Recovery of carbon dioxide from gas mixture

Abstract

Carbon dioxide is recovered from gas mixtures containing it in a concentration not greater than the equilibrium concentration at the freezing temperature of the mixture, by subjecting the gas mixture to membrane separation and recovering from the membrane separation a permeate having a carbon dioxide concentration between the equilibrium concentration and 98% (by volume), distilling said permeate at subambient temperature above the freezing temperature of the permeate and recovering substantially pure carbon dioxide as a liquid bottoms product of the distillation. Carbon dioxide is recovered from gas mixtures containing it in a high concentration by supplying the gas mixture at superatmospheric pressure and distilling said gas mixture at sub-ambient temperature in a distillation column, recovering substantially pure carbon dioxide as a liquid bottoms product of the distillation, warming the overhead stream from the distillation to a temperature suitable for membrane separation, passing the overhead stream at superatmospheric pressure over a membrane which is selectively permeable for carbon dioxide and thereafter recycling carbon dioxide-rich permeate for recompression and feeding to the distillation column.

Dependencies are inferred from the claim text.