Question 18.1: A mixture of 50 mole percent benzene and 50 mole percent tol......
A mixture of 50 mole percent benzene and 50 mole percent toluene is subjected to Hash distillation at a separator pressure of 1 atm. The vapor-liquid equilibrium curve and boiling-point diagram are shown in Figs. 18.2 and 18.3. Plot the following quantities, all as functions of f, the fractional vaporization: (a) the temperature in the separator, (b) the composition of the liquid leaving the separator, and (c) the composition of the vapor leaving the separator.
For each of several values of/corresponding quantities – [(1/f)- 1] are calculated. Using these quantities as slopes, a series of straight Jines each passing through point (x_{F},\,x_{F}) is drawn on the equilibrium curve of Fig. 18.2. These lines intersect the equilibrium curve at corresponding values of x_{B} and y_{D}· The temperature of each vaporization is then found from Fig. 18.3. The results are shown in Table 18.1 and plotted in Fig. 18.4. The limits for 0 and 100 percent vaporization are the bubble and dew points, respectively.
| TABLE 18.1 | ||||
| Data for Example 18.1 | ||||
| Concentration, mole fraction \mathrm{C}_{6}\mathrm{H}_{6} | ||||
| Fraction vaporized f | \mathrm{Slope-}{\frac{1-f}{f}} | \operatorname{Liquid}x_{B} | Va\mathrm{por}\;y_{D} | Temperature, °c |
| 0 | {\infty} | 0.5 | 0.71 | 92.2 |
| 0.2 | -4 | 0.455 | 0.67 | 93.7 |
| 0.4 | -1.5 | 0.41 | 0.63 | 95 |
| 0.6 | -0.67 | 0.365 | 0.585 | 96.5 |
| 0.8 | -0.25 | 0.325 | 0.54 | 97.7 |
| 1 | 0 | 0.29 | 0.5 | 99 |