Methanol is a potential clean fuel for gasoline engines and its synthesis reactions occur in gas phase, where the products are subsequently liquefied to split the un-reacted reagent gases - carbon dioxide (CO2), carbon monoxide (CO) and hydrogen (H2). In addition to these metha- nol synthesis reactions, reverse water-gas shift reaction occurs in the process, where CO2 and H2 react to form CO and water vapour. The liquid stream leaving the separator consists of methanol and water with the separation of un-reacted reagent as exhaust gases.
A methanol synthesis plant is designed to produce 50,000 kg/hr of 99.8% methanol, using the feed gas with the composition of 5 mol% methane (CH4), 25 mol% CO, 5 mol% CO2 and 65 mol% H2. The product liquid stream leaving the separation process has the methanol purity of 99.8 wt%. The single pass conversions of CO and CO2 are assumed to be 45% and 30%, re- spectively. A graduate engineer has devised a simulation model of the reactions of the metha- nol synthesis plant and based on the kinetic equations of those reactions, following conver- sions of CO and CO2 were predicted.
Table 1.1 Reactions and simulated conversions
Reaction Conversion (%)
CO reaction 45%
CO2 reaction 30%
Reverse water-gas shift reaction 0%
(i) Write down the three equilibrium reactions involved in the process.
(ii) Draw a flowsheet to represent the methanol production process - clearly label each process streams and also indicate all known and unknown flowrates and compositions
of the streams.
(iii) Using the provided conversion of CO and CO2, calculate the amount of feed required
to produce methanol and also determine the molar composition of each stream.
(iv) Is this process efficient? If not give a reason why and suggest what can be done to
make it more efficient.
Methanol is a potential clean fuel for gasoline engines and its synthesis reactions occur in gas phase, where the products are subsequently liquefied to split the un-reacted reagent gases - carbon dioxide (CO2), carbon monoxide (CO) and hydrogen (H2). In addition to these metha- nol synthesis reactions, reverse water-gas shift reaction occurs in the process, where CO2 and H2 react to form CO and water vapour. The liquid stream leaving the separator consists of methanol and water with the separation of un-reacted reagent as exhaust gases.
A methanol synthesis plant is designed to produce 50,000 kg/hr of 99.8% methanol, using the feed gas with the composition of 5 mol% methane (CH4), 25 mol% CO, 5 mol% CO2 and 65 mol% H2. The product liquid stream leaving the separation process has the methanol purity of 99.8 wt%. The single pass conversions of CO and CO2 are assumed to be 45% and 30%, re- spectively. A graduate engineer has devised a simulation model of the reactions of the metha- nol synthesis plant and based on the kinetic equations of those reactions, following conver- sions of CO and CO2 were predicted.
Table 1.1 Reactions and simulated conversions
Reaction Conversion (%)
CO reaction 45%
CO2 reaction 30%
Reverse water-gas shift reaction 0%
(i) Write down the three equilibrium reactions involved in the process.
(ii) Draw a flowsheet to represent the methanol production process - clearly label each process streams and also indicate all known and unknown flowrates and compositions
of the streams.
(iii) Using the provided conversion of CO and CO2, calculate the amount of feed required
to produce methanol and also determine the molar composition of each stream.
(iv) Is this process efficient? If not give a reason why and suggest what can be done to
make it more efficient.
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