CN202209845U

CN202209845U - Pre-cooling type mixed refrigerant cryogenic gas liquefaction system

Info

Publication number: CN202209845U
Application number: CN201120238076XU
Authority: CN
Inventors: 郭开华; 鹿来运; 张镨; 许功铎
Original assignee: National Sun Yat Sen University
Current assignee: Sun Yat Sen University; National Sun Yat Sen University
Priority date: 2011-07-07
Filing date: 2011-07-07
Publication date: 2012-05-02
Anticipated expiration: 2021-07-07

Abstract

A pre-cooling type mixed refrigerant cryogenic gas liquefaction system comprises a compressor module (CU), a pre-cooling module (PU), a recooling segregation module (SU) and a liquefaction separation module (LU). The connection mode of the pre-cooling type mixed refrigerant cryogenic gas liquefaction system is that a high pressure outlet of the compressor module (CU) is connected with a high pressure inlet of the pre-cooling module (PU), a high pressure outlet of the pre-cooling module (PU) is connected with a high pressure inlet of the recooling segregation module (SU), a high pressure outlet of the recooling segregation module (SU) is connected with a high pressure inlet of the liquefaction separation module (LU), a low pressure inlet of the compressor module (CU) is connected with a connector of a three-way pipe, the one of the other two connectors of the three-way pipe is connected with a low pressure outlet of the recooling segregation module (SU), and the other connector of the three-way pipe is connected with a low pressure outlet of the liquefaction separation module (LU). The pre-cooling type mixed refrigerant cryogenic gas liquefaction system utilizes a conventional water-cooled condensing unit as a system precooling device, thereby being simplified in system flow, modularized and skid-mounted in whole machine, low in energy consumption, little in investment and reliable in operation.

Description

A kind of pre-cooling type mixed working fluid cryogenic gas liquefaction system

Technical field

The utility model relates to the gas liquefaction system in the Refrigeration & Cryogenic Technique field, especially relates to a kind of pre-cooling type mixed working fluid cryogenic gas liquefaction system.

Background technology

LNG (Liquefied Natural Gas), promptly liquefied natural gas is that natural gas in gaseous state under the normal pressure after treatment is cooled to-162 ℃, makes it to condense into liquid.The volume of LNG is about 1/625 of its gaseous state volume, has practiced thrift storage and transportation space and cost greatly, and has characteristics such as calorific value is big, performance height, so LNG is a kind of cleaning, the energy efficiently.The energy resource structure of China is main with coal, and oil, natural gas only account for very little ratio.The accounting of natural gas is merely 4% in the China energy consumption structure at present; And in the world energy sources consumption structure; Natural gas consumption then accounts for 24.1% of energy resource consumption total amount, is about the sixth of world average, and this shows that from a side China's natural gas industry also has very big extending space.China " 12 " planning outline proposes the target of " descending 40% to 45% than 2005 to the CO2 emission of the year two thousand twenty per GDP ".Realize this target for energy-saving and emission-reduction, must advocate the mode of production of saving, cleaning, circulation, green, low-carbon (LC), greatly develop recycling economy simultaneously, promote energy-conserving and emission-cutting technology innovation and technical application.Natural gas can effectively solve energy supply safety and the dual problem of ecological environmental protection, has both helped promoting energy-saving and emission-reduction, in realizing economical and social sustainable development, plays a significant role again, and therefore, China LNG industry will be stepped into fast-developing track.

The liquefaction process of natural gas can be divided into three kinds of modes with the refrigeration modes branch: 1. cascade type liquefaction flow process; 2. mix refrigerant liquefaction flow path; 3. with the liquefaction flow path of decompressor.Practical application in industry shows, precooling zone is set in liquefaction flow path natural gas is carried out thermodynamic efficiency and the production scale that precooling can improve system greatly.Most typical is the propane precooling mix refrigerant liquefaction flow path (C3/MR) of APCI (US Air gas liquefaction company) in 1973 exploitation; Adopt the propane refrigeration circulation that mix refrigerant and natural gas are carried out precooling; Flow process not only efficiently but also simple, the employing of the base load type natural gas liquefaction device 80% or more C3/MR liquefaction flow path in the world at present.Some improved pre-cooling type natural gas liquefaction flow processs have also been developed in recent years in the industry; Adopt the propane refrigeration circulation like the Phillips Optimized Cascade Process of U.S. Cophi Co., Ltd precooling level; Its Driven Compressor adopts the variable-ratio gas turbine, thereby has more high flexibility and easy to operate; The Germany Linde Mixed Fluid Cascade Process of company (MFCP) precooling zone adopts azeotrope; System's thermodynamic efficiency and wall scroll production line scale have all had further raising, and on Norway Snohvit LNG project (4,300,000 tons/year) project, obtain application; The Holland Dual Mixed Refrigerant Process of Shell Co. Ltd (DMR) precooling zone adopts ethane, propane and a small amount of methane, butane mixture as cold-producing medium, and the natural gas precooling temperature reaches-40 ℃, and its process equipment is less, and flexibility is bigger; The France Axens Axens Liquefin of company ^TMThe Process precooling zone substitutes propane with mix refrigerant, it is said that the expense of this explained hereafter LNG is per ton to reduce by 25%, has the equipment series of the Liquefin technology of the accurate combustion gas turbine of 2 station symbols, and can produce 6,000,000 tons liquefied natural gas every year.

Can find out from the Evolution Development of natural gas liquefaction technology, the efficient that the precooling level can improve system greatly is set in liquefaction flow path, and the mix refrigerant circulation is used for liquefaction flow path precooling level, the precooling effect is better than pure matter circulation.But the precooling circulation constitution equipment that is adopted in the above-mentioned natural gas liquefaction flow process is more, and structure is complicated, and control is difficulty, and particularly precooling compressor manufacturing cost is higher, does not meet the growth requirement of small-sized cryogenic gas liquefying plant.In view of being provided with of precooling level in the flow process has very big influence to system complexity and cost of investment, some small-sized cryogenic gas liquefaction flow paths simply are not provided with the precooling level, like U.S. Patent No.3; 768,273 (D.J. Missimer, 1973), U.S.Patent No.5; 337,572 (R.C.Longsworth, 1994); Though said system can reach certain refrigeration warm area, its thermodynamic efficiency is unsatisfactory.In the last few years, utilized the refrigeration system low pressure working fluid to backflow and realized that precooling Research on effect thinking also was suggested, like U.S. Patent No.5; 724,832 (W. A. Little, 1995), C.N. Patent ZL99203770.0 (Chen Guangming; 2000), European Patent No.1,167,903A1 (R.Arman; 2002), C.N. Patent 101625191A (Wu Jianfeng; 2010), because a plurality of heat exchangers of addition in the system flow, the stability of a system and cost of investment all receive certain influence.Therefore, take all factors into consideration cost of investment, than factors such as power consumption, service requirement and flexibilities, exploitation has that energy consumption is low, small investment, equipment cryogenic gas liquefaction flow path reliable, that be easy to the maintenance technology characteristics have important commercial and be worth and practical significance.

The utility model content

The purpose of the utility model is; A kind of pre-cooling type mixed working fluid cryogenic gas liquefaction system is provided; The precooling level adopts conventional water-cooled condensation unit; Other capital equipments adopt conventional freezers spare, have both guaranteed that liquefaction flow path has higher liquefied fraction and lower power consumption, greatly reduced the cost of investment of system again; System flow is simplified, and is simple and compact for structure, is easy to adopt flexibly in various occasions.

To achieve these goals; The technical scheme of the utility model is: a kind of pre-cooling type mixed working fluid cryogenic gas liquefaction system; Comprise compressor module, precooling module, return cold fractional condensation module and liquefaction separation module; Its connected mode is: the high-pressure outlet of compressor module connects the high-pressure inlet of precooling module, and the high-pressure outlet of precooling module connects back the high-pressure inlet of cold fractional condensation module, and the high-pressure outlet that returns cold fractional condensation module connects the high-pressure inlet of liquefaction separation module; The low pressure inlet of compressor module is connected with an interface of a three-way pipe, low tension outlet that connects back cold fractional condensation module of two other interface of three-way pipe, and another interface connects the low tension outlet of liquefaction separation module.Compressor module is the power source of liquefaction system; The precooling module is carried out precooling to system's mixed working fluid; Return cold fractional condensation module and when system's mixed working fluid is carried out vapor-liquid separation, also reclaim the cold that utilizes the fractional condensation liquid phase refrigerant to expand and lower the temperature and produce; The liquefaction separation module is main refrigeration unit, and compressed air is carried out cooling liquid.

As a kind of preferred version; Said compressor module comprises gas-liquid separator, main compressor, condenser and oil eliminator; Its connected mode is: the inlet of gas-liquid separator serves as the low pressure inlet of compressor module; The outlet of gas-liquid separator connects the low-pressure inlet of main compressor, and the high-pressure outlet of main compressor connects the import of condenser, and the outlet of condenser connects the import of oil eliminator; The lubricating oil outlet of oil eliminator connects the oil return opening of main compressor, and the cold-producing medium high-pressure outlet of oil eliminator constitutes the high-pressure outlet of compressor module;

Said precooling module comprises precooling compressor, preceding cooler, first throttle element and plate type heat exchanger; Its connected mode is: the import of cooler before the high-pressure outlet of precooling compressor connects; The outlet of preceding cooler connects the first throttle element; The outlet of first throttle element connects the low pressure inlet of plate type heat exchanger; The low tension outlet of plate type heat exchanger connects the low-pressure inlet of precooling compressor, and the cold-producing medium high-pressure inlet of plate type heat exchanger connects the high-pressure outlet of compressor module, and the cold-producing medium high-pressure outlet of plate type heat exchanger constitutes the high-pressure outlet of precooling module.

Said time cold fractional condensation module comprises the vapour liquid separator and second restricting element; Its connected mode is: the cold-producing medium high pressure entry of vapour liquid separator is back the high-pressure inlet of cold fractional condensation module; The highly pressurised liquid outlet of vapour liquid separator connects second restricting element; The outlet of second restricting element connects the low-pressure fluid inlet of vapour liquid separator; The low tension outlet of cold fractional condensation module is returned in the low-pressure fluid export mixes of vapour liquid separator, and the high-pressure outlet of cold fractional condensation module is returned in the gases at high pressure export mixes of vapour liquid separator.

Said liquefaction separation module comprises multiple flow heat exchanger, the 3rd restricting element, choke valve and liquid nitrogen container; Its connected mode is: the cold-producing medium high-pressure inlet of multiple flow heat exchanger is the high-pressure inlet of liquefaction separation module; The cold-producing medium high-pressure outlet of multiple flow heat exchanger connects the 3rd restricting element; The outlet of the 3rd restricting element connects the cold-producing medium low pressure inlet of multiple flow heat exchanger, and the cold-producing medium low tension outlet of multiple flow heat exchanger is the low tension outlet of liquefaction separation module, and the air inlet of multiple flow heat exchanger is connected with system external world's compressed air; The liquid air outlet of multiple flow heat exchanger connects choke valve, and the outlet of choke valve connects liquid nitrogen container.

Preferably, main compressor adopts the single-stage oil lubricating compressor in the said compressor module, and pressure ratio is 1.0～10.0, and pressure at expulsion is less than 50.0bar.

Preferably, the refrigeration working medium of said main compressor adopts multicomponent mixture work medium; Said multicomponent mixture work medium comprise the alkyl hydrocarbons of inert gas, a 1-5 carbon atom, not chloride atom fluoride wherein one or more; Said inert gas is neon, argon gas, nitrogen, and its molar concentration is 0～30%; The molar concentration of the alkyl hydrocarbons of 1-5 carbon atom is 5%～50%; The molar concentration of the fluoride of chloride atom is not 5%～30%.

Preferably, said precooling module adopts conventional water-cooled condensation unit as precooling equipment; Said precooling compressor is the single-stage oil lubricating compressor, and pressure ratio is 1.0～6.0, and pressure at expulsion is less than 30.0bar.

Preferably, the refrigeration working medium of said precooling equipment adopt following compound wherein one or more: hydrocarbon HCs, chloro-fluoro-carbon kind CFCs, hydrochlorofluorocarsolvent class HCFCs, hydrogen fluorohydrocarbon class HFCs, perfluoro alkanes FCs, organic compound R1120, R1130, inorganic compound R704, R717, R728, R729, R744, R764;

Said hydrocarbon HCs is R50, R170, R270, R290, R600, R600a, R601, R601a, R601b, R1150, R1270; Said chloro-fluoro-carbon kind CFCs is R11, R12, R13, R111, R112, R113, R114, R115, R211, R212, R213, R214, R215, R216, R217; Said hydrochlorofluorocarsolvent class HCFCs is R21, R22, R31, R121, R122, R123, R124, R132, R133, R141, R141b, R142, R142b, R151, R221, R222, R223, R224, R225, R225ca, R225cb, R226, R231, R232, R233, R234, R235, R241, R242, R243, R244, R251, R252, R253, R261, R271; Said hydrogen fluorohydrocarbon class HFCs is R23, R32, R41, R125, R134, R134a, R143, R143a, R152a, R161, R227, R227ea, R236ea, R236fa, R245ca, R245cb, R245eb, R245fa, R254cb; Said perfluoro alkanes FCs is R14, R116, R218, R1216.

Preferably, said time cold fractional condensation module also adopts vapour liquid separator to recycle the cold that liquid phase separation working medium expands and lowers the temperature and produce in it.

Compared with prior art, the utlity model has following advantage:

(1) the utility model system architecture is simple, and the complete machine modularized design is easy to skidization, only needs when install the job site to connect reserving pipeline, greatly reduces the cost of investment and the maintenance cost of system;

(2) system's precooling level adopts conventional water-cooled condensation unit, and other capital equipments adopt conventional freezers spare, have both guaranteed that liquefaction flow path has higher liquefied fraction and lower power consumption, greatly reduced the cost of investment of system again; System flow is simplified, and equipment is few, and control is particularly suitable for small-sized gas liquefaction device demand occasion easily;

(3) vapour liquid separator of employing independent design; Recycle the further purifying mixed working fluid of cold that liquid phase separation working medium expands and lowers the temperature and produce in it; Guarantee that the mixed working fluid that in the whole system circulation, gets into the multiple flow heat exchanger contains lubricated wet goods impurity hardly; Improve the stability and the reliability of system greatly, also improved system effectiveness and energy utilization rate simultaneously.

Description of drawings

Fig. 1 is the structural representation block diagram of the utility model;

Fig. 2 is the structural representation of compressor module;

Fig. 3 is the structural representation of precooling module;

Fig. 4 is back the structural representation of cold fractional condensation module;

The liquefy structural representation of separation module of Fig. 5;

Fig. 6 is the structural representation of the utility model embodiment.

Wherein: 1, gas-liquid separator; 2, main compressor; 3, condenser; 4, oil eliminator; 5, precooling compressor; 6, preceding cooler; 7, first throttle element; 8, plate type heat exchanger; 9, vapour liquid separator; 10, second restricting element; 11, multiple flow heat exchanger; 12, the 3rd restricting element; 13, choke valve; 14, liquid nitrogen container; A1: main compressor oil return opening; A2: oil eliminator lubricating oil outlet; B1: plate type heat exchanger cold-producing medium high pressure entry; B2: plate type heat exchanger cold-producing medium high-pressure outlet; C1: vapour liquid separator cold-producing medium high pressure entry; C2: vapour liquid separator highly pressurised liquid outlet; C3: vapour liquid separator low-pressure fluid inlet; C4: vapour liquid separator low-pressure fluid outlet; C5: vapour liquid separator gases at high pressure outlet; D1: multiple flow heat exchanger cold-producing medium high pressure entry; D2: multiple flow heat exchanger cold-producing medium high-pressure outlet; D3: multiple flow heat exchanger cold-producing medium low-pressure inlet; D4: multiple flow heat exchanger cold-producing medium low tension outlet; D5: multiple flow heat exchanger air inlet; D6: multiple flow heat exchanger liquid air outlet; CU: compressor module; PU: precooling module; SU: return cold fractional condensation module; LU: liquefaction separation module.

The specific embodiment

Below in conjunction with accompanying drawing the utility model is described in further detail:

The utility model adopts a throttling refrigeration circulation of single-stage oil lubricating compressor driving mixed working fluid to reach liquid nitrogen temperature, and system's pre-cooler adopts conventional water-cooled condensation unit, and system flow is simplified; Complete machine modularization, skidization; Energy consumption is low, and small investment is reliable.

Shown in Fig. 1-6; Compressor module CU comprises gas-liquid separator 1, main compressor 2, condenser 3, oil eliminator 4, and wherein main compressor 2 adopts the single-stage oil lubricating compressor, and pressure ratio is 1.0～10.0; Pressure at expulsion is less than 50.0bar; Gas-liquid separator 1, condenser 3, oil eliminator 4 are conventional refrigeration part, and its connected mode is: the inlet of gas-liquid separator 1 constitutes the low pressure inlet of compressor module CU, and the outlet of gas-liquid separator 1 connects the low-pressure inlet of main compressor 2; The high-pressure outlet of main compressor 2 connects the inlet tube of condenser 3; The outlet of condenser 3 connects the inlet tube of oil eliminator 4, and the lubricating oil outlet A2 of oil eliminator 4 connects the oil return opening A1 of main compressor 2, and the cold-producing medium high-pressure outlet of oil eliminator 4 constitutes the high-pressure outlet of compressor module CU.Precooling module PU is made up of precooling compressor 5, preceding cooler 6, first throttle element 7, plate type heat exchanger 8; Wherein precooling compressor 5 is the single-stage oil lubricating compressor; Pressure ratio is 1.0～6.0, and pressure at expulsion is less than 30.0bar, and preceding cooler 6 is the shell-tube type counterflow heat exchanger; Plate type heat exchanger 8 is conventional brazing plate type heat exchanger; Its connected mode is: the inlet tube of cooler 6 before the high-pressure outlet of precooling compressor 5 connects, and the outlet of preceding cooler 6 connects first throttle element 7, and the outlet of first throttle element 7 connects the low pressure inlet of plate type heat exchanger 8; The low tension outlet of plate type heat exchanger 8 connects the low-pressure inlet of precooling compressor 5; The high-pressure outlet of previous stage module connects the cold-producing medium high-pressure inlet B1 of plate type heat exchanger 8, and the cold-producing medium high-pressure outlet B2 of plate type heat exchanger 8 constitutes the cold-producing medium high-pressure outlet of precooling module PU, links to each other with the cold-producing medium high pressure entry of next stage module.Return cold fractional condensation module SU and comprise vapour liquid separator 9, second restricting element 10; Its connected mode is: the cold-producing medium high-pressure outlet of previous stage module connects the cold-producing medium high pressure entry C1 of vapour liquid separator 9; The highly pressurised liquid outlet C2 of vapour liquid separator 9 bottoms connects second restricting element 10; The outlet of second restricting element 10 connects the low-pressure fluid inlet C3 of vapour liquid separator 9, and the low-pressure fluid outlet C4 of vapour liquid separator 9 is back the low tension outlet of cold fractional condensation module SU, links to each other with the low-pressure inlet of previous stage module; The gases at high pressure outlet C5 of vapour liquid separator 9 is back the high-pressure outlet of cold fractional condensation module SU, links to each other with the high pressure entry of next stage module.Liquefaction separation module LU comprises multiple flow heat exchanger 11, the 3rd restricting element 12, choke valve 13, liquid nitrogen container 14; Its connected mode is: the cold-producing medium high-pressure outlet of previous stage module connects the cold-producing medium high-pressure inlet D1 of multiple flow heat exchanger 11; The cold-producing medium high-pressure outlet D2 of multiple flow heat exchanger 11 connects the 3rd restricting element 12; The outlet of the 3rd restricting element 12 connects the cold-producing medium low pressure inlet D3 of multiple flow heat exchanger 11; The cold-producing medium low tension outlet D4 of multiple flow heat exchanger 11 links to each other with the low-pressure inlet of previous stage module for the low tension outlet of liquefaction separation module LU, and the extraneous compressed air of system is introduced from the air inlet D5 of multiple flow heat exchanger 11; The liquid air outlet D6 of multiple flow heat exchanger 11 connects choke valve 13, and the outlet of choke valve 13 connects liquid nitrogen container 14.

The refrigeration working medium of main compressor 2 adopts multicomponent mixture work medium in the native system; Said multicomponent mixture work medium comprise the alkyl hydrocarbons of inert gas, a 1-5 carbon atom, not chloride atom fluoride wherein one or more; Said inert gas is neon, argon gas, nitrogen, and its molar concentration is 0～30%; The molar concentration of the alkyl hydrocarbons of 1-5 carbon atom is 5%～50%; The molar concentration of the fluoride of chloride atom is not 5%～30%.

The refrigeration working medium of said precooling equipment adopt following compound wherein one or more: hydrocarbon HCs, chloro-fluoro-carbon kind CFCs, hydrochlorofluorocarsolvent class HCFCs, hydrogen fluorohydrocarbon class HFCs, perfluoro alkanes FCs, organic compound R1120, R1130, inorganic compound R704, R717, R728, R729, R744, R764;

Said time cold fractional condensation module SU also adopts the vapour liquid separator of independent design; Recycle the further purifying mixed working fluid of cold that liquid phase separation cold-producing medium expands and lowers the temperature and produce in it, guarantee that the mixed working fluid that in the whole system circulation, gets into the multiple flow heat exchanger contains lubricated wet goods impurity hardly.

The concrete course of work of native system is: the low pressure multicomponent mixture work medium is in compressor module CU; Gas through main compressor 2 compressions becoming HTHP; Get into condenser 3 and be cooled to environment temperature; Get into oil eliminator 4 and carry out oil and separate, the lubricating oil of separating returns the lubricating oil return mouth A1 of main compressor 2 from the lubricating oil outlet A2 of oil eliminator 4, and the high pressure mixing working medium after oil strain is handled gets into the cold-producing medium high pressure entry B1 of the interior plate type heat exchanger 8 of precooling module PU; Cold-producing medium high-pressure outlet B2 from plate type heat exchanger 8 flows out by conventional water-cooled condensation unit cooling back, gets into back that vapour liquid separator 9 carries out flash separation among the cold fractional condensation module SU.The deposit fluid that comprises liquid-phase mixing working medium and remaining lubricating oil in the vapour liquid separator 9 is drawn by the highly pressurised liquid outlet C2 of bottom; Behind second restricting element, 10 puffings; Get into the conduction pipe that is built in finned heat exchanger the vapour liquid separator 9 from the low-pressure fluid inlet C3 of vapour liquid separator 9, carry out heat exchange with the gas phase mixed working fluid that rises; Be cleaned gas phase mixed working fluid after the purification is got into multiple flow heat exchanger 11 among the liquefaction separation module LU by the gases at high pressure outlet C5 of vapour liquid separator 9 cold-producing medium high pressure entry D1; The high-pressure refrigerant that effluents becomes the low-pressure low-temperature two-phase working substance after 12 throttlings of the 3rd restricting element; Absorb high-pressure side hot-fluid heat, cooling of realization system and gas liquefaction; Going out liquid phase mixture that low pressure mixed working fluid that head piece D4 flows out and low-pressure fluid outlet C4 from vapour liquid separator 9 return from multiple flow heat exchanger 11 low pressure refluxes and converges; All backflow and to go into main compressor 2 through gas-liquid separator 1 gas-liquid separation is laggard, accomplish the one action process.The compressed air that is cleaned after the processing is introduced from the air inlet D5 of multiple flow heat exchanger 11; In the multiple flow heat exchanger, cooled by the low pressure mix refrigerant; Change liquid state into, D6 draws from the outlet of the liquid air of multiple flow heat exchanger 11, gets into liquid nitrogen containers 14 through choke valve 13.The present embodiment lowest refrigerating temperature can reach about 80K, and can certain refrigerating capacity be provided at this warm area, is applicable to small-sized cryogenic gas liquefying plant demand occasions such as natural gas peak-shaving station, oxygen generating station.

Above embodiment only is used to explain the technical scheme of the utility model, but not to its restriction; Although the utility model has been carried out detailed explanation with reference to preferred embodiment; The those of ordinary skill in affiliated field is to be understood that; Still can make amendment and perhaps the part technical characterictic is equal to replacement the specific embodiment of the utility model; And not breaking away from the spirit of the utility model technical scheme, it all should be encompassed in the middle of the technical scheme scope that the utility model asks for protection.

Claims

1. pre-cooling type mixed working fluid cryogenic gas liquefaction system; It is characterized in that; Comprise compressor module (CU), precooling module (PU), return cold fractional condensation module (SU) and liquefaction separation module (LU); Its connected mode is: the high-pressure outlet of compressor module (CU) connects the high-pressure inlet of precooling module (PU); The high-pressure outlet of precooling module (PU) connects back the high-pressure inlet of cold fractional condensation module (SU), and the high-pressure outlet that returns cold fractional condensation module (SU) connects the high-pressure inlet of liquefaction separation module (LU); The low pressure inlet of compressor module (CU) is connected with an interface of a three-way pipe, and one two other interface of three-way pipe connects back the low tension outlet of cold fractional condensation module (SU), and another interface connects the low tension outlet of liquefaction separation module (LU).

2. pre-cooling type mixed working fluid cryogenic gas liquefaction system according to claim 1; It is characterized in that; Said compressor module (CU) comprises gas-liquid separator (1), main compressor (2), condenser (3) and oil eliminator (4); Its connected mode is: the inlet of gas-liquid separator (1) is the low pressure inlet of compressor module (CU); The outlet of gas-liquid separator (1) connects the low-pressure inlet of main compressor (2), and the high-pressure outlet of main compressor (2) connects the import of condenser (3), and the outlet of condenser (3) connects the import of oil eliminator (4); The lubricating oil outlet (A2) of oil eliminator (4) connects the oil return opening (A1) of main compressor (2), and the cold-producing medium high-pressure outlet of oil eliminator (4) is the high-pressure outlet of compressor module (CU).

3. pre-cooling type mixed working fluid cryogenic gas liquefaction system according to claim 1 and 2; It is characterized in that; Said precooling module (PU) comprises precooling compressor (5), preceding cooler (6), first throttle element (7) and plate type heat exchanger (8); Its connected mode is: the import of cooler (6) before the high-pressure outlet of precooling compressor (5) connects; The outlet of preceding cooler (6) connects first throttle element (7); The outlet of first throttle element (7) connects the low pressure inlet of plate type heat exchanger (8); The low tension outlet of plate type heat exchanger (8) connects the low-pressure inlet of precooling compressor (5), and the cold-producing medium high-pressure inlet (B1) of plate type heat exchanger (8) connects the high-pressure outlet of compressor module (CU), and the cold-producing medium high-pressure outlet (B2) of plate type heat exchanger (8) is the high-pressure outlet of precooling module (PU).

4. according to claim 1 or 3 described pre-cooling type mixed working fluid cryogenic gas liquefaction systems; It is characterized in that; Said time cold fractional condensation module (SU) comprises vapour liquid separator (9) and second restricting element (10); Its connected mode is: the cold-producing medium high pressure entry (C1) of vapour liquid separator (9) is back the high-pressure inlet of cold fractional condensation module (SU); The highly pressurised liquid outlet (C2) of vapour liquid separator (9) connects second restricting element (10); The outlet of second restricting element (10) connects the low-pressure fluid inlet (C3) of vapour liquid separator (9), and the low-pressure fluid outlet (C4) of vapour liquid separator (9) is back the low tension outlet of cold fractional condensation module (SU), and the gases at high pressure outlets (C5) of vapour liquid separator (9) are back the high-pressure outlet of cold fractional condensation module (SU).

5. according to claim 1 or 4 described pre-cooling type mixed working fluid cryogenic gas liquefaction systems; It is characterized in that; Said liquefaction separation module (LU) comprises multiple flow heat exchanger (11), the 3rd restricting element (12), choke valve (13) and liquid nitrogen container (14); Its connected mode is: the cold-producing medium high-pressure inlet (D1) of multiple flow heat exchanger (11) is the high-pressure inlet of liquefaction separation module (LU); The cold-producing medium high-pressure outlet (D2) of multiple flow heat exchanger (11) connects the 3rd restricting element (12); The outlet of the 3rd restricting element (12) connects the cold-producing medium low pressure inlet (D3) of multiple flow heat exchanger (11), and the cold-producing medium low tension outlet (D4) of multiple flow heat exchanger (11) is the low tension outlet of liquefaction separation module (LU), and the air inlet (D5) of multiple flow heat exchanger (11) is connected with system external world's compressed air; The liquid air outlet (D6) of multiple flow heat exchanger (11) connects choke valve (13), and the outlet of choke valve (13) connects liquid nitrogen container (14).

6. pre-cooling type mixed working fluid cryogenic gas liquefaction system according to claim 2 is characterized in that, main compressor (2) adopts the single-stage oil lubricating compressor in the said compressor module (CU), and pressure ratio is 1.0～10.0, and pressure at expulsion is less than 50.0bar.

7. pre-cooling type mixed working fluid cryogenic gas liquefaction system according to claim 3 is characterized in that, said precooling module (PU) adopts water-cooled condensation unit as precooling equipment; Said precooling compressor (5) is the single-stage oil lubricating compressor, and pressure ratio is 1.0～6.0, and pressure at expulsion is less than 30.0bar.

8. pre-cooling type mixed working fluid cryogenic gas liquefaction system according to claim 4 is characterized in that, said time cold fractional condensation module (SU) also adopts vapour liquid separator to recycle the cold that liquid phase separation cold-producing medium expands and lowers the temperature and produce in it.