A process for removing a foulant from a gas stream is disclosed. The gas stream, containing a foulant, is cooled across a first heat exchanger and a second heat exchanger, producing a solid foulant entrained in cryogenic liquid as a foulant slurry, and a foulant-depleted gas stream. The foulant-depleted gas stream is passed through a cryogenic turbine and a first separation vessel, producing a light gas stream and further solid foulant. The solid foulants are recovered by a combination of pressurization, melting, and distillation to produce a liquid foulant product. Heat is recovered from the various streams in the various heat exchangers and the melter.

A method for separating a gas mixture comprising carbon monoxide, nitrogen and hydrogen involves sending a hydrogen-depleted fluid to a denitrification column (K2) having a top condenser (C1) and a bottom reboiler (R2) in order to produce a nitrogen-enriched gas at the top of the column and a nitrogen-depleted liquid at the bottom of the column, cooling the condenser of the denitrification column by means of a nitrogen cycle using a nitrogen compressor (V1, V2, V3), vaporising, in the heat exchanger of the condenser, the liquid nitrogen (53) from the nitrogen cycle, and returning the nitrogen (55) vaporised in the heat exchanger to the nitrogen compressor.

A process for separating a mixture of hydrogen, methane and carbon monoxide by cryogenic distillation. The mixture is cooled in a first heat exchanger and is partially condensed in at least one second heat exchanger which is a bottom reboiler of a first or second column of the column system and at least one portion of the liquid produced by the partial condensation is sent to an intermediate level of the first column.

The present invention is directed to a method and system of separating carbon monoxide from syngas mixtures with low methane content by cryogenic means where a partial condensation cycle is generally employed, and more specifically towards providing a methane slip stream to the feed in order to reduce the potential for any carbon dioxide entering the cold box to freeze, thereby preventing plugging of the cold box heat exchanger.

The invention relates to a method for separating a synthesis gas comprising hydrogen and carbon monoxide by cryogenic distillation, according to which the synthesis gas (1, 5) is cleaned and cooled to a cryogenic temperature, the cooled synthesis gas is separated by a first means (15) in order to produce a hydrogen-depleted liquid (33), the hydrogen-depleted liquid is introduced into the upper part of a stripping column (25) and a hydrogen-enriched gas (27) is drawn off at the head of the stripping column, at least partially condensed and sent back to the upper part of the stripping column.

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.

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.

In a method for separating a synthesis gas containing carbon monoxide and hydrogen, a synthesis gas flow from a synthesis gas source is compressed in a compressor and separated into at least three gaseous products. If there is insufficient synthesis gas, at least three separation products are recycled in the compressor in order to separate said products.

The present invention relates to an integrated method and apparatus for providing a synthesis gas to a cryogenic separation unit installed for separating synthesis gas into products selected from carbon monoxide, crude hydrogen, methane-rich fuel and syngas with a particular H.sub.2:CO ratio. More specifically, the invention relates to the purification of synthesis gas routed to a downstream cryogenic separation unit and minimizing temperature disturbances in the separation unit.

A process for purification of a current of hydrogen synthesis gas (100), particularly in the front-end of an ammonia plant, wherein said gas contains hydrogen and minor amounts of carbon monoxide, carbon dioxide, water and impurities, said process including steps of methanation (13) of said current (100), converting residual amounts of carbon monoxide and carbon dioxide to methane and water, dehydration (14) of the gas to remove water, and then a cryogenic purification (15) such as liquid nitrogen wash, to remove methane and Argon; a corresponding plant and method for revamping an ammonia plant are also disclosed.