A method of cooling a boil-off gas (BOG) stream from a liquefied gas tank comprising at least the step of heat exchanging the BOG stream with a first refrigerant in a heat exchanger, the heat exchanger having an entry port and a warmer exit port, and comprising at least the steps of: (a) passing the first refrigerant into the entry port of the heat exchanger and into a first zone of the heat exchanger to exchange heat with the BOG stream, to provide a first warmer refrigerant stream; (b) withdrawing the first warmer refrigerant stream from the heat exchanger at an intermediate exit port between the entry port and the warmer exit port; (c) passing the first warmer refrigerant stream through an entry port located in a second zone of the heat exchanger that is warmer than the first zone (d) passing an oil-containing refrigerant stream through an entry port located in a second zone of the heat exchanger that is warmer than the first zone; (e) mixing the first warmer refrigerant stream and the oil-containing stream in the heat-exchanger to form a combined refrigerant stream; and (f) passing the combined refrigerant stream out of the heat exchanger through the warmer exit port.

A liquefied gas cooling apparatus including: a gas flow path for carrying a liquefied gas that is liquefied by cooling; and a refrigeration unit including a refrigerating cycle formed by a compressor, a cooling unit, and an expander. The compressor is driven through an electric motor contained in a sealed housing together with a compressor mechanism.

Cryogenic refrigeration device comprising a working circuit intended to cool a working fluid circulating in the said circuit, the working circuit comprising, arranged in series in a loop: a compression portion, a cooling portion, a portion with valve(s), an expansion portion and a reheating portion, in order to subject the working fluid to a recuperative working cycle comprising compression, then cooling, then expansion and then reheating to prepare for a new cycle, wherein the compression portion comprises at least one compressor having a linear piston driven by a linear motor, the expansion proportion comprises at least one expander with a linear piston, the portion with valve(s) comprises at least one regulating valve linearly actuated by a linear motor and controlled in order to supply or extract the working fluid from the at least one expansion piston.

A ship comprises: a tank; a multistage compressor for compressing a boil-off gas discharged from a storage tank and comprising a plurality of compression cylinders; a first heat exchanger for heat exchanging a fluid, which has been compressed by the multistage compressor, with the boil-off gas discharged from the storage tank and thus cooling the same; a first decompressing device for expanding a flow (“flow a1”) partially branched from the flow (“flow a”) that has been cooled by the first heat exchanger; a third heat exchanger for heat exchanging, by “flow a1” which has been expanded by the first decompressing device as a refrigerant, the remaining flow (“flow a2”) of “flow a” after excluding “flow a1” that has been branched and thus cooling the same; and a second decompressing device for expanding “flow a2” which has been cooled by the third heat exchanger.

A gas recovery system for a compressor, said gas recovery system being equipped with: a distillation column that brings a supply gas in a liquid state into contact with a mixed gas, thereby cooling and liquefying a process gas in the mixed gas, and heating and gasifying the liquid supply gas; a process gas recovery line that is connected to the lower part of the distillation column and recovers the liquid process gas discharged from the distillation column; and a supply gas recovery line that is connected to the upper part of the distillation column and recovers the gaseous supply gas discharged from the distillation column.

Disclosed are a helium gas liquefier and a method for liquefying a helium gas. The disclosed helium gas liquefier includes: a first cooling part including a first cooling column; a first cold head installed on the first cooling column, and a first cylinder in which the first cooling column and the first cold head are built; a second cooling part including a second cooling column, a second cold head installed on the second cooling column, and a second cylinder in which the second cooling column and the second cold head are built; and a liquid helium storage disposed under the second cooling part.

In an aspect, a system comprises a water stream in fluid communication with an electrolyzer; the electrolyzer comprising an anode and a cathode side chamber; a deep space oxygen radiator in fluid communication with the anode side chamber of the electrolyzer; a cryogenic heat exchanger comprising an oxygen storage tank in fluid communication with the deep space oxygen radiator; an electrochemical hydrogen compressor in fluid communication with the cathode side chamber; a hydrogen storage tank in fluid communication with the electrochemical hydrogen compressor via a cooled hydrogen stream; wherein at least a portion of the cooled hydrogen stream is in a first fluid communication with an expansion valve and the cryogenic heat exchanger; wherein the hydrogen storage tank is in a second fluid communication with the electrochemical hydrogen compressor via a warmed hydrogen stream; and wherein the cryogenic heat exchanger is in fluid communication with the warmed hydrogen stream.

A method for separating nitrogen from an inlet gas having less than 25 mole % nitrogen includes supplying the inlet gas having less than 25 mole % nitrogen to a nitrogen separation system configured with cryogenic refrigeration.

Disclosed is a method of discharging lubricant oil from a BOG reliquefaction system configured to reliquefy BOG by compressing the BOG by a compressor, cooling the compressed BOG through heat exchange with non-compressed BOG by a heat exchanger, and reducing a pressure of fluid cooled through heat exchange by a pressure reducer. In the lubricant oil discharge method, the compressor comprises at least one oil-lubrication type cylinder and it is determined that it is time to discharge condensed or solidified lubricant oil, if at least one of preset conditions is satisfied.

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.