Bagasse as an alternative source of energy
Dharmendra D. Sapariya1, Prof. Nilesh R. Sheth2, Prof. Vijay K. Patel3
M-Tech Student of Energy engineering, Department of Mechanical engineering in Gujarat technical University GEC Valsad,
Gujarat, India1[
[email protected], Mob:-8866245022]
Assistant Professor at Department of Energy engineering, Mechanical engineering GEC Valsad, Gujarat, India2
Head of the Electrical Engineering Department, N.G. Patel Polytechnic, Isroli, Bardoli, Gujarat, India3
Abstract: Every year millions of tons of agricultural wastes are generated which are either destroyed or burnt inefficiently in
loose form causing air pollution. These wastes can be recycled & can provide a renewable source of energy by converting
biomass waste into different form of energy sources. This recycled fuel is beneficial for the environment as it conserves natural
resources. For this the biomass is the main renewable energy resource.
In this paper the raw material including bagasse as biomass. Bagasse is the crushed outer stalk material formed after
the juice is squeezed from sugar cane, in sugar mills. Bagasse characteristics vary in composition; consistency, etc. were
densified into briquettes at high temperature and pressure using different technologies. We discuss the various advantages,
factors that affecting the biomass briquetting and comparison between coal and bagasse briquetting. The details of the study
were highlighted in this paper.
Keywords: Biomass, Bagasse, Briquetting, Potential, Process, Technologies, sugarcane
I.
INTRODUCTION
Many of the developing countries produce huge quantities of agro residues but they are used inefficiently causing
extensive pollution to the environment. The major residues are bagasse as sugarcane production waste, rice husk, coffee husk,
coir pith, jute sticks, groundnut shells, mustard stalks and cotton stalks.[1,2] India is the second biggest sugarcane growing
country in the World, only behind Brazil. Pondicherry has many sugarcane plantations of its own, and surrounding Tamil Nadu
is the biggest sugarcane growing states in the India. [3]
Sugar industry is the second largest agro based industry in India after textile. About 5 crores of sugarcane farmers, their
dependents and large mass of labourers are involved in sugarcane cultivation, harvesting and ancillary activities. This
constitutes 7.5% of rural population. Dry leaves, left in field after harvest of sugarcane, are called trash. On an average, a
hectare of sugarcane generates about 10 tonnes of trash. Because it has no value as cattle fodder, and because it also resists
decomposition, the trash is burnt in situ, in order to clear the field for the next crop. The main waste product of sugarcane
production is a material known as bagasse. Bagasse is the fibrous residue that remains in large quantities upon the crushing of
sugarcane to remove the sugar juices. For each tonne of sugarcane crushed, about 300 kg of bagasse is retrieved.
1 Ton sugarcane = 300 Kg of bagasse
Bagasse Pith is cellulose but not fibrous, and must be removed from bagasse in order to make good quality pulp from which
to produce paper. Bagasse pith is usually removed in a process known as “moist de-pithing’ in the sugar factory itself.
Following table indicate top most sugar factory in terms of sugar crushing across the south Gujarat. [2]
Factory
Sugarcane
crushed(MT)
Factory
Bardoli
Gandvi
Madhi
Chalthan
Maroli
Valsad
Sayan
Mahuva
Unai
1954267
1107100
1210012
1105891
243573
265332
1137206
661029
78961
Ganesh
Coper
Kamrej
Pandvai
Narmada
Vadodara
Kodinar
Talala
592370
400219
510063
556741
715592
367029
241159
120936
Sugarcane
crushed(MT)
TABLE 1.1: SUGERCANE FACTORIES AT SOUTH GUJARAT[2]
FIG 1.1 SUGAR CROP DISTRIBUTION AREA ON THE INDIAN MAP
FIG. 1.2 GUJARAT SUGAR INDUSTRIES MAP
II. ADVANTAGES AND DISADVANTAGES OF BAGASSE BRIQUETTING
Briquetting technique is densification of the loose biomass; this is achieved by subjecting the biomass to heavy
mechanical pressure to form compact cylindrical form known as briquettes. Owing to high moisture content direct burning of
loose bagasse in conventional grates is associated with very low thermal efficiency and widespread air pollution. The
conversion efficiencies are as low as 40% with particulate emissions in the flue gases in excess of 3000 mg/ Nm³ In addition, a
large percentage of unburnt carbonaceous ash has to be disposed off.
Fuel
Coal
Bagasse
Saw dust
Ground Nutshell
Rice husk
Saw dust cotton
Density
Calorific value
g/cm3
Kcal/Kg
1.3
3800-5300
Biomass Briquette from
0.074
4200
1.7
4600
1.05
4750
1.3
3700
1.12
4300
Ash
content %
20-40
4.0
0.7
2.0
18.0
8.0
TABLE 2.1: COMPARISON COAL AND BIOMASS CHARACTERISTICS SOURCE (FARM WASTE UTILIZATION –SINGH)
Briquetted bagasse has low moisture content and densified form which overcomes the above mentioned problems with
direct firing of bagasse. Thus briquetted bagasse can be used as a potential fuel to substitute the fossil fuels. [2]
Following are the advantages of briquetting bagasse:
- High calorific value ranges between 3,500-5,000 Kcal/Kg
- Moisture percentage is very less (2-5%) compared to lignite, firewood & coal where it is 25-30%
- Economic to users compared to other forms
- Briquettes can be produced with a density of 1.2g/cm³ from loose biomass of bulk density 0.1 to 0.2 g / cm³.
- Easy in handling and storage due to its size.
- Consistent quality.
Disadvantages of biomass briquetting:
- High investment cost and energy consumption input to the process
- Undesirable combustion characteristics often observed e.g., poor ignitability, smoking, etc.
- Tendency of briquettes to loosen when exposed to water or even high humidity weather text into it.[1]
III. COMPARISON BETWEEN BAGASSE BASED BRIQUETTE AND COAL
Bagasse based
Characteristics
Bagasse
Coal
Calorific Value(CV)X 100
4000 Kcal/Kg
4080 Kcal/Kg
4000 Kcal/Kg
Moisture content(M)
45-55 % by weight
2-5 % by weight
4-6% by weight
Ash Content(A)
2 – 10 %
2 – 10 %
25-30%
Briquette
TABLE 3.1 COMPARISONS OF BAGASSE AND COAL [4]
COMPARISION CHART
60
50
Content
40
30
20
10
0
CV X 100
%M
%A
Cost X 100
Bagasse
40
45
4
30
Briquette
40.86
5
2.88
45
40
6
30
50
Coal
FIG. 3.1 COMPARISON CHART OF BAGASSE, BAGASSE BASED BRIQUETTE, COAL [4]
IV) FACTORS AFFECTING DENSIFICATION / BRIQUETTING
The factors that greatly influence the densification process and determine briquette quality are:
4.1 Temperature and pressure:
It was found that the compression strength of densified biomass depended on the temperature at which
densification was carried out.
Maximum strength was achieved at a temperature around 220°C.
It was also found that at a given applied pressure, higher density of the product was obtained at higher temperature.
4.2 Moisture Content:
Moisture content has an important role to play as it facilitates heat transfer.
Too high moisture causes steam formation and could result into an explosion. - Suitable moisture content could be of
8-12%.
4.3 Drying:
Drying depends on factors like initial moisture content, particle size, types of densifier, throughout the process.
The finer the particle size, the easier is the compaction process.
Fine particles give a larger surface area for bonding.
It should be less that 25% of the densified product.
4.4 Particle Size and Size reduction:
Could be done by means of a hammer mill.
Wood or straw may require chopping before hammer mill.
V. BAGASSE BRIQUETTING PROCESS
Briquetting is the process of densification of biomass to produce homogeneous, uniformly sized solid pieces of high
bulk density which can be conveniently used as a fuel. The densification of the biomass can be achieved by any one of the
following methods: (i) Pyrolysed densification using a binder, (ii) Direct densification of biomass using binders and (iii) Binderless briquetting.[5] Depending upon the type of biomass, three processes are generally required involving the following steps:
5.1 Sieving - Drying - Preheating - Densification - Cooling –Packing
5.2 Sieving - Crushing - Preheating - Densification - Cooling –Packing
5.3 Drying - Crushing - Preheating - Densification - Cooling –Packing
When sawdust is used, process A is adopted. Process B is for agro- and mill residues which are normally dry. These materials
are coffee husk, rice husk, groundnut shells etc. Process C is for materials like bagasse, coir pith (which needs sieving), mustard
and other cereal stalks.
Dry Material
Raw
materials
Storage
Wet
material
Powder Material
Drying
Grinding
Buffer
storage
Powder Material
Packing
Briquette
Cooling
Briquetting
FIG. 5.1 BRIQUETTE MAKING PROCESSES
VI. BIOMASS BRIQUETTING TECHNOLOGIES
Biomass densification represents a set of technologies for the conversion of biomass residues into a convenient fuel.
The technology is also known as briquetting or agglomeration. Depending on the types of equipment used, it could be
categorized into five main types:
-
Piston press densification
-
Pelletizing
-
Screw press densification
-
Low pressure or manual presses
- Roll press densification
6.1 Piston press densification
There are two types of piston press 1) the die and punch technology; and 2) hydraulic press. In the die and punch
technology, which is also known as ram and die technology, biomass is punched into a die by a reciprocating ram with a very
high pressure thereby compressing the mass to obtain a compacted product. The standard size of the briquette produced using
this machine is 60 mm, diameter. The power required by a machine of capacity 700 kg/hr is 25 kW. The hydraulic press process
consists of first compacting the biomass in the vertical direction and then again in the horizontal direction. The standard
briquette weight is 5 kg and its dimensions are: 450 mm x 160 mm x 80 mm. The power required is 37 kW for 1800 kg/h of
briquetting.[6] This technology can accept raw material with moisture content up to 22%. The process of oil hydraulics allows a
speed of 7 cycles/minute (cpm) against 270 cpm for the die and punch process. The slowness of operation helps to reduce the
wear rate of the parts. The ram moves approximately 270 times per minute in this process.
FIG. 6.1 BRIQUETTES MADE FROM A HYDRAULIC PRESS
FIG. 6.2 BRIQUETTE MADE BY SCREW EXTRUDER
6.2 Screw press
The compaction ratio of screw presses ranges from 2.5:1 to 6:1 or even more. In this process, the biomass is extruded
continuously by one or more screws through a taper die which is heated externally to reduce the friction.[7] Here also, due to
the application of high pressures, the temperature rises fluidizing the lignin present in the biomass which acts as a binder. The
outer surface of the briquettes obtained through this process is carbonized and has a hole in the centre which promotes better
combustion. Standard size of the briquette is 60 mm diameter.
6.3 Roller Press
In a briquetting roller press, the feedstock falls in between two rollers, rotating in opposite directions and is compacted
into pillow-shaped briquettes. Briquetting biomass usually requires a binder. This type of machine is used for briquetting
carbonized biomass to produce charcoal briquettes.
FIG. 6.3 ROLLER PRESS FOR AGGLOMERATION OF BIOMASS
FIG. 6.4 BRIQUETTES MADE FROM A PELLET MILL.
6.4 Pelletizing
Pelletizing is closely related to briquetting except that it uses smaller dies (approximately 30 mm) so that the smaller
products are called pellets. The pelletizer has a number of dies arranged as holes bored on a thick steel disk or ring and the
material is forced into the dies by means of two or three rollers. The two main types of pellet presses are: flat/disk and ring
types. Other types of pelletizing machines include the Punch press and the Cog-Wheel pelletizer. Pelletizers produce
cylindrical briquettes between 5mm and 30mm in diameter and of variable length. They have good mechanical strength and
combustion characteristics. Pellets are suitable as a fuel for industrial applications where automatic feeding is required.
Typically pelletizers can produce up to1000 kg of pellets per hour but initially require high capital investment and have high
energy input requirements.
6.5 Manual Presses and Low pressure Briquetting.
There are different types of manual presses used for briquetting biomass feed stocks. They are specifically designed for
the purpose or adapted from existing implements used for other purposes. Manual clay brick making presses are a good
example. They are used both for raw biomass feedstock or charcoal. The main advantages of low-pressure briquetting are low
capital costs, low operating costs and low levels of skill required to operate the technology. Low-pressure techniques are
particularly suitable for briquetting green plant waste such as coir or bagasse (sugar-cane residue). The wet material is shaped
under low pressure in simple block presses or extrusion presses. The resulting briquette has a higher density than the original
material but still requires drying before it can be used. The dried briquette has little mechanical strength and crumbles easily.
The use of a binder is imperative.
VII. Economic analysis of biomass briquetting
About 70 biomass briquetting machines were installed in India by 1995. By 2007 the number of briquetting plants
increased to 250. As the technology is locally mastered and economically viable, the number is increasing annually. Two
biomass briquetting technologies dominate the Indian market: the ram and die machine and the screw machine. These two
machines use different processes to densify sawdust and agricultural waste, and the end products also have different densities
and shapes. The two types of machines are locally manufactured. A third kind of press, the hydraulic press has not been used
in India and is considered unsuitable for Indian raw materials. The most common raw materials for heated-die screw-press
briquetting machines are saw dust and rice husk.
In this paper economic analysis of biomass briquetting is studied. The table 7.1 presents the values of different heads
for economic analysis of biomass briquetting factory in India.
Head (unit)
Value (Rs.)
Head (unit)
Value (Rs.)
Initial cost of machine
Life (yr)
Annual use time (hr)
Interest on cost (%)
Depreciation (%)
12,00,000
10
960
15
10
Labour required
Labour rate (Rs./hr)
Av. machine capacity (t/hr)
Fuel consumption (kwh)
Fuel cost (Rs/kwh)
4
30
1
9
4.68 (commercial charges)
Junk value (%)
10
5% of the initial
cost of machine
Oil and lubricant charges
20% of fuel cost
Annual repair
Working capital
12,000,000
TABLE 7.1 VALUES OF DIFFERENT HEADS FOR ECONOMIC ANALYSIS OF BIOMASS BRIQUETTING FACTORY IN INDIA
It is concluded that two biomass briquetting technologies dominate the Indian market: the ram and die machine and the
screw machine. These two machines use different processes to densified bagasse and agricultural waste, and the end
products also have different densities and shape. The hydraulic press has not been used in India and is considered unsuitable
for Indian raw materials. The most common raw materials for heated-die screw-press briquetting machines are saw dust and
rice husk. The economic analysis of biomass briquetting in India is shown in table 8.2. We conclude that apart from the
transportation, storage and handling problems biomass briquetting have several advantages over coal, oil etc. so we have to
use it for our domestic purposes like heating and cooking. Thus Bagasse in form of Briquette is an Alternative Source of
Energy.
Item
Value (Rs.) Item
Value (Rs.)
Fixed costs
4,29,000
2,736,000
Variable costs
12,98,035.2
Total cost /yr
Revenue :
17,27,035.2
3-Total revenue per yr
4- Total cost incurred per
year
5- Net profit per year (3-4)
6- Total initial cost
7- Payback period
6 months
1-Returns from 960 tons of
briquettes at Rs. 3.0 per kg
2- net returns
(assuming 5% losses during storage)
1,727,035.2
1,008,657.2
1,825,000
2,880,000
TABLE 7.2 ECONOMIC ANALYSIS FOR BIOMASS BRIQUETTING FACTORY
VIII. CO-FIRING METHOD OF GENERATION OF HEAT FROM BAGASSE
Co-firing is combustion of two different types of materials at the same time. Two distinct techniques are available to
co-fire bio-fuels in utility boilers:
8.1 Direct co-firing:- Biomass fuels are blended with coal in coal yard and the blend is sent to the firing system which is
seen in Fig. 8.1.
FIG. 8.1 DIRECT CO-FIRING SYSTEM
FIG. 8.2 INDIRECT CO-FIRING SYSTEM
8.2 Indirect co-firing:- The biomass is prepared separately from the coal and injected into the boiler without impacting
the coal delivery process Fig. 8.2. The first approach, in general, is used with less than 5 wt. % co-firing. [8]
8.3 Case study on Vasudhara Dairy- Co-firing system of steam-coal and Bio-coal.
Cost effectiveness with use of steam-coal and Bio-coal as a Boiler fuel.
Sr.
No
Month
Milk
Throuput(Lit)
Cones of Steam
coal+ Bio
Coal(Kg)
Total
Rate/Ton(Rs)
Landed
Total
Cost(RS
)
Milk
proc./Kg
coal
Coal/Li
t (Rs.)
1
2
3
4
Jan 10
Feb 10
Mar 10
Apr10
1,10,20,788
97,68,185
1,07,33,252
1,05,00,000
203116+0
21352+189632
12580+209758
173400+0
203116
210984
222338
173400
4000+0
4000+3550
4000+3550
4100+0
812464
758601
794960
710940
54.25
46.29
48.27
60.55
0.073
0.077
0.074
0.067
TABLE: 8.1 VASUDHARA DAIRY- CO-FIRING SYSTEM DATA
Name of supplier
M/s Narayan Traders
Material
Steam coal
M/s Jayshree Traders
Steam coal
M/s Renewal BioEnergy
Bio coal
Name of testing Lab
Premier Analytical
Laboratory, Nagpur
Premier Analytical
Laboratory, Nagpur
Mantra, Surat
GCV
5168 Kcal
DOS
02.01.2010
4809 Kcal
09.01.2010
4790 Kcal
17.02.2010
TABLE: 8.2 THE GROSS CALORIFIC VALUE CERTIFICATES FROM THE SUPPLIER FOR FUEL SUPPLY
As per trial results
1) The consumption ratio of steam coal: Biocoal = 1 : 1.19
2) The GCV comparison of steam coal : Biocoal = 5100 : 4700 (1 : 0.92)
3) The Rate comparison of steam coal : Biocoal = 4100 : 3550 (1 : 0.86)
Example of trial during April 2010
Qty of
Cond.
Recovery
per day.
11351
9371
13167
12897
Sr. No.
1
2
3
4
5
Parameter
Consumption
Rate
GCV
Total Cost
Saving
Steam Coal (Actual )
173.400 MT
4100/ Ton
5100
Rs. 7,10,940
Rs. 21,588.30
Biocoal(Expected)
206.346 MT
3550/Ton
4700
Rs. 7,32,528
TABLE: 8.3 BOILER TRIALS DURING APRIL 2010
SR NO.
1
2
3
4
5
6
Rate different
550
655
700
800
900
1000
Steam coal
Economic
At par
Costly
Costly
Costly
Costly
Biocoal
Costly
At par
Economic
Economic
Economic
Economic
Saving
21588
0
9363
29998
50632
71267
TABLE: 8.4 RATE DIFFERENT OF STEAM COAL & BIOCOAL WITH RESPECT TO GCV
Year
Price of fuel(Rs./TR)
2006
2010
Biocoal
2800
3550
Steam coal
3500
4100
2013-2014
5000
6300
TABLE: 8.5 PRICE OF FUEL USED AT VASUDHARA DAIRY IN BOILER DURING DIFFERENT YEAR.
From above case study and below graph conclude that if different in price of Biocoal and Steam coal increase result in
increase in saving of overall fuel cost of the plant as the plant run on co-firing generation method.
Fuel cost during diffrent Year
Price of fuel(Rs./TR)
7000
6000
5000
4000
3000
2000
1000
0
2006
2010
2013-2014
Bio-Coal
2800
3550
5000
Steam-Coal
3500
4100
6300
FIG: 8.3 FUEL COST OF VASUDHARA DAIRY
IX. ETHANOL AS A BIOFUEL PRODUCTION FROM BAGASSE
9.1 Production of Bio-ethanol from Sugar Molasses Using Saccharomyces Cerevisia
Experimental methods: A known quantity of sugar molasses and Baker’s Yeast (saccharomyces cerevisiae) were
taken in fermentation flask and kept in a constant temperature shaker. An anaerobic condition was maintained for
four days and during this period, the strain converts sugar into bio-ethanol with the evolution of CO2. A known
fermented sample was collected for every 12 h interval. The same procedure was repeated to optimize the
parameters such as pH, Temperature, substrate concentration and yeast concentration.
Identification of bio-ethanol: About 5 to 10 ml fermented sample was taken and pinch a of potassium dichromate
and a few drop of H2SO4 were added. The colour of the sample turns from pink to green which indicates the
presence of bio-ethanol.
Determination of sugar concentration: 100 ml of distilled water and mixed with 5 ml of conc. HCL acid and is
heated at 70 ˚C for a period of 10 min. The obtained sample was neutralized by adding NaOH and it was prepared
to 1000 ml and taken into burette solution. The 5 ml of Fehling A and 5 ml of Fehling B were taken and mixed
with 10 to 15 ml of distilled water in a conical flask and Methylene blue indicator was added. The conical flask
solution was titrated with burette solution in boiling conditions until disappearance of blue colour. The sugar
concentration was calculated by using the formula given below.
Determination of ethanol concentration and pH: The sample was fermented to different pH values between 1.0
and 8.0 to obtain maximum yield of bio-ethanol by adding lime or sulphuric acid. The samples were kept in
anaerobic condition for a period of four days and the fermented solution was analyzed for every 12 h intervals.
Bio-ethanol increases along with the increase in fermentation period. The optimized conditions of sugar molasses
are of temperature 350C, pH 4.0 and the time 72 h which gives maximum bio-ethanol yield of 53%. The
fermentation was carried out under anaerobic condition.[9]
1. Fermentation:
1 kg of Molasses
(42% Fermentable sugar)
(yeast)
C6H12O6+yeast 2C2H5OH + CO2
(0.42kg)
(0.214kg) (0.206kg)
7 – 9% v/v dilute aqueous solution
Total Energy Consumption = 0.252
MJ (thermal)
2. Distillation:
Auxiliary Energy
Consumption:
(Lights, pneumatic systems)
Total in Thermal 0.0355
MJ(th)
Primary and secondary: 7%
to 96% v/v
Total Energy Input = 2.004
MJ (th)
3. Dehydration: 96% to 99.8% v/
v
Total Energy Input = 0.816 MJ(th)
Effluent Treatment:
Energy output from Biogas Effluent 1.904 MJ (th)
Total Power Consumption in Thermal
0.553 MJ(th)
Net Total Power Effluent Treatment 1.352 MJ (th)
214.2 g of
Bioethanol
FIG. 9.1 ENERGY ANALYSIS OF BIOCHEMICAL CONVERSION OF MOLASSES TO BIOETHANOL
X. GASSES FUEL GENERATED FROM BAGASSE
Biogas is a mixture of 60–75% CH4 and 40–25% CO2, can be produced from a variety of organic compound through a
complex anaerobic digestion processes, and can be upgraded by further steps to bio-methane. It has a calorific value of about
20–25 MJ/m3 which can be upgraded by removing the carbon dioxide. The produced slurry as digester residue has a potential to
be used as fertilizer and soil conditioner. Biogas digester can be operated in different range of temperature as thermophilic
system operated at high temperature (50-70˚C), mesophilic system, moderate temperature ranging between 35-40˚C and
psychrophilic system that operate at temperature range of 15-25˚C. Operating temperature is very detrimental factor to obtain
high gas conversion efficiency with short hydraulic retention time, it takes up to months in a very low temperature. [9]
Biomass
Electricity and
heat
CO2
removal
Gasification
Biosyngas
Cryogenic
distrillation
Transportation fuels
- Fischer- Tropsch diesel
- Hydrogen
- Methane
Gaseous fuels
- Methane
- Synthetic Natural
Gas
Torrefaction
Products:
- Hydrogen
- Carbon monoxide
- Carbon dioxide
- Methane
- Acetylene
- Ethylene
- Benzene, Toluene, Xylene
- Light tars
- Heavy tars
- Ammonia
- Water
Tar Distillation
Heavy tars
Light tars
Solvents
Fertilizer
FIG. 10.1 PRODUCTS FROM GASIFICATION PROCESS
10.1 Bagasse gasification in gasifier:
The gasification of biomass is a thermal treatment, which results in a high production of gaseous products and small
quantities of char and ash. It is a well-known technology that can be classified depending on the gasifying agent: air, steam,
steam–oxygen, air–steam, oxygen-enriched air, etc. Gasification is carried out at high temperatures in order to optimize the gas
production. The resulting gas, known as producer gas, is a mixture of carbon monoxide, hydrogen and methane, together with
carbon dioxide and nitrogen.
10.2 Downdraft gasifier model:
Downdraft gasifiers are very similar to updraft gasifiers (Fig. 10.2), except that the feedstock and oxidizer in downdraft
gasifiers both enter from the top of the gasifier. The gas passes though the hot zone combusting the tars and leaving the reactor
from the bottom. Some of the advantages of this design are that it has a fairly simple design and is low cost, and it produces a
relatively cleaner gas with very low tar formation. Some of the disadvantages are that the system requires low moisture and ash
feedstock, can only use feedstocks within a limited particle size range (between 1-30 cm), and it has low efficiency because the
product gas leaves the gasifier at higher temperatures, which requires an additional cooling system as compared to an updraft
gasifier.
Four distinct processes take place in a gasifier as the fuel makes its way to gasification. They are:
a) Drying of fuel
b) Pyrolysis –a process in which tar and other volatiles are driven off
c) Combustion
d) Reduction
a) Drying of fuel
The first stage of gasification is drying. Usually air-dried biomass contains moisture in the range of 7-15 %. The
moisture content of biomass in the upper most layers is removed by evaporation using the radiation heat from oxidation zone.
The temperature in this zone remains less than 120 °C.
b) Pyrolysis
The process by which biomass loses all its volatiles in the presence of air and gets converted to char is called pyrolysis.
At temperature above 200°C, biomass starts losing its volatiles. Liberation of volatiles continues as the biomass travels almost
until it reaches the oxidation zone. Once the temperature of the biomass reaches 400°C, a self-sustained exothermic reaction
takes place in which the natural structure of the wood breaks down. The products of pyrolysis process are char, water vapour,
Methanol, Acetic acid and considerable quantity of heavy hydrocarbon tars.
FIG. 10.2 DOWNDRAFT GASIFIER MODEL
c)
Combustion
The combustible substance of a solid fuel is usually composed of elements carbon, hydrogen and oxygen. In complete
combustion carbon dioxide is obtained from carbon in fuel and water is obtained from the hydrogen, usually as steam. The
combustion reaction is exothermic and yields a theoretical oxidation temperature of 1400 °C. The main reactions, therefore,
are:
C + O2 = CO2 (+ 393 MJ/kg mole)
(1)
2H2 + O2 = 2H2 O (- 242 MJ/kg mole)
(2)
d) Reduction
The products of partial combustion (water, carbon dioxide and un-combusted partially cracked pyrolysis products) now
pass through a red-hot charcoal bed where the following reduction reactions take place:
C + CO2 = 2CO (- 164.9 MJ/kg mole)
(3)
C + H2O = CO + H2 (- 122.6 MJ/kg mole)
(4)
CO + H2O = CO + H2 (+ 42 MJ/kg mole)
(5)
C + 2H2 = CH4 (+ 75 MJ/kg mole)
(6)
CO2 + H2 = CO + H2O (- 42.3 MJ/kg mole)
(7)
Reactions (3) and (4) are main reduction reactions and being endothermic have the capability of reducing gas temperature.
Consequently the temperatures in the reduction zone are normally 800-1000˚C. Lower the reduction zone temperature (~ 700800˚C), lower is the calorific value of gas.[10]
XI. CONCLUSION
By the use of bagasse as a fuel in three different form of energy result in a sustainable production and power generation can
solve the vital issues of atmospheric pollution, energy crisis, wasteland development, rural employment generation and
power transmission losses. The energy requirement of any countries can be fulfilled by different form of bagasse without
emission of GHG and pollutant substance in the atmosphere. Bagasse provides both, thermal energy as well as reduction for
oxides. It is renewable, widely available carbon-neutral and has the potential to provide significant employment in the rural
areas. Also reduce dependency on other countries for energy sources requirement.
From this paper can be said that Bagasse is an Alternate source of energy.
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