A method for recovering boil-off gas from a system including one or more liquefaction trains including transport trucks or loading bays, a gaseous hydrogen feed stream, a lower-temperature cold box, and a low-pressure hydrogen compressor. The method including collecting a boil-off gas stream from the transport trucks or loading bays, determining the pressure of the boil-off gas stream, and depending on the pressure, recycling the boo-off gas stream to predetermined destinations. Wherein the boil-off gas stream has either a low-pressure, having a pressure of less than 2 bara, or a medium-pressure, having a pressure equal to or greater than 2 bara.

A raw material gas vaporization system includes: a storage tank for storing raw material gas and a transfer line for transferring the raw material gas; a reforming system including a reformer for producing hydrogen by reacting the raw material gas with water, a burner for applying heat to the reformer, and Pressure Swing Adsorption (PSA) for separating the hydrogen in the mixed gas generated from the reformer; a CO.sub.2 separation device for receiving off-gas in which the hydrogen has been removed in the mixed gas from the PSA to remove by liquefying CO.sub.2 by exchanging heat with the transfer line of the raw material gas vaporization system; and a gas supply line for supplying the remaining gas in which the CO.sub.2 has been removed in the CO.sub.2 separation device to a burner as fuel.

Low-temperature refrigeration device arranged in a frame and comprising a working circuit forming a loop and containing a working fluid, the working circuit forming a cycle comprising in series: a compression mechanism, a cooling mechanism, an expansion mechanism and a heating mechanism, the device comprising a refrigeration heat exchanger intended to extract heat from at least one member by exchanging heat with the working fluid, the mechanisms for cooling and reheating the working fluid comprising a common heat exchanger in which the working fluid transits in counter-flow in two separate transit portions of the working circuit, the compression mechanism comprising at least two compressors and at least one motor for driving the compressors, the working fluid expansion mechanism comprising at least one rotary turbine, the device comprising at least one drive motor comprising a drive shaft, one end of which drives a compressor and the other end of which is coupled to a turbine, the motor being attached to the frame at at least one fixed point, the common heat exchanger being attached to the frame at at least one fixed point, the two counter-flow transit portions of the common heat exchanger being orientated in a longitudinal direction of the frame, the drive shaft of the drive motor being orientated in a direction parallel or substantially parallel to the longitudinal direction and the turbine and the compressor being arranged relatively longitudinally such that the turbine is located longitudinally on the side corresponding to the relatively cold end of the common heat exchanger when the device is being operated and the compressor is located longitudinally on the side corresponding to the relatively hot end of the common heat exchanger when the device is being operated.

Disclosed is a low-temperature refrigeration device which is arranged in a frame and comprises a working circuit that forms a loop and contains a working fluid, the working circuit forming a cycle comprising, connected in series: a compression mechanism, a cooling mechanism, an expansion mechanism and a heating mechanism, wherein the mechanisms for cooling and heating the working fluid comprise a common heat exchanger in which the working fluid flows in opposite directions in two separate transit portions of the working circuit, the device further comprising a refrigeration heat exchanger for extracting heat from at least one member by exchanging heat with the working fluid flowing in the working circuit, the compression mechanism comprising two separate compressors, the mechanism for cooling the working fluid comprising two cooling heat exchangers which are arranged respectively at the outlet of the two compressors and ensure heat exchange between the working fluid and a cooling fluid, wherein the frame extends in a longitudinal direction and comprises a lower base intended to be mounted on a support, the cooling heat exchangers are located in the frame about the common heat exchanger, i.e. the cooling heat exchangers are not located below the common heat exchanger between the common heat exchanger and the lower base of the frame.

Disclosed is a BOG reliquefaction system. The BOG reliquefaction system includes: a compressor compressing BOG; a heat exchanger cooling the BOG compressed by the compressor through heat exchange using BOG discharged from a storage tank as a refrigerant; a bypass line through which the BOG is supplied to the compressor after bypassing the heat exchanger; a second valve disposed on a second supply line through which the BOG used as the refrigerant in the heat exchanger is supplied to the compressor, the second valve regulating a flow rate of fluid and opening/closing of the second supply line; and a pressure reducer disposed downstream of the heat exchanger and reducing a pressure of fluid cooled by the heat exchanger, wherein the compressor includes at least one oil-lubrication type cylinder and the bypass line is joined to the second supply line downstream of the second valve.

A liquefaction and subcooling system, comprising a refrigeration device to provide a refrigerant fluid at a first and a second cold temperature that correspond to temperatures of the first and second gases, a subcooling arrangement coupled to the refrigeration device such that the refrigerant fluid is supplied to the subcooling arrangement, the subcooling arrangement having first and second subcoolers for exchanging heat between a gas to be liquefied and/or subcooled and the refrigerant fluid, wherein, when the gas to be liquefied and/or subcooled is the first gas, the refrigeration device is configured to provide the refrigerant fluid and the subcooling arrangement is configured to guide the refrigerant fluid and the gas through the first subcooler; and, when the gas to be liquefied and/or subcooled is the second gas, the refrigeration device is configured to provide the refrigerant fluid.

A method for determining an operating condition of a liquefied natural gas plant (2) includes preparing a training model (88) generated by machine learning using training data in which operating conditions data including a composition of a feed gas, a composition of a mixed refrigerant, and an ambient temperature and operation result data including a production efficiency of a liquefied product containing liquefied natural gas and a heavy component of the feed gas are associated together; and determining, as one new operating condition, a composition of the mixed refrigerant that optimizes a production efficiency of the liquefied natural gas predicted by the training model (88) from a latest composition of the feed gas in the liquefied natural gas plant (2) and a latest ambient temperature.

A method of cooling a boil off gas stream (01) from a liquefied cargo having a boiling point of greater than −110° C. when measured at 1 atmosphere in a liquefied cargo tank (50) in a floating transportation vessel, said method comprising at least the steps of: compressing a boil off gas stream (01) from said liquefied cargo in two or more stages of compression comprising at least a first compression stage (65) and a final compression stage (75) to provide a compressed BOG discharge stream (06), wherein said first compression stage (65) has a first stage suction pressure and said final compression stage (75) has a final stage suction pressure; cooling the compressed BOG discharge stream (06) against one or more first coolant streams (202, 302) to provide a first cooled compressed BOG stream (08); providing a gaseous vent stream (51) from the first cooled compressed BOG stream (08); cooling the first cooled compressed BOG stream (08) against a second coolant stream (33) to provide a second cooled compressed BOG stream (35); expanding a portion of the second cooled compressed BOG stream (35) to the first stage suction pressure or below to provide a first expanded cooled BOG stream (33); using the first expanded cooled BOG stream (33) as the second coolant stream to provide a first expanded heated BOG stream (38); and cooling the gaseous vent stream (51) against the second coolant stream (33) to provide a cooled vent stream (53), wherein cooling of the first cooled compressed BOG stream (08) and cooling of the gaseous vent stream (51) occurs in a heat exchanger located adjacent to the liquefied cargo tank (50).

A cryogenic fluid containment system is disclosed. The system can store a fluid such as hydrogen at a cryogenic temperature and pressure. As the fluid naturally warms, boil-off fluid is produced by the fluid and can be directed to a backup power system that is configured to consume the boil-off fluid. The boil-off fluid being extracted from the cryogenic fluid containment system causes additional boil-off fluid to be generated from the fluid and refrigerate the fluid within the cryogenic fluid containment system. Additionally, the boil-off fluid can be monitored over time such that as the boil-off fluid accumulates within the storage tank, a boil-off controller can determine whether the boil-off fluid is to be extracted from the storage tank. The boil-off controller can enable the fluid to be maintained below a pressure threshold within the storage tank.

A method for liquefying a feed gas stream. A refrigerant stream is cooled and expanded to produce an expanded, cooled refrigerant stream. Part or all of the expanded, cooled refrigerant stream is mixed with a make-up refrigerant stream in a separator, thereby condensing heavy hydrocarbon components from the make-up refrigerant stream and forming a gaseous expanded, cooled refrigerant stream. The gaseous expanded, cooled refrigerant stream passes through a heat exchanger zone to form a warm refrigerant stream. The feed gas stream is passed through the heat exchanger zone to cool at least part of the feed gas stream by indirect heat exchange with the expanded, cooled refrigerant stream, thereby forming a liquefied gas stream. The warm refrigerant stream is compressed to produce the compressed refrigerant stream.