Mass and Energy Balances P8.30 G.V. Reklaitis
A
synthesis gas is upgraded to a higher methane content in the recycle system
shown in figure P8.30. The feed gas contains a small amount of methane and
analyzes 22% CO, 13% CO2, and 65% H2 (mol %) on a methane-free basis. The product stream
(stream 6) analyzes (all mol %) CO 5%, H2 9%, CH4 50%, CO2
27% , and H2O 9%. Both feed and product are gases at 200˚F. In the
reactor the two reactions
CO + 3H2
→ CH4 + H2O
CO + H2O → CO2 + H2
take
place. The reactor effluent is cooled to 500˚F in exchanger 1 and then is
further cooled in exchanger 2. Part of the effluent is split off as product.
The remainder is sent to a separator in which the stream is cooled to 90˚F and
95% of the H2O is separated as liquid. The remaining gas stream is
reheated in exchanger 2, mixed with the fresh feed, and returned to the
reactor. Assume that mixer, the splitter, exchanger 2, and the reactor operate
adiabatically. Use average Cp
values as given on the flowsheet.
(a)
Construct a
degree-of-freedom table and show that the process is correctly specified.
(b)
Determine a
calculation order for the problem.
(c)
Calculate the
reactor outlet temperature.
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