pyrolysis of empty oil palm fruit bunches using the quartz
TRANSCRIPT
PYROLYSIS OF EMPTY OIL PALM FRUIT BUNCHES USING THE QUARTZ FLUIDISED-
FIXED BED REACTOR
A DISSERTATION SUBMITTED TO THE FACULTY OF SCIENCE UNIVERSITY OF MALAYA IN FULLFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE
MOHAMAD AZRI BIN SUKIRAN
FACULTY OF SCIENCE UNIVERSITY OF MALAYA
KUALA LUMPUR
2008
UNIVERSITI MALAYA
ORIGINAL LITERARY WORK DECLARATION
Name of Candidate: (I.C/Passport No: )
Registration/Matric No:
Name of Degree:
Title of Project Paper/Research Report/Dissertation/Thesis (“this Work”):
Pyrolysis of Empty Oil Palm Fruit Bunches using the Quartz Fluidised- Fixed Bed Reactor
Field of Study: I do solemnly and sincerely declare that:
(1) I am the sole author/writer of this Work;
(2) This Work is original;
(3) Any use of any work in which copyright exists was done by way of fair dealing and for permitted purposes and any excerpt or extract from, or reference to or reproduction of any copyright work has been disclosed expressly and sufficiently and the title of the Work and its authorship have been acknowledged in t is Work;
(4) I do not have any actual knowledge nor do I ought reasonably to know that the making of this work constitutes and infringement of any copyright work;
(5) I hereby assign all and every rights in the copyright to this Work to the University of Malaya (“UM”), who henceforth shall be owner of the copyright in this Work and that any reproduction or use in any form or by any means whatsoever is prohibited without the written consent of UM having been first had and obtained;
(6) I am fully aware that if in the course of making this Work I have infringed any copyright whether intentionally or otherwise, I may be subject to legal action or any other action as may be determined by UM.
Candidate’s Signature Date Subscribed and solemnly declared before, Withness’s Signature Date Name: Designation:
ACKNOWLEDGEMENT
I gratefully acknowledge and thank my supervisor Dr. Nor Kartini Abu Bakar, Lecturer
in Department of Chemistry, University of Malaya for helpful guidance, advice and
encouragement throughout this work. I am also very grateful to my co-supervisor Dr.
Chow Mee Chin, Senior Research Officer in the Malaysian Palm Oil Board (MPOB) for
advice and guidance in making this research possible. Their enthusiasm and expertise
inspired my work and guidance, suggestions and patience are greatly appreciated.
Thanks also to my family members and my friends for their encouragements and
supports. Also, I would like to thank the supporting staffs of Energy and Environment
Unit for their assistance in various ways.
I would like to thank Yang Berbahagia Dato’ Dr. Mohd Basri Wahid, Director General of
MPOB for his kind approval of my MPOB Post Graduate Research Assistantship.
i
ABSTRACT
In this study, pyrolysis of oil palm empty fruit bunches (EFB) was investigated using a
quartz fluidized-fixed bed reactor. The effects of pyrolysis temperatures, particle sizes,
heating rates, different oil palm biomass and different type of fluidised beds material on
the yields of the products were investigated. The temperature of pyrolysis and heating
rate were varied in the range 300-700 ºC and 10-100 ºC min-1 respectively. The particle
size was varied in the range of <90, 91-106, 107-125 and 126-250 µm. EFB, trunk, frond
and fiber were used to investigate effect of different oil palm biomass on pyrolysis yields.
Meanwhile, zircon sand, spent bleaching earth and spent bleaching earth washing with
hexane were used to investigate effect of different type of fluidised bed material on
pyrolysis yields.
The products obtained from pyrolysis of EFB were bio-oil, char and gas. The maximum
bio-oil yield was 42.28% obtained at 500 ºC, with a heating rate of 100 ºC min-1 and
particle size of 91-106 µm. The maximum product yield of char was 41.56% obtained at
pyrolysis temperature of 300 ºC, heating rate of 30 ºC min-1 and particle size of 91 – 106
µm. Meanwhile, the optimum yield of gas was 46.00% could be achieved at the pyrolysis
temperature of 700 ºC, heating rate of 30 ºC min-1 and particle size of 91 – 106 µm.
The calorific value, total ash, density, total acid, moisture content, pH and elemental
analysis of bio-oil were determined. Characterisation of the char includes calorific value,
surface area, total volume pore and elemental analysis. The gases detected were carbon
monoxide, carbon dioxide, methane, ethane and ethylene depending on the pyrolysis
temperature.
ii
ABSTRAK
Dalam kajian ini, pirolisis buah tandan kosong kelapa sawit dikaji menggunakan reaktor
kuartz “fludised-fixed bed”. Kesan pirolisis ke atas suhu, saiz partikel, kadar pemanasan,
penggunaan biojisim kelapa sawit yang berbeza-beza dan penggunaan “fluidized bed
material” yang berlainan ke atas produk pirolisis dikaji. Suhu dan kadar pemanasan yang
digunakan masing-masing di dalam julat 300-700 ºC dan 10-100 ºC min-1. Saiz partikel
yang digunakan pula adalah di dalam julat seperti berikut: <90, 91-106, 107-125 and 126-
250 µm. Buah tandan kosong, batang, pelepah dan serat kelapa sawit digunakan untuk
mengkaji kesan penggunaan biojisim yang berbeza ke atas hasil pirolisis. Sementara itu,
pasir zirkon, peluntur bumi terguna dan peluntur bumi terguna yang dibilas dengan
larutan heksana digunakan untuk mengkaji kesan “fluidised bed” yang berbeza ke atas
hasil pirolisis.
Produk-produk yang diperolehi daripada pirolisis buah tandan kosong adalah minyak-bio
(bio-oil) , arang (char) dan gas. Nilai maksimum bagi produk minyak-bio terhasil pada
suhu 500 ºC, dengan kadar pemanasan 100 ºC min-1 dan saiz partikel 91-106 µm iaitu
42.28%. Nilai maksimum bagi arang pula terhasil pada suhu 300 ºC, dengan kadar
pemanasan 30 ºC min-1 dan saiz partikel 91-106 µm iaitu 41.56%. Sementara itu, hasil
gas maksimum tercapai pada suhu 700 ºC, dengan kadar pemanasan 30 ºC min-1 dan saiz
partikel 91-106 µm iaitu sebanyak 46.00%.
Analisis-analisis untuk minyak-bio adalah seperti nilai kalori, jumlah abu, ketumpatan,
jumlah asid, kandungan air, nilai pH dan analisis untuk unsur. Analisis bagi arang pula
adalah seperti nilai kalori, luas permukaan, jumlah isipadu dan analisis unsur. Sementara
iii
itu, gas-gas yang didapati hadir adalah seperti karbon monoksida, karbon dioksida,
metana, etana dan etilena yang mana penghasilannya bergantung pada suhu pirolisis.
iv
TABLE OF CONTENTS
Contents: Page
Acknowledgement i
Abstract ii
Abstrak iii
Contents v
List of Table ix
List of Figure x
List of Abbreviations xi
Chapter 1: Introduction 1
1.1 Introduction 1
1.2 Biofuel in Malaysia 4
1.3 Objectives of this study 5
Chapter 2: Literature Reviews 8
2.1 Biomass as a source of renewable energy 8
2.2 Biofuel and its environmental impact 10
2.3 Properties and composition of biomass 12
2.3.1 Cellulose 13
2.3.2 Hemicellulose 14
2.3.3 Lignin 15
2.3.4 Inorganic Minerals 17
2.3.5 Organic Extractives 18
2.4 Empty Fruit Bunches (EFB) 18
2.5 Spend Bleaching Earth (SBE) 20
2.6 Type of pyrolysis 20
2.6.1 Slow pyrolysis 21
2.6.2 Fast pyrolysis 25
2.7 Pyrolysis products 29
v
2.7.1 Introduction of bio-oil 29
2.7.2 Characterisation of bio-oil 31
2.7.3 Char 32
2.7.4 Gas 33
2.8 Application for bio-oil 33
Chapter 3: Methodology 36
3.1 Introduction 36
3.2 Materials 36
3.2.1 Empty Fruit Bunches (EFB) 36
3.2.2 Oil Palm Trunk, Frond and Fiber 37
3.2.3 Zircon sand 37
3.2.4 Solvent 37
3.2.5 Spend Bleaching Earth 38
3.3 Methodology 38
3.3.1 Pyrolysis trial 38
3.3.2 Optimization of pyrolysis parameters 40
3.3.2.1 Effect of Temperature 40
3.3.2.2 Effect of Particle Size 41
3.3.2.3 Effect of Heating Rate 41
3.3.2.4 Effect of different Oil Palm Biomass Materials 41
3.3.2.5 Effect of different Fixed-bed 42
3.4 Characterisation of Empty Fruit Bunches (EFB) 43
3.4.1 Determination of Proximate analysis 43
3.4.2 Calorific Value 44
3.4.3 Elemental Analysis 44
3.5 Characterisation of bio-oil 45
3.5.1 Density (ASTM D 4052) 45
3.5.2 Ash (ASTM D 482) 46
3.5.3 Moisture Content-Karl Fischer Titration (ASTM D 1744) 47
3.5.4 Calorific value (ASTM D 240) 47
3.5.5 Acid value (ASTM D 664) 47
vi
3.5.6 pH 48
3.5.7 Gas Chromatography-Mass Spectroscopy (GC-MS) 48
3.5.8 Fourier Transform Infra-red (FTIR) 49
3.5.9 Elemental Analysis 50
3.6 Characterisation of char 50
3.6.1 Elemental Analysis 50
3.6.2 Calorific value (ASTM D 4809) 51
3.6.3 Surface area and total pore volume 51
3.7 Gas analysis 54
Chapter 4: Pyrolysis Products 57
4.1 Introduction 57
4.2 Results and Discussion 57
4.2.1 Effect of Temperature 57
4.2.2 Effect of Particle Size 60
4.2.3 Effect of Heating rate 62
4.2.4 Effect of different Oil Palm Biomass 64
4.2.5 Effect of different Type Fludised Bed 67
Chapter 5: Characterisation of Pyrolysis Products 70
5.1 Introduction 70
5.1.1 Characterisation of Empty Fruit Bunches (EFB) 71
5.2 Results and Dicussion 73
5.2.1 Characterisation of Bio-oil Product 73
5.2.1.1 Physical Properties of Bio-oil 73
5.2.1.2 FTIR Analysis of Bio-oil 86
5.2.1.3 GC/MS Analysis of Bio-oil 89
5.2.2 Characterisation of Char Product 98
5.2.3 Influence of Temperature on Gas Products 104
Chapter 6: Conclusion and Recommendations 107
6.1 Conclusion 107
vii
6.2 Recommendations 110
References 113
List of Publications 119
Appendix 120
viii
LIST OF TABLE
Table 2.1 Typical Mineral Components of Plant Biomass 17
Table 2.2 Nutrient Content of Empty Fruit Bunches (EFB) 18
Table 2.3 Typical Composition of Different Biomass Resources 19
Table 2.4 Pyrolysis Method and their Variants 21
Table 2.5 A Summary of Researcher Pyrolysis of Biomass 28
Table 2.6 Standard Methods Properties of Bio-oil Product 31
Table 2.7 Typical Properties of Bio-oil, Compared to Heavy Fuel Oil 32
Table 4.1 The Comparison of Pyrolysis Product Yields at Different Temperature 57
Table 4.2 The Comparison of Pyrolysis Product Yields at Different Particle Size 60
Table 4.3 The Comparison of Pyrolysis Product Yields at Different Heating Rate 62
Table 4.4 The Comparison of Pyrolysis Product Yields Using Different Oil Palm Biomass
64
Table 4.5 Typical Composition of Different Oil Palm Biomass Materials 66
Table 4.6 The Comparison of Pyrolysis Product Yields Using Different Type of Fluidised Bed
67
Table 5.1 Main Characteristics of the Treated Oil Palm Empty Fruit Bunches (EFB)
71
Table 5.2 Properties of Bio-oil Product According to Different Temperature 73
Table 5.3 Properties of Bio-oil Product According to Different Particle Size 73
Table 5.4 Properties of Bio-oil Product According to Different Heating Rate 74
Table 5.5 Elemental Analysis of Bio-oil Product According to Different Temperature
81
Table 5.6 Elemental Analysis of Bio-oil Product According to Different Particle Size
82
Table 5.7 Elemental Analysis of Bio-oil Product According to Different Heating Rate
84
Table 5.8 Possible Chemical Compounds of Bio-oil According to the GC/MS Analysis of Different Temperature
92
Table 5.9 Possible Chemical Compounds of Bio-oil According to the GC/MS Analysis of Different Particle Size.
94
Table 5.10 Possible Chemical Compounds of Bio-oil According to the GC/MS Analysis of Different Heating Rate
96
Table 5.11 Properties of Char Product According to Different Temperature. 98
Table 5.12 Properties of Char Product According to Different Particle Size 99
Table 5.13 Properties of Char Product According to Different Heating 100
ix
LIST OF FIGURE
Figure 1.1 Outline of this Study 6
Figure 2.1 General Components in Plant Biomass 12
Figure 2.2 Chemical Structure of Cellulose 13
Figure 2.3 Scheme of Glucosan Radical to Produces Levoglucosan 14
Figure 2.4 Main Components of Hemicellulose 15
Figure 2.5 Chemical Structures of Lignin 17
Figure 3.1 Schematic Diagram of the Pyrolysis System 39
Figure 4.1 Effect of Temperature on Pyrolysis Yields 58
Figure 4.2 Effect of Particle Size on Pyrolysis Yields 60
Figure 4.3 Effect of Heating Rate on Pyrolysis Yields 63
Figure 4.4 Effect of Different Oil Palm Biomass on Pyrolysis Yields 65
Figure 4.5 Effect of Different Fluidised Bed on Pyrolysis Yields 68
Figure 5.1 Effect of Temperature on Calorific Value and Yield of Bio-oil 77
Figure 5.2 Effect of Particle Size on Calorific Value and Yield of Bio-oil 78
Figure 5.3 Effect of Heating Rate on Calorific Value and Yield of Bio-oil 79
Figure 5.4 Effect of Temperature on Oxygen and Carbon Content of Bio-oil 82
Figure 5.5 Effect of Particle Size on Oxygen and Carbon Content of Bio-oil 83
Figure 5.6 Effect of Heating Rate on Oxygen and Carbon Content of Bio-oil 85
Figure 5.7 FTIR Spectra of Bio-oil at Different Temperature 87
Figure 5.8 FTIR Spectra of Bio-oil at Different Particle Size 87
Figure 5.9 FTIR Spectra of Bio-oil at Different Heating Rate 88
Figure 5.10 Effect of Temperature on Oxygen and Carbon Content of Char 101
Figure 5.11 Effect of Particle Size on Oxygen and Carbon Content of Char 102
Figure 5.12 Effect of Heating Rate on Oxygen and Carbon Content of Char 103
Figure 5.13 Gases Emitted as the Temperature was Increased 106
x
LIST OF ABBREVIATIONS
% Percentage
β Beta
µm Micro meter
8MP Eighth Malaysian Plan
º C Degree Celsius
º K Kelvin
ASTM American Society for Testing and Materials
CHON Carbon, Hydrogen, Oxygen and Nitrogen
cm Centimeter
cm3 Centimeter cubes
CO Carbon Monoxide
CO2 Carbon Dioxide
DTA Differential Thermal Analysis
EFB Empty Fruit Bunches
EU European Union
FFB Fresh Fruit Bunches
FTIR Fourier Transform Infrared
g Gram
GC Gas Chromatography
GCMS Gas Chromatography Mass Spectroscopy
H2SO4 Acid Sulfuric
HCl Hydrochloric
HNMR Proton Nuclear Magnetic Resonance
HNO3 Nitric Acid
IR Infrared
kg Kilogram
M Molar
min Minute
min-1 Per minute
MJ/Kg Mega Joule per kilogram
xi
ml Mililitre
mm Millimeter
MPOB Malaysian Palm Oil Board
N2 Nitrogen
NO Nitrogen Monoxide
OPP3 Third Outline Perspective Plan
POME Palm Oil Mill Effluent
SBE Spent Bleaching Earth
SO2 Sulphur Dioxide
t EFB hr-1 Tonnes Empty Fruit Bunches per hour
t FFB hr-1 Tonnes Fresh Fruit Bunches per hour
wt Weight
xii
Introduction
CHAPTER 1
INTRODUCTION
1.1 Introduction
Oil palm (Elaeis guineensis) was introduced in Peninsular Malaysia in 1870, and
was commercially exploited in the 1900s. Nowadays, oil palm was the most
economically attractive crop in Malaysia. With a total planted area of 4.2 million
hectares, oil palm plays a prominent role in the socio-economic and well being of the
country (MPOB, 2006).
Biomass is an important contributor to the world economy. Today, various forms
of biomass energy are consumed all over the world. Biomass provides a clean, renewable
energy source that could dramatically improve the environment, economy and energy
security. In developing countries, the use of biomass is of high interest, since these
countries have economy largely based on agriculture and forestry. The use of these
materials will depend on the state of the art of safe economic technologies which be able
to transform them into manageable products (Sensoz et al., 2006). At present the palm oil
industry generates the most biomass from the oil extraction process such as the mesocarp
fiber, shell, empty fruit bunch (EFB) and palm oil mill effluent (POME). About 9.9
million tons of palm oil wastes are generated every year in Malaysian alone, and this
keep increasing at 5% annually (Yang et al., 2006).
In Malaysia, there is a voluminous amount of various palm biomass. While much
research has been carried out to utilise them for manufacture of value-added products, its
1
Introduction
commercial utilization is not widespread; some are returned to the field as mulch. As
fossil fuel gets depleted, exploitation of biomass as a renewable materials by conversion
to a transportable form of green fuel could potentially place Malaysia as a producer of
renewable energy; besides the utilisation of the palm oil as fuel, pyrolysis of the biomass
into high value energy resource is attractive as it may eventually become a secondary
commodity besides palm oil. Certain crops have been adopted as renewable sources in
the production of liquid fuels because of the ease of production and supply advantages.
Biomass may vary in its physical and chemical properties due to its diverse origin
and species. However, biomass is structurally composed of cellulose, hemicellulose,
lignin, extractives and inorganics. From the chemistry point of view, biomass is
composed of series of long chain hydrocarbons with functional groups such as hydroxyls
and carboxyls.
Experiment with biomass fuels has indicated that one of the promising renewable
energy sources is vegetable oil, a simple product of solar energy. In fact when Rudolf
Diesel first developed the engine that bears his name in 1895, he intended to use fuels
like vegetable oils rather than petroleum to run the engine.
Pyrolysis is one of the most promising technologies of biomass utilization, and it
is also the first stage of biomass thermochemical conversion, which converts biomass
resource to bio-oils, char and gases of which depend on pyrolysis condition. Pyrolysis
maybe described as a thermal degradation of materials in the complete absence on
inadequate presence oxygen (Ozbay et al., 2006). More recently, pyrolysis is meant for
2
Introduction
liquid production although char and gas are also obtained as by-product (Kawser et al.,
2004). However, it is essentially a complex process.
Among the thermochemical process, pyrolysis has become an alternative because
of the ease of operation. The yields and compositions of end products of pyrolysis are
highly dependent on biomass species, chemical and structural composition of biomass,
temperature, heating rates, reactors, particles size, co-reactant and others. To achieve an
advanced process for improving product yields from pyrolysis of selected biomass, in-
depth investigations on the mechanism of biomass pyrolysis are needed.
The liquid product, pyrolytic oil, approximates to biomass in elemental
composition, and is composed of a very complex mixture of oxygenated hydrocarbons,
reflecting the oxygen contents of the original substrates. These products are usually quite
reactive and their characteristics change rapidly (Gercel, 2002a). Bio-oils are generally
preferred products because of their high calorific values, their ease of transportation and
storage, their low nitrogen and sulphur content and their opportunity to be converted into
chemicals. It is useful as a fuel, may be added to petroleum refinery feedstocks or
upgraded by catalysts to produce premium grade refined fuels, or may have a potential
use as chemical feedstocks.
The solid product, char, can be used as a fuel either directly as briquettes or as
char–oil or char–water slurries since it has a high calorific value or it can be used as
feedstocks to prepare activated carbons. The gas generated has a high content of
hydrocarbons and sufficiently high calorific value to be used for the total energy
requirements of a biomass pyrolysis plant (Karaosmanoglu et al., 1999).
3
Introduction
1.2 Biofuel program in Malaysia
Presently, non-renewable fossil fuels, such as petroleum and its derivatives, coal
and natural gas, are the primary sources of energy worldwide. However, such fuels emit
among others, carbon dioxide (CO2), which gives rise to greenhouse effect in the
atmosphere, contributing to global warming and long-term climate change. As a result,
there are continuous global efforts and initiatives to protect the environment, notably
commitment under the Kyoto Protocol (1997) to reduce greenhouse gas emission to an
average of 5% below levels. The European Union (EU) too has a set target to gradually
increase the use of biofuel in the transport sector from 2% of the total diesel consumption
in 2005 to 5.75% by 2010. Consequently, world demand for biofuel has increased
(Economic Report, 2006/2007).
The main advantages of using this biofuel are its renewability, better quality
exhaust gas emission, its biodegradability and, it does not contribute to a net rise in the
level of CO2 in the atmosphere, and consequently to the green house effect (Sensoz et al.,
2006).
The implementation of biofuel program in Malaysia is in line with the
Government policy of ensuring sustainable development of the energy sector as well as
promoting a cleaner environment. For examples, the Government has embarked on the
growth of renewable energy as the fifth fuel after oil, gas, hydro, and coal, initiated
earlier under the Third Outline Perspective Plan (OPP3), 2001-2010 and the Eighth
Malaysian Plan (8MP), 2001-2005. Biodiesel from palm oil was earmarked as a
promising renewable energy in line with the Government’s fifth fuel policy.
4
Introduction
Malaysia is blessed with natural resources, particularly crude oil and natural gas,
which are the main sources of energy. However, these are depleting energy resources and
increasing demand has made it necessary for the Government to embark on alternative
energy sources. Rising crude oil prices have led to higher government expenditures on
subsidies to keep retail fuel prices at relatively low levels. Consequently, biodiesel as an
alternatives energy source has become more viable. In addition, palm oil is a more
competitive alternative to rapeseed, soybean and sunflower oils as feedstock in the
production of biodiesel. In terms of oil yield per hectare per year, palm oil (3.8
tonne/hectare) is significantly higher than rapeseed oil (1.3 tonne/hectare) and soybean
oil (0.5 tonne/hectare). Hence, palm oil-based biodiesel has enormous export potential as
it can be competitively priced against its major competitors (Economic Report,
2006/2007).
1.3 Objectives of this study
In this study, empty fruit bunches (EFB) were chosen as the biomass source. Its
pyrolysis was conducted under different conditions in a fluidised-fixed bed reactor.
Particularly, the influence of the final pyrolysis temperature, heating rate, particle size,
different oil palm biomass materials and different fluidised bed material on the pyrolysis
yields were investigated. Characterisation of the bio-oil and char products was also
studied in order to determine its possibility of being a potential source of renewable fuel
and chemical feedstock. The outline of this study is given in Figure 1.1.
5
Introduction
Bio-oils GasChar
EFB
Temperature Heating Rate Particle Size Different fluidised bed material
Different oil palm biomass
materials
Pyrolysis Products
Parameter
PYROLYSIS
Figure 1.1 Outline of this study.
6
Introduction
Objectives of Research:
1. To investigate the effect of various pyrolysis parameters on product yields
2. To characterize liquid product, char and gases obtained under different
condition.
This dissertation is organized in the following manner: Following the brief
introduction regarding the biofuels industry in Malaysia, source of biomass and pyrolysis
process in the Chapter 1, the literature review of pyrolysis of biomass is presented in the
Chapter 2.
Chapter 3 details the experimental procedure and characterization techniques of
pyrolysis products (bio-oil, char and gas). Chapter 4 deals with the results and discussion
on the pyrolysis yields under different conditions. The results and discussion of
characterisation of pyrolysis products are presented in the final chapter (Chapter 5).
7
Literature Review
CHAPTER 2
LITERATURE REVIEW
2.1 Biomass as a source of renewable energy Biomass, the name given to the plant matter which is created by photosynthesis,
includes firewood plantations, forestry residues, animal waste, agricultural residues, etc.
Photosynthesis involves the use of energy in sunlight to convert carbon dioxide (from air)
and water into carbohydrates, which are a source of chemical energy. The supply of
energy from biomass plays an increasing role in the debate on renewable energies. The
relative large amount of biomass has already used for energy generation that reflects
mainly the use of wood and traditional fuels in the developing countries. Nevertheless,
the use of biomass in industrialised countries is also significative (Zanzi, 2001, Gercel,
2002a). In particular, Malaysia generated about 9.9 million tons of palm oil waste as a
main of biomass sources included empty fruit bunch (EFB), shell and fiber, which keep
increasing at 5% annually (Yang et al., 2006).
The energetic and industrial usage of biomass is becoming more and more
technologically and economically attractive. The use of biomass offers the advantages of
benefits, such as biomass is available in every country in various forms. Thus, assures a
secure supply of raw material to the energy system. Maintaining biomass as a significant
contributor to the national energy supply is for many countries, the best way of ensuring
greater autonomy and cheap energy for the industry. From environmental benefits, the
utilization of biomass for energy is an alternative for decreasing current environment
problems such an increase of CO2 in the atmosphere caused by the use of fossil fuels
8
Literature Review
(Li et al., 2008). Furthermore, biofuels contain minimal sulphur, thus avoiding SO2
emissions. To be successful, alternative fuels need to give low emission and rival
gasoline and diesel in terms of cost, supply, distribution, delivery to vehicles, on-board
storage and power density.
9
Literature Review
2.2 Biofuel and Environmental impact
Atmospheric gases such as carbon dioxide, nitrous oxide and methane can
regulate temperature of the earth. These greenhouse gases particularly CO2 allow energy
from the sun to penetrate to the earth, but trap the heat radiated from the earth’s surface.
Researchers, scientists and others are concerned about those gases being emitted to
atmosphere by human activities which will increase the global warming at a rate
extraordinary in human history. The CO2 emission from the usage of fossil fuels that
provide about 85% of the total world demand for primary energy, cause an increase of the
CO2 concentration in the atmosphere (Zanzi, 2001).
The use of biomass fuels in a closed carbon cycle as a substitute for fossil fuels, is
one of the most promising ways for tentative the increase of the CO2 concentration.
Biomass fuels make no net contribution to atmospheric CO2 if used sustainable to allow
regrowth (Onay et al., 2001). Biomass plays a significant role in reducing CO2 by acting
both as a reservoir of carbon, absorbing CO2 from the atmosphere during growth and as
direct substitute for fossil fuels. Furthermore, reforestations and introduction of
alternative crops are needed to stop and revert phenomena like erosion and desertification
(Zanzi, 2001, Gercel 2002a).
Emission of mainly sulphur dioxide, nitrous oxide and hydrochloric gases to
atmosphere can caused acid rain. Sulphur oxides and nitrogen oxides can be transformed
in the atmosphere to H2SO4 and HNO3. Sulphur oxides are produced in combustion of
sulphur–bearing fuels such as petroleum and coal. Sulphur oxides emission from the
utilization of biomass fuel is negligible because biomass contains minimal sulphur.
10
Literature Review
Another acidic gaseous pollutant is hydrochloric acid (HCl) gas, produced from
chlorine and mainly associated with combustion of municipal wastes. HCl also plays an
important role for dioxin formation during combustion.
Special attention is being paid to the nitrogen oxides emission from combustion of
nitrogen-containing fuels such as biomass, coal, peat or municipal waste. The nitrogen
oxides emission from combustion of a nitrogen-containing fuel comes from two sources,
thermal nitrogen oxides and fuel nitrogen oxides. The formed from the nitrogen in the
combustion air and its formation is more or less dependent on the temperature and
pressure in the combustor. The latter comes from the oxidation of nitrogen in the fuel and
is not particularly temperature sensitive. All the oxides of nitrogen also enhance the
greenhouse effect.
During gasification, the fuel-nitrogen mainly forms ammonia (NH3). Some
hydrogen cyanide (HCN) and nitrogen monoxide (NO) may also be formed. During
combustion of the gases, ammonia and cyanides undergo oxidation to nitrogen oxides the
pyrolysis in the initial step in both gasification and combustion.
During pyrolysis part of the nitrogen in the fuel is converted to ammonia as a
main product, hydrogen cyanide (HCN) and nitric oxide (NO). The conversion of
nitrogen may be also form N2. Other part of the nitrogen remains in the char (Zanzi,
2001).
11
Literature Review
2.3 Properties and composition of biomass
The chemical composition of biomass is very different from that of coal oil, oil
shales, etc. The presence of large amounts of oxygen in plant carbohydrate polymers
means the pyrolytic chemistry differs sharply from these other fossil feeds. Plant biomass
is essentially a composite material constructed from oxygen-containing organic polymers.
The major structural chemical components with high molar masses are carbohydrate
polymers and oligomers and lignin. Minor low-molar-mass extraneous materials mostly
organic extractives and inorganic minerals are also present in biomass. The major
constituents consist of cellulose (a polymer glucosan), hemicelluloses (also called
polyose), lignin, organic extractives, and inorganic minerals. The outline of general
components in plant biomass is given in Figure 2.1.
Figure 2.1. General components in plant biomass
Macromolecular substances
Polysaccharides
Cellulose Hemicellulose
Inorganic matter
Organic matter
Ash Extractives
Lignin
Low-molecular-weight substances
Plant Biomass
Figure 2.1: General Component in Plant Biomass.
12
Literature Review
2.3.1 Cellulose
Cellulose is a high molecular-weight (106 or more) linear polymer of β-(1→4)-D-
glucopyranose units in the 4C1 conformation. The fully equatorial conformation of β-
linked glucopyranose residues stabilizes the chair structure, minimizing flexibility.
Glucose anhydride, which is formed via the removal of water from each glucose, is
polymerized into long cellulose chains that contain 5000-10000 glucose units. The basic
repeating unit of the cellulose polymer consists of two glucose anhydride units, called a
cellobiose unit. Cellulose consists of between 2000 and 14000 residues which is
crystalline. A chemical structure of cellulose is shown in Figure 2.2.
Figure 2.2: Chemical Structure of Cellulose.
Cellulose forms long chains that are bonded to each other by a long network of
hydrogen bonds. Groups of cellulose chains twist in space to make up ribbonlike
microfibril sheets, which are the basic construction units for a variety of complex fibers.
These microfibrils form composite tubular structures that run along a longitudinal tree
axis. The crystalline structure resists thermal decomposition better than hemicelluloses.
Amorphous regions in cellulose exist that contain waters of hydration, and free water is
present within the wood. This water, when rapidly heated, disrupts the structure by a
steam explosion-like process prior to chemical dehydration of the cellulose molecules.
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Cellulose degradation occurs at 240-350 °C to produce anhydrocellulose and
levoglucosan. When cellulose is pyrolyzed at a heating rate of 12 °C/min under helium
gas, an endotherm is observed at 335 °C (temperature of maximum weight loss). The
reaction is completed at 360 °C. Levoglucosan is produced when the glucosan radical is
generated without the bridging oxygen from the preceding monomer unit (Mohan et al.,
2006). The scheme of glucosan radical to produce levoglucosan is given in Figure 2.3.
Figure 2.3: Scheme of Glucosan Radical to Produces Levoglucosan.
2.3.2 Hemicellulose
A second major wood chemical constituent is hemicellulose. Hemicellulose is a
mixture of various polymerized monosaccharides such as glucose, mannose, galactose,
xylose, arabinose, 4-O-methyl glucuronic acid and galacturonic acid residues.
Hemicelluloses exhibit lower molecular weights than cellulose. The number of repeating
saccharide monomers is only ∼150, compared to the number in cellulose (5000-10000).
Cellulose has only glucose in its structure, whereas hemicellouse has a
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heteropolysaccharide makeup and some contains short side-chain “branches” pendent
along the main polymeric chain.
The onset of hemicellulose thermal decomposition occurs at lower temperatures
than crystalline cellulose. The loss of hemicellulose occurs in slow pyrolysis of wood in
the temperature range of 130-194 °C, with most of this loss occurring above 180 °C.
However, the relevance of this more rapid decomposition of hemicellulose versus
cellulose is not known during fast pyrolysis, which is completed in few seconds at a rapid
heating rate. Main components of hemicellulose are given in Figure 2.4.
Figure 2.4: Main Components of Hemicellulose.
2.3.3 Lignin
The third major component of wood is lignin. Lignin is the most abundant
polymeric aromatic organic suctance in the plant world. Lignin occurs together with
cellulose and other polysaccharides in the cell walls of the plants, particularly in woody
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plants where lignin accumulates between cellulose microfibrils in the middle lamelle and
the primary and secondary walls of the xylem elements. Unlike cellulose, lignin is a
highly cross-linked polyphenolic polymer without any ordered repeating units (Sharma et
al., 2004).
A typical structure of lignin is shown in Figure 2.5. The most common
monomeric unit in lignin is a phnylpropanoid unit linked to other units via ether linkages
as well as carbon-to –carbon bonds.
Lignin is a three-dimensional, highly branched, polyphenolic substance that
consists of an irregular array of variously bonded “hydroxy-” and “methoxy- ”substituted
phenylpropane units. These three general monomeric phenylpropane units exhibit the p-
coumaryl, coniferyl, and sinapyl structures. Lignin has an amorphous structure, which
leads to a large number of possible interlinkages between individual units, because the
radical reactions are nonselective random condensations.
The physical and chemical properties of lignins differ, depending on the
extraction or isolation technology used to isolate them. Because lignin is inevitably
modified and partially degraded during isolation, thermal decomposition studies on
separated lignin will not necessarily match the pyrolysis behavior of this component
when it is presented in the original biomass. Lignin decomposes when heated at 280-500
ºC. Lignin pyrolysis yields phenols via the cleavage of ether and carbon-carbon linkages.
Lignin is more difficult to dehydrate than cellulose or hemicelluloses. Lignin pyrolysis
produces more residual char than does the pyrolysis of cellulose (Mohan et al., 2006).
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Figure 2.5: Chemical Structures of Lignin
2.3.4 Inorganic Minerals
Biomass also contains a small mineral content that ends up in the pyrolysis ash.
Table 2.1 shows some typical values of the mineral components in plant biomass,
expressed as a percentage of the dry matter.
Table 2.1: Typical Mineral Components of Plant Biomass
Element Percentage of dry matter Potassium, K 0.10 Sodium, Na 0.02 Phosphorus, P 0.02 Calcium, Ca 0.20 Magnesium, Mg 0.04
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2.3.5 Organic Extractives
A fifth biomass component is comprised of organic extractives. These can be
extracted from biomass with polar solvents such as water, methylene chloride, or alcohol
or nonpolar solvents such as toluene or hexane. Example extractives include fats, waxes,
alkaloids, proteins, phenolics, simple sugars, pectins, mucilages, gums, resins, terpenes,
starches, glycosides, saponins, and essential oils. Extractives function as intermediates in
metabolism, as energy reserves, and as defenses against microbial and insect attack.
2.4 Empty Fruit Bunches (EFB)
Empty fruit bunches (EFB) of oil palm is one of the major solid wastes from oil
palm industry in Malaysia besides fiber and shell. EFB is another valuable source of
biomass that can be readily converted into energy. Table 2.2 shows some typical nutrient
content of empty fruit bunches, expressed as a percentage of the dry matter. The weight
percent of cellulose, hemicellulose, and lignin varies in different biomass species (Mohan
et al., 2006). Table 2.3 shows a typical composition of EFB compared with another palm
biomass materials.
Table 2.2: Nutrient content of empty fruit bunches (EFB). Element Percentage of dry matter Potassium, K 2.24 Nitrogen, N 0.44 Phosphorus, P 0.14 Calcium, Ca 0.36 Magnesium, Mg 0.36 Adapted from Menon et al., 2003
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Table 2.3: Typical Composition of Different Oil Palm Biomass Materials. Biomass (% of dry matter)
Cellulose Hemicellulose Lignin Glucose Xylose
EFB 39.0 22.0 29.0 0.43 0.26 Trunk 59.0 10.0 11.0 0.65 0.12 Frond 42.0 21.0 23.0 0.47 0.24 Fiber 21.0 16.0 43.0 0.23 0.18 Adapted from Malaysian - Danish, 2006.
Oil palm bunches processed in an oil mill generate between 20% and 25% EFB,
the ligno-cellulose fibrous medium left after bunch stripping. A mill with a capacity of 60
t fresh fruit bunches (FFB) hr-1 will thus produce almost 83 000 t EFB yr-1. These
considerable volumes of organic waste, which are produced on a continuous basis,
require effective removal procedures adapted to the nature of the by-product. EFB is
mostly used as a mineral fertilizer substitute by direct application in the field or, in some
cases, after incineration and occasionally after composting. In fact, fresh EFB returns
mineral nutrients and organic matter to the soil and helps to maintain soil fertility (Salates
et al., 2004).
EFB has traditionally been burnt and their ash recycled into the plantation as
fertilizer. However, due to the pollution problem, incineration of EFB has been
discouraged. Instead EFB is returned to the field to act as mulch or used as a fuel to meet
energy demand of the palm oil mills. This solution cannot be regarded as the end of the
chain, because the amount of biomass is much too large to get rid of in this way. And the
last few years, several research teams began to regard the EFB and other residues from
the palm oil industry as sources of energy or as raw materials for industry such as paper
production.
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2.5 Spent Bleaching Earth (SBE) After use in the crude oil palm refining, the spent bleaching earth is usually
disposed to landfill. The SBE contains about 30-40% (Lee et al., 2000; Seng et al., 2001)
oil weight. Currently, world production of edible oil and fat industries amounts to more
than 65 million tons and production of SBE is estimated at 650,000 tons worldwide (Lee
et al., 2000). The disposal of SBE to landfill may be limited by strict environment
regulations in the near future. SBE also present fire hazard in spontaneous combustion
because it possesses the pyrogenic nature due to the unsaturation of the fatty acids in the
retained oils. Obviously, SBE contributes to economics loss in oil retention.
SBE from edible oil industry may be profitably used in another industry. SBE is
employed for the manufacture of plastic waterproof cement obtained from lubricating oil
refineries. The SBE is added during the manufacture of cement into the tube mill when
the clinker is being grounded. The resultant product is a plastic waterproof cement of
excellent quality. In this study, SBE was investigated as a potential co-reactant in
pyrolysis process.
2.6 Type of Pyrolysis
Thermochemical process is thought to have a great promise as a means for
efficiency and economically converting biomass into higher value fuels. There are four
main thermochemical method of converting biomass: pyrolysis, liquefaction, gasification
and combustion. Each gives different range of products. Pyrolysis lies at the heart of all
thermochemical fuel conversion processes. It is attractive because solid biomass and
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wastes, which are difficult and costly to manage, can be readily converted to liquid
products. These liquids have advantages in transport, storage, combustion, retrofitting
and flexibility in production and marketing. Pyrolysis also gives gas and solid (char)
products, the relative proportions of which depend very much on the pyrolysis method
and process condition (Putun et al., 2002). As usual, the pyrolysis processes under
development are based on two different concepts: slow pyrolysis and fast or flash
pyrolysis. These differ from each other in terms of chemistry, overall yields and quality
of products. Pyrolysis method and their variants is given in Table 2.4.
Table 2.4: Pyrolysis Method and their Variantsa.
Pyrolysis technology
Residence time Heating rate Temperature (°C)
Products
Carbonization Days Very low 400 Charcoal Slow 5-30 min Low 600 Bio-oil, gas, char Fast 0.5-5s Very high 650 Bio-oil Flash-liquid < 1s High < 650 Bio-oil Flash-gas < 1s High < 650 Chemicals, gas Ultra < 0.5 Very high 1000 Chemicals, gas Vacuum 2-30s Medium 400 Bio-oil Hydro-pyrolysis < 10s High < 500 Bio-oil Methano-pyrolysis < 10s High > 700 Chemicals a Data taken from Mohan, et al., 2006.
2.6.1 Slow Pyrolysis
Slow pyrolysis has been applied for thousands of years and has been mainly used
for the production of charcoal. In slow pyrolysis, biomass typically was heated to ~ 500
ºC. The vapor residence time varies from 5 min to 30 min (Mohan et al., 2006). Vapors
do not escape as rapidly as they do in fast pyrolysis. Thus, the components in the vapor
phase continue to react with each other, as the solid char and any liquid are being formed.
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The heating rate in slow pyrolysis is typically much slower than that used in fast
pyrolysis. A feedstock can be held at constant temperature or slowly heated. Vapor can
be continuously removed as they are formed. Slow pyrolysis processes produce 18-30
wt% of liquid bio-oil, 20-35-wt% of solid char, and 30-40-wt% of gases, depending on
the feedstock used.
Mesa-Perez et al. (2005) carried out slow pyrolysis of packed cylindrical sample
of elephant grass (Pennicetum purpureum) and sugar cane bagasse in a fixed bed reactor.
The kinetic properties during biomass carbonisation, where the heat transfer phenomena
are significant were carried out. The temperature profiles along the reactor height during
pyrolysis were measured by means of a computer- aided data acquisition system. The
mass loss of biomass, proximate analysis and higher heating values (HHV) of all
products found in the layer were also analysed.
Karaosmanoglu et al. (1999) studied slow pyrolysis of the straw and stalk of the
rapeseed inside a tubular reactor under static atmosphere. The characterization of the bio-
oil was accomplished by the study of the pyrolytical behavior of rapeseed straw and
stalks using two different heating rates at varying temperatures. The best bio-oil yield
amongst experimental conditions was established to be at the ending pyrolysis
temperature of 650 °C with 30°C min-1 heating rate and the fact was emphasized that the
temperature is more effective than the heating rate in the pyrolysis.
Yorgun et al. (2001a) studied slow pyrolysis of sunflower –extracted bagasse
which has been conducted under different pyrolysis conditions in order to investigate the
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optimum pyrolysis parameters given maximum oil yield in a fixed –bed reactor. The
chemical composition of the pyrolytic oil was investigated using some chromatography
and spectroscopic techniques. The maximum oil yield of 23% was obtained at a final
pyrolysis temperature of 550 °C with particle size of 0.425-0.850 mm, with a heating rate
of 7 °C min-1 and nitrogen flow rate of 100 cm3 min-1.
Sensoz (2003) carried out slow pyrolysis of bark from Turkish red pine, namely
P. brutia Ten in a fixed bed reactor. The specified objective of this study was to assess
the potential of the pyrolysis technology to transform bark residues to useful products
such as bio-oil. The maximum liquid yield of 33.25% was obtained at a final pyrolysis
temperature of 450 °C with a heating rate of 40 °C min-1. It was concluded that both the
temperature and heating rate had a significant effect on both yield of liquids and char
resulting from pyrolysis of biomass.
Apaydin-Varol et al. (2007) investigated the effect of pyrolysis temperature of
pistachio shell on products yields in a fixed-bed reactor. The aim was to find out the final
temperature that gives the maximum bio-oil yield. It was observed that the bio-oil yield
sensitive to pyrolysis temperature in the range of 300-700 °C. Bio-oil yield has showed
an increase till the final temperature of 500-550 °C, and a decrease between the ranges of
550-700 °C. The char yield decreased with an amount of ∼ 21% while increasing the
pyrolysis temperature from 300 to 700 °C. The opposite was observed for the gas yield, it
increased significantly when temperature was increased.
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Stamatov et al. (2006) focused primarily on spray combustion at atmospheric
pressure of slow pyrolysis bio-oil. The researcher concentrated on slow pyrolysis bio-oil
because it is potentially valuable bi-product of Australian charcoal industry, currently
being not properly utilised. Parts of the bio-oil samples were diluted with analytical grade
ethanol to investigate the offset of solvent blending. Results from the experiments were
used to address two of the major issues relevant to the bio-oil combustion: poor
atomisation into droplets of bio-oils, and increased emission of nitrogen oxides from bio-
oils flames.
William et al. (1996) investigated the composition of the products from the slow
pyrolysis of biomass in the form of pine wood in relation to pyrolysis temperature and
heating rate in a static batch rector at pyrolysis temperature range from 300-700 °C and
heating rate from 5-80 K min-1. In addition, the wood and the major cellulose,
hemicellulose and lignin were pyrolysed in a thermogravimetric analyzer (TGA) under
the same condition of temperature and heating rate.
All researcher above studied slow pyrolysis under different condition to get a
maximum bio-oil yield with a different reactor. Operating conditions of these studies
mostly are temperature, heating rate, particle size and gas flow rate. The best result was
obtained at average temperature of 500 °C with heating rate of 30-40 °C min-1.
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2.6.2 Fast Pyrolysis
Fast pyrolysis is a high-temperature process in which biomass is rapidly heated in
the absence of oxygen. Biomass decomposes to generate vapors, aerosol, and char. After
cooling and condensation of the vapors and aerosol, a dark brown mobile liquid is formed
which has a heating value of about half of the conventional fuel oil.
Fast pyrolysis processes produce 60-75 wt% of liquid bio-oil, 15-25-wt% of solid
char, and 10-20-wt% of noncondensable gases, depending on the feedstock used. No
waste is generated; because the bio-oil and solid char can each be used as a fuel and the
gas can be recycled back into the process. Fast pyrolysis uses much faster heating rates
than slow pyrolysis.
Yorgun et al. (2001b) studied fast pyrolysis performed on sunflower press cake in
a tubular transport reactor. The effect of final temperature, nitrogen flow rate and particle
size on the yields of the pyrolysis products were investigated. The maximum oil yield of
45-wt % was obtained at the pyrolysis temperature of 550 °C, with sweep gas flow rate of
300cm3 min-1 and particle size of 0.425-0.850 mm. The bio-oil was identified and
presented as biofuel candidate. The liquid product may be used as a source of low-grade
fuel directly, or it may be upgraded to higher quality liquid fuels.
Tsai et al. (2007) investigated the fast pyrolysis of rice husk in an induction –
heating rate furnace. In particular, the influences of pyrolysis temperature, heating rate,
holding time at specified pyrolysis temperature, particle size, N2 sweep gas flow rate and
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cryogenic temperature in the condenser on the product yields were studied. The optimum
bio-oil yield of 40% achieved at the pyroysis temperature of 500 ° C, heating rate of 200
°C min-1, holding time of 2 min, condensation temperature of -10 °C and particle size of
0.50 mm.
Onay et al. (2001) studied the fast pyrolysis of rape seed in a weel-swept fixed –
bed tubular reactor. These researchers focused on the influence of final pyrolysis
temperature, particle size range, heating rate, and sweep gas velocity on the product
yield. In addition, the pyrolysis oil obtained under the condition of the maximum liquid
product yield was investigated, using chromatographic and spectroscopic techniques, to
determine its possibility of being a potential source of renewable fuel and chemical
feedstock.
Acikgoz et al. (2007) carried out flash pyrolysis experiments on Linseed in a
tubular transport reactor. The effects of final temperature and particle size on the yields
of the pyrolysis products were investigated. The highest liquid yield of 68.8% was
obtained at a final pyrolysis temperature of 550 °C with a particle size of >1.8 mm, and
nitrogen flow rate of 100cm3 min-1.
Zanzi et al. (2002) studied concerning the fast pyrolysis of agricultural residues at
high temperature of 800–1000°C performed in a free-fall reactor at pilot scale. These
conditions are of interest for gasification in fluidised beds. Of main interest are the gas
and char production, the gas composition and the reactivity of the produced char in
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gasification, because fast pyrolysis is the first step in gasification and combustion in
fluidised bed reactors.
Yang et al. (2006) investigated the pyrolysis of palm oil wastes using a
countercurrent fixed bed reactor under different operating conditions of temperature,
residence time and catalyst adding, in order to achieve an improved performance of palm
oil wastes conversion to energy with a higher yield of H2- rich gases. Gas yield increased
greatly whilst solid and liquid yields decreased straightly as temperature increases from
500 to 900 °C. The gas products mainly consist of H2, CO, CO2 and CH4 with trace
amounts of C2H4 and C2H6. High temperature is favorable for the enhancement of
flammable gas products including H2, CO and CH4.
Uzun et al. (2006) studied the role of important parameters influencing pyrolysis
yields from soybean cake. The fast pyrolysis experiments were conducted under nitrogen
atmosphere in a well-swept resistively fixed-bed reactor with a length of 90 cm and an
inner diameter of 8 mm, made of 310 stainless steel. Experiments were carried out at
temperatures ranging from 400 to 700 °C, for various nitrogen flow rates, heating rates
and particle sizes. The maximum liquid yield was 42.83% at a pyrolysis temperature of
550 °C with a sweeping gas rate of 200 cm3min-1 and heating rate of 700 °C min-1 for a
soybean cake sample having 0.425 - 0.85 mm particle size.
All researchers above studied the fast pyrolysis under different condition to get a
maximum bio-oil yield with a different reactor. Operating conditions of these studies
mostly are temperature, heating rate, particle size and gas flow rate. The researchers
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conducted the fast pyrolysis at the higher temperature to get a various rich gases
especially hydrogen. The best result obtained at average temperature of 500 °C with
heating rate of 30 - 40 °C min-1. A summary of pyrolysis biomass researchers is shown in
Table 2.5.
Table 2.5: A Summary of Pyrolysis Biomass Researchers.
Type of feed (biomass) Type of pyrolysis
Reactor Maximum bio-oil yield
Researcher
Sunflower press cake Fast pyrolysis Tubular transport reactor
45.0% Yorgun et al. (2001)
Rice husk Fast pyrolysis Induction –heating rate furnace
40.0% Tsai et al. (2005)
Rape seed Fast pyrolysis Well-swept fixed –bed tubular reactor
68.0% Onay et al. (2001)
Straw and stalk rapeseed
Slow pyrolysis Tubular reactor ∼18.0% Karaosmanoglu et al. (1999)
Pistachio shell Slow pyrolysis Fixed-bed reactor 21.0% Apaydin-Varol et al (2007)
Soybean cake Fast pyrolysis Well-swept resistively fixed-bed reactor
42.8% Uzun et al (2006)
Sunflower–extracted bagasse
Slow pyrolysis Fixed-bed reactor 23.0% Yorgun et al (2001a)
Linseed Fast pyrolysis Tubular transport reactor
68.8% Acikgoz et al. (2007)
Bark from Turkish red pine
Slow pyrolysis Fixed-bed reactor 33.3% Sensoz (2003)
Palm oil wastes Fast pyrolysis Countercurrent fixed bed reactor
∼57.0% Yang et al. (2006)
Rice straw, sugarcane baggase, coconut shell
Fast pyrolysis Induction-heating reactor
40.0% Tsai et al. (2006)
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2.7 Pyrolysis Products 2.7.1 Introduction of Bio-oil
Bio-oils are dark brown, free-flowing organic liquids that are comprised of highly
oxygenated compounds. The synonyms for bio-oil include pyrolysis oils, pyrolysis
liquids, bio-crude oil (BCO), wood liquids, wood oil, liquid smoke, wood distillates,
pyroligneous acid, and liquid wood.
Pyrolysis liquids are formed by rapidly and simultaneously depolymerizing and
fragmenting cellulose, hemicellulose, and lignin with a rapid increase in temperature.
Rapid quenching then “freezes in” the intermediate products of the fast degradation of
hemicellulose, cellulose, and lignin. Rapid quenching traps many products that would
further react (degrade, cleave, or condensate with other molecules) if the residence time
at high temperature were extended. Bio-oils contain many reactive species, which
contribute to unusual attributes. Chemically, bio-oil is a complex mixture of water,
guaiacols, catecols, syringols, vanillins, furancarboxaldehydes, isoeugenol, pyrones,
acetic acid, formic acid, and other carboxylic acids. It also contains other major groups of
compounds, including hydroxyaldehydes, hydroxyketones, sugars, carboxylic acids, and
phenolics. Oligomeric species in bio-oil are derived mainly from lignin, but also
cellulose. Oligomer molecular weights from several hundred to as much as 5000 or more
can be obtained. They form as part of the aerosols. Free water in the biomass explosively
vaporizes upon fast pyrolysis. Cellulose and hemicellulose also lose water, which
contributes to the process. The molecular mass distribution is dependent on the heating
rate, residence time, particle size, temperature, and biomass species used.
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Bio-oil can be considered as a microemulsion in which the continuous phase is an
aqueous solution of holocellulose decomposition products and small molecules from
lignin decomposition. The continuous liquid phase stabilizes a discontinuous phase that is
largely composed of pyrolytic lignin macromolecules. Microemulsion stabilization is
achieved by hydrogen bonding and nanomicelle and micromicelle formation. The exact
chemical nature of each bio-oil is dependent on the feedstock and the pyrolysis variables,
as defined above.
Bio-oil contains aldehydes, ketones, and other compounds that can react via aldol
condensations during storage or handling to form larger molecules. These reactions cause
undesirable changes in physical properties. Viscosity and water content can increase,
whereas the volatility will decrease. The most important variable driving this “aging” is
temperature. Bio-oil is produced with ∼ 25wt % water, which cannot readily be separated.
In contrast to petroleum fuels, bio-oil contains large oxygen content, usually 45%-50%.
Thus, its elemental composition resembles the biomass from which it was derived far
more than it resembles petroleum oils. The presence of oxygen is the primary reason for
the difference in the properties and behavior between hydrocarbon fuels and biomass
pyrolysis oils. The bio-oil is immiscible with liquid hydrocarbons because of its high
polarity and hydrophilic nature (Mohan et al., 2006).
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2.7.2 Characterisation of bio-oil
All researchers select bio-oil for analysis were those obtained at the maximum
yield. The optimum bio-oil was obtained in temperature ranges of 500 °C - 550 °C, with
a heating rate of 30 °C min-1-50 °C min-1 (Gercel, 2002b, Onay et al., 2001, Apaydin-
Varol et al., 2007). Characteristics of the bio-oil product includes density, water content,
viscosity, calorific value, pH, ash and pour point. The elemental analysis of carbon,
hydrogen, nitrogen and oxygen of bio-oil were also determined. Then, the chemical
compositions of the bio-oil were investigated using chromatography and spectroscopic
techniques comprise of 1H NMR, IR, GC/MS and column chromatography. Standard
method properties of bio-oil product from previous works are presented in Table 2.6.
Typical properties of bio-oil wood and sunflower from previous work compared to heavy
fuel oil are given in Table 2.7 (Mohan et al., 2006, Yorgun et al., 2001a).
Table 2.6: Standard Methods Properties of Bio-oil Product.
Properties Methods Density, (kg/m3) ASTM D 4052 Water content (w/w%) (Karl Fisher Titration)
ASTM D 1744
Calorific value (MJ/kg) ASTM D 2015 Viscosity (cSt) ASTM D 445 Ultimate analysis (w/w%) Carbon ASTM D 482 Hydrogen ASTM D 3177 Oxygen By different Adapted from Sensoz et al., 2006, Karaosmanoglu et al., 1999
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Table 2.7: Typical Properties of Bio-oils, Compared to Heavy Fuel Oil.
Value Physical property Bio-oil from wooda Bio-oil from soybeanb Heavy fuel oila
Moisture content (wt%)
15-30 None 0.1
Density (kg/m3) 1.20 1.11 0.94 Calorific value (MJ/kg)
16-19 34 40
Viscosity, at 50°C (cSt)
40-100 72 180
Elemental composition (wt%)
Carbon 54-58 68 85 Hydrogen 5.5-7.0 8 11 Oxygen 35-40 14 1.0 Nitrogen 0-0.2 10.8 0.3 a Data taken from Mohan et al., 2006, b Data taken from Yorgun et al., 2001a.
2.7.3 Char
Char are black solid. The char is intermediate solid residue, which is formed in
the pyrolysis of most biomass. The char is believed to contribute to the formation of
polycyclic aromatic hydrocarbon (PAHs) during biomass pyrolysis, particularly at low
temperature (Sharma et al., 2004). The solid char can be used as a fuel in form of
briquettes or as a char-oil, char-water slurry; alternatively the char can be upgraded to
activated carbon and used in purification processes (Islam et al., 2005).
The properties of the char obtained after biomass pyrolysis have a direct influence
on subsequent char oxidation step, since the amount and type of pores determine the gas
accessibility to the active surface sites. Properties of char are decisively affected, not only
by properties of parent material, but also by operating conditions used, mainly the heating
rate, the maximum temperature experienced and the residence time at this temperature.
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This is due to the fact that these variables, together with biomass properties, influence the
amount and nature of volatiles produced during pyrolysis, as well as their rate of release.
These factors also determine both the macroscopicmorphology and themicroscopic
porosity of the resultant char (Onay, 2007). Characteristics of the char product include
calorific value, elemental composition, surface area property and scanning electron
microscopy (SEM).
2.7.4 Gas
The third main product from pyrolysis is gas. Typically the gas was intermittently
trapped in a gas bottle or gasbag, and then was analysed using gas chromatography (GC).
The gas component mainly consisted of H2, CO2, CO, and CH4 together with traces of
C2H4 and C2H6. CO2 and CO evolved out at lower temperature, while H2 released at
higher temperature.
2.8 Application for bio-oil
Bio-oil is a liquid fuel that can be used to replace fossil fuel in “green power”
generation, transportation and district heating. Global demand to accelerate clean energy
production, improve air quality and reduce industrial waste has created to powerful
market context for bio-oil. The nearest term commercial application for bio-oil is as clean
fuel for generating power and heat from small stationary diesel engines, gas turbines and
boilers. They also a range of chemicals that can be extracted or derived including food
flavourings, resins, agri-chemicals, fertilizers, and emission control agents (Acikgoz et
al., 2004). This application will be the primary focus for bio-oil demonstration and
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commercial projects over the next several years (DynaMotive Energy Systems
Corporation, 1999).
DynaMotive (Canada) is working with several manufacturers of stationary diesel
engines and gas turbines to test and develop bio-oil fuels for power generation. Early
problems related to fuel corrosivity, lubricity and viscosity have largely been solved and
bio-oil power generation is ready for demonstration.
As a diesel substitute, bio-oil fuel can produce power in small stationary diesel
engines and gas turbines in the range of 1-10 MW. A commercial scale bio-oil plant
capable of processing 200 tonnes per day of biomass feedstock would provide enough
fuel to generate 6 to 10 megawatts of electricity depending on the configuration of the
power generating equipment. Bio-oil has also been demonstrated as a clean boiler fuel by
major European utilities and energy producers in Sweden and Finland where it has
proven effective in small district heating system below 1 megawatt (DynaMotive Energy
Systems Corporation, 1999).
As a clean fuel, bio-oil contains no SOX emission. That is because bio-oil
produces virtually no heavily regulated SOX emissions and would not be subjected to
SOX taxes. Bio-oil contains a low NOX and neutral CO2. Because bio-oil manufactured
from organic waste, it is considered greenhouse gas neutral and can generate carbon
dioxide credits. Compared to other biomass fuel, bio-oil can be stored, pumped and
transported in a manner similar to petroleum based products to equalize energy demand
and distribution. This can make bio-oil more economical to use because transportation
34
Literature Review
and storage of liquid fuels are much less expensive than for competing fuels such as
wood, straw and peat.
35
Methodology
CHAPTER 3
METHODOLOGY
3.1 Introduction
In this chapter, the material and methodology employed in the experiment were
described. Pyrolysis of oil palm empty fruit bunches on different parameter was
investigated using a quartz reactor of fluidised-fixed bed reactor. The procedure for
physical characterization of bio-oil and char was performed according to ASTM
(American Society for Testing and Material) methods. The chemical composition of the
bio-oil was investigated using chromatography and spectroscopic techniques.
3.2 Materials
3.2.1 Empty Fruit Bunch
The main of oil palm biomass used in this study was empty fruit bunches (EFB).
The empty fruit bunches sample investigated in this study was collected from palm oil
mill located in Padang Jawa, Klang. Empty fruit bunches used in the work is the biomass
remaining as a by-product of industrial processes after removal of the nuts. A whole
empty fruit bunch was dried at 100 ± 5 °C and cut. It was then milled, sieved and
separated in fractions of different particle size using the test sieve shaker, Endecotts EFL
2000. The ranges of particle size obtained namely size < 90 µm, 91-106 µm, 107-125 µm
and 126-250 µm.
36
Methodology
3.2.2 Oil Palm Trunk, Frond and Fiber
The oil palm trunk, frond and fiber samples investigated in this study were taken
from MPOB palm oil mill, located in Labu, Negeri Sembilan. A whole oil palm biomass
was dried at 100 ± 5 ºC and cut. It was then milled, sieved and separated in fractions of
different particle size using the testy sieve shaker, Endecotts EFL, 2000. The ranges of
particle size obtained namely size < 90 µm, 91-106 µm, 107-125 µm and 126-250 µm.
The particle size of trunk, frond and fiber used was 91-106 µm.
3.2.3 Zircon Sand
The zircon sand in the fluidized-fixed bed reactor was of mean size 250 µm
diameter. The steps to prepare zircon sand are as follow. First, the zircon sand is
immersed in 0.1 M sulphuric acid for 3 days. Then, the sand are washed repeatedly with
distilled water until a pH of 4.5 - 5.0 is achieved. Finally, the sand are dried in an oven at
60°C.
3.2.4 Solvent
Analytical grade of hexane, ethanol and sulfuric acid (minimum purity 99.99%)
were used as solvent. These solvents were obtained from Fisher Scientific Sdn. Bhd.
37
Methodology
3.2.5 Spent Bleaching Earth (SBE)
The spent bleaching earth investigated in this study was collected from palm oil
mill located in Johor. Naturally bleaching earth comprises of a number of layered
silicates such as bentonite, polygorskite, hectorite or sepiolite. The SBE contains about
30-40% oil weight (Lee et al., 2000; Seng et al., 2001). In this study, two types of spent
bleaching earth were used as a fluidised bed. First, a prior spent bleaching earth from
palm oil mill and second is a spent bleaching earth washing with hexane. The steps to
prepare a spent bleaching earth washing with hexane were as follow. Firstly, 10 g of
spend bleaching earth was immersed in 50 ml hexane for one day. Then, the spent
bleaching earth was dried in an oven at 60 °C. The purpose of this step is to remove oil
from the spent bleaching earth.
3.3 Methodology
3.3.1 Pyrolysis Trial
Pyrolysis of the oil palm empty fruit bunches was carried out using a quartz
reactor of fluidised-fixed bed reactor. An electric furnace heated the reactor with a heated
length of 135 mm and an inner diameter of 40 mm. The temperature of the reactor was
determined by inserting a thermocouple as near the upper fritz as possible. The whole
experimental rig that consists of the volatiles and gas collection system is as illustrated in
Figure 3.1.
38
Methodology
1
2
4
5
3
Volatiles
6
(1) Tem perature recorder; (2) Furnace; (3) Fluidising Gas; (4) Reactor; (5) Quartz fritz; (6) Sand bed;(7) Volatiles collector; (8) Gas dryer
2
5
.
7
8
Figure 3.1: Schematic Diagram of the Pyrolysis System.
The sand bed was fluidised using argon at a rate of 1.5 litre per min. 160 g zircon
sand of 180-250 µm was used as the sand bed. For each experiment, 2 g of EFB
feedstock was introduced into the bed of zircon sand. The whole experiment must be held
for either a minimum of 10 minutes or until no further significant release of gas was
observed. The connection tubes between the reactor and the cooling system were heated
using heating tape to avoid condensation of pyrolysis vapors.
Before a run, the reactor was weighed. After a run, the cooled reactor was
weighed again and the char yield was calculated from the difference. The char remaining
in the reactor was elutriated by introducing argon into sand bed. The bio-oil was collected
in a series of flask placed in a cold trap containing ice. The bio-oil accumulated in the
39
Methodology
flask was transferred into a small bottle and the remaining liquid product left behind in
the flask including all connection tubes were dissolved with ethanol.
The solvent part of the bio-oil dissolved in ethanol was extracted in a rotary
evaporator and the quantity of the bio-oil was thus established. The bio-oil comprised of
a dark liquid was weighed. After that, gas was intermittently trapped in a gas bottle as the
temperature of the pyrolisis was increased. The gas was analyzed using micro gas
chromatography model Agilent 3000 Micro GC. Finally, the gas yield was calculated
from the material balance. Each experiment was repeated three times.
3.3.2 Optimization of pyrolysis parameters.
3.3.2.1 Effect of temperature
The first series of experiments was perform to determine the effect of the
pyrolysis temperature on pyrolysis yields. For each experiment, 2 g of air-dried empty
fruit bunches were sieved to the range of 91-106 µm particle size and placed in the
reactor. The temperature was raised at 30 °C min-1 to a final temperature of either 300,
400, 500, 600 or 700 °C. The gas was intermittently trapped in a gas bottle as the
temperature of the pyrolisis was increased.
40
Methodology
3.3.2.2 Effect of particle size
The second series of experiments was performed to investigate the effect of
particle size on the pyrolysis yields. These experiments were conducted using four
different particle size ranges, namely size < 90 µm, 91-106 µm, 107-125 µm and 126-250
µm with heating rate of 30 °C min-1. Based on the results obtained from the first series of
experiments, the pyrolysis temperature of the second series was maintained at 500 °C.
3.3.2.3 Effect of heating rate
The third series of experiments was conducted to study the effect of heating rate
on the pyrolysis yields. Experiments were conducted at different heating rates of 10 °C
min-1, 30 °C min-1, 50 °C min-1 and 100 °C min-1. The final pyrolysis temperature was
maintained at 500 °C and the particles size of empty fruit bunches was from 91-106 µm.
3.3.2.4 Effect of different oil palm biomass materials
The fourth series of experiments was performed to study the effect of different oil
palm biomass materials on the pyrolysis yields. Experiment was conducted using four
type of biomass as follow; EFB, Trunk, Frond and Fiber. For each experiment, 2 g of oil
palm biomass feedstock was introduced into the bed of zircon sand. The final pyrolysis
temperature was maintained at 500 °C, the particles size of oil palm biomass was from
91-106 µm and the heating rate of 30 °C min-1.
41
Methodology
3.3.2.5 Effect of different fluidised bed material
The last series of experiment was carried out to investigate the effect of different
fluidised bed material on the pyrolysis yields. The type of fludised bed using in this
experiment was spent bleaching earth + zircon sand, spent bleaching earth washing with
hexane + zircon sand and zircon sand. For the first trial, 2 g of spent bleaching earth
together with 158 g of zircon sand were used. For the second trial, 2 g spent bleaching
earth washing with hexane mixed with 158 g zircon sand were used as a fluidised bed.
The last trial used 160 g of zircon sand as a fluidized bed. The final pyrolysis temperature
was maintained at 500 °C, particles size of empty fruit bunches was from 91-106 µm and
heating rate of 30 °C min-1.
42
Methodology
3.4 Characterisation of Empty Fruit Bunches (EFB).
3.4.1 Determination of Proximate Analysis
The proximate analysis is defined as the loss in weight of the empty fruit bunches
(EFB) sample heated under the test condition specified. The proximate analysis was done
to determine the moisture content, volatile matter, fixed carbon, and ash content in the oil
palm empty fruit bunches. EFB sample was dried in an oven at 103°C to a constant
weight in order to determine residual moisture. The sample was then heated in a covered
crucible (to prevent oxidation) at 900°C to a constant weight. The weight loss is referred
to a volatile matter. The remaining sample was then placed in the oven at 750°C with the
cover off so that the sample was combusted. The weight loss upon combustion is termed
fixed carbon. The remaining residue is defined as ash.
Calculation:
Moisture content (wt%) = W0-W1/ W0 x 100%
Volatile matter (wt%) = W1-W2/ W1 x 100%
Fixed carbon (wt%) = W2-W3/ W2 x 100%
where W0 is the weight of sample in g before heating
W1 is the weight of sample in g after heating at 103ºC
W2 is the weight of sample in g after heating at 900ºC
W3 is the weight of sample in g after heating at 750ºC
43
Methodology
3.4.2 Calorific Value
Knowledge of calorific value of feedstock is essential when considering the
thermal efficiency of equipment for producing either power or heat. In this study, the heat
of combustion was determined by burning a weighed sample in an oxygen-bomb
calorimeter, Leco AC-350 under controller conditions based on ASTM D-240. The test
procedure consists of adding the weighed of empty fruit bunches (EFB) samples to the
cup (approximately 0.5 – 1.0 g), installing a fuse, and charging the bomb with oxygen to
approximately 200 psi. The heat of combustion was computed from temperature
observations before, during, and after combustion, with proper allowance for
thermochemical and heat transfer corrections.
3.4.3 Elemental Analysis
The purpose of this test is to determine element percent of carbon, hydrogen,
nitrogen and oxygen in the EFB. The elemental analysis was determined using an
Elemental Analyser, Euro EA 3000 using Callidus Software Interface Version 4.1. The
main components of Elemental Analyzer consist of quartz tube reactor (packed CHNS
kits), column, gas chromatography oven, front furnace (temperature maximum 1020 °C),
the detecting system used thermal conductivity detector and oxygen trap.
Separation of elemental carbon, hydrogen and nitrogen was determined by using
Gas Chromatography Column under operating temperature programmed condition.
44
Methodology
Identification by reference to standard calibration and percent element of samples were
determined by peak areas.
Method parameter CHN test:
Carrier gas Helium, 80 kPa Combustion gas Oxygen, 10 ml Oxidation time 8.7 sec Sampling delay 10 sec Run time 320 sec Front furnace 1020°C GC oven 115°C ∆ PO2 35 kPa 3.5 Characterisation of Bio-oil
Characteristics of the bio-oil product include density, water content, viscosity,
calorific value, pH, ash and total acid. The elemental analysis of carbon, hydrogen,
nitrogen and oxygen of bio-oil also were determined. Then the chemical compositions of
the bio-oil were investigated using chromatography and spectroscopic techniques
comprise FTIR and GC/MS.
3.5.1 Density (ASTM D 4052)
Density is a fundamental physical property that can be used in conjunction with
other properties to characterise the bio-oil products. Determination of the density or
relative density of bio-oil is necessary for the conversion of measured volumes to
volumes at the standard temperature. For liquid, density is used which is the ratio of the
mass of an equal volume of water. The density of bio-oil was determined by using Digital
Density Meter, type DE 40, Mettler Toledo.
45
Methodology
First, the density meter was calibrated by water at 25 °C before measurement in
order to minimize the errors. Then, 1 ml of bio-oil was injected into density meter at 25
°C and repeated for three times. The recorded value is the final result, expressed as
density in g/cm3.
3.5.2 Ash (ASTM D 482)
Knowledge of the amount of ash-forming material present in a product can
provide information as to whether or not the product is suitable as a fuel. Ash can result
from oil or water-soluble metallic compounds or from extraneous solids such as dirt and
rust. In this study, the sample contained in a suitable vessel was ignited and allowed to
burn until only ash and carbon remain. The carbonaceous residue was reduced to an ash
by heating in a furnace at 775°C with a heating time of 20 minutes, followed by cooling
and weighing.
The mass of the ash was calculated as a percentage of the original samples as
followed:
Ash, mass % = (w/W) × 100
where:
w = mass of ash, g, and
W = mass of sample, g.
46
Methodology
3.5.3 Moisture Content- Karl Fisher Titration (ASTM D 1744)
Knowledge of the water content of bio-oil products can be useful to predict the
quality and performance characteristics of the product. In this study, water content of the
bio-oil product was measured using Karl Fischer Titrator, type 784 KFP Titrino,
Metrohm based on ASTM D 1744. The bio-oil to be analysed was titrated with standard
Karl Fischer reagent to an electrometric end point.
3.5.4 Calorific Value (ASTM D 240)
The heat of combustion is a measure of the energy available from fuel.
Knowledge of this value is essential when considering the thermal efficiency of
equipment for producing either power or heat (Refer section 3.4.2).
3.5.5 Acid Value (ASTM D 664)
Bio-oil product may contain acidic constituents that are present as additives or as
degradation products formed during pyrolysis. The relative amount of these materials can
be determined by titrating with bases. The acid number is a measure of this amount of
acidic substance in the oil under of the test. The total acid value is determined by using
Potentiometric Titrimeter, 702 SM Titrino, Metrohm automatic recording. The
determination was done by titrimetry based on ASTM D 664. The acid value is expressed
as the amount (in miligrammes) of potassium hydroxide required to neutralize one
gramme of the bio-oil (mg KOH g-1).
47
Methodology
In this study, the sample was dissolved in a mixture of toluene and isopropyl
alcohol containing a small amount of water and titrated potentiometrically with alcoholic
potassium hydroxide using a glass indicating electrode and colomel reference electrode.
The meter reading was plotted automatically against the respective volumes of titrating
solution and the end points were taken only at well defined inflection in the resulting
curve. When no definite inflections were obtained, the end points were taken from meter
reading corresponding to those found for freshly prepared non-aqueous acidic and basic
buffer solutions. The acid number was used as a guide in the quality control of lubricating
formulations.
3.5.6 pH
In order to evaluate the corrosive property of the bio-oil products, the pH of the
bio-oil was measured using a pH meter from Eutech Instruments, type of pH tutor. The
electrode was directly dipped into the bio-oil sample. The sample size of bio-oil was 1-2
ml. The recorded value is the final result, expressed as a pH of bio-oil.
3.5.7 Gas chromatography/mass spectroscopy (GC-MS)
Gas chromatography (GC) was used to separate various organic compounds that
were formed during the pyrolysis process. Mass spectroscopy (MS) was used to
determine the molecular formula of organic compounds that were separated from the GC.
From the GC-MS spectra, each peak had its own retention time and percentage area. With
the system, a library search on each components of the mixture can be conducted. If the
components are known compounds, they can be identified by comparisons with
48
Methodology
compounds found in the computer library. A list can be generated and reports on the
probability that the compound in the library matches the known substance.
In this study, the gas chromatography/mass spectroscopy (GC-MS) analysis of the
bio-oil product was performed using a Agilent Technologies GC 6890N with 5973N
mass selective detector (MS), using a 30 mm x 250 mm x 0.25 mm SGE BPX5 capillary
column supplied by scientific Glass Engineering SGE Pty Ltd. The oven temperature was
started at 35 °C for 2 minutes, increased to 250 °C at a rate of 20 °C min-1 and held at this
temperature for 20 minutes. The injector port temperature and the detector temperature
was set at 280 °C. The carrier gas, helium, was set at a flow rate of 47.5 liter per minutes
and the split ratio of the injector port was set at 50:1.
0.03 g of bio-oil was used and diluted with methanol HPLC grade to the volume
of 0.5 ml using a vial. After that, the mixture was shaked and filtered. Finally, 1.0 µl of
mixture was injected with a 5.0 µl syringe into the GC-MS apparatus.
3.5.8 Fourier Transform infra-red (FTIR)
FTIR is based on interferometry and thus differs fundamentally from traditional
dispersive infrared spectroscopy (Gladys, 2006). The spectra data was used to identify
organic compounds by matching the fingerprint of a sample with those on the computer.
In addition, the functional groups and structural characteristics of a compound enable us
to elucidate possible structural types.
49
Methodology
In this study, functional groups analysis of the bio-oil was carried out using
Fourier transform infra-red (FTIR) spectroscopy, Magna-IR550 (Nicolet, Madison).
FTIR with an online pen plotter was used to produce the infra-red (IR) spectra of the
derived liquids. A small amount of the bio-oil was mounted on a potassium bromide
(KBr) disc that had been previously scanned as a background. The FTIR spectrum in the
ranges of 500-3500 cm-1 was measured and recorded with a 8.0 cm-1 resolution and
number of reading taken was 16. The absorption frequency spectra were recorded and
plotted. The standard IR- spectra of hydrocarbons were used to identify the functional
group of the component of the derived liquid oil.
3.5.9 Elemental Analysis
The purpose of this test is to determine element percent of carbon, hydrogen,
nitrogen and oxygen in the bio-oil (Refer section 3.4.3).
3.6 Characterisation of char
3.6.1 Elemental Analysis
The purpose of this test is to determine the element percent of carbon, hydrogen,
nitrogen, and oxygen in the char (Refer section 3.4.3).
50
Methodology
3.6.2 Calorific Value (ASTM D 4809)
The purpose of this test is to determine the heat of combustion of the char. In this
study, the heat of combustion was determined by burning a weighed of char sample in an
oxygen bomb calorimeter under controlled conditions (Refer section 3.4.2).
3.6.3 Surface Area and total pore volume
The physical properties of the char relating to specific surface area and total pore
volume were obtained by measuring their nitrogen adsorption-desorption isotherms at -
196°C in an Accelerated and Porosimetry System (ASAP 2010, Micromeritics USA.
Brunauer-Emmet-Teller (BET) surface area, SBET was calculated using the adsorption
data in relative pressure ranges from 0.05 to 0.20. The total pore volume, VT was
assessed by converting the amount of nitrogen gas adsorbed (expressed in cm3 g-1 at STP)
at relative pressure 0.97 to the volume of liquid adsorbate. The analytical method consists
of three steps including dehydration of samples, degassing of sample under low vacuum
pressure and nitrogen gas adsorption at –196 °C.
Dehydration of sample
Dehydration of sample was conducted by using Carbolite box furnace at a
temperature of 80 °C for overnight. Before performing gas adsorption experiment, the
adsorbent must be free from any trace contaminants such as water and oil on the surface
or within the pores of the particles. The sample powder was put in a quartz sample holder
and placed at the bottom of holder prior to degassing step.
51
Methodology
Degassing of sample
The sample of solid was placed in a quartz sample holder and was heated at a
temperature of 200 °C under a vacuum atmosphere in order to remove the desorbed gases
that performed surface cleaning or degassing. The degassing was carried out at an
extended period of time, minimally from 4 to 6 hours to ensure effective cleaning of the
sample prior to analysis. Once clean, the sample mass should be determined since
significant reduction of mass was due to the desorbed contaminants in the sample.
Degassed samples would be directed to the analysis port almost immediately after
degassing to prevent any exposure to the atmosphere.
Physisoprtion Analysis of Sample.
Final weight was recorded and key-in for analysis. The sample was analyzed by
using adsorptive nitrogen gas. The application of nitrogen required the bath to be of
liquid nitrogen. In order to cross-examine the system function and confirming the
operation of the instrument, reference material silica alumina standards were evaluated.
A well-calibrated system function would then be ready for sample analyses. At the
meantime, the suitable methods were selected to determine the properties of sample. For
the initial experiment, adsorption isotherm, BET surface area, t-plot and Barret-Joyner-
Halenda (BJH) desorption were chosen because these methods are suitable for
microporous material such as highly microporous chars.
Analysis Measurement
The analyses of samples involve the selection of suitable relative pressure range
in accordance to the type of material. The analyses of typically microporous materials
52
Methodology
(i.e. char) are conducted in the region of 0.0001 to 0.1 of relative pressure, P/Po, which is
the actual gas pressure, P divided by the vapor pressure Po of the adsorbing gas at the
temperature at which the test is conducted. In this study, an automatic adsorption
instrument, Micromeritics ASAP 2010, was used to examine a specific surface area, total
pore volume, and pore size distribution of the sample. Data were automatically collected,
displayed and analyzed by computer. The determination of the pore size distribution and
surface area by the machine was based on the relative pressure applied to effect
penetration of the nitrogen into the pores. The resulting isotherm was analyzed using
BET method, while pore size distributions were carried out by BJH desorption method.
53
Methodology
3.7 Gas Analysis
Micro gas chromatography (GC), Agilent, 3000 Micro GC has been used to
analyze qualitatively and quantitatively the gas components from pyrolysis of EFB. Gas
chromatography (GC) is an analytical technique for separating compound based on
volatility. This technique provides quantitative and qualitative information for individual
compound present in a sample.
Qualitative analysis is to indicate the presence of compound by co-elution
technique whereas quantitative analysis will provide the amount of compound present in
the mixture. The determination of the composition of a mixture can be based on the peak
area or peak height of the compound. However, the peak area in GC may vary
considerably from one injection to another. Therefore, automatic sampling and injection
aids or by one of the following methods were used;
(i) Internal normalization
Internal normalization is a calibration method normally used in GC. It is based on
measuring the area of every peak in the chromatogram, the total area is normalized to
100% and each peak is then reported as a percentage of the total.
(ii) External standardization
External standardization involves the construction of the calibration plot using
standard of known concentration or mass. A fixed volume of each standard is the injected
54
Methodology
and chromatogram analyzed in terms of plotting peak size as functional of concentration
or mass. In most cases, calibration plots will be linear and should be extrapolated through
the origin.
(iii) Internal standardization
Internal standardization is a technique most commonly used in which an identical
volume or mass of a compound not present in the sample under investigation and ratio of
the peak size of the sample to the peak size of the standard added was calculated. An
exact and constant amount of a pure compound known as the internal standard is added to
specified volume of the unknown sample and also to several standard mixtures containing
known amount of the constituent of the unknown sample may be calculated.
In this study, qualitative and quantitative analyses were used to identify the
presence and percent yield of products. Micro gas chromatography (GC) has been used to
analyze qualitatively and quantitatively the gas components from pyrolysis of EFB,
because of the following advantages: small amount of sample (×10-6cm3) needed, short
retention time (∼160 s) high accuracy, speed and profitability (Yang et al., 2006).
The gas products from oil palm empty fruit bunches pyrolysis were analysed
using a dual –channel micro-GC with thermal conductivity detector (TCD). Channel A
with molecular sieve 5A column (MS-5A) was set at 90 °C for determination of H2
(hydrogen), CO (carbon monoxide) and CH4 (methane). Channel B with Plot-U was set
at 70°C for checking CO2 (carbon dioxide), C2H4 (ethane) and C2H6 (ethylene). A
55
Methodology
cylinder of standard gas containing CO (carbon monoxide) 0.1 mol%, CO2 (carbon
dioxide) 0.05 mol%, C2H4 (ethane) 0.05 mol%, C2H6 (ethylene) 0.05 mol% and CH4
(methane) 98.0 mol% was purchased from a Agilent company, and the calibration was
carried our regularly. The bottle gas collectors were cleaned using argon purge.
56
Pyrolysis Products
CHAPTER 4
PYROLYSIS PRODUCTS
4.1 INTRODUCTION
The products obtained from the pyrolysis of empty fruit bunches were
fractionated into bio-oil, char and gaseous materials. The yields and compositions of end
products of pyrolysis are highly dependent on various parameters. In this study, the effect
of temperature, particle size, heating rate, different oil palm biomass and different
fluidised bed on pyrolysis products was investigated. The material and methodology
employed in the experiments were described in Chapter 3. In this study, bio-oil yield
obtained from all pyrolysis experiments were considered consisting of water content.
4.2 RESULTS AND DISCUSSION 4.2.1 Effect of Temperature
In this study, the pyrolysis processes were carried out at the heating rate of 30 °C
min-1 and particle size of 91 – 106 µm for obtaining the bio-oil, char and gaseous
products from the EFB at different temperatures; 300, 400, 500, 600 and 700 °C.
Table 4.1: The Comparison of Pyrolysis Product Yields at Different Temperature.
Yields (%) Temperature (°C) Bio-oil Char Gasa
300 26.89 41.56 31.55 400 33.22 27.81 38.97 500 35.36 24.95 39.69 600 32.86 24.16 42.98 700 30.76 23.24 46.00
a By different weight of bio-oil and char.
57
Pyrolysis Products
20
25
30
35
40
45
50
200 300 400 500 600 70
Temperature, oC
Yiel
d, %
Figure 4.1: Effect of Temperature on Pyrolysis Yields.
As shown in Table 4.1 and Figure 4.1, at the lowe
°C, a decomposition process was relatively slow and a char
temperature increased from 300 °C to 500 °C, the amount
increased to a maximum value in the range of 33 –
temperatures of 600 °C and 700 °C, the bio-oil decreased
(2001b) and Acikgoz et al., (2007) studies on pyrolysis of s
respectively, indicated the same trend. The higher treatmen
bio-oil cracking resulting in higher gas yield and lower bio
Chen et al., 2003, Ji-lu, 2007). The results obtained from
showed that the maximum bio-oil yield obtained was 35.36
of 500 °C. The lowest of bio-oil yield was 26.89% at tempe
58
Gas
Bio-oilChar
0 800
st pyrolysis temperature, 300
was the major product. As the
of condensable liquid product
35%. At a higher pyrolysis
to 30 - 32%. Yorgun et al.,
unflower oil cake and linseed
t temperature has led to more
-oil yield (Zanzi et al., 2002,
the first series of experiments
% at the pyrolysis temperature
rature of 300 °C.
Pyrolysis Products
The char yield significantly decreased as the final pyrolysis temperature was
raised from 300 °C to 700 °C. The char yields were 41.56, 27.81, 24.95, 24.16 and
23.24% for the temperature of 300, 400, 500, 600 and 700 °C, respectively. The highest
char yield was 41.56% obtained at the temperature of 300 °C. And the lowest char yield
was 23.24% obtained at the temperature of 700 °C. In other words, the pyrolysis
conversion was increased as the temperature raised (Onay et al., 2001, Tsai et al., 2006,
Ozcimen and Karaosmanoglu, 2004). The decrease in char yield with an increase in
temperature could either be due to the greater primary decomposition of the EFB at
higher temperatures or through secondary decomposition of the char residues.
As shown in Table 4.1 and Figure 4.1, the gas yields were 31.55, 38.97, 39.69,
42.98 and 46.00% at temperature of 300, 400, 500, 600 and 700 °C, respectively. The
highest and lowest of gas obtained was 46.00% and 31.55% at the temperature of 700 °C
and of 300 °C, respectively. The gas product increased with an increase in pyrolysis
temperature. An increase in gas products is thought to occur predominantly due to the
secondary cracking of the pyrolysis vapours at higher temperatures. However, the
secondary decompositions of the char at the higher temperatures may also give other non-
condensable gas products (Horne and William, 1996). The gases identified during the
pyrolysis of the EFB were carbon monoxide, carbon dioxide, methane and some low
molecular weight hydrocarbons such as ethane, and ethylene.
59
Pyrolysis Products
4.2.2 Effect of Particle Size
In this study, the experiments were conducted by using four different particle size
ranges, namely size < 90 µm, 91 – 106 µm, 107 – 125 µm and 126 – 250 µm with
temperature of 500 °C and heating rate of 30 °C min-1.
Table 4.2: The Comparison of Pyrolysis Product Yields at Different Particle Size.
Yields (%) Sample Size (µm)
Bio-oils Char Gasa
< 90 33.45 29.45 37.10 91-106 35.36 24.95 39.69 107-125 30.18 27.00 42.82 126 -250 31.05 27.56 41.39
a By different weight of bio-oil and char.
20
25
30
35
40
45
50
<90 91-106 107-125 126-250
Particle Size,
Yiel
d, %
Gas
Bio-oil
Char
Figure 4.2: Effect of Particle Size on Pyrolysis Yields.
60
Pyrolysis Products
The second series of experiment was performed to establish the effect of particle
size on the pyrolysis product yields. The effect of particle size on the product yields is
given in Table 4.2 and Figure 4.2 under the temperature of 500 °C and heating rate of 30
°C min-1. The smallest particle size of < 91 µm produced a bio-oil yield of 33% was only
about 2% higher than that of the highest particle size (31%) with a char yield of 29% and
gas yield of 37%. Larger particle size of 126-250 µm produced a bio-oil yield of 31%
with a char yield of 28% and gas yield of 41%. A maximum of bio-oil yield was obtained
at particle size of 91-106 µm which was 35.36%. The lowest of bio-oil yield was
obtained at particle size of 107 – 125 µm which was 30.18%.
As shown in Figure 4.2, the char yields were 29.45, 24.95, 27.00 and 27.56% for
the particle size of < 90 µm, 91 – 106 µm, 107 – 125 µm and 126 – 250 µm,
respectively. The highest char yield was 29.45% obtained at the particle size of < 90 µm.
And the lowest char yield was 24.95% obtained at the particle size of 91 – 106 µm. The
gas yields were 37.10, 39.69, 42.83 and 41.40% for the particle size of < 90 µm, 91 – 106
µm, 107 – 125 µm and 126 – 250 µm, respectively. The highest and lowest gas yields
were obtained at the particle size of 107 – 125 µm (42.83%) and at the particle size of <
90 µm (37.10%).
Encinar et al (2000) pyrolysed cardoon (Cynara cardunculus L.) with size ranged
0.43 - 2.00 mm was hypothesized that an increase in particle size causes greater
temperature gradients inside the particle so that at a given time the core temperature is
lower than that of the surface, which possibly gives rise to an increase in the char yields
and a decrease in liquids and gases. Particle size is known to influence pyrolysis products
61
Pyrolysis Products
yield. If the particle size is sufficiently small it can be heated uniformly, as the results
obtained was consistent with the earlier studies (Seebauer et al., 1997).
However, in this work it was observed that the particle size had no significant
influence on the production of bio-oil during pyrolysis. Only small differences were
obtained probably being due to experimental error. These results were also in agreement
with others previously published which reported that particle sizes below 5 mm do not
exert any influence on the process rate (Sensoz et al., 2006).
4.2.3 Effect of Heating Rate
The third series of experiment was performed to establish the effect of heating
rate on the pyrolysis product yields. In this study, experiments were conducted at
different heating rate of 10, 30, 50 and 100 °C min-1 with temperature of 500 °C and
particle size of 91 – 106 µm. The effect of heating rate on the product yields is given in
Table 4.3 and Figure 4.3.
Table 4.3: The Comparison of Pyrolysis Product Yields at Different Heating Rate.
Yields (%) Heating Rate (°C min-1) Bio-oils Char Gasa
10 30.44 26.17 43.39 30 35.36 24.95 39.69 50 39.81 21.95 38.24 100 42.28 21.44 36.28
a By different weight of bio-oil and char.
62
Pyrolysis Products
20
25
30
35
40
45
50
0 10 20 30 40 50 60 70 80 90 100 110
Heating Rate, oC min-1
Yiel
d, %
Bio oil
Gas
Char
Figure 4.3: Effect of Heating Rate on Pyrolysis Yields.
The results obtained in this study showed that the increase of the heating rate
leads to an increase in a yield of bio-oil. It was noted that, the higher heating rate, the
lower effect of mass transport limitations ( Sensoz, 2003). The bio-oil yield reached a
maximum value of 42% with the highest heating rate of 100 °C min-1. The lowest of bio-
oil yield were obtained at heating rate of 10 °C min-1 (30.44%).
As shown in Figure 4.3, the char yields were 26.17, 24.95, 21.44 and 21.95% for
the heating rate of 10, 30, 50 and 100 °C min-1, respectively. The highest char yield was
obtained at the heating rate of 10 °C min-1 (26.17%). And the lowest char yield was
obtained at the heating rate of 50 °C min-1 (21.44%). As observed, the increase of the
heating rate leads to a decrease in the char yield. This may be related to the rapid heating
leads to a fast depolymerization of the solid material to primary volatiles, whilst at the
lower heating rate a dehydration is to be more stable and an anhydrocellulose is too slow
and is limited to occur (Chen et al., 1997).
63
Pyrolysis Products
As shown in Table 4.3 and Figure 4.3, the gas yields were 43.39, 39.69, 38.76
and 35.77% at the heating rate of 10, 30, 50 and 100 °C min-1, respectively. The highest
and lowest of gas obtained was 43.39% and 35.77% at the heating rate of 10 °C min-1 and
100 °C min-1, respectively.
4.2.4 Effect of different Oil Palm Biomass
In this study, the pyrolysis processes were carried out at the temperature of 500
°C, heating rate of 30 °C min-1 and particle size of 91 – 106 µm for obtaining the bio-oil,
char and gaseous products from the EFB, trunk, frond and fiber.
Table 4.4: The Comparison of Pyrolysis Product Yields Using Different Oil Palm Biomass.
Yields (%) Type of Oil Palm Biomass Bio-oils Char Gasa
EFB 35.36 24.95 39.69 Trunk 30.95 25.78 43.27 Frond 31.21 26.68 42.11 Fiber 27.26 28.16 44.58
a By different weight of bio-oil and char.
64
Pyrolysis Products
20
25
30
35
40
45
50
EFB Trunk Frond Fiber
Type of Oil Palm Biomass
Yiel
d, %
Gas
Bio-oil
Char
Figure 4.4: Effect of different Oil Palm Biomass on Pyrolysis Yields.
The aim of this study was to investigate the EFB as a better oil palm biomass
product compared to other oil palm biomass based on the yield of pyrolysis especially for
the production of bio-oil. Each experiment was conducted at the optimum conditions to
produce bio-oil product. The optimum conditions chosen were based on the previous
experimental work as reported in this study. The effect of different oil palm biomass on
the pyrolysis products yields is given in Table 4.4 and Figure 4.4.
By comparing the bio-oil yield of the four oil palm biomass materials, it can be
observed the EFB has the highest bio-oil yield (35.36%). The lowest of bio-oil yield was
obtained from the fiber samples (27.26%). The bio-oil yield of trunk and frond was
30.95% and 31.21%, respectively. As shown in Table 4.4 and Figure 4.4, the char yields
were 24.95, 25.78, 26.68 and 28.16% for EFB, trunk, frond and fiber, respectively. The
highest char yields were obtained from the fiber samples (28.16%). And the lowest char
yields were obtained from the EFB samples (24.95%). In this study, the gas yields were
36.69, 43.27, 42.11 and 44.58% for EFB, trunk, frond and fiber, respectively. The highest
65
Pyrolysis Products
and lowest of gas obtained is 44.58% and 36.69% from the fiber and EFB samples,
respectively. The difference of the bio-oil yield observed among the four oil palm
biomass might be attributed to their different chemical structure. The chemical structure
of oil palm biomass consists of a large amount of O-bearing functional groups, which
generally have low thermal stability (Yang et al., 2006). The chemical compositions of
biomass materials depend on percentage of cellulose, hemicellulose and lignin. Table 4.5
shows the typical compositions (cellulose, hemicellulose and lignin) of different oil palm
biomass materials.
Table 4.5: Typical compositions of different oil palm biomass materials.
Biomass (% of dry matter)
Cellulose Hemicellulose Lignin
EFB 39.0 22.0 29.0 Trunk 59.0 10.0 11.0 Frond 42.0 21.0 23.0 Fiber 21.0 16.0 43.0
Uzun et al (2007) pyrolysed olive-oil residues at various temperature (400, 500,
550 and 700 ºC) and a heating rate of 300 ºC min-1. It was hypothesized that an increase
in cellulose and hemicellulose content causes an increase in the release of volatiles yield.
Furthermore, an increase in the lignin content causes an increase in the char yield. This
hypothesis is similar to the results obtained in this study which fiber has the highest char
yield because it has higher lignin content. The bio-oil yield of fiber is lower compared
with another oil palm biomass because it has lower cellulose and hemicellulose content.
The bio-oil yield obtained from EFB, trunk and frond was more than 30 % compared
with fiber because cellulose and hemicellulose content is too high.
66
Pyrolysis Products
4.2.5 Effect of different Type of Fluidised Bed Material
The last series of experiment was performed to establish the effect of fludised bed
on the pyrolysis product yields. In this study, the experiments were conducted at
temperature of 500 °C, particle size of 91 – 106 µm and heating rate of 30 °C min-1 using
the different type of fludised bed. The types of fludised bed used in this experiment were
the spent bleaching earth + zircon sand, the spent bleaching earth washing with hexane +
zircon sand and the zircon sand. The effect of the fluidised bed on the product yields is
given in Table 4.6 and Figure 4.5.
Table 4.6: The Comparison of Pyrolysis Product Yields Using Different Type of Fludised Bed.
Yields (%) Type of Fludised bed materials Bio-oils Char Gasa
Spent Bleaching Earth + Zircon sand
42.57 13.17 44.26
Spent Bleaching Earth washing with Hexane + Zircon sand
42.82 12.44 44.74
Zircon sand 35.36 24.95 39.69 a By different weight of bio-oil and char.
67
Pyrolysis Products
101520253035404550
0 1 2 3
Type of Fixed-bed
Yiel
d ,%
Spent BleachingEarth washing with
Hexane+Zircon Sand
Zircon Sand
Bio oilGas
Char
Spent BleachingEarth+Zircon Sand
Figure 4.5: Effect of Fludised Bed on Pyrolysis Yields.
The optimum of bio-oil obtained was 42.82% using a fluidised bed of the spent
bleaching earth washing with hexane + zircon sand. The bio-oil yields of the fluidised
bed using the zircon sand and the spent bleaching earth + zircon sand was 42.57% and
35.36%, respectively. In this study, the char yield was 13.17, 12.44 and 24.95% for the
fluidised bed of the spent bleaching earth washing with hexane + zircon sand, the spent
bleaching earth + zircon sand and the zircon sand, respectively. The highest char yield
was obtained from the spent bleaching earth washing with hexane + zircon sand
(42.57%). The highest and lowest of gas obtained was 44.74% and 36.69% from the
spent bleaching earth + zircon sand and the zircon sand, respectively.
From the results obtained in this study, the products yield of the spent bleaching
earth washing with hexane + zircon sand and the spent bleaching earth + zircon sand used
as a fixed-bed was quite close to each other. This might be due to the washing with
hexane could not remove all the oil content in the spent bleaching earth. The bio-oil
68
Pyrolysis Products
product obtained from the spent bleaching earth was higher compared with the zircon
sand as a fluidised bed. This might be due to the spent bleaching earth contained about
30-40% of oil (w/w) and 20 % (w/w) of moisture content. Consequently, these can
contribute to higher percentage of moisture content in bio-oil. The zircon sand and the
zircon sand mixed with the spent bleaching earth was used as heat carrier from wall side
to the object to be pyrolyzed. The fluidization of the sand together with spent bleaching
earth enhanced the heat transfer rate to the EFB particles so as to increase the bio-oil
yield.
69
Characterisation of Pyrolysis Products
CHAPTER 5
CHARACTERISATION OF PYROLYSIS PRODUCTS
5.1 INTRODUCTION
This chapter deals with the characterisation of the pyrolysis products obtained
from the empty fruit bunches. These pyrolysis products includes bio-oil, char and gas
obtained from different temperature, particle size and heating rate. Characterisation of
the EFB includes proximate analysis, calorific value and elemental analysis (w/w
percentage of carbon, oxygen, nitrogen and hydrogen). The proximate analysis consists
of determination of moisture content, volatile matter, fixed carbon and ash content in
EFB. The physical characterisation of bio-oil includes calorific value, total ash, pH,
moisture content, total acid, density and elemental analysis. The bio-oil was analysed by
using Fourier Transform infra-red (FTIR) spectroscopy and gas chromatography/mass
spectrometry (GCMS). Meanwhile, the characterisation of the char includes calorific
value, surface area, total volume pore and elemental analysis. Gas analysis according to
different pyrolysis temperatures was detected using micro gas chromatography model
Agilent 3000 Micro GC.
70
Characterisation of Pyrolysis Products
5.1.1 Characterisation of empty fruit bunches (EFB) Table 5.1: Main Characteristics of the Treated Oil Palm Empty Fruit Bunches (EFB). Characteristics EFB Approximate analysis (wt. %) Volatiles 81.9 Fixed Carbon 12.6 Ash 3.1 Moisture 2.4 Ultimate analysis (wt. %) Carbon 53.78 Hydrogen 4.37 Nitrogen 0.35 Oxygen 41.50 H/C molar ratio 0.98 O/C molar ratio 0.58 Empirical formula CH0.98O0.58N 0.01Calorific value (MJ kg-1) 17.08
The results of proximate and ultimate analysis of oil palm empty fruit bunches are
listed in Table 5.1, showing that oil palm empty fruit bunches are environment friendly
energy sources since containing trace amount of N. As can be seen in Table 5.1, the
moisture content of EFB was 2.4 wt%. By comparing the moisture content in EFB with
olive baggase of Turkey, it has been found that the moisture content of EFB is lower than
the moisture content of olive baggase (6.8 wt%)(Sensoz et al., 2006). For pyrolysis,
higher water content in the feedstock has some adverse role such as an extra heat is
required for vaporizing the moisture (Asadullah et al., 2008).
In this study, the calorific value of the empty fruit bunches was determined in
order to evaluate the energy content of the biomass used during pyrolysis. The result
obtained showed that the calorific value of the empty fruit bunches was 17.08 MJ/kg.
71
Characterisation of Pyrolysis Products
The volatile matter, fixed carbon and ash content of empty fruit bunches was 81.9
wt%, 12.6 wt% and 3.1 wt%, respectively. Major fractions of cellulose and hemicellulose
present in the empty fruit bunches are converted to the volatile fraction. In the pyrolysis
of biomass, the volatile fraction is usually converted to the bio-oil upon condensation.
The carbon which is converted to char is called the fixed carbon which is formed from
different composition of biomass in the order of lignin > hemicellulose > cellulose.
According to Asadullah et al (2008) the fixed carbon is difficult to vaporize at pyrolysis
temperature around 500 ºC.
The ultimate analysis provides the chemical composition of the EFB in elemental
terms, and is used to determine combustion air requirements, flue losses and likely
emission levels. From this analysis, it has been found that the EFB contains 53.78 wt% of
carbon, 4.37 wt% of hydrogen, 41.50 wt% of oxygen and 0.35 wt% of nitrogen. The H/C
and O/C ratios of EFB were 0.98 and 0.58, respectively. If considering only the main
elements (C, H, O, N), the molecular formula of the samples based on one C atom can be
written as CH0.98 O0.58N0.01.
72
Characterisation of Pyrolysis Products
5.2 RESULTS AND DISCUSSION 5.2.1 Characterisation of bio-oil product 5.2.1.1 Physical properties of bio-oil
The physical properties of the bio-oil were determined according to different
temperature, particle size and heating rate. The results obtained are given in Tables 5.2,
5.3 and 5.4, respectively.
Table 5.2: Properties of Bio-oil Product* According to Different Temperature.
Note: *Obtained at heating rate of 30 °C min-1 and particle size of 91-106 µm.
Temperature (°C) Properties 300 400 500 600 700
1. Calorific Value (MJ/kg) 18.32 20.23 21.41 21.17 20.41 2. Ash content (%) 0.64 0.49 0.65 0.37 0.26 3. pH 3.9 3.4 3.0 3.0 2.9 4. Moisture content (%) 18.01 17.89 18.74 18.21 21.32 5. Total Acid (mg KOH/g) 92.30 81.81 75.62 67.75 62.19 6. Density (g/cm3) 0.90 1.00 0.90 0.99 0.88
Table 5.3: Properties of Bio-oil Product* According to Different Particle Size.
Particle Size (µm) Properties <90 91 - 106 107 - 125 126 - 250
1. Calorific Value (MJ/kg) 21.41 21.41 20.52 23.88 2. Ash content (%) 0.65 0.65 0.47 0.23 3. pH 3.4 3.0 3.5 3.2 4. Moisture content (%) 21.98 18.74 19.08 20.54 5. Total Acid (mg KOH/g) 66.64 74.23 67.75 71.25 6. Density (g/cm3) 0.9653 0.8962 0.8874 0.9012
Note: *Obtained at temperature of 500 °C with heating rate 30 °C min-1
73
Characterisation of Pyrolysis Products
Table 5.4: Properties of Bio-oil Product* According to Different Heating Rate.
Note: *Obtained at temperature of 500 °C and particle size of 91-106 µm.
Heating Rate (°C min-1) Properties 10 30 50 100
1. Calorific Value (MJ/kg) 16.42 21.41 20.19 19.92 2. Ash content (%) 0.41 0.65 0.43 1.11 3. pH 2.6 3.0 3.5 3.1 4. Moisture content (%) 19.01 18.74 20.68 18.07 5. Total Acid (mg KOH.g-1) 85.83 75.62 91.75 68.63 6. Density (g/cm3) 1.00 0.90 0.99 0.88
As can be seen in Table 5.2, the moisture content of bio-oil was varied between
18 % and 21 % depending on the production condition. The highest moisture content of
bio-oil obtained is 21.32 % at pyrolysis temperature of 700 ºC. Furthermore, the lowest
moisture content of bio-oil obtained is 17.89 % at pyrolysis temperature of 400 ºC.
According to different particle size, the moisture content of bio-oil was varied
between 19 and 22% (Table 5.3). The results obtained in this study indicate that there is
no significant effect of particle size on moisture content of bio-oil. The highest moisture
content of bio-oil obtained is 21.98% at particle size of < 90 µm. The lowest moisture
content of bio-oil obtained is 18.74% at particle size of 91-106 µm.
According to different heating rate, the moisture content of bio-oil was varied
between 18% and 21% as shown in Table 5.4. The highest moisture content of bio-oil
obtained is 20.68% at heating rate of 50 ºC min-1. The lowest moisture content of bio-oil
obtained is 18.07 % at heating rate of 100 ºC min-1. The water produced in the pyrolysis
reaction together with any water contained from the biomass feedstock contributed to the
moisture content. The amount of moisture content (water) in the product also depends on
74
Characterisation of Pyrolysis Products
the process parameters including the extent of secondary reaction or cracking and the
temperature of the product gases leaving the liquid collection system. When substantial
gas flows are involved in the process such as with fluidized bed type reactors, water is
considered lost as a saturated vapour in the exit gas as well as losses from light ends.
According to different temperature, the pH value of the bio-oil was varied
between 2.9 and 3.9 as shown in Table 5.2. The highest pH of bio-oil obtained is 3.9 at
pyrolysis temperature of 300 ºC. The results obtained indicated that an increase in
temperature leads to a slightly decrease in pH of the bio-oil. There is no significant
change in the pH value of bio-oil as the temperature varied from 300 to 700 ºC at heating
rate of 30 ºC min-1 and particle size of 91-106 µm.
According to different particle size, the pH value of the bio-oil was varied
between 3.0 and 3.5 as shown in Table 5.3. The highest pH of bio-oil obtained is 3.5 at
particle size of 107-125 µm. The pH values of the bio-oil were 2.6, 3.0, 3.5 and 3.1 for
the heating rate of 10, 30, 50 and 100 °C min-1, respectively (Table 5.4). The highest pH
of bio-oil obtained is 3.5 at the heating rate of 50 °C min-1. The lowest pH of bio-oil
obtained is 2.6 at the heating rate of 10 °C min-1. This finding is in agreement with the
same published data (Bridgwater et al., 1999) that is, bio-oil generally contained
substantial amount of organic acids, mostly acetic acids and formic acids, which give the
bio-oil its low pH value.
The acid values of the bio-oil are changing between 62 and 92 mgKOHg-1 (Table
5.2) when varying the temperature from 300 ºC to 700 ºC. The highest acid value of bio-
75
Characterisation of Pyrolysis Products
oil obtained is 92.30 mgKOHg-1 at pyrolysis temperature of 300 ºC. For the effect of
particle size, the acid values of the bio-oil are changing between 67 and 74 mgKOHg-1 as
shown in Table 5.3. The highest acid value of bio-oil obtained is 74.23 mgKOHg-1 at
particle size of 91-106 µm.
The acid values of the bio-oil are changing between 69 and 92 mgKOHg-1 (Table
5.4) when the heating rate is increased from 10 °C min-1 to 100 °C min-1. The highest and
lowest acid value of bio-oil obtained is 91.75 mgKOHg-1 and 68.63 mgKOHg-1 at heating
rate of 50 °C min-1 and 100 °C min-1, respectively. Hemicellulose from EFB contain
glucuronic acids, this might be the reason for the higher amount of free acids which can
cause polycondensation reactions of aldehydes and phenol. As pH measures to
concentration of H3O+ ions, KOH addition may be lead to some saponification of esters
and hence an unproportional consumption of alkali (Bridgwater, 1997).
The calorific values of bio-oils are changing from 18 and 21 MJ/kg (Table 5.2)
when the pyrolysis temperature increased from 300 ºC to 700 ºC. As shown in Figure 5.1,
the highest bio-oil yield and calorific value obtained at temperature of 500 ºC, heating
rate of 30 °C min-1 and particle size of 91 – 106 µm. As the temperature increased from
300 ºC to 500 ºC, the bio-oil yield and calorific value increased together to a maximum
value. Meanwhile, at the higher pyrolysis temperature of 600 and 700 ºC, the bio-oil yield
and calorific value are decreased. The study of the effect of temperature on bio-oil yield
and calorific value had shown that a 500 ºC was the optimum temperature to produce the
bio-oil product with highest calorific value.
76
Characterisation of Pyrolysis Products
1818.5
1919.5
20
20.521
21.522
200 300 400 500 600 700 800
Temperature, oC
Cal
orifi
c V
alue
, MJ/
kg
25
27
29
31
33
35
37
Yie
ld o
f Bio
-oil,
%Calorif ic Value
Bio-oil
Figure 5.1: Effect of Temperature on Calorific Value and Yield of Bio-oil.
According to different particle size, the calorific values of bio-oils are changing
between 21 and 24 MJ/kg as shown in Table 5.3. As shown in Figure 5.2, the highest
calorific value of bio-oil obtained is 24 MJ/kg at particle size of 126 – 250 µm.
Nevertheless, in these conditions only 31 % of bio-oil was produced compared with the
highest bio-oil obtained is 35 % at particle size of 91 – 106 µm.
77
Characterisation of Pyrolysis Products
20
21
22
23
24
25
<90µm 91µm -106µm
107µm-125µm
126µm-250µm
Particle Size
Cal
orifi
c Va
lue,
MJ/
kg
30
31
32
33
34
35
36
Yiel
d of
Bio
-oil, %
Bio-oil
Calorific Value
Figure 5.2: Effect of Particle Size on Calorific Value and Yield of Bio-oil.
The calorific values of bio-oil were 16.42, 21.41, 20.19 and 19.92 MJ/kg for the
heating rate of 10, 30, 50 and 100 °C min-1, respectively (Table 5.4). As shown in Figure
5.3, the highest calorific value of bio-oil obtained is 21 MJ/kg at heating rate of 30 °C
min-1 and the maximum of bio-oil yield obtained is 42% at heating rate of 100 °C min-1.
As the heating rate increased from 10 °C min-1 to 30 °C min-1, the calorific value and bio-
oil yield increased together. Meanwhile, at the higher heating rate of 50 °C min-1 and 100
°C min-1, the bio-oil yield slightly increased but the calorific value are decreased. The
study of the effect of heating rate on bio-oil yield and calorific value had shown that a
100 ºC min-1 was the best heating rate to produce maximum of bio-oil with high calorific
value.
For the bio-oils, high water content in combination with a high O/C atomic ratio
gives poor calorific values. On the other hand, at similar water content the calorific value
of bio-oil is higher due to its lower O/C atomic ratio (Meier and Scholze, 1997).
78
Characterisation of Pyrolysis Products
16
17
18
19
20
21
22
10 20 30 40 50 60 70 80 90 100 110
Heating Rate, oCmin-1
Calo
rific
Val
ue, M
J/kg
30
32
34
36
38
40
42
44
Yiel
d of
Bio
-oil,
%
Calorif ic Value
Bio-oil
Figure 5.3: Effect of Heating Rate on Calorific Value and Yield of Bio-oil.
According to different temperature, the ash content in the bio-oils was varied
from 0.26 and 0.64 % (Table 5.2). The highest total ash of bio-oil obtained was 0.64 %
at pyrolysis temperature of 700 ºC. For the effect of particle size, the ash content in the
bio-oils was ranged between 0.23 and 0.65 wt% as shown in Table 5.3. The highest ash
content in the bio-oil obtained was 0.65 % at particle size of 91-106 µm.
The ash content of bio-oils was varied between 0.41 and 1.11 % (Table 5.4) when
increasing the heating rate from 10 °C min-1 to 100 °C min-1. The highest total ash of bio-
oil obtained was 1.11 % at heating rate of 100 °C min-1. The lowest total ash of bio-oil
obtained was 0.41 % at heating rate of 10 °C min-1. Oil or water soluble metallic
compounds or from extraneous solids such as dirt and rust might contributed to the ash
content in the bio-oils. The main metals in ash for biomass pyrolysis liquid were Ca, K,
Si, Mg, Fe, S, Al, P, Na and Zn (Asadullah et al., 2008).
79
Characterisation of Pyrolysis Products
Density is a fundamental physical property that can be used in conjunction with
other properties to characterize of bio-oil products. Determination of the density or
relative density of bio-oil is necessary for the conversion of measured volumes to
volumes at the standard temperature. In the study of the effect of temperature, the density
of bio-oil was ranged between 0.88 and 1.00 g/cm3 as shown in Table 5.2. At the lowest
pyrolysis temperature of 300 ºC and at the highest pyrolysis temperature of 700 ºC
density of bio-oil was 0.90 g/cm3 and 0.88 g/cm3 respectively. The highest density of bio-
oil obtained was 1.00 g/cm3 at temperature of 400 ºC.
Varying the particle size from < 90 µm to 250 µm at 500 ºC with the heating rate
of 30 °C min-1, the density of bio-oil was changing between 0.89 and 0.97 g/cm3 (Table
5.3). The highest density of bio-oil obtained was 0.97 g/cm3 at particle size of < 90 µm.
And then, the lowest density of bio-oil obtained was 0.89 g/cm3 at particle size of 107-
125 µm. The densities of bio-oil were 1.00, 0.90, 0.99 and 0.88 g/cm3 for the heating rate
of 10, 30, 50 and 100 °C min-1 (Table 5.4), respectively. The highest and lowest density
of bio-oil obtained was 1.00 g/cm3 and 0.88 g/cm3 at the heating rate of 10 °C min-1 and
100 °C min-1, respectively.
80
Characterisation of Pyrolysis Products
Table 5.5: Elemental Analysis of Bio-oil Product* According to Different Temperature.
Temp (°C)
C (wt. %)
H (wt. %)
O (wt. %)
N (wt. %)
H/Ca O/Ca Molecular formula
300 43.04 8.13 47.7 1.13 2.27 0.83 CH2.27O0.83N0.02400 35.29 6.67 57.02 1.02 2.27 1.21 CH2.27O1.21N0.02500 49.80 7.98 40.29 1.93 1.92 0.61 CH1.92O0.61N0.03600 53.75 8.81 36.04 1.40 1.97 0.50 CH1.97O0.50N0.02700 34.39 5.97 57.58 2.06 2.08 1.26 CH2.08O1.26N0.05
Note: *Obtained at heating rate of 30 °C min-1 and particle size of 91-106 µm. a Molar ratio
Table 5.5 shows the elemental compositions analysis, H/C molar ratio, O/C molar
ratio and empirical formula of the bio-oils according to different temperature. The H/C
ratios of bio-oils are ranged between 1.92 and 2.27. The highest H/C ratio of bio-oil
obtained was 2.27 at both pyrolysis temperatures of 300 ºC and 400 ºC. According to
different temperature, the O/C ratios of bio-oil are ranged between 0.50 and 1.26. The
highest O/C ratio of bio-oil obtained was 1.26 at the pyrolysis temperature of 700 ºC. The
percentage of hydrogen and nitrogen was ranged from 6-9 % and 1-2 % respectively. The
highest hydrogen and nitrogen content obtained was 8.8 % and 2.06 % at the final
pyrolysis temperatures of 600 ºC and 700 ºC respectively. The average chemical
composition of the bio-oil at different temperatures also listed in Table 5.5.
As shown in Figure 5.4, the percentage of carbon was ranged from 34 and 53%
with the highest percentage of carbon obtained was 53% at the pyrolysis temperature of
600 ºC. Meanwhile, the percentage of oxygen was ranged from 36 and 58% with the
highest percentage of oxygen obtained was 58% at the pyrolysis temperature of 700 ºC.
As it is known, the high carbon content and low oxygen content of bio-oil make it
suitable to act as fuel. The study of the effect of temperature on carbon and oxygen
81
Characterisation of Pyrolysis Products
content had shown that a 600 ºC was the best temperature to produce bio-oil with high
carbon content and low oxygen content.
30
35
40
45
50
55
60
200 300 400 500 600 700 800
Temperature, oC
wt.
%
Carbon
Oxygen
Figure 5.4: Effect of Temperature on Oxygen and Carbon Content of Bio-oil.
Table 5.6: Elemental Analysis of Bio-oil Product* According to Different Particle Size.
Particle Size (µm)
C (wt. %)
H (wt. %)
O (wt. %)
N (wt. %)
H/Ca O/Ca Molecular formula
<90 42.43 4.94 51.61 1.02 1.40 0.91 CH1.40O0.91N0.02
91 - 106 49.80 7.98 40.29 1.93 1.92 0.61 CH1.92 O0.61N0.03107 - 125 56.29 6.77 35.38 1.56 1.44 0.47 CH1.44 O0.47N0.02126 - 250 42.29 7.02 49.24 1.45 1.99 0.87 CH1.99 O0.87N0.03
Note: *Obtained at temperature of 500 °C with heating rate 30 °Cmin-1. a Molar ratio
For the different particle size, the H/C ratios of bio-oils are changing between1.40
and 1.99 as shown in Table 5.6. The highest H/C ratio of bio-oil obtained was 1.99 at
particle size of 126 - 250 µm. According to different particle size the O/C ratios of bio-oil
are ranged between 0.47 and 0.91. The highest O/C ratio of bio-oil obtained was 0.91 at
particle size of < 90 µm. The percentage of hydrogen and nitrogen was ranged from 5 -
82
Characterisation of Pyrolysis Products
8% and 1 - 2% respectively. The highest hydrogen and nitrogen content obtained was
7.98% and 1.93% respectively at particle size of 91 – 106 µm. The average chemical
composition of the bio-oil at different particle sizes also listed in Table 5.6.
As shown in Figure 5.5, the percentage of carbon was ranged from 42 and 56%
with the highest percentage of carbon obtained was 56% at particle size of 107 - 125 µm.
Meanwhile, the percentage of oxygen was ranged from 35 and 52% with the highest
percentage of oxygen obtained was 52% at particle size of < 90 µm. The study of effect
of particle size on carbon and oxygen content had shown that a 107 - 125 µm was the
best particle size to produce bio-oil, which high carbon content and low oxygen content
make it suitable to act as fuel.
30
35
40
45
50
55
60
<90µm 91µm -106µm
107µm-125µm
126µm-250µm
Particle size
wt.
%
Carbon
Oxygen
Figure 5.5: Effect of Particle Size on Oxygen and Carbon Content of Bio-oil.
83
Characterisation of Pyrolysis Products
Table 5.7: Elemental Analysis of Bio-oil Product* According to Different Heating Rate.
Heating Rate (°Cmin-1)
C (wt. %)
H (wt. %)
O (wt. %)
N (wt. %)
H/Ca O/Ca Molecular formula
10 47.77 6.69 43.86 1.68 1.68 0.69 CH1.68O0.69N0.0330 49.80 7.98 40.29 1.93 1.92 0.61 CH1.92O0.61N0.0350 35.28 5.67 57.64 1.41 1.93 1.23 CH1.93O1.23N0.03100 38.91 7.09 52.63 1.37 2.19 1.01 CH2.19O1.01N0.03
Note: *Obtained at temperature of 500 °C and particle size of 91-106 µm. a Molar ratio
The elemental compositions analysis, H/C molar ratio, O/C molar ratio and
empirical formula of the bio-oils according to different hating rate are listed in Table 5.4.
The H/C ratios of bio-oils are changing between 1.68 and 2.19. The highest H/C ratio of
bio-oil obtained was 2.19 at heating rate of 100 °C min-1. The lowest H/C ratio of bio-oil
obtained was 1.68 at heating rate of 10 °C min-1. The O/C ratios of bio-oil are ranged
between 0.61 and 1.23 when increasing the heating rate from 10 °C min-1 to 100 °C min-
1. The highest O/C ratio of bio-oil obtained is 1.23 at heating rate of 50 °C min-1. The
percentage of hydrogen and nitrogen was ranged from 6-8 %, and 1-2 % respectively.
The highest hydrogen and nitrogen content obtained was 7.98% and 1.93% at heating rate
of 30 °C min-1. The average chemical composition of the bio-oil at a different heating rate
also listed in Table 5.4.
As shown in Figure 5.6, the percentage of carbon was ranged from 35 and 50%
with the highest percentage of carbon obtained was 50% at heating rate of 30 °C min-1.
Meanwhile, the percentage of oxygen was ranged from 40 and 58% with the highest
oxygen content of bio-oil obtained was 58 % at heating rate of 50 °C min-1. As it is
known, the high carbon content and low oxygen content of bio-oil make it suitable to act
as fuel.
84
Characterisation of Pyrolysis Products
The study of the effect of heating rate on carbon and oxygen content had shown
that a 30 ºC min-1 was the best heating rate to produce bio-oil with high carbon content
and low oxygen content.
In addition, the high oxygen and water contents make it incompatible with
conventional fuels although it may be utilized in a similar way. Some conversion or
upgrading for oxygen and water removal and stabilization is necessary to give a product
that is fully compatible with conventional fuels. Actually, the high oxygen contents in the
bio-oil not attractive for transport fuel. An alternative approach is to reduce the oxygen
content to a sufficiently low level that it may be satisfactory blended with conventional
fuels. This might be achieved by less complete hydrogenation.
30
35
40
45
50
55
60
0 20 40 60 80 100
Heating Rate, oC min-1
wt.
%
Oxygen
Carbon
Figure 5.6: Effect of Heating Rate on Oxygen and Carbon Content of Bio-oil.
85
Characterisation of Pyrolysis Products
5.2.1.2 FTIR Analysis of Bio-oil
The FTIR spectra of bio-oil from pyrolysis of EFB at different temperature,
particle size and heating rate are given in Figures 5.7, 5.8 and 5.9 (refer Appendixes 1 -
3). The O-H stretching vibrations between 3200 and 3400 cm-1 indicate the presence of
phenol and alcohols. The C-H stretching vibrations between 2850 and 2930 cm-1 and C-H
deformation vibrations between 1380 and 1460 cm-1 indicate the presence of alkanes. The
C=O stretching vibrations between 1700 cm-1 and 1720 cm-1 represent the presence of
ketones, aldehydes, carboxylic acids and their derivatives. The absorbance peaks between
1510 cm-1 and 1640 cm-1 represent C=C stretching vibrations indicative of alkenes and
aromatics. Absorptions possibly due to C-O vibrations from carbonyl components (i.e.,
alcohols, esters, carboxylic acids or ether) occur between 1060 cm-1 and 1240 cm-1 of the
bio-oil. Absorbance peaks between 700 and 760 cm-1 indicate the possible presence of
single, polycyclic and substituted aromatic groups.
86
Characterisation of Pyrolysis Products
Figure 5.7: FTIR Spectra of Bio-oil at Different Temperature. (Note: T300 = 300 ºC, T400 = 400 ºC, T500 = 500 ºC, T600 = 600 ºC and T700 = 700 ºC).
Figure 5.8: FTIR Spectra of Bio-oil at Different Particle Size. (Note: A01 = < 90 µm, A02 = 91 – 106 µm, A03 = 107 – 125 µm and A04=126 – 250 µm).
87
Characterisation of Pyrolysis Products
Figure 5.9: FTIR Spectra of Bio-oil at Different Heating Rate. (Note: HR10 = 10 ºC min-1, HR 30 = 30 ºC min-1, HR = 50 = 50 ºC min-1 and HR 100 = 100 ºC min-1).
88
Characterisation of Pyrolysis Products
5.2.1.3 GCMS Analysis of Bio-oil
Influence of temperature on components of Bio-oil.
GCMS analysis was carried out with typical bio-oil in order to get an idea of the
nature and type of possible compounds found in the bio-oils. This is due to the rather
similar peak patterns of chromatograms of the bio-oil obtained from other pyrolysis
parameters. All the possible compounds obtained from bio-oils identified by the MS
search libraries (Wiley7n.L and NIST 98.L). The possible compounds of bio-oil detected
using GCMS analysis at different pyrolysis temperatures are listed in Table 5.8 (Refer
Appendixes 4 - 8). A total of 35 possible compounds were obtained at different pyrolysis
temperature existing in various chemical compounds. The results indicated that two
compounds were mainly obtained at all pyrolysis temperatures. The compounds are
furfural and phenol. The highest area percentage for phenol was 22.19% at 700 ºC. The
highest area percentage for furfural was 10.68% which obtained at 500 ºC. A total of 11
and 10 compounds were obtained at 300 ºC and 400 ºC, respectively. The maximum of
18 compounds were obtained at 500 ºC. The results indicated that the number of
compounds produced significantly decreased as the pyrolysis temperature increased.
89
Characterisation of Pyrolysis Products
Influence of particle size on components of Bio-oil.
Table 5.9 lists the possible compounds of bio-oil according to the GCMS analysis
at different particle size (Refer Appendixes 9 - 12). A total of 44 possible compounds are
obtained at different particle size existing in various chemical compounds, which highest
value compare with different temperature and heating rate. The results show that three
compounds are obtained at all particle size. The compounds were phenol, phenol, 2,6-
dimethoxy and 1,2-benzenediol. The highest area percentage of phenol was 18.85%
obtained at particle size of < 90 µm. The highest area percentage of phenol, 2,6-
dimethoxy and 1,2-benzenediol were 8.25% and 5.27% obtained at particle size of 126 –
250 µm and 91 – 106 µm, respectively. The maximum number of compound according to
different particle size obtained was 21 at at particle size of 107 – 125 µm. A total of 19
and 18 were obtained at particle size of < 90 µm and 91 – 106 µm, respectively. At the
highest particle size in the range of 126 – 250 µm the number of compounds was 16.
Influence of heating rate on components of Bio-oil.
Table 5.10 lists the possible compounds found in bio-oil according to GCMS
analysis at different heating rates (Refer Appendixes 13 - 16). A total of 34 possible
compounds were obtained at different heating rate. Three compounds were 3,4-dihydro-
2H-Pyran, phenol 2-methoxy and phenol obtained at all heating rate. The highest area
percentage for phenol was 19.06% at heating rate of 50 ºC min-1. The highest area
percentage for phenol 2-methoxy and 3,4-dihydro-2H-Pyran was 5.04% and 4.97%
which obtained at heating rate of 100 ºC min-1 and 30 ºC min-1, respectively. The
maximum of 18 compounds were obtained at heating rate of 30 ºC min-1. The results
90
Characterisation of Pyrolysis Products
91
indicated that the number of compounds increased as the heating rate increased. The
results obtained showed the chemical compositions of the bio-oil are very similar to the
inclusion of a lot of aromatics and oxygenated compounds such as carboxylic acids,
phenols, ketones, aldehydes, etc. The presence of these aromatics and oxygenated
compounds was attributed to its biopolymer textures such as cellulose, hemicellulose and
lignin of the oil palm EFB. Some of these compounds have been mentioned previously in
various study (Tsai, et al., 2006). The components of bio-oils are strongly dependent on
the process or condition.
Characterisation of Pyrolysis Products
Table 5.8: Possible Chemical Compounds* of Bio-oil According to the GC/MS Analysis of Different Temperature.
Area, % (Retention Time)Peak No. Possible Chemical Compounds 300 °C 400 °C 500 °C 600 °C 700 °C
1 Furfural 4.49 (3.13) 6.54 (3.13) 10.68 (3.03) 7.85 (3.13) 7.42 (3.13) 2 2H-Pyran, 3,4-dihydro 4.15 (3.82) 8.45 (3.82) 4.97 (3.81) 2.45 (3.82) - 3 3-Furanmethanol 15.58 (3.85) - - - -4 Phenol 11.94 (4.23) 18.68 (4.23) 15.91 (4.23) 14.04 (4.23) 22.19 (4.23) 5 2-Methoxytetrahydrofuran 3.71 (4.81) - - - - 6 Hexanal, 4,4-dimethyl 5.05 (4.86) - - - - 7 Ethanone, 1-(1-cyclohexen-1-yl) 2.01 (5.17) - - - - 8 1,1,3-Trimethoxypropane 3.34 (5.46) - - - -9 Propanoic acid, 2-methyl 4.19 (5.99) - - - - 10 Acrolein, dimethyl acetal 4.40 (6.05) - - - - 11 Cyclopentanecarboxylic acid 8.86 (7.61) - - - -12 2,5-Dimethoxytetrahyrdofuran - 4.77 (3.36) 2.01 (3.51) 2.47 (3.52) - 13 Furan, tetrahydro-2, 5-dimethoxy - 3.63 (3.51) 2.06 (3.36) 2.82 (3.37) 1.93 (3.37) 14 2 (3H)-Furanone, 5-methyl - 11.02 (3.85) 6.36 (3.85) - 6.35 (3.85) 15 2-Cyclopenten-1-one, 2-hydroxy - 5.10 (4.66) 3.16 (4.67) 7.19 (3.84) 2.15 (3.65) 16 Phenol, 2-methoxy - 7.17 (5.17) 4.30 (5.17) 3.40 (5.18) 5.49 (5.17) 17 1,2-Benzenediol - 6.22 (5.96) 5.27 (5.96) 3.94 (5.95) - 18 Phenol, 2,6-dimethoxy - 6.05 (7.12) 5.50 (7.13) 3.91 (7.13) 5.73 (7.12) 19 Butanoic acid, 3-methyl - - 8.56 (1.46) - - 20 Butanal, 2-methyl - - 2.33 (2.65) - -21 Phenol, 2-methyl - - 2.72 (4.85) 1.60 (4.85) 1.48 (4.85) 22 Phenol, 4-methyl - - 3.38 (5.02) 1.96 (5.02) 1.94 (5.02) 23 1,2-Benzenediol, 3-methoxy - - 1.34 (6.50) - - 24 Phenol, 4-ethyl-2-methoxy - - 1.91 (6.57) - 1.86 (6.57) 25 Dehydroacetic acid - - 1.65 (7.74) 1.25 (7.74) - 26 Phenol, 2,6-dimethoxy-4- (2-propenyl) - - 1.37 (9.31) 1.61 (9.31) -
92
Characterisation of Pyrolysis Products
Table 5.8, continued.
Area, % (Retention Time)Peak No. Possible Chemical Compounds 300 °C 400 °C 500 °C 600 °C 700 °C
27 3,6-Heptadienoic acid - - - 1.32 (2.07) -28 3-Hepten-2-one, 4-methyl - - - 1.43 (4.01) -29 3-Cyclobutene-1, 2-dione - - - 2.51 (4.51) -30 1,2-Benzenedicarboxylic acid - - - 4.65 (8.36) -31 Propanoic acid, 2,2-dimethyl - - - - 1.55 (2.65) 32 2 (5H)-Furanone - - - - 2.82 (3.82)33 2 (1H)-Pyridinone, 5-hydroxy - - - - 1.59 (4.01) 34 Phenol, 2-ethoxy - - - - 5.79 (5.95)35 Phenol, 4-methoxy-3 - - - - 1.69 (7.73)* Only showed the possible chemical compounds in the bio-oil.
93
Characterisation of Pyrolysis Products
Table 5.9: Possible Chemical Compounds* of Bio-oil According to the GC/MS Analysis of Different Particle Size.
Area, % (Retention Time)Peak No.
Possible Chemical Compounds < 90 µm 91-106 µm 107-125 µm 126-250 µm
1 Acetic acid, pentyl ester 1.98 (1.83) - - - 2 Phenol 18.85 (4.22) 15.91 (4.23) 13.99 (4.22) 16.70 (4.22) 3 Furan, 2,5-diethoxytetrahydro 1.24 (4.40) - - 3.81 (4.40) 4 2-Cyclopenten-1-one, 2-hydroxy 2.60 (4.60) 3.16 (4.67) - - 5 Phenol, 3-methyl 2.64 (4.85) - 2.69 (5.01) 3.15 (5.02) 6 Phenol, 4-methyl 3.70 (5.02) 3.38 (5.02) - - 7 Phenol, 2-methoxy 3.55 (5.17) 4.30 (5.17) 3.53 (5.16) - 8 Phenol, 2,4-dimethyl 1.31 (5.61) - - - 9 1,2-Benzenediol 5.06 (5.95) 5.27 (5.96) 4.43 (5.95) 5.27 (5.95) 10 Propanoic acid, 2-methyl 7.91 (6.46) - - - 11 1,4-Benzenediol, 2-methoxy 2.08 (6.50) - - - 12 1,2-Benzenediol, 3-methyl 2.61 (6.66) - 1.24 (6.66) 2.95 (6.66) 13 Phenol, 2,6-dimethoxy 8.05 (7.12) 5.50 (7.13) 4.40 (7.12) 8.25 (7.12) 14 1,2,4-Trimethoxybenzene 2.17 (7.73) - - - 15 Phenol, 2,6-dimethoxy-4- (1-propenyl) 1.62 (7.79) - 1.30 (7.79) - 16 Phenol, 2,6-dimethoxy-4- (2-propenyl) 1.52 (8.68) 1.37 (9.31) 2.26 (9.30) - 17 n-Hexadecanoic acid 2.95 (10.52) - - - 18 Hexadecanoic acid, ethyl ester 3.23 (10.65) - - 1.18 (10.66) 19 Ethyl 9-hexadecenoate 1.75 (11.57) - - - 20 Furfural - 10.68 (3.13) 5.56 (3.12) - 21 2H-Pyran, 3,4-dihydro - 4.97 (3.81) - - 22 2,5-Dimethoxytetrahyrdofuran - 2.01 (3.51) - -23 Furan, tetrahydro-2, 5-dimethoxy - 2.06 (3.36) - - 24 2 (3H)-Furanone, 5-methyl - 6.36 (3.85) 7.62 (3.84) - 25 Butanoic acid, 3-methyl - 8.56 (1.46) - - 26 Butanal, 2-methyl - 2.33 (2.65) - -
94
Characterisation of Pyrolysis Products
Table 5.9, continued.
Area, % (Retention Time)Peak No. Possible Chemical Compounds < 90 µm 91-106 µm 107-125 µm 126-250 µm
27 Phenol, 2-methyl - 2.72 (4.85) 1.89 (4.84) 1.68 (4.85) 28 1,2-Benzenediol, 3-methoxy - 1.34 (6.50) 1.25 (6.50) 3.20 (6.50) 29 Phenol, 4-ethyl-2-methoxy - 1.91 (6.57) 2.04 (6.56) - 30 Dehydroacetic acid - 1.65 (7.74) - - 31 1,2-Cyclopentanedione, 3-methyl - - 2.60 (4.66) 2.32 (4.67)32 Ethanone, 1-(1-cyclohexen-1-yl) - - - 3.12 (5.17)33 3-Methyl-3-hexene - - - 1.36 (6.23)34 Butanoic acid, 2-propenyl ester - - - 9.64 (6.46) 35 Heptane, 1-1-diethoxy - - - 3.19 (6.89)36 Benzene, 1-methyl-4- (phenylmethyl) - - - 1.53 (8.21) 37 Benzaldehyde, 4-hydroxy - - - 1.34 (9.13)38 2- Furan methanol - - 1.03 (3.23) - 39 2-Cyclopenten-1-one, 2-methyl - - 1.40 (3.69) -40 2 (5H)- Furanone - - 4.65 (3.81) - 41 2 (5H)-Furanone, 5-methyl - - 1.01 (4.01) - 42 2-Methoxy-4-vinylphenol - - 1.76 (6.86) -43 Benzoic acid, 4-hydroxy - - 0.54 (8.14) - 44 2-Propenoic acid, 3-(4-hydroxy) - - 0.67 (8.68) - * Only showed the possible chemical compounds in the bio-oil.
95
Characterisation of Pyrolysis Products
Table 5.10: Possible Chemical Compounds* of Bio-oil According to the GC/MS Analysis of Different Heating Rate.
Area, % (Retention Time)Peak No.
Possible Chemical Compounds 10 °C min-1 30 °C min-1 50 °C min-1 100 °C min-1
1 16-Hydroxyhexadecanoic acid 4.45 (1.22) - - - 2 Furan, 2,5-dimethyl- 4.26 (3.02) - - - 3 2 (5H) – Furanone, 5-methyl- 3.77 (3.83) - - - 4 2H-Pyran, 3,4-dihydro- 2.71 (3.89) 4.97 (3.81) 3.37 (3.90) 2.71 (3.90) 5 3- Furanmethanol 5.96 (3.92) - - - 6 Phenol 15.32 (4.30) 15.91 (4.23) 19.90 (4.31) 19.06 (4.31) 7 1,2- Cyclopentanedione-3-methyl- 1.85 (4.71) - - 4.46 (4.75) 8 2- Cyclopenten-1-one, 2-hydroxy- 3.05 (4.74) 3.16 (4.67) 4.18 (4.75) - 9 Phenol, 2-methoxy 3.45 (5.25) 4.30 (5.17) 4.95 (5.26) 5.04 (5.26) 10 1,2 Benzenediol 7.64 (6.04) 5.27 (5.96) - 6.04 (6.05) 11 Phenol, 2,6-dimethoxy- - 5.50 (7.13) 4.92 (7.21) 5.61 (7.21) 12 Phenol, 2-methoxy-4- (1-propenyl)- 2.22 (7.88) - 1.80 (7.88) - 13 Nonanoic acid 4.60 (8.290 - - - 14 Phenol, 2, 6-dimethoxy-4- (2-propenyl)- 2.58 (9.39) 1.37 (9.31) - - 15 Butanoic acid, 3-methyl - 8.56 (1.46) - - 16 Butanal, 2-methyl - 2.33 (2.65) - - 17 Furfural - 10.68 (3.13) - 8.17 (3.20) 18 Furan, tetrahydro-2, 5-dimethoxy - 2.06 (3.36) - - 19 2,5-Dimethoxytetrahyrdofuran - 2.01 (3.51) - - 20 2 (3H)-Furanone, 5-methyl - 6.36 (3.85) 10.99 (3.92) 6.77 (3.92) 21 Phenol, 2-methyl - 2.72 (4.85) 2.53 (4.93) 2.59 (4.93) 22 Phenol, 4-methyl - 3.38 (5.02) - - 23 1,2-Benzenediol, 3-methoxy - 1.34 (6.50) - - 24 Dehydroacetic acid - 1.65 (7.74) - - 25 2-Methylheptanoic acid - - 2.70 (2.11) -
96
Characterisation of Pyrolysis Products
97
Table 5.10, continued.
Area, % (Retention Time)Peak No.
Possible Chemical Compounds 10 °C min-1 30 °C min-1 50 °C min-1 100 °C min-1
26 2- Pentadecanone - - 3.55 (2.85) -27 Furan, 2,4-dimethyl- - - 8.20 (3.20) -28 Phenol, 3-methyl- - - 3.45 (5.11) 3.86 (5.10) 29 Phenol, 2-methoxy-4-methyl - - 4.29 (6.05) -30 2- Cyclopenten-1-one, 2-methyl - - - 1.43 (3.77) 31 Ethanone, 1-(2,5-dihydroxyphenyl)- - - - 2.37 (2.70)32 Heptanoic acid - - - 5.01 (8.28)33 Phenol, 2,6-dimethoxy-4- (2-propenyl) - - - 1.63 (9.39) 34 2H-Pyran-2-one, 3-acetyl-4-hydroxy-6-
methyl - - - 2.21 (7.82)
* Only showed the possible chemical compounds in the bio-oil.
Characterisation of Pyrolysis Products
5.2.2 Characterisation of Char Product
The properties of the char according to different temperature, particle size and
heating rate were determined and the results obtained are given in Table 5.11, Table 5.12
and Table 5.13, respectively. The calorific values of char according to different
temperature are changing between 23 and 26 MJ/kg (Table 5.11). There is no significant
effect of temperature on calorific value of char. The highest calorific value of char
obtained is 25.98 MJ/kg at pyrolysis temperature of 400 ºC.
Table 5.11: Properties of Char Product* at Different Temperature.
Temperature (°C) Properties 300 400 500 600 700
1. Calorific Value (MJ/kg) 23.23 25.98 22.94 22.98 22.98 2. Ultimate analysis wt. % Carbon 59.62 65.94 65.32 67.87 68.63 Hydrogen 4.02 4.42 4.56 4.04 2.71 Oxygen 34.05 25.73 28.69 25.27 27.45 Nitrogen 2.31 3.91 1.43 2.82 1.21 H/C molar ratio 0.81 0.80 0.84 0.71 0.47 O/C molar ratio 0.43 0.29 0.33 0.28 0.30 Empirical formula CH0.81
O0.43N0.03
CH080 O0.29N0.05
CH0.84 O0.33N0.02
CH0.71 O0.28N0.04
CH0.47 O0.30N0.02
3. Surface Area (m2/g) 4.54 5.76 4.85 3.95 3.34 4. Total pore volume (cm3/g) 0.02 0.02 0.01 0.01 0.01
Note: *Obtained at heating rate of 30 °C min-1 and particle size of 91-106 µm.
The calorific value of char according to different particle size was varied between
21 and 24 MJ/kg (Table 5.12). The highest calorific value of char obtained is 23.88
MJ/kg at particle size of 126 – 250 µm. When changing the heating rate from 10 °C min-1
to 100 °C min-1 the calorific value of char varied between 22 and 26 MJ/kg (Table 5.13).
This indicates that the heating rate of pyrolysis has a significant effect on calorific value
98
Characterisation of Pyrolysis Products
of the char. The highest calorific value of char obtained was 26.01 MJ/kg at heating rate
of 10 °C min-1. Calorific value is a major quality index for fuels. Calorific value obtained
defines the energy content of a fuel. The estimation of calorific value from elemental
composition of the fuel is one of the basic steps in the performance modelling and
calculations of thermal systems (Maiti et al., 2006).
Table 5.12: Properties of Char Product* at Different Particle Size.
Particle Size (µm) Properties <90 91 - 106 107 - 125 126 - 250 1. Calorific Value (MJ/kg) 22.89 24.27 20.76 24.28 2. Ultimate analysis (wt. %) Carbon 65.66 65.32 67.67 67.47 Hydrogen 3.89 4.56 3.95 3.84 Oxygen 28.22 28.69 27.17 23.93 Nitrogen 2.23 1.43 1.21 4.76 H/C molar ratio 0.71 0.84 0.70 0.68 O/C molar ratio 0.32 0.33 0.30 0.27 Empirical formula CH0.71
O0.32N0.03
CH0.84 O0.33N0.02
CH0.70 O0.30N0.02
CH0.68 O0.27N0.06
3. Surface Area (m2/g) 4.78 4.85 4.97 5.11 4. Total volume pore (cm3/g) 0.01 0.01 0.01 0.01
Note: *Obtained at temperature of 500 °C with heating rate 30 °Cmin-1
The surface area of char according to different temperature varied between 3.3
and 5.8 m2/g (Table 5.11) depending on the production conditions. The maximum surface
area of the char occurred at 400 ºC (5.76 m2/g) and appeared to be associated with the
completion of the solidification stage within the char. Surface area is important in
chemical kinetics. Increasing the surface area of a substance generally increases the rate
of a chemical reaction. The ensuing carbonization step at high temperature was
detrimental to the development of a porous structure in the char (Guo et al., 1998). The
total pore volume ranged between 0.01 and 0.02 cm3/g. For the different particle size, the
99
Characterisation of Pyrolysis Products
surface area of char varied between 4.8 and 5.1 m2/g (Table 5.12). There is no significant
effect of particle size on surface area of char. The highest surface area of char obtained
was 5.11 m2/g at particle size of 126 – 250 µm. The total pore volume of char according
to different particle size was 0.01 cm3/g at all particle size. The surface area of the char
was 4.56, 4.85, 4.12 and 4.32 g/cm3 for the heating rates of 10, 30, 50 and 100 °C min-1,
respectively (Table 5.13). The highest surface area of char obtained was 4.85 m2/g at
heating rate of 30 °C min-1. The total pore volume of char obtained was 0.01 cm3/g at all
of heating rate.
Table 5.13: Properties of Char Product* at Different Heating.
Heating Rate (°Cmin-1) Properties 10 30 50 100
1. Calorific Value (MJ/kg) 26.01 22.13 24.22 25.58 2. Ultimate analysis (wt. %) Carbon 70.52 65.32 69.69 72.33 Hydrogen 3.89 4.56 4.11 4.06 Oxygen 22.18 28.69 23.25 21.22 Nitrogen 3.41 1.43 2.95 2.39 H/C molar ratio 0.66 0.84 0.71 0.67 O/C molar ratio 0.24 0.33 0.25 0.22 Empirical formula CH0.66
O0.24N0.04
CH0.84 O0.33N0.02
CH0.71 O0.25N0.04
CH0.67 O0.22N0.03
3. Surface Area 4.56 4.85 4.12 4.32 4. Total volume pore 0.01 0.01 0.01 0.01
Note: *Obtained at temperature of 500 °C and particle size of 91-106 µm.
The elemental compositions analysis, H/C molar ratio, O/C molar ratio and
empirical formula of the char according to different temperatures are listed in Table 5.11.
The H/C ratios of char were changing between 0.47 and 0.84. The highest H/C ratio of
char obtained was 0.84 at pyrolysis temperatures of 500 ºC. The O/C ratios of char were
100
Characterisation of Pyrolysis Products
changing between 0.28 and 0.43. The highest O/C ratio of char obtained was 0.43 at
pyrolysis temperature of 300 ºC. The percentage of hydrogen and nitrogen ranged from
3 - 5% and 1 - 4% respectively. The highest hydrogen and nitrogen content obtained was
4.56 % and 3.91 % at final pyrolysis temperature of 500 ºC and 400 ºC respectively. The
molecular formula of the char based on one carbon atom as listed in Table 5.11.
As shown in Figure 5.10, the percentage of carbon was ranged from 60 - 69%
with the highest percentage of carbon obtained was 69% at pyrolysis temperature of 700
ºC. The percentage of oxygen was ranged from 25 - 34% with the highest percentage of
obtained was 34% at pyrolysis temperature of 300 ºC. The study of the effect of
temperature on carbon and oxygen content had shown that a 600 ºC was the best
temperature to produce char with high carbon content and low oxygen content.
20
30
40
50
60
70
200 300 400 500 600 700 800
Temperature, oC
wt.
%
Carbon
Oxygen
Figure 5.10: Effect of Temperature on Oxygen and Carbon Content of Char.
When varied the particle size of EFB, the H/C ratios of char were changing
between 0.68 and 0.84 (Table 5.12). The highest H/C ratio of char obtained was 0.84 at
101
Characterisation of Pyrolysis Products
particle size of 91 – 106 µm. The O/C ratios of char were changing between 0.27 and
0.33. The highest O/C ratio of char obtained was 0.33 at particle size of 91 - 106 µm. The
percentage of hydrogen and nitrogen was ranged from 4 - 5% and 1 - 5%, respectively.
The highest percentage of hydrogen and nitrogen content was 4.56% and 4.76% at
particle size of 91 – 106 µm and 126 – 250 µm, respectively. The molecular formula of
the char based on one carbon atom as listed in Table 5.12.
As shown in Figure 5.11, the percentage of carbon was ranged from 65 - 68%
with the highest percentage of carbon obtained is 68% at particle size of 107 – 125 µm.
Meanwhile, the percentage of oxygen was ranged from 24 - 29% with the highest oxygen
content of char obtained was 29% at particle size of 91 - 106 µm. The study of effect of
particle size on carbon and oxygen content of char had shown that a 126 - 250 µm was
the best particle size to produce char.
20
30
40
50
60
70
<90µm 91µm -106µm
107µm-125µm
126µm-250µm
Particle Size
wt.
%
Carbon
Oxygen
Figure 5.11: Effect of Particle Size on Oxygen and Carbon Content of Char.
102
Characterisation of Pyrolysis Products
The H/C ratios of char according to different heating rate were changing between
0.66 and 0.84 (Table 5.13). The highest H/C ratio of char obtained was 0.84 at heating
rate of 30 °C min-1. The O/C ratios of char were changing between 0.22 and 0.33. The
highest O/C ratio of char obtained was 0.33 at heating rate of 30 °C min-1. The percentage
of hydrogen and nitrogen was ranged from 4 - 5% and 1 - 3% respectively. The highest
hydrogen and nitrogen content obtained was 4.56 % and 3.41 % at heating rate of 30 °C
min-1 and 10 °C min-1 respectively. The molecular formula of the char based on one
carbon atom as listed in Table 5.13. As shown in Figure 5.12, the percentage of carbon
was ranged from 65 and 72% with the highest percentage of carbon obtained is 72% at
heating rate of 10 °C min-1. The oxygen content was ranged 21 - 29% with the highest
oxygen content of char obtained was 29% at heating rate of 30 °C min-1. The study of
effect of heating rate on carbon and oxygen content of char had shown that a 100 °C min-
1 was the best heating rate to char production.
10
20
30
40
50
60
70
80
0 10 20 30 40 50 60 70 80 90 100 110
Heating Rate, oC min-1
wt.
%
Carbon
Oxygen
Figure 5.12: Effect of Heating Rate on Oxygen and Carbon Content of Char.
103
Characterisation of Pyrolysis Products
5.2.3 Influence of Temperature on Gas Product
The distribution of gaseous products from pyrolyzing oil palm empty fruit
bunches mainly depends on reaction temperature. In this study, products were measured
by Micro- Gas Chromatography (Micro-GC, Agilent, model 3000) with a TCD detector.
The gas species distribution profile obtained at different final temperatures is showed in
Figure 5.13 (area percent age is based on five gases identified). The gases detected were
carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), ethane (C2H6), and
ethylene (C2H4).
At the temperatures of 300 and 400°C the gas mixture mainly composed of CO2
and together with CO and the some CH4. The origin of the CO2 is mainly dependent on
decomposition of cellulose and hemicellulose. On the other hand, CO2 evolution at higher
temperature can be due to the lignin degradation (Uzun et al., 2007). The CO2 content
decreased as the temperature increased from 400 to 500°C. After that, with the
temperature increased further, it increased again from 50 to 60 of area percent based on 5
gases identified (Figure 5.13).
Increasing temperature increases the release of CH4. As the temperature increased
from 300 °C to 500 °C, CH4 contents increased linearly with an increase in temperature,
but start decreasing above 500 °C. After 600 °C, a second formation of CH4 was occurred
due to the lignin decomposition. The formation of CH4 and other light hydrocarbons
found could be mainly related to the degradation of lignin, since their concentration
increased as degradation processes at high temperatures. The formation of CH4 was due
104
Characterisation of Pyrolysis Products
to the release of methoxy groups, involving C-C rupture, and it was controlled by
hydrogen transfer reactions.
As the temperature increased from 300 °C to 600 °C, CO contents slightly
decreased with an increased in temperature. Whilst C2H4 and C2H6 contents were very
low, only evolved at temperature of 500 °C. The area percent of C2H4 and C2H6
decreased above 500 °C due to the release of hydrogen at those temperatures. The H2
contents were not detected in this work, this might be the production of H2 only occurred
at high temperature possibly above 600°C. The decrease in the area percent of some
components at high temperatures could be due to their conversion to other products
(Uzun et al., 2007).
105
Characterisation of Pyrolysis Products
5.3 Conclusion
0
10
20
30
40
50
60
70
200 300 400 500 600 700
Temperature, OC
Are
a %
bas
ed o
n 5
gase
s id
entif
ied
CO2
CO
CH4C2H4 C2H6
Fig 5.13: Gases emitted as the temperature was increased.
106
Conclusion and Recommendations
CHAPTER 6
CONCLUSION AND RECOMMENDATIONS
6.1 CONCLUSION
During this study, the experiments of pyrolysis on oil palm biomass were
performed in a fluidised-fixed bed reactor. The main products obtained from the
pyrolysis of oil palm biomass were bio-oil, char and gas, the yields of which depend
mostly on the pyrolysis conditions. The pyrolysis conversion increases up to the final
pyrolysis temperature of 700 ºC, although the bio-oil yield increase up to 500 ºC, after
which there is a significant decrease in the yield. As a result of breaking heat and mass
transfer limitations in the pyrolysis of EFB by increasing the heating rate from 10 ºC min-
1 to 50 ºC min-1, there was a significant change in the bio-oil yield. The results obtained
in this work indicated that the particles size had no influence on the pyrolysis products. In
addition, the small differences obtained probably being due to experimental error.
The study of the effect of temperature on products yield had shown that a 500 ºC
was the optimum temperature to produce the bio-oil product, a 300 ºC is the best
temperature to produce the char product and a 700 ºC is the maximum temperature to
produce the gas product under the same conditions of particle size and heating rate. In
this study, the effect of particle size on products yields was observed in the range of 91 –
106 µm indicating the optimum particle size to produce bio-oil and char products, and the
particle size within the range of 107 – 125 µm was the optimum particle size to produce
gas product at the same temperature (500 ºC) and heating rate (30 ºC min-1).
107
Conclusion and Recommendations
A 100 ºC min-1 was the optimum heating rate to produce the bio-oil and a 10 ºC
min-1 was the optimum heating rate to produce the char and gas products according to the
effect of heating rate on products yield. Furthermore, the EFB was the best oil palm
biomass to produce the bio-oil product in pyrolysis, fiber to produce char product and
trunk to produce gas product at the optimum pyrolysis conditions. The mixer of spent
bleaching earth and zircon sand can be used as a fluidised bed in order to increase the
percentage of bio-oil but the moisture content would be slightly higher (50 wt%)
compared to when zircon sand was used as a fluidized bed (18 wt%).
As a conclusion, the optimum yield of bio-oil could be achieved at the pyrolysis
temperature of 500 ºC, heating rate of 100 ºC min-1, particle size of 91 – 106 µm and EFB
used as a biomass feedstock. The maximum product yield of char obtained at the
pyrolysis temperature of 300 ºC, heating rate of 30 ºC min-1 and particle size of 91 – 106
µm. Fiber can be utilized as oil palm biomass feedstock to increase char product. Fiber
has high lignin content which can increase yield of char. The optimum yield of gas could
be achieved at the pyrolysis temperature of 700 ºC, heating rate of 30 ºC min-1 and
particle size of 91 – 106 µm.
The calorific values of bio-oil ranged from 16 to 23 MJ/kg, which is much lower
than that of gasoline (47 MJ/kg), diesel fuel (43 MJ/kg) or petroleum (42 MJ/kg) (Sensoz
et al., 2000). The ash content in the bio-oil varied from 0.2 to 0.65%. Knowledge of the
amount of ash-forming material present in a product can provide information as to
whether or not the product is suitable as a fuel. The pH values of the bio-oil varied
between 2.6 and 3.9. Meanwhile, the acid values of bio-oil in the range of 62 and 92 mg
KOH g-1 depending on the production condition.
108
Conclusion and Recommendations
The moisture content of bio-oil varied between 18% and 22%. Water is important
in many ways-increasing water usually reduces viscosity, improves stability and reduces
heating value. The density of bio-oil varied between 0.9 and 1.0 g/cm3. The carbon
content of bio-oil was ranged 34 and 56%. The oxygen, hydrogen and nitrogen content of
bio-oil were ranged from 35 - 58%, 5 - 9% and 1 - 2%, respectively. The H/C and O/C
ratios of bio-oil varied between 1.4 - 2.3 and 0.5 - 1.3, respectively.
A great range of functional groups of phenol, alcohols, ketones, aldehydes and
carboxylic acids were indicated in FTIR spectrum. The FTIR analysis showed that the
bio-oil composition was dominated by oxygenated species. The high oxygen content is
reflected by the presence of mostly oxygenated fractions such as carboxyl and carbonyl
groups produced by pyrolysis of the cellulose and phenolic and methoxy produced by
pyrolysis of the lignin. GC-MS analysis was carried out in order to get an idea of the
nature and type of organic compounds in the pyrolysis liquid products. The results
obtained show that the chemical compositions of the bio-oil were very similar to the
inclusion of a lot of aromatics and oxygenated compounds such as carboxylic acids,
phenols, ketones, aldehydes, etc.
FTIR and GC/MS results showed a lot of chemical constituents have been
identified to date in bio-oil, and increasing attention is being paid to the possibility of
recovering individual compounds or families of chemicals. The potentially much higher
value of speciality chemicals compared with fuels could make recovery of even small
concentrations viable. An integrated approach to chemicals and fuels production offers
interesting possibilities.
109
Conclusion and Recommendations
The calorific values of char ranged from 21 to 26 MJ/kg. The surface area of char
varied between 3.3 and 5.8 m2/g and the total pore volume ranged from 0.01 to 0.02
cm3/g. The carbon content of char ranged from 60 to 72%. As it is known, the high
carbon content of char makes it suitable to act as fuel and chemical feedstock. The
oxygen, hydrogen and nitrogen content of char were ranged from 21 - 34%, 3 - 5% and 1
- 5%, respectively. The H/C and O/C ratios of char varied between 0.5 - 0.8 and 0.2 - 0.4,
respectively.
In this study, the gases were detected as pyrolysis products were carbon
monoxide, carbon dioxide, methane, ethane and ethylene depending on the final pyrolysis
temperature.
6.2 RECOMMENDATIONS
At the evaluation and the employment of the bio-oil as a fuel, the following
options should be recommended. Crude bio-oil derived from empty fruit bunches maybe
combusted in existing fuel burning systems or as a mixture with other fuel-oils as it has
good fuel characteristics. Its low nitrogen content is quite promising for its evaluation as
fuel from the view point of environmental pollution. Besides that, bio-oil may be used as
a raw material in fractioning processes for obtaining specific fuels. By its distillation,
gasoline, diesel oil or alternative fractional products to fuel oils may be obtained. These
fractions may either be used directly or by mixing with other conventional fuels. By the
application of various processes such as cracking, hydrogenation, etc. fuel characteristics
may be improved and under this circumstance oil may either be used directly or its
110
Conclusion and Recommendations
fractions may be evaluated as an alternative to gasoline, diesel fuel and fuel-oil
(Karaosmanoglu et al., 1999).
The liquid product, known as bio-oil, might have been burnt and has been
employed for this purpose. Some problems encountered, have been reported in use,
particularly in storage, where phase separation, polymerisation, and corrosion of
container might occur. In addition, the high oxygen and water contents make it
incompatible with conversion fuels although it may be utilised in a similar way. Some
conversion or upgrading for oxygen and water removal and stabilisation is necessary to
give a product that is fully compatible with conventional fuel. In laboratory investigations
it is normally not possible to achieve simultaneously both adequate conditions for the
chemical reaction and technically reliable hydrodynamic conditions.
Char residues can be used for physical or chemical absorption and as catalyst
support or base material for fertilizer. A possible outlet for the char is slurring with the
bio-oil, or with water, or with both oil and water. Only a limited amount of char can be
introduced into oil as unacceptably high viscosities result from a char concentration
higher than about 25 % wt. The maximum concentration of char in water that can be
handled is about 60% to retain mobility. The costs of the additives are significant at up to
one-third of the slurry preparation cost. A recent development is the production of ternary
mixture of char, water and mineral oil which is claimed to have several advantages
(Bridgwater and Bridge). Coal-water slurry are increasing used in large boilers and these
slurries cab be simply and/ or partially replaced by char-water slurries. The ash content of
the char is an important consideration in developing liquid fuels, and de-ashing is
necessary. Although in principle it seems to be attractive to remix all products of
111
Conclusion and Recommendations
pyrolysis processing into one single liquid biomass-derived fuel, this does not currently
seem possible.
The gaseous product from pyrolysis is usually has a high level of hydrocarbons,
particularly methane, and saturated and unsaturated hydrocarbons from the complex
thermal degradation processes. The heating value is enhanced if the gas is used hot, from
the sensible heat and the relatively high tar content. The gas may be used for feed drying,
process heating, power generation, or exported for sale.
112
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List of Publications The outcome of the present study has been presented / submitted either wholly or as part in the following articles:
(A) Journal Paper
1. Mohamad Azri Sukiran., Chow Mee Chin., and Nor Kartini Abu Bakar.
(2008). Bio-oils from Pyrolysis of oil palm empty fruit bunches. (Submitted to Bioresource Technology Journal).
(B) Seminar/ Conference
1. Mohamad Azri Sukiran., Chow Mee Chin and Nor Kartini Abu Bakar. (2008). Pyrolysis of oil palm empty fruit bunches. 2nd International Conference for Young Chemists, 18-20 June 2008, University Sains Malaysia, Peneng.
2. Chow Mee Chin and Mohamad Azri Sukiran. (2007). Pyrolysis of oil palm empty fruit bunches. 5th Euro Fed Lipid Congress- Oils, Fats and Lipids: From Science to Applications, 16-19 September 2007, Gothenburg, Germany. 3. Mohamad Azri Sukiran and Chow Mee Chin. (2007). Pyrolysis of oil
palm empty fruit bunches. MPOB International Palm Oil Congress 2007 (PIPOC), 26-30 August 2007, KLCC, Kuala Lumpur.
4. Mohamad Azri Sukiran., Chow Mee Chin and Nor Kartini Abu Bakar.
(2007). Pyrolysis of oil palm empty fruit bunches. 12th Asean Chemical Congress (12ACC) 2007, 23-25 August 2007, PWTC, Kuala Lumpur.
5. Mohamad Azri Sukiran., Chow Mee Chin and Nor Kartini Abu Bakar.
(2006). Pyrolysis of oil palm empty fruit bunches. Mathematics and Physical Science Graduate Congress (MPSGC), 12-14 December 2006, National University of Singapore, Singapore.
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Appendix 1: FTIR Analysis of Bio-oil According to Different Temperature.
Absorbance (cm-1) Group 300 °C 400°C 500°C 600°C 700°C
OH (phenols and alcohols) 3373 3398 3398 3397 3405 C-H stretching (alkenes) 2852 and 2924 2929 2941 2854 and 2927 - C=O (ketone, aldehyde, carboxylic acids) 1713 1719 1720 1706 1720 C=C (alkenes and aromatics) 1514 and 1607 1512 and 1640 1513 and 1641 1513 and 1641 1515 C-H deformation (alkenes) 1375 and 1464 1378 and 1460 1380 1377 and 1462 1386 C-O (ether, esther)/ OH deformation 1113 and 1220 1113 and 1236 1058 and 1239 1115 and 1218 1097 and 1264 Aromatic rings 696 and 762 - - - 759 and 883 Obtained at heating rate of 30 °C min-1 and particle size of 91-106 µm.
Appendix 2: FTIR Analysis of Bio-oil According to Different Particle Size.
Absorbance (cm-1) Group <90 µm 91 – 106 µm 107 – 125 µm 126 – 250 µm
OH (phenols and alcohols) 3392 3386 3400 3410 C-H stretching (alkenes) 2931 and 2976 2932 2931 2934 C=O (ketone, aldehyde, carboxylic acids) 1720 1719 1721 1721 C=C (alkenes and aromatics) - 1514 and 1607 1514 1514 and 1606 C-H deformation (alkenes) 1379 and 1459 1375 and 1461 1377 and 1462 1376 and 1462 C-O (ether, esther)/ OH deformation 1087 and 1269 1113 and 1220 1110 and 1221 1112 and 1219 Aromatic rings 881 756 757 - Obtained at temperature of 500 °C with heating rate 30 °Cmin-1
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Appendix 3: FTIR Analysis of Bio-oil According to Different Heating Rate.
Absorbance (cm-1) Group 10 °C min-1 30 °C min-1 50 °C min-1 100 °C min-1
OH (phenols and alcohols) 3383 3402 3424 3419 C-H stretching (alkenes) 2937 2938 2936 2942C=O (ketone, aldehyde, carboxylic acids) 1714 17105 1718 1717 C=C (alkenes and aromatics) 1515 and 1639 1515 and 1640 1515 and 1641 1515 and 1641 C-H deformation (alkenes) - 1381 1386 1385C-O (ether, esther)/ OH deformation 1112 and 1234 1057 and 1223 1054 and 1267 1055 and 1266 Aromatic rings 615 and 761 756 and 882 756 and 882 756 and 882 Obtained at temperature of 500 °C and particle size of 91-106 µm.
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