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 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.

A method and system for liquefying a natural gas feed stream and removing nitrogen therefrom.

The invention relates to an integrated process and apparatus for liquefaction of natural gas and recovery of natural gas liquids. In particular, the improved process and apparatus reduces the energy consumption of a Liquefied Natural Gas (LNG) unit by using a portion of the already cooled overhead vapor from a fractionation column from an NGL (natural gas liquefaction) unit to, depending upon composition, provide, for example, reflux for fractionation in the NGL unit and/or a cold feed for the LNG unit, or by cooling, within the NGL unit, a residue gas originating from a fractionation column of the NGL unit and using the resultant cooled residue gas to, depending upon composition, provide, for example, reflux/feed for fractionation in the NGL and/or a cold feed for the LNG unit, thereby reducing the energy consumption of the LNG unit and rendering the process more energy-efficient.

A variable speed liquid LNG expander (X1) and a variable speed two-phase LNG expander (X2) in line, downstream from X1. The rotational speed of both expanders can be controlled and changed independent from each other. The speed of expander X1 and expander X2 is determined in such way that the amount of liquid LNG downstream from the PHS compared to the feed gas supply is maximized and the amount of vapor and boil-off downstream of X2 is minimized.

A process for liquefying a natural gas comprising a mixture of hydrocarbons predominating in methane, the process comprising a first semi-open refrigerant cycle with natural gas in which any natural gas liquids that have condensed are separated from the natural gas feed stream, which stream then passes through a main cryogenic heat exchanger (4) in order to contribute by heat exchange to pre-cooling a main natural gas stream (F-P) and to cooling an initial refrigerant gas stream (G-0), a second semi-open refrigerant cycle with natural gas for contributing to pre-cooling the natural gas and the refrigerant and also to liquefying the natural gas, and a closed refrigerant cycle with refrigerant gas for subcooling the liquefied natural gas and for delivering refrigeration power in addition to the other two cycles. The invention also provides a natural gas liquefaction installation for performing such a process.

A process of liquefying a natural gas stream in a liquefied natural gas facility is provided. The process includes cooling the natural gas stream in a first refrigeration cycle to produce a cooled natural gas stream. The process also includes cooling the cooled natural gas stream in a first chiller of a second refrigeration cycle, the cooled natural gas stream exiting the first chiller at a first pressure. The process further includes cooling the cooled natural gas stream in a first core of a second chiller of the second refrigeration cycle. The process yet further includes cooling a refrigerant of a refrigerant recycle stream separate from the cooled natural gas stream in a second core of the second chiller of the second refrigeration cycle, wherein the refrigerant recycle stream enters the second chiller at a second pressure that is lower than the first pressure of the cooled natural gas stream.

A main heat exchanger receives and partially condenses an effluent fluid stream so that a mixed phase effluent stream is formed. A primary separation device receives and separates the mixed phase effluent stream into a primary vapor stream including hydrogen and a primary liquid stream including an olefinic hydrocarbon. The main heat exchanger receives and warms at least a portion of the primary vapor stream to provide refrigeration for partially condensing the effluent fluid stream. The main heat exchanger also receives, warms and partially vaporizes the primary liquid stream. A mixed refrigerant compression system also provides refrigeration in the main heat exchanger.

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).

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.