Problem
Styrene can be produced by the reactions:
Ethylbenzene ! Styrene+H2
Ethylbenzene ! Benzene+Ethylene
Ethylbenzene+H2 ! Toluene+CH4
The reactions take place at 600C and 1.7 bar. We want to produce 100 mol
h of styrene. The market prices
are 22 £/mol for styrene, 10 £/mol for benzene and 7 £/mol for toluene. The ethylbenzene feed stream
contains 2% benzene and costs 16 £/mol. Fuel price is £10 for 106 cal. Assume that fuel components
have normal boiling points larger than 50C. For the product distribution, the following correlations have
been determined experimentally by chemists:
mol Benzene
mol Styrene = 0:333x??0:215x2+2:547x3
mol Toluene
mol Styrene = 0:084x??0:264x2+2:638x3
where x is the ethylbenzene conversion.
Determine and justify the following decisions (remember: think as an engineer!):
1. Should the above process be continuous or batch?
2. Based purely on the level 0 information, what is a reasonable upper bound on the conversion we
should consider?
3. Do we need feed purification?
4. Do we use gas recycle and purge stream(s)?
5. What is the number of product streams?
6. Draw the input-output flowsheet.
7. Develop the overall material balances for the input-output structure as a function of the clearly identified
design variable(s).
8. Plot the economic potential as a function of the design variables.
9. Above what conversion does the above process become unprofitable?
10. Produce a stream table for what you would consider to be a good conversion.