Separation of carbon dioxide and other acid gas components from hydrocarbon feeds containing admixtures of methane and hydrogen

Claim 1

In a process for the separation of carbon dioxide from a gaseous mixture comprising carbon dioxide and methane, the improvement comprising: (a) forming a feed stream from said gaseous mixture containing from about 6 to about 35 mol percent hydrogen and from about 30 to about 85 mol percent methane; (b) distilling said feed in a low pressure zone while maintaining said zone at a total pressure below about 1073 psia with the upper stage of said zone at a temperature above about -100° F., said low pressure zone being operated such that the sum of the carbon dioxide partial pressure and the methane partial pressure, in psia at all points in the low pressure zone is greater than -1023- T(237.36+1.285T) when T is the temperature in degrees Fahrenheit and when T is within the range from -100° F. to -69.9° F.; (c) separating carbon dioxide as a primary component of a liquid bottom product withdrawn therefrom, while withdrawing a vapor effluent from said low pressure zone; and (d) introducing said vapor effluent into a high pressure zone maintained at a pressure above about 600 psia and a temperature above about -170° F., said high pressure zone being operated such that the total pressure in psia is less than 673+488Y.sub.H.sbsb.2,2 +11,280Y.sub.H.sbsb.2,2.sup.2 where: ##EQU5## and: Z H .sbsb.2 =mol fraction H 2 in feed Z CO =mol fraction CO in feed (when present) Z N .sbsb.2 =mol fraction N 2 in feed (when present) Z CH .sbsb.4 =mol fraction CH 4 in feed L/D=mol liquid reflux/mols vapor distillate but greater than: ##EQU6## where: Z H .sbsb.2 =mol fraction H 2 in feed Z CO =mol fraction CO in feed (when present) Z N .sbsb.2 =mol fraction N 2 in feed (when present) Z CH .sbsb.4 =mol fraction CH 4 in feed L/D=mol liquid reflux/mols vapor distillate. (e) separating a liquid, a part of which is recycled to the low pressure zone, and recovering a hydrocarbon product from said high pressure distillation zone, said low pressure zone being operated at a pressure more than about 50 psia below the pressure in said high pressure zone.