Application and scope of atom economy green chemistry
MINOR REPORT
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MINOR PROJECT REPORT ON:
SYNTHESIS OF METHANOL FROM SYN GAS – MODELLING APPROACH
Submitted by:
ANKISH KHANDELWAL 12112012
DHARMENDRA KUMARCHOUDHARY 12112024
B.Tech Chemical engineering
IIT Roorkee
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ACKNOWLEDGEMENTS
I feel immense pleasure and privilege to express my deep gratitude, indebtedness and thankfulness
towards those who generously helped me to furnish this project with their knowledge, expertise and
memories.
For his invaluable guidance, kind cooperation, inspiration and encouragement during all the stages of
my project, I would also like to express my deep sense of gratitude to Mr. P. Mondal (associate
professor IITR) for allotting me this project & for providing me with necessary inputs as and when
needed. I would also like to thank Mr. Mumtaz (Ph.D. IITR)
After the completion of the minor project, I found it to be of immense help, not only in supplementing
the theoretical knowledge, but also highly practical knowledge. At the end, I again express my
gratitude to all those who helped me in any way to complete my training successfully
ANKISH KHANDELWAL
DHARMENDRA CHOUDHARY
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INTODUCTION
Nowadays the society we are living in is experiencing high oil prices and global warming threats, which
are mainly caused by extensive use of traditional fossil fuels such as coal and crude oil. In the future,
renewable and environmental friendly sources of energy would be more and more attractive. Synthesis
gas (also called as syngas, which is a mixture of mainly CO and H2) could potentially play a significant
role in addressing the above mentioned problems. Basically it can be derived from any carbon
containing raw material: coal, biomass such as straw and wood or even wastes. Provided that a
sustainable and effective way of electrochemical conversion is found, even CO2 and H2O could serve
as initial materials for syngas production. (Electrochemical fixation of CO2, CASE project). Then, syngas
can be converted to various liquid fuels such as methanol, Fisher-Tropsch oil (FT oil, a mixture of
hydrocarbons) and higher alcohols.
Alcohols are widely used in our society as solvents, pharmaceuticals, and starting materials for
synthesis of various chemicals, including fuels or fuel additives.1,2,3. The scope of this project is to
develop catalysts for the direct conversion of syngas to alcohols, either methanol (low pressure
synthesis) or higher alcohols
Global economic, environmental, and political forces have increased interest in developing sources of
liquid transportation fuels that are not petroleum based. Renewable biomass has the potential to
provide an alternative energy source that offers many long-term advantages over petroleum. Biomass
can be converted into synthesis gas by gasification, and the synthesis gas can be efficiently converted
into methanol using existing technology. Methanol is one of the prime candidates for providing an
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alternative to petroleum-based liquid transportation fuels.
It is possible that, in the not-to-distant future, most liquid-consuming transportation vehicles (cars,
trucks, trains, and planes) may use methanol as their energy source. It can be made from any
renewable biomass hydrocarbon source by partial oxidation in an oxygen-blown gasifier to produce
synthesis gas, which is then converted into methanol.
SAFETY MEASURES
Methanol is a colorless, odorless liquid at room temperature. Methanol exposure can occur through
swallowing, inhalation, or through contact with skin. It is highly toxic if ingested and therefore should
be handled with care. Ingesting 25-90ml can be fatal if medical attention is not sought immediately
after ingestion. Methanol poisoning causes the human body’s pH to drop making bodily systems highly
acidic. Symptoms of methanol poisoning include loss of cognitive ability, vomiting, and blindness which
can be permanent. Methanol poisoning can be treated in a variety of ways. Many times sodium
bicarbonate is administered to help neutralize acidity. There are also medications which can stop the
body from metabolizing methanol. Methanol is also corrosive and flammable at room temperature. It
is easily ignited and burns with an almost invisible flame.
Storing and transferring methanol can be dangerous if proper procedures and equipment are not
utilized. When storing methanol a dedicated storage area is needed to ensure that cross
contamination doesn’t occur. The storage area needs to be identified clearly. The area also needs to
have working detection devices such as alarms which can notify personnel if there is a leak or
unhealthy levels of methanol. Personnel entering the area should make sure that proper personal
protective equipment is worn to minimize the chance of exposure. At minimum, personal protective
equipment should include eye shields and chemical resistant gloves. There should also be an eyewash
and shower located in the methanol storage area in case of personnel exposure. Other equipment
needed by individuals in the storage area include fire extinguishers, a first aid kit, clean drinking water,
and an emergency communication device. When methanol is being transferred to a storage area,
trucks as well as storage containers need to be grounded to limit the sources of ignition. Finally, only
specified electronic devices can be used within twenty feet of the storage area.
If there is a leak or an explosion at a methanol facility, response procedures will prove to be the
difference between a manageable incident and a catastrophe. Ideally, once an incident occurs the first
step to take would be to contain the leak or fire if possible. If the leak is small enough and water is
readily available the methanol can be diluted since methanol is completely miscible in water. However,
diluted methanol should not be washed down regular drain systems. Small pools of methanol can also
be absorbed with chemical absorbents. If the spill is larger, the area should be evacuated and sources
of ignition should be eliminated. Once the area is evacuated, personnel should stay upwind from the
spill or fire, and emergency responders should be contacted. Appropriately treating risks associated
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with methanol production and storage will ensure safe working conditions for everyone involved.
Syngas storage and transport can also pose serious risks if proper procedures are not in place. The
main risk associated with syngas is the potential for inhalation. Symptoms of inhalation of syngas
include headache, nausea, confusion, excess salivation, and possible hallucinations. Long term,
repeated exposure to syngas can cause permanent nervous system and/or brain damage. Any
personnel who is suspected of syngas exposure should be removed to an area with fresh air, and
medical help should be sought.
Syngas can also form highly a highly flammable mixture when exposed to air. If a syngas fire is
detected, personnel should not try to extinguish the fire due to the possibility of re-ignition. Instead,
water should be sprayed on all things that are in contact with the fire, and the flow of syngas should
be shut off. However, shutting off syngas flow should only be attempted if the fire is small enough to
be managed. Protective clothing and a breathing apparatus should be utilized to avoid fire and
inhalation exposure. In the event of a fire or a syngas leak all non-essential personnel should be
evacuated from the area.
BACKGROUND AND SCOPE OF WORK
The purpose of this report is to study the methanol reactor/distillation column system with three gas
recycle streams to produce high-purity methanol from synthesis gas. A plantwide control structure is
developed that is capable of effectively handling large disturbances in the production rate and
synthesis gas composition. The unique features of this control scheme are a lack of control of pressure
in the reactor/recycle gas loop and a high-pressure override controller to handle stoichiometric
imbalances in the composition of the synthesis gas feed. This report studies the process to convert
synthesis gas into methanol. A cooled tubular reactor is used to react hydrogen with the carbon
monoxide and carbon dioxide in the synthesis gas to produce methanol. Water is a byproduct. The gas-
phase exothermic reactions are conducted in a packed tubular reactor, which is cooled by generating
steam. A large gas recycle stream is required to obtain high overall conversion. A distillation column
separates methanol from water.
A fixed amount of synthesis gas is fed into the system, and the effects of the many design optimization
variables on the yield of methanol are evaluated. These variables include reactor pressure, reactor size,
concentration of inert components in the recycle gas, and pressure in a flash tank upstream of the
column. The purpose of the flash tank is to keep light components from entering the column that
would blanket the condenser.
The study reveals that the economics are dominated by methanol yield. The major energy cost is
compression of the synthesis gas, so the optimum reactor operating pressure is a trade-off between
compression costs and methanol yield. Reactor temperature is set such that high-pressure steam can
be produced in the reactor. Reactor size is a trade-off between reactor and catalyst capital investment
and recycle compression costs. Inert component concentration in the recycle gas is a trade-off
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between methanol yield (reactant losses in the vent) and compression costs. Selection of pressure in
the flash tank is a trade-off between compressor costs in two compressors that are affected in
opposite directions by varying the flash-tank pressure.
THEORY
The reaction kinetics data were taken from various research papers (in references).
Reaction Kinetics
Methanol synthesis has been a commercial process since long, the reaction mechanism and kinetics
are still an open question. However, based on previous researches, the prevailing view is that methanol
is produced primarily through CO2 hydrogenation.
Although there are many kinetic rate equations for the methanol synthesis reaction in literature, I used
the kinetic equation proposed by Bussche and Froment. The reason for this is that the catalysts used in
the plant and in the study carried out by Bussche and Froment are both of a commercial type and have
similar chemical compositions. In addition, operating conditions and feed composition are also similar.
In this kinetic model, two independent reactions (hydrogenation of carbon dioxide and reverse water-
gas shift reaction) out of the three following dependent reactions are considered:
CO + 2H2 ↔ CH3OH ……… (1)
CO2 + 3H2 ↔ CH3OH + H2O ……… (2)
CO2 + H2 ↔ CO + H2O ………. (3)
Rate of reactions for (2) and (3) are as follows:
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k1= 1.07 exp(-36696 kJ/ kmol/RT), reaction rate constant;
k2 = 1.22 exp(-94 765 kJ/ kmol/RT), reaction rate constant;
Pi = partial pressure of component i (bar), i = CO2 , H2, CH3OH, CO, H2O;
Ke,1 = equilibrium constant, log10Ke,1 = (3066/T)–10.592;
Ke,2 = equilibrium constant, log10Ke,2 = (–2073/T)+2.029;
K2 = 6.62*10-11 exp(124119 KJ/ kmol/RT, adsorption constant;
K3 = 3453.38, adsorption constant.
Some impurities are also generated:
2CO + 4H2 ↔ CH2CH3OH + H2O …….. (6)
2CO + 2H2 ↔ HCOOCH3 …….. (7)
3CO + 6H2 ↔ C3H7OH + 2H2O …….. (8)
Reactor model
The reactor simulation is defined taking into account the following assumptions:
Unidimensional model, negligible axial dispersion and heat conduction, and constant catalyst
effectiveness. It was assumed that energy losses to the surrounding are zero.
Starting from these premises, the reactor is simulated in Aspen Plus version v 8.4. The plug flow
reactor model with countercurrent coolant with the Langmuir-Hinshelwood- Hougen-Watson (LHHW)
kinetics is used to describe the reaction mechanism. Steam is used as a coolant in the reactor which
contain tubes in which reaction is taking place in the presence of catalytic surface composed of
Cu/ZnO/Al2O3. Catalyst is used to increase the selectivity of MeOH production, resulting in a more
efficient reaction. The catalyst is on the inside of the reactor.
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Procedure
Various other equipment are used in the process. They include heater, heat exchanger, flash drum,
distillation column, compressors, mixers etc.
The process flowsheet is presented in the Figure. The syngas feed stream was set at 50 °C and 51.2 bar.
Syn gas used contain H2, CO, CO2, N2, CH4, H2O etc. The syngas fed was compressed, heated and mixed
with recycle streams and heated in a heat exchanger before entering the reactor. The flowsheet is
composed of a compressors, a loop of reaction, and a purification section. In the first section, the
syngas is compressed, and then heated in a heat integration exchanger before entering the reactor.
The reaction occurs in the PFR, a fixed bed reactor with cooling between tubes steam. The heat
exchangers perform energy integration and cooling temperature was set to maximize recovery of
methanol in the separation vessel. Effluent stream of the reactor is heated and flashed in a drum.
Vapors are recycled and the liquid is sent to another flash column. The gas phase with very low
methanol content is recycled to the reaction´s loop where a purge is calibrated appropriately. The
recycle increases the reaction conversion and yield of methanol, but should be considered carefully
due to the costs associated to the recycle. The liquid phase rich in methanol goes to another flash
column and then follows to the methanol purification section (in a distillation column). Simulated
conditions needed only one distillation column to fulfill the separation requirements for water, light
components and methanol. The bottom product from the distillation column is mainly of water. The
distillate is flashed and compressed to generate the final product stream. The overhead vapor is
formed by light gases, which were discarding for the process. These simplifications make the
simulation less complex in the reaction loop and separation section, but comparison between two
processes is still valid.
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Result and Discussion
The steady-state behavior of the process as a function of coolant pressure, syngas inlet
temperature and cooling water volumetric flow rate was investigated by sensitivity analysis
in aspen plus.
Graphs were drawn between reactor length and methanol flow rate. Also between
temperature of coolant v/s methanol flow rate and pressure v/s flow rate.
A comparison was done between single reactor and when reactor is combined with the
whole plant.
And the results are shown.
Conversion was found to be: 45 %
% Yield: 10% (final)
% Yield: 82.6% (final)
It was found that on recycling the methanol yield increased many fold.
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REFERENCES
1. http://www.supermethanol.eu/index.php%3Fid%3D21%26rid%3D12%26r%3Dmetha
nol_synthesis
2. https://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/48_2_New%20York_10-
03_0775.pdf
3. https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&ved=0CDw
QFjAGahUKEwjUn523hujIAhVlKaYKHUsSBUM&url=http%3A%2F%2Fwww.netl.doe.go
v%2Fresearch%2Fcoal%2Fenergy-
systems%2Fgasification%2Fgasifipedia%2Fmethanol&usg=AFQjCNF3KgkNcZyBjdsY1N
s82S6b_5jSQQ&bvm=bv.106130839,d.dGY&cad=rja
4. http://pubs.rsc.org/en/Content/ArticleLanding/2012/CY/c2cy20315d
5. http://pubs.acs.org/doi/pdf/10.1021/ef020240v
6. Optimization of methanol yield from lurgi reactor : research article
7. Simulation of methanol synthesis from synthesis gas in fixed bed catalytic reactor
using mathematical modeling and neural networks : research article
8. Design and Control of a Methanol Reactor/Column Process: research article
9. Methanol Synthesis from Syngas
Austin Cochrane, Zachary Davis, Donald Fetzer, Ducien Mitchell : research article
10. Industrial methanol from syn gas: kinetic study & process simulation : research paper
11. Dynamic modeling of a H2O-permselective membrane reactor to enhance methanol
synthesis from syngas considering catalyst deactivation : research paper
12. Modeling, simulation and control of a methanol synthesis fixed-bed reactor : research
article
13. Mal-distribution of temperature in an industrial dual-bed reactor for conversion of
CO2 to methanol
