Abstract: A process is disclosed for the purification of a gaseous mixture, for example, consisting essentially of hydrogen and containing impurities, e.g., carbon monoxide, methane and argon. The gaseous mixture is scrubbed with liquid nitrogen in a scrubbing column having two sections. In order to be able to process the residual gases formed during the scrubbing step, containing especially CO, argon and CH.sub.4, in a simple way and without great investment costs, liquid nitrogen is introduced in a quantity sufficient for an almost complete scrubbing out of the carbon monoxide, and a partial amount of the scrubbing liquid, enriched with carbon monoxide, is withdrawn between the upper and lower sections. The partial amount withdrawn is dimensioned so that the residual quantity of scrubbing agent delivered to the lower section of the scrubbing column is enough to scrub out the methane from the gaseous mixture, but yet also leaves a major portion of the carbon monoxide in the gaseous mixture.

Abstract: For separating a higher boiling component from a liquefied gas, e.g., CO, rectification is used wherein a partial stream of the liquefied gas is vaporized, superheated, and then fed into the lower portion of a rectification column. The remainder of the liquefied gas in the liquid phase is fed into the upper portion of the rectification column. The rectification results in the higher boiling component being concentrated in the bottoms, and the overhead gas product being purified thereby. Additional purification is possible by liquefying and refluxing part of the overhead gas product, and in this case, it is possible to superheat the entire liquefied gas so as to obtain ultra high purity product.

Abstract: In a low temperature process for the fractionation of ammonia synthesis waste gas (N.sub.2, H.sub.2, Ar, CH.sub.4) comprising two successive separating stages and a nitrogen refrigeration cycle for supplying reboiler heat to each of the stages and also liquid nitrogen, wherein nitrogen is compressed in a compressor to a final pressure, cooled, expanded, and partially liquefied, gaseous and revaporized liquid nitrogen being recompressed, the improvement comprising compressing the nitrogen to a medium pressure, e.g., 6-20 bar, withdrawing a portion of resultant medium-pressure nitrogen from the compressor, compressing remaining medium-pressure nitrogen to the final pressure, e.g.