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.

vi

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

REFERENCES

Abdullah, N., and Sulaiman, F. (2013). The properties of the washed empty fruit

bunches of oil palm. Journal o f Physical Science, 24(2), 117-137.

Baharuddin, A. S., Sulaiman, A., Kim, D. H., Mokhtar, M. N., Hassan, M. A.,

Wakisaka, M., Shirai, Y, and Nishida, H. (2013). Selective component

degradation of oil palm empty fruit bunches (OPEFB) using high-pressure steam.

Biomass and Bioenergy, 55, 268-275.

Balat, M. (2011). Production of bioethanol from lignocellulosic materials via the

biochemical pathway: A review. Energy Conversion and Management, 52(2),

858-875.

Caughran, M. (2013), Chemical Processing: Jacketed Heating - Improve Batch

Reactor Temperature Control. Wisconsin: Pick Heater Inc.

Chemical Engineering (2016). Economic Indicator: Chemical Engineering Plant Cost

Index. Chemical Engineering, October Issue, 80.

Choi, W.-I., Park, J.-Y., Lee, J.-P., Oh, Y.-K., Park, Y. C., Kim, J. S., Park, J. M., Kim,

C.H, and Lee, J.-S. (2013). Optimization of NaOH-catalyzed steam pretreatment

of empty fruit bunch. Biotechnology for Biofuels, 6(1), 170-178.

Choo, Y. M. (2016). Overview o f the Malaysian Oil Palm Industry 2015. Economics

& Industry Development Division, Malaysian Palm Oil Board, Kuala Lumpur.

Dyment, J., Reimers, C., and Beck, R. (2013). Overview o f Solids Modeling for

Chemical Processes, Aspen Technology, Inc, Bedford.

Edwards, D. (2015). Scaling Up Bioenery Technologies, American Institute of

Chemical Engineers (AIChE) CEP, March Issue, 58.

Green, D. W. and Perry, R. H. (2008). Perry's Chemical Engineer's Handbook (8th

ed.). New York: The McGraw-Hill Companies, Inc.

67

Hamid, H. (2015). Combination o f Low Pressure Steam Heating and Dilute Acid

Pretreatment o f Palm Biomass For Fermentable Sugar Production. Master

Thesis, Universiti Teknologi Malaysia, Skudai.

Himmelblau, D. M., and Riggs, J. B. (2009). Basic Principles and Calculations in

Chemical Engineering (7th ed.). New York: Prentice Hall.

Humbird, D., Davis, R., Tao, L., Kinchin, C., Hsu, D., and Aden, A. (2011). Process

Design and Economics fo r Biochemical Conversion o f Lignocellulosic Biomass

to Ethanol. National Renewable Energy Laboratory, Colorado.

Jayawardhana, K., and Van Walsum, G. P. (2004). Modeling of carbonic acid

pretreatment process using ASPEN-Plus. Applied Biochemistry and

Biotechnology, 113-116, 1087-1102.

Jeon, H., Kang, K.-E., Jeong, J.-S., Gong, G., Choi, J.-W., Abimanyu, H., ... Choi, G -

W. (2014). Production of anhydrous ethanol using oil palm empty fruit bunch in

a pilot plant. Biomass and Bioenergy, 67, 99-107.

Jung, Y. H., Kim, I. J., Han, J. I., Choi, I. G., and Kim, K. H. (2011). Aqueous ammonia

pretreatment of oil palm empty fruit bunches for ethanol production. Bioresource

Technology, 102(20), 9806-9809.

Kidam, K. (2012) Process Safety Enhancement in Chemical Engineering Plant Design

by Exploiting Accident Knowledge. PhD Dissertation, Aalto University, Espoo.

Kim, S., Park, J. M., Seo, J. W., and Kim, C. H. (2012). Sequential acid-/alkali-

pretreatment of empty palm fruit bunch fiber. Bioresource Technology, 109, 229­

233.

Lopez-Arenas, T., Rathi, P., Ramirez-Jimenez, E., and Sales-Cruz, M. (2010). Acid

pretreatment of lignocellulosic biomass: Steady state and dynamic analysis.

Chemical Engineering Transactions, 21, 445-450.

Magnusson, H. (2011). Process Simulation in Aspen Plus o f an Integrated Ethanol and

CHP plant. Master Thesis, Universitet UMEA, UMEA.

Najafpour, G., Ideris, A., Salmanpour, S., and Norouzi, M. (2007). Acid Hydrolysis of

Pretreated Palm Oil Lignocellulosic Wastes. IJE Transaction B: Applications,

20(2), 147-156.

Pederson, M. (2010). Lignocellulose pretreatment for maximal enzymatic

degradation. PhD Thesis. Technical University of Denmark, Copenhagen.

68

Rao, S. R. (2005). Biomass to Ethanol: Process Simulation, Validation and Sensitivity

o f a Gasifier and a Bioreactor. Master Thesis, Oklahoma State University,

Stillwater.

Renewable Fuels Association. (2016). 2016 Ethanol Industry Outlook. Washington.

Sales-Cruz, M., Ramirez-Jimenez, E., and Lopez-Arenas, T. (2011). Design and

Operation of a Continuous Reactor for Acid Pretreatment of Lignocellulosic

Biomass, 1426-1430.

Schefflan, R. (2011). Teach Yourself the Basics o f Aspen Plus. New Jersey: John Wiley

& Sons. Inc.

Seider, W. D., Seader, J. D., Lewin, D. R., and Widagdo, S. (2009). Product and

Process Design Principles - Synthesis, Analysis and Evaluation (3rd ed.). New

Jersey: John Wiley & Sons. Inc.

Sinnott, R. K. (2005). Richardson & Coulson's Chemical Engineering Design (4th ed.)

Oxford: Elsevier Butterworth-Heinemann.

Turton, R., Bailie, R. C., Whiting, W. B., Shaewitz, J. A., and Bhattacharya, D. (2012).

Analysis Synthesis and Design o f Chemical Processes (4th ed.). Michigan:

Prentice Hall.

Wahab, A. G. (2015). Malaysia Biofuels 2015 Annual Report. Global Agricultural

Information Nework: USDA Foreign Agricultural Service, Kuala Lumpur.