Question

A feed mixture composed of 42 mol % heptane and 58 mol % ethyl benzene is to be fractionated at 760 mmHg to produce a distillate containing 97 mol % heptane and a residue containing 98 mol % ethyl benzene. Equilibrium data is given as:
x 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.9
y 0.26 0.44 0.566 0.65 0.73 0.79 0.85 0.953
Find:
(a) the minimum reflux ratio?
(b) the minimum number of equilibrium stages (at total reflux)?
(c) the number of plates required in the design of the distillation column operating at reflux ratio twice the minimum reflux ratio?
(d) Repeat (a – c) if the feed entering the tower is partially vaporized so that 40 mol % is liquid.