Membrane processes for the removal of acid gases from natural gas. II. Effects of operating conditions, economic parameters, and membrane properties

Abstract

The optimum process configuration and operating conditions of membrane processes for the removal of CO 2 from crude natural gas have been identified in a previous study [B.D. Bhide and S.A. Stern, J. Membrane Sci. 81 (1993) 209–237]. The present study compares the separation cost for those membrane processes with that for diethanolamine (DEA) gas-absorption processes and also presents the results of further economic assessments of the membrane processes. For the selected base-case operating conditions, membrane processes for the removal of CO 2 from natural gas are more economical than DEA gas-absorption processes over the entire range of CO 2 concentrations considered. The effects of variations in the following factors on the relative economics of membrane and DEA gas absorption processes were also considered: (1) presence of H 2O vapor and H 2S in the natural gas feed, (2) flow rate of feed, (3) pressure of feed, (4) cost of feed, (5) permeability, expected life, effective thickness, and replacement cost of membranes, and (6) selectivity of polymer membranes, α*(CO 2/CH 4). These studies identify the ranges of economical operating conditions for membrane processes for the removal of CO 2 and H 2S from natural gas, and offer guidance for future improvements in membrane properties.