US 12,275,909 B1
System and method for producing renewable natural gas from biogas
Benjamin Bikson, Newton, MA (US)
Assigned to Unconventional Gas Solutions, LLC, Houston, TX (US)
Filed by Unconventional Gas Solutions, LLC, Houston, TX (US)
Filed on Oct. 9, 2024, as Appl. No. 18/910,255.
Application 18/910,255 is a continuation of application No. 18/644,398, filed on Apr. 24, 2024, granted, now 12,139,681.
This patent is subject to a terminal disclaimer.
Int. Cl. C10L 3/10 (2006.01); B01D 53/00 (2006.01); B01D 53/04 (2006.01); B01D 53/22 (2006.01); B01D 53/84 (2006.01)
CPC C10L 3/103 (2013.01) [C10L 3/104 (2013.01); C10L 3/105 (2013.01); C10L 3/106 (2013.01); C10L 2200/0469 (2013.01); C10L 2290/08 (2013.01); C10L 2290/30 (2013.01); C10L 2290/542 (2013.01); C10L 2290/548 (2013.01)] 76 Claims
OG exemplary drawing
 
1. A method of generating a high-purity hydrocarbon stream from a raw biogas feed gas stream at a substantially atmospheric pressure, said method comprising the steps of:
(i) compressing said raw biogas feed gas stream mixed with a first recycled permeate gas stream and a recycled retentate gas stream in a first compressor, thereby forming a first effluent stream;
(ii) passing the first effluent stream into a first membrane separation unit, wherein the first membrane separation unit removes a portion of oxygen and hydrogen sulfide from the first effluent stream, thereby forming a retentate second effluent stream having a reduced content of oxygen and hydrogen sulfide as compared to the first effluent stream and a permeate third effluent stream enriched in oxygen and hydrogen sulfide as compared to the first effluent stream;
(iii) passing the retentate second effluent stream to a second membrane separation unit, wherein the second membrane separation unit removes a portion of oxygen and hydrogen sulfide from the retentate second effluent stream, thereby forming a retentate fourth effluent stream having a lower oxygen and hydrogen sulfide content as compared to the retentate second effluent stream and a permeate fifth effluent stream enriched in oxygen and hydrogen sulfide content as compared to the retentate second effluent stream;
(iv) compressing said permeate third effluent stream mixed with a second recycled permeate gas stream in a second compressor, thus forming a sixth effluent stream;
(v) passing the sixth effluent stream to a third membrane separation unit, wherein the third membrane separation unit removes a portion of oxygen and hydrogen sulfide from the sixth effluent stream, thereby forming a retentate eighth effluent stream, having a lower oxygen and hydrogen sulfide content as compared to the sixth effluent stream and a higher oxygen content as compared to the raw biogas feed stream, and a permeate seventh effluent stream;
(vi) passing the retentate eighth effluent stream to a fourth membrane separation unit, wherein the fourth membrane separation unit removes a portion of oxygen and hydrogen sulfide from the retentate eighth effluent stream, thereby forming a retentate tenth effluent stream having a lower oxygen and hydrogen sulfide content as compared to the retentate eighth effluent stream and a permeate ninth effluent stream with increased oxygen and hydrogen sulfide content as compared to the retentate eighth effluent stream; and
(vii) collecting the retentate fourth effluent stream generated by the second membrane separation unit as a high-purity hydrocarbon product, wherein the retentate fourth effluent stream has an increased methane content and reduced hydrogen sulfide and oxygen content as compared to the raw biogas feed gas stream;
wherein the retentate fourth effluent stream has a methane content of at least 95% mole, an oxygen content of at most 0.1% mole and a hydrogen sulfide content of at most 0.075% mole.