Patent ID: 8357230

Claim:
A process for purifying crude synthesis gas containing metal carbonyls and undesirable substances selected from sulphur components, carbon dioxide (CO 2 ), and/or hydrocyanic acid (HCN), said process comprising: scrubbing said crude synthesis gas in a main scrub with a physically acting scrubbing medium for scrubbing out said undesirable substances, wherein, before being introduced into said main scrub, said crude synthesis gas is subjected to a carbonyl scrub with a partial amount of laden scrubbing medium removed from said main scrub, wherein said partial amount of laden scrubbing medium is chosen so that said metal carbonyls are selectively separated off from said crude synthesis gas in said carbonyl scrub substantially independently of other gas components, and wherein separation of said metal carbonyls from said crude synthesis gas in said carbonyl scrub is carried out in at least two successive scrubbing steps, wherein the amount of scrubbing medium used in each of said two successive scrubbing steps is selected so that different metal carbonyls are separated off substantially selectively in each of said two successive scrubbing steps.