Production of purified synthesis gas h.sub.2 -rich gas, and by-product

Abstract

A raw synthesis gas feed stream, e.g., gaseous mixtures comprising H.sub.2 and CO and containing gaseous impurities including CO.sub.2, H.sub.2 S, COS, and mixtures thereof (acid gas) and CH.sub.4, optionally in admixture with a CO-rich gas stream produced subsequently in the process, is introduced into a water-gas shift reactor to produce H.sub.2 and CO.sub.2. Acid gases are then removed to produce a stream of purified synthesis gas by contacting the process gas stream with a first liquid solvent absorbent such as methanol, N-methyl-pyrrolidone, or dimethyl ether of polyethylene glycol. An H.sub.2 -rich gas stream may be obtained by removing CO from the purified synthesis gas stream. This may be done by physical absorption in a second liquid solvent absorbent comprising an aqueous solution of cuprous ammonium acetate. By regenerating the second liquid solvent, the aforesaid CO-rich stream may be produced. The first liquid solvent absorbent may be desorbed of said acid gas and regenerated for reuse by such techniques as flashing plus reboiling or stripping. Advantageously, the gas used for stripping the first liquid solvent absorbent may be a portion of the synthesis gas feed either before or after removal of said acid-gas, or a portion of said H.sub.2 -rich product gas. The CO.sub.2 -rich gas optionally in admixture with stripping gas which is produced during the regeneration of said first liquid solvent absorbent may be injected into a subterranean oil reservoir to effect secondary or tertiary recovery of oil. Optionally, H.sub.2 S may be in admixture with said CO.sub.2 -rich gas mixture.