One hundred moles of feed, containing 50 percent A (more volatile component), are flash vaporized to produce 60 moles of distillate at one atmosphere system pressure. Equilibrium data of this binary mixture can be generated using relative volatility value of 2.16. Calculate composition of vapor leaving the separator. Also find out the liquid composition leaving the bottom of the separator.
Solution:
Equilibrium data can be computed using relative volatility
value: y is equal to alpha time x over
(one plus (alpha minus x) time x).
Calculate y for different values of x, say, 0.2, 0.4, 0.5, 0.6, and 0.8
and draw the equilibrium curve. Draw an
operating line that represents the individual component mass balance. Its equation is as follows: y is equal to
minus W over D time x plus xF time (one plus w over D). This line passes through point (xF,
xF) and has a slope of minus W over D. For our case, D is 60, and W is F minus D or 40 moles.
Slope of the operating line is found to be minus 0.667 and
the line intersects the equilibrium curve at a point (0.386, 0.576). The composition of liquid and vapor leaving
separator is 38.6 and 57.6 percent, respectively.