Page 75 - Chemical engineering design

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CHEMICAL ENGINEERING
(c) the composition of the flue gases, on a dry basis.
Assume complete combustion.
2.2. Ammonia is removed from a stream of air by absorption in water in a packed
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column. The air entering the column is at 760 mmHg pressure and 20 C. The
air contains 5.0 per cent v/v ammonia. Only ammonia is absorbed in the column.
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If the flow rate of the ammonia air mixture to the column is 200 m /sand the
stream leaving the column contains 0.05 per cent v/v ammonia, calculate:
(a) The flow-rate of gas leaving the column.
(b) The mass of ammonia absorbed.
(c) The flow-rate of water to the column, if the exit water contains 1% w/w
ammonia.

2.3. The off-gases from a gasoline stabiliser are fed to a reforming plant to produce
hydrogen.
The composition of the off-gas, molar per cent, is: CH 4 77.5, C 2 H 6 9.5, C 3 H 8 8.5,
C 4 H 10 4.5.
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The gases entering the reformer are at a pressure of 2 bara and 35 C and the feed
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rate is 2000 m /h.
The reactions in the reformer are:
1. C 2 H 2nC2 C n H 2 O ! n CO C 2 n C 1 H 2
2. CO C H 2 O ! CO 2 C H 2
The molar conversion of C 2 H 2nC2 in reaction (1) is 96 per cent and of CO in
reaction (2) 92 per cent.
Calculate:
(a) the average molecular mass of the off-gas,
(b) the mass of gas fed to the reformer, kg/h,
(c) the mass of hydrogen produced, kg/h.
2.4. Allyl alcohol can be produced by the hydrolysis of allyl chloride. Together with
the main product, allyl alcohol, di-ally ether is produced as a by-product. The
conversion of allyl chloride is typically 97 per cent and the yield to alcohol 90
per cent, both on a molar basis. Assuming that there are no other significant side
reactions, calculate masses of alcohol and ether produced, per 1000 kg of allyl
chloride fed to the reactor.

2.5. Aniline is produced by the hydrogenation of nitrobenzene. A small amount of
cyclo-hexylamine is produced as a by-product. The reactions are:
1. C 6 H 5 NO 2 C 3H 2 ! C 6 H 5 NH 2 C 2H 2 O
2. C 6 H 5 NO 2 C 6H 2 ! C 6 H 11 NH 2 C 2H 2 O
Nitrobenzene is fed to the reactor as a vapour, with three times the stoichiometric
quantity of hydrogen. The conversion of the nitrobenzene, to all products, is 96
per cent, and the yield to aniline 95 per cent.
The unreacted hydrogen is separated from the reactor products and recycled to
the reactor. A purge is taken from the recycle stream to maintain the inerts in the