Final_Project_Report-_10BEM00886710bme0016

SYNTHESIS OF BIO-OIL FROM PROSOPIS JULIFLORA
USING FAST PYROLUSIS
A Thesis submitted in partial fulfillment of the
requirements for the degree
of
B.TECH MECHANICAL with SPECIALIZATION IN ENERGY
ENGINEERING
by
ARJUN DAVIS -10BEM0067
GEORGE KUTTUKARAN -10BME0017
NISHANT SINGH -10BEM0088
SCHOOL OF MECHANICAL AND BUILDING SCIENCES
VIT
UNIVERSITY
(Estd. U/s 3 of UGC Act 1956)
Vellore – 632014, Tamil Nadu, India
www. vit.ac.in
MAY, 2014
i

Dedication to
This thesis is dedicated to my parents for their unwavering support and patience during
my project semester.
ii

CERTFICATE
This is to certify that the thesis entitled “Synthesis of bio-oil from saw dust by fast
pyrolysis” is submitted by ARJUN DAVIS -10BEM0067
GEORGE KUTTUKARAN -10BME0017
NISHANT SINGH -10BEM0088
to the School of Mechanical and Building Sciences, VIT University, Vellore, for the
award of the degree in B.Tech Mechanical with Specialization in Energy Engineering is a
bona fide record of work carried out by him under my supervision. The contents of this
thesis, in full or in parts have not been submitted to any other Institute or University for
the award of any degree or diploma.
Guide Program Chair
Internal Examiner External Examiner

ACKNOWLEDGEMENT
I would like to thank Prof. G Vignesh for giving us this great opportunity to work on such
an innovative project. His extensive experience in the field of renewable energy has
taught us something new every day.
I would also like to thank Dr. Murugavel for guiding us through the chemistry related to
the pyrolysis reactions. His input has been vital for us to interpret the results at each stage.
I am also thankful to Dr. J Ranjitha for aiding us in sample preparation, testing and
spectroscopy analysis interpretation.
I am grateful to VIT University for giving me this opportunity and permitting me to work
at the CO2 Research and Green Technologies Center.
Without the help of the technicians in the CO2 Research and Green Technologies Center,
it would have been impossible for me to complete this project. I would like to thank
Saravanaraj along with all the other support staff for their patience and support.
Last but not the least, my parents, for always being there.
iv

ABSTRACT
The biomass pyrolysis of saw dust is performed in a pilot plant developed in CO2
Research and Green Technologies Center at VIT University. The plant was based on an
auger screw design which was heated using electrical heaters from the outside to prevent
combustion of feedstock. The plant was built on a large scale capacity with intended feed
rate of 10 kg /hr. This thesis covers the various trials performed on saw dust pyrolysis to
achieve bio-oil yield in different operating conditions.
Proximate analysis were deployed on the sawdust to determine its composition. Proximate
analysis results showed a moisture content of ~9 %. Drying trials were also performed on
the sample to determine the equilibrium moisture content in the sample which was around
14 %.
The plant was operated in two conditions where different heating methods were used to
pyrolyse the feedstock. The first trials were based on electrical heating only where the
operating conditions achieved were 350
o
C at a feed rate of 5 kg / hr. The auger was
operated at speeds of 15 RPM with condensing drum temperatures at 10
o
C. Rated feed
rate of 10 kg/hr could not be used due to the blockage that occurred at the feed hopper.
The saw dust did not receive any pre-treatment but was dried using an exhaust dryer to
reduce the moisture content. Direct feeding of saw dust in the trial runs showed high
smoke emission due to the hygroscopic nature of the material. The trials with only heaters
could not achieve the required pyrolysis temperature leading to low temperature pyrolysis.
The trials showed predominantly high char output and tar presence in the oil obtained.
From the empirical data collected in the heater trials various modifications were made to
the reactor. Glass wool was used to insulate the reactor to prevent the heat losses. To
achieve the high pyrolysis temperature a hot Nitrogen line was added to the inlet of the
auger. The nitrogen was supplied at ~700
o
C and 1.5 bar pressure. The nitrogen also was
useful for creating an inert atmosphere in the auger to reduce the high smoke emissions in
the initials trials. The nitrogen also prevented blockages in the reactor inlet which also
v

reduced the retention time. The trial showed promising results with lower tar formation
and higher oil output. Due to the distant location of the nitrogen plant there was a
significant drop in temperature observed at the reactor inlet. This accounts for the lower
quantity of bio-oil and the high water content in the oil.
The characterization of the sample is done to validate physical and chemical properties of
the bio-oil against literature. The auger type reactor is currently less researched than other
systems, and the results from this study suggest the design is well suited for fast pyrolysis
processing.
vi

CONTENTS
Chapter Title Page
no. no.
Chapter 1 Introduction 1
1.1 Background 2
1.2 Project Brief 3
1.3 Research Objectives 3
Chapter 2 Literature Review 4
2.1 Prosopis Juliflora 5
2.2 Pyrolysis Mechanism 7
2.2.1 Physical Process 9
2.2.2 Chemical Process 9
2.2.2.1 Cellulose 10
2.2.2.2 Hemicellulose 10
2.2.2.3 Lignin 11
2.2.3 Overall Process 11
2.3 Pyrolysis Model 12
2.4 Products 15
2.4.1 Char 16
2.4.2 Bio-oil 17
2.4.3 Syngas 19
2.5 Alternate Technologies 19
2.6 Processing Parameters of Pyrolysis 20
2.7 Reaction Kinetics 21
2.8 Thermo gravimetric Analysis 22
2.8.1 Constant Heating Rate TGA 23
2.8.1 Constant Reaction rate TGA 23
2.8.3 Dynamic Heating Rate TGA 23
vii

Chapter 3 Methodology 24
3.1 Introduction 25
3.2 Reagents 25
3.3 Equipment 25
3.4 Feedstock Characterization 26
3.4.1 Proximate Analysis 26
3.4.1.1 Moisture Content 26
3.4.1.2 Ash Content 26
3.4.2 Drying Characteristics 26
3.4.2.1 Aim 27
3.4.2.2 Theory 27
3.4.2.3 Experimental setup 29
3.4.3 Thermo gravimetric Analysis 30
3.5 Plant Experimental Setup 30
3.5.1 Design of Experiment 30
3.5.1.1 Variables of Electrical Heating Trials 31
3.5.1.2 Variables of Nitrogen Heating Trials 32
3.5.2 Auger Conveyer 32
3.5.3 Screw Motor 33
3.5.4 Condenser 35
3.5.5 Feed Material 36
3.5.6 Nitrogen Process Plant 36
3.5.7 Process Flow 40
3.5.8 Material flow 41
3.5.9 Energy balance 42
Chapter 4 Results and Discussion 44
4.1 Introduction 45
4.2 Feedstock Characterization 45
4.2.1 Introduction 45
viii

4.2.2 Composition Analysis 45
4.2.3 Drying Characteristics 46
4.2.4 Reaction Kinetic 49
4.2.4.1 TGA Analysis 50
4.3 Pilot Plant Trials 51
4.3.1 Trials with Electrical Heating 51
4.3.1.1 Experimental data 51
4.3.1.2 Plant process description 52
4.3.1.3 Feedstock Performance 52
4.3.1.4 Products Obtained 55
4.3.1.5 Discussion 55
4.3.1.6 Conclusion 58
4.3.2 Trials with electrical heating and N2 supply 59
4.3.2.1 Experimental data 59
4.3.2.2 Plant Process Description 60
4.3.2.3 Initial trials 60
4.3.2.4 Final trials 61
4.3.2.5 Feedstock performance 61
4.3.2.6 Products Obtained 64
4.4 Product Characterization 65
4.4.1 Solubility Test 65
4.4.2 Solid particles 67
4.4.3 GC/MS characterization of Bio-oil 69
Chapter 5 Conclusion and Future work 75
5.1 Conclusion 76
5.2 Recommendations for future work 77
References 79
ix

LIST OF TABLES
Table No Title Page
2.1 Energy properties of wood samples 5
2.2 Proximate analysis of dry wood from literature 9
3.1 Auger specifications 33
3.2 Motor specs 34
3.3 Worm reducer specs 34
3.4 Properties of various reagents 42
3.5 Energy requirements of equipment used 43
3.6 Energy balance calculation results 43
4.1 Proximate analysis of sawdust 45
4.2 Comparative ultimate analysis data 46
4.3 Drying experiment results 46
4.4 Experimental setup 52
4.5 Raw data of electrical heating trials 54
4.6 Raw data of electrical heating with nitrogen trials 63
4.7 Product distribution of final trials 64
4.8 Results of solubility test 66
4.9 Representation of GC-MS analysis of bio-oil from BO3 73
4.10 Representation of GC-MS analysis of bio-oil from BO1 74
x

LIST OF FIGURES
Figure No Title Page
2.1 Distribution of Prosopis juliflora in India 6
2.2 Product yields from some thermochemical 8
Conversion technologies
2.3 Conversion Technologies for Biomass 8
2.4 Structure of biomass 10
2.5 Decomposition of cellulose 12
2.6 Broido-Shafizadeh model conversion 12
2.7 Cellulose thermochemical degradation reaction 13
2.8 Mechanism of cellulose depolymerisation 14
2.9 Laevoglucosan unzipping mechanism 15
2.10 Char sample from a pyrolysis reaction 16
2.11 Bio-oil from a pyrolysis reaction 17
3.1 Drying Characteristics 29
3.2 Block Diagram of the auger reactor 31
3.3 Auger Reactor 33
3.4(a) Motor Speed control unit 34
3.4(b) DC Motor 34
3.4(c) Worm reducer unit 35
3.5 Suction Unit 35
3.6 Chilling drum 35
xi

3.7 Dried saw dust 36
3.8 Drying chamber 36
3.9 Nitrogen generation plant schematic 38
3.10 Nitrogen receiving tank 38
3.11(a) Nitrogen sent to furnace at 5 bar 39
3.11(b) LPG burner 39
3.12 Gas fired nitrogen furnace 39
3.13 Process flow diagram 40
3.14 Material flow diagram 41
4.1 Mass vs Time plot of drying experiments 47
4.2 Mass Percentage vs Time plot of drying experiments 48
4.3 TGA and DSC plots 50
4.4 Comparative TGA results from theory 51
4.5 Steel shots 53
4.6 Electric heater control panel 53
4.7(a) Tar 55
4.7(b) Oil with high water content 55
4.7(c) Bio oil 55
4.8 Bio oil mixed with water and tar 56
4.9 Gravity separation 56
4.10 Lignin transformation stages 58
4.11 Cellulose lignin interactions 58
4.12 Puncture in N2 pipeline 61
4.13 The auger reactor after complete glass wool insulation 62
4.14 Nitrogen control panel with furnace
temperature set at 715
o
C 63
4.15 bio-oils obtained in each tank 64
xii

4.16 Phase separation graph of pyrolysis oil 65
4.17 Whatman number 42 Filter paper 67
4.18 Centrifuge 68
4.19(a) Before centrifugation 68
4.19(b) After centrifugation 68
4.20 Representation of GC Chromatogram
of saw dust bio-oil Tank 3 upper layer-BO1 70
4.21 Representation of GC chromatogram
of saw dust bio oil Tank 3 bottom layer-BO3 71
4.22 Representation of GC chromatogram
of saw dust bio oil Tank 1-BO4 72
xiii

NOMENCLATURE
Nw - mass transfer flux (drying rate), (kg.m
-2
s
-1
or mol.m-
2
s
-
1
) kc - mass transfer coefficient (kg.m
-2
s
-1
or mol.m
-2
s
-1
)
aw -is the water activity coefficient
psatw - saturation pressure of the water (kg m
-2
s
-1
or mol m
-2
s
-1
)
T∞ - the temperature of the air (°C)
Φ - the relative humidity
Ts - temperature of solids (
o
C)
xiv

1.1 Background:
With the depletion of fossil fuel and the concern of environmental protection, the
utilization of biomass resources has attracted increasing worldwide interest. Pyrolysis, as
one of the promising thermochemical conversion routes, plays a vital role in biomass
conversion. However, pyrolysis is an extremely complex process; it generally goes
through a series of reactions and can be influenced by many factors .It is thus essential to
study the fundamentals of biomass pyrolysis.
All types of biomass can be thermo chemically transformed. In recent years there has been
an intensification of research in the field of thermal conversion of biomass to liquid, solid
or gaseous products. These conversion technologies are combustion, gasification,
pyrolysis and liquefaction. Comparing the first three processes, pyrolysis is at a relatively
early stage of development. It can be distinguished as fast and slow, depending on the
operating conditions. The main product of fast pyrolysis is bio- oil, whereas the main
product of slow pyrolysis is char.
Lignocellulose is the type of biomass used in pyrolysis. Lignocellulose refers to plant dry
matter (biomass), so called lignocellulose biomass. It is the most abundantly available raw
material on the Earth for the production of bio-fuels, mainly bio-ethanol. It is composed
of carbohydrate polymers (cellulose, hemicellulose), and an aromatic polymer (lignin).
These carbohydrate polymers contain different sugar monomers (six and five carbon
sugars) and they are tightly bound to lignin. The pyrolysis involves different stages in
which the three compounds lignin, cellulose and hemicellulose are treated at different
temperatures to break the long chain polymers into shorter chains. The product yield is
around 60-75wt% bio-oil which has a Higher Heating Value of the range 18-23MJ/kg.
The product characteristics depend on the composition of biomass used and the procedure
followed.
2

The bio-oil is also known as pyrolysis oil obtained after quenching of the gaseous vapors
from the reactor. The oil obtained is a thick viscous liquid which is widely used as
industrial fuel to substitute furnace oil or industrial diesel. Due to the high oxygen content
and water content it has not been successful in replacing conventional hydrocarbon fuels.
1.2 Project Brief:
The plant installed in CO2 Research and Green Technologies Center is a auger based fast
pyrolysis plant funded by Ministry Of New and Renewable Energy, Government of India.
The objective is to use the excess agro-waste produced in the nearby area and to convert it
into bio-oil. The scale of the plant big to achieve a commercial viability in producing bio-
oil. The main aim of the project is to plan the installation and running parameters of the
plant to achieve favorable bio-oil yield.
1.3 Research Objectives:
Based on the areas detailed in the project brief, the objectives of the thesis include
 To plan operation and trials under varying parameters to observe the yield of bio-
oil and other components 

 To perform basic characterization studies on the bio-oil product obtain and
compare it with literature. 
3

2.1 Prosopis juliflora
Prosopis juliflora is a tree that grows in arid and semiarid regions. Prosopis juliflora is
native to a region from Mexico to Peru. People have developed local economies based on
this tree and its products. Introduced in India from Mexico, juliflora has found regular
users in the rural community. It is mainly used as firewood.
The saw dust that we are working on is obtained from the Prosopis juliflora. Prosopis
Juliflora wood burns evenly and hot. The good heat of combustion of Prosopis Juliflora
wood is due to its high carbon content and high levels of lignin. Since the lignin content
and carbon content is high in juliflora, the bio oil output will be significantly high. Thus a
highly efficient pyrolysis can be carried out on the Prosopis juliflora saw dust.
It was found from literature that the moisture content in juliflora wood sample is as low as
7.3% and the calorific value is 4.95 kcal [1]. The juliflora wood burns evenly and hot due
to its high carbon content and high levels of lignin. The superior qualities of firewood are
present even in juvenile wood and Prosopis juliflora wood burns well even when green.
Table 2.1: Energy Properties of wood samples (Nellie M. Oduor et al, [1])
Coming to the distribution of Prosopis juliflora, it is concentrated in the western part of
India, mostly Rajasthan. But as it can be seen in the map below, it is significantly
available in Tamil Nadu too. This is due to the semi-arid conditions in various regions of
Tamil Nadu.
5

Figure 2.1: Distribution of Prosopis juliflora in India [2]
6

2.2 Pyrolysis Mechanism
Pyrolysis is essentially the thermal decomposition of organic matter under inert
atmospheric conditions or in a limited supply of air, leading to the release of volatiles and
formation of char. Pyrolysis in wood is typically initiated at 200C and lasts till 450-500C,
depending on the species of wood. Pyrolysis has an important role in the combustion of
wood and sawdust since the products of this stage, namely, volatiles and char,
subsequently undergo flaming and glowing combustion respectively to release thermal
energy
Biomass is a general term for all organic materials derived from plants. From the chemical
viewpoint is a composite material, constituted by a mixture of hemicellulose, cellulose,
lignin and extracts, and affected by the chemical structure of the species
.Today it is of second energy source, with a contribution of 14% of the world energy
consumption, in comparison to the 12% provided by coal and 15% corresponding to gas.
Biomass is primarily composed of hemicellulose, cellulose and lignin, it can be
decomposed at a temperature range of 225-325, 300-375 and 250-500 °C [3], respectively
.Similarly it has been determined that cellulose is much higher than that corresponding to
lignin, which makes a larger amount of cellulose become more volatile
.This leads to the fact that the bigger the lignin composition, the greater the amount of
char produced or carbonaceous residues, because of a lower thermal degradation.
7

Figure 2.2: product yields from some thermochemical conversion technologies [4]
Figure 2.3: Conversion Technologies for Biomass [5]
8

2.2.1 Physical process
The phenomena that take place during pyrolysis are: heat transfer from a heat source
leading to an increase in temperature inside the fuel; initiation of pyrolysis reactions due
to this increased temperature leading to the release of volatiles and the formation of char;
flow of volatiles towards the ambient resulting in heat transfer between hot volatiles and
cooler non pyrolyzed fuel. Condensation of some of these volatiles produces tar and other
secondary reactions
2.2.2 Chemical process
The chemistry of the reaction is understood by categorizing the components in the source.
This is mainly done by proximate and ultimate analysis. Ultimate Analysis gives the
elemental distribution in the biomass i.e. Carbon, Oxygen, Nitrogen etc. A fair idea of the
percentage of the major products of pyrolysis (volatiles and char) is obtained from
proximate analysis. Table 2.2 gives the proximate analysis by percentage weight. It is to
be noted that volatiles are almost 77% by weight of dry wood. Thus, a weight loss of this
order may be expected after pyrolysis is complete and all the volatile matter is released.
Table 2.2: Proximate analysis of dry wood from literature (Sinha et al [3])
The major constituents of wood are cellulose (glucosan), hemicellulose (wood sugars),
and lignin (multi-ring organic compound). There is some variation in the relative
abundance of these constituents in different species of wood but as a rough guideline
cellulose is taken to be 50%-60% and the other two 20%-25% each by dry weight [14].
Most fuels of biological origin such as woods of different species of plants and agro-
wastes contain the same principal constituents and differ only in their percentage
composition.
9

Figure 2.4: Structure of biomass (manuel garcia-perez [5])
2.2.2.1 Cellulose
Cellulose is a polymer consisting of linear chains of B(1,4) d-glucopyranose units. Its
average molecular weight is roughly in 1,00,000. Combination of these linear chains with
the microstructure of the wood makes it inert to most chemical reagents. Cellulose
component normally constitutes 45-50% of the dry wood [6]. At temperatures less than
300
o
C, the main decomposition reaction occurs where cellulose starts breaking down.
Eventually beyond 300
o
C it starts to give products such as tar, char, syngas and oil. The
major component of tar is laevoglucosan that vaporizes and then decomposes with
increasing temperature.
2.2.2.2 Hemicellulose
Hemicellulose is a mixture of polysaccharides mainly composed of glucose, mannose,
galactose, xylose, arabinose, and 4-0 methylglucuronic acid and galacturonic acid
residues [3]. It is of much lower molecular weight than cellulose and is amorphous in
structure unlike cellulose. Wood constitutes hemicellulose from the range of 20-40% [3]
10

[6]. Hemicellulose is thermally most sensitive and decomposes in the temperature range
200
o
C to 260
o
C. This decomposition may occur in two steps; decomposition of the
polymer into soluble fragments or conversion into monomer units that further decompose
into volatile products. As compared to cellulose, hemicellulose gives rise to more
volatiles, less tar and char. The components of tar are organic acids such as acetic acid,
formic acid and a few other derivatives of furfural.
2.2.2.3 Lignin
Lignin is amorphous in nature and a random polymer of substituted phenyl propane units
that can be processed to yield aromatics [3]. It is said to be the main binder that hold
together the wood cell structure. The lignin component in biomass varies between 17 and
30%. Lignin decomposes when heated between 280
o
C and 500
o
C. Char is the more
abundant constituent in the products of lignin pyrolysis with a yield of 55% [6].
2.2.3 Overall Process
The overall process of pyrolysis of wood is believed to proceed as follows. At around
120
o
C the removal of all moisture (dehydration) is complete. Over the temperature range
200
o
C to 280
o
C, all the hemicellulose decomposes, yielding predominantly volatile
products such as carbon dioxide, carbon monoxide and condensable vapors. From 280
o
C
to 500
o
C the decomposition of cellulose picks up and reaches a peak around 320
o
C. The
products are again predominantly volatiles. The decomposition rate of lignin increases
rapidly at temperatures beyond 320
o
C. This is accompanied by a comparatively rapid
increase in the carbon content of the residual solid material [7].
Thus, thermal decomposition of cellulosic materials such as wood proceeds through a
complex series of chemical reactions, coupled with heat and mass transfer processes.
11

Figure 2.5: Decomposition of cellulose (Sinha et al [3])
2.3 Pyrolysis Model
Biomass pyrolysis technology could be used to produce liquid fuels and syngas, even high
quality chemicals. Due to the complexity in biomass composition, the pyrolysis behavior
of biomass was usually studied based on three main components, namely, cellulose,
hemicellulose, and lignin. Regarding the reaction route of cellulose pyrolysis, it was
proposed by the widely accepted Broido-Shafizadeh (B-S) mechanism that a series of
complex reactions occurred initially when heated, and a substance with relatively simple
composition and lower degree of polymerization, namely active cellulose, was generated.
Model of Broido-Shafizadeh postulates that the cellulose is converted into a more active
form and that this is a rate limiting step followed by the formation of either char or
volatile compounds. This concept was developed as a consequence of experimental
evidences showing the formation of cellulose of lower degree of polymerization at low
pyrolysis temperature. Broido (1973) found that crystalline cellulose undergoes a large
change in degree of polymerization before weight loss occurs. (Shafizadeh et al [8])
Figure 2.6: Broido-Shafizadeh model conversion (manuel garcia-perez [5])
12

Figure 2.7: Cellulose thermochemical degradation reaction (manuel garcia-perez [5])
The fast pyrolysis mechanism proceeds through two major reactions i.e. the unzipping
mechanism & fragmentation of levoglucosan [9].
The unzipping mechanism is the step which involves depolymerisation [10] of active
cellulose. First noted that the chain length rapidly became fairly constant at about 200 to
30 units over a degree of decomposition of the celluloses from 4 to 80 %. These cellulose
units are called by the broido-shafizadeh model as “active cellulose”[5]. It was proposed
that the thermal decomposition of the active cellulose to levoglucosan occurred by a
splitting off glucosidic units from the end of polymer chains. The thermal decomposition
involved the consecutive chemical conversion of cellulose to monomeric unit, which is
converted by internal isomerization into levoglucosan. So, it is proposed that once a chain
reaction is initiated, the whole chain “unzips”.
13

Figure 2.8: Mechanism of cellulose depolymerisation according to Evans et al [11]
The second step involves fragmentation of levoglucosan in aldehydes ketones and other
smaller products. This products are the main components of the volatile tar which is
produced alongside with the char and gasses (CO2 , CO etc). These reaction gasses are
cooled to condense the bio-oil at room temperature.
14

Figure 2.9: Laevoglucosan unzipping mechanism (Evans et al [11])
2.4 Products
As described above there are various products in a pyrolysis reaction. The main products
are syngas bio-oil and char. Although bio-oil is our aim the other products also have their
own individual uses. This section provides literature on the products of biomass pyrolysis.
It gives a description of the product and its potential applications
15

2.4.1 Char
Figure 2.10: Char sample from a pyrolysis reaction
Char is the solid product from the fast pyrolysis process. Biochar is a carbon-rich material
that is virtually non-biodegradable and thus stable in soils. The solid product from fast
pyrolysis is a black, powdery substance known as biochar, char, agri-char or just charcoal.
Biochar yields from fast pyrolysis range from approximately 11%-wt. to around 25%-wt.,
with 13%-wt. to 15%-wt [12]. being common values for fast pyrolysis of wood biomass.
Bio-char also has agricultural use as it has shown increased crop performance because of
its carbon rich content. Char obtained is not always fine powder and depends on the feed
material and particle size. Excess char deposits usually indicate incomplete reaction or
lack in temperature.
Applications
Application of bio-char are
1. Fuel source – Due to low smoke it can be used for cooking.
2. Filter medium – Char is fine and porous thus helps in cleaning of air and water by
acting as a filter.
16

3. Catalyst support - The above mentioned property also allows char to have a
favorable surface for reactions and nucleation especially when housing catalysts.
4. Bio remediation – It can be used to improve nutrient transfer in soil helping in
increasing agricultural performance.
5. Reducing agent – Char is a very powerful reducing agent because of its carbon
content.
2.4.2 Bio-Oil
Figure 2.11: Bio-oil from a pyrolysis reaction
Bio-oil is a complex mixture of more than 300 organic compounds [10] formed during
pyrolysis reactions that are essentially converted in a liquid form. Bio-oil is very different
from traditional fossil-fuel based liquids, and many times in literature it is referred to as
pyrolysis liquid or pyrolysis oil. Many of these differences and the unique properties of
bio-oil are attributed to its high oxygen content, which originates from the oxygen
contained in the biomass feedstock. The bio-oil composition is very similar to
17

the feedstock as the only major change that occurs is the breaking of long chains into
shorter chains. Bio-oil also contains significant amounts of water, which results from
condensing any moisture contained in the feedstock as well as significant reaction water
formed during the process. Due to the high oxygen and water contents, bio-oil has a lower
heating value than petroleum based fuel-oils. In addition to higher oxygen and water
contents, bio-oil is more acidic than petroleum based fuel-oils, with a common pH value
of 2.5. There are many applications for bio-oil, in varying stages of research and
commercial implementation. As produced, bio-oil can be considered a fuel source for
standard industrial equipment such as boilers, furnaces, burners, stationary diesel engines,
gas turbines and stirling engines .Bio-oil used for generating heat or electricity in these
applications displaces the use of light fuel oil, heavy fuel-oil or even diesel fuel; however
modifications are often required to accommodate the unique properties of bio-oil as
discussed.
Applications
Applications of bio-oil are [13]-
1. Organic derivative-It can be used as a precursor for other chemical products by
upgrading the existing bio-oil.
2. Fuel – it can be combusted and used for heat or power generation (HHV of 17
MJ/kg [14]).
3. Bio-fuel – It can be upgraded to a fuel that can be directly used in a conventional
engine.
18

2.4.3 Syngas
Syngas, also known as synthesis gas is mainly composed of hydrogen, carbon monoxide,
methane, carbon dioxide and small hydrocarbons. It is primarily the incondensable gas
product of pyrolysis left over once the oil is condensed out.
Applications
Applications of syngas are
1. Fuel for electricity generation, heating, gas cells.
2. Biodiesel feedstock in the Fischer-Tropsch process [15].
3. Direct heating-The hot gasses can be recirculated for heating the pyrolysis process
2.5 Alternate Technologies
There are other alternatives to process biomass such as -
 Gasification 

 Fischer Tropsch 

 Torrefaction. 
These processes are also based on thermo chemical decomposition of carbonaceous
matter. However, these have some differences from pyrolysis in operating parameters
such as the maximum temperature used and amount of air added. These differences are
crucial and alter the reaction mechanisms and end products.
19

Gasification – In this process, organic matter is heated to 1200-1500
0
C in the presence
of oxygen, but using less oxygen than stoichiometric ratios to prevent complete feedstock
combustion. The highly exothermic combustion provides energy for gasification of the
feedstock. Gasification is often used on pyrolysis by-products to produce syngas for
electricity and heat generation, but is also be used on raw feedstock [16].
Fischer Tropsch – This process is used to convert natural gas and syngas into liquid
alkane fuels. The process normally uses pyrolysis or gasification or a combination of both
to produce the syngas which is then converted into the liquid fuels via catalytic cracking
and reformation of gases [16].
Torrefaction – This is a mild form of pyrolysis where the biomass is heated to
temperatures ranging from 230-300°C in the absence of oxygen. It is usually used as an
intermediate process. Heating the biomass dries it and some volatile matter is driven off.
A brittle material is left behind with low oxygen and water content. This makes a better
feedstock for combustion or gasification [16].
2.6 Effects of Processing Parameters on Pyrolysis
The pyrolysis reaction kinetics rates are mainly dependent on the following parameters:
1. Residence Time – Fast pyrolysis usually requires a low residence time of 2-3
seconds. A very high residence time causes the oxygen in the biomass to react
with the carbon and result in a high ash and char content. This reduces the bio-oil
output. Thus the residence time is kept low [17] [14].
2. Heating rate – In fast pyrolysis, good oil and syngas yield requires a higher
heating rate [14]. If the heating rate is high, the feedstock reaches a higher degree
of volatilization in a short time. Moreover, literature also states that lower the
20

heating rates, higher the char formation. Thus to obtain high bio-oil yield and
reduce the char output, higher heating rate is used [17].
3. Reaction temperature – It governs the degree of volatilization exhibited by the
feedstock. High reaction temperatures result in the desired gas production while
low reaction temperatures support the undesirable char and tar formation [14]. If a
higher reaction temperature is maintained, then hydrogen fraction and calorific
value of the syngas also increases [17].
4. Operating pressure – This affects the equilibrium temperature for volatilization.
A lower pressure reduces the required reaction temperature [17] [14].
2.7 Reaction Kinetics
Biomass pyrolysis reactions are considered to be heterogeneous solid state reactions.
There are many models for solid state reactions most of which can be classified by the
following mechanisms [16]:
 Reaction order – uses the rate law based on homogeneous kinetics. 

 Diffusion – the reaction rate is limited by the diffusion of the reactant or product. 

 Nucleation – the favorability of nuclei formation and growth define the reaction
rates simultaneously. 

 Geometrical contraction – a reduction in active reactive surface area are definitive
of the reaction rates. 
21

2.8 Thermo gravimetric Analysis
Pyrolysis experiments can be analyzed using thermal analysis methods such as [15][18]:
 Differential thermal analysis (DTA) 

 Thermo gravimetric analysis (TGA) 

 Differential scanning calorimeter (DSC) 

 Simultaneous DSC and TGA (SDT) 
The data from these experimental methods are plotted and the shape of the graph will
determine which reaction mechanism best suits the reaction kinetics of the process.
There are various techniques devised to model the reaction kinetics for the pyrolysis
process.
These are [19]:
 The constant heating rate TGA 

 The constant reaction rate TGA 

 The dynamic heating rate TGA 
These techniques can be used to predict the decomposition rates of homogeneous organic
matter [16]. However, most biomass does not have a homogeneous structure. For example
pine sawdust is mainly comprised of lignin, cellulose and hemicellulose. Decomposition
kinetics can be obtained from TGA tests performed in inert atmosphere to prevent
combustion or addition of oxygen. In this model, the reaction order is normally assumed
to be 1. This means the model can be described using the Arrhenius equation for
decomposition.
k=Aexp
(-B/RT)
……..
Equation 2.1 Arrhenius equation
22

The constants relating to the activation energy and frequency factor can be calculated
using empirical data whilst the reaction rate constant will normally be calculated using the
change in mass.
2.8.1 Constant Heating Rate TGA
This model is simple and assumes the reactor has a constant heating rate. This makes it
easier to approximate the thermal properties of the sawdust as it is conveyed through the
reactor. This means the temperature profile of the feedstock and the heating medium will
be linear assuming no heat losses [19] [18].
2.8.2 The Constant Reaction Rate TGA
In this type of experiment, a desired reaction rate is defined and the feedstock is heated
gradually. Once the desired reaction rate is achieved, the heating rate is adjusted by
automatic control functions in an attempt to keep the mass loss rate constant [19] [18].
2.8.3 Dynamic Heating Rate TGA
This model attempts to improve on the accuracy by accounting for the change of heat
exchange driving force. This means the thermal properties of the feedstock changes as it is
conveyed along the reactor. This approach is less pessimistic but more detailed and
therefore requires more monitoring and calculations [19] [18].
23

3.1 Introduction
This section presents the methodology of the experiments in this project.
There were three main areas of experimental work:
1. Feedstock characterization – This included shaping characteristic properties of the
biomass such as moisture content, ash content, etc. The drying characteristics and
decomposition reaction kinetics were also examined.
2. Pilot plant trials – This involved pyrolysis of sawdust using the CO2 Research and
Green Technologies Center pilot plant at varied working environment by varying
the reaction temperature, auger speed and moisture content. The different product
yields were collected to study the main effects of the variation in the parameters.
3. Product characterization – This was similar to feedstock characterization and
involved determining product characteristics such as moisture content, ash
content, etc.
3.2 Reagents
The juliflora saw dust was used as the biomass for the experiments. This was received
directly from the woodcutting activities in VIT University and other facilities around VIT.
Nitrogen gas was used for heating the reactor. This was obtained from the Nitrogen Plant
setup in CO2 Research and Green Technologies Center at VIT University.
3.3 Equipment
In addition to the pilot plant provided by CO2 Research and Green Technologies Center,
VIT University the following equipment was used:
1. Hot Air Oven
2. TGA instrument <SDT Q600 V20.9> -Perkin elmers
3. Exhaust dryer
25

4. Nitrogen production plant
5. LPG fired Furnace
3.4 Feedstock Characterization Experiments
3.4.1 Proximate Analysis
3.4.1.1 Moisture Content
Biomass samples were placed in crucibles of known mass and mass of sample was
measured using a balance. Sample was dried at 105°C until a constant mass was achieved.
The difference between wet and dry weight divided by the wet weight gave the total
moisture content in percentage.
3.4.1.2 Ash Content
The saw dust sample was dried and the mass was measured. Then it was heated in a
Moufle Furnace, available in the Materials and Engineering Technology laboratory, to a
temperature of 650
0
C for two hours. For measurements, cylindrical silica crucibles were
used. The final mass was measured which is the weight of the ash. Ash content was
calculated by dividing the ash weight by the initial weight.
3.4.2 Drying Characteristics
Green sawdust is normally received with moisture levels higher than typical wood due to
the use of water as a coolant for the saws. The moisture content will need to be reduced
before the feedstock is introduced into the reactor to prevent processing issues. Drying
trials were conducted on the prospective feedstock. Drying experiments were set up in an
attempt to obtain drying characteristics of the sawdust. Drying trials were performed on
the selected feedstock for property characterization purposes. The trials were performed at
temperature of 105
o
C in an attempt to find an optimal drying temperature.
26

The drying rate for the sawdust is expected to vary depending on the temperature, grain
size and the relative humidity.
3.4.2.1 Aim
The aim of the drying trials is to investigate the drying characteristics of sawdust. This is
done because the moisture available in the product is not completely free moisture. Thus,
the drying rates are based on diffusion of the liquid through the material. This function is
very complex for heat sensitive materials such as sludge due to physical transformations
caused by the heat. However the function can be made simpler for materials that are
thermally stable within the operational temperatures especially when their water activity
coefficient is known.
3.4.2.2 Theory
Drying will occur while the moisture within the solid is not at equilibrium with the
moisture in the drying medium (usually air).
Nw=kc[awpw
sat
(Ts)- Φpw
sat
(T∞)
Equation 3.1: Mass transfer flux
Where Nw is the mass transfer flux (drying rate), (kg.m
-2
s
-1
or mol.m-
2
s
-
1
) kc is mass transfer coefficient (kg.m
-2
s
-1
or mol.m
-2
s
-1
)
aw is the water activity coefficient
psatw is saturation pressure of the water (kg m
-2
s
-1
or mol m
-2
s
-1
)
T∞ is the temperature of the air (°C)
Φ is the relative humidity
Ts is temperature of solids (
o
C)
27

Since the solids content is assumed to remain constant, the drying rate Nw may be
evaluated a number of different ways:
NwA=dM/dt = dMw/dt
Equation 3.2: Different expression of Nw
Where A is the surface area of the sawdust dM/dt
is the change in mass of the whole sample
dmw/dt is the change in mass of the water content for a given time period dt.
A plot of drying rate vs. time reveals a lot about the drying process. In particular, some
key periods may be observed. The plot consists of following result.
Settling-Down Period
Typically the sample to be dried is initially lower than the wet and dry bulb temperatures
in the oven. During this period much of the heat arriving at the sample‟s surface is being
used to heat the sample rather than evaporate water so initially drying rates are low. As
the temperature rises, the evaporation rate increases until the cooling effect of the
evaporation matches the rate of heat transfer to the surface, at which point the constant-
rate period begins.
Constant-Rate Period
During this period the surface water activity is close to unity and the rate of moisture
evaporation matches the rate at which heat is arriving at the surface, and hence the surface
temperature remains constant, approximately equal to the wet-bulb temperature.
Assuming the humidity, oven temperature and heat and mass transfer coefficients
28

remain relatively constant, the drying rate will also be approximately constant (hence its
name).
Figure 3.1 Drying Characteristics
Falling-rate period
If the rate of moisture removal from the surface is greater than the rate at which water
migrates to the surface from within the sample, the surface water activity will drop below
unity and the evaporation rate will decrease, which will mean that the surface temperature
will rise, which in turn will mean that the driving force for the drying process will
decrease and the drying rate will fall (hence its name).
3.4.2.3 Experimental Setup
Drying trials were performed on the selected feedstock for property characterization
purposes. The trials were performed at temperature of 105
o
C in an attempt to find an
optimal drying temperature. The drying rate for the sawdust is expected to vary depending
on the temperature, grain size and the relative humidity.
29

3.4.3 Thermo gravimetric Analysis
The Thermo-gravimetric analysis of sawdust was performed using the TGA instrument
SDT Q600 V20.9- Perkin Elmers provided by the School of Advanced Sciences, VIT
University. Saw dust was heated up to 600
o
C and the weight was continuously noted. A
mass vs time plot was obtained for further studies.
3.5 Plant Experimental Setup
3.5.1 Design of Experiments
The different products of biomass pyrolysis can be very resourceful and thus the process
is complex. It can be simplified by monitoring the variable parameters and modifying
them to achieve the desired output.
Each biomass has to be treated and studied separately since the biomass pyrolysis research
has not yet defined a universal model for pyrolysis. The pyrolytic process is being
comprehended using mock reactions, however, there are differences based on the origin of
the biomass feedstock. Thus there is a necessity for extensive experimental setup to
analyze the effects of the variable parameters on the pyrolysis process.
The design of experiment will look at systematically reducing the number of variables to
be investigated based on the main effects they can have on the process. The first set of
trials was based on heating via electric heaters. The electric heaters were attached on the
outside of the rector to provide heat along the length of the auger. The sawdust which was
already in a fine particulate state did not require any specific pre-treatment other than
drying. Saw dust is hygroscopic in nature thus it was required to be dried before feeding
to prevent high water content. The drying was performed using hot exhaust gasses from a
diesel generator also present in the CO2 Research and Green Technologies Center, which
were passed over the feed in a dryer. For uniform distribution of heat along the reactor
steel shots where used along with the saw dust. The steel shots were fed at a ratio of 1:2
along with the saw dust.
30

For the second set of trials hot nitrogen was used to alleviate the reaction temperature and
prevent clogging at the start of the reactor. The nitrogen used was heated to ~700C, at 1.5
bar using a LPG fired furnace and supplied using pipes insulated by glass wool wiring. A
3HP motor was connected via coupling for running the auger blade and was controlled by
a DC speed control unit. The exhaust gasses were sent to condenser drums with chilled
water from the water plant which was operated at 10
0
C & room temperature alternatively
to condense the gasses. The condensed liquid was collected in receiver drums below.
Figure 3.2 Block Diagram of the auger reactor
3.5.1.1 Variables for Electrical heating Trials
It had been determined that the main driving variables were pyrolysis temperature,
feedstock moisture content and feed rate. The effects of these factors were investigated
on:
 Char, syngas, and oil yields 

 Fixed carbon in char 
31

 Syngas composition 
3.5.1.2 Variable of Nitrogen heating trials
 N2 flow rate 

 N2 temperature 

 Heater temperature 
3.5.2 Auger Conveyer
An Auger conveyor, also known as a Screw conveyor, is a mechanism that uses a rotating
helical screw blade. The setup is used to push granular or liquid materials. Screw
conveyors nowadays are frequently used horizontally or at a calculated incline as an
effective way to move semi-solid materials, including food waste, wood chips, aggregates,
animal feed, boiler ash, meat, municipal solid waste etc. The first time auger was used
was around 1969 for production of laevoglucosan from starch and cellulose.
The auger reactor has not been researched as much as the fluidized bed combustion.
Despite being in use since 1960‟s, utilization of auger in fast pyrolysis is a less
investigated field. The Auger conveyer used in our trials is 6 ft. in length and 1 ft. in
diameter. Unlike pilot plants employed in lab scale reactors, CO2 Research Centre has
deployed a large scale reactor for studying the commercial applications of biomass
pyrolysis using auger conveyor. For heating the large screw conveyer four 5 kW electrical
heaters were used along the length of the auger. To prevent the heat from escaping and
affecting the control panel glass wool was used along the front length of the reactor [20].
32

Table 3.1 Auger Specifications
Diameter 1 ft.
Length 6 ft.
Feeder Diameter 11.46 cm
Feeder Height 58cm
Feed Rate 10 kg/hr.
N2 Flow Rate 120 m
3
/hr.
Operating Temperature 350
0
C to 450
0
C
Figure 3.3 Auger Reactor
3.5.3 Screw Motor
The screw motor being used was a 3 HP motor attached to the auger screw via a worm
reducer. It is common practice to use an electric motor coupled with an industrial gear
reducer to achieve the required speed and torque. The worm reducer multiplies the
33

output torque coming from the motor and reduces the motor output speed by the same
ratio.
The setup is coupled using rubber bushes to prevent wear and tear of the motor. The DC
motor is controlled using a DC speed controller that inputs variable voltages into the
motor to reduce or increase the RPM. The motor created heavy vibration at high RPMs,
thus for optimal conditions the motor was operated at 15-18 RPM.
Table 3.2 Motor Specs
Make ELMO
Current DC
Speed 1500 rpm
Volts 230
Amp 11.8
Power (kW/H.P) 3.0
Figure 3.4(a). Motor Speed control unit Figure 3.4(b) DC Motor
Table 3.3 Worm Reducer Specs
Make Greaves Gears
Type AUD 237
Ratio 100/1 R/L
34

Figure 3.4(c) Worm Reducer Unit
3.5.4 Condenser
The exhaust gasses were sent through circular steel pipes immersed in condenser drums.
Three drums were used for condensing the received gasses, the first and the third drums
had chilled water at approximately 10
o
C and the second drum had water at room
temperature. The chilled water was generated using a refrigeration system developed at
CO2 Research Centre. Each condensing drum had a receiver tank at the bottom that
received the condensed liquid. The non-condensable gasses were driven out using a
suction pump at the end of the setup.
Figure 3.5 Suction Unit Figure 3.6 Chilling Drum
35

3.5.5 Feed Material
The material fed was Prosopis juliflora saw dust obtained from nearby villages and the
woodcutting activities in VIT University. The saw dust being in a fine particulate state did
not require any pre-processing. But due to the hygroscopic nature of saw dust it had to be
heated to reduce the moisture content. The drying was done using an exhaust gas oven
which used the exhaust fumes of a diesel generator. The biomass was dried 3 kg at a time
in the oven and hand fed to the reactor.
Figure 3.7 Dried saw dust Figure 3.8 Drying Chamber
3.5.6 Nitrogen Process Plant
It was highly essential that a temperature above 400
0
C be maintained in the auger reactor
for pyrolysis of saw dust. The electric heaters fixed on our auger reactor could not solely
heat the reactor to the required temperature. Thus it was necessary to use another source
of heating. This role was played by high temperature N2 gas. N2 at temperatures of 600
0
C
to 700
0
C was supplied in order to achieve a final temperature of atleast 450
0
C to 500
0
C.
The hot N2 gas also played the role of fluidizing agent in the reactor.
36

First N2 gas was produced from atmospheric air using adsorption technique. The
adsorption gas separation process in nitrogen generators was based on the phenomenon of
fixing various gas mixture components by a solid substance called an adsorbent. This
phenomenon was brought about by the gas and adsorbent molecules‟ interaction. The
principal of the adsorption technology was based upon the dependence of the adsorption
rates featured by various gas mixture components upon pressure and temperature factors.
The air was first compressed and collected in a receiver for filtration to remove the dust
partiles and other colloids. The dust particles could easily damage the adsorption
membranes and clog the adsorbents. Thus it was crucial that the air be treated before
sending it for further processing. Next the pretreated air was sent to the adsorption
chambers 1 and 2. In these chambers the temperature and pressure were maintained in
such a way that only N2 gets adsorbed to the surface of the adsorbent and the remaining
gases were let out into the atmosphere or can be used for other purposes. This adsorbed
N2 was set free by changing the pressure and temperature appropriately and then
accumalated in another receiver which at the end contained 99.9995% N2.
After the seperation of N2 from atmospheric air, it was compressed to about 5 bar and
then supplied to a gas fired furnace for heating. The furnace was fueled by 5 lpg gas
cylinders. It took about 6 hours for the N2 gas to reach the 700
0
C. The N2 gas was
obtained at an output pressure of 1.5 bar and a flow rate of 120 m
3
/hr. This was supplied
from the furnace to the auger reactor via steel pipes that were insulated using glass wool
ropes.
37

Figure 3.9 Nitrogen generation plant schematic
Figure 3.10 Nitrogen receiving tank
38

Figure 3.11(a) Nitrogen sent to furnace at 5 bar Figure 3.11(b) LPG gas burner
Figure 3.12 Gas fired nitrogen furnace
39

3.5.7 Process Flow
The whole process is mentioned in the Figure below:
a) The dark blue line represents the chilled water inlet.
b) The green line represents the water outlet from cooling drums.
c) The red line represents the gas outlet from reactor to the cooling drums.
d) The orange line represents the outlet of gas and bio oil yield into the collecting
drums.
Figure 3.13 Process Flow Diagram
40

3.5.8 Material Flow
The flow of the material can be visualized with the help of the following Figure:
Figure 3.14 Material Flow Diagram
41

3.5.9 Energy balance
The life cycle assessment studies were examined to formulate energy balance for the
auger reactor [21]. All standard values are taken within the range of deviation and
energy input and output is calculated at each section of the process [22].
Table 3.4 Properties of various reagents
Sl no. Specification Value
1 Specific heat of bio-oil (kJ/kg/K) 2.4346
2 Heat of Vaporization of bio-oil (kJ/kg) 609.9312
3 Specific heat capacity of char (kJ/Kg/K) 1956
4 Specific Calorific Value of LPG (kJ/kg) 46100
5 Cp of water (kJ/kg/K) 4.1806
6 Latent heat of vaporization of water (kJ/kg) 2322.8
7 Cp of water vapour (kJ/kg/K) 2.13
8 Heat of combustion of gas (kJ/kg) 18270
9 Heat of combustion of char (kJ/kg) 26400
10 Heat of Pyrolysis (kJ/kg) 1640
42

Table 3.5 Energy requirement of Equipment Used
SL NO PROCESS AND EQUOIPMENTS ENERGY USED (MJ/HR)
1 DRYER 21.737
2 GRINDER 1.4715
3 SCREW FEEDER 9.1
4 BIO OIL COMPRESSER 19.8
5 ELECTRICAL HEATER 72
6 CHILLER PLANT 25.25
TOTAL 149.3585
Table 3.6 Energy Balance Calculation Results [23]
SL NO PRODUCT ENERGY OBTAINED (MJ/HR)
1 BIO OIL 57
2 CHAR 72.6
3 GAS 56.5
TOTAL 186.1
43

CHAPTER 4
Results and Discussion
44

4.1 Introduction
Experimental work done and the empirical data collected are presented in this section.
The results of different trials done under different operating conditions are presented in
the form of raw data and discussion. Both trials showed different product yields and
comparative data is shown for all the products obtained in a trial.
4.2 Feedstock Characterization
4.2.1 Introduction
Pyrolysis is a process that gives out large number of complex organic molecules. Many of
these reaction pathways are hard to keep track, thus a characterization of feedstock is
required to understand the reaction pathways. Another important use is to obtain the
composition of the feedstock to better optimize the pyrolysis process.
In some cases feedstock pretreatment is required to achieve the required operating
conditions during pyrolysis. Plants that run municipal solid wastes have to process and
pre-treat their feed before pyrolysis.
In the case of saw dust, the hygroscopic nature of the material causes a major concern in
terms of high water output in the end products. Understanding the composition of the
material helps design the required pre-treatment exercises.
4.2.2 Composition Analysis
The sawdust used as the feedstock is from breed of wood native to India called Prosopis
Juliflora. This has a lignocellulose structure and a particle size ranging from 1.5-2 mm.
The sawdust obtained is of uneven particle size as it is directly supplied from saw mills.
Table 4.1Proximate Analysis of sawdust
Components Volatile Matter Fixed Carbon Ash Moisture
% 68.2 19.3 3.0 9.5
45

Table 4.2 Comparative ultimate analysis data from Wan Nor Roslam Wan Isahak et al
4.2.3 Drying Characteristics
This section presents the results of drying trials conducted on the prospective feedstock.
Drying experiments were set up in an attempt to obtain drying characteristics of the
sawdust
Results
Data from the drying experiments was recorded and plotted to give mass loss curves
Table 4.3 Drying Experiment Results
time mass mass fraction
0 1 100
5 0.91 35.71428571
10 0.89 21.42857143
15 0.88 14.28571429
20 0.87 7.142857143
25 0.87 7.142857143
30 0.86 0
35 0.86 0
40 0.86 0
45 0.86 0
50 0.86 0
46

Thus the moisture content in the saw dust is found to be 14 %. This doesn‟t align with the
proximate analysis results due to the equilibrium maintained between atmospheric
moisture and the moisture in the saw dust. The readings were taken after a rainy day, thus
there seems to be an unusual amount of moisture in the biomass probably due to the high
relative humidity.
The rate at which wood dries depends upon a number of factors, the most important of
which are the temperature, the dimensions of the wood, and the relative humidity
(Simpson and Tschernitz 1979).
The following graphs were obtained for mass vs time and mass fraction vs time:
Mass vs Time
1.02
1
0.98
0.96
(g)
0.94
Mass
0.92
0.9
0.88
0.86
0.84
0 10 20 30 40 50 60
Time (m)
Series1
Figure 4.1 Mass vs Time plot of drying experiments
47

Mass % vs Time
Mass(%) 120
100
80
60
Series1
40
20
0 0 10 20 30 40 50 60
-20
Time (m)
Figure 4.2 Mass Percentage vs Time plot of drying experiments
.
The curves can be defined by the following expression
Y (t) = (Mt -Mf) / (M0 -Mf)
Equation 4.1 Mass fraction
Where M0 is the initial mass;
Mf is the final mass and
Mt is the mass at a given time
The plots show an increase of mass loss for the first mass value reading. This was due to
the driving force for surface water evaporation governing the mass transfer rates. The rate
of mass loss decreased with time for all samples until the sawdust reached equilibrium
moisture conditions. This behavior is characteristic of the falling rate period. It appears
that the drying experiments do not exhibit the first two stages of drying as predicted by
theory. This is because the theory is based on tray drying of materials of
48

larger size. The small grain size means the bulk load has a higher surface area to volume
and this accelerates evaporation from the surface. Once surface moisture is evaporated the
drying rate is controlled by the moisture diffusion through the sawdust.
4.2.4 Reaction Kinetic
The reaction pathways of pyrolysis are complex and it is difficult to develop a model for
these reactions. These are a lot of models available in theory for wood pyrolysis. These
are important to understand the reaction occurring inside a plant during a trial.
The lab scale simulation using thermo-gravimetric analysis (TGA) can be used to predict
the behavior of the feedstock as it is processed in the plant.
To simulate the exact conditions of the plant the following steps were taken [24]:
 Using N2 (Nitrogen) as an inert medium, ensuring no combustion occurs 

 Using a controlled heating rate 

 The plant operates at 500
0
C, however, to understand the thermal properties of the
feedstock the experiment was performed till 600
o
C. 
49

4.2.4.1 TGA Analysis
TGA analysis of sawdust was performed up to 873 °K (600 °C). Mass loss curves were
obtained for sawdust at 10K/min.
Figure 4.3 TGA and DSC plots
The mass loss curves each give a sinusoidal shape for the decomposition reaction. The
first drop is for the moisture content at 9.9% which escapes roughly around 105
o
C. The
second drop is for the volatile matter which is roughly around 57.1 %. Due to low
resolution of the TGA the char content is not covered in the full spectrum. Extending the
temperature band to 800
o
C would give a better picture of the char content.
50

Figure 4.4 Comparative TGA results from theory [16]
4.3 Pilot Plant Trials
4.3.1 Trials with electrical heating
4.3.1.1 Experimental data
The plant trials were performed from 14
th
to 18
th
September, 2014. The operating
conditions were assigned as:
 14 % moisture content feedstock: From the oven heating trials presented
previously, the moisture content is is found to be at this equilibrium point. 

 Pyrolysis Temperature at 350
o
C : This temperature falls in the slow pyrolysis
range but due to the high losses of heat from the sides of the auger this is the
maximum temperature reached. 
51

 Auger Speed 15 RPM : Giving a very high auger speed gives excess char
whereas very low speeds gives high non condensable gasses. This RPM is set
considering the motor capacity, high auger screw friction and saw dust feed
rate. 
Table 4.4 Experimental Setup
Trial # Moisture (%) Temperature (
o
C) Auger speed
(RPM)
0 9.5 350 15
4.3.1.2 Plant process description
 Prepare the feed by heating it under the sun or in a exhaust dryer 

 Start the electrical heaters 

 Start the chilled water plant. 

 Prepare the feed by the time the electrical heaters reach peak temperature 

 Mix steel shots with saw dust in a ratio of 1:2 by mass 

 Start the motor and reach the required RPM. 

 Feed the saw dust /shot mixture at the required feed rate. 

 Wait for the steel shots to reach the char box and recycle them in the next
process. 

 Start the condenser pump once the gasses are emitted. 

 Start the suction for the exhaust non condensable gasses. 



4.3.1.3 Feedstock Performance
Qualitative observations were made during running the plant to find the parameters to be
optimised in a large scale plant. The saw dust was fed along with steel shots (1:2 mass
ratio) at a rate of ~5 kg/hr .It was observed that there was an unusual amount of smoke
52

developed from every outlet. This was mainly due to the high moisture content in the saw
dust.
Figure 4.5 Steel Shots
The saw dust also caused blockage due to compressive action of the screw. This also
caused a minor choking at the inlet of the auger. Although due to the high moisture
content the saw dust moved efficiently through the screw.
Hot volatiles were observed 30 minutes after the start of the feeding and starting the
motor. Based on visual interpretation, the change of reaction variables changed the output
according to the theory. Although the initial temperature was 300
o
C the value was
eventually increased to 350
o
C which showed reduced char formation and increased
syngas formation. Though required temperature was well above 450
o
C, this shortage of
temperature was reciprocated in the form of high char output.
Figure 4.6 Electric Heater Control Panel
53

The steel shots were collected from the char box and fed again. This served two purposes;
firstly due to the high shot temperature from the outlet, feeding it again in the inlet caused
faster pyrolysis of saw dust. Secondly there was a shortage of steel shots which was
compensated by the recycling. Initially there was also unburnt saw dust with the char
which was fed again into the feeder again.
For a fixed temperature and fixed motor speed the increase of moisture content in the
sawdust showed a reduction in feedstock flow properties. This was because the moisture
could have acted as a lubricant which allowed the sawdust a higher degree of shear strain.
This in turn caused an increase in density of the sawdust, thus causing a need for a larger
mechanical driving force. The lower moisture feed generally produced more volatiles.
For a fixed temperature and fixed moisture content increase in feed rate via an increase in
motor speed increased the amount of char produced. The char also appeared to be cooked
less compared to slower feed rates. The products obtained were mainly bio-oil, bio-char
and bio tar along with non-condensable gasses.
Table 4.5 Raw data of electrical heating trials
Trial Sample Moisture Temp. Auger Feed Char Oil Syngas
ID Content- (
o
C) speed Rate Mass Mass Mass
% (RPM) (kg/hr) (kg/hr) (kg/hr) (kg/hr)
1 00 9.5 350 15 1.5 - - -
2 01 9.5 350 15 0.75 - - -
3 02 9.5 350 15 2.75 - - -
Total 5 0.75 1.5 2.75
54

4.3.1.4 Products obtained
Figure 4.7 (a) Tar Figure 4.7 (b) Oil with Figure 4.7 (c) Bio oil
High water content
 The products obtained are collected in the receiver drums. Each drum had a
different concentration of oil. The First drum had large amount of tar deposits and
water. The tar was an unexpected side product which was a sticky polymer like
substance. The major disadvantages of tar build up was the clogging of delivery
pipes and reduction of bio-oil content. 

 The second drum had oil content but there was a unusual amount of water content.
The sample obtained from this drum is almost unusable condition for testing or
further upgrading process. 

 The sample obtained from the third drum had resemblance to bio-oil and it had
considerably less water content. But the yield in the last drum was low. Partly due
to the clogging of the tar deposits the final product yield was very low. 
4.3.1.5 Discussion
The products obtained were individually analyzed to understand the path of the reaction.
The tar obtained was clearly polymeric substance that did not dissolve in water or respond
to heat treatment. Upon vigorous heating of the sample the tar turned into a thick liquid
which would immediately solidify upon cooling.
55

Figure 4.8 Bio oil mixed with water and tar
The high water content bio-oil was subjected to agitation and gravity separation. After 24
hours of gravity separation there was no noticeable separation of oil from the water
.The sample was then heated to 100
o
C to evaporate the water. After ~5 minutes of heating
the sample showed deposits of thick viscous oil .The oil couldn‟t be separated as it was
mixed with tar which solidified immediately after cooling.
Figure 4.9 Gravity Separation
56

Upon literature survey we concluded that the formation of tar was due to the secondary
reaction „Lignin Pyrolysis‟ [9] [25]. Wood is composed of lignin, cellulose and
hemicellulose. Due to the low temperature band attained due to the electrical heaters we
have pyrolised ligin instead of cellulose [26].
Lignin is not of great use in reactions and in turn causes formation of unnecessary side
products. Lignin is composed of three types of phenyl propanoid monomer units linked
together by various C-C and C-O bonds. Owing to the highly cross-linked structure, the
transformation of lignin during fast pyrolysis or acidolysis results in tarry and resin-like
fractions that cause clogging of reactors [25]. It is important to know that lignin that is
usually separated in process strategies like aqueous phase reforming of sugars and
fermentation of sugars is simply burnt for power.
The major reaction happening is due to the lignin and as explained below it has two stages
of decomposition. As the temperature increases the lignin breaks down into high
molecular weight elements at temperatures around 250-350
o
C. These high molecular
weight elements are them broken down into low molecular weight elements at
temperatures around 450
o
C. These low MW substances emit secondary char.
250-350
o
C 450
o
C >500
o
C
Lignin High MW Low MW Secondary
char
Figure 4.10 Lignin Transformation Stages [26] [10]
Also a major component of bio-oil production is levoglucosan which is an intermediate
formed during high temperature pyrolysis of cellulose. This occurs at temperature beyond
450
o
C. ). Lignin inhibited the thermal depolymerization of levoglucosan formed from
cellulose and enhanced the formation of the low molecular weight products from
cellulose. Cellulose reduced the secondary char formation from lignin and enhanced the
formation of some lignin-derived products including guaiacol, 4-methyl-guaiacol, and 4-
vinyl-guaiacol.
57

Figure 4.11 Cellulose Lignin Interactions
4.3.1.6 Conclusion
The literature data matches the plant trial data obtained. Due to the low operation
temperature of the electrical heaters the reaction temperature never crossed 350
o
C. This
caused the following phenomenon.
 Lignin pyrolysis was triggered which caused deposits of high molecular weight
elements which in turn deposited as tar [25]. 

 Due to low reaction temperature cellulose reaction was not triggered thus leading
to low bio-oil yield [27] [14]. 

 The high amount of gasses in the reaction were justified by the high water content
in the biomass which also condensed as water along with the oil and tar. 
These observations were made and the corrective measures were put in place for the next
trial .Addition of a hot nitrogen pipeline to increase the reaction temperature. Nitrogen
acts as inert atmosphere reducing the oxygen content in the bio oil. Nitrogen also has the
secondary benefit of removing any form of clogging in the system.
58

4.3.2 Trials with electrical heating and N2 supply
There are certain disadvantages of running the reactor with only the electrical heating.
a) Presence of O2 in the reactor: Presence of oxygen results in formation of tar and
high water content in the output. The bio oil yield is minimal [14] [20].
b) Low heating temperature: the electrical heaters alone cannot raise the temperature
of the reactor to the optimum temperature required for pyrolysis [27].
c) High residence time: the residence time of the biomass has to be around 1 to 3
seconds [14] for fast pyrolysis and only then we obtain a good bio oil yield. But
due to heating only with the electric heaters, there is no way of reducing residence
time to the required value.
These problems can be solved by supplying N2 gas at very high temperatures like
700
0
C.
a) N2 provides inert atmosphere which reduces the oxygen content in the bio-oil.
b) High temperature of N2 results in the equilibrium temperature inside the reactor
being higher.
c) If we control the flow rate of the N2 supply, then we control the residence time.
4.3.2.1 Experimental data
The plant trials were performed on 19
th
April, 2014. The operating conditions were
assigned as:
 9 % moisture content feedstock: From the oven heating trials presented previously,
the moisture content is found to be at this equilibrium point. 

 Expected Pyrolysis Temperature at 500
0
C: This temperature is optimum for
pyrolysis. It was achieved by supplying N2 gas at around 650
0
C and additionally
heating the auger using the electrical heaters. 

 Auger Speed 5 RPM: Giving a very high auger speed gives excess char whereas
very low speeds gives high non condensable gasses. This RPM is set considering
the motor capacity, high auger screw friction and saw dust feed rate. 
59

4.3.2.2 Plant process description
• Measure the amount of Biomass material and Steel shots
• Mix the Biomass and Steel shots in the mass ratio of 1:2
• Fill the Hopper with the mixed feed
• Note the time of feeding
• Start the chilled water circulation
• Fill the ambient temperature water in the Ambient Water Heat Exchanger
• Start the electrical heaters and allow the temperature to reach 350°C
• Supply N2 gas at high temperature and wait till the auger reaches 500
0
C
• Run the Auger Shaft
• Empty the Hopper
• Fill the hopper again with Biomass and steel shots
• Start the suction pump
-
4.3.2.3 Initial trials
 The auger reactor temperature falls due to the flow of ambient temperature N2
gas through the reactor which is being heated by the electric heaters. 

 On supplying N2 gas, there were sparks coming out of the char collection
chamber. This could result in a major fire accident when the feed rate and
reactor temperature are very high. 

 The N2 was rerouted to another pipeline so that it gets heated to the required
temperature without cooling down the reactor. But due to the high pressure of
the N2 gas, the weld joints in this pipeline failed and the N2 was released out with
an explosion. This could have been fatal if the N2 had attained very high
temperatures. 
60

Figure 4.12 Puncture in the N2 pipeline
4.3.2.4 Final Trials
Based on the initial trials with nitrogen further improvements were made to the
experimental setup to increase safety and temperature of the nitrogen delivery
 The pressure of Nitrogen was reduced to 1.5 bar to better regulate the gas flow. 

 The joints were reinforced with additional welding to prevent high temperature
breakdown 

 Additional glass wool insulation was done on the auger to prevent temperature
loss 
4.3.2.5 Feedstock Performance
The same parameters were used to run the trial in addition with nitrogen. The nitrogen
plant took approximately 4 hours to achieve the required temperature of 653
o
C at 1.5 bar
pressure. To prevent any accidents the nitrogen was allowed to heat parallel to the
electrical heaters so that both can be operated simultaneously. To prevent blockage lower
feed rate was used starting with 1kg and the steel shots of 2kg.
The chiller plant was also run parallel to the heater to achieve condensing temperature of
10
o
C. Due to the high sink temperature the chiller could only achieve 22
o
C and the
ambient water temperature was 37
o
C.The auger was run at a low speed of 5 RPM to
allow the feedstock to undergo complete pyrolysis. Each feed took approximately 15
minutes to travel the length of the reactor. Once all the steel shots were collected at the
61

char box the shots were recycled and feed again with the next feed. The bio-oil condenser
pump was switched on immediately after the feeding.
Figure 4.13 The auger reactor after complete glass wool insulation
The Nitrogen inlet temperature was 653
o
C but due to the pipe losses the actual delivery
temperature at the inlet of the auger was lower. The inlet temperature at the auger was
~329
o
C and the exit temperature was ~230
o
C .The plant was run for a total time of 3.5
hours in which a mass of 5 kg of saw dust was fed to the auger. The char weight was
approximately ~20% by mass of the feedstock. The liquid products obtained were
distributed into the three condensing tanks. At the end of each feed trial the products were
flushed out and weighed. The char also was regularly cleaned and measured at the end of
every trial.
62

Figure 4.14 Nitrogen control panel with furnace temperature set at 715
o
C
Table 4.6 Raw data from electrical with nitrogen heating trials
Run Biomass Steel Feed Feed Inlet Outlet Outlet Auger Nitrogen
No. Feed
shots
Time Rate Temperature Temperature Reactor Air Speed Flow
mass
(surface) (surface) Temperature Rate
(kg) (kg) (min) (kg/hr) (°C) (°C) (°C) (rpm) (lpm)
1 1 2 13 4.61 328 316 230 5 0.5
2 1 2 16 3.75 329 315 244 5 0.5
3 1 2 18 3.33 329 315 229 5 0.5
4 1 2 14 4.28 330 314 230 5 0.5
5 1 2 20 3 329 315 222 5 0.5
63

Table 4.7 Product distribution of final trials
Run No. Bio-Oil Bio-Char Uncondensed +
Escaped gases
Mass Yield Mass Yield Mass Yield
Tank 1 Tank 2 Tank 3
(g) (g) (g) (%) (g) (%) (g) (%)
1 29 30 100 15.9 210 21 631 63.1
2 30 24 120 17.4 200 20 626 62.6
3 31 26 128 18.5 320 32 495 49.5
4 22 20 110 15.2 230 23 618 61.8
5 25 29 130 18.4 280 28 536 53.6
4.3.2.6 Products obtained
Figure 4.15 bio-oils obtained in each tank
 There was considerable change in the reaction parameters which was clearly
reflected in the products obtained from each tank. There were no tar deposits and
bio-oil samples in all three tanks. 

 The distribution of products in the tanks were 137g , 129g and 588g in tank 1 to
3 respectively 
64

 Each tank showed different water content with the first tank being the most dilute
and the third tank being viscous. 

 All three samples were subjected to gravity separation, the oil from the third tank
showed phase separation 

 The samples from all the three tanks were subjected to further tesing and
characterization. 

4.4 Product Characterization
4.4.1 Solubility Test
Water solubility
Pyrolysis oils are mixture of many organic and inorganic compounds. The solubility of
the fractions varies depending on the compounds in the oil. Lignin derivatives are
usually water insoluble and comprise of 20% of the liquid. The water in the bio-oil
ranges from 20-30% wt [28]. The image below shows a typical phase separation graph
for a pyrolysis oil.
Figure 4.16 Phase separation graph of pyrolysis oil [29]
65

The line at the top right corner represents the single phase of the liquid, addition of water
causes phase separation at 25%. Two distinct layers are formed, the top layer being the
aqueous layer and the bottom layer being the organic layer. Further addition of water
causes separation of lignin derivatives from the aqueous phase.
Organic and inorganic solubility
Solubility of bio-oil depends mainly upon the polarity of the compounds in the bio-oil.
There are polar and non-polar components in bio-oil but majority is polar. Thus bio-oil is
mostly completely soluble in low molecular weight alcohols such as methanol and ethanol
[28]. Unlike conventional fuels bio-oil does not dissolve in hexane or diesel.
The sample was also tested for organic and inorganic solvent solubility. First the sample
was passed through Whatman number 42 filter paper to remove any existing solid
particles. Then it was tested for solubility in Methanol (organic) and Chloroform
(inorganic). Sample from each tank was taken and tested for solubility and the results are
shown in table 4.7. It is clear that tank one contains a polar organic material as it is
soluble in methanol. Tank 2 is soluble in chloroform thus indicating no presence of polar
compound. The third tank had shown phase separation, each layer was tested indicating
that the lower layer is possibly the polar bio-oil that is produced. To further analyze the
organic composition of the materials they are sent for GC/MS analysis.
Table 4.8 Results of Solubility Test
Methanol Chloroform
(Organic) (Inorganic)
Contents in Tank 1 Soluble Insoluble
Contents in Tank 2 Insoluble Soluble
Contents in Tank 3
Top Layer Insoluble Soluble
Bottom Layer Soluble Insoluble
66

Figure 4.17 Whatman number 42 Filter paper
4.4.2 Solid Content
The solid content of the bio-oil is an important fuel property as it affects combustion
behavior and particulate emissions. All three samples from each tanks were mixed
homogeneously using an agitator, the obtained sample was sent for centrifuge. To test the
presence of solid contents in the bio oil obtained, a centrifuge was used. 1.75 ml of bio oil
was taken in a small test tube and centrifuged at 5000 rpm for 10 minutes. At the end
there were three layers, two layers of bio oil and solid particulate matter at the bottom.
The solid part obtained was 5.71% by volume.
67

Figure 4.18 Centrifugation Equipment
Figure 4.19 (a) Before centrifuge Figure 4.19 (b) After centrifuge
68

4.4.3 GC/MS characterization of Bio-oil
The GC-MS analysis was carried out with two phases that were obtained with a
centrifugal separator: the upper phase and the lower phase. Table -1 and 2 show the
qualitative and relative peaks areas of the GC-MS total ion chromatograms of the bio-oils
obtained from Auger reactor experiment. In the table, only major compounds of the bio-
oils are listed. The major compounds of saw dust bio-oil were phenolics, acetic acid,
levoglucosan, guaiacol, alkyl guaiacol, alcohols, ketones, and Aldehydes, etc [28]. The
compounds identified in this study are similar to those in other bio-oils produced through
fast pyrolysis[30].
BO1-Bio-oil from tank three upper layer.
BO3- Bio-oil from tank three lower layer.
BO4- Bio-oil from tank one.
From the graphs we can see that BO1 and BO3 have clear peaks corresponding to each
elements. The major component corresponding to each peak is shown in the table. There
is a trace of Hentriacontane found is each sample. This is a long chain hydrocarbon found
commonly in plants and wax. The trace of this element proves that there is still presence
of plant material in the products. The long chain high molecular weight compounds have
to be further broken down into lower molecular weight elements. This can only be
achieved my higher temperature maintained in the auger reactor.
69

Figure 4.20 Representation of GC Chromatogram of saw dust bio-oil
Tank 3 upper layer-BO1
70

Figure 4.21 Representation of GC chromatogram of saw dust bio oil
Tank 3 bottom layer-BO3
71

Figure 4.22 Representation of GC chromatogram of saw dust bio oil
Tank 1-BO4
72

Table 4.9: Representation of GC-MS analysis of bio-oil from BO3
S.No: Components (% area) Rice straw
(Bio-oil)
RT
1. DODECANE 7.23
2. PROPANOIC ACID 8.79
3. HENTRIACONTANE 8.94
4. DODECYL 2-ETHYLHEXYL ESTER 9.79
5. HEPTADECANE 10.21
6. HEPTATRIACTONTADIEN-2-ONE 10.40
8. 2-ETHYLHEXYL TETRADECYL ESTER 11.21
9. TRITETRACONTANE 11.55
10. 6-ETHYLOCT-3-YL ISOBUTYL ESTER 12.30
11. 6-METHYL-PENTADECANE 13.37
12. BUTYL OCTADECYL ESTER 13.55
13. 1,10-HEXADECANEDIOL 14.20
14. 2-AZIDO-2,4,4,6,6-PENTAMETHYLHEPTANE 14.50
15. EICOSANE 15.14
16. PENTATRIACONTANE 15.32
17. 2,4,6,8-TETRAMETHYL-, (ALL-R)-1- 15.57
OCTACOSANOL
18. OCTATRIACONTYL 16.10
PENTAFLUOROPROPIONATE
19. METHYL 9-METHYLTETRADECANOATE 17.46
21. METHYL 14-METHYL-EICOSANOATE 19.34
22. OCTADECANOIC ACID, 19.35
23. BUTYL OCTADECYL ESTER 21.11
24. DOTRIACONTANE 22.44
73

Table 4.10: Representation of GC-MS analysis of bio-oil from BO1
S.No: Components (% area) Saw dust
(Bio-oil)
RT
1. 1-HEXANOL 8.79
2. 4-METHYL, 2-UNDECENE 9.42
3. 2-ETHYLHEXYL OCTADECYL ESTER 9.79
5. 5,5-DIMETHYL-CYCLOHEX-3-EN-1-OL 10.86
7. 2,6,10,15-TETRAMETHYL-HEPTADECANE, 11.40
8. 3-METHYL-2-(2-OXOPROPYL)FURAN 11.97
9. HEXACOSANOL, ACETATE 12.40
10. 4,8-DIAZA-2,9-DIBENZOYL-5,6-DIPHENYL-2,8- 12.53
DECADIENEDIOIC ACID DIETHYL ESTER
11. 3-(3,3-DIMETHYLBUTYL)- SYDNONE 13.54
14. 1,54-DIBROMO-TETRAPENTACONTANE 14.69
15. 2-ETHYLHEXYL TRIDECYL ESTER 15.12
16. 1-FLUORO-DODECANE 15.78
17. HENEICOSANE 16.18
18. Z,Z-6,28-HEPTATRIACTONTADIEN-2-ONE 16.89
19. 1,54-DIBROMO-TETRAPENTACONTANE, 17.89
21. 1-O-(22-HYDROXYDOCOSYL)-D-MANNITOL, 20.37
22. DOTRIACONTANE 20.83
23. BUTYL HEPTADECYL ESTER 22.46
74

Chapter 5
Conclusion and Future work
75

5.1 Conclusion
The Auger reactor developed at CO2 Research and green technologies center is used to
perform fast pyrolysis on saw dust. The objective of the trials has been to pyrolyze agro-
biomass and produce bio-oil. The work documented in thesis explains the various trials
taken on the Auger reactor in different operating conditions. The goal has always been to
achieve a favorable yield and to showcase the functionality of a reactor of such a large
scale.
The main objectives of the wok have been completed and compared to existing literature.
Feedstock characterization showed moisture content of the sample a various conditions.
Proximate analysis concluded a moisture content of around 9.5 % and TGA analysis gave
a moisture content of 9.5%. Drying trials were also performed on the saw dust to
understand the equilibrium moisture content in the sample and was found to be 14%. Saw
dust is very hygroscopic and it is recommended to perform through drying before using it
in pyrolysis to reduce water in the bio-oil.
The trials performed can be classified into two sections. The first trials were based solely
on electrical heating and the second trials were with both electrical heating and hot
nitrogen supply. The first trials with electrical heating showed high tar output. The
reaction temperature was very low and the oxygen content in the reactor was high which
led to high tar and water output in the condensing tanks.
The second set of trials introduced hot nitrogen pipe to reduce the oxygen content in the
bio-oil and to increase the pyrolysis temperature. The results obtained were positive as
there was no tar formation and district homogeneous products were obtained in each tank.
Despite the positive results there were minor setbacks in the trials, the major one being the
nitrogen delivery system. Test trials with nitrogen initially led to minor problems in the
designs such as poor weld joints in the pipes and low insulation on the auger. These
problems were rectified and trials were performed with better insulation. The end results
from each tank were subjected to testing to understand the nature of the products obtained.
76

Product analysis included solubility test, solid content test and GC/MS analysis. Solubility
tests showed that the tank one and three contained a lot of polar organic compound.
Solubility in methanol proved that the product obtained had the physical similarity to bio-
oil. The centrifuge results showed a char content of 5% which was very less. GC/MS
results obtained were compared to literature .The major compounds of saw dust bio-oil
were phenolics, acetic acid, levoglucosan, guaiacol, alkyl guaiacol, alcohols, ketones, and
Aldehydes, etc. All the major functional groups present in bio-oil were present in the
results obtained. There were traces of hentriacontane which is a long chain hydrocarbon
found in plants and wax proving that there is still a need to attain higher reaction
temperatures to breakdown these long chain hydrocarbons. Thus after the physical and
chemical characterizations the products are concluded to be pyrolysis oils.
5.2 Recommendations for future work
 Further characterizations tests such as ultimate analysis can be performed on the
biomass to better track the reaction pathways leading to the products. 

 The temperature range of TGA analysis was 600
o
C which was insufficient to see
the char content in the products. Future work can increase the temperature range to
900
o
C. 

 Drying characteristics were performed just to attain the moisture content. Future
work can include drying models and comparative assessment to better understand
biomass drying. 

 The tar is a major side product obtained in the reactions. The tar can either directly
be used for roads or can be upgraded using hydrodeoxydation (HDO) in an
autoclave at high pressure. 

 The nitrogen plant can be moved closer to the auger reactor to reduce heat losses.
This also reduced the cost of insulating the pipelines. 

 Glass wool provided good insulation but there was considerable heat losses from
the auger. High temperature industrial sealant such as isofrax (1200
o
C) can be
used to seal the reactor. 
77

 There was high resistance at high RPM of the auger motor. This caused excessive
wear and tear in the couplings. High durability motor couplings can be installed to
prevent vibrations. 
78

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