Page 171 - Chemical engineering design

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CHEMICAL ENGINEERING
Partial pressure of
pressure of water)
non-condensables D (total pressure) (vapour pressure of EDC C vapour
D 4 0.16 0.055 D 3.79 bar
vapour press. EDC
Flow of EDC in vapour D ð flow non-condensables
partial press.
non-condensables
0.16
D ð 213.4 D 9kmol/h
3.79
Similarly, flow of H 2 O 0.055
in vapour D 3.79 ð 213.4 D 3.1kmol/h
So composition of gas streams is

kmol/h Per cent mol kg/h
EDC 9 4.0 891
H 2 O 3.1 1.4 56
Inerts 208 92.3 6640
C 2 H 4 5.4 2.3 150

Check on dissolved ethylene

Partial pressure of ethylene D total pressure ð mol fraction
2.3
D 4 ð D 0.092 bar
100
By assuming EDC and C 2 H 4 form an ideal solution, the mol fraction of ethylene
dissolved in the liquid can be estimated, from Raoults Law (see Chapter 8).
x A P Ž A
y A D
P

y A D gas phase mol fraction,
x A D liquid phase mol fraction,
Ž
P D sat. vapour pressure,
A
P D total pressure,
Substituting
2.3 x A 70.7
D
100 4
x A D 1.3 ð 10 3
hence quantity of ethylene in liquid D kmol EDC ð x A
D 64 9 ð 1.3 ð 10 3 D 0.07 kmol/h
so kmol ethylene in gas phase D 5.4 0.07 D 5.33 kmol/h