Abstract: In the method of separating a methane-containing light gas from a feed gas containing heavier hydrocarbons by (i) cooling the feed gas at superatmospheric pressure to partially condense it, (ii) separating a first condensate from the uncondensed gas, (iii) rectifying the uncondensed gas to produce the light gas and a second condensate (preferably by further cooling the uncondensed gas in a refluxing heat exchanger), and (iv) stripping at least one of the condensates in a distillation column to obtain an overhead stream and a liquid product stream, the power requirement is reduced by providing at least part of the cooling for step (i) by expanding at least a part of the feed gas in a turbo-expander which provides energy for compression of product gas comprising said light gas and/or uncondensed gas from the overhead from the distillation column.

Abstract: Helium contaminated with minor amounts of air, water vapor and carbon dioxide and from an envelope (10) is compressed in a compressor (12) and thereafter cooled in cooler (18) and fed via water separator (20) to a first of two substantially helium-permeable, oxygen/nitrogen-impermeable membranes (28,34), the permeate from which is substantially pure helium. The impermeate still containing helium is fed to the second membrane (34), the permeate from which is recycled to the first membrane while the impermeate is rejected with little loss of helium. The method is useful in purifying helium in an airship or balloon.

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.

Abstract: A process and apparatus for the production of nitrogen from air by the cryogenic fractionation of the air at superatmospheric pressure and which permits the production of variable quantities of nitrogen from a constant supply of air at superatmospheric pressure by periodically distilling less than all of the air which is supplied at superatmospheric pressure and work expanding a stream of air at superatmospheric pressure provided from the balance of said supply whereby to produce additional refrigeration for the process, and recovering condensed nitrogen vapor thereby formed in excess of that required for reflux.