In a hydrogen liquefaction process, a hydrogen-rich gas originating from an apparatus for separation by distillation and/or stripping and/or partial condensation, the gas exiting from the separation apparatus at a temperature of at most 103K containing at least 99.9 mol % of hydrogen and at a pressure between 20 and 30 bar, is sent to a hydrogen liquefier, without having heated the hydrogen-rich gas to a temperature above 0 C.

In a process for the combined production of a) a hydrogen-enriched gas and a carbon monoxide-enriched gas and/or b) a mixture of hydrogen and carbon monoxide by cryogenic distillation and scrubbing, a still liquor is extracted from a scrubbing column and sent to a stripping column, a still liquor is extracted from the stripping column and sent to a separating column for carbon monoxide and methane and a cooling fluid is used at a pressure greater than that of the head of the separating column for cooling at least one fluid extracted at an intermediate level from the scrubbing column.

In a process of the separation of a mixture of carbon monoxide, hydrogen and methane, the mixture is sent to a scrubbing column, a bottom liquid withdrawn at the bottom of the scrubbing column is depleted in hydrogen with respect to the mixture and is sent to a stripping column, a bottom liquid from the stripping column is sent to a separation column and a liquid enriched in methane withdrawn from the bottom of the separation column is vaporized in order to form a final product.

In a process for the cryogenic separation of a feed mixture of at least carbon monoxide, hydrogen and methane, the feed mixture is separated in a methane wash column fed by a liquid methane stream at the top of the methane wash column to produce a gas enriched in hydrogen, a liquid stream from the bottom of the methane wash column is treated to produce a mixture of carbon monoxide and methane, the mixture of carbon monoxide and methane is separated in a separation column to produce a gas enriched in carbon monoxide and a liquid methane flow at least part of which forms a purge stream, the purge stream being varied to take account of load variations.

In a process for separating a mixture containing carbon monoxide, hydrogen and carbon dioxide, the mixture cooled in a heat exchanger is contacted by a stream of liquid methanol at a temperature below ?40? C. to produce carbon dioxide enriched methanol and a carbon dioxide depleted gas relative to the cooled mixture, the carbon dioxide depleted gas is cooled in the heat exchanger and is sent to a separation unit to produce a carbon monoxide enriched stream and a hydrogen enriched stream and the streams enriched in carbon monoxide and hydrogen are heated in the heat exchanger by exchanging heat with the mixture.

Process for the combined production of a mixture of hydrogen and nitrogen, and of carbon monoxide by cryogenic distillation and cryogenic scrubbing, wherein a methane-rich liquid is introduced at a first intermediate level of a scrubbing column as first scrubbing liquid and at least one nitrogen-rich liquid is introduced at a level higher than the first level of the scrubbing column as second scrubbing liquid and a mixture of hydrogen and nitrogen is drawn off as overhead gas from the scrubbing column.

In a method for producing a gaseous mixture of CO and H.sub.2, a first gas comprising at least 50% CO is compressed in a first compressor to form a first compressed gas cooled to a first temperature and mixes with a second gas comprising at least 50% hydrogen in order to form the gaseous mixture, at least one of the first and second gases originating from a cryogenic distillation separation unit in which a feed gas containing H.sub.2 and CO cools in a first heat exchanger and is separated in at least one distillation column and at least one part of the second gas heats in the separation unit to a third temperature lower than the first temperature and is then sent to mix with the first gas.

A process and apparatus for separating a feed containing hydrogen, carbon monoxide, methane, and optionally nitrogen to form a product gas having a desired H.sub.2:CO molar ratio and optionally a hydrogen product gas and a carbon monoxide product gas. The feed is partially condensed to form a hydrogen-enriched vapor fraction and a carbon monoxide-enriched liquid fraction. The hydrogen-enriched vapor fraction and carbon monoxide-enriched liquid fraction are combined in a regulated manner to form an admixture, which is cryogenically separated to form the product mixture having the desired H.sub.2:CO molar ratio.

The present invention relates to a cold box cycle which allows for independent control of the heat supplied for reboilers associated with the separation columns. More specifically, the invention relates to the tight control of the hydrogen removal separation, thus avoiding the possibility of excess reboiling in this separation. Optimal reboiling also results in a lower temperature of the hydrogen depleted liquid from this separation. As this stream is used to provide a portion of the cooling at the cold end of the primary heat exchanger, lower temperatures facilitate cooling of the incoming syngas feed, reducing carbon monoxide (CO) losses into the crude hydrogen stream from the high pressure separator. Lower CO in the crude hydrogen allows for smaller hydrogen purification equipment.

A method for separating a feed gas, containing nitrogen and carbon monoxide as main components, in a distillation column: the feed gas is cooled in a heat exchanger; at least a portion of the feed gas, or at least a portion of a gas derived from the feed gas, is sent to a reboiler of the distillation column so as to condense the gas while producing a liquid, and optionally a gas; at least a portion of the liquid is sent to the distillation column; a nitrogen gas-rich flow is extracted from the distillation column; a carbon monoxide-rich flow is extracted from the distillation column, heated in the heat exchanger, and compressed so as to provide a carbon monoxide-rich material at production pressure.