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UNIVERSITI PUTRA MALAYSIA
EVALUATION OF MICROWAVE PYROLYSIS OF OIL PALM EMPTY FRUIT BUNCHES
ROZITA OMAR
FK 2010 94
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EVALUATION OF MICROWAVE PYROLYSIS OF OIL PALM EMPTY
FRUIT BUNCHES
By
ROZITA OMAR
Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia,
in Fullfilment of the Requirements for the Degree of Doctor of Philosophy
July 2010
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For my beloved Hafizul, Hanz and Dayana
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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment
of the requirement for the degree of Doctor of Philosophy
EVALUATION OF MICROWAVE PYROLYSIS OF OIL PALM EMPTY
FRUIT BUNCHES
By
ROZITA OMAR
July 2010
Chair: Azni Idris, PhD
Faculty: Faculty of Engineering
Agriculture waste such as oil palm empty fruit bunch (EFB) is an environmental
concern to our country as one of the world’s biggest oil palm producers. Pyrolysis
has been used as a thermal process to treat biomass wastes due to its flexibility in
producing solid, liquid and gas products. This study evaluated the possibility to treat
EFB via microwave pyrolysis. In this study, the EFB taken from a local oil palm
mill was directly placed inside a fixed-bed quartz reactor which was placed in a
modified household microwave oven, where both drying and pyrolysis took place
simultaneously. Microwave absorbers were added to elevate the reaction temperature
so as to reach the required temperature for a pyrolysis reaction to take place.
Parameters, such as effects of residence time, addition of inorganic materials
(catalysts) and pre-treatment of the EFB, were studied. Meanwhile, a comparison
experiment with a conventionally heated reactor was also conducted.
Fuel, chemical and dielectric characterization of the EFB undertaken in this study
confirmed that it is a good candidate for a microwave pyrolysis process as it is
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comparable to other biomass. However, dielectric properties of the EFB indicated
that it is almost a transparent material to microwave, and for this reason, addition of
microwave absorber is required. Studying several microwave absorbers, namely
SiC, activated carbons (coconut and palm kernel shell) and char which were
produced from a previously conducted experiment, concluded that 5% coconut
activated carbon in a granular form was enough to maintain a reaction temperature
above 500oC within 15 minutes (60.8
oC/min) with highest productivity of 5.1 mol%
syngas per g EFB per g absorber.
Two types of common pre-treatment, namely cutting and drying, were also studied.
Reduction of the EFB size without drying seemed to favor gas production; however,
untreated sample was found to give the highest H2 composition but with a similar
CH4 concentration as in the other treatments. A slow release of volatile matters in
the untreated sample might have provided the opportunity for secondary reaction to
produce more H2. Nevertheless, the addition of inorganic materials for tar
minimization and syngas enhancement (NaCO3, HSZM5, CaO and CaCO3) did not
influence the product distribution. On the other hand, the composition of gas was
found to be greatly influenced by the addition of HSZM5, especially H2. Meanwhile,
increasing residence time (0.02 - 0.10 s) of volatiles within the reactor was shown to
have increased gas composition (increment of 68.4% for H2), particularly for the
production of CH4 which resulted in a higher calorific value of the gas.
Liquid product (bio-oil) and solid product (char) were also characterized for their
potential end use. The char produced in this study has high carbon content (68%),
giving it a moderate calorific value at 21.5 MJ/kg, which is similar to that of the
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commercially produced EFB char, rendering it a good candidate for solid fuel
substitute. The EFB char is characterized as mesoporous with highest pore size
distribution around 4 nm. The BET surface area is modest at 14.2 m2g
-1 and has high
mesopore area of 28.3 m2g
-1. These characteristics present microwave pyrolysis of
EFB as a superior alternative for the carbonization step for activated carbon
preparation. Also, EFB char produced from this study is suitable for soil
amendment. Highly oxygenated, acidic and viscous bio-oil produced from pyrolysis
of EFB has high heating value (30.8 MJ/kg) which is higher than wood tar. Palmitic
acid is the most abundant chemical component (12.0-36.4%) in bio-oil.
A shorter time was needed in the microwave pyrolysis of EFB compared to the
conventional one, and this gives a higher gas production with four times better
calorific value (7.6 MJ/m3) but lower calorific value as compared to pyrolyzed coffee
hulls and rice straw. The energy cost to produce twelve times higher energy products
in the EFB microwave pyrolysis is lower, i.e. at 1.90 cent/MJ as compared to 49.90
cent/MJ in conventional heating. These findings reflect the potential of microwave
pyrolysis as an alternative method to both treat waste and produce energy.
In summary, EFB was successfully pyrolyzed using microwave as heating source.
The bio-oil product has better quality compared to wood oil therefore it has
potentially for fuel oil substitute. The char also has the potential for activated carbon
or solid fuel. EFB pyrolysis using microwave produced better syngas and cost
cheaper compared to conventional heating. Further study is needed to optimize the
parameters as to produce product of choice.
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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai
memenuhi keperluan untuk ijazah Doktor Falsafah
PENILAIAN PIROLISIS GELOMBANG MIKRO TANDAN KELAPA
SAWIT KOSONG
Oleh
ROZITA OMAR
Julai 2010
Pengerusi: Azni Idris, PhD
Fakulti: Fakulti Kejuruteraan
Bahan buangan pertanian seperti tandan kelapa sawit kosong (TKSK) adalah
kerisauan alam sekitar kepada negara kita yang merupakan antara pengeluar minyak
kelapa sawit terbesar dunia. Pirolisis merupakan proses terma yang telah digunakan
untuk merawat bahan buangan biojisim kerana fleksibilitinya untuk menghasilkan
produk pepejal, cecair dan gas. Kajian ini menilai kemungkinan untuk merawat
TKSK menggunakan pirolisis gelombang mikro untuk menghasilkan gas sintesis
(singas) yang tinggi. Di dalam kajian ini, TKSK yang diperoleh dari sebuah kilang
pemprosesan minyak kelapa sawit tempatan telah diletakkan ke dalam reaktor
lapisan tetap yang diperbuat daripada kuarza yang ditempatkan di dalam ketuhar
gelombang mikro domestik, yang mana proses pengeringan dan pirolisis berlaku
secara serentak. Sementara itu, bahan penyerap gelombang mikro telah ditambah
untuk menaikkan suhu tindakbalas sehingga mencapai suhu yang diperlukan untuk
membolehkan tindakbalas pirolisis berlaku. Parameter-parameter seperti kesan masa
mastautin, penambahan bahan tak-organik (pemangkin) dan pra-rawatan TKSK telah
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dikaji. Ekperimen perbandingan dengan reaktor yang dipanaskan secara
konvensional juga dijalankan.
Ciri-ciri bahan api dan kimia TKSK telah memastikan bahawa ia ialah kandidat yang
sesuai untuk proses pirolisis gelombang mikro yang sebanding dengan biojisim lain.
Sifat dielektrik TKSK telah membuktikan bawa ia merupakan bahan yang telus
gelombang mikro, dan oleh itu penambahan bahan penyerap gelombang mikro
adalah diperlukan. Kajian beberapa bahan penyerap gelombang mikro seperti SiC,
karbon-karbon teraktif (tempurung kelapa dan kelompang kepala sawit) serta arang
yang dihasilkan dari eksperimen terdahulu menyimpulkan bahawa 5% karbon
teraktif dari tempurung kelapa berbentuk butiran adalah cukup untuk mengekalkan
suhu tindakbalas di atas 500oC didalam masa 15 minit (60.8
oC/min) dengan
produktiviti tertinggi iaitu 5.1 mol% singas per g EFB per g penyerap.
Dua jenis pra-rawatan am iaitu pemotongan dan pengeringan juga telah dikaji.
Pengurangan saiz TKSK tanpa dikeringkan didapati telah membantu produksi gas
tetapi sampel tanpa rawatan memberikan komposisi H2 yang tertinggi walaupun
kepekatan CH4 adalah sebanding dengan pra-rawatan lain. Pembebasan jirim
meruap oleh sampel tidak dirawat yang lambat mungkin telah memberi peluang
tindakbalas sekunder untuk menghasilkan lebih banyak H2. Bagaimanapun,
penambahan bahan tak-organik untuk mengurangkan penghasilan tar dan
penambahan singas (NaCO3, HSZM5, CaO dan CaCO3) tidak mempengaruhi taburan
produk. Walau bagaimanapun, komposisi gas adalah sangat dipengaruhi oleh
penambahan HSZM5, terutamanya H2. Kenaikan masa mastautin (0.02 - 0.10 s)
jirim di dalam reaktor telah membantu menaikkan komposisi gas (kenaikan 68.4%
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untuk H2), terutamanya penhasilan CH4 yang telah menyebabkan gas berkalori tinggi
dihasilkan.
Produk cecair (bio-minyak) dan produk pepejal (arang) juga dicirikan untuk menilai
potensi kegunaan bahan-bahan ini. Arang yang dihasilkan dari kajian ini didapati
mengandungi kandungan karbon yang tinggi yang telah memberikan nilai kalori
sebanyak 21.5 MJ/kg iaitu sebanding dengan arang TKSK yang dihasilkan secara
komersil, dan dapatan ini telah menjadikan ia kandidat yang baik untuk bahan api
pepejal gantian. Arang daripada TKSK telah dicirikan sebagai berliang-meso dengan
agihan liang tertinggi bersaiz 4 nm. Luas permukaan BET adalah sederhana pada
14.2 m2g
-1 dan keluasan berliang-meso yang tinggi pada 28.3 m
2g
-1. Ciri-ciri ini
membuatkan pirolisis gelombang mikro satu alternatif yang lebih baik untuk langkah
karbonisasi untuk penyediaan karbon teraktif. Arang daripada TKSK dari kajian ini
sesuai untuk pengubahsuaian tanah. Bio-minyak yang dihasilkan adalah beroksigen
tinggi, berasid dan likat yang mempunyai nilai pemanasan yang tinggi (30.8 MJ/kg),
lebih tinggi dari tar daripada kayu. Asid palmitik ialah bahan kimia yang terbanyak
(12.0-36.4%) di dalam bio-minyak yang mungkin diwarisi dari buah kelapa sawit.
Hanya masa yang singkat diperlukan dalam pirolisis gelombang mikro TKSK
berbanding dengan cara konvensional dengan memberikan hasil produk gas yang
tinggi dengan nilai kalori empat kali lebih tinggi (7.6 MJ/m3) sesuai untuk digunakan
sebagai bahan api pemanasan sederhana tetapi nilai kalorinya adalah kurang
berbanding gas pirolisis kulit kopi dan jerami padi. Kos tenaga untuk menghasilkan
dua belas kali lebih tinggi tenaga produk dalam pirolisis gelombang mikro TKSK
adalah kurang iaitu 1.90 sen/MJ berbanding 49.90 sen/MJ. Hasil penyelidikan ini
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menunjukkan bahawa pirolisis mikro gelombang adalah satu metod alternatif untuk
merawat bahan buangan dan juga penghasilan tenaga.
Kesimpulannya, TKSK telah berjaya dipirolisis menggunakan gelombang mikro
sebagai sumber pemanas. Produk bio-minyak adalah lebih berkualiti berbanding
minyak kayu oleh itu ia berpotensi untuk dijadikan bahan bakar gentian. Produk
arang juga berpontensi sebagai karbon teraktif atau bahan bakar pepejal. Pirolisis
EFB menggunakan gelombang mikro menghasilkan produk syngas yang lebih baik
dan lebih murah berbanding pemanasan konvensional. Walaubagaimana pun, kajian
mendalam diperlukan untuk mendapatkan parameter optimum untuk menghasilkan
produk yang dipilih.
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ACKNOWLEDGEMENTS
Alhamdulillah to Almighty for giving me the patience and perseverance to finish this
thesis to the end. To my beloved husband, children and parents, I appreciate all the
love and support. I would like to dedicate my gratitude to my supervisors Prof. Dr.
Azni Idris, Prof. Dr. Kaida Khalid, Associate Prof. Dr. Robiah Yunus and Prof. Dr.
Gwendoline Ee Cheng Lian. My deepest thanks are for my examiners Prof. Jim
Swithenbank, Associate Prof. Dr. Norhafizah and Prof. Dr. Dzulkifly Kuang for their
constructive comments on my thesis. My special appreciation is extended to my
colleagues Dr. Tinia, Dr. Salmiaton, Dr. Dayang, Dr. Siti Mazlina, Dr. Wan Azlina,
Mdm. Faezah, Mr. Razif Harun and all Chemical Engineering Department lecturers
for helping me in any way throughout my study. My appreciation also goes to the
technicians, research officers and science officers at Department of Chemical
Engineering, Department of Mechanical Engineering, Departments of Physics and
Chemistry and Department of Soil Science who have helped me at the experimental
stage. My heartfelt gratitude to have helping hands of my fellow friends Aida Isma,
Dr. Chong, Brother Asri, Mohamed, Mohamad, Mr. Ali, Baiti, Mustika, Taha, Faiz,
Shanti, Pak Darmadi, Azahari, Mustafa, Fioni and others that I might have forgotten
to mention their names. Thank you also to Universiti Putra Malaysia for giving me
the scholarship to further my study and MOSTI for trusting me the grant to pursue
this project. Lastly to those I failed to remember, thank you very much.
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I certify that a Thesis Examination Committee has met on 2 July 2010 to conduct the
final examination of Rozita Omar on her thesis entitled “Evaluation of Microwave
Pyrolysis of Oil Palm Empty Fruit Bunch” in accordance with the Universities and
University Colleges Act 1971 and the Constitution of the Universiti Putra Malaysia
[P.U.(A) 106] 15 March 1998. The Committee recommends that the student be
awarded the Doctor of Philosophy.
Members of the Thesis Examination Committee were as follows:
Salmiaton Ali, PhD
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Chairman)
Norhafizah Abdullah, PhD
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Internal Examiner)
Dzulkifly Kuang Abdullah, PhD
Professor
Faculty of Science
Universiti Putra Malaysia
(Internal Examiner)
Jim Swithenbank, PhD
Professor
Chemical and Biological Engineering
Faculty of Engineering
University of Sheffield
United Kingdom
(External Examiner)
________________________________
SHAMSUDDIN SULAIMAN, PhD
Professor and Deputy Dean
School of Graduate Studies
Universiti Putra Malaysia
Date: 2 September 2010
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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been
accepted as fulfilment of the requirement for the degree of Doctor of Philosophy.
The members of the Supervisory Committee were as follows:
Azni Idris, PhD
Professor
Faculty of Engineering
Universiti Putra Malaysia
(Chairman)
Kaida Khalid, PhD
Professor
Faculty of Science
Universiti Putra Malaysia
(Member)
Robiah Yunus, PhD
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Member)
Gwendoline Ee Chiang Lian, PhD
Professor
Faculty of Science
Universiti Putra Malaysia
(Member)
________________________________________
HASANAH MOHD GHAZALI, PhD
Professor and Dean
School of Graduate Studies
Universiti Putra Malaysia
Date: 6 September 2010
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DECLARATION
I declare that the thesis is my original work except for quotations and citations which
have been duly acknowledged. I also declare that it has not been previously, and is
not concurrently, submitted for any other degree at Universiti Putra Malaysia or at
any other institution
___________________________
ROZITA OMAR
Date: 2 July 2010
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TABLE OF CONTENTS
Page
DEDICATIONS ii
ABSTRACT iii
ABSTRAK vi
ACKNOWLEDGEMENTS x
APPROVAL SHEET xi
DECLARATION FORM xiii
LIST OF TABLES xvii
LIST OF FIGURES xix
LIST OF NOMENCLATURE xxii
LIST OF ABBREVIATION AND ACRONYMS xxiv
CHAPTER
1 INTRODUCTION 1.1
1.1 Background 1.1
1.2 Problem Statements 1.5
1.3 Research Objectives 1.10
1.4 Thesis Layout 1.11
2 LITERATURE REVIEW 2.1
2.1 Introduction 2.1
2.2 Properties of Oil palm Solid Waste 2.1
2.3 Thermal Conversion of Oil palm Waste 2.3
2.3.1 Combustion in Boiler 2.3
2.3.2 Combustion in Fluidized Bed 2.7
2.3.3 Gasification 2.9
2.3.4 Pyrolysis 2.11
2.4 Pyrolysis Process 2.13
2.4.1 Pyrolysis Mechanism 2.13
2.4.2 Conventional Pyrolysis 2.18
2.4.3 Fast Pyrolysis 2.19
2.5 Main Parameters Governing Pyrolysis 2.20
2.5.1 Effect of Temperature 2.20
2.5.2 Effect of Particle Size 2.26
2.5.3 Effect of Heating Rate 2.28
2.5.4 Effect of Residence Time 2.29
2.5.5 Effect of Initial Moisture 2.31
2.5.6 Effect of Catalyst Addition 2.32
2.6 Pyrolysis Products 2.35
2.6.1 Char 2.35
2.6.2 Bio-oil 2.41
2.6.3 Non-condensable Gas 2.46
2.6.4 Synthesis Gas 2.49
2.7 Microwave Fundamentals 2.51
2.7.1 The Interactions between Microwave and Materials 2.51
2.7.2 Conductive Losses 2.54
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2.7.3 Polarization 2.54
2.7.4 Variation of Dielectric Properties with Moisture
and Temperature
2.57
2.8 Microwave Volumetric Heating 2.57
2.9 Addition of Absorber in Microwave Pyrolysis 2.63
2.10 Benefits and Challenges of Microwave Heating 2.66
2.11 Microwave Treatment of Waste 2.69
2.11.1 Microwave Pyrolysis of Tyres 2.70
2.11.2 The Microwave Pyrolysis of Sludge 2.71
2.11.3 The Microwave Pyrolysis of Glycerol 2.73
2.11.4 The Microwave Pyrolysis of Agro-wastes 2.75
3 CHARACTERIZATION OF EMPTY FRUIT BUNCH AND
MICROWAVE PRELIMINARY
3.1
3.1 Introduction 3.1
3.2 Materials and Methods 3.1
3.2.1 Empty Fruit Bunch 3.1
3.2.2 Microwave Absorbers 3.2
3.2.3 Characterization of Empty Fruit Bunch 3.3
3.2.4 Microwave Electric Properties, Power Output and
Distribution
3.9
3.3 Results and Discussions 3.15
3.3.1 Proximate, Decomposition and Ultimate Analysis 3.15
3.3.2 Physical, Thermal and Inorganic Characteristics 3.22
3.3.3 Dielectric Properties of EFB 3.26
3.3.4 Microwave Heating Preliminary 3.32
3.4 Conclusions 3.40
4 MICROWAVE PYROLYSIS OF EMPTY FRUIT BUNCH 4.1
4.1 Introduction 4.1
4.2 Materials and Methods 4.1
4.2.1 Empty Fruit Bunch 4.1
4.2.2 Modification of House-hold Microwave Oven 4.3
4.2.3 Experimental Set-up 4.3
4.2.4 Experimental Procedure 4.8
4.2.5 Inorganic Materials Addition 4.9
4.2.6 Conventional Pyrolysis of EFB 4.10
4.2.7 Product Recovery 4.11
4.2.8 Product Gas Analysis 4.12
4.3 Results and Discussion 4.16
4.3.1 Effect of Microwave Absorbers Type and Concentration 4.16
4.3.2 Effect of Pre-treatment of Sample 4.25
4.3.3 Effects of Inorganic Materials Addition 4.30
4.3.4 Effect of Residence Time 4.33
4.3.5 Comparison between Conventional and Microwave
Pyrolysis
4.36
4.4 Conclusion 4.43
5 CHARACTERIZATION OF PYROLYSIS PRODUCTS 5.1
5.1 Introduction 5.1
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5.2 Materials and Methods 5.1
5.2.1 Materials 5.1
5.2.2 Characterization of Bio-oil and Char 5.2
5.3 Results and Discussion 5.4
5.3.1 Characteristics of Char 5.4
5.3.2 Characteristics of Bio-oil 5.15
5.3.3 Quality of Produced Gas 5.24
5.3.4 Energy Comparison between Microwave and
Conventional
5.27
5.4 Conclusion 5.29
6 CONCLUSION AND RECOMMENDATIONS 6.1
6.1 Conclusions 6.1
6.2 Recommendations for Future Works 6.4
REFERENCES R.1
APPENDICES A.1
APPENDIX A – Lignocellulosic Content Determination A.1
APPENDIX B – Calculation of Residence Time A.3
APPENDIX C – Chromatogram for Gas Sample Analysis A.5
APPENDIX D – Conditions of Conventional Pyrolysis A.9
APPENDIX E – GC-MS Analysis of Bio-oil A.10
APPENDIX F – Scanning Electron Microscopy Images A.21
APPENDIX G – Waterloo-mechanism A.22
BIODATA OF STUDENT A.5
LIST OF RELATED PUBLICATIONS A.6