Page 189 - Chemical engineering design

166
CHEMICAL ENGINEERING
Quantity of solution produced by dilution of 1 kmol 100 per cent HNO D
3 63 ð 100
45
D 140 kg,
so, heat generated on dilution of 1 kmol D 140 ð 115.9 D 16,226 kJ,
so, total heat generated D 13.5 ð 16,226 D 219,051 kJ/h
D 0.22 GJ/h.
6. Sensible heat of acid
Ž
Acid outlet temperature was taken as 40 C, which is above the datum temperature.
Sensible heat of acid D 0.67 ð 4.186 40 25 ð 1860.7 D 78,278 kJ/h D 0.08 GJ/h

Heat balance (GJ/h)

Heat to cooling
water
Oxidation 1.97
Condensation 3.02
Gas in Gas out
HNO formation 0.86
2.81 3 0.15
Dilution 0.22
Total 6.07
Liquid out
0.08

Heat transferred to cooling water D 2.81 C 6.07 0.15 0.08
D 8.65 GJ/h

Air cooler
The secondary air from the compressor must be cooled before mixing with the process
gas stream at the absorber inlet; to keep the absorber inlet temperature as low as possible.
Ž
Take the outlet temperature as the same as exit gases from the cooler condenser, 40 C.
Secondary air flow, from flow-sheet, 1754.8 kg/h
Specific heat of air 1 kJ/kgK
Heat removed from secondary air D 1754.8 ð 1 ð 230 40
D 333,412 kJ/h D 0.33 GJ/h

Absorber
The sources of heat in the absorber will be the same as the cooler-condenser and the same
calculation methods have been used. The results are summarised below:
Sensible heat in inlet gases from cooler-condenser D 0.15 GJ/h
Sensible heat in secondary air D 1754.8 ð 1.0 40 25 D 0.018 GJ/h
Sensible heat in tail gases (at datum) D 0
Sensible heat in water feed (at datum) D 0