JP2019505755A - Inflator-based LNG production process reinforced with liquid nitrogen - Google Patents

Abstract

A method for producing liquefied natural gas (LNG). A natural gas stream is directed to a mechanical refrigeration unit to liquefy the natural gas stream to form a pressurized liquefied natural gas (LNG) stream having a pressure greater than 50 psia (345 kPa) and less than 500 psia (3445 kPa). A liquid refrigerant subcool unit is provided at the first location. A liquid refrigerant is generated at a second location that is geographically separated from the first location. The generated liquid refrigerant is transported to the first location. The pressurized LNG stream is subcooled in the liquid refrigerant subcooling unit by exchanging heat between the pressurized LNG stream and at least one stream of liquid refrigerant, thereby producing an LNG stream. [Selection] Figure 3

Description

[Cross-reference to related applications]
This application is a US Provisional Patent Application No. 62/62, entitled “Expansion-Based LNG Production Process Intensified by Liquid Nitrogen”, filed December 14, 2015, which is incorporated herein by reference in its entirety. Claims the benefit of 266,979.

  This application, which has a common inventor and assignee, was filed on the same date as this specification, the disclosure of which is incorporated herein by reference in its entirety. US Provisional Patent Application No. 62 / 266,976 entitled “Method and System for Separating Nitrogen from Liquefied Natural Gas”, United States of America, entitled “Method of Natural Gas Liquefaction on LNG Carriers that Store Liquid Nitrogen” Related to provisional patent application 62 / 266,983 and US provisional patent application 62 / 622,985 entitled "Precooling Natural Gas by High Pressure Compression and Expansion".

  The present disclosure generally relates to the field of natural gas liquefaction to form liquefied natural gas (LNG). More specifically, the present disclosure relates to the production and transfer of LNG from offshore and / or remote natural gas sources.

  This section is intended to introduce various aspects of the art that can be related to the present disclosure. This discussion is intended to provide a framework for facilitating a better understanding of certain aspects of the present disclosure. Therefore, it should be understood that this section should be read from this perspective, not necessarily as an acceptance of the prior art.

  LNG is a rapidly growing means of supplying natural gas from locations with a rich supply of natural gas to remote locations where demand for natural gas is high. The conventional LNG cycle consists of a) initial treatment of natural gas resources to remove contaminants such as water, sulfur compounds, and carbon dioxide, and b) some heavier, such as propane, butane, pentane, etc. Separation of various hydrocarbon gases by various possible methods including self-refrigeration, external refrigeration, lean oil, etc. c) substantially external refrigeration to form liquefied natural gas at or near atmospheric pressure and at about -160 ° C D) refrigeration of natural gas, d) transportation of LNG products to a market place in a ship or tanker designed for transportation, and e) formation of a pressurized natural gas stream that can be distributed to natural gas consumers Including re-pressurization and regasification of LNG in a regasification plant for Stage (c) of the conventional LNG cycle usually requires the use of a large refrigeration compressor that is often powered by a large gas turbine driver that substantially releases carbon and other emissions. Multi-billion dollar large capital investments and large infrastructure are required as part of the liquefaction plant. Step (e) of a conventional LNG cycle generally involves repressurizing LNG to the required pressure using a cryogenic pump and then heat exchange through seawater and ultimately with seawater. Or regasifying the LNG to form pressurized natural gas by burning a portion of the natural gas to heat and vaporize the LNG. In general, the available energy of cryogenic LNG is not utilized.

  A relatively new technology for producing LNG is known as floating LNG (FLNG). FLNG technology involves building gas treatment and liquefaction facilities on floating structures such as barges or ships. FLNG is a technical solution for monetizing offshore residual gas, where gas pipeline construction on the coast is not economically viable. FLNG is also increasingly being considered for onshore and coastal gas fields located in remote, environmentally sensitive and / or politically challenging areas. This technology has certain advantages over conventional land-based LNG in that it has a smaller environmental footprint at the production site. This technology also allows projects to be delivered more quickly and at a lower cost since the majority of LNG facilities are built at shipyards with low wage rates and low contract fulfillment risks.

  Although FLNG has several advantages over conventional terrestrial LNG, significant technical challenges remain in the application of this technology. For example, a FLNG structure must provide the same level of gas treatment and liquefaction in an area that is often less than a quarter of the area that can be utilized in an onshore LNG plant. For this reason, technology must be developed that reduces the overall project cost by reducing the footprint of the FLNG facility while maintaining the capacity of the liquefaction facility. One promising means to reduce the footprint is to modify the liquefaction technology used in the FLNG facility. Known liquefaction techniques include a single mixed refrigerant (SMR) process, a double mixed refrigerant (DMR) process, and an expander base (or expansion) process. The inflator-based process has several advantages that make it well suited for FLNG projects. The most significant advantage is that this technique provides liquefaction without the need for an external hydrocarbon refrigerant. Eliminating liquid hydrocarbon refrigerant inventory such as propane storage significantly reduces serious safety concerns, especially in FLNG projects. An additional advantage of the expander base process compared to the mixed refrigerant process is that the expander base process is less sensitive to offshore sway because most of the main refrigerant remains in the gas phase.

  Although the expander-based process has its advantages, it has been found that applying this technology to FLNG projects with LNG production exceeding 2 million tons (MTA) per year is not as attractive as using a mixed refrigerant process. ing. The capacity of known expander-based process trains is typically less than 1.5 MTA. In contrast, a mixed refrigerant process train, such as a propane precooling process or a double mixed refrigerant process, can have a train capacity greater than 5 MTA. The size of the expander-based process train is limited because most of the refrigerant remains in the vapor state throughout the process and the refrigerant absorbs energy through its sensible heat. For these reasons, the refrigerant volume flow is large throughout the process, and the heat exchanger and piping sizes are proportionally larger than those used in the mixed refrigerant process. In addition, the companding horsepower scale limitation results in parallel rotating machines as the capacity of the expander-based process train increases. The production rate of a FLNG project that uses an expander-based process can be greater than 2 MTA when multiple expander-based trains are enabled. For example, in the case of a 6 MTA FLNG project, 6 or more parallel expander-based process trains may be sufficient to achieve the required production. However, total equipment, complexity, and cost are all increased for multiple inflator trains. In addition to this, when the expander-based process requires multiple trains, while the mixed refrigerant process can obtain the required production rate with one or more trains, compared to the mixed refrigerant process The simplicity of the assumed inflator-based process is questioned. For these reasons, an FLNG liquefaction process must be developed that has the advantages of an expander-based process while achieving high LNG production capacity. There is a further need to develop FLNG technology solutions that can better cope with the challenges of ship shaking with gas handling challenges.

  U.S. Pat. No. 3,400,547 to Williams et al. Describes a process in an LNG production facility where liquid nitrogen (LIN) produced at different locations is used as a refrigerant to liquefy natural gas. Disclosure. This process cools the natural gas using a propane cooler before condensing the natural gas by indirect heat exchange with the evaporating LIN. British Patent 1,596,330 granted to Thompson discloses a process in an LNG production facility where liquid nitrogen (LIN) produced at different locations is used as a refrigerant to liquefy natural gas. doing. This process uses a propane and ethylene cooler combined with LIN to liquefy natural gas to LNG. The processes disclosed by these two patents have the disadvantage of using a mechanical refrigeration system while still requiring a significant amount of LIN to produce LNG. Both processes estimate that about one ton or more of LIN is required for each ton of LNG produced. In FLNG applications, space for LIN storage, either on the upper deck of floating structures or in the hull, may be limited. Having LNG production technology over FLNG using LIN would be advantageous as it would significantly reduce the upper deck space required for the liquefaction process. In addition, LNG production technology that uses less than 1 ton of LIN, or more preferably less than 0.75 ton, or more preferably less than 0.5 ton for each ton of LNG produced It would be advantageous to have

  US Pat. No. 6,412,302 to Foglietta describes a feed gas expander-based process that uses two separate closed refrigeration loops to cool the feed gas to form LNG. ing. The first closed refrigeration loop uses a supply gas or a component of the supply gas as a refrigerant. Nitrogen gas is used as a refrigerant for the second closed refrigeration loop. This technique has the advantage of requiring less equipment and upper deck space than a double loop nitrogen expander based process. For example, the volume flow of refrigerant into the low pressure compressor can be reduced by 20 to 50% in this technique compared to a double loop nitrogen expander based process. However, this technology is still limited to capacities below 1.5 MTA.

  U.S. Pat. No. 8,616,012 to Minta describes a feed gas expander based process in which the feed gas is used as a refrigerant in a closed refrigeration loop. Within this closed refrigeration loop, the refrigerant is compressed to a pressure higher than or equal to 1500 psia or more preferably higher than 2500 psia. This refrigerant is then cooled and expanded to achieve a cryogenic temperature. This cooled refrigerant is then used in a heat exchanger to cool the feed gas from a warm temperature to a cryogenic temperature. Next, a subcooled refrigeration loop is used to further cool the feed gas to form LNG. In one embodiment, the subcooled refrigeration loop is a closed loop that uses flash gas as the refrigerant. This feed gas expander based process has the advantage that it is not limited to a train capacity range of less than 1 MTA. A train size of about 6 MTA is considered. However, this technique has the disadvantage that the total number of equipment is increased and the complexity is increased due to the two independent refrigeration loops and their requirement for compression of the feed gas. Furthermore, high pressure operation also means that the equipment and piping will be much heavier than those of other inflator-based processes.

  British Patent 2,486,036, granted to Maunder et al., Is an open loop refrigeration cycle including a pre-cooled expander loop and a liquefied expander loop that liquefy natural gas using the expanded gas phase. The process of the supply gas expander base is described. According to Maunder, including a liquefaction expander in this process significantly reduces the regeneration gas rate and the overall required refrigeration power. This technique is simpler than the technique described by Foglietta and Minta because only one type of refrigerant is used with a single compression string. However, this technique still requires the use of a liquefier inflator that is limited to a capacity of less than 1.5 MTA and is not a standard instrument for LNG production. This technique has also been shown to be less efficient than the technique described by Foglietta and Minta for liquefying dilute natural gas.

US Provisional Patent Application No. 62 / 266,976 US Provisional Patent Application No. 62 / 266,983 US Provisional Patent Application No. 62 / 622,985 US Pat. No. 3,400,547 British Patent 1,596,330 US Pat. No. 6,412,302 US Pat. No. 8,616,012 British Patent 2,486,036

  There remains a need to develop an LNG production process that has the advantages of an inflator-based process, while reducing the facility footprint and having a high LNG production capacity. There is yet another need to develop an LNG technology solution that can better cope with the challenges of ship shaking with gas processing challenges. Such a high volume expander-based liquefaction process is believed to be particularly suitable for FLNG applications where the intrinsic safety and simplicity of the expander-based liquefaction process are highly appreciated.

  The present disclosure provides a method for producing liquefied natural gas (LNG). The natural gas stream is directed to a mechanical refrigeration unit to liquefy the natural gas stream to form a pressurized liquefied natural gas (LNG) stream having a pressure that is greater than 50 psia (345 kPa) and less than 500 psia (3445 kPa). A liquid refrigerant subcool unit is provided at the first location. The liquid refrigerant is generated at a second location that is geographically separated from the first location. The generated liquid refrigerant is transported to the first location. The pressurized LNG stream is subcooled within the liquid refrigerant subcooling unit by exchanging heat between the pressurized LNG stream and at least one stream of liquid refrigerant, thereby producing an LNG stream.

  The present disclosure also provides a system for producing liquefied natural gas (LNG). A pressurized liquefied natural gas (LNG) stream in which a mechanical refrigeration unit liquefies a natural gas stream using a feed gas expander-based process and has a pressure that is greater than 50 psia (345 kPa) and less than 500 psia (3445 kPa) Form. A liquid nitrogen (LIN) subcool unit is disposed at the first location. A liquid nitrogen (LIN) stream is generated at a second location that is geographically separated from the first location. The LIN stream is transported to the LIN subcool unit. The LIN subcooling unit subcools the pressurized LNG stream by exchanging heat between the pressurized LNG stream and at least one of the LIN streams, whereby the LNG stream and at least one evaporation LIN stream are Generate.

  The foregoing has outlined rather broadly the features of the present disclosure in order that the detailed description that follows may be better understood. Additional features are also described herein below.

  These and other features, aspects and advantages of the present disclosure will become apparent from the following description, the appended claims and the accompanying drawings briefly described below.

FIG. 6 is a graph showing a temperature cooling curve for an expander-based heat exchanger process. 1 is a simplified diagram of the value chain of a known FLNG technology. FIG. 6 is a simplified diagram of the value chain of the disclosed embodiment. 1 is a schematic diagram of a system according to disclosed aspects. FIG. 1 is a schematic diagram of a mechanical refrigeration unit according to a disclosed aspect. FIG. 1 is a schematic diagram of a liquid nitrogen (LIN) subcooling unit according to disclosed aspects. FIG. FIG. 4 is a schematic diagram of a LIN subcool unit according to a disclosed aspect. 6 is a flowchart illustrating a method according to the disclosed aspects.

  It should be noted that the drawings are merely examples and are not intended to limit the scope of the present disclosure. Further, the drawings are not generally drawn to scale, but rather are for convenience and clarity in describing various aspects of the present disclosure.

  In order to facilitate an understanding of the principles of the present disclosure, reference will now be made to the features illustrated in the drawings and specific language will be used to describe the same. This description is not intended to limit the scope of the present disclosure. Any alterations and further modifications and further uses of the principles of the present disclosure described herein are intended to be commonly found by those skilled in the art to which the present disclosure pertains. For clarity, some features not related to the disclosure of the present invention may not be shown in the drawings.

  First, for convenience of reference, certain terms used in this application and their meanings used in the context are listed. Unless a term used herein is defined below, it should give the broadest definition that the relevant artisan has given that term as reflected in at least one published document or issued patent. is there. Furthermore, since all equivalents, synonyms, new developments, and terms or techniques that serve the same or similar purpose are considered to fall within the scope of the claims, the techniques of the invention are limited by the use of the terms set forth below. Never happen.

  As those skilled in the art will appreciate, people may refer to the same feature or component under different names. This document does not intend to distinguish between components or features that differ only in name. The drawings are not necessarily to scale. Certain features and components of the specification may be shown in exaggerated scale or in schematic form, with some details of conventional elements not being shown for clarity and brevity. There is a case. When referring to the drawings described herein, the same reference numbers may be referred to in the drawings for simplicity. In the following description and claims, the terms “including” and “comprising” are used non-limitingly and therefore should be construed to mean “including but not limited to”.

  A noun that is not a plural expression is not necessarily limited to mean only one, but rather is comprehensive and non-limiting to include a plurality of such elements as appropriate.

  As used herein, the terms “approximate”, “about”, “substantial”, and similar terms refer to accepted usage common to those of ordinary skill in the art to which the disclosed subject matter relates. It shall have a broad and harmonious meaning. These terms are intended to allow the description of certain features to be described and claimed without limiting the scope of these features to a given exact numerical range. Those of skill in the art who review the disclosure must understand. Accordingly, these terms should be construed as indicating that insubstantial or insignificant modifications or changes in the subject matter described are considered to be within the scope of the present disclosure.

  The term “heat exchanger” refers to a device designed to efficiently transfer or “exchange” heat from one substance to another. Exemplary heat exchanger types include co-current or counter-current heat exchangers, indirect heat exchangers (eg, spiral fin heat exchangers, plate fin heat exchangers such as brazed aluminum plate fin molds, shell-and- -Tube heat exchangers, etc.), direct contact heat exchangers, or any combination thereof.

  A “dual-purpose carrier” refers to a vessel that is capable of (a) transporting LIN to a natural gas and / or export terminal for LNG, and (b) transporting LNG to an LNG import terminal.

  As mentioned above, the conventional LNG cycle consists of (a) initial treatment of a natural gas source to remove contaminants such as water, sulfur compounds, and carbon dioxide, (b) such as propane, butane, pentane. Separation of some heavier hydrocarbon gases by various possible methods such as self-freezing, external refrigeration, dilute oil, (c) to form LNG at or near atmospheric pressure at about −160 ° C. Refrigeration of natural gas by external refrigeration, (d) transportation of LNG products to the market place by ship or tanker designed for transportation, and (e) addition that can be distributed to natural gas consumers Including re-pressurization and regasification of LNG in a regasification plant to form a pressurized natural gas stream. The present disclosure generally involves liquefying natural gas using liquid nitrogen (LIN). In general, the step of producing LNG using LIN is the step (c) described above is replaced by a natural gas liquefaction process using a significant amount of LIN as an open loop cooling source, Modify e) to use the energy of cryogenic LNG to facilitate liquefaction of nitrogen gas to form a LIN that can then be transported to a resource location and used as a refrigeration source for LNG production This is an unprecedented LNG cycle. The disclosed LIN to LNG concept may further include transport of LNG in a ship or tanker from a resource location (export terminal) to a market location (import terminal) and reverse transport from the LIN market location to the resource location. it can.

  Aspects disclosed herein provide a method for enhancing a mechanical refrigeration process for LNG production using liquid refrigerant generated at different locations to subcool liquefied natural gas resulting from a mechanical refrigeration process To do. More specifically, a process that can direct the treated natural gas to a mechanical refrigeration process is described. Natural gas can be fully liquefied in a mechanical refrigeration process to produce a pressurized LNG stream, where the pressure of the pressurized LNG stream is greater than 50 psia (or 345 kPa) and less than 500 psia (or 3445 kPa), or More specifically, it is higher than 100 psia (or 690 kPa) and lower than 400 psia (or 2758 kPa), or more specifically higher than 200 psia (or 1379 kPa) and lower than 300 psia (or 2068 kPa). The pressurized LNG stream can then be subcooled by exchanging heat with at least one liquid refrigerant stream to form an LNG stream. The liquid refrigerant stream is generated in a different geographical location from where the natural gas is liquefied, which is 50 miles, or 100 miles, or 200 miles, or 500 miles, or 1, from where the natural gas is liquefied. It may be 1,000 miles or 1,000 miles. Mechanical refrigeration processes can be any single mixed refrigerant process, pure component cascade refrigerant process, double mixed refrigerant process, expander-based refrigeration process, or any natural gas stream that can be liquefied to produce a pressurized LNG stream. Other known refrigeration processes can be used.

  In certain aspects, the expander-based process for LNG production can be enhanced by using LIN generated at different locations to subcool the pressurized LNG resulting from the expander-based process. In order to make natural gas suitable for liquefaction, impurities such as water, heavy hydrocarbons, and acid gases can be removed when the natural gas is processed and present. The treated natural gas can be fully liquefied in an expander-based process to produce a pressurized LNG stream, the pressure of the pressurized LNG stream being greater than 50 psia (or 345 kPa) and 500 psia (or 3445 kPa). ), Or more specifically greater than 100 psia (or 690 kPa) and less than 400 psia (or 2758 kPa), or more specifically greater than 200 psia (or 1379 kPa) and less than 300 psia (or 2068 kPa). The pressurized LNG stream can then be subcooled by exchanging heat with at least one LIN stream to form an LNG stream. The expander based process may be a nitrogen gas expander based process or may be a feed gas expander based process.

  FIG. 1 shows a typical temperature cooling curve 100 for an expander-based liquefaction process. The higher temperature curve 104 is the temperature curve for the natural gas stream. The lower temperature curve 102 is a combined temperature curve of the cold and hot cooling streams. As shown, the cooling curve is characterized by three temperature pinch points. The lowest temperature pinch point 106 is the cooler of the two cooling streams and typically occurs where the cold cooling stream enters the heat exchanger. The intermediate temperature pinch point 108 is the second cooling stream, typically occurring where the hot cooling stream enters the heat exchanger. A warm temperature pinch point 110 occurs where the cold and hot cooling streams exit the heat exchanger. The lowest temperature pinch point 106 sets the required flow rate for the cold cooling stream. Since the cold cooling stream is first cooled by the hot cooling stream before it is expanded to a lower temperature, the flow of the cold cooling stream also affects the flow required for the hot cooling stream. One way to increase the capacity of the expander-based process without significantly increasing the equipment size and power required is to increase the temperature of the lowest temperature pinch point. In such cases, additional refrigeration is required to subcool the pressurized LNG coming from the expander-based process to produce LNG. Subcooling pressurized LNG in a separate mechanical refrigeration cycle is neither advantageous nor efficient. For this reason, the aspects described herein propose the use of liquid refrigerant generated at different locations to subcool the pressurized LNG. The liquid refrigerant can be LIN.

  Under certain circumstances, the liquid refrigerant can be generated with an amount of energy that makes the overall process of generating pressurized LNG and liquefied refrigerant thermodynamically more efficient than conventional LNG production processes. For example, the liquid refrigerant can be nitrogen generated from an air separation plant, and the nitrogen is liquefied using cold heat obtained from LNG gasification. In general, during the gasification of LNG, all the energy obtained from the gasification stage of LNG is lost to the environment. Using this energy allows the LIN to be generated at a low energy cost sufficient to make the overall energy requirement of the disclosed aspects comparable or less than the energy cost of a conventional LNG production process. To do.

  In accordance with the disclosed aspects, the expander-based process may be a feed gas expander-based process. The feed gas expander based process may be an open loop feed gas process where the recycle loop has a warm end expander loop and a cold end expander loop. The warm end expander can discharge a first cooling stream and the cold end expander can discharge a second cooling stream. The temperature of the first cooling stream can be higher than the temperature of the second cooling stream. The pressure of the first cooling stream can be the same as or similar to the pressure of the second cooling stream. The cold end expander can discharge a two-phase stream that is separated into a second cooling stream and a second pressurized LNG stream. Natural gas can be treated to make it suitable for liquefaction, and impurities such as water, heavy hydrocarbons, and acid gases, if present, can be removed. The treated natural gas can be completely liquefied by indirect heat exchange between the first and second cooling streams to produce a first pressurized LNG stream. The first pressurized LNG stream can be combined with the second pressurized LNG stream to form one pressurized LNG stream. The pressure of the pressurized LNG stream is greater than 50 psia (or 345 kPa) and less than 500 psia (or 3445 kPa), or more specifically greater than 100 psia (or 690 kPa) and less than 400 psia (or 2758 kPa), or more specifically 200 psia ( Or 1379 kPa) and less than 300 psia (or 2068 kPa). The pressurized LNG stream can be subcooled by exchanging heat with at least one LIN stream to form an LNG stream. The subcooling process can include the use of at least one heat exchanger that allows indirect heat exchange between the evaporating LIN stream and the pressurized LNG stream. The subcooling process can further include other equipment such as a compressor, expander, separator, and / or other known equipment to facilitate cooling of the pressurized LNG stream. After heat exchange with the pressurized LNG stream, the evaporated LIN stream can be used to liquefy the second stream of processed natural gas to produce an additional pressurized LNG stream. The additional pressurized LNG stream can be combined with the pressurized LNG stream before subcooling the pressurized LNG stream with LIN.

  In one disclosed aspect, the produced LNG is loaded into an LNG carrier and / or dual-purpose carrier at the LNG production site and transported to an import terminal at a different location where the LNG is unloaded and regasified. Is done. The cold energy derived from LNG gasification can be used to liquefy the nitrogen that is subsequently loaded into the LNG carrier and / or dual-purpose carrier and sent back to the LNG production site, where the LIN was processed Used to liquefy natural gas.

  2A and 2B are simplified diagrams highlighting the difference between the value chain of the embodiment disclosed herein and the value chain of conventional FLNG technology, where the FLNG facility is required to process and liquefy natural gas. Accommodates all or virtually all equipment. As shown in FIG. 2A, the LNG cargo ship 200a transports the LNG from the FLNG facility 202 to the land import terminal 204, where the LNG is unloaded and regasified. At this time, the LNG cargo ship 200b whose cargo and ballast are empty returns to the FLNG facility, and LNG is loaded again. In contrast, the embodiment disclosed herein and shown in FIG. 2 provides a floating processing unit (FPU) 206 having a much smaller footprint than the FLNG facility 202 (FIG. 2A). Referring to FIG. 2B, a LIN cargo ship or dual purpose ship 208a loaded with LIN at the import terminal 204 arrives at the FPU 206 and unloads the LIN load into a storage tank on and / or in the FPU. On the FPU 206, a mechanical refrigeration unit cools natural gas to a pressurized LNG stream. The pressurized LNG stream is then subcooled in the LIN subcool unit on the FPU 206 to produce LNG. The produced LNG is transported to the LNG cargo ship or the dual purpose ship 208b. At this point, the LNG cargo ship or dual purpose ship 208b loaded with LNG is sent to the import terminal 204, where the LNG is unloaded and regasified. The cold energy from the LNG regasification is used to liquefy the nitrogen at the import terminal 204. Nitrogen liquefied at the import terminal 204 can be generated by the air separation unit 210. The air separation unit 210 may be part of the import terminal 204 or may be in the import terminal 204 or a separate facility from the import terminal 204. The LIN can then be loaded into a LIN cargo ship or a dual purpose ship, which returns to the FPU 206 to repeat the liquefaction process.

  In another aspect, LIN can be used to liquefy LNG boil-off gas from a tank during LNG production, transport, and / or unloading. In another aspect, LIN from the subcooling process and / or evaporated LIN can be used to cool the inlet air entering the gas turbine of the mechanical refrigeration process. In another aspect, LIN and / or LIN boil-off gas can be used to keep the liquefier equipment cool during the liquefaction process turndown or shutdown. In another aspect, nitrogen vapor can be used to defrost a cryogenic heat exchanger during the period between LNG production. Nitrogen vapor containing pollutants can be released to the atmosphere.

  FIG. 3 is a schematic diagram of a system 300 in accordance with the disclosed aspects. Natural gas can be treated to produce a treated natural gas stream 302 suitable for liquefaction, and impurities such as water, heavy hydrocarbons, and acid gases, if present, can be removed. The treated natural gas stream 302 can be directed to a mechanical refrigeration unit 304 that fully liquefies the treated natural gas 302 to produce a pressurized LNG stream 306. The pressure of the pressurized LNG stream 306 is greater than 50 psia (or 345 kPa) and less than 500 psia (or 3445 kPa), or more specifically greater than 100 psia (or 690 kPa) and less than 400 psia (or 2758 kPa), or more specifically 200 psia. (Or 1379 kPa) and less than 300 psia (or 2068 kPa). The mechanical refrigeration unit 304 liquefies a single mixed refrigerant process, a pure component cascade refrigerant process, a double mixed refrigerant process, an expander-based refrigeration process, or a processed natural gas stream 302 into a pressurized LNG stream 306. Any other known refrigeration process can be used. The mechanical refrigeration unit 304 can have a gas turbine that is used to provide mechanical power to drive a compressor within the mechanical refrigeration unit 304. The pressurized LNG stream 306 can be directed to a liquid refrigerant subcooling unit 308 that forms a LNG stream 312 that is subcooled by heat exchange of the pressurized LNG stream 306 with the liquid refrigerant stream 310. The liquid refrigerant stream 310 is generated at a location different from the location of the mechanical refrigeration unit 304 and the liquid refrigerant subcool unit 308. The liquid refrigerant stream 310 is evaporated and heated in the liquid refrigerant subcool unit 308 and then exits the liquid refrigerant subcool unit 308 as the refrigerant gas exhaust 314. The liquid refrigerant subcool unit 308 has at least one heat exchanger that allows indirect heat exchange between the liquid refrigerant stream 310 and the pressurized LNG stream 306. The liquid refrigerant subcooling unit 308 may further include other equipment such as a compressor, expander, separator, and / or other known equipment to facilitate cooling of the pressurized LNG stream 306. After heat exchange with the pressurized LNG stream 306, the evaporated LIN stream 310 can be used to liquefy the treated second stream of natural gas 316 to form an additional pressurized LNG stream. . Additional pressurized LNG streams can be combined with the pressurized LNG stream 306 before subcooling the pressurized LNG stream 306 with the liquid refrigerant stream 310 to form the pressurized LNG stream 312.

  FIG. 4 is a diagram of a mechanical refrigeration unit 400 in accordance with the disclosed aspects. The mechanical refrigeration unit 400 includes a feed gas expander based process. Processes natural gas liquefied by mechanical refrigeration unit 400 to produce a processed natural gas stream 402 suitable for liquefaction, and removes impurities such as water, heavy hydrocarbons, and acid gases when present can do. A combined natural gas stream 402 is combined with a recycled refrigerant stream 404 using a combination device 403. The combined natural gas stream 405 is then separated by a one or more manifolds, shunts, or other types of separators 406, 408, 409 and second processed as described herein. Natural gas stream 410, first refrigerant stream 412, second refrigerant stream 414, and processed natural gas substream 415 that is liquefied using liquid refrigerant can be generated. The first refrigerant stream 412 is expanded in the first expander 417 to produce a first cooling stream 416. The first cooling stream 416 enters at least one heat exchanger 418 that exchanges heat with the second treated natural gas stream 410 and the second refrigerant stream 414 to cool the two streams. The warmed first cooling stream 416 exits at least one heat exchanger 418 as a first hot stream 420. The second refrigerant stream 414 is cooled by at least one heat exchanger 418 and then expanded by the second expander 422 to produce a two-phase stream 424. The pressure of the two-phase stream 424 can be the same as or approximately the same as the pressure of the first cooling stream 416. The two-phase stream 424 can be separated into its vapor component and its liquid component in a two-phase separator 426 to form a second cooling stream 428 and a second pressurized LNG stream 430. The temperature of the first cooling stream 416 can be higher than the temperature of the second cooling stream 428. The second pressurized LNG stream 430 can be compressed to a higher pressure after leaving the two-phase separator 426 using the pump 432. The second cooling stream 428 may enter at least one heat exchanger 418 that exchanges heat with the second processed natural gas stream 410 and the second refrigerant stream 414 to cool those streams. . The warmed second cooling stream exits at least one heat exchanger 418 as a second warm stream 434. The second treated natural gas stream 410 can be heat exchanged with the first cooling stream 416 and the second cooling stream 428 to produce a first pressurized LNG stream 436. After the first pressurized LNG stream 436 exits the at least one heat exchanger 418, the first pressurized LNG stream 436 can be decompressed with a hydraulic turbine 437 or other decompression device. The first pressurized LNG stream 436 can be combined with the second pressurized LNG stream 430 to form a combined pressurized LNG stream 438. The pressure of the combined pressurized LNG stream 438 is greater than 50 psia (or 345 kPa) and less than 500 psia (or 3445 kPa), or more specifically greater than 100 psia (or 690 kPa) and less than 400 psia (or 2758 kPa), or more specifically It may be greater than 200 psia (or 1379 kPa) and less than 300 psia (or 2068 kPa). As further described herein, the pressurized LNG stream 438 can be directed to the LIN subcooling unit.

  The first thermal stream 420 can be combined with the second thermal stream 434 in the combination device 440 to form a combined thermal refrigerant stream 442. The combined hot refrigerant stream 442 can be compressed in multiple compressor stages to form a recycled refrigerant stream 404. The compressor stage can include a first compressor stage 444, a second compressor stage 446, and a third compressor stage 448. The first compressor stage 444 can be driven by a gas turbine (not shown). The second compressor stage 446 can be driven solely by the shaft power generated by the first expander 417. The third compressor stage 448 can be driven solely by the shaft power generated by the second expander 422. The coolers 450, 452, and 454 can cool the combined hot refrigerant stream 442 after the first, second, and third compressor stages 444, 446, 448, respectively.

  FIG. 5 is a schematic diagram of a LIN subcool unit 500 in accordance with the disclosed aspects. The LIN subcool unit 500 can be used with the mechanical refrigeration unit 400 shown in FIG. The LIN generated at a location different from the location of the LIN subcool unit 500 is transported to the location of the LIN subcool unit 500 and directed to the at least one heat exchanger 502 as a LIN stream 504. The LIN stream 504 evaporated and evaporated by subcooling the pressurized LNG stream 506 (which can be the same as the combined pressurized LNG stream 438 of FIG. 4) in at least one heat exchanger 502. A nitrogen stream 508 and an LNG stream 510 are generated. The evaporated nitrogen stream 508 is directed to the second heat exchanger 512 to liquefy the processed natural gas stream 514, which can be the same as the processed natural gas substream 415, and to add an additional pressurized LNG stream 516. Can be formed. The additional pressurized LNG stream 516 can be combined with the pressurized LNG stream 506 at the combination device 518 before entering the at least one heat exchanger 502. The additional pressurized LNG stream 516 can be depressurized with a hydraulic turbine 520 or other depressurization device before being combined with the pressurized LNG stream 506. The evaporated nitrogen stream 508 is heated in the second heat exchanger 512 by the treated natural gas stream 514 and released into the atmosphere or in other areas of the gas treatment facility where the LIN subcool unit 500 is located. To form a nitrogen release gas stream 522 that can be used in

  FIG. 6 is a schematic diagram of a LIN subcool unit 600 in accordance with the disclosed aspects. The LIN subcool unit 600 can be used with the mechanical refrigeration unit 400 shown in FIG. The LIN generated at a location different from the location of the LIN subcool unit 600 is transported from the different location and directed to the LIN subcool unit 600 as a LIN stream 602. Pump 604 can pump LIN stream 602 to a pressure greater than 400 psi to form high pressure LIN stream 606. The high pressure LIN stream 606 exchanges heat with the pressurized LNG stream 608 (which can be the same as the combined pressurized LNG stream 438 of FIG. 4) in the at least one heat exchanger 610 for first application. A warm nitrogen gas stream 612 is formed. The first warm nitrogen gas stream 612 can be expanded in the first expander 614 to produce a first further cooled nitrogen gas stream 616. The first further cooled nitrogen gas stream 616 exchanges heat with the pressurized LNG stream 608 in at least one heat exchanger 610 to form a second warmed nitrogen gas stream 618.

  The second warm nitrogen gas stream 618 is compressed by exchanging heat indirectly with other process streams, for example, in the second heat exchanger 619 before being compressed in one or more compressor stages. A nitrogen gas stream 620 can be formed. As shown in FIG. 6, one or more compressor stages may have two compressor stages including a first compressor stage 622 and a second compressor stage 624. The second compressor stage 624 can be driven solely by the shaft power generated by the first expander 614. The first compressor stage 622 can be driven solely by the shaft power generated by the second expander 626. After each compression stage, the compressed nitrogen gas stream 620 can be cooled individually by indirect heat exchange with the environment in the coolers 628, 630. The compressed nitrogen gas stream 620 can be expanded in the second expander 626 to produce a second, further cooled nitrogen gas stream 632. The second further cooled nitrogen gas stream 632 is heat exchanged with the pressurized LNG stream 608 in at least one heat exchanger 610 to form a third warm nitrogen gas stream 634. Pressurized LNG stream 608 is subcooled to exchange LNG stream 636 by exchanging heat with high pressure LIN stream 606, first further cooled nitrogen gas stream 616, and second further cooled nitrogen gas stream 632. Form. The third heated nitrogen gas stream 634 is directed to the third heat exchanger 638 and liquefies the processed natural gas stream 640, which can be the same as the processed natural gas substream 415 of FIG. An additional pressurized LNG stream 642 can be formed. The additional pressurized LNG stream 642 can be combined with the pressurized LNG stream 608 in the combination device 644 before subcooling the pressurized LNG stream 608 in the at least one heat exchanger 610. Prior to being combined with the pressurized LNG stream 608, the additional pressurized LNG stream 642 can be depressurized with the hydraulic turbine 646. The third warm nitrogen gas stream 634 is heated by the treated natural gas stream 640 and released into the atmosphere or used in other areas of the gas treatment facility where the LIN subcool unit 600 is located. A possible nitrogen release gas 648 can be formed. The LIN subcool unit 600 shown in FIG. 6 reduces the LIN requirement for subcooling the pressurized LNG stream by about 20-25% compared to the LIN subcool unit 500 shown in FIG. However, the selection of the subcool unit may depend on criteria such as the cost of the LIN and the available upper deck space for the LIN storage and / or the LIN subcool unit itself.

  FIG. 7 is a flowchart of a method 700 for producing liquefied natural gas (LNG). At block 702, a natural gas stream is directed to a mechanical refrigeration unit to liquefy the natural gas stream and have a pressure liquefied natural gas (LNG) stream having a pressure greater than 50 psia (345 kPa) and less than 500 psia (3445 kPa). Is formed. At block 704, a liquid refrigerant subcooling unit is provided at the first location. At block 706, liquid refrigerant is generated at a second location that is geographically separated from the first location. At block 708, the generated liquid refrigerant is transported to the first location. At block 710, the pressurized LNG stream is subcooled within the liquid refrigerant subcooling unit by exchanging heat between the pressurized LNG stream and at least one stream of liquid refrigerant, thereby producing an LNG stream.

  The steps shown in FIG. 7 are provided for illustrative purposes only, and no particular steps may be required to perform the disclosed method. Furthermore, FIG. 7 does not show all possible steps that can be performed. The claims and only that define the disclosed system and method.

  The embodiments described herein have several advantages over known techniques. For example, the described aspects can significantly increase the capacity of conventional mechanical refrigeration processes without significantly increasing the power and footprint required for the mechanical refrigeration process. For example, compared to the known feed gas expander-based process, the feed gas expander-based process coupled to the LIN subcool described herein can increase LNG by about 50% with comparable mechanical refrigeration power. Can be produced. The amount of LIN required is about 0.28 tons of LIN for each ton of LNG produced. By reducing the amount of LIN, this technique becomes particularly suitable for FLNG applications. Using the disclosed aspects, the 50% extra throughput due to the feed gas expander-based process requires the required volumetric flow and cryogenic heat exchanger load to the low pressure compressor compared to known feed gas expander technology. Are only increased by about 10% each.

The disclosed aspects can include any combination of the methods and systems shown in the following numbered paragraphs. Since any number of variations can be envisaged from the above description, this should not be regarded as a complete list of all possible aspects.
1. Directing the natural gas stream to a mechanical refrigeration unit to liquefy the natural gas stream to form a pressurized liquefied natural gas (LNG) stream having a pressure greater than 50 psia (345 kPa) and less than 500 psia (3445 kPa); Providing a liquid refrigerant subcooling unit at a first location, generating liquid refrigerant at a second location geographically separated from the first location, and transporting the generated liquid refrigerant to the first location And subcooling the pressurized LNG stream within the liquid refrigerant subcooling unit by exchanging heat between the pressurized LNG stream and at least one stream of liquid refrigerant, thereby producing an LNG stream. A method for producing liquefied natural gas (LNG).
2. The method of paragraph 1, wherein the mechanical refrigeration unit comprises an expander-based refrigeration process.
3. Item 3. The method of Item 2, wherein the expander-based refrigeration step is a feed gas expander-based step.
4). Item 4. The method of Item 3, wherein the feed gas expander-based process is an open loop feed gas expander-based process.
5. Item 4. The method of Item 3, wherein the supply gas expander-based process is a closed-loop supply gas expander-based process.
6). A feed gas expander based process includes discharging a first cooling stream from the warm end expander and discharging a two phase stream from the cold end expander, wherein the temperature of the first cooling stream is two phase. The method of paragraph 3, wherein the temperature is higher than the temperature of the stream.
7). The method of paragraph 3, wherein the pressurized LNG stream is a first pressurized LNG stream, and the method further comprises the step of separating the two-phase stream into a second cooling stream and a second pressurized LNG stream.
8). A feed gas expander-based process includes discharging a first cooling stream from the warm end expander and discharging a second cooling stream from the cold end expander, wherein the temperature of the first cooling stream is Item 4. The method of Item 3, wherein the temperature is higher than the temperature of the second cooling stream.
9. Item 9. The method of Item 7 or 8, wherein the pressure of the first cooling stream is the same as or substantially the same as the pressure of the second cooling stream.
10. The method of clause 9, further comprising the step of mixing the second pressurized LNG stream with the first pressurized LNG before directing the pressurized LNG stream to the liquid refrigerant subcooling unit.
11. Item 11. The method according to any one of Items 1 to 10, wherein the liquid refrigerant subcool unit includes at least one heat exchanger.
12 Item 12. The method according to any one of Items 1 to 11, wherein the liquid refrigerant subcool unit includes at least one compressor and / or expander.
13. Item 13. The method of any of paragraphs 1-12, wherein the evaporated liquid refrigerant stream is used to liquefy the second treated natural gas stream to produce an additional pressurized LNG stream.
14 The method of paragraph 13, wherein the additional pressurized LNG stream is mixed with the pressurized LNG stream prior to subcooling the pressurized LNG stream with a liquid refrigerant.
15. Item 15. The method according to any one of Items 1 to 14, further comprising disposing a mechanical refrigeration unit and a liquid refrigerant subcooling unit on the floating LNG facility.
16. Item 16. The method according to any one of Items 1 to 15, further comprising the step of reliquefying the LNG boil-off gas using a liquid refrigerant.
17. Item 1-16 wherein the liquid refrigerant and / or boil-off gas of the liquid refrigerant is used to keep the mechanical refrigeration unit and / or liquid refrigerant subcooling unit equipment cool during the mechanical refrigeration unit turndown and / or shutdown period. Either way.
18. Item 18. The method according to any one of Items 1 to 17, wherein the heat exchanger used for heat exchange is defrosted using the hot liquid refrigerant vapor.
19. Transporting an LNG stream from a first location to a second location within a dual purpose carrier, and first from a second location within the dual purpose carrier after the LNG stream is unloaded from the dual purpose carrier. The method according to any one of Items 1 to 18, further comprising the step of transporting the liquid refrigerant to the location.
20. Item 20. The method of any of paragraphs 1-19, wherein the mechanical refrigeration unit comprises one of a single mixed refrigerant process, a pure component cascade refrigerant process, or a double mixed refrigerant process.
21. The method of any of paragraphs 1-20, wherein the pressurized LNG stream has a pressure that is greater than 100 psia (690 kPa) and less than 400 psia (2758 kPa).
22. The method of any of paragraphs 1-21, wherein the pressurized LNG stream has a pressure that is greater than 200 psia (1379 kPa) and less than 300 psia (2068 kPa).
23. Item 23. The method according to any one of Items 1 to 22, wherein the liquid refrigerant contains liquid nitrogen (LIN).
24. 24. The method of paragraph 23, further comprising the step of generating LIN by exchanging heat with LNG during LNG regasification.
25. 24. The method of paragraph 23, further comprising pressurizing LIN to a pressure greater than 400 psia (2758 kPa) to form a high pressure liquid nitrogen stream.
26. 26. The method of paragraph 25, further comprising the step of heat exchanging between the high pressure liquid nitrogen stream and the pressurized LNG stream to form a hot nitrogen gas stream.
27. Of the at least one heated nitrogen gas stream in the at least one expander service to reduce the pressure of the at least one heated nitrogen gas stream, thereby producing at least one further cooled nitrogen gas stream. 24. The method of paragraph 23, further comprising the step of reducing the pressure within the liquid refrigerant subcooling unit.
28. 28. The method of paragraph 27, wherein the at least one further cooled nitrogen gas stream is heat exchanged with the pressurized LNG stream to form a heated nitrogen gas stream.
29. 28. The method of clause 27, further comprising combining the at least one expander service with at least one generator that generates power.
30. 28. The method of paragraph 27, further comprising combining at least one expander service with at least one compressor used to compress the warm nitrogen gas stream.
31. 31. The method of any of paragraphs 1-30, further comprising producing at least one LNG stream from the plurality of mechanical refrigeration units to the liquid refrigerant subcooling unit.
32. The feed gas expander based process was used to liquefy the natural gas stream and configured to form a pressurized liquefied natural gas (LNG) stream at a pressure greater than 50 psia (345 kPa) and less than 500 psia (3445 kPa) A mechanical refrigeration unit, a liquid nitrogen (LIN) subcool unit located at the first location, and liquid nitrogen generated at a second location geographically separated from the first location and transported to the LIN subcool unit The LIN subcooling unit subcools the pressurized LNG stream by exchanging heat between the pressurized LNG stream and at least one of the LIN streams, and thereby the LNG stream Producing at least one evaporated LIN stream System for the production of sea urchin composed liquefied natural gas (LNG).
33. A mechanical refrigeration unit includes a warm end expander configured to discharge a first cooling stream therefrom, and a cold end expander configured to discharge a two phase stream therefrom, the first The temperature of the cooling stream is higher than the temperature of the two-phase stream, the pressurized LNG stream is a first pressurized LNG stream, the two-phase stream is a second cooled stream and a second pressurized LNG stream, 32. The system of clause 32 configured to be divided into:
34. A mechanical refrigeration unit includes a warm end expander configured to discharge a first cooling stream therefrom, and a cold end expander configured to discharge a second cooling stream therefrom; The system of paragraph 32, wherein the temperature of the first cooling stream is higher than the temperature of the second cooling stream.
35. 35. The system of paragraph 33 or 34, wherein the pressure of the first cooling stream is the same as or substantially the same as the pressure of the second cooling stream.
36. 36. The system of paragraph 35, wherein the second pressurized LNG stream is mixed with the first pressurized LNG before directing the pressurized LNG stream to the liquid refrigerant subcooling unit.
37. 36. The system of any of paragraphs 32-35, wherein the at least one evaporated liquid refrigerant stream is used to liquefy the second treated natural gas stream to produce an additional pressurized LNG stream.
38. Item 37. The system according to any one of Items 32 to 36, wherein the mechanical refrigeration unit and the liquid refrigerant subcool unit are arranged on the floating LNG facility.
39. Liquid in the dual-purpose carrier from the second location to the first location after the LNG stream has been unloaded from the dual-purpose carrier to transport the LNG stream from the first location to the second location 38. The method of any of paragraphs 32-37, further comprising a dual purpose carrier configured to transport the refrigerant.

  It should be understood that many variations, modifications, and alternatives to the previous disclosure are possible without departing from the scope of the present disclosure. Accordingly, the above description is not intended to limit the scope of the present disclosure. Rather, the scope of the disclosure should be determined only by the appended claims and their equivalents. It is contemplated that the structure and features of embodiments of the present invention can be changed, rearranged, replaced, deleted, duplicated, combined, or added to each other.

Claims (28)

A method for producing liquefied natural gas (LNG) comprising:
Directing the natural gas stream to a mechanical refrigeration unit to liquefy the natural gas stream to form a pressurized liquefied natural gas (LNG) stream having a pressure greater than 50 psia (345 kPa) and less than 500 psia (3445 kPa); ,
Providing a liquid refrigerant subcooling unit at a first location;
Generating a liquid refrigerant at a second location geographically separated from the first location;
Transporting the generated liquid refrigerant to the first location;
Subcooling the pressurized LNG stream in the liquid refrigerant subcooling unit by exchanging heat between the pressurized LNG stream and at least one stream of the liquid refrigerant, thereby producing an LNG stream; including,
A method characterized by that. The mechanical refrigeration unit includes an expander-based refrigeration process,
The method of claim 1. The expander-based refrigeration process is one of an open-loop feed gas expander-based process and a closed-loop feed gas expander-based process.
The method of claim 2. The expander-based refrigeration process includes:
Discharging the first cooling stream from the warm end expander;
Discharging the two-phase stream from the cold end expander;
A supply gas expander based process comprising:
The temperature of the first cooling stream is higher than the temperature of the two-phase stream;
The method of claim 2. The pressurized LNG stream is a first pressurized LNG stream;
The method further includes separating the two-phase stream into a second cooling stream and a second pressurized LNG stream.
The method of claim 4. The expander-based refrigeration process includes:
Discharging the first cooling stream from the warm end expander;
Discharging a second cooling stream from the cold end expander;
A supply gas expander based process comprising:
The temperature of the first cooling stream is higher than the temperature of the second cooling stream;
The method of claim 3. The pressure of the first cooling stream is the same as or substantially the same as the pressure of the second cooling stream;
The method according to claim 5 or 6. Further comprising mixing the second pressurized LNG stream with the first pressurized LNG before directing the pressurized LNG stream to the liquid refrigerant subcooling unit;
The method of claim 7. The liquid refrigerant subcool unit is:
Comprising at least one heat exchanger, or at least one compressor and / or expander,
9. A method according to any one of claims 1 to 8. Liquefying a second treated natural gas stream using the evaporated liquid refrigerant stream to produce an additional pressurized LNG stream;
Mixing the additional pressurized LNG stream with the pressurized LNG stream prior to the subcooling of the pressurized LNG stream with the liquid refrigerant.
10. A method according to any one of claims 1-9. Further comprising disposing the mechanical refrigeration unit and the liquid refrigerant subcooling unit on a floating LNG facility,
11. A method according to any one of claims 1 to 10. Re-liquefying LNG boil-off gas using the liquid refrigerant;
12. A method according to any one of the preceding claims. The liquid refrigerant and / or liquid refrigerant boil-off gas is used to keep the mechanical refrigeration unit and / or liquid refrigerant subcooling unit equipment cool during the mechanical refrigeration unit turndown and / or shutdown period,
13. A method according to any one of claims 1-12. The hot liquid refrigerant vapor is used to defrost the heat exchanger used to exchange heat,
14. A method according to any one of claims 1 to 13. Transporting the LNG stream from the first location to the second location within a dual purpose carrier ship;
Transporting the liquid refrigerant from the second location to the first location within the dual-purpose carrier after the LNG stream has been unloaded from the dual-purpose carrier.
15. A method according to any one of claims 1 to 14. The mechanical refrigeration unit includes one of a single mixed refrigerant process, a pure component cascade refrigerant process, or a double mixed refrigerant process.
16. A method according to any one of claims 1 to 15. The pressurized LNG stream has a pressure that is greater than 100 psia (690 kPa) and less than 400 psia (2758 kPa);
The method according to any one of claims 1 to 16. The pressurized LNG stream has a pressure that is greater than 200 psia (1379 kPa) and less than 300 psia (2068 kPa);
18. A method according to any one of claims 1 to 17. The liquid refrigerant includes liquid nitrogen (LIN),
The method comprises
Further comprising generating said LIN by exchanging heat with LNG during LNG regasification;
The method according to any one of claims 1 to 18. The liquid refrigerant includes liquid nitrogen,
The method comprises
Pressurizing the LIN to a pressure greater than 400 psia (2758 kPa) to form a high pressure liquid nitrogen stream;
Exchanging heat between the high pressure liquid nitrogen stream and the pressurized LNG stream to form a hot nitrogen gas stream;
At least one warmed natural gas in at least one expander service to reduce the pressure of the at least one warmed nitrogen gas stream, thereby producing at least one further cooled nitrogen gas stream Reducing the pressure of the stream within the liquid refrigerant subcooling unit,
20. A method according to any one of claims 1-19. The at least one further cooled nitrogen gas stream exchanges heat with the pressurized LNG stream to form a heated nitrogen gas stream;
The method of claim 20. The at least one inflator service;
Further comprising coupling with at least one generator for generating electrical power or at least one compressor used to compress the heated nitrogen gas stream;
The method of claim 20. Further comprising producing at least one LNG stream from a plurality of mechanical refrigeration units to the liquid refrigerant subcool unit from a pressurized LNG stream;
23. A method according to any one of claims 1 to 22. A system for producing liquefied natural gas (LNG),
Configured to liquefy a natural gas stream using a feed gas expander based process to form a pressurized liquefied natural gas (LNG) stream having a pressure greater than 50 psia (345 kPa) and less than 500 psia (3445 kPa) A mechanical refrigeration unit,
A liquid nitrogen (LIN) subcooling unit disposed in the first location;
A liquid nitrogen (LIN) stream produced at a second location geographically separated from the first location and transported to the LIN subcooling unit;
The LIN subcooling unit subcools the pressurized LNG stream by exchanging heat between the pressurized LNG stream and at least one of the LIN streams, thereby LNG stream and at least one evaporation. Configured to generate a LIN stream,
A system characterized by that. The mechanical refrigeration unit is
A warm end expander configured to discharge a first cooling stream therefrom;
A cold end expander configured to discharge a two-phase stream therefrom,
The temperature of the first cooling stream is higher than the temperature of the two-phase stream;
The pressurized LNG stream is a first pressurized LNG stream;
The two-phase stream is configured to be divided into a second cooling stream and a second pressurized LNG stream;
25. The system according to claim 24. The mechanical refrigeration unit is
A warm end expander configured to discharge a first cooling stream therefrom;
A cold end expander configured to discharge a second cooling stream therefrom,
The temperature of the first cooling stream is higher than the temperature of the second cooling stream;
25. The system according to claim 24. The mechanical refrigeration unit and the liquid refrigerant subcool unit are disposed on a floating LNG facility,
27. A system according to any one of claims 24 to 26. Transporting the LNG stream from the first location to the second location and unloading the subcooled LNG stream from the second location within the dual-purpose carrier after the unloading from the dual-purpose carrier. Further comprising a dual-purpose carrier configured to transport the liquid refrigerant to one location;
28. A system according to any one of claims 24 to 27.

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