Removal of Acid Gas from Natural Gas: A Comparison of Conventional and Selective Membrane Processes

Natural gas often contains impurities such as nitrogen, hydrogen sulphide, carbon dioxide and water vapor. These impurities have to be removed prior to gas processing. Sometimes it is purified at the gas field. The complicated distillation and cryogenic processes are now replaced by novel membrane separation systems which offer lower costs, less maintenance and more flexibility. Membranes are widely used in a variety of industrial gas separation. They have been used since 1970 after the adaption of the first flat sheet of cellulose acetate. They were proved to be technologically and economically preferred against most of the conventional gas separation processes. This paper reviews the use of membranes in gas separation with emphasis on the removal of acid gas from natural gas. Technological and economical comparison of the feasible gas membrane systems with conventional gas separation processes are presented.