Internal coupling process of membrane/distillation column hybrid configuration for ethylene/ethane separation

Abstract

A new internal coupling process, especially installing the membrane module inside the distillation column and between the stripping and rectifying sections, is introduced and optimized for ethylene/ethane separation. The Fenske-Underwood-Gilliland short-cut method is extended to achieve the initial equipment design and operating parameters including the number of trays, the reflux ratio and the area of the membrane module. Basing on a central composition design with 3 free variables, 19 design cases are obtained and simulated in Aspen Plus software. The simulation results are then used to optimize the internal coupling process with response surface methodology. An iterative procedure is proposed to make the predicted value and the simulation results agree well. The comparison with the conventional cryogenic distillation based on total annual cost (TAC) demonstrates a significant economic saving of 50.58%. The effect of feed compositions is also investigated and shows the internal coupling process offers great application potential in various feed conditions. The internal coupling process is further compared with the case established in the open literature implemented membrane externally. It can be observed that the internal coupling process can effectively decrease the heat duties of condenser and reboiler.