A system and method for argon and nitrogen extraction and liquefaction from a low-pressure tail gas of an ammonia production plant is provided. The preferred tail gas of the ammonia production plant comprises methane, nitrogen, argon, and hydrogen. The disclosed system and method provides for the methane rejection via rectification and hydrogen rejection by way of a side stripper column or phase separator. The resulting nitrogen and argon containing stream is separated and liquefied in a double column distillation system.

A process for producing biomethane by scrubbing a biogas feed stream includes introducing the feed gas stream into a pretreatment unit wherein a CO.sub.2-depleted gas stream is partially separated from a CO.sub.2 stream and an oxygen stream and is compressed to a pressure P1 above 25 bar abs. Subjecting the CO.sub.2-depleted gas stream to cryogenic separation in a distillation column to separate a nitrogen stream and produce a CH.sub.4-enriched stream, the distillation column comprising n plates, n being an integer between 8 and 100. Recovering a pressurized CH.sub.4-enriched stream by pumping the CO.sub.2-depleted gas stream to a pressure P2 above 25 bar absolute.

A process for producing biomethane by scrubbing a biogas feed stream, including introducing a feed gas stream into a pretreatment unit thereby partially separating a CO.sub.2 stream and an oxygen stream and producing a CO.sub.2-depleted gas stream which is then compressed to a pressure P1 above 25 bar abs; introducing the CO.sub.2-depleted gas stream to cryogenic separation in a distillation column to separate a nitrogen stream, the distillation column having n plates, n being an integer between 8 and 100; recovering a pressurized CH.sub.4-enriched stream by pumping the CO.sub.2-depleted gas stream) at a pressure P2 above 25 bar, wherein, when the molar concentration of nitrogen of the CO.sub.2-depleted gas stream is less than a predetermined threshold, nitrogen is injected prior to introduction into the distillation column, in order that the stream introduced into said column has a molar concentration of nitrogen at least equal to said predetermined threshold.

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.

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.

A method for producing liquefied natural gas and a stream of liquid nitrogen including step a): producing gaseous nitrogen in an air separation unit; step b): liquefying a stream of natural gas in a natural gas liquefaction unit including a main heat exchanger and a system for producing cold; step c): liquefying the nitrogen stream resulting from step a) in the main exchanger of the natural gas liquefaction unit in parallel with the liquefied natural gas in step b); wherein all the cold necessary for liquefying the stream of nitrogen and for liquefying the natural gas is supplied by the system for producing cold of the natural gas liquefaction unit.

Methods and systems of the current invention separate condensable vapors such as carbon dioxide from light gases or liquids in a mixed process stream. The separation is carried out in a cryogenic process using one or more external cooling loops (ECLs) that first cool down a mixed process stream containing condensable vapors and light gases or liquids, causing the condensable vapors to desublimate and form solids. Next, the solids are separated from the light gases or liquids, forming a solid stream and a light gas or liquid stream. Then the refrigerants of the ECL are cooled by warming the separated solid stream and light gas or liquid stream, efficiently recovering energy used in cooling and desublimating the condensable vapors.

A cryogenic technology for the cost-efficient capture of each known component of emissions, such as carbon dioxide, sulfur oxides, nitrogen oxides, carbon monoxide, any other acid vapor, mercury, steam, in a liquefied or frozen/solidified form, and unreacted nitrogen (gas) from industrial plants, such that each of the components is captured separately with minimum use of energy and is industrially useful.

The invention relates to a cryogenic process for recovering valuable components, in particular hydrogen, from a hydrogen-rich feed gas, in particular a hydrogen-rich natural gas, comprising the following steps: in a first separation column (T1), hydrocarbons having two or more carbon atoms are separated off, in a second separation column (T2), methane is separated off, and in a third separation column (T3) nitrogen is separated off, the hydrogen-rich feed gas, after optional precleaning R, being fed to the separation columns T1 to T3 according to steps a) to c) and being separated in the separation columns into a liquid fraction, the bottom product, and a gas fraction, the overhead product. In the cryogenic process according to the invention, the cold supply preferably takes place at least partially through one or more refrigeration cycles.