a) A liquid mixture containing 50 mol% n-heptane and 50 mol% n-octane at 30 C is to be flash continuously distilled at 1 atm to evaporate 60% of the mixture.

What will be the composition of the vapor, the composition of the liquid, and the temperature in the separator for an ideal stage?

At what temperature should the mixture be fed to the flash tank to achieve separation?

Cp Heptane=224.72 J/mol K Cp Octane=232.74 J/mol K

v Heptane=36 kJ/mol v Octane=41 kJ/mol

b) If the same mixture is subjected to a differential distillation process at atmospheric pressure to evaporate and condense 60% of the initial liquid, what will be the composition of the residual liquid and the average composition of the condensate?

Liquid and vapor phase fractions of n-heptane at equilibrium

Use of boiling point diagram, equilibrium line and equations for flash distillation.

Graphic solution, Simpson 3/8 method and by adjustment to a quadratic equation and its subsequent solution for differential distillation.

T (C)	x	y
125.6	0	0
124	0.039	0.078
122	0.097	0.184
120	0.156	0.282
118	0.220	0.375
116	0.284	0.450
114	0.352	0.541
112	0.421	0.613
110	0.495	0.681
108	0.569	0.743
106	0.647	0.801
104	0.733	0.862
102	0.824	0.912
100	0.922	0.963
98.4	1	1