WO2016152651A1 - Refrigerant circulation system - Google Patents

Refrigerant circulation system Download PDF

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Publication number
WO2016152651A1
WO2016152651A1 PCT/JP2016/058135 JP2016058135W WO2016152651A1 WO 2016152651 A1 WO2016152651 A1 WO 2016152651A1 JP 2016058135 W JP2016058135 W JP 2016058135W WO 2016152651 A1 WO2016152651 A1 WO 2016152651A1
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Prior art keywords
refrigerant
return
vapor
pressure
cooling
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PCT/JP2016/058135
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French (fr)
Japanese (ja)
Inventor
池田　健
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千代田化工建設株式会社
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Publication of WO2016152651A1 publication Critical patent/WO2016152651A1/en

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0022—Hydrocarbons, e.g. natural gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0047—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle
    • F25J1/0052—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by vaporising a liquid refrigerant stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
    • F25J1/008—Hydrocarbons
    • F25J1/0087—Propane; Propylene
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2341/00—Details of ejectors not being used as compression device; Details of flow restrictors or expansion valves
    • F25B2341/001—Ejectors not being used as compression device
    • F25B2341/0011—Ejectors with the cooled primary flow at reduced or low pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/12—Inflammable refrigerants
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B5/00—Compression machines, plants or systems, with several evaporator circuits, e.g. for varying refrigerating capacity
    • F25B5/02—Compression machines, plants or systems, with several evaporator circuits, e.g. for varying refrigerating capacity arranged in parallel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B6/00—Compression machines, plants or systems, with several condenser circuits
    • F25B6/04—Compression machines, plants or systems, with several condenser circuits arranged in series
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/60—Expansion by ejector or injector, e.g. "Gasstrahlpumpe", "venturi mixing", "jet pumps"

Definitions

  • the present invention relates to a refrigerant circulation system used in a gas liquefaction process in which a raw material gas is cooled and liquefied to produce a liquefied gas.
  • a pre-cooling step in which a raw material gas is pre-cooled (cooled to about ⁇ 30 ° C.) with a single component refrigerant (propane: C3), and a mixed refrigerant (a mixture of nitrogen, methane, ethane, propane, etc .: MR And a final cooling step in which the raw material gas is finally cooled (cooled to about ⁇ 160 ° C.).
  • a single component refrigerant propane: C3
  • a mixed refrigerant a mixture of nitrogen, methane, ethane, propane, etc .: MR
  • MR mixed refrigerant
  • the refrigerant is compressed by a compressor, and after the compressed refrigerant is cooled and condensed, the refrigerant is expanded and evaporated to exchange heat with the source gas. Then, the raw material gas is cooled. The refrigerant whose temperature has been increased by cooling the raw material gas is circulated and sent to the compressor again. By repeating this circulation, the cooling process is continuously performed.
  • the compressor when re-compressing the refrigerant after cooling the raw material gas in multiple stages, the compressor is arranged in the middle stage of the compressor in accordance with the respective pressure values in the order of refrigerant having a low temperature (low pressure) to refrigerant having a high temperature (high pressure).
  • the compression efficiency of the compressor can be increased.
  • the relationship between the pressure (saturated vapor pressure) and temperature (boiling point) is unique to the single component and is uniquely determined.
  • the first stage suction pressure at the time of pressurization by the compressor is determined by the final cooling stage temperature, and the required performance of the compressor is determined.
  • Compressors that can be compressed by introducing a refrigerant at a temperature lower and lower than the normal boiling point have a large number of stages and a large size, which exceeds the physical equipment production limit or greatly increases the equipment production cost. End up.
  • the cooling efficiency of the raw material gas is relatively increased due to the low outside air temperature
  • the lower limit of the initial temperature of the refrigerant that can be introduced into the compressor must be equal to or higher than the normal boiling point.
  • the cooling capacity of the precooling system is limited, and the capacity balance between the precooling refrigerant compressor and the mixed refrigerant compressor cannot be optimized, and the cooling performance is limited.
  • An object of the present invention is to provide a refrigerant circulation system capable of improving the cooling performance of the entire cooling process without limiting the cooling capacity by the operating pressure of the refrigerant to be circulated in the cooling process using a single component refrigerant. .
  • the refrigerant circulation system of the present invention is a refrigerant circulation system that circulates a refrigerant composed of a single component to cool a target gas, and includes a compression unit that compresses the refrigerant in a plurality of stages, and a refrigerant that is compressed by the compression unit.
  • Cooling means for cooling, a plurality of pipes for returning the refrigerant refrigerant after cooling the target gas to a plurality of stages and sending it to the compression means, and a middle of at least one of the plurality of pipes on the low pressure stage side
  • pressurizing means for pressurizing the return refrigerant vapor, wherein the pressurizing means introduces a part of the compressed refrigerant vapor cooled by the cooling means, and the injection pressure of the compressed refrigerant vapor causes the It is an ejector that sucks the return refrigerant vapor and mixes and pressurizes the return refrigerant vapor and the compressed refrigerant vapor.
  • the return refrigerant vapor can be adjusted to a predetermined pressure before being sent to the compression means.
  • the circulation process can be operated within the physical limits of the compression means.
  • a part of the compressed refrigerant vapor cooled by the cooling means is introduced into the ejector, the return refrigerant vapor is sucked by the injection pressure of the compressed refrigerant vapor, and the return refrigerant vapor and the compressed refrigerant vapor are mixed and pressurized.
  • the pressure of the return refrigerant vapor can be adjusted without adding compression means. Furthermore, by using the compressed refrigerant vapor in the circulation process as a drive medium, the cooling performance of the entire cooling process can be enhanced without adding a separation device or the like.
  • the refrigerant circulation system of the present invention includes an adjusting unit that adjusts the amount of the compressed refrigerant vapor introduced into the pressurizing unit in accordance with the pressure of the return refrigerant vapor.
  • the pressure of the return refrigerant vapor can be increased to the optimum pressure as the input pressure to the compression means regardless of the pressure of the return refrigerant vapor by the adjustment by the adjustment means.
  • the pressurizing means is equivalent to the pressure of the high-pressure-stage return refrigerant vapor flowing in the high-pressure stage-side pipe by a predetermined number of stages from the one pipe among the plurality of pipes.
  • the return refrigerant vapor flowing through the one pipe is pressurized to a pressure, and the return refrigerant vapor after being pressurized by the pressurizing means and the high-pressure stage side return refrigerant vapor are mutually in the compression means. Preferably they are sent to the same stage.
  • the cooling performance of the entire cooling process can be enhanced without limiting the cooling capacity by the operating pressure of the refrigerant to be circulated.
  • FIG. 1 It is a schematic structure figure showing a refrigerant circulation system concerning an embodiment of the present invention. It is a schematic diagram which shows the ejector shown by FIG.
  • the refrigerant circulation system 1 of the present embodiment is installed in a liquefied natural gas (LNG) production facility.
  • LNG liquefied natural gas
  • the refrigerant circulation system 1 of this embodiment is in charge of the pre-cooling step in this C3-MR process.
  • the refrigerant circulation system 1 is a system that circulates propane and cools a raw material gas, and includes a compressor 11 (compression unit) that compresses propane vapor in a plurality of stages.
  • a compressor 11 compression unit
  • compressed propane vapor having a temperature of about 75 ° C. and an absolute pressure of about 1850 kPaA is obtained.
  • a first cooling means 12 and a second cooling means 13 are provided at the subsequent stage of the compressor 11.
  • the compressed propane vapor is converted into compressed propane vapor having a temperature of about 55 ° C. and an absolute pressure of about 1800 kPaA.
  • the compressed propane vapor becomes a propane liquid having a temperature of about 50 ° C. and an absolute pressure of about 1750 kPaA by cooling with the second cooling means 13 as a condenser.
  • Compressed propane vapor that has been cooled by the first cooling means 12 is liquefied by the second cooling means 13 to become liquid propane Pr.
  • a storage tank 14 as a refrigerant buffer is provided downstream of the second cooling means 13.
  • the liquid propane Pr is sent from the storage tank 14 to a plurality of heat exchangers (not shown) provided for precooling the raw material gas.
  • the liquid propane Pr cools the source gas to a temperature corresponding to each stage by exchanging heat with the source gas while expanding and evaporating at a pressure and temperature corresponding to each stage. In this embodiment, such cooling is performed over four stages.
  • the propane that has finished cooling returns to the refrigerant circulation system 1 again as propane vapor.
  • the return propane vapor returns in four stages from the first return propane vapor Pb1 to the fourth return propane vapor Pb4 from the one having a high temperature and high pressure.
  • the first return propane vapor Pb1 is, for example, a propane vapor having a temperature of ⁇ 10 ° C. and an absolute pressure of about 300 kPaA
  • the second return propane vapor Pb2 is, for example, a temperature of ⁇ 24 ° C.
  • the third return propane vapor Pb3 is, for example, a propane vapor having a temperature of ⁇ 37.5 ° C. and an absolute pressure of about 130 kPaA
  • the fourth return propane vapor Pb4 is As an example, the propane vapor has a temperature of ⁇ 50 ° C. and an absolute pressure of about 60 kPaA.
  • the first to fourth return propane vapors Pb1, Pb2, Pb3, Pb4 are sent to the compressor 11 through the pipes 15-1, 15-2, 15-3, 15-4 of each stage. Separations for removing liquid components from the first to fourth return propane vapors Pb1, Pb2, Pb3, and Pb4 are provided in the first stage of the compressor 11 in the pipes 15-1, 15-2, 15-3, and 15-4 in each stage. Devices 16-1, 16-2, 16-3 and 16-4 are provided. In each of the separators 16-1, 16-2, 16-3, 16-4, the first to fourth return propane vapors Pb1, Pb2, Pb3, Pb4 are passed through a mist eliminator 161 composed of a wire mesh filter, The liquid component is removed. After the removal, the dry first to fourth return propane vapors Pb1, Pb2, Pb3, Pb4 are sent to the compressor 11.
  • the following ejector 17 is provided as a pressurizing means for pressurizing the fourth return propane vapor Pb4 at a position in the middle of the separator 16-4.
  • the ejector 17 introduces a part of the compressed propane vapor Pp having a temperature cooled by the first cooling means 12 of 55 ° C. and an absolute pressure of about 1800 kPaA, and the fourth return propane vapor Pb4 is generated by the injection pressure of the compressed propane vapor Pp.
  • the fourth return propane vapor Pb4 and the compressed propane vapor Pp are mixed and pressurized.
  • FIG. 2 is a schematic diagram showing the ejector shown in FIG.
  • the ejector 17 is pressurized by mixing the suction port 171 of the fourth return propane vapor Pb4, the introduction port 172 for introducing a part of the compressed propane vapor Pp cooled by the first cooling means 12, and the compressed propane vapor Pp.
  • the fourth return propane vapor Pb 4 ′ has a discharge port 173 and a mixing chamber 174.
  • the introduction port 172 and the discharge port 173 are opposed to each other with a predetermined interval inside the mixing chamber 174.
  • a negative pressure is generated in the mixing chamber 174 by the injection pressure of the compressed propane vapor Pp introduced from the introduction port 172, and the fourth return propane vapor Pb4 is sucked into the suction port 171 by this negative pressure.
  • the sucked fourth return propane vapor Pb4 is mixed together with the compressed propane vapor Pp toward the discharge port 173, and is discharged from the discharge port 173.
  • the fourth return propane vapor Pb4 is heated and pressurized and discharged.
  • a regulating valve 18 is provided in the upstream of the inlet 172 of the compressed propane vapor Pp in the ejector 17. Further, in the fourth return propane vapor Pb4 pipe 15-4, the pressure of the fourth return propane vapor Pb4 is detected, and the opening degree of the regulating valve 18 is controlled in accordance with the detection result. Is provided. Thereby, the introduction amount of the compressed propane vapor Pp to the ejector 17 is adjusted according to the pressure of the fourth return propane vapor Pb4.
  • the pressure (that is, the absolute pressure) equivalent to the pressure of the third return propane steam Pb3 flowing through the pipe 15-3 on the high pressure stage side by one stage from the pipe 15-4 of the fourth return propane steam Pb4. Until the pressure of the fourth return propane vapor Pb4 is increased up to 130 kPaA).
  • the piping 15-4 of the fourth return propane vapor Pb4 ′ and the piping 15-3 of the third return propane vapor Pb3 thus pressurized are connected to the downstream side of the separators 16-3 and 16-4.
  • the returned propane vapor after joining is, for example, propane vapor having a temperature of ⁇ 35 ° C. and an absolute pressure of about 130 kPaA, and this propane vapor is sent to the most upstream stage (lowest pressure stage) in the compressor 11.
  • the first return propane steam Pb1 and the second return propane steam Pb2 are sent as they are to the stages of the compressor 11 corresponding to the pressure of each return propane steam.
  • the second return propane vapor Pb2 is sent to the downstream side (high-pressure stage side) of the combined return propane vapor in the compressor 11. Then, the first return propane vapor Pb1 is sent to the downstream side (high pressure stage side) of the second return propane vapor Pb2 in the compressor 11. These return propane vapors are compressed by the compressor 11 and again used for pre-cooling the raw material gas.
  • the fourth return propane vapor Pb4 is pressurized by the ejector 17 so that the fourth return propane vapor Pb4 falls below the atmospheric pressure boiling point. Even if this steam is, the fourth return propane steam Pb4 can be adjusted to a predetermined pressure before being sent to the compressor 11. Thus, the circulation process can be operated within the physical limits of the compressor 11.
  • the equipment configuration can be simplified and the pressure of the fourth return propane steam Pb4 can be adjusted without adding a new compressor or the like. Furthermore, by using the compressed propane vapor Pp in the circulation process as a driving medium, it is possible to improve the cooling performance of the entire cooling process without adding a separation device or the like.
  • the following effects can be obtained when installed in a cold region.
  • cold regions although the cooling efficiency of the raw material gas is relatively increased due to the low outside air temperature, if the lower limit value of the initial temperature of propane that can be introduced into the compressor 11 must be equal to or higher than the normal pressure boiling point, the cooling capacity Will be subject to restrictions.
  • the fourth return propane vapor Pb4 on the low pressure stage side is sent to the compressor 11 after being pressurized and heated. For this reason, about the 4th return propane vapor
  • an adjustment valve 18 that adjusts the introduction amount of the compressed propane vapor Pp according to the pressure of the fourth return propane vapor Pb4 is provided.
  • the pressure of the fourth return propane vapor Pb4 can be increased to the optimum pressure as the input pressure to the compressor 11 regardless of the pressure of the fourth return propane vapor Pb4.
  • the ejector 17 has the third return propane steam Pb3 flowing through the pipe 15-3 on the high-pressure stage side by one stage from the pipe 15-4 of the fourth return propane steam Pb4.
  • the fourth return propane vapor Pb4 is pressurized to a pressure equivalent to the pressure of the (high pressure stage side return refrigerant vapor).
  • the fourth return propane vapor Pb4 and the third return propane vapor Pb3 after pressurization are sent to the same stage in the compressor 11.
  • the present invention is not limited to the above-described embodiment, and includes other configurations and the like that can achieve the object of the present invention, and the following modifications and the like are also included in the present invention.
  • the refrigerant circulation system 1 installed in the liquefied natural gas (LNG) manufacturing facility has been described.
  • the present invention is not limited to liquefied natural gas, but liquefied petroleum gas (LPG), liquefied nitrogen,
  • LPG liquefied petroleum gas
  • the present invention can be used as a refrigerant circulation system in any liquefied gas production facility such as liquefied oxygen.
  • the refrigerant circulation system 1 adopting C3-MR is described as an example of the gas liquefaction process.
  • the present invention is not limited to C3-MR, and the refrigerant circulation system adopting a cascade process or an expander process. Can also be used.
  • the refrigerant circulation system 1 that cools the raw material gas as the cooling target gas has been described.
  • the present invention is not limited to the raw material gas. It can also be used as a refrigerant circulation system that cools the mixed refrigerant as a cooling target gas.
  • Refrigerant circulation system 11 Compressor (an example of compression means) 12 1st cooling means (an example of cooling means) 13 Second cooling means (an example of cooling means) 14 Storage tank 15-1, 15-2, 15-3, 15-4 Piping 17 Ejector 18 Adjusting valve (an example of adjusting means) 19 Controller Pb1 First return propane vapor Pb2 Second return propane vapor Pb3 Third return propane vapor Pb4 Fourth return propane vapor Pb4 ′ Pressurized fourth return propane vapor Pp Compressed propane vapor Pr Liquid propane

Abstract

Provided is a refrigerant circulation system that allows the overall cooling performance of the cooling process with a single-ingredient refrigerant to be improved without causing the cooling capacity to be limited due to the operating pressure of the circulated refrigerant. A refrigerant circulation system (1) is characterized in that: the refrigerant circulation system is provided with a compressor (11), a first cooling means (12) for cooling compressed propane, pipes (15-1) to (15-4), and a pressurization means for pressurizing fourth return propane vapor (Pb4) which is interposed in a pipe (15-4) on the low pressure stage side; and the pressurization means is an ejector (17) which partially introduces the compressed propane vapor (Pp) cooled by the first cooling means (12) and sucks the fourth return propane vapor (Pb4) with the injection pressure of the compressed propane vapor (Pp), and which mixes and pressurizes the fourth return propane vapor (Pb4) and the compressed propane vapor (Pp).

Description

冷媒循環システムRefrigerant circulation system
　本発明は、原料ガスを冷却して液化し、液化ガスを製造するガス液化プロセスに利用される冷媒循環システムに関する。 The present invention relates to a refrigerant circulation system used in a gas liquefaction process in which a raw material gas is cooled and liquefied to produce a liquefied gas.
　従来、ガス液化プロセスとしては、単一成分冷媒（プロパン：Ｃ３）によって原料ガスを予冷（－３０℃程度まで冷却）する予冷工程と、混合冷媒（窒素、メタン、エタン、プロパン等の混合物：ＭＲ）によって原料ガスを最終冷却（－１６０℃程度まで冷却）する最終冷却工程と、を備えたＣ３－ＭＲプロセスが知られている。（例えば、特許文献１及び特許文献２参照。）。 Conventionally, as a gas liquefaction process, a pre-cooling step in which a raw material gas is pre-cooled (cooled to about −30 ° C.) with a single component refrigerant (propane: C3), and a mixed refrigerant (a mixture of nitrogen, methane, ethane, propane, etc .: MR And a final cooling step in which the raw material gas is finally cooled (cooled to about −160 ° C.). (For example, refer to Patent Document 1 and Patent Document 2.)
　予冷工程及び最終冷却工程の各冷却プロセスでは、冷媒を圧縮機（コンプレッサー）で圧縮し、圧縮した冷媒を冷却して凝縮させた後に、この冷媒を膨張、蒸発させつつ原料ガスと熱交換することで、原料ガスを冷却する。原料ガスを冷却して昇温した冷媒は、循環されて再び圧縮機に送られ、この循環を繰り返すことで、冷却プロセスが連続的に行われる。 In each cooling process of the pre-cooling step and the final cooling step, the refrigerant is compressed by a compressor, and after the compressed refrigerant is cooled and condensed, the refrigerant is expanded and evaporated to exchange heat with the source gas. Then, the raw material gas is cooled. The refrigerant whose temperature has been increased by cooling the raw material gas is circulated and sent to the compressor again. By repeating this circulation, the cooling process is continuously performed.
　原料ガスを冷却する際、常温（２０℃程度）から予冷温度（－３０℃程度）まで１段階の冷媒温度で冷却すると冷却効率が悪いため、原料ガスとの熱交換は複数段（例えば、４段）で行われる。このように複数段の冷却においては、原料ガス上流から下流に向かって順に低温となるように予冷冷媒の温度が設定されている。 When the raw material gas is cooled, if it is cooled at a single stage refrigerant temperature from room temperature (about 20 ° C.) to a precooling temperature (about −30 ° C.), the cooling efficiency is poor. Stage). As described above, in the multi-stage cooling, the temperature of the precooling refrigerant is set so that the temperature becomes lower in order from the upstream of the raw material gas to the downstream.
　一方、複数段で原料ガスを冷却した後の冷媒を再圧縮する際においては、温度が低い冷媒（低圧）から温度が高い冷媒（高圧）の順にそれぞれの圧力値に合った圧縮機中間段に導入して圧縮することによって圧縮機の圧縮効率を高めることができる。 On the other hand, when re-compressing the refrigerant after cooling the raw material gas in multiple stages, the compressor is arranged in the middle stage of the compressor in accordance with the respective pressure values in the order of refrigerant having a low temperature (low pressure) to refrigerant having a high temperature (high pressure). By introducing and compressing, the compression efficiency of the compressor can be increased.
特開平６－２９９１７４号公報JP-A-6-299174 特開２００１－１６５５６０号公報JP 2001-165560 A
　ここで、単一成分冷媒（プロパン等）を用いる場合、その圧力（飽和蒸気圧）と温度（沸点）との関係は単一成分固有のものであり、一義的に決まることから、冷媒蒸気を圧縮機で加圧する際の第１段吸入圧力が最終冷却段温度によって決定され、圧縮機の要求性能が決定されてしまう。 Here, when a single component refrigerant (such as propane) is used, the relationship between the pressure (saturated vapor pressure) and temperature (boiling point) is unique to the single component and is uniquely determined. The first stage suction pressure at the time of pressurization by the compressor is determined by the final cooling stage temperature, and the required performance of the compressor is determined.
　圧縮機に導入される第１段の運転温度が低ければ低いほど、圧縮後の冷媒による冷却能力が高くなるものの、常圧沸点を下回るほど温度が低くなると冷媒蒸気体積が圧力に反比例して大きくなってしまうため、圧縮機の第１段吸入側サイズを非常に大きくしなければならない。 The lower the operating temperature of the first stage introduced into the compressor, the higher the cooling capacity by the refrigerant after compression, but the refrigerant vapor volume increases in inverse proportion to the pressure when the temperature becomes lower as it falls below the normal pressure boiling point. Therefore, the size of the first stage suction side of the compressor must be very large.
　常圧沸点よりも低温かつ低圧な冷媒を導入して圧縮可能な圧縮機は、高段数かつ大型なものとなり、物理的な機器製作限界を超えてしまうか、機器製作コストが非常に増大してしまう。 Compressors that can be compressed by introducing a refrigerant at a temperature lower and lower than the normal boiling point have a large number of stages and a large size, which exceeds the physical equipment production limit or greatly increases the equipment production cost. End up.
　また、寒冷地においては、外気温の低さによって原料ガスの冷却効率は相対的に上がるものの、圧縮機に導入可能な冷媒の初期温度の下限値が常圧沸点以上でなければならないとすると、予冷システムの冷却能力に制限を受けることになり、予冷冷媒圧縮機と混合冷媒圧縮機の能力バランスを最適にすることができず、冷却性能の向上に制約を受けることとなる。 In cold regions, although the cooling efficiency of the raw material gas is relatively increased due to the low outside air temperature, the lower limit of the initial temperature of the refrigerant that can be introduced into the compressor must be equal to or higher than the normal boiling point. The cooling capacity of the precooling system is limited, and the capacity balance between the precooling refrigerant compressor and the mixed refrigerant compressor cannot be optimized, and the cooling performance is limited.
　本発明の目的は、単一成分冷媒による冷却プロセスにおいて、循環させる冷媒の運転圧力によって冷却能力を制限させることなく、冷却プロセス全体の冷却性能を高めることができる冷媒循環システムを提供することにある。 An object of the present invention is to provide a refrigerant circulation system capable of improving the cooling performance of the entire cooling process without limiting the cooling capacity by the operating pressure of the refrigerant to be circulated in the cooling process using a single component refrigerant. .
　本発明の冷媒循環システムは、単一成分からなる冷媒を循環させて対象ガスを冷却する冷媒循環システムであって、前記冷媒を複数段で圧縮する圧縮手段と、前記圧縮手段で圧縮した冷媒を冷却する冷却手段と、前記対象ガスを冷却した後の戻り冷媒蒸気を複数段に分けて前記圧縮手段に送る複数の配管と、前記複数の配管のうち、少なくとも低圧段側の１つの配管の途中に設けられて前記戻り冷媒蒸気を加圧する加圧手段と、を備え、前記加圧手段は、前記冷却手段で冷却した圧縮冷媒蒸気の一部を導入し、該圧縮冷媒蒸気の噴射圧によって前記戻り冷媒蒸気を吸引するとともに、該戻り冷媒蒸気と前記圧縮冷媒蒸気とを混合して加圧するエジェクターであることを特徴とする。 The refrigerant circulation system of the present invention is a refrigerant circulation system that circulates a refrigerant composed of a single component to cool a target gas, and includes a compression unit that compresses the refrigerant in a plurality of stages, and a refrigerant that is compressed by the compression unit. Cooling means for cooling, a plurality of pipes for returning the refrigerant refrigerant after cooling the target gas to a plurality of stages and sending it to the compression means, and a middle of at least one of the plurality of pipes on the low pressure stage side And pressurizing means for pressurizing the return refrigerant vapor, wherein the pressurizing means introduces a part of the compressed refrigerant vapor cooled by the cooling means, and the injection pressure of the compressed refrigerant vapor causes the It is an ejector that sucks the return refrigerant vapor and mixes and pressurizes the return refrigerant vapor and the compressed refrigerant vapor.
　以上のような本発明によれば、加圧手段によって戻り冷媒蒸気を加圧することで、戻り冷媒蒸気が常圧沸点を下回るような低温かつ低圧の蒸気となっている場合であっても、この戻り冷媒蒸気を所定の圧力に調整してから圧縮手段に送ることができる。従って、圧縮手段の物理的限界の範囲内で循環プロセスを運転することができる。また、冷却手段で冷却した圧縮冷媒蒸気の一部をエジェクターに導入し、この圧縮冷媒蒸気の噴射圧によって戻り冷媒蒸気を吸引するとともに、戻り冷媒蒸気と圧縮冷媒蒸気とを混合して加圧することで、圧縮手段を追加することなく戻り冷媒蒸気の圧力を調整することができる。さらに、循環プロセス内の圧縮冷媒蒸気を駆動媒体として利用することによって、分離装置等を追加することなく、冷却プロセス全体の冷却性能を高めることができる。 According to the present invention as described above, even when the return refrigerant vapor is a low-temperature and low-pressure vapor below the normal pressure boiling point by pressurizing the return refrigerant vapor by the pressurizing means, The return refrigerant vapor can be adjusted to a predetermined pressure before being sent to the compression means. Thus, the circulation process can be operated within the physical limits of the compression means. Also, a part of the compressed refrigerant vapor cooled by the cooling means is introduced into the ejector, the return refrigerant vapor is sucked by the injection pressure of the compressed refrigerant vapor, and the return refrigerant vapor and the compressed refrigerant vapor are mixed and pressurized. Thus, the pressure of the return refrigerant vapor can be adjusted without adding compression means. Furthermore, by using the compressed refrigerant vapor in the circulation process as a drive medium, the cooling performance of the entire cooling process can be enhanced without adding a separation device or the like.
　この際、本発明の冷媒循環システムでは、前記戻り冷媒蒸気の圧力に応じて、前記圧縮冷媒蒸気の前記加圧手段への導入量を調整する調整手段を備えることが好ましい。 At this time, it is preferable that the refrigerant circulation system of the present invention includes an adjusting unit that adjusts the amount of the compressed refrigerant vapor introduced into the pressurizing unit in accordance with the pressure of the return refrigerant vapor.
　この構成によれば、調整手段での調整により、戻り冷媒蒸気の圧力によらず圧縮手段への入力圧力として最適な圧力へと、その戻り冷媒蒸気の圧力を加圧することができる。 According to this configuration, the pressure of the return refrigerant vapor can be increased to the optimum pressure as the input pressure to the compression means regardless of the pressure of the return refrigerant vapor by the adjustment by the adjustment means.
　また、本発明の冷媒循環システムでは、前記加圧手段が、前記複数の配管のうち、前記１つの配管よりも所定段数だけ高圧段側の配管を流れる高圧段側戻り冷媒蒸気の圧力と同等な圧力まで、前記１つの配管を流れる前記戻り冷媒蒸気を加圧するものであり、前記加圧手段による加圧後の前記戻り冷媒蒸気と、前記高圧段側戻り冷媒蒸気とは、前記圧縮手段における互いに同じ段に送られることが好ましい。 Moreover, in the refrigerant circulation system of the present invention, the pressurizing means is equivalent to the pressure of the high-pressure-stage return refrigerant vapor flowing in the high-pressure stage-side pipe by a predetermined number of stages from the one pipe among the plurality of pipes. The return refrigerant vapor flowing through the one pipe is pressurized to a pressure, and the return refrigerant vapor after being pressurized by the pressurizing means and the high-pressure stage side return refrigerant vapor are mutually in the compression means. Preferably they are sent to the same stage.
　この構成によれば、冷却の段数を増やして効率的な冷却を行いつつも、圧縮手段の段数の増加を抑えることで、設備コストの低減等を図ることがきる。 According to this configuration, it is possible to reduce the equipment cost and the like by suppressing the increase in the number of stages of the compression means while increasing the number of cooling stages and performing efficient cooling.
　以上のような本発明の冷媒循環システムによれば、単一成分冷媒による冷却プロセスにおいて、循環させる冷媒の運転圧力によって冷却能力を制限させることなく、冷却プロセス全体の冷却性能を高めることができる。 According to the refrigerant circulation system of the present invention as described above, in the cooling process using a single component refrigerant, the cooling performance of the entire cooling process can be enhanced without limiting the cooling capacity by the operating pressure of the refrigerant to be circulated.
本発明の実施形態に係る冷媒循環システムを示す概略構成図である。It is a schematic structure figure showing a refrigerant circulation system concerning an embodiment of the present invention. 図１に示されているエジェクターを示す模式図である。It is a schematic diagram which shows the ejector shown by FIG.
　以下、本発明の実施形態を図面に基づいて説明する。本実施形態の冷媒循環システム１は、液化天然ガス（ＬＮＧ）の製造設備に設置される。本実施形態では、この製造設備におけるガス液化プロセスとして、単一成分冷媒（プロパン：Ｃ３）によって原料ガスを予冷（－３０℃程度まで冷却）する予冷工程と、混合冷媒（窒素、メタン、エタン、プロパン等の混合物：ＭＲ）によって原料ガスを最終冷却（－１６０℃程度まで冷却）する最終冷却工程と、を備えたＣ３－ＭＲプロセスが採用されている。本実施形態の冷媒循環システム１は、このＣ３－ＭＲプロセスにおける予冷工程を担当する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. The refrigerant circulation system 1 of the present embodiment is installed in a liquefied natural gas (LNG) production facility. In the present embodiment, as a gas liquefaction process in this production facility, a precooling step of precooling (cooling to about −30 ° C.) the raw material gas with a single component refrigerant (propane: C3), and a mixed refrigerant (nitrogen, methane, ethane, And a final cooling step in which the raw material gas is finally cooled (cooled to about −160 ° C.) by a mixture of propane and the like (MR). The refrigerant circulation system 1 of this embodiment is in charge of the pre-cooling step in this C3-MR process.
　図１に示されているように、冷媒循環システム１は、プロパンを循環させて原料ガスを冷却するシステムであって、プロパン蒸気を複数段で圧縮するコンプレッサー１１（圧縮手段）を備えている。コンプレッサー１１での圧縮により、一例として温度が７５℃、絶対圧が１８５０ｋＰａＡ程度の圧縮プロパン蒸気となる。 As shown in FIG. 1, the refrigerant circulation system 1 is a system that circulates propane and cools a raw material gas, and includes a compressor 11 (compression unit) that compresses propane vapor in a plurality of stages. By the compression by the compressor 11, as an example, compressed propane vapor having a temperature of about 75 ° C. and an absolute pressure of about 1850 kPaA is obtained.
　コンプレッサー１１の後段には、第１冷却手段１２と第２冷却手段１３とが設けられている。上記の圧縮プロパン蒸気は、第１冷却手段１２により、一例として温度が５５℃、絶対圧が１８００ｋＰａＡ程度の圧縮プロパン蒸気となる。さらに、その圧縮プロパン蒸気が、凝縮器としての第２冷却手段１３での冷却により、一例として温度が５０℃、絶対圧が１７５０ｋＰａＡ程度のプロパン液となる。 A first cooling means 12 and a second cooling means 13 are provided at the subsequent stage of the compressor 11. By way of example, the compressed propane vapor is converted into compressed propane vapor having a temperature of about 55 ° C. and an absolute pressure of about 1800 kPaA. Further, the compressed propane vapor becomes a propane liquid having a temperature of about 50 ° C. and an absolute pressure of about 1750 kPaA by cooling with the second cooling means 13 as a condenser.
　第１冷却手段１２での冷却を経た圧縮プロパン蒸気は、第２冷却手段１３において液化して液体プロパンＰｒとなる。第２冷却手段１３の下流には、冷媒バッファーとしての貯槽１４が設けられている。その液体プロパンＰｒは、貯槽１４から、原料ガスの予冷のために設けられた不図示の複数段の熱交換器へと送られる。各段の熱交換器において、液体プロパンＰｒは、各段に応じた圧力と温度で膨張、蒸発しつつ原料ガスと熱交換することで、原料ガスを各段に応じた温度に冷却する。本実施形態では、このような冷却が、４段に亘って行われる。 Compressed propane vapor that has been cooled by the first cooling means 12 is liquefied by the second cooling means 13 to become liquid propane Pr. A storage tank 14 as a refrigerant buffer is provided downstream of the second cooling means 13. The liquid propane Pr is sent from the storage tank 14 to a plurality of heat exchangers (not shown) provided for precooling the raw material gas. In each stage heat exchanger, the liquid propane Pr cools the source gas to a temperature corresponding to each stage by exchanging heat with the source gas while expanding and evaporating at a pressure and temperature corresponding to each stage. In this embodiment, such cooling is performed over four stages.
　冷却を終えたプロパンは、再びプロパン蒸気となって冷媒循環システム１に戻ってくる。戻りプロパン蒸気は、温度が高く圧力が高いものから、第１の戻りプロパン蒸気Ｐｂ１から第４の戻りプロパン蒸気Ｐｂ４まで４段に分かれて戻ってくる。本実施形態では、第１の戻りプロパン蒸気Ｐｂ１が、一例として温度が－１０℃、絶対圧が３００ｋＰａＡ程度のプロパン蒸気であり、第２の戻りプロパン蒸気Ｐｂ２が、一例として温度が－２４℃、絶対圧が２５０ｋＰａＡ程度のプロパン蒸気であり、第３の戻りプロパン蒸気Ｐｂ３が、一例として温度が－３７．５℃、絶対圧が１３０ｋＰａＡ程度のプロパン蒸気であり、第４の戻りプロパン蒸気Ｐｂ４が、一例として温度が－５０℃、絶対圧が６０ｋＰａＡ程度のプロパン蒸気となっている。 The propane that has finished cooling returns to the refrigerant circulation system 1 again as propane vapor. The return propane vapor returns in four stages from the first return propane vapor Pb1 to the fourth return propane vapor Pb4 from the one having a high temperature and high pressure. In the present embodiment, the first return propane vapor Pb1 is, for example, a propane vapor having a temperature of −10 ° C. and an absolute pressure of about 300 kPaA, and the second return propane vapor Pb2 is, for example, a temperature of −24 ° C. The propane vapor having an absolute pressure of about 250 kPaA, the third return propane vapor Pb3 is, for example, a propane vapor having a temperature of −37.5 ° C. and an absolute pressure of about 130 kPaA, and the fourth return propane vapor Pb4 is As an example, the propane vapor has a temperature of −50 ° C. and an absolute pressure of about 60 kPaA.
　第１～第４の戻りプロパン蒸気Ｐｂ１，Ｐｂ２，Ｐｂ３，Ｐｂ４は、各段の配管１５－１，１５－２，１５－３，１５－４によってコンプレッサー１１に送られる。各段の配管１５－１，１５－２，１５－３，１５－４におけるコンプレッサー１１の前段には、第１～第４の戻りプロパン蒸気Ｐｂ１，Ｐｂ２，Ｐｂ３，Ｐｂ４から液状成分を除去する分離器１６－１，１６－２，１６－３，１６－４が設けられている。各分離器１６－１，１６－２，１６－３，１６－４では、第１～第４の戻りプロパン蒸気Ｐｂ１，Ｐｂ２，Ｐｂ３，Ｐｂ４をワイヤーメッシュフィルタからなるミストエリミネーター１６１に通すことで、液状成分が除去される。除去後のドライな第１～第４の戻りプロパン蒸気Ｐｂ１，Ｐｂ２，Ｐｂ３，Ｐｂ４がコンプレッサー１１に送られる。 The first to fourth return propane vapors Pb1, Pb2, Pb3, Pb4 are sent to the compressor 11 through the pipes 15-1, 15-2, 15-3, 15-4 of each stage. Separations for removing liquid components from the first to fourth return propane vapors Pb1, Pb2, Pb3, and Pb4 are provided in the first stage of the compressor 11 in the pipes 15-1, 15-2, 15-3, and 15-4 in each stage. Devices 16-1, 16-2, 16-3 and 16-4 are provided. In each of the separators 16-1, 16-2, 16-3, 16-4, the first to fourth return propane vapors Pb1, Pb2, Pb3, Pb4 are passed through a mist eliminator 161 composed of a wire mesh filter, The liquid component is removed. After the removal, the dry first to fourth return propane vapors Pb1, Pb2, Pb3, Pb4 are sent to the compressor 11.
　ここで、本実施形態では、４つの配管１５－１，１５－２，１５－３，１５－４のうち、最も低圧段側（即ち、最も低温で低圧側）の１つの配管１５－４における分離器１６－４の前段となる途中の位置に、第４の戻りプロパン蒸気Ｐｂ４を加圧する加圧手段として、次のようなエジェクター１７が設けられている。エジェクター１７は、第１冷却手段１２で冷却した温度が５５℃、絶対圧が１８００ｋＰａＡ程度の圧縮プロパン蒸気Ｐｐの一部を導入し、その圧縮プロパン蒸気Ｐｐの噴射圧によって第４の戻りプロパン蒸気Ｐｂ４を吸引するとともに、第４の戻りプロパン蒸気Ｐｂ４と圧縮プロパン蒸気Ｐｐとを混合して加圧する。 Here, in the present embodiment, among the four pipes 15-1, 15-2, 15-3, and 15-4, in one pipe 15-4 on the lowest pressure stage side (that is, the lowest temperature and low pressure side). The following ejector 17 is provided as a pressurizing means for pressurizing the fourth return propane vapor Pb4 at a position in the middle of the separator 16-4. The ejector 17 introduces a part of the compressed propane vapor Pp having a temperature cooled by the first cooling means 12 of 55 ° C. and an absolute pressure of about 1800 kPaA, and the fourth return propane vapor Pb4 is generated by the injection pressure of the compressed propane vapor Pp. And the fourth return propane vapor Pb4 and the compressed propane vapor Pp are mixed and pressurized.
　図２は、図１に示されているエジェクターを示す模式図である。エジェクター１７は、第４の戻りプロパン蒸気Ｐｂ４の吸引口１７１と、第１冷却手段１２で冷却した圧縮プロパン蒸気Ｐｐの一部を導入する導入口１７２と、圧縮プロパン蒸気Ｐｐとの混合によって加圧された第４の戻りプロパン蒸気Ｐｂ４’の排出口１７３と、混合室１７４とを有している。導入口１７２と排出口１７３とは、混合室１７４内部において所定間隔を空けて対向している。導入口１７２から導入される圧縮プロパン蒸気Ｐｐの噴射圧によって混合室１７４内に負圧が生じ、この負圧によって吸引口１７１に第４の戻りプロパン蒸気Ｐｂ４が吸引される。吸引された第４の戻りプロパン蒸気Ｐｂ４は、圧縮プロパン蒸気Ｐｐとともに排出口１７３へと向かって混合され、その排出口１７３から排出される。上記の混合により、第４の戻りプロパン蒸気Ｐｂ４は加熱されるとともに加圧されて排出される。 FIG. 2 is a schematic diagram showing the ejector shown in FIG. The ejector 17 is pressurized by mixing the suction port 171 of the fourth return propane vapor Pb4, the introduction port 172 for introducing a part of the compressed propane vapor Pp cooled by the first cooling means 12, and the compressed propane vapor Pp. The fourth return propane vapor Pb 4 ′ has a discharge port 173 and a mixing chamber 174. The introduction port 172 and the discharge port 173 are opposed to each other with a predetermined interval inside the mixing chamber 174. A negative pressure is generated in the mixing chamber 174 by the injection pressure of the compressed propane vapor Pp introduced from the introduction port 172, and the fourth return propane vapor Pb4 is sucked into the suction port 171 by this negative pressure. The sucked fourth return propane vapor Pb4 is mixed together with the compressed propane vapor Pp toward the discharge port 173, and is discharged from the discharge port 173. By the above mixing, the fourth return propane vapor Pb4 is heated and pressurized and discharged.
　ここで、本実施形態では、図１に示されているように、エジェクター１７における圧縮プロパン蒸気Ｐｐの導入口１７２の前段に、調整弁１８が設けられている。また、第４の戻りプロパン蒸気Ｐｂ４の配管１５－４には、この第４の戻りプロパン蒸気Ｐｂ４の圧力を検知するとともに、その検知結果に応じて調整弁１８の開度を制御する制御部１９が設けられている。これにより、第４の戻りプロパン蒸気Ｐｂ４の圧力に応じて、圧縮プロパン蒸気Ｐｐのエジェクター１７への導入量が調整される。 Here, in the present embodiment, as shown in FIG. 1, a regulating valve 18 is provided in the upstream of the inlet 172 of the compressed propane vapor Pp in the ejector 17. Further, in the fourth return propane vapor Pb4 pipe 15-4, the pressure of the fourth return propane vapor Pb4 is detected, and the opening degree of the regulating valve 18 is controlled in accordance with the detection result. Is provided. Thereby, the introduction amount of the compressed propane vapor Pp to the ejector 17 is adjusted according to the pressure of the fourth return propane vapor Pb4.
　本実施形態では、第４の戻りプロパン蒸気Ｐｂ４の配管１５－４よりも１段だけ高圧段側の配管１５－３を流れる第３の戻りプロパン蒸気Ｐｂ３の圧力と同等な圧力（即ち、絶対圧で１３０ｋＰａＡ）まで、第４の戻りプロパン蒸気Ｐｂ４の圧力が加圧されるように、上記の調整弁１８の開度が制御される。 In the present embodiment, the pressure (that is, the absolute pressure) equivalent to the pressure of the third return propane steam Pb3 flowing through the pipe 15-3 on the high pressure stage side by one stage from the pipe 15-4 of the fourth return propane steam Pb4. Until the pressure of the fourth return propane vapor Pb4 is increased up to 130 kPaA).
　このように加圧された第４の戻りプロパン蒸気Ｐｂ４’の配管１５－４と、第３の戻りプロパン蒸気Ｐｂ３の配管１５－３とは、各分離器１６－３，１６－４の後段側で合流する。合流後の戻りプロパン蒸気は、一例として温度が－３５℃、絶対圧が１３０ｋＰａＡ程度のプロパン蒸気であり、このプロパン蒸気が、コンプレッサー１１における最上流段（最低圧段）に送られる。第１の戻りプロパン蒸気Ｐｂ１と第２の戻りプロパン蒸気Ｐｂ２は、そのまま、各戻りプロパン蒸気の圧力に応じたコンプレッサー１１の各段に送られる。第２の戻りプロパン蒸気Ｐｂ２は、コンプレッサー１１において、上記の合流後の戻りプロパン蒸気よりも下流側（高圧段側）に送られる。そして、第１の戻りプロパン蒸気Ｐｂ１が、コンプレッサー１１において、第２の戻りプロパン蒸気Ｐｂ２よりも下流側（高圧段側）に送られる。これらの戻りプロパン蒸気がコンプレッサー１１によって圧縮されて再度、原料ガスの予冷に供される。 The piping 15-4 of the fourth return propane vapor Pb4 ′ and the piping 15-3 of the third return propane vapor Pb3 thus pressurized are connected to the downstream side of the separators 16-3 and 16-4. Join at. The returned propane vapor after joining is, for example, propane vapor having a temperature of −35 ° C. and an absolute pressure of about 130 kPaA, and this propane vapor is sent to the most upstream stage (lowest pressure stage) in the compressor 11. The first return propane steam Pb1 and the second return propane steam Pb2 are sent as they are to the stages of the compressor 11 corresponding to the pressure of each return propane steam. The second return propane vapor Pb2 is sent to the downstream side (high-pressure stage side) of the combined return propane vapor in the compressor 11. Then, the first return propane vapor Pb1 is sent to the downstream side (high pressure stage side) of the second return propane vapor Pb2 in the compressor 11. These return propane vapors are compressed by the compressor 11 and again used for pre-cooling the raw material gas.
　以上に説明した本実施形態の冷媒循環システム１によれば、エジェクター１７によって第４の戻りプロパン蒸気Ｐｂ４を加圧することで、第４の戻りプロパン蒸気Ｐｂ４が常圧沸点を下回るような低温かつ低圧の蒸気となっている場合であっても、この第４の戻りプロパン蒸気Ｐｂ４を所定の圧力に調整してからコンプレッサー１１に送ることができる。従って、コンプレッサー１１の物理的限界の範囲内で循環プロセスを運転することができる。また、第１冷却手段１２で冷却した圧縮プロパン蒸気Ｐｐの一部をエジェクター１７に導入し、この圧縮プロパン蒸気Ｐｐの噴射圧によって第４の戻りプロパン蒸気Ｐｂ４を吸引するとともに、第４の戻りプロパン蒸気Ｐｂ４と圧縮プロパン蒸気Ｐｐとを混合して加圧することで、新たなコンプレッサー等を追加することなく機器構成を単純化して第４の戻りプロパン蒸気Ｐｂ４の圧力を調整することができる。さらに、循環プロセス内の圧縮プロパン蒸気Ｐｐを駆動媒体として利用することによって、分離装置等を追加することなく、冷却プロセス全体の冷却性能を高めることができる。 According to the refrigerant circulation system 1 of the present embodiment described above, the fourth return propane vapor Pb4 is pressurized by the ejector 17 so that the fourth return propane vapor Pb4 falls below the atmospheric pressure boiling point. Even if this steam is, the fourth return propane steam Pb4 can be adjusted to a predetermined pressure before being sent to the compressor 11. Thus, the circulation process can be operated within the physical limits of the compressor 11. Further, a part of the compressed propane vapor Pp cooled by the first cooling means 12 is introduced into the ejector 17, and the fourth return propane vapor Pb4 is sucked by the injection pressure of the compressed propane vapor Pp, and the fourth return propane By mixing and pressurizing the steam Pb4 and the compressed propane steam Pp, the equipment configuration can be simplified and the pressure of the fourth return propane steam Pb4 can be adjusted without adding a new compressor or the like. Furthermore, by using the compressed propane vapor Pp in the circulation process as a driving medium, it is possible to improve the cooling performance of the entire cooling process without adding a separation device or the like.
　また、本実施形態の冷媒循環システム１によれば、寒冷地に設置する場合に、次のような効果を得ることができる。寒冷地においては、外気温の低さによって原料ガスの冷却効率は相対的に上がるものの、コンプレッサー１１に導入可能なプロパンの初期温度の下限値が常圧沸点以上でなければならないとすると、冷却能力に制限を受けることとなる。これに対し、本実施形態の冷媒循環システム１によれば、コンプレッサー１１には、低圧段側の第４の戻りプロパン蒸気Ｐｂ４が加圧及び加熱されてから送られる。このため、第４の戻りプロパン蒸気Ｐｂ４については常圧沸点以下であってもコンプレッサー１１に導入可能となっている。これにより、Ｃ３－ＭＲの冷却プロセスにおける予冷冷媒圧縮機（本実施形態のコンプレッサー１１）と不図示の混合冷媒圧縮機の能力バランスを最適にすることができ、冷却プロセス全体の冷却性能を向上させることができる。 Moreover, according to the refrigerant circulation system 1 of the present embodiment, the following effects can be obtained when installed in a cold region. In cold regions, although the cooling efficiency of the raw material gas is relatively increased due to the low outside air temperature, if the lower limit value of the initial temperature of propane that can be introduced into the compressor 11 must be equal to or higher than the normal pressure boiling point, the cooling capacity Will be subject to restrictions. On the other hand, according to the refrigerant circulation system 1 of the present embodiment, the fourth return propane vapor Pb4 on the low pressure stage side is sent to the compressor 11 after being pressurized and heated. For this reason, about the 4th return propane vapor | steam Pb4, even if it is below an atmospheric pressure boiling point, it can be introduce | transduced into the compressor 11. FIG. This makes it possible to optimize the performance balance between the precooling refrigerant compressor (the compressor 11 of the present embodiment) and the mixed refrigerant compressor (not shown) in the C3-MR cooling process, and improve the cooling performance of the entire cooling process. be able to.
　また、本実施形態の冷媒循環システム１では、第４の戻りプロパン蒸気Ｐｂ４の圧力に応じて、圧縮プロパン蒸気Ｐｐの導入量を調整する調整弁１８が設けられている。これにより、第４の戻りプロパン蒸気Ｐｂ４の圧力によらずコンプレッサー１１への入力圧力として最適な圧力へと、その第４の戻りプロパン蒸気Ｐｂ４の圧力を加圧することができる。 In the refrigerant circulation system 1 of the present embodiment, an adjustment valve 18 that adjusts the introduction amount of the compressed propane vapor Pp according to the pressure of the fourth return propane vapor Pb4 is provided. As a result, the pressure of the fourth return propane vapor Pb4 can be increased to the optimum pressure as the input pressure to the compressor 11 regardless of the pressure of the fourth return propane vapor Pb4.
　また、本実施形態の冷媒循環システム１では、エジェクター１７が、第４の戻りプロパン蒸気Ｐｂ４の配管１５－４よりも１段だけ高圧段側の配管１５－３を流れる第３の戻りプロパン蒸気Ｐｂ３（高圧段側戻り冷媒蒸気）の圧力と同等な圧力まで、第４の戻りプロパン蒸気Ｐｂ４を加圧する。そして、加圧後の第４の戻りプロパン蒸気Ｐｂ４と、第３の戻りプロパン蒸気Ｐｂ３とは、コンプレッサー１１における互いに同じ段に送られる。これにより、冷却の段数を増やして効率的な冷却を行いつつも、コンプレッサー１１の段数の増加を抑えることで、設備コストの低減等が図られている。 Further, in the refrigerant circulation system 1 of the present embodiment, the ejector 17 has the third return propane steam Pb3 flowing through the pipe 15-3 on the high-pressure stage side by one stage from the pipe 15-4 of the fourth return propane steam Pb4. The fourth return propane vapor Pb4 is pressurized to a pressure equivalent to the pressure of the (high pressure stage side return refrigerant vapor). Then, the fourth return propane vapor Pb4 and the third return propane vapor Pb3 after pressurization are sent to the same stage in the compressor 11. Thereby, while increasing the number of stages of cooling and performing efficient cooling, the increase in the number of stages of the compressor 11 is suppressed, thereby reducing the equipment cost and the like.
　なお、本発明は、前記実施形態に限定されるものではなく、本発明の目的が達成できる他の構成等を含み、以下に示すような変形等も本発明に含まれる。例えば、前記実施形態では、液化天然ガス（ＬＮＧ）の製造設備に設置される冷媒循環システム１について説明したが、本発明は、液化天然ガスに限らず、液化石油ガス（ＬＰＧ）や液化窒素、液化酸素など任意の液化ガスの製造設備における冷媒循環システムとして利用可能である。 It should be noted that the present invention is not limited to the above-described embodiment, and includes other configurations and the like that can achieve the object of the present invention, and the following modifications and the like are also included in the present invention. For example, in the above embodiment, the refrigerant circulation system 1 installed in the liquefied natural gas (LNG) manufacturing facility has been described. However, the present invention is not limited to liquefied natural gas, but liquefied petroleum gas (LPG), liquefied nitrogen, The present invention can be used as a refrigerant circulation system in any liquefied gas production facility such as liquefied oxygen.
　また、前記実施形態では、ガス液化プロセスの一例としてＣ３－ＭＲを採用した冷媒循環システム１について説明したが、本発明は、Ｃ３－ＭＲに限らず、カスケードプロセスやエキスパンダープロセスを採用した冷媒循環システムとしても利用可能である。 In the above embodiment, the refrigerant circulation system 1 adopting C3-MR is described as an example of the gas liquefaction process. However, the present invention is not limited to C3-MR, and the refrigerant circulation system adopting a cascade process or an expander process. Can also be used.
　また、前記実施形態では、冷却対象ガスとして原料ガスを冷却する冷媒循環システム１について説明したが、本発明は、原料ガスに限らず、例えばＣ３－ＭＲにおける最終冷却系やシングルＭＲプロセス（ＳＭＲ）における混合冷媒を冷却対象ガスとして冷却する冷媒循環システムとしても利用可能である。 In the above-described embodiment, the refrigerant circulation system 1 that cools the raw material gas as the cooling target gas has been described. However, the present invention is not limited to the raw material gas. It can also be used as a refrigerant circulation system that cools the mixed refrigerant as a cooling target gas.
　また、前記実施形態では、単一成分からなる冷媒としてプロパンＣ３を用いる冷媒循環システム１について説明したが、本発明は、プロパンＣ３に限らず、他の軽炭化水素ガス（メタンＣ１、エタンＣ２、エチレンＣ２＝、ブタンＣ４）を単一成分からなる冷媒として用いる冷媒循環システムとしても利用可能である。 Moreover, although the said embodiment demonstrated the refrigerant | coolant circulation system 1 which uses propane C3 as a refrigerant | coolant which consists of single components, this invention is not restricted to propane C3, Other light hydrocarbon gas (Methane C1, ethane C2, It can also be used as a refrigerant circulation system using ethylene C2 =, butane C4) as a refrigerant composed of a single component.
　その他、本発明を実施するための最良の構成、方法などは、以上の記載で開示されているが、本発明は、これに限定されるものではない。すなわち、本発明は、主に特定の実施形態に関して特に図示され、且つ、説明されているが、本発明の技術的思想および目的の範囲から逸脱することなく、以上述べた実施形態に対し、形状、材質、数量、その他の詳細な構成において、当業者が様々な変形を加えることができるものである。従って、上記に開示した形状、材質などを限定した記載は、本発明の理解を容易にするために例示的に記載したものであり、本発明を限定するものではないから、それらの形状、材質などの限定の一部、もしくは全部の限定を外した部材の名称での記載は、本発明に含まれるものである。 In addition, the best configuration and method for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of materials, quantity, and other detailed configurations. Therefore, the description limiting the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such is included in this invention.
　１　　　　冷媒循環システム
　１１　　　コンプレッサー（圧縮手段の一例）
　１２　　　第１冷却手段（冷却手段の一例）
　１３　　　第２冷却手段（冷却手段の一例）
　１４　　　貯槽
　１５－１，１５－２，１５－３，１５－４　　配管
　１７　　　エジェクター
　１８　　　調整弁（調整手段の一例）
　１９　　　制御部
　Ｐｂ１　　第１の戻りプロパン蒸気
　Ｐｂ２　　第２の戻りプロパン蒸気
　Ｐｂ３　　第３の戻りプロパン蒸気
　Ｐｂ４　　第４の戻りプロパン蒸気
　Ｐｂ４’　加圧された第４の戻りプロパン蒸気
　Ｐｐ　　　圧縮プロパン蒸気
　Ｐｒ　　　液体プロパン 1 Refrigerant circulation system 11 Compressor (an example of compression means)
12 1st cooling means (an example of cooling means)
13 Second cooling means (an example of cooling means)
14 Storage tank 15-1, 15-2, 15-3, 15-4 Piping 17 Ejector 18 Adjusting valve (an example of adjusting means)
19 Controller Pb1 First return propane vapor Pb2 Second return propane vapor Pb3 Third return propane vapor Pb4 Fourth return propane vapor Pb4 ′ Pressurized fourth return propane vapor Pp Compressed propane vapor Pr Liquid propane

Claims (3)

  1. 　単一成分からなる冷媒を循環させて対象ガスを冷却する冷媒循環システムであって、
    　前記冷媒を複数段で圧縮する圧縮手段と、
    　前記圧縮手段で圧縮した冷媒を冷却する冷却手段と、
    　前記対象ガスを冷却した後の戻り冷媒蒸気を複数段に分けて前記圧縮手段に送る複数の配管と、
    　前記複数の配管のうち、少なくとも低圧段側の１つの配管の途中に設けられて前記戻り冷媒蒸気を加圧する加圧手段と、
    を備え、
    　前記加圧手段は、前記冷却手段で冷却した圧縮冷媒蒸気の一部を導入し、該圧縮冷媒蒸気の噴射圧によって前記戻り冷媒蒸気を吸引するとともに、該戻り冷媒蒸気と前記圧縮冷媒蒸気とを混合して加圧するエジェクターであることを特徴とする冷媒循環システム。     A refrigerant circulation system for circulating a refrigerant composed of a single component to cool a target gas,
    Compression means for compressing the refrigerant in a plurality of stages;
    Cooling means for cooling the refrigerant compressed by the compression means;
    A plurality of pipes for dividing the return refrigerant vapor after cooling the target gas into a plurality of stages and sending it to the compression means;
    A pressurizing means provided in the middle of at least one of the plurality of pipes on the low-pressure stage side to pressurize the return refrigerant vapor;
    With
    The pressurizing unit introduces a part of the compressed refrigerant vapor cooled by the cooling unit, sucks the return refrigerant vapor by the injection pressure of the compressed refrigerant vapor, and combines the return refrigerant vapor and the compressed refrigerant vapor. A refrigerant circulation system characterized by being an ejector for mixing and pressurizing.
  2. 　前記戻り冷媒蒸気の圧力に応じて、前記圧縮冷媒蒸気の前記加圧手段への導入量を調整する調整手段を備えたことを特徴とする請求項１に記載の冷媒循環システム。 The refrigerant circulation system according to claim 1, further comprising adjusting means for adjusting the amount of the compressed refrigerant vapor introduced into the pressurizing means in accordance with the pressure of the return refrigerant vapor.
  3. 　前記加圧手段が、前記複数の配管のうち、前記１つの配管よりも所定段数だけ高圧段側の配管を流れる高圧段側戻り冷媒蒸気の圧力と同等な圧力まで、前記１つの配管を流れる前記戻り冷媒蒸気を加圧するものであり、
    　前記加圧手段による加圧後の前記戻り冷媒蒸気と、前記高圧段側戻り冷媒蒸気とは、前記圧縮手段における互いに同じ段に送られることを特徴とする請求項１又は２に記載の冷媒循環システム。     The pressurizing means flows through the one pipe up to a pressure equivalent to the pressure of the high-pressure-stage return refrigerant vapor that flows through the pipe on the high-pressure stage side by a predetermined number of stages from the one pipe among the plurality of pipes. Pressurizes the return refrigerant vapor,
    The refrigerant circulation according to claim 1 or 2, wherein the return refrigerant vapor after pressurization by the pressurizing means and the high-pressure stage-side return refrigerant vapor are sent to the same stage in the compression means. system.
PCT/JP2016/058135 2015-03-20 2016-03-15 Refrigerant circulation system WO2016152651A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10204455A (en) * 1997-01-27 1998-08-04 Chiyoda Corp Liquefaction of natural gas
US20070204649A1 (en) * 2006-03-06 2007-09-06 Sander Kaart Refrigerant circuit
JP2011214741A (en) * 2010-03-31 2011-10-27 Mitsubishi Electric Corp Refrigeration cycle device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10204455A (en) * 1997-01-27 1998-08-04 Chiyoda Corp Liquefaction of natural gas
US20070204649A1 (en) * 2006-03-06 2007-09-06 Sander Kaart Refrigerant circuit
JP2011214741A (en) * 2010-03-31 2011-10-27 Mitsubishi Electric Corp Refrigeration cycle device

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