The optimum process configuration and operating conditions of membrane processes for the removal of CO2 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 bask-case operating conditions, membrane processes for the removal of CO2 from natural gas are more economical than DEA gas-absorption processes over the entire range of CO2 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 H2O vapor and H2S 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, alpha*(CO2/CH4). These studies identify the ranges of economical operating conditions for membrane processes for the removal of CO2 and H2S from natural gas, and offer guidance for future improvements in membrane properties.
