Batch Rectification of an Ideal Benzene/Toluene Binary Mixture
Consider an ideal binary mixture composed of benzene and toluene. This Demonstration performs the dynamic simulation of a batch rectification of such a mixture. Temperature is plotted versus time for selected values of the initial composition, reflux ratio, and number of theoretical stages.[more]
The still is charged with 1000 kmol of the initial mixture. The vapor rate is assumed constant and equal to 10 kmol/hr. The molar hold-up of all stages and the condenser are 5 and 20 kmol, respectively.
It is found that (1) the products that exit the column are benzene first and toluene next; and (2) if the initial composition is very rich in either benzene or toluene then the constant temperature segment at 80.1°C or 110.6°C, respectively, is quite large.
In addition, the separation is improved if you choose large reflux ratios or a large number of theoretical stages. Otherwise you get sloppy separation and neither pure benzene nor pure toluene.[less]
The reflux ratio is given by:
where is the flow rate of the liquid refluxing to the column.
When the flow rate of the distillate, , is close to zero, the reflux ratio is very high; a situation commonly called near total reflux operation.