Page 190 - Chemical engineering design

202.5 21.9
NO oxidised
D
D 6.02 kmol/h
30 FLOW-SHEETING 167
Heat generated D 6.02 ð 57,120 D 0.34 GJ/h
1704
HNO 3 formed D D 27.05 kmol/h
63
Heat generated D 27.05 ð 63,640 D 1.72 GJ/h
Ž
Heat of dilution to 60 per cent at 25 C D 27.05 ð 14,207 D 0.38 GJ/h
Water condensed D 29.4 26.3 D 3.1 kg/h
Ž
Latent heat at 40 C D 2405 kJ/h
Sensible heat above datum temperature D 4.18 (40 25) D 63 kJ/kg
Heat released D 3.1 2405 C 63 D 7.6 ð 10 3 GJ/h (negligible)
Sensible heat in acid out, specific heat 0.64, take temperature out as same as gas
Ž
inlet, 40 C
D 0.64 40 25 4.18 ð 2840 D 0.11 GJ/h
Heat balance (GJ/h)

Tail gas Oxidation 0.34 Water
0.0 HNO 1.72 0.0
3
Dilution 0.38

Condensation
2.44 Heat to
cooling
water
Gas
in
0.15

Sec. air
0.018
0.11
Acid out
Heat transferred to cooling water D 0.15 C 0.018 C 2.44 0.11 D 2.5GJ/h

Mixer
Calculation of mixed acid temperature.
Ž
Taking the datum as 0 C for this calculation, so the enthalpy-concentration diagram
can be used directly.
From diagram:
Ž
enthalpy 45 per cent acid at 0 C D 186 kJ/kg
Ž
specific heat D 0.67 kcal/kg C
Ž
enthalpy 60 per cent acid at 0 C D 202 kJ/kg
Ž
specific heat D 0.64 kcal/kg C