Systems and methods for liquefying a gaseous hydrogen that include a first refrigeration stage and a second refrigeration stage. The first refrigeration stage includes a first heat exchanger configured to flow a first refrigerant to pre-cool the gaseous hydrogen. The second refrigeration stage includes a second heat exchanger configured to flow a second refrigerant to liquefy and sub-cool the hydrogen. The second refrigerant is split into two streams that flow through two compressor-expanders and multiple passes through the second heat exchanger before being recombined to repeat the second refrigeration stage circuit.

Systems and methods for liquefying a gaseous hydrogen that include a first refrigeration stage and a second refrigeration stage. The first refrigeration stage includes a first heat exchanger configured to flow a first refrigerant to pre-cool the gaseous hydrogen. The second refrigeration stage includes a second heat exchanger configured to flow a second refrigerant to liquefy and sub-cool the hydrogen. The second refrigerant is split into two streams that flow through two compressor-expanders and multiple passes through the second heat exchanger before being recombined to repeat the second refrigeration stage circuit.

Closed-loop refrigeration cycles for liquid oxygen densification are disclosed. The disclosed refrigeration cycles may be turbine-based refrigeration cycles or a Joule-Thompson (JT) expansion valve based refrigeration cycles and include a refrigerant or working fluid comprising a mixture of neon or helium together with nitrogen and/or oxygen.

Plant and process for the production of liquid methane from a feed gas stream comprising at least methane and carbon dioxide. A feed gas stream is injected into a CO.sub.2 crystallizer in countercurrent fashion against a stream of predominantly liquid methane, thereby crystallizing amounts of carbon dioxide from the feed gas stream. Gaseous methane recovered from the CO.sub.2 crystallizer is liquefied at a liquefaction exchanger.

Plant and method for producing hydrogen at cryogenic temperature, in particular liquefied hydrogen, comprising: an electrolyzer having an oxygen outlet and a hydrogen outlet; a hydrogen circuit to be cooled, comprising an upstream end connected to the hydrogen outlet and a downstream end to be connected to a member for collecting cooled and/or liquefied hydrogen, the plant also comprising a set of heat exchanger(s) in heat exchange with the hydrogen circuit to be cooled, the plant further comprising at least one cooling device in heat exchange with at least a portion of the set of heat exchanger(s), the hydrogen circuit to be cooled comprising a system for expanding the hydrogen stream and at least one hydrogen compressor upstream of the hydrogen stream expansion system, the hydrogen stream expansion system comprising at least one expansion turbine, wherein said at least one expansion turbine and said at least one compressor are coupled to the same rotating shaft to transfer expansion work from the pressurized hydrogen stream to the compressor in order to compress the hydrogen stream upstream of the turbine.

The present invention relates to a method for liquefying hydrogen, the method comprises the steps of: cooling a feed gas stream comprising hydrogen with a pressure of at least 15 bar(a) to a temperature below the critical temperature of hydrogen in a first cooling step yielding a liquid product stream. According to the invention, the feed gas stream is cooled by a closed first cooling cycle with a high pressure first refrigerant stream comprising hydrogen, wherein the high pressure first refrigerant stream is separated into at least two partial streams, a first partial stream is expanded to low pressure, thereby producing cold to cool the precooled feed gas below the critical pressure of hydrogen, and compressed to a medium pressure, and wherein a second partial stream is expanded at least close to the medium pressure and guided into the medium pressure first partial stream.

Cooling system, preferably adapted for use in or including a refrigeration plant and/or liquefier plant, having a refrigeration circuit (1) configured to use a refrigerant including a mixture of helium and neon; wherein the refrigerant is based on a raw mixture, preferably is the raw mixture, including helium and neon, extracted from air by an air separation plant (2). Method for producing a refrigerant usable in a refrigeration circuit (1), comprising: extracting a raw mixture including helium and neon from air, wherein the raw mixture preferably further includes nitrogen and hydrogen; and using the raw mixture as the refrigerant or obtaining the refrigerant from the raw mixture.

The present invention relates to a refrigerant composition comprising neon and hydrogen. The present invention further relates to the use of the refrigerant composition in liquefying gaseous substances such as hydrogen or helium.

Closed-loop refrigeration cycles for liquid oxygen densification are disclosed. The disclosed refrigeration cycles may be turbine-based refrigeration cycles or a Joule-Thompson (JT) expansion valve based refrigeration cycles and include a refrigerant or working fluid comprising a mixture of neon or helium together with nitrogen and/or oxygen.

Closed-loop refrigeration cycles for liquid oxygen densification are disclosed. The disclosed refrigeration cycles may be turbine-based refrigeration cycles or a Joule-Thompson (JT) expansion valve based refrigeration cycles and include a refrigerant or working fluid comprising a mixture of neon or helium together with nitrogen and/or oxygen.