DESIGN OF COMBINED MEMBRANE AND DISTILLATION PROCESSES

The performance of three hybrid membrane and distillation processes is compared theoretically, using the separation of propylene and propane as a representative case. For each system configuration the effect of the main design variables is illustrated through parametric studies. Results dealing with both design of new processes and retrofit of exis ting distillation-based separation processes are presented. The result s show qualitative trends which may serve as guidelines for design of hybrid membrane and distillation processes. If the membrane is placed parallel to the column, the optimal position for the membrane feed str eam is close to the column feed plate, which represents a potential pi nch point in the column. The optimal membrane cut rate for this config uration is generally close to the molefraction of propylene in the mem brane feed stream. The comparison of the systems performances indicate s that placing the membrane in parallel or on the bottom stream of the column gives the best performance of the hybrid process, both in term s of compressor duty and in terms of installed membrane area.