Method and apparatus for adjustably treating a sour gas

A feed gas comprising CO.sub.2, H.sub.2S and H.sub.2 is treated to produce an H.sub.2-enriched product and an H.sub.2S-lean, CO.sub.2 product. The feed gas is separated to provide the H.sub.2-enriched product and a stream of sour gas. The stream of sour gas is divided into two parts, one of which is processed in an H.sub.2S removal system to form one or more streams of sweetened gas, and the other of which bypasses the H.sub.2S removal system, the stream(s) of sweetened gas and the sour gas bypassing the H.sub.2S removal system then being recombined to form the H.sub.2S-lean, CO.sub.2 product gas. The division of the sour gas between being sent to and bypassing the H.sub.2S removal system is adjusted responsive to changes in the H.sub.2S content of the sour gas, so as to dampen or cancel the effects of said changes on the H.sub.2S content of the H.sub.2S-lean, CO.sub.2 product gas.