SIMULATION AND OPTIMIZATION OF ETHANOL AUTOTHERMAL REFORMER FOR FUEL CELL APPLICATIONS

MUHAMAD SYAFIQ BIN ADAM

A report submitted in partial fulfilment of the

requirements for the award of the degree of

Bachelor of Engineering (Chemical)

Faculty of Chemical Engineering and Natural Resources Engineering

Universiti Teknologi Malaysia

NOVEMBER 2006

v

ABSTRACT

Fuel cell application from hydrogen was one of alternative energy that

being studied and widely accepted in industry. This case study focused on

optimization of hydrogen production for fuel cell applications. In this case study,

ethanol was chosen as a raw material and with autothermal reforming as a process of

produce hydrogen. Using a commercial dynamic flow sheeting software, HYSYS

3.2, the process of hydrogen production was successfully simulated. In this research,

fuel processor consists of an autothermal reactor, three water gas shift reactors and a

preferential oxidation reactor was successfully developed. The purpose of this case

study is to identify the effect of various operating parameters such as air-to-fuel

(A/F) ratio and steam-to-fuel (S/F) ratio to get the optimum hydrogen production

while made carbon monoxide lower than 10 ppm. From the results, an optimum A/F

and S/F ratio are 5.5 and 1.5, respectively to produce 34 % of hydrogen and 10.055

ppm of CO. Under these optimum conditions, 83.6% of fuel processor efficiency was

achieved.

vi

ABSTRAK

Penggunaan sel bahan api daripada hidrogen merupakan salah satu tenaga

yang masih dikaji dan diterima dalam kebanyakan industri. Kajian ini memfokuskan

tentang pengeluaran hidrogen untuk penggunaan sel bahan api secara dinamik.

Dalam kajian ini, etanol dipilih sebagai bahan mentah dan pembentukan autoterma

(auto thermal reforming) merupakan proses untuk menghasilkan hidrogen. Dengan

menggunakan perisian ‘HYSYS 3.2, proses pengeluaran hidrogen ini berjaya

dilakukan secara simulasi. Dalam kajian ini, pemproses minyak mengandungi reaktor

autoterma,, tiga reaktor anjakan air gas dan reaktor pilihan pengoksidaan telah

berjaya dihasilkan. Kajian ini bertujuan untuk mengenalpasti kesan pengandelaian

parameter yang berlainan seperti ratio udara-ke-minyak (A/F) dan ratio stim-ke-

minyak (S/F) untuk mendapatkan pengeluaran hydrogen yang optimum sementara

CO dihasilkan rendah dari 10 ppm. Daripada keputusan ujikaji, nilai ratio A/F dan

S/F yang optima adalah 5.5 dan 1.5 masing-masing. Dengan ratio tersebut,34%

hydrogen dan 10.055 ppm CO dapat dihasilkan. Dibawah keadaan pengoptimaan ini,

sebanyak 83.6 % kecekapan pemproses minyak didapati.

vii

LIST OF CONTENTS

CHAPTER TITLE PAGE

Tittle Page i

Declaration ii

Dedication iii

Acknowledgements iv

Abstract v

Abstrak vi

List of Contents vii

List of Figures xi

List of Tables xiii

List of Symbols xiv

I INTRODUCTION

1.1 Background Research 1

1.2 Problems Statement 2

1.3 Research Objective 2

1.4 Scopes of study 3

1.5 Thesis Organizations 4

II LITERATURE REVIEW

2.1 Introduction 6

2.2 Hydrogen Production for Fuel Cell Application in

General 6

2.2.1 Natural Gas 7

viii 2.2.1.1 Methane 7

2.2.1.2 Ethane 8

2.2.1.3 Propane 9

2.2.1.4 Butane 9

2.2.2 Alcohol 9

2.2.2.1 Methanol 10

2.2.2.2 Ethanol 10

2.2.2.3 Propanol 11

2.2.3 Petroleum Fractional 12

2.2.3.1 Kerosene 12

2.2.3.2 Gasoline 12

2.2.3.3 Diesel 13

2.3 Hydrogen Production for Fuel Cell from Ethanol 13

2.3.1 Steam Reforming 14

2.3.2 Partial Oxidation 15

2.4 Steam Reforming of Ethanol for Hydrogen

Production 16

2.5 Optimization simulation of Hydrogen Production 17

2.6 Summary 17

III METHODOLOGY

3.1 Research Tools 18

3.1.1 Aspen HYSYS 18

3.2 Research Activities 19

3.2.1 Data Collection 19

3.2.2 Base Case Stoichiometry 19

3.2.3 Base Case Validation 21

3.2.4 Auto-thermal Reactor Optimization 21

3.2.5 Heat Integration 21

3.2.6 Carbon Monoxide Clean Up 22

3.2.6.1 Water Gas Shift 22

3.2.6.2 Preferential Oxidation 22

3.2.7 Plant Wide Optimization 23

ix 3.2.7.1 ATR Optimization 23

3.2.7.2 Water Gas Shift Optimization 23

3.2.7.3 Preferential Oxidation Optimization 24

3.2.8 Temperature and Component Profile 24

3.2.9 Fuel Processor Efficiency 24

3.3 Summary 25

IV SIMULATION AND OPTIMIZATION OF HYDROGEN

PRODUCTION PLANT FROM ETHANOL FOR FUEL CELL

APPLICATION

4.1 Process Description of Hydrogen Production from

Ethanol 26

4.2 Modelling and Simulation of Hydrogen Production

From Ethanol for Fuel Cell 27

4.2.1 Thermodynamic Properties 31

4.2.2 Physical Properties 32

4.2.3 Integration Algorithm 33

4.2.4 Mathematical Modelling of the Reactor

Operating 33

4.2.4.1 Linear and Non-Linear System 33

4.2.4.2 Material Balance 34

4.2.4.3 Component Balance 35

4.2.4.4 Energy Balance 36

4.2.5 Degree of Freedom Analysis 38

4.2.6 Analysis of Optimization Response 38

4.3 Summary 39

V RESULTS AND DISCUSSION

5.1 Results for Base Case Study 40

5.2 Results for Validation 43

5.3 Results for Heat Integration 44

5.4 Results for Carbon Monoxide Clean Up 46

5.4.1 Water Gas Shift 46

x 5.4.2 Preferential Oxidation 47

5.5 Plant Wide Optimization 48

5.5.1 ATR Optimization 49

5.5.2 Water Gas Shift Optimization 50

5.5.3 Preferential Oxidation Optimization 53

5.6 Temperature Profile of fuel Processor System 55

5.7 Component Profile of the Fuel Processor System 56

5.8 Fuel Processor Efficiency 57

5.9 Summary 57

VI CONCLUSION AND RECOMMENDATIONS

6.1 Summary 58

6.2 Conclusion 59

6.3 Recommendation 59

REFERENCES 61

APPENDIX

APPENDIX A Final result of simulation HYSYS 3.2 66

xi

LIST OF FIGURES

FIGURE NO. TITLE PAGE

3.1 Algorithm for methodology. 25

4.1 The operation conditions for the major unit

operation 27

4.2 The whole plant system by Aspen HYSYS 3.2 29

4.3 HYSYS simulation environment 30

4.4 Reactor operating 35

4.5 Block diagram of the simulation of hydrogen

plant using Aspen HYSYS 3.2 39

5.1 Process flow diagram of the base case 41

5.2 The heater attachment on the ATR reactor 45

5.3 The heaters at the feed streams were exchange

with the heat exchanger 46

5.4 The WGS reactor 47

5.5 The PROX reactor 48

xii 5.6 Temperature of ATR vapour for varies air feed

molar flow 49

5.7 Molar flow of CO and H2 effluent for varies

air feed molar flow 50

5.8 Molar flow of CO and H2 effluent for varies

water feed molar flow 51

5.9 Temperature to ATR outlet for varies water feed

molar flow 52

5.10 CO Molar flow in PROX effluent for varies air

feed molar flow 54

5.11 Temperature profile for the whole unit operation 55

5.12 H2 and CO profile for the whole unit operation 56

xiii

LIST OF TABLES

TABLE NO. TITLE PAGE

4.1 Physical property of the component 32

5.1 Molar flow of ATR effluent for base case 43

5.2 Validation for simulation effluent compare

with calculated effluent 44

5.3 Effluent molar flow after water gas shift

reaction for each reactor 47

5.4 Effluent molar flow after preferential

oxidation reaction 48

5.5 Molar flow of the effluent before optimization

for ATR,HTS, MTS and LTS. 52

5.6 Molar flow of the effluent after optimization

for ATR,HTS, MTS and LTS. 53

5.7 Molar flow of the effluent before and after

optimization for PROX 54

xiv

LIST OF SYMBOLS

A Heat transfer area

a Parameter, cubic equation of state

b Parameter, cubic equation of state

C Concentration

F Volumetric flow rate

g Local acceleration of gravity

H Molar or specific enthalpy

h Step size

k Kinetic energy •

m Mass flow rate

MW Molecular weight

Nm Number of independent variables

Nom Number of manipulated variables with no steady state effect

Noy Number of variables that need to be controlled from Nm

Nss Number of variables needed to be specified

P Absolute pressure

Po Reference pressure

Pci Critical pressure, species i

Pri Reduced pressure, species i

Q Heat

Qr Heat generated by reaction

R Universal gas constant

r Rate of reaction

t Time

u Internal energy

V Volume

xv Y Process Variable

Greek letters

α Function, cubic equation of state

ε Error

μ Viscosity

ρ Density

φ Potential energy

ω Acentric factor

Abbreviations

ATR Auto thermal reforming

ca. at approximate

CO Carbon Monoxide

CO2 Carbon Dioxide

et al. et alias: and others

etc. et cetera

H2 Hydrogen

HTS High Temperature Shift

LTS Lower Temperature Shift

PROX Preferential Oxidation

MTS Medium Temperature Shift

WGS Water Gas Shift

CHAPTER Ι

INTRODUCTION

1.1 Background Research

Hydrogen was expected to become an important energy carrier for

sustainable energy consumption with a significantly reduced impact on the

environment. Hydrogen’s benefit and disadvantages differ from the fossil fuels

common place in advanced energy utilizing society. It is because characteristics of

hydrogen that cheap, easy to obtain, high efficiency, virtually silent operation and

less pollutant emissions. (Fuel cell store website, 2006)

From that perspective, researcher over the world tries to make use the

hydrogen as an alternative energy by converting into fuel cell. Hydrogen as fuel cell

technology currently needed in large quantities, and is projected to be the fuel of

choice for a number of advanced technologies that are being pursued. Fuel cell will

supply the energy that a global society requires to support the growing number of

people that demanding on fuel cell technology using hydrogen. (Fuel cell store

website, 2006)

For that purpose, some fossil fuels which have high hydrogen to oxygen ratio

were the best candidates to produce hydrogen. The more hydrogen present and the

fewer extraneous compounds was the idea to get it. One of the methods which

commonly being used was the steam reforming. Other established methods include

partial oxidation of residual oil, coal gasification, water electrolysis and etc. The new

2

technologies such as high-temperature electrolysis of steam, thermal cracking of

natural gas, thermo chemical water splitting, solar photovoltaic water electrolysis,

and plasma decomposition of water is still investigated its efficiency. These

technologies can be classified as thermal, thermo chemical, electrochemical,

photochemical, and plasma chemical methods. (Fuel cell store website, 2006)

Seven common fuels are the postulated hydrogen sources studied in this work

alcohol, natural gas, gasoline, diesel fuel, aviation jet fuel, and hydrogen itself.

Among the bio-fuel candidates for carriers of hydrogen, ethanol is of particular

interest because its low toxicity, low production costs, the fact that is a relative

clean fuel in terms of composition, relatively high hydrogen content and availability

and ease of handling. Hydrogen can be obtained directly from ethanol by two main

processes; partial oxidation and steam reforming. (Fuel cell store website, 2006)

1.2 Problem Statement

In reality, chemical plants are never truly at steady state. Feed and

environmental disturbances, heat exchanger fouling, and catalytic degradation

continuously upset the conditions of a smooth running process. Optimization

simulation can help researcher to make better design, optimize, and operate process

or refining plant. In this research, ethanol is the main focus to study the steady state

behaviour. Furthermore, the optimization is the main case study that will make more

yield selectivity hydrogen. The important of this study is to identify design

parameters and also to estimate fuel processor efficiency.

1.3 Research Objectives

The main objective of this research is to simulate and optimize the hydrogen

production plant for fuel cell application using ethanol via autothermal reformer.

3

1.4 Scope of Study

To achieve above objective, several scopes has be drawn:

i. Base case simulation development

By using Aspen HYSYS 3.2, hydrogen production simulation plant was

being developed with data from Akande et al. (2005)

ii. Base case simulation validation

From base case simulation that being developed with Aspen HYSYS 3.2, it

was validated using theoretically data from total reactions stoichiometry

coefficient.

iii. ATR optimization

ATR was optimizing by optimized the air feed molar that enter the ATR

while monitoring the production of hydrogen and carbon monoxide (CO) in a

certain range of temperature.

iv. Heat integration

This system is used to increase the efficiency of the plant by using heat

exchanger to cool down the ATR vapour out with the hot stream from the

feed.

v. Carbon monoxide clean up

Carbon monoxide that produced by the total reaction in ATR need to be

reduced their concentration by introducing water gas shift reaction and

preferential oxidation reactions.

a. Water gas shift

Equilibrium reactors were placed to the plant to convert CO into carbon

dioxide (CO2). Three reactors were needed for conversion with water

gas shift (WGS) reaction as the main reaction.

4

b. Preferential oxidation

To maximum reducing CO, preferential oxidation (PROX) reaction was

introduced.

vi. Plant wide optimization

It was develop to optimized all the reactors used in the plant developed using

Aspen HYSYS 3.2 and to reduced CO concentration to the specific

requirement.

a. ATR optimization

It’s used to optimize the ATR temperature outlet for heat integration.

b. Water gas shift optimization

It’s used to optimize water molar flow to the ATR and reduces the CO

concentration with WGS reaction.

c. Preferential oxidation optimization

It was formed to maintain the amount of air into PROX reactor that

reduced the CO concentration to the specification.

vii. Temperature and component profile

The profile of temperature and components for every unit operations involve

in this research was analyzed.

1.5 Thesis Organizations

This thesis involves the conclusion of the several tasks to achieve the

objective. Chapter Two is discuss about the literature survey that related in synthesis

of hydrogen for fuel cell applications. In this chapter, internal researched of

hydrogen production using ethanol by autothermal reforming was been concentrated.

This chapter is the major chapter because the development of the of hydrogen

production are based on the literature survey that we had researched.

5

Chapter Three is about the methodology for the methods that we need in

scope. Fundamentally, there are five methods that we carried out. The next chapter;

Chapter Four, is optimization simulation of hydrogen production plant from ethanol

for fuel cell application. We are using Aspen HYSYS 3.2 as a simulator to simulate

the plant.

Chapter Five is the results and discussion based on the methodology that we

use and developed from chapter four. Finally, Chapter Six is the conclusion all what

we have done in this entire thesis.

61

REFERENCES

Aartun, I., Silberova, B., Venvik, H., Pfeifer, P., Go¨rke, O., Schubert, K. and

Holmen, A. (2005). “Hydrogen production from propane in Rh-impregnated

metallic microchannel reactors and alumina foams”. Catalysis Today. 105.

469–478.

Akande, A.J., Raphael O. Idem, R.O. and Dalai, A.K. (2005). “Synthesis,

characterization and performance evaluation of Ni/Al2O3 catalysts for

reforming of crude ethanol for hydrogen production”. Applied Catalysis A:

General. 287. 159–175.

Aupretre, F., Descorme. C., Duprez, D., Casanave, D. and Uzio, D. (2005). “Ethanol

steam reforming over MgxNi1−xAl2O3 spinel oxide-supported Rh catalysts”.

Journal of Catalysis. 233. 464–477.

Avci, A.K., Trimm, D.L., Aksoylu, A.E. and Önsan, Z.I. (2003). “Hydrogen

production by steam eforming of n-butane over supported Ni and Pt-Ni

catalysts”. Applied Catalysis A: General. 258. 235–240.

Basile, A., Gallucci, F. and Paturzo, L. (2005). “Hydrogen production from methanol

by oxidative steam reforming carried out in a membrane reactor”. Catalysis

Today. 104. 251–259.

Bingue, J.P., Saveliev, A.V. and Lawrence ans Kennedy, A.L. (2004). “Optimization

of hydrogen production by filtration combustion of methane by oxygen

enrichment and depletion”. International Journal of Hydrogen Energy. 29.

1365 – 1370.

Brown, L.F. (2001). “A comparative study of fuels for on-board hydrogen production

for fuel-cell-powered automobiles”. International Journal of Hydrogen

Energy. 26. 381–397.

Cheekatamarla, P.K. and Lane, A.M. (2005). “Efficient bimetallic catalysts for

hydrogen generation from diesel fuel”. International Journal of Hydrogen

Energy. 30. 1277–1285.

62

Chin, S.Y., Chin, Y.H. and Amiridis, M.D. (2005). “Hydrogen production via the

catalytic cracking of ethane over Ni/SiO2 catalysts”. Applied Catalysis A:

General. 300. 8–13.

Comas, J., Laborde, M. and Amadeo, N. (2004). “Thermodynamic analysis of

hydrogen production from ethanol using CaO as a CO2 sorbent”. Journal of

Power Sources. 138. 61–67.

Cook, B.(2001). “An introduction to fuel cells and hydrogen technology”.

Heliocentris, 652 West 5th Avenue, Vancouver, BC V6R-1S2, Canada.

Ferna´ndez, E.O., Rusten, H.K., Jakobsen, H.A., Rønning, M., Holmen, A. and Chen,

D., (2005). “Sorption enhanced hydrogen production by steam methane

reforming using Li2ZrO3 as sorbent: Sorption kinetics and reactor

simulation”. Catalysis Today.106. 41–46.

Fierro, V., Akdim, O., Provendier, H. and Mirodatos, C. (2005). “Ethanol oxidative

steam reforming over Ni-based catalysts”. Journal of Power Sources. 145.

659–666.

Freni, S., Cavallaro, S., Mondello, N., Spadaro , L. and Frusteri, F. (2003).

“Production of hydrogen for MC fuel cell by steam reforming of ethanol over

MgO supported Ni and Co catalysts”. Catalysis Communications. 4. 259–268.

Fuel Cell Store Website. http://www.fuelcellstore.com. Accessed on 21st March

2006 at 4:39 AM.

Galvita, V. and Sundmacher, K. (2005). “Hydrogen production from methane by

steam reforming in a periodically operated two-layer catalytic reactor”.

Applied Catalysis A: General. 289. 121–127.

HYSYS 2.2 Documentation (2000), Hyprotech Ltd. Calgary, Canada.

Jiménez, M.O. (2006). “Hydrogen production study using autothermal reforming of

biodiesel and other hydrocarbons for fuel cell applications”. University of

Puerto Rico Mayagüez Campus.

Lee, K.K., Han, G.Y., Yoon, K.J. and Lee, B.K. (2004). “Thermocatalytic hydrogen

production from the methane in a fluidized bed with activated carbon

catalyst”. Catalysis Today. 93–95. 81–86.

Lenz, B. and Aicher, T. (2005). “Catalytic autothermal reforming of Jet fuel”.

Journal of Power Sources. 149. 44–52.

63

Liguras, D.K., Kondarides, D.I. and Verykios, X.E. (2003). “Production of hydrogen

for fuel cells by steam reforming of ethanol over supported noble metal

catalysts”. Applied Catalysis B: Environmental. 43. 345–354.

Liu, Z.W., Jun, K.W., Roh and H.S., Park, S.E. (2002). “Hydrogen production for

fuel cells through methane reforming at low temperatures”. Journal of Power

Sources. 111. 283-287.

Mattos, L.V. and Noronha, F.B. (2005a). “Partial oxidation of ethanol on supported

Pt catalysts”. Journal of Power Sources. 145. 10–15.

Mattos, L.V. and Noronha, F.B. (2005b). “Hydrogen production for fuel cell

applications by ethanol partial oxidation on Pt/CeO2 catalysts: the effect of

the reaction conditions and reaction mechanism”. Journal of Catalysis. 233.

453–463.

Minutillo, M. (2005). “On-board fuel processor modeling for hydrogen-enriched

gasoline fuelled engine”. International Journal of Hydrogen Energy. 30.

1483-1490.

Mizuno, T., Matsumura, Y., Nakajima, T. and Mishima, S. (2003). “Effect of support

on catalytic properties of Rh catalysts for steam reforming of 2-propanol”.

International Journal of Hydrogen Energy. 28. 1393 – 1399.

Nakagawa, K.,Gamo, K.N. and Ando, T. (2004). “Hydrogen production from

methane for fuel cell using oxidized diamond-supported catalysts”.

International Journal of Hydrogen Energy. 30. 201–207.

Navarro, R.M., Galva´n, M.C.A., Sa´ncheza, M.C.S., Rosa, F. and Fierro, J.L.G.

(2004). “Production of hydrogen by oxidative reforming of ethanol over Pt

catalysts supported on Al2O3 modified with Ce and La”. Applied Catalysis B:

Environmental. 55. 229–241.

Otsuka, K., Shigeta, Y. and Takenaka, S. (2002). “Production of hydrogen from

gasoline range alkanes with reduced CO2 emission”. International Journal of

Hydrogen Energy. 27. 11–18.

Ozdogan, S., Ersoz, A., and Olgun, H(2006).. “Smulation study of a PEM fuel cell

system fed by hydrogen produced by partial oxidation”. Journal of Power

Sources 2003;118; 384-392.

Perry, R.H. and Green, D. (1997). “ Perry’s Chemical Engineers’ Handbook”.

McGraw-Hill. 7th ed. Sec. 2.

64

Resini, C., Delgado, M.C.H., Arrighi, L., Alemany, L.J., Marazza, R. and Busca, G.

(2005). “Propene versus propane steam reforming for hydrogen production

over Pd-based and Ni-based catalysts”. Catalysis Communications. 6. 441–

445.

Silberova, B., Venvik, H.J., Walmsley, J.C. and Holmen, A. (2005) “Small-scale

hydrogen production from propane”. Catalysis Today. 100. 457–462.

Shebaro, L., Abbott, B., Hong, T., Slenczka, A., Friedrich, B. and Herschbach, D.

(1997). “Facile production of higher hydrocarbons from ethane in a catalytic

supersonic nozzle” Chemical Physics Letters. 271. 73-78.

Shetian Liu, S., Takahashi, K., Uematsu, K.and Ayabe, M. (2004). “Hydrogen

production by oxidative methanol reforming on Pd/ZnO”. Applied Catalysis

A: General. 283. 125–135.

Stephanopoulos, G. (1984). “Chemical Process Control: An Introduction to Theory

and Practice.” Eaglewood Cliffs, New Jersey: Prentice Hall.

Sun, J., Qiu, X.P., Wu, F. and Zhu, W.T. (2005). “H2 from steam reforming of

ethanol at low temperature over Ni/Y2O3,Ni/La2O3 and Ni/Al2O3 catalysts for

fuel-cell application”. International Journal of Hydrogen Energy. 30. 437–

445.

Suzuki, T., Iwanami, H. and Yoshinari, T. (2000). “Steam reforming of kerosene on

Ru/Al2O3 catalyst to yield hydrogen”. International Journal of Hydrogen

Energy. 25. 119-126.

Tsolakis, A. and Megaritis, A. (2004). “Catalytic exhaust gas fuel reforming for

diesel engines-effects of water addition on hydrogen production and fuel

conversion efficiency”. International Journal of Hydrogen Energy. 29. 1409

– 1419.

Vaidya, P.D. and Rodrigues, A.E. (2005). “Insight into steam reforming of ethanol to

produce hydrogen for fuel cells”. Chemical Engineering Journal. 117. 39–49.

Wanat, E.C., Suman, B. and Schmidt, L.D. (2005). “Partial oxidation of alcohols to

produce hydrogen and chemicals in millisecond-contact time reactors”.

Journal of Catalysis. 235. 18–27.

Wang, L., Murata, K. and Inaba, M. (2003). “Production of pure hydrogen and more

valuable hydrocarbons from ethane on a novel highly active catalyst system

with a Pd-based membrane reactor”. Catalysis Today. 82. 99–104.

65

Xu, Y., Kameoka, S., Kishida, K., Demura, M., Tsai, A. and Hirano, T. (2004).

“Catalytic properties of alkali-leached Ni3Al for hydrogen production from

methanol”. Intermetallics. 13. 151–155.