Two miscible liquids, A and B, having equal molar heats of vaporisation, are being separated by batch rectification. At a particular point of the distillation, the composition of the vapour leaving the still is 44% A and that of the overhead product being produced at that time is 95% A.

a) If the reflux ratio is set at 3:1, estimate:

i. the number of equilibrium stages in the column,

ii. the temperature of the liquid leaving each stage,

iii. the temperature and composition of the liquor in the still.

b) Using the equilibrium data and the equation of the operating line, make a stage to stage CALCULATION of the stream compositions.

Equilibrium data:

T(°C) 138.0 131.5 126.2 121.5 117.2 113.5 110.0 107.0 104.0

xA 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900

yA 0.330 0.530 0.660 0.750 0.820 0.875 0.920 0.955 0.980

The boiling temperatures of the pure components are 102.0°C and 145.0