To produce a high-purity carbon monoxide (CO) stream, and a moderate-purity hydrogen (H2) stream, plus a ratio adjusted synthesis gas stream for use as a chemical feedstock. The synthesis gas stream is typically the product of partial oxidation reaction (POX).
Feed gas for CO recovery is pretreated to remove carbon dioxide and water, which will freeze at the cryogenic temperatures encountered in the process. The feed gas is cooled against products in the warm exchanger, and is then further cooled providing heat for reboiling the CO/CH4 splitter. Condensed CO and methane (CH4) are removed from uncondensed vapor in the warm separator. Vapor from the warm separator is cooled in the cold exchanger where most of the remaining CO is condensed and separated in the cold separator. The liquid from this vessel is a high-purity CO stream used as reflux for the CO/CH4 splitter.
Liquid from the warm separator is reduced in pressure and flashed in the flash separator to remove dissolved H2. The vapor from this separator is rewarmed, compressed and recycled to the feed to recover CO. The liquid from the flash separator is sent to the CO/CH4 splitter. The CO overhead from this tower is warmed and recovered as product. The bottoms, containing CO and CH4, is also warmed and is available as byproduct fuel gas. The H2 from the cold separator is warmed in the cold exchanger, expanded to provide refrigeration for the cycle, warmed in the cold and warm exchangers and leaves the process at 97–98% purity.
Variations on this basic cycle are possible depending on feed gas pressure and gas composition, and desired product purity. The H2 product is delivered at high pressure, but the CO exits the process at low pressure. Therefore, a CO-product compressor is usually required to deliver the product to a downstream process.
Licensor: Air Products and Chemicals, Inc.