Methanol is produced by reaction carbon monoxide and hydrogen. A fresh feed stea
ID: 985084 • Letter: M
Question
Methanol is produced by reaction carbon monoxide and hydrogen. A fresh feed steam containing CO and H2 joins a recycle stream and the combined stream is fed to a reactor. The reactor outlet stream flows at a rate of 350 mol/min and contains 10.6 wt% H2, 64.0 wt% CO and 25.4 wt% CH2OH. This stream enters a cooler in which most of the methanol is condensed. The liquid methanol condensate is withdrawn as a product, and the gas stream leaving the condenser, which contains CO, H2 and 0.40 mole% uncondensed CH2OH vapor, is the recycle stream that combines with the fresh feed. Determine the molar flow rates of CO and H2 in fresh feed. The production rate of liquid methanol. The single pass and overall conversions of CO.Explanation / Answer
The reactor outlet contains 10.6 wt% H2, 64 wt% CO and 25.4 wt% CH3OH.
Basis : 100 grams of reactor outlet, it contains 10.6 gram of H2, 64 grams of CO and 25.4 grams of CH3OH
Molecular weights : H2=2 CO= 12+16=28 and CH3OH= 12+4+16=32
Mole = Mass/Molecular weights H2= 10.6/2=5.8, CO= 64/28=2.29, CH3OH= 25.4/32=0.794
Total moles= 5.80+2.29+0.794=8.884
Mole fractions: Moles of given component/ total moles, H2= 65.3% CO= 25.7% and CH3OH= 9%
350 mole/min contains : H2= 350*0.653=229, CO= 90 and CH3OH= 350-(229+90)=31moles/min
Recycle stream contains 0.4mole% CH3OH and balance is CO.H2= 100-0.4=99.6 mole%
This correspond to total amount of H2 and CO leaving the reactor which is =229+90=319 moles/min
99.6 % correspond to 319 moles/min
100 % corresponds to 319*100/99.6=320.3 moles/min of Recycle
CH3OH in the recycle = 320.3*0.4/100 =1.3 moles/min
CO and H2 in the recycle need to be calculated = CO in recycle =320.3*0.996/3= 106.3 moes/min H2=212.7 moles/min
CH3OH in the products= 31-1.3= 29.7 mole/min
The reaction for producing CH3OH is CO+2H2-à CH3OH
29,7 moles/min of CH3OH requires 29.7 moles/min of CO and 2*29.7=59.4 moles/min of H2 ( This is fresh feed)
Total CO entering the reactor = Fresh CO+ Recycle CO= 29.7+ 106.3=136 moles/min and
H2= 59.4+212.7= 272.1 moles/min
Since one mole of CO produces 1 mole of CH3OH
Conversion per pass =100*{ total CO consumed for formation of CH3OH/ (total CO used)}=100*31/136=22.8%