CN104089462A - Method and system for refrigerating and liquefying natural gas by mixed refrigerants in two-level precooling mode - Google Patents
Method and system for refrigerating and liquefying natural gas by mixed refrigerants in two-level precooling mode Download PDFInfo
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- CN104089462A CN104089462A CN201410339084.1A CN201410339084A CN104089462A CN 104089462 A CN104089462 A CN 104089462A CN 201410339084 A CN201410339084 A CN 201410339084A CN 104089462 A CN104089462 A CN 104089462A
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- azeotrope
- precooling
- natural gas
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- precooling agent
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 142
- 239000003345 natural gas Substances 0.000 title claims abstract description 68
- 238000000034 method Methods 0.000 title claims abstract description 53
- 239000003507 refrigerant Substances 0.000 title abstract 4
- 238000001816 cooling Methods 0.000 claims abstract description 42
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000003795 chemical substances by application Substances 0.000 claims description 101
- 239000007788 liquid Substances 0.000 claims description 45
- 239000007789 gas Substances 0.000 claims description 38
- 239000012071 phase Substances 0.000 claims description 36
- 239000007791 liquid phase Substances 0.000 claims description 32
- 238000005057 refrigeration Methods 0.000 claims description 27
- 238000000926 separation method Methods 0.000 claims description 25
- 239000004215 Carbon black (E152) Substances 0.000 claims description 22
- 229930195733 hydrocarbon Natural products 0.000 claims description 22
- 150000002430 hydrocarbons Chemical class 0.000 claims description 22
- 230000018044 dehydration Effects 0.000 claims description 15
- 238000006297 dehydration reaction Methods 0.000 claims description 15
- 238000007906 compression Methods 0.000 claims description 14
- 230000006835 compression Effects 0.000 claims description 14
- 230000006837 decompression Effects 0.000 claims description 6
- 239000002253 acid Substances 0.000 claims description 5
- 239000007792 gaseous phase Substances 0.000 claims description 3
- 238000005265 energy consumption Methods 0.000 abstract description 8
- 239000002808 molecular sieve Substances 0.000 abstract description 8
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 abstract description 8
- 230000008929 regeneration Effects 0.000 abstract description 4
- 238000011069 regeneration method Methods 0.000 abstract description 4
- 238000010521 absorption reaction Methods 0.000 abstract 1
- 230000003044 adaptive effect Effects 0.000 abstract 1
- 238000001704 evaporation Methods 0.000 abstract 1
- 230000008020 evaporation Effects 0.000 abstract 1
- 239000003949 liquefied natural gas Substances 0.000 description 11
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 10
- 238000005516 engineering process Methods 0.000 description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 239000001294 propane Substances 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000004519 manufacturing process Methods 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
Classifications
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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
- F25J1/0047—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
- F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
- F25J1/008—Hydrocarbons
- F25J1/0087—Propane; Propylene
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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
- F25J1/0215—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 with one SCR cycle
- F25J1/0216—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 with one SCR cycle using a C3 pre-cooling 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.
- F25J1/0292—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
- 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
Landscapes
- 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 relates to a method and system for refrigerating and liquefying natural gas by mixed refrigerants in a two-level precooling mode. According to the method and system, two levels of precoolers are arranged, and the evaporation pressure of the first level precooler and the second level precooler is adjusted to achieve level-by-level precooling of the natural gas and mixed refrigerants, wherein the temperature of a natural gas outlet of the first level precooler is 5-30 DEG C, the temperature of a natural gas outlet of the second level precooler is -40-0 DEG, and the natural gas is finally cooled to -162 - -140 DEG C through a cooling box to obtain LNG products. According to the method, the temperature gradient of precooling and mixed refrigerating process is increased, so that while the energy efficiency is close to that of a traditional step type refrigerating process, the process similarity of the refrigerating process is also guaranteed. In addition, according to the method, after a natural gas dewatering unit is placed behind the first level precooling process, the content of water entering a molecular sieve bed layer is lowered, and the absorption and regeneration load of the molecular sieve bed layer is reduced. The method for refrigerating and liquefying the natural gas by the mixed refrigerants in the two-level precooling mode is low in energy consumption, high in variable working condition adaptive capacity, and high in operability.
Description
Technical field
The present invention relates to liquefied natural gas (LNG) production field, relate to especially a kind of method and system of two-stage pre-cooling type azeotrope refrigeration liquefying natural gas.
Background technology
Natural gas is as a kind of energy of clean, high-quality, and its demand is just along with the raising of China's expanding economy and environmental protection requirement expands rapidly.Due to the huge advantage that liquefied natural gas (LNG) has in natural gas storage and transport, liquefied natural gas becomes the first-selection of Natural Gas Demand just gradually.
At present, the natural gas liquefaction process conventionally adopting both at home and abroad roughly has three kinds: tandem type circulation technology, azeotrope circulation technology and expander cycle technique.Tandem type circulation technology is the mode of the pure component single cycle one-level throttling refrigeration on multiple not equalities of temperature rank, although energy consumption is low, flow process complexity, invest high.Expander cycle technological process is the simplest, equipment also less and investment economize most, but this process energy consumption is the highest in all technology, only can in small part mini liquefier and sea floating hydrodynamic gasifying device, be applied.Natural gas liquefaction process flow process taking azeotrope circulation as core compared with tandem type circulation technology greatly simplify, equipment is few, reduced investment, but that energy consumption really increases is relatively larger.For this reason, also have based on azeotrope refrigeration process and improve and add propane pre-cooling, so also play the effect of reduction energy consumption, but compare equally tandem type circulation technology high, result can not be satisfactory.And traditional mixed refrigeration process gas dehydration operation with precooling can only be carried out before precooling, thereby cannot utilize the advantage of precooling that the gas water content that enters dehydration procedure is down to minimum, molecular sieve dehydration operation load is high, regeneration gas consumption is large, affects equally the energy consumption index of whole technical process.
Summary of the invention
In order to overcome the deficiencies in the prior art, method of the present invention arranges two-stage forecooler before ice chest deep cooling operation, natural gas and azeotrope two-stage are sent into ice chest after cooling again, at two-stage precooling inter process, molecular sieve dehydration operation is set simultaneously, thereby provide a kind of thermograde that had both increased process of refrigerastion, make energy efficiency approach traditional stepwise refrigeration process, reduce again the gas water content that enters molecular sieve dehydration operation, ensure again the method for the two-stage pre-cooling type azeotrope refrigeration liquefying natural gas of the flow process terseness of kind of refrigeration cycle technique simultaneously.
The method of two-stage pre-cooling type azeotrope refrigeration liquefying natural gas of the present invention, specifically comprises the following steps:
1) the liquid precooling agent I in precooling agent storage tank 18 being obtained to temperature through the first pressure-reducing valve V3 decompression is the precooling agent II of 0～28 DEG C, and the shell side Q that is passed into one-level forecooler 1 evaporates to provide cold under constant temperature, obtains precooling agent steam I simultaneously;
2) to obtain temperature through the second pressure-reducing valve V4 decompression be the precooling agent III of 0～28 DEG C to the liquid precooling agent I in precooling agent storage tank 18, and precooling agent III is passed into and in precooling economizer 19, carries out gas-liquid separation, the precooling agent IV of the gas phase obtaining and the precooling agent V of liquid phase;
3) to obtain temperature through the 3rd pressure-reducing valve V5 decompression be the precooling agent VI of-42～-2 DEG C to precooling agent V, and the shell side Q that precooling agent VI is passed into secondary forecooler 5 evaporates to provide cold under constant temperature, obtains precooling agent steam VII simultaneously;
4) precooling agent steam VII is sent into after 16 1 sections of compressions of pre-cold compressor, make itself and step 1) the precooling agent steam I and the step 2 that obtain) the precooling agent IV that obtains mixes and together enters two sections of pre-cold compressor 16 and continue compression, obtain precooling agent VIII, enter next pre-cooling cycle in passing into precooling agent storage tank 18 after it is condensed into liquid phase in pre-cool condenser 17;
5) the first tube side O that the natural gas I after acid gas removal is passed into one-level forecooler 1 is chilled in advance 5～30 DEG C and obtains natural gas II, and the second tube side P that the azeotrope I after pressurization is passed into one-level forecooler 1 is chilled to 5～30 DEG C in advance, obtains azeotrope II;
6) natural gas II is passed in separator 2 and removes aqueous water, gas phase is carried out deep dehydration and demercuration by mole sieve drier 3 and demercuration bed 4 successively, obtains natural gas III;
7) the first tube side R that natural gas III is passed into secondary forecooler 5 is chilled in advance-40～0 DEG C and obtains natural gas IV, and the second tube side S that azeotrope II is passed into secondary forecooler 5 is chilled to-40～0 DEG C in advance, obtains azeotrope III;
8) azeotrope III is passed into azeotrope knockout drum 20 and carry out gas-liquid separation, obtain the azeotrope IV of liquid phase in the bottom of azeotrope knockout drum 20, top obtains the azeotrope V of gas phase;
9) azeotrope IV is passed in the first flow A of ice chest 6 and be chilled in advance-110～-45 DEG C, obtain azeotrope VI through first throttle valve V1 throttling afterwards, azeotrope VI is passed into the second knockout drum 10 and carry out gas-liquid separation, isolated gas-liquid two-phase logistics passes into the 4th runner D of ice chest 6 after the second blender 9 evenly mixes;
10) azeotrope V is passed in the second runner B of ice chest 6 and be chilled in advance-162～-135 DEG C, obtain azeotrope VII through first throttle valve V1 throttling afterwards, azeotrope VII is passed into the first knockout drum 11 and carry out gas-liquid separation, isolated gas-liquid two-phase logistics passes into the 3rd runner C of ice chest 6 after the first blender 8 evenly mixes, re-heat to the 4th runner D that passes into ice chest 6 after-120～-45 DEG C with together with step 9, continue re-heat and draw ice chest to-42～-2 DEG C and obtain azeotrope VIII;
11) azeotrope VIII is passed into azeotrope compressor 12 through one section of compression, cooling, separate, two sections of compressions and obtain azeotrope I after cooling and enter next kind of refrigeration cycle;
12) step 7 being obtained to the 5th runner E that natural gas IV passes into ice chest 6 is cooled to-45～-65 DEG C and obtains azeotrope V, azeotrope V is passed into heavy hydrocarbon knockout drum 7 and carry out gas-liquid separation, obtain the heavy hydrocarbon I of liquid phase in the bottom of heavy hydrocarbon knockout drum 7, top obtains the azeotrope VI of gas phase, and the 6th runner F that azeotrope VI is passed into ice chest 6 continues deep cooling and obtains LNG product to-140～-162 DEG C.
In above-mentioned technical scheme, step 10) in obtain azeotrope VIII pressure be 120～550kPa.
In above-mentioned technical scheme, step 11) in obtain azeotrope I pressure be 2200～4200kPa.
The present invention also provides a kind of system of two-stage pre-cooling type azeotrope refrigeration liquefying natural gas, comprise: one-level forecooler 1, secondary forecooler 5, pre-cold compressor 16, azeotrope compressor 12, separator 2, mole sieve drier 3, demercuration bed 4, ice chest 6, heavy hydrocarbon knockout drum 7, the first knockout drum 11, the second knockout drum 10, the first blender 8, the second blender 9, the first cooler 13, the first surge tank 14, the second cooler 15, azeotrope knockout drum 20, pre-cool condenser 17, precooling agent storage tank 18, precooling economizer 19, first throttle valve V1, the second choke valve V2, the first pressure-reducing valve V3, the second pressure-reducing valve V4 and the 3rd pressure-reducing valve V5, wherein, natural gas line connects the first tube side O of one-level forecooler 1 successively, separator 2, mole sieve drier 3, demercuration bed 4, the first tube side R of second-stage separator 5, the 5th runner E of cold 6, the 6th runner F of heavy hydrocarbon knockout drum 7 and cold 6, the final LNG pipeline that connects, connect successively a section of azeotrope compressor 12 from the azeotrope pipeline of the 4th runner D of ice chest 6, the first cooler 13, the first surge tank 14, two sections of azeotrope compressor 12, the second cooler 15, the second tube side P of one-level forecooler 1, the second tube side S of secondary forecooler 5 and the entrance of azeotrope knockout drum 20, the bottom liquid phases outlet of azeotrope knockout drum 20 connects the first flow A of ice chest 6 successively, first throttle valve V1, the second separator 10, the 4th runner D of the second blender 9 and ice chest 6, the top gaseous phase outlet of azeotrope knockout drum 20 connects the second runner B of ice chest 6 successively, the second choke valve V2, the first separator 11, the first blender 8, the 3rd runner C of ice chest 6 and the 4th runner D, connect successively one section of pre-cold compressor 16, two sections of pre-cold compressor 16, pre-cool condenser 17 and precooling agent storage tank 18 from the pipeline of secondary forecooler 5 shell side T, the bottom liquid phases pipeline one tunnel second pressure-reducing valve V4 of precooling agent storage tank 18 is connected with the entrance of precooling economizer 19, the bottom liquid phases pipeline of precooling economizer 19 is connected with the shell side T of secondary forecooler 5 through the 3rd pressure-reducing valve V5, and another road of the bottom liquid phases pipeline of precooling agent storage tank 18 the first pressure-reducing valve V3 is connected with the shell side Q of one-level forecooler 1.
In the system of above-mentioned two-stage pre-cooling type azeotrope refrigeration liquefying natural gas, the top gas phase pipeline of precooling economizer 19 and the shell side Q of one-level forecooler 1 outlet gas phase pipeline are all connected with two sections of suction lines of pre-cold compressor 16.
In the system of above-mentioned two-stage pre-cooling type azeotrope refrigeration liquefying natural gas, one-level forecooler 1 and secondary forecooler 5 are shell-and-tube two-tube-pass heat exchanger, shell-and-plate two-tube-pass heat exchanger or plate type heat exchanger.
In the system of above-mentioned two-stage pre-cooling type azeotrope refrigeration liquefying natural gas, precooling preshrinking machine 16 and azeotrope compressor 12 are screw, reciprocating or centrifugal compressor.
Technical scheme of the present invention is by before ice chest deep cooling operation, two-stage forecooler being set, and natural gas and azeotrope two-stage sent into ice chest after cooling again, thereby increased the thermograde of process of refrigerastion, makes energy efficiency approach traditional stepwise refrigeration process; This scheme arranges molecular sieve dehydration operation at two-stage precooling inter process simultaneously, reduces again the gas water content that enters molecular sieve dehydration operation, has ensured the flow process terseness of kind of refrigeration cycle technique, and energy efficiency is high, simple process, and reduced investment, workable.
Advantage of the present invention and positive role are:
1) the two-stage pre-cooling type adopting mixes the form of cold system refrigeration, and natural gas is cooling step by step, has increased the thermograde of process of refrigerastion when ensureing flow process terseness, has improved the energy efficiency of technique, has reduced energy consumption, thereby has produced obvious economic benefit.
2) the two-stage precooling inter process adopting arranges the form of dehydration procedure, reduce the gas water content that enters dehydration procedure, alleviate molecular sieve dehydration operation load, reduced regeneration frequency and regeneration gas consumption, further optimized the energy consumption index of whole technical process.
Brief description of the drawings
Fig. 1 is process flow diagram of the present invention.
In figure, code name implication is as follows:
1. one-level forecooler; 2. separator; 3. mole sieve drier; 4. demercuration bed; 5. secondary forecooler; 6. ice chest; 7. heavy hydrocarbon knockout drum; 8. the first blender; 9. the second blender; 10. the second knockout drum; 11. first knockout drums; 12. azeotrope compressors; 13. first coolers; 14. first surge tanks; 15. second coolers; 16. pre-cold compressor; 17. pre-cool condensers; 18. precooling agent storage tanks; 19. precooling economizers; 20. azeotrope knockout drums; V1. first throttle valve; V2. the second choke valve; V3. the first pressure-reducing valve; V4. the second pressure-reducing valve; V5. the 3rd pressure-reducing valve.
Detailed description of the invention
Below in conjunction with embodiment and accompanying drawing, the present invention is explained
Embodiment 1
The concrete technology flow process of the present embodiment refers to Fig. 1.
A kind of system of two-stage pre-cooling type azeotrope refrigeration liquefying natural gas, comprise: one-level forecooler 1, secondary forecooler 5, pre-cold compressor 16, azeotrope compressor 12, separator 2, mole sieve drier 3, demercuration bed 4, ice chest 6, heavy hydrocarbon knockout drum 7, the first knockout drum 11, the second knockout drum 10, the first blender 8, the second blender 9, the first cooler 13, the first surge tank 14, the second cooler 15, azeotrope knockout drum 20, pre-cool condenser 17, precooling agent storage tank 18, precooling economizer 19, first throttle valve V1, the second choke valve V2, the first pressure-reducing valve V3, the second pressure-reducing valve V4 and the 3rd pressure-reducing valve V5.Wherein, natural gas line connects the 6th runner F of the 5th runner E, heavy hydrocarbon knockout drum 7 and the cold 6 of the first tube side R, the cold 6 of the first tube side O, separator 2, mole sieve drier 3, demercuration bed 4, the second-stage separator 5 of one-level forecooler 1 successively, finally connects LNG pipeline, connect successively a section of azeotrope compressor 12 from the azeotrope pipeline of the 4th runner D of ice chest 6, the first cooler 13, the first surge tank 14, two sections of azeotrope compressor 12, the second cooler 15, the second tube side P of one-level forecooler 1, the second tube side S of secondary forecooler 5 and the entrance of azeotrope knockout drum 20, the bottom liquid phases outlet of azeotrope knockout drum 20 connects the first flow A of ice chest 6 successively, first throttle valve V1, the second separator 10, the 4th runner D of the second blender 9 and ice chest 6, the top gaseous phase outlet of azeotrope knockout drum 20 connects the second runner B of ice chest 6 successively, the second choke valve V2, the first separator 11, the first blender 8, the 3rd runner C of ice chest 6 and the 4th runner D, connect successively one section of pre-cold compressor 16, two sections of pre-cold compressor 16, pre-cool condenser 17 and precooling agent storage tank 18 from the pipeline of secondary forecooler 5 shell side T, the bottom liquid phases pipeline one tunnel second pressure-reducing valve V4 of precooling agent storage tank 18 is connected with the entrance of precooling economizer 19, the bottom liquid phases pipeline of precooling economizer 19 is connected with the shell side T of secondary forecooler 5 through the 3rd pressure-reducing valve V5, and the top gas phase pipeline of precooling economizer 19 and the shell side Q of one-level forecooler 1 outlet gas phase pipeline are all connected with two sections of suction lines of pre-cold compressor 16, another road of the bottom liquid phases pipeline of precooling agent storage tank 18 the first pressure-reducing valve V3 is connected with the shell side Q of one-level forecooler 1.Above-mentioned one-level forecooler 1 and secondary forecooler 5 are shell-and-tube two-tube-pass heat exchanger, and precooling preshrinking machine 16 and azeotrope compressor 12 are screw compressor.
Select propane as precooling agent, liquid precooling agent I in precooling agent storage tank 18 is decompressed to 475kPa through the first pressure-reducing valve V3, and to obtain temperature be the precooling agent II of 0 DEG C, the shell side Q that is passed into one-level forecooler 1 evaporates to provide cold under constant temperature, afterwards the precooling agent steam I of generation is sent into two sections of entrances of pre-cold compressor 16; Liquid precooling agent I in precooling agent storage tank 18 is decompressed to 475kPa through the second pressure-reducing valve V4, and to obtain temperature be the precooling agent III of 0 DEG C, and precooling agent III is passed into and in precooling economizer 19, carries out gas-liquid separation, the precooling agent IV of the gas phase obtaining and the precooling agent V of liquid phase; Precooling agent V is decompressed to 102kPa through the 3rd pressure-reducing valve V5, and to obtain temperature be the precooling agent VI of-42 DEG C, and the shell side Q that precooling agent VI is passed into secondary forecooler 5 evaporates to provide cold under constant temperature, obtains precooling agent steam VII simultaneously; Precooling agent steam VII is sent into 16 1 sections of pre-cold compressor to be compressed to after 475kPa, it is mixed with precooling agent steam I and precooling agent IV together enters two sections of pre-cold compressor 16 and continues to be compressed to 1600kPa, obtain precooling agent VIII, it is cooled in pre-cool condenser 17 to 45 DEG C and enters next pre-cooling cycle in passing into precooling agent storage tank 18 after being condensed into liquid phase.
Azeotrope is made up of nitrogen, methane, ethene and propane, is that 2200kPa, temperature are that the second tube side P that the azeotrope I of 45 DEG C passes into one-level forecooler 1 is chilled to 5 DEG C in advance by pressure, obtains azeotrope II.The the second tube side S that azeotrope II is passed into secondary forecooler 5 is chilled to-40 DEG C in advance, obtains azeotrope III.Azeotrope III is passed into azeotrope knockout drum 20 and carry out gas-liquid separation, obtain the azeotrope IV of liquid phase in the bottom of azeotrope knockout drum 20, top obtains the azeotrope V of gas phase.Azeotrope IV is passed in the first flow A of ice chest 6 and be chilled in advance-110 DEG C, obtain azeotrope VI through first throttle valve V1 throttling afterwards, azeotrope VI is passed into the second knockout drum 10 and carry out gas-liquid separation, isolated gas-liquid two-phase logistics passes into the 4th runner D of ice chest 6 after the second blender 9 evenly mixes; Azeotrope V is passed in the second runner B of ice chest 6 and be chilled in advance-135 DEG C, obtain azeotrope VII through first throttle valve V1 throttling afterwards, azeotrope VII is passed into the first knockout drum 11 and carry out gas-liquid separation, isolated gas-liquid two-phase logistics passes into the 3rd runner C of ice chest 6 after the first blender 8 evenly mixes, re-heat is drawn ice chest to-42 DEG C and is obtained azeotrope VIII with continuing re-heat together with step 9 to the 4th runner D that passes into ice chest 6 after-120 DEG C, and its pressure is 120kPa; By azeotrope VIII pass into azeotrope compressor 12 through one section of compression, cooling, separate, two sections of compressions and cooling after to obtain pressure be that 2200kPa, temperature are that the azeotrope I of 45 DEG C enters next kind of refrigeration cycle;
Be that 4500kPa, temperature are that the first tube side O that the natural gas I of 45 DEG C passes into one-level forecooler 1 is chilled in advance 5 DEG C and obtains natural gas II by pressure after acid gas removal, natural gas II is passed in separator 2 and removes aqueous water, gas phase is carried out deep dehydration and demercuration by mole sieve drier 3 and demercuration bed 4 successively, obtains natural gas III.The first tube side R that natural gas III is passed into secondary forecooler 5 is chilled in advance-40 DEG C and obtains natural gas IV, and the 5th runner E that natural gas IV is passed into ice chest 6 is cooled to-65 DEG C and obtains azeotrope V.Azeotrope V is passed into heavy hydrocarbon knockout drum 7 and carry out gas-liquid separation, obtain the heavy hydrocarbon I of liquid phase in the bottom of heavy hydrocarbon knockout drum 7, top obtains the azeotrope VI of gas phase, and the 6th runner F that azeotrope VI is passed into ice chest 6 continues deep cooling and obtains LNG product to-140 DEG C.
Embodiment 2
The concrete technology flow process of the present embodiment refers to Fig. 1.
Device as shown in the figure, one-level forecooler 1 and secondary forecooler 5 are shell-and-plate two-tube-pass heat exchanger, and precooling preshrinking machine 16 is that screw compressor, azeotrope compressor 12 are centrifugal compressor.
Select liquefied ammonia as precooling agent, liquid precooling agent I in precooling agent storage tank 18 is decompressed to 610kPa through the first pressure-reducing valve V3, and to obtain temperature be the precooling agent II of 10 DEG C, the shell side Q that is passed into one-level forecooler 1 evaporates to provide cold under constant temperature, afterwards the precooling agent steam I of generation is sent into two sections of entrances of pre-cold compressor 16; Liquid precooling agent I in precooling agent storage tank 18 is decompressed to 610kPa through the second pressure-reducing valve V4, and to obtain temperature be the precooling agent III of 10 DEG C, and precooling agent III is passed into and in precooling economizer 19, carries out gas-liquid separation, the precooling agent IV of the gas phase obtaining and the precooling agent V of liquid phase; Precooling agent V is decompressed to 130kPa through the 3rd pressure-reducing valve V5, and to obtain temperature be the precooling agent VI of-28 DEG C, and the shell side Q that precooling agent VI is passed into secondary forecooler 5 evaporates to provide cold under constant temperature, obtains precooling agent steam VII simultaneously; Precooling agent steam VII is sent into 16 1 sections of pre-cold compressor to be compressed to after 610kPa, it is mixed with precooling agent steam I and precooling agent IV together enters two sections of pre-cold compressor 16 and continues to be compressed to 1800kPa, obtain precooling agent VIII, it is cooled in pre-cool condenser 17 to 45 DEG C and enters next pre-cooling cycle in passing into precooling agent storage tank 18 after being condensed into liquid phase.
Azeotrope is made up of nitrogen, methane, ethene, propane and butane, is that 4200kPa, temperature are that the second tube side P that the azeotrope I of 40 DEG C passes into one-level forecooler 1 is chilled to 15 DEG C in advance by pressure, obtains azeotrope II.The the second tube side S that azeotrope II is passed into secondary forecooler 5 is chilled to-23 DEG C in advance, obtains azeotrope III.Azeotrope III is passed into azeotrope knockout drum 20 and carry out gas-liquid separation, obtain the azeotrope IV of liquid phase in the bottom of azeotrope knockout drum 20, top obtains the azeotrope V of gas phase.Azeotrope IV is passed in the first flow A of ice chest 6 and be chilled in advance-80 DEG C, obtain azeotrope VI through first throttle valve V1 throttling afterwards, azeotrope VI is passed into the second knockout drum 10 and carry out gas-liquid separation, isolated gas-liquid two-phase logistics passes into the 4th runner D of ice chest 6 after the second blender 9 evenly mixes; Azeotrope V is passed in the second runner B of ice chest 6 and be chilled in advance-162 DEG C, obtain azeotrope VII through first throttle valve VI throttling afterwards, azeotrope VII is passed into the first knockout drum 11 and carry out gas-liquid separation, isolated gas-liquid two-phase logistics passes into the 3rd runner C of ice chest 6 after the first blender 8 evenly mixes, re-heat is drawn ice chest to-25 DEG C and is obtained azeotrope VIII with continuing re-heat together with step 9 to the 4th runner D that passes into ice chest 6 after-90 DEG C, and its pressure is 350kPa; By azeotrope VIII pass into azeotrope compressor 12 through one section of compression, cooling, separate, two sections of compressions and cooling after to obtain pressure be that 4200kPa, temperature are that the azeotrope I of 40 DEG C enters next kind of refrigeration cycle;
Be that 5500kPa, temperature are that the first tube side O that the natural gas I of 40 DEG C passes into one-level forecooler 1 is chilled in advance 15 DEG C and obtains natural gas II by pressure after acid gas removal, natural gas II is passed in separator 2 and removes aqueous water, gas phase is carried out deep dehydration and demercuration by mole sieve drier 3 and demercuration bed 4 successively, obtains natural gas III.The first tube side R that natural gas III is passed into secondary forecooler 5 is chilled in advance-23 DEG C and obtains natural gas IV, and the 5th runner E that natural gas IV is passed into ice chest 6 is cooled to-45 DEG C and obtains azeotrope V.Azeotrope V is passed into heavy hydrocarbon knockout drum 7 and carry out gas-liquid separation, obtain the heavy hydrocarbon I of liquid phase in the bottom of heavy hydrocarbon knockout drum 7, top obtains the azeotrope VI of gas phase, and the 6th runner F that azeotrope VI is passed into ice chest 6 continues deep cooling and obtains LNG product to-162 DEG C.
Embodiment 3
The concrete technology flow process of the present embodiment refers to Fig. 1.
Device as shown in the figure, one-level forecooler 1 is that plate type heat exchanger, secondary forecooler 5 are shell-and-tube heat exchanger, precooling preshrinking machine 16 is that reciprocating compressor, azeotrope compressor 12 are centrifugal compressor.
Select R410A as precooling agent, liquid precooling agent I in precooling agent storage tank 18 is decompressed to 1135kPa through the first pressure-reducing valve V3, and to obtain temperature be the precooling agent II of 28 DEG C, the shell side Q that is passed into one-level forecooler 1 evaporates to provide cold under constant temperature, afterwards the precooling agent steam I of generation is sent into two sections of entrances of pre-cold compressor 16; Liquid precooling agent I in precooling agent storage tank 18 is decompressed to 1135kPa through the second pressure-reducing valve V4, and to obtain temperature be the precooling agent III of 28 DEG C, and precooling agent III is passed into and in precooling economizer 19, carries out gas-liquid separation, the precooling agent IV of the gas phase obtaining and the precooling agent V of liquid phase; Precooling agent V is decompressed to 468kPa through the 3rd pressure-reducing valve V5, and to obtain temperature be the precooling agent VI of-2 DEG C, and the shell side Q that precooling agent VI is passed into secondary forecooler 5 evaporates to provide cold under constant temperature, obtains precooling agent steam VII simultaneously; Precooling agent steam VII is sent into 16 1 sections of pre-cold compressor to be compressed to after 1135kPa, it is mixed with precooling agent steam I and precooling agent IV together enters two sections of pre-cold compressor 16 and continues to be compressed to 1550kPa, obtain precooling agent VIII, it is cooled in pre-cool condenser 17 to 40 DEG C and enters next pre-cooling cycle in passing into precooling agent storage tank 18 after being condensed into liquid phase.
Azeotrope is made up of nitrogen, methane, ethene and propane, is that 3700kPa, temperature are that the second tube side P that the azeotrope I of 40 DEG C passes into one-level forecooler 1 is chilled to 30 DEG C in advance by pressure, obtains azeotrope II.The the second tube side S that azeotrope II is passed into secondary forecooler 5 is chilled to 0 DEG C in advance, obtains azeotrope III.Azeotrope III is passed into azeotrope knockout drum 20 and carry out gas-liquid separation, obtain the azeotrope IV of liquid phase in the bottom of azeotrope knockout drum 20, top obtains the azeotrope V of gas phase.Azeotrope IV is passed in the first flow A of ice chest 6 and be chilled in advance-45 DEG C, obtain azeotrope VI through first throttle valve VI throttling afterwards, azeotrope VI is passed into the second knockout drum 10 and carry out gas-liquid separation, isolated gas-liquid two-phase logistics passes into the 4th runner D of ice chest 6 after the second blender 9 evenly mixes; Azeotrope V is passed in the second runner B of ice chest 6 and be chilled in advance-145 DEG C, obtain azeotrope VII through first throttle valve V1 throttling afterwards, azeotrope VII is passed into the first knockout drum 11 and carry out gas-liquid separation, isolated gas-liquid two-phase logistics passes into the 3rd runner C of ice chest 6 after the first blender 8 evenly mixes, re-heat is drawn ice chest to-2 DEG C and is obtained azeotrope VIII with continuing re-heat together with step 9 to the 4th runner D that passes into ice chest 6 after-45 DEG C, and its pressure is 550kPa; By azeotrope VIII pass into azeotrope compressor 12 through one section of compression, cooling, separate, two sections of compressions and cooling after to obtain pressure be that 3700kPa, temperature are that the azeotrope I of 40 DEG C enters next kind of refrigeration cycle;
Be that 4500kPa, temperature are that the first tube side O that the natural gas I of 45 DEG C passes into one-level forecooler 1 is chilled in advance 30 DEG C and obtains natural gas II by pressure after acid gas removal, natural gas II is passed in separator 2 and removes aqueous water, gas phase is carried out deep dehydration and demercuration by mole sieve drier 3 and demercuration bed 4 successively, obtains natural gas III.The first tube side R that natural gas III is passed into secondary forecooler 5 is chilled in advance 0 DEG C and obtains natural gas IV, and the 5th runner E that natural gas IV is passed into ice chest 6 is cooled to-55 DEG C and obtains azeotrope V.Azeotrope V is passed into heavy hydrocarbon knockout drum 7 and carry out gas-liquid separation, obtain the heavy hydrocarbon I of liquid phase in the bottom of heavy hydrocarbon knockout drum 7, top obtains the azeotrope VI of gas phase, and the 6th runner F that azeotrope VI is passed into ice chest 6 continues deep cooling and obtains LNG product to-146 DEG C.
Claims (7)
1. a method for two-stage pre-cooling type azeotrope refrigeration liquefying natural gas, is characterized in that, the method comprises the following steps:
1) the liquid precooling agent I in precooling agent storage tank (18) being obtained to temperature through the first pressure-reducing valve (V3) decompression is the precooling agent II of 0～28 DEG C, the shell side (Q) that is passed into one-level forecooler (1) evaporates to provide cold under constant temperature, obtains precooling agent steam I simultaneously;
2) to obtain temperature through the second pressure-reducing valve (V4) decompression be the precooling agent III of 0～28 DEG C to the liquid precooling agent I in precooling agent storage tank (18), precooling agent III is passed in precooling economizer (19) and carries out gas-liquid separation, the precooling agent IV of the gas phase obtaining and the precooling agent V of liquid phase;
3) to obtain temperature through the 3rd pressure-reducing valve (V5) decompression be the precooling agent VI of-42～-2 DEG C to precooling agent V, the shell side (Q) that precooling agent VI is passed into secondary forecooler (5) evaporates to provide cold under constant temperature, obtains precooling agent steam VII simultaneously;
4) precooling agent steam VII is sent into after (16) one sections of compressions of pre-cold compressor, make itself and step 1) the precooling agent steam I and the step 2 that obtain) the precooling agent IV that obtains mixes and together enters two sections of pre-cold compressor (16) and continue compression, obtain precooling agent VIII, enter next pre-cooling cycle in passing into precooling agent storage tank (18) after it is condensed into liquid phase in pre-cool condenser (17);
5) the first tube side (O) that the natural gas I after acid gas removal is passed into one-level forecooler (1) is chilled in advance 5～30 DEG C and obtains natural gas II, the second tube side (P) that azeotrope I after pressurization is passed into one-level forecooler (1) is chilled to 5～30 DEG C in advance, obtains azeotrope II;
6) natural gas II is passed in separator (2) and removes aqueous water, gas phase is carried out deep dehydration and demercuration by mole sieve drier (3) and demercuration bed (4) successively, obtains natural gas III;
7) the first tube side (R) that natural gas III is passed into secondary forecooler (5) is chilled in advance-40～0 DEG C and obtains natural gas IV, the second tube side (S) that azeotrope II is passed into secondary forecooler (5) is chilled to-40～0 DEG C in advance, obtains azeotrope III;
8) azeotrope III is passed into azeotrope knockout drum (20) and carry out gas-liquid separation, obtain the azeotrope IV of liquid phase in the bottom of azeotrope knockout drum (20), top obtains the azeotrope V of gas phase;
9) azeotrope IV is passed in the first flow (A) of ice chest (6) and be chilled in advance-110～-45 DEG C, obtain azeotrope VI through first throttle valve (V1) throttling afterwards, azeotrope VI is passed into the second knockout drum (10) and carry out gas-liquid separation, isolated gas-liquid two-phase logistics passes into the 4th runner (D) of ice chest (6) after the second blender (9) evenly mixes;
10) azeotrope V is passed in second runner (B) of ice chest (6) and be chilled in advance-162～-135 DEG C, obtain azeotrope VII through first throttle valve (V1) throttling afterwards, azeotrope VII is passed into the first knockout drum (11) and carry out gas-liquid separation, isolated gas-liquid two-phase logistics passes into the 3rd runner (C) of ice chest (6) after the first blender (8) evenly mixes, re-heat is to the 4th runner (D) and step 9 that passes into ice chest (6) after-120～-45 DEG C) together with continue re-heat extremely-42～-2 DEG C draw ice chest and obtain azeotrope VIII,
11) azeotrope VIII is passed into azeotrope compressor (12) through one section of compression, cooling, separate, two sections of compressions and obtain azeotrope I after cooling and enter next kind of refrigeration cycle;
12) by step 7) obtain the 5th runner (E) that natural gas IV passes into ice chest (6) and be cooled to-45～-65 DEG C and obtain azeotrope V, azeotrope V is passed into heavy hydrocarbon knockout drum (7) and carry out gas-liquid separation, obtain the heavy hydrocarbon I of liquid phase in the bottom of heavy hydrocarbon knockout drum (7), top obtains the azeotrope VI of gas phase, and the 6th runner (F) that azeotrope VI is passed into ice chest (6) continues deep cooling and obtains LNG product to-140～-162 DEG C.
2. method according to claim 1, is characterized in that step 10) in obtain azeotrope VIII pressure be 120～550kPa.
3. method according to claim 1, is characterized in that step 11) in obtain azeotrope I pressure be 2200～4200kPa.
4. a system for two-stage pre-cooling type azeotrope refrigeration liquefying natural gas, is characterized in that, this system comprises: one-level forecooler (1), secondary forecooler (5), pre-cold compressor (16), azeotrope compressor (12), separator (2), mole sieve drier (3), demercuration bed (4), ice chest (6), heavy hydrocarbon knockout drum (7), the first knockout drum (11), the second knockout drum (10), the first blender (8), the second blender (9), the first cooler (13), the first surge tank (14), the second cooler (15), azeotrope knockout drum (20), pre-cool condenser (17), precooling agent storage tank (18), precooling economizer (19), first throttle valve (V1), the second choke valve (V2), the first pressure-reducing valve (V3), the second pressure-reducing valve (V4) and the 3rd pressure-reducing valve (V5), wherein, natural gas line connects first tube side (O) of one-level forecooler (1) successively, separator (2), mole sieve drier (3), demercuration bed (4), first tube side (R) of second-stage separator (5), the 5th runner (E) of cold (6), the 6th runner (F) of heavy hydrocarbon knockout drum (7) and cold (6), finally connects LNG pipeline, connect successively a section of azeotrope compressor (12) from the azeotrope pipeline of the 4th runner (D) of ice chest (6), the first cooler (13), the first surge tank (14), two sections of azeotrope compressor (12), the second cooler (15), second tube side (P) of one-level forecooler (1), second tube side (S) of secondary forecooler (5) and the entrance of azeotrope knockout drum (20), the bottom liquid phases outlet of azeotrope knockout drum (20) connects the first flow (A) of ice chest (6) successively, first throttle valve (V1), the second separator (10), the 4th runner (D) of the second blender (9) and ice chest (6), the top gaseous phase outlet of azeotrope knockout drum (20) connects second runner (B) of ice chest (6) successively, the second choke valve (V2), the first separator (11), the first blender (8), the 3rd runner (C) of ice chest (6) and the 4th runner (D), connect successively a section of pre-cold compressor (16) from the pipeline of secondary forecooler (5) shell side (T), two sections of cold compressor (16) in advance, pre-cool condenser (17) and precooling agent storage tank (18), bottom liquid phases pipeline one tunnel second pressure-reducing valve (V4) of precooling agent storage tank (18) is connected with the entrance of precooling economizer (19), the bottom liquid phases pipeline of precooling economizer (19) is connected with the shell side (T) of secondary forecooler (5) through the 3rd pressure-reducing valve (V5), another road first pressure-reducing valve (V3) of the bottom liquid phases pipeline of precooling agent storage tank (18) is connected with the shell side (Q) of one-level forecooler (1).
5. the system of a kind of two-stage pre-cooling type azeotrope refrigeration liquefying natural gas according to claim 4, it is characterized in that, the top gas phase pipeline of precooling economizer (19) and the shell side (Q) of one-level forecooler (1) outlet gas phase pipeline are all connected with two sections of suction lines of pre-cold compressor (16).
6. the system of a kind of two-stage pre-cooling type azeotrope refrigeration liquefying natural gas according to claim 4, it is characterized in that, one-level forecooler (1) and secondary forecooler (5) are shell-and-tube two-tube-pass heat exchanger, shell-and-plate two-tube-pass heat exchanger or plate type heat exchanger.
7. the system of a kind of two-stage pre-cooling type azeotrope refrigeration liquefying natural gas according to claim 4, it is characterized in that, precooling preshrinking machine (16) and azeotrope compressor (12) are screw, reciprocating or centrifugal compressor.
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| CN101644527A (en) * | 2009-08-26 | 2010-02-10 | 四川空分设备(集团)有限责任公司 | Refrigeration system and liquefaction system for liquefaction process of natural gas |
| CN102954668A (en) * | 2011-08-19 | 2013-03-06 | 李志远 | Method for producing liquefied natural gas by multi-component refrigerant double-stage compression |
| CN102748919A (en) * | 2012-04-26 | 2012-10-24 | 中国石油集团工程设计有限责任公司 | Single-cycle mixed-refrigerant four-stage throttling refrigeration system and method |
| CN203949440U (en) * | 2014-07-16 | 2014-11-19 | 北京安珂罗工程技术有限公司 | A kind of system of two-stage pre-cooling type azeotrope refrigeration liquefying natural gas |
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| CN106679332A (en) * | 2017-02-17 | 2017-05-17 | 查都（上海）科技有限公司 | System for improving LNG yield of methane cryogenic separation |
| CN108775770A (en) * | 2018-05-30 | 2018-11-09 | 科霖恩新能源科技（江苏）有限公司 | A kind of brazing plate type heat exchanger natural gas liquefaction system using mixed-refrigerant cycle |
| RU2753206C1 (en) * | 2021-01-26 | 2021-08-12 | Юрий Васильевич Белоусов | Method for autonomous production of liquefied natural gas and installation for its implementation |
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