A process and an apparatus are disclosed for a compact processing assembly to improve the recovery of C.sub.2 (or C.sub.3) and heavier hydrocarbon components from a hydrocarbon gas stream. The preferred method of separating a hydrocarbon gas stream generally includes producing at least a substantially condensed first stream and a cooled second stream, expanding both streams to lower pressure, and supplying the streams to a fractionation tower. In the process and apparatus disclosed, the tower overhead vapor is directed to an absorbing means and a heat and mass transfer means inside a processing assembly. A portion of the outlet vapor from the processing assembly is compressed to higher pressure, cooled and substantially condensed in a heat exchange means inside the processing assembly, then expanded to lower pressure and supplied to the heat and mass transfer means to provide cooling. Condensed liquid from the absorbing means is fed to the tower.

A combined plant for cryogenic separation and liquefaction of methane and carbon dioxide in a biogas stream, including a mixing means, a compressor, a first exchanger, a distillation column, a second exchanger, a separating means, an expanding means, and a separator vessel. Wherein, the mixing means is configured such that the recycle gas is the overhead vapour stream, and the first exchanger and the expanding means are combined.

A method and system for producing liquid air wherein liquid refrigerant is cycled between two core tanks maintained at a temperature sufficient to liquify compressed air passed through condensing tubing in the interior of the core tanks. Liquid refrigerant is cycled by alternating high pressure gas from a high pressure tank to one of the core tanks, which forces liquid refrigerant from this tank through an expansion device to expand a portion of the liquid refrigerant to absorb heat in the other core tank, the resulting refrigerant gas being driven into a low pressure tank. A compression device transfers the refrigerant gas from the low pressure tank to the high pressure tank and maintains the pressure in the high pressure tank. Connections between the low and high pressure tanks and the core tanks are reversed with each cycle.

This process comprises quenching and washing with water a gas stream derived from pyrolysis, and separating an aqueous phase from a washed gas stream; compressing, then cooling a washed gas stream; washing the compressed gas stream under pressure; passing the washed gas stream through at least one acid removal unit; drying the acid-depleted gas stream; passing the dry gas stream through at least one impurity removal unit; and feeding the purified gas stream into a cryogenic absorption unit and supplying the cryogenic absorption unit with a hydrocarbon cryogenic solvent to obtain a light gas residue, and a fraction of C.sub.2.sup.+ hydrocarbons.

A system for separating carbon dioxide from a carrier gas includes a CO.sub.2 enrichment subsystem that receives a carrier gas stream and produces an enriched carbon dioxide fluid stream. The system also includes a CO.sub.2 polishing subsystem in fluid communication with the CO.sub.2 enrichment subsystem that produces a carbon dioxide rich fluid stream. In a corresponding method, a carrier gas is received in a CO.sub.2 enrichment subsystem and an enriched carbon dioxide fluid stream is produced. The enriched carbon dioxide fluid stream is directed to a CO.sub.2 polishing subsystem wherein a stream further enriched in carbon dioxide is produced.

A combined plant for cryogenic separation and liquefaction of methane and carbon dioxide in a biogas stream, including a mixing means, a compressor, a first exchanger, a distillation column, a second exchanger, a separating means, an expanding means, and a separator vessel. Wherein the mixing means is configured such that the recycle gas is the overhead vapour stream, and the first exchanger and the expanding means are combined.

A combined plant for cryogenic separation and liquefaction of methane and carbon dioxide in a biogas stream, including a mixing means, a compressor, a first exchanger, a distillation column, a second exchanger, a separating means, an expanding means, and a separator vessel. Wherein, the mixing means is configured such that the recycle gas is the overhead vapour stream, and the first exchanger and the expanding means are combined.

A combined plant for cryogenic separation and liquefaction of methane and carbon dioxide in a biogas stream, including a mixing means, a compressor, a first exchanger, a distillation column, a second exchanger, a separating means, an expanding means, and a separator vessel. Wherein, the mixing means is configured such that the recycle gas is the overhead vapour stream, and the first exchanger and the expanding means are combined.

A combined plant for cryogenic separation and liquefaction of methane and carbon dioxide in a biogas stream, including a mixing means, a compressor, a first exchanger, a distillation column, a second exchanger, a separating means, an expanding means, and a separator vessel. Wherein, the mixing means is configured such that the recycle gas is the overhead vapour stream, and the first exchanger and the expanding means are combined.

A combined plant for cryogenic separation and liquefaction of methane and carbon dioxide in a biogas stream, including a mixing means, a compressor, a first exchanger, a distillation column, a second exchanger, a separating means, an expanding means, and a separator vessel. Wherein, the mixing means is configured such that the recycle gas is the overhead vapour stream, and the first exchanger and the expanding means are combined.