Heterogeneous batch distillation with variable decanter hold-up

A general model of batch heteroazeotropic distillation is proposed, in which both liquid phases present in the decanter can be refluxed or withdrawn as distillate, their hold-up can be increased, decreased or kept constant, as well. A feasibility study is performed with the assumption of maximal separation, that is, that the composition of the condensate always equals to that of the heteroazeotrope. The still path directions are determined for all the 16 possible operation policies, and the results are validated by rigorous simulations for three cases not published yet. The still path can be steered in any direction by changing the operational parameters, allowing the recovery of a pure component in the still.