Mohammed Hussein Ahmed Al-hwayzee

326 Pages·2017·11.35 MB·English

Design and Development of Gasification
Processes in Fluidised Bed Chemical
Reactor Engineering

Thesis Submitted to Cardiff University in Fulfilment of the
Requirements for the Degree of Doctor of Philosophy in Chemical
Engineering-Reactor Design

By
Mohammed Hussein Ahmed Al-hwayzee
B.Sc. Chemical Eng. & M.Sc. Chemical Eng.

School of Engineering - Cardiff University
Cardiff, Wales, United Kingdom
September 2016
DECLARATION
This work has not previously been accepted in substance for any degree and is not
concurrently submitted in candidature for any degree.
Signed …………………….…... (Mohammed H. A. Al-hwayzee) Date 30/09/2016
STATEMENT 1
This thesis is being submitted in partial fulfilment of the requirements for the degree of
Doctor of Philosophy (PhD).
Signed …………………….…. (Mohammed H. A. Al-hwayzee) Date 30/09/2016
STATEMENT 2
This thesis is the result of my own independent work/investigation, except where
otherwise stated. Other sources are acknowledged by explicit references.
Signed …………………….… (Mohammed H. A. Al-hwayzee) Date 30/09/2016
STATEMENT 3
I hereby give consent for my thesis, if accepted, to be available for photocopying and
inter-library loan, and for the title and summary to be made available to outside
organisations.
Signed …………………….…. (Mohammed H. A. Al-hwayzee) Date 30/09/2016

III
ABSTRACT
This thesis focuses on studying and investigation the effects of the hydrodynamic and
operating parameters in the air-biomass gasification in a bubbling fluidised bed gasifier
under low temperature (<800oC) conditions and evaluating the potential of the
gasification of two solid biomass waste materials, Iraqi date palm wastes and sawdust
pinewood. These parameters are air flowrate, particle size of the sand bed material,
biomass particle size, static bed height, air equivalence ratio, bed temperature, number
of holes in distributor plates and biomass fuel type.
A design study was conducted to provide preliminary data for designing and
constructing a large lab-scale fluidised bed column, diameter D=8.3cm, for cold and hot
fluidisation experiments. Cold fluidisation experiments were conducted to provide the
fluidisation behaviour data for the sand, biomass and their mixture.
The design and cold fluidisation results have shown a compatible finding in the
following: 1) the design parameter U has shown that, it increases as sand particle size
mf
increases. 2) It was not affected by static bed height. In addition, cold fluidisation results
show that: sand has a high fluidisation quality compared to pure biomass and sand-
biomass mixture and there is no effect of the bed static height on the U .
mf
In general, the studied parameters on the air-biomass gasification performance have
shown that: 1) air flowrate has a considerable effect, 2) as sand and biomass particle
size increases a weakened gasification was achieved. 3) The static height effect has been
observed due to the location of the biomass feeding position thereby affecting reactant
residence time. 4) For equivalence ratio range (0.2-0.4) the lowest value provided
optimum gas composition and LHV values, whereas the highest value ER= 0.43
provided highest (CCE), CGE) and (GY). 5) No significant effect was seen for bed
temperature between 360 to 465oC. 6) A considerable effect has been shown for the
distributor plate configuration.
Finally, the results has shown that SPWB has potential compared to IDPWB for energy
generation. However, additional simulation, optimization and experimental studies on
the bubbling fluidised biomass gasification for a broad range of operating and
hydrodynamic parameters are hereby suggested.
IV
DEDICATION

To my Imam Al Hujjah Ibnu Alhassen (ajtf)
I am your soldier
To my parents ……
To my wife ….. my love
To my lovely daughters…..
Safa, Amenah, Nusk and Gherked
To my brothers and Sisters

V
ACKNOWLEDGEMENTS
Foremost, I would like to praise and thank my GOD (ALLAH) for helping me to
complete this thesis.
I would like to extend my thanks to the Iraqi Government-Ministry of Higher Education
and Scientific Research, in particular Kerbala University for granting the opportunity
to study and complete the PhD. Thanks for the staff of the Iraqi cultural attaché in
London for their help during my stay in the UK.
The words are not sufficient to express my gratefulness and deepest thanks to my
supervisor, Dr. Richard Marsh for his continuous supervision, positive discussions,
important ideas through this research work and his various support along my study.
Again I repeat my grate thank for him.
I would like also to thank the staff of School of Engineering and the staff of the
Mechanical Engineering Work Shop. Special thanks for Mr Malcolm Seaborne and
other technical staff for their technical supports during experimentation. My thanks for
Dr. Julian Steer for his help and support.
I must also thank Mr Hussein, the director of the project of the Organic Fertilizer
Preparation and Mushroom Cultivation - Karbala City-Iraq and other staff for their help
for providing my research an Iraqi date palm wastes biomass material IDPWB.
I wish also to thank all the staff of the Research Office, Finance Office and the IT staff
in School of Engineering for their help during my study period.
I would like to present my thanks for the staff of the Cardiff University Student Support
for their helps and advice.
I am greatly indebted to my devoted wife. My gratefulness for her love, care, encourage,
support, patience in best and worse conditions. My, thanks to my lovely daughters Safa,
Amenah, Nusk and Gherked who have suffered the most during my absence in their
most needed times. My apology for them.
Finally, my deepest thanks and gratitude to my big family, brothers, sisters and my
relatives for their helps, supports and prayers.
VI
TABLE OF CONTENTS

Contents
DECLARATION ....................................................................................................... III
ABSTRACT ................................................................................................................ IV
DEDICATION ............................................................................................................. V
ACKNOWLEDGEMENTS ....................................................................................... VI
TABLE OF CONTENTS ......................................................................................... VII
Chapter 1 ...................................................................................................................... 1
1.1 Background ..................................................................................................... 2
1.2 Gasification and biomass gasification ............................................................. 4
1.3 Fluidised Bed Reactors .................................................................................... 7
1.4 Energy in Iraq .................................................................................................. 7
1.5 Iraqi Biomass Energy-Date Palm Wastes ....................................................... 8
1.6 Motivation and Aims ..................................................................................... 11
1.7 Research Hypothesis ..................................................................................... 11
1.8 Layout of the thesis structure ........................................................................ 12
Chapter 2 .................................................................................................................... 14
2.1 Introduction ................................................................................................... 15
2.2 Biomass Gasification Reactions .................................................................... 15
2.2.1 Water-gas reaction (R2.7) ...................................................................... 17
VII
2.2.2 Boudouard reaction (R2.13) ................................................................... 17
2.2.3 Water-gas shift reaction (R2.8) .............................................................. 17
2.2.4 Methanation reaction (R2.12) ................................................................ 17
2.2.5 Steam methane reforming reaction (R2.9) ............................................. 17
2.3 Key factors affecting the gasification process ............................................... 18
2.3.1 Gasifier design ....................................................................................... 18
2.4 Gasification of biomass in the bubbling fluidised bed gasifiers BFBGs ...... 23
2.4.1 Factors affecting biomass gasification process in bubbling fluidised bed
gasifiers …………………………………………………………………………24
2.4.2 Hydrodynamic factors ............................................................................ 31
2.5 Fluidisation phenomena and fluidised bed .................................................... 35
2.5.1 Fluidised bed column ............................................................................. 36
2.5.2 Solid particles classification: ................................................................. 37
2.5.3 Types of fluidisations (fluidisation regimes) ......................................... 37
2.5.4 Minimum fluidization velocity and pressure drop ................................. 40
2.5.5 Biomass fluidisation ............................................................................... 44
2.5.6 Parameters affect minimum fluidisation velocity .................................. 47
2.6 Summary ....................................................................................................... 52
Chapter 3 .................................................................................................................... 54
VIII
3.1 Introduction ................................................................................................... 55
3.2 Geometry and hydrodynamic design of the bubbling fluidised bed gasifier. 56
3.2.1 Theoretical model of bubbling fluidising bed reactor ............................ 56
3.2.2 Design equations for the reaction bed section........................................ 57
3.2.3 Freeboard Section................................................................................... 64
3.2.4 Distributor plate and air box section ...................................................... 65
3.3 Rig and gasifier operating flexibility ............................................................. 68
3.3.1 Design procedure and design steps ........................................................ 69
3.3.2 Design Results ........................................................................................ 72
3.3.3 Summary of the flexible design and geometry parameters of the gasifier
76
3.4 Summary ....................................................................................................... 79
Chapter 4 .................................................................................................................... 80
4.1 Introduction ................................................................................................... 81
4.2 Characterization of quartz sand material ....................................................... 81
4.2.1 Sand material preparation ...................................................................... 81
4.3 Characterisation of biomass materials ........................................................... 87
4.3.1 Sample preparation................................................................................. 87
4.3.2 The composition analysis of biomass solid fuels ................................... 93
IX
4.4 Cold rig prepared materials ......................................................................... 101
4.4.1 Fluidised bed cold column (transparent pipe) ...................................... 101
4.4.2 Air flow-box pipe section..................................................................... 103
4.4.3 Stainless steel flanges ........................................................................... 104
4.4.4 Perforated Distributor Plate ................................................................. 104
4.4.5 Air flow measurements ........................................................................ 105
4.4.6 Air pressure regulator control .............................................................. 106
4.4.7 Pressure drop device (Manometer) ...................................................... 106
4.5 Hot rig prepared materials ........................................................................... 107
4.5.1 The pipe of fluidised bed reaction section ........................................... 107
4.5.2 Freeboard pipe section- second part ..................................................... 108
4.6 Summary ..................................................................................................... 109
Chapter 5 .................................................................................................................. 110
5.1 Introduction ................................................................................................. 111
5.2 Cold experiment rig hardware ..................................................................... 111
5.2.1 Feed air pressure regulator ................................................................... 112
5.2.2 Rotameters............................................................................................ 113
5.2.3 Bubbling fluidised bed column ............................................................ 113
X