Disclosed is a low-temperature refrigeration device comprising a working circuit that forms a loop and contains a working fluid, the device further comprising a cooling exchanger for extracting heat from at least one member by exchanging heat with the 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 mechanism for cooling the working fluid and the heating mechanism comprise a common heat exchanger in which the working fluid flows in opposite directions in two separate transit portions of the circuit according to whether it is cooled or heated, the device being designed to ensure equal mass flow rates in the two transit portions in the common heat exchanger, the device also comprising a bypass for bypassing one of the two transit portions, said bypass comprising a bypass valve which, in the open state, changes the mass flow rate in one of the two transit portions.

Described herein is a method of removing refrigerant from a natural gas liquefaction system in which vaporized mixed refrigerant is withdrawn from the closed-loop refrigeration circuit and introduced into a distillation column so as to be separated into an overhead vapor enriched in methane and a bottoms liquid enriched in heavier components. Overhead vapor is withdrawn from the distillation column to form a methane enriched stream that is removed from the liquefaction system, and bottoms liquid is reintroduced from the distillation column into the closed-loop refrigeration circuit. Also described are methods of altering the rate of production in a natural gas liquefaction system in which refrigerant is removed as described above, and a natural gas liquefaction systems in which such methods can be carried out.

A drive system for liquefied natural gas (LNG) refrigeration compressors in a LNG liquefaction plant. Each of three refrigeration compression strings include refrigeration compressors and a multi-shaft gas turbine capable of non-synchronous operation. The multi-shaft gas turbine is operationally connected to the refrigeration compressors and is configured to drive the one or more refrigeration compressors. The multi-shaft gas turbine uses its inherent speed turndown range to start the one or more refrigeration compressors from rest, bring the one or more refrigeration compressors up to an operating rotational speed, and adjust compressor operating points to maximize efficiency of the one or more refrigeration compressors, without assistance from electrical motors with drive-through capability and variable frequency drives.

A method of operating, during an at least partial shutdown of a refrigerant distribution subsystem in a natural gas liquefaction facility, can include: draining down at least a portion of a mixed refrigerant in one or more components of the refrigerant distribution subsystem into a high-pressure holding tank of a drain down subsystem, wherein draining down to the high-pressure holding tank is achieved by pumping the mixed refrigerant from the refrigerant distribution subsystem to the high-pressure holding tank or backfilling the refrigerant distribution subsystem with a backfill gas; and optionally, transferring at least a portion of the mixed refrigerant into a low-pressure drum from the high-pressure holding tank.

A BOG reliquefaction system includes: a compressor; a heat exchanger cooling the BOG compressed by the compressor through heat exchange using BOG not compressed by the compressor; a pressure reducer disposed downstream of the heat exchanger and reducing a pressure of fluid cooled by the heat exchanger; and a combination of a first temperature sensor disposed upstream of a cold fluid channel of the heat exchanger and a fourth temperature sensor disposed downstream of a hot fluid channel of the heat exchanger, combination of a second temperature sensor disposed downstream of the cold fluid channel of the heat exchanger and a third temperature sensor disposed upstream of the hot fluid channel of the heat exchanger, or combination of a first pressure sensor disposed upstream of the hot fluid channel of the heat exchanger and a second pressure sensor disposed downstream of the hot fluid channel of the heat exchanger.

Provided herein are systems and methods for utilizing a natural gas letdown generator at a natural gas regulating station. The system utilizes the gas letdown generator to generate electricity by converting high pressure inlet gas to low pressure outlet gas, which in turn creates low temperature outlet gas. Electricity generated can power a data center. Heat may be transferred, using a heat exchanger, from dielectric fluid of the data center to the natural gas prior to entering the gas letdown generator. Heat may be further transferred, using a second heat exchanger, from the dielectric fluid to the natural gas at the output of the gas letdown generator. The heat exchange may substantially cool the dielectric fluid for transmission to the data center and may heat the low temperature outlet gas for transmission to an end user.

A drive system for liquefied natural gas (LNG) refrigeration compressors in a LNG liquefaction plant. Each of three refrigeration compression strings include refrigeration compressors and a multi-shaft gas turbine capable of non-synchronous operation. The multi-shaft gas turbine is operationally connected to the refrigeration compressors and is configured to drive the one or more refrigeration compressors. The multi-shaft gas turbine uses its inherent speed turndown range to start the one or more refrigeration compressors from rest, bring the one or more refrigeration compressors up to an operating rotational speed, and adjust compressor operating points to maximize efficiency of the one or more refrigeration compressors, without assistance from electrical motors with drive-through capability and variable frequency drives.

There is provided a system and method for producing liquefied natural gas (LNG). An exemplary method includes flowing a high-pressure stream of LNG through a first series of liquid turbines. The exemplary method also includes generating electricity by reducing the pressure of the high-pressure stream of LNG to form a low-pressure stream of LNG. The exemplary method additionally includes bypassing any one the liquid turbines that has a failure while continuing to produce electricity from the first series.

A raw material gas liquefying device includes a feed line which feeds a raw material gas, a refrigerant circulation line which circulates a refrigerant, the refrigerant circulation line including an expansion unit of a turbine type which expands the refrigerant to generate cryogenic energy, and an expansion unit entrance valve provided at an entrance side of the expansion unit, a heat exchanger which exchanges heat between the raw material gas and the refrigerant, a cooler which performs initial cooling of the raw material gas and the refrigerant by heat exchange with liquid nitrogen, and a controller which manipulates the opening rate of the expansion unit entrance value and performs a feedback control so that the rotation speed of the expansion unit reaches a predetermined target value, and outputs the opening rate command to the expansion unit entrance valve, at start-up and stop of the expansion unit.

Provided herein are systems and methods for utilizing a natural gas letdown generator at a natural gas regulating station. The system utilizes the gas letdown generator to generate electricity by converting high pressure inlet gas to low pressure outlet gas, which in turn creates low temperature outlet gas. Electricity generated can power a data center. Heat may be transferred, using a heat exchanger, from dielectric fluid of the data center to the natural gas prior to entering the gas letdown generator. Heat may be further transferred, using a second heat exchanger, from the dielectric fluid to the natural gas at the output of the gas letdown generator. The heat exchange may substantially cool the dielectric fluid for transmission to the data center and may heat the low temperature outlet gas for transmission to an end user.