The disclosure includes a process for treating a natural gas containing carbon dioxide wherein the natural gas is separated by a cryogenic process in order to provide, on the one hand, a stream of liquid carbon dioxide, containing hydrocarbons, and, on the other hand, purified natural gas; at least one part of the natural gas is cooled in a first heat exchanger and then in a second heat exchanger before the cryogenic process and/or before a reflux to the cryogenic process; at least one part of the stream of liquid carbon dioxide is recovered in order to provide a stream of recycled carbon dioxide; the stream of recycled carbon dioxide is divided into a first portion and a second portion; the first portion is expanded and then heated in the first heat exchanger, in order to provide a first stream of heated carbon dioxide; the second portion is cooled, then at least one part of the second portion is expanded and then heated in the second heat exchanger, in order to provide a second stream of heated carbon dioxide; at least some of the hydrocarbons contained in the first stream of heated carbon dioxide and in the second stream of heated carbon dioxide are recovered by liquid/gas separation.

The invention relates to a method for the low-temperature separation of a gas containing CO.sub.2 in order to produce a CO.sub.2-rich fluid, in which method a gas containing CO.sub.2 and at least one component lighter than CO.sub.2 is compressed in a compressor comprising at least two stages, the gas being cooled downstream of at least one of the stages in a cooler and by exchanging heat with air and then being cooled in a first heat exchanger, the gas cooled in the first heat exchanger is separated at low temperature by partial condensation and/or distillation in order to produce a fluid rich in CO.sub.2 and depleted in the component lighter than CO.sub.2 and a gas depleted in CO.sub.2 and enriched in the component lighter than CO.sub.2. The gas depleted in CO.sub.2 is first heated in the first heat exchanger and then in the cooler before being expanded in a turbine.

The invention relates to a method for the low-temperature separation of a feed gas containing CO.sub.2, at least one component lighter than CO.sub.2 and at least one component heavier than CO.sub.2, wherein, in order to produce a CO.sub.2-rich fluid, the feed gas is compressed, the compressed gas being cooled in a first heat exchanger, the gas cooled in the first heat exchanger is separated at low temperature in a first distillation column to produce a liquid that is enriched in CO.sub.2 and depleted in the at least one component lighter than CO.sub.2 and a gas that is depleted in CO.sub.2 and enriched in the at least one component lighter than CO.sub.2, the gas depleted in CO.sub.2 is heated in the first heat exchanger, a first part of the liquid enriched in CO.sub.2 is expanded and sent to a second distillation column in liquid form, a second part of the liquid enriched in CO.sub.2 is vaporized in the first heat exchanger then sent in gas form into the tank of the second distillation column, a liquid depleted in CO.sub.2 and enriched in the at least one heavier component is withdrawn from the second column, and a gas enriched in CO.sub.2 and depleted in the at least one heavier component is withdrawn at the top of the second column as product.

In a method for liquefying a gas rich in carbon dioxide, the gas is compressed to a first pressure greater than its critical pressure in a compressor to form a compressed gas, the compressed gas is cooled through heat exchange with a refrigerant to a variable temperature to form a cooled compressed gas with a density between 370 and 900 kg/m.sup.3, the cooled compressed gas is cooled at supercritical pressure in a first heat exchanger to a temperature below the critical temperature, the gas cooled below the critical temperature is expanded to a second pressure between 45 and 60 bara to form a diphasic fluid which is separated in a phase separator to form a liquid and a gas, and a liquid portion originating from the phase separator provides cold to the first heat exchanger.

A carbon-capture cooling system comprises: a refrigeration system comprising an evaporator and arranged to supply a liquid refrigerant to the evaporator, an air compressor arranged to compress air including gaseous carbon dioxide; and a compressed air storage vessel arranged to receive the compressed air from the air compressor and comprising an air outlet. The evaporator is arranged to extract heat from the compressed air in the compressed air storage vessel by evaporation of the liquid refrigerant, thereby to cool the compressed air to liquidise the gaseous carbon dioxide for capture. The air outlet is arranged to release the cooled compressed air from the compressed air storage vessel for cooling an external environment of the carbon-capture cooling system.