Mech Report Edit Final

8/11/2019 Mech Report Edit Final

1/48

INTRODUCTION

This section briefly describes the Boiler and various auxiliaries in the Boiler

Room.

A boiler is an enclosed vessel that provides a means for combustion heat to be

transferred to water until it becomes heated water or steam. The hot water or steam

under pressure is then usable for transferring the heat to a process. Water is a useful

and inexpensive medium for transferring heat to a process. When water at

atmospheric pressure is boiled into steam its volume increases about 1,600 times,

producing a force that is almost as explosive as gunpowder. This causes the boiler to

be an equipment that must be treated with utmost care.

The boiler system comprises of: a feed water system, steam system and fuel

system. The feed water system provides water to the boiler and regulates it

automatically to meet the steam demand. Various valves provide access for

maintenance and repair. The steam system collects and controls the steam produced in

the boiler. Steam is directed through a piping system to the point of use. Throughout

the system, steam pressure is regulated using valves and checked with steam pressure

gauges. The fuel system includes all equipment used to provide fuel to generate the

necessary heat. The equipment required in the fuel system depends on the type of fuel

used in the system.

The water supplied to the boiler that is converted into steam is called feed

water. The two sources of feed water are: (1) Condensate or condensed steam returned

from the processes and (2) Makeup water (treated raw water) which must come from

outside the boiler room and plant processes. For higher boiler efficiencies, an

economizer preheats the feed water using the waste heat in the flue gas.


2/48

TYPES OF BOILER

This section describes the various types of boilers: Fire tube boiler, Water tube

boiler, Packaged boiler, Fluidized bed combustion boiler, Stoker fired boiler,

Pulverized fuel boiler, Waste heat boiler and Thermic fluid heater.

2.1 FIRE TUBE BOILER

In a fire tube boiler, hot gases pass through thetubesand boiler feed water in

the shell side is converted into steam. Fire tube boilers are generally used for

relatively small steam capacities and low to medium steam pressures. As a guideline,

fire tube boilers are competitive for steam rates up to 12,000 kg/hour

andpressures up to 18 kg/cm2. Fire tubeboilers are available for operation with

oil, gas or solid fuels. For economic reasons,most fire tube boilers are of

packaged construction (i.e. manufacturer erected) for all fuels.


3/48

2.2 Water Tube Boiler

In a water tube boiler, boiler feed water flows through the tubes and enters the

boiler drum. The circulated water is heated by the combustion gases and converted

into steam at the vapour space in the drum. These boilers are selected when the steam

demand as well as steam pressure requirements are high as in the case of process cum

power boiler / power boilers.

Most modern water boiler tube designsare within the capacity range 4,500

120,000 kg/hour of steam, at very high pressures. Many water tube boilers are of

packaged construction if oil and /or gas are to be used as fuel. Solid fuel fired water

tube designs are available but packaged designs are less common.

The features of water tube boilers are:

Forced, induced and balanced draft provision help to improve combustion

efficiency.

Less tolerance for water quality calls for water treatment plant.

Higher thermal efficiency levels are possible


4/48

2.3 Packaged Boiler

The packaged boiler is so called because it comes as a complete package.

Once delivered to a site, it requires only the steam, water pipe work, fuel supply and

electrical connections to be made to become operational. Package boilers are

generally of a shell type with a fire tube design so as to achieve high heat transfer

rates by both radiation and convection.

The features of packaged boilers are:

Small combustion space and high heat release rate resulting in faster evaporation.

Large number of small diameter tubes leading to good convective heat transfer.

Forced or induced draft systems resulting in good combustion efficiency.

Number of passes resulting in better overall heat transfer.

Higher thermal efficiency levels compared with other boiler.


5/48

These boilers are classified based on the number of passes - the number of

times the hot combustion gases pass through the boiler. The combustion chamber is

taken, as the first pass after which there may be one, two or three sets of fire-tubes.

The most common boiler of this class is a three-pass unit with two sets of fire-tubes

and with the exhaust gases exiting through the rear of the boiler.

2.4 Fluidized Bed Combustion (FBC) Boiler

Fluidized bed combustion (FBC) has emerged as a viable alternative and has

significant advantages over a conventional firing system and offers multiple benefits

compact boiler design, fuel flexibility, higher combustion efficiency and reduced

emission of noxious pollutants such as SO2and NO2. The fuelsburnt in these boilers

include coal, washer rejects, rice husk, biogases& other agricultural wastes. The

fluidized bed boilers have a wide capacity range- 0.5 T/hr to over 100 T/hr.When an

evenly distributed air or gas is passed upward through a finely divided bed of solid

particles such as sand supported on a fine mesh, the particles are undisturbed at low

velocity. As air velocity is gradually increased, a stage is reached when the individual

particles are suspended in the air streamthe bed is called fluidized.

With further increase in air velocity, there is bubble formation, vigorous

turbulence, rapid mixing and formation of dense defined bed surface. The bed of solid

particles exhibits the properties of a boiling liquid and assumes the appearance of a

fluidbubbling fluidized bed.

If sand particles in a fluidized state are heated to the ignition temperatures of

coal, and coal is injected continuously into the bed, the coal will burn rapidly and the

bed attains a uniform temperature. The fluidized bed combustion (FBC) takes place at

about 8400c to 9500c. Since this temperature is much below the ash fusion

temperature, melting of ash and associated problems are avoided.

The lower combustion temperature is achieved because of high coefficient of

heat transfer due to rapid mixing in the fluidized bed and effective extraction of heat

from the bed through in-bed heat transfer tubes and walls of the bed. The gas velocity

is maintained between minimum fluidization velocity and particle entrainment


6/48

velocity. This ensures stable operation of the bed and avoids particle entrainment in

the gas stream.

Most operational boiler of this type is of the Atmospheric Fluidized Bed

Combustion. (AFBC). This involves little more than adding a fluidized bed combustor

to a conventional shell boiler. Such systems have similarly being installed in

conjunction with conventional water tube boiler.

Coal is crushed to a size of 1 10 mm depending on the rank of coal, type of

fuel fed to the combustion chamber. The atmospheric air, which acts as both the

fluidization and combustion air, is delivered at a pressure, after being preheated by the

exhaust fuel gases. The in-bed tubes carrying water generally act as the evaporator.

The gaseous products of combustion pass over the super heater sections of the boiler

flowing past the economizer, the dust collectors and the air pre-heater before being

exhausted to atmosphere.

2.4.1Pressurized Fluidized Bed Combustion (PFBC) Boiler

In Pressurized Fluidized Bed Combustion (PFBC) type, a compressor supplies

the Forced Draft (FD) air and the combustor is a pressure vessel. The heat release rate

in the bed is proportional to the bed pressure and hence a deep bed is used to extract

large amounts of heat. This will improve the combustion efficiency and sulphur

dioxide absorption in the bed. The steam is generated in the two tube bundles, one in

the bed and one above it. Hot flue gases drive a power generating gas turbine. The

PFBC system can be used for cogeneration (steam and electricity) or combined cycle

power generation. The combined cycle operation (gas turbine & steam turbine)

improves the overall conversion efficiency by 5 to 8 percent.


7/48

2.4.2Atmospheric Circulating Fluidized Bed Combustion Boilers (CFBC)

In a circulating system the bed parameters are maintained to promote solids

elutriationfrom the bed.

They are lifted in a relatively dilute phase in a solids riser, and a down-

comerwith a cyclone provides a return path for thesolids.There are no steam

generation tubes immersedin the bed. Generation and superheating of steam takes

place in the convection section, water walls, at the exit of the riser.CFBC boilers are

generally more economical than AFBC boilers for industrial application requiring

more than 75100 T/hr of steam. For large units, the taller furnace characteristics of

CFBC boilers offers better space utilization, greater fuel particle and sorbent

residence time for efficient combustion and SO2 capture, and easier application of

staged combustion techniques for NO2control than AFBC steam generators.


8/48

2.5 Pulverized Fuel Boiler

Most coal-fired power station boilers use pulverized coal, and many of the

larger industrial water-tube boilers also use this pulverized fuel. This technology is

well developed, and there are thousands of units around the world, accounting for

well over 90 percent of coal-fired capacity.

The coal is ground (pulverized) to a fine powder, so that less than 2 percent is

+300 micrometre (m) and 70-75 percent is below 75 microns, for a bituminous coal.

It should be noted that too fine a powder is wasteful of grinding mill power. On

the other hand, too coarse a powder does not burn completely in the combustion

chamber and results in higher unburnt losses.

The pulverized coal is blown with part of the combustion air into the boiler

plant through a series of burner nozzles. Secondary and tertiary air may also be added.

Combustion takes place at temperatures from 1300-1700 C, depending largely on

coal grade.Particle residence time in the boiler is typically 2 to 5 seconds, and the

particles must be small enough for completecombustion to have taken place during

this time.


9/48

This system has many advantages such as ability to fire varying quality of

coal, quick responses to changes in load, use of high pre-heat air temperatures etc.One

of the most popular systems for firing pulverized coal is the tangential firing using

four burners corner to corner to create a fireball at the centre of the furnace.

2.6 Waste Heat Boiler

Wherever the waste heat is available atmedium or high temperatures,

a waste heat boiler can be installed economically.

Wherever the steam demand is more than the steam generated during waste heat,auxiliary fuelburners are also used.If there is no direct use of steam, the steam may be

let down in a steam turbine- generator setand power produced from it.It is widely used

in the heat recovery from exhaust gases from gas turbineand diesel engine.


10/48

BOILER INDUSTRY RAKHOH INDUSRIES PVT.LTD

This section gives the details about RAKHOH INDUSRIES PVT.LTD. Its

the location, mode of transport, capacity and establishment of plant.

3.1 RAKHOH Boilers

RAKHOH is a 30 years old an ISO 9001:2008 Certified Companyby TUV

NORD. It is inprocess of obtaining U STAMP, S STAMP AND R STAMP

THESAME WILL BE AN ADDED FEATHER TO THERE CAP and will further

improve of capabilities to cater the Domestic as well as International market. It is

engaged in manufacturing of wide range of Steam boilers with fuel range consisting

of furnace Oil, LDO, Heavy Fuel Oil, Natural gas and solid fuels like Coal, Wood,

Baggase, Rice Husks etc. It also manufacture Waste Heat Recovery Systems, Thermic

Fluid heaters, Thermic Fluid Steam boiler & Hot Water Boilers, Coded Pressure

Vessels, Storage Tanks, Structural, Water Tube Boiler Components like, Convection

Tubes, Headers, Super Heater Coils, Economizer Coils, Drums, Boiler accessories

like Economizers, Air pre-heaters, Wind Turbine equipments, carriers and High

capacity Tower and Nacelle Lifting Jigs etc.

3.2 Location

Company is located in the heart of Punes Industrial Area with apresent

working area of 1,00,000 Sq. ft. and is managed andcontrolled by experienced

technocrats each of them follows the corporate philosophy, to achieve the desired goal

and also satisfy the customers.The mainmanufacturing unit of RAKHOH is located at

MIDC Bhosari,Pimrichinchwad,Pune.

3.3. Testing facility

a) Facilities available in house

1). Hydraulic Test up to 500 Kg / Cm2.

2). Pneumatic Test: up to 100 PSI


11/48

3). Dye Penentrant Test

4). Soap Bubble Test.

5). Hardness Test.

b) Facilities available on contract

(Lloyds / IBR approved agency)

1. Radiography

2. Ultrasonic Test

3. Magnetic Test

4. Chemical Test

5. Physical Test

6. Heat- Treatment

7. Mechanical Testing

8. Normalizing

9. Sand Blasting

Rakhoh truly adherersto it tagline

WHEN IT COMESTO FUEL ECONOMY. ITS RAKHOH


12/48

Heat loss due to dr flue as

Heat loss due to stem in flue gas

Heat loss due to moisture in fuel

Heat loss due to moisture in air

Heat loss due to unburnt in residue

Heat loss due to radiation & other

Heat in steam

Fuel

CHAPTER 4

ASSESSMENT OF A BOILER

This section describes the Performance evaluation of boilers (through the

direct and indirect method including examples for efficiency calculations), boiler

blow down, and boiler water treatment.

4.1. Performance Evaluation of a Boiler

The performance parameters of a boiler, like efficiency and evaporation ratio,reduces with time due to poor combustion, heat transfer surface fouling and poor

operation and maintenance. Even for a new boiler, reasons such as deteriorating fuel

quality and water quality can result in poor boiler performance. A heat balance helps

us to identify avoidable and unavoidable heat losses. Boiler efficiency tests help us to

find out the deviation of boiler efficiency from the best efficiency and target problem

area for corrective action.

4.1.1 Heat balance

The combustion process in a boiler can be described in the form of an

energy flow diagram. This shows graphically how the input energy from the

fuel is transformed into the various useful energy flows and into heat and

energy loss flows.

12.7% 8.1%

100% BOILER 1.7%

0.3% 2.4%

0.3%

73%

Figure12.TypicalLossesfromCoalFiredBoiler


13/48

The thickness of the arrows indicates the amount of energy contained in the

respective A heat balance is an attempt to balance the total energy entering a boiler

against that leaving the boiler in different forms. The following figure illustrates the

different losses occurring for generating steam

The energy losses can be divided in unavoidable and avoidable losses. The goal of a

Cleaner Production and/or energy assessment must be to reduce the avoidable losses,

i.e. to improve energy efficiency. The following losses can be avoided or reduced:

Stack gas losses: Excess air (reduce to the necessary minimum which depends

from burner technology, operation, operation (i.e. control) and maintenance).

Stack gas temperature (reduce by optimizing maintenance (cleaning), load;

better burner and boiler technology).

Losses by unburnt fuel in stack and ash (optimize operation and

maintenance; better technology of burner).

Blow down losses (treat fresh feed water, recycle condensate)

Condensate losses (recover the largest possible amount of condensate)

Convection and radiation losses (reduced by better insulation of the boiler).

Definition of Boiler Efficiency is The percentage of the total absorption heating

value of outlet Steam in the total supply heating value.In other word, it is a rate

how the boiler runs efficiently.

There are two method of assessing boiler efficiency:

1.The Direct Method: The energy gain of the working fluid (Water and Steam) is

compared with the energy content of the boiler fuel.

2.The indirect Method: The efficiency is the difference between the losses and the

energy input.


14/48

Methodology

A. Direct Method of determining boiler efficiency

This is also known as input output method due to that fact that it need only the

useful output (steam) and the heat input (i.e. fuel) for evaluating the efficiency.

This efficiency can be evaluated using the formula:

Boiler efficiency = (heat output/heat input) *100

Boiler efficiency = (Q *(hghf))/ (q*GCV)*100

Parameters to be monitored for the calculation of boiler efficiency by direct methodare:

Quantity of steam generated per hour (Q) in kg/hr.

Quantity of fuel used per hour (q) in kg/hr.

The working pressure (in kg /cm2(g) and superheat temperature (C) , if any

The temperature of feed water (C0)

Type of fuel and gross calorific value of the fuel (GCV) in kcal/ kg of fuel

Boiler efficiency = {Qg*(hghf) / q* GCV} * 100

and where

HgEnthalpy of saturated steam in kcal/kg of steam

HfEnthalpy of feed water in kcal/kg of water

Example

Find out the efficiency of the boiler by direct method with the the data given

below:

Type of boiler: - coal fired

Quantity of steam (dry) generated 10TPH

Steam pressure (gauge)/temp 10kg/cm2(g)/180 C

Quantity of cola consumed 2.25TPH


15/48

Feed water temperature 85

GCV of coal 3200kcal/kg

Enthalpy of steam at 10 kg/cm2pressure 665kcal/kg

Enthalpy of feed water 85 kcal/kg

Boiler efficiency

= [8*(665-85)*1000] / [1.8* 3200*1000]*100 = 80%

It should be noted that boiler may not generate 100% saturated dry steam, and there

may be some amount of wetness in the steam

Advantage of direct method

Plant workers can evaluate quickly the efficiency of boiler

Require few parameters for computations.

Needs few instrument for monitoring.

Easy to compare various evaporation accountable for various efficiency level.

Disadvantage of direct method

Does not give clue to the operator as to why efficiency of the system is lower

Does not calculate various losses accountable for various efficiency level

B. Indirect Method


16/48

The reference standards for Boiler Testing at Site using indirect method namely

British Standard, BS 845: 1987 and USA Standard is ASME PTC-4-1 Power

Test Code Steam Generating Units.

The Indirect method is also called as heat loss method. The efficiency can be

arrived at, by subtracting the heat loss fractions from 100. The standards do not

include blow down loss in the efficiency determination process. A detailed

procedure for calculating boiler efficiency by indirect method is given below.

However, it may be noted that the practicing energy mangers in industries prefer

simpler calculation procedures .

The principle losses that occur in a boiler are:

Loss of heat due to dry flue gas.

Loss of heat due to moisture in fuel and combustion air.

Loss of heat due to combustion of hydrogen.

Loss of heat due to radiation.

Loss of heat due to unburnt.

In the above, loss due to moisture in fuel and the loss due to combustion of

hydrogen are dependent on the fuel, and cannot be controlled by design.

The data required for calculation of boiler efficiency using indirect method are:

Ultimate analysis of fuel (H2, O2, S, C, moisture content, ash content).

Percentage of Oxygen or CO2 in the flue gas.

Flue gas temperature in C0(Tf).

Ambient temperature in C0(Ta) & humidity of air in kg/kg of dry air.

GCV of fuel in kcal/kg.

Percentage combustible in ash (in case of solid fuels).

GCV of ash in kcal/kg (in case of solid fuels).


17/48


18/48

= (M * {584 + Cp(Tf-Ta)}/ GCV of fuel *100

Where,

MKg of moisture in 1kg of fuel

CpSpecific heat of superheated steam (0.45 kcal/kg) 0C

d) Percentage heat loss due to moisture present in air

= {AAS * humidity factor * Cp* (Tf-Ta)}*100/GCV of fuel

CpSpecific heat of superheated steam (0.45 kcal/kg)

e) Percentage heat loss due to unburnt in fly ash

= (Total ash collected /kg of fuel burnt* GCV of fly ash)/

GCV of fuel*100

f) Percentage heat loss due to unburnt in bottom ash

= (Total ash collected /kg of fuel burnt* GCV of bottom ash)/

GCV of fuel *100

g) Percentage heat loss due to radiation and other unaccounted loss

The actual radiation and convection losses are difficult to assess because of

particular emissivity of various surfaces, its inclination, air flow pattern etc. In a

relatively small boiler, with a capacity of 10 MW, the radiation and unaccounted

losses could amount to between 1% and 2% of the gross calorific value of the fuel,

while in a 500 MW boiler, values between 0.2% to 1% are typical. The loss may be

assumed appropriately depending on the surface condition.


19/48

5) Boiler efficiency and Boiler evaporation ratio

Efficiency of boiler = 100- (a+b+c+d+e+f+g)

Evaporation ratio = heat utilized for steam generation/Heat addition to steam.

Evaporation ratio means kilogram of steam generated per kilogram of fuel consumed.

Typical Ex: Coal fired boiler: 6 (1 kg of coal can generate 6 kg of steam)

Oil fired boiler: 13(1 kg of oil can generate 13 kg of steam)

However, this figure will depend upon type of boiler, calorific value of the fuel and

associated efficiencies.

Example:

The following are the data collected for a typical oil fired boiler. Find

out the efficiency of the boiler by indirect method and Boiler Evaporation

ratio.

Type of boiler : Oil fired

Ultimate analysis of Oil

C: 84.0 % H2: 12.0%

S: 3.0 % O2: 1.0 %

GCV of Oil : 1020kcal/kg

Steam Generation Pressure: 7kg/cm2 (g)

-saturated

Enthalpy of steam : 660 Kcal/kg

Feed water temperature: 60oC


20/48

Percentage of Oxygen in flue gas: 7

Percentage of CO2 in flue gas : 11

Flue gas temperature (Tf : 220 0C

Ambient temperature (Ta): 27 0C

Humidity of air: 0.018 kg/kg of Dry air

Solution:-

Step-1: Find the theoretical air requirement

= [(11.6*C) + {34.8*(H2-O2/8)} + (4.35*S)]/100 kg/kg of oil

= [(11.6*84) + {34.8*(12-1/8)} + (4.35*3)]/100 kg/kg of oil

= 14 kg of air /kg of fuel

Step-2: Find the %Excess air supplied

Excess air supplied (EA) = (O2%)/ (21-O2%)*100

= 7 %/( 21-7)*100

= 50%

Step-3: Find the Actual mass of air supplied

Actual mass of air supplied /kg of fuel = [1 + EA/100] x Theoretical Air

(AAS) = [1 + 50/100] x 14

= 1.5 x 14

= 21 kg of air/kg of oil

Step-4: Estimation of all losses


21/48

i. Dry flue gas loss

Percentage heat loss due to dry flue gas = {m*Cp*(Tf-Ta)}/GCV of fuel * 100

m= mass of CO2 + mass of SO2 + mass of N2 + mass of O2

m = (0.84*44/12) + (0.03*64)/32+ (21*77)/100+ ((21-4)*(23/100)7)

m= 21 kg /kg of oil

= (21*0.23*(220-27))/10200*100

=9.57%

ii. Heat loss due to evaporation of water formed due to H2 in fuel

=[(9*H2*{584+Cp(Tf-Ta)})/GCV of fuel] /100

Where,

H2percentage of H2in fuel

= [(9*12*{584+0.45(220-27)})/10200] /100

=7.10%

iii. Heat loss due to moisture present in air

= [(AAS*humidity *Cp*(TfTa))/GCV of fuel]/100

= [(21*0.018*0.45*(220-27)/10200]*100

=0.322

iv. Heat loss due to radiation and other unaccounted losses

For a small boiler it is estimated to be 2%


22/48

5) Boiler Efficiency and boiler evaporation ratio

i. Heat loss due to dry flue gas: 9.14%

ii. Heat loss due to evaporation of water formed due to H2 in fuel: 7.10 %

iii. Heat loss due to moisture present in air: 0.322 %

iv. Heat loss due to radiation and other unaccounted loss: 2%

Boiler Efficiency

= 100- [9.14+7.10+0.322+2]

= 10018.56 = 81 (app)

EvaporationRatio

=Heatutilizedforsteamgeneration/Heatadditiontothesteam

=10200x0.83/(660-60)

=14.11(comparedto13foratypicaloilfiredboiler)

CHAPTER 5


23/48

ENERGY EFFICIENCY OPPORTUNITIES

This section includes energy efficiency opportunities related to combustion,heat transfer, avoidable losses, auxiliary power consumption, water quality and blow

down. Energy losses and therefore energy efficiency opportunities in boilers can be

related to combustion, heat transfer, avoidable losses, high auxiliary power

consumption, water quality and blow down.

The various energy efficiency opportunities in a boiler system can be related

to:

1.

Stack temperature control

2.

Feed water preheating using economizers

3.

Combustion air pre-heating

4.

Incomplete combustion minimization

5.

Excess air control

6.

Radiation and convection heat loss avoidance

7.

Automatic blow down control

8.

Reduction of scaling and soot losses9.

Reduction of boiler steam pressure

10.

Variable speed control for fans, blowers and pumps

11.

Controlling boiler loading

12.

Proper boiler scheduling

13.

Boiler replacement

These are explained in the sections below.

5.1 Stack Temperature Control

The stack temperature should be as low as possible. However, it should not be

so low that water vapour in the exhaust condenses on the stack walls. This is

important in fuels containing significant sulphur as low temperature can lead to


24/48

sulphur dew point corrosion. Stack temperatures greater than 200C indicates

potential for recovery of waste heat. It also indicates the scaling of heat

transfer/recovery equipment and hence the urgency of taking an early shut down for

water / flue side cleaning.

5.2Feed Water Preheating using Economizers

Typically, the flue gases leaving a modern 3-pass shell boiler are at temperatures

of 200 to300 oC. Thus, there is a potential to recover heat from these gases. The flue

gas exit temperature from a boiler is usually maintained at a minimum of 200 oC, so

that the sulphuroxides in the flue gas do not condense and cause corrosion in heattransfer surfaces. When a clean fuel such as natural gas, LPG or gas oil is used, the

economy of heat recovery must be worked out, as the flue gas temperature may be

well below 200 oC.

The potential for energy savings depends on the type of boiler installed and the

fuel used. For a typically older model shell boiler, with a flue gas exit temperature of

260 oC, an economizer could be used to reduce it to 200 oC, increasing the feed water

temperature by 15 oC. Increase in overall thermal efficiency would be in the order of 3

percent. For a modern 3-pass shell boiler firing natural gas with a flue gas exit

temperature of 140 oC a condensing economizerwould reduce the exit temperature to

65 oC increasing thermal efficiency by 5 percent.

5.3Combustion Air Preheating

Combustion air preheating is an alternative to feed water heating. In order to

improve thermal efficiency by 1 percent, the combustion air temperature must be

raised by 20oC. Most gas and oil burners used in a boiler plant are not designed for

high air-preheat temperatures.Modern burners can withstand much higher combustion

air preheat, so it is possible to consider such units as heat exchangers in the exit flue

as an alternative to an economizer, when either space or a high feed water return

temperature make it viable.


25/48

5.4Incomplete Combustion Minimization

Incomplete combustion can arise from a shortage of air or surplus of fuel or poor

distribution of fuel. It is usually obvious from the colour or smoke, and must be

corrected immediately.In the case of oil and gas fired systems, CO or smoke (for oil

fired systems only) with normal or high excess air indicates burner system problems.

A more frequent cause of incomplete combustion is the poor mixing of fuel and air at

the burner. Poor oil fires can result from improper viscosity, worn tips, carbonization

on tips and deterioration of diffusers or spinner plates.With coal firing, unburned

carbon can comprise a big loss. It occurs as grit carry-over or carbon-in-ash and may

amount to more than 2 percent of the heat supplied to the boiler. Non-uniform fuel

size could be one of the reasons for incomplete combustion. In chain grate stokers,

large lumps will not burn out completely, while small pieces and fines may block the

air passage, thus causing poor air distribution. In sprinkler stokers, stoker grate

condition, fuel distributors, wind box air regulation and over-fire systems can affect

carbon loss. Increase in the fines in pulverized coal also increases carbon loss.

5.5Excess Air Control

The table below gives the theoretical amount of air required for combustion of

various types of fuel.Excess air is required in all practical cases to ensure complete

combustion, to allow for the normal variations in combustion and to ensure

satisfactory stack conditions for some fuels. The optimum excess air level for

maximum boiler efficiency occurs when the sum of the losses due to incomplete

combustion and loss due to heat in flue gases is minimized. This level varies with

furnace design, type of burner, fuel and process variables. It can be determined by

conducting tests with different air fuel ratios.


26/48

THEORETICAL COMBUSTION DATA

COMMON BOILER FUELS

(National Productivity Council, field experience)

Fuel kg of air req./kg

of fuel

CO2 percent in flue gas

achieved in practice

Solid Fuels

3.3 10-12

Bagasse

Coal (bituminous) 10.7 10-13

Lignite 8.5 9 -13

Paddy Husk 4.5 14-15

Wood 5.7 11.13

Liquid Fuels 13.8 9-14

Furnace Oil

LSHS 14.1 9-14

TYPICAL VALUES OF EXCESS AIR

LEVELS FOR DIFFERENT FUELS

(National Productivity Council, field

experience)

Fuel Type of Furnace or

Burners

Excess Air

(percent by

wt)

Pulverized coal Completely water-cooled furnace for

slag-tap or dry-ash removal

15-20

Partially water-cooled furnace for 15-40


27/48

dry-ash removal

Coal Spreader stoker 30-60

Water-cooler vibrating-grate stokers 30-60

Chain-grate and traveling-grate

stokers

15-50

Underfeed stoker 20-50

Fuel oil Oil burners, register type 15-20

Multi-fuel burners and flat-flame 20-30

Natural gas High pressure burner 5-7

Wood Dutch over (10-23 percent through

grates) and Hofft type

20-25

Bagasse All furnaces 25-35

Black liquor Recovery furnaces for draft and soda-

pulping processes

30-40

Controlling excess air to an optimum level always results in reduction in flue gas

losses; for every 1 percent reduction in excess air there is approximately 0.6 percent

rise in efficiency.

Various methods are available to control the excess air:

1.

Portable oxygen analyzers and draft gauges can be used to make periodic

readings to guide the operator to manually adjust the flow of air for optimum

operation. Excess air reduction up to 20 percent is feasible.

2.

The most common method is the continuous oxygen analyzer with a

local readoutmounted draft gauge, by which the operator can adjust air flow.

A further reduction of 10- 15 percent can be achieved over the previous

system.

3.

The same continuous oxygen analyzer can have a remote controlled pneumatic


28/48

damper positioner, by which the readouts are available in a control room. This

enables an operator to remotely control a number of firing systems

simultaneously.

4.

The most sophisticated system is the automatic stack damper control, whose

costis really justified only for large systems.

5.6 Radiation and Convection Heat Loss Avoidance

The external surfaces of a shell boiler are hotter than the surroundings. The

surfaces thus lose heat to the surroundings depending on the surface area and the

difference in temperature between the surface and the surroundings.

The heat loss from the boiler shell is normally a fixed energy loss, irrespective of

the boiler output. With modern boiler designs, this may represent only 1.5 percent on

the gross calorific value at full rating, but will increase to around 6 percent, if the

boiler operates at only 25 percent output.Repairing or augmenting insulation canreduce heat loss through boiler walls and piping.

5.7 Automatic Blow down Control

Uncontrolled continuous blow down is very wasteful. Automatic blow down

controls can be installed that sense and respond to boiler water conductivity and pH.

A 10 percent blow down in a 15 kg/cm2 boiler results in 3 percent efficiency loss.

5.8

Reduction of Scaling and Soot Losses

In oil and coal-fired boilers, soot build-up on tubes acts as an insulator against

heat transfer. Any such deposits should be removed on a regular basis. Elevated stack

temperatures may indicate excessive soot build-up. Also same result will occur due to


29/48

scaling on the water side. High exit gas temperatures at normal excess air indicate

poor heat transfer performance. This condition can result from a gradual build-up of

gas-side or waterside deposits. Waterside deposits require a review of water treatment

procedures and tube cleaning to remove deposits.

An estimated 1 percent efficiency loss occurs with every 22oC increase in stack

temperature.

Stack temperature should be checked and recorded regularly as an indicator of

soot deposits. When the flue gas temperature rises to about 20 oC above the

temperature for a newly cleaned boiler, it is time to remove the soot deposits. It is

therefore recommended to install a dial type thermometer at the base of the stack to

monitor the exhaust flue gas temperature.

It is estimated that 3 mm of soot can cause an increase in fuel consumption by 2.5

percent due to increased flue gas temperatures. Periodic off-line cleaning of radiant

furnace surfaces, boiler tube banks, economizers and air heaters may be necessary to

remove stubborn deposits.

5.9 Reduction of Boiler Steam Pressure

This is an effective means of reducing fuel consumption, if permissible, by as

much as 1 to 2 percent. Lower steam pressure gives a lower saturated steam

temperature and without stack heat recovery, a similar reduction in the temperature of

the flue gas temperature results.

Steam is generated at pressures normally dictated by the highest pressure /

temperature requirements for a particular process. In some cases, the process does not

operate all the time, and there are periods when the boiler pressure could be reduced.

But it must be remembered that any reduction of boiler pressure reduces the specific

volume of the steam in the boiler, and effectively derates the boiler output. If the

steam load exceeds the rerated boiler output, carryover of water will occur. The

energy manager should therefore consider the possible consequences of pressure


30/48

reduction carefully, before recommending it. Pressure should be reduced in stages,

and no more than a 20 percent reduction should be considered.

5.10

Variable Speed Control for Fans, Blowers and Pumps

Variable speed control is an important means of achieving energy savings.

Generally, combustion air control is affected by throttling dampers fitted at forced and

induced draft fans. Though dampers are simple means of control, they lack accuracy,

giving poor control characteristics at the top and bottom of the operating range. In

general, if the load characteristic of the boiler is variable, the possibility of replacing

the dampers by a VSD should be evaluated.

5.11

Controlling Boiler Loading

The maximum efficiency of the boiler does not occur at full load, but at about

two-thirds of the full load. If the load on the boiler decreases further, efficiency also

tends to decrease. At zero output, the efficiency of the boiler is zero, and any fuel

fired is used only to supply the losses. The factors affecting boiler efficiency are:

1.

As the load falls, so does the value of the mass flow rate of the flue gases

through thetubes. This reduction in flow rate for the same heat transfer area

reduces the exit flue gas temperatures by a small extent, reducing the sensible

heat loss.

2.

Below half load, most combustion appliances need more excess air to

burn the fuelcompletely. This increases the sensible heat loss.

In general, efficiency of the boiler reduces significantly below 25 percent of the

rated load and operation of boilers below this level should be avoided as far as

possible.


31/48

5.12Proper Boiler Scheduling

Since, the optimum efficiency of boilers occurs at 65-85 percent of full load, it is

usually more efficient, on the whole, to operate a fewer number of boilers at higher

loads, than to operate a large number at low loads.

5.13Boiler Replacement

The potential savings from replacing a boiler depend on the anticipated change

in overall efficiency. A change in a boiler can be financially attractive if the existing

boiler is:

1.

Old and inefficient

2.

Not capable of firing cheaper substitution fuel

3.

Over or under-sized for present requirements4.

Not designed for ideal loading conditions

The feasibility study should examine all implications of long-term fuel availability

and company growth plans. All financial and engineering factors should be

considered. Since boiler plants traditionally have a useful life of well over 25 years,

replacement must be carefully studied.

CHAPTER6

OPTION CHECKLIST

This section includes the most common options for improving a boilers

energy efficiency.


32/48

6.1Periodic tasks and checks outside of the boiler

1. All access doors and plate work should be maintained air tight with effective

gaskets.

2. Flue systems should have all joints sealed effectively and be insulated where

appropriate.

3.

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.

4.

At the end of the heating season, boilers should be sealed thoroughly, internal

surfaceseither 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)

6.2

Boilers: extra items for steam raising and hot water boilers

1. 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.

2. With steam boilers, is water treatment adequate to prevent foaming or

priming andconsequent excessive carryover of water and chemicals into the

steam system?

3. For steam boilers:- are automatic water level controllers operational? The

presence of inter-connecting pipes can be extremely dangerous.

4.

Have checks been made regularly on air leakages round boiler


33/48

inspection doors, orbetween boiler and chimney? The former can reduce

efficiency; the latter can reduce draught availability and may encourage

condensation, corrosion and smutting.

5. Combustion conditions should be checked using flue gas analyzers at

least twice perseason and the fuel/air ratio should be adjusted if required.

6.

Both detection and actual controls should be labeled effectively and checked

regularly.

7. Safety lockout features should have manual re-set and alarm features.

8. Test points should be available, or permanent indicators should be fitted to oil

burners to give operating pressure/temperature conditions.

9. 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.

10.The emergency shut down facility is to be situated at the exit door of the boiler

house.

11.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.

12.

Very large fuel users may have their own weighbridge and so can operate a

direct checkon deliveries. If no weighbridge exists, occasionally ask your

supplier to run via a public weighbridge (or a friendly neighbor with a

weighbridge) just as a check? With liquid fuel deliveries check the vehicles

dipsticks?

13.

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 designeroriginally intended. With oil fuel, ensure that viscosity

is correct at the burner, and check the fuel oil temperature.

14.The monitoring of fuel usage should be as accurate as possible. Fuel stock

measurementsmust be realistic.

15.With oil burners, examine parts and repairs. Burner nozzles should be changed

regularly and cleaned carefully to prevent damage to burner tip.

16.Maintenance and repair procedures should be reviewed especially for burner

equipment,controls and monitoring equipment.

17.Regular cleaning of heat transfer surfaces maintains efficiency at the highest


34/48

possible level.

18.Ensure that the boiler operators are conversant with the operational

procedures, especiallyany new control equipment.

19.Have you investigated the possibility of heat recovery from boiler exit gases?

Modern heat exchangers/ remunerators are available for most types and sizes

of boiler.

20.Do you check feed and header tanks for leaking make up valves, correct

insulation or loss of water to drain?

21.The manufacturer may have originally provided the boiler plant with

insulation. Is thisstill adequate with todays fuel costs? Check on optimum

thickness.

22.

If the amount of steam produced is quite large, invest in a steam meter.

23.Measure the output of steam and input of fuel. The ratio of steam to fuel is the

main measure of efficiency at the boiler.

24.

Use the monitoring system provided: this will expose any signs of

deterioration.

25.Feed water should be checked regularly for both quantity and purity.

26.

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.

27.Check all pipe work, connectors and steam traps for leaks, even in inaccessible

spaces.

28.

Pipes not in use should be isolated and redundant pipes disconnected.

29.Is someone designated to operate and generally look after the installation?

This work should be included in their job specification.

30.

Are basic records available to that person in the form of drawings,

operationalinstructions and maintenance details?

31.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?

32.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


35/48

burner cut-out, or limit the maximum firing rate of the burner.

33.Examine the need for maintaining boilers in standby conditionsthis is

often anunjustified loss of heat. Standing boilers should be isolated on the

fluid and gas sides.

34.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.

35.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.

36.

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 additives NOT put into the domestic hot water heater tank, it will

contaminate water going to taps at sinks and basins.

37.Recover all condensate where practical and substantial savings are possible.

6.3

Boiler rooms and plant rooms

1.

Ventilation openings should be kept free and clear at all times and the

opening area should be checked to ensure this is adequate.

2.

Plant rooms should not be used for storage, airing or drying purposes.

3.

Is maintenance of pumps and automatic valves carried out in accordance

with the manufacturers instructions?

4.

Are run and standby pump units changed over approximately once per month?

5.

Are pump isolating valves provided?

6. Are pressure/heat test points and/or indicators provided on each side of the

pump?

7. Are pump casings provided with air release facilities?

8. Are moving parts (e.g. couplings) guarded?

9.

Ensure that accuracy of the instruments is checked regularly.10.Visually inspect all pipe work and valves for any leaks.


36/48

11.

Check that all safety devices operate efficiently.

12.

Check all electrical contacts to see that they are clean and secure.

13.

Ensure that all instrument covers and safety shields are in place.

14.

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 hot pipes or a process plant.

15.Ensure that only authorized personnel have access to control equipment.

16.Each section of the plant should operate when essential, and should

preferably be controlled automatically.

17.

Time controls should be incorporated and operation of the whole plant should,

preferably, be automatic.

18.

In multiple boiler installations, isolate boilers that are not required on the

waterside and, ifsafe and possible, on the gas side. Make sure these boilers

cannot be fired.

19.Isolation of flue system (with protection) also reduces heat losses.

20.In multiple boiler installations the lead/lag control should have a change round

facility.

21.

Where possible, reduction of the system operating temperature should be made

with devices external to the boiler and with the boiler operating under a normal

constant temperature range.

6.4Water and steam

1. Water fed into the boilers must meet the specifications given by the

manufacturers. The water must be clear, colorless and free from suspended

impurities.

2.

Hardness nil. Max. 0.25 ppm CaCO3.

3. pH of 8 to 10 retard forward action or corrosion. pH less than 7 speeds up

corrosion due to acidic action.

4.

Dissolved O2 less than 0.02 mg/l. Its presence with SO2 causes corrosion

problems.


37/48

5. CO2 level should be kept very low. Its presence with O2 causes corrosion,

especially in copper and copper bearing alloys.

6.

Water must be free from oilit causes priming

6.5Blow down (BD) procedure

A conventional and accepted procedure for blowing down gauge is as follows:

Close water lock

Open drain cock (note that steam escapes freely)

Close drain cock

Close steam cock

Open water cock

Open drain cock (note that water escapes freely)

Close drain cock

Open steam cock

Open and then close drain cock for final blow through.

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.

6.5 Boiler water

1.

Water must be alkalinewithin 150 ppm of CaCO3 and above 50 ppm of

CaCO3 at pH.

2.

Alkalinity number should be less than 120.3. Total solids should be maintained below the value at which contamination of


38/48

steam becomes excessive, in order to avoid cooling over and accompanying

danger of deposition on super heater, steam mains and prime movers.

4.

Phosphate should be no more than 25 ppm P2 O5.

5.

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.

6. Water treatment plants suitable for the application must be installed to ensure

water purity, and a chemical dosing arrangement must be provided to furthe

Maximum Boiler Water Concentrations

recommended by the American Boiler

Manufacturers Association

Boiler Steam Pressure (ata) Maximum Boiler Water

Concentration (ppm)

0-20 3500

20-30 3000

30-40 2500

40-50 2000


39/48

control boiler water quality. Blow downs should be resorted to when

concentration increases beyond the permissible limits stipulated by the

manufacturers.

7.

Alkalinity should not exceed 20 percent of total concentration. Boiler water

level should be correctly maintained. Normally, 2 gauge glasses are provided

to ensure this.

50-60 1500

60-70 1250

70-100 1000


40/48

CHAPTER 7

WORKSHEETSANDOTHERTOOLS

This section includes worksheets (Boiler Performance; Data Collection

Sheet ;FuelAnalysis Sheet) and other tools (Boiler Performance Checklist ; Rules

of Thumb; Dos and Donts)

7.1 Worksheets

7.1.1.Worksheet Boiler:- BOILER PERFORMANCE

No. Parameter reference Units Readings

1 Ultimate Analysis

Carbon percent 48.54

Hydrogen percent 3.35

Oxygen percent 4.42

Sulphur percent 0.27

Nitrogen percent 0.88

Moisture percent 9

Ash percent 33.662 GCV of Fuel K Cal/kg 4200

3 Oxygen in Flue Gas percent 7

4 Flue Gas Temperature(Tf) 0

230

5 Ambient Temperature(Ta) 0

30

6 Humidity in Air Kg/kg of dry0.018

7 Combustible in Ash percent 17.91

8 GCV of Ash K Cal/kg452.95(Fly ash)

600 (Bottom ash)


41/48

9 Excess Air

Supplied(EA)(O2x100)/

percent 31.25

10 Theoretical air requirement (TAR)

[11xC+{34.5x(H2O2/8)}+4.32xS]/100

kg/kg of fuel 6.316

11 Actual mass of air supplied

{1+EA/100}x theoretical air

kg/kg of fuel 9.474

12 Percentage heat loss due to dry flue gas

{k x (TfTa)}/percentCO2

Where,K (Seigertconst.)

= 0.65 for Coal

= 0.56 for Oil

percent 13

13 Percentage heat loss due to evaporation of

water formed due to H2 in fuel

[9xH2{584+0.45(TfTa)}]/GCV of Fuel

percent 4.89

14 Percentage heat loss due to evaporation

of moisture present in fuel

[M x{584+0.45x(TfTa)}]/GCV of Fuel

percent 1.68

15 Percentage heat loss due to moisture present in

air

{AASxHumidityx0.45(TfTa)x100}/GCV of

percent 1.2983

16 Percentage heat loss due to combustibles in ash

{Ash x(100

percent 8.42

17 Total Losses percent 31.28

18 Efficiency percent 68.72


42/48

7.1.2 Worksheet Boiler 3 : FUEL ANALYSIS SHEET

No. Parameter reference Units Readings

1 Ultimate Analysis

Carbon Percent 48.54

Hydrogen percent 3.35

Oxygen percent 4.42

Sulphur percent 0.27

Nitrogen percent 0.88

Moisture percent 9

Ash percent 33.66

2 GCV of Fuel K Cal/kg 4200

7.1.3 Boiler Periodic Checklist

BD and Water

Treatment

Check BD

valves.Do not

-

Make sure

solids do

-


43/48

Feed Water

System

Check and

correctUnsteady

water level.

Ascertain

Cause ofunsteady

water

Check controls by

Stopping the

feed water pump

and

Allow control to

stop fuel

Nil Condensate

receiver, de-aerator

system pumps.

Flue Gases Check temp. at

two

different points

Measure temp.

andCompare

composition at

Selected firings

andAd ust

Same as

weekly.

Compare

with previous

readin s.

Same as weekly

Record

references.

Combustion Air

Supply

Check

adequate

Openings exist

Burners Check control sare

Operating

properly. May

Clean burners ,pilot

assemblies, check

condition of spark

Same as

weekly

Same as weekly,

Clean and

recondition

Boiler operating

Characteristics

Observe flame

Failure and

Relief Valve Check for leakages Remove and

Recondition

Steam Pressure Check for excess


44/48

Loads which will

Cause

excessive

Fuel System

Check pumps,

Pressure

gauges,

transfer lines.

Clean and

Recondition system

Belt for gland

Packing

Check

damages.

Checkgland

packing

Air leaks in water

Side and

fireside

Clean surface as per

manufacturers

recommendation

Air leaks Check for leaks

Around access

openings and flame

Refractories on

fuel side

Repair

Elec. System

Clean panels

Outside

Inspect panels

inside

Clean ,repair

Terminals and

contactsetc.


45/48

Hydraulic and

Pneumatic valves

Clean

equipment,

Oil spillages

to bear rested

Repair all defects

And check for

proper operation


46/48

7.2.General rules (Rules of Thumb)

5percentreductioninexcessairincreasesboilerefficiencyby1percent(or1percentre

duction ofresidualoxygeninstackgasincreasesboilerefficiencyby1percent).

22Creductioninfluegastemperature increasestheboiler efficiencyby1percent.

6Criseinfeedwatertemperaturebroughtaboutbyeconomizer/condensaterecover

ycorrespondstoa1percentsavingsinboilerfuelconsumption.

20Cincreaseincombustionairtemperature,pre-heatedbywaste heat

recovery,resultsina1percentfuelsaving.

A3mmdiameterholeinapipecarrying7kg/cm2steamwouldwaste32,650litersoffu

eloil peryear.

100mofbaresteampipewithadiameterof 150 mm

carryingsaturatedsteamat8kg/cm2wouldwaste25000litersfurnace oilinayear.

70 percent of heat losses can be reduced by floating a layer of 45 mm

diameterpolypropylene(plastic)ballsonthesurfaceofa90Chotliquid/condensate.

A0.25mmthickairfilmoffersthesameresistancetoheattransferasa330mmthickCopp

erwall.

A3mmthicksootdepositonaheattransfersurfacecancausea2.5percentincreaseinf

uelconsumption.

A1mmthickscaledepositonthewatersidecouldincreasefuelconsumptionby5to8per

cent.


47/48

CHAPTER8

CONCLUSION AND DISCUSSION

A case study on boiler efficiency manufactured by RAKHOH INDUSTRIES

PVT.LTD ,PUNE have been presented. From the case study following conclusion

are drawn:

1.Boiler efficiency is 68.72 %.

2. 2% of heat is unaccounted during process.

3. Percentage heat loss due to dry flue gas is 13 %.

4. Percentage heat loss due to evaporation of water formed due

toH2 in fuel is 4.89 %.

5.Percentage heat loss due to evaporation of moisture present in fuel

is 1.68 %.

6. Percentage heat loss due to moisture present in air is 1.29 %.

7. Percentage heat loss due to combustibles in ash is 8.42 %.

8. Total losses are 31.28% .

It is clear from the above efficiency that the energy transferred in form heat

from fuel to the water has a difference of about 10%. So there is scope to improve the

efficiency of boiler.

Suggestions:-


48/48

1. Coal of higher grade must be used.

2. Coal must be dried before feeding for firing.

3.

Moisture in the air supplied must be removeed by using air preheater or

using one more air preheater.

4. Quantity of excess air must be optimized.

BIBLIOGRAPHY

REFERENCES BOOKS

1.

THERMAL ENGINEERING by R.K GUPTA

2.

THERMAL ENGINEERING BY R.S KHURMI AND R.K GUPTA

3.

EFFICIENT OPERATION OF BOILER BY NATIONA PRODUCTIVITY

COUNCIL

WEB SEARCH

www.beeindia.org

www.energyefficiencyasia.org

www.rakhoh.com

www.energy-efficiency.org

Mech Report Edit Final

Documents