PERFORMANCE EVALUATION OF BOILER IN 46MW

BAGASSE BASED COGENERATION POWER PLANT Thesis submitted in the partial fulfilment of the

Requirement for the award of the degree

of

MASTER OF TECHNOLOGY

in

ENERGY SYSTEMS ENGINEERING

by

SHUBHAM RATHI

Registration No: 2015PGMEES06

Under the supervision of

Dr. Laljee Prasad

(Assistant Professor)

&

Mr. Vikas Agarwal

(AGM, Co-Gen, Power Plant)

DEPARTMENT OF MECHANICAL ENGINEERING

NATIONAL INSTITUTE OF TECHNOLOGY JAMSHEDPUR

JAMSHEDPUR-831014 (INDIA)

JUNE 2017

NATIONAL INSTITUTE OF TECHNOLOGY

JAMSHEDPUR

CERTIFICATE

I hereby certify that this work is being proposed in the thesis entitled “Performance

Evaluation of Boiler In 46MW Bagasse Based Cogeneration Power Plant.”In partial

fulfillment for the award of degree of Master of Technology and submitted in Mechanical

Engineering Department, National Institute of Technology, Jamshedpur is an authentic

record of my own work carried out during a period from August 2016 to May 2017 under the

supervision of Dr. Laljee Prasad, Assistant Professor, Department of Mechanical Engineering,

National Institute of Technology, Jamshedpur & Mr. Vikas Agarwal, (AGM) Cogeneration

Power Plant, Triveni Engineering and Industries Limited.

The matter embodied in this thesis has not been submitted by me for the award of any other

degree.

SHUBHAM RATHI

This is to certify that the above statement made by the candidate is true and correct to the best

of my/our knowledge and belief.

Date:

Dr. Laljee Prasad Mr. Vikas Agarwal

(Assistant Professor) ( AGM, Cogen, Power Plant)

( NIT Jamshedpur ) ( Triveni Engineering and industries ltd )

The viva-voce examination of Mr. Shubham Rathi has been held on………………

Examined and Approved

Internal Examiner External Examiner

Dr. Prabha Chand

H.O.D.(Dept. of Mechanical Engg. )

ACKNOWLEDGEMENT

I would like to thank, my guide Dr. Laljee Prasad, Assistant Professor, Department

of Mechanical Engineering, NIT Jamshedpur & Mr.Vikas Agarwal, (AGM) Cogeneration

Power Plant of Triveni Engineering and Industries Limited. for his support, encouragement

and guidance during the period with a keen interest, enthusiasm, vigor and his ever helping

nature from the starting of the project to the completion of this thesis. It is all because of his

untiring endeavours, able guidance and valuable suggestions, that could synchronize my

efforts in covering the many diverse features of the project and thus helped me for the smooth

progress and success of the project.

I express my sincere thanks to Dr. Prabha Chand, Head of the Department,

Mechanical Engineering, NIT Jamshedpur for providing me the necessary facilities in the

department.

I would also take this opportunity to express my gratitude and sincere thanks to Dr.

Laljee Prasad, Associate Professor, Department of Civil Engineering, NIT Jamshedpur &

Mr. Vikas Agarwal, (AGM) Cogeneration Power Plant of Triveni Engineering and

Industries Limited. for his kind co-operation during my dissertation work. I would like to

thank all the faculty members of the Department of Mechanical Engineering for their support

and guidance.

I sincerely acknowledge the education and working environment provided to me at

NIT, Jamshedpur. I have been fortunate to make good friends at NIT, Jamshedpur and the

times that have been spent with them are the best in my life. I acknowledge all my batch

mates with whom I have enjoyed the most and shared many happy moments. Finally, I

sincerely appreciate the consistent support and encouragement by my Parents and my Brother

in all my endeavors.

Date……………………..

Place: Jamshedpur Shubham Rathi

ABSTRACT

In the past years there are a number of ways to increase boiler performance like air pre-heater

which recover waste heat from flue gases then use it to pre-heat combustion air. Economizers

works much like pre-heaters takes waste heat and transfer it to boiler’s feedwater Rather then

combustion air. Preheated water is obviously closer to the temperature needed to produce

steam .So this saves energy when preheated feed water enters the steam drum or furnace. Air

infiltration reduction is also necessary for boiler and it’s auxiliaries performance

improvement. Air infiltration can cause negative pressure in furnace leading “Stack effect” or

“Thermal head” due to leakages power consumption of fans increases so we can locate the

sights where infiltration is occuring. Then prioritize repairs accordingly. Installation of VFDs

i.e variable frequency drives. But for better performance of sugar industry boiler and boiler

auxiliaries like boiler feed pump FD, ID, SA Fans. Bagasse drying technology is in use now

a days in many sugar industries cogeneration power plant because it reduces the moisture

content of bagasse and increase the GCV of fuel and at the same time volume of boiler exit

gas is reduced. Specific heat of water vapour is almost twice that of other gases the heat loss

by exit flue gases are also reduced.

Water vapour reduction also decreases the load of boiler auxiliaries like ID, FD, SA fans.

Bagasse drying can save more energy then APH. Drying sugar cane bagasse in an integrated

system makes possible to obtain exit gas from a steam generating system at lower

temperature. At present pneumatic dryers are used in cogeneration power plants because of

their low price and small area requirement. Bagasse dryer undoubtedly promote energy

saving as well as fuel saving that increase the efficiency of steam generation.

The objective of this paper is to do a comparative study of boiler performance with and

without using bagasse dryer. In this paper the data has been collected from two different sugar

industries and boiler performance has been checked by using bagasse dryer the performance

of boiler improves and major losses gets minimized. The cost estimation and amount of fuel

saving has also been done in this study on the basis of that the payback period of bagasse

dryer has also been calculated. This paper will be very helpful for researchers who are

working on biofuels like bagasse and are trying to analyse the energy potential of bagasse

because this fuel is been used by cogeneration power plants for power generation.

CONTENTS

CHAPTER-1 Introduction

1.1. Energy Alternatives…………………………………….………...1

1.2. Common type of Alternatives…………………………………....1

1.3. Energy potential of bagasse……………………………………...2

1.4. Need for Cogeneration…………………………………………...3

1.5. Principle of Cogeneration………………………………………..4

1.6. Cogeneration………………………………………………….....5

1.7. Steam Turbine Cogeneration System…………………………...6

CHAPTER- 2 Literature Review

2.1 Boiler…………………………………………………………...7

2.2 Boiler Types……………………………………………………8-11

2.3 Bagasse dryer…………………………………………………11-13

2.4 Types of Dryer………………………………………………..14-15

2.5 Review of drying concepts…………………………………...15-16

2.6 Bagasse drying Review……………………………………….16-21

2.7 Research Gap………………………………………………….21

2.8 Objective of study……………………………………………..22

CHAPTER- 3 Methodology

3.1 Direct method…………………………………………………...23

3.2 Indirect method………………………………………………....24

3.3 Application of bagasse dryer…………………………………..25

CHAPTER- 4 Experimental Setup and Fuel Analysis

4.1 Experimental Set-Up……………………………………………26-28

4.2 Data Collection………………………………………………....29

4.3 Fuel Analysis and losses………………………………………..30-32

4.4 Data Collection………………………………………………....33-36

CHAPTER- 5 Results And Discussion

5.1 Performance of boiler………………………………………..37-38

5.2 Losses in boiler without dryer…………………………….....39

5.3 Losses in boiler with dryer…………………………………..40

5.4 Comparison of major losses in boiler……………….……....41

5.5 Variation of efficiency of boiler…………………………….42-43

5.6 Amount of bagasse Saved and dryer cost estimation…….....44-46

CHAPTER- 6 Conclusion & Future Scope

Conclusion & Future Scope ……………………………………47-48

CHAPTER- 7. References ………………………………….……..49-51

LIST OF FIGURES

Title of figure Page No.

Fig 1.1: Balance in Typical Coal fired Power station……………………………….3

Fig 1.2: Cogeneration Advantage…………………………………………………...4

Fig 1.3: Schematic diagram of steam Turbine cogeneration system………………..6

Fig 2.1: Fire Tube Boiler……………………………………………………………8

Fig 2.2: Water Tube Boiler………………………………………………………....9

Fig 2.3: Spreader stoker…………………………………………………………….10

Fig 2.4: FBC Boiler………………………………………………………………...11

Fig 2.5: Schematic diagram of case 1……………………………………………...12

Fig 2.6: Flow diagram of case 2……………………………………………….... 13

Fig 2.7: Cyclone Type dryer……………………………………………………....14

Fig 3.1: Boiler Performance by direct method…………………………………….23

Fig 3.2: Boiler Performance by Indirect method……………………………….....24

Fig 4.1: Bomb Calorimeter………………………………………………………...26

Fig 4.2: Muffle Furnace……………………………………………………………27

Fig 4.3: Oven………………………………………………………………………28

Fig 5.1: Losses Without Dryer…………………………………………………....39

Fig 5.2: Losses With Dryer…………………………………………………….....40

Fig 5.3: Comparison of Major Losses in Boiler……………………………….....41

Fig 5.4: Variation of Boiler Efficiency without dryer……………………………42

Fig 5.5: Variation of Boiler Efficiency with dryer……………………………....43

NOMENCLATURE

O2 Oxygen

GCV Gross Calorific Value of Fuel

M Moisture

VM Volatile Matter

FC Fixed Carbon

H2 Amount of hydrogen In Fuel

N2 Amount of Nitrogen in Fuel

H2O Amount of Moisture in Fuel

m Mass flow Rate of dry flue gas

Cp Specific heat of dry flue gas

Tf Dry flue gas Temperature

Ta Ambient Temperature

L Losses in boiler

AAS Actual air supplied

EA Excess air

C Carbon

CO Carbon Monoxide

Cp Specific heat of moisture

S Amount of sulphur present in the Fuel

1

CHAPTER-1

INTRODUCTION

The rapid depletion of fossil fuel resources has necessitated an urgent search for

alternative sources of energy. Every country draws its energy needs from a variety of

sources. These sources can be categorized broadly as commercial sources and non –

commercial sources. The commercial sources include the fossil fuels ( coal, oil and

natural gases ), hydroelectric power and nuclear power, while the non-commercial

sources includes wood, animal wastes and agriculture wastes. In an industrialized

country like USA most of the energy requirements are met from commercial sources,

while in a industrially less developed like INDIA, The use of commercial and non-

commercial sources is about equal.

1.1. Energy Alternatives :-

1. Nuclear option

2. Miscellaneous sources

Of the many alternatives, Bio-fuel stands out as brightest long range promise towards

meeting the continuously increasing demand for energy . Bio-fuel is available freely

omnipresent and indigenous source of energy provides clean and pollution free

atmosphere. The simplest and the most efficient way to utilize bio- As conventional

sources of energy are depleting at alarming rate, It is evident that a need exists for

developing alternative energy sources. The primary sources of alternative energy which

hold potential for the future can be broadly classified under the categories as;

3. Solar option

fuel is to convert it into thermal energy for heating and steam producing in the

combined heat and power cycle used in cogeneration power plants.

1.2. Common types of alternative energy

Biofuel and Ethanol :- Biofuel and ethanol are plant derived substitutes of gasoline

for powering vehicles and producing electricity.

2

Solar Energy :- it is the generation of electricity from the sun.

Wind Energy :- it is the generation of electricity from the wind.

Geothermal Energy :- it is using hot water or steam from the earth’s interior for

heating building or electricity generation.

Nuclear Binding Energy :- it uses nuclear fission to create energy

1.3. Energy Potential of Bagasse

Sugarcane is one of the most promising agricultural source of biomass energy in the

world. Sugarcane produce mainly two types of biomass , cane trash and bagasse.

Bagasse is the fibrous residue left over after milling the cane , with 45-50% moisture

content. The composition of baggase depends on the variety and maturity of sugarcane.

Bagasse is usually combusted in furnaces to produce steam for power generation. The

value of bagasse as a fuel depends largely on its calorific value , which in turn is

affected by its composition, especially with respect to its water content and to the

calorific value of the sugarcane crop, which depends mainly on its sucrose content.

Moisture content is the main determinant of the calorific value i.e lower the moisture

content, higher the calorific value. A good milling process will result in low moisture

of 45%. Most mills produce bagasse of 50% moisture and most boilers are designed to

burn bagasse at around 50% moisture. For every 100 tons of sugarcane crushed, a sugar

factory produce nearly 30 tons of wet bagasse. Bagasse is often used as a primary fuel

source for sugar mills, when burned in quantity it produces sufficient heat and electrical

energy to supply all the needs of a typical sugar mill, with energy to spare. The

resulting CO2 emissions are equal to the amount of CO2 that the sugarcane plant

absorbed from the atmosphere during its growing phase, which makes the process of

cogeneration greenhouse gas-neutral. Cogeneration of bagase is one of the most

attractive and successful energy projects that have already been demonstrated in many

sugarcane producing countries. Combined heat and power from sugarcane in the form

of power generation offers renewable energy options that promote sustainable

development, take advantage of domestic resources, increase profitability and

competitiveness in the industry.

3

1.4. Need For Cogeneration

Thermal power plants are a major source of electricity supply in India. The

conventional method of power generation and supply to the customer is wasteful in the

sense that only about a third of the primary energy fed into the power plant is actually

made available to the user in the form of electricity (Figure 7.1). In conventional power

plant, efficiency is only 35% and remaining 65% of energy is lost. The major source of

loss in the conversion process is the heat rejected to the surrounding water or air due to

the inherent constraints of the different thermodynamic cycles employed in power

generation. Also further losses of around 10–15% are associated with the transmission

and distribution of electricity in the electrical grid.

.

Fig 1.1 BALANCE IN A TYPICAL COAL FIRED POWER STATION

4

1.5. Principle of Cogeneration

Cogeneration or Combined Heat and Power (CHP) is defined as the sequential

generation of two different forms of useful energy from a single primary energy source,

typically mechanical energy and thermal energy. Mechanical energy may be used either

to drive an alternator for producing electricity, or rotating equipment such as motor,

compressor, pump or fan for delivering various services. Thermal energy can be used

either for direct process applications or for indirectly producing steam, hot water, hot

air for dryer or chilled water for process cooling. Cogeneration provides a wide range

of technologies for application in various domains of economic activities. The overall

efficiency of energy use in cogeneration mode can be up to 85 per cent and above in

some cases.

Fig 1.2 Cogeneration advantage

For example in the scheme shown in Figure 1.2, an industry requires 24 units of

electrical energy and 34 units of heat energy. Through separate heat and power route

the primary energy input in power plant will be 60 units (24/0.40). If a separate boiler

is used for steam generation then the fuel input to boiler will be 40 units (34/0.85). If

the plant had cogeneration then the fuel input will be only 68 units (24+34)/0.85 to

meet both electrical and thermal energy requirements. It can be observed that the

losses, which were 42 units in the case of, separate heat and power has reduced to 10

5

units in cogeneration mode. Along with the saving of fossil fuels, cogeneration also

allows to reduce the emission of greenhouse gases (particularly CO2 emission). The

production of electricity being on-site, the burden on the utility network is reduced and

the transmission line losses eliminated. Cogeneration makes sense from both macro and

micro perspectives. At the macro level, it allows a part of the financial burden of the

national power utility to be shared by the private sector; in addition, indigenous energy

sources are conserved. At the micro level, the overall energy bill of the users can be

reduced, particularly when there is a simultaneous need for both power and heat at the

site, and a rational energy tariff is practiced in the country.

1.6. Cogeneration

Cogeneration is the production of more than one useful form of energy (such as process

heat and electric power) from the same energy source. Cogeneration systems often

capture otherwise wasted thermal energy, usually from an electricity producing device

like a heat engine (e.g., steam-turbine, gas-turbine, diesel-engine), and use it for space

and water heating, industrial process heating, or as a thermal energy source for another

system component.

The ‘‘cascading” of energy use from high- to low-temperature uses, often

distinguishes cogeneration systems from conventional separate electrical and thermal

energy systems (e.g., a power plant and an industrial boiler), and from simple heat

recovery strategies.

The principal technical advantage of cogeneration systems is their ability to improve

the efficiency of fuel use in the production of electrical and thermal energy. Less fuel is

required to produce a given amount of electrical and thermal energy in a single

cogeneration unit than is needed to generate the same quantities of both types of energy

with separate, conventional technologies (e.g., turbine- generator sets and steam

boilers). This is because heat from the turbine-generator set, which uses a substantial

quantity of fuel to fire the turbine, becomes useful thermal energy (e.g., process steam)

in a cogeneration system rather waste heat. Different types of co-generators have

different fuel-use characteristics and produce different proportions of electricity and

steam. The electricity to heat ratio refers to the relative proportions of electrical and

thermal energy produced by a cogeneration unit.

6

1.7 Steam Turbine Cogeneration System

The two types of steam turbines most widely used are backpressure and the extraction-

condensing type. The choice between back pressure turbine and extraction-condensing

turbine depends mainly on the quantities of power and heat, quality of heat and

economic factors. the extraction points of steam could be more than one, depending on

the temperatures levels of heat required by the processes.

Fig 1.4 Schematic Diagrams Of Steam Turbine Co-Genereation Systems

7

CHAPTER 2

LITERATURE REVIEW

2.1. Boiler

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

transferred into 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 cheap medium for transferring heat to a process. When water 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 extremely dangerous equipment that must be

treated with utmost care.

The process of heating a liquid until it reaches its gaseous state is called evaporation.

Heat is transferred from one body to another by means of (1) radiation, which is the

transfer of heat from a hot body to a cold body without a conveying medium, (2)

convection, the transfer of heat by a conveying medium, such as air or water and (3)

conduction, transfer of heat by actual physical contact, molecule to molecule.

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 steamdemand. Various valves provide access for maintenance

and repair. The steam systemcollects 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.

8

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.

Thetwo sources of feed water are: Condensate or condensed steam returned from the

processes and 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.

2.2. Boiler Types

There are virtually infinite numbers of boiler designs but generally they fit into one of

two categories:

Fire tube or “fire in tube” boilers; contain long steel tubes through which the hot

gasses from a furnace pass and around which the water to be converted to steam

circulates. (Refer Figure 2.2). Fire tube boilers, typically have a lower initial cost, are

more fuel efficient and easier to operate, but they are limited generally to capacities of

25 tons/hr and pressures of 17.5 kg/cm2.

Fig 2.1 Fire tube boiler

9

Water tube or “water in tube” boilers in which the conditions are reversed with the

water passing through the tubes and the hot gasses passing outside the tubes. These

boilers can be of single- or multiple-drum type. These boilers can be built to any steam

capacities and pressures, and have higher efficiencies than fire tube boilers

.

Fig. -2.2 Water tube boiler

Spreader stokers utilize a combination of suspension burning and grate burning. The

coal is continually fed into the furnace above a burning bed of coal. The coal fines are

burned in suspension; the larger particles fall to the grate, where they are burned in a

thin, fastburning coal bed. This method of firing provides good flexibility to meet load

fluctuations, since ignition is almost instantaneous when firing rate is increased.

Hence, the spreader stoker is favored over other types of stokers in many industrial

applications.

10

Fig 2.3 Spreader Stoker

FBC Boiler 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 stream. Further, increase in

velocity gives rise to bubble formation, vigorous turbulence and rapid mixing and the

bed is said to be fluidized. If the sand in a fluidized state is heated to the ignition

temperature of the coal and the coal is injected continuously in to the bed, the coal will

burn rapidly, and the bed attains a uniform temperature due to effective mixing. Proper

air distribution is vital for maintaining uniform fluidisation across the bed.). Ash is

disposed by dry and wet ash disposal systems.

11

Fig 2.4 Fluidised Bed combustion

2.3. BAGASSE DRYERS

There are a number of methods for drying the bagasse. These methods can be

classified according to the drying medium to the followings: (a) bagasse drying by

using flue gases from boilers; (b) bagasse drying by using heated air (c) bagasse drying

by using solar energy and (d) bagasse drying by using high pressure superheated steam.

12

Fig 2.5 A schematic diagram of case 1

The cheapest and most efficient means are to bring the bagasse in direct contact with

the flue gases from boilers and this can be done without setting the bagasse on fire in

the dryer. Theoretically [7] the wasted heat in stack is more than sufficient to evaporate

all the moisture from the bagasse. The drying process requires approximately 60 % of

the hot gases generated in the furnace [3]. These 60 % of the gases after drying the

bagasse are relatively cooler and attain a higher degree of humidity. These are then

mixed with rest of 40 % of hot gases. The resulting mixture has an average

temperature between 130–140 oC, which is well above the low corrosion point of

carbon steel.

13

Fig 2.6 Flow diagram of case 2

The advantages of using the flue gases in drying of bagasse can be summarized as: (1)

reduction of the air pollution from values of about 10,000 mg/Nm3 of ash to less than

300 mg/Nm3 and (2) reduction of the heat losses in the flue gases due to decreasing the

exit temperature of gases. (The bagasse dryer allows cooling of the gases to 90oC the

only limit being imposed by the necessity to avoid cooling to the dew point of

60 – 70oc.) The types of dryers which can be used for bagasse drying by using the flue

gases are given below.

14

2.4. TYPES OF DRYERS

1 Tower Dryer

Tower dryer is the oldest type which was built in 1910 by E. W. Kerr

[2,7]. It is a square tower with bagasse descending and stack gas rising in a

countercurrent manner. The tower is equipped with deflectors to promote better gas-

solid contact. This dryer was not used commercially.

2 Rotary Drum Dryers

The principle of single or multiple passage of hot gases contact

in parallel with the bagasse to be dried inside a rotary drum type is similar to the sugar

dryer. The dry bagasse is then separated from the wet gases in large diameter cyclone.

as shown in Rotary drum dryers have the following advantages: (i) they can give

uniform final moisture content with non-uniform particle size and inflow; (ii) they are

more suitable for medium and large units; (iii) they tend to discharge less dust to

atmosphere; (iv) its specific energy consumption is less than pneumatic dryers (it is 20

kWh/t-water evaporated). But they are big dryers, of low efficiency, occupying large

areas. Their construction and installation are quite complex. They need an extra

conveyor to transport bagasse to the drums and then back to the boilers.

Fig 2.7 cyclone type dryer

15

Drying is perhaps the oldest and most diverse of engineering operations. Over four

hundred types of dryers have been reported in the literature and more than one hundred

distinct types are commonly available. Energy consumption in drying ranges from a

low value of under five percent in the chemical process industries to thirty five percent

in the papermaking operations (Syahrul et al., 2002). Drying occurs by effecting

vaporization of the liquid by supplying heat to the wet feedstock. This is one of the

most energy-intensive unit operations due to the high latent heat of vaporization and the

inherent inefficiency of using hot air as the (most common) drying medium. It is

reported that in most industrialized countries, the energy used in drying accounts for 7-

15% of the nation’s industrial energy, often with relatively low thermal efficiencies

(Syahrul et al., 2002). Over 85 percent of industrial dryers are of the convective type

with hot air or direct combustion gases as the drying medium. Over 99 percent of the

applications involve removal of water.

The sugar industry is a typical industry which uses its own by-product bagasse, as fuel.

As mentioned in the previous Chapter, the mill run bagasse has a high moisture content

which reduces its gross calorific value. The moisture level of the fuel can be reduced by

drying it, using the waste heat available in the plant. In this way, it is expected to

conserve bagasse, providing energy conservation in the process. Hence, in this study,

drying of bagasse using available waste heat is envisaged.

2.5. Review of drying concepts

Drying is generally used to remove moisture or liquid from a wet solid by bringing this

moisture into a gaseous state. In most drying operations, water is the liquid evaporated

and air is the normally employed purge gas. In general, the main goal of drying is to

decrease the moisture content of solid materials to below a certain limit, which results

in quality enhancement, and ease of handling and further processing (Sokhansanj and

Jayas 1995). A drying process is fundamentally a simultaneous heat and mass transfer

operation and is widely used in a variety of thermal energy applications (Hossain and

Bala 2002). Generally, the heat supplied is transported by convection from the

surroundings to the particle surfaces and from there by conduction further into the

particle throughout the drying process (Midilli 2001; Dincer and Hussain 2002). The

16

moisture is removed in the opposite direction as a liquid or vapor. On the surface, it

evaporates and passes on by convection to the surroundings (Midilli and Kucuk 2003;

Syahrul et al 2002).

Thus, one of the most important challenges of the drying industry is to reduce the cost

of energy sources for good quality dried products (Dincer 1998). The heat sources with

the greatest potential for drying energy in process industries are secondary heat flows

like flue gases and low pressure steam varying from 3 to 4 bar. Most investigations of

drying have been made from the external viewpoint, wherein the effects of the external

drying medium such as air velocity, humidity, temperature, and wet material shape and

subdivision are studied with respect to their influence on the drying rate. The results of

such investigations are usually presented as drying rate curves, and the natures of these

curves are used to interpret the drying mechanism.

2.6. Bagasse Drying Review

The flue gases flowing from bagasse fired boilers have temperatures around 300°C.

The first interest shown in bagasse drying with boiler stack gases dates back to 1910,

when Prof. E.W.Kerr (Louisiana Bulletin 1911) showed that it was impossible in Som

Louisiana mill at that time to cover the sugar mill’s energy demands with bagasse

alone, owing to its high moisture content. He built a dryer which reduced the moisture

content from 54.47 to 44.45 %, raising the steam production from 1.63 to 2.53 kg

steam/kg bagasse. His dryer was a square tower with bagasse descending and stack gas

rising in a counter current manner. The tower was equipped with deflectors to promote

better gas-solid contact. Between 1910 and 1970, only very few bagasse drying works

were reported. The reason for the lack of interest in bagasse drying during this period

was the low cost of fossil fuel. Bagasse was not very attractive as an alternative even in

cases where it was a residue, dueto the usage of cheap oil. Because of the energy crisis

in 1970’s, efforts have been concentrated in further reducing the bagasse moisture.

Since then a number of technical reports on bagasse drying both theoretical and

practical have appeared.

Roy et al., (1980) and Keenliside (1983) have reported the use of moving bed dryers for

bagasse drying. Roy et al., (1980) studied the effect of the temperature of the outgoing

flue gases, the velocity of air, length of dryer and annual profit with that of the

17

percentage of moisture removed the mass of air flow and the width of the drier and the

air heater. The air used for bagasse drying was first heated using flue gases and then

passed through bagasse. Keenliside (1983) compared three different boiler

configurations viz. i) boiler with no air preheater or bagasse dryer ii) boiler with air

preheater and iii) boiler with bagasse dryer. He showed that the overall increase in

steam production using a bagasse dryer is not significantly greater than when using air

pre-heaters due to the extra peripheral equipment required to operate the drying

systems. Massarani and Valenca (1981) studied intensively the drying of bagasse in a

moving bed dryer. They investigated from a laboratory scale to a pilot one. The pilot

installation was composed of a dryer of 0.40 x 0.50 x 2 m. These two steps led to

satisfactory results.

During the fuel crisis, Furines (1976) prepared a feasibility study of bagasse pre-drying

with waste stack gases. He worked with three rotary-drum type dryers of maximum

capacity to operate with the existing boilers, based on the flue gases temperature of

218ºC. These three dryers processed all the bagasse produced and lowered the moisture

content from 54 to 46% (w.b.), provided the gases had a temperature of 218ºC or more.

The use of rotary dryers for bagasse drying was also reported by Guanzon (1980) and

Sarnobat (1987). Guanzon (1980) plotted the capacity of dryer versus moisture content

of bagasse as a function of inlet flue gas temperature. The moisture removal rate

increases with an increase in the capacity of the bagasse dryer. Sarnobat (1987)

calculated the heat transfer area for a rotary drum dryer inclined at 30º. He reported a

bagasse saving of around 30% and pay back period of three months for a bagasse dryer.

In pneumatic transport, the velocity at which a gas will begin to transport a specific

particle is called the terminal velocity. The terminal velocity for different bagasse size

fractions were determined by Grobert (1971). They show that at a terminal velocity

higher than 13.9 m/s, all the bagasse particles will be transported pneumatically. At a

terminal velocity lower than 13.9 m/s the raw bagasse will be separated into two

fractions. This separation could enable the use of more efficient systems of pneumatic

transport, and storage in silos, which would be placed between the mill train and the

boilers.

18

Arrascaeta and Friedman (1987) designed and constructed a bagasse dryer in 1983 that

elutriates the bagasse, separating the particles in different sizes. This dryer could work

with 7 ton/hr and was in operation until 1985. Later the design was patented in 1987,

which used fluidized and pneumatic conceptions. Nebra and Macedo (1989), developed

an industrial dryer which was designed and built according to a project developed by

the Centro de Tecnologia Copersucar, Brazil. It was a flash drier that could work with

25 tons of bagasse/hour. That is the biggest flash dryer reported until now.

Alarcon and Justiz (1993) also worked with a pneumatic dryer which reduced the

moisture content from 50 to 30% (w.b.) and separated the particles into different sizes.

The biggest particles were used as raw material for paper and pharmacy industries and

the smaller ones were burned. Cardenas et al (1994), described a pneumatic dryer of an

industrial size. They studied the energetic and exergetic efficiencies of a boiler-dryer

system. They concluded that the use of a dryer will improve the boiler efficiency.

Keller (1980) reported the advantages of a suspension dryer over a rotary drum dryer.

He reported the effect of moisture content on combustion temperature in bagasse

furnaces. It was found that with a decrease in moisture content, furnace temperature

increases. He also reported an increase of heat transmitted to steam per kg of bagasse

with a reduction of bagasse moisture content. Morales (1982) reported the use of a

suspension type bagasse dryer consisting of two units. Each unit was designed for 17.5

ton/hr, with an initial moisture content of 56% to a final moisture content of 35%. He

has reported bagasse dryer operating data over a period of one year.

Bose et al., (1984) have carried out studies on a fluidized bed bagasse dryer. Results

show a reduction of moisture content from 49-50% to 41-42%. Steam generation

increased by 10% and a saving of 0.6 metric ton/hr of bagasse is achieved. Choh et al.,

(1984) investigated bagasse drying with an impulsive fluidized dryer. They found that

the temperature of the flue gases has a great influence on the bagasse drying. At a flue

gas temperature of 200°C, the moisture content of the bagasse could be lowered by

10%, whereas at about 140°C it was 6-8% only. An impulsive fluidized bed dryer with

a contracted-expanded pipe, had a better drying efficiency than a straight pipe, because

the impulsive action in the contracted-expanded pipe changes the relative velocity and

mixing of bagasse particles with the gas flow, inducing turbulence and improving the

heat and mass transfer. Besides, the velocity of the flow the power consumption is also

reduced. They have obtained a steam output with wet and dry bagasse as 1.94 and 2.4

19

kg/kg respectively indicating 23% more steam production using dry bagasse. Boiler

efficiency was also shown to increase from 63 to 79%.

In the past years there are a number of ways to increase boiler and boiler auxiliaries’

performance like air pre-heater, economizer, air infiltration reduction installation of

variable frequency drives etc. but for better performance of sugar industry boiler and

boiler auxiliaries like boiler feed pump FD,ID,SA Fans. Bagasse drying technology is

in use nowadays in many sugar industries cogeneration power plant because it reduce

the moisture content of bagasse and increases GCV of fuel and at the same time volume

of exit gases from boiler is also reduced. Water vapor reduction also decreases the load

of boiler auxiliaries like ID,FD,SA Fans. Bagasse drying can save more energy then

APH. Bagasse dryer promotes energy saving as well as fuel saving that increase the

efficiency of steam generation.

Jorge Barrosoet al. (2003)The present investigation has been carried out in order to

increase the efficiency of the boiler, used in the Cuban sugar mills. Test methods

generally used in the evaluation process and further adjustment of the boilers operation

have been analyzed, pointing the attention on the importance of the stoichiometric ratio

and steam power on the overall efficiency. Important general rules have been extracted

from the complete regular tests following ASME and GOST methodologies, and, as a

result, a simplified test code has been obtained. Boiler design optimization has also

been achieved determining the optimum waste heat recovery scheme from both,

thermal and economical viewpoints. As a result, the optimal stack gas temperature has

been calculated as well as the range of the optimal value for the excess air fraction.

Their influence on the efficiency has been analyzed and the total costs determined.

Once the total costs are included in the analysis, the most efficient low-temperature

heat recovery scheme results to be the combination of an economizer followed, in the

direction of the exhaust gas flow, by an air heater.

Juan H. Sosa and Silvia A Nebra (2009).In this paper bagasse dryer role is shown in the

enrgy recovery of water tube boiler the sugar and ethanol industry, which uses

sugarcane as raw material, utilizes the by-product, bagasse, as fuel. The bagasse is fed

with a moisture content of 50% (w.b). Dryers are not being used in the way it is

20

proposed here. This article proposes the introduction of bagasse dryers connected to the

energy recovery system of the boilers operating with the exhaust gases. The

combination of the dryer with other thermal energy recovery devices, such as an air

heater and economizer, is considered. The performance improvement is evaluated.

Costs are also taken into account. Finally, an optimized solution for the boiler energy

recovery system is proposed. A methodology to improve the design of thermal energy

recovery systems for biomass-fired boilers is shown in this study. The energy recovery

system proposal includes the use of an economizer, an air heater, and a dryer. The

whole system operates with the boiler exhaust gases.

Geethanjali S. Yarnal, Vinod S. Puranik (2010)In this paper baggase drying methods

based on flue gas and steam drying in the sugar industry are analyzed and new methods

are proposed for maximum removal of moisture to save energy. Wet bagasse having

50% moisture indian sugar cane industry has been taken as a case for improving

calorific value. The combined flue gas / steam drying techniques is compared with

parallel and sequential heating techniques for the moisture removal boiler efficiency,

increase in calorific value etc.In this article a new technique based on combined flue

gas and steam drying developed and the energy requirements for drying wet bagasse

are calculated theoretically also, the experiments were conducted to show the impact of

using the technique on the performance of boiler and boiler auxiliaries.

Juan H.Sosa et al. (2013) Sugar cane bagasse is the only fuel used in the sugar-alcohol

industry in Brazil, the world's leading sugar cane producer. The sugar alcohol industry

produces cogenerated electrical energy for its own consumption and the surplus is sold

to the market. Improving the use of bagasse in furnaces is currently an important

industrial strategy. The topic has aroused great interest due to an increase in the

cogeneration level in recent years. This work reviews the state of the art of sugar cane

bagasse drying.This paper focus on the reduction of cane bagasse moisture increase

LHV and at the same time volume of the boiler exit gas is reduced. Specific heat of

water vapour is almost twice that of other gases the heat loss by exit flue gas are also

reduced. Water vapourreduction also decrease the load of fans. Sugar cane bagasse

drying in an integrated system makes possible to obtain exit gas from steam generating

system at the lower temperature. Bagasse dryer undoubtedly promote energy savings

that increase the efficiency of steam generation.

21

Performance Assesment of Boilers (Bureau of Energy Efficiency)

Performance of the boiler, like efficiency and evaporation ratio reduces with time, due

to poor combustion, heat transfer fouling and poor operation and maintenance.

Deterioration of fuel quality and water quality also leads to poor performance of boiler.

Efficiency testing helps us to find out how far the boiler efficiency drifts away from the

best efficiency. Any observed abnormal deviations could therefore be investigated to

pinpoint the problem area for necessary corrective action. Hence it is necessary to find

out the current level of efficiency for performance evaluation, which is a pre requisite

for energy conservation action in industry.

2.7. Research Gap

In the past years there are a number of ways to increase boiler and boiler auxiliaries

performance like air pre-heater which recover waste heat from flue gases then use it to

pre-heat combustion air. Economizers works much like pre-heaters takes waste heat

and transfer it to boiler’s feed water Rather then combustion air. Preheated water is

obviously closer to the temperature needed to produce steam. So this saves energy

when preheated feedwater enters the steam drum or furnace. Air infiltration reduction is

also necessary for boiler and it’s auxiliaries performance improvement. Air infiltration

can cause negative pressure in furnace leading “Stack effect” or “Thermal head” due to

leakages pwer consumption of fans increases so we can locate the sights where

infiltration is occuring. Then prioritize repairs accordingly. Installation of VFDs i.e

variable frequency drives. But for better performance of sugar industry boiler and

boiler auxiliaries like boiler feed pump FD, ID, SA Fans. Bagasse drying technology is

in use now a days in many sugar industries cogeneration power plant because it

reduces the moisture content of bagasse and increase the GCV of fuel and at the same

time volume of boiler exit gas is reduced. Specific heat of water vapour is almost twice

that of other gases the heat loss by exit flue gases are also reduced.

Water vapour reduction also decreases the load of boiler auxiliaries like ID,FD,SA

fans. Bagasse drying can save more energy then APH. Drying sugar cane bagasse in an

integrated system makes possible to obtain exit gas from a steam generating system at

lower temperature. At present pneumatic dryers are used in cogeneration power plants

22

because of their low price and small area requirement. Bagasse dryer undoubtedly

promote energy saving as well as fuel saving that increase the efficiency of steam

generation.

2.8. Objective of this work are as follows :-

To evaluate the boiler performance without dryer and current boiler auxiliaries

To find the major losses related to boiler and to find optimum combustion zone

without dryer.

To evaluate the boiler performance with bagasse dryer.

.

To find the major losses related to boiler and to find out the optimum

combustion zone with dryer.

To find out the amount of fuel saving by applying bagasse dryer.

23

CHAPTER -3

METHODOLOGY

There are two methods to evaluate the boiler efficiency.

3.1 Direct Method

3.2 Indirect Method

3.1 Direct Method

This is also known as ’input-output method’ due to the fact that it needs only the useful

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

can be evaluated using the formula:

Fig 3.1 Boiler Performance by direct method

24

3.2 Indirect Method

The efficiency can be measured easily by measuring all the losses occurring in the

boilers using the principles to be described. The disadvantages of the direct method can

be overcome by this method, which calculates the various heat losses associated with

boiler. The efficiency can be arrived at, by subtracting the heat loss fractions from

100.An important advantage of this method is that the errors in measurement do not

make significant change in efficiency. Thus if boiler efficiency is 90% , an error of 1%

in direct method will result in significant change in efficiency. i.e. 90 ± 0.9 = 89.1 to

90.9. In indirect method, 1% error in measurement of losses will result in Efficiency =

100 . (10 ± 0.1) = 90 ± 0.1 = 89.9 to 90.1

Fig 3.2 Boiler Performance by Indirect method

25

Losses in Boiler:

The following losses are applicable to liquid, gas and solid fired boiler

L1. Loss due to dry flue gas (sensible heat)

L2. Loss due to hydrogen in fuel (H2)

L3. Loss due to moisture in fuel (H2O)

L4. Loss due to moisture in air (H2O)

L5. Loss due to carbon monoxide (CO)

L6. Loss due to surface radiation, convection and other unaccounted*.(Losses

which are insignificant and are difficult to measure)

The following losses are applicable to solid fuel fired boiler in addition to above

L7. Unburnt losses in fly ash (Carbon)

L8. Unburnt losses in bottom ash (Carbon)

Boiler Efficiency by indirect method = 100 - (L1 + L2 + L3 + L4 + L5 + L6 +

L7 + L8)

3.3 Application of Bagasse Dryer:

At present, pneumatic dryers are most often used in factories because of their low price

and small space requirements. Bagasse dryers undoubtedly promote energy savings that

increase the efficiency of the steam generation system. With the current increase in

export cogeneration in most Brazilian factories, the bagasse dryer could become an

important element of the system, even though studies about trade-off between the air

pre-heater, the economizer and the drier are necessary, taking into account costs and

energy consumption, aiming to determine the best seating arrangement between these

pieces of equipment.

26

CHAPTER-4

EXPERIMENTAL SETUP AND FUEL ANALYSIS

This chapter deals with the experimental setup used for fuel testing and fuel analysis for

boiler performance evaluation.

4.1 Experimental setup

Bomb Calorimeter

A bomb calorimeter is a type of constant volume calorimeter used measuring the heat

of combustion of a particular reaction. Electrical energy is used to ignite the fuel ; as

the fuel is burning, it will heat the surrounding air, which expands and escapes through

a tube that leads the air out of the tube. The change in temperature of water allows for

calculating calorie content of the fuel.

Fig 4.1 Bomb Calorimeter

27

Parameters

From the above set-up we can measure temperature diffrence, and with a bomb factor

(which dependent on the heat capacity of the metal bomb parts) is used to calculate the

energy given by sample burn.

GCV = Water Constant Temperature Change Of Fuel – (E1 + E2)

Taken Sample

Where,

E1 = Weight Of Cotton Thread 4.18 1000

E2 = Nichrome Wire Weight Loss 0.335 1000

Water Constant = 2511

Muffle Furnace

The woring principle of muffle furnace is to heat the air in the chamber by heating the

nichrome wires which are generally referred to as electrically operated heating

elements.The control of furnace temperature majorly depends on the efficency of

electronic controller unit and best results can only be obtaned from PID controlled

units, PID stands for proportional integral derivative controller.

Fig 4.2 Muffle Furnace

28

Parameters

The maximum working temperature of this muffle furnance 1100 – 1200 C.

Oven

Laboratory ovens are ovens for high-forced volume thermal convection applications.

These ovens generally provide uniform temperatures throughout. Process applications

for laboratory ovens can be for annealing, die-bond curing, drying, Polyimide baking,

sterilizing, and other industrial laboratory functions.

Fig 4.3 Oven

Parameters

The maximum working temperature of oven used in power plant to remove moisture is

250C.

29

4.2 Fuel Analysis and losses

Fuel analysis can be done by proximate and ultimate analysis without dryer.

Proximate Analysis of fuel i.e bagasse

4.2 Data collected from Triveni Engineering and industries ltd. Without dryer

( 24 hr. )

O2 % Unburnt Fly % Flue gas

temperature (Tf)

Unburnt

bottom %

GCV (kcal/kg)

3.6 11 130 35.67 2150.42

4.25 10.97 129 36.82 2182.72

4.22 12.52 132 38.44 2192.72

3.5 14.20 128 42.00 2160.64

3.2 11.56 130 40.4 2220.50

4 10.90 131 36.7 2170.82

4.02 12.44 127 42.8 2240.46

5.2 14.40 129 35.9 2170.24

3.9 12.20 132 36.27 2230.42

4.4 11.82 130 38.8 2160.24

5.6 11.56 128 40.23 2210.50

3.8 14.10 129 42.28 2180.30

1. Test for moisture of bagasse has been conducted, M=50%

2. Volatile matter test for bagasse has been conducted.VM= 40%

3. Ash test for bagasse has been conducted, ASH=1.75%

4. Fix carbon for bagasse can be calculated as

FC% = 100 – (VM% + M% + ASH%)

=100 – (40% + 0% + 1.75%)

=8.25% on dry basis

30

Ultimate Analysis of fuel.

Conversion formula for proximate analysis to ultimate analysis

%C = 0.97C + 0.7 (VM + 0.1A) - M(0.6 - 0.01M) = 31.125%

%H2 = 0.036C + 0.086 (VM - 0.1xA) - 0.0035M2 (1 - 0.02M) = 3.7219%

%N2 = 2.10 - 0.020 VM = 1.3%

%O2 = 13.8531%

%H2O = 50 %

where C = % of fixed carbon

A = % of ash

VM = % of volatile matter

M = % of moisture

Theoretical air required for combustion = 4.3032 kg/kg of fue

% of Excess Air supplied = 23.67%

Actual air supplied per kg of fuel = 5.32 kg / kg of fuel

Mass of dry flue gas, mdfg = 5.48 kg/ kg of fuel

31

Heat loss due to dry flue gas :-

L1 = � ×��×( �����)

���× ���

= �.��× .�� ×( ������ )

����.��× 100

= 5.40 %

% Heat loss due to formation of water from H2 in fuel :-

L2 = (�×��×{ ������ ( ����� )}

���× ���

= .�� ×{ ���� .��×��}

����.��× 100

= 9.23 %

Heat loss due to moisture in fuel :-

L3 = (�×{ ������ ( ����� )}

���× ���

= .�×{����.��×��}

����.��× 100

= 13.99%

32

Heat loss due to moisture in air :-

L4 = ���×��������×��×(�����)

���× ���

= �.��×.����×.��×��

����.��× 100

= .20%

Heat loss due to partial conversion of C to CO :-

L5 = 2.5% ( standard )

Heat loss due to radiation

L6 = .25% ( standard )

Heat loss due to unburnt in fly ash :-

L7 = .53%

Heat loss due to unburnt in Bottom ash :-

L8 = .64%

33

4.3 Data collected from dhampur sugar mill with dryer ( 24 hr. )

O2 % Unburnt Fly

(%)

Flue gas

temperature (Tf)

Unburnt

bottom %

GCV (kcal/kg)

3.5 11.14 142 35.82 2652.28

3.8 12.56 139 36.27 2672.75

4.2 12.82 144 40.40 2710.82

4.6 11.56 146 42.28 2650.40

3.7 13.28 143 45.27 2720.25

5.2 14.20 144 36.28 2740.34

3.8 11.56 144 37.78 2650.50

4.2 12.52 144 38.82 2670.84

4.6 13.26 143 42.24 2712.40

4.5 11.25 146 44.44 2720.50

5.2 12.20 142 46.64 2730.42

3.2 14.20 145 36.62 2680.55

4.4 Fuel analysis can be done by proximate and ultimate analysis with

bagasse dryer

Proximate Analysis of fuel i.e bagasse

1. Test for moisture of bagasse has been conducted, M=40%

2. Volatile matter test for bagasse has been conducted.VM= 48%

3. Ash test for bagasse has been conducted, ASH= 2.1%

4. Fix carbon for bagasse can be calculated as

FC% = 100 – (VM% + M% + ASH%)

=100 – (48% + 0% + 2.1%)

=9.9 % on dry basis

34

Ultimate Analysis of fuel with bagasse dryer.

Conversion formula for proximate analysis to ultimate analysis

%C = 0.97C + 0.7 (VM + 0.1A) - M(0.6 - 0.01M) = 35.35 %

%H2 = 0.036C + 0.086 (VM - 0.1xA) - 0.0035M2 (1 - 0.02M) = 3.33%

%N2 = 2.10 - 0.020 VM = 1.14%

%O2 = 20.18%

%H2O = 40 %

where C = % of fixed carbon

A = % of ash

VM = % of volatile matter

M = % of moisture

Theoretical air required for combustion = 4.38 kg/kg of fuel

% of Excess Air supplied = 22.09%

Actual air supplied per kg of fuel = 5.34 kg / kg of fuel

Mass of dry flue gas, mdfg = 5.42 kg/ kg of fuel

Heat loss due to dry flue gas :-

L1 = � ×��×( �����)

���× ���

= �.��× .�� ×( ������ )

����.��× 100

= 5.03 %

35

% Heat loss due to formation of water from H2 in fuel :-

L2 = (�×��×{ ������ ( ����� )}

���× ���

= �.�� ×{ ���� .��×���}

����.��× 100

= 7.02 %

Heat loss due to moisture in fuel :-

L3 = (�×{ ������ ( ����� )}

���× ���

= .��×{����.��×���}

����.��× 100

= 8.99%

Heat loss due to moisture in air :-

L4 = ���×��������×��×(�����)

���× ���

= �.��×.����×.��×���

����.��× 100

= .21%

Heat loss due to partial conversion of C to CO :-

L5 = 2.5% ( standard )

36

Heat loss due to radiation

L6 = .25% ( standard )

Heat loss due to unburnt in fly ash :-

L7 = .43%

Heat loss due to unburnt in Bottom ash :-

L8 = .80%

37

CHAPTER-5

RESULTS AND DISCUSSIONS

5.1 PERFORMANCE OF BOILER

In this section a comparative study is shown between performance of bagasse fired

boiler by using bagasse dryer and without using the bagasse dryer in the form of heat

balance sheet, bar chart for major losses and efficiency variation with excess air and

oxygen percentage inside the furnace.

120 TPH Boiler heat balance without baggase dryer :-

Input / output parameter kCal / kg of fuel %

Heat input in fuel 2240.46 100

Various heat losses in boiler

1. Dry flue gas loss 120.98 5.4

2. Loss due to hydrogen in fuel 206.79 9.23

3. Loss due to moisture in fuel 313.44 13.99

4 loss due to moisture in air 4.48 .20

5 partial conversion of C to Co 56.011 2.5

6 surface heat losses 5.6 .25

7 loss due to unburnt in fly ash 11.87 .53

8 loss due to unburnt in bottom ash 14.33 .64

Total losses 733.97 32.74

Boiler efficiency = 100 – ( 1+2+3+4+5+6+7+8) = 67.26%

The above heat balance sheet shows the different losses in bagasse fired boiler when

bagasse dryer is not used at this moment the moisture content of bagasse is 50 % . The

38

major losses are dry flue gas loss, loss due to hydrogen in fuel and loss due to moisture

in fuel.

120 TPH Boiler heat balance with baggase dryer :-

Input / output parameter kCal / kg of fuel %

Heat input in fuel 2672.75 100

Various heat losses in boiler

1. Dry flue gas loss 134.43 5.03

2. Loss due to hydrogen in fuel 187.62 7.02

3. Loss due to moisture in fuel 240.28 8.99

4 loss due to moisture in air 5.61 .21

5 partial conversion of C to Co 66.81 2.5

6 surface heat losses 6.68 .25

7 loss due to unburnt in fly ash 11.49 .43

8 loss due to unburnt in bottom ash 21.38 .80

Total losses 674.33 25.23

Boiler efficiency = 100 – ( 1+2+3+4+5+6+7+8) = 74.77%

The above heat balance sheet is for the bagasse fired boiler when bagasse dryer is used

as we can compare the efficiency of boiler with and with out the use of bagasse dryer

the losses gets minimize when bagasse dryer is used specially the moisture loss which

was around 14% when dryer was not used after using dryer this loss becomes around 9

% so overall the performance of bagasse fired boiler increased when bagasse dryer is

used. The above data is collected from two different sugar mills cogeneration power

plants .

39

1 . TRIVENI ENGINEERING AND INDUSTRIES .LTD

2 . DHAMPUR SUGAR MILLS

5.2 LOSSES IN BOILER WITHOUT DRYER :-

Fig 5.1 - Losses In boiler without dryer

The above graph shows the different losses which occurs in boiler without dryer . There

are 8 losses in boiler some are major losses and some are minor losss

0

2

4

6

8

10

12

14

16

L

o

s

s

%

Losses

losses %

losses %

40

5.3 LOSSES IN BOILER WITH DRYER :-

Fig 5.2 – Losses in boiler with dryer

The above graph shows the different losses which occurs in boiler with dryer. There are

8 losses in boiler some are major losses and some are minor losses.

0

1

2

3

4

5

6

7

8

9

10

L

o

s

s

%

Losses

losses %

losses %

41

5.4 COMPARISON OF MAJOR LOSSES IN BOILER :-

Fig 5.3 -Comparison of major losses

There are 3 major losses in bagasse fired boiler which are shown by the above bar

graph. Here the comparison of all the major losses is shown for best performance of

bagasse fired boiler we can see with bagasse dryer all the major losses gets minimize

and performance of bagasse fired boiler gets increase. The bar graph gives the idea of

comparison of the major losses which occurs in boiler.

0

2

4

6

8

10

12

14

16

dry flue gasloss

loss due toformation of

water

loss due tomoisture

loss due tounburnt

L

o

s

s

%

Losses

losses without dryer

losses with dryer

42

5.5 VARIATION OF EFFICIENCY OF BOILER :-

In the graphs shown below the variation of boiler efficiency is shown with respect to

oxygen and excess air .

1. WHEN BAGASSE DRYER IS NOT USED :-

Fig 5.4 – Variation of boiler efficiency with O2 and excess air ( without dryer )

The above graph shows the variation of boiler efficiency with oxygen and excess air

supplied in the furnace so from here we can observe that best boiler performance is

obtained when oxygen percentage is 3.8 % and excess air supplied in the furnace is

23.67 % so according to our results this is the optimum combustion zone on which

boiler should operate to obtain best performance when bagasse dryer is not used.

efficiency % 65.94 66.18 66.04 66.24 66.87 66.32 67.16 65.75 66.73 65.81 66.18 66.43

excess air % 20.68 25.37 25.54 20 17.97 23.52 23.67 32.91 22.8 26.5 36.36 22.09

oxygen % 3.5 3.8 4.2 4.6 3.7 5.2 3.8 4.2 4.6 4.5 5.2 3.2

0

10

20

30

40

50

60

70

80

E

f

f

i

c

i

e

n

c

y

%

Variation of boiler efficiency with O2 and excess air ( without dryer )

43

2. WHEN BAGASSE DRYER IS USED :-

Fig 5.5 - Variation of boiler efficiency with O2 and excess air ( with dryer )

The above graph shows the variation of boiler efficiency with oxygen and excess air

supplied in the furnace so from here we can observe that best boiler performance is

obtained when oxygen percentage is 3.8 % and excess air supplied in the furnace is

22.09 % so according to our results this is the optimum combustion zone on which

boiler should operate to obtain best performance when bagasse dryer is used.

efficiency % 74.31 74.77 74.34 73.62 74.74 74.48 74.31 74.31 74.18 74.44 74.12 74.5

excess air % 20 22.09 25 28.04 21.38 32.91 22.09 25 28.04 27.27 32.91 17.97

oxygen% 3.5 3.8 4.2 4.6 3.7 5.2 3.8 4.2 4.6 4.5 5.2 3.2

0

10

20

30

40

50

60

70

80

E

f

f

i

c

i

e

n

c

y

%

Variation of boiler efficiency with O2 and excess air

( with dryer )

44

5.6 Amount of bagasse save and estimation of dryer cost :-

During Season

Sr.

No.

In Normal Case Boiler

Parameters

1 Bagasse Moisture 50%

2 Steam Produce 115 ton/hr

3 Steam temperature 500 deg c

4 Baggase to steam ratio 2.1

5 Baggase used/hr 54.8ton/hr

The above data shows the parameters when bagasse dryer is not used it shows the

bagasse to steam ratio without dryer.

Sr

no.

Parameters if Bagasse

Dryer is Used

1 Capacity of baggase Dryer 50 ton /hr

2 Baggase Moisture 40%

3 Steam produce 115 ton/hr

4 Baggase to steam ratio 2.5

5 Baggase used/hr 46 ton/hr

The above data shows the parameters when bagasse dryer is used it shows the bagasse

to steam ratio with dryer.

45

in normal case the temp. of id fan outlet is about 120 deg celcius but in case of bagasse

dryer it goes up to 140 degree for better result of bagasse dryer through this the

efficiency. Of boiler decreases by 1 % in both cases we consider this efficiency Matter

Sr

no.

Difference between in

normal case and if

bagasse dryer used

54.8-46 = 8.8

Ton

1

If rate of baggase is Rs

3000/ton

2 Net saving in one hr is

8.8x3000 = Rs

26,400

3 Net saving in one Day is

26400x 24 = Rs

6,33,600

4

If Season is about 120

Days

633600 x 120 =

Rs 7,60,32000

.

The above table shows the amount of bagasse save and the revenue generated by using

bagasse dryer in a complete season which is around 120 days in any sugar industry.

46

Esimated cost of baggase

dryer installation ( 50 ton)

1 Iron and Steal 140 ton 140x40000 5,600,000

2 Auxillaries 6 Rav 6x7,50000 4,500,000

3 ID fan 2 Nos 2 x10,50,000 2,100,000

4 Civil Work 25,00,000x1 2,500,000

5

Electrical & instrument

work 20,00,000x1 2,000,000

6 Job work 10,00,000x1 1,000,000

7 Insulation work 12,00,000x1 1,200,000

8 Consultant Fees 3,200,000 3,200,000

9 Auxiliary Load 450Kw/hr

unit rate -

5.66kwh

for one hr 450x5.66= 2547

for one day 2567x24=61,128

for 120 days 61,128x120 7,335,360

Total

Installation

Cost Rs 2,94,35,360

The above analysis shows the amount of bagasse save and cost estimation of bagasse

dryer based upon which we can calculate the payback period of bagasse dryer. Here

installation cost is shown and the amount of bagasse is shown when dryer is used. The

payback period of bagasse dryer is about 50 days.

47

CHAPTER 6

CONCLUSIONS AND FUTURE SCOPE

In this dissertation an attempt has been made to account various losses occurs in

bagasse fired boiler and to improve the performance boiler by using bagasse dryer .

Different losses are taken in to consideration to analyse and compare the performance

of boiler in cogeneration power plant .

On the basis of experimental work the following conclusions are drawn :

The performance of boiler increase with bagasse dryer.

The major losses like dry flue gas loss, loss due to formation of water from

hydrogen in fuel and loss due to moisture in fuel is less when bagasse dryer is

used

The aim of the introduction of dryer was to reduce the bagasse moisture content

in order to improve the boiler performance. The results obtained show that these

aims were succeeded.

It is important for all sugar mills to install bagasse dryer.

The bagasse drying by using the flue gases is an economic necessity for sugar

mills where it can realizes self sufficiency of fuel .

It is an environmental necessity where it reduces the air pollution.

Bagasse has not become by-product of sugar industry, but it has become main

product.

Many types of bagasse dryers have been installed in different countries.

Here we have shown the comparative study of boiler when it is used with dryer

and without dryer and we clearly shown the amount of bagasse saved when

dryer is used.

So overall we can say that installation of bagasse dryer is beneficial for any

sugar industry because it saves fuel as well as improve the performance of

boiler by minimizing the major losses which occurs in bagasse fired boiler.

The payback period of bagasse dryer is also very less it is around 50 days in

normal working season.

48

Scope for Future work :-

In this work the boiler performance has been analysed based on dryer and

without using bagasse dryer as we know there are different auxiliaries related to

boiler like feed pump, ID Fan , Primary air Fan , Secondary air fan so if we

calculate total auxiliaries power consumption without dryer and compare with

the power consumption of auxiliaries when bagasse dryer is used then overall

auxiliaries power consumption can be optimized and boiler operation will be

smooth there will not be any need to change the boiler parameters like furnace

draft, fuel feeding etc. so bagasse dryer can play in important role in the

optimization of auxiliaries power consumption related to boiler.

49

CHAPTER-7

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