Patent ID: 7617701

Claim:
A process for producing a mixture ( 73 ) containing at least 10% carbon monoxide by cryogenic separation of a feed gas ( 1 ) containing at least carbon monoxide, hydrogen and methane as principal components in a separation unit in a system of columns including a methane wash column ( 7 ), comprising the steps of a) treating the feed gas to form a first gas stream enriched in hydrogen; b) scrubbing the feed gas or a gas derived from the feed gas with a liquid methane stream ( 9 ) in the methane wash column; c) withdrawing a second gaseous stream enriched in hydrogen from the methane wash column; d) separating a first carbon monoxide enriched stream ( 13 ) from the bottom of the methane wash column to produce a second carbon monoxide enriched stream; e) separating the second carbon monoxide enriched stream to form a third carbon monoxide rich stream and a liquid methane stream ( 27 ); f) sending at least part of the liquid methane stream to the methane wash column; and g) mixing at least part of the third carbon monoxide rich stream with the first gas stream enriched in hydrogen to form the mixture containing at least 10% carbon monoxide as a product stream.