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A Model and Simulation of Methanol Synthesis System
Issa Idriss Mohammed Ismail
B.Sc. in Chemical Engineering Technology
University of Gezira (1999)
A Dissertation
Submitted to the University of Gezira in Partial Fulfillment of
the Requirements for the Award of the
Degree of Master of Science
in
Chemical Engineering
Department of Chemical Engineering and Chemical Technology
Faculty of Engineering and Technology
August, 2015
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A Model and Simulation of Methanol Synthesis System
Issa Idriss Mohammed Ismail
Supervision Committee:
Name Position Signature
Dr. Babiker Karama Abdalla Main Supervisor --------------------
Dr. Mustafa Ohaj Mohammed Co-supervisor -----------------
---
August, 2015
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A Model and Simulation of Methanol Synthesis System
Issa Idriss Mohammed Ismail
Examination Committee:
Name Position Signature
Dr. Babiker Karama Abdallah Chair Person --------------
Prof. Gurashi A. Gasmelseed External Examiner ------------
--
Dr. Magdi Ali Osman Internal Examiner -----------
---
Date of Examination: 29/8/2015
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Dedication
This dissertation is entirely dedicated to the souls of my beloved father and
Dr. Mohammed Osman Abdelrahman Alagooz may Allah bless them and award them
the highest Paradise.
5
Acknowledgements
I lay the completion of these endeavors at the door of the Almighty
Allah. To him are all praise, glory and thanks for making this dissertation a befitting
success.
First and foremost, I would like to thank Dr. Babiker Karama Abdallah
as supervisor of this dissertation .His never ending support and encouragement made
me come to an end, so I have to express my appreciation to him for his golden rules,
guidance, constructive advice, continual suggestions and encouragement throughout
this dissertation. His willingness to help has inspired to continue this dissertation, his
dense knowledge in this area of specialization beside his easy going way of
welcoming his students as colleagues give his students straight forward and clear map
road to good steps about how to conduct research. In respect my endless thanks and
gratitude to Professor Kamel Mohammed Wagieallah, a professor of Modeling and
Simulation at the University of Khartoum for not inspiring but also invited to attend
lectures with his master students and his care continues. My equal thanks to Engineer
Ammar Magzoub Omer for his efforts in this area where very relevant and long
armed.
I owe my deepest gratitude to my mother for her strong support, she is
the rock of my family and everything I have become, I owe to her selfless love. To
my family thank you for your comedic support over the years. I am immensely
grateful to my wife Bederia, my daughters Nidal, Nihal, along with my sons Mubarak
and Muiad for their love. It is impossible to forget the debt I owe to Dr. Ahamed and
Dr. Zeinab from Sudan University of Science and Technology, for their strong role
and endless help and good hints. Equal thanks to Alnazeer Ahamed from Tax
Authority, I have to add my friend engineer Mahdi Mohamed Ali head of the
Department of Production and stores at Wafra Pharmaceutical Company LMTD to the
list of who backed me a lot, heartfull thanks to my colleague during course work
Yassir Abdallah, and now his my fellow at the university for his good help with
Aspen Plus hints. Last and not least, my special thank to engineer Mubarak Ahamed
and his colleague chief engineer from ministry of industry for their endless help and
constructive criticize for a whole modeling work. My heartfull, appreciation to my
examination’s committee members for their invaluable suggestions and a good
feedback. Heart thanks to the Director of the University of Gezira complex in
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Khartoum engineer Amjad Abdu, his role will never be forgotten and also my thanks
to the staff members of the Department of chemical engineering of the University of
Gezira for their great help and support.
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Model and Simulation of Methanol Synthesis System
Issa Idriss Mohammed Ismail
Abstract
Methanol is one of the prime candidates for future coming clean biofuel, it
is the most promising intermediate raw material in the most industrial plants .It will
be the of the best one suited for racing cars and polymer industries as well as
refreezing agent. An innovative process scheme to produce methanol from hydrogen
and carbon dioxide is here presented and accessed via modeling and simulation. The
main objective of this study is to introduce a novel approach to synthesis methanol
using modeling and simulation techniques to come up with feasible plant design and
operating conditions. This study is dedicated to use modeling and simulation
techniques, the main raw materials were carbon dioxide, hydrogen, water and
methanol as a seed product, the Aspen HYSYS v.7.3 software was used as a
complete environment platform for developing a complete system mimics logical
natural real life steps, at first basic conditions were set up, these conditions were
CO2/H2 ratio; as feed with 40 0C, 4000 kPa, and SRK(Soave Redlich Kwong)
equation for ideal gases as fluid package for vapour phase reactions to yield liquid,
two case studies were performed first one, was pressure versus actual conversion, in
the first case study pressures were 2000, 3000, 4000, 4500 and 5000 kPa, the yield
was 0.95, 0.96, 0.96, 0.96 and 0.97 mole fractions respectively, the second case, was
temperature values were 25, 30, 40, 50 and 60 0C; the yield in each temperature, was
0.96, 0.97, 0.95, 0.96 and 0.96 mole fractions respectively; for both cases CO2/H2
ratio was 0.3 these conversion rates and product of methanol were recorded. After the
thorough investigations, the result for methanol was 0.98 as the optimum result, when
pressure was 2000 kPa and ratio of CO2/H2 was 0.18, on the other hand 0.77 mole
fraction was the least value, when feed temperature was 40 0C, pressure 4000 kPa
and CO2/H2 ratio was 0.5. Finally, the area of modeling and simulation are promising
approach, so the study recommends researcher conducting more comprehensive
researches using modeling and simulation techniques. In terms of raw materials
natural gas is the one of substances for this study, beside this CO can be used instead
of CO2, in addition to that synthesis gas is also suitable.
8
نظبو حصيع انيزبلرس يحبكبة
عيغي إدسيظ يحذ إعبعيم
يهخص انذساعت
يزم أى عيط اعذ كبدة خبو في ,أى انبذائم انغخقبهيت نهقد انحيي انيزبل أحذيعخبش
إني أ يبدة غيبساث انغببق صبعت انبنيشاث ببلإضبفت ن يبعب كقد ,ءاث انصبعيتآيعظى انش
ببعخخذاو أعبنيب انزصت انيزبلحذف ز انذساعت إني حقذيى يقبسبت صذيذة في حصيع . نهخبشيذ انخضيذ
ز انذساعت ,ث راث صذي إقخصبديت فيت يع ظشف حشغهيت يزبنيتآءشنانحبكبة نضع حصيى
ربي أكغيذ انكشب انيذسصي الاحيت:انخبو ببعخخذاو اناد انيزبلخصصج نزصت يحبكبة حصيع
كبيئت يصت حطيش يخكبيهت نخطيش ظبو Aspen HYSYS v7.3اعخخذيج بشيضيت انيزبل.انبء
04 :أعذث انظشف انخشغيهيت عهي انح انخبني ,ة حقيقيتؤيخكبيم يحبكي انخطاث انطقيت انطبيعيت نش
نهغبصاث انزبنيت كحضيت Soave Redlich Kwong كيه بغكبل يعبدنت 0444 دسصت يئيت انضغط
: خيي رى أصشيج دساعت حبن .كيت ي يخصصت نهخفبعلاث في انطس انغبصي لاخبس انغائميريشيديبي
0444, 0444, 0444 عهي انح انخبنيقيى انضغط كبجش انضغط عهي يعذل انخحل حؤريالأني
عهي كغس ينيت 0..4 0..4 , 0..4, 4.0 ,0..4 كبجكيه بغكبل, كيت انخش 0444 0044,
04 ,04 ,04 ,00: كبجش دسصت انحشاسة عهي يعذل انخحل , دسصبث انحشاسة يؤرحانخشحيب انحبنت انزبيت
عهي انخشحيب .ي رى كغس ينيت 0..4 0..4 ,0..4 ,0..4 ,0..4كيت انخش : ,دسصت يئيت 04
عهي أعبط كغش يني 0..4دج خبئش يعذلاث انخحل نكم حبنت دساعيت أخزث انخبئش , إر ظشث
كيه 0444انضغط ,دسصت يئيت 04نكيت انكحل انخش كؤفضم ضعيت نلإخبس , عذ دسصت انحشاسة
عهي أعبط 4.00نهخش ي غبت بيب أقم 0..4إني انيذسصي ببعكبل غبت ربي أكغيذ انكشب
كيه ببعكبل غبت ربي أكغيذ انكشب 0444دسصت يئيت , انضغط 04كغش يني عذ دسصت انحشاسة
. حصي انذساعت انببحذ ببنضي قذيب بإصشاء بحد أكزش شنيت في ييبدي 4.0إني انيذسصي ي
بحيت ي بإعخببس أ إصشاء الابحبد نهشبسيع انكييبئيت انصبعيت راث كهفت عبنيت. حبكبةانزصت ان
انغبص انطبيعي يعخبش انبذيم انششح لإ ز انذساعت , إضبفت إني أ يك اعخخذاو أل صشاء اناد انخبو , أ
ي انقخشحبث انضيذة . أكغيذ انكشب بذيلا نزبي أكغيذ انكشب انغبص انصبعي كاحذ
9
Table of Contents
PP Title Item
ii Examination Committee………………………………………....
iii Examination Committee…………………………………………
iv Dedication………………………………………………………..
v Acknowledgements………………………………………………
vi Abstract…………………………………………………………..
vii Abstract (Arabic)………………………………………………...
viii Table of Contents………………………………………………...
xi List of Figures……………………………………………………
xii List of Tables……………………………………………………
xiii Abbreviations……………………………………………………
Chapter One: Introduction
1 Problem Statement ……………………………………………… 1.1
1 History of Methanol …………………………………………….. 1.2
2 Motivations (Research Needs)…………………………………... 1.3
3 Objectives………………………………………………………. 1.4
3 Outlines (Work Organization)………………………………….. 1.5
Chapter Two: Literature Review
4 Background …………………………………………………….. 2.1
6 Literature Review……………………………………………….. 2.2
14 Kinetics of Methanol Synthesis…………………………………. 2.3
15 Methanol Synthesis Processes…………………………………... 2.4
11
17 Chemical Systems Synthesis (Chem Systems)………………….. 2.4.1
19 Imperial Chemical Industries Synthesis………………………… 2.4.2
20 Lurgi Synthesis………………………………………………….. 2.4.3
Chapter Three: Materials and Methods
23 Instruments ……………………………………………………. 3.1
23 Methods……………………………………………………….. 3.2
24 Modeling Process Flow sheets in Aspen HYSYS v. 7.3 ……... 3.3
25 Types of Models……………………………………………… 3.4
25 Mathematical Models………………………………………… 3.4.1
27 Physical Models ……………………………………………… 3.4.2
27 Chemical Models…………………………………………........ 3.4.3
28 Production Technologies............................................................. 3.5
28 Synthesis Gas.............................................................................. 3.5.1
28 Steam Reforming........................................................................ 3.5.2
29 Auto Thermal Reforming............................................................ 3.5.3
29 Carbon Dioxide Reforming......................................................... 3.5.4
30 Methanol Synthesis..................................................................... 3.6
31 Methanol Reactors...................................................................... 3.7
31 Multiple Bed Reactors................................................................ 3.7.1
32 Single Bed Reactors.................................................................... 3.7.2
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33 Catalysts...................................................................................... 3.8
34 Reactions of Methanol……………………………………........ 3.9
35 Model Formulation and Process……………………………… 3.10
35 Process Description……………………………………………. 3.10.1
37 Starting Aspen HYSYS v.7.3…………………………………. 3.10.2
38 Reactions of Methanol Synthesis Using Aspen HSYSv.7.3…... 3.10.3
38 Basis Components of Methanol Reactions……………………. 3.10.4
38 Parameters of Arrhenius Equation…………………………….. 3.10.5
39 Experimental Data…………………………………………….. 3.10.6
Chapter Four: Results and Discussion
40 Results ………………………………………………... 4.1
42 Discussion…………………………………………….. 4.2
Chapter Five: Conclusions and Recommendations
46 Conclusions……………………………………………………. 5.1
46 Recommendations…………………………………………….. 5.2
48 References…………………………………………………….................
Appendix
12
List of Figures
pp Title Item
16 Block Diagram of Major Process Unit of Methanol Synthesis…… Fig
(2.1)
18 Chem Systems Synthesis…………………………………………... Fig
(2.2)
21
Flow Diagram of Low pressure methanol process based on ICI
process………………………………………………………………
Fig
(2.3)
36 Methanol Synthesis Flow Diagram ……………………………… Fig(
3.1)
42 Pressure Versus Conversion Effect………………………………… Fig
(4.1)
43 Temperature Versus Conversion…………………………………… Fig(
4.2)
44 Ratio of CO2/H2 vs. % Conversion………………………………… Fig
(4.3)
44 Ratio CO2/H2 and Product………………………………………….
Fig(
4.4)
13
List of Tables
pp Title Item
38 Kinetic of Methanol Reaction Data Table(3.1)
40 Ratio of CO2/H2 vs. %conv Table(4.1)
40 Temp vs. %conv and Product Table(4.2)
41 Pressure vs. %conv and Product Table(4.3)
41 Properties of Final Product Table(4.4)
14
Abbreviations
ICI Imperial Chemical Industries
Aspen Advanced System for Process Engineering
DHFC Direct Hydrogen Fuel Cell
MTBE Methyl tertiary Butyl Ether
RMFCS Reformed Methanol Fuel Cell System
COG Coke Oven Gas
CP Conventional Process
ASU Air Separation Unit
HHV Higher Heating Value
LHV Lower Heating Value
LDC Lesser Developing Countries
TAME Tertiary Amino Methyl Ether
WGS Water Gas Shift
kPa Kilo Pascal
DOE Department of Energy
GUI Graphical User Interface
ATR Auto Thermal Reforming
FKG Fluid Package
CNV Conversion
PFD Process Flow Diagram
Temp Temperature (0C)
P Pressure (bar)
SRK Soave Redlich Kwong Equation
CTM CO2 to Methanol
CC Carbon dioxide Capture
CSTR Continuous Stirred Tank Reactor
15
Chapter One
Introduction
16
Chapter One
Introduction
1.1 Problem Statement:
Methanol is considered as one of the essential raw materials for many
chemical organic compounds, so the problem how to come up with an optimum
producing conditions for manufacturing this compound. Accordingly, in this study
Aspen HYSYS v7.3 software is a good alternative solution for this simulation at
various factors.
1.2 History of Methanol
Methyl alcohol or Methanol, CH3OH, is sometimes called wood alcohol
(Weissermel and Arpe, 1993), it was formerly produced by the destructive distillation
of wood. In Greek methe means wine , and hyle means wood , then methyl alcohol is
the wine of wood .Also it can be said methanol, a C1-molecule , is mainly produced
from synthesis gas and is the simplest of the series of aliphatic alcohol(
Rahman,2011).
Methanol is believed to have been discovered by R.Doyle in 1661 through
the rectification of crude vinegar over milk of lime. He named the new product a
diaphorus spirit lignorum. There was no written history or record of its use for any
purpose, either domestic or industrial, before the 19th
century.
The chemical or molecular identity of methanol was first established independently
by J.B.A.Dumas and J.Von Liebig in 1834.The term methyl was introduced into
chemistry in 1835 on the basis of their work.
Since then, efforts have been made various investigators to synthesize methanol, and
a successful attempt was synthesis by dry distillation of wood, obtained by
M.Berthelot in 1857. Referring to its synthesis origin and route, methanol has since
been called wood spirit by some people (Lausanne, EPFL, 1998). Obviously this nick
name is fading away due to its totally different synthesis route.
The most important synthetically method is that originally discovered
by Sabatier in 1905, which effected the catalytic combination of carbon monoxide and
hydrogen. In 1913 The Badische Anilin und Soda Farbrik patented the use of a wide
range of catalysts for promoting the conversion of the constituents of water gas into a
complex mixture of methyl and other alcohols, aldehydes and ketones .A variety of
17
patents quickly followed, but perhaps the most outstanding work is that of Patart in
France, who used as raw materials either carbon monoxide and hydrogen or methane
and oxygen (Kent, 1974). In addition to that, A.Mittasch and coworkers at BASF
successfully produced organic compounds containing oxygen, including methanol,
from carbon monoxide and hydrogen in presence of iron oxide catalyst during
development work on the synthesis of ammonia.
The decisive step in the large scale industrial production of methanol was made by
M.Pier and coworkers in the early 1920s, with the development of a sulfur resistant
zinc oxide chromium oxide catalyst.
1.3 Motivations (Research Need):
Methanol is the most promising fuel for fuel cells (Methanex 2000a, Statoil
2000a). A fuel cell converts chemical energy directly into electrical energy.
Hydrogen is the 'dream' fuel for fuel cells because the only reaction product is water.
The Direct Hydrogen Fuel Cell (DHFC) technology is well developed. However,
There are many unsolved problems with production, storage, transportation and
Safety of hydrogen gas. There are two alternatives for the use of methanol in fuel
Cells; Reformed Methanol Fuel Cell System (RMFCS), where methanol is steam
Reformed to provide hydrogen to a fuel cell engine, and Direct Methanol Fuel Cell
(DMFC) where methanol, is used as reducing agent in the fuel cell engine.
Reforming of methanol is considered to be the easiest way to supply
hydrogen from a liquid fuel. The RMFCS is technologically mature and is expected to
reach the market in few near years. The emissions of CO2 on a life cycle basis from
fuel cell vehicles will be reduced by 42 % compared to today's gasoline vehicles.
Several producers have developed methanol driven fuel cell vehicles with this
Technology. Methanex and Statoil have started a pilot programme on the supply,
distribution and marketing of methanol for fuel cell vehicles (Statoil,2000a).
Pilot programmes on domestic and industrial use of methanol driven fuel
cells are also started by the two companies and Northwest Power Systems (Statoil,
2000c).
The DMFC eliminates the need for a methanol reformer, which reduces the
cost and weight of the fuel cell engine. Methanol is an important industrial material
and it is used in the manufacture of formaldehyde, and as an anti-Freeze in car
radiators.
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1.4 Objectives:
1.4.1 General objectives:
The overall theme for this study is to define optimal operating conditions
for methanol Synthesis.
1.4.2 Specific objectives:
1. To introduce a novel approach using software to come up with a better way of
synthesis methanol for commercial use.
2. To develop methods of modeling; steady state and dynamic .which can be
developed into a realistic large-scale industrial case.
3 . Contribute to better understanding of the methanol synthesis process.
4 . To run simulation at different operating conditions and investigate the results
so as to set the optimum design parameters.
1.5 Outline (Organization) of Work:
This thesis consists of five chapters, they are organized as follows:
Chapter one is an introductory one , it presents the research (statement) problem ,
objectives of study, the importance of the study, then chapter two's concentration is
mainly devoted to the literature review to have a good background about previous
studies to explore some vital points before go far away in the topic, as long as to know
limitations of previous studies to find out the effectives points in each study , that
will be a good road map for a whole study, thus it will be known what can be
presented in this current work.
Chapter three's core issue is materials and methods ; this chapter will give
a good introduction to the modeling approach as a new noble solution to the most
vital and highly risk engineering problems with approximately costs , beside this ,
types of models will be demonstrated a long with their different categories .
Rate of equations, thermodynamics parameters, state variables, process
conditions and dynamic modeling approaches will be on the focused.
This consequence will lead to the target the modeling of methanol synthesis
plant design using Aspen HYSYS 7.3 Suite Package .In addition to that , chapter four
will be directed to discussion of obtained results from this work in light of modeling
criteria a long with the literature review presented before .
The last chapter will be conclusion of whole research work, and propose future
work for overcoming problems and incompleteness in this work.
19
Chapter Two
Literature Review
21
Chapter Two
2. Literature Review
2.1 Background
Before 1926 ,all methanol especially American one , was produced by
the destructive distillation , that year, however, marked the first appearance in the
world of German synthetic methanol .Today, almost (Kent, 1992) all of the
approximately 8.3billion lb/year .of methanol made in the USA comes from large
scale , integrated plants for conversion of natural gas to synthesis gas to methanol.
In principle, methanol is derived from synthesis gas can be made not
only from convenient natural gas but from any source of reduced organic such as coal,
wood, or cellulosic agricultural waste. It then can be used as a readily stored fuel, or
shipped for use as fuel or raw material elsewhere (Kent, 1992). As petroleum and
natural gas become more difficult to recover, alternative carbon sources such as these
will be used more .An example involving methanol is a coal based acetic anhydride
facility started in the 1980s in USA (Kent, 1992).
Industrially, (Weissermel and Arpe, 1993) methanol is converted into
formaldehyde or used to synthesize other chemicals. It is used as solvent and a clean-
burning fuel, especially for racing cars.
Unlike beverage alcohol, methanol is toxic when ingested in small
quantities. Blindness is a symptom of methanol poisoning, since it damages the optic
nerve; death can also result.
In addition to fore mentioned, methanol is used as solvent, antifreeze, a
refrigerant and chemical intermediate. The greatest chemical uses for methanol is raw
material for, formaldehyde, methyl tertiary butyl ethylene (MTBE), and acetic acid.
Other chemical derived from methanol include methyl halides,
methylcrylate, and methylamines. Additional methanol capacity will be required to
meet the expected growth of MTBE consumption.
The methanol synthesis reactions are highly exothermic; the catalysts
used were based on ZnO-Cr2O3 compounds and the process was operated at
temperatures between 300 and 400°C and at pressures between 250 and350 bars. This
is the well-known high pressure process. The zinc-chromate catalyst had a very high
resistance to catalyst poisoning, especially towards sulphur, which was quite abundant
in the early coal-based synthesis gases. Later, ICI developed the low pressure process,
21
which was made possible by two developments which took place simultaneously. It
had become possible to produce large amounts of pure synthesis gas, essentially free
of poisons like sulphur and chlorine and a better catalyst was discovered; the
combination Cu/ZnO which was clearly much more active. The problem with this Cu-
catalyst was its sensitivity under process conditions. It became possible during the
mid-sixties to produce a catalyst that was stable under process conditions by using
support materials like Al2O3 and Cr2O3. With the low pressure process the synthesis
takes place at pressures of 50-100 bar and temperatures of 220-280°C.
Modern methanol synthesis plants use a Cu/ZnO/Al2O3 catalyst.
Reproducible preparation of this catalyst is very difficult, as the catalyst precursor
must consist of several phases, of which the mixed metal hydroxyl carbonates rosasite
and hydrotalcite are the most important for achieving the desired activity and
stability. A high catalyst activity is related to a high copper surface area or small
crystallite size combined with intimate contact with the zinc promoter. The decrease
in activity is connected with the loss of copper surface area by crystal growth,
although the relationship is not unambiguous.
The synthesis gas needed for the process can be prepared in several
ways. In the past steam reforming of naphtha was frequently used. Another possibility
was the partial oxidation of vacuum residues. Nowadays most synthesis gas is
produced by reacting methane with steam. Natural gas and the gas which is released
in oil production are particularly cheap raw materials. The synthesis gas is obtained
by steam reforming (over a Ni/α-Al2O3 catalyst at 1100 K).
In the 1960s, however, ICI (Imperial Chemical Industries) introduced a
highly selective copper zinc oxide catalyst, putting an end to the higher pressure
methanol synthesis technology. These catalysts operated at fairly mild reaction
conditions (50-100 bar and 200-300C0). Today's industrial production of methanol is
exclusively based on this technology. As an example, in 1995, 25.1*106 tones of
methanol were produced worldwide, unfortunately there is no official records in
Sudan show how much of methanol is produced because there is no plant.
Today, the most widely used catalyst is a mixture of copper, zinc oxide,
and alumina oxide first used by The Imperial Chemical Industries (ICI) in 1966. At 5
- 10 MPa and 250 °C, it can catalyze the production of methanol from carbon
monoxide and hydrogen with high selectivity. The reaction is carried out in the gas
phase in a fixed bed reactor. The good catalyst life and selectivity, larger capacity
22
single-train convertor designs, power requirements, and improved reliability of the
low pressure technology result in lower energy consumption and economy of scale.
Current catalysts may contain, next to copper and zinc oxide on alumina, other
stabilizers and promoters, such as alkaline earth oxides. These have several roles,
including inhibition of sintering, and poison traps that prevent poisoning of the active
metal surface.
In this chapter some studies and efforts will be presented, these trials
will be a road map for coming chapters, herein some of these work.
2.2 literature Review:
It was reported by (Bermudez et al.) a novel method of producing
methanol from coke oven gas (COG), it was involving CO2 reforming of COG to
obtain appropriate syngas for the synthesis of methanol was proposed. This new
approach was compared with conventional process (CP) of methanol synthesis from
natural gas. It reported that in terms of energy costs and CO2 emissions, raw
materials, exploitation and methanol quality.
According to this study, the energy consumption was found in
conventional process (CP) has higher energy requirements than the (COG) process.
However, the (CP) process allows a higher energy recovery, this leads to lower
energy consumption per kg of methanol production than in the case of (COG). At the
other hand the CO2 balance showed (revealed) that the (COG) process is more
sustainable than the (CP) process. The study went ahead to add, that both processes
showed a high level of exploitation, though (COG) is more efficient, this also the
same for yield of hydrogen.
In addition to that, the study the raw methanol obtained with the (COG)
process also fulfills the purity requirements for use without need for additional
purification stages, though; a higher level of purification will be required for other
uses. In (CP) process the level of purity achieved is lower, and further purification
will be required in all cases, which will entail higher costs.
The sum up of this study reflected that the (COG) process has been
shown to be superior to the (CP) process from perspective of environment, raw
materials exploitation and purification costs. From the point of energy an appropriate
energy integration strategy will play a decisive role in turning the scales in favor of
one process or other (COG) requires lower energy inputs, but the possibility of
23
recovering energy is considerably higher in the (CP), which could result in a reduction
in energy consumption to a level below that achieved by (COG).
A conventional process of coal to methanol was carried by( Chen et al.
,2010) with system level of simulation model has four major processes: include Air
Separation Unit (ASU), gasification process gas cleanup modules, and methanol
synthetic unit. The simulation procedures were performed in benchmark models and
case study of methanol production. The benchmark models are built to verify the
reference data in clean syngas providing and methanol synthetic process, respectively.
The deviations compared with reference data are relatively reasonable in general.
Thus the model of methanol production plant employs the verified model and takes
necessary modification to make the processes co-operate well. The results show that
gross and net efficiency in the case study are 77.7% higher heating value (HHV) and
63.3% lower heating value (LHV), respectively. It is relatively higher than
counterparts in traditional plants and the poly generation plant of electricity and
methanol .The study suggested to shift to alternative choice to reduce the dependence
on methanol importing in some countries with plants converting coal to methanol, if
the process is efficient and cost effective.
This study under took by (Chatterjee and Chatterjee, 1981) in early
eighties due to the crisis of fuel and energy especially petroleum resources; this study
was to find alternative energy sources which will release a worldwide bottleneck of
fuels availability in the most parts of the world. The starting point of the problem is,
the rising cost of imported fuel in many countries, especially lesser developing
countries (LDCs) were watching their hard earned export revenues disappear as they
pay the price of imported fuel. So, the study proposed alternative energy source of
energy, by United States Department of Agriculture and methanol was the best
choice. As this study stated methanol has a good heat content which makes it an
attractive to imported fuel.
The study was mainly concentrated on production of methanol via the
gasification of coal, naphtha; natural gas at the industrial level was approved.
Thus, for the (LDCs) where fossil fuels are scarce and expensive and a large biomass
resource exist, the production methanol from biomass derived synthesis gas represents
an attractive alternative to fossil fuels.
24
In addition to that, the study remarked by saying "However, since
only technologically and economically proven process can be recommended for use in
LDCs"
This study took into consideration the availability of raw materials,
agricultural and silvicultural, beside other renewable sources; because fossil fuels are
scarce and expensive in LDCs where a large amount of biomass exists.
Brown reported that, smaller quantities of methanol can be produced
economically in plants where part of the investment is borne by another product. In
case of urea producers can extend their plant to resins, refiners can back integrate to
make the other feedstock for (MTBE) methyl tertiary butyl ether and (TAME) tertiary
amino methyl ether. The study also proposed the same for ammonia producers who
decide to co-operate methyl maybe thinking of trading some of the products to nearby
resin producers.
Jiyong et al. (2011), described a novel solar based for production of
methanol from carbon dioxide and water. The system utilizes concentrated solar
energy in a thermo chemical reactor to reenergize CO2 into CO and then water gas
shift (WGS) to produce syngas (a mixture of CO and H2) to feed a methanol
synthesis reactor.
This works presents an initial assessment of energy efficiency and
economic feasibility of this baseline configuration for an industrial scale methanol
plant. The trail showed that the produced methanol is higher than current prices is
comparable to other renewable resources based alternatives.
However, this work has highlighted the cost drivers and technology gaps and shows
that, there are many opportunities to optimize the system design.
Here are lists of literature review cited by:
Yoshihara and Campbell, (1996) studied the kinetics of simultaneous
methanol synthesis and reverse water–gas shift from CO2/H2 and CO2/CO/H2
mixtures. The analysis was conducted at low conversions over a clean Cu (110)
single-crystal surface at pressures of 0.51 MPa. They reported a conversion of 8 × 103
methanol molecules per second per Cu surface atom with the absence of CO. This
study was conducted at 530 K; in which the activation energy was 67 × 17 kJ/mol.
They reported a CO production at a rate of 5 molecules per second per Cu surface
atom; and activation energy of 78 × 14 kJ/mol. When compared with previous rates of
Cu (100) and polycrystalline copper foil, these rates were found to be higher in both
25
methanol synthesis and CO production. The surface of the catalyst was covered after
the reaction by nearly a full narrow layer of adsorbed formate. However, the other
species like carbon or oxygen were not observed. Moreover, the addition of CO in to
the feed caused an increase methanol production rate. It should be noted that Cu
(100) and (110) are both crystal structures of copper; however, the direction vectors in
their cubic unit cells are different.
Li et al. (1997) used Cu-Zn-Al and Cu-Zn-Al-Mn catalysts for
methanol synthesis. These catalysts were arranged by a high speed collision co-
precipitation method. The methanol yields reported were 28.4 and 33.8 mol/l.cat.h
over the ternary and quaternary catalysts, respectively. The results showed that Mn
allows diffusion of copper in the catalysts, avoiding the copper particles from
sintering. The diffuse reflectance spectra advised that the formate might be the
intermediate in the methanol synthesis.
Fisher and Bell (1998) studied the relations of CO and H2/CO with
Cu/SiO2, ZrO2/SiO2, and Cu/ZrO2/SiO2 in infrared spectroscopy with the purpose of
understanding the nature of the species involved in methanol synthesis, the kinetics of
the formation and consumption of these species. For Cu/SiO2, they showed that
carbonate species adsorbed on Cu sites and methoxide (CH3O-) species adsorbed on
Cu and Silica site. These results were observed at 523 K, a total pressure of 0.65 MPa
and a rate of H2/CO=3. The formations of carboxylate, bicarbonate, and formate
species on zirconium were observed when carbon monoxide adsorption occurred on
either ZrO2/SiO2 or Cu/ZrO2/SiO2. In the existence of hydrogen, formate species were
hydrogenated to methoxide species adsorbed on ZrO2. The existence of Cu greatly
accelerates the rate of formate hydrogenation to methoxide species. In this process,
methylenebisoxy species were observed as intermediates. Cu also supported the
reductive elimination of methoxide species as methanol. Therefore, methanol
synthesis over Cu/ZrO2/SiO2 was intended to occur on ZrO2; with the main role of
Cu, adsorption of H2 had occurred. The overflow of atomic hydrogen onto ZrO2
provides the source of hydrogen required to hydrogenate the carbon-containing
species. Overflow of absorbed CO from Cu to zirconium enabled formate creation on
zirconium at lower temperatures than with the lack of Cu. The reductive elimination
of methoxide is performed to the slow stage in methanol creation from CO
hydrogenation. The lower rate of methanol synthesis over Cu/ZrO2/SiO2 from CO as
compared to CO2 hydrogenation was credited to the absence of H2O formation in the
26
former reaction. The improved rate of methanol synthesis from carbon monoxide over
Cu/ZrO2/SiO2 as compared to Cu/SiO2 was due to the lower energy-barrier (formate)
pathway available on Cu/ZrO2/SiO2.
Nerlov and Chorkendorff (1999) studied the catalytic activity of Cu
(100) and Ni/Cu (100) regarding methanol synthesis from different combinations,
which contained carbon dioxide, carbon monoxide, and hydrogen. The reactions
occurred in a combined ultra-high vacuum /high pressure cell device; with conditions
of reactor pressure of 0.15 MPa and temperature of 543 K. It was observed that the
charge of CO to a reaction combination containing carbon dioxide and hydrogen does
not cause an increase in the rate of methanol production. The investigation showed
that the role of carbon monoxide in the industrial methanol process relates to the
alteration in reduction potential of the synthesis gases. Furthermore, for the Ni/Cu
(100) surface, it was observed that Ni does not stimulate the rate of methanol
formation from mixtures containing carbon dioxide and hydrogen. On the other hand,
the charge of carbon dioxide to the reaction mixture causes an important rise in the
rate of methanol production. It was found that the charge of carbon monoxide to the
synthesis gas creates exclusion of Ni to the surface, whereas this was not the case for
a reaction involving carbon dioxide and hydrogen. It was suggested that carbon
monoxide serves as an organizer in the system.
Jung and Bell (2000) showed that the synthesis of methanol from both
carbon dioxide and carbon monoxide, associated with Cu/ZrO2 catalyst, involved the
overflow of hydrogen molecules formed on Cu to the surface of ZrO2. The atomic
hydrogen then participated in the hydrogenation of carbon-covering species (such as:
HCOO-Zr and HCO3-Zr) to methanol. Based on their analysis, it was determined that
the rate of hydrogen overflow from Cu was more than an order of scale faster than the
rate of methanol production.
Tsubaki et al. (2001) developed a new system to synthesize methanol
from hydrogen and carbon monoxide. This system worked at high pressure and low
temperature. Carbon dioxide as well as water was involved in the system which was
copper-based. Alcohol, as a catalytic liquid medium, with the support of copper-based
solid catalyst, reformed the reaction path to a low-temperature direction.
Velardi and Barresi (2002) studied the feasibility of the methanol
synthesis process in unsteady-state conditions. They used three catalytic fixed bed
reactors with periodic alteration of the inlet situation, in order to investigate benefits
27
and limitations in comparison with the former proposed reactor. The influences of the
chief operating limitations (such as initial temperature, switching time, and initial
flow rate) were studied.
Mignard et al .( 2002) studied the feasibility of methanol production
from flue gas carbon dioxide with the aim of reducing carbon dioxide emission levels
and increasing the level of renewable energy. It was showed that important benefits
accumulate from successful development of a methanol process and that it may
facilitate the absorption of increasing levels of carbon dioxide.
It was found that the nano particle ZnO, Cue/ZnO and NiO were much
more active catalysts than the commercially available materials. The nano crystalline
CuO sample was found to rapidly reduce to Cu, where it lost all activity. The results
suggested that the catalytic process was efficient for several nano particle metal oxide
formulations, however, copper metal is not active, but small copper particles in a
CuO/ZnO matrix are a very active combination.
Kordabadi and Jahanmiri (2005) proposed a method through which an
optimization of methanol synthesis can be achieved to improve total production. A
mathematical heterogeneous model of the reactor was investigated in order to increase
the reactor performance. This study was performed for both steady state and dynamic
conditions. Genetic algorithms were carried out as authoritative methods for
optimization of the problems. Initially, an ideal temperature profile for the reactor
was calculated. In order to maximize methanol production, a stepwise method was
monitored to develop an optimum two-stage cooling shell. This optimization method
provided a 2.9% additional methanol yield in 4 years, which is the catalyst lifetime.
Golindo and Badr (2007) compared different methods of methanol
synthesis from different sources of CO2. They showed that methanol production from
biomass is cheaper and more efficient than from CO2 of flue gases.
Gallucci and Basile (2007) proposed a theoretical method for carbon
dioxide conversion to synthetic methanol from both a traditional reactor and a
membrane reactor. The aim of this method was to study the prospect of increasing
carbon dioxide conversion into methanol, regarding a traditional reactor. A
mathematical model is investigated in order to simulate a traditional chemical reactor.
When comparing experimental with modeled data, the validation of the simulation
was studied. Moreover, the model was carried out in order to predict the performance
of carbon dioxide conversion and methanol selectivity. The results illustrated that it is
28
possible to achieve both higher carbon dioxide conversion and methanol selectivity
regarding a traditional reactor performance at the same experimental conditions.
Toyir et al.( 2009) studied methanol synthesis from carbon dioxide and
hydrogen in order to achieve to carbon dioxide mitigation. Highly efficient Cu/ZnO
based material catalysts were investigated. They categorized the metal oxides
contained in Cu/ZnO-based catalysts into two classifications. Al2O3 or ZrO2 enhanced
the diffusion of copper elements in the catalyst. Ga2O3 or Cr2O3 enhanced the
chemical potential per unit copper surface area of the catalyst. The durability of
Cu/ZnO-based catalysts had been enhanced by adding a small quantity of silica to the
catalysts. The additional Silica caused the catalysts to be repressed in the
crystallization of ZnO which was controlled in the catalysts. The catalysts were very
active and exceedingly stable in methanol synthesis from carbon dioxide and
hydrogen.
An et al. (2009) developed an extremely active Cu/Zn/Al/Zr fibred
catalyst for methanol synthesis from carbon dioxide hydrogenation. Several factors
had an influence on the performance of the catalyst, such as the reactor temperature,
reactor pressure and space velocity, were analyzed. In order to model the methanol
synthesizer, the kinetic factors in Graaf's kinetic model were used. A carbon
monoxide circulation was considered and consequently, a higher methanol production
was obtained. According to the simulation, the space time yield of methanol improved
and there was no carbon monoxide in the production stream, which proved a decent
potential application for industry.
Rihko-Struckmann et al. (2010) simulated a low-pressure methanol
production process with CO2 and H2. They designed a methanol reactor cascade with
a recycle loop to increase the methanol production. They used a Cu/ZnO2/Al2O3
catalyst as well. The exergy efficiency was reported as 83.1%.
Nieskens et al. (2011) described experimental results which were
achieved from a fixed bed reactor by means of a CoMoS catalyst. Only carbon
dioxide and hydrogen were used as the feed of the reactor. In order to use CoMoS
catalysts, they proposed that carbon dioxide and hydrogen can be used. The molar
ratio of hydrogen to carbon dioxide was three. A slight temperature increase did not
disturb the conversion, because of a thermodynamic equilibrium constraint. Although
the hypothesis was proven, a method in which carbon dioxide and hydrogen were
29
changed into alcohols is economically feasible only if the hydrogen can be achieved
in a cost effective manner.
Farsi and Jahanmiri (2011) performed on an investigation and
optimization of methanol production in a dual-membrane reactor. They assumed that a
connector reaction and parting in a membrane reactor increases the reactor efficiency
and decreases the distillation cost in stages. In this arrangement, a methanol reactor is
sustained by Pd/Ag membrane tubes for hydrogen saturation and alumina–silica
compound membrane tubes for water vapour elimination from the reaction sector. A
Pd/Ag membrane was used for water-shift reaction and methane steam reforming
process. A steady state one-dimensional mathematical model was established to
calculate the efficiency of the pattern. The results of the conventional reactor s were
compared with existing industrial plant data. The main benefits of the improved dual
membrane reactor are given as :
i. advanced CO2 conversion;
ii. disabling the limitations which are enforced by thermodynamic equilibrium;
and
iii. Enhancement of the methanol synthesis rate and its purity. A genetic
algorithm was employed as an evolutionary method to maximize the methanol
production as the target function. This configuration predicted a 13.2%
improvement in methanol production.
The methanol process consists of three parts; synthesis gas preparation,
the methanol synthesis and methanol distillation. The following introduction is based
on Lange (2001) and Skrzypek et al.( 1994). The first technology, the high-pressure
synthesis, was commercialized in 1923. It operated above 300 bar and used a Cr-based
catalyst. The low-pressure methanol synthesis replaced the high-pressure methanol
synthesis in the 60s. The low-pressure process resulted from the formulation of a
new and more active Cu-based catalyst, and the ability from the formulation of a
new and more active Cu-based catalyst, and the ability to produce a sulphur-free
synthesis gas. The low-pressure synthesis operates between 50 and100 bar. Two low-
pressure methanol processes dominate the market; the ICI process uses multi-bed
synthesis reactors with feed-gas quench cooling and the Lurgi process uses multi
tubular synthesis reactors with internal cooling. The synthesis gas is a mixture of (CO ,
and H2) that can be produced form different feed stocks: natural gas, higher hydro
carbons and coal.
31
The conventional process for synthesis gas production is steam
reforming, but partial oxidation, CO2 reforming, auto thermal reforming or
combinations are also used. The natural gas is first desulphurized and saturated with
process steam, then reformed in three steps; pre reforming, steam reforming, and
auto thermal reforming.
2.3 Kinetics of Methanol Synthesis:
Three overall reactions are possible in the methanol synthesis
hydrogenation of carbon monoxide, hydrogenation of carbon dioxide and the reverse
water-gas shift reaction
CO +2H2 CH3OH 2.1
CO2 +3H2 CH3OH + H2O 2.2
CO2 + H2 CO + H2O 2.3
Hydrogenation of carbon monoxide used to be viewed as the principal
reaction. The present view is that methanol is formed from CO2 over copper
containing catalyst. This is confirmed by C14
labeling (Chinchen et al. 1987) and in-
situ measurements (Muhler et al. 1994). Only two of these reactions are linearly
independent and define the equilibrium composition. The first kinetic equation was
proposed by (Natta, 1955) for the ZnO/Cr2O3 catalyst used in the high-pressure
process:
The following kinetic models from recent literature have been evaluated:
Graaf et al. (1988), based on the three reactions (labelled2.4, 2.5 and 2.6).
))/((1(
))/((11
222/1
22
2/1
22
1
2
2/1
32
2/3
OfHkHOkHHffCOkCOkCOfCO
keqHfOHfCHHfCOfkCOkr
2.4
))/((1(
))/((22
222/1
22
2/1
22
2
2
2/3
32
2/3
22
OfHkHOkHHffCOkCOkCOfCO
keqHfOHfCHHffCOkCOkr
2.5
))/((1(
))/((33
222/1
22
2/1
22
3
222
OfHkHOkHHffCOkCOkCOfCO
fkeqOfCOfHfCOfHkCOkr
2.6
31
Dual site Langmuir Hinshelwood mechanism where CO and CO2 absorb on
site s1 and H2 and H2O absorb on site s2. Formation of ethanol occurs through
successive hydrogenation and the water gas shift reaction by a formate mechanism.
2.4 Methanol Synthesis Processes
Many companies offer methanol synthesis processes:
Vulcan- Cincinnati, ICI, Lurgi, Mitsubishi and Selas-Polimex are examples of a few.
In recent years ICI and Lurgi have dominated most of the contract awards. Recent
methanol production has been based on a copper-catalyst in a "so called" low
pressure methanol process. The ICI process utilizes a quench type reactor while
the Lurgi process uses a tubular reactor (analogous to a heat exchanger) with
boiling water in the jacket and catalyst in the tubes. Lurgi's success is due
largely to this "iso-thermal" steam recovery type of reactor which allows for a
high process efficiency. Naturally, licensees of ICI have countered with various
designs involving improved heat recovery from the methanol loop (Chatterjee
and Chatterjee,1981).
Methanol production is a highly competitive field with a number of
proven processes as described earlier. A promising new process, supported by
E.P.R.I., is Chem Systems' Liquid Phase Methanol Synthesis. By utilizing an
inert liquid to absorb the heat of reaction they have been able to reduce the
gas recycle substantially. The Chem Systems' synthesis does show potential for a
somewhat higher thermal efficiency and lower capital cost than the ICI or Lurgi
system. It should be noted, however, that the Chem Systems' process has yet to
be proven, both technically and economically, at the industrial level. Hence, its
applicability to LDC’s cannot be recommended at this stage.
32
Fig(2-1) : Block Diagram of Major Process Unit of Methanol Synthesis
1. Wood handling and preparation 2. Feed stock 3. Wood gasification
4.Clean raw gas 5. Compression and hydrogenation 6. High temperature shift
7. Raw syngas 8. Pox of purge gas 9. Pox of tars oils 10. Oxygen 11. Air
separation 12. Light ends to fuel 13. Methanol distillation 14. Product Storage
15. Crude Methanol 16. Methanol synthesis 17. Purge to Gas Fuel
18. Make up syngas 19. Acid gas removal.
1 2 3 4 5
7
6
8 11 9
11 13 16
11 19
15
14
12
33
2.4.1 Chemical Systems Synthesis (Chem Systems)
A promising new high pressure methanol synthesis process has been
designed by Chem Systems. A schematic flow diagram is shown in figure (2.2).
In this process, fresh syngas is mixed with recycled syngas. The optimum
recycled syngas to fresh syngas ratio, entering the methanol synthesis
reactor is 5 to 1. The mixture is then passed upwards through an expanded
catalyst bed which is fluidized by an inert, non-miscible hydrocarbon liquid.
This works as a heat sink, absorbing the heat generated by the methanol
synthesis. The heated liquid is utilized to generate steam. This is accomplished
by continuously circulating the liquid from the top of the reactor through a
boiler. Steam is generated by feeding water into the boiler, and is used as
a means of removing heat from the reactor. The use of the non-miscible
hydrocarbon liquid allows close uniform temperature control in the reactor,
allowing a higher per pass conversion of syngas to methanol .The reactor
effluent gas is then passed through stripper column, where the inert liquid
is separated from the gas. The gas is then condensed to form the product
methanol and any other entrained hydrocarbon liquid. (Chatterjee and
Chatterjee, 1981).
The non-condensable gases are piped off the methanol tank and
recycled to the reactor, except for a small purge stream which is withdrawn
to prevent the buildup of methane and nitrogen gases in the loop. These
purged gases are then burned to produce high pressure steam or is used as
plant fuel. Rather than burning this purge stream, one could also utilize a
power recovery turbine on the purge stream and recover additional methanol.
For the final purification steps the product methanol passes through a
topping column, where light gases are removed and utilized as plant fuel,
and then is passed through a refining column to remove any remaining
water and impurities, yielding a fuel grade methanol.
The fuel gas from the cryogenic tail stream and the purge stream
of the methanol loop could be burned to produce high pressure steam. The
flue gas resulting from the combustion process is mixed with air to form a
700°F stream which can be used for wood drying. If additional synthesis gas
production is desired, the fuel gas can be redirected to a steam-methane
34
reformer. This , however, would necessitate the use of another source of hot
gases to dry the wood. In addition Chem Systems has suggested that this
process may be more economically feasible operated at 1100 psi rather than
500 psi.
Fig (2.2): Chem systems synthesis Source (Chatterjee and Chatterjee,1981).
1. H2 rich syngas 2.CC rich syngas 3.Fresh syngas 4.Recycled syngas
5. Steam 6.Purge gas to plant fuel 7. Fuel crude methanol
8. Boiler feed water
1
2
3
4 5 6
7
8
35
2.4.2 Imperial Chemical Industries (ICI) Synthesis
ICI has developed a copper based methanol synthesis catalyst which
is more active and selective than the conventional zinc-chrome variety. The
greater activity of the catalyst permits a lower pressure and temperature
synthesis process. Methanol plants using the ICI low pressure synthesis
process normally consist of:
i. A synthesis gas plant
ii. A low pressure ICI methanol synthesis plant
iii. A distillation plant.
The low pressure process, originally introduced in1966 by Imperial
Chemical Industries (ICI), represented a major breakthrough in methanol
synthesis. ICI discovered that it is possible to achieve high methanol yields
by utilizing low operating pressures (50 to 100 atm) and a fixed bed of
copper-zinc-chromium catalyst . As a result, large numbers of methanol plants
today are operating on ICI's low pressure synthesis process design. The catalyst's
high selectivity produces a 99.85 percent pure methanol product. This
subsequently reduced purification costs. The catalyst is, however, very sensitive to
sulfur poisoning. Thus the H2S concentration of the feed must be limited to
0.5ppm to maintain catalyst activity.
However, unlike the high pressure process catalyst, the low pressure
catalyst cannot be regenerated . Catalyst life operating in the pressure range of
50 to 60 atm is between 3 to 4 years, and at 100 atm the longest life achieved is 2-
1/2 years. After direct gasification the resulting syngas is compressed to about 50
atm and then passed through an absorption sequence to remove H2S or any
other sulfur compounds. The syngas is then sent to a series of guard
chambers where any unsaturated compounds are hydrogenated, and any
remaining H2S and chlorine compounds ,which inhibit catalyst activity, are
removed.
Next, CO and steam from the syngas are converted to CO2 and
hydrogen in a water-gas shift reactor, utilizing an iron-oxide catalyst. This
adjusts the hydrogen to carbon monoxide ratio to that desired for methanol
synthesis. This reaction takes place in a temperature range of 380-510°C (650-
36
850)0F. After this reaction, excess CO, is again removed in an effort to decrease
the load on the methanol reactor and other downstream equipment. The purified
syngas is reacted in a quench reactor, over a copper-zinc-chromium catalyst at 250
0C (480°F),at a pressure of 50 atm, to form methanol. This product methanol is
then purified in a devolatization column and dewatering column. If the methanol
is to be used strictly as a fuel, no further treatment is necessary since any
higher alcohols present in the product could only increase its Btu content.
However, if a pure or chemical grade methanol is desired, the methanol must be
further distilled to separate it from the heavier and higher alcohols.
2.4.3 Lurgi Synthesis
Since the advent of the ICI process there have been many variations
on the same low pressure synthesis principle . One of the most successful of these
variations was developed by Lurgi engineers. At the heart of the Lurgi process is
a tubular reactor . It is a vertical reactor equipped with long carbon steel tubes
similar to a shell and tube heat exchanger. These tubes are closed at their lower
ends by a hinged grid with a screen containing a catalyst. The void around the
tubes is filled with boiling water. This affords a nearly uniform catalyst
temperature over the reactor cross section and over the length of the tubes.
Lurgi uses a copper catalyst rather than ICI's copper-zinc-chromium catalyst. In order
to maximize the catalyst life, a constant catalyst temperature must be obtained. In
addition the temperature profile of the tubular reactor drops towards the outlet
thus contributing to a better equilibrium while each stage of the quench type
reactor has an increasing temperature profile.
Another major advantage of the tubular reactor is that nearly all of
the reaction heat can be utilized to produce high pressure steam at constant
temperature conditions. In the quench type reactor this reaction heat is used
mainly to raise the quench gas to reaction temperature. In addition, steam
generation from the waste heat reactor exit gas can only occur at falling exit
gas temperatures. This limits the maximum steam pressure to only10 atm.
The actual Lurgi low pressure synthesis loop does not vary very
much from other low pressure processes. There are different gasifies technologies
employed in the production of syngas. Figure (2.3) a flow Low pressure methanol
process based on ICI process.
37
Figure (2.3) A flow Low pressure methanol process based on ICI process.
1. Dry gas 2. Compressor 3. H2S Removal 4. Gas purification
5. Steam 6. Shift reactor (high temp MeOH) 7. H2S convertor 8. CO2 9. H2O
10. Synthesis gas 11. CO2 12. Purified synthesis gas 13. Recycle 14.Purge to Fuel
15.Methanol Reactor 16. Volatiles to process heat 17.Industrail Methanol
18. Crude Methanol 19. Water and Heavy Ends 20. Higher alcohols
21. Methyl fuel blend
PUMP
6
20
1214
38
Although methanol synthesis technology has been studied since the
1920s, there is a lack of studies related to the investigation of renewable and
sustainable energy sources in order to decrease carbon dioxide emissions; because the
planet earth suffers greatly due irrational human activities. There is great diversity in
how to produce methanol in terms of synthesis materials and environmental
requirements; this variation also based on availability of raw materials along with
capabilities of a country or market competence. Accordingly, petroleum countries will
choose natural gas, naphtha, as the best choice, where as in poor agricultural
countries, the following raw materials: biogas, switch grass and green biomass are the
model alternatives .In this study the best raw material choice is carbon dioxide and
hydrogen; it is available a round , beside availability of water resources in the Sudan ,
in case not CO2 from near ammonia factory will do the job. Accordingly this research
will be conducted, by using first source. The main technique is a soft ware approach,
Aspen HYSYS. v7.3; this soft ware is a good modeling and simulation technique
proved to be utilized as a novel approach to tackle the most industrial large scale
plants.
39
Chapter Three
Materials and Methods
41
Chapter Three
3. Materials and Methods
3.1 Instruments:
To accomplish this work these materials are necessary and vital to be
located at hand, the under mentioned are minimum specifications for the following
materials:
i. Personal Computer (PC) /laptop
- CPU (Intel(R) Pentium(R) CPU 2.0 GHz)
- 2.00 GB of RAM
- 450 GB of hard disk
ii. Operating System: Microsoft Window7 Ultimate 32 bit (6.1, build7600)
iii. Software
- Microsoft Word
- Microsoft Excel
- ASPEN HYSYS v7.3
3.2 Methods
ASPEN HYSYS v 7.3 Simulation Software:
ASPEN HYSYS v7.3 is a process modeling software suitable for a variety
of steady state modeling applications. The Aspen HYSYS 7.3 system is based on
“Streams” corresponding to unit operations as well as chemical reactors, through
which most industrial operations can be simulated. By interconnecting the steams
using material, work and heat streams, a complete process flow sheet can be
constructed. ASPEN HYSYS 7.3 includes several databases containing physical,
chemical and thermo dynamical data for a wide variety of chemical compounds, as
well as a selection of fluid packages required for accurate simulation of any given
chemical system. Simulation is performed by specifying:
i. Flow rates, compositions and operating conditions of the inlet streams;
ii. Operating conditions of the streams used in the process, e.g. temperature,
pressure, number of stages and
iii. Heat and/or work inputs into the process.
41
Based on this data, Aspen HYSYSv. 7.3 calculates flow rates, compositions
and state conditions of all outlet material streams, as well as the heat and work output
of all outlet heat and work streams.
3.3 Modeling Process Flow sheets in Aspen HYSYS v.7.3
ASPEN HYSYS v7.3 is a process simulation package that solves steady-
state material and energy balances, estimates physical properties of a large number of
species, calculates phase and chemical equilibriums, and sizes and costs various types
of process units (Aspen Technology, Inc., 1996). ASPEN stands for Advanced
Systems for Process Engineering. It was originally developed under government
contract for the Department of Energy (DOE) by Massachusetts Institute of
Technology in 1987. ASPEN HYSYS v7.3 is a commercial version developed by
Aspen Technology, Inc. (Aspen Tech) and is widely used in process industries.
Aspen Tech developed Model Manager, a graphical user interface (GUI) program to
simplify building a flow sheet and running process simulation. The user creates a
schematic process flow sheet using Model Manager which then translates the flow
sheet into the equivalent ASPEN HYSYS 7.3 input file and runs the simulation.
(Aspen Tech, 1996). The ASPEN HYSYS 7.3 framework includes a number of
generalized unit operations “streams”, which are models of specific process
operations or equipment (e.g., chemical reactions, pumps, compressors, distillation
columns, etc.). By specifying configurations of unit operations and the flow of
material, heat, and work streams it is possible to represent a process plant in ASPEN
HYSYS 7.3. In addition to a varied set of unit operation units, ASPEN HYSYS 7.3
also contains an extensive physical property database and convergence algorithm for
calculating results in closed loop systems, all of which make ASPEN HYSYS 7.3 a
powerful tool for process simulation (Akunuri, 1999). ASPEN HYSYS 7.3 uses a
sequential-modular approach to flow sheet convergence. In this approach, mass and
energy balances for individual unit operation blocks are computed sequentially, often
in the same order as the sequencing of mass flows through the system being modeled.
However, when there are recycle loops in an ASPEN HYSYS 7.3 flow sheet, stream
and block variables have to be manipulated iteratively in order to converge upon the
mass and energy balance. ASPEN HYSYS 7.3 has a capability for converging recycle
loops using a feature known as “tear streams”.
42
In addition to calculations involving unit operations, there are other types of
block used in ASPEN HYSYS v7.3 to allow for iterative calculations or incorporation
of user-created code. These include Design Specifications and FORTRAN blocks. A
Design Specification is used for feedback control. The user can set any flow sheet
variable or function of flow sheet variables to a particular design value. A stream
variable or block input variable is designated to be manipulated in order to achieve the
design value.
3.4 Types of Models
According to professional criteria, a model can be defined as the
approximate representation of a process, mechanism or phenomenon. This
presentation may or may not rely on concrete material support.
This definition leads us to classify models into three main classes;
mathematical models, physical models, and chemical models; which are useful for
chemical reactors. Generally, modeling is used for the following objectives:
i. The need to represent and condense the data by restoring to known basic
equations, or to similar cases previously encountered.
ii. Separation of the essential from the accessory; simplification, clarification,
identification of controlling mechanisms.
iii. Forecasting the behavior of the system beyond the domain investigated.
iv. Establishment of scale up rules for designing industrial plants.
v. Development of an optimal control system for a given operation.
vi. Training in running production units.
3.4.1 Mathematical models:
A mathematical model can assume different forms according to its level
of description.
i. Fundamental model and formal model
The fundamental model, sometimes called the representational model ,
knowledge model or phenomenological model, is defined as a set of equations
essentially related to the description in time and space; of mass and energy balances
compiled on the different compounds of an elementary cell with given contours , of
mass ,heat and momentum transfer and other transferable quantities.
ii. Simple model and complex model
43
In given installation, the behavior of each piece of equipment can generally be
described by a simple model .However, these components virtually never operate in
isolation, and the different parts interaction the other hand, the complex model is made
up of all the specific simple models, combined with input and output conditions for
each of the interconnected parts, and generally involving models with very different
structures.
iii. Steady state and dynamic models
Depending on whether time is a factor in a model, the model can be stated
to be dynamic or steady state.
The steady state model refers to steady state conditions. The values of the
variable shaving been fixed, the system has responded by shifting towards a state of
equilibrium, and this state is examined without being concerned with the way in which
this state has been reached.
In the contrary, a dynamic (unsteady state ) model is encountered; in batch
operations in which the values of variables change constantly over time ,in continuous
operations in a transient phase of start up, altered conditions or shutdown. In
continuous operations in which certain variables are subject to disturbances such that
the system never reaches its stable position.
In short, for a given set of variables, the static model serves to describe the
situation which should be established more or less rapidly, whereas the dynamic model
allows a description of the unsteady state periods in approaching this state of
equilibrium.
iv. Deterministic and probabilistic models
It is implicitly assumed that all the aforementioned observe the principle of
determinism, that is to say support the fact that any given cause will always have the
same effects. It is hence inappropriate to speak of statistical or probabilistic model,
because it is inconceivable for effects to exist without causes, unless all attempts at a
modeling strategy are a abandoned.
The stochastic approach to a problem can, however, prove to be highly
instructive .examples include the coalescence of bubble trains, the path followed by
liquid streams on surfaces and in granular materials.
44
3.4.2 Physical models
Mathematical models are abstract. Physical models are based on a concrete
support the mockup.
Physical models supplement mathematical models in two ways; they rely on
qualitative data which can be translated directly in terms of design, they help to collect
quantified data; which are indispensable for mathematical treatment and inaccessible
by other means.
The use of physical model is ideally recommended when the operation is
liable to involve problems of transfer, diffusion, dispersion and flow, possibly
combined with thermal effects .In actual fact, practically every operation involving at
least two phases incorporates all these factors, and this sometimes even true with a
single phase.
3.4.3 Chemical models
Chemical models are concerned with chemical reactors, that is to say
equipment in which chemical transformations take place .It is often wise to model not
only the aerodynamic and hydrodynamic conditions in which the transformation takes
place, but also the transformation itself.
This usually concerns reactions involving a specific compound whose
behavior approximates the average behavior of the family of compounds in such a way
that the performance obtained during the test reaction serves to make comparisons
between different catalysts or different combinations of operating conditions.
In other cases, the chemical model is used as a test reaction to obtain
numerical values of transfer parameters, the thermal effects specific to the chemical
reaction can also be investigated by this means .These chemical models help to
simplify the overall approach to the mechanisms, by highlighting the major features
of the transformation and the presumed relative importance of the different factors
involved: chemical kinetics, more or less disturbed by the transfer limitations.
Valuable information can be obtained on the location of the reaction and the limitative
steps of the process, and this is further facilitated if one examines identifiable model
molecules instead of complex sets for which a detailed analysis is possible.
The application of chemical models allows both a rigorous investigation of
the reaction processes involved and the collection of quantified data useful in
designing the chemical reactor.
45
3.5 Production Technologies
The main steps in producing methanol are the following:
i. Production of synthesis gas
ii. Synthesis gas compression
iii. Conversion of the synthesis gas into methanol
iv. Distillation
Each step will now be explained.
3.5.1 Synthesis Gas
Synthesis gas, or syngas, denotes mainly CO/H2 mixtures in different
proportions. Raw materials for synthesis gas generation can be coal, natural gas or
mineral oil fractions. Due to the high H2 content, natural gas and light oil fractions are
best suited for synthesis gas. Since the methanol production in this study is based on
natural gas as raw material, production methods of synthesis gas from natural gas will
be explored. These methods are usually divided into three types (Lee. C. J, 2009);
i. Steam reforming
ii. Oxy reforming
iii. CO2 reforming
The selection of the production method for syngas generation depends on
the price and composition of the natural gas, acceptance of energy export and the
plant capacity.
3.5.2 Steam reforming
A majority of the methanol plants operating today are based on steam
reforming of natural gas .The reaction is described as follows:
4 2 23CH H CO H ∆H(298K) = 247kJ/mol 3.1
The equation shows that there is an excess of hydrogen. This means that
there are more hydrogen obtained than is required to convert the carbon oxides to
methanol. The reaction in the steam reformer is endothermic, which means that it
prefers high temperatures. Nevertheless, a limitation for the reformer temperature is to
make the material of the reformer withstand the high temperatures. Today new tube
materials make it possible to design tubular reformers for tube wall temperatures up to
1050°C. Reactor simulations and experiments have shown that the reformer exit
temperature can indeed be reduced to below 700C while maintaining the same
46
conversion (Aasberg-Petersen, 2001). Process data for the steam reforming section are
as follows:
The synthetic ratio of the syngas from the steam reformer can be adjusted by
lowering the hydrogen concentration through the reverse water-gas shift reaction
shown below:
2 2 2CO H O CO H ∆H(298K) = -47kJ/mol 3.2
This can be achieved by addition of carbon dioxide. CO2 is added to match
the excess hydrogen, thereby producing a syngas containing carbon oxides and
hydrogen in Stoichiometry proportions. This would reduce the feed and fuel
requirement per ton methanol .Taking into account the CO2 politics of today one
would actually be paid for using CO2, so adding CO2 could be an economical gain.
The hydrogen-carbon ratio in the syngas can also be adjusted by a secondary
reforming reaction, such as oxy reforming or auto thermal reforming (Lee. C. J,
2009).
3.5.3 Auto Thermal Reforming
Auto thermal reforming (ATR) is the combination of steam reforming
and oxy reforming. Oxy reforming uses oxygen as a reactant to produce syngas and is
generally used to adjust the synthetic ratio. Oxygen, or air with high concentration of
oxygen, is fed into the reformer where it reacts with methane from the natural gas
trough the following reaction:
4 2 22 2 4CH O CO H H(298K) = -36kJ/mol 3.3
This reaction is exothermic which makes it thermodynamically
preferable compared to the steam reforming process. Oxy reforming also gives syngas
with the synthetic ratio 2, which is the Stoichiometry ratio for methanol production
from carbon monoxide (Lee. C. J, 2009). A drawback with this method is that one has
to separate oxygen from the air to avoid large amounts of nitrogen as an inert in the
system. The air separation can be a cost intensive operation.
3.5.4 Carbon Dioxide Reforming
This process uses CO2 as a reactant to produce syngas through the following
reaction
4 2 22 2CH CO CO H ∆H(298K) = 206kJ/mol 3.4
47
As can be seen from the equation that the synthetic ratio for carbon
dioxide reforming is 1, and the maximum yield for syngas can be obtained when the
feed gas is supplied with a CO2/CH4 ration of 1. The reaction is endothermic which
means that the conversion increases as the reaction temperature rises (Lee. S, 2009). It
may be argued that CO2 reforming would be better than steam reforming to meet the
required gas compositions, but CO2 reforming is rarely feasible. At the economic
pressure of the synthesis gas plant, Stoichiometry reforming will result in incomplete
conversion of CH4 due to thermodynamics, and further the process economy depends
strongly on the pressure and the cost of the CO2 available. An option can be combined
steam and CO2 reforming. This may be feasible with natural gas containing CO2 and
with cheap CO2 available (Aasberg-Petersen, 2001). The production economics of
CO2 reforming is known to be similar to the steam reforming process (Lee. C. J,
2009).
3.6 Methanol Synthesis
Methanol is produced from synthesis gas through the following
equations:
2 32CO H CH OH ∆H(298K) = -91kJ/mol 3.5
2 2 3 23CO H CH OH H O ∆H(298K) = -50kJ/mol 3.6
In addition the water gas shift reaction occurs over the copper-catalyst:
2 2 2CO H O CO H ∆H(298K)= -47kJ/mol 3.7
There are three common processes for methanol production existing
today. These are the BASF high pressure process, the UK-Wessling high pressure
process and the ICI low pressure process. Their characterizations are given below.
BASF is a German chemical company, founded in 1865. The BASF process, also
known as the high pressure process, for production of methanol is conducted at 320-
380C and approximately 340 bar (Olah, 2006). The process uses the ZnO-Cr2O3
catalyst. To avoid high temperatures (exothermic reaction) cold gas is injected in the
catalyst bed. Short residence time (1 to 2 seconds) is used to prevent equilibrium from
taking place. Conversions of 12-15% for a single pass through the reactor are typical
for this process. Another similar process was developed by UK Wesseling. This
process operates at low CO partial pressure (≈13 bar in gas recycle) and reaction
conditions at 300 bar and 350C (Olah, 2006).
48
To be able to operate at lower pressures, more active Cu-based catalysts
were introduced. In 2003 about 65% of the methanol production in the world was
based on the ICI low pressure process (Olah, 2006). This process is characterized by
lower investment and process costs. The operating conditions in the converter are 50-
100 bar and 240-260C. The ICI process uses a CuO-ZnO/Al2O3 catalyst.
An elegant method for methanol production is partial oxidation of methane, known as
the direct route. The reaction mechanism is
1 2
4 2 3 20,5 2k k
CH O CH OH CO H 3.8
The problem with this method is that k2 is much larger than k1 and thus
methanol production is not profitable with today’s technology. However, there is
currently being put a lot of research on this field (Lødeng, 1991)
3.7 Methanol Reactors
The most important section of the methanol synthesis process is the
methanol reactor. As the synthesis reaction is strongly exothermic, heat removal is an
important process (Tijm, 2001). High average heat flux leads to fewer tubes, smaller
furnaces and thus reduced costs (Aasberg-Petersen, 2001).
The methanol reaction is exothermic, so the primary task of the reactor is
to control the temperature. The reactor technologies have been used extensively in
commercial settings fall into two categories; multiple catalyst bed reactors and single
bed converters.
3.7.1 Multiple Bed Reactors
The multiple catalyst bed reactors controls the reaction temperature by
separating the catalyst mass into several sections with cooling devices placed between
the sections. Bed sizes are generally designed to allow the reaction to go to
equilibrium. In the following, three different multiple bed reactors will be presented
(Tijm, 2001).
i. Haldor Topsoe collect, mix, distribute converter:
This reactor has catalyst beds separated by support beams. The gas that is
leaving the upstream catalyst is then collected and mixed with a quench gas for
cooling. The mixed gas stream is evenly spread over the downstream catalyst bed.
The reaction temperature is lowered and the conversion per pass rate is increased.
ii. Kellog, Brown and Root’s adiabatic reactors in series:
49
In these reactors, which are in series, each catalyst layer is accommodated
in a separate reactor vessel with intercoolers between each reactor. The feed gas is fed
directly into the first reactor which increases the kinetic driving force for the reaction.
This leads to a reduced catalyst volume compared to a quench-type reactor.
iii. Toyo Engineering Corporation’s MRF-Z reactor:
This reactor is a multi-stage radial flow reactor with intermediate cooling.
This indirect cooling keeps the temperature close to the path of the maximum reaction
rate curve (when the methanol concentration is plotted against temperature).
Maximum, or close to maximum, conversion per pass is then achieved.
3.7.2 Single Bed Reactors
In single bed reactors, heat is continuously removed from the reactor by
transfer to a heat-removing medium. The reactor runs effectively as a heat exchanger.
In most commercial methanol production today the gas phase reactor technology,
which is a two-phase gas-solid reactor, is in use. Recently a three phase, gas-solid-
liquid, technology has been introduced. These liquid phase technologies are
contributing to cost reduction in the methanol industry through the simplicity of their
converter design.
In the following three different single bed reactors will be presented
(Tijm, 2001).
i. Linde Isothermal Reactor:
In this reactor design helically-coiled tubes are embedded in the
catalyst bed. It is very much similar to LNG (liquefied natural gas heat exchangers)
with catalyst around the tubes. The Linde isothermal reactor allows for up to 50%
more catalyst loading per unit of reactor volume. Compared to reactors with the
catalyst inside the tubes, the heat transfer on the catalyst side is significant higher for
a Linde isothermal reactor. As a result, material costs are saved since less cooling area
is required.
ii. Lurgi Methanol Reactor:
The Lurgi Methanol Reactor is much like a heat exchanger; it has a
vertical shell and tube heat exchanger with fixed tube sheets. The catalyst in the tubes
rests on a bed of inert material. Steam is generated by the heat of reaction and drawn
off below the upper tube sheet. To achieve precise control of the reaction temperature,
steam pressure control is applied. Operating at isothermal conditions enables high
51
yields at low recycles. In addition the amount of by-products produces is minimized
(Almeland et al.2009).
For plant capacities above 3000 tonnes per day, a two-stage converter
system using two Lurgi methanol reactors in combination has been developed. As it
needs to achieve only partial conversion of synthesis gas to methanol, the first
converter can operate at higher space velocities and temperatures than a single-stage
converter. Operating at higher temperatures, enable the production of high-pressure
steam. Also, the converter can be made smaller. The exit gas is led into the second
converter, which operates at a lower reaction rate.
iii. Mitsubishi Gas Chemical/Mitsubishi Heavy Industry super converter
This super converter has double-tubes with the catalyst packed between
the inner and the outer tubes. The feed enters the inner tubes and is heated when
flowing through the tubes. The gas then enters the space between the inner and the
outer tubes and flows through the catalyst bed. In addition to being cooled by the gas
in the inner tubes, the catalyst is also cooled by boiler water outside the double-tube.
Since the catalyst bed temperature is higher near the inlet of the reactor, and then
lowers towards the outlet, the gas proceeds along the maximum reaction rate line.
This means that a higher conversion per pass rate is achieved.
3.8 Catalysts
A good catalyst should remain active for several years, so as to sustain
high plant output. Over time catalysts may be poisoned by impurities or deactivated
by thermal sintering or carbon deposition. Research findings have suggested that
carbon dioxide-rich conditions may cause irreversible damage to the catalysts (Tijm,
2001). The current catalysts used in low pressure methanol synthesis are composed of
copper oxide and zinc oxide on a carrier of aluminium oxide; Cu/ZnO/Al2O3. This
catalyst is proven to have a high activity, particularly at lower temperatures, and it
perform well in both adiabatic and isothermal reactor systems. However, the catalyst
is very sensitive to sulphur and the synthesis gas should be free of both sulphur and
chlorine. This catalyst is known as a second-generation catalyst. (Olah, 2006)
ZnO-Cr2O3 is known as a first-generation catalyst. The catalyst has a maximum
activity when the Zn/Cr ratio is about 70:30 (Weissermel, 2003). Because the catalyst
is very resistant to typical catalyst poisons, the catalyst can be used for several years.
51
The metal catalysts active for steam reforming are the group VIII metals,
and usually nickel. Drawbacks with the other metal groups are that the iron rapidly
oxidizes and the cobalt cannot withstand the partial pressure of steam. Also, rhodium,
ruthenium, platinum and palladium are too expensive for commercial operation. A
typical nickel catalyst is made from 15-25 wt% nickel that is dispersed onto the
support material. As for the Cu/ZnO/Al2O3 catalyst, also the nickel catalyst is highly
sensitive to poisoning by sulphur compounds (Lee. S, 1997).
3.9 Reactions of Methanol
There are many proposed kinetics for methanol synthesis, this study will
take two of the most famous kinetics models; the first one G.H. Graaf, E.J. Stamhuis
and A.A.C.M. Beenackers kinetic model, and the second by Vanden Bussche and
Forment.
The Stoichiometry of methanol reactions is involves the reaction of both
carbon dioxide and carbon monoxide with hydrogen.
Methanol synthesis has nearly always been expressed in terms of the hydrogenation
of CO, first reaction and kinetics goes as follows:
CO +2H2 CH3OH 3.9
But methanol synthesis over Cu-based catalysts proceeds exclusively via
CO2 +3H2 CH3OH + H2O 3.10
Simultaneously with methanol synthesis, the reverse water gas shift reaction
(RWGS) takes place depending on the reaction conditions:
CO2 + H2 CO + H2O 3.11
Three overall reactions are possible in the methanol synthesis hydrogenation
of carbon monoxide, hydrogenation of carbon dioxide and reverse water gas shift
reaction:
CO +2H2 CH3OH 3.12
CO2 +3H2 CH3OH + H2O 3.13
CO2 + H2 CO + H2O 3.14
3.10 Model Formulation and Process
52
In this section our main practical work will be presented using aspen
HYSYS software to simulate and model methanol synthesis system .First a brief
description of process will be provided as follows hereunder:
3.10.1 Process Description:
Methanol can be made from hydrogen plus carbon monoxide and/or carbon
dioxide.
0 H2 + CO CH3OH 3.15
0 H2 + CO2 CH3OH + H2O 3.16
Recent studies suggest that the first reaction actually proceeds as
CO + H2O H2 + CO2 3.17
(the water gas shift reaction) followed by the second reaction).
For this study we will work with the simplest version – the second reaction
only. By the way, running this reaction backwards provides a method of operating a
hydrogen fuel cell with methanol as a feed.
The following diagram figure (3.1) shows the process we will work on. It is
important to recognize that this is not suggested as a good way to make methanol. The
design has been formulated to demonstrate many key aspects of HYSYS, without
getting overwhelmed by detail.
A mixture of H2 and CO2 is heated to the required temperature and fed to a
stirred reactor. As noted above, the reaction is 3H2 + CO2 CH3OH + H2O.
The product of the reaction is partially condensed. The vapour (mostly H2 and
CO2) is compressed and recycled back to the beginning of the process. The liquid
(mostly CH3OH and H2O) is fed to a distillation column.
The column produces a product stream (mostly methanol) and a waste stream
(mostly water). The product is cooled to a temperature that is reasonable for storage.
A pump is required provide cooling water for this heat exchanger.
53
Fig (3.1): Methanol Synthesis Flow Diagram.
54
3.10.2 Starting aspen HYSYSv7.3
To launch into program the following steps should be followed carefully, first
begin with:
Start/Programs/ Aspen HYSYS
Basic Steps:
1. Create a unit set
2. Choose a property package
3. Select the components
4. Create and specify the feed streams
5. Install and define the unit operations
6. Install and define the column
7. View and analyze the results
Then the next job is to set basis for setting session preferences like, units
either with SI units or any other system and clone for a new user .this step is the first
step for setting up data for a model. After that the coming job is selecting
thermodynamics; here termed by fluid package.
Fluid Package is HYSYS’s terminology for a collection of data that
includes all the thermodynamic, component, and reaction parameters required to run
the model. It is possible to have more than one package in a model. For example, it
would be possible to use one thermodynamics model in the reactor, and another in the
distillation column.
Fluid package will be selected as seen in the window (3.3) below, for this
project Soave-Redlich-Kwong (SRK) method, a popular equation of state model.
The same window will be our basic for adding components and reactions, just
click on the appropriate tab to the wanted job.
After these steps the next step is to jump to the second stage, which will
complete; the process of modeling. This stage is simulation phase which consists of
simulation tools; feed streams, reactors, pumps, mixers, distillation columns and a few
to mention.
55
3.10.3 Reactions of Methanol Synthesis Using Aspen HSYS.v.7.3
A Kinetic reaction is one which will be supplied the kinetic constants
that define the rate of reaction. This allows sizing the reactor. If it was only interested
in simulating the heat and mass balances, it could use the simpler form, a
“Conversion” reaction. Then it would only have to define the percent conversion.
Kinetic reaction for methanol can be described in a form (3.1) below.
Table (3.1): Kinetic of Methanol Reaction Data
Component Molecular wt Stioch coeff Fed order Rev Order
CO2 44.010 -1 1 0
Hydrogen 2.016 -3 3 0
Methanol 32.042 1 0 1
H2O 18.015 1 0 1
3.10.4 Basis
Basis is Molar Concentration means, that the reaction rate equation uses
concentrations of the reactants in moles/m3. Base Component = CO2 means that the
reaction rate equation describes the rate of consumption of CO2, not consumption of
H2 or production of methanol (since CO2 consumption = methanol production,
methanol could be specified here).
Rxn Phase = Liquid Phase means that the reaction takes place in the liquid. Since
there will not be any liquid in the reactor, this is not helpful. Change it to “Vapour
Phase”.
Finally, change “Rate Units” from “kgmole/m3.s” to “kgmole/m
3.h”. Since
everything else in the model is in units of hours, it is best to be consistent.
The important consideration is to ensure that the treatment here is compatible with
what was used in generating the constants describing the reaction rate.
3.10.5. Parameters
A=1.04e22
B=1.7e5
A/ =2.6e28
B/ =2.2e5
These are the kinetic constants for an Arrhenius equation: k = A e(-E/RT)
.
56
3.10.6 Experimental Data
This data was collected from previous studies; it’s advice able to take this
for scheme if there any, in this case there is no plant available , accordingly the base
of our coming work, it will be based on the following feed data:
Stream Name = Feed
Temperature = 40 ºC
Pressure = 4000 kPa
Mass Flow = 1000 kg/h. Composition was as follows 0.25 CO2 and 0.75 was H2.
The second stream is recycle stream with the following conditions
Temperature and pressure were the same with previous feed, along with 200 kgmole/h
mole flow; the concentrations were assigned as 0.1 for CO2 and 0.9 for H2.
The reactor was of 2.215 m3, 1.78m diameter and 0.89m height.
The trail was repeated with the following conations:
Temperature was 25, 30, 40, 50, 60oC .
Pressure was 2000, 3000, 4000, 4500, 5000 kPa
Concentration was 15/85, 25/75, 40/60, 50/50, 75/25 CO2/H2 ratio.
Then results were obtained accordingly.
57
Chapter Four
Results and Discussion
58
Chapter Four
Results and Discussion
4.1 Results
Table (4.1): Ratio of CO2/H2 vs. %conv
CO2/H2 ratio 15/85 25/75 40/60 50/50 75/25 P=4000KPa
T=40C
%conversion
H=1
D=2
23.01 44.72 0.9529 0.4987 6.819e-2
%conversion
H=0.8901
D=1.78
15.18 43.37 0.7845 0.3735 4.98e-2
CH3OH
Product
0.9792 0.9526 0.9575 0.7696 0.8859
Table (4.2): Temp vs. %conv and Product
Temperature(0C) 25 30 40 50 60 P=4000kPa
%conversion H=1
D=2
44.72 44.03 44.72 41.12 37.16
%conversion H=0.8901
D=1.78
43.37 42.72 43.37 39.90 36.15
CH3OH Product 0.9531 0.9549 0.9526 0.9655 0.9640
59
Table (4.3): Pressure vs. %conv and Product
Pressure
(kPa)
2000 3000 4000 4500 5000 T=400C
CO/H2=
25/75
%conversion
H=1
D=2
2.69 29.68 44.57 47.80 51.56
%conversion
H=0.8901
D=1.78
1.225 24.52 43.68 46.93 50.90
CH3OH Product 0.9527 0.9612 0.9526 0.9573 0.9556
Table (4.4): Properties of Final Product(Methanol)
Stream Name Final
Product
Vapor Phase Liquid
Phase
Vapour/Phase Fraction 0.0004 0.0004 0.9996
Temperature(0C) 33.9 33.9 33.9
Pressure(kPa) 950 950 950
Molar Flow(kg mole/h) 15.96 6.815e-003 15.96
Mass flow(kg/h) 507.7 2.815e-002 507.7
Std Ideal liq flow(m3/h) 0.637 2.041e-004 0.6368
Molar Enthalpy(kJ/kgmole) -2.426e005 -1.786e004 -2.427e005
Molar Entropy(kJ/kg mole .c) 19.23 109.4 19.19
Heat flow(kJ/h) -3.873e0006 -121 -3.873e006
61
4.2 Discussion
In this section, the results will be discussed based upon the tables 1, 2 and 3.
These results simply can be categorized into subsections.
The first and second are case studies; the first one is about effect of
pressure versus conversion, pressure ranges from 2000 kPa up to 5000 kPa with 500
interval for each figure (4.1)shows the obtained results :
Fig (4.1) Pressure versus conversion effect at constant temperature.
It can be clearly seen from the figure above, that conversion goes up with
systematic increasing of pressure with constant rate. This increasing reaches its peak
value at 4000 kPa, then the conversion keeps constant; this trend will maintain this
route of this fixed rate if pressure continues in this manner.
It’s important to mention that, this case study was conducted at feed
temperature of 40oC and 0.33 ratio of CO2/H2 in terms of mole fractions.
The second case study was about relationship between temperatures
which ranges from 25 o
C up to 60 oC along with conversion rate. It’s quite obvious
that the rate of conversion keeps constant value despite variety of temperature values;
this fact leads to conclusion that temperature is not a function in conversion rate; the
fig (4.2) shows this trend.
It is also noteworthy that high pressure favors the selectivity for methanol
production. On the other hand, at the short contact time, the reactions are controlled
mainly by kinetics, the thermodynamic limitation is lowered.
61
Fig (4.2): Temperature vs. conversion
To be more accurate temperature with other factors, like pressure and type
of reaction will make a great change in conversion rates with variety of temperature
ranges.
This case study basically conducted with the same pressure of 4000 kPa
and the mole fraction as the first one.
The third fact, which was taken from this study, the relationship between
conversion rate of CO2/H2, with values of 15/85, 25/75, 40/60, 50/50, and 75/25 in
terms of mole fraction. The study showed that more ratios of CO2/H2 value leads to
decreasing a conversion rate, beside this fact there was another point to be noticed
from fig (4.3) that, at ratio of 40/60 of CO2/H2 conversion reaches its peak value, then
followed by sharp drop.
It can be concluded that the ratio of CO2/H2 is decisive point to increase
the conversion rate of this reaction; the less ratio of CO2/H2 definitely leads to get a
good conversion value. Fig (4.3) reflects this evidence.
62
Fig (4.3) Ratio of CO2/H2 vs. %cnv
The amount of conversion increases gradually with ratio of CO2/H2, till it
reaches a peak value at 45, then starts dropping sharply at 0.9. This due to, the
conversion acts well at lesser values of CO2/H2, thus, it better to use adjusted
quantities of ratio to gain better results of conversion, this fact should note other
factors like, space velocity, type of catalyst and reactor type a long with kinetics.
Figure (4.4) a pointer to this fact.
Fig (4.4): Ratio of CO2/H2 and Product
y = 1.7725x R² = -0.487
0
5
10
15
20
25
30
35
40
45
50
0 1 2 3 4
conversion
CO2/H2 ratio
Ratio of CO2/H2 vs conversion
%cnv
(cnv)%خطي
y = 0.3844x R² = -43.03
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 1 2 3 4
MeOH Product
Ratio of CO2/H2
Ratio of CO2/H2 vs Product
Product
(Product)خطي
63
Generally, this chart goes with fact that the less ratio of CO2/H2 will lead to
a good product of methanol.
An important point should be put into consideration based on the
mentioned fact, it is advisable to observe a relationship between the ratio of CO2/H2
and product of methanol; it is no doubt that , to obtain a maximum amount of
methanol product there should be a minimum ratio of CO2/H2 as possible followed by
carefully pressure increasing; to prove this fact, at the ratio of CO2/H2 equals to 0.1
the product of methanol is 0.98 in terms of mole fraction, on the other hand when the
ratio of CO2/H2 is three the obtained amount of product is 0.76 in terms of mole
fraction .
64
Chapter Five
Conclusion and Recommendations
65
Chapter Five
5. Conclusions and Recommendations
5.1. Conclusions
In this chapter, a simulation study of methanol system based has been
carried out .The main objective of the current work is to develop a method that can be
used to provide studies for temperature and pressure effects on rate conversion of
CO2/H2 to methanol. More recent and previous studies were tended to explore kinetics
and economical feasibility of methanol synthesis models, the SRI study used Aspen
Plus software along with two tubular reactors in series, obtained result was 0.80 mole
fraction, that study used natural gas as a raw material.
The approach in this study used CO2 and H2 as raw materials, as long as
using Aspen HYSYS software for this simplified model which revealed its
approximate plant operating under different conditions of pressure variation and feed
temperature ranges, with sufficient accuracy and a good performance compared to
previous Stanford University Institute Research. Obtained result due to this study it is
above 0.9 in the most runs, the best result was 0.98 mole fraction , this prove that
using this software along with the these raw materials is very promising area to
continue further studies to optimum results .
Another aspect of environmental relevance is the mitigation of
industrial emissions of carbon dioxide CO2 through of CO2 capture by one process of
hydrogenation. Hydrogenation of CO2 reduces the major man-made cause of
global warming. However, it is worth noting that rendering effective CO2
reduction requires the use of low CO2 emitting sources of energy (e.q., solar
energy, hydro energy, nuclear energy, or biomass). The CTM (CO2 to Methanol)
Process stands as a promising alternative to CO2 reutilization due to the expanding of
methanol.
5.2. Recommendations
The researcher recommends conducting more comprehensive researches
in areas of modeling and simulation, because chemical projects and industrial
schemes are man power consuming besides the trial and error methodology is very
costing without any tangible fruits.
66
For this reason, it is very vital to direct studies in this field of modeling
and simulation to minimize man efforts and machinery, then projects will cruise
safely exploring points of weakness and strongest .
Methanol is as one of the prime candidates for future racing vehicles,
intermediate raw materials for a lot of chemical industries and freezing gases, and
consuming CO2 as one the most active gases in green house gases, so it deserve to
draw attention and concentrate very deep research to get rid of this gas, and can be a
raw material instead of harmful by product.
While the approach used here for developing methanol synthesis system
to come up with a comprehensive system consists of the most vital and essential
components of Aspen HYSYS software capabilities, the aim was accomplished
successfully, this for encouraging, yielding almost an accurate predicted results.
Although , this study did not orient to thorough investigation of all aspects like heat
integration ,economical studies, thus further improvements can be made , in terms of
software and raw materials, more the less the following titles can be proposed as areas
of enhancements :
Aspen Plus software is very promising for dealing with a lot of industrial
plant. This software has a very rich library to tackle all pure chemicals a long with
hypothetical components, beside this, Fortran embedded routines in this software is
very useful tool for more thorough studies .
In terms of raw materials natural gas is the one of candidates for this
study, beside this CO can be used instead of CO2, and synthesis gas is a good
proposed one
In future, the energy balance will be added to predict temperature changes
in reactor. The temperature is an important variable considering the performance of
process, and thus it should be taken into consideration, where as in this study
temperature range was taken on feed entering feed.
67
References
1. Aasberg-Petersen, K., Hansen., J.-K.B., Christensen, T.S., Dybkjaer, I.,
Christensen, P. S., Nielsen, C. S., Madsen, S. E. L. W. and Rostrup-Nielsen,
J.R.: Technologies for large-scale gas conversion. Applied Catalysis A:
General, 221, 379-387, 2001
2. Aksgaard, T.S., J.K. Nrskov, C.V. Ovesen and P. Stoltze (1995). A kinetic
model of methanol synthesis. Journal of Catalysis156, 1995
3. Alain Bill, carbon dioxide hydrogenation to methanol at low pressure , PhD A
Thesis Ecole polytechique federale de Lausanne .
4. An X, Zuo Y, Zhang Q, Wang J (2009), Methanol Synthesis from CO2
Hydrogenation with a Cu/Zn/Al/Zr Fibrous Catalyst, Chinese Journal of
Chemical Engineering, Volume 17, Issue 1, February 2009, Pages 88-94.
5. Aspen Tech, Inc., 1996, “Aspen Plus User Guide Volume 1-2”.
6. Baha (2011), Plant Design: Student’s Lecture Notes Chem Eng: Karary
University.
7. Chatterjee .B.K. and Chatterjee. P.R. (1981) State of the Art Review on the
production of methanol and its derivatives from biogas, report prepared for
USA dept of Agriculture, 1981, available at: www.methanol plant literature
review, accessed on 17.8.2013.
8. Chinchen, G.C., P.J. Denny, D.G. Parker, M.S. Spencer, K.C.Waugh and
D.A.Whan (1987) Mechanism of methanol synthesis from CO2=CO=H2
mixtures over copper/zinc oxide/alumina catalysts - Use of C-14-labeled
reactants. Applied Catalysis 30, 330.
9. Commercial Cu/ZnO/Al2O3 Catalyst”, Journal of Catalysis 161, 1-10, 1996.
10. Daaniya.R,(2012), Kinetic Modeling of Methanol Synthesis From Carbon
dioxide Carbon monoxide and Hydrogen Over A Cu/ZnO/Cr3O2 catalyst,
Master Thesis ,San jose state University [online] available at
http://scholarworks.SjSu.edu, Accessed on march 2014.
11. P.Trambouze, J.P.Wauquier, Euzen P.Trambouze, J.P.Wauquier, (1993),
Scale up Methodology for chemical process, France.
12. Farsi .M and Jahanmiri. A, (2011), Methanol production in an optimized dual-
membrane fixed-bed reactor, Chemical Engineering and Processing: Process
Intensification, Volume 50, Issues 11–12, November–December 2011, Pages
1177-1185.
68
13. Fisher .L. A. and Bell .A. T, In Situ Infrared Study of Methanol Synthesis
from H2/CO over Cu/SiO2 and Cu/ZrO2/SiO2, Journal of Catalysis, Volume
178, Issue 1, 15 August 1998, Pages 153-173.
14. Galindo. C. P, and Badr. O, Renewable hydrogen utilization for the production
of methanol, Energy Conversion and Management, Volume 48, Issue 2,
February 2007, Pages 519-527.
15. Gallucci. F. and Basile. A, A theoretical analysis of methanol synthesis from
CO2 and H2in a ceramic membrane reactor. International Journal of Hydrogen
Energy, vol. 32, (2007) Pages. 5050-5058.
16. G.H. Graaf, E.J. Stamhuis and A.A.C.M. Beenackers, “Kinetics of low-
pressure methanol synthesis”, Chem. Eng. Sci. 43 (1988), Page. 3185
17. Ingvild (2001). Modeling, Estimation and Optimization of the Methanol
Synthesis with Catalyst Deactivation: A thesis submitted in partialfulment of
the degree of Doctor Ingenir Norwegian University of Science and
Technology Department of Chemical Engineering www.methanol plant
Design On 15/8/2013
18. Jiyong .K, Carl.A, Henao, Terry. A. Johnson, Daniel E, Dedrick, James E,
Miller, Ellen. B, Stechel and Christos T.Marvelias, Methanol production from
CO2 using solar thermal energy: process development and techno economic
analysis, J, sci, 2011,4,3122-3132. www.methanol synthesis .com accessed on
20.8.2013.
19. Jung. K. D, and Bell .A .T, Role of hydrogen spillover in methanol synthesis
over Cu/ZrO2, Journal of Catalysis, Volume 193, Issue 2, 25 July 2000, Pages
207-223.
20. Abdalla, B,K (2011), Chemical Reactor Design: Student's Lecture Notes:
Chem Eng - Karary University
21. Kent (1992), Fundamentals of Organic Chemistry: Handbook of Industrial
Chemistry, Van Nostrand Reinhold, New York, NY, USA.
22. Kordabadi. H, Jahanmiri. A, Optimization of methanol synthesis reactor
using genetic algorithms, Chemical Engineering Journal, Volume 108, Issue
3, 15 April 2005, Pages 249-255.
23. Lange. J. P. (2001) Methanol synthesis: a short review of technology
improvements. Catalysis Today, vol. 64, p. 3-8.
24. Lee. C. J, Optimal Gas-To-Liquid Product Selection from Natural Gas under
Uncertain Price Scenarios’. Ind. Eng. Chem. Res., 48, 794-800, 2009.
25. Li J, Zhang W, Gao L, Gu P, Sha K, Wan H.(1997). Methanol synthesis on
Cu-Zn-Al and Cu-Zn-Al-Mn catalysts, Applied Catalysis A: General, Volume
165, Issues 1–2, 31 December 1997, Pages 411-417.
69
26. Lødeng. R.(1991), “A Kinetic Model for Methane Directly to Methanol”,
Ph.D. Thesis, NTNU.
a. Lovik, “Modeling, Estimation and Optimization of the Methanol
Synthesis with Catalyst Deactivation”, Ph.D. Thesis, Norwegian
27. Methanex (2000a). Emerging energy. http://www.methanex.com.
28. Methanol production from biogas , Int .J of math and computers in simulation
, issue 2 vol4,2010 .www.methanol synthesis plant design.com accessed on
20.8.2013.
29. Mignard. D, Sahibzada M, Duthie J M, Whittington H W, Methanol synthesis
from flue gas CO2 and renewable electricity: a feasibility study, International
Journal of Hydrogen Energy, Volume 28, Issue 4, April 2003, Pages 455-464.
30. Muhler, M., E. Tornquist, L.P. Nielsen, B.S.Clausen and H.Topse (1994).On
the role of adsorbed atomic oxygen and CO2 in copper-based methanol
synthesis catalysts. Catalysis Letter 25(1-2),1-2.
31. Natta. G. (1955), synthesis of methanol, institute of industrial chemistry
polytechnic of Milan, Italy.
32. Nerlov .J and Chorkendorff. L, Methanol Synthesis from CO2, CO, and H2
over Cu (100) and Ni/Cu (100), Journal of Catalysis, Volume 181, Issue 2, 25
January 1999, Pages 271-279.
33. Nieskens D L S, Ferrari D, Liu .Y, Kolonko .Jr R., The conversion of carbon
dioxide and hydrogen into methanol and higher alcohols, Catalysis
Communications, Volume 14, Issue 1, October 2011, Pages 111-113.
34. Nithi (2009), Simulation and Design of Ammonia Process from Natural Gas
Reforming. Master of Engineering (Chemical Engineering), www.methanol
plant design : Graduate School, Kasetsart University
35. Olah, G.A., Goeppert, A. and Prakash, G.K.: Beyond Oil and Gas: The
Methanol Economy, Wiley-VCH, Darmstad, 2006
36. Osman. M (2012) , Modeling Chemical Engineering: Student's Lecture Notes:
Chem Eng – University of Gezira.
37. Rihko-Struckmann. L. K, Peschel. A, Hanke-Rauschenbach. R, Sundmacher
Kai, Assessment of Methanol Synthesis Utilizing Exhaust CO2 for Chemical
Storage of Electrical Energy Industrial and Engineering Chemistry
Research, Volume 49, Issue 21, 2010, Pages 11073-11078.
38. Sinnot (2005). Chemical Engineering Design, vol 6 :6th
ed
39. Statoil (2000a). Allianse for methanol. http://www.statoil.com.
40. Statoil (2000c). Samarbeid Om brenselsceller. http://www.statoil.com.
41. Toyir .J, Miloua .R, Elkadri. N .E, Nawdali .M, Toufik. H, Miloua. F, Saito
M.(2009), Sustainable process for the production of methanol from CO2 and
H2 using Cu/ZnO-based multi component catalyst, Physics Procedia, Volume
2, Issue 3, November 2009, Pages 1075-1079.
71
42. N. Tsaubaki.M. Ito, K. Fujimoto, A New Method of Low-Temperature
Methanol Synthesis, Journal of Catalysis, Volume 197, Issue 1, 1 January
2001, Pages 224-227.
43. Vanden Bussche, K.M. and Froment, G.F, A Steady-State Kinetic Model for
Methanol Synthesis and The Water Gas Shift Reaction an a commercial
Cu/ZnO/Al2O3 Catalyst, Journal of Catalysis 161, 1-10, 1996.
44. Velardi .S .A, and Barresi .A, Methanol synthesis in a forced unsteady-state
reactor network, Chemical Engineering Science, Volume 57, Issue 15, August
2002, Pages 2995-3004.
45. Weissermel, K. and Arpe.H.-J (2003). Industrial Organic Chemistry, 4th
ed.,
Wiley-VCH, Darmstad.
46. Yoshihara .J .and Campbell. C .T, Methanol Synthesis and Reverse Water–
Gas Shift Kinetics over Cu (110) Model Catalysts: Structural Sensitivity,
Journal of Catalysis, Volume 161, Issue 2, July 1996, Pages 776-782.
47. Skrzypek, J., J. Sloczynski and S. Ledakowicz (1994).Methanol Synthesis.
Polish Scientific Publishing.
48. Tijm, P.J.A., Waller, F. J. and Brown, D.M.: Methanol technology
developments for the new millennium. Applied Catalysis A: General, 221,
275-282, 2001.
49. Silje Kreken Almeland, Knut Åge Meland and Daniel Greiner Edvardsen
(2009), Process Design and Economical Assessment of a Methanol Plant:
MSC Thesis Norwegian University of Science Department of Chemical
Engineering and Technology.
50. Lee, S, Methane and its Derivatives, Marcel Dekker Inc., New York, 1997
71
Appendix (A): Modeling Tools
Fig (1): Reactions’ window
72
Fig (2): Enter the Simulation Environment: modeling tools are shown at right side of
figure.
73
The fig (3): shows simulation basis manager.
74
Fig(4): Selecting Fluid Package ( SRK).
Fig(5): Mixer
75
Fig(6): Heater
Fig(7): CSTR Reactor
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Fig(8) : Cooler
Fig (10): Separator
77
Fig (11): Splitter
Fig (12): Recycle Compressor
78
Fig (13): Distillation Column
Fig (14): Water Pump
79
Fig (15): Heater exchanger
Fig (16): Methanol Tank
81
Fig (17): Recycle Stream
81
Appendix (B): Reports
Fig (1):CO2/H2=25/75, T=400C, P=2000kPa
82
Fig (2): CO2/H2=15/85, T=400C, P=4000kPa
83
Fig (3): CO2/H2=75/25, T=400C, P=4000kPa
84
Fig (4): CO2/H2=40/60, T=400C, P=4000kPa
85
Fig (5): CO2/H2=50/50, T=400C, P=4000kPa
86
Fig (6): CO2/H2=25/75, T=400C, P=2000kPa
87
Fig (7): CO2/H2=25/75, T=400C, P=3000kPa
88
Fig (8): CO2/H2=25/75, T=400C, P=4500kPa
89
Fig (9): CO2/H2=25/75, T=400C, P=5000kPa
91
Fig (10): CO2/H2=25/75, T=250C, P=4000kPa
91
Fig (11): CO2/H2=25/75, T=500C, P=4000kPa
92
Fig (12): CO2/H2=25/75, T=600C, P=4000kPa
93
Fig (13): CO2/H2=25/75, T=300C, P=4000kPa
94
Fig (14): CO2/H2=25/75, T=400C, P=4000kPa
95
Fig (15): CO2/H2=25/75, T=600C, P=4000kPa
96
Fig (16): CO2/H2=25/75, T=500C, P=4000kPa
