reactor design for production of fermentable …
TRANSCRIPT
REACTOR DESIGN FOR PRODUCTION OF FERMENTABLE SUGARS FROM
EMPTY FRUIT BUNCH
NOR AIN BINTI ABU SAMAH
A dissertation submitted in partial fulfilment of the
requirements for the award of the degree of
Master of Engineering
Faculty of Chemical and Energy Engineering
Universiti Teknologi Malaysia
MARCH 2017
iv
ACKNOWLEDGEMENT
Alhamdulillah, with His blessing, I am able to complete this dissertation. I
would like to express my sincere appreciation and greatest gratitude to my supervisor
Dr Umi Aisah binti Asli for her motivation and guidance throughout my study. Her
advice and suggestion had encouraged me to further work on my dissertation. Special
thanks also to my Post Graduate Student Society team, for our friendship and for
always providing assistance in any occasions. My journey here in UTM was more
meaningful and memorable with all the activities that we have organized together, for
the benefits of our faculty members. Next, I am also truly grateful for the Ministry of
Higher Education and UiTM for funding my studies. Without their financial support,
I might have to face another hurdle along this road. Most importantly, I wish to credit
millions of thanks to my family and friends for their endless support and love. Thank
you for always standing by my side especially during the moment when I need you the
most.
v
ABSTRACT
Bioethanol is a fuel produced from sugar fermentation process that used bio
based renewable sources as feedstock. As the second largest producer of oil palm,
Malaysia has abundant of empty fruit bunch (EFB) waste. Despite of tremendous
experimental studies done on effectiveness of using EFB for production of bioethanol,
the process implementation in industry is still discouraging. This is due to lack of
proven technology and high capital cost of investment. Hence, there is a need to find
a straight-forward and cost effective process with a promising glucose yield. From
previous experimental work, it has been proven that combination of low pressure
steam heating (LPSH) and dilute acid pretreatment (DAP) able to gain a glucose yield
of 78.6%, which is comparably higher than other pretreatment methods. In this present
study, a block flow diagram was developed based on the data provided in the
experimental work. The analysis then continued with mass balance calculation of
process operation. With a scale up feedstock to ratio of 10 (to 100g of EFB), both
pretreatment and hydrolysis process unit operations were modelled in Aspen Plus
simulator for production of fermentable sugars. The reactors were based on RStoich
and RYield reactor block due to unavailability of kinetic rate of reactions. Mass
balance results from both experimental and simulation were compared and the
difference was found to be around 0.73% to 0.85%. This indicated that the
assumptions in simulation modelling were almost accurate to the actual experimental
works. The reactor was sized based on the largest unit operations volume, which was
determined to be 0.01791 m3. Detailed reactor’s mechanical design was illustrated
using Microsoft Visio. Using bare module cost technique, the cost estimated to build
this fermentable sugars reactor was around RM 111 000. This design work could be
considered as a significant progress in the effort to bring the experimental works to
industrial application.
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ABSTRAK
Bioetanol adalah bahan api yang dihasilkan daripada proses penapaian gula
yang menggunakan sumber yang boleh diperbaharui sebagai bahan mentah. Sebagai
negara pengeluar kedua terbesar kelapa sawit, Malaysia mempunyai banyak sisa
tandan kosong. Walaupun banyak kajian eksperimen telah dilakukan ke atas
keberkesanan penggunaan tanda kosong terhadap pengeluaran bioethanol,
pelaksanaan proses ini dalam industri masih tidak menggalakkan. Ini adalah
disebabkan oleh kekangan teknologi dan kos modal pelaburan yang tinggi. Oleh itu,
terdapat keperluan untuk mencari satu proses yang mudah dan berbaloi dari segi kos,
di samping menjanjikan hasil glukosa yang baik. Hasil dari kerja eksperimen sebelum
ini mendapati bahawa gabungan stim pemanasan tekanan rendah dan prarawatan asid
cair berjaya menghasilkan glukosa sebanyak 78.6%, yang mana antara lebih tinggi
berbanding dengan kaedah prarawatan yang lain. Dalam kajian ini, gambar rajah blok
telah digambarkan berdasarkan data yang disediakan dalam kerja eksperimen.
Analisis ini diteruskan dengan pengiraan imbangan jisim terhadap proses operasi.
Dengan menggunakan bahan mentah yang telah diskalakan kepada nisbah 10
(sehingga 100 g EFB), unit-unit operasi proses prarawatan dan hidrolisis dimodelkan
di simulator Aspen Plus simulator untuk pengeluaran gula beragi. Reaktor yang dipilih
adalah berdasarkan blok RStoich dan RYield kerana ketiadaan kadar kinetik tindak
balas. Hasil keputusan pengiraan imbangan jisim dari kedua-dua eksperimen dan
simulasi dibandingkan dan didapati berbeza sekitar 0.73% hingga 0.86%. Ini
menunjukkan bahawa andaian dalam pemodelan simulasi hampir tepat kepada kerja
eksperimen yang sebenar. Saiz reaktor dikira berdasarkan jumlah operasi unit yang
terbesar, iaitu 0.01791 m3. Reka bentuk mekanikal reaktor yang terperinci telah dilukis
menggunakan Microsoft Visio. Dengan menggunakan teknik kos modul terdedah,
anggaran kos untuk membina reaktor ialah sekitar RM 111 000. Kerja-kerja mereka
bentuk ini boleh dianggap sebagai peningkatan besar dalam usaha membawa kerja-
kerja eksperimen kepada kegunaan industri.
vii
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES x
LIST OF FIGURES xii
LIST OF ABBREVEATIONS xiv
LIST OF SYMBOLS xv
LIST OF APPENDICES xvii
1 INTRODUCTION 1
1.1 Overview 1
1.2 Background of Study 1
1.3 Problem Statement 5
1.4 Objectives 6
1.5 Scope of Study 6
1.6 Significant of Study 7
2 LITERATURE REVIEW 8
2.1 Overview 8
2.2 EFB as Biomass Feedstock for Bioethanol Production 8
2.3 EFB Pretreatment Process 9
2.3.1 Aqueous Ammonia Pretreatment 10
TABLE OF CONTENTS
2.3.2 High Pressure Stream Pretreatment 10
2.3.3 Sequential Acid and Alkali Pretreatment 10
2.3.4 NaOH and Catalyzed Steam Pretreatment 11
2.3.5 Multiexplosion Pretereatment and NaOH 11
2.3.6 LPSH and DAP 12
2.4 From Research and Development to Preliminary ProcessDesign 14
2.5 Practical Consideration for Scale Up 16
2.6 Transformation of Experimental Data to Process Design 17
2.7 Development of Base Case Process Modelling 18
2.8 Built-in Reactor Model in Aspen Plus 23
2.8.1 RStoich Block 23
2.8.2 RYield Block 24
2.9 Current Available Process Modelling and Design usingAspen Plus 25
2.9.1 Production of Bioethanol from Corn Stover by usingCo-Current Dilute Acid Prehydrolysis and Enzymatic Hydrolysis 25
2.9.2 Production of Bioethanol using Biomass Gasificationand Syngas Fermentation Technique 27
2.9.3 Steady State and Dynamic Analysis for Dilute AcidPretreatment of Corn Stover 27
2.10 Mechanical Design of a Reactor 30
2.7.1 Available Pilot Scale Pretreatment Reactors 30
2.7.3 Additional Information on Reactor Configuration 33
2.11 Concluding Remarks 34
3 METHODOLOGY 35
3.1 Overview of the Work Flow 35
3.2 Process Flow and Mass Balance 36
3.2.1 List of Assumptions 37
3.3 Process Simulation in Aspen Plus 38
3.3.1 Equipment Setup 39
3.4 Reactor Sizing and Costing 40
viii
4 RESULTS AND DISCUSSIONS 42
4.1 Process Flow and Mass Balance 42
4.2 Simulation in Aspen Plus 45
4.2.1 Equipment Configurations 45
4.2.1.1 Mixer 45
4.2.1.2 Heater 46
4.2.1.3 Separator 46
4.2.1.4 Reactor 47
4.2.2 Mass Balance Results from Aspen Simulation 49
4.3 Sizing, Mechanical Design and Costing of FermentableSugar Reactor 53
4.3.1 Reactor Sizing 53
4.3.2 Heat Transfer to Process Vessel 55
4.3.2.1 External Jacket 55
4.3.2.2 Internal Coil 56
4.3.3 Selection of Reactor’s Construction Material 56
4.3.4 Choice of Continuous versus Batch Operation 58
4.3.5 Reactor’s Specification and Process Operation 58
4.3.6 Estimated Reactor’s Cost 60
4.4 Summary of Results 62
5 CONCLUSIONS AND RECOMMENDATIONS 64
5.1 Conclusions 64
5.2 Recommendations 65
ix
REFERENCES
Appendices A-B
66
69-83
x
LIST OF TABLES
TABLE NO. TITLE
2.1 Composition from Different Sources of Lignocellulosic Materials (Najafpour et al., 2007)
2.2 Summary of different pretreatment methods that employed EFB as feedstock
2.3 Plant design phases (in sequence) with specific purpose and main tasks (Kidam, 2012)
2.4 Recommended scale-up factor and feed’s mass flowrate adapted from Zeton Inc. (Edwards, 2015)
2.5 Upgrade features in Aspen Plus (Dyment et. al., 2013)
2.6 Solid unit operations available in Aspen Plus V8.4(Dyment et al., 2013)
2.7 Reactions that took place inside pretreatment reactor and its conversion (Humbird et al., 2011)
2.8 Pre-hydrolysis reaction and its conversion (Lopez-Arenas et al., 2010)
2.9 Reactor dimension for different reactor operating conditions (Jayawardhana and Van Walsum, 2004)
2.8 Recommended material of construction (Turton et al., 2009)
3.1 Mandatory input requirement for each type of equipment
4.1 Split fraction for S101
PAGE
9
13
14
17
19
20
26
29
33
29
39
46
4.2 Reactions involved in R101 47
xi
48
49
51
52
53
57
58
58
62
Normalized yield (mass basis) for R103
Mass balance comparison between experiment and simulation for 100 g feedstock
Stream summary for Aspen simulation
Continue stream summary for Aspen simulation
Volume of respective major unit operations
Recommended material of construction (Turton et al., 2009)
Continuous versus batch reactor (Sinnott, 2005)
Reactor specifications
Results’ summary
xii
LIST OF FIGURES
FIGURE NO. TITLE PAGE
1.1 Global Ethanol Production and Top US Ethanol Exporterin 2015 (Renewable Fuels Association, 2016) 2
1.2 Ethanol price trend as compared to Toluene and Benzene(Renewable Fuels Association, 2016) 3
1.3 Four major processes in production of bioethanol 3
2.1 Simulation model development algorithm (Rao, 2005) 21
2.2 Simplified process flow for pretreatment and conditioningprocess (Humbird et al., 2011) 25
2.3 Aspen Flowsheet for conditioning and pretreatment area(Lopez-Arenas et al., 2010) 28
2.4 Dimension of looped pump reactor (Pederson, 2010) 30
2.5 Actual configuration of Bioprocess Engineering Reactor developed in Technical University of Denmark(Pederson, 2010) 31
2.6 Schematic pretreatment reactor design adapted fromAndriz Inc. (Humbird et. al., 2011) 32
2.7 Common temperature control strategy for jacketed batch 34reactors (Coughran, 2013)
3.1 W ork flowchart of thi s study 35
4.1 Block flow diagram 43
xiii
4.2 Mass balance for 10g EFB feedstock (experimental) 44
4.3 Mass balance for 100g EFB feedstock (scale up) 44
4.4 Simulation of pretreatment and hydrolysis process inAspen Plus based on 100 g EFB feedstock 50
4.5 Conventional, Dimple and Half-Pipe Jacketed- from left to right (Sinnott, 2005) 55
4.6 Configuration of internal coil inside a vessel(Sinnott, 2005) 56
4.7 Final configuration of fermentable sugars reactor 59
xiv
LIST OF ABBREVIATIONS
AFEX - Ammonia Fiber Explosion
ASL - Acid Soluble Lignin
ASME - American Society of Mechanical Engineering
CEPCI - Chemical Engineering Plant Cost Index
CHEMEX - Changhae Ethanol Multiexplosion
DAP - Dilute Acid Pretreatment
EFB - Empty Fruit Bunch
EOS - Equation of State
HPST - High Pressure Steam Pre-Treatment
LPSH - Low Pressure Steam Heating
NaOH - Sodium Hydroxide
NREL - National Renewable Energy Laboratory
NRTL - Non Random Two Liquid
PSD - Particle Size Distribution
US - United State
xv
LIST OF SYMBOLS
a
A
Ai
Apolymer
b
B
B1
B2
Bmonomer
c
C
Cacid
Cb m
oCp
d
Di
E
Ei
Fai
Fao
Fm
Fp
H2 SO4
ki
K1
Stoichiometry coefficient of component a
Acceptable
pre-exponential constant
xylan, glucan, arabinan, galactan, mannan, lignin
Stoichiometry coefficient of component b
acceptable up to 30°C
constant for vertical process vessel
constant for vertical process vessel
xylose, glucose, arabinose, galacton, mannose, ASL
Stoichiometry coefficient of component c
Caution
Acid concentration (%w/w)
Bare module cost
Equipment purchase cost for base condition
Stoichiometry coefficient of component d
Internal vessel diameter
Fractional weld efficiency
activation energy
Final amount of component A in product stream
Initial amount of component A in feed stream
Material factor
Pressure factor
Sulfuric acid
kinetic rate constant
constant to calculate cost of vertical agitated and jacketed process vessel
xvi
K2 - constant to calculate cost of vertical agitated andjacketed process vessel
K3 - constant to calculate cost of vertical agitated andjacketed process vessel
L - Length of reactor
N - Not recommended
Pd - Design pressure
Po - Operating pressure psig
R - Gas Constant
S - Maximum allowable stress
T - Temperature
tp - Wall thickness
W - Reactor weight
X - Conversion
Ani - Number of moles of component i (consumed orproduced)
p - Density of carbon steel
n - pi (=3.143)
xvii
LIST OF APPENDICES
APPENDIX TITLE PAGE
A Sample Mass Balance Calculations 69
B Full Aspen Plus Report 70
CHAPTER 1
INTRODUCTION
1.1 Overview
In this chapter, general background knowledge of the present study will be
introduced. Key important issues, objectives, scope as well as the significant of study
will also be presented.
1.2 Background of Study
World energy consumption rate is increasing tremendously each day. Due to
this, there has been rising concern on the energy sources. Energy sources can be
classified into two types; non-renewable and renewable sources. Example of non
renewable source is fossil fuels. As the fossil fuel sources are going to deplete, people
starts to look at other alternative renewable energy sources such as solar, wind, water
and biomass. Bioenergy could benefit us in terms of economy, environment and
energy security (Balat, 2011). From economy point of view, renewable energy will
contribute to the sustainability, fuel diversity and reducing the dependency on
imported petroleum. As for the environment, the emission greenhouse gases can be
reduced and at the same time, the usage of bioenergy material can contribute to higher
combustion efficiency and reduce the air pollution impact. Besides that, bioenergy
will also give advantage on the energy security of a nation, as it would reduce the
dependency of fossil fuel (Balat, 2011).
2
Bioethanol is an example of renewable energy derived from several biomass
feedstock. Bioethanol can be blend with gasoline to be used as transportation fuel.
The suffix “bio” only signifies that it is produced from fermentation of biomass
sources. In terms of chemical compound, it is exactly the same as synthetic ethanol,
C2H5 OH. Currently, United State (US) is the leading producer of ethanol with 57%
market share, follow by 28% market share in Brazil and 5% Europe. Most of the
ethanol produced from US is imported to Canada (31%), Brazil (15%) and China (8%)
(Renewable Fuels Association, 2016). Figure 1.1 shows the market distribution of
ethanol.
Figure 1.1 Global Ethanol Production and Top US Ethanol Exporter in 2015
(Renewable Fuels Association, 2016)
Besides promote to decrease the greenhouse gases emission and reduce the
dependency on petroleum, another key important benefits of ethanol usage is its octane
rating of 113. Octane rating is a measure of fuel’s ability to resist knocking, which is
the burning of fuel in engine’s combustion chamber. Higher fuel’s octane number
would resulted in better engine performance, increase fuel efficiency as it is more
resistant to knocking, and eventually help to decrease greenhouse gases (Renewable
Fuels Association, 2016). According to US Department of Energy and Sources,
ethanol’s octane rating is the second best after methanol; which has an octane rating
of 115 (Renewable Fuels Association, 2016). In addition, the price of ethanol is also
relatively cheaper than other key octane sources as observed in Figure 1.2.
3
Figure 1.2 Ethanol price trend as compared to Toluene and Benzene (Renewable
Fuels Association, 2016)
Bioethanol can be produced from either sucrose-rich crops, starch-rich crops
or lignocellulosic materials (Balat, 2011). The lignocellulosic materials, which also
known a second generation materials, are more preferable compared to the other
biomass feedstock because they are non-edible raw materials, and thus, they will not
affect the food-supply chain. The sequence of general operations in lignocellulose-
based bioethanol production is illustrated in Figure 1.3.
Referring to Figure 1.3, biomass feedstock will first go through pretreatment
process to break the biomass recalcitrant structure and enhance digestibility for the
next process; hydrolysis. In hydrolysis process, cellulose, hemicellulose and lignin
will decompose to simpler compounds through either chemical reaction with H+ ions
or using enzymatic hydrolysis technique. The output of hydrolysis process is known
as fermentable sugars as they are ready to be fermented and later on produce
4
bioethanol. Finally, the bioethanol obtained from fermentation process will be purified
to increase the final bioethanol’s product quality.
Globally, Malaysia is the largest exporter and second largest producer for crude
palm oil. Latest data from Malaysian Palm Oil Board recorded that there was an
increment 46% of total planted oil palm area in year 2015 as compared to year 2014.
This has made the total area covered for oil palm planted area by December 2015 to
be 5.64 million hectare (Choo, 2016). It was also reported that amount of crude palm
oil produced throughout 2015 was 19.96 million tonnes, an increase of 1.5% from
previous year (Choo, 2016). Hence, there are abundant of expected waste generated
based on the statistic in the report. One of massive waste generated from the
production of crude palm oil is empty fruit bunch (EFB).
Various studies on pretreatment technology have been conducted to explore
the best method to improve the glucose yield from the palm’s EFB. These include
pretreatment using chemical (acid/alkali), physio-chemical (steam, liquid hot water,
ammonia fiber explosion) and also biological approach. As the second largest
producer of palm oil, Malaysia has huge potential for production of bioethanol as it
has an ample amount of lignocellulosic materials. Currently, the EFB is being burnt
as feedstock for boiler to generate energy. This activity could lead to air pollution.
Thus, converting these lignocellulosic materials into renewable energy such as
bioethanol would be a better option in terms of sustainability and environmental
concern.
Based on the recent Malaysia Annual Biofuel report from United State
Department of Agriculture, the production of biodiesel is forecast to increase from 359
million liters to 537 million liters annually (Wahab, 2015). Production of biodiesel in
Malaysia has shown positive growth from year to year. However, there is still no
significant production of bioethanol in commercial quantities yet in Malaysia. The
commercialization of the process is still discouraging as there is limited or known
proven industrial scale technology developed from laboratory scale. There are five
major phases in designing a chemical process industry. Standard process flow in
building a chemical plant starts with research and development phase, then preliminary
5
process design phase, followed by basic engineering, detailed engineering,
construction and start-up, plant operation, retrofit, and finally decommissioning phase
(Kidam, 2012). The experimental works are considered as part of research and
development (R&D) stage in the chemical plant design. This is the fundamental basis
to the conceptual preliminary design. Recently, the sequence process of combined
method of low pressure steam heating (LPSH) and dilute acid pretreatment (DAP) has
been successfully developed. In the study, the glucose yield was increased from
30.1wt % to 78.6 wt% (Hamid, 2015). This is in fact among the highest glucose yield
that could be obtained from EFB feedstock. Due to the positive potential seen from
this developed method, an initiative has been attempted to advance this method into a
mini-pilot scale with a better reactor configuration.
1.3 Problem Statement
Some of the issues that have made the bioethanol project in Malaysia became
unfeasible include high capital investments, lack of advance technology and
difficulties to have a constant supply of feedstock (Wahab, 2015). The LPSH and DAP
pretreatment methods are chosen not only because its ability to produce high glucose
yield but also because of process simplicity (Hamid, 2015). Hence, this present work
will focus on designing a scale up mini-pilot reactor that apply these two methods;
LPSH followed by DAP for fermentable sugars production. One challenge in this
work is the absence of kinetic rate of reactions. The reactor will be designed based on
conversion factor or yield instead of the rate of reactions. This actually limits the user
to perform process optimization from simulation study as the output is fixed. Another
challenge will be choosing an appropriate scale up factor for the preliminary design.
Various literature sources has to be gathered to ensure a reliable simulation results. As
the feedstock contains majority of cellulose, hemicellulose and lignin, it will also be a
challenge to define these lignocellulosic materials as solids in simulation study. These
challenges were taken into the consideration when designing the fermentable sugars
reactor.
6
1.4 Objectives
In general, the aim of this project is to design a reactor for production of
fermentable sugars from EFB using combined methods of low pressure steam heating
and dilute acid pretreatment. With this aim, the objectives of the present study were
divided as follows;
i. To develop process block flow diagrams based on experimental data and
perform mass balance on both current and scale up process operations.
ii. To simulate scale up pretreatment and hydrolysis process unit operation
models in Aspen Plus by employing integrated LPSH and DAP methods. The
simulation results and experimental results shall be validated in term of
fermentable sugars yield.
iii. To perform preliminary sizing, illustrate mechanical design using Microsoft
Visio and costing for fermentable sugars reactor.
1.5 Scope of Study
In order to achieve the stated objectives of this study, the scope is limited to:
• Only covered until hydrolysis process where fermentable sugars are produced.
• The process simulation in Aspen Plus will used an EFB feedstock of 100g,
which scaled up to a factor of 10 from the initial experimental data (10g).
• Equipment selection, preliminary sizing and costing will only be done for
reactor. Sizing of other process unit operations and auxiliary equipment are
not included.
7
1.6 Significant of Study
This study presents a preliminary design of a reactor for production of
fermentable sugars from EFB. Data from laboratory work which contributed to the
highest glucose yield was chosen as the base case for this study. With the Aspen
simulation, one will be able to determine whether it is technically feasible to develop
the similar LPSH and DAP concept for scale up amount of raw EFB feedstock. The
development of Aspen simulation model for pretreatment and hydrolysis processes is
another significant contribution of this work as it can be used for future improvement
studies. This preliminary design work is part of the motivation to bring experimental
works for industrial application by taking the advantage and huge opportunities for the
country, Malaysia, as the largest exporter and second largest producer of crude palm
oil.
66
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