UNIVERSITI PUTRA MALAYSIA

MOHAMMED MAHMOUD AHMAD AL-OBAIDI

FK 2011 152

CATALYTIC GASIFICATION OF EMPTY FRUIT BUNCH FOR TAR-FREE HYDROGEN RICH-GAS PRODUCTION

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CATALYTIC GASIFICATION OF EMPTY FRUIT BUNCH FOR TAR-FREE HYDROGEN RICH-GAS PRODUCTION

By

MOHAMMED MAHMOUD AHMAD AL-OBAIDI

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirements for the Degree of Doctor of Philosophy

November 2011

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DEDICATION

To my beloved mother, my father, my wife, my sisters, my daughters (Raneia and

Reem), and longtime friends

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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

CATALYTIC GASIFICATION OF EMPTY FRUIT BUNCH FOR TAR-FREE HYDROGEN RICH-GAS PRODUCTION

By

MOHAMMED MAHMOUD AHMAD AL-OBAIDI

November 2011

Chairman: Salmiaton Ali, PhD

Faculty : Faculty of Engineering

Palm oil industry in Malaysia generates huge quantity of solid biomass every year

including trunks, fronds, empty fruit bunches (EFB), shells and fibers as wastes from

palm oil fruit harvest and oil extraction processing. These large volumes of wastes

represent a big environmental threat for Malaysia. The great potential of oil palm

biomass has motivated an increasing interest in the utilization of these wastes (i.e.

EFB) as a source of clean energy. Fuel and chemical characteristics of the EFB

undertaken in this study confirmed that it is a good candidate for gasification process

as it is comparable to other lignocellulosic biomass.

As a thermal process, gasification has been used to treat oil palm wastes due to its

high conversion efficiency. This study evaluated the possibility to treat EFB via

gasification process for hydrogen-rich gas production. In this study, the EFB

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obtained from a local palm oil mill was gasified in an atmospheric bench-scale

fluidized-bed gasifier (FBG) using air as gasifying agent. The operating parameters,

such as effects of gasifier temperature (700–1000 °C), equivalence ratio (0.15-0.35),

feedstock particle size (<0.3, 0.3–0.5, 0.5–1.0 mm), and addition of catalysts (as a

primary and secondary) were studied to evaluate the gasification yields and

performance so as to reach maximum tar-free hydrogen-rich gas production.

The main gas species generated, as identified by a gas chromatography (GC), were

H2, CO, CO2 and CH4. With gasification temperature increases the total gas yield

was enhanced greatly and reached the maximum value at 1000 °C with a large

fraction of H2 (38.02 vol.%) and CO (36.36 vol.%). Equivalence ratio (ER) showed a

significant influence on the upgrading of hydrogen production and product

distribution. The optimum ER value of 0.25 was found to attain a higher H2 yield.

Feedstock particle size showed an influence on the improvement of the gas yield.

Smaller EFB particles size produced more H2, CO, CH4 and less CO2.

Tar formation is a major drawback when EFB is converted via gasification to obtain

fuel gas. Catalytic cracking is an efficient method to eliminate the tar content in the

gas mixture. In this study, three types of Malaysian natural dolomites namely, P1, P2

and P3 in addition to spent mixed metal oxide (SMMO) were used as catalysts to

reduce tar contents in the produced gas and for further improvement of hydrogen

yield. Various types of analysis techniques such as X-ray fluorescence (XRF),

thermogravimetry (TGA), X-ray diffraction (XRD), scanning electron microscopy

(SEM) and nitrogen adsorption-desorption isotherm have been used to characterize

the catalyst morphology.

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The effect of the primary catalyst (dry-mixed with biomass) under different ratios of

catalyst to biomass (C/B) varied from 0.05 to 0.3 was carried out in fluidized-bed

gasifier. The performance of gasification process is improved by increasing C/B

ratio. Malaysian dolomites as primary catalyst showed a better catalytic effect

compared to spent mixed metal oxide. With 30% of P1 dolomite, the total gas yield

increased by 8%, hydrogen content increased by 18%, and total tar content in flue

gas decreased by 78% at gasification temperature of 850 °C.

In the second part of the catalytic experiments, the calcined catalysts were placed in a

fixed-bed catalytic cracking reactor located downstream from the fluidized-bed

gasifier to investigate the effect of secondary catalyst at different cracking

temperatures in the range of 700–900 °C. The results show that raising the

temperature in the catalytic bed increases the cracking activity of the catalysts and

then significantly improve the gasification yields and performance. As in primary

position, Malaysian dolomites showed a stronger catalytic activity as a secondary

catalyst compared to spent mixed metal oxide. As cracking temperature increasing to

900 °C, total gas yield increased by 20%, hydrogen increased by 66%, and almost

99% reduction in tar content were obtained with P1 dolomite.

ASPEN PLUS simulation using thermodynamic equilibrium model based on

minimization of Gibbs free energy used to predict the EFB gasification yields under

selected experimental parameters and to compare the simulation results with

experimental data. The analysis of data for product gases and carbon conversion

efficiency obtained from the simulation agreed satisfactorily with the experimental

data.

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As a conclusion, both EFB as untapped waste and Malaysian dolomite as a cheap

catalyst that can significantly reduce tar content of the product gas, could greatly

contribute to the Malaysian economy in terms of producing clean environmentally

renewable energy.

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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Doktor Falsafah

PENGGASAN BERMANGKIN TANDAN KELAPA SAWIT KOSONG UNTUK PENGELUARAN GAS KAYA HIDROGEN BEBAS TAR

Oleh

MOHAMMED MAHMOUD AHMAD AL-OBAIDI

November 2011

Pengerusi: Salmiaton Ali, PhD

Fakulti : Fakulti Kejuruteraan

Industri minyak kelapa sawit di Malaysia menghasilkan kuantiti biojisim pepejal

yang besar setiap tahun termasuk sesalur, pelepah, tandan buah kosong (EFB),

kelompang dan gentian sebagai sisa daripada penuaian buah kelapa sawit dan

pemprosesan pengekstrakan minyak. Isipadu sisa yang amat besar ini merupakan

ancaman alam sekitar yang besar untuk Malaysia. Potensi bagus biojisim kelapa

sawit telah mendorong minat meningkat dalam penggunaan sisa ini (iaitu EFB)

sebagai sumber tenaga bersih. Ciri-ciri bahan bakar dan kimia EFB yang digunakan

dalam penyelidikan ini mengesahkan yang EFB adalah calon yang baik untuk proses

penggasan kerana ianya standing dengan biojisim lignoselulosa yang lain.

Sebagai proses terma, penggasan telah digunakan untuk merawat sisa kelapa sawit

kerana kecekapan penukaran yang tinggi. Dalam penyelidikan ini, EFB yang

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diperolehi daripada kilang kelapa sawit tempatan telah digaskan dalam penggas

lapisan terbendalir skala makmal atmosfera (FBG) dengan menggunakan udara

sebagai agen penggaskan. Parameter kendalian seperti kesan suhu lapisan penggas

(700–1000 °C), nisbah kesetaraan (0.15-0.35), saiz zarah suapan (<0.3, 0.3–0.5, 0.5–

1.0 mm), dan penambahan mangkin (sebagai primer dan sekunder) telah diperiksa

untuk menilai hasil dan prestasi penggasan dalam mencapai pengeluaran gas kaya

hidrogen bebas tar yang maksima.

Spesies gas utama yang dihasilkan, seperti yang dikenalpasti oleh kromatografi gas

(GC), adalah H2, CO, CO2 dan CH4. Dengan kenaikan suhu penggasan, jumlah

keseluruhan hasil gas telah bertambah dengan jayanya dan mencapai nilai maksima

pada 1000 °C dengan bahagian besar H2 (38.02 %isipadu) dan CO (36.36 %isipadu).

Nisbah kesetaraan (ER) menunjukkan pengaruh bermakna terhadap peningkatan

pengeluaran hidrogen dan taburan keluaran. Nilai ER optima 0.25 didapati mencapai

hasil H2 yang lebih tinggi. Saiz zarah suapan juga menunjukkan pengaruh ke atas

peningkatan hasil gas. Saiz zarah EFB yang lebih kecil menghasilkan lebih gas H2,

CO, CH4 dan kurang CO2.

Formasi tar merupakan kelemahan utama apabila EFB ditukarkan melalui penggasan

untuk memperolehi gas kaya hidrogen dengan sasaran untuk penggunaan di loji

penjanaan kuasa atau untuk pengeluaran bahan kimia. Keretakan bermangkin

merupakan satu kaedah yang cekap dalam penyingkiran kandungan tar dalam

campuran gas. Dalam penyelidikan ini, tiga jenis dolomit Malaysian asli iaitu P1, P2

dan P3, disamping campuran logam beroksida terpakai telah digunakan sebagai

mangkin untuk pengurangan kandungan tar dalam gas keluaran.

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Pelbagai jenis teknik analisis seperti pendarkilau sinar-X (XRF), termogravimetri

(TGA), belauan sinar-X (XRD), kemikroskopan elektron imbasan (SEM) dan

isoterma jerapan-nyaherapan nitrogen telah digunakan untuk mencirikan morfologi

mangkin.

Kesan mangkin primer (campur-kering dengan biojisim) di bawah berlainan nisbah

mangkin kepada biojisim (C/B=0.05–0.30) telah dilaksanakan dalam penggas lapisan

terbendalir. Prestasi proses penggasan telah diperbaiki dengan meninggikan nisbah

C/B. Dolomit Malaysian sebagai mangkin primer menunjukkan kesan mangkin yang

lebih baik berbanding dengan campuran logam beroksida. Dengan 30% dolomit P1,

jumlah keseluruhan hasil gas telah meningkat sebanyak 8%, dan kandungan hidrogen

sebanyak 18%, manakala jumlah keseluruhan kandungan tar telah menurun secara

dramatik sebanyak 78% pada suhu penggasan 850 °C.

Dalam bahagian kedua ujikaji bermangkin, mangkin berkalsin telah diletakkan di

dalam reaktor pemecahan bermangkin lapisan tetap bertempat di hilir daripada

penggas lapisan terbendalir untuk menyiasat kesan mangkin sekunder pada suhu

pemecahan yang berlainan dalam julat 700–900 °C. Keputusan tersebut

menunjukkan bahawa dengan menaikkan suhu di dalam lapisan bermangkin, aktiviti

pemecahan oleh mangkin telah meningkat menyebabkan hasil dan prestasi

penggasan telah diperbaiki dengan jayanya. Serupa dengan keputusan oleh mangkin

primer, dolomit Malaysia menunjukkan aktiviti bermangkin yang lebih kuat sebagai

mangkin sekunder berbanding dengan campuran logam beroksida. Apabila suhu

pemecahan meningkat kepada 900 °C, jumlah keseluruhan hasil gas dengan dolomit

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P1 telah meningkat sebanyak 20%, pengeluaran hidrogen sebanyak 66%, manakala

hampir 99% tar telah terdegradasi.

Simulasi ASPEN PLUS menggunakan model keseimbangan termodinamik

berdasarkan peminimuman tenaga bebas Gibbs telah digunakan untuk meramalkan

hasil penggasan EFB di bawah parameter uji kaji terpilih dan untuk mengesahkan

keputusan simulasi terhadap data uji kaji. Analisis data untuk gas keluaran dan

kecekapan penukaran karbon diperolehi daripada simulasi bersetuju dengan

memuaskan dengan data uji kaji.

Secara kesimpulannya, kedua-dua EFB sebagai sisa terpendam dan dolomit Malaysia

sebagai mangkin murah yang dapat mengurangkan dengan nyata kandungan tar di

dalam gas keluaran, boleh menyumbang dengan banyak ke atas ekonomi Malaysia

dari segi pengeluaran tenaga boleh dibaharui persekitaran bersih.

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ACKNOWLEDGEMENTS

Thank Allah to Almighty for giving me the patience and perseverance to finish this

thesis to the end.

I hereby convey my sincere gratitude and appreciation to my venerable supervisor

Associate Prof. Dr. Salmiaton Ali, how gave me invaluable and worthwhile advice

on this thesis, and gave me a panorama of observance into knowledge in my field.

I also would like to appreciate the efforts of my co-supervisors Prof. Dr. Fakhru’l-

Razi Ahmadun, Prof. Dr. Taufiq Yab, Dr. Wan Azlina and Dr. Mohamad Amran for

their support, advice, recommendation and comments through my research.

I would like to extend my appreciation to former head of department Prof. Dr. Azni

Idris and the entire staff of the Department of Chemical and Environmental

Engineering, UPM.

My special appreciation is extended to Prof. Dr. Robiah Yunus and Dr. Rozita Omar

for providing me with fruitful information. My appreciation also goes to the

technicians, research officers and science officers at Department of Chemical

Engineering, Department of Civil Engineering, Department of Food Engineering,

Department of Physical and Chemistry, Center of Excellence for Catalysis Science

and Technology how have helped me at the experimental stage.

My heartfelt gratitude to have helping hands of my fellow friends Dr. Ali Riza, Dr.

Azahari, Maziyar, Ahmad, Baba, Shehab, Riza, Mustika, Baiti, Taha, Amir and

others that I might have forgotten to mention their names.

Finally, thanks to beautiful Malaysia for giving me the care and tenderness to

achieve my dreams and finish my study.

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I certify that a Thesis Examination Committee has met on 22 November 2011 to conduct the final examination of Mohammed Mahmoud Ahmad Al-Obaidi on his thesis entitled "Catalytic gasification of empty fruit bunch for tar-free hydrogen rich-gas production" 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: Dayang Radiah Binti Awang Biak, PhD Lecturer Faculty of Engineering University Putra Malaysia (Chairman) Robiah Binti Yunus, PhD Professor Faculty of Engineering University Putra Malaysia (Internal Examiner) Thomas Choong Shean Yaw, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) John R. Grace, PhD Professor Faculty of Engineering / Chemical and Biological Engineering (CHBE) The University of British Columbia Canada (External Examiner)

SEOW HENG FONG, PhD

Professor and Deputy Dean School of Graduate Studies Universiti Putra Malaysia Date:

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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: Salmiaton Binti Ali, PhD Associate Professor Faculty of Engineering University Putra Malaysia (Chairman) Wan Azlina Binti Wan Ab Karim Ghani, PhD Associate Professor Faculty of Engineering University Putra Malaysia (Member) Mohamad Amran Bin Mohd. Salleh, PhD Lecturer Faculty of Engineering University Putra Malaysia (Member) Fakhru’l-Razi Bin Ahmadun, PhD Professor Faculty of Engineering University Putra Malaysia (Member) Taufiq Yap Yun Hin, PhD Peofessor Faculty of Science University Putra Malaysia (Member)

BUJANG BIN KIM HUAT, PhD Professor and Dean School of Graduate Studies Universiti Putra Malaysia Date:

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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 institutions.

MOHAMMED MAHMOUD AHMAD AL-OBAIDI Date: 22 November 2011

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TABLE OF CONTENTS

Page DEDICATION ii ABSTRACT iii ABSTRAK vii ACKNOWLEDGEMENTS xi APPROVAL xii DECLARATION xiv LIST OF TABLES xx LIST OF FIGURES xxii LIST OF ABBREVIATION AND ACRONYMS xxvii CHAPTER 1  INTRODUCTION 1 

1.1  Background 1 1.2  Problem Statement 7 1.3  Research Objectives 10 1.4  Thesis Layout 11

2  LITERATURE REVIEW 13 

2.1  Introduction 13 2.2  Chronology of Palm Oil Plantation in Malaysia 13 2.3  Availability of Oil Palm Biomass in Malaysia 15 2.4  Bio-fuel and Biopower Programs in Malaysia 19 2.5  Composition and Properties of Oil Palm Biomass 25 

2.5.1  Oil Palm Composition 25 2.5.2  Oil Palm Properties 28 

2.6  Thermal Conversion of Oil Palm Biomass 30 2.6.1  Combustion 31 2.6.2  Liquefaction 33 2.6.3  Pyrolysis 33 2.6.4  Gasification 36 2.6.5  Comparison among Different Thermal Conversion Processes 37 

2.7  Gasification Process 38 2.7.1  Gasification Mechanism 39 2.7.2  Types of Gasifiers 43 

2.8  Main Parameters Governing Gasification 52 2.8.1  Effects of Gasification Agent 52 2.8.2  Effects of Operating Temperature 55 2.8.3  Effects of Equivalence Ratio 57 

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2.8.4  Effects of Biomass Particle Size 59 2.8.5  Effects of Catalyst 61 

2.9  Hydrogen 70 2.9.1  Hydrogen Applications 71 2.9.2  Hydrogen Generation 72 

2.10  Technologies for Hydrogen Production from Biomass 73 2.10.1  Hydrogen from Supercritical Water Extraction 73 2.10.2  Hydrogen from Fast Pyrolysis 77 2.10.3  Hydrogen from Gasification 79 

2.11  Hot Gas Cleaning Technologies 83 2.12  Catalytic cracking of Tar 85 

2.12.1  Primary Methods 87 2.12.2  Secondary Methods 90 

2.13  ASPEN PLUS® Simulation of Biomass Gasification Process 92 3  RESEARCH METHODOLOGY 96 

3.1  Introduction 96 3.2  Materials 96 

3.2.1  Empty Fruit Bunch 96 3.2.2  Sand 97 3.2.3  Chemicals 97 3.2.4  Catalysts 97 

3.3  Apparatus 99 3.3.1  Fluidized-bed Gasifier 99 3.3.2  Fixed-bed Catalytic Cracking Unit 101 

3.4  Experimental Setup 103 3.5  Preliminary Experiments 107 3.6  Experimental Procedure 107 3.7  Experimental Parameters 109 

3.7.1  Effect of Gasifier Bed Temperature 109 3.7.2  Effect of Equivalence Ratio 109 3.7.3  Effect of Feedstock Particle Size 109 3.7.4  Effect of Catalysts 109 

3.8  Characterization of Empty Fruit Bunch 111 3.8.1  Proximate Analysis 111 3.8.2  Ultimate Analysis 112 3.8.3  Calorific Value 112 3.8.4  Apparent Density 112 

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3.8.5  Analysis of Lignocellulosic Content 113 3.8.6  Inorganic Element Analysis 115 3.8.7  Thermal Decomposition and Kinetics Analysis 115 

3.9  Catalyst Characterization 118 3.9.1  XRF Analysis 118 3.9.2  Thermal Analysis 118 3.9.3  XRD Analysis 118 3.9.4  FTIR Spectral Analysis 119 3.9.5  SEM Analysis 119 3.9.6  Analysis of Physical Properties 119 

3.10  Product Recovery 120 3.11  Product Gas Analysis 121 3.12  Tar Sampling and Analysis 124 3.13  Simulation Work 127 

3.13.1  ASPEN PLUS 127 3.13.2  Flow of Simulation Work 128 3.13.3  Modeling Approach 130 3.13.4  Assumptions 130 3.13.5  Model Description 130 3.13.6  Model Comparison 136

4  CHARACTERIZATION AND KINETIC OF EMPTY FRUIT BUNCH 138 

4.1  Introduction 138 4.2  Proximate and Ultimate Analysis 138 4.3  Lignocellulosic Content Analysis 142 4.4  Physical and Inorganic Characteristics 143 4.5  Thermal Decomposition Analysis 146 4.6  Thermal Conversion Characteristic and Kinetic Behavior of EFB 148 

4.6.1  Effect of heating rate 148 4.6.2  Effect of Particle Sizes 151 4.6.3  Kinetic Analysis of EFB Gasification 153

5  AIR-GASIFICATION OF EMPTY FRUIT BUNCH 156 

5.1  Introduction 156 5.2  Effect of Reactor Bed Temperature 156 5.3  Effect of Equivalence ratio (ER) 160 5.4  Effect of Feedstock Particle Size 164 5.5  Effect of Gasification Temperature on Bio-oil Components 166 

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5.6  Effect of Gasification Temperature on Tar Compounds 170 6  CATALYSTS AND CATALYST CHARACTERISATION 172 

6.1  Introduction 172 6.2  Catalyst Chemical Composition 172 6.3  Thermal Decomposition Behaviour 174 6.4  XRD Analysis 177 6.5  FTIR Spectral Analysis 179 6.6  SEM Analysis 182 6.7  Analysis of Surface area and Total Pore Volume 184

7  CATALYTIC GASIFICATION OF EMPTY FRUIT BUNCH 186 

7.1  Introduction 186 7.2  Influence of the Primary Catalyst 187 

7.2.1  Overall Product Yields and Performance 187 7.2.2  Tar Content and Conversion Efficiency 195 7.2.3  Tar Components Analysis 197 

7.3  Influence of the Secondary Catalyst 199 7.3.1  Overall Product Yields and Performance 199 7.3.2  Tar Content and Conversion Efficiency 204 7.3.3  Tar Components Analysis 206 

7.4  Dolomite Deactivation - Regeneration 209 7.5  Comparison of Primary and Secondary Catalyst 211 7.6  Cost Analysis 213

8  ASPEN SIMULATION OF EMPTY FRUIT BUNCH GASIFICATION 216 

8.1  Introduction 216 8.2  ASPEN PLUS Model 216 8.3  Model validation 218 

8.3.1  Effect of Gasifier Temperature 218 8.3.2  Effect of Equivalence Ratio (ER) 220 8.3.3  Effect of Feedstock Particle Size 222

9  CONCLUSIONS AND RECOMMENDATIONS 225 

9.1  Conclusions 225 9.2  Recommendation for Future Work 229

REFERENCES 231 APPENDICES 251 BIODATA OF STUDENT 271