Ammonia Process: Simultaneous Solution (Reklaitis, 1983,
p. 273) We have solved this problem using the sequential
modular approach; see Chapter 3, Problem 3.15 (solution
provided).
A simplified flow sheet for an ammonia process is shown
in Figure P4.10. In the ammonia plant, a feed gas consisting
of 24.5% N2, 74% H2, 1.2% CH4, and 0.3% argon is catalytically reacted to produce NH3. The reaction is
N H NH 2 2 + = 3 2 3,
and 65% of the N2 entering the reactor is converted per pass.
The products of reaction are refrigerated to separate out 75%
of the NH3 product per pass. The remaining process stream
is recycled back to the reactor. In order to stabilize the
buildup of the inerts CH4 and A in the process, part of the
recycled gas is purged. Suppose the splitter purge rate
(stream 6) is set at 5% of the stream into the splitter (stream
5) or from Equation (3.17), N6 = α6
N5
, with α6 = 0.05. Calculate all flows in the process using the simultaneous solution approach. Assume a basis of 1000 mol/h for the feed
stream (stream 1).
Solution: Problem 4.10.xls