JP2019536969A - Natural gas liquefaction system including an integrated geared turbo compressor - Google Patents

Abstract

According to one aspect of the present disclosure, a natural gas liquefaction system (100) is provided. The system includes an integrated geared turbocompressor with multiple compressor stages (150), a prime mover (160) for driving the compressor, and a precooling loop adapted to circulate a first coolant. A pre-cooling loop (110), wherein one or more first compressor stages (151) of the plurality of compressor stages are adapted to pressurize the first coolant; A cooling loop adapted to circulate a second coolant stage, wherein one or more second compressor stages of the plurality of compressor stages are adapted to pressurize a second coolant. A first heat exchanger device (170) for transferring heat from natural gas and / or from a second coolant to a first coolant; Heat exchanger device (180) for transferring from a second coolant to a second coolant Equipped with a. A further aspect relates to a compressor device for a natural gas liquefaction system. Yet a further aspect relates to a method for liquefying natural gas. [Selection] Figure 2

Description

  The present disclosure relates to systems and methods for liquefying natural gas. More specifically, the present disclosure relates to a system for liquefying natural gas with an integrated geared turbocompressor, and to a compressor device that includes an integrated geared turbocompressor. Further, the present disclosure relates to a method of liquefying natural gas with an integrated geared turbocompressor.

  Natural gas is becoming an increasingly important source of energy. Smaller gas volumes can be beneficial to enable cost-effective transfer of natural gas from a source to a point of use. Cryogenic liquefaction has become a routinely practiced process for converting natural gas into a liquid, making the process more convenient, cheap and safer to store and transport. Transport of liquefied natural gas (LNG) by pipeline or transport pipe is made possible at ambient pressure by maintaining the cooling gas and liquefied gas at a temperature below the liquefaction temperature at ambient pressure.

  To store and transport natural gas in a liquid state, the natural gas is preferably cooled to about -150 to -170C, and the gas has a pressure that is approximately near atmospheric vapor pressure.

  Several processes and systems are known for the liquefaction of natural gas, which are provided for the continuous passage of natural gas at elevated pressure, through multiple cooling stages, wherein the gas has a liquefaction temperature. Until the temperature is reached, a continuous refrigeration cycle cools down the temperature continuously.

  Prior to passing the natural gas through the cooling stage, the natural gas is generally pre-treated to remove impurities that can interfere with processing, damage machinery, or are undesirable in the final product. You. Impurities include acid gases, sulfur compounds, carbon dioxide, mercaptans, water, and mercury. The pre-treated gas to remove impurities is then typically cooled by a refrigerant stream to separate heavier carbohydrates. The remainder of the gas consists primarily of methane and usually contains less than 0.1% of a higher molecular weight hydrocarbon, such as propane or heavier hydrocarbons. Cleaned and washed natural gas is cooled to a final temperature in a cold section. The resulting LNG can be stored and transported at about atmospheric pressure.

  Cryogenic liquefaction is typically performed by means of a multiple cycle process (ie, a process that uses more than one refrigeration cycle). Depending on the type of process, each cycle can use a different coolant, or, alternatively, the same coolant can be used in more than one cycle. In a standard cryogenic liquefaction system (eg, in a so-called APCI process), natural gas is first cooled by a first coolant circulating in a pre-cooling loop, followed by a second coolant circulating in a cooling loop. Cooled by coolant.

  In the pre-cooling loop, circulating the first coolant may be compressed, condensed, and expanded to subsequently remove heat from the natural gas. In the cooling loop, circulating the second coolant may be compressed and cooled to subsequently remove heat from the natural gas. However, driving two cooling loops (a pre-cooling loop and a cooling loop) consumes a lot of energy, costs a lot and takes up a lot of space.

  Therefore, it would be beneficial to design and provide methods and systems for liquefying natural gas that provide better energy efficiency and consume less space.

  In view of the above, there is provided a natural gas liquefaction system, a compressor device, and a method for liquefying natural gas.

  According to one aspect of the present disclosure, a natural gas liquefaction system is provided. The system includes an integrated geared turbocompressor with a plurality of compressor stages, a prime mover for driving the compressor, and a pre-cooling loop adapted to circulate a first coolant, comprising: A pre-cooling loop, wherein one or more first compressor stages of the compressor stage are adapted to pressurize the first coolant, and a cooling loop adapted to circulate the second coolant. A cooling loop, wherein one or more second compressor stages of the plurality of compressor stages are adapted to pressurize a second coolant, and the heat from natural gas and / or from the second coolant. A first heat exchanger device for transferring heat to a first coolant and a second heat exchanger device for transferring heat from natural gas to a second coolant.

  An integrated geared turbocompressor according to embodiments described herein connects at least one force transmission mechanism, specifically between two or more compressor stages of a plurality of compressor stages. Includes gears.

  According to another aspect, a compressor device for compressing a plurality of coolants is provided. The compressor device is an integrated geared turbocompressor with a plurality of compressor stages, and a first cooling loop adapted to circulate a first coolant, wherein one of the plurality of compressor stages. A first cooling loop, wherein the first compressor stage is adapted to pressurize a first coolant, and a second cooling loop adapted to circulate a second coolant. A second cooling loop, wherein one or more second compressor stages of the plurality of compressor stages are adapted to pressurize a second coolant.

  According to another aspect, a method is provided for liquefying natural gas. The method includes providing an integrated geared turbocompressor having a plurality of compressor stages, driving a compressor with a prime mover, and one or more first compressor stages of the plurality of compressor stages. Circulating a first coolant through one or more of the plurality of compressor stages; circulating a second coolant through one or more second compressor stages of the plurality of compressor stages; Cooling at least one of the natural gas and the second coolant by heat exchange in contact with the material; and cooling the natural gas by heat exchange in contact with the second coolant.

  Further aspects, advantages and features of the present disclosure are apparent from the dependent claims, the description and the accompanying drawings.

  A more specific description of the present disclosure, briefly summarized above, may be made by reference to embodiments so that a detailed understanding of the above-enumerated features of the present disclosure may be understood in detail. The accompanying drawings are described below with reference to embodiments of the present disclosure. Some embodiments are illustrated in the drawings and are described in detail in the description that follows.

1 is a schematic diagram of a standard APCI process for liquefying natural gas. 1 is a schematic diagram of a natural gas liquefaction system according to embodiments described herein. FIG. 3 is a schematic diagram of a natural gas liquefaction system according to further embodiments described herein. FIG. 2 is an enlarged schematic view of a compressor device for a natural gas liquefaction system according to embodiments described herein. FIG. 3 is a schematic diagram of a natural gas liquefaction system according to further embodiments described herein. FIG. 3 is a flow diagram illustrating a method for liquefying natural gas, according to embodiments described herein.

  At this point, one or more examples thereof are shown in the figures, where reference will be made to various embodiments of the present disclosure. Each example is provided by way of explanation, and is not meant as a limitation. For example, features illustrated or described as part of one embodiment, can be used on or in conjunction with any other embodiments to yield yet further embodiments. It is intended that the present disclosure include such modifications and variations.

  In the following description of the drawings, the same reference numerals refer to corresponding or similar components. Generally, only the differences with respect to the individual embodiments are described. Unless otherwise indicated, description of a portion or aspect of one embodiment applies equally to the corresponding portion or aspect of another embodiment.

  FIG. 1 shows a schematic diagram of a standard natural gas liquefaction system using the so-called APCI process. The process shown uses two cooling cycles. The pre-cooling cycle 12 uses a first coolant, and the cooling cycle 2 uses a second coolant.

  The system (collectively labeled 1) includes a cooling cycle 2, which includes a line formed by a gas turbine 3 driving a compressor train. The compressor train includes a first compressor 5 and a second compressor 7 arranged in series for compressing a second coolant. The interstage cooler 9 cools the second coolant delivered by the first compressor 5 before entering the second compressor 7 to reduce the temperature and reduce the volume of the second coolant. May be provided to The compressed second coolant delivered by the second compressor 7 may condense on air or moisture in the second condenser 11. The second coolant is cooled and partially liquefied by heat exchange with the first coolant circulating in the precooling cycle 12.

  Precooling cycle 12 includes a line that includes gas turbine 13 that drives compressor 15. The compressed first coolant delivered by the compressor 15 condenses in the first condenser 17 on contact with moisture or air. The condensed first coolant is used for pre-cooling the natural gas down to -40 ° C and for cooling and partially liquefying the second coolant. Pre-cooling of the natural gas and partial liquefaction of the second coolant takes place in a plurality of pressurized processes of the example shown in FIG.

  The condensed first coolant stream from the first condenser 17 is used to cool and partially liquefy the second coolant from the first of four auxiliary heat exchangers that are sequentially arranged. Delivered to one set and delivered to a second set of four pre-cooled heat exchangers arranged in series to pre-cool natural gas. A first portion of the compressed first coolant flowing from the first condenser 17 is delivered via pipe 19 to a first set of heat exchangers, with four gradually decreasing different pressure levels. Until the inflators 21, 23, 25 and 27 are arranged in series. Downstream from each expander, a portion of the expanded first coolant branches to a respective heat exchanger 29, 31, 33, and 35.

  The compressed second coolant delivered from the second condenser 11 can flow through the pipe 37 to the main cold heat exchanger 38. The pipe 37 passes continuously through the heat exchangers 29, 31, 33, and 35, whereby the second coolant is gradually cooled against the expanded first coolant and partially liquefied. I do.

  A second fraction of the condensed first coolant from the first condenser 17 is delivered to a second pipe 39 and comprises four expanders 41, 43, 45 and arranged in series. 47 expands continuously. A portion of the first coolant expanded in each expander diverges toward a corresponding pre-cooled heat exchanger 49, 51, 53, and 55, respectively. The main natural gas line 61 flows continuously through the pre-cooled heat exchangers 49, 51, 53 and 55 so that natural gas is pre-cooled before entering the main cold heat exchanger 38. The heated first coolant from the pre-cooled heat exchangers 49, 51, 53, and 55 is collected together with the first coolant from the heat exchangers 29, 31, 33, and 35, and again. , Supplied to the compressor 15, which collects the four evaporative streams of the first coolant and recompresses the steam.

  The system shown in FIG. 1 is driven by at least one compressor driven by a gas turbine 13 for compressing a first coolant and a gas turbine 3 for compressing a second coolant. At least one further compressor. Therefore, the energy efficiency of the system shown in FIG. 1 is limited and the two gas turbines 3, 13 consume a considerable amount of space.

  A natural gas liquefaction system 100 according to embodiments described herein is schematically illustrated in FIG.

  The natural gas liquefaction system 100 includes an integrated geared turbo with multiple compressor stages configured to be driven by a prime mover 160, specifically, a single prime mover such as an internal combustion engine or an electric motor. A compressor 150 (also simply referred to as compressor 150). In other words, each compressor stage of the plurality of compressor stages of compressor 150 may be driven directly or indirectly by prime mover 160. The transmission mechanism 301, specifically the gears of the compressor, including one or more gear wheels and / or other transmission units such as pinions, pulleys, gears, etc., compresses to rotationally drive multiple compressor stages. The compressor 150 may be connected between multiple compressor stages. Drive may be provided by the prime mover 160, for example, via a main drive shaft connected to an integrated geared turbocompressor.

  By providing a compressor with an integral gear, the direction of the speed, torque, and / or torque provided by the prime mover can be changed as needed. For example, the rotational speed and / or torque of the impellers of a plurality of compressor stages can be individually adjusted as needed. In some embodiments, the transmission mechanism may include a gear train or transmission. A compressor stage impeller can be mounted on each shaft that can be rotationally driven by one of the transmission elements of the gear. For example, the gear may include at least one gear wheel that can rotationally drive one or more shafts. A pinion can be mounted on each of the shafts that can mesh with at least one gear wheel. Further, one or two impellers of a plurality of compressor stages may be mounted on each of the shafts.

  In a one-piece geared compressor, at least one or more transmission units, such as one or more gear wheels, are connected between at least a portion of the plurality of compressor stages, such that each of the compressor stages is The impeller can rotate at different rotational speeds. When a gear or another force transmission mechanism is connected between at least some compressor stages, the compressor stages can be provided on different shafts, which can be adapted to rotate at different rotational speeds. . For example, the impeller of one or more first compressor stages may rotate at a different rotational speed than the impeller of one or more second compressor stages.

  For example, in some embodiments, one or more force transmission elements, such as one or more central gear wheels, may have different rotational speeds, one or more first compressor stages and one or more second compressor stages. To drive the compressor stages. The one or more first compressor stages may be provided on a different shaft than the one or more second compressor stages.

  In some embodiments, which may be combined with other embodiments described herein, one or more force transmitting elements, such as a central gear wheel, may be driven at different rotational speeds and at two or more first compressors. It can be configured to drive a stage. In some embodiments, which may be combined with other embodiments described herein, one or more force transmitting elements, such as a central gear wheel, may be driven at different rotational speeds and at two or more second compressors. It can be configured to drive a stage. In some embodiments, the integral geared compressor may include multiple force transmitting elements, such as multiple central gear wheels, to drive each of the multiple compressor stages at a desired rotational speed.

  Further, as shown in FIG. 2, the natural gas liquefaction system 100 is a pre-cooling loop 110 adapted to circulate a first coolant, wherein the pre-cooling loop 110 includes one or more first compression stages of a plurality of compressor stages. A pre-cooling loop 110 wherein stage 151 is adapted to pressurize the first coolant, and a cooling loop 130 which is adapted to circulate second coolant, wherein one of a plurality of compressor stages. The second compressor stage 155 includes a cooling loop 130 adapted to pressurize the second coolant.

  Each compressor stage of the plurality of first and second compressor stages may include a gas inlet, a gas outlet, and at least one impeller rotating on a respective shaft. The compressor stage may be an axial or radial compressor stage.

  One or more first compressor stages 151 for pressurizing the first coolant may be driven directly or indirectly by the prime mover 160, for example, via a transmission mechanism or gears of the compressor. One or more second compressor stages 155 for pressurizing the second coolant may also be directly or indirectly driven by the prime mover 160, for example, via the transmission mechanism or gears of the compressor 150. Can be done.

  In accordance with embodiments described herein, a single integrated geared multi-stage compressor driven by prime mover 160 may be provided in more than one cooling loop, for example, in pre-cooling loop 110 and in cooling loop 130. May be provided to pressurize two or more coolants circulating in the. In some embodiments, the entire LNG liquefaction system may include a single integral geared compressor configured to pressurize two or more coolants used to liquefy natural gas. .

  The first and second compressor stages of the compressor may be housed in a single compressor casing, for example, in a compact and space-saving manner. For example, the wall of the compressor housing surrounds a first plurality of compressor stages, a second plurality of compressor stages, and a compressor gear transmission element interconnecting the compressor stage drive shafts. obtain.

  By using a multi-stage compressor with integrated gears to pressurize two, three or more coolants of the LNG liquefaction system, energy and space were previously reduced to include one or more separate compressors. Savings can be made compared to the system used. Adjustment of the rotational speed of the compressor stages may be further possible because the multiple compressor stages are drivingly connected by integral gears of the compressor.

  Further, as shown in FIG. 2, the natural gas liquefaction system 100 may further transfer heat from natural gas to the first coolant and / or from the second coolant to the first coolant. And a second heat exchanger device 180 for transferring heat from natural gas to a second coolant.

  In some embodiments, the natural gas is adapted to be continuously cooled by the first coolant and by the second coolant. Natural gas may be directed through one or more first heat exchangers of the first heat exchanger device 170, wherein the natural gas is, for example, down to a temperature below 0 ° C., specifically − It can be pre-cooled by the first coolant to below 40 ° C. Subsequently, natural gas may be directed through the second heat exchanger device 180, where the natural gas is cooled by the second coolant. The second heat exchanger device 180 may be the primary low temperature heat exchanger of the system configured to cool the natural gas down to the liquefaction temperature.

  2, the second heat exchanger device 180 removes heat from the natural gas flowing through the main natural gas line 61 and transfers the heat to the second coolant flowing through the cooling loop 130. It is shown in a simplified way as a transporting device.

  The first coolant circulating in the pre-cooling loop 110 may be used to pre-cool natural gas at the location of the main natural gas line 61 upstream from the second heat exchanger device 180. Alternatively or additionally, the first coolant may be used to cool the second coolant at a location in the cooling loop 130 that is upstream from the second heat exchanger device 180.

  In the embodiment shown in FIG. 2, the first heat exchanger device 170 is configured to pre-cool natural gas and further to cool a second coolant. Heat exchanger. First coolant exiting the first heat exchanger device 170 is directed back to the compressor 150 and may be recompressed in one or more first compressor stages 151 of the compressor.

  In some embodiments, the second coolant exiting the first heat exchanger device 180 is directed back to the compressor 150 and one or more second compressor stages 155 of the compressor. Can be recompressed within

  In some embodiments, which may be combined with other embodiments described herein, the pre-cooling loop 110 includes a first condenser 17 for removing heat from the first coolant after compression. The pre-cooling loop may further include, upstream from the first heat exchanger device 170, at least one expansion element (not shown in FIG. 2) for expanding the first coolant.

  Cooling loop 130 may include a second condenser 11 for removing heat from the second coolant after compression.

  In some embodiments that may be combined with other embodiments described herein, the first coolant is a gas having a molecular weight of 35 or more, specifically 40 or more, more specifically , Including propane.

  In some embodiments, which may be combined with other embodiments described herein, the second coolant may be a mixed, which may include a mixture comprising at least one or more of nitrogen, methane, ethane, and propane. Coolant.

  In some embodiments, which may be combined with other embodiments described herein, at least one of the plurality of compressor stages is capable of self-sustaining flow entering at least one compressor stage. A movable inlet guide vane is provided that adjusts the inlet. For example, each of the one or more first compressor stages 151 may include a respective movable inlet guide vane.

  As shown schematically in FIG. 2, a single prime mover may be provided to drive each of the one or more first and second compressor stages. In some embodiments, prime mover 160 may be or include a gas turbine and / or a motor (eg, an electric motor or an internal combustion engine). One or more gearbox elements of the integrated geared turbocompressor may be connected between the prime mover, one or more first compressor stages, and / or one or more second compressor stages. For example, at least some of the impellers of the one or more first compressor stages rotate at different rotational speeds and are provided on a different rotating shaft than at least some of the impellers of the one or more second compressor stages. Can be

  A natural gas liquefaction system 200 according to the embodiments described herein is schematically illustrated in FIG. The basic settings of the natural gas liquefaction system 200 are similar to the system shown in FIG. 2 so that the above description can be referred to and will not be repeated here.

  The natural gas liquefaction system 200 includes an integrated gear stage with multiple compressor stages configured to be driven by a prime mover 160, specifically a single prime mover, such as a gas turbine or another internal combustion engine. Includes turbo compressor 150 with attached. In other words, each compressor stage of the plurality of compressor stages of compressor 150 may be driven directly or indirectly by prime mover 160. For example, a transmission mechanism, specifically a compressor gear with multiple gear wheels and / or other transmission units such as pinions and / or pulleys, rotationally drives multiple compressor stages at the appropriate rotational speed. To be connected between the prime mover 160 and a plurality of compressor stages of the compressor 150.

  In some embodiments, compressor 150 includes a plurality of first compressor stages 151 configured to pressurize a first coolant circulating in precooling loop 110. For example, four first compressor stages may be provided. In other embodiments, a different number of first compressor stages (eg, more than two, three, or four first compressor stages) may be provided.

  The plurality of first compressor stages 151 may be arranged sequentially in a pre-cooling loop. For example, the first coolant entering the compressor 150 in the first first compressor stage is subsequently arranged by and downstream from the first first compressor stage. Pressurized by another first compressor stage (s). The pressure of the first coolant may increase in each of the first compressor stages 151 that are sequentially arranged.

  In some embodiments, which may be combined with other embodiments described herein, the compressor 150 includes a plurality of compressors configured to pressurize a second coolant circulating in the cooling loop 130. A second compressor stage 155 may be included. For example, two, three, four or more second compressor stages 155 may be provided. The second compressor stage 155 may be arranged continuously in the cooling loop. In other words, the second coolant entering the compressor 150 in the first second compressor stage is subsequently arranged by and downstream from the first second compressor stage. May be pressurized by additional second compressor stage (s). The pressure of the second coolant may be increased by each of the second compressor stages 155 that are sequentially arranged. The impellers of the two or more second compressor stages may, in some embodiments, be mounted on different shafts and rotate at different rotational speeds.

  For example, compressor 150 may include four first compressor stages for pressurizing a first coolant and three (or alternatively, four) fourth stages for pressurizing a second coolant. And two compressor stages.

  In some embodiments, the pre-cooling loop 110 may be configured to distribute the first coolant to a plurality of pre-cooled streams directed to each one of the plurality of first compressor stages 151. The number of pre-cooled streams may correspond to the number of first compressor stages. Each of the pre-cooled streams is recompressed by the associated first compressor stage and, if applicable, potentially by a further first compressor stage (s) arranged downstream thereof. It can enter the compressor in one compressor stage.

  In some embodiments, the plurality of first expansion elements 241, 243, 245, 247 are sequentially arranged in the pre-cooling loop 110 and configured to expand the first coolant at a plurality of reduced pressure levels. Can be done. The plurality of first heat exchangers 249, 251, 253, 255 of the first heat exchanger device 270 are expanded by at least one of the plurality of first expansion elements 241, 243, 245, 247. Provision may be made to receive a pre-cooled flow of each of the one coolant and to transfer heat from natural gas to the first coolant.

  The pre-cooled flow of the first coolant is configured to return from each of the plurality of first heat exchangers 249, 251, 253, 255 to one of the plurality of first compressor stages 151. A plurality of return paths 261, 263, 265, 267 may be provided.

  According to some embodiments that may be combined with other embodiments described herein, the at least one first auxiliary expansion element may be arranged in a pre-cooling loop. Further, the at least one first auxiliary heat exchanger is configured to receive at least a portion of the first coolant expanded by the at least one first auxiliary expansion element and to transfer heat from the second coolant to the second coolant. It may be provided to transfer to one coolant.

  According to some embodiments that may be combined with other embodiments described herein, the system includes a first coolant that is continuously arranged in a pre-cooling loop 110 and at a plurality of vacuum levels. It may include a plurality of first auxiliary inflation elements 221, 223, 225, 227 configured to inflate. The plurality of first auxiliary heat exchangers 229, 231, 233, 235 of the first heat exchanger device 270 are expanded by at least one of the plurality of first auxiliary expansion elements 221, 223, 225, 227. It is configured to receive each portion of the first coolant and to transfer heat from the second coolant to the first coolant.

  The plurality of return paths 261, 263, 265, 267 allow a portion of the first coolant to pass from the plurality of first auxiliary heat exchangers 229, 231, 233, 235 and / or the first heat exchanger 249. , 251, 253, 255 to each one of the plurality of first compressor stages 151.

  During operation of the natural gas liquefaction system 200, the compressed first coolant stream is delivered to the first condenser 17 from the most downstream of the first compressor stage of the plurality of first compressor stages 151. Can be done. The first coolant stream delivered through the first condenser 17 can be cooled and condensed, for example, against moisture or air.

  In some embodiments, the condensed first coolant circulates in a pre-cooling loop 110 to pre-cool natural gas in a plurality of first heat exchangers 249, 251, 253, 255, and / or Alternatively, the second coolant circulating in the cooling loop 130 of the plurality of first auxiliary heat exchangers 229, 231, 233, 235 is cooled and optionally partially liquefied.

  In some embodiments, the pre-cooling loop 110 may be distributed over a plurality of n pressure levels (eg, four pressure levels). The number of n pressure levels may correspond to the n numbers of the first compressor stage of compressor 150 configured to compress the first coolant. The first coolant stream delivered through the first condenser 17 may, for example, expand continuously to n decreasing pressure levels and be distributed into n partial streams. Each of the first coolant partial flows may return to the compressor 150 to flow laterally at the inlet of a corresponding one of the plurality of first compressor stages 151.

  The first delivery line 217 may deliver a first portion of the condensed first coolant stream to a plurality of first expansion elements 241, 243, 245, 247. A second delivery line 218 diverging from the first delivery line 217 delivers a second portion of the condensed first coolant flow to a plurality of first auxiliary expansion elements 221, 223, 225, 227. I can do it.

  A first portion of the condensed first coolant from the first condenser 17 is provided within the plurality of first expansion elements 241, 243, 245, 247 at n decreasing pressure levels. Can swell continuously. Downstream from each of the first expansion elements, a portion of the partially expanded first coolant stream branches to a respective one of the plurality of first heat exchangers 249, 251, 253, 255. obtain. The remaining portion of the partially expanded first coolant may be flowed through the next first expansion element and the like. The remaining first coolant flowing through the most downstream element (247) of the plurality of first expansion elements 241, 243, 245, 247 is supplied to the plurality of first heat exchangers 249, 251, 253, 255. To the most downstream element (255).

  In each one of the plurality of first heat exchangers 249, 251, 253, 255, the first coolant may perform a heat exchange in contact with the natural gas flowing in the main natural gas line 61, and thus the natural gas Is precooled and optionally partially liquefied.

  A second portion of the condensed first coolant expanded in at least one of the plurality of first auxiliary expansion elements 221, 223, 225, 227 is coupled to the plurality of first auxiliary heat exchangers 229, 231. , 233, 235 to the corresponding ones. A portion of the first coolant delivered by each one of the plurality of first auxiliary expansion elements 221, 223, 225, 227 and not flowed through each first auxiliary heat exchanger is a plurality of first coolants. It is delivered through a subsequent one of the first auxiliary inflation elements 221, 223, 225, 227. The most downstream element 235 of the plurality of first auxiliary heat exchangers 229, 231, 233, 235 expands in the most downstream element 227 of the plurality of first auxiliary expansion elements 221, 223, 225, 227. Receive the remaining small portion of the first coolant. In each of the first auxiliary heat exchangers, the first coolant performs a heat exchange in contact with a second coolant circulating in the cooling loop 130, whereby the plurality of first auxiliary heat exchangers 229 are provided. , 231, 233, 235, the second coolant is cooled and, optionally, at least partially liquefied.

  The heated first coolant from the plurality of first heat exchangers 249, 251, 253, 255 is heated first cooling from the first auxiliary heat exchangers 229, 231, 233, 235. It may be collected with the material and again supplied to the integrated geared turbocompressor 150 at the inlet of each first compressor stage.

  In some embodiments, the heated first coolant exiting one of the plurality of first auxiliary heat exchangers 229, 231, 233, 235 comprises a plurality of first heat exchangers 249, 251. At about the same pressure as the heated first coolant emanating from that corresponding to 253,255. First coolant collected at a corresponding pressure level may be delivered to an inlet of a corresponding one of the plurality of first compressor stages of compressor 150. Thus, the plurality of tributaries of the first coolant return at the inlet of the first compressor stage 151, which is arranged in sequence, at a gradually decreasing pressure level.

  In some embodiments, the plurality of return paths 261, 263, 265, 267 direct the expanded and depleted tributaries of the first coolant from the plurality of first heat exchangers 249, 251, 253, 255. And / or from a plurality of first auxiliary heat exchangers 229, 231, 233, 235 to a corresponding one of the plurality of first compressor stages 151.

  In some embodiments, which may be combined with other embodiments described herein, the second coolant circulating in the cooling loop 130 includes a plurality of second coolants that may be sequentially arranged in the cooling loop 130. It may be compressed by two compressor stages 155. The plurality of second compressor stages 155 are part of the same integral geared compressor as the plurality of first compressor stages 151.

  In some embodiments, the integrated geared compressor comprises at least one multi-stage compressor unit (eg, a multi-stage centrifugal compressor) with two or more compressor stages sequentially arranged on a single shaft. Unit).

  The prime mover 160 that drives the compressor may include an internal combustion engine or an electric motor. The prime mover 160 may be a gas turbine (eg, an aeroderivative gas turbine).

  In some embodiments, the at least one first intercooler is arranged between at least two consecutively arranged first compressor stages of the plurality of first compressor stages 151. obtain. In some embodiments, the at least one second intercooler is arranged between at least two consecutively arranged second compressor stages of the plurality of second compressor stages 155. obtain. Intercoolers reduce the temperature and volume of each coolant delivered by each compressor stage before the coolant enters or exits a subsequent compressor stage. It can be configured as follows.

  The second coolant delivered by the most downstream one of the plurality of second compressor stages 155 may be condensed by the second condenser 11. The second condenser 11 may be an air condenser of a water condenser, and the second coolant may be condensed by performing a heat exchange on air or moisture. Subsequently, the condensed second coolant may be delivered by a delivery line passing through the plurality of first auxiliary heat exchangers 229, 231, 233, 235 and, as described above, the second coolant The material may be cooled and optionally liquefied by performing heat exchange with the first coolant circulating in the pre-cooling loop 110.

  Cooled second coolant delivered from the plurality of first auxiliary heat exchangers can be directed toward a second heat exchanger device 180, which can be a primary cold heat exchanger, and the second cooling The material can remove additional heat from the pre-cooled natural gas to complete the liquefaction process. The heated second coolant may return to the first one of the plurality of second compressor stages 155 of compressor 150 via return line 269.

  In FIG. 3, the multiple compressor stages of the integrated geared turbocompressor 150 are shown only in a schematic manner. The compressor 150 of the exemplary embodiment is shown in more detail in FIG.

  FIG. 4 is an enlarged schematic diagram of a compressor device with an integrated geared turbocompressor 150 according to embodiments described herein. Compressor 150 may be driven by prime mover 160 and may include a plurality of compressor stages driven directly or indirectly by prime mover 160. The plurality of compressor stages include one or more first compressor stages 151 for pressurizing a first coolant circulating in the first pre-cooling loop 110 and a second circulating in the cooling loop 130. And one or more second compressor stages 155 for pressurizing the coolant. More details of the pre-cooling loop 110 and the cooling loop 130 have been described above with reference to FIGS. 2 and 3, and the description will not be repeated here.

  Compressor 150 may include a transmission mechanism 301 (eg, integral gear) that may be arranged within compressor housing 330 and configured to be driven by prime mover 160. The compressor 150 is further configured to be rotationally driven by the transmission mechanism 301 and configured to drive at least one of the plurality of first compressor stages 151. One shaft 303 may be included. In other words, the impeller of at least one first compressor stage may be mounted on at least one first shaft 303, for example, to rotate with the first shaft. Further, the compressor 150 is configured to be rotationally driven by the transmission mechanism 301 and configured to drive at least one of the plurality of second compressor stages 155. May include two shafts 305. Therein, the impeller of at least one second compressor stage may be mounted on at least one second shaft 305, for example, to rotate with the second shaft.

  In some embodiments, the at least one first shaft 303 includes two first compressor stages of the plurality of first compressor stages (eg, two subsequent first compressor stages). Can be driven. Alternatively, or in addition, at least one second shaft 305 may include two second compressor stages of a plurality of second compressor stages (eg, two subsequent second compressor stages). Can be driven.

  In some embodiments, at least one first shaft 303 may include a pinion that meshes with a gear wheel of transmission mechanism 301 and / or at least one second shaft 305 further includes transmission mechanism 301 May be provided with a pinion that meshes with the gear wheel. For example, in some embodiments, the transmission mechanism 301 drives a first gear wheel 307 configured to drive at least one first shaft 303 and at least one second shaft 305. And a second gear wheel 308 configured as such.

  Alternatively, for example, in the embodiment shown schematically in FIG. 5, the transmission mechanism 301 is configured to drive at least one first shaft 303 and to drive at least one second shaft 305. One central gear wheel 307 may be included. For example, a single bull gear configured to drive (eg, directly) each of the first and second compressor stages may be provided.

  In other words, a first pinion having a first diameter may be connected to at least one first shaft 303 and / or a second pinion having a second diameter may be connected to at least one second shaft 305 can be connected. A central gear wheel 307 of the gear may directly mesh with the first and second pinions to rotationally drive at least one first shaft and at least one second shaft. In the embodiment shown in FIG. 5, the central gear wheel 307 meshes directly with each pinion connected to two or more first shafts 303 and two or more second shafts 305. For example, a (single) central gear wheel may directly drive the shafts of three, four or more first compressor stages and three, four or more second compressor stages.

  The first diameter of the first pinion may correspond to the second diameter of the second pinion. Thus, the first shaft and the second shaft may rotate at a corresponding rotational speed. Alternatively, the first diameter and the second diameter can be different. Thus, the rotational speeds of the first shaft and the second shaft can be adjusted differently as needed. For example, the rotational speeds of the first and second compressor stages may be adapted to the characteristics of each coolant guided therethrough.

  In an alternative embodiment, two or more bull gears may be provided to drive multiple compressor stages. For example, a first bull gear may drive one or more first compressor stages, and a second bull gear may drive one or more second compressor stages.

  Note that in some embodiments, at least one first shaft and / or at least one second shaft may drive two compressor stages that may be arranged at opposite ends of each shaft. . In FIGS. 3 and 5, the two compressor stages provided on a single shaft are schematically indicated by two oppositely pointing arrows connected by a connecting line indicating a common shaft. For example, a first impeller of one compressor stage may be mounted on a first portion of a common shaft, and a second impeller of a further compressor stage may be mounted on a second portion of a common shaft.

  Referring back to FIGS. 3 and 4, in some embodiments that may be combined with other embodiments described herein, first gear wheel 307 includes a plurality of first compressor stages 151. , And the second gear wheel 308 may drive a plurality of second compressor stages 155. The gear wheels may each be a gear that is directly or indirectly driven to rotate by the prime mover 160. The first and second shafts may each include a pinion mounted thereon and meshing with a respective gear. Thus, the first and second shafts and the impeller (s) mounted on the shafts can rotate at different rotational speeds.

  The diameter of the second gear wheel 308 may be smaller than the diameter of the first gear wheel 307. When the first gear wheel 307 directly meshes with the second gear wheel 308, the second gear wheel 308 may rotate at a higher rotation speed than the first gear wheel 307. Accordingly, at least one second shaft 305 driven by the second gear wheel 308 may rotate at a higher rotational speed than at least one first shaft 303 driven by the first gear wheel 307. Thus, the impeller (s) of the first compressor stage (s) mounted on at least one first shaft 303 will have a second compression stage mounted on at least one second shaft 305. It may rotate at a higher rotational speed than the impeller (s) of the stage (s).

  In some embodiments, which may be combined with other embodiments described herein, the compressor may include more than one first shaft driving a plurality of first compressor stages 151; Two or more first shafts may be driven by a first gear wheel 307. The at least one first shaft may be configured to drive two consecutively arranged first compressor stages. Alternatively or additionally, at least one first shaft may be configured to drive a single first compressor stage. In the latter case, a single first compressor stage impeller may be mounted on the first shaft.

  In some embodiments, which may be combined with other embodiments described herein, the compressor includes two or more second shafts for driving a plurality of second compressor stages 155. Thus, two or more second shafts may be driven by a second gear wheel 308. The at least one second shaft may be configured to drive two sequentially arranged second compressor stages. Alternatively or additionally, the at least one second shaft may be configured to drive a single one of the plurality of second compressor stages.

  Each compressor stage of the plurality of compressor stages may include a gas inlet, a gas outlet, and at least one impeller mounted on each shaft. Each impeller can be a radial impeller having an axial inlet and a radial outlet. Fluid that is processed through the impeller may be collected in the spiral structure of each of the compressor stages. The impellers may be a set, and a pair of impellers (eg, belonging to two subsequent compressor stages) may be mounted on a common rotating shaft.

  In some embodiments, the plurality of first compressor stages 151 may be configured to compress the first coolant, such that the first coolant under pressure is between 10 bar and 40 bar. At a pressure ranging from 20 bar to 30 bar absolute, more specifically from 22 bar to 24 bar absolute, the plurality of first compressor stages 151 from the most downstream first compressor stage 312. The pressure of the first coolant at the inlet of the most upstream first compressor stage 315 may be between 1 bar (absolute) and 2 bar (absolute) in some embodiments.

  Alternatively or additionally, the plurality of first compressor stages 151 may be configured to compress the first coolant, such that the first coolant under pressure is between 60 ° C and 100 ° C. ° C, specifically from the most downstream first compressor stage 312 of the plurality of first compressor stages 151 at a temperature ranging from 75 ° C to 85 ° C. For example, an intercooling stage may not be provided between the two first compressor stages.

  In some embodiments, at least one first shaft 303 on which one or more impellers of one or more first compressor stages 151 is mounted has a speed of between 3,000 rpm (rev / min) and 7,000 rpm. Specifically, it can be configured to rotate at a rotation speed of about 4,000 rpm to about 5,500 rpm. In some embodiments, two or more first shafts may be provided, on which the impellers of all of the first compressor stages are mounted. Each of the first shafts may be configured to rotate at a rotational speed from 3000 rpm to about 7000 rpm. The shaft of the most upstream first compressor stage may rotate at a lower speed than the shaft of the most downstream first compressor stage.

A plurality of first compressor stage 151, the flow rate ranging from about ^{10,000actual m 3 / h~70,000actual m 3 /} h, can deliver a first coolant compressed.

  The plurality of first compressor stages 151 may absorb power ranging from about 10 MW to about 40 MW, specifically, ranging from about 25 MW to about 35 MW. Alternatively or additionally, the plurality of second compressor stages 155 may absorb power ranging from about 10 MW to about 40 MW, specifically ranging from about 25 MW to about 35 MW. Thus, in some embodiments, prime mover 160 may provide power ranging from 20 MW to 80 MW, specifically, 50 MW to 70 MW.

  In some embodiments, the plurality of second compressor stages 155 may be configured to compress the second coolant, such that the pressurized second coolant is between 50 bar and 100 bar. Delivered from the second compressor stage 316, which is the most downstream of the plurality of second compressor stages 155, at pressures ranging from 55 bar (absolute), specifically 55 bar to 65 bar (absolute). . The pressure of the second coolant at the inlet of the most upstream second compressor stage 319 may be less than 10 bar (absolute) in some embodiments.

  In some embodiments, the plurality of second compressor stages 155 may be configured to compress the second coolant, such that the pressurized second coolant is between 60C and 120C. ° C, specifically at a temperature ranging from 80 ° C to 100 ° C, and is delivered from the second most downstream compressor stage 316 of the plurality of second compressor stages 155. For example, one, two or more intercooling stages 320 may be provided between at least two subsequent compressor stages. Therefore, the outlet temperature of the second coolant can be reduced.

  The at least one second shaft 305 on which the one or more second compressor stage impeller (s) is mounted may be between 7,000 rpm and 20,000 rpm, specifically between about 8,000 rpm and about 15 rpm. It can be configured to rotate at a rotational speed of 2,000 rpm. In some embodiments, two or more second shafts may be provided to drive the impellers of all second compressor stages 155. The shaft of the most upstream second compressor stage 319 is slower (e.g., from 9,000 rpm) than the shaft of the most downstream second compressor stage 316 (e.g., a speed of 14,000 to 16,000 rpm). (A speed of 11,000 rpm).

  FIG. 4 illustrates an exemplary embodiment in which the plurality of first compressor stages 151 include a total of four consecutively arranged first compressor stages. The upstream pair of the first compressor stage is driven by a rotating shaft, the downstream pair of the first compressor stage is driven by a further rotating shaft, and both rotating shafts are driven by a first gear wheel 307. . In other words, a pair of impellers upstream of the first compressor stage are mounted on a common rotating shaft, and a pair of impellers downstream of the first compressor stage are mounted on a further common rotating shaft. Alternatively, only the upstream pair of the first compressor stages may be driven by a common rotating shaft, while the two downstream first compressor stages may each be driven by a separate rotating shaft, or The reverse is also true.

  In the exemplary embodiment of FIG. 4, the plurality of second compressor stages 155 includes a total of four consecutively arranged second compressor stages. The upstream pair of the second compressor stage is driven by a rotating shaft, the downstream pair of the second compressor stage is driven by a further rotating shaft, and both rotating shafts are driven by a second gear wheel 308. . In other words, a pair of impellers upstream of the second compressor stage are mounted on a common rotating shaft, and a pair of impellers downstream of the second compressor stage are mounted on a further common rotating shaft. Alternatively, only three consecutively arranged second compressor stages may be provided, an upstream pair of the second compressor stages being driven by a common rotating shaft and a downstream second compressor stage. May be driven by a separate rotating shaft, or vice versa.

  Other possible arrangements and numbers of the first and second compressor stages on each rotating shaft driven by the transmission mechanism or gears of the compressor will be apparent to those skilled in the art.

  According to a further aspect, a compressor device for compressing a plurality of coolants is provided. The compressor device includes an integrated geared turbocompressor 150 with multiple compressor stages, which may have some or all of the compressor features described above.

  The compressor arrangement may include a first cooling line (e.g., which may be part of a pre-cooling loop adapted to flow the first coolant), and wherein one or more of the plurality of compressor stages has one or more first cooling lines. Are adapted to pressurize the first coolant flowing through the first cooling line. The compressor device may further include a second cooling line (e.g., which may be part of a pre-cooling loop adapted to flow the second coolant), wherein one or more of the plurality of compressor stages is provided. The second compressor stage is adapted to pressurize the second coolant flowing through the second cooling line.

  The compressor device may be used in a natural gas liquefaction system according to any of the embodiments described above.

  The compressor device may include a transmission mechanism or gear with some or all of the features of the embodiments described above. Further, all compressor stages may, in some embodiments, be contained within a single housing.

  According to another further aspect described herein, there is provided a method of liquefying natural gas. A flow diagram of a method according to embodiments described herein is schematically illustrated in FIG.

  At box 710, an integrated geared turbo compressor having a plurality of compressor stages is provided. In box 720, the compressor is driven by the prime mover. In box 730, a first coolant circulates through one or more first compressor stages of the plurality of compressor stages and a second coolant circulates through one of the plurality of compressor stages. Circulates through the second compressor stage. In box 740, at least one of the natural gas and the second coolant is cooled by heat exchange in contact with the first coolant. In box 750, the natural gas is cooled by heat exchange in contact with the second coolant.

  In some embodiments, the compressed first coolant and / or the compressed second coolant may condense. For example, the condensed first coolant may expand in a plurality of sequentially arranged first expansion elements.

  In some embodiments, the first coolant may be divided into multiple partial flows.

  In some embodiments, at least a portion of the first coolant is continuously compressed by a plurality of first compressor stages (eg, three, four or more first compressor stages). The obtained and / or second coolant may be continuously compressed by a plurality of second compressor stages (eg, three, four or more second compressor stages).

  A movable inlet guide vane may be provided at an inlet of at least one of the plurality of first compressor stages. The movable inlet guide vanes may be independently controlled to regulate the partial flow on the suction side of the plurality of first compressor stages, in particular, depending on the flow state of the partial flow. .

  In some embodiments, the method further comprises expanding the first coolant with the plurality of sequentially arranged first expansion elements at the plurality of reduced pressure levels; Circulating a portion of the material from the first expansion element through the plurality of first heat exchangers to remove heat from the natural gas; and removing a portion of the expanded first coolant to the plurality of first heat exchangers. Returning from one heat exchanger to each one of the one or more first compressor stages.

  In some embodiments, the method further comprises expanding the first coolant with the plurality of consecutively arranged first auxiliary expansion elements at the plurality of reduced pressure levels; Circulating a portion of the coolant through the plurality of first auxiliary heat exchangers to remove heat from the second coolant, and removing a portion of the first coolant to the plurality of first auxiliary heat exchangers; Returning from the heat exchanger to each one of the one or more first compressor stages.

  The prime mover may drive a transmission mechanism (eg, an internal gear) of the compressor, and the transmission mechanism may rotationally drive at least one first shaft and at least one second shaft.

  At least one first shaft can be rotationally driven by the transmission mechanism at a rotational speed of 3,000 rpm or more and 7,000 rpm or less. The impellers of one or two first compressor stages may be mounted on at least one first shaft and may rotate at a rotational speed of at least one shaft.

  At least one second shaft may be rotationally driven by the transmission mechanism at a rotational speed of 8,000 rpm or more and 15,000 rpm or less, and may drive at least one second compressor stage. In other words, the impeller of at least one second compressor stage may be mounted on at least one second shaft.

  In some embodiments, the first coolant is continuously circulated through three, four or more first compressor stages of the compressor, from 10 bar to 40 bar (abs), Specifically, it can be compressed to an outlet pressure ranging from 20 bar to 30 bar (absolute).

  In some embodiments, the second coolant circulates continuously through three, four or more second compressor stages of the compressor, from 40 bar to 100 bar (absolute); In particular, it may be compressed to an outlet pressure ranging from 50 bar to 80 bar (absolute).

  The use of an integrated geared turbocompressor to pressurize two or more different coolants circulating in two or more cooling loops results in an increase in the efficiency of the natural gas liquefaction system and thus a reduction in power consumption. And may also result in significant cost savings when compared to systems with two or more separate compressors and compressor drive units. In addition, the gears of the compressor can be adjusted so that each compressor stage can rotate at the appropriate rotational speed. The use of a single compressor unit in a natural gas liquefaction system has advantages in terms of cost, footprint, and flexibility.

  The number of first and second compressor stages, as well as details of the internal gears of the compressor (eg, details of the transmission mechanism) may depend on the characteristics of the coolant being compressed. Furthermore, if three, four or more coolants are compressed by the integral geared compressor, a large or improved transmission mechanism may be provided.

  While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from its basic scope, the scope of which is set forth in the following claims. Range ".

Claims (18)

A natural gas liquefaction system (100),
An integrated geared turbocompressor (150) with multiple compressor stages;
A single prime mover (160) for driving the compressor (150);
A pre-cooling loop (110) adapted to circulate a first coolant, wherein one or more first compressor stages (151) of the plurality of compressor stages apply the first coolant; Said pre-cooling loop (110) adapted to pressurize;
A cooling loop (130) adapted to circulate a second coolant, wherein one or more second compressor stages (155) of the plurality of compressor stages apply the second coolant. Said cooling loop (130) adapted to pressurize;
A first heat exchanger device (170) for transferring heat from natural gas and / or from the second coolant to the first coolant;
A second heat exchanger device (180) for transferring heat from the natural gas to the second coolant.
The natural gas liquefaction system, wherein the single prime mover (160) drives each of the one or more first compressor stages (151) and the one or more second compressor stages (155). (100).   The compressor (150) includes a plurality of first compressor stages (151) for pressurizing the first coolant, specifically, four consecutively arranged first compressor stages. And / or a plurality of second compressor stages (155) for pressurizing said second coolant, in particular three or four consecutively arranged second compressor stages The system of claim 1, comprising: The compressor (150) includes:
Specifically, a transmission mechanism (301) including a gear configured to be rotationally driven by the prime mover;
At least one first shaft (303) configured to be rotationally driven by the transmission mechanism (301) and configured to drive at least one of the first compressor stages; ,
At least one second shaft (305) configured to be rotationally driven by the transmission mechanism (301) and configured to drive at least one of the second compressor stages; ,
The system according to claim 1, comprising:   The transmission mechanism (301) meshes with at least one first pinion connected to the at least one first shaft (303) for driving the at least one first compressor stage. The system according to claim 3, comprising a gear wheel (307).   The first gear wheel (307) further includes at least one second pinion connected to the at least one second shaft (305) for driving the at least one second compressor stage. The system according to claim 3 or 4, wherein the system meshes with a.   The transmission mechanism (301) connects a first gear wheel (307) configured to drive the at least one first shaft (303) and the at least one second shaft (305). A second gear wheel (308) configured to drive, wherein the diameter of the second gear wheel (308) is greater than the diameter of the first gear wheel (307). 4. The system of claim 3, wherein the first and / or second gear wheels are small and / or directly meshed with a gear wheel.   The at least one of the at least one first shaft and the at least one second shaft drives two compressor stages arranged at opposite ends of the respective shafts. The system according to any one of the above.   The compressor (150) includes a plurality of first compressor stages (151), and the pre-cooling loop (110) transfers the first coolant to the plurality of first compressor stages (151). The system according to any of the preceding claims, configured to distribute a plurality of pre-cooled streams, each directed to one. A plurality of first expansion elements (241, 243, 245) continuously arranged in the pre-cooling loop (110) and configured to expand the first coolant at a plurality of reduced pressure levels. , 247),
Receiving a pre-cooled flow of each of the first coolants expanded by at least one of the plurality of first expansion elements (241, 243, 245, 247), and transferring heat from the natural gas to the first coolant. A plurality of first heat exchangers (249, 251, 253, 255) of said first heat exchanger device (170, 270) for transferring to a coolant of
Returning the pre-cooled stream of the first coolant from the plurality of first heat exchangers (249, 251, 253, 255) to each one of the plurality of first compressor stages (151). Return paths (261, 263, 265, 267) configured as described above,
The system of claim 8, comprising:   At least one first auxiliary expansion element arranged in the pre-cooling loop (110) and for receiving a portion of the first coolant expanded by the at least one first auxiliary expansion element; and At least one first auxiliary heat exchanger of the first heat exchanger device (170, 270) configured to transfer heat from the second coolant to the first coolant; The system of any of the preceding claims, comprising: A plurality of first auxiliary expansion elements (221, 223,...) Continuously arranged in the pre-cooling loop (110) and configured to expand the first coolant at a plurality of reduced pressure levels. 225, 227),
Receiving a portion of each of the first coolant expanded by at least one of the plurality of first auxiliary expansion elements (221, 223, 225, 227); and transferring heat from the second coolant. A plurality of first auxiliary heat exchangers (229, 231, 233, 235) of the first heat exchanger device (170, 270) configured to transfer to the first coolant;
Returning said portion of said first coolant from said plurality of first auxiliary heat exchangers (229, 231, 233, 235) to each one of said plurality of first compressor stages (151). Return paths (261, 263, 265, 267) configured as described above,
The system according to claim 10, comprising:   The first coolant includes a gas having a molecular weight of 40 or more, specifically, propane, and / or the second coolant includes a mixed coolant, specifically, methane, ethane, propane, The system according to any of the preceding claims, wherein the system is a mixture comprising and / or nitrogen.   The system according to any of the preceding claims, wherein the prime mover (160) comprises an electric motor or an internal combustion engine, in particular a gas turbine. A method of liquefying natural gas,
Providing an integrated geared turbocompressor (150) having a plurality of compressor stages;
Driving said compressor (150) with a single prime mover (160);
Circulating a first coolant through one or more first compressor stages (151) of the plurality of compressor stages, wherein the first coolant stage comprises: 151) are each driven by the single prime mover (160), the circulating;
Circulating a second coolant through one or more second compressor stages (155) of the plurality of compressor stages, the second coolant stage comprising: 155) each being driven by the single prime mover (160), the circulating;
Cooling at least one of natural gas and the second coolant by heat exchange in contact with the first coolant;
Cooling the natural gas by heat exchange in contact with the second coolant;
Said method. Expanding the first coolant with a plurality of sequentially arranged first expansion elements (241, 243, 245, 247) at a plurality of reduced pressure levels;
Circulating a portion of the first coolant from the plurality of sequentially arranged first expansion elements through a plurality of first heat exchangers (249, 251, 253, 255); Removing heat from the natural gas;
Returning the portion of the first coolant from the plurality of first heat exchangers to each one of the one or more first compressor stages;
15. The method of claim 14, further comprising: The transmission mechanism (301) of the compressor is driven by the prime mover (160),
At least one first shaft (303) is rotationally driven by the transmission mechanism (301) at a rotational speed of 3,000 rpm or more and 7,000 rpm or less, and drives at least one of the first compressor stages. ,
At least one second shaft (305) is rotationally driven by the transmission mechanism (301) at a rotation speed of 8,000 rpm or more and 20,000 rpm or less, and drives at least one of the second compressor stages. ,
A method according to claim 14.   Said first coolant is continuously circulated through three, four or more first compressor stages and is compressed to an outlet pressure ranging from 10 bar to 40 bar (absolute); and And / or the second coolant is continuously circulated through three, four or more second compressor stages and compressed to an outlet pressure ranging from 50 bar to 100 bar (absolute). 17. The method according to any one of claims 14 to 16, wherein the method is performed.   The movable inlet guide vanes are independently controlled, and in particular, depending on the flow state of each partial flow, the partial flow on the suction side of said one or more first compressor stages 18. The method according to any one of claims 14 to 17, further comprising adjusting.