16

CHAPTER 2

REVIEW OF LITERATURE

2.1 GENERAL

The increase in energy demand and environmental pollution can be

solved by renewable energy sources. The use of biomass energy for this

purpose has wide scope. Agricultural residue is one type of biomass, which is

available in larger quantity and distributed uniformly in all the areas.

Pyrolysis is one of the biomass energy conversion process used for converting

solid agricultural residues (biomass) into improved energy content products of

liquid, gas and solid. The pyrolysis of biomass is becoming interesting among

various systems for the energy utilization of biomass. Earlier investigators

have shown that pyrolysis has received special attention in current biomass

energy conversion technologies. It involves complex process of heat and mass

transfer between the biomass and heating medium. The pyrolysis products

yield and its composition depends upon the various operating parameters and

feedstock compositions. The research performed so far on pyrolysis show that

in order to meet the energy demand and environmental norms, especially in

developing countries like India, agricultural residues that are available in

larger quantities to be used for the production of energy content products.

Since the liquid products have high energy density, ease of transportation and

storage and the potential to be upgraded as fuels similar to refined premium-

grade fuels, the process conditions to be optimized to maximize the liquid

yield is to be employed.

17

Several pyrolysis processes have been studied for different biomass

and agricultural residues and still a good deal of work are continuing in this

direction. The current research works related to biomass pyrolysis process are

focusing on maximizing the liquid yield and to study the functional groups

and chemical compounds present in the liquid products. The pyrolysis process

and its product yields are mainly dependent upon the process parameters. The

optimization of different process parameters is very important to maximize

the liquid yield from pyrolysis process. In this chapter, the information

available in the literature on the pyrolysis of different biomass, effects of

process parameters on pyrolysis product yields, the compositions and

properties of liquid, gas and solid obtained from different biomass are

reviewed.

2.2 EFFECT OF PROCESS PARAMETERS ON PYROLYSIS

Haiping Yang et al (2007) investigated the effect of the main

components of biomass on the pyrolysis characteristics, using respectively, a

thermo gravimetric analyzer (TGA) with differential scanning calorimeter

(DSC) detector and a pack bed. Hemi-cellulose was easily degraded, and its

pyrolysis happened at 220–315°C. The pyrolysis of cellulose mainly

happened at 315–400°C. The pyrolysis of lignin covered a whole temperature

range (150–900°C). The effect of cellulose, hemi cellulose and lignin on the

main gas products in pyrolysis process showed that, CO2 releasing was

mainly caused by the primary pyrolysis, while secondary pyrolysis was the

main source for releasing of CO and CH4. Hemi cellulose, with higher

carboxyl content, accounted for a higher CO2 yield. Cellulose displayed a

higher CO yield, mainly attributed to the thermal cracking of carbonyl and

carboxyl. With a higher presence of aromatic ring and methoxyl, the cracking

and deformation of lignin released out much more H2 and CH4.

18

Kirubakaran et al (2009) reviewed the effect of size, structure,

environment, temperature, heating rate, composition of biomass and ash on

the gasification / pyrolysis of biomass. The conclusions from their studies are

The sweeping gas flow prevent the secondary cracking of the

char to gas and yields more amount of char equal to fixed

carbon content in the biomass.

Every biomass has sufficient quantity of oxygen (biooxygen)

to convert the solid combustible matter into gaseous fuel.

Ash catalyzes the gasification. The absences of ash in the

biomass increase the liquid yield and decrease the gas yield.

Bridgwater (1996) has analyzed the upgrading of the pyrolysis

liquid and production of chemicals from biomass by pyrolysis process in

addition of different catalysts with their economic analysis. The natural

catalysts present in the biomass influenced the production of high yielding

chemicals. Removal or reinforcement of these catalysts has a dramatic effect

on product yield and composition and concluded that, the use of catalysts to

improve either the yield or quality of gas. Considerably more research and

development is needed to develop and prove suitable catalyst systems.

Islama and Ani (2000) studied and compared the techno-economic

assessment of bio oil production from rice husk through fast pyrolysis in a

fluidized bed with and without catalysts in a three different-scale pyrolysis

units of capacity 0.3, 100 and 1000 kg/h. The study concluded that the

fluidized bed fast pyrolysis process with rice husk as feedstock is

economically better than the fluidized bed fast pyrolysis–catalytic treatment

process for each of the three different-scales pyrolysis plants. The greater the

feed throughput (i.e., the plant capacity) the lower is the unit production cost.

Thus, the large-scale plants are favorable, with better techno-economics.

19

The effect of variables, temperature between 300°C and 800°C,

particle sizes between 0.4 and 2 mm diameter, initial sample weight between

2.5 and 10 g and nitrogen flow rates between 100 and 300 cm3/min on the

pyrolysis of Cynara cardunculus L (cardoon) and the heating value of the

pyrolysis products were investigated by Encinar et al (2000) in a fixed bed

reactor. The study explored that, the yields were strongly dependent on

temperature but independent of particle size, nitrogen flow rate, and initial

sample weight. The gas distribution varied with temperature, with increasing

formation of H2, CH4, CO and CO2. The maximum liquid yield was obtained

at the temperatures between 400°C and 500°C. The highest heating value of

obtained char was 31 MJ/kg.

An experimental study of the pyrolysis/gasification of grape and

olive bagasses by carbon dioxide was carried out by Encinar et al (1998). The

yields and characteristics of the solids formed (proximate and ultimate

analysis), pore volume and specific surface were analyzed as a function of

temperature, particle size of samples, additive or activating agents, chemical

pretreatment and concentration. The different experiments were carried out

by varying temperature between 300–900°C, particle size 0.4 to 2 mm

diameter, additive or activating agent type (NaCl, LiCl, KCl, AlCl3 6H2O,

ZnCl2 ) and concentration (0.1 to 10% by weight of metal cation). Sulfuric and

phosphoric acids at concentration ranged between 10 to 40% and 10 to 85%

by weight, respectively, were used for chemical pretreatment. There was no

effect on influence on the yields of fractions, proximate analysis, and

structural characteristics of activated carbon, liquid phase composition and

gas production by the particle size. A higher fixed carbon content, slight

increase of ash and a decrease of volatile matter, and gas distribution changes

notably, increasing hydrogen, methane and carbon monoxide production were

notified with higher temperature compared with lower temperature range. A

20

maximum liquid yield was attained with the temperature close to 600–700°C.

The presence of additives increased the char fraction and decreased the liquids.

Suping Zhang et al (2005) conducted the fast pyrolysis process of

sawdust with particle size of 0.1–0.2 mm in a fluidized bed reactor with CO2

as a fluidizing medium. Effects of reaction conditions temperature, reaction

time, cold hydrogen pressure and catalyst on product distribution were

investigated with the objective of finding the optimal conditions to maximize

the liquid yield. The comparison of raw oil phase and the upgraded liquid fuel

were also made. At lower temperature, conversion and oil yield both were

very low, and increased rapidly with reaction temperature. Gas yield

increased steadily as temperature was increased. But char yield decreased

sharply as temperature was raised up to 360°C. The raw oil was upgraded by

tetralin and tar oil as solvent. Higher liquid yield resulted with tetralin as

solvent since tetralin acted as hydrogen vehicle that transferred hydrogen

from the gas phase in active form to the radical fragments for their

stabilization. A significant decrease in oxygen content (O2: Raw bio oil

41.8 wt%: Upgraded oil: 3 wt%) resulted in an increase in the heating value

( HHV: Raw bio oil 21.3 MJ/kg: Upgraded oil 41.4 MJ/kg) of the upgraded

oil. The raw bio-oil had poor miscibility in toluene; it dissolved well in

methanol because of the large amount of hydroxyl groups. However, the

upgraded oil was oil-soluble. The optimum conditions were temperature

360°C, reaction time 30 min and cold hydrogen pressure 2 MPa.

Hyun Ju Park et al (2008) studied the fast pyrolysis of Japanese

larch with a bubbling fluidized bed reactor. The effects of various reaction

conditions, such as the reaction temperature, feed size, flow rate, feeding rate

and fluidizing medium on pyrolysis yield and its compositions were analyzed.

The chemical and physical characteristics of bio-oil were also analyzed. The

bio-oil yield was increased to 55 wt% when the reaction temperature was

21

increased to 450°C. The bio-oil yield decreased with further increase of

temperature. The char yield decreased as the reaction temperature was

increased to 550°C. When a particle size was decreased from 1.2 mm to less

than 0.3 mm, the bio-oil yield decreased from 58 to 47 wt% while the gas

yield increased to 32 wt%. The bio-oil yield decreased at a low feeding rate

due to secondary cracking, which was followed by an increase in gas yield.

The Bio-oil had a higher heating value of 22 MJ/kg, approximately half that

of conventional fuel, and comparable to that of oxygenated fuels such as

methanol, ethanol, and coal. A high reaction temperature resulted with higher

proportion of CO and CH4 and a low proportion of CO2. The increase in the

content of CO and C1–C4 hydrocarbons with high caloric values suggested

that the gas products can be used as energy sources for the pyrolysis process

or other applications.

Putun et al (2001) conducted the pyrolysis of euphorbia rigida,

sunflower pressed bagase and hazelnut shells in a fixed bed tubular reactor

with the heating rate of 7 K/min for determining the possibility of each being

a potential source of renewable fuels and chemical. The analysis was made to

find the effects of pyrolysis temperature and sweep gas (N2) flow on pyrolysis

yields and its chemical compositions with the aim of determining the suitable

regimes for obtaining oils in high yields, high H/C ratios and high calorific

values with low oxygen content. The experiments were conducted with the

average particle size of 0.55 mm for euphorbia rigida, 0.425 to 0.850 mm for

sunflower pressed bagase and hazelnut shells. The highest liquid yields of

31.5, 45.7 and 23.1 wt% were obtained from euphorbia rigida, sunflower

pressed bagase and hazelnut shells respectively, with a heating rate of

7 K/min, nitrogen flow rates of 400, 200 and 100 cm3/min, respectively and

final temperature of 773, 823 and 773 K. All of the bio-crude were

characterized by low oxygen content with a higher H/C ratio than the original

feedstock’s. The H.C ratios of the bio crude’s obtained were between those of

22

light and heavy petroleum products of currently utilized transport fuels. The

calorific values of the bio crude obtained from euphorbia rigida, sunflower

pressed bagase and hazelnut shells were 39.667 MJ/kg, 37.649 MJ/kg and

26.317 MJ/kg respectively. The higher oxygen content in the hazelnut shell

produced lower calorific value of the bio crude compared to other 2 biomass.

Zabaniotou et al (2008) compared the experimental results of

slow, fast and catalytic pyrolysis of five lignocellulosic residues (corncobs

and corn stalks, sunflower residues, olive kernels and olive tree prunings).

A captive sample wire mesh reactor and a fixed bed reactor were used for fast

pyrolysis and non-catalytic and catalytic slow pyrolysis respectively. Helium

and N2 were used as a carrier gas in order to create an inert atmosphere and to

sweep the produced gas from the reactor into the water container. The gas

yield from fast pyrolysis was higher than that from the slow pyrolysis of both

non-catalytic and catalytic. Corn stalks produced higher gas yields compared

to other feedstocks. Residues with more cellulose and hemicellulose content

produced more hydrogen- rich gas than those characterized by higher lignin

content. High flow rates of the carrier gas minimized vapor residence time

and secondary reactions in the reaction zone and increased the liquid yield.

Olive kernels and corn residues (cobs and stalks) gave the highest percentages

of liquids, followed by olive tree prunings and sunflower residues. The

catalyst seemed to enhance liquid production from olive kernels and

corncobs, but it exhibited the opposite effect for the rest of feedstocks. The

addition of catalysts increased the production of water and decreased the

production of organics. The sunflower residues gave higher char yields than

the other agro residues under both fast and slow pyrolysis processes. The

addition of catalyst decreased the char yield.

The fast pyrolysis of washed and unwashed Empty Fruit Bunches

(EFB), a waste of the palm oil industry, was investigated with the aim of

23

determining and comparing the liquid yield with wood derived bio-oil and

petroleum by Abdullah et al (2008). The organic phase generated from the

fast pyrolysis of unwashed feedstock had a very large higher heating value of

36 MJ/kg nearly the calorific value of petroleum fuels. The liquids produced

from washed EFB and unwashed EFB was around 72% and 50% respectively.

The study found that, the ash content of the feedstock significantly influenced

the yield of organics. The higher the concentration of ash in the feedstock

produced lower yield of pyrolysis liquid. The overall product yields from

washed EFB were comparable well, with low ash woody feedstocks. The

yield of carbon dioxide increased substantially with increase of ash content.

Zabaniotou et al (2008) carried out a study of the pyrolytic behavior

of sunflower residues at temperature from 300 to 600°C in a captive sample

reactor under atmospheric pressure and helium as sweeping gas. The

influence of temperature on the product yield with constant sweeping gas

flow of 50 cm3/min and heating rate of 40°C/s was determined. For the

sunflower residues, the char yield decreased as the temperature was increased

and above 450°C, the yield was constant with a value of 32 wt% of dry

sunflower residue. The gaseous product yield increased with the increase of

temperature and reached a maximum yield of 53 wt%. The maximum oil

yield of 21 wt% was obtained at a temperature of 400°C.

Pyrolysis products yield and liquid product compositions of apricot

pulps was studied by Nurgul Ozbay et al (2008) in a fixed-bed reactor under

different pyrolysis conditions of final temperature, static condition, sweeping

gas flow rate and steam velocity with a heating rate of 5°C/min. Peach pulp

was also pyrolyzed with the optimum conditions obtained from apricot pulps

pyrolysis. The oil yield increased from 18.6% to 22.4% when the pyrolysis

temperature was increased from 300 to 550°C and decreased to 18.8% when

the temperature further increased to 700°C under the static conditions. The oil

24

yield reached a maximum value of 23.3% under the sweeping gas flow rate of

100 cm3/min and decreased with further increase of sweeping gas flow rate. In

this study the maximum apricot pulp bio-oil yield of 27.2% was reached

under steam atmosphere with the steam velocity of 2.5 cm3/min. Bio-oils

obtained under steam atmosphere have the highest calorific value

(35.63 MJ/kg) when compared with bio-oils obtained under static (24.44

MJ/kg) and nitrogen gas atmospheres (26.82 MJ/kg). The char and bio oil

yield from peach pulp were 25.2% and 27.7% respectively at 550°C and with

a steam flow rate of 2.5 m3/min. The study suggested that the bio-oil obtained

under these conditions can be utilized as either synthetic fuels or chemical

feedstock.

Piyali Das and Anuradda Ganesh (2003) have studied the effect of

temperature on pyrolysis of cashewnut shell in a fixed bed vacuum pyrolysis

unit. The maximum percentage of bio oil was obtained at a temperature of

500°C. The calorific value of the oil obtained from cashewnut shell was 40

MJ/kg which was nearer to the calorific value of the petroleum fuel and

concluded that the oil obtained can be considered to be a promising bio-oil

with a potential as fuel. The oil also consisted of low ash (0.01%) and water

content was limited to only 3-3.5% of oil.

Anuradda Ganesh and Rangan Banerjee (2001) made a comparative

study of biomass pyrolysis technology for power generation (Biomass

Pyrolysis-Combined Cycle), with other technologies of biomass combustion -

Rankine cycle, biomass gasification-gas engine, and biomass gasification -

combined cycle to determine its economic viability. The study concluded that

pyrolysis is relatively new in the learning curve, it is found comparable with

the other routes studied. The biomass prices have a strong influence in the

economics, and using pyrolysis for power generation would be a more

favored route, than others, at higher biomass prices. The study clearly brought

25

out that power generation through pyrolysis as a potential route and deserves

attention.

Raveendran and Anuradda Ganesh (1996) studied the pyrolysis

characteristics of 14 different biomass and biomass components in a thermo

gravimetric analyzer and a packed-bed pyrolyser in an inert atmosphere of

nitrogen (50 cm3/ min) and the influence of the composition of the ash on the

pyrolysis process. The different pyrolysis zones are described as

zone I : <373 K, mainly moisture evolution

zone II : 373-523 K, extractives start decomposing

zone III : 523-623 K, predominantly hemi cellulose decomposition

zone IV : 623-773 K, mainly cellulose and lignin decomposition

zone V : >773 K, mainly lignin decomposition

The study found that, the components played significant roles in

determining the pyrolysis characteristics of biomass. Also, the basic structure

or degree of polymerization of the biomass was less significant than its

composition. The biomass with more ash or lignin formed more char during

pyrolysis. The conclusion from their study is ash present in biomass seems to

have a strong influence on both the pyrolysis characteristics and the product

distribution.

The slow pyrolysis of pine wood in a static batch reactor was

investigated by Paul and Serpil Besler (1996) at pyrolysis temperature from

300 to 720°C and heating rates from 5 to 80 K/min. The liquid and gas yields

were increased from 31.6 to 50% and 14.6 to 26.8% respectively, when the

temperature was increased from 300 to 720°C at a heating rate of 5 K/min.

The liquid and gas yield were increased from 50 to 53.6% and 26.8 to 30.2%

when heating rate increased from 5 K/min to 80 K/min at a temperature of

720 K/min. The functional group, compositional analysis of the derived oils

26

by Fourier Transform Infra-Red Spectrometry (FT-IR) indicated that the oil

contains carboxylic acids and their derivatives, ketones, aldehydes, alkanes,

ethers, primary, secondary and tertiary alcohols and phenols. The calorific

values of obtained char and oils were 32 MJ/kg and 23 MJ/kg.

Paul and Nittaya Nugranad (2000) investigated the effect of

catalysts on the pyrolysis product yields and its compositions, of rice husk, in

a fluidized bed reactor. The gases were analyzed off-line by packed column

gas chromatography. Zeolite ZSM-5 catalyst was used for the upgrading of

the pyrolysis oils. The pyrolysis oils before the addition of catalysis were

homogeneous, of low viscosity and highly oxygenated. Polycyclic aromatic

hydrocarbons (PAH) were present in the oils at low concentration and

increased in concentration with increasing temperature of pyrolysis. The yield

of oil was markedly reduced and the oxygen content of the oil was also

reduced when the catalyst were added. The oxygen in the pyrolysis oil was

converted to largely H2O at the lower catalyst temperatures and to largely CO

and CO2 at the higher catalyst temperatures. The yield of gas with catalyst

was higher than that of pyrolysis process without catalyst. The maximum oil

yield of 46.5% and 7.2% were obtained in pyrolysis and catalytic pyrolysis

process respectively. The maximum gas yield was 34.5% and 41% under no

catalytic and catalytic additions.

Patrick and Paul (1996) studied the flash pyrolysis of wood waste

in a fluidized bed reactor. The liquid, gas and char yield and their

characteristics were analyzed with different temperature. The liquid and gas

yield were increased from 65.5 to 66.2% and 10.2 to 15.2% respectively, but

the solid yield decreased from 24.1 to 17.1% when the temperature was

increased from 400 to 550°C. The carbon, hydrogen and oxygen contents in

the liquid, before removal of water in the liquid were 38.1%, 8.46% and

27

52.8% respectively at the temperature of 550°C. These values were changed

to 59.6%, 6.05% and 33.5% when the water was removed from the liquid.

Slow pyrolysis of Olive bagase was investigated in a fixed-bed

reactor under different operating conditions by Sevgi Sensoz et al (2006). The

effect of temperature between 350 and 550°C with heating rates of 10 and

50°C/min on pyrolysis yield was investigated. The particle size and sweep gas

flow rate varied in the ranges 0.224–1.8 mm and 50–200 cm3/min,

respectively. For the heating rate of 10°C/min the bio-oil yield was 27.8% at

the pyrolysis temperature of 350°C; it appeared to go through a maximum

(34.4%) at the final temperature of 500°C. Then, at the final pyrolysis

temperature of 550°C, the bio-oil yield decreased to 30.7%. At the lower

heating rate of 10°C/min, the bio-oil yield was about 3.4–8.4% higher than

those at 50°C/min. The gas yield obtained was found to be a minimum of

9.0% at 350°C and maximum of 14.0% at 550°C for the heating rate of

10°C/min. Gas yield was obtained at the level of 14.8–18.0% for the heating

rate of 50°C/min. The smallest (0.224–0.425 mm) particle size produced a

bio-oil yield of 33.4% with a char yield of 32.9%. Larger (0.85–1.8 mm)

particle sizes produced bio-oil and char products of 32.6 and 30.9%

respectively. The obtained bio-oil yield was 34.4%, without any sweep gas

and increased to 37.7 wt% with the sweep gas flow rate of 150 cm3/min. The

bio oil yield at the optimum temperature (500°C) was increased by only 3.7%

when the nitrogen flow rate was increased from 50 to 150 cm3/min.The

increase in the nitrogen flow rate from 150 to 200 cm3/min reduced the bio-oil

yield from 37.7% to 36.8%. The chemical characterization showed that the

bio-oil obtained from olive bagasse may be potentially valuable as a fuel and

chemical feedstock.

Fast pyrolysis of apricot stone, in a free-fall reactor, was studied by

Shiguang Li et al (2004). The study concluded that the decrease of particle

28

size from 0.90–2.00 to 0.20–0.30 mm resulted in decrease of, both the liquid

and solid yield and increase of the gas yield. The char yield decreased from

30.7 to 3.2%, the bio-oil yield decreased from 48.3 to 17.8% and the gas

increased from 16.3 to 71.3%, when the particle size was decreased from

0.90–2.00 to 0.20–0.30 mm.

Putun et al (2002) conducted the slow pyrolysis of soyabean cake in

a fixed-bed reactor and studied the effect of particle size on the oil yield. The

study observed that the increase of oil yield from 26.74 to 30.23% when the

particle size was increased from 0.224-0.425 mm to 0.850-1.250 mm and

increase of oil yield from 28.02 to 30.23% when the particle size was

decreased from Dp>1.80 mm to 0.850-1.250 mm. The study concluded that

the maximum oil yield was obtained at the optimum particle size of

0.850-1.250 mm.

The pyrolysis of cotton stalk was studied for determining the main

characteristics and quantities of liquid and solid products by Putun et al

(2005). The study was carried out with the particle size from 0.225-0.425 mm

to greater than 1.80 mm, pyrolysis temperature of 550°C and heating rate of

7°C/min. The study concluded that the particle size had no significant effect

on char. However, increasing particle size from 0.225-0.425 mm to

0.85-1.80 mm increased the yield of pyrolysis oil from 20.98% to 23.82%.

The slow pyrolysis of rice straw was studied by Putun et al (2004)

to estimate the effect of pyrolysis conditions on product yields. The sweeping

gas flow rates varied from 50 to 400 ml/min with the particle size of 0.425-

0.850 mm. The study found that, the highest bio-oil yield, achieved under

static atmosphere, is 27.77%, which reached a maximum value of 30.23%

with nitrogen flow rate of 200 cm3 /min and increased to 33.41 % and 35.86

% with the steam velocity of 1.3 cm/s and 2.7 cm/s respectively.

29

The slow pyrolysis of soyabean cake in a fixed-bed reactor was

investigated under three different atmospheres by Ozbay et al (2001). The

steam velocities were varied with 0.6, 1.3 and 2.7 cm/s. The bio-oil yield

reached a maximum value of 42.79% at a steam velocity of 1.3 cm/s, while it

had a maximum value of 30.00% at the static retorting. The opposite trend

was observed for the solid product: char yield decreased from 25.1 to 15.86%

when the steam was used instead of a static atmosphere.

Ersan et al (2008) investigated the thermal conversion of biomass

sample with catalyst, in inert (N2) and steam atmospheres with the heating

rate of 7°C/min ( slow pyrolysis), the oil yield of 34.5%, 38.6% and 38.2%

was obtained with the steam flow rate of 25 cm3/min and catalyst percentage

of 5%, 10% and 20% respectively. The maximum oil yield was obtained as

38.6% at 25 cm3/min when a 10% catalyst by weight in relation to the

biomass was used. At higher steam flow rate greater than 25 cm3/min, the

liquid yield decreased because the residence time of the steam in the reactor

was reduced and no sufficient time for the conversion of solid material to

liquid product.

Young et al (2009) investigated the pyrolysis characteristics and

kinetics of oak trees in thermo gravimetric analyzer at heating rates of

5–20°C/min. The final size of the sample was between 600 µm and 850 µm

after sieving. A small change of conversion in the samples was observed at

the temperature lower than 200°C due to vaporization of moisture that was

attached on the surface of the samples. The TGA curves of the oak trees

shows that one weight loss step and the major decomposition occurred

between 250°C and 380°C. The hemicelluloses started to decompose at

around 300°C and the cellulose was found to decompose between 320°C and

380°C. Lignin had a broad decomposition temperature range between 200 and

500°C. It was observed that the decomposition of oak trees at 400°C or higher

30

progressed slowly because of the remaining lignin or char. The DTG curve of

each heating rate has one extensive peak, occurred between 230°C and 400°C.

The maximum points of the DTG curves occurred at 348°C, 359°C, 363°C

and 368°C for heating rate of 5°C/min, 10°C/min, 15°C/min and 20°C/min,

respectively. The maximum rate of decomposition tends to increase at higher

heating rate because it provided higher thermal energy to facilitate better heat

transfer between the surrounding and inside of the samples.

Wanignon et al (2009) studied the pyrolysis of pinus pinaster in a

two-stage gasifier (pyrolysor and gasifier unit) to analyze the influence of

process parameters and thermal cracking of tar. The effect of temperature,

residence time and biomass flow rate were investigated. The experiments

were carried out with biomass flow rate of 10, 15, 20 kg/h, residence time of

15, 30, 60 min and the pyrolysis temperature of 450°C, 550°C, 650°C and

750°C. The study found that temperature between 650°C and 750°C,

residence time of 30 min, biomass flow rate between 10 and 15 kg/h are the

most convenient experimental conditions to get higher efficiency of tar

cracking, the quality and the heating value of the charcoal and the gas. The

increasing temperature and residence time improved the cracking of tars, gas

production and char quality. The char quality was decreased with the increase

of biomass flow rate.

The pyrolysis yields of rapeseed were investigated by thermo

gravimetric analysis technique by Haykiri et al (2006). The heating rates

varied with 5, 10, 20, 30, 40 or 50 K/min with a temperature up to 1273 K and

dynamic nitrogen flow of 40 cc/min. The DTG profile show that considerable

different trends in the rates of mass losses when heating rate increased from 5

to 50 K/min. The maximum rates of mass losses were found to be 1.1 mg/min

for 5 K/min and 2.2 mg/min for 10 K/min and increased to 5.2, 8.3 and 10.0

mg/min for the heating rates of 30, 40 and 50 K/min, respectively. Total mass

31

losses from the sample were determined as 75.0, 76.8, 77.5, 78.0, 79.5 and

85.0% on original basis at the heating rates of 5, 10, 20, 30, 40 and 50 K/min,

respectively. The final pyrolysis temperatures were also affected from the

variation of the heating rate. They were determined as 753, 938, 1257, 776,

1045 and 1175 K for the heating rates of 5, 10, 20, 30, 40 and 50 K/min,

respectively. Because of insufficient interaction of the particles at high

heating rates, the pyrolysis process was actually continued even at relatively

higher temperatures.

Wen et al (2009) carried out the pyrolytic experiments of three-

sewage sludge’s from the food processing factories (fructose manufacturing

factory, milk-derivative factory and beer brewing factory) in an externally

heated fixed bed reactor. The experiments were carried out with the

temperature, heating rate and holding time of 500-800°C, 200-500°C/min and

1-8 min respectively. The sludge sample mass and N2 flow rate were fixed at

about 10 g and 1000 cm3/min respectively. The thermo gravimetric analysis

(TGA) curves showed that the pyrolysis reaction finished in the temperature

range of 450–750°C. The first one ranging from 30 to 120°C represents the

stage of moisture release with the peak at about 60°C in a DTG curve. The

second region is the temperature range 200–400°C, where most of the volatile

matters were released one narrow peak at about 270°C in the corresponding

DTG curve. The third stage is 450–750°C, where slight mass loss caused by

the further degradation of volatile matters with the peak in the range of 540 to

600°C in the DTG curve. The study found that, the liquid yield increased with

the increase of temperature from 500-800°C for 2 samples and it was

decreased with the increase of temperature for other sample. The optimum

amount of liquid yield was obtained with the temperature, heating rate and

holding time of 500°C, 200°C/min and 2 min respectively. Functional group

analysis of the pretreated pyrolysis liquid product was carried out using

Fourier transform infra-red spectrometry. It was noted that the pyrolysis

32

liquid product contained a significant amount (73–90% by weight) of water,

and fewer contents of complex compounds mostly composed of aromatic and

carbonyl structures, resulting in low pH and low calorific values.

Ajay Kumar et al (2008) investigated the thermo gravimetric

analyses of corn stover with nitrogen (inert) and air (oxidizing) atmospheres.

The heating rates were maintained at 10, 30, and 50°C/min. All TGA

experiments were conducted at a constant purge flow rate of 40ml/min.

Samples were held at 25°C for 1 min, heated to 850°C at the respective

temperature scan rates and then held at 850°C for 1 min. The weight losses of

corn stover in both inert and oxidizing atmospheres were found to occur in

three stages. The study found that in nitrogen atmosphere the decomposition

taken place with, the first stage ranged from 25 to 125°C, the second stage

from 250 to 450°C and the third stage from 420–470 to 850°C. In oxygen

atmosphere, the first stage of decomposition happened at (25–125°C) , which

was similar to that in the inert atmosphere. The second stage occurred very

rapidly and contributed to most of the weight loss (around 70%). The third

stage, which ranged from 400 to 560°C, contributed to 10% of the weight

loss. The third stage in the oxidizing atmosphere had a very narrow

temperature range as compare with the third stage in the inert atmosphere and,

third stage in the inert and oxidizing atmospheres were different.

Asri Gani and Ichiro Naruse (2007) tested the pyrolysis and

combustion behaviors of biomass samples by a thermo-gravimetric analyzer.

The study found that the main compositions in the biomass consisted of

cellulose and lignin. The cellulose content was more than lignin content. The

reaction for the actual biomass samples proceeded with the two stages. The

first and second stage corresponded to devolatilization and char combustion

during combustion, respectively. The first stage showed rapid mass decrease

caused by cellulose decomposition. At the second stage, lignin decomposed

33

for pyrolysis and its char burned for combustion. For the biomass with higher

cellulose content, the pyrolysis rate became faster. The biomass with higher

lignin content gave slower pyrolysis rate. The study concluded that, the

cellulose and lignin content in the biomasses was one of the important

parameters to evaluate the pyrolysis characteristics.

Gang Wang et al (2008) conducted the thermo gravimetric analysis

of sawdust and compared the same with cellulose, hemicelluloses and lignin

pyrolysis under syngas and hydrogen. The investigation mainly focused on

the effect of heating rates. The heating rate was varied with 5, 10, 15 and

20°C/min. In the experiment, First the sample was heated from 30 to 100°C at

prefixed heating rate (5, 10, 15 or 20°C/min) and kept isothermal for 20 min

to remove moisture. Then it was further heated to 600°C continuously at the

same heating rate. The flow rate of hydrogen or syngas was kept constant at

45 ml/min. The study found that the pyrolysis of hemi cellulose and sawdust

started at about 196°C, its weight loss rate increased with increase

temperature and reached maximum value at about 287°C, then decreased and

reached low when temperature was above 340°C, The pyrolysis of cellulose

started at 283°C and reached maximum value at 333°C. When temperature

was above 370°C, its weight loss rate was low. The pyrolysis of lignin has the

widest temperature range and it had two peaks at 279 and 450°C, respectively.

The pyrolysis of sawdust started at about 196°C, same as that of hemi

cellulose, and has the maximum weight loss rate at about 361°C. The study

concludes that, heating rate could not only affect the temperature at which the

highest weight loss rate reached, but also affected the maximum value of

weight loss rate. The maximum weight loss rate of sawdust was reached at

347°C at heating rate of 5°C/min, while it was 373°C at 20°C/min. The study

also concluded that the profiles were same with both the case of syngas and

hydrogen flow.

34

Zheng Jiao et al (2009) studied the pyrolysis characteristics of

plastic, rubber, paper, wood, fabric, food residue that are the representative

organic components from municipal solid waste and their mixtures in a

thermo gravimetric analyzer. The high heating rate pyrolysis behavior of each

component was characterized, with a maximum-recorded heating rate of

864.8°C/min. The study found that the pyrolysis of rubber was the most

difficult of all the components in that study, next was food residue, followed

by wastepaper. Wood chips and fabric were at the same level, and PE was the

easiest. The pyrolysis behavior at high heating rates was observed as quite

different from that observed at low heating rates. The reaction rate was

increased with the increase of final pyrolysis temperature.

Thermal degradation of cotton stalk (CS), sugarcane bagase (SB)

and shea meal(SM) were investigated by Munir et al (2009) under pyrolysis

(N2) and oxidizing (dry air) conditions in a thermo gravimetric analyzer. The

samples were prepared with a particle size less than 300 µm. The initial

weight loss of 4%, 11%, 12% and 9.6% were observed for cotton stalk,

sugarcane bagase and shea meal respectively between temperatures of 25°C

and 105°C corresponding to moisture removal. The study found that the initial

devolitlization temperature and total losses at the end of 950°C temperature

were varied with individual sample due to the differences in the elemental and

chemical compositions of the samples. The devolitlization starts with 200°C,

216°C and 190°C for CS, SB and SM respectively. The total % weight losses

were 77, 84 and 70 for the same sample sequence. The anticipated final

temperatures of the major devolatilization zone for CS, SB and SM were

425°C, 455°C and 437°C, respectively.

Hyun Ju Park et al (2009) studied the pyrolysis characteristics of

oriental white oak under fast pyrolysis conditions, the variation of chemical

and physical characteristics of the bio oil with the variation of pyrolysis

35

conditions were also determined. The major weight loss was observed

between 250 and 400°C in a TGA analysis. The maximum yield of bio oil

was observed in the temperature range from 400 to 450°C. The effect of

particle size between 0.3 mm to 1.0 mm had an adverse effect on the

production of bio oil. The affect of feed rates and gas flow rates on the bio oil

production was observed as low. The physical and chemical characteristics of

bio oil only varied with the variation of temperature and did not varied with

the variation of other operating conditions. The GC/MS analysis showed that

the major compounds in the bio-oil were phenolics, ketones and aldehydes.

2.3 PROPERTIES OF PYROLYSIS PRODUCTS

Ioannidou and Zabaniotou (2007) reviewed the production of

activated carbon from agricultural residue by pyrolysis process. The study

found that, the char obtained from pyrolysis of agricultural residues are

suitable for activated carbon. There was a difference in the elemental analysis

of activated carbon produced from different raw materials, under the same

conditions, due to the influence of the composition and structure of the raw

material on the pyrolysis reactions. Activated carbon concerned many

industries as diverse as food processing, pharmaceuticals, chemical,

petroleum, mining, nuclear, automobile and vacuum manufacturing.

Fahmi et al (2008) described the effect of lignin and composition of

the biomass on pyrolysis process, oil yield, quality and stability of the

pyrolysis oil. Four reference fuels (willow, switch grass, reed canary grass

and wheat straw) and three low lignin grasses (Dactylics glomerata, Festuca

arundinacea and Lolium perenne), with varying organic and inorganic

compositions were selected for their study. The lower ash content samples

produced more liquid yields and less char and gas yield as compare to the

samples having higher ash content. The removal of alkali metals in washing

process reduced ash content and improved the organic liquid yield. A

36

catalytic effect on the thermal degradation of biomass during pyrolysis was

happened by char and alkali metals. The effect of ash on pyrolysis process

was more dominant than effect of lignin. The aged oils differed in quality

characteristics compared to the fresh oil, due to reactions occurring as the oil

aged. The study found that stable pyrolysis oil can be produced if an energy

crop is used. However this would affect the yield by lowering the organic

yield due to the high level of ash/metal content and producing a high level of

reaction water, resulting in a reduction of the heating value of the oil as well

as risking phase separation.

Sut Ucar and Ahmet (2008) investigated the product distribution

and characterization of the pyrolysis products from the pyrolysis of rapeseed

oil cake in a fixed bed reactor at 400, 450, 500, 700 and 900°C. The yield of

bio-oil was increased with increasing the temperature from 400 to 500°C. By

increasing the temperature from 500 to 700 and 900°C, the bio-oil yield

decreased slightly. Empirical formula of bio-oil from the pyrolysis of

rapeseed oil cake was arrived at CH1.59 O0.16 N0.116S0.003 for 500°C and the

gross calorific value of the bio oil were calculated as 32.85, 33.05 and

33.17 MJ/kg at the pyrolysis temperature of 400, 450 and 500°C. Bio-char

yield decreased when the pyrolysis temperature was increased. By increasing

the temperature from 400 to 900°C, the amount of fixed carbon in bio-char

increased from 57.08 to 73.05 wt% and the ash contents of bio-chars was

increased slightly. The heating values of bio-chars were found to be similar

(24 MJ/kg) at all pyrolysis temperatures. The gas products mainly consisted

of CO2, CO, CH4 and H2S at 500°C. The CO2 was found to be highest amount

in the gas products.

Raveendran et al (1996) conducted the studies for finding the

heating value of various types of biomass components and their pyrolysis

products such as char, liquids and gases. Heating values of chars were

37

comparable with those of lignite and coke; heating values of liquids were

comparable with those of oxygenated fuels such as methanol and ethanol,

which were much lower than those of petroleum fuels. Heating values of

gases were comparable with those of producer gas or coal gas and are much

lower than that of natural gas. The study concluded that the heating values of

products were functions of the initial composition of biomass; the heating

values of the chars are the highest, followed by those of the liquids, and the

heating values of the gases were the lowest. The higher the lignin content of

the biomass, the higher should be the fraction of energy held in its char

product. Correspondingly, the higher the cellulose content of the biomass, the

higher should be the energy content of its liquid product, and the higher the

hemi-cellulose content of the biomass, the higher should be the fraction of

energy held in its gas fraction. The heating values of liquids varied narrowly

from 22 to 25 MJ /kg, those of the gases are the lowest and varied from 5 to

16 MJ/ kg, and of the char varied from 24-44 MJ/kg. The effect of De-ashing

was also explored by present investigators. De-ashing increased the heating

values of the biomass pyrolysis liquids and decreased the heating values of

the gas.

Pyrolysis of wood feedstock’s and rice husk were experimentally

analyzed in a fluidized bed reactor with inert atmosphere by Zhongyang Luo

et al (2004). The results from their studies are the optimum temperature of

about 773 K to produce more high-quality bio-oil, high temperature would

lead to a high proportion of CO and CH4, while a low proportion of CO2, at a

higher reaction temperature, a higher heating-value gas could be obtained in

pyrolysis of biomass for gas. Particle size had no obvious effect on products

distribution when less than 1 mm. Adjusting the reactor height and feed rate

could alter the residence time of particle and volatile. Biomass species played

a significant role in its pyrolysis. Wood feedstock’s produced bio-oil with

high yield, heating value and low water content compared to rice husk

38

pyrolysis. The value of bio oil density was located in the range of 1130 –1200

kg/m3. The kinetic viscosity of bio-oil varied largely with biomass species.

Higher ash content in biomass was disadvantageous to obtain high quality

bio-oil production.

The detailed chemical compositional analysis of pyrolysis oil

obtained from cashew nut shell in a fixed bed reactor under vacuum condition

was done by Piyali Das et al (2004). The study reviled that unlike other bio

oils, the cashew nut shell oils have fairly stable and completely miscible in

diesel , the oil have low corrosivity towards copper and stainless steel. The

high C/H ratio in the oil contributes to the high heating value of 40 MJ/kg,

which is equivalent to that of fuel oil. The pyrolysis oil obtained having

higher cetane number, this could qualify the cashew nut shell oils as a

compression ignition fuels with probably slight modification in the injection

system and ignition timing over conventional diesel engine.

Pyrolysis of three agricultural residues (corncob, straw and

oreganum stalks) at 500°C in a fluidized bed reactor was experimentally

investigated by Jale Yanik et al (2007). The maximum oil yield from

oreganum stalks, corncob and straw were 45%, 47% and 41% respectively,

the maximum gas yield were 32%, 30% and 39% respectively. The oil and

gas yield from these biomass species ranged from 41 to 47% and 30 to 39%

respectively. The higher ash content in the straw produced low liquid and

high gas yield. The composition of oil varied with individual agricultural

residues. The heating value of the char was between 4600 and 6000 kcal/ kg.

The GC–MS and HPLC analyses showed that the organic contents in the oils

were carboxylic acids, mainly acetic acid, nonaromatic ketones, mainly

acetone, methanol and phenols. The authors concluded that the oil could

constitute one important source of specialty chemicals.

39

Ayhan Demirbas (2007b) examined the properties of liquid product

obtained from the pyrolysis of different biomass with the effect of

temperature and chemical composition of the biomass. The yields of liquid

products from pyrolysis increased with the increase of lignin contents of the

biomass samples. The kinematic viscosity of pyrolysis oil varied from 11 cSt

to 115 mm2/s (measured at 313 K) depending on the nature of the feedstock

and temperature of pyrolysis process. The density of the pyrolysis oil was

about 1200 kg/m3 which was higher than that of fuel oil (860 kg/m3) and

significantly higher than that of the original biomass.

Rapid Pyrolysis of corn stalks in a batch wise laboratory captive

reactor was conducted by Zabaniotou and Ioannidou (2007), the process was

studied by varying the temperature between 470 and 710°C with an average

heating rate of 60°C/min. The liquid, char and gas yield were found to be

10%, 26% and 64% respectively at the pyrolysis temperature of 710°C .The

maximum liquid yield of 28 wt% was attained at the pyrolysis temperature of

550°C. The heating value of char increased with the increase of temperature

and it increased from 17.09 to 19.64 MJ/kg when the temperature was

increased from 300 to 560°C. In gas the CO, H2 and CH4 were found to be

higher at higher temperature and the CO2 was low. The composition of the

gas at 660°C was 65.1 v/v% of carbon monoxide, 28.34 v/v% of hydrogen

and 13.77 v/v% of methane. The lower calorific value of the gas was between

14 and 16 MJ/kg.

Sensoz et al (2000) studied the effect of particle size on the

pyrolysis yield and it composition of rapeseed in a heinze reactor under static

atmosphere. The temperature and heating rate were maintained at 500°C and

40°C/min. The yield of pyrolysis oil was maximum (46.1%) for the particle of

0.8 –1.80 mm. The smallest particles (0.224 mm) produced an oil yield of

42.9% and larger particle (> 1.80 mm) produced 44.6%. The char and gas

40

yield were between 20.44 to 22.81% and 18–19% respectively. The FT-IR

analysis showed that the pyrolysis oil was highly dominant with oxygenated

species and oil contained aromatic rings, carbonyl, and methyl and phenol

groups. The H/C ratios obtained from the pyrolysis oil showed that the

fractions were quite similar to transport fuels. The energy content of pyrolysis

oil was 38.4 MJ/kg which was slightly lower than that of gasoline (47 MJ/kg),

diesel fuel (43 MJ/kg) or petroleum (42 MJ/kg), but higher than coal

(32-37 MJ/kg).

Flash pyrolysis experiments of rapeseed were performed in a free

fall reactor at atmospheric pressure under nitrogen atmosphere by Ozlem

Onay and Mete Kochar (2006). The temperature of pyrolysis, particle size and

sweep gas flow rate were varied in the ranges of 400 to 700°C, 0.224 to 1.8

mm and 50–400 cm3 /min, respectively. The maximum bio-oil yield of 75%

was obtained at a final pyrolysis temperature of 600°C, particle size range of

0.224 to 0.6 mm and sweep gas flow rate of 100 cm3/min respectively. The

increase of particle size from less than 0.224 to greater than 1.8 mm decreased

the pyrolysis yield. Sweep gas flow rate showed that the flow rates greater

than 50 cm3/min had no significant effect on the liquid product yields. The

calorific value of the produced oil and char were in the range of 36-38 MJ/kg

and 31-34 MJ/kg respectively with different pyrolysis temperature. The IR

spectrum of the oil showed that oil contains phenols and alcohols, alkanes,

ketones or aldehydes, alkenes and aromatics. The physical properties of the

bio-oil was determined according to ASTM standards and compared with that

of diesel fuel, the viscosity, density, flash point and higher heating value of

the oil were 36 cSt, 984 kg/m3, 75°C and 37.9 MJ/kg respectively. The values

of diesel were 2.1 cSt, 838 kg/m3, 54°C and 45.5 MJ/kg. Higher flash point in

the pyrolysis oil indicates that it can be stored safely at room temperature.

41

Tsai (2007) prepared a series of pyrolysis oil and char from

agricultural residue by product rice husk in a lab-scale fast pyrolysis system.

The pyrolysis yield and its compositions were analyzed with different

operating parameters: temperature, heating rate, nitrogen flow rate, and

condensation temperature and particle size. The optimal oil yield of 41 wt%

was achieved at the pyrolysis temperature of 500°C, heating rate of

200°C/min, holding time of 2 min and condensation temperature of 10°C and

particle size of 0.50 mm. The maximum calorific value of the pyrolysis oils

was 1820 Kcal/kg, a considerable amount of oxygen content with a higher

H/C molar ratio (6.1) than the rice husk (1.5) )and conventional fuels (2.0),

resulting in the low energy content of the pyrolysis oil. The pH values of the

pyrolysis oil were in the range of 2.3-2.7. The calorific value of the obtained

char was 5089 kcal/kg. The FT-IR spectrum of the pyrolysis oil showed that

the presence of ketones, phenols, carboxylic acids or aldehydes, alkenes,

aromatics, and alkane groups in the pyrolysis oil. GC/MS analysis of the oil

indicted the presence of a very complex mixture of organic compounds and a

lot of aromatics and oxygenated compounds such as carboxylic acids,

phenols, ketones etc in the pyrolysis oil.

Fast pyrolysis of safflower seed (Carthamus tinctorius L.) was

investigated by Ozlem Onay (2007) in a well-swept fixed bed reactor with the

aim of finding the product distribution and its chemical compositions to

identify optimum process conditions for maximizing the bio-oil yield. The

temperature was raised from 100, 300 or 800°C to the final temperature of

400, 500, 550, 600 or 700°C and held at that temperature for 10 min. the

second group of experiments was carried out for four different nitrogen flow

rates of 50, 100, 200 or 400 cm3/min. The maximum oil yield of 54% was

obtained at the final pyrolysis temperature of 600°C, sweeping gas flow rate

of 100 cm3/min and heating rate of 300°C/min. The IR spectrum of the fast

pyrolysis oil indicated that the bio oil consisted of mainly alkanes, alkenes,

42

aromatic rings and phenols. The density, viscosity and flash point were 1020

kg/m3,33 cSt (at 50°C) and 76°C respectively. The higher heating value of the

obtained bio oil was 40.9 MJ/kg. The elements present were carbon 76.8%,

hydrogen 12.1%, nitrogen 2.6% and oxygen 8.5%. Both the hydrogen and

oxygen content of char decreased with increase in temperature, indicating an

increase in the carbonaceous nature of the char and concluded that the char

obtained in safflower seed could be used for the production of activated

carbon and also as a solid fuel in boilers. In addition, it can be used further for

the gasification process to obtain hydrogen rich gas by thermal cracking.

Esin Apaydin-Varol et al (2007) investigated the effects of

pyrolysis temperature on the product yields and composition of pistachio shell

in a fixed bed reactor with slow pyrolysis process under the heating rate and

particle sizes of 7°C/min and 1.82 mm. The liquid product obtained under

optimum temperature and solid products obtained at all temperatures were

characterized. The char, gas and oil yields were 23 wt%, 30 wt% and 19 wt%

respectively at 700°C. The maximum oil yield of 20.5 wt% was attained at

550°C. The calorific value of the bio oil obtained at 550°C was 30 MJ/kg.

The FT-IR spectra representing functional groups, of the bio-oil at 550°C

represented the presence of phenols and alcohols, aliphatic, alkanes, ketones

or aldehydes and alkenes in the bio oil. The chars obtained at higher

temperature having higher H/C and O/C ratios than that for raw material and

chars produced from low temperature pyrolysis. Average calorific value of

the chars was 30 MJ/kg.

Fast pyrolysis of four kinds of biomass (legume straw, tobacco

stalk, pine sawdust and apricot stone) was conducted in a free fall reactor by

Ligang Wei et al (2006).The effects of pyrolysis conditions and biomass

feedstock on hydrogen rich gas evolution were investigated with a particle

size of 0.30-0.45 mm. The system was controlled at atmospheric pressure by a

43

vacuum pump with N2 (30 ml/min) as a balance gas. The gaseous product was

collected in a gasbag and offline analyzed by gas chromatograph (GC-920)

(column: GDX104 and 5A molecular sieve; detector: TCD). The

concentrations of H2, CO, CO2, N2, CH4 and hydrocarbons were determined.

The H2, CO and CH4 contents were increased with the increase of the reactor

temperature, while CO2 content exhibited the opposite trend. The efficient gas

(H2+CO) content in dry gas increased with the increase of the reactor

temperature, and reached 72.4 mol% for legume straw and 71.8 mol% for

pine sawdust at 800°C. The gas yields increased with the steam-feeding rate,

while the tar and char yields slightly decreased. The CO and CH4 contents in

the dry gas decreased with the addition of steam, whereas CO2 and H2

contents increased. The addition of steam favors H2 formation through the

water–gas shift reaction in vapor phase. H2 content of the gas produced from

legume straw reached 38.7 mol% at the steam feeding rate of 1.6 ml/min,

while that from pine sawdust is 31.3 mol%. The effects of particle size on

products distribution from pyrolysis of pine sawdust and apricot stone were

investigated at the reactor temperature of 800°C. The char yield from

pyrolysis of pine sawdust decreased from 10.3 wt% to 3.8 wt% with the

decrease of particle size from 0.90–1.20 mm to 0.20–0.30 mm, while that

from pyrolysis of apricot stone it decreased from 30.5 wt% to 14.6 wt%. No

remarkable differences in the char yields from biomass pyrolysis were found

for particle sizes smaller than 0.20 mm. In the case of particle size of above

0.20 mm, H2 and CO contents in the dry gas increased with the decrease of

biomass particle size, while CO2 content decreased.

Joel Blin et al (2007) studied the biodegradability of biomass

pyrolysis oils derived from different biomass both in fast and slow pyrolysis

process and compared the same with the biodegradability of petroleum and

current alternative fuels. The results demonstrated that all fast pyrolysis oils

assessed were biodegradable with similar shaped curves with 41–50%

44

biodegradation after 28 days. The slow pyrolysis sample achieved 62%

biodegradation after 28 days. Higher the biodegradation in slow pyrolysis

process was observed by the production of light functionalized compounds

and more stable heavy organic compounds due to secondary reactions. Lower

heating rate and gas flow encouraged the higher residence time and secondary

cracking in slow process. The opposite trends were observed in fast pyrolysis

process. Heavy fuel oils have low biodegradation of 11% in 28 day laboratory

studies, due to its higher proportion of high molecular weight aromatics.

Diesel and gasoline, which are light crude oil derived fuels, are more

biodegradable and achieve up to 24–36% and 28% respectively. Vegetables

oils were rapidly degraded to reach biodegradation of between 76% and 90%.

The biodegradability value of fast pyrolysis oils show that in case of

accidental spillages this fuel would be biodegraded better than all fossil fuels,

but not as well as vegetables oils.

Zabaniotou et al (2008) comparatively studied the gaseous products

obtained from rapeseed residues by the fast pyrolysis at high temperature in a

captive sample reactor and fixed bed air gasification in a batch, laboratory

scale, and fixed bed reactor. The temperature range and heating rates were

480–790°C and 48°C/s respectively. The study found that within the

components present with the pyrolysis gas the carbon monoxide reached

44.1% (v/v) at 620°C, while hydrogen reached 45.8% (v/v) at 790°C. Carbon

dioxide reached 11% (v/v), while methane gave a percentage of 13.62% (v/v).

In gasification under steady oxidizing conditions, CO production reached a

maximum at the highest gasification temperature, of 24.48% (v/v), H2

concentration increased with the increase of temperature and reached a

maximum yield of 28.77% (v/v) at 900°C, while the content of CH4 showed

an almost stable production trend of 8% (v/v). The study concluded that the

gas obtained from gasification process was a low heating value gas (lower

45

calorific value between 8 to 10 MJ/m3) and from the fast pyrolysis was a

medium heating value gas (lower calorific value between 14 to 14.5 MJ/m3).

Fagbemi et al (2001) evaluated the amounts of various pyrolysis

products (gases, water, tar and charcoal) from wood, coconut shell and straw

and suggested a kinetic equation for the thermal cracking of tar at

temperatures varying from 400 to 900°C. The particle size of the wood,

coconut shell and straw were 4 mm, 10 cm and 10 cm respectively. The

residence time of the volatile products in the cracking zone (packing) was

varied between 0.3s to a few seconds by varying the depth of the packing and

the flow rate of the gas-circulation pump. The sharp increase of gas volume

was observed in above 500°C. Straw produced more gas yield than the wood

and coconut shells. The low thickness of the wall of the straw wisp, compared

with the others bio-materials, results in a higher heat-transfer, and hence a

higher rate of pyrolysis, which was favorable to gas and tar production. The

concentrations of CH4 and C2Hx reached a maximum value at about 750°C.

A regular decrease in CO2 concentration with temperature occurs with a

simultaneous increase in CO and H2 concentration. For straw the CO

increased from 35.0 to 53.3% volume, CO2 decreased from 40.7 to 53.3%

volume, H2 increased from 7.4 to 24.6% volume, CH4 increased from 11.8 to

12.1 % volume and C2Hx increased from 5.1 to 5.5 % volume, when

temperature increased from 500 to 900°C. The yield in solid residue regularly

decreased with increasing temperature. The quantity of tar reached a

maximum value at about 500°C, and then dropped with increasing

temperature. The average heating value of the obtained solid fractions of

wood, coconut shell and straw were 34, 33 and 25 MJ/kg at different

temperature ranges.

Zheng Jilu et al (2007) investigated the bio-oil obtained from the

fast pyrolysis of cotton stalk at temperatures between 480°C and 530°C in a

46

fluidized bed with two screw feeders to prevent the jamming of the feeding

system. The highest liquid yield of 56% was obtained at the temperature

range of 480–530°C. The energy density of the bio-oil was much higher than

that of the cotton stalks, so it is convenient for transportation and utilization.

The S, N and other pollutants concentrations in the bio oil was very low. The

energy performance of the pyrolysis process showed that the energy cascade

was about 42% for bio-oil and about 69% for all other products. The thermal

energy contained in the charcoal was more than the energy consumed by

electric heating. The study explored that the bio-oil obtained can be directly

used as a fuel oil for combustion in a boiler or a furnace without any

upgrading. Alternatively, the fuel can be refined to be used by vehicles.

Qing Cao et al (2004) conducted the slow pyrolysis of agricultural

waste corn cob in a tube- typed stainless steel reactor under N2 atmosphere at

a temperature below 600°C and heating rate of 30 k/min for the analysis of

the compositions of the gases and liquid obtained at different temperatures.

The obtained liquid products were approximately 34–40.96 wt%, the gas

products were 27–40.96 wt% and the solid products were 23.6–31.6 wt%. The

study found that above 600°C the changes of theses products yields were less.

The gas products were analyzed by gas chromatography (GC) as CO2, CO,

H2, CH4, C2H4, C3H6, C3H8, etc. The yields of H2, CH4, C2H4, C3H6 and C3H8

gradually increased with the increase of temperature. At 350–400°C the gases

primarily consisted of carbon dioxide and carbon monoxide with account of

nearly 82–98% (v/v) and at 450–500°C the amount of hydrogen and carbon

monoxide was about 50% (v/v). The liquid products were identified by

GC/MS as phenols, 2-furanmethanol, 2-cyclopentanedione, etc. The Fourier

transform infra-red spectrophotometer (FT-IR) analysis of the liquid product

showed a strong–OH group absorption peak of the liquid products.

Differential Thermo Gravimetric (DTG) analysis showed that thermal

decomposition process of the biomass involved with two steps.

47

Vladimir Strezov and Tim (2009) investigated the pyrolysis of

paper sludge, which was generated as a waste product in a paper and pulp

manufacturing industry. The pyrolysis was done with the argon atmosphere.

The heating rate and maximum temperature were 10°C/min and 700°C

respectively. The study found that the release of CO2 and CO reached the

maximum yield at 340°C, the release of hydrocarbons occurred above 300°C

and reached maximum yield at 470°C (C2H4 and C2H6) and 530°C in case of

CH4. The hydrogen yield was observed only at temperature above 470°C. The

collected bio-oil was composed primarily of linoleic acid, also known as

9,12-octadecadienoic acid and a smaller fraction of 2,4-decadienal and oleic

acid. The organic acids were the most dominant liquid species in the bio-oil

fraction. The pH value of the bio oils was ranging between 2 and 3.7 with

acidic in nature. The yield of charcoal was 36% of the total dry paper sludge

weight at 500°C and 10°C/min. The FT-IR spectra of the char indicated that

the char primarily comprised of organic acids with the major contribution

being linoleic acid, 2,4-decadienal acid and oleic acid, the char also having

silica and iron oxide. The measured gross calorific value of the charcoal was

13.3 MJ/kg. The study concluded that, the energy potential of the produced

biogas compounds could be utilized to recover the heat required for pyrolysis,

hence reducing the requirement for external heat supply.

Huang et al (2008) experimentally studied the microwave–induced

pyrolysis process of rice straw for the total recovery of resources and energy

from it. The study found that the particle size of the feedstock and micro

power were the most important parameters which influencing the

performance of microwave –induced pyrolysis process. The H2, CO2, CO,

CH4 were the major compositions in the gaseous product with the

concentrations of 55, 17, 13 and 10% volume respectively. The liquid product

was analyzed by Perkin–Elmer Turbo Mass Gold Gas Chromatography/

Mass Spectrometry (GC/MS), the Alkanes, polars, and low-ringed polycyclic

48

aromatic hydrocarbons were three primary kinds of compounds in the liquid

product. The authors concluded that the feasibility and practicability of this

technology still need to be further researched.

Jianguo Liu et al (2009) studied the pyrolysis characteristics of tank

bottom oil sludge in a fixed bed quartz reactor. The change of mass loss and

pyrolysis gas compositions were analyzed. The first stage of mass decrease

was found at 393 k with 18-20 wt% mass loss. Around 18 wt% of mass loss

was observed between 393 and 805 K due to volatilization and decomposition

of organic matters in the oil sludge. A third stage of mass decrease was

observed between 805 and 1023 K with a relatively small weight loss (around

7.5 wt% of the original weight). The CHs (Hydrocarbons), CO2, H2 and CO

volume fractions were 42.1, 41.5, 14 and 2.0% at 850 K and 28.5, 47.4, 15.4

and 8.6% at 1100 K, respectively excluding the N2 emission. The CO and

CO2 were released at high temperature and reached peak value at the

temperature of 981 and 950 K respectively. The yield of CHs was significant

in the range of 600–723 K. Higher heating rate caused the peak intensity of

CHs evolution. The temperatures corresponding to the maximum evolution

rate of CHs are 678, 691,705 and 705K at different heating rates of 10, 20, 40

and 50 K/min, respectively.

Paul and Patrick (1994) studied the effect of metal salt and its

concentrations on the pyrolysis of cellulose biomass in a thermo gravimetric

analyzer and static batch reactor. The Reagent Grade, NaC1, Na2CO3, NaOH,

NiCI2, ZnC12, FeSO4 and CuSO4 were used as a metal salts. The sample was

heated to 720°C at 20°C/min heating rate using nitrogen as the purge gas in a

thermo gravimetric analyzer. The thermo grams show that there is an initial

loss of moisture from the samples, followed by the thermal decomposition of

the cellulose which starts at approximately 300°C and is essentially complete

by 450°C. The percentage mass of residual char was also dependent on the

49

type of added salt, with all the added salts resulting in a significant increase in

the residual char. As the metal salt concentration was increased there was a

marked decrease in the temperature where the onset of the weight loss and

also the temperature where the main weight loss occurred. The percentage

mass of residual char increased with increasing added salt concentration. The

static batch reactor results showed that the added metal salts increased the

concentration of H2 in all cases, however, CuSO4, NaCI and FeSO4 produced

lower concentrations of hydrocarbons, CO and CO, compared to untreated

cellulose. The influence of added metal salt was to decrease the percentage

mass of derived liquid and increase the percentage mass of char.

Aho et al (2008) studied the effect of zeolite structures in catalytic

pyrolysis of pine wood in a fluidized bed reactor. The study focused with the

influence of Beta, Y, ZSM-5 and mordenite on the yields and the chemical

composition of the bio-oil. The quartz sand was used as a reference material

in the non-catalytic pyrolysis experiments. The study found that, the gas yield

was not significantly influenced by the different structures of the acidic

zeolite catalysts used as the bed material. The bio-oil obtained was diluted in

methanol and analyzed by GC–MS. Ketones and phenols were the dominating

groups of compounds. The three most dominant compounds in the bio oil

were: acetic acid, 1-hydroxy-2-propanone, and 2-methoxy-4-methyl-phenol.

The formation of ketones was higher over ZSM-5 and the amount of acids

and alcohols lower than over the other bed materials tested. Mordenite and

quartz sand produced smaller quantities of polyaromatic hydrocarbons than

the other materials tested.

Keri et al (2008) reviewed the various bio chemical and thermo-

chemical energy conversion methods to convert the livestock waste to bio

energy generation opportunities. Slow pyrolysis converts animal wastes into

char, providing farmers with potential economic benefits due to energy

50

production and carbon credits generated from carbon sequestration. Char can

be used as a feedstock (‘‘green coal”) for existing coal combustion and

gasification plants. Char can also be applied to soil as a soil amendment to

improve fertility. Char produced from animal waste can become a source of

activated carbon when compared to commercial granular activated carbon, the

poultry and turkey-based chars had greater copper ion adsorption showing

promise in potential metal ion removal applications. The biochemical process

of anaerobic digestion is an established technology capable of biogas

production; however, other biological processes like bio-hydrogen and bio-

methanol production are still in early research stages and show promise to

become a sustainable, renewable energy resource. Within the thermo-

chemical conversion processes, pyrolysis, direct liquefaction, and

gasification, both dry and wet, also have the capabilities of converting

livestock waste into value-added products like gaseous fuels and combustible

oils. Integration of biological and thermal-based conversion technologies by:

(1) recapturing the evolved CO2 to promote algal growth and (2) utilizing wet

gasification as the algal energy recovery component holds promise for a

highly efficient and resource sustainable waste-to-bio-energy scheme.

Lu Qiang et al (2008) studied the influence of catalyst on the

pyrolysis vapour property changes. The use of the SBA-15 and Al/SBA-15

catalysts altered the product distribution of the pyrolysis vapors. The study

found that, the yields of heavy phenols, heavy furans and many light

carbonyls decreased, while the yields of light phenols, light furans, acetic acid

and hydrocarbons increased with the addition of catalysts. The formation of

acetic acid with the catalytic cracking limits the usage of bio-oils as a liquid

fuel.

Adisak Pattiya et al (2007) conducted the fast pyrolysis

experiments on cassava rhizome and stalk for producing bio-oil, the

51

thermochemical characteristics and pyrolysis behavior of agricultural residues

from cassava plantation was determined, the optimum process conditions for

maximum bio-oil yield also determined. The GC/MS analysis showed that the

pyrolysis vapours mainly consist of phenolics, ketones, aldehydes and

alcohols. The 26 liquid-range compounds identified from the chromatogram

analysis some of the compounds are acetaldehyde, 2,3 Butanedione,

2-Furanmethanol, 2-Methoxyphenol and 2,6-Dimethoxy phenol. The highest

liqid yield was obtained at 500°C. The study also found that demineralization

of biomass prior to pyrolysis processing could be beneficial to the production

of pyrolysis liquid.

Deris et al (2006) studied the pyrolysis of oil palm trunk with the

increase of temperature from 200 to 600°C under the heating rate of

10°C/min.The highest percentage of oil produced was at 600°C. The liquid

and solid yield increased with the increase of particle size from 0.25 mm to

2.25 mm, but the gas yield decreased with the increase of particle size.

GC-MS analyses have shown that carboxylic acid, phenol, alcohol and

branched oxygenated hydrocarbon are the main compounds of bio-oil. Based

on observation, there was significant amount of water contained in the liquid

products.

Hasfi and Benbouzid (2007) experimentally studied the slow and

fast pyrolysis of eucalyptus globules wood. The TG analysis in air and in

nitrogen atmosphere was done. The GC/MS analysis was used to identify the

presence of valuable chemicals. The evolution of organic degradation was

observed between 165 and 380°C. The study found that the carboxylic acids,

resin acids, ketones, phenols, furans, alkenes and polycyclic aromatic

hydrocarbons are present in the pyrolysis products.

52

2.4 PYROLYSIS GENERAL

Murugan et al (2008) experimentally studied the performance,

emission and combustion of distilled tyre pyrolysis oil-diesel fuel blends at

lower and higher concentrations in a four stroke single cylinder air cooled

diesel engine without any engine modification and compared the same with

diesel fuel. Before testing the crude tyre pyrolysis oil was modified with

moisture removal, desulphurization and vacuum distillation. The results from

the studies are, the engine is able to run up to 90% distilled tyre pyrolysis oil

and 10% diesel fuel, engine failed to run satisfactorily with 100% distilled

tyre pyrolysis oil. Brake thermal efficiency increased with increase in

percentage of distilled tyre pyrolysis oil blends but the increase was lesser

than the diesel fuel. The thermal efficiency of the engine with distilled tyre

pyrolysis oil was 1-2% lesser than the diesel fuel operated mode and NOx

was lowered by about 22% and 18% in distilled tyre pyrolysis oil 20% and

distilled tyre pyrolysis oil 90% respectively than that of diesel fuel operation.

HC emission was higher by about 7% and 11% for distilled tyre pyrolysis oil

20% and distilled tyre pyrolysis oil 90%, respectively at full load than that of

diesel fuel operation. Smoke emission was higher with tyre pyrolysis mode

compared to diesel fuel mode. Cylinder peak pressures was higher by about

2.8 bar for distilled tyre pyrolysis oil 90% and 3.2 bar lesser for distilled tyre

pyrolysis oil 20% than that of diesel fuel operation.

Jagtar Singha et al (2008) made a case study in Punjab, India for

the energy potential of the state from agricultural residues and made a model

for unit collection cost of agricultural biomass from the field. The result from

their study show that electricity consumption in the state has increased from

15.8 TWh in 1995–1996 to 32.12 TWh in 2005–2006 and the average annual

growth rate of electricity consumption was 14.98%. The total amount of

unused agricultural biomass in Punjab during 2000-2001 was about 13.73

53

Mt/year and the corresponding energy and power generation potential was

about 235.14 TJ and 900 MW per annum respectively in the state. The

availability of unused agricultural biomass for energy was determined by

subtracting the current utilization of biomass from the total production of each

crop residue. The unit collection cost in the field decreased with the increase

in spatial density of biomass, while it marginally increased with increase in

carrying capacity of transport unit. The average unit collection cost in the

field for spatial biomass density of 500 tonns /km2 has been found to be Rs

180 /ton.

Ayhan Demirbas (2008) studied bio-fuel sources, bio-fuel policy,

bio-fuel economy and global biofuel projections. The information received

from their studies indicate that, bio-fuels include bio-ethanol, bio-methanol,

vegetable oils, bio-diesel, biogas, bio-synthetic gas (bio-syngas), bio-oil, bio-

char, Fischer-Tropsch liquids and bio-hydrogen. Bio-fuels are easily available

from common biomass sources, they are representing a carbon dioxide-cycle

in combustion, bio fuels have a considerable environmentally friendly

potential. The usage of bio fuels giving many benefits to the environment,

economy and consumers and they are biodegradable and contribute to

sustainability. The HHV of rapeseed cake oil was found as 36.4 MJ/ kg. The

authors concluded that, this bio-oil can be used in engines and turbines in

practice. The predictions say that the modernized biomass energy contribution

by 2050 will be about one half of total energy demand in developing countries

during that period. EU has set the goal of obtaining 5.75% of their

transportation fuel needs from bio-fuels by 2010 in all member states. The

recent commitment by the USA government indicated that to increase bio-

energy to three-fold within 10 years. The Kyoto Protocol cannot be achieved

without establishing a large role for biofuel in the global energy economy by

2050.

54

Ayhan Demirbas (2007a) studied global bio-fuel scenarios, the

various methods of producing the bio-fuels like bioethanol, biomethanol,

biodiesel and bio-oil from biomass. The conclusions from their studies are the

Biomass appears to be an attractive feedstock for three main reasons. First, a

renewable resource could be sustainably developed in the future. Second, it

appears to have formidably positive environmental properties resulting in no

net releases of carbon dioxide (CO2) and very low sulfur content. The usage

of bio-fuels in the transportation sector is increasing continuously due to its

easy availability, represent a CO2 cycle in it combustion, a considerable

environmentally friendly potential and biodegradability of its nature

contributes to sustainability. Bio-fuels include energy security reasons,

environmental concerns, foreign exchange savings, and socioeconomic issues

related to the rural sector.

Phan et al (2008) studied the characterization of slow pyrolysis

products of segregated wastes from wood, cardboard and textile residues for

energy production in a small packed bed reactor with a heating rate and

nitrogen flow rate of 10°C/min and 2 l/min respectively. The wood sample of

20 mm cubes, cardboard sample thickness of about 3–5 mm was cut into 20

mm squares; textile sample with an average size of 30 mm to 50 mm was

used. The study explored that, the produced char contained about 38–55% of

the energy content in the raw material. The pyrolysis liquids had a gross

calorific value of about 10–12 MJ/kg, representing about 20–30% of the

energy content in the raw material. The liquids consisted mainly of water and

oxygenated compounds such as furans, derivative carboxylic acids and

anhydrous sugars. Over two thirds of the gases produced were CO and CO2

with increased proportions of CH4 and H2 at high temperatures above 500°C.

The GCV of the gases from waste wood, cardboard and textile residues was

around 12.6, 13.3 and 16.0 MJ/Nm3, respectively. The study also concluded

that, the pyrolysis temperature should be below 500°C when pyrolysis is

55

applied to produce the two products (solid and liquid) with a maximum

energy yield.

Abdurrahman et al (2008) experimentally studied the flash

pyrolysis of asphaltite in a fixed bed reactor. The effects of pyrolysis

temperature and particle size were investigated with a heating rate of 40°C/

min under nitrogen atmosphere. The temperature varied from 400 to 800°C.

An optimum temperature for the maximum liquid yield was found to be at

550°C. The composition of aliphatic, aromatic, and polar fractions and solid

residue were characterized by FTIR. The conversion and oil yield increased

rapidly between 400 and 550°C, and then slightly decreased at higher

temperature. The increase in temperature from 550 to 800°C had negligible

effect on oil yield. Gas products increased with the temperature while solid

residue yield decreased. The study found that oil obtained from the asphaltite

is mainly of aliphatic character according to FTIR spectrum.

The literature is also available with high capacity disordered

carbons from coconut shells as anode materials for lithium batteries by Yun

Ju Hwang et al(2008), activated carbons from the coconut shells under the

physical methods by Afrane et al (2008) and Gratuito et al (2008), the

wastewater treatment by the low cost activated carbons derived from coconut

shells and coconut shell fibers by Dinesh Mohan et al (2008), a highly

effective adsorbent material from the coconut shell combined with aquatic

waste for the removal of heavy metal from industrial wastewater by Amudaa

et al (2007)and micro porous activated carbon from raw coconut shell by

Wel su et al (2006).

Umamaheswaran et al investigated that higher silica, Ca, Mg, K

and P content in the groundnut shell ash leads its utilization for soil

amendment. Susana Rodriguez Couto et al (2006) experimentally proved that

extra cellular liquid from groundnut shell cultures is used to decolorize the

56

dye Acid Black 48. Purified groundnut shells are used to remove the heavy

metal ions namely Cu(II), Ni(II) and Zn(II) from their aqueous solutions by

adsorption Shukla et al (2005). The kinetics and mechanism of methylene

blue adsorption from groundnut shell is studied by Nagarethinam Kannan et

al (2001). Taiwo et al (2001) studied the characteristics of soap produced by

groundnut shell ash and concluded that soaps from groundnut shell ash having

more solubility, consistency, cleansing and leathering. Minimum fludization

velocities of groundnut shell and sand mixture is studied by Rao et al (2001).

2.5 SUMMARY

The literature revealed that the pyrolysis behavior of biomass, its

products and characteristics mainly depends upon the following parameters

Pyrolysis temperature

Heating rate

Particle size

Composition of the biomass

Pyrolysis process condition (Inert or static)

Residence time

Feeding rate ( initial amount of the sample)

Inert gas flow rate

The quantity of final product yield and its composition mainly

depend upon the temperature of the pyrolysis process. The temperature

between 350°C and 550°C is the most rewarding range because, in this

temperature range, the liquid fraction yield reaching its maximum level. Some

resistances to mass or heat transfer inside the particles of biomass at lower

heating rates reduce the liquid yield and increasing the heating rate breaks the

heat and mass transfer limitation in the pyrolysis and increases the oil yield

57

and decreases the char formation. The effect of particle size on the pyrolysis

process varies with different agricultural residue; it mainly depends upon

composition of the agricultural residues and its density. Lower residence time

leads to higher char yield and lower oil yield because of incompleteness of

pyrolysis, the higher the residence time leads to more gas yield and lesser oil

yield because of the thermal degradation of the oil. The sweeping gas in the

pyrolyser process increases the oil yield due to the removal of the products

from the hot zone to minimize secondary reactions such a thermal cracking, re

polymerization, and re condensation of the char residue. Higher ash content in

the biomass influence the catalytic action on secondary cracking of volatiles

and decreases high-molecular weight volatiles collected in the liquids and

increases the gas composition.

Ozlem Onay and Mete Kochar (2006) studied the influence of the

final pyrolysis temperature, particle size range and sweep gas velocity on

pyrolysis products yield. Ayhan Demirbas (2004) and (Rolando Zanzi 2002)

experimentally investigated the effect of biomass species, chemical and

structural composition of biomass, particle size, temperature, heating rate,

atmosphere, pressure and reactor configuration on pyrolysis product yields.

Esin Apaydin-Varol (2007) studied the influence of pyrolysis atmosphere,

final temperature, particle size, heating rate, reactor type and initial amount of

the sample on the products yield. Haykiri-Acman (2006) studied the influence

of the conditions applied during pyrolysis and the properties of the material

used on the product yields by different carbonaceous raw material.

Ozlem Onay (2006) proved that the proportion of gas, liquid, and

solid products depends very much on the pyrolysis technique used and on the

reaction parameters. Chen et al (2003) examined the effect of catalysts on the

pyrolysis process and concluded that the yields of products are also depends

up on the type of catalyst used. Sevgi Sensoz et al (2003) studied the

58

pyrolysis with different biomass samples and concluded that pyrolysis

parameters such as feedstock, pyrolysis temperature and pressure, vapour

residence time and heating rate have a strong effect on the yield and

composition of the resultant oil, gas and char, in addition, the type of biomass

also affects both biomass devolatilization and char conversion. Ersan Putun

(2008) concluded that pyrolysis conditions such as particle size, temperature,

heating rate, residence time, catalyst, different atmospheres and biomass type

strongly affect the yield and properties of products

The literature review may be summarized as follows:

The agricultural residues had the potential to give energy in

the future.

Pyrolysis process is the most efficient way of getting

improved products from the agricultural resides.

The pyrolysis product yields (liquids, solids and gas) could be

varied by adjusting the operating parameters.

Only few articles are available with pyrolysis of Indian

agricultural residues, optimization of product yields and

pyrolysis with static conditions.

Temperature, particle size, heating rate, residence time and

feeding rater are the important parameters which influences

the pyrolysis product yields.

The pyrolysis yield could be varied with individual biomass

based on its compositions.

The improved products liquid, solid and gas from pyrolysis of

biomass had higher energy and mass density compared to it

original solid form.

59

The liquids from pyrolysis had different valuable chemicals

and it is more suitable for the feedstock to refinery or

chemical industry.

The current research of the pyrolysis process is mainly

concerned with the compositions present with the liquid

products.

Adjusting the reactor height and feed rate could alter the

residence time of particle and volatile.

Low feeding rate increase the secondary cracking and

decrease the liquid yield and increase the gas yield.

The H.C ratios of the bio crude’s obtained were between those

of light and heavy petroleum products of currently utilized

transport fuels.

The biomass with more cellulose and hemicellulose content

will produce more hydrogen- rich gas than those characterized

by higher lignin content.

The higher the concentration of ash in the feedstock the lower

the yield of pyrolysis liquid.

A lower ash content sample produce more liquid yield and

less char and gas yield as compare to the samples having

higher ash content. The effect of ash on pyrolysis process was

more dominant than effect of lignin.

The bio-oil obtained from pyrolysis can be utilized as either

synthetic fuels or chemical feedstock and power generation

through pyrolysis as a potential route and deserve attention.

Heating values of chars are comparable with those of lignite

and coke; heating values of liquids are comparable with those

60

of oxygenated fuels such as methanol and ethanol, which are

much lower than those of petroleum fuels. Heating values of

gases are comparable with those of producer gas or coal gas

and are much lower than that of natural gas.

The slow pyrolysis sample achieved 62% biodegradation after

28 days. Heavy fuel oils have low biodegradation of 11%, in

28 day laboratory studies, Diesel and gasoline, which are light

crude oil derived fuels, are more biodegradable and achieve

up to 24–36% and 28% respectively. Vegetables oils were

rapidly degraded to reach biodegradation of between 76% and

90%.

The low thickness of the wall of the straw wisp, compared

with the other bio-materials, results in a higher heat-transfer,

and hence a higher rate of pyrolysis, which is favorable to gas

and tar production.

For the biomass with higher cellulose content, the pyrolysis

rate became faster. The biomass with higher lignin content

gives slower pyrolysis rate. The yield of liquid products from

pyrolysis increased with the increase of lignin contents of the

biomass samples

The predictions say that the modernized biomass energy

contribution by 2050 will be about one half of total energy

demand in developing countries during that period.

61

2.6 OBJECTIVES

To study the influence of process parameters on the pyrolysis behavior and its product yields (liquid, gas and solid) of coconut shell, groundnut shell, rice husk, corncob, sugarcane bagase and sawdust in a fixed bed and free fall reactor.

To find the decomposition of solid sample with the increase of temperature and heating rate by thermo gravimetric and differential thermo gravimetric analysis.

To identify the functional groups and chemical compounds present in the pyrolysis liquid and solid obtained from all samples in this study by FT-IR and GC/MS techniques respectively and compare the same with conventional petrol and diesel fuel.

2.7 SCOPE

The scopes of the present work include

i) Design and fabrication of a pyrolyser system with the screw feeder arrangements for the production of improved products like liquid, gas and solid from agricultural residues(coconut shell, groundnut shell, rice husk, corn cop, sugarcane bagase) and saw dust.

ii) Study the thermal degradation of the samples with the increase of temperature and heating rate by Thermo Gravimetric (TG) and Differential Thermo Gravimetric (DTG) curves.

iii) Study the influence of different operating parameters: temperature, particle size, heating rate, reactor length and batch feeding on the pyrolysis process and its products yield of samples in a fixed bed reactor.

62

iv) Optimize the operating parameters for maximizing the liquid

yield from the samples in a fixed bed reactor.

v) Study the effect of particle size on a pyrolysis yield in a free

fall reactor using screw feeder for continuous feeding.

vi) Investigate the influence of composition and properties of

samples on pyrolysis yields.

vii) Determine the functional groups present in the liquids and

solids obtained from optimum conditions for all the samples

by Fourier Transform–Infrared (FT-IR) spectroscopy and

compare the same with conventional diesel and petrol fuel.

viii) Identify chemical compounds present in the liquid obtained

from individual sample at optimum conditions by Gas

Chromatography- Mass Spectrometry and compare the same

with the chemical compounds present in the conventional

petrol and diesel fuel.