A method for liquefying a natural gas feed stream and removing nitrogen therefrom, the method comprising passing a natural gas feed stream through a main heat exchanger to produce a first LNG stream, and separating a liquefied or partially liquefied natural gas stream in a distillation column to form nitrogen-rich vapor product, wherein a closed loop refrigeration system provides refrigeration to the main heat exchanger and to a condenser heat exchanger that provides reflux to the distillation column.

A precool heat exchanger system receives a stream of first cryogenic fluid for warming a second cryogenic fluid. A first splitter receives and divides a first cryogenic fluid stream into a motive stream and a secondary cooling stream. An ejector receives the motive stream. An expansion device receives and expands the secondary cooling stream and directs at least a portion of it to the precool heat exchanger system so that a second cryogenic fluid is cooled. First cryogenic fluid from the precool heat exchanger is directed into the ejector suction port and the pressure therein is reduced. A primary separation device divides a first cryogenic fluid mixed phase stream from the ejector into a first cryogenic fluid vapor stream and a liquid recycle stream that exit the primary separation device. A recycle pump directs first cryogenic fluid to the first splitter.

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 method for separating nitrogen from an LNG stream with a nitrogen concentration of greater than 1 mol %. A pressurized LNG stream is produced at a liquefaction facility by liquefying natural gas, where the pressurized LNG stream has a nitrogen concentration of greater than 1 mol %. At least one liquid nitrogen (LIN) stream is received from storage tanks, the at least one LIN stream being produced at a different geographic location from the LNG facility. The pressurized LNG stream is separated in a separation vessel into a vapor stream and a liquid stream. The vapor stream has a nitrogen concentration greater than the nitrogen concentration of the pressurized LNG stream. The liquid stream has a nitrogen concentration less than the nitrogen concentration of the pressurized LNG stream. At least one of the one or more LIN streams is directed to the separation vessel.

A LNG liquefaction plant system includes concurrent power production, wherein the refrigeration content of the refrigerant or SMR is used to liquefy and sub-cool a natural gas stream in a cold box or cryogenic exchanger. For concurrent power production, the system uses waste heat from refrigerant compression to vaporize and superheat a waste heat working fluid that in turn drives a compressor for refrigerant compression. The refrigerant may be an external SMR or an internal LNG refrigerant working fluid expanded and compressed by a twin compander arrangement.

A cryogenic turbine expander system which consists essentially of a cryogenic liquid pressure vessel, and the vessel further accommodating a turbine expander, an internal bypass configuration, which are operable in parallel, a three-way valve to direct incoming high pressure liquefied gas flow to the turbine expander, or the internal bypass configuration, which further consists a Joule-Thomson valve, when the turbine expander is not operational.

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 LNG liquefaction plant system includes concurrent power production, wherein the refrigeration content of the refrigerant or SMR is used to liquefy and sub-cool a natural gas stream in a cold box or cryogenic exchanger. For concurrent power production, the system uses waste heat from refrigerant compression to vaporize and superheat a waste heat working fluid that in turn drives a compressor for refrigerant compression. The refrigerant may be an external SMR or an internal LNG refrigerant working fluid expanded and compressed by a twin compander arrangement.

A LNG liquefaction plant system includes concurrent power production, wherein the refrigeration content of the refrigerant or SMR is used to liquefy and sub-cool a natural gas stream in a cold box or cryogenic exchanger. For concurrent power production, the system uses waste heat from refrigerant compression to vaporize and superheat a waste heat working fluid that in turn drives a compressor for refrigerant compression. The refrigerant may be an external SMR or an internal LNG refrigerant working fluid expanded and compressed by a twin compander arrangement.