Impact of process configuration on energy consumption and membrane area in hybrid separation process using olefin-selective zeolite membrane

Abstract

Light olefins, such as ethylene and propylene, are industrially produced in mixtures with paraffin, such as ethane and propane, and are generally separated from mixtures via distillation. Since distillation separation processes, especially for separating propylene–propane mixtures, have the largest energy consumption compared to other separation processes, more efficient separation processes are necessary. In this study, two hybrids of distillation and membrane-separation processes (Cases 1 and 2) were designed for separating a propane/propylene mixture: Case 1 includes single-stage membrane separation before the propylene–propane distillation column, and Case 2 is a configuration using two-stage membrane separation instead of the propylene–propane distillation column. The Ag-FAU and Ag-BEA zeolite membranes, where preferentially adsorbed olefins fill the pores, inhibiting paraffin permeance, were used in the separation processes. To evaluate separation performance, two indicators, i.e., energy consumption and membrane area were calculated via simulation. Furthermore, the operating condition in Case 2 was modified by utilizing the characteristics of the Ag-FAU membrane in Case 3, where a mixture of ethane and propane was obtained in the retentate stream. These results were compared with the distillation process as a benchmark, and the advantages of these hybrid separation processes were discussed.