production of synthesis gas by steam reforming of

PRODUCTION OF SYNTHESIS GAS BY STEAM REFORMING OF METHANE 20,000 TON/YEAR Project Design Research Submitted to Faculty of Engineering / Chemical Engineering Department In Partial of Fulfillment of the Requirements for the Degree of Bachelor of Chemical Engineering

Supervised by: Mr.Ghazi Faisal

Prepared by:

Sajjad Khudhur Abbas Zahra'a Ali Hamid Wail Khalil Ibrahim

CERTIFICATION This is to certify that work incorporated in the project “Production of Synthesis gas by steam reforming of methane” has been carried out by Mr. Sajjad Khudhur Abbas , Mr. Wail Khalil Ibrahim and Mrs. Zahra'a Ali Hamid under my direct supervision and guidance in the Chemical Engineering Department, College of Engineering, Al-Muthanna University. The investigations have been carried out by the candidates themselves.

Signature: Name: Ghazi Faisal ( Supervisor)

Date:

/

/

Signature: Name: Assist Prof. Ahmed H. Ali (Head of Department)

Date:

/

/

CERTIFICATE We certify, as an examining committee, that we have read this project entitled “Production of Synthesis gas by steam reforming of methane”, examined the students Mr. Sajjad Khudhur Abbas , Mr. Wail Khalil Ibrahim and Mrs. Zahra'a Ali Hamid in its contents and found it meets the standards of the final year project for the degree of Bachelor of Science in Chemical Engineering.

Signature: Name: Assist Lect. Ghazi Faisal ( Supervisor) Date:

/

/

Signature:

Signature:

Name: Asst. Lect. Soud Ali Soud

Name: Assist Prof. Dr. Ahmed Hassan Ali

(Member)

(Chairman)

Date:

/

/

Date:

/

/

Approval of the Chemical Engineering Department Signature: Name: Assist Prof. Dr. Ahmed H. Ali (Head of Department) Date:

/

/

AKNOWLEGEMENT

I

would like to express my gratefulness to Allah S.W.T for giving me strength and wisdom in my research work. In preparing this project I was in

contact with many people, researchers, academicians, technicians and practitioners. They all have contributed to my understanding and valuable thoughts during my research. First and foremost, I would like to express my special thanks to my supervisor, Mr. Ghazi Faisal, for his encouragement, guidance, ideas which enlighten my curiosity, suggestion, advice and friendship. I am gratefully expressing my thanks to my whole family who understand me and gave me the spirit and continuing support to finish this study. I am grateful to my fellow collogues who also should be recognized for their moral support. Their view and tips are useful indeed, but it is not possible to list them all in this limited space.

‫إهداء‬ ‫ْزِ خطٕاد جش‪ٚ‬ئخ اخٕضٓب يزأيهّ ٔيزذًسخ د‪ٛ‬ث أْذ‪ٓٚ‬ب انٗ كم يٍ صسع ف‪ ٙ‬شفبْ‪ٙ‬‬ ‫االثزسبيخ ٔانذت ٔانسؼبدح ٔيٍ يُذُ‪ ٙ‬انذت انكج‪ٛ‬ش ٔانؼطف انغض‪ٚ‬ش ٔانٗ كم يٍ أَبس طشقبر‪ٙ‬‬ ‫انًظهًخ ثًؼشفزخ‬ ‫انٗ كم يٍ أضبء ثؼهًّ ػقم غ‪ٛ‬شِ أٔ ْذٖ ثبنجٕاة انصذ‪ٛ‬خ د‪ٛ‬شح سبئه‪ ّٛ‬فأظٓش ثسًبدزّ‬ ‫رٕاضغ انؼهًبء ٔ ثشدبثزّ سًبدخ انؼبسف‪ .... ٍٛ‬أسبرزر‪ٙ‬‬ ‫انٗ كم يٍ ػهًُ‪ ٙ‬انُجبح ٔ انصجش ‪ ,‬انٗ سجت ٔجٕد٘ ف‪ ٙ‬انذ‪ٛ‬بح ‪ ,‬انٗ انُٕس انز٘ ‪ُٛٚ‬ش ن‪ ٙ‬دسة‬ ‫انُجبح‬ ‫ٔانذ٘ انذج‪ٛ‬ت نك كم انزجه‪ٔ ٙ‬االدزشاو انٗ يٍ نى رأل جٓذا ف‪ ٙ‬رشث‪ٛ‬ز‪ ٔ ٙ‬رٕج‪ , ٙٓٛ‬انٗ يٍ‬ ‫رزسبثق انكهًبد نزخشج يؼجشح ػٍ يكٌُٕ رارٓب ‪ ,‬يٍ ػهًزُ‪ ٔ ٙ‬ػبَذ انصؼبة ‪ٜ‬صم انٗ يب آَب‬ ‫ف‪ , ّٛ‬انٗ يٍ ػهًزُ‪ ٙ‬انصًٕد يًٓب رجذنذ انظشٔف أي‪ٙ‬‬ ‫انٗ يٍ كبَٕا ‪ٚ‬ض‪ٛ‬ئٌٕ ن‪ ٙ‬انطش‪ٚ‬ق ٔ‪ٚ‬سبَذَٔ‪ٚٔ ٙ‬زُبصنٌٕ ػٍ دقٕقٓى إلسضبئ‪ ٔ ٙ‬انؼ‪ٛ‬ش ف‪ُْ ٙ‬بء‬ ‫‪ ..‬أخٕر‪ٙ‬‬

‫‪Signature:‬‬ ‫‪Name: Zahra'a Ali Hamid‬‬ ‫) ‪( Engineer‬‬

‫‪/‬‬

‫‪/‬‬

‫‪Date:‬‬

‫اْذاء‬ ٙ‫جز‬ٛ‫ خط‬, ‫يكشسّ ثذت انٗ ْبنّ ثٓبء ٔرٕد‬

Signature: Name: Sajjad Khudhur Abbas ( Engineer )

Date:

/

/

‫إهذاء‬ ‫إىل الٍنبىع الزي ال ميل العطاء إىل هي حاكج سعادحً خبٍىط هنسىجت هي قلبها إىل‬ ‫والذحً العضٌضة‪.‬‬ ‫إىل هي سعى وشقى ألًعن بالشاحت واهلناء الزي مل ٌبخل بشًء هي أجل دفعً يف طشٌق‬ ‫النجاح الزي علوين أى أسحقً سلن احلٍاة حبكوت وصرب إىل والذي العضٌض‪.‬‬ ‫إىل هي حبهن جيشي يف عشوقً وٌلهج بزكشاهن فؤادي إىل إخىاًً وأخىاحً‪.‬‬ ‫إىل هي سشًا سىٌاً وحني ًشق الطشٌق هعاَ حنى النجاح واإلبذاع إىل صهالئً و صهٍالحً‬

‫‪.‬‬

‫إىل هي علوىًا حشوفا هي رهب وكلواث هي دسس وعباساث هي أمسى وأجلى عباساث‬ ‫يف العلن إىل هي صاغىا لنا علوهن حشوفا وهي فكشهن هناسة حنري لنا سرية العلن والنجاح إىل‬ ‫أساحزحنا الكشام‪.‬‬ ‫‪Signature:‬‬ ‫‪Name :Wail Khalil Ibrahim‬‬ ‫)‪(Engineer‬‬ ‫‪/‬‬

‫‪/‬‬

‫‪Data:‬‬

Abstract Steam reforming of methane is the main industrial route to produce hydrogen and synthesis gas (a mixture of hydrogen and carbon monoxide) Syngas, or synthesis gas, is a fuel gas mixture consisting primarily of hydrogen, carbon monoxide, and very often some carbon dioxide. The name comes from its use as intermediates in creating synthetic natural gas and for producing ammonia or methanol. Syngas is combustible and often used as a fuel of internal combustion engines.

I

‫الملخص‬ ‫التكسٌر البخاري للمٌثان هو الطرٌقة الصناعٌة الرئٌسٌة إلنتاج الهٌدروجٌن و الغاز الصناعً‬ ‫( خلٌط من الهٌدروجٌن و أحادي أوكسٌد الكاربون)‪.‬‬ ‫الغاز الصناعً هو مزٌج غاز وقود ٌتكون بصورة رئٌسٌه من الهٌدروجٌن و احادي اوكسٌد‬ ‫الكاربون و على االغلب ثنائً اوكسٌد الكاربون ‪ .‬تسمٌته تأتً من استخدامه كمركب وسطً‬ ‫فً أنتاج الغاز الطبٌعً الصناعً وإلنتاج االمونٌا و المٌثانول ‪.‬‬ ‫الغاز الصناعً هو قابل لالحتراق وفً اغلب االحٌان ٌستخدم كوقود للمحركات ذات االحتراق‬ ‫الداخلً ‪.‬‬

‫‪II‬‬

List of Contents Content Abstract ………………………………………………………………………………………

Page I

List of content …………………………………………………………………………….. III Nomenclature …………………………………………………………………………….

IIII

List of Figures ……………………………………………………………………………..

VIII

List of Tables ………………………………………………………………………………

VIII

Chapter One : Introduction 1.1 Historical Overview ……………………………………………………...

2

1.2 Physical Properties of Hydrogen (H2) …………………………………...

4

1.3 Chemical properties of hydrogen ………………………………………..

7

1.4 Physical and Chemical Properties of Carbon Monoxide (CO) …………..

8

1.5 Physical properties of Carbon Dioxide (CO2) …………………………..

11

1.6 Synthesis gas …………………………………………………………….

12

1.7 Uses of syngas …………………………………………………………..

15

1.8 Production of Synthesis Gas …………………………………………….

16

1.9 Production of Synthesis Gas from Hydrocarbons ……………………….

17

1.10 Methane ………………………………………………………………..

18

1.11 Sources of Methane …………………………………………………..

19

1.12 Reactions and thermodynamics ………………………………………..

20

1.13 Steam Reforming (Tubular Reforming) ………………………………..

20

1.14 The Advantages of (SMR) ………………………………………………

22

1.15 Description of Reformer ………………………………………………..

23

III

Chapter Two: Material Balance 2.1 Introduction ………………………………………...……………………

26

2.2 Material Balance on Reactor (Reformer) …………………………………

32

2.3 Material Balance on Separator (Knockout) ………………………………

34

2.4 Material Balance on Absorber …………………………………………….

35

2.5 Material Balance on Stripper ……………………………………………...

46

Chapter Three: Energy Balance 3.1 Introduction …………………………………………..…………………

50

3.2: Energy Balance on Compressor …………………………………………

51

3.3 Energy Balance on Heat Exchanger ( 1 ) ………………………………..

53

3.4 Energy balance on pump …………………………………………………

55

3.5 Energy balance on furnace ……………………………………………….

56

3.6 Energy balance on Mixer ………………………………………………… 58 3.7 Energy balance on Reactor ''Reformer'' ………………………………….

59

3.8 Energy Balance on Heat Exchanger (2) ………………………………….

63

3.9 Energy Balance on Heat Exchanger (3)…………………………………..

66

3.10 Energy Balance on Condenser ( 1 ) ……………………………………… 67 3.11 Energy Balance on Absorber …………………………………………… 72 3.12 Energy Balance on Stripper …………………………………………….. 77 3.13 Energy Balance on Condenser ( 2 ) …………………………………….. 81 3.14 Energy Balance on Reboiler …………………………………………….

83

3.15 Energy Balance on Condenser ( 3 ) ……………………………………... 84

IV

Chapter Four: Equipment Design 4.1 Introduction …………..…………………………………………………

89

4.2 Separator ( Knockout ) Design …………………………………………… 90 4.3 Condenser design ………………………………………………………… 94

Chapter Five : Plant Layout & Treatment 5.1 GENERAL DESIGN CONSIDERATIONS 5.1.1 Health and Safety Hazards ……………………………………….. 101 5.1.2 Environmental Considerations ……………………………………

101

5.1.3 Plant Location …………………………………………………….

102

5.1.4 Plant Layout ………………………………………………………

103

5.1.5 Plant Operation and Control ……………………………………...

103

5.1.6 Utilities …………………………………………………………...

103

5.1.7 Storage …………………………………………………………...

104

5.1.8 Materials Handling ……………………………………………...

104

5.1.9 Structural Design ………………………………………………..

104

5.1.10 Patent Considerations …………………………………………

104

Chapter Six : Cost Estimation 6.1 Introduction …………..…………………………………………………

106

6.2 Separator Vessel (Knockout ) Cost ………………………………………. 107 6.3 Shell and tube heat exchanger '' condenser '' cost ………………………... 108

APPENDIX A .........................................................................................

109

APPENDIX B .........................................................................................

114

REFERENCES ........................................................................................

115 V

NOMENCLATUR

Symbol

Definition

Unit

F1

Amount of methane reacted in reaction 1

Kmole

F2

Amount of CO2 reacted in reaction 2

Kmole

X

Conversion

-

NT

Total number of moles

Kmole

Keq

Equilibrium Constant

-

R1

Amount of CH4 input to the refoemer

Kmole / hr

R2

Amount of Steam input to the refoemer

Kmole / hr

Y

Mole fraction of gases

-

Q

Amount of heat

KJ / hr

Cp

Heat Capacity

KJ / Kmole . K

hf

Specific Enthalpy at Saturated liquid

KJ / Kg

hg

Specific Enthalpy at Saturated vapor

KJ / Kg

ʎ

Latent heat

KJ / Kg

V

Vapor mass flow rate

Kg / s

L

Liquid mass flow rate

Kg / s

µL

Liquid Viscosity

N.s / m2

µv

Vapor Viscosity

N.s / m2

𝜌

Liquid density

Kg / m3

ρ

Vapor density

Kg / m3

Gs

Mass Flux in shell side

Kg / m2 .s

P

Total Pressure

Pa

ΔP

Pressure drop

Pa

R

Universal gas constant

KJ / Kmole . K

Dv

Diameter of Vessel

m

M.wt

Molecular weight

Kg / Kmole

ho

Outside fluid heat transfer coefficient

W / m2 .℃

hi

Inside fluid heat transfer coefficient

W / m2 .℃

hof

Outside fouling coefficient

W / m2 .℃

hif

Inside fouling coefficient

W / m2 .℃ VI

Symbol

Definition

Unit

Uo

The Overall heat transfer coefficient

W / m2 .℃

W

Work of pump

KJ / Kmole

Ep

Efficiency of pump

-

di

Tube inside diameter

m

do

Tube outside diameter

m

ΔTLM

The Log mean temperature difference

Pt

Tube Pitch

℃ m

Db

Banddle Diameter

m

Ds

Shell Diameter

m

Nt

Number of tubes

-

F

Temperature Correction factor

-

de

Equivalent diameter

m

ut

Tube velocity

m/s

us

Settling Velocity

m/s

Jf

Friction Factor

-

L

Tube Length

m

Np

Number of tube side passes

-

Baffle Spacing

m

Kw

Thermal Conductivity of the tube wall material

W / m .℃

(hc)b

Mean condensation film coefficient

W / m2 .℃

Γ Nr

Horizontal tube loading

Kg / m.s

Average number of tubes in a vertical center row

-

Wc

Total Condensate Flow

Kg / s

Re

Reynold's number

-

VII

List of Figures Figure 2-1 2-2 3-1 3-2 3-3 3-4 4-1 4-2 4-3 4-4 6-1 6-2

Table

Title

Appendix Flow sheet of Material Balance -----Equilibrium constants as a function of temperature A Approximate polytropic efficiencies centrifugal A and axial-flow compressors Generalized Compressibility Chart specific heat for monoethanolamine, diethanolamine & triethanolamine. Flow sheet of Energy Balance Knockout drum Shell-bundle clearance Shell-side friction factors, segmental baffles Tube-side friction factors

Vertical Pressure Vessels. Time base mid 2004 Shell and tube heat exchangers. Time base mid2004

List of Tables Title

Page 27 109 110

A A

110 111

----------A A A A A

87 93 111 112 112 113 113

Appendix

Page

1-1 1-2

Physical properties of hydrogen Some physical and thermodynamic properties of gaseous n-hydrogen

-------------------------

5 7

1-3 1-4 1-5

Physical properties of Monoxide The Physical Properties of carbon Dioxide Examples of H2 , CO and Synthesis gas products The physical properties of Methane gas Production Technology Scorecard

-------------------------------------

9 11 15

-------------------------

18 24

Worksheet of the process compositions of stream leaving from the reformer compositions of stream leaving from knockout

-------------

28 34

1-6 1-7 2-1 2-2 2-3

------------35 -------------

2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-11 4-1 4-2

compositions of stream leaving from Absorber Molecular weight of gases Mole fraction & Molecular weight for each component output from absorber Input & output streams of Reformer Input & output streams of knockout Input & output streams of Absorber Input & output streams of Absorber Input & output streams of Stripper Typical overall coefficients Estimation of the Bundle Diameter

36 ------------------------------------------------------------------------------------------------Appendix B Appendix B

37 37 39 40 41 45 48 114 114 VIII

IX

CHAPTER TWO MATERIAL BALANCE

25

2.1 Introduction In this chapter, steam methane reforming is used to produce synthesis gas with capacity of ( 20,000 Ton / year ) was studied. Material balance was made for the complete process starting from the raw materials ( methane and H 2O ) and ending with the products ( CH4 , CO , CO2 and H2 ) . Material balance was made on reactor (reformer), separator (Knockout), absorber, and stripper. Methane will mix with steam at 400 ℃ and then reacted in reformer at 800 ℃ to produce ( CH4 , CO2 , CO , H2 and H2O ) The products will enter to knockout to separate water from the gases. In absorber column ,CO2 amount will decrease approximately 95% of the feed to the absorber by react with Mono ethanol amine with water coming from stripper ''In continuous process''.

26

27

Table (2-1) :- Worksheet of the process N. Stream

Compositions

Mass Flow

Temperature

Pressure

rate (kg/hr.)

℃

'atm'

1

methane

1749.64

25

1

2

methane

1749.64

208.5

8

3

methane

1749.64

400

8

4

water

6056.91

25

1

5

water

6056.91

25

1.5

6

steam

6056.91

400

1.5

7

steam , CH4

7851.55

400

8

CH4,H2O,CO CO2,H2 CH4,H2O,CO CO2,H2

7849.531

800

20

7849.531

600

19

10

CH4,H2O,CO CO2,H2

7849.531

400

18

11

CH4 ,H2O,CO CO2 ,H2

7849.531

200

18

12

H2O

3430.230

200

18

13

CH4 , CO CO2 , H2

4419.301

200

18

14

CH4 , CO CO2 , H2

2778.327

52.9

1

15

MEA , H2O

24543.771

52.9

1

9

(HOCH2NH3)2CO3 16

CO2 , H2O

20798.596

100

1

17

CO2

1640.936

100

1

18

MEA , H2O

23947.075

116

1

19

MEA , H2O

23947.075

25

1

28

Basis : 1

of methane

Ratio :

=

Reaction (1): CH4 + H2O 1 3 - F1 -F1 1-F1

CO + 3H2 0 0 +F1 +3F1

3-F1

F1

X1 = 95 %

3F1

Reaction ( 2 ): CO + F1 -F2 F1- F2

H2O 3-F1 -F2 3 - F1- F2

CO2 + H2 0 0 +F2 +F2 F2 F2

X2 = ?

Number of total moles in two Reaction : Total moles = N CH4 + N H2O + N CO + N H2 +N CO2 Total moles = [(1-F1) +(3-F1-F2)+(F1-F2)+(3F1+F2)+F2] = 4+2F1 For reaction (1) : Conversion = 95% of CH4

…………..

[ industrial fuel gas ]

X1= Conversion = 0.95 = So : F1= 0.95

29

For reaction (2) : CO + H2O YCO =

CO2 + H2

=

(

)

YH2O = YCO2 = YH2 = Keq..=

[

] [

[

]

] [

]

*By using figure (2-2,Appendix A) we found (K) at T=800 C . Tk = 273 + Tc = 273 + 800 =1073 K (

)

Ln Keq = 0.1 (Y-axis)

(

1.105 =

1.105

) (

(

)

) ( (

(

Keq. = 1.105

)

) (

)

) (

)

F1= 0.95 ( ( 0.105

) ) (

)

- 6.165 F2 + 2.151 = 0

30

√(

a= 0.105

)

b = - 6.165 √(

F2 =

c =2.151

)

F2 = either : F2 = 58.362

X2 =

''ignore'' or

F2 = 0.352 X2 =

( )

X2 = X2= 0.3705 Conversion for reaction (2) = 37.05 %

31

2.2 Material Balance on Reactor (Reformer):

Reformer Ni catalyst

H2O

CO2 H2 H2O CO CH4

CH4

R1 = Moles of CH4 R2 = Moles of H2O Reaction (1) : CH4

+

H2O

Conversion =

CO + 3H2 ,

X1=

Reacted = ( input ) * X1    

Reacted of CH4 = R1 X1 Reacted of H2O = R1 X1 Produce of CO = R1 X1 Produce of H2 = 3R1 X1

(Kmole / hr) (Kmole / hr) (Kmole / hr) (Kmole / hr)

32

Reaction (2): CO + H2O

CO2 + H2

Reacted = ( Input ) * X2    

Reacted of CO = R1 X1 X2 Reacted of H2O = R1 X1 X2 Produce of CO2 = R1 X1 X2 Produce of H2 = R1 X1 X2

In ± reacted = out

(Kmole / hr) (Kmole / hr) (Kmole / hr) (Kmole / hr) (For two reactions)

Out of CH4 = R1 – R1 X1 = R1 – 0.95 R1 = 0.05 R1 Out of H2O = R2 – (R1X1+R1X1X2) = 3R1 – (R1X1+R1X1X2) = 3R1 – (0.95 R1 +0.95 *0.37 R1) = 1.699 R1 Out of CO = R1 X1 – (R1 X1 X2 ) = 0.95 R1 – (0.95 *0.37 R1) =0.95 R1 -0.35 R1 = 0.6 R1 Out of H2 = 3 R1 X1 + R1 X1 X2 = 3*0.95 R1 +0.95*0.37*R1 =3.2 R1 Out of CO2 = Input CO2 + Reacted CO2 =

0

+ R1 X1 X2

= 0.35 R1

33

Table (2-2) : compositions of stream leaving from the reformer .

Component CH4 H2O CO H2 CO2

output 0.05R1 1.699R1 0.6R1 3.2R1 0.35R1 Total = 5.899 R1

Y 0.008476 0.288015 0.101712 0.542464 0.059332 ∑

%Y 0.8476 28.8015 10.1712 54.2464 5.9332 ∑

2.3 Material Balance on Separator (Knockout) :  Number of input moles is equal to output     

CH4 H2O CO H2 CO2

:- input – reacted = out = 0.05 R1 :- input – reacted = out = 1.699 R1 :- input – reacted = out = 0.6 R1 :- input – reacted = out = 3.2 R1 :- input – reacted = out = 0.35 R1

'' vapor'' ''liquid '' '' vapor '' '' vapor '' '' vapor '' CH4 = 0.05 R1 CO = 0.6 R1 CO2 = 0.35 R1 H2 = 3.2 R1

CH4 = 0.05 R1 H2O = 1.699 R1 CO = 0.6 R1 H2 = 3.2 R1 CO2 = 0.35 R1

Knockout

H2O = 1.699 R1 34

Table (2-3) : compositions of stream leaving from knockout .

Components CH4 CO H2 CO2 Components H2O

Output from Knockout as a vapor 0.05 R1 0.6 R1 3.2 R1 0.35 R1 Output from Knockout as a liquid 1.699 R1

2.4 Material Balance on Absorber :

CH4 CO2 CO H2

20% MEA 80% H2O

Absorber

CH4 = 0.05 R1 CO = 0.6 R1 H2 = 3.2 R1 CO2 = 0.35 R1

MEA H2O (HOCH2NH3)2CO3

35

 Recovery = 95% of CO2 CH4 :-

input = output = 0.05 R1

CO :-

input = output = 0.6 R1

H2

input = output = 3.2 R1

:-

CO2 :-

output = input – Absorbed Absorbed = 0.95 * 0.35 R1 Output = 0.35 R1 – 0.95 * 0.35 R1 Output ''CO2'' = 0.0175 R1

Number of total moles [output from Absorber] NT = N CH4 + N CO +N H2 + N CO2 NT = 0.05 R1 + 0.6 R1 + 3.2 R1 +0.0175 R1 NT = 3.8675 R1

(Total Moles Produced)

Mole fraction [output from Absorber] Y CH4 = Y CO = Y H2 = Y CO2 = Table (2-4) : compositions of stream leaving from Absorber .

Component CH4 CO H2 CO2

No. of moles 0.05 R1 0.6 R1 3.2 R1 0.0175 R1 Total =3.8675 R1

Mole fraction 0.01293 0.1551 0.8274 0.00452 ∑

Y% 1.293 15.51 82.74 0.452 ∑

36

Production capacity = 20,000 year = 300 day Production Capacity = = 2777.777 Kg/hr Number of moles = Molecular weight of mixture = ∑

(

)

(M.wt)mix = Y CH4 * M.wt CH4 + Y CO * M.wt CO+Y H2*M.wt H2 + YCO2 *M.wt CO2 Table (2-5) : Molecular weight of gases .

Molecular weight for each component CH4 16 CO 28 H2 2 CO2 44 (M.wt) mixture = 0.01293 * 16 + 0.1551 *28 + 0.8274 *2 +0.00452*44 = 6.40336 Number of moles =

= 433.799

Table (2-6) : Mole fraction & Molecular weight for each component output from absorber

Component CH4 CO H2 CO2

Mole fraction 0.01293 0.1551 0.8274 0.00452

M.wt 16 28 2 44

Yi * M.wt 0.20688 4.3428 1.6548 0.19888 ∑ Yi * (M.wt)i =6.40336

37

Total moles [output from Absorber] = production capacity 3.8675 R1 = 433.799

,

R1 = 112.165

To find R2 ,We use a ratio :

R2 = 3 R1 R2 = 3 *112.165 = 336.495

Reformer :  Input [ CH4 ] = R1 * M.wt = 112.165 * 16 = 1794.64  Input [ H2O ] = R2 * M.wt = 336.495 *18 = 6056.91 o Out CO = 0.6 R1 *M.wtCO = 1884.372 o Out CO2 = 0.35 R1*M.wtCO2 = 1727.341 o Out H2 = 3.2 R1 * M.wtH2 = 717.856 o Out H2O = 1.699 R1 *M.wt H2O = 3430.230 o Out CH4 = 0.05 R1* M.wtCH4 = 89.732

38

Table (2-7) : Input & output streams of Reformer .

Components CH4 H2O CO CO2 H2 H2O CH4

Input ( ) 112.165* M.wt CH4 1794.64 336.495* M.wt H2O 6056.91 -----------------------------------------

output ( ) --------------------------------0.6 R1 *M.wtCO 1884.372 0.35 R1*M.wtCO2 1727.341 3.2 R1 * M.wtH2 717.856 1.699 R1 *M.wt H2O 3430.230 0.05 R1* M.wtCH4 89.732

For checking: Input = 1794.64 + 6056.91 = 7851.55 kg/hr Output = 1884.372 + 1727.341 + 717.856 + 3430.230 + 89.732 = 7849.531 kg/hr

CH4 =89.732

H2O=3430.23 CH4 = 1794.64

Reformer Ni catalyst

CO=1884.372 CO2=1727.341 H2=717.856

H2O = 6056.91

39

Separator [knockout]: Table (2-8) : Input & output streams of knockout .

Component CH4 H2O CO CO2 H2

In ( ) 89.732 3430.230 1884.372 1727.341 717.856 ∑in=7849.531

Out( ) 89.732 3430.230 1884.372 1727.341 717.856 ∑out=7849.531

For checking: Input = 1884.372 + 1727.341 + 717.856 + 3430.230 + 89.732= 7849.531 kg/hr Output = 1884.372 + 1727.341 + 717.856 + 3430.230 + 89.732 = 7849.531 kg/hr

CH4 = 89.732 CO = 1884.372 CO2 = 1727.341 H2 =717.856

CH4 = 89.732 CO = 1884.372

Knockout

CO2 = 1727.341 H2 =717.856 H2O = 3430.23

H2O = 3430.23

40

Absorber : Table (2-9) : Input & output streams of Absorber .

Component CH4 CO H2 CO2

In ( ) 89.732 1884.372 717.856 1727.341

Out ( ) 89.732 1884.372 717.856 86.367

CH4 = 89.732

20% MEA 80% H2O

CO = 1884.372 H2 = 717.856 CO2 = 86.367

Absorber

CH4 = 89.732 CO = 1884.372 H2 = 717.856 CO2 = 1727.341

MEA H2O (HOCH2NH3)2CO3

41

The reaction in Absorber is : 2NH2CH2CH2OH + CO2 + H2O

(HOCH2NH3)2CO3

Output amounts from '' Absorber '' are: Out = In ± Reacted  For CH4 : Out (CH4) = In(CH4) – Reacted (CH4)

Reacted = 0

Out = In =89.732  For CO : Out = In – Reacted

Reacted = 0

Out CO = In ( CO ) = 1884.372  For H2 : Out = In – Reacted

Reacted = 0

Out (H2) = In = 717.856  For CO2 : Recovery of CO2 = 95 % Absorbed of CO2 = 0.95 * Input CO2 = 0.95 * 1727.341 =1640.974 Out CO2 =In – Absorbed = 1727.341 – 1640.974 = 86.367

42

From the Chemical reaction : 2NH2CH2CH2OH + CO2 + H2O

(HOCH2NH3)2CO3

To find Input of MEA : 2NH2CH2CH2OH

CO2

2

1

X

0.35 R1

X = 2 *0.35 R1 = 2 * 0.35 * 112.165 = 78.515

''Input of MEA''

Molecular weight of ''MEA'' =61 Input MEA = 78.515 * 61 = 4789.415 To find Input of H2O : …………………………………. ''1'' ………………………………...... ''2'' Dividing eq'1' on eq'2' :

Input H2O = 19157.66

43

To find output from the following equation : In ± Reacted = out For H2O Out = In – Reacted Input of H2O =

=1064.314

Absorbed (Reacted) of CO2 = 0.95 * 0.35 R1 = 0.95 * 0.35 * 112.165 =37.294 CO2

H2O

1

1

37.294

X

X=37.294

(Reacted of H2O)

Out H2O = 1064.314 -37.294 = 1027.02

= 18486.36

For (HOCH2NH3)2CO3 : Output = Input + Reacted Output = Reacted CO2

(HOCH2NH3)2CO3

1

1

37.294

X

X=37.294

[output of (HOCH2NH3)2CO3]

Molecular weight of (HOCH2NH3)2CO3 = 156 Output of (HOCH2NH3)2CO3 = 37.294 *156 = 5817.864

44

For NH2CH2CH2OH : Output = Input – Reacted NH2CH2CH2OH

CO2

2

1

X

37.294

X=74.588

[ reacted of MEA ]

Output of MEA = 78.515 – 74.588 = 3.927 Kmol /hr = 239.547

Table (2-10) : Input & output streams of Absorber .

Component CH4 CO H2 CO2 NH2CH2CH2OH H2O (HOCH2NH3)2CO3

Input 89.732 1884.372 717.856 1727.341 4789.415 19157.66 0

Output 89.732 1884.372 717.856 86.367 239.547 18486.36 5817.864

For checking : Input = 89.732 + 1884.372 + 717.856 + 1727.341 + 4789.415 + 19157.66 = 28366.376 kg/hr Output = 89.732 + 1884.372 + 717.856 + 86.367 + 4789.415 + 19157.66 = 26725.402 kg/hr

45

2.5 Material Balance on Stripper:

CO2

H2O (HOCH2NH3)2CO3 NH2CH2CH2OH

Stripper

MEA H2O

The chemical reaction in stripper is : (HOCH2NH3)2CO3

2NH2CH2CH2OH + CO2 + H2O

Input ± Reacted = output For (HOCH2NH3)2CO3 : Input – reacted = output Input = reacted =37.294 =5817.864

46

For CO2 Output CO2 = Input CO2 + Reacted CO2 Output CO2 = reacted CO2 (HOCH2NH3)2CO3

CO2

1

1

37.294

X

X= 37.294

[output of CO2]

Output of CO2 =37.294 *44 = 1640.936 For H2O Output H2O = Input H2O + Reacted H2O = 1027.02 + 37.294 = 1064.314 = 19157.66 For NH2CH2CH2OH Output = Input +Reacted = 3.927 + 74.588 = 78.515

* 61

= 4789.415

47

Table (2-11) : Input & output streams of Stripper .

Component H2O (HOCH2NH3)2CO3 NH2CH2CH2OH CO2

Input 18486.36 5817.864 239.547 0

Output 19157.66 0 4789.415 1640.936

For checking : (

MEA =

(

)

)

(

=

= 20% (

H2O =

)

(

)

) (

)

= For checking : Input = 18486.36 + 5817.864 + 239.547 = 24543.771 kg/hr Output = 19157.66 + 4789.415 + 1640.936 = 25588.011 kg /hr

48

CHAPTER THREE ENERGY BALANCE

49

3.1 Introduction Energy balance was made on compressor, heat exchangers, mixer, pump, furnace, reactor (reformer), condenser, absorber, and stripper. Methane will enter at 25℃ to compressor to rise it's pressure and temperature ,then heated to 400℃ by heat exchanger. Water will enter to furnace at 25℃ to rise it's temperature to 400 ℃. In mixer the methane and steam will mixed and then enter the reformer at 400℃.The reaction will happened at 800℃ inside the tubes of reformer. The product gases will cooled from 800℃ to 200℃ by heat exchangers to condense the steam to water liquid and then separate the water from the gases by knockout. The CO2 amount decreased approximately 95% in the Absorber by react with Mono ethanol amine and the reaction will occur at 38℃ inside the Absorber . In stripper , CO2 will separated from the feed and recycle Mono ethanol amine with H2O back to absorber.

50

3.2: Energy Balance on Compressor:

CH4 T1=25 ℃ P=1 atm

=(

Compressor

)

CH4 T2= ? P2 =8 atm

…….[J.M. Smith & H.C Van ness, Introduction to chemical engineering thermodynamics, 4thedition]

For Polyatomic Gas:

Cv = R

, Cp =

R

( )

T2 = 481.53 K. T2 =208.5 ˚C.

51

*( )

+

…….[J.M. Smith & H.C Van ness, Introduction to chemical engineering thermodynamics, 4thedition]

n= 𝜌

= 112.165 Kmole / hr. = 0.717 Kg / m3.

m = 1794.64 Kg / hr.

= 0.695 m3/ sec.

Volumetric flow rate = By using Figure (3-1,Appendix A ) Efficiency = Ep = 67 % For Methane: Pc = 45.99 bar , Tc = 190.6 K

Pr =

=

= 0.021 , Tr =

=

= 1.563

From Figure (3-2,Appendix A) We Find Z = 0.98

*( ) Compressor Power =

=

+ = 4984.451 KJ / Kmol = 231.791 Kw.

52

3.3 Energy Balance on Heat Exchanger ( 1 ): Tin=500 ℃ steam

CH4 T=400 ℃

CH4 T=208.5 ℃

Tout=350 ℃ steam

Q= ∫

dt

Cpgas = A + BT + CT2 + DT3 +ET4

(KJ/kmol.k)

Where A, B, C, D, and E are constant from table (3-1,Appendix B)

QCH4 = (

) * [34.942(673 – 481.5) – (

+(

)*( 6733– 481.53) – (

+(

)*( 6735 – 481.55)]

)*( 6732 – 481.52) )*( 6734 – 481.54)

Q = 1090073.309 kJ / hr

53

Heating medium: Tin=500 ℃= 773 K Tout = 350 ℃ = 623 K From steam table : At T=500 ℃

H1= 3488.1 KJ/kg

AT T=350 ℃

H2=3175.6 KJ/kg

Q = m ΔH m=

= 3488.234 kg/hr

54

3.4 Energy balance on pump: T=25 ℃ H2O

T=25 ℃ H2O

W= - ∫

= - v * (P2 - P1)

mH2O= 6056.91 Kg/hr 𝜌 H2O = 997 Kg/m3

at 25 ℃

𝜌

P1= 1 bar = 100 Kpa P2= 1.5 bar = 150 Kpa Ws = - v * ∆P =-

* (150 -100 )

= - 0.05 kJ/ kg = 0.75 Wact. = Power =

…………….. =

[ Perry ]

= 0.067 KJ / kg = 67 J/kg

=

= 150 w

55

3.5 Energy balance on furnace :

H2O 25 ℃

steam 400 ℃

Furnace

Q2

Q1 Liquid 25 ℃

Sat. 112 ℃ liquid

Q3 Sat. 112 ℃ vapor

400℃ Superheated steam

Path (1) n=

= 336.495 kmol/hr

Q1= 336.495 * [33.933*(385- 298) – ( +(

)*( 3853 – 2983) – (

+(

)*( 3855 – 2985)]

)*( 3852 - 2982) )*( 3854 – 2984)

Q1 = 992276.645 KJ/hr

56

Path (2) Q2 = m * ʎ ʎ = hg - h f From steam table hf = 469.8 KJ/kg

hg=2694.3 KJ/kg

ʎ= 2224.5 KJ/kg Q2 = 6056.91 * 2224.5 = 13473596.3 KJ/hr Path (3) Q3 = 336.495 * [33.933*(673- 385) – ( +(

)*( 6733 – 3853) – (

+(

)*( 6735 – 3855)]

)*( 6732 - 3852) )*( 6734 – 3854)

Q3 = 3445493.443 KJ/hr QTotal = Q1+Q2+Q3 = 17911366.39 KJ/hr

57

3.6 Energy balance on Mixer :

CH4 T=400℃ H2O T=400 ℃

Mixer

H2O & CH4 Tmix = 400 ℃

QH2O = 17911366.39 KJ/hr Q CH4 = 1090073.309 kJ / hr. Qtotal = QH2O + Q CH4 = 19001439.7 KJ/hr

58

3.7 Energy balance on Reactor ''Reformer'' :-

CH4 , T =400 ℃

CH4 CO CO2 H2O H2 T= 800 ℃

T = 800 P = 20 atm

H2O T= 400 ℃

800 ℃

400 ℃ Path (3) Q3

Path (1) Q1

25 ℃

25 ℃ Path (2) Q2

59

For path 1 Tin = 400 ℃ = 673 K Tout = 25 ℃ = 298 K Q1 = Q CH4 + Q H2O Q CH4 = n ∫ =

( )

=112.165 * 17149.271 = - 1923547.982 KJ/hr QH2O = n ∫ ( ) = 336.495 * 13188.232 = - 4437774.127 KJ/hr Q1 = Q CH4 + Q H2O = -1923547.982 – 4437774.127 = - 6361322.109 KJ/hr

60

Path 2 T1=T2 =25 ℃= 298 K CH4 + H2O CO + H2O

CO + 3H2 CO2 + H2

Q2= ∆Hr =∆Hr1 + ∆Hr2 For reaction (1) : ∆Hr1=∑ni * ∆Hf (prod.) - ∑ni*∆Hf (reacted) ∆Hr1 = (nCO * ∆HfCO + n H2 *∆Hf H2) – (n CH4 * ∆Hf CH4 + n H2O * ∆Hf H2O) *Standard enthalpies can be obtained from '' thermodynamic Tables ,J.M.Smith)

∆Hr1= [1*(-110525) +3 *0] – [ 1*-74520 + 1 *(-241818)] = 205813 kJ/hr For reaction (2): ∆Hr2 =∑ni * ∆Hf (product) - ∑ni*∆Hf (reacted) ∆Hr2 = (nCO2 *∆Hf CO2 + n H2 * ∆Hf H2) - (nCO *∆Hf CO + nH2O *∆Hf H2O) =[1*(-393509)+1*0] - [1*(-110525)+1*(-241818)] = - 41166 kJ/hr Q2 = ∆Hr1 + ∆Hr2 =205813 - 41166 = 164647 KJ/hr

61

For path( 3) Q3 = QCH4 + Q H2 + QH2O+QCO +QCO2 Tin = 25 ℃ = 298 K

,

Tout = 800 ℃ = 1073 K

Q CH4 = n ∫ = QH2O =

= 5.608 * 43914.426 = 246272.101 kJ/hr = 190.568 * 290.568 = 5536736.374 KJ/hr

QH2O = 5536736.374 KJ/hr QCO = QCO2 = QH2 =

= 67.299 * 24136.139 = 1624338.019 KJ/hr = 39.257 * 37095.736 = 1456267.308 KJ/hr = 8212325.402 KJ/hr

Q3 = 246272.101 + 5536736.374 + 1624338.019 + 1456267.308 + 8212325.402 = 17075939.2 KJ/hr Qtotal = Q1 +Q2 + Q3 = - 6361322.109 + 17075939.2 + 164647 = 10879264.09 KJ/hr

62

3.8 Energy Balance on Heat Exchanger (2):

T in=25℃ CH4 CO2 CO H2 H2O

CH4 CO2 CO H2 H2O

T1= 800 ℃

T2= 600 ℃

T out=70℃

Cpmix = ∑ Yi * Cpi Cpmix = YCH4 * CpCH4 + YH2O * CpH2O + YCO * CpCO + YCO2 * CpCO2 + YH2 * CpH2

Table (3-1) :- compositions of stream leaving from the reformer .

Component CH4 H2O CO CO2 H2

Number of Moles (kmole / hr) 5.608 190.56 67.299 39.257 358.92 Total = 661.644

Y% 8.47*10-3 0.288 0.101 0.059 0.542 ∑=1

63

CpCH4 = 0.295 – (3.384*10-4 ) T +(1.624*10-6 ) T2 – (1.296*10-9 ) T3 + (3.33*10-13) T4 CpH2O = 9.772 – (2.424*10-3) T + (8.612*10-6 ) T2 – (5.1336*10-9 ) T3 + (1.063*10-12) T4 CpCO = 2.985 – (6.646 *10-4 ) T + (2.033*10-6 ) T2 – (1.2349 *10-9 ) T3 +(2.284*10-13) T4 CpCO2 = 1.618 + (2.496 *10-3 ) T – (1.153*10-6 ) T2 + (2.358*10-10) T3 – (1.762*10-14) T4 CpH2 = 13.766 + 0.0109 T – (2.0893*10-5) T2 +(1.727*10-8) T3 – (4.747*10-12) T4

Cpmix = 28.436 + (9.969*10-3) T – (9.777*10-6 ) T2 + (9.841*10-9) T3 - (3.14*10-12) T4

QT = ∫

dt

QT = 661.644 [ 28.436*(873-1073) + ( –(

)*(8733 – 10733) + (

–(

)*(8735 – 10735)]

)*(8732 - 10732) )*(8734 – 10734)

QT = - 4649260.156 kJ / hr .

64

Cooling medium: Use " H2O Liquid " Tin = 25 ℃ = 298 K. Tout = 70 ℃ = 263 K. From Steam table: At Tin = 25 ℃

,

H1 = 104.8 KJ / kg.

At Tout = 70 ℃

,

H2 = 293 KJ / kg.

Q = m ∆H m=

= 24703.826 kg / hr.

65

3.9 Energy Balance on Heat Exchanger (3): T in=25℃ CH4 CO2 CO H2 H2O

CH4 CO2 CO H2 H2O

T1= 600 ℃

T2= 400 ℃

T out=70℃

QT = 661.644 [ 28.436*(673 - 873) + (

)*(6732 - 8732)

–(

)*(673 3 – 8733) + (

)*(6734 – 8734)

–(

)*(6735 – 8735)]

QT = - 4463482.117 kJ / hr

Cooling medium: Use " H2O Liquid " From Steam table: At Tin = 25 ℃

,

At Tout = 70 ℃ , m=

H1 = 104.8 KJ / kg. H2 = 293 KJ / kg.

= 23716.695 kg / hr.

66

3.10 Energy Balance on Condenser ( 1 ):

T in=25℃ CH4 CO2 CO H2 H2O

CH4 CO2 CO H2 H2O

T1= 400 ℃

T2= 200 ℃

T out=50℃

In this condenser, we want to separate the water steam, therefore from steam table, we found the saturation temperature of water at( P = 18 bar ) is (Tsat.= 208 ℃)(by interpolation).

400 ℃

200 ℃

QT

For H2O: 400 ℃

Q1

208 ℃

H2O (Superheated)

Sat.Vap

Q2

208 ℃ Sat.Liq

Q3

200 ℃ Liquid

67

QT = QCH4 + QCO + QCO2 + QH2 + QH2O QH2O = Q1 + Q2 + Q3 T1 = 400 ℃ = 673 K. T2 = 208 ℃ = 481 K. T3 = 208 ℃ = 481 K. T4 = 200 ℃ = 473 K. For H2O Path (1): T1 = 400 ℃ = 673 K. T2 = 208 ℃ = 481 K.

)*(4812 - 6732)

) * [33.933*(481- 673) – (

Q1= ( +(

)*(4813 – 6733) – (

+(

)*( 4815 – 6735)]

)*( 4814 – 6734)

Q1 = - 1318564.097 kJ / hr . Path (2): Q2 = m*ʎ ʎ = hf – h g From Steam table: At

Tsat.= 208 ℃ , hf = 888.6 KJ / kg.

,

hg = 2795.3 KJ / kg.

ʎ = 888.6 - 2795.3 = - 1906.7 KJ / kg. Q2 = - 1906.7 * 3430.23 = - 6540419.541 kJ / hr . 68

Path (3): T3 = 208 ℃ = 481 K. T4 = 200 ℃ = 473 K. Q3 = (

)*(4732- 4812)

) * [33.933*(473- 481) – (

+(

)*(4733- 4813) – (

+(

)*(4735- 4815)]

)*(4734- 4814)

Q3 = - 53326.347 kJ / hr . QH2O = Q1 + Q2 + Q3 = - 1318564.097 - 6540419.541 - 53326.347 = - 7912309.985 kJ / hr . For CH4 QCH4 = (

) * [34.942(473 – 673) – (

+(

)*(4733 – 6733) – (

+(

)*(4735 – 6735)]

)*(4732 – 6732) )*(4734 – 6734)

QCH4 = - 56645.006 kJ / hr .

69

For H2 QH2 = (

) * [25.399*(473 – 673) + (

-(

)*(4733 – 6733) + (

-(

)*(4735 – 6735)]

)*(4732 – 6732) )*(4734 – 6734)

QH2 = - 2106881.517 kJ / hr . For CO QCO = (

) * [29.556*(473 – 673) – (

+(

)*(4733 – 6733) – (

+(

)*(4735 – 6735)]

)*(4732 – 6732) )*(4734 – 6734)

QCO = - 408504.526 kJ / hr .

For CO2 QCO2 = (

) * [27.437*(473 – 673) + (

-(

)*(4733 – 6733) + (

-(

)*(4735 – 6735)]

)*(4732 – 6732) )*(4734 – 6734)

QCO2 = - 360681.499 kJ / hr .

70

QT = QCH4 + QCO + QCO2 + QH2 + QH2O = - 56645.006 - 408504.526 - 360681.499 - 2106881.517 - 7912309.985 = - 10845022.53 kJ / hr .

Cooling medium: Use " H2O Liquid " From Steam table: At Tin = 25 ℃ At Tout = 50 ℃

, H1 = 104.8 KJ / kg. , H2 = 209.3 KJ / kg.

Q = m ∆H m=

= 103780.119 kg / hr.

71

3.11 Energy Balance on Absorber:

CH4 CO2 CO H2

T=25℃

20% MEA 80% H2O

T= ?

Absorber

CH4 CO2 CO H2

20% MEA T=? 80% H2O (HOCH2NH3)2CO3

T= 200 ℃

200 ℃ Path 1

T=? Path 3 38 ℃

38 ℃ Path 2

72

Path (1): T1 = 200 ℃ = 473 K. T2 = 38 ℃ = 311 K. Q1 = QCH4 + QH2 + QCO + QCO2 + QMEA + QH2O For CH4 QCH4 = (

) * ( - 6572.966)

= - 36862.836 kJ / hr . For H2O QH2O = (

)*(437.724)

= 465875.975 kJ / hr . For CO QCO = (

) * ( - 4763.395)

= - 320571.72 kJ / hr . For MEA QMEA = m Cp ∆T Cp From Figure (3-3,Appendix A ) = 0.675 cal / gm .℃ Cp = 0.675 Cp = 2.821

℃

*

*

*

℃

m = 4789.415 kg / hr. QMEA = 175642.216 kJ / hr .

73

For CO2 QCO2 = (

) * ( - 6677.67 )

= - 262150.299 kJ / hr . For H2 QH2 = (

)*( - 4710.233)

= - 1690634.51 kJ / hr . Q1 = QCH4 + QH2 + QCO + QCO2 + QMEA + QH2O = - 36862.836 - 1690634.51 - 320571.72 - 262150.299 + 175642.216 + 465875.975 = - 1668701.174 kJ / hr . Path (2): 2 NH2CH2CH2OH + CO2 + H2O

(HOCH2NH3)2CO3

Q2 = ∆Hr = 72

…………….. (Perry)

Absorbed of CO2 = 1640.974 kg / hr. Number of moles of CO2 (Absorbed) =

= 37.294 Kmole / hr.

Q2 = 72 * 1000 * 37.294 = 2685168 kJ / hr. Qin – Qreact = Qout Qin = Q1 = -1668701.174 kJ / hr. Qreact = Q2 = 2685168 kJ / hr. Qout = 1668701.174 – 2685168 Qout = - 1016466.826 kJ / hr. 74

Path (3): Q3 = QCH4 + QH2O + QCO2 + QCO + QH2 + QMEA + Q(HOCH2NH3)2CO3 For CH4 QCH4 = 195.954*(T2 – 311) – 0.112*( - 2.145*10-7 *(

- 3112 ) +3.586*10-4 *(

- 3114 ) + 4.41*10-11 (

- 3113 )

- 3115 ) …………. ( 1 )

For H2O - 3112 ) + 0.0102*(

QH2O = 34849.869*( T2 – 311) – 4.323*( - 4.576*10-6 *(

- 3114 ) + 7.586*10-10 *(

- 3113 )

- 3115 ) ……… ( 2 )

For CO2 QCO2 = 53.831*( T2 – 311) + 0.041*( + 1.96*10-9 *(

- 3112 ) – 1.278*10-5 *(

- 3114 ) – 1.172*10-13 *(

- 3113 )

- 3115 ) ………. ( 3 )

For H2 QH2 = 9116.412*( T2 – 311) + 3.619*( + 2.86*10-6 *(

- 3112 ) – 4.612*10-3 *(

- 3114 ) – 6.287*10-10 *(

- 3113 )

- 3115 ) ……….. ( 4 )

For CO QCO = 1989.089*( T2 – 311) – 0.221*( - 2.057*10-7 *(

- 3112 ) + 4.515*10-4 *(

- 3114 ) + 3.044*10-11 *(

- 3113 )

- 3115 ) ………. ( 5)

For MEA M.wt for ( MEA) = 61 kg / kmole. m = 239.547 kg / hr. QMEA = m Cp ∆T = 239.547 * 2.821 *( T2 -311 ) = 675.762 *( T2 -311 ) ……….. ( 6 )

75

For (HOCH2NH3)2CO3 M.wt for (HOCH2NH3)2CO3 = 156 kg / kmole. ………… (Perry)

Cp for (HOCH2NH3)2CO3 = 539.12 kJ / kmole .℃ Q(HOCH2NH3)2CO3 = (

) * 539.12 * ( T2 – 311 )

= 20105.941 * ( T2 – 311 ) …………… ( 7 )

Q3 = 66986.858 *( T2 – 311 ) – 0.996 *( - 2.134*10-6 *(

- 3112 ) + 6.385*10-3 *(

- 3114 ) + 2.043*10-10 *(

- 3113 )

- 3115 ) = 1016466.826

By using MATLAB, we find T = 325.9 K. T = 52.9 ℃

76

3.12 Energy Balance on Stripper:

T=100 ℃

MEA T=52.9 ℃ H2O (HOCH2NH3)2CO3

Stripper

CO

MEA H2O T=116 ℃

77

H2O MEA T = 116 ℃

Q4

T = 100

T = 52.9 ℃

MEA

CO2 T = 100 ℃

(HOCH2NH3)2CO3

Q3

H2O

Q1 T = 38 ℃

Q2

T = 38 ℃

MEA CO2 H2O

Qstripper = QB + QC Path ( 1): T1 = 52.9 ℃ = 325.9 K. T2 = 38 ℃ = 311 K. Q1 = QH2O + QMEA + Q(HOCH2NH3)2CO3 For H2O QH2O = (

) * (- 502.837 )

= - 516423.655 kJ / hr. For MEA QMEA = 239.54 * 2.821 * ( 311 – 325.9 ) = - 10068.56 kJ / hr. 78

For (HOCH2NH3)2CO3

) * 539.12 * ( 311 – 325.9 )

Q(HOCH2NH3)2CO3 = (

= - 299578.525 kJ / hr. Q1 = - 516423.655 - 10068.56 - 299578.525 = - 826070.74 kJ / hr. Path (2) (HOCH2NH3)2CO

2 NH2CH2CH2OH + CO2 + H2O

Q2 = ∆Hr = - 72 Q2 = - 72 * 1000 * 37.294 = - 2685168 kJ / hr. Path ( 3 ) T1 = 38 ℃ = 311 K. T2 = 100 ℃ = 373 K. For CO2 Q3 = QCO2 = (

) * 2465.88

= 91962.528 kJ / hr. Path (4) Q4 = QMEA + QH2O T1 = 38 ℃ = 311 K. T2 = 116 ℃ = 389 K.

79

For H2O QH2O = (

) * 2647.959

= 2818261.012 kJ / hr. For MEA From Figure (3-3,Appendix A), we find ( CpMEA ) at Tav. = 77 ℃. CpMEA = 0.725 cal / gm . ℃ = 3.03 kJ / kg . ℃ QMEA = 4789.415 * 3.03 * ( 389 – 311 ) = 1131930.341 kJ / hr. Q4 = 2818261.012 + 1131930.341 = 3950191.353 kJ / hr. Qstripper = Q1 + Q2 + Q3 + Q4 = - 826070.74 – 2685168 + 91962.528 + 3950191.353 = 530915.141 kJ / hr.

80

3.13 Energy Balance on Condenser ( 2 ):

Qc CO2 H2O(steam)

T=100 ℃

CO2 T=100 ℃

H2O ''Liquid'' T=100 ℃

Operating Condition T = 100 ℃ The pressure of the system =20 Psia = 137.8 Kpa That mean, Water vapor will be Saturated with CO2 gas at 137.8 Kpa and 100 ℃ The Vapor Pressure of H2O at 100 ℃ = 101.3 Kpa

=

…………… (David M. Himmelblau)

PT = PCO2 + PH2O PCO2 = PT – PH2O = 137.8 – 101.3 = 36.5 Kpa. Number of moles of CO2 (Absorbed ) = 37.294 kmole / hr.

(From M.B)

= nH2O = 103.503 kmole / hr.

81

From Steam table at T = 100 ℃ , We find : ʎ = hf – hg = 419.1 – 2676 = - 2256.9 KJ / kg. Qc = 103.503 * 18 * ( -2256.9 ) = - 4204726.573 kJ / hr.

Cooling medium: Use " H2O Liquid " From Steam table: Tin = 25 ℃ , H1 = 104.8 KJ / kg. Tout = 40 ℃ , H2 = 167.5 KJ / kg. Q = m ∆H m=

= 67061.029 kg / hr.

82

3.14 Energy Balance on Reboiler: Qb MEA H2O P=24 psi T=116 ℃

MEA H2O

Qstripper = QB + QC QB = 530915.141 – ( - 4204726.573 ) = 4735641.714 kJ / hr.

Heating medium: Use Superheated Steam table At P = 1.5 bar Tin = 250 ℃ , H1 = 2972.9 KJ / kg. Tout = 150 ℃ , H2 = 2772.5 KJ / kg. Q = m ∆H m=

= 23630.946 kg / hr.

83

3.15 Energy Balance on Condenser ( 3 ): Tin=25 ℃

MEA H2O

MEA H2O T=25 ℃

T=116 ℃

Tout=60 ℃

T1 = 116 ℃ = 389 K. T2 = 25 ℃ = 298 K. Qc = QH2O + QMEA For H2O 116 ℃

Q1

100 ℃

H2O (Superheated)

Sat.Vap

Q2

100 ℃ Sat.Liq

Q3

25 ℃ Liquid

T1 = 116 ℃ = 389 K. T2 = 100 ℃ = 373 K. T3 = 100 ℃ = 373 K. T4 = 25 ℃ = 298 K.

84

Path ( 1): T1 = 116 ℃ = 389 K. T2 = 100 ℃ = 373 K. Q1 = (

) * ( - 546.543 )

= - 581693.609 kJ / hr. Path ( 2 ) Q2 = m*ʎ ʎ = hf – h g From Steam table: At Tsat. = 100 ℃

, hf =419.1 KJ / kg. , hg = 2676 KJ / kg.

ʎ = 419.1 - 2676 = - 2256.9 KJ / kg. Q2 = 19157.66 * ( - 2256.9 ) = - 43236922.85 kJ / hr. Path ( 3 ) Q3 = (

) * ( - 2539.141 )

= - 2702444.443 kJ / hr.

QH2O = - 581693.609 - 43236922.85 - 2702444.443 = - 46521060.9 kJ / hr.

85

For MEA QMEA = m Cp ∆T m = 4789.415 kg / hr. From figure (3-3,Appendix A), We find ( CpMEA ) at Tav. = 70.5 ℃ CpMEA = 0.715 cal /gm . ℃ = 2.9887 kJ / kg .℃ QMEA = 4789.415 * 2.9887 * ( 298 – 389 ) = - 1302585.34 kJ / hr. Qc = QH2O + QMEA = - 46521060.9 - 1302585.34 = - 47823646.24 kJ / hr.

Cooling medium: Use " H2O Liquid " From Steam table: Tin = 25 ℃ , H1 = 104.8 KJ / kg. Tout = 60 ℃ , H2 = 251.1 KJ / kg. Q = m ∆H m=

= 326887.534 kg / hr.

86

87

CHAPTER FOUR EQUIPMENT DESGIN

88

4.1 Introduction : In this chapter, Knockout and Condenser will be designed. Knockout column will be designed to separate water liquid from the gases at temperature 200 ℃ and 18 bar . Condenser (2) will be designed to condense saturated vapor to saturated liquid of H2O back to the stripper .

89

4.2 Separator ( Knockout ) Design: Specification: Vapor Rate CH4 = 89.732 kg / hr. CO = 1884.372 kg / hr. CO2 = 1727.341 kg / hr. H2 = 717.856 kg / hr. Total mass flow rate = V = 4419.301 kg / hr. CH4 = 5.608 kmole / hr. CO = 67.299 kmole / hr. CO2 = 39.257 kmole / hr. H2 = 358.928 kmole / hr. Total moles flow rate = 471.092 kmole / hr. YCH4 = 0.012 YCO = 0.1428 YCO2 = 0.0833 YH2 = 0.7619

90

Liquid Rate L = H2O = 3430.230 kg / hr = 190.568 kmole / hr. Operating Condition: T = 200 ℃ P = 18 bar Physical Properties: Vapor P1 = 1 bar

, T1 = 298 K.

P2 = 18 bar , T2 = 473 K.

𝜌 = 𝜌 𝜌 ρ

=

= 8.1 kg / m3

= 14.175 kg / m3 = 22.275 kg / m3

𝜌 𝜌

= 1.012 kg / m3

= ∑ 𝜌 * Yi = 0.012 * 8.1 + 0.1428 * 14.175 + 0.0833 * 22.275 + 0.7619 * 1.012 = 4.747 kg / m3

91

Liquid P = 18 bar From Steam table:

𝜌

= 865.051 kg / m3

ut = 0.07 * * = 0.07 * *

(

)

+

(

)

+

= 0.942 m / s * Demister is used, therefore:

us = ut = 0.942 m / s Vapor Volumetric flow rate =

= 0.258 m3 / s

Dv = √

Dv = √

= 0.59 m.

Liquid Volumetric flow rate = VL =

= 1.1014 * 10-3 m3 / s

Allow a minimum time = 10 min. Volume held in Vessel = VL * 10 = 1.1014 * 10-3 * 60 * 10 = 0.66 m3

92

Cross Sectional area = =

* * ( 0.59 ) 2 = 0.273 m2

Liquid depth =

=

= 2.417 m.

Increase ( 0.15 m ) to allow Space for positioning the level Controller. Liquid depth = H = 2.417 + 0.15 = 2.567 m.

Dv=0.59 m

Figure (4-1) :- Knockout drum

93

4.3 Condenser (2) design : Qc = 4204726.573 KJ/hr = 1167.979 kw m = cooling water flow = 67061.29 Kg/hr = 18.628 kg/sec mcondensate= Amount H2O input to condenser = 103.503 * 18 = 1863.054 kg/hr = 0.517 kg/sec

T1= 100 ℃

shell H2O vapor & CO2

t2=40 ℃

T2 =100 ℃

Tube Cold H2O t1=25 ℃

ΔTLm =

=

[

]

[

]

= 67.22

Assumed overall coefficient:

U= 1000 W/m2.℃

………

Table (4-1,Appendix B)

Type of condenser is shell & tube, horizontal exchanger, condensation in the shell, one shell and two tube passes. No correction factor for multiple passes. Correction factor F=1

94

Q= U*A* ΔTLm*F A= do= 20mm

= 17.375 m2

= di =16mm

L= 4.88 m ''ignore thickness of tube sheet '' *4.88 = 0.306 m2

surface area of one tube = 3.14*20* Number of tubes =

56.78 = 57

Number of tubes = 58 Use square pitch Db = do( )

Pt= 1.25 * do = 1.25 * 20 = 25 mm (

=

)

Number of tubes in center row =

= 264.8 mm ……… Table (4-2, Appendix B) =

=10.592 = 10

Shell side coefficient: = 100 ℃

Taverage = ρ = 958.4 kg/m3

Cp = 4211 J/Kg.℃ KL = 0.682 W/m.℃ µ= 0.278 * ρ = 5.97*

N.s/m2 kg/m3

95

(hc)b= 0.95*KL*(

(

)

) Kg/s.m

Nr = (

(hc)b = 0.95*0.682 *(

)

)

= 12316.9 W/m2.℃

Tube side coefficient: = 32.5 ℃

Tube temperature =

(

Tube cross sectional area = (

hi =

ρ

,

Tube velocity =

/m3

(for cupro nickel alloys) )

(

=

m2

= 3.21 m/s

Kw=50 W/m.℃ (

= 5.82 *

)

At Taverage = 32.5 ℃

hi =

)

=12264.76 W/m2.℃ )

( )

Uo =1118.06 W/m2.℃ (well above assumed value 1000 W/m2 .℃)

96

Shell side pressure drop Db = 264.8 mm Use pull through floating head Select baffle spacing = shell diameter , 45% cut From figure (4-2,Appendix A) clearance = 88 mm Dshell = Db + clearance = 264.8 + 88 = 352.8 mm Use kern's method As =

= 0.024 m2

=

Mass flow = Ws= Gs=

= 0.972 kg/sec kg/m2.s

Total moles = nCO2 + nH2O = 103.503 + 37.294 = 140.797 kmol/hr Mole % H2O = Mole % CO2 = Operating condition P =20 psia = 137.8 kpa

, T =100 ℃

(Molecular weight)mix = 44*0.265 + 18*0.735 = 24.89 kg/kmol

ρ

(

)

=1.106 kg/m3

97

us =

=

36.618 m/s

de =

(

=

(

)

(For a square pitch) )

Re = µ for CO2 at 100℃ = 1.9 * 10-5 N.s/m2

………….. [perry]

µ for H2O at 100 ℃ = 1.4 * 10-5 N.s/m2

.…………. [perry]

µaverage = 0.735 * 1.4 * 10-5+0.265 *1.9*10-5=1.532*10-5 N.s/m2 Re =

= 52205.87

From figure (4-3,Appendix A) : Jf = 2.5*10-2 (

)

[

(

[

𝜌

) (

)

]

]

= 18323.61 Pa

98

Tube side Pressure drop The Viscosity ( µ ) at 32.5 ℃ = 0.756 * 10-3 N.s/m2 [

Re =

(

)

]

𝜌

= 67630.79

From figure (4-4,Appendix A ) Jf = 3*10-3

*

+

=100730.923 Pa

99

CHAPTER FIVE PLANT LAYOUT & TREATMENT

100

5.1 GENERAL DESIGN CONSIDERATIONS 5.1.1 Health and Safety Hazards The potential health hazard to an individual by a material used in any chemical process is a function of the inherent toxicity of the material and the frequency and duration of exposure. It is common practice to distinguish between the short-term and long-term effects of a material. A highly toxic material that’ causes immediate injury is classified as a safety hazard while a material whose effect is only apparent after long exposure at low concentrations is considered as an industrial health and hygiene hazard. The permissible limits and the precautions to be taken to ensure that such limits will not be exceeded are quite different for these two classes of toxic materials. 5.1.2 Environmental Considerations Vigilance is required in both the design and operation of process plant to ensure that no harm is done to the environment. Consideration must be given to: 1. All emissions to land, air, water. 2. Waste management. 3. Smells. 4. Noise. 5. The visual impact. 6. Any other nuisances. 7. The environmental friendliness of the products. Waste management: Waste arises mainly as byproducts or unused reactants from the process, or as off-specification product produced through mis-operation. The designer must consider all possible sources of pollution and, where practicable, select processes that will eliminate or minimize waste generation. Unused reactants can be recycled and off-specification product reprocessed. Integrated processes can be selected: the waste from one process becoming the raw material for another. When waste is produced, processes must be incorporated in the design for its treatment and safe disposal. The following techniques can be considered: 1. Dilution and dispersion. 2. Discharge to foul water sewer (with the agreement of the appropriate authority). 3. Physical treatments: scrubbing, settling, absorption and adsorption. 4. Chemical treatment: precipitation (for example, of heavy metals), neutralization. 101

5. Biological treatment: activated sludge and other processes. 6. Incineration on land, or at sea. 7. Landfill at controlled sites. 8. Sea dumping (now subject to tight international control). Noise: Noise can cause a serious nuisance in the neighborhood of a process plant. Care needs to be taken when selecting and specifying equipment such as compressors, air-cooler fans, induced and forced draught fans for furnaces, and other noisy plant. Excessive noise can also be generated when venting through steam and other relief valves, and from flare stacks. Such equipment should be fitted with silencers. 5.1.3 Plant Location Considerable care must be exercised in selecting the plant site, and many different factors must be considered. Primarily, the plant should be located where the minimum cost of production and distribution can be obtained, but other factors, such as room for expansion and safe living conditions for plant operation as well as the surrounding community, are also important. The following factors should be considered in selecting a plant site: 1. Raw materials availability 2. Markets 3. Energy availability 4. Climate 5. Transportation facilities 6. Water supply 7. Waste disposal 8. Labor supply 9. Taxation and legal restrictions 10. Site characteristics 11. Flood and fire protection 12. Community factors

102

5.1.4 Plant Layout After the process flow diagrams are completed and before detailed piping, structural, and electrical design can begin, the layout of process units in a plant and the equipment within these process units must be planned. This layout plays an important role in determining construction and manufacturing costs, and thus must be planned carefully with attention being given to future problems that may arise. Proper layout in each case will include arrangement of processing areas, storage areas, and handling areas in efficient coordination and with regard to such factors as: 1. New site development or addition to previously developed site 2. Type and quantity of products to be produced 3. Type of process and product control 4. Operational convenience and accessibility 5. Economic distribution of utilities and services 6. Type of buildings and building-code requirements 7. Health and safety considerations 8. Waste-disposal requirements 9. Auxiliary equipment 10. Space available and space required 11. Roads and railroads 12. Possible future expansion 5.1.5 Plant Operation and Control The methods which will be used for plant operation and control help determine many of the design variables. For example, the extent of instrumentation can be a factor in choosing the type of process and setting the labor requirements. The engineer must recognize the importance of such factors which are directly related to plant operation and control and must take them into proper account during the development of a design project. 5.1.6 Utilities These include: 1- Electric Power generated inside or outside the plant site. 2- Steam generated in reboilers using fuel or by exploiting the waste heat. 3- Water for industrial purposes can be obtained from the plant’s own source or a municipal supply.

103

5.1.7 Storage It is important to have adequate storage facilities for raw materials, intermediate products, final products, recycle materials, off-grade materials, and fuels. 5.1.8 Materials Handling Liquids and gases are handled by means of pumps and blowers; in pipes, and ducts; and in containers such as drums, cylinders, and tank cars. Solids may be handled by conveyors, bucket elevators, chutes and lift trucks. 5.1.9 Structural Design One of the most important aspects in structural design for the process industries is a correct foundation design with allowances for heavy equipment and vibrating machinery used. The purpose of the foundation is to distribute the load so that excessive or damaging settling will not occur. The type of foundation depends on the load involved and the material on which the foundation acts. It is necessary; therefore, to know the characteristics of the soil at a given plant site before the structural design can be started. The allowable bearing pressure varies for different types of soils, and the soil should be checked at the surface and at various depths to determine the bearing characteristics. The allowable bearing pressure for rock is 30 or more ton/ft2 (30 × 104 kg/m2), while that for soft clay may be as low as 1 ton/ft2 (1 × 104 kg/m2). Intermediate values of 4 to 10 ton/ft2 (4 × 104 to 10 × 104 kg/m2) apply for mixtures of gravel with sand and hard clay. 5.1.10 Patent Considerations A patent is essentially a contract between an inventor and the public. In consideration of full disclosure of the invention to the public, the patentee is given exclusive rights to control the use and practice of the invention.

104

CHAPTER SIX COST ESTIMATION

105

6.1 Introduction : In this chapter , Cost will be made on Knockout column and condenser (2) . Knockout cost will estimated depending on the column height and it's diameter and then calculate the purchased cost at 2014 . Condenser (2) cost will estimated depending on the total surface area and then calculate the purchased cost at 2014 .

106

6.2 Separator Vessel (Knockout ) Cost: Height = 4.567 m Diameter = 0.59 m Using Figure (6-1,Appendix A), Purchased Cost = Bare Cost from figure * Material factor * Pressure factor Purchased Cost = 8,500 * 2 * 1.2 = 20,400 $ at 2004

Cost in year 2014 = Cost in year 2004 *

The average increase in cost ( cost index ) =

= 2.75

The Cost index in 2014 = 10 * 2.75 + 111 = 138.5 Cost in year 2014 = 20,400 *

= 25,454 $

107

6.3 Shell and tube heat exchanger '' condenser '' cost A=17.375 m2 Using figure (6-2,Appendix A ) , Purchased cost = bare cost from figure * Type factor * pressure factor = 30,000 * 1 * 1 = 30,000 $ at 2004

Cost in year 2014 = Cost in year 2004 *

The average increase in cost ( cost index ) =

= 2.75

The Cost index in 2014 = 10 * 2.75 + 111 = 138.5 Cost in year 2014 = 30,000 *

= 37,432 $

108

Appendix A The Diagrams Figure (2-2) : Equilibrium constants as a function of temperature [ Introduction to Chemical Engineering Thermodynamics]

109

Figure (3-1) : Approximate polytropic efficiencies centrifugal and axial-flow compressors [ Vol. 6, Chemical engineering Design, Fourth Edition,Page (83)]

Figure (3-2):- Generalized Compressibility Chart for lower pressures showing Z as a function of Pr,Tr, and Vri [ David M.Himmelblau]

110

Figure (3-3) : specific heat for monoethanolamine, diethanolamine & triethanolamine. [ Austin P.Kirk, Ethanol amines, DOW, 2009]

Figure (4-2):Shell-bundle clearance [ Vol. 6, Chemical engineering Design, Fourth Edition ]

111

Figure (4-3):Shell-side friction factors, segmental baffles [ Vol. 6, Chemical engineering Design, Fourth Edition]

Figure (4-4):Tube-side friction factors [ Vol. 6, Chemical engineering Design, Fourth Edition]

112

Figure (6-1): Vertical Pressure Vessels. Time base mid 2004 [ Vol. 6, Chemical engineering Design, Fourth Edition]

Figure (6-2): Shell and tube heat exchanger. Time base mid-2004 [ Vol. 6, Chemical engineering Design, Fourth Edition]

113

Appendix B The Tables Heat capacities: Cpgas = A + BT + CT2 + DT3 +ET4

kJ/kmol.k

Table (3-1):- Heat Capacities of gas – Inorganic Components [ Chemical properties handbook]

Comp.

A

B

C

D

E

Tmin

Tmax

CH4 H2O H2 CO CO2

34.942 33.933 25.399 29.556 27.437

-3.9957E-02 -8.4186E-03 2.017E-02 -6.5807E-03 4.2315E-02

1.9184E-04 2.9906E-05 -3.8549E-05 2.013E-05 -1.9555E-05

-1.5303E-7 -1.7825E-08 3.188E-08 -1.2227E-08 3.9968E-09

3.9321E-11 3.6934E-12 -8.7585E-12 2.2617E-12 -2.9872E-13

50 100 250 60 50

1500 1500 1500 1500 5000

Table (4-1):Typical overall coefficients [Vol. 6, Chemical engineering Design, Fourth Edition ]

Table (4-2):- Estimation of the Bundle Diameter. [ Vol. 6, Chemical engineering Design, Fourth Edition]

114

References 1. Andre L. Boehman and Olivier LeCorre. Combustion of syngas in internal combustion engines. Combustion Science and Technology, 2008. 2. Austin P.Kirk, Ethanol amines, DOW, 2009. 3. Al-Qahtani, 1997; Pedernera et al., 2007 4. Bharadwaj and Schmidt, 1995 5. Coulson & Richardson, chemical engineering, Volume 6,3rd edition. 6. Coulson & Richardson, chemical engineering, Volume 2,5th edition. 7. Davis S.Carmen, steam methane reforming, EIGA, 2009. 8. David M. Himmelblau, Basic principle and calculations in chemical engineering, 7th edition. 9. Dybkjaer, 1995 10.Froment and Bischoff, 1990 11.Fred C.Riesenfeld, Gas purification, 2nd edition. 12.Goff L.Barnet, Acid gas removal, Hydrocarbon processing, 1980, 13(6) 245-251. 13.Heinz-Wolfgang. Industrial Gases Processing.,2008. 14.Harold A.Gunardson ,Industrial gases in petrochemical processing.1998. 15.Hellen T.Samuel, Environmental control in hydrogen production, Fuels, 2001, 18(5), 211-220. 16.J.M. Smith & H.C Van ness, Introduction to chemical engineering thermodynamics, 4th edition. 17.Jean & Stephen C.Bradely,Best available techniques for hydrogen production by steam methane reforming , EIGA,2009.P.2-3. 18.Moulijn et al., 2003 19.National Hydrogen Association. www.hydrogenus.com. 20.P.L. Spath and D.C. Dayton.,2003 21.Robert H.Perry, Perry 's chemical engineering handbook, 7th edition. 115

22.Ullmann's Encyclopedia of Industrial Chemistry, 40 Volume Set. 23.Ullman‟s, 1985

116

CHAPTER ONE

INTRODUCTION

1

1.1 Historical Overview : In its simplest form, syngas is composed of two diatomic molecules, CO and H2, that provide the building blocks upon which an entire field of fuel science and technology is based. Over the years, the gaseous mixture of CO and H2 has had many names depending on how it was formed; producer gas, town gas, blue water gas, synthesis gas, and syngas, to name a few. In the 1800’s coal gasification was used to provide much of the syngas used for lighting and heating. The beginning of the 20th century saw the dawn of fuels and chemicals synthesis from syngas. The synthesis of hydrocarbons from CO hydrogenation was discovered in 1902 by Sabatier and Sanderens who produced methane by passing CO and H2 over Ni, Fe, and Co catalysts. At about the same time, the first commercial hydrogen from syngas produced from steam methane reforming was commercialized. Haber and Bosch discovered the synthesis of ammonia from H2 and N2 in 1910 and the first industrial ammonia synthesis plant was commissioned in 1913. The production of liquid hydrocarbons and oxygenates from syngas conversion over iron catalysts was discovered in 1923 by Fischer and Tropsch. Variations on this synthesis pathway were soon to follow for the selective production of methanol, mixed alcohols, and isosynthesis products. Another outgrowth of Fischer-Tropsch Synthesis (FTS) was the hydroformylation of olefins discovered in 1938. Much of the syngas conversion processes were being developed in Germany during the first and second world wars at a time when natural resources were becoming scare and alternative routes for hydrogen production, ammonia synthesis, and transportation fuels were a necessity. Thus the poor economics of some of these syngas conversion processes were of little consequence. With the development of the petroleum 2

industry in the 1940’s and beyond, the unattractive economics of many of these syngas routes became an issue and were replaced by petroleumbased processes. To this day, however, methanol and ammonia are still produced from syngas using essentially the same processes originally developed and, apart from hydrogen production, constitute the major uses of syngas. While petroleum-derived transportation fuels and chemicals were taking center stage in the worldwide market, certain political and environmental drivers were helping to develop improved commercial syngas conversion processes. The political situation in South Africa and the abundance of local coal reserves in that country helped bring about the most successful commercial FTS industry in the world based on syngas production from coal gasification. Sasol currently supplies diesel, gasoline, and other highvalue hydrocarbons to local and global markets. The Arab oil embargo in the 1970’s also highlighted the US dependence on foreign oil imports and helped renew interest in syngas conversion technologies. The

increasing

environmental

concerns

and

tighter

regulations

surrounding fossil fuel use also provided impetus for syngas conversion technologies to produce cleaner (virtually no sulfur) fuels and chemicals. The use of methanol and isobutene for the production of methyl tert-butyl ether (MTBE), an octane enhancing oxygenated component in reformulated gasoline, also increased demand for syngas conversion technologies. MTBE itself, however, is becoming an environmental concern as a watershed pollutant and the future use of this oxygenate is uncertain. The latest environmental driver to likely increase demand for syngas even more is the goal of establishing a hydrogen economy. The vision is for hydrogen to be the fuel of choice for transportation and

3

electricity generation via high efficiency, environmentally benign fuel cells[P.L. Spath and D.C. Dayton.,2003].

1.2 Physical Properties of Hydrogen (H2): With only one proton and one electron, hydrogen is the lightest of all chemical elements. At ambient temperature, molecular hydrogen, H2, is a colourless and odourless gas. At 0 °C and 1 bar, one liter weighs 0.0899 gm. Consequently, H2 is14 times lighter than air and with this, a suitable filling gas for balloons. The lift of 1 m3 of H2 in air amounts to 1.2 kg. Disadvantageous for this application is its high combustibility, since hydrogen in a concentration range of 4–77% of volume fraction in air forms an explosive mixture. At –252.78 °C (1 bar), hydrogen condenses to a colourless liquid, it freezes at –259.15 °C. Its high diffusion capability owing to its low molar mass respectively its solubility in a number of metals has to be considered in the handling of hydrogen and selection of materials, e.g. regarding the embrittlement of steels. On the other hand, the good solubility of H2 in metallic platinum and palladium respectively its extraordinarily high diffusion selectivity due to dense membranes of these noble metals can be utilized for the separation of H2. Two other isotopes of hydrogen exist. On earth, heavy hydrogen (D , deuterium ), which is stable, occurs in the natural isotopic distribution with an atomic fraction of 0.015%; tritium (T) is a weak β-radiator with a half-life of about 12.3 years, on earth represented in the natural isotopic distribution with an atomic fraction of only about 10–12–10–13%. Further important physical properties of (n-hydrogen) is show in the following Table (1-1) :

4

Table (1-1): Physical properties of hydrogen [Industrial Gases Processing , Heinz-Wolfgang Haring.,2008]

[Property

Unit

Value

Molar mass

g mol–1

2.016

Heat of evaporation

J mol–1

898

Properties at 273.15 K, 101.3 kPa Density

kg m–3

0.0899

Molar heat

J mol–1 K–1

Cp = 28.6, Cv = 20.2

Thermal conductivity

W m–1 K–1

0.1645

Boiling point (101.3 kPa) Temperature

K

20.37

Density (liquid)

kg m–3

70.00

Density (gas)

kg m–3

1.319

Liquid at boiling point (101.3 kPa) Molar heat

J mol–1 K–1

Cp = 22.0, Cv = 6.51

Enthalpy

J mol–1

–7918

Thermal conductivity

W m–1 K–1

0.117

Gas at boiling point (101.3 kPa) Specific heat capacity

J mol–1 K–1

Cp = 23.49, Cv = 12.8

5

Property

Unit

Value

Enthalpy

J mol–1

–7020

W m–1 K–1

0.0185

Thermal conductivity

Critical Point Temperature

K

33.00

Pressure

kPa

1339

Density

kg m–3

30.09

Triple point Temperature

K

13.81

Pressure

Kpa

6.14

Density (Solid)

kg m–3

86.7

Density (Liquid)

kg m–3

76.4

Density (Gas)

kg m–3

0.12

6

Table (1-2): Some physical and thermodynamic properties of gaseous n-hydrogen [Ullmann's Encyclopedia of Industrial Chemistry, 40 Volume Set] Density

Cp

Cv

Enthalpy

Entropy

kJ/mol

(J/mole.K)

T, °C

(Kg/m3)

-150

0.1994

23.97

15.65

3.7086

191.38

-150

0.1418

26.42

18.08

4.9434

126.98

-50

0.1100

27.85

19.55

6.3342

133.87

0

0.0899

28.61

20.32

7.7492

139.59

+50

0.0760

29.03

20.68

9.1914

144.44

+100

0.0658

29.20

20.84

10.6461

148.62

+150

0.0580

29.20

20.91

12.1062

152.30

(J/mole.K) (J/mole.K)

1.3 Chemical properties of hydrogen: In air, H2 combusts to water with a hardly visible, weakly bluish flame (detonating gas reaction). The chemical bond between hydrogen and oxygen is very strong and can only be ruptured by adding considerable energy (∆Hf of H2O = –286 kJ mol–1). The hydrogen bridge bonds occurring between the hydroxyl groups (-OH) of two water-molecules are important intermolecular bonds that sharply increase the melting and boiling points of light molecules. Hydrogen combines with almost any other element. Metal compounds with negatively charged hydrogen are called metal hydrides (e.g. CaH 2, NaH, LiH). With water, they form metal hydroxides and gaseous hydrogen. Through thermal cracking of ethane or naphtha (dehydration), for example, ethylene, propene and H2 are obtained. In addition to that, the hydration of unsaturated hydrocarbons, as for instance in fat hardening, plays an important role. Hydrogen has a reducing effect on a 7

lot of metal oxides when heated. Thus CuO with H2, for example, reacts to Cu and H2O. [Industrial Gases Processing , Heinz-Wolfgang Haring.,2008]

1.4 Physical and Chemical Properties of Carbon Monoxide (CO): Carbon monoxide with the molar mass of 28.01 g mol –1 is colourless, odourless and tasteless and does not irritate the respiratory tracts. It is highly toxic, slightly lighter than air, poorly soluble in water (solubility: 23 mL L–1 at 20 °C and 1 bar) and combustible. Together with air, carbon monoxide forms explosive mixtures in the concentration range of a COvolume fraction of (10.9-76%). It combusts in air with a bluish, very hot flame. The calorific value is 12.69 kJ m–3 resp. 12.93 kJ kg–1. Carbon monoxide liquefies at 1 bar and (-191.5 °C) and solidifies at (-199 °C). In the laboratory, carbon monoxide (anhydride of formic acid) is obtained by dripping concentrated sulphuric acid into formic acid at temperatures over 100 °C. In engineering, it is obtained by separation from synthesis gas. In steel production, CO occurs as reducing agent of ferric oxide, where it exhausts as blast-furnace gas in large quantities. There are numerous complex bonds of transition metals with CO called carbonyl complexes . Examples are Ni(CO)4 and Fe(CO)5. The possibility of a carbonyl formation at high CO-partial pressure has to be taken into consideration when choosing the material of equipment and piping. The lifespan of CO in the atmosphere is assessed at 1–2 months, with the reaction of CO with OH-radicals to CO2 and H being regarded as decomposition reaction.

8

CO is a highly toxic gas with a threshold limit value (TLV) of 30 vppm. The reason for its toxicity is its property to displace the oxygen from the hemoglobin-complex of blood, since the affinity of hemoglobin (Hb) to CO is about 300 times higher than to O2. A concentration of 660 vppm of CO is enough to block about half of the Hb for the oxygen transport. The bond of CO to hemoglobin is reversible, the CO-decomposition however occurs very slowly. In CO-free air the whole adsorbed CO can be replaced by O2 again, thus re-establishing the functional capability of the hemoglobin. Through ventilation with pure O2, this process is accelerated considerably. The symptoms of a CO-intoxication mainly arise through oxygen deficiency in the tissue. The hemoglobin of a heavy smoker of cigarettes can reach a CO-saturation of up to 15% in the course of a day. Other important properties of carbon monoxide are listed in Table (1-3): Table (1-3): Physical properties of Carbon Monoxide [Industrial Gases Processing , Heinz-Wolfgang Haring.,2008]

[Property

Unit

Value

Molar mass

g mol–1

28.01

% Volume fraction

10.9 – 76

Explosion range (in air at 101.3 kPa)

Properties at 273.15 K, 101.3 kPa Density

kg m–3

1.250

Molar heat

J mol–1 K–1

Cp = 29.05,Cv = 20.68

Thermal conductivity

W m–1 K–1

0.02324

Viscosity of gas

µN.s m-2

16.62

9

Property

Unit

Value

Boiling point at (101.3 kPa) Temperature

K

81.65

Heat of vaporization at Boiling point

kJ mol -1

6.042

Normal Freezing point Temperature

K

67.9

Critical point Temperature

K

132.29

Pressure

Kpa

3496

Density

kg m–3

301

Triple point Temperature

K

68.05

Pressure

Kpa

15.25

Heat of fusion at triple point Heat of sublimation at triple point

J mol -1

837.3

kJ mol -1

7.366

Other physical properties Entropy of gas at 298 K, 101.3 kpa Enthalpy of formation of gas (ΔHf)

J mol-1 K-1

197.89

kJ mol -1

-110.63

11

1.5 Physical properties of Carbon Dioxide (CO2) Table (1-4): The Physical Properties of carbon Dioxide. [Ullmann's Encyclopedia of Industrial Chemistry, 40 Volume Set]

Property Molar Mass Color Odor Density at 0 °C , 0.1 MPa Specific density Molar heat (Cp) at 25 ◦C Specific heat (Cp) at 0 °C, 0.1 Mpa Entropy Heat of formation ΔH Heat of sublimation Heat of vaporization Heat of fusion Critical Temperature Critical Pressure Critical Density

Unit -1

g mol Kg m-3

-

J mol−1 K−1 J g−1 K−1 J mol−1 K−1 kJ mol -1 J g-1 J g-1 J g-1 °C MPa Kg m-3

Value 44.010 Colorless Odorless 1.977 1.5291 37.13 0.8277 213 −393.51 573.02 347.86 195.82 31.04 7.383 468

11

1.6 Synthesis gas: In its simplest form, syngas (also called producer gas, town gas, blue water gas, and synthesis gas among others) is composed of carbon monoxide (CO) and hydrogen (H2), which provide the building blocks to produce a number of organic compounds. During the 1800’s, coal gasification was used for lighting and heating. The production of fuels and chemicals from syngas began in the early 20th century. Today, hydrogen, along with methanol and ammonia, constitute the major chemicals commercially produced from syngas. Syngas, or synthesis gas, is a fuel gas mixture consisting primarily of hydrogen, carbon monoxide, and very often some carbon dioxide. The name comes from its use as intermediates in creating synthetic natural gas (SNG)[ Beychok.,1975] and for producing ammonia or methanol. Syngas is combustible and often used as a fuel of internal combustion engines. It has less than half the energy density of natural gas. Production methods include steam reforming of natural gas or liquid hydrocarbons to produce hydrogen and/or mono oxide carbon, the gasification of coal, biomass, and in some types of waste-to-energy gasification facilities. In principle, syngas can be produced from any hydrocarbon feedstock, including: natural gas, naphtha, residual oil, petroleum coke, coal, and biomass. The lowest cost routes for syngas production, however, are based on natural gas, the cheapest option being remote or stranded reserves. Economic considerations dictate that the production of liquid fuels from syngas today translates into the use of natural gas as the hydrocarbon source. Nevertheless, the syngas production operation in a gas-to-liquids plant amounts to greater than half of the capital cost of the 12

plant. The choice of technology for syngas production also depends on the scale of the synthesis operation. Syngas production from solid fuels can require an even greater capital investment with the addition of feedstock handling and more complex syngas purification operations. The greatest impact on improving the economics of gas-to liquids plants can be had by decreasing capital costs associated with syngas production and improving the thermal efficiency with better heat integration and utilization. Improved thermal efficiency can be obtained by combining the gas-to-liquids plant with a power generation plant to take advantage of the availability of low-pressure steam. The syngas composition, most importantly the H2/CO ratio, varies as a function of production technology and feedstock. Steam methane reforming yields H2/CO ratios of 3/1 while coal gasification yields ratios closer to unity or lower. Conversely, the required properties of the syngas are a function of the synthesis process. Fewer moles of product almost always occur when H2 and CO are converted to fuels and chemicals. Consequently, syngas conversion processes are more thermodynamically favorable at higher H2 and CO partial pressures. The optimum pressures depend on the specific synthesis process. With the exception of methane steam reforming, catalytic syngas conversion processes are exothermic reactions generating large excesses of heat. This highlights the specific need for removing this heat of reaction to carefully control reaction temperatures to maintain optimized process conditions. Maximizing product yields, minimizing side or competing reactions, and maintaining catalyst integrity dictate optimum synthesis reaction temperatures. Catalysts play a pivotal role in syngas conversion reactions, in fact, fuels and chemicals synthesis from syngas does not occur in the absence of 13

appropriate catalysts. The basic concept of a catalytic reaction is that reactants adsorb onto the catalyst surface and rearrange and combine into products that desorb from the surface. One of the fundamental functional differences between syngas synthesis catalysts is whether or not the adsorbed CO molecule dissociates on the catalyst surface. For FTS and higher alcohol synthesis, CO dissociation is a necessary reaction condition. For methanol synthesis the CO bond remains intact. Hydrogen has two roles in catalytic syngas synthesis reactions. In addition to being a reactant needed for CO hydrogenation, it is usually used to reduce the metalized synthesis catalysts and activate the metal surface. Since the genesis of syngas conversion to fuels and chemicals a tremendous amount of research and development has been devoted to optimizing product yields and process efficiencies. This includes the discovery of catalysts with optimized formulations containing the most active metals in combination with appropriate additives to improve activity and selectivity in a given process. Mechanistic studies have been conducted to interpret the fundamentals of specific conversion processes and measure the kinetic rates of key chemical reactions. Reactor design and engineering is another active research and development area of syngas conversion technology. Temperature control and stability in conversion reactors is a critical process parameter because of the large excess heat of reaction. Detailed process engineering and integration with respect to heat integration and syngas recycle to improve conversion efficiencies is used optimize commercial synthesis processes. [P.L. Spath and D.C. Dayton.,2003].

14

1.7 Uses of syngas: 1- Syngas can be used to produce a variety of chemicals like ammonia and methanol. 2- Raw material for the formation of aldehydes and alcohols from Olefins. 3- Syngas is also used as an intermediate in producing synthetic petroleum for use as a fuel or lubricant via the Fischer–Tropsch process and previously the Mobil methanol to gasoline process. 4- Syngas itself can be used as a fuel in internal combustion engine. 5- syngas can be used to produce organic molecules such as synthetic natural gas (SNG-methane) or liquid biofuels such as synthetic diesel (via Fischer-Tropsch synthesis). 6- Fuel for the generation of electricity in power stations Nowadays, synthesis gas is mainly used for production of the products listed in Table (1-5): Table (1-5): Examples of H2 , CO and Synthesis gas products [Industrial Gases Processing , Heinz-Wolfgang Haring.,2008]

Produce

Uses

H2 and N2 CO

Various hydrogenations, as e.g. the fat hydrogenation in the food industry and the desulphurization in refineries, energy carrier for fuel cells and a future hydrogen infrastructure. Ammonia Phosgene, Polycarbonate, Formic acid.

H2 and CO in spilt flow

Acetic acid, intermediate products for the production of polyurethane foams.

Mixtures (H2 & CO)

Oxo-alcohols, reduction gas for the steel industry, fuel for gas turbines, synthetic fuels from natural gas (Fischer-TropschSynthesis: Gas to liquid: GTL)

Mixtures of (H2, CO and CO2)

Methanol

H2

15

1.8 Production of Synthesis Gas The term synthesis gas stands for a multitude of different gas mixtures consisting of H2, CO and N2, partially with traces of hydrocarbons, CO2 and Ar. Similarly high as the number of the different and technically relevant synthesis gases is the number of the practically applied production processes. For some years, central importance has been attributed to hydrogen as a future energy carrier. However, the use of this energy carrier represents a solution to the problem of carbon dioxide emissions only if hydrogen is generated from regenerative energy sources like sun, wind or renewable organic raw materials, without carbon dioxide as a by-product]. All production processes from regenerative energy sources are not yet on a technical level that would enable to meet the current demand for hydrogen, aside from the demand that would arise with the utilization as an energy carrier of the future. Nevertheless, the development regarding the use of hydrogen as energy carrier is progressing rapidly, although at present the conventional hydrogen production from hydrocarbons is still to prevailing. [Industrial Gases Processing.,2008]

16

1.9 Production of Synthesis Gas from Hydrocarbons: In the production of synthesis gases from hydrocarbons, the components hydrogen and carbon monoxide usually appear as complementary products, carbon dioxide can be obtained as a by-product as well. Apart from hydrocarbons and steam (steam reforming), some processes require carbon dioxide (CO2 reforming) as well as oxygen or air (partial oxidation and autothermal reforming ) as feedstock. There are Several Methods to Production the Synthesis Gas from Hydrocarbons : 1- Generation of Synthesis Gas by Steam Reforming. 2- Synthesis Gas Generation by Partial Oxidation (PO ). 3- Generation of Synthesis Gas by Autothermal Reforming ( ATR). The Process Selection depends on Two factors: 1- The desired product composition, usually characterized by the socalled H2/CO ratio in the raw synthesis gas. 2- The feedstock available (natural gas, residual gases from refineries, LPG(Liquefied Petroleum Gas), naphtha, heavy oils, distillation residues, pitch, coal, carbon dioxide, oxygen) and process utilities (steam, cooling water, …) [Industrial Gases Processing.,2008]. The selected process in this project is Production Synthesis Gas by steam reforming of Methane Gas.

17

1.10 Methane: Methane is a chemical compound with the chemical formula CH4 (one atom of carbon and four atoms of hydrogen). It is the simplest alkane and the main component of natural gas. Methane is a colorless, odorless gas with a wide distribution in nature. It is the principal component of natural gas, a mixture containing about 75% CH4, 15% ethane (C2H6), and 5% other hydrocarbons, such as propane (C3H8) and butane (C4H10). Table (1-6): The physical properties of Methane gas [Ullmann's Encyclopedia of Industrial Chemistry, 40 Volume Set]

Property

Unit

value

Molecular formula

-

CH4

Molar Mass

g mol-1

16.04

Density at 25 °C , 1 atm

g cm-3

0.656

Viscosity at -170 °C

mPa.s

0.142

Specific heat capacity at -100 °C

J g-1 k-1

5.34

Melting point

°C

-182

Flame Velocity

cm s-1

43.4

Entropy

J K−1mol−1

186.31

Compressibility Factor

-

0.299

Density

g cm-3

0.162

Temperature

°C

- 82.5

Pressure

MPa

4.67

Critical Values

18

1.11 Sources of Methane Natural sources  Wetlands  Oceans  Geological sources  Wild animals  Wildfires (Leif Backman., 2009)

Artificiality Sources 1- Oil and Gas System: Emitted during normal operations, routine maintenance, and system disruptions in the oil and natural gas industry. 2- Landfills: Produced through the decomposition of organic waste under an aerobic conditions typically found in landfills and large dump sites. 3- Wastewater: Produced by decay of organic material in wastewater as it decomposes in an aerobic environments. 4- Coal Mines: Most methane emissions from coal mining occur during the mining process in underground mining operations. 5- Agriculture: Produced from decomposition of livestock and poultry manure stored or treated in systems that promote anaerobic conditions. 19

1.12 Reactions and thermodynamics: The standard enthalpies of reaction (at 298 K) are given in brackets. The most important reactions in steam reforming (SR) of methane are [Moulijn et al., 2003]: 1. CH4(g) + H2O(g) ↔ CO(g) + 3H2(g) 2. CO(g) + H2O(g) ↔ CO2(g) + H2(g)

(∆H = +206 kJ/mol) (water-gas-shift, ∆H = -41 kJ/mol)

1.13 Steam Reforming (Tubular Reforming): Steam Reforming Methane (SMR) has been used for several decades since it has been developed in 1926 and over the years substantial improvements have been introduced. A conventional SMR process consists of gas feed pre-heating and pre-treatment, reforming, high and low shift. Steam reforming of methane is the main industrial route to produce hydrogen and synthesis gas (a mixture of hydrogen and carbon monoxide) [al-Qahtani, 1997; Pedernera et al., 2007]. In the steam reforming process, a light hydrocarbon feedstock (such as natural gas, refinery gas, LNG, or naphtha) is reacted with steam at elevated temperatures(typically 700° C to 900° C), and elevated pressures (15 to 30 bar) in nickel-based catalyst filled tubes to produce a synthesis gas. This gas consists primarily of hydrogen and carbon monoxide, but other gases such as carbon dioxide and nitrogen, as well as water vapor are also present. The typical ratio of this gas exiting the reformer is approximately 50% hydrogen, 10% carbon monoxide, with the balance being the other gases. Increasing the amount of steam used in the reaction will increase the hydrocarbon conversion rate, but the economic cost of the steam must be taken into account in the overall process. The typical steam to carbon ratio falls in the range of (2.8 to 3.2 to 1). 21

The overall steam reforming (SR) is highly endothermic and it is carried out at high temperature (700 - 900 ºC) and at pressures between 15 and 30 bar [Moulijn et al., 2003] over a Ni/Al2O3 catalyst [Bharadwaj and Schmidt, 1995]. The composition of the gas at the reactor outlet reflects the equilibrium of reaction (1) and (2) above. In some cases, it is advantageous to add CO2 at the inlet of the reformer. This is done in order to save hydrocarbon feedstock and decrease the H2/CO ratio in the product gas. The CO2 coming out from the reformer is then recycled, and in some cases CO2 is also imported. CO2 then is supposed to react to form CO via the reverse WGS-reaction, and this is favored at low S/C ratios. However, low S/C ratios leads to high methane concentrations in the outlet. To compensate for this, a higher temperature can be used [Dybkjaer, 1995]. The Ni-catalyst is needed since methane is a very thermodynamically stable molecule even at high temperatures. The steam reformer consists of two sections – a convection section and a radiant section. In the convection section, methane and steam are preheated to 500 ºC [Ullman‟s, 1985] by heat exchange with the hot flue gases from the fuel combusted in the reformer furnace, and in the radiant section the reforming reactions take place in the catalyst filled tubes which are hanging in rows inside of the reformer furnace [Moulijn et al., 2003]. The process gas is heated gradually to approximately 800 ºC inside of the tubes [Ullman‟s, 1985]. All tubular reformers use catalyst inside the tubes in order to reduce the operating temperature. This is important in order to reduce the tube stresses resulting from high pressure and high temperatures [Froment and Bischoff, 1990]. Steam for the reforming is produced from the heat in the product gas out from the reformer. One furnace can contain 500 – 600 tubes with inner diameters of 70 –130 mm 21

and lengths of 7 – 12 m [Moulijn et al., 2003]. The wall thickness of the tubes is between 10 – 20 mm [Ullman‟s, 1985]. The tubes have small diameters in order to achieve the highest possible heat flux to the catalyst, and hence to achieve the highest possible capacity for a given amount of catalyst [Froment and Bischoff, 1990].

1.14 The Advantages of (SMR): Steam reforming of natural gas offers an efficient, economical, and widely used process for hydrogen and monoxide production, and provides near- and mid-term energy security and environmental benefits. The efficiency of the steam reforming process is about 65% to 75%, among the highest of current commercially available production methods. The SMR produces a H2/CO ratio equal to three, which is high when compared to other reforming processes. The cost of hydrogen produced by SMR is acutely dependant on natural gas prices and is currently the least expensive among all bulk hydrogen production technologies. A well-developed natural gas infrastructure already exists in the U.S., a key factor that makes hydrogen production from natural gas attractive.

22

1.15 Description of Reformer The steam reformer is a rectangular insulated structure containing vertically supported tubes filled with nickel oxide catalyst in which the steam reforming takes place at elevated temperatures. The endothermic heat of reaction is supplied from downward firing burners situated in the roof of the Reformer. These are fired on a mixture of combined process waste gas streams supplemented with natural gas. The burners are arranged in rows between the reforming tubes and are positioned such that no flame impingement occurs on the tubes or on the furnace walls. The natural gas and steam reactants are evenly distributed by a system of headers on the top of the reforming furnaces and the connections to each tube are made by solid drawn alloy flexible connectors.

23

Production Process Table(1-7):- Production Technology Scorecard

Production Technology Scorecard

Description

Feedstock

Other

Challenge

Steam reforming converts methane (and other hydrocarbons in natural gas) into hydrogen and carbon monoxide by reaction with steam over a nickel catalyst.

Natural Gas (CH4) 70% efficient. Will require carbon sequestration. Improve reforming efficiencies, identify more durable reforming catalysts, and reduce carbon sequestration costs. Develop advanced reforming and shift technologies.

24