CN114963689A - Dual-cycle mixed refrigerant natural gas liquefaction system - Google Patents
Dual-cycle mixed refrigerant natural gas liquefaction system Download PDFInfo
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- CN114963689A CN114963689A CN202210710671.1A CN202210710671A CN114963689A CN 114963689 A CN114963689 A CN 114963689A CN 202210710671 A CN202210710671 A CN 202210710671A CN 114963689 A CN114963689 A CN 114963689A
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- heat exchanger
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- tube heat
- precooling
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- 239000003507 refrigerant Substances 0.000 title claims abstract description 163
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 104
- 239000003345 natural gas Substances 0.000 title claims abstract description 47
- 238000001816 cooling Methods 0.000 claims abstract description 84
- 238000005057 refrigeration Methods 0.000 claims abstract description 46
- 239000007788 liquid Substances 0.000 claims description 34
- 238000000926 separation method Methods 0.000 claims description 29
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 13
- 239000001294 propane Substances 0.000 claims description 12
- 239000007789 gas Substances 0.000 claims description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 239000003949 liquefied natural gas Substances 0.000 claims description 8
- 239000012071 phase Substances 0.000 claims description 8
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 claims description 7
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 7
- 239000005977 Ethylene Substances 0.000 claims description 7
- 229930195733 hydrocarbon Natural products 0.000 claims description 7
- 150000002430 hydrocarbons Chemical class 0.000 claims description 7
- 239000004215 Carbon black (E152) Substances 0.000 claims description 6
- QWTDNUCVQCZILF-UHFFFAOYSA-N isopentane Chemical compound CCC(C)C QWTDNUCVQCZILF-UHFFFAOYSA-N 0.000 claims description 6
- 239000007791 liquid phase Substances 0.000 claims description 6
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 238000003860 storage Methods 0.000 claims description 4
- AFABGHUZZDYHJO-UHFFFAOYSA-N dimethyl butane Natural products CCCC(C)C AFABGHUZZDYHJO-UHFFFAOYSA-N 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- 238000007906 compression Methods 0.000 description 4
- 230000006835 compression Effects 0.000 description 4
- 238000009833 condensation Methods 0.000 description 3
- 230000005494 condensation Effects 0.000 description 3
- 238000002309 gasification Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- NNPPMTNAJDCUHE-UHFFFAOYSA-N isobutane Chemical compound CC(C)C NNPPMTNAJDCUHE-UHFFFAOYSA-N 0.000 description 2
- 238000004781 supercooling Methods 0.000 description 2
- VOPWNXZWBYDODV-UHFFFAOYSA-N Chlorodifluoromethane Chemical compound FC(F)Cl VOPWNXZWBYDODV-UHFFFAOYSA-N 0.000 description 1
- 241000237983 Trochidae Species 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000001282 iso-butane Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 1
- 239000013526 supercooled liquid Substances 0.000 description 1
- 230000005514 two-phase flow Effects 0.000 description 1
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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
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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.
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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
- F25J1/003—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
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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
- F25J1/003—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
- F25J1/0055—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 originating from an incorporated cascade
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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
- F25J1/0211—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
- F25J1/0214—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 a dual level refrigeration cascade with at least one MCR cycle
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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.
- F25J1/0291—Refrigerant compression by combined gas compression and liquid pumping
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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.
- F25J1/0292—Refrigerant compression by cold or cryogenic suction of the refrigerant gas
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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
- F25J2210/00—Processes characterised by the type or other details of the feed stream
- F25J2210/62—Liquefied natural gas [LNG]; Natural gas liquids [NGL]; Liquefied petroleum gas [LPG]
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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
- F25J2220/00—Processes or apparatus involving steps for the removal of impurities
- F25J2220/60—Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
- F25J2220/64—Separating heavy hydrocarbons, e.g. NGL, LPG, C4+ hydrocarbons or heavy condensates in general
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Separation By Low-Temperature Treatments (AREA)
Abstract
The invention discloses a double-circulation mixed refrigerant natural gas liquefaction system. The double-circulation mixed refrigerant natural gas liquefaction system comprises a precooling coiled tube heat exchanger, a liquefaction coiled tube heat exchanger and a copious cooling coiled tube heat exchanger; the pre-cooling refrigerant flows through the pre-cooling coiled tube heat exchanger to realize the refrigeration cycle of the pre-cooling mixed refrigerant; the cryogenic refrigerant flows through the liquefaction coiled pipe heat exchanger and the cryogenic coiled pipe heat exchanger to realize the refrigeration cycle of the liquefied cryogenic mixed refrigerant; the pre-cooling refrigerant and the deep cooling refrigerant are mixed refrigerants; the natural gas is liquefied through precooling mixed refrigerant refrigeration cycle and liquefied cryogenic mixed refrigerant refrigeration cycle in sequence. The double-circulation mixed refrigerant natural gas liquefaction system provided by the invention is suitable for large and medium LNG factories with annual LNG production scale of more than 100 million tons, adopts double refrigeration cycles, adopts mixed refrigerants and a coiled tube heat exchanger for the two refrigeration cycles, and is convenient for expanding single-line capacity.
Description
Technical Field
The invention relates to a double-circulation mixed refrigerant natural gas liquefaction system, and belongs to the technical field of natural gas liquefaction.
Background
At present, a large-scale natural gas liquefaction device mainly adopts a mixed refrigerant liquefaction process of propane precooling, a cascade type liquefaction process and a double-circulation mixed refrigerant liquefaction process. The mixed refrigerant liquefaction process for propane precooling adopts pure propane as a precooling refrigerant, the precooling temperature is certain, the adaptability and the adjustability to the environmental temperature and natural gas are weak, the number of heat exchangers of a propane precooling system is large, and the system is complex; three sets of refrigeration systems of the cascade type liquefaction process respectively adopt propane, ethane and methane as refrigerants, the requirement on the purity of the refrigerants is high, the flow of the liquefaction process is complex, the number of equipment is large, and the investment is large; the double-circulation mixed refrigerant liquefaction process has the advantages of strong adaptability to the environmental temperature and natural gas, strong self-regulation capacity, small equipment quantity and low energy consumption.
Disclosure of Invention
The invention aims to provide a double-circulation mixed refrigerant natural gas liquefaction system which can be applied to large and medium-sized LNG factories.
The invention provides a double-circulation mixed refrigerant natural gas liquefaction system which comprises a precooling coiled tube heat exchanger, a liquefaction coiled tube heat exchanger and a copious cooling coiled tube heat exchanger;
the precooling refrigerant flows through the precooling coiled tube heat exchanger to realize precooling mixed refrigerant refrigeration circulation;
the cryogenic refrigerant flows through the liquefaction coiled pipe heat exchanger and the cryogenic coiled pipe heat exchanger to realize the refrigeration cycle of the liquefied cryogenic mixed refrigerant;
the pre-cooling refrigerant and the deep cooling refrigerant are mixed refrigerants;
and the natural gas sequentially passes through the precooling mixed refrigerant refrigeration cycle and the liquefying copious cooling mixed refrigerant refrigeration cycle to realize liquefaction.
Specifically, the pre-cooling mixed refrigerant refrigeration cycle is formed by a primary pre-cooling refrigerant compressor, a pre-cooling refrigerant cooler I, a pre-cooling refrigerant gas-liquid separation tank, a secondary pre-cooling refrigerant compressor, a liquid pump, a pre-cooling refrigerant cooler II and the pre-cooling coiled tube heat exchanger;
the inlet of the primary precooling refrigerant compressor is communicated with the bottom of the precooling coiled tube heat exchanger;
a gas phase outlet of the pre-cooling refrigerant gas-liquid separation tank is communicated with the secondary pre-cooling refrigerant compressor, and a liquid phase outlet is communicated with the liquid pump;
an outlet of the pre-cooling refrigerant cooler II is communicated with the bottom of the pre-cooling wound tube heat exchanger and is connected with a heat exchange tube I, and the other end of the heat exchange tube I is led out from the top of the pre-cooling wound tube heat exchanger, is communicated with the top of the pre-cooling wound tube heat exchanger and is connected with a shell layer of the pre-cooling wound tube heat exchanger; a throttle valve is arranged on the leading-out pipeline.
Specifically, the refrigerating cycle of the liquefied cryogenic mixed refrigerant is formed by a liquefied cryogenic refrigerant compressor, a compressor outlet cooler, a liquefied cryogenic refrigerant gas-liquid separation tank, the liquefied coiled tube heat exchanger and the cryogenic coiled tube heat exchanger;
the inlet of the liquefied cryogenic refrigerant compressor is communicated with the bottom of the liquefied coiled tube heat exchanger, the outlet of the liquefied cryogenic refrigerant compressor is communicated with the inlet of the compressor outlet cooler, the outlet of the compressor outlet cooler is communicated with the bottom of the precooling coiled tube heat exchanger and is connected with a heat exchange tube II, and the heat exchange tube II is communicated with the liquefied cryogenic refrigerant gas-liquid separation tank after being led out from the top of the precooling coiled tube heat exchanger;
a gas phase outlet of the liquefied cryogenic refrigerant gas-liquid separation tank is communicated with the bottom of the liquefied coiled tube heat exchanger and is communicated with a heat exchange tube III, and the heat exchange tube III is led out from the top of the liquefied coiled tube heat exchanger, is communicated with the bottom of the cryogenic coiled tube heat exchanger and is communicated with a heat exchange tube IV; the heat exchange tube IV is led out from the top of the copious cooling wound tube heat exchanger, then is communicated with the top of the copious cooling wound tube heat exchanger and is connected with a shell layer of the copious cooling wound tube heat exchanger; a throttle valve is arranged on the leading-out pipeline;
a liquid phase outlet of the liquefied cryogenic refrigerant gas-liquid separation tank is communicated with the bottom of the liquefied coiled tube heat exchanger and is communicated with a heat exchange tube V, and the heat exchange tube V is led out from the top of the liquefied coiled tube heat exchanger, is communicated with the top of the liquefied coiled tube heat exchanger and is connected with a shell layer of the liquefied coiled tube heat exchanger; a throttle valve is arranged on the leading-out pipeline; and the pipeline behind the throttling valve is communicated with the bottom of the copious cooling pipe-wound heat exchanger.
Specifically, the precooling coiled tube heat exchanger, the liquefying coiled tube heat exchanger and the heat exchange tubes in the copious cooling coiled tube heat exchanger are connected in sequence to realize the liquefaction of the natural gas.
Specifically, a heavy hydrocarbon separation tank is connected between the precooling coiled tube heat exchanger and the liquefaction coiled tube heat exchanger to remove heavy hydrocarbons possibly existing in the raw natural gas;
and a throttle valve is arranged between the copious cooling coiled pipe heat exchanger and the liquefied natural gas storage tank.
On the basis of the natural gas liquefaction system, the invention also provides a natural gas liquefaction method, which comprises pre-cooling refrigerant refrigeration, cryogenic refrigerant refrigeration and natural gas liquefaction which are carried out by adopting the natural gas liquefaction system;
the refrigeration of the pre-cooling mixed refrigerant is realized through the refrigeration cycle of the pre-cooling mixed refrigerant, and the pre-cooling mixed refrigerant can be pre-cooled to about minus 30 to minus 60 ℃;
the cryogenic refrigerant refrigeration is realized through the refrigeration cycle of the liquefied cryogenic mixed refrigerant, and the temperature can reach about-160 ℃;
the natural gas liquefaction is realized through the precooling mixed refrigerant refrigeration cycle and the liquefaction cryogenic mixed refrigerant refrigeration cycle in sequence;
the qualified natural gas needs to be pretreated, namely, the quality requirement of a base load type natural gas liquefaction factory on the natural gas entering a liquefaction unit is met after impurities such as desulfurization, decarburization, dehydration, demercuration, debenzolization and the like are carried out, and partial heavy hydrocarbon is fractionated and removed.
The pre-cooling refrigerant comprises propane, isopentane and any one of ethane and ethylene;
the cryogenic refrigerant includes propane, methane, nitrogen, and any one of ethylene and ethane.
The double-circulation mixed refrigerant natural gas liquefaction system provided by the invention is suitable for large and medium LNG factories with annual LNG production scale of more than 100 ten thousand tons, double refrigeration cycles are adopted, and the mixed refrigerant and the coiled tube heat exchanger are adopted in the two refrigeration cycles, so that the single-line capacity is conveniently expanded; the double-circulation mixed refrigerant natural gas liquefaction system provided by the invention firstly precools the qualified pretreated natural gas in a precooling coiled heat exchanger, then further cools the precooled natural gas in two coiled heat exchangers for liquefaction and copious cooling, and finally enters a liquefied natural gas storage tank through throttling, wherein the precooling mixed refrigerant refrigeration cycle and the copious cooling mixed refrigerant refrigeration cycle adopt independent processes of compression, cooling, condensation, throttling expansion and heat exchange.
Drawings
FIG. 1 is a schematic structural view of a dual cycle mixed refrigerant natural gas liquefaction system of the present invention;
the respective symbols in the figure are as follows:
the system comprises an E1 precooling coiled tube heat exchanger, a C21 primary precooling refrigerant compressor, a C22 secondary precooling refrigerant compressor, a W21 precooling refrigerant primary compressor outlet cooler, a W22 precooling refrigerant secondary compressor outlet cooler, a V21 precooling refrigerant gas-liquid separation tank and a precooling refrigerant throttle VALVE VALVE 21;
the device comprises an E2-1 liquefaction coiled tube heat exchanger, an E2-2 cryogenic coiled tube heat exchanger, a C31 liquefaction cryogenic refrigerant compressor, a W31 compressor outlet cooler, a V31 liquefaction cryogenic refrigerant gas-liquid separation tank, a throttle VALVE VALVE31, a throttle VALVE VALVE32, a V31 liquefaction cryogenic refrigerant gas-liquid separation tank and a V11 heavy hydrocarbon separation tank.
Detailed Description
The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.
Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
As shown in fig. 1, the dual-cycle mixed refrigerant natural gas liquefaction system provided by the invention comprises a pre-cooling coiled tube heat exchanger, a liquefaction coiled tube heat exchanger, a cryogenic coiled tube heat exchanger, a pre-cooling mixed refrigerant refrigeration cycle and a liquefaction cryogenic mixed refrigerant refrigeration cycle.
The pre-cooling mixed refrigerant refrigeration cycle comprises a first-stage pre-cooling refrigerant compressor C21 and a second-stage pre-cooling refrigerant compressor C22; the outlet of the first-stage pre-cooling refrigerant compressor is communicated with a pre-cooling refrigerant cooler W21 and a pre-cooling refrigerant gas-liquid separation tank V21 in sequence; a gas-phase outlet of the pre-chilled-refrigerant gas-liquid separation tank V21 is communicated with a secondary pre-chilled-refrigerant compressor phase C22, and a liquid-phase outlet is communicated with a liquid pump P21; an outlet of the secondary pre-refrigerant compressor C22 and an outlet of the liquid pump P21 are both communicated with the pre-refrigerant cooler W22; and the pre-cooling mixed refrigerant 28 is completely condensed and then enters a pre-cooling coiled tube heat exchanger E1, flows out of the top of E1, is throttled by VALVE21 and then flows back to the shell layer at the top of E1, pre-cooling refrigerant fluid 20 uniformly distributed on the shell layer at the top of E1 after heat exchange and gasification flows out of the bottom of E1 and enters an inlet of a pre-cooling compressor C21, and the refrigeration cycle of the pre-cooling mixed refrigerant is completed.
The refrigeration cycle of the liquefied cryogenic mixed refrigerant comprises a liquefied coiled tube heat exchanger E2-1, a cryogenic coiled tube heat exchanger E2-2, a liquefied cryogenic refrigerant compressor C31, a C31 compressor outlet cooler W31, a liquefied cryogenic refrigerant gas-liquid separation tank V31, a liquefied throttle VALVE VALVE31 and a VALVE 32. The outlet of the liquefied cryogenic refrigerant compressor C31 is communicated with a cooler W31; an outlet of the compressor outlet cooler W31 is communicated with the bottom of the pre-cooling coiled tube heat exchanger E1 through a pipeline 33, and the pipeline 33 is led out from the top of the pre-cooling coiled tube heat exchanger E1 after passing through the pre-cooling coiled tube heat exchanger E1 and is communicated with the cryogenic refrigerant gas-liquid separation tank V31; a gas phase outlet of the cryogenic refrigerant gas-liquid separation tank V31 is communicated with the bottom of a liquefaction coiled tube heat exchanger E2-1 through a pipeline 36, a pipeline 38 is led out from the top of the liquefaction coiled tube heat exchanger E2-1, enters a cryogenic coiled tube heat exchanger E2-2, is led out from the top of the cryogenic coiled tube heat exchanger, is throttled by a throttling VALVE VALVE32 and then flows back to the top shell layer of the cryogenic coiled tube heat exchanger E2-2, is led out from the bottom of the E2-2 after gasification heat exchange, and flows into the top of the E2-1 together with 30.
The liquid phase outlet of the cryogenic refrigerant gas-liquid separation tank V31 is communicated with the bottom of a liquefaction coiled tube heat exchanger E2-1 through a pipeline 35, the pipeline 35 penetrates through the liquefaction coiled tube heat exchanger E2-1, then is led out from the top of the liquefaction coiled tube heat exchanger E2-1, and is led out from the bottom of E2-1 after passing through a liquefaction throttle VALVE VALVE31, a liquefied refrigerant 30 and a cryogenic coiled tube heat exchanger E2-2 shell side refrigerant 41 can be merged at the top of E2-1, and then flows back to the shell side at the top of E2-1, and is led out from the bottom of E2-1 after heat exchange of E2-1, and then enters a liquefied cryogenic refrigerant compressor C31 for compression, so that the refrigeration cycle of liquefied cryogenic mixed refrigerant is completed.
The two-stage mixed refrigerant circulating liquefaction system is used for carrying out natural gas liquefaction to liquefy the raw material natural gas of the gas field: the feed gas comprises 93.5 percent of methane, 2.46 percent of ethylene, 3.1 percent of nitrogen, 0.51 percent of propane, 0.13 percent of butane, 0.12 percent of isobutane and 0.18 percent of C5+ component; the adopted pre-cooling refrigerant: consists of 45.4% propane, 19.6% isopentane, 35% ethylene (or ethane); the cryogenic refrigerant adopted is as follows: consisting of 36.4% methane, 16.9% propane, 5.8% nitrogen, 40.9% ethylene (or ethane) can be carried out according to the following steps:
the low-pressure gas-phase refrigerant which is heat exchanged from the pre-cooling coiled tube heat exchanger E1 is subjected to secondary compression through the refrigeration cycle of the pre-cooling mixed refrigerant and is cooled into 3.09MPag and 38 ℃ supercooled liquid; liquid precooling refrigerant enters a precooling coiled tube heat exchanger E1 from the bottom of a precooling coiled tube heat exchanger E1, is cooled to about minus 50 ℃ in E1 and is led out from the top of the E1 heat exchanger, throttling and pressure reduction are carried out to 0.23MPag through a precooling refrigerant throttle VALVE VALVE21, the temperature is further reduced to minus 53.25 ℃ and enters a shell layer of the precooling coiled tube heat exchanger E1 from the top, the liquid flows downwards from the top through a shell layer flow passage of the precooling coiled tube heat exchanger E1, the raw material natural gas 11, the high-pressure precooling refrigerant 22 and the cryogenic refrigerant 33 are cooled to about minus 50 ℃ in the gasification process, the gasified low-pressure precooling refrigerant is discharged from the bottom of the precooling coiled tube heat exchanger E1 and enters a first-stage precooling compressor C21 for compression, W21 for cooling, V21 separation, C22 and P21 pressurization and W21 for condensation, and a precooling refrigeration cycle is completed.
High-pressure cryogenic refrigerant gas enters a pre-cooling coil heat exchanger E1 through a pipeline 33, is partially condensed when being cooled to-50 ℃ in E1, enters a liquefied cryogenic refrigerant gas-liquid separation tank V31, separated liquid enters a liquefied coil heat exchanger E2-1 through a pipeline 35 for supercooling, is led out from the top of the liquefied coil heat exchanger E2-1 after being cooled to-120 ℃, and is reduced in pressure to about 0.22MPag through a throttle VALVE VALVE 31; the gas separated from the top of the liquefied cryogenic refrigerant gas-liquid separation tank V31 enters a liquefied coiled tube heat exchanger E2-1 through a pipeline 36, is completely condensed through the liquefied coiled tube heat exchanger E2-1, is cooled to-119.7 ℃, is led out from the top of E2-1, enters a cryogenic coiled tube heat exchanger E2-2 for supercooling, is led out from the top of the cryogenic coiled tube heat exchanger E2-2 when the temperature reaches-155 ℃, is throttled and depressurized to about 0.23MPag through a throttle VALVE VALVE32, and is at about-161.4 ℃; the throttled two-phase flow enters a shell layer of a cryogenic coiled tube heat exchanger E2-2 from the top of E2-2 through a pipeline 40 to provide cold energy for heat exchange of the cryogenic coiled tube heat exchanger, natural gas and high-pressure cryogenic refrigerant are cooled to about minus 155 ℃, low-pressure cryogenic refrigerant 40 in the shell layer of E2-2 flows from top to bottom and is rewarming to about minus 122.7 ℃, the low-pressure cryogenic refrigerant is led out from the bottom of the cryogenic coiled tube heat exchanger E2-2 and is mixed with fluid 30 obtained by throttling the previous liquid refrigerant, and the mixture enters a liquefied coiled tube heat exchanger E2-1 to provide cold energy; the gasified cryogenic refrigerant is discharged from the bottom of the E2-1 liquefaction coiled tube heat exchanger through a pipeline 31, enters a liquefied cryogenic refrigerant compressor C21, is compressed to about 2.94MPag, enters a liquefied cryogenic refrigerant cooler W31, is cooled to 38 ℃, and then enters the bottom of a precooling coiled tube heat exchanger E1 through a pipeline 33 to finish a refrigeration cycle;
the pretreated qualified raw material natural gas is precooled to about minus 50 ℃ in a precooling coiled tube heat exchanger E1, heavy hydrocarbon is separated by a heavy hydrocarbon separation tank V11 and then enters an E2-1 liquefaction coiled tube heat exchanger for condensation and liquefaction, the temperature reaches minus 119.7 ℃, condensed LNG enters an E2-2 copious cooling coiled tube heat exchanger through a pipeline 15 for further cooling to about minus 155 ℃, and finally enters a liquefied natural gas storage tank through a throttle VALVE VALVE 11.
Claims (7)
1. A dual-cycle mixed refrigerant natural gas liquefaction system comprises a precooling coiled tube heat exchanger, a liquefaction coiled tube heat exchanger and a copious cooling coiled tube heat exchanger;
the precooling refrigerant flows through the precooling coiled tube heat exchanger to realize precooling mixed refrigerant refrigeration circulation;
the cryogenic refrigerant flows through the liquefaction coiled pipe heat exchanger and the cryogenic coiled pipe heat exchanger to realize the refrigeration cycle of the liquefied cryogenic mixed refrigerant;
the pre-cooling refrigerant and the deep cooling refrigerant are mixed refrigerants;
and the natural gas sequentially passes through the precooling mixed refrigerant refrigeration cycle and the liquefying copious cooling mixed refrigerant refrigeration cycle to realize liquefaction.
2. The natural gas liquefaction system of claim 1, wherein: the pre-cooling mixed refrigerant refrigeration cycle is formed by a primary pre-cooling refrigerant compressor, a pre-cooling refrigerant cooler I, a pre-cooling refrigerant gas-liquid separation tank, a secondary pre-cooling refrigerant compressor, a liquid pump, a pre-cooling refrigerant cooler II and the pre-cooling coiled tube heat exchanger;
the inlet of the primary precooling refrigerant compressor is communicated with the bottom of the precooling coiled tube heat exchanger;
a gas phase outlet of the pre-cooling refrigerant gas-liquid separation tank is communicated with the secondary pre-cooling refrigerant compressor, and a liquid phase outlet of the pre-cooling refrigerant gas-liquid separation tank is communicated with the liquid pump;
an outlet of the precooling refrigerant cooler II is communicated with the bottom of the precooling wound tube heat exchanger and is connected with a heat exchange tube I, and the other end of the heat exchange tube I is led out from the top of the precooling wound tube heat exchanger, is communicated with the top of the precooling wound tube heat exchanger and is connected with a shell layer of the precooling wound tube heat exchanger; a throttle valve is arranged on the leading-out pipeline.
3. The natural gas liquefaction system according to claim 1 or 2, characterized in that: the refrigerating cycle of the liquefied cryogenic mixed refrigerant is formed by a liquefied cryogenic refrigerant compressor, a compressor outlet cooler, a liquefied cryogenic refrigerant gas-liquid separation tank, the liquefied coiled pipe heat exchanger and the cryogenic coiled pipe heat exchanger;
the inlet of the liquefied cryogenic refrigerant compressor is communicated with the bottom of the liquefied coiled tube heat exchanger, the outlet of the liquefied cryogenic refrigerant compressor is communicated with the inlet of the compressor outlet cooler, the outlet of the compressor outlet cooler is communicated with the bottom of the precooling coiled tube heat exchanger and is connected with a heat exchange tube II, and the heat exchange tube II is led out from the top of the precooling coiled tube heat exchanger and then is communicated with the liquefied cryogenic refrigerant gas-liquid separation tank;
a gas phase outlet of the liquefied cryogenic refrigerant gas-liquid separation tank is communicated with the bottom of the liquefied coiled tube heat exchanger and is communicated with a heat exchange tube III, and the heat exchange tube III is led out from the top of the liquefied coiled tube heat exchanger, is communicated with the bottom of the cryogenic coiled tube heat exchanger and is communicated with a heat exchange tube IV; the heat exchange tube IV is led out from the top of the copious cooling wound tube heat exchanger, then is communicated with the top of the copious cooling wound tube heat exchanger and is connected with a shell layer of the copious cooling wound tube heat exchanger; a throttle valve is arranged on the leading-out pipeline;
a liquid phase outlet of the liquefied cryogenic refrigerant gas-liquid separation tank is communicated with the bottom of the liquefied coiled tube heat exchanger and is communicated with a heat exchange tube V, and the heat exchange tube V is led out from the top of the liquefied coiled tube heat exchanger, is communicated with the top of the liquefied coiled tube heat exchanger and is connected with a shell layer of the liquefied coiled tube heat exchanger; a throttle valve is arranged on the leading-out pipeline; and the pipeline behind the throttling valve is communicated with the bottom of the copious cooling pipe-wound heat exchanger.
4. The natural gas liquefaction system according to any one of claims 1 to 3, wherein: the precooling coiled tube heat exchanger, the liquefying coiled tube heat exchanger and the heat exchange tubes in the copious cooling coiled tube heat exchanger are sequentially connected to realize the liquefaction of the natural gas.
5. The natural gas liquefaction system of claim 4, wherein: a heavy hydrocarbon separation tank is connected between the precooling coiled tube heat exchanger and the liquefying coiled tube heat exchanger;
and a throttle valve is arranged between the copious cooling coiled pipe heat exchanger and the liquefied natural gas storage tank.
6. A natural gas liquefaction process comprising pre-refrigerant refrigeration, cryogenic refrigerant refrigeration and natural gas liquefaction carried out using the natural gas liquefaction system of any of claims 1-5;
the refrigeration of the pre-cooling refrigerant is realized through the refrigeration cycle of the pre-cooling mixed refrigerant;
the cryogenic refrigerant refrigeration is realized through the refrigeration cycle of the liquefied cryogenic mixed refrigerant;
and the natural gas liquefaction is realized through the precooling mixed refrigerant refrigeration cycle and the liquefaction cryogenic mixed refrigerant refrigeration cycle in sequence.
7. The natural gas liquefaction process of claim 6, characterized in that: the pre-cooling refrigerant comprises propane, isopentane and any one of ethane and ethylene;
the cryogenic refrigerant comprises propane, methane, nitrogen and any of ethylene and ethane.
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| WO2022095691A1 (en) * | 2020-11-05 | 2022-05-12 | 华南理工大学 | Process and system for preparing lng from coal-based methane-rich synthesis gas by means of cryogenic separation |
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