JP2018538506A - Natural gas precooling by high pressure compression and expansion - Google Patents

Abstract

A method of producing liquefied natural gas (LNG) is disclosed. The natural gas stream is provided from a natural gas supply. The natural gas stream is compressed to a pressure of at least 138 bara (2,000 psia) in at least two serially arranged compressors (102, 112) to form a compressed natural gas stream (114). The compressed natural gas stream (116) is cooled to form a cooled compressed natural gas stream (118). The cooled compressed natural gas stream is less than 207 bara (3,000 psia) and at least one work producing natural gas expander to a pressure not greater than the pressure at which two in series compressors compress the natural gas stream Expands in (120), thereby forming a cold natural gas stream (122). The chilled natural gas stream is liquefied.
[Selection] Figure 1

Description

[Cross-reference to related applications]
This application is a benefit of US Provisional Patent Application No. 62 / 266,985, filed December 14, 2015, entitled “Natural Gas Pre-Cooling by High Pressure Compression and Expansion”, which is incorporated herein by reference in its entirety. Is an insistence.

  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”, US Provisional Patent entitled “Expander-Based LNG Production Process Enhanced by Liquid Nitrogen” Related to application 62 / 266,979 and US provisional patent application 62 / 266,983 entitled “Method of Natural Gas Liquefaction on an LNG Carrier Containing Liquid Nitrogen”. .

  The present invention relates to liquefaction of natural gas to form liquefied natural gas (LNG), and more specifically, construction and / or maintenance of major facilities and / or environmental impact of conventional LNG plants. It relates to the production of LNG in remote or susceptible areas that may be harmful.

  LNG production is a rapidly growing means of supplying natural gas from locations with a rich supply of natural gas to remote locations with strong demand for natural gas. Traditional LNG production cycles include a) initial processing of natural gas resources to remove contaminants such as water, sulfur compounds, and carbon dioxide, b) self-refrigeration, external refrigeration, lean oil, etc. Separation of some heavy hydrocarbon gases such as propane, butane, pentane, etc. by possible methods, c) natural by substantially external refrigeration to form liquefied natural gas at about atmospheric pressure and about -160 ° C Refrigeration of gas, d) transportation of LNG products to the market place by ship or tanker designed for this purpose, e) regasification plant to pressurized natural gas that can be distributed to natural gas consumers Including re-pressurization and regasification of LNG. Step (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 emits substantial carbon and other emissions. Billions of US dollars and large capital investments in large infrastructure are required as part of the liquefaction plant. Step (e) of a conventional LNG cycle generally involves repressurizing the LNG to the required pressure using a cryogenic pump, and then finally exchanging heat with seawater through the intermediate fluid. Or regasifying the LNG to pressurized natural gas by burning a portion of the natural gas to heat and evaporate the LNG.

  While LNG production is generally known, technological improvements can still provide significant opportunities for LNG producers when maintaining their leading position in the LNG industry. For example, floating LNG (FLNG) is a relatively new technology option for producing LNG. This technique involves the construction of gas treatment and liquefaction facilities on floating structures such as barges or ships. FLNG is a technical solution for monetizing offshore residual gas that cannot economically build gas pipelines to the coast. FLNG is also increasingly being considered for land and coastal gas fields located in remote, environmentally sensitive and / or politically difficult areas. This technique has certain advantages over conventional terrestrial LNG in that it has a reduced environmental footprint at the production site. This technology can also deliver projects faster and cheaper because most of the LNG facilities are built at shipyards with lower labor costs and reduced contracting risk.

  Although FLNG has several advantages over conventional terrestrial LNG, significant technical problems remain in technology applications. For example, FLNG structures need to provide the same level of gas treatment and liquefaction in less than a quarter of the area or space that is often considered to be available for onshore LNG plants. For this reason, there is a need to develop technologies that reduce the liquefaction facility footprint while maintaining its capacity, thereby reducing overall project costs. Several liquefaction techniques have been proposed for use with the FLNG project. Leading technologies include single mixed refrigerant (SMR) processes, double mixed refrigerant (DMR) processes, and expander-based (or expansion) processes.

  Unlike the DMR process, the SMR process has the advantage of fitting all equipment and bulk associated with a complete liquefaction process within a single FLNG module. The SMR liquefaction module is placed on the upper deck of the FLNG structure as a complete SMR train. This “in-box LNG” concept is preferred for delivery of FLNG projects because it allows testing and commissioning of the SMR train at a location different from where the FLNG structure is built. It can also allow labor costs to be reduced because it reduces working hours at shipyards where labor costs tend to be higher than labor costs in conventional production yards. The SMR process has the added advantage of being a relatively efficient, simple and small refrigerant process when compared to other mixed refrigerant processes. Furthermore, SMR liquefaction processes are typically 15% to 20% more efficient than expander-based liquefaction processes.

  While the choice of SMR process for LNG liquefaction within the FLNG project has its advantages, the SMR process has several drawbacks. For example, the required use and storage of a flammable refrigerant such as propane significantly increases the loss prevention problem for FLNG. The SMR process is also limited in capacity, which increases the number of trains needed to reach the desired LNG production. For these reasons and others, significant amounts of upper deck space and weight are required for the SMR train. Since upper deck space and weight are significant drivers for FLNG project costs, there is a need to improve the SMR liquefaction process to further reduce upper deck space, weight, and complexity, thereby improving project economics. Remaining.

  The inflator-based process has several advantages that make it well suited for FING projects. The most significant advantage is that this technique provides liquefaction without the need for external hydrocarbon refrigerants. Eliminating liquid hydrocarbon refrigerant inventory such as propane storage significantly reduces safety concerns regarding FLNG projects. An additional advantage of the expander-based process compared to the mixed refrigerant process is that the expander-based process is less sensitive to offshore motion because the main refrigerant remains mostly in the gas phase. However, the application of expander-based processes to FLNG projects with LNG production exceeding 2 million tonnes per year (MTA) has been shown to be less attractive than the use of mixed refrigerant processes. The capacity of the expander-based process train is typically less than 1.5 MTA. In contrast, a mixed refrigerant process train, such as a known dual mixed refrigerant process, can have a train capacity in excess of 5 MTA. The size of the expander-based process train is limited because the refrigerant remains largely vaporized throughout the process and the refrigerant absorbs energy through its sensible heat. For this reason, the volume flow of the refrigerant is large throughout the process, and the size and piping of the heat exchanger is proportionally larger than that of the mixed refrigerant process. Further, the compander horsepower size limitation results in a parallel rotating machine as the capacity of the expander-based process train increases. The production rate for FLNG projects using inflator-based processes can be greater than 2 MTA when multiple inflator-based trains are allowed. For example, for a 6MTA FLNG project, 6 or more parallel expander-based process trains may be sufficient to achieve the required production. However, total equipment, complexity, and cost all increase with multiple inflator trains. In addition to this, if multiple trains are required for the expander-based process, while the mixed refrigerant process can achieve the required production rate with one or two trains, it is compared to the mixed refrigerant process. The assumed process simplicity of the inflator-based process begins to be questioned. For these reasons, there is a need to develop a high LNG production capacity FLNG liquefaction process that has the advantages of an expander-based process. There is a further need to develop FLNG technology solutions that can better address the challenges that ship motion has on gas treatment.

  US Pat. No. 6,412,302 describes a feed gas expander-based process that uses two independently closed refrigeration loops to cool the feed gas to form LNG. In an embodiment, 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 technology requires 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 a capacity of less than 1.5 MTA.

  U.S. Pat. No. 8,616,012 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 greater than or equal to 1,500 psia (10,340 kPa), or more preferably greater than 2,500 psia (17,240 kPA). Next, the refrigerant is cooled and expands, and reaches an extremely low temperature. The cooled refrigerant is used in a heat exchanger to cool the supply gas from a warm temperature to a very low 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 with a flash gas used as a 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 disadvantages of high equipment count and increased complexity due to its two independent refrigeration loops and its requirement for feed gas compression. Furthermore, high pressure operation also means that the equipment and piping will be much heavier than those of other inflator-based processes.

  GB 2,486,036 describes a feed gas expander-based process that is an open loop refrigeration cycle that includes a pre-cooled expander loop and a liquefied expander loop that liquefies natural gas using the expanded gas phase. Yes. This document significantly reduces the percentage of recycled gas and the overall required refrigeration power by including a liquefaction expander in the process. This technique has the advantage of being simpler than other techniques because only one type of refrigerant is used in a single compression string. However, this technology is still limited to volumes below 1.5 MTA, which requires the use of a liquefier inflator that is not a standard instrument for LNG production. This technique has also been shown to be less efficient than other techniques for diluting natural gas.

  U.S. Pat. No. 7,386,996 describes an expander-based process with a pre-cooling refrigeration process preceding the main expander-based cooling circuit. The pre-cooling refrigeration process includes a cascaded carbon dioxide refrigeration circuit. The carbon dioxide refrigeration circuit is mainly at three pressure levels: a high pressure level that provides warm end cooling, an intermediate pressure level that provides intermediate temperature cooling, and a low pressure level that provides cold end cooling for the carbon dioxide refrigeration circuit. The supply gas and refrigerant gas of the expander-based cooling circuit can be cooled. This technique is more efficient and has a higher production capacity than an expander-based process that lacks a pre-cooling stage. This technology has additional advantages over FLNG applications because the pre-cooling refrigeration circuit uses carbon dioxide as the refrigerant instead of the hydrocarbon refrigerant. However, the carbon dioxide refrigeration circuit introduces additional refrigerant and a substantial amount of extra equipment, thus at the cost of additional complexity to the liquefaction process. For LNG applications, the carbon dioxide refrigeration circuit is in its own module and can be sized to provide pre-cooling for multiple expander-based processes. This arrangement has the disadvantage of requiring a significant amount of pipe connection between the pre-cooling module and the main expander-based process module. The “in-box LNG” advantages discussed above are no longer realized.

US Provisional Patent Application No. 62 / 266,976 US Provisional Patent Application No. 62 / 266,979 US Provisional Patent Application No. 62 / 266,983 US Pat. No. 6,412,302 US Pat. No. 8,616,012 GB 2,486,036 US Pat. No. 7,386,996

  That is, there remains a need to develop a pre-cooling process that does not require additional refrigerant and does not introduce a significant amount of extra equipment into the LNG liquefaction process. There is an additional need to develop a pre-cooling process that can be placed in the same module as the liquefaction module. Such a pre-cooling process in combination with an SMR process or an inflator-based process is considered particularly suitable for FLNG applications where upper deck space and weight significantly affect project economics. There remains a particular need to develop an LNG production process that has the advantages of an inflator-based process and in addition to having a high LNG production capacity without significantly increasing the facility footprint. There is a further need to develop FLNG technology solutions that can better address the challenges that ship motion has to gas processing. Such a high volume expander-based liquefaction process is considered particularly suitable for FLNG applications where the inherent safety and simplicity of the expander-based liquefaction process are highly appreciated.

  The present invention provides a method for producing liquefied natural gas (LNG). The natural gas stream is provided from a natural gas supply. The natural gas stream can be compressed to a pressure of at least 2,000 psia in at least two serially arranged compressors to form a compressed natural gas stream. The compressed natural gas stream can form a cooled cooled compressed natural gas stream. The cooled compressed natural gas stream expands in at least one work-generating natural gas expander to a pressure less than 3,000 psia and no greater than the pressure at which at least two in-line compressors compress the natural gas stream therewith. Thereby forming a cold natural gas stream. The cooled natural gas stream can then be liquefied.

  The present invention also provides an apparatus for liquefaction of natural gas. At least two compressors arranged in series compress the natural gas stream to a pressure greater than 2,000 psia, thereby forming a compressed natural gas stream. The cooling element cools the compressed natural gas stream to form a cooled compressed natural gas stream. The at least one work generating expander expands the cooled compressed natural gas stream to a pressure less than 3,000 psia and not greater than the pressure at which at least two of the serially arranged compressors compress the natural gas stream thereto, Forms a cold natural gas stream. The liquefaction train liquefies a cold natural gas stream.

  The present invention further provides a floating LNG structure. At least two compressors arranged in series compress the natural gas stream to a pressure greater than 2,000 psia, thereby forming a compressed natural gas stream. The cooling element cools the compressed natural gas stream to form a cooled compressed natural gas stream. The at least one work generating expander expands the cooled compressed natural gas stream to a pressure less than 3,000 psia and not greater than the pressure at which at least two of the serially arranged compressors compress the natural gas stream thereto, Forms a cold natural gas stream. The liquefaction train liquefies a cold natural gas stream.

1 is a schematic diagram of a high pressure compression and expansion (HPCE) module according to disclosed aspects. Figure 5 is a graph showing heating and cooling curves for an expander-based refrigeration process. 1 is a schematic diagram showing the arrangement of a single mixed refrigerant (SMR) liquefaction module according to known principles. FIG. 6 is a schematic diagram illustrating an arrangement of SMR liquefaction modules according to the disclosed aspects. FIG. 6 is a schematic diagram of an HPCE module according to the disclosed aspects. FIG. 3 is a schematic diagram of an HPCE module and a feed gas expander based liquefaction module according to the disclosed aspects. 3 is a flowchart of a method for liquefying natural gas to form LNG according to the disclosed aspects.

  Various specific aspects, embodiments, and versions are now described below, including the definitions employed herein. Those skilled in the art will appreciate that such aspects, embodiments, and versions are exemplary only and that the invention can be practiced using other methods. Any reference to “the present invention” may refer to one or more of the embodiments defined by the claims, but not necessarily all. The use of headings is for convenience only and does not limit the scope of the invention. For purposes of clarity and brevity, like reference numerals in some figures may represent like items, steps, or structures and may not be described in detail in all figures.

  All numerical values in the detailed description and claims herein are modified by “about” or “approximate” readings to account for experimental errors and variations expected by those skilled in the art.

  As used herein, the term “compressor” means a machine that increases the pressure of a gas upon application of work. A “compressor” or “refrigerant compressor” includes any unit, device, or apparatus that can increase the pressure of a gas stream. This includes a compressor with a single compression process or stage, or a compressor with multistage compression or stages, or in particular a multistage compressor in a single casing or shell. The vaporized stream to be compressed can be provided to the compressor at various pressures. Some stages or stages of the cooling process may involve two or more compressors in parallel, in series, or both. The present invention is not limited by the type or arrangement or layout of one or more compressors, particularly in any refrigerant circuit.

  As used herein, “cooling” broadly refers to reducing and / or reducing the temperature and / or internal energy of a material by any suitable desired or necessary amount. Cooling is at least about 1 ° C, at least about 5 ° C, at least about 10 ° C, at least about 15 ° C, at least about 25 ° C, at least about 35 ° C, or at least about 50 ° C, or at least about 75 ° C, or at least about 85 ° C. Or a temperature decrease of at least about 95 ° C, or at least about 100 ° C. Cooling can use any suitable heat sink such as steam generation, hot water heating, cooling water, air, refrigerant, other process streams (integrated), and combinations thereof. One or more sources of cooling can be combined and / or cascaded to reach the desired outlet temperature. The cooling stage can use a cooling unit with any suitable device and / or equipment. According to some embodiments, cooling can include indirect heat exchange, such as with one or more heat exchangers. Alternatively, the cooling can use evaporation (heat of evaporation) cooling and / or direct heat exchange, such as a liquid sprayed directly into the process stream.

  As used herein, the term “expansion device” is used to reduce the pressure of a fluid in a line (eg, a liquid stream, a vapor stream, or a multiphase stream containing both liquid and vapor). Refers to one or more suitable devices. Except where a specific type of inflation device is specifically defined, the inflation device may be (1) at least partially by an isoenthalpy means, or (2) at least partially by an isentropic means. Or (3) a combination of both isentropic means and isenthalpy means. Devices suitable for isoenthalpy expansion of natural gas are known in the art and generally include, but are not limited to, for example, valves, control valves, “Joule Thompson (JT)” valves, or venturis. Includes a manually or automatically activated iris device such as a device. Devices suitable for isentropic expansion of natural gas are known in the art and generally include equipment such as expanders or turbo expanders that extract or derive work from such expansion. Devices suitable for isentropic expansion of a liquid stream are known in the art and are generally used for expanders, hydraulic expanders, liquid turbines, or turbo expanders that extract or derive work from such expansion. Including such equipment. An example of a combination of both isentropic means and isoenthalpy means may be a parallel “Joule Thompson” valve and a turbo expander, which uses either a J-T valve and a turbo expander alone. Or the ability to use both at the same time. Isoenthalpy or isentropic expansion can be performed in the entire liquid phase, the entire vapor phase, or the mixed phase, from a vapor stream or liquid stream to a multiphase stream (a stream having both a vapor phase and a liquid phase), or It can be done to facilitate a phase change to a single phase stream different from the initial phase. In the description of the drawings herein, references to more than one inflation device in every drawing do not necessarily mean that each inflation device is of the same type or size.

  The term “gas” is used interchangeably with “vapor” and is defined as a substance or mixture of substances that is in a gaseous state to distinguish it from a liquid or solid state. Similarly, the term “liquid” refers to a substance or mixture of substances in a liquid state as distinguished from a gas or solid state.

  “Heat exchanger” means any device in a broad sense that can transfer thermal or cold energy from one medium to another, such as between at least two different fluids. The heat exchanger includes “direct heat exchange” and “indirect heat exchange”. Thus, the heat exchanger can be a co-current or counter-flow heat exchanger, indirect heat exchange (eg, a plate fin heat exchanger such as a spiral wound heat exchanger or brazed aluminum plate fin type), a direct contact heat exchanger, With any suitable design such as shell-and-tube heat exchanger, spiral, hairpin, core, core-and-kettle, printed circuit, double pipe, or any other type of known heat exchanger can do. A “heat exchanger” also allows the passage of one or more streams therethrough, affecting a direct or indirect heat exchanger between one or more lines of refrigerant and one or more feed streams. Refers to any column, tower, unit, or other arrangement that has come to give.

  As used herein, the term “indirect heat exchange” means the introduction of two fluids into a heat exchange relationship without any physical contact, or the mixing of fluids with each other. Core-in-kettle heat exchangers and brazed aluminum plate fin heat exchangers are examples of equipment that facilitates indirect heat exchange.

As used herein, the term “natural gas” refers to a multi-component gas obtained from a crude oil well (associated gas) or from an underground gas-bearing formation (non-associated gas). The composition and pressure of natural gas can be significantly different. A typical natural gas stream contains methane (C ₁ ) as a significant component. The natural gas stream may also contain ethane (C ₂ ), higher molecular weight hydrocarbons, and one or more acid gases. Natural gas may also contain small amounts of contaminants such as water, nitrogen, iron sulfide, waxes, and crude oil.

  Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges from any lower limit to any upper limit are contemplated unless otherwise indicated. All numerical values are “about” or “approximate” readings, and take into account experimental errors and variations expected by those skilled in the art.

  All patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent that such disclosure does not contradict this application and to any administrative jurisdiction in which such incorporation is permitted. It is built in.

  The aspects disclosed herein describe a process for precooling natural gas for the liquefaction process of LNG production by the addition of high pressure compression and expansion processes to the feed gas. More specifically, the present invention describes a process in which pretreated natural gas is compressed to a pressure greater than 2,000 psia (13,790 kPA) or more preferably greater than 3,000 psia (20,680 kPA). . The hot compressed gas is cooled by exchanging heat with the environment to form a pre-compression gas. The compressed pretreatment gas is expanded approximately isentropically to a pressure of less than 3,000 psia (20,680 kPA) or more preferably less than 2,000 psia (13,790 kPA) to form a cooled pretreatment gas; Here, the pressure of the cooled pretreatment gas is smaller than the pressure of the compression pretreatment gas. The cooled pretreatment gas can be directed to one or more SMR liquefaction trains, or the cooled pretreatment gas can be one or more expander based liquefaction trains in which the gas is further cooled to form LNG. Can be directed to.

  FIG. 1 is a diagram illustrating an example of a precooling process. The precooling process is referred to herein as the high pressure compression and expansion (HPCE) process 100. The HPCE process 100 may include a first compressor 102 that includes a pre-treated natural gas stream 104 and forms an intermediate pressure gas stream 106. The intermediate pressure gas stream 106 can flow through a first heat exchanger 108 that is cooled by indirectly exchanging heat with the environment to form a cooled intermediate pressure gas stream 110. . The first heat exchanger 108 can be an air-cooled heat exchanger or a water-cooled heat exchanger. The cooled intermediate pressure gas stream 110 can then be compressed in the second compressor 112 to form a high pressure gas stream 114. The pressure of the high pressure gas stream 114 may be greater than 2,000 psia (13,790 kPA), or more preferably greater than 3,000 psia (20,680 kPA). The high pressure gas stream 114 can flow through a second heat exchanger 116 that is cooled by indirectly exchanging heat with the environment to form a cooled intermediate pressure gas stream 118. The second heat exchanger 116 can be an air-cooled heat exchanger or a water-cooled heat exchanger. The cooled high pressure gas stream 118 can then be expanded in the expander 120 to form a cooled pretreatment gas stream 122. The pressure of the chilled pretreatment gas stream 122 can be less than 3,000 psia (20,680 kPA), or more preferably less than 2,000 psia (13,790 kPA), and the pressure of the chilled pretreatment gas stream 122 can be Less than the pressure of the cooled high pressure gas stream 118. In a preferred embodiment, the second compressor 112 can be driven solely by the shaft power generated by the expander 120 as indicated by the dashed line 124.

  In an aspect, the SMR liquefaction process can be enhanced by the addition of an HPCE process upstream of the SMR liquefaction process. More specifically, in this embodiment, the pretreated natural gas can be compressed to a pressure greater than 2,000 psia (13,790 kPA), or more preferably greater than 3,000 psia (20,680 kPA). . The hot compressed gas is then cooled by indirectly exchanging heat with the environment to form a pre-compression treatment gas. Next, the compressed pretreatment gas is cooled by approximately isentropically expanded to a pressure less than 3,000 psia (20,680 kPA), or more preferably less than 2,000 psia (13,790 kPA). Where the pressure of the cooled pretreatment gas is less than the pressure of the compressed pretreatment gas. The cooled pretreatment gas is then directed to a plurality of SMR liquefaction trains where the cooled pretreatment gas is further cooled to form LNG.

  The combination of SMR train and HPCE has several advantages over conventional SMR processes where pretreated natural gas is sent directly to the SMR liquefaction train. For example, natural gas pre-cooling using the HPCE process allows an increase in the LNG production rate in the SMR train for a given horsepower in the SMR train. As described in connection with FIGS. 3 and 4, SMR trains, each powered by a gas turbine having an output of approximately 50 megawatts (MW), are 1 out of 5 trains each producing LNG at 1.5 MTA. The increase in capacity of .9 MTA can be reduced to 4 trains each with. For this given example, the HPCE module has substantially replaced one of the SMR modules. Replacing the SMR module with the HPCE module is advantageous because the HPCE module is expected to be smaller, lighter, and much cheaper than the SMR module. Like the SMR module, the HPCE module can have a similarly sized gas turbine to provide compressed power, which will also have an equal amount of air or water cooler. However, unlike SMR modules, HPCE modules do not have expensive main cold heat exchangers. Containers and pipes associated with the refrigerant flow in the SMR module are eliminated in the HPCE module. Furthermore, there are no expensive cold pipes in the HPCE module and all fluid streams remain single phase in the HPCE module.

  Another advantage is that the required storage of refrigerant is reduced because the number of SMR trains is reduced by one. Similarly, most of the warm temperature for cooling the gas occurs in the HPCE module, so that the heavy hydrocarbon component of the mixed refrigerant can be reduced. For example, the propane component of the mixed refrigerant can be eliminated without any significant decrease in the efficiency of the SMR process.

  Another advantage is that for the SMR process that accepts the cold pretreatment gas from the HPCE process, the volumetric flow rate of the evaporative refrigerant in the SMR process is more than 25% smaller than that of the conventional SMR process that accepts the warm pretreatment gas. Is that you can. The lower volume flow of refrigerant can reduce the size of the main cryogenic heat exchanger and the size of the low pressure mixed refrigerant compressor. The lower volume flow rate of the refrigerant is due to its higher vapor pressure compared to that of the conventional SMR process.

  The known propane pre-cooled mixed refrigeration process and double mixed refrigeration (DMR) process can be considered as a version of the SMR process combined with a pre-cooled refrigeration circuit, but significant between such a process and the embodiments disclosed in the present invention. There is a big difference. For example, known processes use a cascade propane refrigeration circuit or a warm-end mixed refrigerant to precool the gas. Both of these known processes have the advantage of providing 5% to 15% higher efficiency than the SMR process. Furthermore, the volume of a single liquefaction train using these known processes can be significantly greater than that of a single SMR train. However, these technology pre-cooling refrigeration circuits introduce additional refrigerants and significant amounts of extra equipment, and thus pay for the additional complexity of the liquefaction process. For example, the drawbacks of higher complexity and weight of DMR may exceed its advantages of high efficiency and performance when deciding between DMR and SMR processes for FLNG applications. Known processes contemplate adding a pre-cooling process upstream of the SMR process when driven primarily by the need for higher thermal efficiency and higher LNG production capacity for a single train. The HPCE process combined with the SMR process has not been achieved previously because it does not provide higher thermal efficiency than does a refrigerant-based precooling process. As described above, the thermal efficiency of the HPCE process having SMR is almost the same as that of the stand-alone SMR process. The disclosed aspect is in its description of a pre-cooling process that seeks to reduce the weight and complexity of the liquefaction process rather than increasing the thermal efficiency, which was previously the biggest driver for the addition of a pre-cooling process for onshore LNG applications. It is considered novel based at least in part. For newer applications of FLNG, the liquefaction process footprint, weight, and complexity will be drivers that are greater than the project cost. Accordingly, the disclosed aspects are of particular value.

  In an aspect, the expander-based liquefaction process can be enhanced by the addition of an HPCE process upstream of the expander-based process. More specifically, in this aspect, the pretreated natural gas stream may be compressed to a pressure greater than 2,000 psia (13,790 kPA), or more preferably greater than 3,000 psia (20,680 kPA). it can. The hot compressed gas can then be cooled by exchanging heat with the environment to form a pre-compression treatment gas. The compressed pretreatment gas is expanded approximately isentropically to a pressure of less than 3,000 psia (20,680 kPA), or more preferably less than 2,000 psia (13,790 kPA) to form a cooled pretreatment gas. Where the pressure of the cooled pretreatment gas is less than the pressure of the compressed pretreatment gas. The cooled pretreatment gas is directed to an expander-based process where the gas is further cooled to form LNG. In a preferred embodiment, the cooled pretreatment gas can be directed to a feed gas expander based process.

  FIG. 2 shows a typical temperature cooling curve 200 for an expander-based liquefaction process. The hotter curve 202 is the temperature curve of the natural gas stream. The cooler curve 204 is a combined temperature curve of the cold and warm cooling streams. As shown, the cooling curve is marked by three temperature pinch points 206, 208, and 210. Each pinch point is a location in the heat exchanger where the combined heat capacity of the cooling stream is smaller than that of the natural gas stream. This imbalance in heat capacity between streams results in a decrease in temperature difference between cooling streams relative to the minimum allowable temperature difference that provides an effective heat transfer rate. The lowest temperature pinch point 206 occurs where the colder of the two cooling streams, typically the cold cooling stream, enters the heat exchanger. An intermediate temperature pinch point 208 occurs where the second cooling stream, typically the warm cooling stream, enters the heat exchanger. A hot temperature pinch point 210 occurs where the cold and warm cooling streams exit the heat exchanger. The warm temperature pinch point 210 needs to have a high mass flow rate for the warmer cooling stream, which substantially increases the power requirements of the expander-based process.

  One proposed method for eliminating the warm temperature pinch point 210 is to precool the feed gas with an external refrigeration system, such as a propane cooling system or a carbon dioxide cooling system. For example, US Pat. No. 7,386,996 eliminates warm temperature pinch points by using a pre-cooling refrigeration process that includes a cascaded carbon dioxide refrigeration circuit. This external pre-cooling refrigeration system has the disadvantage of significantly increasing the complexity of the liquefaction process as an additional refrigerant system with all relevant equipment is introduced. Embodiments disclosed herein precool the feed gas stream by compressing the feed gas to a pressure greater than 2,000 psia (12,790 kPA), cool the compressed feed gas stream, and 3,000 psia (20 , 690 kPA) to reduce the effect of warm temperature pinch point 210 by expanding the compressed gas stream to a pressure less than 690 kPA, where the expansion pressure of the feed gas stream is less than the compression pressure of the feed gas stream. This step of cooling the feed gas stream results in a significant reduction in the required mass flow rate of the expander based process cooling stream. It also improves the thermodynamic efficiency of the expander-based process without significantly increasing the total equipment and without the addition of external refrigerant.

  In a preferred embodiment, the expander-based process can be a feed gas expander-based process. The feed gas expander based process may be an open loop feed gas process where the recirculation loop includes 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 is higher than the temperature of the second cooling stream. In some aspects, the pressure of the first cooling stream is higher than the pressure of the second cooling stream. In another aspect, the cold end expander discharges a two-phase stream that is separated into a second cooling stream and a second pressurized LNG stream. Specifically, the natural gas stream produced can be processed to remove natural impurities such as water, heavy hydrocarbons, and acid gases, if present, to make natural gas suitable for liquefaction. The treated natural gas can be directed to an HPCE process where it is compressed to a pressure greater than 2,000 psia (12,790 kPA), or more preferably greater than 3,000 psia (20,680 kPA). The hot compressed gas can then be cooled by exchanging heat with the environment to form compressed natural gas. The compressed natural gas is expanded approximately isentropically to a pressure of less than 3,000 psia (20,680 kPA), or more preferably less than 2,000 psia (12,790 kPA) to form refrigerated natural gas. Where the pressure of the refrigerated natural gas is less than the pressure of the compressed natural gas. The refrigerated natural gas can be fully liquefied by indirect heat exchange with the first cooling stream and the second cooling stream to produce a first pressurized LNG stream. The first pressurized LNG stream can be mixed with the second pressurized LNG stream to form a pressurized LNG stream. The pressurized LNG stream can be directed to at least one two-phase separation stage where the pressure of the pressurized LNG stream is reduced and the resulting two-phase stream is separated into a flash gas stream and an LNG product stream. The flash gas stream is heat exchanged with the pressurized LNG stream and the refrigerated natural gas stream before being compressed to fuel gas and / or compressed to mix with a recirculated second cooling stream. be able to.

  The combination of the feed gas expander-based process and the HPCE process has several advantages over the conventional feed gas expander-based process. Including the HPCE process with it can increase the efficiency of the feed gas expander based process by 20-25%. Thus, the feed gas expander process of the present invention has an efficiency approaching that of the SMR process, while still providing the benefits of no external refrigerants, ease of operation, and reduced total equipment. Furthermore, the refrigerant flow rate and the size of the recirculation compressor are expected to be significantly lower for the expander-based process combined with the HPCE process. For this reason, the production capacity of a single liquefaction train according to the disclosed aspects can exceed the production capacity of a similarly sized conventional expander-based liquefaction process by more than 50%.

  FIG. 3 is a diagram illustrating an arrangement of the SMR liquefaction module with respect to the FLNG 300. Natural gas 302 that has been pretreated or otherwise suitable for liquefaction can be evenly distributed among five identical or nearly identical SMR liquefaction modules or trains 304, 306, 308, 310, 312. As an example, each SMR liquefaction module can receive approximately 50 MW of compressed power from either a gas turbine or an electric motor (not shown) to drive the compressor of the SMR liquefaction module. Each SMR liquefaction module can produce about 1.5 MTA of LNG for a total stream daily production of about 7.5 MTA of LNG for FLNG applications.

  FIG. 4 is a diagram illustrating the placement of an HPCE module 404 having SMR liquefaction modules or trains 406, 408, 410, 412 on FLNG 400 in accordance with the disclosed aspects. Natural gas 402 that has been pretreated or otherwise suitable for liquefaction can be directed to HPCE module 404 to produce a chilled pretreatment gas stream 405. The HPCE module 404 can receive approximately 50 MW of compressed power, for example, from either a gas turbine or an electric motor (not shown) to drive one or more compressors in the HPCE module 404. The cooled pretreatment gas can be evenly distributed between four identical or nearly identical SMR liquefaction modules 406, 408, 410, 412. Each SMR liquefaction module can receive approximately 50 MW of compressed power from either a gas turbine or an electric motor (not shown) to drive the compressor of the respective SMR liquefaction module. Each SMR liquefaction module can produce about 1.9 MTA of LNG for a total stream daily production of about 7.6 MTA of LNG for FLNG applications.

  FIG. 5 is a diagram illustrating aspects of the HPCE module 500 referred to in FIG. A natural gas stream 502 that has been pretreated to remove impurities or otherwise suitable for liquefaction is fed into a first compressor 504 to form a first intermediate pressure gas stream 506. The first intermediate pressure gas stream 506 is cooled to form a first intermediate pressure gas stream 510 that is cooled and cooled by indirectly exchanging heat with the environment. It can flow through heat exchanger 508. The first heat exchanger 508 can be an air-cooled heat exchanger or a water-cooled heat exchanger. The cooled first intermediate pressure gas stream 510 can then be compressed in the second compressor 512 to form a second intermediate pressure gas stream 514. The second intermediate pressure gas stream 514 is cooled to form a second intermediate pressure gas stream 518 that is cooled and cooled by indirectly exchanging heat with the environment. It can flow through heat exchanger 516. The second heat exchanger 516 can be an air-cooled heat exchanger or a water-cooled heat exchanger. The cooled second intermediate pressure gas stream 518 can then be compressed in a third compressor 520 to form a high pressure gas stream 522. The pressure of the high pressure gas stream 522 may be greater than 2,000 psia (13,790 kPA), or more preferably greater than 3,000 psia (20,680 kPA). The high pressure gas stream 522 can flow through a third heat exchanger 524 that forms a cooled high pressure gas stream 526 that is cooled by indirectly exchanging heat with the environment. The third heat exchanger 524 can be an air-cooled heat exchanger or a water-cooled heat exchanger. The cooled high pressure gas stream 526 can then be expanded in the compressor 528 to form a cooled pretreatment gas stream 530. The pressure of the cooled pretreatment gas stream 530 can be less than 3,000 psia (20,680 kPA), or more preferably less than 2,000 psia (13,790 kPA), and the pressure of the chilled pretreatment gas stream 530 can be The pressure of the cooled high pressure gas stream 526 can be reduced. In some aspects, the third compressor 520 can be driven solely by the shaft power generated by the expander 528, as indicated by line 532.

  FIG. 6 is a diagram illustrating an HPCE process 601 in combination with a feed gas expander-based LNG liquefaction process 600. Natural gas can be processed to remove impurities such as water, heavy hydrocarbons, and acid gases, if present, to produce a processed natural gas stream 602 suitable for liquefaction. The treated natural gas stream 602 can be mixed with the recycled refrigerant gas stream 604 to form a combined stream 606. The combined stream 606 can be directed to an HPCE process 601 where the combined stream 606 is compressed in a first compressor 608 to form an intermediate pressure gas stream 610. The intermediate pressure gas stream 610 flows through a first heat exchanger 612 that forms a cooled intermediate pressure gas stream 614 that is cooled by indirectly exchanging heat with the environment. Can do. The first heat exchanger 612 can be an air-cooled heat exchanger or a water-cooled heat exchanger. The cooled intermediate pressure gas stream 614 can then be compressed in a second compressor 616 to form a high pressure gas stream 618. The pressure of the high pressure gas stream 618 may be greater than 2,000 psia (13,790 kPA), or more preferably greater than 3,000 psia (20,680 kPA). The high pressure gas stream 618 may flow through a second heat exchanger 620 that forms a cooled high pressure gas stream 618 that is cooled by indirectly exchanging heat with the environment. The second heat exchanger 620 can be an air-cooled heat exchanger or a water-cooled heat exchanger. The cooled high pressure gas stream 622 can then be expanded in the HPCE expander 624 to form a cooled pretreatment gas stream 626. The pressure of the chilled pretreatment gas stream 626 is less than 3,000 psia (20,680 kPA), or more preferably less than 2,000 psia (13,790 kPA), where the pressure of the chilled pretreatment gas stream 626 is Less than the pressure of the cooled high pressure gas stream 622. In some aspects, the second compressor 616 can be driven solely by the shaft power generated by the expander 624, as represented by the dashed line 628.

  As shown in FIG. 6, the chilled pretreatment gas stream 626 is directed off the HPCE process 601 to a feed gas expander based process 600. The cooled pretreatment gas stream 626 can be separated into a second chilled pretreatment gas stream 630, a first refrigerant stream 632, and a second refrigerant stream 634. The first refrigerant stream 632 can be expanded in a first expander 636 to produce a first cooling stream 638. The first cooling stream 638 enters at least one cold heat exchanger 640 that exchanges heat with the second chilled pretreatment gas stream 630 and the second refrigerant stream 634 to cool this stream. The first cooling stream 638 exits at least one low temperature heat exchanger 640 as a first warm stream 642. The second refrigerant stream 634 can be cooled in at least one low temperature heat exchanger 640 and then expanded in the second expander 644 to produce a two-phase stream 646. The pressure of the two-phase stream 646 can be the same as the pressure of the first cooling stream 638 or can be lower. The two-phase stream 646 can be separated into its vapor component and its liquid component in a first two-phase separator 648 to form a second cooling stream 650 and a second pressurized LNG stream 652. The temperature of the first cooling stream 638 is higher than the temperature of the second cooling stream 650. The second cooling stream 650 enters at least one cold heat exchanger 640 where it exchanges heat with the second chilled pretreatment gas stream 630 and the second refrigerant stream 634 to cool this stream. The second cooling stream 650 exits at least one heat exchanger 640 as a second warm stream 642. The second chilled pretreatment natural gas stream 630 exchanges heat with the first cooling stream 638 and the second cooling stream 650 to produce a first pressurized LNG stream 656. The first pressurized LNG stream 656 can be depressurized in the hydraulic turbine 658 after leaving the at least one heat exchanger 640. The first pressurized LNG stream 656 can be mixed with the second pressurized LNG stream 652 to form a combined pressurized LNG stream 660. The combined pressurized LNG stream 660 can be directed to a second two-phase separator 662 where the pressure of the combined pressurized LNG stream 660 is reduced, and the resulting two-phase stream is the end flash gas stream 664 and the product LNG stream 667. Separated. End flash gas stream 664 can exchange heat with first pressurized LNG stream 656 in end flash gas heat exchanger 668 before directing first pressurized LNG stream 656 to hydraulic turbine 658. In addition, the end flash gas stream 664 enters at least one low temperature heat exchanger 640 and exchanges heat with the second chilled pretreatment gas stream 630 and the second refrigerant stream 634 to cool the stream. can do. End flash gas stream 664 exits at least one heat exchanger 640 as a third warm stream 670. The third warm stream 670 can be compressed in the first recycle gas compressor 672 and exchange heat with the environment in the first recycle heat exchanger 674 to exchange the first recycle gas stream. 676 can be formed. The first recycle gas stream 676 can be combined with the second warm stream 654 and simultaneously compressed in the second recycle gas compressor 678, and the second recycle heat exchanger 680. Within which the environment and heat can be exchanged to form a second recycled gas stream 682. The second recycled gas stream 682 can be combined with the first warm stream 642 and simultaneously compressed in the third and fourth recycled gas compressors 684, 686, and the third recycled gas stream 682 can be compressed. The circulating heat exchanger 688 can exchange heat with the environment to form a recirculated refrigerant gas stream 604. The third recycled gas compressor 684 can be driven solely by the shaft power generated by the first expander 636, as indicated by the dashed line 690. The fourth recycle gas compressor 686 can be driven solely by the shaft power generated by the second expander 644, as indicated by the dashed line 692.

  FIG. 7 illustrates a method 700 for producing LNG in accordance with the disclosed aspects. At block 702, a natural gas stream may be provided from a natural gas supply. At block 704, the natural gas stream may be compressed to a pressure of at least 2,000 psia in at least two serially arranged compressors to form a compressed natural gas stream. At block 706, the compressed natural gas stream can be cooled to form a cooled compressed natural gas stream. At block 708, the cooled compressed natural gas stream is at least one work-produced natural gas expansion to a pressure less than 3,000 psia and no greater than the pressure at which at least two compressors arranged in series compress the natural gas stream therethrough. It can be expanded in the vessel, thereby forming a chilled natural gas stream. At block 710, the cooled natural gas stream can be liquefied.

  The disclosed aspects can include any combination of the methods and systems shown in the following numbered paragraphs. This should not be considered a complete list of all possible aspects, as any number of variations are possible from the above description.

  1. Providing a natural gas stream from a supply of natural gas; compressing the natural gas stream to a pressure of at least 2,000 psia in at least two in-line compressors to form a compressed natural gas stream; Cooling the compressed natural gas stream to form a cooled compressed natural gas stream, and at least to a pressure of less than 3,000 psia and at least two in series arranged compressors not compressing the natural gas stream therewith A liquefied natural gas (LNG) comprising the steps of expanding a cooled compressed natural gas stream within a work-generating natural gas expander thereby forming a cooled natural gas stream and liquefying the cooled natural gas stream How to produce.

  2. The method of claim 1, wherein the step of liquefying the cooled natural gas stream is performed in one or more single mixed refrigerant (SMR) liquefaction trains.

  3. The method of claim 1, wherein liquefying the chilled natural gas stream is performed in one or more expander-based liquefaction modules.

  4). 4. The method of item 3, wherein the expander-based liquefaction module is a nitrogen gas expander-based liquefaction module.

  5. The method of claim 3, wherein the expander-based liquefaction module is a feed gas expander-based liquefaction module.

  6). 6. The method of claim 5, wherein the feed gas expander based liquefaction module is an open loop feed gas expander based liquefaction module.

  7). The process of claim 6 wherein the recirculated refrigerant stream of the open loop feed gas expander based process is combined with the natural gas stream prior to the compression stage.

  8). The chilled natural gas stream is a first chilled natural gas stream, and the method converts the first chilled natural gas stream into a second chilled natural gas stream, a first refrigerant stream, and a second refrigerant. 8. The method of claim 7, further comprising separating into streams.

  9. Discharging a first cooling stream having a first temperature from a warm-end expander forming part of a feed gas expander-based liquefaction module; and supplying a second cooling stream having a second temperature to the feed gas Discharging from a cold end expander forming part of an expander-based liquefaction module, wherein the first temperature is higher than the second temperature.

  10. Expanding the first refrigerant stream in the warm end expander to generate a first cooling stream, and expanding the second refrigerant stream in the cold end expander to generate a second cooling stream. The method of claim 9, further comprising:

  11. Discharging a first cooling stream having a first temperature from a warm end expander forming part of a feed gas expander based liquefaction module; and supplying a two phase stream having a second temperature to the feed gas expander Discharging from a cold end expander that forms part of the base liquefaction module, wherein the first temperature is higher than the second temperature.

  12 Expanding the first refrigerant stream in the warm-end expander to generate a first cooling stream; and expanding the second refrigerant stream in the cold-end expander to generate a two-phase stream. Item 11. The method according to Item 11, further comprising:

  13. The method of 11, further comprising separating the two-phase stream into a second cooling stream and a first pressurized LNG stream.

  14 14. The method of any of 9-13, wherein the pressure of the first cooling stream is the same as or similar to the pressure of the second cooling stream.

  15. 14. The method of any of 9-13, wherein the pressure of the first cooling stream is higher than the pressure of the second cooling stream.

  16. The liquefaction stage includes cooling the second cooled natural gas stream by exchanging heat with the first and second cooling streams to form a second pressurized LNG stream 9-13. The method of any of the paragraphs.

  17. The method of claim 16, wherein the second pressurized LNG stream is mixed with the first pressurized LNG stream prior to expanding the second pressurized LNG stream.

  18. Reducing the pressure of the second pressurized LNG stream so that the second pressurized LNG stream is subjected to at least one stage pressure drop; and depressurizing the second pressurized LNG stream into the end flash gas stream and the LNG stream. 16. The method of claim 16, further comprising the step of:

  19. 19. The method of claim 18, further comprising cooling the second pressurized LNG stream and the second chilled natural gas stream using an end flash gas stream.

  20. Compressing the end flash gas stream after cooling the second pressurized LNG stream and the second chilled natural gas stream using the end flash gas stream, and one or more recirculated refrigerant streams and compression ends 20. The method of claim 19, further comprising mixing the flash gas stream.

  21. Compressing the end flash gas stream after cooling the second pressurized LNG stream and the second chilled natural gas stream using the end flash gas stream; and using the compressed end flash gas stream as fuel. 20. The method of paragraph 19, further comprising:

  22. The method of any of claims 1-21, wherein the at least two compressors compress the natural gas stream to a pressure greater than 3,000 psia.

  23. 23. The method of any of claims 1 to 22, wherein the natural gas expander is a work producing expander that expands a cooled compressed natural gas stream to a pressure of less than 2,000 psia.

  24. 24. The method of any of 1-23, wherein the natural gas expander is mechanically coupled to at least one compressor.

  25. 25. The method of any of claims 1-24, wherein cooling the compressed natural gas stream comprises cooling the compressed natural gas stream in at least one heat exchanger that exchanges heat with the environment.

  26. 26. The method of any of 1-25, wherein one of the at least two compressors arranged in series is driven by a natural gas expander.

  27. The at least two serially arranged compressors include three serially arranged compressors, one of the three serially arranged compressors being driven by a natural gas expander. 27. The method according to any one of 26.

  28. 28. The method according to any one of claims 1 to 27, further comprising performing a step of compressing, cooling, inflating, and liquefying on the upper deck of the floating LNG structure.

  29. 29. The method according to 28, wherein the compressing step, the cooling step, and the expanding step are performed in a single module on the upper deck of the floating LNG structure.

  At least two serially arranged compressors configured to compress the natural gas stream to a pressure greater than 30.000 psia, thereby forming a compressed natural gas stream, and to cool the compressed natural gas stream A cooling element configured to form a cooled compressed natural gas stream, and a pressure less than 3,000 psia and at least two compressors arranged in series compress the natural gas stream therewith At least one work generating expander configured to expand a cooled compressed natural gas stream thereby forming a cooled natural gas stream; and a liquefaction train configured to liquefy the cooled natural gas stream. Including equipment for liquefaction of natural gas.

  31. 30. The apparatus of item 30, wherein the liquefaction train comprises one of a single mixed refrigerant (SMR) liquefaction module and an expander-based liquefaction module.

  32. 32. The apparatus of item 31, wherein the expander-based liquefaction module is one of a nitrogen gas expander-based liquefaction module and a feed gas expander-based liquefaction module.

  33. 32. The apparatus of clause 32, wherein the feed gas expander based liquefaction module is an open loop feed gas expander based liquefaction module.

  34. Further comprising a recirculating refrigerant stream of an open loop feed gas expander based process combined with the natural gas stream before the natural gas stream is compressed by two or more in-line compressors 34. The apparatus of 33, wherein the gas stream is a first chilled natural gas stream separated into a second chilled natural gas stream, a first refrigerant stream, and a second refrigerant stream.

  35. A feed gas expander based liquefaction module includes a warm end expander configured to expand a first refrigerant stream and form a first cooling stream having a first temperature discharged therefrom; A cold end expander configured to form one of a second cooling stream and a two-phase stream having a second temperature expanded from the second refrigerant stream and discharged therefrom; 34. The apparatus of item 34, wherein the temperature of is higher than the second temperature.

  36. The apparatus of 35, further comprising separating the two-phase stream into a second cooling stream and a first pressurized LNG stream.

  37. The apparatus of paragraphs 35-36, wherein the pressure of the first cooling stream is the same as or similar to the pressure of the second cooling stream, or is higher than the pressure of the second cooling stream.

  38. A heat exchanger configured to cool the second chilled natural gas stream to form a second pressurized LNG stream by exchanging heat with the first and second cooling streams; 38. The device according to any one of 35 to 37.

  39. 40. The apparatus of any of 30-38, wherein the at least two compressors compress the natural gas stream to a pressure greater than 3,000 psia.

  40. 40. The apparatus of any of 30-39, wherein the natural gas expander is a work producing expander configured to expand a cooled compressed natural gas stream to a pressure of less than 2,000 psia.

  41. 41. The apparatus of any of 30-40, wherein the natural gas expander is mechanically coupled to at least one compressor.

  42. 42. The apparatus of any of 30-41, wherein the cooling element comprises a heat exchanger configured to cool the compressed natural gas stream by exchanging heat with the environment.

  43. 43. Apparatus according to any of 30-42, wherein one of the at least two compressors arranged in series is driven by a natural gas expander.

  44. The at least two serially arranged compressors include three serially arranged compressors, one of the three serially arranged compressors being driven by a natural gas expander 30- 44. The apparatus of any one of 43.

  45. 45. The apparatus of any of 30-44, wherein the at least two compressors arranged in series, the cooling element, the at least one work producing expander, and the liquefaction train are arranged on a floating LNG structure.

  46. 45. The apparatus of clause 45, wherein the at least two compressors arranged in series, the cooling element, and the at least one work generating expander are arranged in a single module on the upper deck of the floating LNG structure.

  At least two compressors arranged in series configured to compress the natural gas stream to a pressure greater than 47.2,000 psia, thereby forming a compressed natural gas stream, and to cool the compressed natural gas stream A cooling element configured to form a cooled compressed natural gas stream, and a pressure less than 3,000 psia and at least two in series compressors compressing the natural gas stream to that extent At least one work generating expander configured to expand the cooled compressed natural gas stream to thereby form a cooled natural gas stream; and a liquefaction train configured to liquefy the cooled natural gas stream A floating LNG structure containing

  While the foregoing relates to aspects of the present disclosure, other and further aspects of the disclosure may be devised without departing from the basic scope thereof, which scope is set forth in the following claims. Determined by the range of

Claims (28)

A method for producing liquefied natural gas (LNG) comprising:
Providing a natural gas stream from a supply of natural gas;
Compressing the natural gas stream in at least two compressors arranged in series to a pressure of at least 2,000 psia to form a compressed natural gas stream;
Cooling the compressed natural gas stream to form a cooled compressed natural gas stream;
Producing at least one work of the cooled compressed natural gas stream to a pressure that is less than 3,000 psia and not greater than the pressure to which the at least two serially arranged compressors compress the natural gas stream thereto Expanding in a natural gas expander, thereby forming a chilled natural gas stream;
Liquefying the chilled natural gas stream,
A method characterized by that. Liquefying the chilled natural gas stream is performed in one or more single mixed refrigerant (SMR) liquefaction trains;
The method of claim 1. The step of liquefying the cooled natural gas stream is performed in one or more expander-based liquefaction modules;
The expander-based liquefaction module is one of a nitrogen gas expander-based liquefaction module and a feed gas expander-based liquefaction module;
The method of claim 1. The feed gas expander based liquefaction module is an open loop feed gas expander based liquefaction module;
The recirculated refrigerant stream of the open loop feed gas expander based process is combined with the natural gas stream prior to the compressing step.
The method of claim 3. The cold natural gas stream is a first cold natural gas stream;
The method comprises
Separating the first chilled natural gas stream into a second chilled natural gas stream, a first refrigerant stream, and a second refrigerant stream;
Discharging a first cooling stream having a first temperature from a warm end expander forming part of the feed gas expander based liquefaction module;
Discharging a second cooling stream having a second temperature from a cold end expander that forms part of the feed gas expander based liquefaction module;
The first temperature is higher than the second temperature;
The method of claim 4. Expanding the first refrigerant stream in the warm end expander to produce the first cooling stream;
Expanding the second refrigerant stream in the cold end expander to produce the second cooling stream;
The method of claim 5. Discharging a first cooling stream having a first temperature from a warm end expander forming part of the feed gas expander based liquefaction module;
Discharging a two-phase stream having a second temperature from a cold end expander forming part of the feed gas expander-based liquefaction module, wherein the first temperature is greater than the second temperature. Said releasing step is also high,
Expanding the first refrigerant stream in the warm end expander to produce the first cooling stream;
Expanding the second refrigerant stream in the cold end expander to produce the two-phase stream;
Separating the two-phase stream into a second cooling stream and a first pressurized LNG stream;
The method of claim 4. The pressure of the first cooling stream is
The same or similar to the pressure of the second cooling stream, or higher than the pressure of the second cooling stream,
One of the
8. A method according to any one of claims 5 to 7. The liquefying step cools the second chilled natural gas stream to form a second pressurized LNG stream by exchanging heat with the first cooling stream and the second cooling stream. Including stages,
8. A method according to any one of claims 5 to 7. The second pressurized LNG stream is mixed with the first pressurized LNG stream before expanding the second pressurized LNG stream.
The method of claim 9. Reducing the pressure of the second pressurized LNG stream such that the second pressurized LNG stream is subjected to at least one stage pressure drop;
Separating the depressurized second pressurized LNG stream into an end flash gas stream and an LNG stream;
Cooling the second pressurized LNG stream and the second chilled natural gas stream using the end flash gas stream.
The method of claim 9. After cooling the second pressurized LNG stream and the second chilled natural gas stream using the end flash gas stream, the end flash gas stream is compressed to reduce the compressed end flash gas stream to 1 or Further comprising mixing with two or more recirculating refrigerant streams;
The method of claim 11. After cooling the second pressurized LNG stream and the second chilled natural gas stream using the end flash gas stream, the end flash gas stream is compressed to use the compressed end flash gas stream as fuel. Further comprising the step of using,
The method of claim 11. The at least two compressors compress the natural gas stream to a pressure greater than 3,000 psia;
14. A method according to any one of claims 1 to 13. The natural gas expander is a work producing expander that expands the cooled compressed natural gas stream to a pressure of less than 2,000 psia.
15. A method according to any one of claims 1 to 14. The natural gas expander is mechanically coupled to at least one compressor;
16. A method according to any one of claims 1 to 15. Cooling the compressed natural gas stream includes cooling the compressed natural gas stream in at least one heat exchanger that exchanges heat with the environment.
The method according to any one of claims 1 to 16. One of the at least two compressors arranged in series is driven by the natural gas expander;
18. A method according to any one of claims 1 to 17. The method further includes the steps of compressing, cooling, expanding, and liquefying the upper deck of the floating LNG structure.
The method according to any one of claims 1 to 18. The compressing, cooling, and expanding steps are performed in a single module on the upper deck of the floating LNG structure.
The method of claim 20. An apparatus for liquefaction of natural gas,
At least two serially arranged compressors configured to compress the natural gas stream to a pressure greater than 2,000 psia, thereby forming a compressed natural gas stream;
A cooling element configured to cool the compressed natural gas stream, thereby forming a cooled compressed natural gas stream;
Natural gas cooled by expanding the cooled compressed natural gas stream to a pressure less than 3,000 psia and not greater than the pressure to which the at least two compressors arranged in series compress the natural gas stream At least one work generating inflator configured to form a stream;
A liquefaction train configured to liquefy the cooled natural gas stream,
A device characterized by that. The liquefaction train comprises one of a nitrogen gas expander based liquefaction module and an open loop feed gas expander based liquefaction module;
The device is
Further comprising a recirculating refrigerant stream of the open loop feed gas expander-based process combined with the natural gas stream before the natural gas stream is compressed by the two or more serially arranged compressors;
The chilled natural gas stream is a first chilled natural gas stream separated into a second chilled natural gas stream, a first refrigerant stream, and a second refrigerant stream.
The apparatus of claim 21. The feed gas expander based liquefaction module comprises:
A warm end expander configured to expand the first refrigerant stream to form a first cooling stream having a first temperature discharged from the expander;
A cold end expander configured to expand the second refrigerant stream to form one of a second cooling stream and a two-phase stream having a second temperature discharged from the expander; Prepared,
The first temperature is higher than the second temperature;
The apparatus of claim 22. The natural gas expander is a work producing expander configured to expand the cooled compressed natural gas stream to a pressure of less than 2,000 psia.
24. Apparatus according to any one of claims 21 to 23. The cooling element comprises a heat exchanger configured to cool the compressed natural gas stream by exchanging heat with the environment;
25. Apparatus according to any one of claims 21 to 24. The at least two compressors arranged in series, the cooling element, the at least one work producing expander, and the liquefaction train are arranged on a floating LNG structure;
26. Apparatus according to any one of claims 21 to 25. The at least two compressors arranged in series, the cooling element, and the at least one work generating expander are arranged in a single module on the upper deck of the floating LNG structure;
27. Apparatus according to claim 26. At least two serially arranged compressors configured to compress the natural gas stream to a pressure greater than 2,000 psia, thereby forming a compressed natural gas stream;
A cooling element configured to cool the compressed natural gas stream, thereby forming a cooled compressed natural gas stream;
Natural gas cooled by expanding the cooled compressed natural gas stream to a pressure less than 3,000 psia and not greater than the pressure to which the at least two compressors arranged in series compress the natural gas stream At least one work generating inflator configured to form a stream;
A liquefaction train configured to liquefy the cooled natural gas stream,
Floating LNG structure.

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