USING ATOMIC SPECIES BALANCE!!!! Solving for all unknowns 4.76. Methanol is prod
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USING ATOMIC SPECIES BALANCE!!!! Solving for all unknowns 4.76. Methanol is produced by reacting carbon monoxide and hydrogen. A fresh feed stream 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 movmin and contains 10.6 wt% H2,64.0 wt% Co, and 25.4 wt% CH30H. (Notice that those are percentages by mass, not mole percents.) 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 The liquid methanol condensate is withdrawn as a product, and the gas stream leaving the condenser.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 CH3OH is the recycle stream that combines with the fresh feed. (a) Without doing any calculations, prove that you have enough information to determine the molar flow rates of CO and H2 in the fresh feed, (ii) the production rate of liquid methanol, and (ii) the single-pass and overall conversions of carbon monoxide. Then perform the calculations. (b) After several months of operation, the flow rate of liquid methanol leaving the condenser begins to decrease. List at least three possible explanations of this behavior and state how you might check the validity of each one. (What would you measure and what would you expect to find if the explanation is valid?)Explanation / Answer
The outlet of reactor contains converted CH3OH and unreacted CO, H2. The condensation process removes most of the methanol.
Weight percents will have to be converred to moles % by assuming suitable basis.
Methanol produced =Methanol in the outlet reactor- Methanol in the vapor
Methanol in the vapor =0.4%, Rest is CO and H2 which is recycled. This corresponds to 100-0.4= 99.4% of CO and H2.
All theCO andH2 are recycled.
Amount of methanol formed from the reaction CO+2H2----àCH3OH
1 mole of Methanol produced requires 1 mole of CO and 2 moles of H2.
This helps in calculating the fresh feed.
Single pass conversion is total moles of CO and H2 entering the reactor = moles of CO and H2 recycled+ moles of CO and H2 consumed for producing CH3OH.
Product from the reactor :
Basis : 1 gm of product. It contains 0.64 gm of CO, 0.106 gm of H2 and rest= 1-0.64-0.106=0.254 gm of CH3OH
Moles = mass/Molar mass
Molar masses : CO=28, H2=2 and CH3OH= 32
Moles : CO= 0.64/28= 0.023, H2= 0.106/2=0.053 and CH3OH= 0.254/32= 0.0079
Total moles = 0.023+0.053+0.0079=0.0839
0.0839 moles are there in 1gm
350 moles correspond to 350/0.0.0839 =4172
Masses of products (gm) : CO: 4172*0.64= 2670 gm, H2= 0.106*4172 =442 and rest CH3OH= 4172 -2670-442 =1060 gm
Moles : :CO= 2670/28= 95, H2= 442/2= 221 and CH3OH= 1060/32=33
All the CO and H2 are recycled. This correspond to 99.6% of recycled product
Hence moles recycled = (221+95)0.996= 317
Moles of CH3OH in recycle = 317*0.4/100 = 1.3 moles
Moles of CH3OH condensed = 33-1.3= 30.7 moles
Methanol in the recycle= 1.3 moles
Total moles of CH3OH produced= 30.7+1.3= 32 moles
Single pass conversion of CO= 100*30.7/32= 95.4%
CO required for producing this = 30.7 and H2 =30.7*2= 61.4
Fresh feed contains: CO= 30.7 moles and H2= 61.4
Total feed entering the reactor
CO: 95+30.7 =125.7
Moles of CH3OH produced= 125.7 moles
% conversion = 100*32/125.7=25.45
2.
CO+ 2H2 ---------> (Cobalt Catalyst) CH3OH
Some of the possibilities of less liquid production
1. Poisioning of Catalyst.
2. Carry over of more of methanol in the recycle. Measuring the composition of recycle
3. Improper condenser cooling medium flow rate. Temperature of cooling medium flow rate at the outlet.
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