Patent ID: 8435326

Claim:
A process for removing CO 2 from a syngas feedstream containing from about 5 to 50 volume percent CO 2 , which process comprises: i) conducting said syngas stream, at a pressure of about 20 psig to about 1000 psig, to a first CO 2 separation zone wherein a first permeation membrane is used having a separation factor of CO 2 to H 2 of at least about 5 to 1, to separate a first retentate stream from a first permeate stream, wherein said first permeate stream is comprised predominantly of CO 2 with smaller amounts of H 2 , CO and other contaminants of the syngas, and wherein said first retentate stream is comprised primarily of the syngas stream but containing a substantially lower level of CO 2 ; ii) collecting said first retentate stream; iii) conducting said first permeate stream to a compression zone wherein its pressure is elevated to an effective pressure for the next downstream CO 2 separation zone; iv) conducting said elevated pressure permeate stream from said compression zone to a second CO 2 separation zone wherein a second permeation membrane is used to result in a second retentate stream and a second permeate stream, wherein at least a portion of said second retentate stream is recycled to said first CO 2 separation zone and wherein said second permeate, which is comprised substantially of CO 2 is collected or vented to the atmosphere.