A method for controlling the flow of natural gas and refrigerant in the main heat exchanger of a natural gas liquefaction facility. The method provides for the automated control of a flow rate of a natural gas feed stream through a heat exchanger based on one or more process variables and set points. The flow rate of refrigerant streams through the heat exchanger is controlled by different process variables and set points, and is controlled independently of the flow rate of the natural gas feed stream.

A refrigerant circuit includes a first compression stage for compressing a mixed refrigerant gas, the first compression stage including at least a first compressor body and a second parallel compressor body, each compressor body including a suction inlet and an outlet, a first distribution means for splitting the flow of refrigerant gas to the first stage of compression across the at least two parallel compressor bodies, such that a first stream of refrigerant gas is fed to the suction inlet of the first compressor body and a second stream of refrigerant gas is fed to the suction inlet of the second compressor body, a second compression stage for compressing the mixed refrigerant gas, and a first merging means for recombining the first stream of refrigerant gas with the second stream of refrigerant gas downstream of the first compression stage for delivery to the second compression stage.

The present invention relates to a method of liquefying a hydrocarbon stream such as a natural gas stream, the method at least comprising the steps of: supplying a partly condensed hydrocarbon feed stream (10) to a first gas/liquid separator (2); separating the feed stream (10) in the first gas/liquid separator (2) into a gaseous stream (20) and a liquid stream (30); expanding the gaseous stream (20) thereby obtaining an expanded stream (40) and feeding it (40) into a second gas/liquid separator (3); feeding the liquid stream (30) into the second gas/liquid separator (3); removing from the bottom of the second gas/liquid separator a liquid stream (60) and feeding it into a fractionation column (5); removing from the top of the second gas/liquid separator (3) a gaseous stream (50) and passing it to a compressor (6) thereby obtaining a compressed stream (70); cooling the compressed stream (70) thereby obtaining a cooled compressed stream (80); heat exchanging the cooled compressed stream (80) against a stream being downstream of the first gas/liquid separator (2) and upstream of the fractionation column (5).

Systems and methods for improving the efficiency of open-cycle cascade-based liquified natural gas systems by utilizing one or more ejectors to reduce and/or eliminate compression stages. The systems and methods may thus, be used to improve the efficiency of new and preexisting open-cycle cascade-based liquified natural gas systems to reduce in the flow rate through each compressor, which reduces the energy consumption of the overall process.

Systems and methods for improving the efficiency of combined cascade and multicomponent refrigeration systems by utilizing one or more ejectors to reduce and/or eliminate compression stages. The systems and methods change the temperature profile, which reduces the energy consumption of both the mixed refrigeration system and the pre-cooling system.

Provided is a technology of searching for operation guidance for efficiently operating a liquefied natural gas plant An operation guidance searching method for a liquefied natural gas plant includes: acquiring data sets of operation data of process variables for a plurality of target devices and disturbance data; generating, through machine learning, a plant model indicating correspondences of output values of process variables with respect to manipulated variables and input values of disturbances; and searching, through reinforcement learning, for input values of the manipulated variables operation variables for with which a compression power per unit production amount is minimized under a condition in which an outlet temperature of a liquefied natural gas is a preset restriction temperature or lower.

The present disclosure provides a heat axchanger and heat exchange method for cooling a gaseous process stream. The heat exchanger unit (100, 200, 300) comprises: a heat exchanger vessel (2), the heat exchanger vessel (2) comprising a plurality of process stream conduits (12, 14) arranged to receive the gaseous process stream (10) and discharge a cooled process stream (18), and a plurality of refrigerant conduits (46, 48, 49) to receive at least part of a pre-cooled mixed refrigerant stream (58) and to discharge at least one cooled mixed refrigerant stream (72, 82); at least one expansion device (74, 84) arranged to receive at least part of the cooled mixed refrigerant stream (72, 82) and discharge a further cooled mixed refrigerant stream (76, 86), the further cooled mixed refrigerant stream (76, 86) being connected to at least one of a third refrigerant inlet (77) and a fourth refrigerant inlet (87) of the heat exchanger vessel (2) to provide cooling to the process stream conduits (12, 14) and the refrigerant conduits (46, 48, 49); a refrigerant bleed vessel (110) arranged to receive a first refrigerant split-off stream (112) from the cooled mixed refrigerant stream (72, 82) and to receive a second refrigerant split-off stream (114) from the pre-cooled mixed refrigerant stream; the refrigerant bleed vessel (110) comprising a bleed outlet (116) to discharge a bleed stream (118) and a recycle outlet (120) to discharge a recycle stream (122), the recycle outlet being fluidly connected to at least one of the third refrigerant inlet (77) and the fourth refrigerant inlet (87) of the heat exchanger vessel (2).

A method of cooling a boil off gas stream from a liquefied cargo (50a) in a floating transportation vessel is described. The method comprises: compressing a boil off gas stream in two or more stages of compression to provide a compressed BOG discharge stream; cooling the compressed BOG discharge stream against one or more first coolant streams to provide a first cooled compressed BOG stream; cooling the first cooled compressed BOG stream against at least one second coolant stream to provide a second cooled compressed BOG stream; providing a vessel fuel stream from the liquefied cargo; using the vessel fuel stream as a coolant stream to cool either the compressed BOG discharge stream, or the first cooled compressed BOG stream, or both said streams.

The invention relates to a method for condensing a gas, wherein the gas is subjected to cooling in indirect heat exchange with a refrigerant and at least part of the refrigerant is subjected, after the heat exchange with the gas, to compression by means of a drive (GT1) that produces waste heat and to a partial or complete condensing process. After the partial or complete condensing process, a first portion of the refrigerant is subjected to the heat exchange with the gas and a second portion of the refrigerant is subjected, in succession, to pressurization, heating by means of the waste heat of the drive (GT1) and work-performing expansion and thereafter is fed back to the partial or complete condensing process. The invention further relates to a corresponding system.

Provided are an apparatus and method for liquefying natural gas. The apparatus for liquefying natural gas includes a gas compressor configured to receive and compress the natural gas from a natural gas feed stream, a heat exchanging unit configured to cool a high-pressure natural gas passing through the gas compressor through heat exchange, an expansion valve configured to expand the cooled natural gas passing through the heat exchanging unit, a hold-up drum configured to phase-separate a gas-liquid mixture produced by passing through the expansion valve and divide the gas-liquid mixture into a liquefied natural gas and a cryogenic recycle gas having nitrogen content greater than that of the liquefied natural gas so as to discharge the liquefied natural gas and the cryogenic recycle gas, and a bypass line configured to provide the recycle gas discharged from the hold-up drum to the heat exchanging unit.