Abstract: An integrated gasification combined cycle (IGCC) system involving CO2 capture is provided comprising a CO2-selective membrane, a pre-compressor, and a sulfur gas removal system to selectively remove H2S and CO2 from shifted syngas, wherein the pre-compressor increases the permeate stream from the CO2-selective membrane from a first pressure to a second pressure prior to entering the sulfur removal system. Also provided herein is a method of maintaining a substantially constant pressure in a sulfur removal system, comprising introducing a feed gas stream to a CO2-selective membrane for separation into a syngas rich stream and a permeate gas stream, wherein the permeate gas stream is at a first pressure; increasing the permeate gas stream from the first pressure to a second pressure; and introducing the permeate gas stream at the second pressure to a sulfur removal system downstream of the pre-compressor.