WO2020248328A1 - 一种适用于超大规模的三循环天然气液化装置及方法 - Google Patents

一种适用于超大规模的三循环天然气液化装置及方法 Download PDF

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Publication number
WO2020248328A1
WO2020248328A1 PCT/CN2019/096445 CN2019096445W WO2020248328A1 WO 2020248328 A1 WO2020248328 A1 WO 2020248328A1 CN 2019096445 W CN2019096445 W CN 2019096445W WO 2020248328 A1 WO2020248328 A1 WO 2020248328A1
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Prior art keywords
propane
cmr
wmr
heat exchanger
compressor
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PCT/CN2019/096445
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English (en)
French (fr)
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蒲黎明
蒋志明
郭成华
郑春来
刘家洪
王科
陈运强
李莹珂
王毅
汤晓勇
黄勇
田静
汪贵
周璇
王刚
李龙
谢顶衫
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中国石油工程建设有限公司
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Publication of WO2020248328A1 publication Critical patent/WO2020248328A1/zh

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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
    • F25J1/0002—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
    • F25J1/0032—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 the feed stream itself or separated fractions from it, i.e. "internal refrigeration"
    • F25J1/0042—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 the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by liquid expansion with extraction of work
    • 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
    • F25J1/003—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
    • F25J1/0057—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 after expansion of the liquid refrigerant stream with extraction of work
    • 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
    • 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
    • F25J1/0211—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 using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle
    • F25J1/0217—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 using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle as at least a three level refrigeration cascade with at least one MCR cycle
    • F25J1/0218—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 using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle as at least a three level refrigeration cascade with at least one MCR cycle with one or more SCR cycles, e.g. with a C3 pre-cooling cycle
    • 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
    • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
    • F25J1/0262—Details of the cold heat exchange system
    • F25J1/0263—Details of the cold heat exchange system using different types of heat exchangers
    • 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
    • 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.
    • F25J1/0292—Refrigerant compression by cold or cryogenic suction of the refrigerant gas

Definitions

  • the invention relates to the technical field of natural gas liquefaction and cryogenic cooling, in particular to a three-cycle natural gas liquefaction device and method suitable for ultra-large scale.
  • a three-stage refrigeration cycle the load of the precooling section, the liquefaction section and the supercooling section is distributed, and the high efficiency Equipment, streamline the process, and meet the requirements for the construction of a large-scale natural gas liquefaction plant with a capacity of 6-8 million tons per year.
  • the liquefaction process technologies used in the construction of large-scale LNG plants in the world mainly include APCI's C3MR, DMR and AP-X processes, ConocoPhillips' Optimized Cascade process, Linde's MFC process and Shell's DMR process.
  • Large-scale LNG plants can reduce unit LNG production costs and achieve economies of scale.
  • the largest single LNG plant in China is 1.2 million tons/year, using multi-stage single-component refrigeration liquefaction process (MSC process). Based on the MSC process, the development of a single 3.5 million tons/year natural gas liquefaction process package has been realized, but this process cannot meet the construction of a single 6-8 million tons/year ultra-large LNG plant.
  • MSC process multi-stage single-component refrigeration liquefaction process
  • the present invention provides a three-cycle natural gas liquefaction device and method suitable for super large-scale, which has the advantages of simple process flow and low energy consumption.
  • the technical scheme adopted by the present invention is: a three-cycle natural gas liquefaction device suitable for super large-scale, including natural gas liquefaction pipeline, propane pre-cooling cycle system, WMR refrigeration cycle system and CMR refrigeration cycle system, in which:
  • the natural gas liquefaction pipe is composed of propane heat exchanger, WMR heat exchanger, CMR heat exchanger, LNG expander, LNG flash tank and LNG booster pump connected in sequence;
  • the propane pre-cooling cycle system includes a propane heat exchanger, a propane compressor, a propane compressor outlet cooler, a high-pressure propane gas-liquid separation tank, a medium-pressure propane gas-liquid separation tank, and a low-pressure propane gas-liquid separation tank for Pre-cooling of natural gas, WMR refrigerant and CMR refrigerant;
  • the WMR refrigeration cycle system includes a WMR heat exchanger, a WMR compressor inlet buffer tank, a WMR compressor, a WMR compressor outlet cooler, and a WMR expander for further cooling and partial liquefaction of natural gas and CMR refrigerant;
  • the CMR refrigeration cycle system includes a CMR heat exchanger, a CMR compressor inlet buffer tank, a CMR compressor, a CMR compressor outlet cooler, and a CMR expander, which are used to provide cold energy for all liquefaction and subcooling of natural gas and CMR refrigerant .
  • the invention also discloses a three-cycle natural gas liquefaction method suitable for super large-scale, including the following steps:
  • the propane cycle system provides cold capacity for natural gas, WMR refrigerant and CMR refrigerant pre-cooling:
  • the propane pressurized by the propane compressor is cooled by the propane cooler and divided into two streams.
  • One of the liquid phase propane passes through the first high-pressure propane throttle valve to throttle and reduce the pressure before entering the propane heat exchanger. It is natural gas, WMR refrigerant and CMR refrigerant cooling provides cold capacity, the gas phase propane from the propane heat exchanger returns to the high pressure suction port of the propane compressor; the other liquid phase propane passes through the second high pressure propane throttle valve to throttle and reduce the pressure and then enters the high pressure propane gas-liquid
  • the separation tank performs gas-liquid separation, where: the gas phase propane at the top of the tank returns to the high pressure suction port of the propane compressor, and the liquid phase at the bottom of the tank is divided into two streams.
  • One of the liquid phase propane passes through the first intermediate pressure propane throttle valve to throttle and reduce the pressure. It enters the propane heat exchanger to provide cold energy for the continuous cooling of natural gas, WMR refrigerant and CMR refrigerant.
  • the gas phase propane from the propane heat exchanger returns to the medium pressure suction port of the propane compressor; the other liquid phase propane passes through the second The medium-pressure propane throttle valve throttles and reduces the pressure and then enters the medium-pressure propane gas-liquid separation tank for gas-liquid separation.
  • the gas-phase propane at the top of the tank returns to the medium-pressure suction port of the propane compressor, and the liquid-phase propane at the bottom of the tank passes through the low-pressure propane throttle valve After throttling and pressure reduction, it enters the propane heat exchanger to provide cold energy for the continuous cooling of natural gas, WMR refrigerant and CMR refrigerant.
  • the gas phase propane from the propane heat exchanger passes through the low-pressure propane gas-liquid separation tank and returns to the propane compressor. Intake port; low pressure propane, medium pressure propane, and high pressure propane are pressurized by a propane compressor to cycle;
  • WMR refrigeration system provides refrigeration for further cooling and partial liquefaction of natural gas and CMR refrigerant:
  • the WMR refrigerant from the bottom of the WMR heat exchanger enters the WMR compressor inlet buffer tank, pressurized by the WMR compressor and cooled by the WMR cooler, then enters the propane heat exchanger for cooling and liquefaction; the liquid WMR enters the WMR heat exchanger for further After cooling, it comes out from the top, expands to a low pressure by the WMR expander, and then enters the WMR heat exchanger to provide cold energy for further cooling and partial liquefaction of natural gas, WMR refrigerant and CMR refrigerant; low pressure WMR coming out of the bottom of the WMR heat exchanger
  • the refrigerant circulates after returning to the buffer tank at the inlet of the WMR compressor;
  • CMR refrigeration system provides cold capacity for all liquefaction and subcooling of natural gas and CMR refrigerant:
  • the CMR refrigerant is pressurized by the CMR compressor and then cooled by the CMR cooler, propane heat exchanger, WMR heat exchanger, and CMR heat exchanger in turn, and then comes out from the top of the CMR heat exchanger, and then expands to a low pressure by the CMR expander. It enters the CMR heat exchanger to provide cold capacity for natural gas and its own liquefaction subcooling; the low-pressure CMR from the bottom of the CMR heat exchanger returns to the CMR compressor inlet buffer tank for circulation.
  • the invention is based on three cycles and shares the refrigeration load of each stage. Natural gas passes through a plate-fin heat exchanger and two coiled-tube heat exchangers for cooling in sequence until the liquefaction is supercooled, the number of process equipment is small, and the natural gas liquefaction device
  • the scale can reach a single train of 6-8 million tons/year; the cooling capacity required for the liquefaction process is provided by the three systems of propane, WMR mixed refrigerant, and CMR mixed refrigerant.
  • the system has rich adjustment methods and can provide matching cooling for the natural gas liquefaction process. Quantity, flexible operation and good adaptability to raw materials. Compared with the prior art, it has the following characteristics:
  • the present invention is an innovation and improvement based on the engineering application practice of the multi-stage single-component liquefaction process (MSC process).
  • MSC process multi-stage single-component liquefaction process
  • propylene pre-cooling + ethylene cooling + mixed refrigerant liquefaction supercooling (mixed refrigerants are mainly methane and nitrogen).
  • the pre-cooling cycle adopts propane
  • the cooling cycle adopts mixed refrigerant, mainly ethane, including methane and propane
  • the liquefied supercooling cycle refrigerant adopts mixed refrigerant, including nitrogen, methane, and ethane.
  • the cooling section and the liquefaction subcooling section all use mixed refrigerants, which can be combined with the optional models of the drive equipment to adjust the refrigeration cycle load, and flexibly adjust the natural gas cooling, liquefaction and subcooling temperature, and the operation adaptability is better.
  • the propylene and ethylene refrigeration system adopts a shell-and-tube heat exchanger or a CIK heat exchanger for heat exchange, and the methane refrigeration cycle adopts a plate-fin heat exchanger;
  • the heat exchange equipment of the propane pre-cooling section of the present invention adopts high-efficiency
  • the plate-fin heat exchanger has the advantages of high integration of the heat exchange system and the advantages of simplified process flow and less area;
  • the WMR and CMR main low-temperature heat exchanger adopts the wound tube heat exchanger, and the wound tube heat exchanger It has the characteristics of a large heat exchange area for a single unit, which is conducive to the realization of large-scale natural gas liquefaction equipment.
  • the dual mixed refrigerant liquefaction process adopts a 2-stage mixed refrigerant refrigeration cycle to realize natural gas pre-cooling, liquefaction and subcooling.
  • the present invention adopts three-cycle refrigeration to share the liquefaction load at all levels and realizes a single line Construction of 6-8 million tons/year super large-scale natural gas liquefaction plant.
  • the MFC process is a three-cycle refrigeration cycle process in which the pre-cooling section, the liquefaction section, and the sub-cooling section are all refrigerated with mixed refrigerant; compared with MFC, the pre-cooling section of the present invention is pure propane refrigerant.
  • AP-X is also a three-cycle refrigeration cycle process.
  • the pre-cooling section adopts propane refrigeration
  • the liquefaction section adopts mixed refrigerant refrigeration
  • the subcooling section adopts nitrogen expansion refrigeration; compared with AP-X process, the supercooling section of the present invention Adopt mixed refrigerant for refrigeration.
  • the WMR throttling, CMR throttling and high-pressure LNG throttling of the present invention all use liquid turboexpanders.
  • the liquid turboexpander is isentropic expansion. Compared with conventional throttling valve isenthalpic expansion, the expansion efficiency is high. Product output can be increased by 1 to 3%, and energy consumption per unit of LNG product can be reduced by 1 to 3%.
  • Figure 1 is a process flow diagram of the present invention.
  • a three-cycle natural gas liquefaction device suitable for super-large scale includes: propane precooling plate-fin heat exchanger 1, WMR wound tube heat exchanger 2, CMR wound tube heat exchanger 3.
  • LNG hydraulic turbine expander 4 LNG flash tank 5, LNG booster pump 6, propane compressor 7, propane compressor outlet cooler 8, first high pressure propane throttle valve 9, second high pressure propane throttle valve 10.
  • High-pressure propane gas-liquid separation tank 11 first medium-pressure propane throttle valve 12, second medium-pressure propane throttle valve 13, medium-pressure propane gas-liquid separation tank 14, low-pressure propane throttle valve 15, low-pressure propane gas Liquid separation tank 16, WMR compressor inlet buffer tank 17, WMR compressor 18, WMR compressor outlet cooler 19, WMR hydraulic turbine expander 20, CMR compressor inlet buffer tank 21, CMR compressor 22, CMR Compressor outlet cooler 23, CMR hydraulic turbine expander 24, of which:
  • the propane compressor 7, the propane compressor outlet cooler 8, the first high-pressure propane throttle valve 9, the propane pre-cooling plate-fin heat exchanger 1, and the high-pressure suction port of the propane compressor 7 are connected in sequence;
  • Propane compressor outlet cooler 8 second high pressure propane throttle valve 10, high pressure propane gas-liquid separation tank 11, first medium pressure propane throttle valve 12, propane pre-cooling plate-fin heat exchanger 1, propane compressor 7
  • the medium pressure suction ports are connected in sequence;
  • High-pressure propane gas-liquid separation tank 11 Second medium-pressure propane throttle valve 13, medium-pressure propane gas-liquid separation tank 14, low-pressure propane throttle valve 15, propane pre-cooling plate-fin heat exchanger 1, low-pressure propane gas-liquid separation Tank 16, propane compressor 7 low pressure suction ports are connected in sequence;
  • the gas phase at the outlet of the high-pressure propane gas-liquid separation tank 11 is connected with the high-pressure suction pipeline of the propane compressor 7; the gas-phase outlet of the medium-pressure propane gas-liquid separation tank 14 is connected with the medium-pressure suction pipeline of the propane compressor 7.
  • WMR compressor inlet buffer tank 17 WMR compressor 18, WMR compressor outlet cooler 19, propane pre-cooling plate-fin heat exchanger 1, WMR wound tube heat exchanger 2, WMR hydraulic turbo expander 20 in turn Connected.
  • the CMR hydraulic turboexpander 24 is connected in sequence.
  • the present invention also provides a three-cycle natural gas liquefaction method suitable for super large-scale, including the following steps:
  • the propane pre-cooling system pre-cools natural gas, WMR and CMR to -30°C ⁇ -39°C:
  • the propane pressurized from the propane compressor 7 to 1.5MPa.a ⁇ 2.5MPa.a is cooled to 20°C ⁇ 50°C by the propane cooler 8, and divided into 2 strands, one of which is liquid phase propane (about 15% ⁇ 25%)
  • the pressure drops to 0.3MPa.a ⁇ 0.6MPa.a and then enters the propane pre-cooling plate-fin heat exchanger 1 to cool the natural gas, WMR refrigerant and CMR refrigerant ( 20°C ⁇ 0°C)
  • the gas phase propane from the plate-fin heat exchanger 1 returns to the high pressure suction port of the propane compressor 7;
  • the other liquid phase propane (75% ⁇ 85%) passes through the second high pressure propane throttle valve
  • the pressure drops to 0.3MPa.a ⁇ 0.6MPa.a and then enters the high-pressure propane gas-liquid separation tank 11 for gas-liquid separation, and the gas-phase propane at the top of the tank returns to the high-pressure suction port of the propane compressor 7;
  • the liquid phase of the high-pressure propane gas-liquid separation tank 11 is divided into two streams.
  • One of the liquid phase propane (45%-55%) is throttled by the first medium-pressure propane throttle valve 12, and the pressure drops to 0.2MPa.a ⁇ 0.35MPa
  • another liquid phase propane (45% to 55%) is throttled by the second medium pressure propane throttle valve 13, and the pressure drops to 0.2MPa.a ⁇ 0.35MPa.a and then enters the middle
  • the pressure propane gas-liquid separation tank 14 performs gas-liquid separation, and the gas-phase propane at the top of the tank returns to the medium pressure suction port of the propane compressor 7;
  • the liquid phase of the medium-pressure propane gas-liquid separation tank 14 is throttled by the throttle valve 15, and the pressure drops to 0.1MPa.a ⁇ 0.2MPa.a, and then enters the propane pre-cooling plate-fin heat exchanger 1, for natural gas and WMR refrigerant Cooling with CMR refrigerant (-30°C ⁇ -39°C), the gas phase propane from the propane pre-cooling plate-fin heat exchanger 1 passes through the low pressure propane gas-liquid separation tank 16 and then returns to the low pressure suction port of the propane compressor 7;
  • the low-pressure propane, medium-pressure propane, and high-pressure propane are pressurized by the propane compressor 7 and then circulated.
  • WMR refrigeration system cools natural gas and CMR refrigerant to -65°C ⁇ -95°C:
  • the WMR refrigerant from the bottom of the WMR wound tube heat exchanger 2 enters the WMR compressor inlet buffer tank 17, pressurized by the WMR compressor 18 to 3MPa.a ⁇ 5MPa.a, and then cooled by the WMR cooler 19 to 20°C ⁇ At 50°C, enter the propane pre-cooling plate-fin heat exchanger 1 to cool to -30°C ⁇ -39°C and liquefy; the liquid WMR enters the WMR wound tube heat exchanger 2 and is further cooled to -65°C ⁇ -95°C from the top , After expanding to 0.2MPa.a ⁇ 0.5MPa.a by WMR hydraulic expander 20 (-70°C ⁇ -100°C), then enter WMR wound tube heat exchanger 2 for natural gas, WMR refrigerant and CMR refrigerant Perform cooling (-65°C ⁇ -95°C); the low pressure WMR (0.2MPa.a ⁇ 0.5MPa.a, -35°C ⁇ -45°C) coming out from the bottom of WMR wound tube
  • CMR refrigeration system provides cold capacity for all liquefaction and subcooling of natural gas and CMR refrigerant:
  • the CMR refrigerant which is the refrigerant of the CMR refrigeration system, is pressurized to 5MPa.a ⁇ 8MPa.a by the CMR compressor 22, then cooled to 20°C ⁇ 50°C by the CMR compressor outlet cooler 23, and replaced by propane precooling plate-fin type Heater 1 is cooled to -30°C ⁇ -39°C, cooled to -65°C ⁇ -95°C by WMR tube-wound heat exchanger 2, and cooled to -155°C ⁇ -160 in CMR tube-wound heat exchanger 3 Come out from the top after °C, then expand to 0.2MPa.a ⁇ 0.5MPa.a by CMR hydraulic expander 24, and then enter CMR coiled tube heat exchanger 3 to provide cold energy for natural gas and its own liquefaction subcooling; from CMR The low pressure CMR (0.2MPa.a ⁇ 0.5MPa.a, -75°C ⁇ -95°C) coming out of the bottom of the tube-wound heat exchanger 3 returns to the
  • the natural gas coming out of the top of the CMR coiled tube heat exchanger 3 has been liquefied and subcooled to -155°C ⁇ -160°C.
  • the subcooled natural gas is expanded to (120kPa.a, -160 by the LNG hydraulic turbine expander 4). °C ⁇ -163°C) then enter the LNG flash tank 5 for flash evaporation, the BOG flashed out is sent to the downstream BOG booster device, the bottom LNG of the LNG flash tank 5 is sent to the LNG booster pump 6 after being pressurized LNG storage unit.
  • the mixed refrigerant WMR is mainly composed of ethane and a certain amount of methane and propane, wherein the volume content of methane is 5%-15%, ethane is 70%-85%, and propane is 10%-20%;
  • the composition of the refrigerant CMR is nitrogen, methane, and ethane, wherein the volume content of nitrogen is 10%-25%, ethane is 40%-65%, and propane is 30%-45%.
  • the working principle of the present invention is:
  • the three-cycle liquefaction system based on high-efficiency equipment provided by the present invention can be applied to a single-line ultra-large-scale natural gas liquefaction plant with an annual production capacity of 6-8 million tons/year. It adopts a three-stage refrigeration cycle, and the pre-cooling section adopts propane refrigerant, liquefaction and over The cold section adopts mixed refrigerant; the pre-cooling cycle, liquefaction and sub-cooling cycle adopt a set of compression, cooling, condensation, turbine expansion and heat exchange processes respectively.
  • hydraulic turbine expanders are selected for WMR, CMR and LNG throttling expansion.
  • the principle is isentropic expansion and higher refrigeration efficiency; hydraulic turbine expanders are used to recover energy for power generation, thereby reducing comprehensive energy Consumption.
  • the invention has the following effects: 1) The composition and ratio of the mixed refrigerant can be reasonably configured according to the changes in the project construction environment and raw gas conditions, thereby optimizing the cooling and liquefaction temperature, so that the energy consumption of the entire process system is the lowest, and the region is adapted Wide range of performance; 2)
  • the three-stage refrigeration cycle adopts high-efficiency plate-fin heat exchanger and tube-wound heat exchanger with high heat exchange efficiency, which can reasonably share the refrigeration load at all levels and realize the large-scale single-line LNG plant.
  • the throttling of WMR and CMR refrigerant adopts hydraulic turbo expander, which has high cooling efficiency and lower energy consumption per LNG product; 4)
  • the throttling of high pressure LNG adopts hydraulic turbo expander, which has good throttling effect.
  • the liquefaction rate of natural gas is higher.

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Abstract

一种适用于超大规模的三循环天然气液化装置及方法，装置包括天然气液化管路、丙烷预冷循环系统、WMR制冷循环系统和CMR制冷循环系统。本装置以三循环为基础，分担每级制冷负荷，天然气依次通过1个板翅式换热器和2个绕管式换热器进行冷却，直至液化过冷；液化过程所需的冷量由丙烷、WMR混合冷剂、CMR混合冷剂三个系统提供，系统调节手段丰富，工艺设备数量少，产量规模大。

Description

一种适用于超大规模的三循环天然气液化装置及方法 技术领域
本发明涉及天然气液化深冷技术领域，具体为一种适用于超大规模的三循环天然气液化装置及方法，通过采用三级制冷循环，分配预冷段、液化段和过冷段的负荷，采用高效设备，简化流程，满足单列产能600～800万吨/年超大规模天然气液化装置建设需求。
背景技术
随着LNG技术装备的不断发展，国际上LNG工厂建设总体趋势是向着大型化发展，单列生产能力多在300～550万吨/年规模，最大规模已达780万吨/年。国际上大规模LNG装置建设采用的液化工艺技术主要有APCI公司的C3MR、DMR和AP-X工艺，康菲公司的Optimized Cascade工艺，Linde公司的MFC工艺和Shell公司的DMR工艺。大规模的LNG装置能够降低单位LNG生产成本，实现规模效益。
国内LNG装置单列最大规模为120万吨/年，采用多级单组分制冷液化工艺(MSC工艺)。基于MSC工艺实现了单列350万吨/年天然气液化工艺包开发，但该工艺无法满足单列600～800万吨/年超大规模的LNG装置建设。
因此，开发一种能适用于600～800万吨/年超大规模天然气液化装置的天然气液化工艺非常必要。
发明内容
为了克服现有技术的缺点，本发明提供了一种适用于超大规模的三循环天然气液化装置及方法，具有流程简洁、能耗低的优点。
本发明所采用的技术方案是：一种适用于超大规模的三循环天然气液化装 置，包括天然气液化管路、丙烷预冷循环系统、WMR制冷循环系统和CMR制冷循环系统，其中：
所述天然气液化管路由丙烷换热器、WMR换热器、CMR换热器、LNG膨胀机、LNG闪蒸罐和LNG增压泵依次连接组成；
所述丙烷预冷循环系统包括丙烷换热器、丙烷压缩机、丙烷压缩机出口冷却器、高压丙烷气液分离罐、中压丙烷气液分液罐和低压丙烷气液分离罐，用于对天然气、WMR冷剂和CMR冷剂进行预冷；
所述WMR制冷循环系统包括WMR换热器、WMR压缩机入口缓冲罐、WMR压缩机、WMR压缩机出口冷却器和WMR膨胀机，用于对天然气、CMR冷剂进一步冷却和部分液化；
所述CMR制冷循环系统包括CMR换热器、CMR压缩机入口缓冲罐、CMR压缩机、CMR压缩机出口冷却器和CMR膨胀机，用于为天然气和CMR冷剂全部液化和过冷提供冷量。
本发明还公开了一种适用于超大规模的三循环天然气液化方法，包括如下步骤：
1)丙烷循环系统为天然气、WMR冷剂和CMR冷剂预冷提供冷量：
从丙烷压缩机增压的丙烷经丙烷冷却器冷却后分成两股，其中一股液相丙烷通过第一高压丙烷节流阀节流降压力后进入丙烷换热器，为天然气、WMR冷剂和CMR冷剂冷却提供冷量，从丙烷换热器出来的气相丙烷回到丙烷压缩机高压吸入口；另一股液相丙烷通过第二高压丙烷节流阀节流降压力后进入高压丙烷气液分离罐进行气液分离，其中：罐顶气相丙烷回到丙烷压缩机高压吸入口，罐底液相分成两股，其中一股液相丙烷通过第一中压丙烷节流阀节流降压力后进入丙烷换热器，为天然气、WMR冷剂和CMR冷剂继续冷却提供冷量，从丙烷 换热器出来的气相丙烷回到丙烷压缩机中压吸入口；另一股液相丙烷通过第二中压丙烷节流阀节流降压力后进入中压丙烷气液分离罐进行气液分离，罐顶气相丙烷回到丙烷压缩机中压吸入口，罐底的液相丙烷通过低压丙烷节流阀节流降压力后进入丙烷换热器，为天然气、WMR冷剂和CMR冷剂继续冷却提供冷量，从丙烷换热器出来的气相丙烷经过低压丙烷气液分离罐后回到丙烷压缩机低压吸入口；低压丙烷、中压丙烷、高压丙烷经丙烷压缩机增压后进行循环；
2)WMR制冷系统为天然气、CMR冷剂进一步冷却及部分液化提供冷量：
从WMR换热器底部出来的WMR冷剂进入WMR压缩机入口缓冲罐，经WMR压缩机增压并经WMR冷却器冷却后，进入丙烷换热器中冷却液化；液态WMR进入WMR换热器进一步冷却后从顶部出来，经WMR膨胀机膨胀至低压后再进入WMR换热器，为天然气、WMR冷剂和CMR冷剂进一步冷却并部分液化提供冷量；从WMR换热器底部出来的低压WMR冷剂回到WMR压缩机入口缓冲罐后进行循环；
3)CMR制冷系统为天然气和CMR冷剂全部液化和过冷提供冷量：
CMR冷剂经CMR压缩机增压后依次经CMR冷却器、丙烷换热器、WMR换热器、CMR换热器冷却后从CMR换热器顶部出来，再经CMR膨胀机膨胀至低压后再进入CMR换热器，为天然气和自身液化过冷提供冷量；从CMR换热器底部出来的低压CMR回到CMR压缩机入口缓冲罐后进行循环。
与现有技术相比，本发明的积极效果是：
本发明以三循环为基础，分担每级制冷负荷，天然气依次经过1个板翅式换热器和2个绕管式换热器进行冷却，直至液化过冷，工艺设备数量少，天然气液化装置规模能够达到单列600～800万吨/年；液化过程所需的冷量由丙烷、WMR混合冷剂、CMR混合冷剂三个系统提供，系统调节手段丰富，能够为天然气液化过程提供匹配的冷量，操作灵活和对原料适应性好。与现有技术相比， 具有如下特点：
1、本发明是在多级单组分液化工艺(MSC工艺)工程应用实践基础上进行的创新和改进，工艺技术具有延续性，与MSC工艺相比，具有如下优点：
1)MSC工艺中采用丙烯预冷+乙烯冷却+混合冷剂液化过冷(混合冷剂以甲烷、氮气为主)。本发明中预冷循环采用丙烷，冷却循环采用混合冷剂，以乙烷为主，包括甲烷和丙烷；液化过冷循环冷剂采用混合冷剂，包括氮气、甲烷、乙烷。
2)冷却段、液化过冷段均采用混合冷剂，可结合驱动设备可选机型调节各制冷循环负荷，灵活地调节天然气冷却、液化和过冷温度，操作适应性更好。
3)MSC工艺中丙烯和乙烯制冷系统采用管壳式换热器或CIK换热器进行换热，甲烷制冷循环采用板翅式换热器；本发明中丙烷预冷段换热设备采用高效的板翅式换热器，换热系统集成度高，具有工艺流程简化、占地少等优势；本发明中WMR和CMR主低温换热器采用绕管式换热器，绕管式换热器具有单台换热面积大的特点，有利于实现天然气液化装置大型化。
2、双混合冷剂液化工艺(DMR工艺)采用2级混合冷剂制冷循环实现天然气预冷、液化和过冷，与DMR工艺相比，本发明采用三循环制冷分担各级液化负荷，实现单列600～800万吨/年超大规模天然气液化装置建设。
3、MFC工艺是一种三循环制冷循环工艺，其预冷段、液化段、过冷段均采用混合冷剂制冷；与MFC相比本发明预冷段为纯丙烷冷剂。
4、AP-X也是一种三循环制冷循环工艺，其预冷段采用丙烷制冷、液化段采用混合冷剂制冷、过冷段采用氮膨胀制冷；与AP-X工艺比较，本发明过冷段采用混合冷剂制冷。
5、本发明WMR节流、CMR节流和高压LNG节流均采用液体透平膨胀 机，液体透平膨胀机为等熵膨胀，与常规节流阀等焓膨胀相比，膨胀效率高，LNG产品产量可提高1～3％，单位LNG产品能耗降低1～3％。
附图说明
本发明将通过例子并参照附图的方式说明，其中：
图1是本发明的工艺流程图。
具体实施方式
一种适用于超大规模的三循环天然气液化装置，如图1所示，包括：丙烷预冷板翅式换热器1、WMR绕管式换热器2、CMR绕管式换热器3、LNG液力透平膨胀机4、LNG闪蒸罐5、LNG增压泵6、丙烷压缩机7、丙烷压缩机出口冷却器8、第一高压丙烷节流阀9、第二高压丙烷节流阀10、高压丙烷气液分离罐11、第一中压丙烷节流阀12、第二中压丙烷节流阀13、中压丙烷气液分液罐14、低压丙烷节流阀15、低压丙烷气液分液罐16、WMR压缩机入口缓冲罐17、WMR压缩机18、WMR压缩机出口冷却器19、WMR液力透平膨胀机20、CMR压缩机入口缓冲罐21、CMR压缩机22、CMR压缩机出口冷却器23、CMR液力透平膨胀机24，其中：
丙烷预冷板翅式换热器1、WMR绕管式换热器2、CMR绕管式换热器3、LNG液力透平膨胀机4、LNG闪蒸罐5、LNG增压泵6依次相连。
丙烷压缩机7、丙烷压缩机出口冷却器8、第一高压丙烷节流阀9、丙烷预冷板翅式换热器1、丙烷压缩机7高压吸入口依次相连；
丙烷压缩机出口冷却器8、第二高压丙烷节流阀10、高压丙烷气液分离罐11、第一中压丙烷节流阀12、丙烷预冷板翅式换热器1、丙烷压缩机7中压吸入口依次相连；
高压丙烷气液分离罐11、第二中压丙烷节流阀13、中压丙烷气液分离罐 14、低压丙烷节流阀15、丙烷预冷板翅式换热器1、低压丙烷气液分离罐16、丙烷压缩机7低压吸入口依次相连；
高压丙烷气液分离罐11出口气相与丙烷压缩机7高压吸入管线相连；中压丙烷气液分离罐14气相出口与丙烷压缩机7中压吸入管线相连。
WMR压缩机入口缓冲罐17、WMR压缩机18、WMR压缩机出口冷却器19、丙烷预冷板翅式换热器1、WMR绕管式换热器2、WMR液力透平膨胀机20依次相连。
CMR压缩机入口缓冲罐21、CMR压缩机22、CMR压缩机出口冷却器23、丙烷预冷板翅式换热器1、WMR绕管式换热器2、CMR绕管式换热器3、CMR液力透平膨胀机24依次相连。
本发明还提供了一种适用于超大规模的三循环天然气液化方法，包括如下步骤：
1)丙烷预冷系统对天然气、WMR和CMR进行预冷至-30℃～-39℃：
从丙烷压缩机7增压至1.5MPa.a～2.5MPa.a的丙烷经丙烷冷却器8冷却至20℃～50℃，分成2股，其中一股液相丙烷(约15％～25％)通过第一高压丙烷节流阀9节流，压力降至0.3MPa.a～0.6MPa.a后进入丙烷预冷板翅式换热器1，对天然气、WMR冷剂和CMR冷剂进行冷却(20℃～0℃)，从板翅式换热器1出来的气相丙烷回到丙烷压缩机7高压吸入口；另一股液相丙烷(75％～85％)通过第二高压丙烷节流阀10节流，压力降至0.3MPa.a～0.6MPa.a后进入高压丙烷气液分离罐11进行气液分离，罐顶气相丙烷回到丙烷压缩机7高压吸入口；
高压丙烷气液分离罐11的液相分成2股，其中一股液相丙烷(45％～55％)通过第一中压丙烷节流阀12节流，压力降至0.2MPa.a～0.35MPa.a后进入丙烷预冷板翅式换热器1，对天然气、WMR冷剂和CMR冷剂进行冷却(-10℃～ -20℃)，从板翅式换热器出来的气相丙烷回到丙烷压缩机7中压吸入口；另一股液相丙烷(45％～55％)通过第二中压丙烷节流阀13节流，压力降至0.2MPa.a～0.35MPa.a后进入中压丙烷气液分离罐14进行气液分离，罐顶气相丙烷回到丙烷压缩机7中压吸入口；
中压丙烷气液分离罐14的液相通过节流阀15节流，压力降至0.1MPa.a～0.2MPa.a后进入丙烷预冷板翅式换热器1，对天然气、WMR冷剂和CMR冷剂进行冷却(-30℃～-39℃)，从丙烷预冷板翅式换热器1出来的气相丙烷经过低压丙烷气液分离罐16后回到丙烷压缩机7低压吸入口；
低压丙烷、中压丙烷、高压丙烷经丙烷压缩机7增压后进行循环。
2)WMR制冷系统将天然气、CMR冷剂冷却至-65℃～-95℃：
从WMR绕管式换热器2底部出来的WMR冷剂进入WMR压缩机入口缓冲罐17，经WMR压缩机18增压至3MPa.a～5MPa.a后经WMR冷却器19冷却至20℃～50℃，进入丙烷预冷板翅式换热器1冷却到-30℃～-39℃并液化；液态WMR进入WMR绕管式换热器2进一步冷却至-65℃～-95℃从顶部出来，经WMR液力膨胀机20膨胀至0.2MPa.a～0.5MPa.a后(-70℃～-100℃)再进入WMR绕管式换热器2，对天然气、WMR冷剂和CMR冷剂进行冷却(-65℃～-95℃)；从WMR绕管式换热器2底部出来的低压WMR(0.2MPa.a～0.5MPa.a,-35℃～-45℃)回到WMR压缩机入口缓冲罐17后进行循环。
3)CMR制冷系统为天然气和CMR冷剂全部液化和过冷提供冷量：
作为CMR制冷系统制冷剂的CMR冷剂经CMR压缩机22增压至5MPa.a～8MPa.a后经CMR压缩机出口冷却器23冷却至20℃～50℃，经丙烷预冷板翅式换热器1冷却到-30℃～-39℃，经WMR绕管式换热器2冷却至-65℃～-95℃，在CMR绕管式换热器3中冷却到-155℃～-160℃后从顶部出来，再经CMR液力 膨胀机24膨胀至0.2MPa.a～0.5MPa.a后再进入CMR绕管式换热器3，为天然气和自身液化过冷提供冷量；从CMR绕管式换热器3底部出来的低压CMR(0.2MPa.a～0.5MPa.a,-75℃～-95℃)回到CMR压缩机入口缓冲罐21后进行循环。
4)高压LNG膨胀闪蒸
从CMR绕管式换热器3顶部出来的天然气已液化并过冷至-155℃～-160℃，过冷后的天然气经LNG液力透平膨胀机4膨胀至(120kPa.a，-160℃～-163℃)后进入LNG闪蒸罐5中闪蒸，闪蒸出的BOG送至下游BOG增压装置，LNG闪蒸罐5罐底LNG经LNG增压泵输6增压后送至LNG存储单元。
所述混合冷剂WMR以乙烷为主，并配一定量的甲烷和丙烷，其中甲烷体积含量为5％～15％、乙烷为70％～85％，丙烷为10％～20％；混合冷剂CMR组成为氮气、甲烷、乙烷，其中氮气体积含量为10％～25％、乙烷为40％～65％，丙烷为30％～45％。
本发明的工作原理是：
本发明提供的基于高效设备的三循环液化系统可适用于单列年产能达600～800万吨/年超大规模天然气液化装置，其采用三级制冷循环，预冷段采用丙烷冷剂、液化和过冷段采用混合冷剂；预冷循环、液化和过冷循环分别采用一套压缩、冷却、冷凝、透平膨胀和换热过程。
本发明中WMR、CMR和LNG节流膨胀选用液力透平膨胀机，其原理为等熵膨胀，制冷效率更高；采用液力透平膨胀机来回收能量，用于发电，从而降低综合能耗。
本发明具有如下效果：1)可根据项目建设地环境和原料气条件的变化，合理配置混合冷剂的组成和配比，从而优化冷却和液化温度，使得整个工艺系 统的能耗最低，地区适应性广；2)三级制冷循环，采用高效的板翅式换热器和绕管式换热器，换热效率高，可合理分担各级制冷负荷，实现单线LNG装置大型化。3)WMR冷剂、CMR冷剂节流采用液力透平膨胀机，制冷效率高，单位LNG产品能耗更低；4)高压LNG节流采用液力透平膨胀机，节流效应好，天然气液化率更高。

Claims (10)

  1. 一种适用于超大规模的三循环天然气液化装置，其特征在于：包括天然气液化管路、丙烷预冷循环系统、WMR制冷循环系统和CMR制冷循环系统，其中：
    所述天然气液化管路由丙烷换热器、WMR换热器、CMR换热器、LNG膨胀机、LNG闪蒸罐和LNG增压泵依次连接组成；
    所述丙烷预冷循环系统包括丙烷换热器、丙烷压缩机、丙烷压缩机出口冷却器、高压丙烷气液分离罐、中压丙烷气液分液罐和低压丙烷气液分离罐，用于对天然气、WMR冷剂和CMR冷剂进行预冷；
    所述WMR制冷循环系统包括WMR换热器、WMR压缩机入口缓冲罐、WMR压缩机、WMR压缩机出口冷却器和WMR膨胀机，用于对天然气、CMR冷剂进一步冷却和部分液化；
    所述CMR制冷循环系统包括CMR换热器、CMR压缩机入口缓冲罐、CMR压缩机、CMR压缩机出口冷却器和CMR膨胀机，用于为天然气和CMR冷剂全部液化和过冷提供冷量。
  2. 根据权利要求1所述的一种适用于超大规模的三循环天然气液化装置，其特征在于：所述丙烷预冷循环系统中，丙烷压缩机、丙烷压缩机出口冷却器、第一高压丙烷节流阀、丙烷换热器和丙烷压缩机高压吸入口依次相连；丙烷压缩机出口冷却器、第二高压丙烷节流阀、高压丙烷气液分离罐、第一中压丙烷节流阀、丙烷换热器、丙烷压缩机中压吸入口依次相连；高压丙烷气液分离罐、第二中压丙烷节流阀、中压丙烷气液分离罐、低压丙烷节流阀、丙烷换热器、低压丙烷气液分离罐、丙烷压缩机低压吸入口依次相连；高压丙烷气液分离罐出口气相与丙烷压缩机高压吸入管线相连；中压丙烷气液分离罐气相出口与丙烷压缩机中压吸入管线相连。
  3. 根据权利要求1所述的一种适用于超大规模的三循环天然气液化装置，其特征在于：所述WMR制冷循环系统中，WMR换热器、WMR压缩机入口缓冲罐、WMR压缩机、WMR压缩机出口冷却器、丙烷换热器、WMR换热器、WMR膨胀机、WMR换热器依次相连。
  4. 根据权利要求1所述的一种适用于超大规模的三循环天然气液化装置，其特征在于：所述CMR制冷循环系统中，CMR换热器、CMR压缩机入口缓冲罐、CMR压缩机、CMR压缩机出口冷却器、丙烷换热器、WMR换热器、CMR换热器、CMR膨胀机、CMR换热器依次相连。
  5. 根据权利要求1至4中任一权利要求要求所述的一种适用于超大规模的三循环天然气液化装置，其特征在于：所述LNG膨胀机、WMR膨胀机和CMR膨胀机均为液力透平膨胀机。
  6. 根据权利要求5所述的一种适用于超大规模的三循环天然气液化装置，其特征在于：所述丙烷换热器为板翅式换热器，所述WMR换热器和CMR换热器均为绕管式换热器。
  7. 一种适用于超大规模的三循环天然气液化方法，其特征在于：包括如下步骤：
    1)丙烷循环系统为天然气、WMR冷剂和CMR冷剂预冷提供冷量：
    从丙烷压缩机增压的丙烷经丙烷冷却器冷却后分成两股，其中一股液相丙烷通过第一高压丙烷节流阀节流降压力后进入丙烷换热器，为天然气、WMR冷剂和CMR冷剂冷却提供冷量，从丙烷换热器出来的气相丙烷回到丙烷压缩机高压吸入口；另一股液相丙烷通过第二高压丙烷节流阀节流降压力后进入高压丙烷气液分离罐进行气液分离，其中：罐顶气相丙烷回到丙烷压缩机高压吸入口，罐底液相分成两股，其中一股液相丙烷通过第一中压丙烷节流阀节流降压力后 进入丙烷换热器，为天然气、WMR冷剂和CMR冷剂继续冷却提供冷量，从丙烷换热器出来的气相丙烷回到丙烷压缩机中压吸入口；另一股液相丙烷通过第二中压丙烷节流阀节流降压力后进入中压丙烷气液分离罐进行气液分离，罐顶气相丙烷回到丙烷压缩机中压吸入口，罐底的液相丙烷通过低压丙烷节流阀节流降压力后进入丙烷换热器，为天然气、WMR冷剂和CMR冷剂继续冷却提供冷量，从丙烷换热器出来的气相丙烷经过低压丙烷气液分离罐后回到丙烷压缩机低压吸入口；低压丙烷、中压丙烷、高压丙烷经丙烷压缩机增压后进行循环；
    2)WMR制冷系统为天然气、CMR冷剂进一步冷却及部分液化提供冷量：
    从WMR换热器底部出来的WMR冷剂进入WMR压缩机入口缓冲罐，经WMR压缩机增压并经WMR冷却器冷却后，进入丙烷换热器中冷却液化；液态WMR进入WMR换热器进一步冷却后从顶部出来，经WMR膨胀机膨胀至低压后再进入WMR换热器，为天然气、WMR冷剂和CMR冷剂进一步冷却并部分液化提供冷量；从WMR换热器底部出来的低压WMR冷剂回到WMR压缩机入口缓冲罐后进行循环；
    3)CMR制冷系统为天然气和CMR冷剂全部液化和过冷提供冷量：
    CMR冷剂经CMR压缩机增压后依次经CMR冷却器、丙烷换热器、WMR换热器、CMR换热器冷却后从CMR换热器顶部出来，再经CMR膨胀机膨胀至低压后再进入CMR换热器，为天然气和自身液化过冷提供冷量；从CMR换热器底部出来的低压CMR回到CMR压缩机入口缓冲罐后进行循环。
  8. 根据权利要求7所述的一种适用于超大规模的三循环天然气液化方法，其特征在于：所述WMR冷剂的组成为甲烷、乙烷和丙烷，其中甲烷体积含量为5％～15％、乙烷为70％～85％，丙烷为10％～20％。
  9. 根据权利要求7所述的一种适用于超大规模的三循环天然气液化方法，其特征在于：所述CMR冷剂的组成为氮气、甲烷、乙烷，其中氮气体积含量 为10％～25％、乙烷为40％～65％，丙烷为30％～45％。
  10. 根据权利要求7所述的一种适用于超大规模的三循环天然气液化方法，其特征在于：从CMR换热器顶部出来的液化并过冷至-155℃～-160℃的天然气，经LNG膨胀机膨胀至120kPa.a进入LNG闪蒸罐中闪蒸，闪蒸出的BOG送至下游BOG增压装置，罐底LNG经LNG增压泵输增压后送至LNG存储单元。
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