Separation of carbon monoxide from gaseous mixtures containing carbon

Abstract

The separation energy requirement of a conventional cryogenic process for separating carbon monoxide ('CO') from a gaseous feed containing primarily CO and hydrogen is reduced by an improvement to the process. In the process, CO is scrubbed from a vapor portion of the feed by a liquid methane wash and dissolved hydrogen is stripped from the resultant CO-loaded liquid methane stream. The hydrogen-stripped CO-loaded liquid methane stream is sub-cooled and split into at least first and second substreams. The first substream is expanded and introduced into a CO/methane fractionation column as a liquid feed. The second substream is partially vaporized and introduced into said fractionating column as a two-phase feed. The fractionating column separates the hydrogen-stripped CO-loaded liquid methane feeds to provide CO-rich vapor overheads and methane-rich bottoms liquid. A 'high pressure' CO recycle heat pump stream provides reboil to the fractionation column. The improvement consists of providing part of the heat duty required to partially vaporize the second substream by heat exchange of the second substream against an 'intermediate pressure' CO recycle heat pump stream of a pressure intermediate that of the CO-rich vapor overheads and the high pressure CO recycle heat pump stream.