US 12,454,654 B1
System and method for producing renewable natural gas from biogas
Benjamin Bikson, Newton, MA (US); and Marc Straub, Cypress, TX (US)
Assigned to Unconventional Gas Solutions, LLC, Houston, TX (US)
Filed by Unconventional Gas Solutions, LLC, Houston, TX (US)
Filed on Mar. 17, 2025, as Appl. No. 19/081,394.
Application 19/081,394 is a continuation in part of application No. 18/910,255, filed on Oct. 9, 2024, granted, now 12,275,909.
Application 18/910,255 is a continuation of application No. 18/644,398, filed on Apr. 24, 2024, granted, now 12,139,681, issued on Nov. 12, 2024.
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); C10L 3/00 (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)] 64 Claims
OG exemplary drawing
 
1. A method of generating a high-purity hydrocarbon stream from a raw biogas feed stream comprised of methane, carbon dioxide, oxygen, water vapor, nitrogen and hydrogen sulfide available at a substantially atmospheric pressure, said method comprising the steps of:
(i) compressing said raw biogas feed stream mixed with recycled permeate gas streams 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 at least oxygen, hydrogen sulfide, water vapor, and carbon dioxide from the first effluent stream, thereby forming a retentate second effluent stream having a reduced content of carbon dioxide, hydrogen sulfide, oxygen, and water vapor as compared to the first effluent stream and a permeate third effluent stream enriched in oxygen, water vapor, hydrogen sulfide, and carbon dioxide 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 at least carbon dioxide, hydrogen sulfide, water vapor, and oxygen from the retentate second effluent stream, thereby forming a retentate fourth effluent stream having a lower carbon dioxide, hydrogen sulfide, water vapor, and oxygen content as compared to the retentate second effluent stream and a permeate fifth effluent stream enriched in carbon dioxide, hydrogen sulfide, water vapor, and oxygen 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 carbon dioxide, hydrogen sulfide, water vapor, and oxygen from the sixth effluent stream, thereby forming a retentate eighth effluent stream having a lower carbon dioxide, hydrogen sulfide, water vapor and oxygen 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 enriched in carbon dioxide, hydrogen sulfide, water vapor and oxygen as compared to the sixth 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 carbon dioxide, hydrogen sulfide, water vapor, and oxygen from the retentate eighth effluent stream, thereby forming a retentate tenth effluent stream having a lower carbon dioxide, hydrogen sulfide, water vapor and oxygen content as compared to the retentate eighth effluent stream and a permeate ninth effluent stream with increased carbon dioxide content as compared to the retentate eighth effluent stream;
(vii) passing said permeate ninth effluent stream to a front end of the second compressor, wherein the permeate ninth effluent stream defines the second recycled permeate gas stream that is mixed with said permeate third effluent stream in step (iv);
(viii) passing said retentate tenth effluent stream to a front end of the first compressor, wherein the retentate tenth effluent stream defines the recycled retentate gas stream that is mixed with said raw biogas feed stream in step (i);
(ix) passing the retentate fourth effluent stream to a fifth membrane separation unit, wherein the fifth membrane separation unit removes a portion of carbon dioxide, hydrogen sulfide, water vapor, and oxygen from the retentate fourth effluent stream, thereby forming a retentate twelfth effluent stream having a lower carbon dioxide, hydrogen sulfide, oxygen and water vapor content as compared to the raw biogas feed stream with increased carbon dioxide content as compared to the retentate fourth effluent stream and a permeate eleventh effluent stream;
(x) passing said permeate fifth effluent stream and said permeate eleventh effluent stream to a front end of the first compressor, wherein the combined permeate fifth effluent stream and permeate eleventh effluent stream define the recycled permeate gas streams that are mixed with said raw biogas feed stream in step (i);
(xi) collecting the retentate twelfth effluent stream generated by the fifth membrane separation unit as a high-purity hydrocarbon product, wherein the retentate twelfth effluent stream has an increased methane content and reduced hydrogen sulfide, oxygen, and carbon dioxide content as compared to the raw biogas feed stream; and
(xii) wherein a deoxygenation unit is disposed between the second and the fifth membrane separation units to remove oxygen from the retentate fourth effluent stream.