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THE COPPERBELT UNIVERSITY

SCHOOL OF MINES AND MINERAL SCIENCES

CHEMICAL ENGINEERING DEPARTMENT

CATALYTIC CONVERTER DESIGN

SUBMITTED

BY

MULOSA JONATHAN

A SPECIAL PROJECT SUBMITTED IN PARTIAL FULFILMENT FOR

THE AWARD OF BACHELOR OF ENGINEERING

IN

CHEMICAL ENGINEERING

DECEMBER, 2012

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CATALYTIC CONVERTER DESIGN Page i

DECLARATION

I declare that "The catalytic converter design project" is my own work, that it has not been

submitted for any degree or examination in any other university, and that all the sources I have

used or quoted have been indicated and acknowledged by complete references.

Signature of student………………….

Date…………………………... ……..

(Mr. Mulosa Jonathan)

Signature of supervisor………………..

Date…………………………………...

(Mr. C. Botha)

Signature of the assistant dean…………

Date…………………............................

(Mr. J. Mundike)

CATALYTIC CONVERTER DESIGN Page ii

DEDICATION

I am honored to dedicate this piece of work to Mum and Dad, my sisters Jesse and Carlo, my

brothers Given and Clive, my cousins Anna and Gadson and Mr. and Mrs. Mwansa. I further

dedicate this work to every Zambian youth who believes that having fun, working hard and

having a positive outlook on life bring success.

CATALYTIC CONVERTER DESIGN Page iii

ACKNOWLEDGMENTS

A lot of thanks go to my supervisor and lecturer Mr. C. Botha whose guidance, criticism and

understanding I can never repay. I also wish to thank Mr. S. Kamutima for the support rendered

to me during the printing out of this book and Mr. Z. Chingangu for the seeing me through.

It would be so unthinkable to forget to appreciate my family and my childhood friend Richard

Akufuna who has seen me this far. My mother Mrs. Joyce K. Mulosa, my dad Mr. J.K Mulosa,

my sisters Carlo and Jesse. My brothers Clive and Given. My cousins Anna and Gadson. Mr.

N. Muleta, Mr. N. Nyirenda and Mr. J. Chokwe, I really appreciate you for the motivation

rendered to me.

Lastly, I wish to Duly acknowledge the candid friendship of the following; Zulu Godfrey, Mwansa

Godfrey, Duncan Balas, Mwandila Kalumpira, Kasongo Michael, Kantu Michael, Bob Mutemwa,

my roommates Mafuleti Chinyama, Chanda Pearson, Banda Mathews and my dear friends,

Elijah Hang’umba, Sandra Chanda, Chimuka Hang’umba, Jean Shimishi, Mwaka Ling’ambi,

Martha Chansa, Benjamin Kasabula, Chegre Kambing’a and all those who contributed in one

way or another and not forgetting my fellow program mates fourth year Chemical Engineering

class of 2012.

CATALYTIC CONVERTER DESIGN Page iv

Table of Contents page

Declaration i

Dedication ii

Acknowledgments iii

Nomenclature viii

Abstract x

List of tables xi

List of figures xiii

List of appendices xiv

CHAPTER ONE, THE DESIGN OF A CATALYTIC CONVERTER

1.0 Introduction 2

1.1 Background 2

1.2 Problem statement 2

1.3 Problem justification 3

1.4 Hypothesis 3

1.5 Aim 3

1.6 Specific objective 3

CHAPTER TWO LITERATRE REVIEW

2.0. Introduction 5

2.1 Description of a catalytic converter 5

2.2. Oxidation of SO2 to SO3 6

2.3. Catalyst holder 8

2.4. Type of catalytic converter designs 10

2.5. Choice of catalyst 11

2.5.1 Catalyst poisons 11

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2.6. Choice of insulation 11

2.7 Designing steps of a catalytic converter 12

2.7.1 Calculating of equilibrium constant 15

2.7.2 Rate constant 15

2.7.3 Specific heat capacity 15

2.7.4 Viscosity 15

2.7.5 Density 16

2.7.6 Conversion 16

2.7.7 Volume required 16

2.7.8 Pressure drop 17

2.7.9 Weight of the catalytic converter 18

2.7.10 Material balance 19

2.7.11 Pipe dimensions 20

2.7.12 Thickness of insulation 21

2.7.13 Space between catalytic beds 21

CHAPTER THREE DESIGN METHODOLOGY

3.0 Introduction 23

3.1 Design 23

3.1.1 Process design methodology 23

3.1.1.1 Catalytic bed volume 23

3.1.1.2 Material balance 23

3.1.1.3 Outlet flow rates 23

3.1.1.4 Equilibrium constant 25

3.2.1.5 Partial pressure 25

3.1.1.6 Reaction rate constant 27

3.1.1.7 Specific heat capacity 27

3.1.1.8 Rate of reaction 28

3.1.1.9 Density 29

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3.1.1.10 Dynamic viscosity 29

3.1.1.11 Volume required 29

3.1.1.11.1 Diameter of the column 30

3.1.1.11.2 Heat of bed 31

3.1.1.11.3 Area of each bed 31

3.1.1.11.4 Superficial velocity 31

3.1.1.11.5 Interstitial velocity 31

3.1.1.12 Catalyst bed characteristic 32

3.1.1.13 Bed density 33

3.1.1.14 Particle weight 33

3.1.1.15 Residence time 33

3.1.1.16 Energy balance 33

3.2 Mechanical design 36

3.2.1 Pressure drop 37

3.2.2 Column thickness 37

3.2.3 Thickness of insulation 37

3.2.4 Thickness of whole vessel 38

3.2.5 Diameter and thickness of pipes 38

3.2.6 Gas velocity in pipes 39

3.2.7 Reactor head 39

3.2.8 Column internals 33

3.2.9 Weight of catalytic converter 43

3.2.9.1 Weight of plate 43

3.2.9.2 Weight of insulation 43

3.2.10 Wind pressure 44

3.2.11 Vessel support 44

CATALYTIC CONVERTER DESIGN Page vii

3.2.12 Design of material and stress analysis 46

CHAPTER F0UR DESIGN RESULTS

4.0 Result of the process design of the catalytic converter 49

4.1. From Material Balance 50

CHAPTER FIVE COST OPTIMISATION AND ESTIMATIONS

5.0 Cost of pipes 54

5.1 Cost of catalyst 55

5.2 Cost of insulation 55

5.3 Cost per plate 55

5.4 Cost of vessel 56

5.5 Total installed cost 56

CHAPTER SIX

6.0 Discussions 58

6.1 Conclusion and recommendations 59

BIBLIOGRAPHY 61

APPENDIX 63

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NOMENCLATURE

Symbol description unit

a reaction coefficient

a Diffusion constant -

A Area

C Concentration

Specific heat capacity .Heat capacity constant -

D Diameter m

Particle Diameter m

Activation Energy ⁄Volumetric gas flow ℎ⁄

G Mass gas flow ⁄h Converter height mℎ Catalyst height m

H Reaction Enthalpy ⁄K Rate constant -

Tuning parameter -

Viscosity constant -

Equilibrium constant

Equilibrium constant

L Length m

m Reaction coefficient -

Molar weight

P Total pressure Pa

CATALYTIC CONVERTER DESIGN Page ix

Partial pressures atm

r Reaction rate .r Radius m

R Gas constant .Re Reynolds number -

t Time s

T Temperature K

Velocity ⁄V Volume

W Catalyst weight Kg

Mole fraction of component i -

Porosity -

Column porosity -

Particle porosity -

Dynamic viscosity Pa s

Density ⁄Dynamic viscosity Pa s

CATALYTIC CONVERTER DESIGN Page x

ABSTRACT

The design of an adiabatic catalytic converter that is capable of converting sulphur dioxide to

sulphur trioxide was done. Commonly in the metallurgical industries there is a problem of

emitting sulphur dioxide in the atmosphere, thus this converter divided into three adiabatic

catalytic beds is to avoid the emission of sulphur dioxide by converting sulphur dioxide to

sulphur trioxide which is later is used in sulphuric acid production. The unit is specifically

designed to convert over 95% of 7% SO2 in a gas stream at a flow rate of 14000 Nm3/h.

More emphasis has been put on the process design obtaining an efficiency of about 99%. The

Ergun equation, data of Eklund, Arrhenius equation material and energy balance were applied

in determining the percentage of conversion, pressure drop, flow rates, catalytic bed volume

and other factors that led to column height and diameter estimation.

An adiabatic catalytic converter column with an internal diameter of 4.5m, a height of 13.5m and

three catalytic beds designed to operate at 1.5 – 2 atm with operating temperature of not less or

more than the range of 380 - 650°C had a total cost estimate of K 3500,000,000.

CATALYTIC CONVERTER DESIGN Page xi

LIST OF TABLES Page

Table 2.1 Advantages and disadvantages of catalysts (11)

Table 2.2 Catalyst poisoning (11)

Table 3.1 Conversion fraction (23)

Table 3.2 Flow rates (25)

Table 3.3 Equilibrium constant (25)

Table 3.4 Stream composition (26)

Table 3.5 Partial pressures (26)

Table 3.6 Reaction rate constant (29)

Table 3.7 Specific heat capacity (27)

Table 3.8 Density (29)

Table 3.9 Catalyst volume and weight (30)

Table 3.10 Height, Area and Velocity (32)

Table 3.11 Characteristic of catalyst bed (33)

Table 3.12 Residence time (35)

Table 3.13 Heat of reaction (34)

Table 3.14 Conversion Vs temperature (35)

Table 3.15 Molar flow rates (36)

Table 3.16 Pipe thickness (38)

Table 3.17 Gas velocity in pipes (39)

Table 3.18 Joint compensation thickness (42)

Table 3.19 Design stress (49)

Table 4.0 Result of process design (50)

Table 4.1 Flow rates and catalyst volume required (50)

Table 4.2 Key for schematic diagram of a catalytic converter (52)

Table 5.0 Pipe cost (54)

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Table 5.1 Catalyst cost (54)

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LIST OF FIGURES Page

Figure 2.0 Schematic of a catalytic converter unit (5)

Figure 2.1b Expanded views of a fixed bed reactor (6)

Figure 2.2 Sieve tray catalyst support (9)

Figure 2.3 Catalysts (10)

Figure 2.4 Mineral wool insulation (12)

Figure 2.5 Pipe insulation (13)

Figure 2.6 Mineral wool insulation K - Value (13)

Figure 2.7 Reactant SO2 over a differential volume (19)

Figure 3.0 Conversion fractions vs. temp and Equilibrium constant vs. temp curve (35)

Figure 3.1 Temperature and stages (36)

Figure 3.2 Torispherical (40)

Figure 3.3 Compensation openings (40)

Figure 3.4 Branch compensation (41)

Figure 3.5 Typical skirt support design (45)

Figure 3.6 Flange ring design (46)

Figure 4.0 Schematic diagram for catalytic converter (51)

CATALYTIC CONVERTER DESIGN Page xiv

LIST OF APPENDICES

Table 1: parameter variation in different temperature intervals

Table 3: composition and temperatures of deactivation, and precipitation for industrial SO2

Oxidation

Table 4: typical properties of the VK – WSA series

Table ll: constants for calculation of the specific heat capacity

Table lll: constants for calculating viscosity

Table lV: molecular weights of species in the bulk gas

Table A.5: Ergun constants for catalyst support balls

Table 6.6: summary of production cost

Figure 1: inter particle void fraction graph

Figure ll: inter particle void fraction vs. modified Reynolds number

Figure 2: vertical vessel purchased equipment cost