henry insiong

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SIMULATION AND OPTIMIZATION OF PROPANE AUTOTHERMAL

REFORMER FOR FUEL CELL APPLICATIONS

HENRY INSIONG

UNIVERSITI TEKNOLOGI MALAYSIA


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UNIVERSITI TEKNOLOGI MALAYSIA

CATATAN: * Potong yang tidak berkenaan

* * Jika Tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/

organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu

dikelaskan sebagai SULIT atau TERHAD.! Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Sarjana secara

penyelidikan, atau disertai bagi pengajian secara kerja kursus dan penyelidikan atau

Laporan Projek Sarjana Muda (PSM).

BORANG PENGESAHAN STATUS TESIS!

JUDUL: SIMULATION AND OPTIMIZATION OF PROPANE

AUTOTHERMAL REFORMER FOR FUEL CELL APPLICATIONS

SESI PENGAJIAN: 2006/2007

Saya: HENRY INSIONG

(HURUF BESAR)

mengaku membenarkan tesis (PSM/Sarjana/Doktor Falsafah)* ini disimpan di Perpustakaan Universiti

Teknologi Malaysia dengan syarat-syarat kegunaan seperti berikut :

1. Tesis adalah hakmilik Universiti Teknologi Malaysia2. Perpustakaan Universiti Teknologi Malaysia dibenarkan membuat salinan untuk tujuan pengajiansahaja.

3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara institusipengajian tinggi.

4. **Sila tandakan ( )SULIT (Mengandungi maklumat yang berdarjah keselamatan atau

kepentingan Malaysia seperti yang termaktub di dalam AKTA

RAHSIA RASMI 1972)TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan

oleh organisasi/badan di mana penyelidikan dijalankan)

TIDAK TERHADDisahkan oleh

WW

P O___

(TANDATANGAN PENULIS) (TANDATANGAN PENYELIA)

Alamat Tetap: LOT 31 ph 3A, Engr Mohd. Kamaruddin bin Abd Hamid

Taman hiburan, Nama Penyelia

88300 Kota Kinabalu, Sabah

Tarikh : Tarikh :

PSZ 19:16 (Pind. 1/97


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I hereby declare that I have read this thesis and in

my opinion this report is sufficient in terms of scope and

quality for the award of the degree of Bachelor of Engineering

(Chemical).

Signature : .

Name : ENGR. MOHD. KAMARUDDIN BIN ABD HAMID

Date : 15 NOVEMBER 2006


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SIMULATION AND OPTIMIZATION OF PROPANE AUTOTHERMAL

REFORMER FOR FUEL CELL APPLICATIONS

HENRY INSIONG

A report submitted in partial fulfilment of the

requirement of the award of the degree of

Bachelor of Engineering (Chemical)

Faculty of Chemical and Natural Resources Engineering

Universiti Teknologi Malaysia

NOVEMBER, 2006


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I declare that this thesis entitled Simulation and Optimization of Propane Autothermal

Reformer for Fuel Cell Applications is the result of my own research except as cited in

the references. This thesis has not been accepted for any degree and is not concurrently

submitted in candidate of any other degree.

Signature : ..

Name : HENRY INSIONG

Date : 15 NOVEMBER 2006


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To my beloved father and mother


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ACKNOWLEDGEMENTS

I am deeply grateful to my thesis supervisor Engr. Mohd. Kamaruddin Bin Abd.

Hamid for his continuous guidance, support and enthusiasm throughout this work, and

being an inspiring teacher for me.

I would like to express my most sincere thanks to Prof. Madya Dr. Maketab

Mohamed for co-supervising my work and invaluable suggestion and advice.

I am also would like to thank to all my friends for their assistance in giving

opinion during the course of my study.

Finally, I would express my gratitude to my mother, father and to all my siblings

for their endless love and support.


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ABSTRAK

ATR merupakan salah satu kaedah yang terbaik untuk menghasilkan hidrogen daripada

hidrokarbon. Ceacir gas petroleum dimana propana dijadikan sebagai bahan utama

menjanjikan bahan mentah utama untuk menghasilkan system hidrogen untuk kenderaan

fuel celldan untuk kegunaan kuasa janafuel cellperalatan domestik. Dalam kajian ini,

reactor ATR mengunakan propana adalah dikaji dan operasi sistemnya dioptimumkan

mengunakan Aspen HYSYS 2004.1 untuk fuel cell aplikasi. Selain itu, integrasi haba

juga diterapkan dan diaplikasi selepas aliran keluar daripada reaktor ATR. Di samping

itu, WGS dan PrOx proses dijalankan untuk proses pembersihan bagi merendahkan

kepekatan CO. Proses pengoptimum dilakukan untuk setiap reaktor bagi menghasilkan

hidrogen yang paling tinggi dan pada masa yang sama kepekatan CO terendah. Butiran

yang lebih terperinci bagi suhu dan komposisi bahan turut dikaji pada setiap unit

operasi. Berdasarkan kepada keputusan akhir yang diperolehi daripada proses simulasi

didapati bahawa sebanyak 100 kgmol/j propana dengan nisbah kepada air dan udara

sebanyak 1 : 7 : 4.3 telah menghasilkan sebanyak 41.62% hidrogen dengan kepekatan

CO dibawah 10 ppm,dan kecekapan sistem penjana adalah 83.14%


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LIST OF CONTENTS

CHAPTER SUBJECT PAGE

TITLE PAGE i

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENTS ivABSTRACT v

ABSTRAK vi

LIST OF CONTENTS vii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF ABBREVIATIONS Xii

LIST OF APPENDICES xv

I INTRODUCTION 1

1.1 Background Research 1

1.2 Problem Statement and Importance of Study 3

1.3 Objective and Scopes of Study1.4 Thesis Organization

3

4

II LITERATURE REVIEW 6

2.1 Hydrogen Production for Fuel Cell Application. 6

2.1.1 Natural Gas 7

2.1.1.1 Methane 8


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2.1.1.2 Ethane 9

2.1.1.3 Propane 9

2.1.1.4 Butane 10

2.1.2 Alcohol 10

2.1.2.1 Methanol 10

2.1.2.2 Ethanol 11

2.1.2.3 Propanol 12

2.1.3 Naphtha 13

2.1.3.1 Gasoline 13

2.1.3.2 Diesel 13

2.1.3.3 Kerosene 14

2.2 Propane as Input for Hydrogen Production 14

2.2.1 Partial Oxidation and Oxidative Steam Reforming 15

2.2.2 Authothermal Reforming 16

2.2.3 Steam Reforming 17

2.2.4 Cracking Method 17

2.2.5 Indirect Partial Oxidation 18

2.3 Steam Reforming of Propane 18

2.4 Simulation of hydrogen Production for Fuel cell

Application using Propane.

2.5 Summary

20

21

III METHODOLOGY 22

3.1 Research Tools 22

3.1.1 Aspen HYSYS 2004.1 22

3.2 Research Activities 23

3.2.1 Data Collection 23

3.2.2 Steady State Model Development 23

3.2.3 Stoichiometry Mathematical Calculation 24

3.2.4 Validation of the Steady State Process 26


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3.2.5 Heat Integration between Processes

3.2.6 Clean up Model Development

3.2.6.1 Water Gas Shift Processes (WGS)

3.2.6.2 Preferential Oxidation Processes (PrOx)

3.2.7 Plan wide Optimization

3.2.8 Temperature and Components Profile

3.2.9 Fuel Processor Efficiency

3.3 Summary

26

27

27

28

28

29

29

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IV OPTIMIZATION AND SIMULATION OF HYDROGEN

PRODUCTION FROM PROPANE FOR FUEL CELL

APPLICATIONS32

4.1 Optimization and Simulation Of Hydrogen Production

from Propane 32

4.1.1 Physical Properties 33

4.1.2 Thermodynamic Properties 34

4.1.3 Integration Algorithm 37

4.1.4 Mathematical Modelling of the Reactor Operating 37

4.1.5 Degree of Freedom Analysis 39

4.1.6 Steady State Simulation 39

4.1.7 Optimization Model Simulation

4.1.8 Summary

40

40

V RESULTS AND DISCUSSIONS

5.1 Base Case of Simulation5.2 Validation of Base Case5.3 ATR Reactor Optimization5.4 Heat Integration5.5 Water Gas Shift (WGS)

5.51 Optimization of WGS

42

42

44

45

48

49

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VI

5.6 Preferential Oxidation (PrOx)

5.6.1 Optimization of PrOx Reactor

5.7 Components and Temperature Profile of the Fuel

Processor System

5.7.1 Components Profile

5.7.2 Temperature Profile

5.8 Fuel Processor Efficiency

5.9 Summary

CONCLUSIONS AND RECOMMENDATIONS

6.1 Introduction6.2 Summary of Results6.3 Conclusions6.4 Recommendations

6.4.1 Purification of Hydrogen

6.4.2 Water Management

52

53

55

56

58

59

60

61

61

62

63

63

63

64

REFERENCES

Appendices (A1-G1)

65

71-87


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LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Feed composition for the steam reforming

experiments 19

2.2

3.1

Stoichiometry for the full steam reforming reactionand the corresponding of "H#and thermal efficiency

Lower heating value

19

30

4.1

5.1

Physical property of the component

Result for base case

34

43

5.2

5.3

5.4

5.5

5.6

5.7

Comparison between molar flow rate calculated and

simulated

Comparison between before and after optimization at

the ATR process

Result after optimization of the WGS reactor

Result for every components at the PrOx reactor

Result of optimization at the PrOx reactor

Components profile for every reactor

45

47

51

53

55

56


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LIST OF FIGURES

FIGURE NO. TITLE PAGE

3.1

4.1

4.2

5.1

5.2

5.3

5.4

5.5

5.6

5.7

5.8

5.9

Algorithm for methodology

HYSYS simulation environment

Block diagram of the simulation of hydrogen plant usingAspen HYSYS 2004.1

PFD of the ATR reactor

Temperature of ATR out, molar flow of carbon monoxide

(CO) and hydrogen (H2) output from ATR versus molar

flow of air

PFD of heat integration process

PFD of water gas shift process

Temperature of HE_3 out , molar flow of carbon monoxide

(CO) and hydrogen (H2) output from WGS reactor versus

molar flow of water

PFD of the PrOx process with entire process

Molar flow of carbon monoxide (CO) and hydrogen (H2)

output from PrOx versus molar flow Air_PrOx

Components profile for hydrogen and carbon monoxide

Temperature profile for every units operation

31

33

41

44

46

48

49

50

52

54

57

58


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LIST OF ABBREVIATIONS

ATR - Autothermal reforming

AES - Aspentech Engineering Suite

CH4 - Methane

C2H6 - Ethane

C3H8 - PropaneC4H10 - Butane

CHP - Combined Heat and Power

CO - Carbon monoxide

CO2 - Carbon dioxide

CPO - Catalytic partial oxidation

CH3OH - Methanol

CMR - Compact methanol reformer

CFBMRR - Circulating Fluidized Bed Membrane Reformer-Regenerator

ESEM-EDAX - Environmental scanning electron microscopy-energy disperse

X-ray analysis

GC - Gas-chromatographs

H2 - Hydrogen

H2O - Water

HSA - Highs surface area

IIR-MCFCs - Indirect internal reformer molten carbonate fuel cells

IPOX - Indirect partial oxidation

LPG - Liquefied petroleum gas

MCFC - Molten carbonate fuel cell

MR - Membrane reactor


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MSR - Methane steam reforming

OSR - Oxidative Steam Reforming

PAFC - Phosphoric acid fuel cell

PEMFC - Proton exchange membrane fuel cell

POX - Partial oxidation

SE-SMR - Sorption-enhanced steam methane reforming

SOFC - Solid oxide fuel cell

SPFC - Solid polymer fuel cell

SR - Steam reforming

TRs - Traditional reactors

$ - Thermal efficiency

% - Activity coefficient

WGS - Water Gas Shift

PrOx - Preferential Oxidation

PFD - Process Flow Diagram


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LIST OF APPENDICES

APPENDIX TITLE PAGE

A1 Result of ATR reactor for base case and before

optimization 71

A2 Result of ATR reactor after the optimization 72

B Result of heat integration process 73

C1 Result of WGS reactor before the optimization 75

C2 Result of WGS reactor after the optimization 78

D1 Result of PrOx reactor before the optimization 81

D2 Result of PrOx reactor after the optimization 83

E1 Calculation of concentration of carbon monoxide 86

F1 Calculation of fuel processor efficiency 86

G1 Component profile for all components 87


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CHAPTER "

INTRODUCTION

1.0 Background Research

Hydrogen is the most abundant element in the universe. Chemically bound

hydrogen is present all over the earth; as part of the Earths water mass (including fossil

substances) (Haussinger et al., 2003). Hydrogen (H2) is a colourless, odourless,

tasteless, flammable and non-toxic gas at atmospheric temperature and pressure. The

gas burns in air with a pale blue, almost invisible flame. Hydrogen is the lightest of all

gasses, approximately one fifteenth as heavy as air. Hydrogen ignites easily and forms

an explosive gas together with oxygen or air.

Hydrogen is used in diverse industries such as a chemical, petrochemical and

petroleum refining, metallurgy, glass and ceramics manufacture, electronic and food

processing. Hydrogen is used in large quantities as a raw material in the chemical

synthesis of ammonia, methanol, hydrogen peroxide, polymers and solvents. It is used

in refineries for desulphurization and hydrotreating. It is used in metallurgical industries

to provide a reducing atmosphere and in the annealing of steel. The electronic industry

uses hydrogen in the manufacture of semiconductor devices. In the food industry,

hydrogen is used for hydrogenation of fats and oils. Hydrogen also finds specialty

application as a rocket fuel duel to its high combustion energy release per unit of

weight.(Newson and Truong, 2001).


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Recently, there has been a tremendous interest in the development of hydrogen

economy based on hydrogen as the energy carrier. Excitement in this field stems from

the fact that hydrogen is a potentially non-polluting, inexhaustible and efficient source of

energy. Hydrogen can be used in a fuel cell to produce electricity and heat or even be

combusted with oxygen to produce energy and the only by product is water (Chris,

2001).

A fuel cell by definition is an electrical cell, which unlike storage cells can be

continuously fed with a fuel so that the electrical power output is sustained indefinitely

(Reed, 1995). They convert hydrogen or hydrogen-containing fuels, directly into

electrical energy plus heat through the electrochemical reaction of hydrogen and oxygen

into water. The process is that of electrolysis in reverse.

Overall reaction:

2H2(gas) + O2(gas) &2H2O+ energy (1.1)

Because hydrogen and oxygen gases are electrochemically converted into water,

fuel cells have many advantages over heat engines. These include high efficiency,

virtually silent operation and, if hydrogen is the fuel, there are no pollutant emissions. If

the hydrogen is produced from renewable energy sources, then the electrical power

produced can be truly sustainable. The two principle reactions in the burning of any

hydrocarbon fuel are the formation of water and carbon dioxide (Espinal et al., 2005).

As the hydrogen content in a fuel increases, the formation of water becomes more

significant, resulting in proportionally lower emissions of carbon dioxide. As fuel use

has developed through time, the percentage of hydrogen content in the fuels has

increased. It seems a natural progression that the fuel of the future will be 100 %

hydrogen.


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Fuel cells are classified according to the electrolyte use. There are the alkaline

fuel cell used in space vehicle power systems, the phosphoric acid fuel cell (PAFC)

used in both road transportation and stationary engines, the solid polymer fuel cell

(SPFC) also used in both road transportation and stationary engines, the molten

carbonate fuel cell (MCFC) used in stationary engines and the solid oxide fuel cell

(SOFC) used only in stationary engines (Chen and Elnashaie, 2004)

In general, fuel cells can be used for a wide variety of applications, the most

important of which are as a power source for vehicles, as a stationary power source (for

example for large-scale power plants generation, power generation in the home or small

power plants for larger industrial or residential sites) and as a power sources for portable

devices (for example laptops, cameras, mobile phones, for replacement of batteries etc.).

Natural gas and propane are attractive for stationary applications since they are low-cost

fuels and the infrastructure for their transportation already exists (Wang et al., 2005).

1.1 Problem Statement and Importance of Study

This research aims to develop an optimized model of hydrogen production plant

using propane for fuel cell application by autothermal reforming. In order to analyze its

performance, well-defined steady state model that will represent the real plant for

hydrogen production is required. In order to do that, Aspen HYSYS 2004.1 is utilized.

The important to have this optimized model is to analyze design parameter for fuel

processor, and also to get preliminary fuel processor efficiency.


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1.2 Objective and Scopes of Study

Objective of this study is to develop an optimized model of hydrogen production

plant using propane for fuel cell applications by autothermal reforming. In order toachieve that objective, the following scopes have been drawn:

i). Steady-state Model for Base Case

Steady-state model of hydrogen plant from propane was carried out bystoichiometry mathematical analysis calculation and the simulation using

Aspen HYSYS 2004.1.

ii). Steady-state Model Validation for Base Case

Steady-state model developed within Aspen HYSYS 2004.1 processsimulator was validated using data from stoichiometry mathematical

analysis calculation

ii). Process Heat Integration Model Development Heat integration model was applied for this simulation using Aspen

HYSYS 2004.1.

iii). Clean Up Model Development Clean up model was applied to reduce the concentration of carbon

monoxide at the reformer.

iv). Plant Wide Optimization

Every reactor had been optimized to achieve the highest hydrogen and thelowest carbon monoxide.

v). Temperature and Components Profile Analysis

To get the overall overview of the process of the reformer.


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1.3 Thesis Organization

The realization of the objective of this thesis involves the culmination of a

number of tasks. The first task, introduced in chapter two is to do the literature surveyabout the synthesis of hydrogen for fuel cell applications. In this chapter, an internal

research of hydrogen production using propane by autothermal reforming was been

concentrated. This chapter is the most important chapter because we developed the

method of hydrogen synthesis are based on the literature survey that we had done.

Chapter three is methodology for this thesis whereby the arrangements for the

methods are based on the scopes. Basically, there are five methods that we carried out.

Then, chapter four is optimization simulation of hydrogen production plant from

propane for fuel cell application. In this chapter we developed the simulation using

Aspen HYSYS 2004.1.

Chapter five is the results and discussion whereby the results are based on the

methodology that is developed from chapter four. Then, chapter six presents the

conclusions and recommendations.


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CHAPTER ""

LITERATURE REVIEW

2.1 Hydrogen Production for Fuel Cell Applications.

In the past 1930s, Lawaczek claimed the hydrogen was an innovative and

cheaper method to send energy through pipelines (Cavallaro et al., 2006). The use of

hydrogen as a fuel is expecting to have advantages with respect to fuel-cell technology

in terms of a sustainable material and energy supply compare to conventional

approaches.

Hohlein et al. (2000) claimed that if hydrogen could produce on a non-fossil

basis, this would offer an option for overcoming the greenhouse effect. Apart from

niche market solutions, however, the energy market, in general will require other energy

carriers for the next 20 to 30 years. For example, natural gas (consist of methane,

ethane, propane and butane) as the primary energy carrier for stationary applications,

alcohol (such as methanol, ethanol and propanol), or higher hydrocarbon such as

naphtha (kerosene or fuel jet, gasoline and diesel) to be used as a raw material for

hydrogen production in applications of fuel cell.


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2.1.1 Natural Gas

Natural gas is made up chiefly of the paraffin (alkenes CnH2n + 2) compound

methane (CH4). It may also contain ethane (C2H6), propane (C3H8), butane (C4H10) andothers. Unlike other fossil fuels, natural gas contains no sulphur and non-reacting

ash/dust and is an ideal fuel. Natural gas is a mixture without fixed composition.

Ersoz et al. (2006) studied that natural gas (methane, ethane, propane and butane)

was the most famous and the best fuel for hydrogen rich gas production due its

composition from lower molecular weight. They found that the highest fuel processing

efficiency was achieved with natural gas steam reforming at about 98 %.

Natural gas is used as a fuel for simulation of fuel cell for power production in

small on-site power/cogeneration plants. The methodology contemplates

thermodynamic and electrochemical aspects related to molten carbonate and solid oxide

fuel cells (MCFC and SOFC, respectively). The simulation of hydrogen production

from natural gas reforming thermodynamic was maximum at 700C, for a steam/carbon

ratio equal to 3 (Matelli et al., 2005).

Natural gas is used as an input for hydrogen production for driving proton

exchange membrane fuel cell in residential small-scale combined heat and power

(CHP) by series of computer simulation. The process using indirect partial oxidation

because of the advantage water injection and energy integration are critical issues in

adjusting product yield in temperature control and beside that, natural gas had the lowest

greenhouse effect in term of carbon dioxide emission (Avci et al., 2002).


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2.1.1.1 Methane

Wang et al. (2005) explored the fundamental analysis of the sorption-enhanced

steam methane reforming (SE-SMR) process in which the simultaneous removal ofcarbon dioxide by hydrotalcite-based chemisorbent. Two sections reactor model were

developed to describe the SE-SMR reactor; an equilibrium conversion section and an

adsorption reforming section.

Fernandez et al. (2005) studied about the kinetic of CO2 sorption on solid

adsorbent in an oscillating microbalance. The hydrogen production by sorption

enhanced reaction process has been simulated by a dynamic one-dimensional pseudo-

homogenous model of a fixed-bed reactor, where a hydrotalcite-derived Ni catalyst has

been used as steam reforming catalysts. They found that the process was capable of

directly producing concentrations of H2larger than 95 mol % with methane as the main

side product with less than 0.2 mol % of CO.

Methane is used for optimization of hydrogen production for fuel cell. In the

optimization of a micro-reformer for fuel cell unit are based on catalytic partial

oxidation using a systematic numerical study of chemical composition and inflow

condition (Chaniotis et al., 2005).

Hoang et al. (2004) presented a mathematical modelling of catalytic

authothermal reforming (ATR) using methane as input for hydrogen production. They

found that under optimal condition for high CH4conversion and high H2yield were at

A/F of 3.5, W/F of 1 and space velocity of the 20000/h. Under this condition, CH4

conversion of 98 % and H2yield of 42 % on dry basis can be achieved and 1 mol of CH 4

can produce 1.9 mol H2an equilibrium reformer temperature of around 1000K.


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Methane (CH4) reforming at low temperature has been researched to produce

hydrogen for fuel cell by thermodynamically and experimentally. Result indicated that

CH4conversion increased significantly with increased O2: CH4or H2O : CH4ratio and

the hydrogen content in dry tail gas increased with the H2O : CH4ratio (Liu et al., 2002).

The designed of adiabatic fixed-bed reactors for the catalytic partial oxidation

(CPO) using methane to synthesis gas at condition are suitable for the production of

methanol and hydrogen production for fuel cells (Smet et al.,2001).

2.1.1.2 Ethane

Production of pure hydrogen and more valuable hydrocarbons from ethane on a

novel highly active catalyst system with a Pd-based membrane reactor is optimum at the

mild reaction temperatures of 773858K and a wide SV range of ethane (Wang et al.,

2003).

Shebaro et al. (1997) studied of dissociative chemisorptions of methane and

ethane on nickel under UHV conditions or in static gas systems (at 500C and 1 Torr).

They found that flowing ethane, typically at 80 Torr, 1000C, and 10 ms contact time,

through a supersonic nozzle made of nickel or molybdenum converts roughly 40 % to

higher hydrocarbons.

2.1.1.3 Propane

Deshmukh et al. (2005) investigated the operation of a multifunctional

microdevice with coupled propane/air gaseous combustion and ammonia decomposition

on Ru for hydrogen production used 2D CFD simulations.


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The conversion at temperature around 500C and atmospheric pressure, of

propane and n-butane on a ZSM-5 catalyst loaded with Pt or Pd and Re, presulfided or

not by hydrogen sulphide was not possible to restore the initial activity by regenerating

the catalyst in air at 550C (Dehertog et al., 1999).

2.1.1.4Butane

Avc et al. (2004) studied steam reforming of n-butane over Ni/'-Al2O3and Pt-

Ni/'-Al2O3 catalysts at temperatures between 578 and 678 K. The major difference

between the two catalysts were found to be at 648 K, at which Pt-Ni/'-Al2O3 showed

superior performance in terms of selective hydrogen production that resulted in lower

carbon dioxide and methane formation.

2.1.2 Alcohol

Alcohol (methanol, ethanol and propanol) as a source of hydrogen production for

fuel cell powered application was now seriously considered (Sun et al., 2005).

2.1.2.1 Methanol

Basile et al. (2005) studied on experimental point of view the oxidative steam

reforming of methanol by investigating the behaviours of a dense Pd/Ag membrane

reactor (MR) in terms of methanol conversion as well as hydrogen production. Two

main operating parameters have been analyzed, the reaction temperature in the range

200260C and the O2/CH3OH feed ratio in the range 00.25. They found that the MR

gives methanol conversions higher than traditional reactors (TRs) at each temperature

investigated, confirming the good potential of the membrane reactor device for this

interesting reaction system.


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Production hydrogen (H2) from methanol by steam reforming, partial oxidation,

or a combination over Cu/ZnO-based catalysts was influenced on the feed of

composition, reaction temperature, and catalyst formulation on H2 production rate,

product distribution, and catalyst lifetime (Agrell et al., 2003).

Wiese et al. (1999) developed a compact methanol reformer (CMR) with specific

weight 2 kg/kW (lower heating value of H2). CMR contained methanol and water

vaporized, a steam reformer, a heat carrier circuit and catalytic burner units.

2.1.2.2Ethanol

Sun et al. (2005) studied those catalysts Ni/La2O3 and Ni/Y2O3 at low

temperature (250C-350C) possess high activity and good stability for steam reforming

of ethanol to hydrogen production.

Ethanol is used as a raw material for the simulation of a fixed bed reactor to form

hydrogen for PEM fuel cell. A commercial Cu/Zn/Ba/Al2O3catalyst is employed and a

one-dimensional heterogeneous model was applied for the simulation (Guinta et al.,

2005).

Mattos and Noronha, (2005) researched the effected of the reaction condition and

catalysts reducibility on the performance of the Pt/CeO2 catalyst in the partial oxidation

of ethanol. They found that the low dispersion and low oxygen transfer capacity led to a

decrease in both the activity and stability of Pt/CeO2 catalysts on partial oxidation of

ethanol.

Cavallaro et al. (2003) studied on optimized a bio-ethanol auto-thermal

reforming (ATR) process over 5 % Rh/Al2O3catalyst homemade, to produce syn-gas for

fuel cell applications. Cavallaro et al. had identified an optimum range where the


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2.1.3 Naphtha

Gasoline, diesel and kerosene (jet fuel) are called primary fuel and consist of

numerous components. Naphtha can also be one of the common inputs for hydrogenproduction for fuel cell.

2.1.3.1Gasoline

Minutillo, (2005) researched the potential of a reforming system, as a means of

producing hydrogen for dual fuel engine fuelling. Minutillo had developed a numerical

model of a compact and simple fuel processor unit, based on a partial oxidation process.

Otsuka et al. (2002) proposed and investigated a new technology using as a fuel

for solid polymer electrolyte fuel cell through the decomposition of gasoline range

alkenes into hydrogen and carbon.

2.1.3.2Diesel

Cheekatamarla et al. (2005) had developed tested and characterized efficient

catalysts for hydrogen generation from diesel autothermal reforming.

The exhaust gas fuel reforming process in diesel engines is used as a way to

assist the premixed charges compression ignition operation by substituting part of the

main fuel with hydrogen-rich gas (Tsolakis et al., 2005).

Tsolakis et al. (2004) had investigated the effects of water addition on the

reformer product gas and the efficiency of the diesel exhaust gas assisted fuel reforming

process.


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Liu et al. (2004) described and investigated reactor characteristics and catalytic

efficiency of a kilowatt-scale catalytic autothermal reformer from heavy hydrocarbon

fuels, such as diesel fuel, for fuel cell or emissions reduction applications.

2.1.3.3Kerosene

Lenz et al. (2005) investigated the autothermal reforming of desulphurised

kerosene with a 15 kW (based on the lower heating value of Jet fuel) test rig.

Suzuki et al. (2000) investigated steam reforming from kerosene on Ru/Al2O3

catalyst to yield hydrogen.

2.2 Propane as an Input for Hydrogen Production.

Propane is a common gaseous fuel that can be stored in liquid form in pressure

vessels and is especially advantageous for distributed power application. Propane was

the best choice as a fuel for hydrogen production based on the following characteristic:

(Wang et al., 2005)

i.) Hydrogen gravimetric density (18.2 wt. %) of fuel,

ii.) Ease of hydrogen extraction from the fuel,

iii.) Cost and availability.

Generally, propane can be use as an input to produce hydrogen using autothermal

reforming (ATR), partial oxidation (POX), indirect partial oxidation (IPOX), steam

reforming (SR) and cracking method.


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2.2.1 Partial oxidation (POX) and Oxidative Steam Reforming (OSR)

The most routes for hydrogen production are partial oxidation of hydrocarbon.

An advantage of this process is that it can utilize all kind of hydrocarbon feed therebyeliminating the need of the pre-reactor. The reaction that occur in partial oxidation is,

CnHm+( 2

n

)O2 n CO + ( 2

m

)H2

C3H8+2

3O2 3 CO + 4H2, !H#298= (229 kJ/mol

Partial oxidation, like the common combustion process, can occur at high

temperature (typically 1200C to1500C) without catalyst. The partial oxidation can be

control by adjusting temperature, oxygen to carbon ratio and gas feed rate. Partial

oxidation does not make use of the heat produce by the fuel cells. Oxidative steam

reforming (OSR) is a combination of partial oxidation and steam reforming, where the

oxidation provides heat for the endothermic reforming reactions.

Aartun et al. (2005) studied Rh-impregnated alumina foams and metallic

microchannel reactor for production of hydrogen-rich syngas through short contact time

catalytic partial oxidation (POX) and oxidative steam reforming (OSR) of propane.

Aartun et al. found that The Rh/Al2O3 foam systems showed higher initial syngas

selectivity than the Rh-impregnated microchannel reactors, but deactivated rapidly upon

temperature cycling, especially when steam added as a reactant.

Partial oxidation and oxidative steam reforming of propane over 0.01 wt %

Rh/Al2O3 foam catalysts was found to have the highest selectivity to hydrogen (0.92)

relative to propane converted at almost complete propane conversion (0.9) and it was

obtained by oxidative steam reforming at 700C (Venvik et al., 2005).


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Partial oxidation (POX) and oxidative steam reforming (OSR) of propane over

Rh-impregnated alumina foams in the short contact time regime were performed over a

wide temperature (300-1000C) at close to atmospheric pressure. Furnace temperature

of 700C was optimal for the production of hydrogen for both reactions (POX and OSR)

in this system (Silberova et al., 2005).

Gjervan et al. (2004) used propane at one bar and in temperature range 500-

1000C as input for the partial oxidation (POX) and oxidative steam reforming (OSR) in

the microstructured reactor. A microstructured reactor has been fabricated from the high

temperature alloy Ferroalloy (72.6 % Fe, 22 % Cr and 4.8 % Al) and was oxidized at

high temperature to form a porous layer of )-Al2O3on the surface of the channel and

subsequently impregnated with Rh. Gjervan et al. found that the Rh/Al2O3/Fecralloy

reactor gave higher selectivity to hydrogen as compared to the reactor made of Rh.

2.2.2 Autothermal Reforming (ATR)

Autothermal reforming (ATR) is a process in which both steam and air are

introduce to be the fuel. Compared to steam reforming, less water needed for

autothermal reforming. In addition, the heat of steam reforming is provided by the

partial oxidation of fuel. Thus, no complex heat management needed, and system design

became a little simple.

Laosiripojana et al. (2005) studied steam and autothermal reforming reaction of

LPG (propane/butane) over highs surface area Ce2O (Ce2O2 (HAS)) under solid oxide

fuel (SOFC) operating condition. The major consideration in the autothermal reforming

operation is the inlet O2/LPG molar ratio, as the presence of too high an oxygen

concentration could oxidize hydrogen and carbon monoxide, produced from the steam

reforming, to steam and carbon dioxide. A suitable O/C molar ratio for autothermal

reforming on CeO2(HAS) been observed to be 0.6.


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2.2.3 Steam Reforming (SR)

Steam reforming is a complex process, which consist of several different

reactions. But the basic reaction that occur in steam reforming is,

nC

mH + nCOOnH !

2+

2

2H

mn !

"

#$%

&+

C3H8+ 3 H2O 3 CO + 7 H2 "H = +497 kJ/mol

In this process, hydrocarbons are catalytically converted by reaction with steam into

hydrogen and carbon monoxide.

Carlo Resini et al. (2006) investigated the conversion of the C3 propane,

propene, isopropanol and acetone in auto-thermal and endothermic steam reforming

conditions over a PdCu/Al2O3catalyst in a flow reactor.

2.2.4 Cracking Method

The generation of a PEMFC hydrogen fuel gas by catalytic cracking in

temperature above 800C at atmosphere is using propane as raw material. Catalytic

cracking of propane can be described by the following main reaction (Hey et al., 2000)

C3H8 3 C + 4 H2 "R H = 103.8 kJ/mol.


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2.2.5 Indirect Partial Oxidation (IPOX)

Caglayan et al. (2005) studied indirect partial oxidation (IPOX) of propane over

bimetallic 0.2 wt %, Pt-15wt %, Ni/'-Al2O3catalyst in the 623-743K temperature range.ESEM-EDAX and X-Ray (XRD) characterized the unreduced and reduced form of the

catalyst. Caglayan et al. found the optimal conditions as S/C = 3, C/O2= 2.70 and W/F

= 0.51 gcat h/mol HC for IPOX of propane on the basis of high hydrogen productivity

and selectivity between 623 and 748 K. The thermo-neutral points obtained showed the

sustainability of reaction in terms of energy.

2.3 Steam Reforming of Propane

Resini et al., (2006) have been investigated the conversion of the C3 organics

propane, propene, isopropanol and acetone in auto-thermal and endothermic steam

reforming conditions over a PdCu/Al2O3catalyst in a flow reactor.

In this study they focused on the production of hydrogen from propane, propene,

isopropanol and acetone, i.e. four C3 organics, over an alumina supported PdCu-based

catalyst. The highly loaded noble metal catalyst also been considered as a model for

catalytic anodes for direct organic fuel cell, as well as catalysts for hydrogen production.

The catalytic experiments were carried out in a fixed bed tubular quartz reactor

containing 150 mg of fresh catalyst mixed with 350 mg of quartz particles; the whole

catalytic run lasts ca. 9 h, the time for each temperature is 45 min. Product analysis was

performed with two on-line gas-chromatographs (GC) in order to detect both carbon

species and H2.


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The catalytic tests were performed in two different feeding conditions, as

summarized in Table 2.1.

Table 2.1: Feed composition for the steam reforming experiments

Auto-thermal

(H2O/C-reactant/O2)

feed rate ml/min

Endothermic

(H2O/C-reactant) feed rate

ml/min

C3H8 4.68 / 1 / 0.77

150

6 / 1

200

Then, endothermic steam reforming, was carried out by feeding stoichiometric water-

to-organic ratios sufficient to obtain the complete steam-reforming reactions as

reported in Table 2.2

Table 2.2 : Stoichiometry for the full steam reforming reaction and the

corresponding of "H#and thermal efficiency.

#H$(kJ/mol) %(thermal efficiency)

C3H8+ 6 H2O &3 CO2+ 10 H2 3.75 *102 1.18

The results of the steam reforming of propane over an alumina supported PdCu-

based catalyst show that, reaction of propane in the presence of O2 started well above

800K whereas the reaction in presence of water and without O2starts above 900 K. The

reactions that involve in this process are;

Dehydrogenation of propane : C3H8&C3H6+ H2.

Steam reforming of propane : C3H8+ 3 H2O &3 CO + 7 H2

Water gas shift reaction : CO + H2O &CO2+ H2


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2.4 Simulation of Hydrogen Production for Fuel Cell Applications using

Propane.

Based on the literature reviews, there is one researcher done the simulation ofhydrogen production plant using propane autothermal reforming as for fuel cell

applications.

Zhixiang et al.,(2006) have investigated operation conditions optimization of

hydrogen production by propane autothermal reforming for PEMFC application. In

their researched, operation condition of the propane autothermal reforming process

suitable for PEMFC application are optimized by means of simulation with PRO/II. The

system regarded included the reformer, water gas shift (WGS), preferential oxidation

(PrOx) and heat exchangers. Important aspects for the system efficiency optimization

are the temperatures of the ATR reformer, LTS reactor and PROX reactor, the carbon

conversion and CO concentration. The simulation results are drawn in contour plots by

varying the steam to carbon ratio and ATR feed temperature.

In such a way operation regions unsuitable for the system operation could be

figured out, like too high temperature regions for ATR, LTS and PROX operation and

carbon forming region, the optimum operation region with the highest efficiency can be

identified. One point was chosen with the following operation conditions: feed

temperature for the ATR reactor is 425C, steam to carbon ratio S/C is 2.08, and air

stoichiometry is 0.256. System efficiency calculated could be as high as 84.2% with

38.27% H2 and 3.2+l.L-1

CO in the product gas.


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2.5 Summary

There have numerous articles on hydrogen production for fuel cell application.

Fundamentally there are three major groups that can synthesis hydrogen for fuel cellswhich are natural gas, alcohol and naphtha. Furthermore, there are many processes that

produce hydrogen such as steam reforming, autothermal reforming, partial oxidation

reforming, etc. The main purpose of this literature survey is to review about propane as

an input for hydrogen production by autothermal reforming. There are a few researchers

have done their researches about propane and for each of that articles had already

studied well and applied for this thesis.


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CHAPTER """

METHODOLOGY

3.1 Research Tools

This research was carried out using Aspen HYSYS 2004.1 for process

flowsheeting to provide data regional analyses. Aspen HYSYS 2004.1 simulator was

also used to perform the new process model control structure for hydrogen production

using propane as a raw material for fuel cell applications.

3.1.1 Aspen HYSYS 2004.1

HYSYS was a product of AEA Technology, which is now part of Aspentech

Engineering Suite (AES). HYSYS was chosen as the process simulator for this research

because of two main advantages over the other software packages. It can interactively

interpret commands as they entered one at a time. Other requires execution after new

entries. HYSYS has the unique feature that information propagates both in forward and

reverse directions, performing back-calculation in a non-sequential manner. The bi-

directionality often makes iterative calculations unnecessary and the solution is fast.


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3.2 Research Activities

3.2.1 Data Collection

Data collection is the most important step in development of high fidelity

models. The variation in the input/output data and the regions of operation are important

factors in determining if the data is a good representation of process behaviour over a

wide range of condition. At this stage, general understanding of the process has to be

obtained whereby, both theoretical analysis and experience of the operators help identify

the variables, variable relationships, approximately correlations and optimization of the

process. For this step, all the data especially for the reaction that involved for propane to

produce hydrogen have been referred and investigated.

3.2.2 Steady State Model Development

HYSYS have produced an extremely powerful approach to steady state

modelling. At a fundamental level, the comprehensive selection of operation and

property method can allow us to model a wide range of processes for the future. Steady

state models can perform steady state energy and material balances and evaluate

different plant scenarios. The design engineer can use steady state simulation to

optimize the process by reducing capital and equipment costs while maximizing

production. For this research we developed a new steady state process for hydrogen

production using propane as a raw material.


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3.2.3 Stoichiometry Mathematical Calculation.

Model for base case is the combination of all the reaction that involved to the

hydrogen production from propane. From the literature survey, hydrogen can beproduced through total oxidation, partial oxidation, steam reforming, dry reforming, and

etc. Then, based on those processes there were nineteenths reactions that take place.

The reactions are:

a.) Oxidation of Propane

i. OHCOOHC22283

435 +!+ (3.1)

ii.2283

432

3HCOOHC +!+ (3.2)

iii. OHHCOHC263283

2

1+!+ (3.3)

b.) Steam and dry reforming of Propane

i. 2283 733 HCOOHHC +!+ (3.4)ii.

242283 3HCOHCOHHC ++!+ (3.5)

iii.2283

463 HCOCOHC +!+ (3.6)

c.) Cracking of Propane

i.26383

HHCHC +! (3.7)

ii. CCHHC +! 483 2 (3.8)iii.

283 43 HCHC +! (3.9)

iv.44283

CHHCHC +! (3.10)


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d.) Steam reforming of Propylene

i.22263

9036 HCOHHC +!+ (3.11)

ii.2263

633 HCOOHHC +!+ (3.12)

e.) Cracking of Ethylene

i.242

22 HCHC +! (3.13)

f.) Oxidation of Ethylene

i. OHCOOHC2242

222 +!+ (3.14)

g.) Oxidation of Methane

i. OHCOOCH2224

22 +!+ (3.15)

ii.2224

22

1HCOOCH +!+ (3.16)

iii. 2224 2HCOOCH +!+ (3.17)

h.) Oxidation of Carbon

i.22

666 COOC !+ (3.18)

i.) Steam reforming of Carbon

i.22

2222 HCOOHC +!+ (3.19)

Then, after that we proceed with the combination for all the reactions to the master

reaction which mean that the reactant minus reactant and product minus product. Thus,


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for the final or master reaction for the process of hydrogen production after the

combination of all reactions:

222283 4819118

2

3310 HCOCOOHOHC ++!++

(3.20)

Based on the master reaction (3.20), we can identify the feed and the most importantly is

we can justify ratio for every feeds and for the base case and for this research, a basis of

100 kgmole/hr of propane will be set as a reference.

For the simulation using HYSYS simulator, all the conversion of the reaction

were set to100 percent and for this base case reactor of conversion is used.

3.2.4 Validation of the Steady State Process.

The key to develop of useful simulation model based on the first standard model

is the validation with the steady state base case. This validation can be done bysimulate the input data from the base case (calculated) and then, compared the output

result for each components. Then, errors for every component were calculated:

(Richard and Ronald, 2000)

simulationncalculatioerror != (3.21)

3.2.5 Heat Integration between Processes.

Integration between processes can reduce energy usage and emissions. The goal

of heat integration between processes is to make the plants more economical and


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profitable. If more heat flow can be recovered, their energy consumption can be

lowered. The heat transfer between the processes can reduce energy usage.

3.2.6 Clean up Model Development

One aspect, which is common to all method of hydrogen production, is that

substantial of carbon monoxide formation as a by-product. PEM fuel cells required a

hydrogen stream which contains less than 10 ppm of carbon monoxide. Therefore,

additional processes involving Water Gas Shift (WGS) reactor and a Preferential

Oxidation (PrOx) reactor are required when the conventional methods of hydrogen

generation are required.

3.2.6.1Water Gas Shift Processes (WGS)

In the WGS process there are three reactors involved which are High

Temperature Shift (HTS), Medium Temperature Shift (MTS) and Low Temperature

Shift (LTS). The reactor used was equilibrium reactor.

The hydrogen-rich syngas goes through a series of reactor to perform the water

gas shift reaction (HTS, MTS and LTS) in which carbon monoxide was converted to

meet the specification. The reactions that involved in each process of the reactor are;

222 HCOOHCO +!+ (3.22)

Based on the water gas shift reaction, carbon monoxide will react with water to convert

it to carbon dioxide and hydrogen. So based on the reaction of WGS we can know that


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besides it will reduce the amount of carbon monoxide, it also will increase the hydrogen

production.

3.2.6.2Preferential Oxidation Processes (PrOx)

PrOx is one of the most effective method to trace CO clean up from the

reformate steam prior to its introduction to fuel cell. The reactor that used for this

process was conversion reactor.

Air was injected to the PrOx reactor, and then carbon monoxide was oxidized to

carbon dioxide, while simultaneously, hydrogen was oxidized to water. Both reactions

in the PrOx are exothermic reaction. The equations that take place in PrOx process are:

22

2

1COOCO !+ (3.23)

OHOH222

2

1!+ (3.24)

Based on that reaction, we will need more or excess air feed to the reactor because the

processes need oxygen supply.

3.2.7 Plan wide Optimization

The main objective for this simulation is to generate the highest hydrogen and

the lowest of carbon monoxide. Therefore, in order to accomplish the objective,

optimization must be done for each reactor. For the ATR reactor, there were two case

studied had been done which are case study one related to the temperature out from ATR


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reactor and the second case study was about the best or the optimum feed for the air to

the ATR reactor.

Case study is a built-in interface within the Aspen HYSYS 2004.1 environmentfor steady-state process optimization. Then, for the WGS reactor (HTS, MTS and LTS)

there were two case studies that had been optimized which are the case study one was

the temperature out from the third heat exchanger and for the second case study was

about the highest hydrogen with the lowest carbon monoxide produced. The last reactor

is PrOx reactor and it was the last stage of reduced the concentration of carbon

monoxide. It was necessary to optimize the input of the new injected of air to the PrOx

reactor. The concentration of carbon monoxide must be in part per million (ppm).

3.2.8 Temperature and Components Profile

Temperature and component profile was investigated for every unit operations to

find out how the process changed for each reactor and why it changed. Then, what the

possibilities happened to the temperature and the component before and after one unit

operation also were studied well.

3.2.9 Fuel Processor Efficiency

The system fuel processor efficiency can be calculated by :

(Lenz and Aicher, 2005)

CxHyOzCxHyOz

COCOHH

LHVn

LHVnLHVn += 22! (3.25)


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The lower heating values (LHV) of hydrogen and carbon monoxide are given in

Table 3.1:

Table 3.1 : Lower heating value

Components LHV(kJmol-1

)

Hydrogen 241.83

Carbon Monoxide 282.00

3.3 Summary

For overall overview, basically for this thesis methodology consists of a few

steps to accomplish. The steps are the stoichiometry mathematical analysis calculation,

base case development with HYSYS, validation, heat integration model, clean up model,

plant wide optimization, components and temperature analysis and fuel processor

efficiency. The summary of methodology is shown in Figure 3.1


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Figure 3.1 : Algorithm for methodology.

Base Case Development with HYSYS Validation

Input Output

Temperature and Components

Anal sis

Plant Wide Optimizations

Clean Up Model

Heat Integration

Stoichiometry Mathematical Analysis


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CHAPTER "V

OPTIMIZATION AND SIMULATION OF HYDROGEN PRODUCTION PLANT

FROM PROPANE FOR FUEL CELL APPLICATIONS

4.1 Optimization and Simulation of Hydrogen Production from Propane

The hydrogen production from propane was simulated using Aspen HYSYS

2004.1 software. Typically, the simulation process takes the following stages;

i. Preparation Stagea) Selecting the thermodynamic modelb) Define chemical components

ii. Building Stagea) Adding and define streamsb) Adding and define unit operationsc) Connecting streams to unit operationsd) Installing valves and controllers

iii. Executiona) Starting integration

HYSYS simulator is made up of four major parts to form a rigorous modelling

and simulation environment.

! A component library consisting of pure component physical properties.! Thermodynamic packages for transport and physical properties prediction.


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! Integrator for dynamic simulation and/or solver for steady-state simulation.! Mathematical modelling of unit operation.

This is demonstrated in Figure 4.1. For this study, each of above components is

described in below.

Figure 4.1: HYSYS simulation environment

4.1.1 Physical Properties

Feedstock to the process consists of propane (C3H8), oxygen and air. Propane

present as liquid at room temperature. The pure component properties of the feedstock

were listed in Table 4.1

Physical

PropertyLibrary

Unit

operationModel

Integrator

/ Solver

Thermo-

dynamicPackage

HYSYSSimulation

Environment


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Table 4.1 : Physical properties of the components.

Components Molecular

formula

MW

(kg/kmol)

Boiling

point,Tb

(oC)

Density,&

(kg/m3)

Viscosity,

'(cP)

Propane C3H8 44.09 -42.07 1.808 0.00848

Water H2O 18.00 100 0.998 1.0050

Hydrogen H2 2.016 -252.76 0.0813 0.0090

Oxygen O2 31.999 -182.97 1.292 0.0209

Nitrogen N2 28.014 -195.8 1.13 0.0179

Carbon dioxide CO2 44.010 -78 1.775 0.0149

Carbon monoxide CO 28.010 -191.5 1.13 0.0182

4.1.2 Thermodynamic Properties

In order to define the process, the thermodynamic property packages used to

model both steady state and optimization of propane must be specified. The feed for the

hydrogen production is considered relatively ideal mixture of propane, oxygen and air.Propane is the primarily characterized as a C3H8. In this approach, a model of Peng-

Robinson Equation of State (EOS) is used to model the thermodynamics of hydrogen

production for both steady state and optimization operations.

This equation has been used to predict phase behaviour for solutes with a wide

range of volatility. In this method, it is assumed that the solute in equilibrium with the

saturated solution is a solid, which contains a negligible amount of the supercritical fluidsubstance. The partial molar volume Vof solid solute in the system at all the considered

pressures and temperatures is equal to its molar volume at atmospheric pressure and

298K. The Peng-Robinson equation of state if given by


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( )

2

11

2

11

1 2 bVbV

Ta

bV

RTp

!+!

!

= (4.1)

whereRis the gas constant, Tis the absolute temperature, Vis the molar volume of the

pure solvent, ais a parameter describing attractive interactions between molecules, and

b is a parameter describing volume exclusion and repulsive interactions. Subscript 1

represents the solvent and 2represent the solute. Parameter aand bare determined from

the critical properties of the components according to;

( )( )[ ]21,

22

1145724.0

r

c

c Twfp

TRa !+= (4.2)

( ) 226992.054226.137464.0 wwwf !+= (4.3)

c

r

T

TT = (4.4)

c

c

p

RTb

07780.0= (4.5)

Where TcandPcare the critical temperature and critical pressure, respectively, and wis

the acentric factor. Thus the pure component parameters, aiand bi, can be calculated as:

( )( )[ ]21,1

1,

2

1,

2

11 11

45724.0r

c

cTwf

p

TRa !+= (4.6)

1,

1,

1

07780.0

c

c

p

RTb = (4.7)

2,

2,

2

07780.0

c

c

p

RTb = (4.8)


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4.1.3 Integration Algorithm

To solve the set of differential equations that are in the dynamic stage model,

integration is required. The integration procedure must be started with a set of initialcondition for each stable variable. There are three different varying step size integration

method available in HYSYS; Euler, Runge-Kutta-Merson and Richard- Laming-Torrey.

For modelling hydrogen production from propane an implicit Euler method is used. The

fixed step size implicit Euler method explains here is knows as the rectangular

integration. It can be described by extending a line slope zero and length h (the step

size) fromtnto tn+1on af(Y)versus time plot. The area under the curve is approximately

by a rectangle of length h and height fn+1(Yn+1) in a function of the following form

(HYSYS Documentation, 2004).

( )dtYfYYnI

I

nn !+

+=+

1

1, where; ( )Yf

dt

dY= (4.11)

To provide a balance between accuracy and speed, Aspen HYSYS employs a

unique integration strategy. The volume, energy and speed composition balances are

solved at different frequencies. Volume balances are defaulted to solve at every

integration step, whereas energy and composition balances are defaulted to solve at

every 2nd

and 10th

integration step, respectively. The integration time step can be

adjusted in Aspen HYSYS to increase the speed or stability of the system. The default

value of 0.5 second was selected.

4.1.4 Mathematical Modelling of the Reactor Operating

The mathematical model of the system in the reformer is being develop based on

two fundamental quantities, which is total mass balance and total energy balance. For N

number of component in the system;


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The overall material balance in the reformer:

!!==

"=outleto

oo

inleti

ii

nFF

dt

dM## (4.12)

With "is component density andFis component flow rate.

The overall energy balance in the reformer

!!==

"=outleto

oooo

inleti

iiii

nnTcFTcF

dt

Mhd##

)( (4.13)

With his the specific enthalpy, cis component heat capacity and Tis temperature.

Applying partial differential to the overall energy balance we got

!!==

"=+outleto

oooo

inleti

iiii

n

n

nTcFTcF

dt

dMh

dt

dhM ## (4.14)

Assume 0!dt

dhn (the change in specific enthalpy is too small)

!!==

"=outleto

oooo

inleti

iiii

n

n TcFTcF

dt

dMh ## (4.15)

Replace equation (4.12) to equation (4.15), the mathematical model is develop

!!!!====

"="outleto

oooo

inleti

iiiio

outleto

o

inleti

iin TcFTcFFFh #### )( (4.16)


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4.1.5 Degree of Freedom Analysis

There are two types of degree of freedom. The first one is dynamic degrees of

freedom,Nm(m denotes manipulated). Nmis usually easily obtained by process insightas the number of independent variables that can be manipulated by external means. In

general, this is the number of adjustable valves plus other adjustable electrical and

mechanical devices. The second is steady state degrees of freedom, Nss which is the

number of variables needed to be specified in order for a simulation to converge. To

obtain the number of steady state degrees of freedom we need to subtract from Nom

which is the number of manipulated variables with no steady state effect and Noywhich

is the number of variables that need to be controlled fromNm

As a result equation 4.6 is obtained

)( oyommss NNNN +!= (4.17)

In any process simulation work, it is essential that the degrees of freedom

analysis be carried out to determine the number of variables to be specified.

4.1.6 Steady State Simulation

Once the required equipment design parameters and thermodynamic-related

properties have been set, the simulation can proceed when the initial conditions of each

process stream is given. In running the simulation it is of great importance to ensure thatproper initial values be used for each stream as failure in doing so may lead to

convergence to different values, which is not desirable due to the non-linearity and

unstable characteristics of the process. Once the initial conditions have been specified,

iterative calculations are automatically performed until all the values in the calculated

streams match those in the assumed stream within some specified tolerances.


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4.1.7 Optimization Model Simulation

This is a guidelines or steps that may follows in order to create and run a

simulation case for optimization process. Firstly, we need to know what variables thatwe need to observe or investigate. Once we already know the variables, we you go to

the tools and proceed with the databook option. Next, we need to insert the variables

from the variable section and select insert. After we select the insert option, the variable

navigator will appear and we can insert ours variable. Then, after we already inserted

the variables, we go to case study option and we will note that all the variables that we

inserted just now appeared. We have to create or add case study and the tick the box of

the variable that we want to optimize. After that, go to the view, we will need to make

an assumption for the low and high bound and also for the step size. We just need to

click the start option to start the process and look the result by click the results option.

The graph will appear and we can optimize or consider the best condition based on the

graph to get the best result for the process.

Finally, after we get the optimize value for the process, we just need to change

the previous value to the optimize value.

4.2 Summary

Generally, this chapter is the development of the simulation using Aspen

HYSYS 2004.1 whereby all the data that collected from literature survey is used. For

the simulation of HYSYS, the equation of state that used is Peng-Robinson to calculate

the stream physical and transport properties. Mass and energy balances have established

for all cases. A brief summary about the simulation of hydrogen plant using Aspen

HYSYS 2004.1 is shown in Figure 4.2.


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CHAPTER V

RESULTS AND DISCUSSIONS

The results obtained for each phase of the research project is presented and discussed in

this chapter.

5.1 Base Case Simulation.

For this base case simulation, the ratio of propane to water and oxygen was 1:

0.8: 1.65. Then, for this process of hydrogen production, the basis for molar flow rate

for the input of propane was 100kgmole/hr. Table 5.1 show the result of the

stoichiometry mathematical calculation based on the nineteenth reactions (3.1-3.19)

involved.


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Table 5.1 : Result for base case

Calculated

Components Input (kgmole/h) Output (kgmole/h)

C3H8 100 -C3H6 - -

C2H4 - -

CH4 - -

C - -

CO2 - 110.0000

CO - 190.0000

O2 165.0000 -

N2 620.7100 620.7100

H2O 80.0000 -

H2 - 480.0000

From Table 5.1, we can see that the input for this production of hydrogen are 100

kgmole/hr of propane, 80 kgmole/hr water and 785.71 kgmole/hr of air, and produced

about 480 kgmole/hr of hydrogen, 110 kgmole/hr of carbon dioxide and 190 kgmole/hr

of carbon monoxide.

For the simulation using HYSYS, all the input data from the calculated method

were used. Figure 5.1 shows the drawing of PFD from the HYSYS simulator. From

Figure 5.1, base case simulation of hydrogen production plant using propane had

successfully developed using Aspen HYSYS 2004.1


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Figure 5.1: PFD of the ATR Reactor.

5.2 Validation of Base Case

Table 5.2 shows the result of the validation of the base case. This validation case

is only for the ATR reactor.


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Table 5.2 : Comparison between molar flow rate calculated and simulated.

Calculated Simulated

Components Input

(mole fraction)

Output

(mole fraction)

Input

(mole fraction)

Output

(mole fraction)

Error

C3H8 0.0722 - 0.0722 - -

C3H6 - - - - -

C2H4 - - - - -

CH4 - - - - -

C - - - 0.0108(liq) 1.00

CO2 - 0.0794 - 0.0908 0.01

CO - 0.1371 - 0.1144 0.02

O2 0.1191 - 0.1191 - -

N2 0.4481 0.4481 0.4481 0.4481 -

H2O 0.0577 - 0.0577 - -

H2 - 0.3466 - 0.3466 -

From the result tabulated in Table 5.2, it was shown that the errors between

calculation and simulation methods are very small. Therefore, the base case simulation

developed using Aspen HYSYS 2004.1 was valid and can be used as a real plant for

further analysis.

5.3 ATR Reactor Optimization

The purpose of optimization is to get or to achieve the highest value of hydrogen

that produced in the ATR reactor based on the optimum input of air to the reactor.

There are two categories that have been investigated in this optimization of the ATR.

First, the temperature out from ATR reactor must be 600-1000oC because at that range

of temperature, the hydrogen production yield is very high (Artun et al., 2004). Then,

we will consider the highest hydrogen and the lowest carbon monoxides produced in


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term of input of air only. Figure 5.2 shows the result of the optimization at the ATR

reactor.

Figure 5.2 : Temperature of ATR out, molar flow of carbon monoxide (CO) and

hydrogen (H2) output from ATR versus molar flow of air.


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From Figure 5.2, molar flow rate that can be considered for the input of the air to

the reactor was 650kgmole/hr and above because we need the temperature high since we

will require more heat supply for the next heat integration process. The optimum molar

flow rate of air that produced the highest hydrogen and the lowest CO flowrate and

temperature above 700oC was 700kgmole/hr.

The comparison between the result before and after optimization were

summarised in Table 5.3.

Table 5.3 : Comparison between before and after optimization at the ATR

process.

Before optimization After optimization

Components Input

(kgmole/h)

Output

(kgmole/h)

Input

(kgmole/h)

Output

(kgmole/h)

C3H8 100.0000 - 100.0000 -

C3H6 - - - -

C2H4 - - - -

CH4 - - - -

C - 15.8118 (liq) - -

CO2 - 125.8118 - 110.1957

H2O 80.0000 - 80.0000 -

O2 165.0000 - 147.0008 -

N2 620.7100 620.7100 552.9992 552.9992

CO - 158.3764 - 153.6102

H2 - 480.0000 - 480.0000

Temperature 100C 910.1C 100 C 810.8 C

From Table 5.3, there was a reduction of the carbon monoxide molar flow rate

from the 158.3764 kgmole/hr to 153.6102 kgmole/hr after the optimization of the air had


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been done. However, the production of hydrogen was still maintained because, we only

modified the air molar flow rate, molar flow rate of the water was not been changed or

optimized yet.

5.4 Heat Integration.

The inputs (air, water and propane) need to be heated up to 100oC before

entering to the reactor, because at that temperature the reactor will operate at its

optimum condition. For that heating process, we need to use heaters for each input

stream. Unfortunately, it consumed a lot of energy to supply heat especially for the

water. So, heat integration was implemented in order to solve the problem besides the

temperature from the ATR out was high enough to supply heat for heat integration.

From Figure 5.1, the highest energy consumed was water stream followed by air

and propane stream. Figure 5.3 shows the flowsheeting of the heat integration

processes. It was shown that, heat integration was successfully developed for hydrogen

plant using Aspen HYSYS 2004.1

Figure 5.3 : PFD of Heat Integration Process


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5.5 Water Gas Shift (WGS)

As we know the carbon monoxide must be reduced as lower as 10 ppm. The first

stage of reducing carbon monoxide is WGS process. Figure 5.4 shows flowsheeting ofATR with the water gas shift reactors:

Figure 5.4 : PFD of Water Gas Shift Process

5.5.1 Optimization of WGS

The optimization of water gas shift process was done by monitoring the

temperature out from the heat exchanger three (HE_3) and the highest hydrogen with the

lowest carbon monoxide produced. Figure 5.5 shows the result of optimization at the

water gas shift process:

From Figure 5.5, molar flow rate of the water that can be taken must be below

than 430 kgmole/hr because we must to get the temperature out over than 100oC before

it entering to the HTS reactor. Then, based on the Figure 5.5, the recommended option

is when the highest hydrogen with the lowest carbon monoxide produced. As a result

from both graph analysis, the optimum molar flow rate of water that can be feed to the


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reactor is 430 kgmole/hr. Table 5.4 shows the result of the simulation after the

optimization has been made:

Figure 5.5 : Temperature of HE_3 out , molar flow of carbon monoxide (CO) and

hydrogen (H2) output from WGS reactor versus molar flow of water


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Table 5.4 : Result after optimization of the WGS reactor.

Components ATR out

(kgmole/h)

HTS out

(kgmole/h)

MTS out

(kgmole/h)

LTS out

(kgmole/h)

C3H8 - - - -

C3H6 - - - -

C2H4 - - - -

CH4 - - - -

C - - - -

CO2 113.5036 287.2429 299.3169 299.5009

H2O 299.0499 125.3107 113.2366 113.0527

O2 5.7240 5.7240 5.7240 5.7240N2 552.9992 552.9992 552.9992 552.9992

CO 186.4964 12.7571 0.6831 0.4991

H2 530.9501 704.6893 716.7634 716.9473

Temperature 518.0 C 234.6 C 109.5 C 100.1 C

Basically, after the optimization has been done, there was more hydrogen

produced and carbon monoxide decrease drastically. This result obtained because therewere enough water supplied for the each process of the water gas shift reactor to

complete the reaction. But, with that molar flow rate, concentration of carbon monoxide

that out from LTS was still high and in order to achieve below than 10 ppm, we need to

perform preferential oxidation reaction (PrOx).


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5.6 Preferential Oxidation (PrOx)

PrOx is the final stage to reduce carbon monoxide from the system. Figure 5.6

illustrates the flowsheeting for entire process with PrOx process.

Figure 5.6 : PFD of the PrOx process with entire process.

Initially, no air was injected to the PrOx reactor. The air stream must be heated

up to 70oC and the stream out from LTS reactor also must be cooled to 70

oC before

entering the reactor. Table 5.5 shows the result from the simulation when zero air was

injected to the reactor.


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Table 5.5 : Result for every component at the PrOx reactor.

Components New stream input

(Air_PrOx)

LTS out

(kgmole/h)

To Fuel Cell

(kgmole/h)

C3H8 - - -

C3H6 - - -

C2H4 - - -

CH4 - - -

C - - -

CO2 - 299.5559 299.5559

H2O - 124.4457 124.4457

O2 - 0 0N2 - 552.9992 552.9992

CO - 0.4441 0.4441

H2 - 705.5543 705.5543

Temperature 100 C 100.1 C 100 C

As we can see from the Table 5.5, there was no change of the hydrogen or

carbon monoxide from the LTS out to the PrOx out because no air was injected to thereactor. Therefore, there was no reactions occurred because of there were no more or

insufficient of oxygen which will be used to complete the reaction at the PrOx.

5.6.1 Optimization of PrOx Reactor

The air must be injected to the PrOx reactor in the optimum molar flow rate in

order to obtain the maximum hydrogen produced with below 10 ppm of carbon

monoxide.


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Thus, in this optimization we will monitor the air molar flowrate to the PrOx

reactor. Figure 5.7 shows the result of optimization at the PrOx reactor.

Figure 5.7 : Molar flow carbon monoxide (CO) and hydrogen (H2) output from PrOx

versus molar flow Air_PrOx

Based on the Figure 5.7, the optimum molar flow rate for air was 7 kgmole/hr

because at that condition the molar flow rate of carbon monoxide was below than 10

ppm. Then, Table 5.6 shows the result of the simulation using the optimum molar flow

rate of air that injected to the PrOx reactor.


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5.7.1 Components Profile

The components profile of the whole processor was illustrated at Table 5.7 and

Figure 5.8:

Table 5.7 : Components profile for every reactor.

ATR

in

ATR

out

HTS

out

MTS

out

LTS

out

PrOx

in

PrOx

out

C3H8 100 - - - - - -

C3H6 - - - - - - -

C2H4 - - - - - - -

CH4 - - - - - - -

C - - - - - - -

O2 147.000 5.724 5.724 5.724 5.724 7.194 -

N2 552.999 552.999 552.999 552.999 552.999 558.529 558.529

CO2 - 113.504 287.246 299.317 299.501 299.501 299.984

H2O 430 299.050 125.307 113.237 113.053 113.053 126.958

CO - 186.496 12.7540 0.6831 0.4991 0.4991 0.0167H2 - 530.950 704.693 716.764 716.948 716.948 703.042


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Figure 5.8: Components profile for hydrogen and carbon monoxide

Based on the Table 5.7 and Figure 5.8, we can observe the whole component

molar flow-rate whereby begin from the input to the ATR reactor until to the last reactor

that is PrOx out. The main purpose for this observation is to maximize hydrogen

production and in the same time to lessen the concentration of carbon monoxide until

below than 10 ppm. This chapter we were only discussed for two components namely

hydrogen and carbon monoxide. For the detail figure for all components please refer to

the appendix G1.

As shown in the Figure 5.8, molar flow rate of hydrogen and carbon monoxide

after the ATR reactor were contradictory. This condition was happened because after

the ATR reactor is the WGS reactor which is known as clean up system for carbon

monoxide, where the hydrogen-rich syngas goes through to the series reactor to reduce

the concentration of carbon monoxide and convert it to hydrogen and carbon dioxide.

We can see that after the LTS out the concentration of carbon monoxide was reduce


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almost to zero. But then, after the PrOx out the amount of hydrogen was a little bit

decrease because of PrOx processes used hydrogen to reduce the concentration of

carbon monoxide with the injected of air. From these results, we can conclude that the

optimization process was successfully done.

5.7.2 Temperature Profile

The temperature profile for the whole system was point up to the Figure 5.9

Figure 5.9: Temperature profile for every units operation

From the Figure 5.9, the entire streams for the input to the ATR reactor were set

to100oC and it increased to 518

oC at the outlet of the ATR. Then, the hot stream was

used as the heater for the three heat exchangers. As the stream flow through the heat

exchanger, the temperature will cooled down from every heat exchanger. Before,

entering to the clean up system, the temperature for the input for HTS, MTS and LTS


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must be cooled down to 100oC and the temperature of the input for the PrOx reactor also

must be 70oC.

Besides that, the temperature that passes through of CO_1, CO_2, CO_3 andCO_4 must be lower than ATR, HTS, MTS and LTS to prevent the reversible process

occur. In the HTS, the inlet temperature is 100oC and the outlet temperature is about

234oC. The slightly increase in the outlet temperature because of the exothermic nature

of the WGS reaction. The same profiles also have been shown for the MTS and LTS.

For the PrOx reactor there is also slightly increased of temperature from 70 oC for the

input to the 135oC at the output because of the exothermic nature of the PrOx reaction.

The temperature of PrOx out was too high for the fuel cell processor and it need to be

cooled down around 80oC. With this temperature profile, we can monitor temperature

changes for every unit operations in the hydrogen production plant. Temperature profile

is very important parameter in designing fuel processor

5.8 Fuel Processor Efficiency

Fuel processor efficiency was calculated using equation (3.25) with Table 3.1 as

well. Therefore, in this study the S/F ratio of 4.3 and A/F ratio of 7, the calculated fuel

processor efficiency is about 83.14% and the detail calculation is shown at the Appendix

F1.

5.9 Summary

Basically, for this chapter there are sevens main section that have been

accomplished which are base case simulation, validation, heat integration, clean up

process (WGS and PrOx), plant wide optimization at the ATR, WGS and PrOx reactor,


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analysis components and temperature profile and the last is fuel processor efficiency.

Results that are obtained from each section have been discussed well.


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CHAPTER VI

CONCLUSIONS AND RECOMMENDATIONS

6.1 Introduction

A variety of fuel cells operating with different fuels and electrolytes are under

investigation, the proton exchange membrane fuel cell (PEMFC) fuelled by hydrogen

seems to be the most promising option for both vehicular and small scale combined heat

and power applications due to its compactness, modularity, high power density and fast

response. PEM fuel cell system application consists of two major subsystems, namely

fuel processing and fuel cell. For this research, fuel processor using propane was

successfully developed using Aspen HYSYS 2004.1

Basically, in this research fuel processor contain two types of reactors which are

conversion reactor and equilibrium reactor. First and the last reactor are the conversion

reactors which are autothermal reactor (ATR) and preferential reactor (PrOx) reactor.

Then for the water gas shift (WGS) or clean up carbon monoxide process that consists of

three reactors (HTS, MTS and LTS) is used equilibrium reactor.

Extensive heat integration has been applied within the PEM fuel cell system to

obtain acceptable net system electrical efficiency levels. There were three heat

exchangers had been installed after the ATR reactor out


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6.2 Summary of Results

There were three inputs for this process of hydrogen production which are

propane, air and water. In general, there were nineteenths reactions involved which aretotal oxidation (TOX), partial oxidation (POX), steam reforming (SR), dry reforming

(DR) and cracking in this processes and three reactions occurred for the clean up of

carbon monoxide at the WGS and PrOx reactor.

Basically, for 100 kgmole/h of propane was inserted to the process and it

produced about 703.0418 kgmole/hr hydrogen. For the first reactor that is at the ATR

reactor, hydrogen that produced after the optimization was 530.9501 kgmole/hr. The

second and until the third reactors were WGS or clean up carbon monoxide process and

the hydrogen produced after the optimization was 716.9473 kgmole/hr. Then, for the

last reactor that is PrOx reactor, hydrogen was reduced to 703.0418 kgmole/hr.

Optimization had been done for every reactor whereby for the ATR reactor, we

got 700 kgmole/hr for the highest hydrogen production and the lowest carbon monoxide

besides temperature around 518.0oC. Then, for the WGS reactor (HTS, MTS and LTS)

we optimized the water molar flow which is 430 kgmole/hr was the best. Air that

injected to the last reactor (PrOx) also was optimized and the best molar flow for air for

PrOx reactor was 7 kgmole/hr only.

Lastly, this simulation of hydrogen production by the authothermal reforming of

propane was been successfully developed using Aspen HYSYS 2004.1.


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6.4.2 Water Management

One of the objectives of the fuel processor system is to maintain self-sufficiency

with respect to water needs. In each of the systems, there is a single exhaust streamconsisting of CO2and water vapour from the complete combustion of the fuel, a small

amount of unused oxygen, and all of the nitrogen that originates with air feed streams.

Recovery of sufficient water from the exhaust stream to meet the steam generation needs

depends on the following four factors:

i. Exhaust temperature. The cooler the exhaust, the more water is recovered bycondensation. The minimum temperature is limited by ambient temperature

and the amount of heat transfer surface area.

ii. Exhaust pressure. Higher pressures allow more water condensation, butrequire an increase in the fuel cell operating pressure.

iii. Air feed rate. The more air that is fed to the system, the more nitrogen must bepurged out with the exhaust. More exhaust nitrogen reduces the recovery of

water condensed from the exhaust. There are two sources of air feed:

Air to autothermal reformer, and Air to the PrOx reactor. These air rates are determined by stoichiometric

ratios, which are not varied for the sake of the water balance.

iv. Fuel processor efficiency. As the fuel processor efficiency is reduced, thehydrocarbon feed rate to the processor is increased. This increases the

production of water vapour, since all hydrocarbons is eventually combusted

completely. With all else held constant, the additional water production will

be recovered in the exhaust condenser.


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Aartun, I., Silberova, B., Venvik, H., Pfeifer, P., Gorke, O., Schubert, K. and Holmen,

A. (2005). Hydrogen Production from Propane in Rh-impregnated Metallic

Microchannel Reactors and Alumina Foams. Catalysis Today 105: 469478.

Aartun, I., Venvik, H. J., Holmen, A., Pfeifer, P., Gorke, O. and Schubert, K. (2005).

Temperature Profiles and Residence Time Effects During Catalytic Partial

Oxidation and Oxidative Steam Reforming of Propane in Metallic Microchannel

Reactors. Catalysis Today 110: 98107.

Aartun, I., Gjervan, T., Venvik, H., Gorke, O., Pfeifer, P., Fathi, M., Holmena, A. and

Schubert, K. (2004). Catalytic Conversion of Propane to Hydrogen in

Microstructured Reactors. Chemical Engineering Journal 101: 9399.

Agrel, J., Birgersson, H., Boutonnet, M., Melian-Cabrera, I., Navarro, R.M. and Fierro,

J. L. G. (2003). Production of Hydrogen from Methanol over Cu/ZnO Catalysts

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Park Cambridge, MA 02141-2201, USA.

Avc, A. K., Trimm, D. L., Aksoylu, A. E. and Onsan, Z. I. (2004). Hydrogen

Production by Steam Reforming of n-butane Over Supported Ni and Pt-Ni

Catalysts. Applied Catalysis A: General 258: 235240.

Avc, A. K., Trimm, D. L. and Onsan, Z. I. (2002). Quantitative Investigation of

Catalytic Natural Gas Conversion for Hydrogen Fuel Cell Applications. Chemical

Engineering Journal 90: 7787.

Avc, A. K., Onsan, Z. I. and. Trimm, D. L (2001). On-board Fuel Conversion for

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Basile, A., Gallucci, F. and P

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