Page 173 - Chemical engineering design

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CHEMICAL ENGINEERING
As a first approximation take organic stream flow D EDC flow in.
0.16
Then water in EDC D ð 5459 D 8.73 kg/h
100
So water flow out D 1075 8.73 D 1066.3 kg/h
1066.3
and EDC dissolved in the water stream D ð 0.86 D 9.2 kg/h
100
so, revised organic stream flow D 5459 9.2 D 5449.8 kg/h

5449.8
and quantity of water dissolved D ð 0.16 D 8.72 kg/h
100
in the stream
Which is not significantly lower than the first approximation. So stream flows, kg/h,
will be:
Stream no. 1 2 3
Title Decanter Organic Aqueous
feed phase phase
EDC 5459 5449.8 9.2
H 2 O 1075 8.7 1066.3
Total 6534 5458.5 1075.5

Example 4.4
This example illustrates the manual calculation of a material and energy balance for a
process involving several processing units.
Draw up a preliminary flow-sheet for the manufacture of 20,000 t/y nitric acid (basis
100 per cent HNO 3 ) from anhydrous ammonia, concentration of acid required 50 to 60
per cent.
The technology of nitric acid manufacture is well established and has been reported in
several articles:

1. R. M. Stephenson: Introduction to the Chemical Process Industries (Reinhold, 1966).
2. C. H. Chilton: The Manufacture of Nitric Acid by the Oxidation of Ammonia
(American Institute of Chemical Engineers).
3. S. Strelzoff: Chem. Eng. NY 63(5), 170 (1956).
4. F. D. Miles: Nitric Acid Manufacture and Uses (Oxford University Press, 1961).

Three processes are used:

1. Oxidation and absorption at atmospheric pressure.
2. Oxidation and absorption at high pressure (approx. 8 atm).
3. Oxidation at atmospheric pressure and absorption at high pressure.
The relative merits of the three processes are discussed by Chilton (2), and Strelzoff (3).