Feasibility of extractive distillation in a batch rectifier



A simple method was developed to study the feasibility of extractive distillation in a batch rectifier. By calculating feasible profiles of different column sections and figuring them in the triangular diagram, the feasibility and limiting values of the most important operational parameters (number of stages, flow rate of entrainer, and reflux ratio) were determined for different steps of the batch extractive distillation. The unusual behavior of extractive distillation was also investigated for this process. An infeasible region can be assigned to the given values of parameters; if the still composition is located within this region, the specified separation cannot be attained. By locating this infeasible region, maximum recoveries attainable in a batch rectifier and in a middle vessel column were compared. The results obtained by this method were verified by pilot-plant expenments for the mixture acetone + methanol water.