Cryogenic Separation of Synthesis Gas

Abstract

A process and apparatus for separating a feed containing hydrogen, carbon monoxide, methane, and optionally nitrogen to form a product gas having a desired H 2 :CO molar ratio and optionally a hydrogen product gas and a carbon monoxide product gas. The feed is partially condensed to form a hydrogen-enriched vapor fraction and a carbon monoxide-enriched liquid fraction. The hydrogen-enriched vapor fraction and carbon monoxide-enriched liquid fraction are combined in a regulated manner to form an admixture, which is cryogenically separated to form the product mixture having the desired H 2 :CO molar ratio.

We claim: 
     
         1 - 12 . (canceled) 
     
     
         13 . An apparatus for separating a feed comprising hydrogen, carbon monoxide, methane, and optionally nitrogen, comprising:
 a first heat exchanger for partially condensing the feed to form a partially condensed feed;   a phase separator for separating the partially condensed feed into a hydrogen-enriched vapor fraction and a carbon monoxide-enriched liquid fraction;   a means for feeding the partially condensed feed to the phase separator from the first heat exchanger, the means for feeding the partially condensed feed configured so that no portion of the partially condensed feed passes through an expander when feeding the partially condensed feed to the phase separator from the first heat exchanger;   a means for combining a portion or all of the carbon monoxide-enriched liquid fraction with a regulated portion of the hydrogen-enriched vapor fraction to form a two-phase admixture, the means for combining operatively disposed to receive the hydrogen-enriched vapor fraction from the phase separator without any other phase separator operatively disposed between the means for combining and the phase separator;   a means for feeding at least one of the portion or all of the carbon monoxide-enriched liquid fraction and at least a portion of the two-phase admixture to the first heat exchanger;   a first fractionator for cryogenically separating the at least a portion of the two-phase admixture to form a first product gas and a hydrogen-depleted liquid fraction; and   a means for feeding the at least a portion of the two-phase admixture to the first fractionator.   
     
     
         14 . The apparatus of  claim 13  further comprising:
 a methane wash column for scrubbing a second portion of the hydrogen-enriched vapor fraction, or a vapor portion from phase separation thereof, with a liquid methane wash stream to provide a hydrogen product gas and a carbon monoxide-loaded methane liquid; and 
 a means for feeding the second portion of the hydrogen-enriched vapor fraction, or a vapor portion from phase separation thereof, to the methane wash column from the phase separator. 
 
     
     
         15 . The apparatus of  claim 14  further comprising:
 a second fractionator for stripping hydrogen from a second portion of the carbon monoxide-enriched liquid fraction and at least a portion of the hydrogen-depleted liquid fraction to form a second hydrogen-enriched vapor fraction and a hydrogen-freed liquid fraction; 
 a means for feeding the second portion of the carbon monoxide-enriched liquid fraction to the second fractionator from the phase separator; 
 a means for feeding the at least a portion of the hydrogen-depleted liquid fraction to the second fractionator from the first fractionator; 
 a carbon monoxide/methane fractionator for separating an intermediate feed ( 36 ,  36 ′) to form a carbon monoxide product gas and a methane-enriched liquid fraction; and 
 a means for feeding at least a portion of the hydrogen-freed liquid fraction to the carbon monoxide/methane fractionator from the second fractionator. 
 
     
     
         16 . The apparatus of  claim 14  further comprising:
 a second fractionator for stripping hydrogen from a second portion of the carbon monoxide-enriched liquid fraction and at least a portion of the hydrogen-depleted liquid fraction to form a second hydrogen-enriched vapor fraction and a hydrogen-freed liquid fraction; 
 a means for feeding the second portion of the carbon monoxide-enriched liquid fraction to the second fractionator from the phase separator; 
 a means for feeding the at least a portion of the hydrogen-depleted liquid fraction to the second fractionator from the first fractionator; 
 a third fractionator for separating at least a portion of the hydrogen-freed liquid fraction to form a nitrogen-enriched vapor fraction and a nitrogen depleted liquid fraction; 
 a means for feeding the hydrogen-freed liquid fraction to the third fractionator from the second fractionator; 
 a carbon monoxide/methane fractionator for separating at least a portion of the nitrogen-depleted liquid fraction to form a carbon monoxide product gas and a methane-enriched liquid fraction; and 
 a means for feeding the at least a portion of the nitrogen-depleted liquid fraction to the carbon monoxide/methane fractionator from the third fractionator. 
 
     
     
         17 . The apparatus of  claim 15  further comprising:
 a means for feeding a portion of the methane-enriched liquid fraction to the methane wash column from the carbon monoxide/methane fractionator. 
 
     
     
         18 . An apparatus for separating a feed comprising hydrogen, carbon monoxide, methane, and optionally nitrogen, comprising:
 a first heat exchanger for partially condensing the feed to form a partially condensed feed;   a phase separator for separating the partially condensed feed into a hydrogen-enriched vapor fraction and a carbon monoxide-enriched liquid fraction;   a means for feeding the partially condensed feed to the phase separator from the first heat exchanger, the phase separator operatively disposed to receive the partially condensed feed from the first heat exchanger via the means for feeding the partially condensed feed to the phase separator without any other phase separator operatively disposed between the first heat exchanger and the phase separator;   a means for combining a portion or all of the carbon monoxide-enriched liquid fraction with a regulated portion of the hydrogen-enriched vapor fraction to form a two-phase admixture, the means for combining operatively disposed to receive the hydrogen-enriched vapor fraction from the phase separator without any other phase separator operatively disposed between the means for combining and the phase separator;   a means for feeding at least one of the portion or all of the carbon monoxide-enriched liquid fraction and at least a portion of the two-phase admixture to the first heat exchanger;   a first fractionator for cryogenically separating the at least a portion of the two-phase admixture to form a first product gas and a hydrogen-depleted liquid fraction; and   a means for feeding the at least a portion of the two-phase admixture to the first fractionator.   
     
     
         19 . The apparatus of  claim 18  further comprising:
 a methane wash column for scrubbing a second portion of the hydrogen-enriched vapor fraction, or a vapor portion from phase separation thereof, with a liquid methane wash stream to provide a hydrogen product gas and a carbon monoxide-loaded methane liquid; and 
 a means for feeding the second portion of the hydrogen-enriched vapor fraction, or a vapor portion from phase separation thereof, to the methane wash column from the phase separator.