Problem #1 (20 + 15: 35 pts)
A binary mixture of toluene (A) and o-xylene (B)
is to be flash vaporized continuously in a flash
drum at 1 atm pressure. The feed rate and feed
composition are:
Heater
F = 100 mol/h, $z_A = 0.3$ and $z_B = 0.7$
The flash is carried out at a temperature such that
only 25% of the feed mixture is vaporized.
Liquid
feed
$F, z_i$
$h_F$
$T_F, P_F$
WW
Valve
Flash drum
$V, y_i$
$P_V, T_V$
$L, x_i$
$P_L, T_L$
You are given T-x-y diagram (Page 3 of 6) of the toluene / o-xylene system at 1 atm. Assume ideal
VLE system.
(a) Using the T-x-y diagram, determine the flash temperature, $T_{flash}$, and the corresponding VLE
compositions, $y_A$ and $x_A$ in mole fractions of toluene. Show your work neatly on the T-x-y
diagram with appropriate labels.
(b) Derive an equation for isothermal flash operation and then determine the slope and y-intercept
of the flash operating line using the results of part (a).