A pilot field study of [CO.sub.2] removal from natural gas by a polymeric membrane system has found that a single-pass membrane process can reduce the [CO.sub.2] concentration from 5 mole % in the feed to less than 2 mole % in the sales gas and [H.sub.2]O from 67 lb/MMscf to less than 7 lb/MMscf. The methane loss through the membrane permeate (acid gas) was approximately 10%, and the total operating cost was $0.14/Mscf. The study was funded by the Gas Research Institute, Chicago, and took place at a 500 Mscfcl plant in Trinity County, Tex. It was implemented cooperatively with Dallas Production Inc., Grace Membrane Systems, and the Institute of Gas Technology, Chicago.
In the past, conventional natural-gas processing has included primarily absorption processes that use either chemical or physical solvents (for example, amines or glycol-based systems) to remove [H.sub.2]S, [CO.sub.2], and [H.sub.2]O.
A recent study performed for GRI on the composition of subquality components of natural gas in the U.S. Lower 48 states indicates that approximately 15% of non-associated gas production contains [CO.sub.2] in concentrations exceeding the typical pipeline specification of 2 mole %.
Although polymeric membrane systems are available for [CO.sub.2] removal, dehydration, and separation of small amounts of [H.sub.2]S, available field-operating data on these systems have been limited. And there are no publicly available multihydrocarbon data on membrane-based [CO.sub.2] separation systems' …