unit production
$ 20 000 000
$ 500 000
500
1 350 000 tons
0.075
3
3 000
1.11
Table D.4: Normalizing CO2 potentialStep 1From your group/companyaccounts, insert the relevantfigures in column 1.
Step 2Divide the total CO2 by column1 and insert the answer incolumn 2.
Step 3Use the answers in column 2 asthe ratio for amount of CO2produced for each of thenormalizing factors, e.g. 1.11 t.CO2 for every ton of cementproduced.
Cleaner Production – Energy Efficiency Manual page 276
Part 3 Tools and resources
E: Information resources
D I S C L A I M E R
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Manual and therefore cannot guarantee that the information held therein will
always be accurate and complete.
Although UNEP DTIE endeavours to provide links to websites which contain
accurate information, we are unable to guarantee that these pages will not
contain errors, or incomplete or out-of-date information.
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for any loss, damage or expense that might be caused by any action, or lack of
action, that a user of this service might take as a result of reading material on a
site found using the links provided. Responsibility for such actions, or lack of
actions, remains with the reader.
This section provides links to Cleaner Production and Energy Efficiency resources on the
Internet. Resources are grouped together under various headings for ease of
navigation. Clicking on the blue hyperlinks in the text will launch your web browser
and link you directly to the appropriate resource.
Please read the Disclaimer (below) before consulting any of the Internet resources listed
in this Manual.
E.1 Energy systems
• Compressed air
An overview of Best Practices for compressed air system resources to help
industrial end users achieve efficiency improvements and related cost savings.
(Resources include compressed air tip sheets; technical publications.)
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Part 3 Tools and resources
Système International (SI) and metric units have been adopted internationally for
energy calculations. For instance, the joule, the SI unit of energy, is commonly used in
conjunction with other SI units such as the metre, the kilogram and the kelvin (for
temperature).
The conversion tables presented below show how some units commonly used in
engineering and other professions equate to SI and metric units.
F: Conversion tables
T = tera = One million million = 1 000 000 000 000 = 1012
G = giga = One thousand million (Also one billion) = 1 000 000 000 = 109
M = mega = One million = 1 000 000 = 106
k = kilo = One thousand = 1 000 = 103
d = deci = One tenth = 0.1 = 10-1
c = centi = One hundredth = 0.01 = 10-2
m = milli = One thousandth = 0.001 = 10-3
m = micro = One millionth = 0.000001 = 10-6
n = nano = One billionth = 0.000000001 = 10-9
p = pico = One millionth of a millionth = 0.000000000001 = 10-12
Table F.1: Abbreviations for quantities
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Part 3 Tools and resources F: Conversion tables
Btu
Btu/lb °F andkJ/kg °C
Btu in/ft 2handW/m2 °C
bar
bbl
cal and(kcal)
grain
ha
HP
imp
J and (kJ)
kWh
l (also ltr)
psiandkPa
therm
tonne
W (kW)
The British thermal unit, a measure of heat energy.
Units for the specific heat capacity of a substance—a measure of the quantity of(heat) energy required to raise the temperature of a given quantity of the substancethrough one degree.
In the imperial system, it is the number of British thermal units required to raise onepound weight of the substance by one degree on the Fahrenheit scale.
In SI units it is the (kilo) joules of heat energy required to raise one kilogram of thesubstance by one degree on the Celsius (or Centigrade) scale.
Thermal conductance—a measure of the rate at which heat energy passes through agiven thickness of material per unit of area, with a one degree temperaturedifference between the two sides.
In imperial units it is the number of British thermal units that will pass through onesquare foot of material of one inch thickness in one hour with a temperaturedifference of one degree Fahrenheit between the warmer and cooler surfaces.
Using SI units, it is watts of heat power that will pass through one square metre ofmaterial with one degree Celsius (Centigrade) difference.
An alternative unit of pressure equal to 105 pascals. Its value is slightly higher thannormal atmospheric pressure. The bar is often divided into millibars, (abbreviationmbar) equal to one thousandth of a bar.
U.S. Barrel, used in the oil industry as a standard unit of oil production (equivalent to42 US gallons or 35 imperial gallons).
The calorie, a metric system unit of energy now superseded by the SI unit, the joule.(1 kcal = 1 000 calories).
An older imperial unit of weight still used occasionally for very small amounts ofmaterial (7 000 grains = 1 pound).
Hectare, metric unit of ground area (equivalent to 2.47 acres), equal to 10 000 m2.
Horsepower, the rate of mechanical work.
Abbreviation for ‘imperial’. When used alongside a unit it indicates that the unitbelongs to the imperial system (e.g. 1 gal (imp) is 1 imperial gallon).
The joule, the SI unit of energy (1 kJ = 1 000 joules).
A measure of energy equivalent to consumption of 1 kW of power for one hour. ThekWh is the traditional ‘unit’ of electricity in industry. It is the unit usually used oninvoices to show the amount of electrical energy used by the consumer.
The litre, a metric unit of volume.
Units of pressure.
In imperial units (pounds per square inch, psi), pounds force applied to one squareinch of surface.
In SI units, (kilo pascals, kPa), a force of 1000 pascals applied over one square metreof surface. (The pascal is a pressure of one newton applied to one square metre).
A unit of heat used traditionally by the gas industry.
The metric tonne, slightly smaller than the imperial ton (around 1.6 per cent less).
The watt, a unit of power (1 kW = 1 000 watts).
Table F.2: Commonly used units and what they mean
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