A raw material gas liquefying device includes a feed line; a refrigerant circulation line; and a controller. In a refrigerant liquefaction route, a refrigerant flows through a compressor, a heat exchanger, a circulation system JT valve, a liquefied refrigerant storage tank, and the heat exchanger, and returns to the compressor. In a cryogenic energy generation route, the refrigerant flows through the compressor, the heat exchanger, an expansion unit, and the heat exchanger, and returns to the compressor. The controller determines if a refrigerant storage tank liquid level is within an allowable range, manipulates a feed system JT valve opening rate to control refrigerant temperature at the high-temperature-side refrigerant flow path exit side of the heat exchanger, and manipulates the opening rate of the feed system JT valve to control the refrigerant storage tank liquid level so that the refrigerant storage tank liquid level falls into the predetermined allowable range.

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 small to mid-scale liquefied natural gas production system and method is provided. The disclosed liquefied natural gas production system employs a nitrogen-based refrigerant, at least one heat exchanger, three turbine/expanders and two or more refrigerant compression stages. The expansion ratio of one turbine/expander is appreciably lower than the expansion ratio of the other turbine/expanders such that the temperature of the exhaust stream from the turbine/expander with the lower expansion ratio is above the critical point temperature of the compressed natural gas containing feed stream but colder than -15° C.

A small to mid-scale liquefied natural gas production system and method is provided. The disclosed liquefied natural gas production system employs a nitrogen-based refrigerant, at least one heat exchanger, three turbine/expanders and two or more refrigerant compression stages. The expansion ratio of one turbine/expander is appreciably lower than the expansion ratio of the other turbine/expanders such that the temperature of the exhaust stream from the turbine/expander with the lower expansion ratio is above the critical point temperature of the compressed natural gas containing feed stream but colder than −15° C.

A small to mid-scale liquefied natural gas production system and method is provided. The disclosed liquefied natural gas production system employs a nitrogen-based refrigerant, at least one heat exchanger, three turbine/expanders and two or more refrigerant compression stages. The expansion ratio of one turbine/expander is appreciably lower than the expansion ratio of the other turbine/expanders such that the temperature of the exhaust stream from the turbine/expander with the lower expansion ratio is above the critical point temperature of the compressed natural gas feed stream but colder than −15° C.

Systems and methods for reducing the pressure of a first pressurized fluid, thereby reducing the temperature of the pressurized fluid, and utilization of the reduced-pressure and temperature fluid to cool a second fluid. Such an approach can enable a reduction in the size and weight of a hydraulic system, utilize waste energy in a system, and/or minimize electrical power requirements of a system, among other benefits.

A system and method for increasing the efficiency of natural gas liquefaction processes by using a hybrid cooling system and method. More specifically, a system and method for converting a transcritical precooling refrigeration process to a subcritical process. In one embodiment, the refrigerant is cooled to sub-critical temperature using an economizer. In another embodiment, the refrigerant is cooled to a sub-critical temperature using an auxiliary heat exchanger. Optionally, the economizer or auxiliary heat exchanger can be bypassed when ambient temperatures are sufficiently low to cool the refrigerant to a sub-critical temperature. In another embodiment, the refrigerant is isentropically expanded.

Implementations described and claimed herein provide systems and methods for processing liquefied natural gas (LNG). In one implementation, a dry feed gas is received. The dry feed gas is chilled with clean vapor from a heavies removal column to form a chilled feed gas. The chilled feed gas is partially condensed into a vapor phase and a liquid phase. The liquid phase retains freezing components. The freezing components are extracted using a reflux stream in the heavies removal column. The freezing components are removed as a condensate. The vapor phase is compressed into a clean feed gas. The clean feed gas is free of the freezing components for downstream liquefaction.

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 system and method for liquefaction of natural gas using two distinct refrigeration circuits having compositionally different working fluids and operating at different temperature levels is provided. The turbomachinery associated with the liquefaction system are driven by a single three-pinion or four-pinion integral gear machine with customized pairing arrangements. The system and method of natural gas liquefaction further includes the conditioning of a lower pressure natural gas containing feed stream to produce a purified, compressed natural gas containing stream at a pressure equal to or above the critical pressure of natural gas and substantially free of heavy hydrocarbons to be liquefied.