ME_63-_ENERGY_AUDIT_OF_APH

ENERGY AUDIT OF AIR PRE-HEATER UNIT AT

WANAKBORI THERMAL POWER STATION

A PROJECT REPORT

Submitted by

AKASH BHAVSAR (110370119109)

HAMZA DHILAWALA (110370119101)

DIPESH BADGUJAR (110370119102)

KARTIK YADAV (110370119155)

In part fulfillment for the award of the degree

Of

BACHELOR OF ENGINEERING

In

Mechanical Engineering Department

Parul Institute of Engineering & Technology

P.O. Limda, Ta. Waghodia,

Dist.Vadodara-391760,

Gujarat, India.

Gujarat Technological University, Ahmadabad

APRIL 2015

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CERTIFICATE

Date: / /

This is to certify that the dissertation entitled “ENERGY AUDIT OF AIR

PRE-HEATER UNIT AT WNAKBORI THERMAL POWER STATION ”

has been carried out by

AKASH BHAVSAR (110370119109)

HAMZA DHILAWALA (110370119101)

DIPESH BADGUJAR (110370119102)

KARTIK YADAV (110370119155)

Under my guidance in partial fulfillment for the degree of Bachelor of

Engineering in Mechanical (Final Year) of Gujarat Technological University,

Ahmadabad during the academic year 2014-15.

Prof. Deman Sahu

Project Guide (Internal)

Prof. N. H. Gandhi Mr. Dinker M. Jethva

Project Head Exe. Engr. Training Dept.

WTPS, GSECL.

Prof. Sohail M. Siddiqi

Head of the Department,

Department of Mechanical Engineering

External Examiner

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ACKNOWLEDGEMENT

We have taken efforts in this project. However, it would not have been possible

without the kind support and help of many individuals and organizations. We would like to

extend our sincere thanks to all of them.

With immense pleasure we express our deep and sincere gratitude, regards and

thanks to our project guide Asst. Prof. Deman Sahu for his excellent guidance,

invaluable suggestions and continuous encouragement at all the stages of our project

work. His wide knowledge and logical way of thinking have been of great value for us. As

a guide he has a great influence on us, both as a person and as a professional.

We wish to express our warm and sincere thanks to Prof. Sohail M. Siddiqi

(Head of Department of Mechanical Engineering, PIET) and Prof. Nirav H. Gandhi

(Project Head) for his support & the facilities provided by him in college.

We would like to express my special gratitude and thanks to our industrial guide

Mr. D. M. Jethva & Mr. Hitesh Nylani for giving us such attention and time for the

project work.

At last, we cannot forget our family members supporting us spiritually throughout

our life and our friends without whom it was really not possible for us to do this

dissertation. Finally, thank you to Parul Institute and all the other people who have

supported us during the course of this work.

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ABSTRACT

Air pre-heater is a heat transfer surface in which air temperature is raised by transferring heat from other media such as flue gas .Hot air is necessary for rapid combustion in the furnace and also for drying coal in milling plants. So an essential boiler accessory which serves this purpose is air pre-heater. The air pre-heater are not essential for operation of steam generator, but they are used where a study of cost indicates that money can be saved or efficient combustion can be obtained by their use. The decision for its adoption can be made when the financial advantages is weighed against the capital cost of heater in the project work we have taken up the operation and performance analysis of Air pre-heater of 210 MW power generation unit at WANAKBORI THERMAL POWER STATION, GUJARAT. In analysis of performance preventive measures for corrosion of heating elements has been studied, and also air heater leakage, corrected gas outlet temperature and finally gas efficiency has been calculated.

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TABLE OF CONTENTSCERTIFICATE 1

AKNOWLEDGEMENT 2

ABSTRACT 3

TABLE OF CONTENT 4

1. INTRODUCTION 6

1.1 ENERGY SCENARIO 6

1.1.1 POWER CAPACITY IN INDIA 7

1.1.2 TOTAL INSTALLED CAPACITY 7

1.2 CONVENTIONAL ENERGY SOURCES 8

1.2.1 RENEWABLE POWER 8

1.2.2 OFF-GRID RENEWABLE POWER PROGRAMME 9

1.3 ENERGY AUDIT - A TOOL 11

1.3.1 DEFINITION & OBJECTIVES OF ENERGY MANAGEMENT11

1.3.2 ENERGY AUDIT: TYPES AND METHODOLOGY 12

1.3.2.1 NEED FOR ENERGY AUDIT 13

1.3.2.2 TYPE OF ENERGY AUDIT 13

2. LITERATURE REVIEW 19

3. PROJECT WORK 22

3.1 INTRODUCTION TO WTPS 22

3.2 LAY-OUT OF COAL FIRED POWER PLANT 22

3.3 AIR PRE-HEATER 23

3.3.1 NEED OF AIR PRE-HEATER 23

3.3.2 AIR PRE-HEATER AT WTPS 24

3.3.3 MAIN COMPONENTS OF RAPH 25

3.4 AIR PRE-HEATER AUDIT 26

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3.4.1 INTRODUCTION 26

3.4.2 OBJECTIVE OF AUDIT 27

3.4.3 PARAMETERS REQUIRED FOR ANALYSIS 28

3.5 TEST PROCEDURE 28

3.5.1 UNIT OPERATION 28

3.5.2 TEST DURATION 29

3.5.3 MEASUREMENT LOCATIONS 29

3.5.3.1 TRAVERSE LOCATION- GAS SIDE 30

3.5.3.2 TRAVERSE LOCATIONS- AIR SIDE 30

3.5.3.3 PORTS AND PROBS 31

3.5.4 DATA COLLECTION PROCEDURE 32

3.5.4.1 CONTROL ROOM DATA 32

3.5.4.2 FLUE GAS & AIR TEMPERATURE 32

3.5.4.3 FLUE GAS COMPOSITION 33

3.5.4.4 SPECIAL TEST INSTRUMENTS 34

3.6 ANALYSIS AND DATA COLLECTION 34

3.6.1 MEASUREMENT OF FLUE GAS O2 35

3.6.2 APH PERFORMANCE INDICES COMPUTATION 36

3.7 MEASUREMENT TABLES (BEFORE) 38

3.8 CALCULATIONS (BEFORE) 39

3.9 AREAS TO BE CONSIDERED FOR IMPROVEMENT 41

3.10 STEPS TAKEN FOR IMPROVEMENT OF APH PERFORMANCE 44

3.11 MEASUREMENT TABLES (AFTER) 45

3.12 CALCULATIONS (AFTER) 46

3.13 COMPARISON OF PARAMETERS 48

3.14 CONCLUSION OF AUDIT 49

REFERENCES 50

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1. INTRODUCTION

1.1 ENERGY SCENARIOAbout 70% energy generation capacity is from fossil fuels in India.

Coal consumption is 40% of India's total energy consumption which is

followed by crude oil and natural gas at 24% and 6% respectively. India is

dependent on fossil fuel import to fulfill its energy demands. The energy

imports are expected to exceed 53% of the India's total energy consumption.

In 2009-10, 159.26 million tones of the crude oil was imported which

amounts to 80% of its domestic crude oil consumption. The percentage of oil

imports is 31% of the country's total imports. The demand of electricity has

been hindered by domestic coal shortages. Cause of this, India's coal imports

is increased by 18% for electricity generation in 2010.

India has one of the world's fastest growing energy markets due to

rapid economic expansion. It is expected to be the second largest contributor

to the increase in global energy demand by 2035. Energy demand of India is

increasing but has limited domestic fossil fuel reserves. The country has

ambitious plans to expand its renewable energy resources and plans to install

the nuclear power industries. India has the world's fifth largest wind power

market and plans to add about 20GW of solar power capacity. India increases

the contribution of nuclear power to overall electricity generation capacity

from 4.2% to 9%. The country has five nuclear reactors under construction.

Now, India has became third highest in the world who is generating the

electricity by nuclear and plans to construct 18 additional nuclear reactors by

2025, then India will become second highest in the world.

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1.1.1 Power Capacity in India

The energy generated by different resources in the given table. This

table also shows the growth of installed power capacity in India.

Thermal (%) Hydro (%) Nuclear (%) RenewableTime period (MW) (>25MW) (MW) Power (%)

(MW1.4.2002 70.85% 25% 2.59% 1.55%

74429 26269 2720 16281.4.2007 64.06% 25.51% 2.87% 7.55%

87015 34654 3900 1025831.9.2010 63.95% 22.41% 2.7% 10.90%

106518 37328 4560 18,155

Table 1.1: Growth of Installed Power Capacity in India(Source: Ministry of New and Renewable Energy, Government of India)

1.1.2 Total Installed Capacity (October 2012)

The installed capacity with respect of various resources is as on

30.06.2012 from the Ministry of Renewable Energy. Note: The Hydro

generating stations with installed capacity less than or equal to 25 MW are

indicated under RES.

Source Total Capacity (MW) PercentageCoal 120,103.38 57.38

Hydroelectricity 39,291.40 18.77

Renewable energy source 24,998.46 11.94

Gas 18,903.05 9.03

Nuclear 4780 2.28

Oil 1,199.75 0.57

Total 2,09,276.04

Table 1.2: Installed capacity in respect of various resources(Source: Ministry of Renewable Energy, Government of India)

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Sector Total Capacity (MW) Percentage

State Sector 86,881.40 41.51Central Sector 62,373.63 29.66Private Sector 60,321.28 28.82Total 2,09,276.04

Table 1.3: Sector wise Generation Total Capacity(Source: Ministry of Renewable Energy Government of India)

1.2 Conventional Energy Sources

India is not endowed with large primary energy reserves in keeping with

large geographical growing population which increase final energy indeed.

Region Target MU Generation* Deviation (+/-)MU MU (%)

Northern 51044.00 55839.79 (+)4795.79 (+)9.40Western 14193.00 15041.53 (+)848.53 (+)5.98Southern 31882.00 30518.04 (-)1363.96 (-)4.28Eastern 9988.00 8991.10 (-)996.90 (-)9.98

N-Eastern 4245.00 3905.33 (-)339.67 (-)8.00All India 111352.00 114295.79 (+)2443.79 (+)2.64

Table 1.4: Region Wise Energy generation in IndiaSource: Central Electricity Authority (CEA)

Energy audit throughout the India indicates that coal is the main energy

resource of the country. The coal contribution is 70% of the total energy

production. The region wise energy generation is indicated in table. The

generation is compared with initiative target in the given table.

1.2.1 Renewable Power

The Government has been promoting private investment for the setting up

of projects for power generation from renewable energy sources and special

tariffs being provided at the State level.

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Resource Potential Up to Plan Plan Plan Cumulative 12th(MW) 9th Up to Up to Target Achievement Plan

10th 11th Up to Projection30.09.10 (2017)

WindPower 48,500 1667 5,427 9,000 4,714 12,809 27300

SmallHydro 15,000 1,438 538 1,400 759 2,823 5000Power

BioPower* 23,700 390 795 1,780 1,079 2,505 5100

Solar 20-30Power MW/sq 2 1 50 8 18 4000

kmTotal l3,497 6,761 12,230 6,560 18,155 41,400

Table 1.5: Share of Different Renewable Sources in India(Source: Ministry of New and Renewable Energy, Government)

These include capital subsidies, accelerated depreciation and customs

duties. The capital subsidy being provided depends on region and the

renewable resources. The capital subsidies vary from 10% to 90% of

project cost. The higher level of capital subsidies are given for projects in

the North-Eastern Region or Special category States. Generation Based

incentives have been introduced recently for Wind Power to attract private

investment by Independent Power Producers. They are not availing

Accelerated Depreciation benefit and feed in tariffs for solar power.

1.2.2 Off-Grid Renewable Power Programs

Most importantly, it provides energy access to large rural populations in

which includes those in unreachable areas. Those meet the un-obtained

demand in many other areas.

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S.No. Resource/System Achievement up to30.09.2010

1. Biomass Power 263.1 MW2. Biomass Gasifier 128.2 MWeq3. Waste to Energy 60.8 MWeq4. Solar PV Power Plants 2.9MWp5. Hybrid Systems 1.1 MWp6. Family type Biogas Plants 4.27 million7. SPV Home Lighting system 6,19,428 nos.8. Solar lantern 8,13,380 nos.9. SPV Street Lighting System 1,21,227 nos.10. SPV Pumps 7,495 nos.11. Solar Water Heating - Collector Area 3.77 million sq m

Table 1.6: Achievement in Off Grid Power System(Source: Ministry of New and Renewable Energy, Government of India)

Perhaps the outmost areas can get electricity only through renewable

sources. Secondly, very important, unrecognized consequence attributed to

off-grid applications. In this way or other, they replace fossil fuels. These

can make a significant contribution to reduction in their consumption which

is most important from the point of view of energy security. For instance,

solar PV replaces diesel or furnace oil in various areas, rural lighting

replaces kerosene, a biogas plant or solar cooking system replace cooking

gas. Renewable energy can also meet the requirement of process heat in

small enterprises and replace small diesel generator sets which consume

diesel oil. It has a giant strength in its ability to supply power in a

decentralized and distributed mode which has the advantage of

consumption at the production point and reduces land and environmental

concerns.

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1.3 To increase the Efficiency of the Power System: Energy Audit a Tool

Energy audit is a powerful tool for exposure operational and equipment

improvements that will reduce energy costs, lead to higher performance and

save energy. Sometimes, the energy audit is also called an “energy

assessment” or “energy study”. Energy audits can be done as a stand-alone

effort but may be conducted as part of a larger analysis across an owner’s

entire group. The purpose of an energy audit is to find out how, when, where

and why energy is used. The energy audit is also used to identify

opportunities in improving the efficiency. Energy auditing services are

offered by engineering firms, energy services companies and energy

consultants. The energy auditors do the audit process.

The first thing energy auditor needs to be aware of end user

expectations and then audit starts with an analysis of historical and current

utility data. This sets the stage for an onsite inspection. The most important

outcome of an energy audit is a list of recommended energy efficiency

measures (EEMs). Energy audit serves the purpose of identifying energy

usage within a facility, process or equipment, and then identifies

opportunities for conservation, called energy conservation measures (ECMs).

Audit provides the most accurate picture of energy savings opportunities.

Energy audits can be targeted to specific systems i.e. boiler, turbine, generator

and any motor etc.

1.3.1 Definition & Objectives of Energy Management

The fundamental goal of energy management is to produce goods and

provide services with the least cost and least environmental effect. The term

energy management means many things to many people. One definition of

energy

management is:

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"The judicious and effective use of energy to maximize profits (minimize

costs) and enhance competitive positions"

(Cape Hart, Turner and Kennedy, Guide to Energy Management Fairmont

press inc. 1997)

Another comprehensive definition is:

"The strategy of adjusting and optimizing energy, using systems and

procedures so as to reduce energy requirements per unit of output while

holding constant or reducing total costs of producing the output from these

systems"

The objective of Energy Management is to achieve and maintain optimum

energy procurement and utilisation, throughout the organization and:

• To minimise energy costs / waste without affecting production & quality

• To minimise environmental effects.

1.3.2 Energy Audit: Types And Methodology

Energy Audit is the key to a systematic approach for decision-making in

the area of energy management.It attempts to balance the total energy inputs

with its use, and serves to identify all the energy streams in a facility. It

quantifies energy usage according to its discrete functions. Industrial energy

audit is an effective tool in defining and pursuing comprehensive energy

management programme.

As per the Energy Conservation Act, 2001, Energy Audit is defined as "the

verification, monitoring and analysis of use of energy including submission of

technical report containing recommendations for improving energy efficiency

with cost benefit analysis and an action plan to reduce energy consumption".

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1.3.2.1 Need for Energy Audit

In any industry, the three top operating expenses are often found to be

energy (both electrical and thermal), labour and materials. If one were to

relate to the manageability of the cost or potential cost savings in each of the

above components, energy would invariably emerge as a top ranker, and thus

energy management function constitutes a strategic area for cost reduction.

Energy Audit will help to understand more about the way energy and fuel are

used in any industry, and helpful in identifying the areas where waste can

occur and where scope for improvement exists.

The Energy Audit would give a positive orientation to the energy cost

reduction, preventive maintenance and quality control programmes which are

vital for production and utility activities. Such an audit programme will help

to keep focus on variations which occur in the energy costs, availability and

reliability of supply of energy, decide on appropriate energy mix, identify

energy conservation technologies, retrofit for energy conservation equipment

etc.

In general, Energy Audit is the translation of conservation ideas into

realities, by lending technically feasible solutions with economic and other

organizational considerations within a specified time frame.

The primary objective of Energy Audit is to determine ways to reduce

energy consumption per unit of product output or to lower operating costs.

Energy Audit provides a "Bench-mark" (Reference point) for managing

energy in the organization and also provides the basis for planning a more

effective use of energy throughout the organization.

1.3.2.2 Type of Energy Audit

The type of Energy Audit to be performed depends on:

- Function and type of industry

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- Depth to which final audit is needed, and

- Potential and magnitude of cost reduction desired

Thus Energy Audit can be classified into the following two types.

i) Preliminary Audit

ii) Detailed Audit

1.3.2.3 Preliminary Energy Audit Methodology

Preliminary energy audit is relatively quick exercise to:

• Establish energy consumption in the organization

• Estimate the scope for saving

• Identify the most likely and the easiest areas for attention

• Identify immediate (especially no-/low-cost) improvements/ savings

• Set a 'reference point'

• Identify areas for more detailed study/measurement

• Preliminary energy audit uses existing, or easily obtained data

1.3.2.4 Detailed Energy Audit Methodology

A comprehensive audit provides a detailed energy project implementation

plan for a facility; since it evaluates all the major energy using systems. This

type of audit offers the most accurate estimate of energy savings and cost. It

considers the interactive effects of all projects, accounts for the energy use of

all major equipment, and includes detailed energy cost saving calculations

and project cost.

In a comprehensive audit, one of the key elements is the energy balance.

This is based on an inventory of energy using systems, assumptions of current

operating conditions and calculations of energy use. This estimated use is

then compared to the utility bill charges.

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Detailed energy auditing is carried out in three phases: Phase I, II and III.

Phase I - Pre-Audit Phase

Phase II - Audit Phase

Phase III - Post Audit Phase

A Guide for Conducting Energy Audit at a Glance

Industry-to-industry, the methodology of Energy Audits needs to be

flexible. A comprehensive ten-step methodology for conduct of Energy Audit

at field level is presented below. Energy Manager and Energy Auditor may

follow these steps to start with and add/change as per their needs and industry

types.

Ten Steps Methodology for Detailed Energy Audit

Phase-I: Pre-Audit Phase

Step 1: Walk through audit

Step 2: Conduct brief meeting with all divisional heads

Phase-II: Audit phase

Step 3: Primary data gathering

Step 4: Conduct survey and monitoring

Step 5: Conduct detailed trial/experiments

Step 6: Analysis of energy use

Step 7: Identification and development of Energy Conservation Opportunity

Step 8: Cost benefit analysis

Step 9: Reporting and presentation to top management

Phase-III: Post Audit phase

Step 10: Implementation and follow-up

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Phase I -Pre Audit Phase Activities

A structured methodology to carry out an energy audit is necessary for

efficient working. An initial study of the site should always be carried out, as

the planning of the procedures necessary for an audit is most important.

Initial Site Visit and Preparation Required for Detailed Auditing

An initial site visit may take one day and gives the Energy

Auditor/Engineer an opportunity to meet the personnel concerned, to

familiarize him with the site and to assess the procedures necessary to carry

out the energy audit.

During the initial site visit the Energy Auditor/Engineer should carry out the

following actions: -

• Discuss with the site's senior management for the aims of the energy audit.

• Discuss economic guidelines associated with the recommendations of the

audit.

• Analyse the major energy consumption data with the relevant personnel.

• Obtain site drawings where available - building layout, steam distribution,

compressed air distribution, electricity distribution, etc.

• Tour the site accompanied by engineering/production

The main aims of this visit are:

• To finalise Energy Audit team

• To identify the main energy consuming areas/plant items to be surveyed

during the audit.

• To identify any existing instrumentation/ additional metering required.

• To decide whether any meters will have to be installed prior to the audit eg.

KWh, steam, oil or gas meters.

• To identify the instrumentation required for carrying out the audit.

• To plan with time frame

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• To collect macro data on plant energy resources and major energy

consuming centres

• To create awareness through meetings/ programmes

Phase II- Detailed Energy Audit Activities

Depending on the nature and complexity of the site, a comprehensive audit

can take from several weeks to several months to complete. Detailed studies

to establish, and investigate, energy and material balances for specific plant

departments or items of process equipment are carried out. Whenever

possible, checks of plant operations are carried out over extended periods of

time, at nights and at weekends as well as during normal daytime working

hours, to ensure that nothing is overlooked. The audit report will include a

description of energy inputs and product outputs by major department or by

major processing function, and will evaluate the efficiency of each step of the

manufacturing process. Means of improving these efficiencies will be listed,

and at least a preliminary assessment of the cost of the improvements will be

made to indicate the expected payback on any capital investment needed. The

audit report should conclude with specific recommendations for detailed

engineering studies and feasibility analyses, which must then be performed to

justify the implementation of those conservation measures that require

investments.

The information to be collected during the detailed audit includes:

1. Energy consumption by type of energy, by department, by major items of

process equipment, by end-use

2. Material balance data (raw materials, intermediate and final products,

recycled materials, use of scrap or waste products, production of by-products

for re-use in other industries, etc.)

3. Energy cost and tariff data

4. Process and material flow diagrams

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5. Generation and distribution of site services (eg. Compressed air, steam).

6. Sources of energy supply (e.g. electricity from the grid or self-generation)

7. Potential for fuel substitution, process modifications and the use of co-

generation systems (combined heat and power generation).

8. Energy Management procedures and energy awareness training programs

within the establishment.

Phase III :Report Preparation Prepare Audit Report: Go over the results of findings and recommendations

in a final report. The report should include a description of the facilities and

their operation. It should also include a debate of all major energy-consuming

systems and an explanation of all recommended ECMs with their specific

energy impact implementation costs and benefits.

Present and Review Report with Facility Management: Clarify the process

and all activities performed to confirm the report’s conclusion. Provide

economic results as a formal presentation of the final recommendations.

Explain the data on the benefits and costs which make a decision or set

priorities on implementation of ECMs.

After the audit: Read the report and understand the contents and give the

prioritize improvements according to choice i.e. Energy reduction, Cost, Need

(equipment failure) etc.

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2. LITERATURE REVIEW

Title of Invention: Quad sector regenerative air preheater for circulating fluidized bed combustion boilerDate of Filing/Application: 07/07/2008

Name of Applicant/Assignee: Bharat Heavy Electricals Limited (Ind)

Summary of Invention: Quad sector Air preheater consists of one gas sector, first secondary sector, one primary sector and second secondary sector compartmented by sector plates and the rotor is driven by the rotor drive and is surrounded by the rotor housing and constructed between the cold end connecting plate at one end and hot end connecting plate at other end. The rotor is supported by the support bearing at the bottom and guide bearing at the top. The cylindrical rotor revolves at a very low speed and the plates are alternatively, exposed to the gas and air flows. In the Quad sector Air preheater design, the primary air sector is sandwiched on either side by secondary air sectors (i.e. one gas sector, first secondary sector, one primary sector and second secondary sector in that order) which helps minimizing the air leakage to the gas side.

Title of Invention: Regenerative Air Preheater Design To Reduce Cold End Fouling

Date of Filing/Application: 09/06/2011

Application No.: 1638/DEL/2011

Name of Inventor: 1)BIRMINGHAM JAMES WILLIAM (US)     2)SEEBALD JAMES DAVID (US)

Summary of Invention: The invention in a preferred form is an air preheater that is more resistant to 'fouling' under varying boiler loads. It is an object of the invention to provide an air preheater that is more resistant to corrosion. It is an object of the invention to provide an air preheater that adjusts to varying

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boiler loads. It is an object of the invention to provide an air preheater that adjusts flue gas velocity under varying boiler loads.

Title of Invention: An improved sealing system for rotary regenerative air preheater to reduce leakage of high pressure air stream to low pressure gas stream.

Date of Filing/Application: 21/09/2007

Application No.:1316/KOL/2007

Name of Inventor: 1 Shri Krishnamurthy Narayanan (Ind)

2 Shri Ganapathy Ramamurthy Venkataraman (Ind)

Summary of Invention: Accordingly there is provided an improved air preheater sealing system which reduces the leakage of high pressure air stream to low pressure gas stream. In the present invention, the diaphragm plate is split into a top diaphragm plate and a bottom diaphragm plate and a first component of the improved sealing system is mounted in between the top and bottom diaphragm plates radial to the rotor post in addition to the existing radial seal fixed above the diaphragm plate. Similarly, a second component of the improved sealing system is mounted between the top diaphragm and bottom diaphragm plates axial to the rotor post in addition to the existing axial seal fixed on the diaphragm plate. During operation of the Air preheater, the rotor gets turn down causing an increase in the gap between the top diaphragm and the bottom diaphragm plates. Because of the provision of the web seals, according to the invention, no passage is available for leakage of the high pressure air stream to the low pressure gas stream and thus the leakage is reduced. The inventive concept resides in configurating the diaphragm plates as 'the splitting diaphragm plates' for example, the top and bottom diaphragm plates and mounting the web seals between the top and bottom diaphragm plates. Accordingly, the web seals function as a sealing means for the gap between the top and bottom diaphragm plates during operation of the Air preheater and thereby leakage of high pressure air stream to low pressure gas stream is reduced considerably.

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Title of Invention: Air preheater adjustable basket sealing system

Date of Filing/Application: 14/06/1996

Publication Number: US5836378 (A)

Name of Inventor: MARK E BROPHY (US)

HARLAN E FINNEMORE (US)

Summary of Invention: The present invention provides an arrangement of means in an air preheater for sealing gaps around the baskets at the periphery of the rotor, thereby eliminating flow paths that would allow portions of the air and gas stream to bypass the heat transfer surface. More particularly, the present invention provides a circumferential sealing system for sealing gaps between the heat exchange baskets and the rotor shell portions. The present invention also provides means in an air preheater to minimize the size of the peripheral seal structure, effectively reducing the weight of the rotor. The present invention further eliminates the cold-end covers and attachment studding, thereby reducing the cost of manufacture.

Title of Invention: Adjustable axial sealing plate for rotary regenerative air preheater

Date of Filing/Application: 21/02/1996

Name of Applicant: ABB AIR PREHEATER, INC (US)

Summary of Invention: The present invention provides an arrangement of means in an air preheater for mounting and adjusting axial seal plates using a reduced number of adjustable mountings and replacing the remaining adjustable mountings with adjustable compression stops which engage but are not attached to the axial seal plates. This reduces cost and facilitates installation.

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3. PROJECT WORK

3.1 INTRODUCTION TO WTPS

Wanakbori Thermal Power Station (WTPS) of Gujarat State Electricity Corporation Ltd. (GSECL) is located at about 7 km away from Sevalia Railway station on board gauge Anand-Godhra railway line and 13 km away from Balasinor and on the bank of river Mahi in Kheda district of Gujarat.

Total installed capacity of Wanakbori TPS is 7x210MW= 1470 MW. The capacity and commissioning date of all the units are given below:

3.2 GENERAL LAYOUT OF COAL FIRED POWER PLANT

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3.3 AIR PRE-HEATER

An air preheater (APH) is a general term used to describe any device

designed to heat air before another process (for example, combustion in a

boiler) with the primary objective of increasing the thermal efficiency of the

process. They may be used alone or to replace a recuperative heat system or

to replace a steam coil.

The purpose of the air preheater is to recover the heat from the boiler flue gas

which increases the thermal efficiency of the boiler by reducing the useful

heat lost in the flue gas. As a consequence, the flue gases are also conveyed to

the flue gas stack (or chimney) at a lower temperature, allowing simplified

design of the conveyance system and the flue gas stack. It also allows control

over the temperature of gases leaving the stack.

3.3.1 NEED OF AIR PRE-HEATER

Stability of combustion is improved by use of hot air.

Intensified and improved combustion.

Burning poor quality fuel efficiently.

High heat transfer rate in the furnace and hence lesser heat transfer area

requirement.

Less unburnt fuel particle in flue gas thus complete combustion is

achieved.

Intensified combustion permits faster load variation. In the case of

pulverized coal combustion, hot air can be used for drying the coal as

well as for transporting the pulverized coal to burners.

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This being a non-pressure part will not warrant shut-down of units due

to corrosion of heat transfer surface which is inherent with lowering of

flue gas temperature

Lower grades of coals can be burnt efficiently with hot air

Faster load variations are possible.

3.3.2 AIR PRE-HEATER AT WTPS

At WANAK BORI THERMAL POWER STATION APHs of Tri-sector

Rotary Vertical Inverted Regenerative are used.

In Regenerative type the heating medium flows through a closely packed

matrix to raise its temperature and then air is passed through the matrix to

pick-up the heat. Either the matrix or the hoods are rotated to achieve this and

hence there is slight leakage through sealing arrangements at the moving

surfaces. Designed for coal-fired applications the Tri-sector air preheater

permits a single heat exchanger to perform two functions: coal drying and

combustion air heating. Because only one gas duct is required, the need for

ductwork expansion Joints, and insulation is greatly reduced when compared

with a separate air heating system. Equipment layout is simplified, less 

Structural steel is needed to install the System and less cleaning equipment is

required.

The duct arrangement of a Tri-Sector shows the air and gas flows through

the unit. The size and location of the primary air duct can vary, depending on

the flow and temperature requirements. The design has three sectors - one

for the flue gas, one for the primary air that dries the coal in the pulverized,

and one for secondary air that goes to the boiler for combustion.

25

3.3.3 MAIN COMPONENTS OF RAPH

• Rotor assembly

• Rotor housing assembly

• Hot end Connecting plate assembly.

• Cold end connecting plate assembly.

• Heating elements

26

• Sealing system (Radial, Axial & Bypass )

• Guide bearing assembly.

• Support bearing assembly.

• Lubrication. oil circulation system

• Main Drive assembly. and air-line components

• Cleaning device assembly.

• Washing & Deluge pipe assembly.

• Fire sensing device assembly.

• Rotor stoppage alarm.

3.4 AIR PRE HEATER ENERGY AUDIT BY PERFORMANCE TEST

3.4.1 Introduction

This procedure provides a systematic approach for conducting routine APH

performance tests on tubular and rotary regenerative APH.

APH leakage % can be determined using this procedure, which is defined

as the weight of air passing from the airside to the gas side of the air heater.

This index is an indicator of the condition of the APH’s seals. As air heater

seals wear, air heater leakage increases. The increase in air heater leakage

increases the station service power requirements of the forced draft and

induced draft fans, increasing unit net heat rate and at times limiting unit

capacity.

APH gas side efficiency can also be determined using this procedure and is

defined as the ratio of the temperature drop, corrected for leakage, to the

temperature head, expressed as a percentage.

27

Gas side efficiency is an indicator of the internal condition of the APH. As

conditions inside the air heater worsen (baskets wear, ash plug gage, etc.), the

APH gas side efficiency decreases. This is generally accompanied by an

increase in exit gas temperature and a decrease in APH air outlet temperature,

resulting in an increase in unit heat rate.

X-Ratio depends on the moisture in coal, air infiltration, air & gas mass

flow rates, leakage from the setting and specific heats of air & flue gas. X-

ratio does not provide a measure of thermal performance of the APH, but is a

measure of the operating conditions. A low X-ratio indicates excessive gas

weight through the APH or that airflow is bypassing the air heater. A lower

than design X-ratio leads to higher than design gas outlet temperature & can

be used as an indication of excessive tempering air to the mills or excessive

boiler infiltration.

3.4.2 OBJECTIVE OF THE AUDIT

1. To identify abnormal changes in air heater leakage or efficiency and

provide information for identifying the cause of performance

degradation.

2. To provide information to allow accounting for the contribution of

APH performance degradation to unit heat rate and capacity.

3. To crosscheck the readings of important station instruments.

3.4.3 PARAMETER REQUIRED FOR APH PERFORMANCE MONITORING:

28

3.5 Test Procedure

3.5.1 Unit Operation- Operating Conditions of Test Runs

Test runs are conducted at an easily repeatable level at defined baseline

conditions at full load with same number of mills in service and same total air

levels as previous tests. The operating conditions for each test run are as

follows.

29

1) No furnace or air heater soot blowing is done during the test.

2) ii. Unit operation is kept steady for at least 60 minutes prior to the test.

3) Steam coil Air heaters’ (SCAPH) steam supply is kept isolated and gas

recirculation dampers if any, are tightly shut.

4) No mill change Over is done during the test.

5) All air and gas side damper positions should be checked and recorded.

6) The test is abandoned in case of any oil support during the test period.

7) Eco hopper de-ashing or Bottom hopper de-ashing is not done during

the test.

8) Regenerative system should be in service with normal operation.

3.5.2 Test Duration

The test run duration will be the time required to complete two traverses for

temperature and gas analysis. Two separate test crews should sample the gas

inlet and outlet ducts simultaneously.

3.5.3 Measurement Locations

The number and type of instruments required for conducting this test depend

on the unit being tested. The following table lists the measurement locations.

Measurement Temperature Gas Analysers Pressure AH Gas Inlet Yes Yes YesAH Gas Outlet Yes Yes YesAH Air Inlet Yes YesAH Air Outlet Yes Yes

3.5.3.1 Traverse Locations – Gas side

30

1) The gas inlet traverse plane should be located as close as possible to

the air heater inlet. This is done to ensure that any air ingress from the

intervening duct / an expansion joint is not included in air heater

performance assessment.

2) The gas outlet traverse plane should be located as far downstream from

the air preheater as possible, to allow mixing of the flow to reduce

temperature and 02 stratification. However, it should not be located

downstream of other equipment or access ways that might contribute to

air ingress (e.g. Mechanical collectors, ESP’s, man ways, ID fans).

3) Iii.ASME PTC 19.10 provides guidelines for the number, location and

orientation of ductwork ports.

3.5.3.2 Traverse Locations – Air side

1) The air inlet traverse plane should be located after any air heating coils

and as close as possible to the air heater inlet. Since the entering air

temperature is usually uniform, a single probe with 2/ 3 temperature

measurement points is adequate.

2) The air outlet traverse plane should be located as far downstream from

the air heater as possible to allow mixing of the flow to reduce the gas

stratification.

31

3.5.3.3 Ports and Probes

Typical Test Port and probe sketches are provided below.

1) Tubes numbered 1,2 & 3 are carbon steel 3/8” OD tubes and tube no. 4

is carbon steel 12-15 mm OD

32

2) Tubes numbered 1, 2 & 3 are for gas sampling while tube no. 4 is for

carrying thermocouple wires for temperature measurement.

3) Tube no. 4 has 2 no. 6 mm dia hole for thermocouple wire tip

protrusion (made elliptical for ease in wire insertion)

4) If d is flue gas duct width at the test cross-section then lengths of tube

1, 2 & 3/4 from flange is d/6 +i , d/2+i, 5d/6 +i respectively (i is the

thickness of the insulation + flange).

5) Tube protrusions beyond the flange are 80 mm for tube 1 and 120 mm

for tube 2 & 150 mm for tubes 3 & 4 (approx.).

6) The probe flanges match the port flanges.

3.5.4 Data Collection Procedure

3.5.4.1 Control Room Data

A separate test log for control room data is created in unit DAS for data

collection at an interval of five minutes or less and averaged over the test

period.

3.5.4.2 Flue Gas & Air Temperatures

The online measurements of flue gas and air temperatures at air heater inlet

and outlet are used for efficiency computations. It’s important to ensure that

the online measurements of air and flue gas temperatures are representative of

average temperatures in the duct. The on line feedback of flue gas exit

temperature after air heaters can be affected by gas stratification and may

require more number of thermocouples than presently installed. In some

layouts, the online thermocouples for flue gas temperature measurement are

mounted too close to air heaters in a cluster and need to be relocated for

representative measurement. Similarly the location and number of

temperature sensors on airside at air heater inlet and outlet should be

33

reviewed to obtain a representative average. The new locations can be

decided only by doing multiple point temperature measurements in a plane

perpendicular to the flow in the respective ducts. The number of measurement

points is determined as per ASME PTC 19.10, ‘Flue and Exhaust Gas

Analysis’ and would vary with duct configuration and size.

3.5.4.3 Flue Gas Composition

A representative value of flue gas composition (O2 / CO2 /CO) is obtained by

grid sampling of the flue gas at multiple points in a plane perpendicular to the

flow at air heater inlet and outlet using a portable gas analyser. Two complete

sets of data are collected for each traverse plane during each test run to ensure

data repeatability. A typical cross section of the flue gas duct with an 18-point

grid is shown here along with a typical probe. Each dot indicates a sampling

point for measurement of gas composition and temperature.(Fig)

Flue gas samples are drawn by a vacuum pump from the test grid probes and

sent to a portable gas analyser through a gas conditioning A B C D E F

system. Typically gas-conditioning system consists of a wash bottle, partially

filled with water for cleaning the sample, a condenser to condense the water

vapour out of the gas sample and a desiccant column to remove any water

vapour that got through the condenser.

34

3.5.4.4 Special Test Instruments

The portable analysers should be calibrated prior to the tests with calibration

gases. Purity grade Nitrogen should be used for ‘Zero’ calibration, while span

calibration should be done with standard calibration gases.

The instrument accuracy requirements are summarized in the following table.

MEASUREMENT RESOLUTION ACCURACYStatic Pressure 2mmWC 2mmWCTemperature 0.1oC 1.0oCGAS ANALYSISO2 0.1% +/- 1%CO2 0.1% +/- 1%CO 1ppm +/- 2%

A thermocouple (such as chromel–alumel) and digital thermometer

3.6 Analysis & Data collection

The test values can be compared with the design / PG test and historical

values. The comparison can also help in detection of measurement errors, if

any. The air heater gas side efficiency, APH leakage, corrected exit gas

temperature and measured exit gas temperature, gas side to air side

differential pressure and gas side pressure drop can be plotted on a time line

graph showing historical, design, and possibly acceptance test data.

If a significant reduction in air heater gas side efficiency occurs and

operator controllable parameters (air heater soot blowing, damper

adjustments, etc.) are determined not to be responsible, an internal inspection

of the air heater should be performed at the next available shutdown. Possible

causes of performance degradation include: bypass, isolation or recirculation

dampers mispositioned, APH baskets corroded/eroded/fouled air heater

baskets. A fouled air heater will experience a significant increase in gas side

pressure drop. Generally, a decrease in gas side efficiency will increase the

measured exit gas temperature.

35

The leakage rates for trisector air heaters should be between 10 - 13%. The

leakage levels depend on the differential pressure between the air and gas side

of the air heater, the degree of air heater pluggage and the condition of the

seals. A significant increase in air heater leakage warrants a physical

inspection of the air heater. Possible causes of increased leakage are axial and

radial seal mechanical damage or wear; sector plate mechanical damage or

warping; rotor eccentricity or excessive air to gas side differential pressure.

Typically recuperative air heaters should have zero leakage, but tube failures

due to corrosion or mechanical damage can result in leakage. If the unit is

equipped with bypass dampers or recirculation dampers, they should also be

inspected. Generally, an increase in air heater leakage will cause a decrease in

the measured exit gas temperature.

All test instrument readings should be compared to station instrument

readings to determine if any station instruments need calibration / up

gradation. The economic impact of increased air heater leakage is typically

reflected in increased station service power consumption of FD and ID fans.

In extreme cases unit de-rating may be caused due to insufficient fan

capacities.

The results should include a narrative describing any unusual findings, plots

of performance indices on a time line graph showing historical, design and/or

acceptance test data with analysis of variations, if any, and the test data listed

in a tabular form.

3.6.1 Measurement of Flue gas Oxygen and Temperature atESP Inlet and ID fan Outlet

Air ingress from eroded ducts, openings, and expansion joints increases the

flue gas volume and leads to loss of draught margins. Increase in oxygen

percentage in the flue gas and drop in temperature of the flue gas provides an

indication of the increase in air ingress. Along with the air heater tests, the

36

oxygen in flue gas at ESP inlet and ID fans’ outlet is measured separately in

each duct and compared to the average oxygen in flue gas at air heater outlet.

Air ingress

Quantification is done with the same formulae as those used for calculation of

AH leakage.

AIRingress=(O 2∈−O 2 out)

¿¿

3.6.2 APH Performance Indices Computation

1. Air heater leakage is determined by an empirical approximation as

following.

AL=(CO2≥−CO2 gl)

CO2 gl× 0.9× 100

AL = air heater leakage (%)CO2ge = percent CO2 in gas entering air heaterCO2gl = percent CO2 in gas leaving air heater

CO2 measurement is preferred due to high absolute values; In case of any

measurement errors, the resultant influence on leakage calculation is small.

Alternatively, the air heater leakage may also be determined from the

following equation:

AL=¿¿

AL = air heater leakage (%)O2ge = percent O2 in gas entering air heater (%)O2gl = percent O2 in gas leaving air heater (%)

The numerical average of the air heater’s gas inlet, gas outlet and air inlet

temperatures is calculated. Then the corrected air heater gas outlet

temperature is calculated using the following formula.

37

Tgnl=AL ×Cpa ×(Tgl−Tge)

100 ×Cpg+Tgl

Tgnl = gas outlet temperature corrected for no leakageCpa = the mean specific heat between Tae and TglTae = temperature of air entering air heater(c)Tgl = temp of gas leaving air heater (c) Cpg = mean specific heat between Tgl and Tgnl

2. The gas side efficiency is defined as the ratio of the temperature drop,

corrected for leakage, to the temperature head, expressed as a percentage.

Temperature drop is obtained by subtracting the corrected gas outlet

temperature from the gas inlet temperature. Temperature head is obtained by

subtracting air inlet temperature from the gas inlet temperature. The corrected

gas outlet temperature is defined as the outlet gas temperature calculated for

‘no air heater leakage’.

GSE= Temp .dropTemp . head

×100

GSE=Tge−TgnlTge−Tae

×100

Tae = Temperature of air entering air heater (C)Tgnl = gas out temp corrected for no leakage (C)

3. X ratio is the ratio of heat capacity of air passing through the APH to the

heat capacity of flue gas passing through the APH and is calculated using the

following formulae:

X−ratio=Wair out ×CpaWgas∈×Cpg

For no air-leakage,

X−ratio= Tgas∈−Tgas outTair out−Tair∈¿¿

38

3.7 Data Collected [Measurement Tables] Before (27/09/14)

APH (A) InletDeep Mid Shallow Deep Mid Shallo

wAVG

% O2 1.68 1.7 1.8 1.7 2.12 2.2 1.87ppm CO 25 25 36 30 30 26 28.67% CO2 16.93 16.86 16.86 16.96 16.54 16.9 16.84ppm NO 243 246 250 240 226 247 242ppm NOx 255 211 - - - - 242.33mm of WC

Draft -37 -37 -37 -37 -37 -37 -37

oC Temp 334 334 336 335 335 336 335

APH (B) InletDeep Mid Shallow Deep Mid Shallo

wAVG

% O2 1.34 1.45 1.44 2.91 2.76 2.84 2.12ppm CO 29 24 20 2 4 5 14% CO2 17.22 17.13 17.14 15.85 15.96 15.91 16.54ppm NO 230 232 233 235 231 233 232.33ppm NOx 241 244 234 247 243 245 242.33mm of WC

Draft -38 -38 -38 -55 -55 -55 -46.5

oC Temp 329 331 332 335 324 324 329.17

APH (A) OutletDeep Mid Shallow Deep Mid Shallo

wAVG

% O2 1.96 2.27 1.79 4.91 5.05 4.9 3.48ppm CO 0 0 0 1 1 2 0.67% CO2 16.67 16.41 16.89 14.1 13.91 14.1 15.35ppm NO 251 212 251 201 198 198 218.50ppm NOx 214 223 264 211 205 208 220.83mm of WC

Draft -105 -105 -105 -105 -105 -105 -105

oC Temp 161 160 161 151 153 152 156.33

39

APH (B) OutletDeep Mid Shallow Deep Mid Shallow AVG

% O2 3.82 3.92 3.8 3.73 3.15 1.99 3.4ppm CO 96 92 39 426 733 81 244.5% CO2 15.6 15.7 15.6 15.1

115.4 16.6 15.67

ppm NO 231 215 220 199 195 222 213.67

ppm NOx 241 212 235 209 205 233 222.5mm of WC Draft -110 -

110-110 -110 -110 -110 -110

oC Temp 151 151 151 151 151 151 151

(A) air inlet temp 41(A) air outlet temp 287

(B) air inlet temp 41(B) air outlet temp 287

3.8 Calculation (Before)

AIR LEAKAGE,

AL=(CO2≥−CO2 gl)

CO2gl×0.9 × 100

Or

AL=¿¿

GAS OUTLET TEMPERATURE CORRECTED FOR NO LEAKAGE,

Tgnl=AL ×Cpa ×(Tgl−Tge)

100 ×Cpg+Tgl

40

GAS SIDE EFFICIENCY,

GSE= Temp .dropTemp . head

×100

GSE=Tge−TgnlTge−Tae

×100

X-ratio,

X−ratio=Wair out ×CpaWgas∈×Cpg

For no air-leakage,

X−ratio= Tgas∈−TgasoutTair out−Tair∈¿¿

FOR AIR PRE-HEATER A,

AL=(3.48−1.87 )(21−3.48)

× 0.9 ×100=8.29

Tgnl=8.29×0.246 (156.33−41)

100 x 0.252+156.33=165.66

GSE=335−165.66335−41

×100=57.60 %

FOR AIR PRE-HEATER B,

AL=(3.40−2.12 )(21−3.40)

× 0.9× 100=6.54

Tgnl=6.54× 0.246 (151−21 )

100 x 0.256+151=158.02

GSE=329.17−158.02329.17−41

×100=59.39 %

41

Result ValuesAPH (A) APH (B)

% Air Leakage 8.29 6.54Tgnl 165.66 158.02Gas Side Efficiency 57.6 59.39X-Ratio 0.69 0.70

3.9 Areas to be considered for improvement

1. Sealing of APH:

Seals are provided at both the end of the APH to minimize leakage from air side and gas side of the APH.

Radial seal: The hot and cold radial seals are attach to each diaphragm of the rotor and are set at a specific clearance from sector plates which separates air and gas streams.

Circumferential seal: Circumferential seals are located on the entire circumference of the air heater rotor, on both the hot end and cold end of the air heater.

Bypass seals: It provides sealing between periphery of the rotor and sealing surface of the connecting plate and/or the preheater housing. Gaps are observed around the Baskets and with Diaphragm/Stay plates. It will by-pass the flue gas: thereby losing the efficiency of the boiler. This is revealed by the high flue gas outlet temperature.

Axial Seals: Axial seals are provided in the rotor shell in line with radial seals.

Reducing and maintaining low air preheater leakage is vital to minimize the fan horsepower required to move the air and gas flows through the air preheater.

It also serves to reduce the dilution effect and corrosion potential of the leaving gas stream due to mixing with colder air at the air inlet temperature.

42

Seals can wear due to soot blowing, corrosion, erosion, and contact with the static sealing surfaces.

2. Erosion of APH material:

Erosion caused by fly ash has resulted in the rapid loss of a heat exchange element as well as damage to perimeter seals, radial seals, and rotor diaphragms. Two other factors with regard to erosion are actually more important than ash content: abrasiveness and ash velocity.

The abrasiveness of fly ash increases as the amount of silica and alumina increases.

Ash velocity is as much as three times more important than ash content or abrasiveness when it comes to determining the rate of erosion. One way to defeat high ash velocity is to increase the fineness of the coal particles leaving the pulverizer and balancing the coal and air flows to each of the burners.

43

[ Corrosion affected buckets] [ Heating surface chocked due to ash]

3. Blockage of APH baskets:

In every power plant exhaust gases carries some amount of flue gases along with it which may deposited between the gaps of corrugated heating material of the APH baskets. This ash and other impurities reduce the rate of heat conduction between the heating material and may result in high exhaust gas temperature.

4. Alignment problem of APH unit:

APH unit must be installed in correct position for its smooth operation and aligned to default values. Faulty alignment of APH unit may lead to excess space between the seals provided increasing leakage of air. It also causes noise between teeth of driving wheels of APH.

5. Corrosion:

Due to the some of the chemical component present in flue gases corrosion of APH material, seals, baskets etc. occurs which also be taken into consideration.

44

3.10 Steps taken for improvement of APH performance

During the period of shutdown for the Power Plant, some steps were taken

to improve the performance of Air Preheater. The steps taken were:

Cleaning of the APH baskets to remove ashes which reduce the heat

exchange between flue gas and fresh air.

Replacement of corrosion affected baskets with new baskets.

Alignment of the APH rotor is done to prevent Air side leakage of the

air from that part.

Various sealing inside the Air Preheater are checked and repaired if

damaged to prevent air leakage to the flue gas side.

Improvement of soot blower system is done which helps to increase the

cleaning of basket in running condition.

Covering the leakages in outer casing of APH by welding them with

suitable materials.

It is recommended to check flue-gas path duct for possible leakages by

opening the insulation at joints, windows, expansion joints, stop-gates,

doors.

[Radial seal before and after maintenance] [Circumferential seal after maintenance]

45

3.11 Data Collected [Measurement Tables] After (19/01/15)

APH (A) InletDeep

Mid Shallow Deep Mid Shallow

AVG

% O2 2.29 2.17 2.98 2.78 2.82 2.68 2.62ppm CO 22 36 26 13 56 36 31.5% CO2 16.4 16.5 16.3 15.98 15.93 16.5 16.27ppm NOx - - - - - -mm of WC Draft -56 -56 -56 -57 -57 -57 -56.5oC Temp 342 342 342 342 342 342 342

APH (B) InletDeep Mid Shallo

wDeep Mid Shallow AVG

% O2 2.21 2.74 2.72 2.45 2.76 2.66 2.59ppm CO 18 12 12 6 6 6 10% CO2 16.47 16 16.02 16.26 16.98 16.1 16.31ppm NOx - - - - - - -mm of WC

Draft -56 -56 -56 -56 -56 -56 -56

oC Temp 340 340 340 340 340 340 340

APH (A) OutletDeep Mid Shallow Deep Mid Shallo

wAVG

% O2 2.76 2.66 2.82 3.72 3.62 3.69 3.21ppm CO 6 3 0 0 0 0 1.5% CO2 15.9 15.9 15.9 13.39 13.45 13.42 14.66ppm NOx - - - - - - -mm of WC Draft -158 -

158-158 -158 -158 -158 -158

oC Temp 152 152 152 152 152 152 152

APH (B) OutletDeep Mid Shallow Dee

pMid Shallo

wAVG

% O2 3.72 3.5 3.55 2.4 2.3 2.33 2.97

46

ppm CO 0 12 3 0 0 0 2.5% CO2 15.41 15.3

115.29 16.3 16.4 16.36 15.8

ppm NOX - - - - - - -mm of WC Draft -160 -160 -160 -160 -160 -160 -160*C Temp 148 148 148 150 150 150 149(A) air inlet temp 35(A) air outlet temp 284

(B) air inlet temp 35(B) air outlet temp 284

3.12 Calculation (After)

AIR LEAKAGE,

AL=(CO2≥−CO2 gl)

CO2gl×0.9 × 100

Or

AL=¿¿

GAS OUTLET TEMPERATURE CORRECTED FOR NO LEAKAGE,

Tgnl=AL ×Cpa ×(Tgl−Tge)

100 ×Cpg+Tgl

GAS SIDE EFFICIENCY,

GSE= Temp .dropTemp . head

×100

GSE=Tge−TgnlTge−Tae

×100

X-ratio,

47

X−ratio=Wair out ×CpaWgas∈×Cpg

For no air-leakage,

X−ratio= Tgas∈−TgasoutTair out−Tair∈¿¿

FOR AIR PRE-HEATER A,

AL=(3.21−2.82 )(21−3.21)

×0.9 × 100=2.99

Tgnl=2.99×0.246 (152.50−35)

100 x 0.252+152.50=155.93

GSE=342−155.93342−35

×100=60.61 %

FOR AIR PRE-HEATER B,

AL=(2.97−2.59 )(21−2.97)

× 0.9 ×100=1.88

Tgnl=1.88×0.246 (149−35 )

100 x 0.256+149=151.09

GSE=340−151.09340−35

×100=61.94 %

Result ValuesAPH (A) APH (B)

% Air Leakage 2.99 1.88Tgnl 155.93 151.09Gas Side Efficiency 60.61 61.94X-Ratio 0.75 0.76

48

3.13 Comparison of parameters

1) Air leakage %

APH A APH B

Before 8.29 6.54

After 2.99 1.88

0.51.52.53.54.55.56.57.58.5

2) Gas side Efficiency

APH A APH B

Before 57.6 59.39

After 60.61 61.94

55.5

56.5

57.5

58.5

59.5

60.5

61.5

62.5

49

3) Temperature at outlet of APH

Shallow 1 Mid 1 Deep 1 Shallow 2 Mid 2 Deep 2 AVG

APH A Before 158 156.5 157.5 154 156.5 155.5 156.33

APH B Before 153 151 155 148 150 149 151

APH A After 151 152 153 150.5 152 153.5 152

APH B After 148 149 150 147 151 149 149

141143145147149151153155157159

3.14 Conclusion of Audit

At the end of this Audit project of Air Preheater, We have concluded that the performance parameters of the Air preheater such as Air-leakage, Gas side efficiency, X-ratio, etc improves satisfactorily.

Improvement values of various performance parameters are shown in table below:

APH A APH BAir leakage -5.3% -4.66%Tgnl +9.73oC +6.93oCGas side efficiency +2.99% +2.55%X-ratio +0.6 +0.6Outlet Temperature -10oC -10oC

It is found that if the outlet temperature increases by 1oC, then the heat rate

produced will also increased by 1 unit. Here we have concluded that after

applying proper steps for the improvement of efficiency the outlet

temperature is increased by 10oC which means it will increase heat rate by 10

units. And that will affect the usage of fuel (coal) consumption for same

amount of power generation in power plant. Calculation has shown that here

we are saving about 3.68% coal consumption by applying this audit process

for the air preheater and improving its performance parameters.

50

REFERENCES

BEE- BUREAU OF ENERGY EFFICIENCY, INDIA. (www.beeindia.in)

P.N.Sapkal, P.R.Baviskar, M.J.Sable, S.B.Barve ¯ “To optimise air preheater design for better performance”. NEW ASPECTS of FLUID MECHANICS, HEAT TRANSFER and ENVIRONMENT. ISSN: 1792-4596, ISBN: 978-960-474-215-8, PP.61-69.

Pipat Juangjandee ¯ “Performance Analysis of Primary Air Heater Under Particulate Condition in Lignite-Fired Power Plant” Engineering,Computing and Architecture, ” ISSN 1934-7197,vol 1,issue 2,2007

Bostjan Drobnic, Janez Oman. ¯ “A numerical model for the analyses of heat transfer and leakages in a rotary air preheater” , International Journal of Heat and Mass Transfer 49, PP.5001–5009, 2006.

Stephen K.Storm,john Guffre, Andrea Zucchelli ”Advancements with Regenerative Airheater Design, Performance and Reliability” POWERGEN Europe 7-9 June 2011.

P.N.Sapkal, P.R.Baviskar, M.J.Sable, S.B.Barve, “Optimization of Air Preheater Design for the Enhancement of Heat Transfer Coefficient”, International Journal of Applied Research in Mechanical Engineering (IJARME), ISSN: 2231 –5950, Volume-1, Issue-2, 2011.

Guidelines for energy auditing of pulverised coal/lignite fired thermal power plants, by BEE.