CN105783424B - The air separating method of high-pressure oxygen-enriched gas is produced using cold energy of liquefied natural gas - Google Patents

The air separating method of high-pressure oxygen-enriched gas is produced using cold energy of liquefied natural gas Download PDF

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CN105783424B
CN105783424B CN201610255634.0A CN201610255634A CN105783424B CN 105783424 B CN105783424 B CN 105783424B CN 201610255634 A CN201610255634 A CN 201610255634A CN 105783424 B CN105783424 B CN 105783424B
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pressure
air
heat exchanger
oxygen
nitrogen
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CN105783424A (en
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熊永强
罗鹏
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Jinan University
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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
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04436—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using at least a triple pressure main column system
    • F25J3/04448—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using at least a triple pressure main column system in a double column flowsheet with an intermediate pressure column
    • 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
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04012—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of warm gaseous streams; details of intake or interstage cooling
    • F25J3/04018—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of warm gaseous streams; details of intake or interstage cooling of main feed air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • 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
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04048—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams
    • F25J3/0406—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams of nitrogen
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    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
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    • F25J3/04078—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression
    • F25J3/0409—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression of oxygen
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    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04163—Hot end purification of the feed air
    • F25J3/04169—Hot end purification of the feed air by adsorption of the impurities
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    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
    • F25J3/04218—Parallel arrangement of the main heat exchange line in cores having different functions, e.g. in low pressure and high pressure cores
    • F25J3/04224—Cores associated with a liquefaction or refrigeration cycle
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    • 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
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04254—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using the cold stored in external cryogenic fluids
    • F25J3/0426—The cryogenic component does not participate in the fractionation
    • F25J3/04266—The cryogenic component does not participate in the fractionation and being liquefied hydrocarbons
    • F25J3/04272—The cryogenic component does not participate in the fractionation and being liquefied hydrocarbons and comprising means for reducing the risk of pollution of hydrocarbons into the air fractionation
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    • 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/50—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column
    • F25J2200/54—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column in the low pressure column of a double pressure main column system
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    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/60—Processes or apparatus using other separation and/or other processing means using adsorption on solid adsorbents, e.g. by temperature-swing adsorption [TSA] at the hot or cold end
    • F25J2205/62—Purifying more than one feed stream in multiple adsorption vessels, e.g. for two feed streams at different pressures
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    • 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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    • F25J2230/04—Compressor cooling arrangement, e.g. inter- or after-stage cooling or condensate removal
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    • F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/02—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams using a pump in general or hydrostatic pressure increase
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    • 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
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/40—Processes or apparatus involving steps for recycling of process streams the recycled stream being air
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    • F25J2270/00—Refrigeration techniques used
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    • F25J2270/00—Refrigeration techniques used
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    • F25J2270/00—Refrigeration techniques used
    • F25J2270/90—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration
    • F25J2270/904—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration by liquid or gaseous cryogen in an open loop

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Abstract

The invention belongs to cold energy of liquefied natural gas to utilize technical field, more particularly to a kind of air separating method that high-pressure oxygen-enriched gas is produced using cold energy of liquefied natural gas.This method has specifically included following steps：(1) air compression and purification；(2) air liquefaction；(3) air rectifying；(4) LNG cold energy uses.On the one hand the inventive method presses aerial condenser to be thermally integrated with lower pressure column by being additionally arranged on the basis of conventional double tower space division flow in a medium pressure column and one, so that some air raw air need to only be compressed to middle pressure and can be separated, the power consumption of air compressor is significantly reduced.And this method utilizes the nitrogen of cold energy of liquefied natural gas condensing high pressure column overhead using circulating nitrogen gas as intermediate medium, cold energy is provided for air separation process, therefore do not only have very high oxygen extraction rate using this method, and On Lng Leakage air inlet rectification cell can be avoided, the security performance of system is high.

Description

The air separating method of high-pressure oxygen-enriched gas is produced using cold energy of liquefied natural gas
Technical field
The invention belongs to cold energy of liquefied natural gas to utilize technical field, more particularly to a kind of to be given birth to using cold energy of liquefied natural gas Produce the air separating method of high-pressure oxygen-enriched gas.
Background technology
In order to tackle climate change, CO is all being researched and developed in countries in the world energetically in recent years2(CCS) technology is trapped and seals up for safekeeping, its Middle oxygen-enriched combusting trapping technique is considered as one of most possible large-scale promotion and commercialized CCS technologies.Large-scale oxygen-enriched combustion Burning capturing device needs to consume the oxygen rich gas that a large amount of molar concentrations are less than 97%, as an oxygen-enriched combusting power plant needs daily Ten thousand tons high-pressure oxygen-enriched, and oxygen energy consumption processed is huge, can make the percentage point of decrease of power generation 6~8 of power plant.
With the development of social economy and the adjustment of energy resource structure, when the Gas Industry in China enters fast development Phase.In order to make up the deficiency of domestic natural gas resource, China every year from external import substantial amounts of liquefied natural gas (LNG), The import volume of 2014 has reached 19,890,000 tons.LNG is a kind of -162 DEG C cryogenic liquid at ambient pressure, is needed before use 7~10MPa (absolute pressure, the pressure appeared below are absolute pressure) is pressurized in receiving station and heats vaporization afterwards, is vaporized During can release about 230kWht-1Cold energy, there is huge value.LNG cold energy can be used for air separation, gently Hydrocarbon separates, low-temperature electricity-generating, CO2Trap, the industry such as low-temperature grinding and low-temperature cold store, save the energy consumption of production process.LNG cold energy Utilization ratio is related to the temperature utilized, lower using temperature, then cold energy use efficiency is higher.Therefore entered using LNG cold energy Row Cryogenic air separation, which can obtain maximum, energy-saving benefit, is most rational LNG cold energy uses mode.It is attached in LNG receiving stations It is near to build oxygen-enriched burning device, utilize LNG cold energy production oxygen-enriched combusting trapping CO2Required high-pressure oxygen-enriched gas, can be significantly Drop oxygen energy consumption processed and CO2The cost of trapping, be advantageous to the large-scale promotion and commercial applications of oxygen-enriched combusting trapping technique.
At present, it is domestic to have issued for multiple air separation patented technologies using LNG cold energy：
(1) given birth to what Chinese invention patent 01127133.7 and 200510124175.4 was introduced using cold energy of liquefied natural gas In the air-separating plant for producing liquid oxygen, liquid nitrogen and liquid argon, nitrogen oxygen separating is carried out using double-column process, and LNG cold energy passes through Nitrogen kind of refrigeration cycle provides the cold energy needed for production liquid space division product for air-separating plant.But because nitrogen compressed and liquefied Journey can only utilize the LNG cold energy of deep cooling part, leave natural gas (NG) temperature of air-separating plant still far below normal temperature, cold energy Fail to make full use of.
(2) liquid is utilized in the grade of Chinese invention patent 200910085213.8,200910059100.0,201010262363.4 In the air separating method for changing natural gas cold energy, to make full use of LNG cold energy, on the one hand the LNG cold energy of deep cooling part is used In the cooling and liquefaction of circulating nitrogen gas, cold energy is provided for air separation process；On the other hand by remaining shallow cold portion after LNG vaporization The cold energy divided is used for air compressor machine cascade EDFA through refrigerant glycol water or freon and final stage cools down so that LNG cold energy obtains To making full use of.
It is all to use double-column process next life production of high purity that the above-mentioned existing air using LNG cold energy, which separates patented method, Full liquid space division product, has the disadvantage that in use：(1) because the freight of fluid product is higher, liquid-containing air The product economy of separating device conveys radius typically within 300km, and market scale is limited；(2) production cost of liquid oxygen is far above Gas products, it also cannot be used directly for oxygen-enriched burning device；(3) the maximum energy consumption of air separation unit comes from air compressor, and mesh The double-column process that preceding most cryogenic air separation plant is all thermally integrated using high-pressure tower (lower tower) and lower pressure column (upper tower) come Oxygen is produced, whole air raw materials is required for being divided from atmospheric compression to high pressure (about 0.6MPa) in order to enter high-pressure tower From, because oxygen energy consumption processed is very high, be not suitable for oxygen-enriched combusting trap CO2Device in use.
The content of the invention
In order to overcome the shortcomings and deficiencies of the prior art described above, primary and foremost purpose of the invention is that providing a kind of utilize liquefies Natural gas cold energy produces the air separating method of high-pressure oxygen-enriched gas.On the one hand, air separation process uses three-column process flow, that is, increases If a medium pressure column is thermally integrated with lower pressure column, so only a part of raw air need to be compressed to high pressure and enter high-pressure tower Separation, and other air raw materials then enter medium pressure column and lower pressure column is separated, and reduce the energy consumption of air compressor machine；Second aspect, from Low pressure midsection takes out a part of cold energy and is used to press air liquefaction in one, it is entered high-pressure tower using liquid pump supercharging Separated, further reduce the energy consumption of air compressor machine；3rd aspect, using circulating nitrogen gas as intermediate medium, utilizes LNG cold energy The nitrogen of condensing high pressure column overhead, cold energy is provided for air separation unit, and can prevent LNG from leaking into inside air separation unit, carried The high security performance of device.
The purpose of the present invention is realized by following proposal：
A kind of air separating method that high-pressure oxygen-enriched gas is produced using cold energy of liquefied natural gas, including following operation step Suddenly：
(1) air compression and purification
Air initially enters self-cleaning air intake filter device 1, removes dust contained in air and its in the filter After its granule foreign, being compressed to low pressure through air compressor 2, (absolute pressure 0.2MPa or so, the pressure appeared below are exhausted To pressure), then 2~10 DEG C are cooled to using the low-temperature glycol aqueous solution in heat exchanger 3, and Air-cooling Process is produced Raw condensed water is separated.The low-pressure air flowed out from heat exchanger 3 is divided into two strands through flow divider 4, the purification of one air inlet Water, carbon dioxide and some hydrocarbons in air are removed in device 11, become low pressure dry air stream；Another strand of low pressure sky Gas is then compressed to middle pressure (pressure is between 0.3~0.4MPa) through air compressor 5, then recirculated cooling water is utilized in heat exchanger 6 It is cooled to close to environment temperature.The middle pressure air flowed out from heat exchanger 6 is separated into two strands through flow divider 7, is pressed wherein in one empty Water, carbon dioxide and some hydrocarbons in air are removed in gas air inlet clarifier 12, become middle pressure dry air Stream, and press air to be then first cooled further to 2~10 DEG C using the low-temperature glycol aqueous solution in heat exchanger 8 in another stock And condensate is isolated, subsequently into being compressed to high pressure (pressure is between 0.5~0.6MPa) in air compressor 9, then exchanging heat Water, the dioxy for entering close to after environment temperature in air purifier 13 and removing in air are water-cooled in device 10 using circulating cooling Change carbon and some hydrocarbons, become high pressure dry air stream.
(2) air cools down
The middle pressure dry air obtained in step (1) is divided into two strands through flow divider 14, then low with the middle acquisition of step (1) Pressure dry air and high pressure dry air are fully entered in main heat exchanger 15, are given up through the low-temp low-pressure with being flowed out from heat exchanger 24 Nitrogen, the high pressure liquid oxygen from liquid oxygen pump 28 and the low-temperature circulating nitrogen from the outflow of heat exchanger 34 are exchanged heat, four strands of dry airs It is cooled to the dew-point temperature close to pressure-air.The low-temp low-pressure air flowed out from main heat exchanger 15 is further through heat exchanger 24 Enter after cooling in lower pressure column 26 and separate, and then enter from the cryogenic high pressure air of the outflow of main heat exchanger 15 in high-pressure tower and divide From.Pressed in the two strands of low temperature flowed out from main heat exchanger 15 in air, one is directly entered medium pressure column 16 and separated, and another stock Then first enter after heat exchanger 18 is further cooled to dew-point temperature cold in the middle pressure aerial condenser 19 being located inside lower pressure column Lime set.The middle press liquid air flowed out from condenser 19 enters in heat exchanger 18 after liquid-containing air air pump 20 increases to high pressure with coming Air heat-exchange is pressed from the low temperature of main heat exchanger 15, then respectively enters medium pressure column and high pressure after flow divider 21 is divided into two strands again Separated in tower.
(3) air rectifying
Air and one highly pressurised liquid air is pressed to enter respectively in the middle part of bottom of towe and tower in one low temperature obtained in step (2) Enter medium pressure column and carry out nitrogen, oxygen rectifying separation, the middle pressure that the medium pressure nitrogen gas for therefrom pressing column overhead to obtain enters inside lower pressure column With all being liquefied after the cryogenic liquid heat exchange in lower pressure column in column overhead condenser 17.Therefrom press and flowed out in column overhead condenser 17 A middle hydraulic fluid nitrogen part return to medium pressure column as overhead reflux liquid for maintaining rectifying operating mode, another part is then through heat exchanger 24 Enter the tower top of lower pressure column after supercooling, the rectifying for nitrogen, oxygen separates.
Cryogenic high pressure air and one highly pressurised liquid air are obtained in step (2) respectively in the middle part of bottom of towe and tower into high Press tower to carry out nitrogen, oxygen rectifying separation, two strands of high pressure nitrogens obtained from high pressure column overhead, one then in heat exchanger 35 with from throttling Liquefied after the circulating liquid nitrogen heat exchange flowed out in valve 34, and be sent into condensation/reboiler 23 positioned at lower pressure column bottom, and another stock High pressure nitrogen also enters with all being liquefied after the low-temperature liquid oxygen heat exchange at lower pressure column bottom in condensation/reboiler 23, and low-temperature liquid oxygen obtains Be partly vaporized into after heat as the upflowing vapor in lower pressure column, for maintaining rectifying operating mode.Flowed out from condensation/reboiler 23 High-pressure liquid nitrogen be divided into two strands, one returns to high-pressure tower as overhead reflux liquid for maintaining rectifying operating mode, and another stock then exists Heat exchanger 24 is divided into two parts through flow divider 25 again after being subcooled, and is partly into the tower top of lower pressure column, the rectifying point for nitrogen, oxygen From, and remaining be then sent into low pressure liquid nitrogen tank 27 is used as liquid nitrogen product.
Obtained from medium pressure column and high pressure tower bottom after two strands of oxygen-enriched liquid airs are further subcooled in heat exchanger 24 into low Separated in the middle part of pressure tower, the nitrogenous higher low temperature waste nitrogen gas discharged from tower top is in heat exchanger 24 after recovery section cold Into main heat exchanger 15, and the oxygen enriched liquid extracted out from bottom of towe then also enters main heat exchanger 15 after the supercharging of liquid oxygen pump 28, for step Suddenly the air cooling in (2) provides cold energy.After reclaiming cold energy in main heat exchanger 15, all vaporization turns into high pressure richness to high pressure liquid oxygen Carrier of oxygen product；Low temperature waste nitrogen be heated near in main heat exchanger 15 regeneration that can be used for air purifier after normal temperature and The cooling of recirculated cooling water.
(4) LNG cold energy uses
The circulating liquid nitrogen flowed out from choke valve 34 described in step (3) all vaporizes after being exchanged heat in heat exchanger 35, Enter again after the recovery section cold energy of main heat exchanger 15 in nitrogen compressor 29 and be pressurized.Circulating nitrogen gas after supercharging are in heat exchanger 30 In with being further pressurized through nitrogen compressor 31 after the high pressure LNG heat exchange from receiving station, be then divided into two in flow divider 32 Strand, wherein one enters in heat exchanger 30 with being liquefied after the LNG charging heat exchange from receiving station, then enters again through main heat exchanger 15 One step is subcooled, and another stock is then directly entered after being exchanged heat in main heat exchanger 15 and all liquefies and be subcooled, and forms two bursts of supercoolings and follows Ring liquid nitrogen.This two strands of circulating liquid nitrogens are mixed into one in mixing valve 33, then through choke valve 34 decompression after enter heat exchanger 35 with High pressure nitrogen heat exchange from high pressure tower top, cold is provided for the rectifying separation of air.
For high pressure LNG from receiving station after heat exchanger 30 make use of a part of cold energy, temperature is still below its bubble point temperature, It is sent in heat exchanger 36 and is exchanged heat with one hot glycol water from mixing valve 39 again.After high pressure LNG heat exchange all Vaporization, temperature are increased to more than 0 DEG C, turn into one high-pressure natural gas, can be directly entered high-pressure natural gas pipe network.From heat exchanger 36 The temperature of the glycol water of middle outflow is reduced to 0 DEG C or so, then is divided into two in flow divider 38 after the supercharging of water pump 37 Strand, wherein one enters in heat exchanger 3 cooling for being used for low-pressure air, is used for air compressor 9 in another strand of feeding heat exchanger 8 Inlet gas cooling.After heat exchange, heat exchange is returned after the blended mixing of valve 39 of two strands of glycol waters flowed out from heat exchanger 3 and 8 In device 36, a cold energy use circulation is formed.
Wherein：The operating pressure of low pressure column overhead described in step (3) is between 0.12~0.15MPa, medium pressure column tower top Operating pressure between 0.25~0.35MPa, the operating pressure of high pressure column overhead is in 0.5MPa or so.
The supercooling high-pressure liquid nitrogen from flow divider 25 described in step (3) enters lower pressure column from tower top, from heat exchanger The opening position of hydraulic fluid nitrogen about 2~5 pieces of theoretical plates under tower top enters lower pressure column in 24 supercooling, the middle pressure flowed out from heat exchanger 24 Oxygen-enriched liquid air and high-pressure oxygen-enriched liquid air enter lower pressure column from the middle part of lower pressure column, wherein being pressed in the charging aperture ratio of high-pressure oxygen-enriched liquid air rich High 5~10 pieces of theoretical plates of charging aperture of oxygen liquid air, and from heat exchanger 24 flow out low-pressure air in high-pressure oxygen-enriched liquid air and middle pressure Enter lower pressure column between the charging aperture of oxygen-enriched liquid air.
Medium pressure column overhead condenser described in step (3) is arranged in lower pressure column, positioned at the charging of middle pressure oxygen-enriched liquid air At lower 2~5 pieces of theoretical plates of mouth, middle pressure aerial condenser is also disposed in lower pressure column, positioned at medium pressure column overhead condenser and bottom of towe Between.
The high-pressure oxygen-enriched gas products from main heat exchanger discharge described in step (3), the mole fraction of wherein oxygen are less than 97%, pressure is in more than 1.0MPa.
The high-pressure liquefaction natural gas pressure from receiving station described in step (4) is 0.5~15MPa.
The intake air temperature of nitrogen compressor 29 and 31 described in step (4) is controlled between -120~-150 DEG C, described The compression ratio of nitrogen compressor 29 and 31 is of substantially equal, and the outlet pressure of nitrogen compressor 31 is more than 5.5MPa.
Low 0.04~the 0.10MPa of outlet pressure higher pressure column overhead operating pressure of choke valve 34 described in step (4).
The present invention mechanism be：
The present invention using cold energy of liquefied natural gas produce high-pressure oxygen-enriched gas air separating method specifically included with Lower step：(1) air compression and purification；(2) air liquefaction；(3) air rectifying；(4) LNG cold energy uses.This method is on the one hand Aerial condenser is pressed to enter with lower pressure column by being additionally arranged on the basis of conventional double tower space division flow in a medium pressure column and one Row is thermally integrated so that some air raw air need to only be compressed to middle pressure and can be separated, and significantly reduce air pressure The power consumption of contracting machine.And this method utilizes the nitrogen of cold energy of liquefied natural gas condensing high pressure column overhead using circulating nitrogen gas as intermediate medium Gas, cold energy is provided for air separation process, therefore do not only have very high oxygen extraction rate using this method, and liquid can be avoided Change natural gas leaking air inlet rectification cell, the security performance of system is high.
The present invention is had the following advantages and beneficial effect relative to prior art：
(1) present invention is additionally arranged a medium pressure column on the basis of conventional double tower space division flow so that portion of air is former Material air, which need to only be compressed to middle pressure, to be separated, and significantly reduce the power consumption of air compressor.
(2) portion of air raw material can utilize the cold energy of liquefied natural gas and from low after low pressure is compressed in the present invention The oxygen enriched liquid product and the cold energy of dirty nitrogen that pressure tower is separated cool down, and then can be directly entered lower pressure column and be divided From, not only reduce the power consumption of air compressor, and need not set in conventional cryogenic air separator freeze necessary to Air turbine expanding machine, save equipment investment expense.
(3) it is in the present invention that medium pressure column overhead condenser, middle pressure aerial condenser and condensation/reboiler is integrally disposed in low Press in tower, the cold energy of cryogenic liquid in lower pressure column has been obtained cascade utilization, liquid in lower pressure column is greatly reduced and re-vaporized Journey it is coldLoss, reduce the production power consumption of air separation unit.
(4) present invention utilizes the cold energy condensation liquefaction high pressure column overhead of liquefied natural gas by intermediate medium of circulating nitrogen gas Nitrogen, cold energy is provided for air separation process.With absorbing the cold of liquefied natural gas using pressure-air in existing other inventions It can compare, the present invention can obtain higher oxygen extraction rate, and can also avoid On Lng Leakage air inlet rectifying Unit, improve the security performance of system.
Brief description of the drawings
Fig. 1 is the workflow diagram of the present invention.
Wherein：
Specific device numbering
1- self-cleaning air intake filter devices；2,5,9- air compressors；
3,6,8,10,18,24,30,35,36- heat exchangers；4,7,14,21,25,32,38- flow dividers；
11,12,13- air purifiers；15- main heat exchangers；
16- medium pressure columns；17- medium pressure column overhead condensers；
Aerial condenser is pressed in 19-；20- liquid-containing air air pumps；
22- high-pressure towers；23- condensations/reboiler；
26- lower pressure columns；27- liquid nitrogen storage tanks；
28- liquid oxygen pumps；29,31- nitrogen compressors；
33,39- mixing valves；34- choke valves；
37- water pumps；
Logistics illustrates
Embodiment
With reference to embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are unlimited In this, for especially not dated technological parameter, routine techniques progress can refer to.
Embodiment 1：
As shown in figure 1, it is a kind of using cold energy of liquefied natural gas produce high-pressure oxygen-enriched gas air separating method include with Lower step and process conditions：
Liquefied natural gas (LNG) mole composition of receiving station is：Methane 88.78%, ethane 7.54%, propane 2.59%, Iso-butane 0.45%, butane 0.56%, nitrogen 0.08%；LNG pressure into air separation unit is 10MPa, and temperature is about -150 DEG C. A mole composition for air raw material is：Nitrogen 77.31%, oxygen 20.73%, argon gas 0.92%, CO2For 0.04%, water 1.02%； Air pressure 0.101MPa, 15 DEG C of temperature.The isentropic efficiency 0.82 of all compressors, mechanical efficiency 0.97；All pumps (including Water pump, liquid oxygen pump and liquid-containing air air pump) isentropic efficiency 0.75, mechanical efficiency 0.97.
Comprise the following steps that：
(1) air compression and purification
Normal pressure, 15 DEG C of air raw material enter self-cleaning air intake filter device 1, remove in the filter contained in air Dust and other granule foreigns, its flow be about 896.4t/h.Then being compressed to low pressure through air compressor 2, (pressure is 0.205MPa), temperature is increased to 93.5 DEG C, then in heat exchanger 3 with one 970t/h in flow divider 38, temperature 0 DEG C the low-temperature glycol aqueous solution (quality of glycol fraction be 30%) heat exchange, low-pressure air is cooled to 10 DEG C, and by low pressure The about 3.0t/h of condensed water caused by Air-cooling Process discharges from heat exchanger 3.From the low-pressure air that heat exchanger 3 flows out through shunting Valve 4 is divided into two strands, removed in the low-pressure air air inlet clarifier 11 that wherein one flow is about 143t/h water in air, Carbon dioxide and some hydrocarbons, become low pressure dry air stream, flow 142.5t/h, temperature is about 20 DEG C, pressure About 0.165MPa；The low-pressure air that another plume amount is about 750.4t/h is then compressed to middle pressure through air compressor 5, and (pressure is 0.352MPa), temperature is increased to 67.6 DEG C, then is water-cooled to 18 DEG C using circulating cooling in heat exchanger 6.Flowed from heat exchanger 6 The middle pressure air gone out is separated into two strands through flow divider 7, and the middle pressure air air inlet that wherein one flow is 304.0t/h purifies Water, carbon dioxide and some hydrocarbons in air are removed in device 12, dry air stream are pressed dry in becoming, its flow is about 302.9t/h, temperature are about 20 DEG C, and pressure is about 0.312MPa；And the middle pressure air that another plume amount is 446.4t/h then first exists It is further cooled down using 171t/h, 0 DEG C of the low-temperature glycol aqueous solution (quality of glycol fraction is 30%) in heat exchanger 8 To 10 DEG C and isolate condensate about 0.6t/h, subsequently into being compressed to high pressure (pressure 0.546MPa) in air compressor 9, Temperature is increased to 56.2 DEG C, then enters after being water-cooled to 18 DEG C using circulating cooling in heat exchanger 10 in air purifier 13 and take off Except the water in air, carbon dioxide and some hydrocarbons, become high pressure dry air stream, flow is about 444.8t/h, temperature About 20 DEG C of degree, pressure is about 0.526MPa.
(2) air cools down
The middle pressure dry air obtained in step (1) is divided into two strands through flow divider 14, flow be respectively 183t/h and 119.9t/h；Then the low pressure dry air and high pressure dry air with being obtained in step (1) are fully entered in main heat exchanger 15, Through the low-temp low-pressure waste nitrogen (flow 651.6t/h, -177.3 DEG C of temperature, pressure 0.128MPa) with being flowed out from heat exchanger 24, High pressure liquid oxygen (flow 218.5t/h, -179.1 DEG C of temperature, pressure 1.884MPa) from liquid oxygen pump 28 and from heat exchanger 34 outflow low-temperature circulating nitrogen (flow 325t/h, -179.9 DEG C of temperature, pressure 0.465MPa) exchanged heat, low pressure and The middle dry air of pressure is cooled to -176 DEG C, and pressure-air is cooled to -174.4 DEG C of dew-point temperature, and four strands of dry airs exist The pressure drop of cooling of being exchanged heat in main heat exchanger is about 0.012MPa.(flow is the low-temp low-pressure air flowed out from main heat exchanger 15 142.5t/h) enter after heat exchanger 24 is cooled further to -182.1 DEG C in lower pressure column 26 and separate, and flowed from main heat exchanger 15 The cryogenic high pressure air (flow 444.8t/h) gone out, which then enters in high-pressure tower, to be separated.The two strands of low temperature flowed out from main heat exchanger 15 In middle pressure air, one flow is that the 183t/h bottom of medium pressure column 16 that is directly entered is separated, and then flow is another stock The 119.9t/h middle pressure then first entered after heat exchanger 18 is cooled to dew-point temperature (about -181.1 DEG C) inside lower pressure column Condensation liquefaction in aerial condenser 19.The middle press liquid air (temperature is about -183.8 DEG C) flowed out from condenser 19 is through liquid-containing air Air pump 20 enters in heat exchanger 18 with pressing air heat-exchange, temperature rise in the low temperature from main heat exchanger 15 after increasing to 0.525MPa To -181.0 DEG C, then it is divided into two strands through flow divider 21 again, one flow is to be separated entering in the middle part of medium pressure column for 26t/h, And another plume amount is to be separated then entering in the middle part of high-pressure tower for 93.9t/h.
(3) air rectifying
Air and one highly pressurised liquid air is pressed to enter respectively in the middle part of bottom of towe and tower in one low temperature obtained in step (2) Enter medium pressure column and carry out nitrogen, oxygen rectifying separation, (molar fraction 99.8%, pressure is about for the medium pressure nitrogen gas that therefrom pressure column overhead obtains For 0.29MPa, flow 194.2t/h) enter in the medium pressure column overhead condenser 17 inside lower pressure column and in lower pressure column All liquefied after cryogenic liquid heat exchange.Therefrom pressing the middle hydraulic fluid nitrogen flowed out in column overhead condenser 17 a part, (flow is about 89.2t/h) return to medium pressure column to be used to maintain rectifying operating mode as overhead reflux liquid, another part (flow is about 105t/h) then passes through Heat exchanger 24 crosses the tower top for being cooled to and entering lower pressure column after -190 DEG C, and the rectifying for nitrogen, oxygen separates.
Cryogenic high pressure air (flow is about 444.8t/h) and one highly pressurised liquid air (flow are obtained in step (2) About 93.9t/h) enter high-pressure tower progress nitrogen, oxygen rectifying separation in the middle part of bottom of towe and tower respectively, obtain two from high pressure column overhead Stock high pressure nitrogen (99.99%) pressure 0.504MPa, the molar fraction of nitrogen are all higher than, one (flow is about 278.1t/h) then (pressure 0.465MPa, 0.15) vapour phase fraction is to the 325t/h circulating liquid nitrogens flowed out in heat exchanger 35 and from choke valve 34 Liquefied after heat exchange, and be sent into condensation/reboiler 23 positioned at lower pressure column bottom, and (flow is about for another strand of high pressure nitrogen 176.6t/h) also enter with all being liquefied after the low-temperature liquid oxygen heat exchange at lower pressure column bottom in condensation/reboiler 23, and low-temperature liquid oxygen obtains Be partly vaporized into after heat as the upflowing vapor in lower pressure column, for maintaining rectifying operating mode.Flowed out from condensation/reboiler 23 High-pressure liquid nitrogen be divided into two strands, one (flow is about 263.7t/h) returns to high-pressure tower and is used to remain smart as overhead reflux liquid Operating mode is evaporated, another stock (flow is about 191t/h) is then divided into two parts through flow divider 25 again after the supercooling of heat exchanger 24, a part (flow is about 171t/h) enters the tower top of lower pressure column, and the rectifying for nitrogen, oxygen separates, and remaining (flow is about 20t/h) Then it is sent into the low pressure liquid nitrogen tank 27 that pressure is 0.2MPa and is used as liquid nitrogen product.
Two strands of oxygen-enriched liquid airs (flow is respectively 104t/h and 347.7t/h) are obtained from medium pressure column and high pressure tower bottom to exist Further enter in heat exchanger 24 in the middle part of lower pressure column after supercooling and separated, it is nitrogenous higher low from the 651.6t/h of tower top discharge Warm waste nitrogen gas (pressure 0.133MPa, the molar fraction of nitrogen about 99.8%) recovery section cold, temperature in heat exchanger 24 Enter main heat exchanger 15 after being increased to -177.3 DEG C, and extracted out from bottom of towe 218.5t/h oxygen enriched liquids (pressure 0.148MPa, The molar fraction of oxygen is in step (2) 95%) then also to enter main heat exchanger 15 after liquid oxygen pump 28 is pressurized to 1.88MPa Air cooling provides cold energy.After reclaiming cold energy in main heat exchanger 15, all vaporization turns into high pressure to 218.5t/h high pressure liquid oxygen Oxygen rich gas product, temperature are about 15.5 DEG C；Low temperature waste nitrogen can be used for sky after 15.5 DEG C are heated in main heat exchanger 15 The regeneration of gas purifier and the cooling of recirculated cooling water.
(4) LNG cold energy uses
The circulating liquid nitrogen of 325t/h, 0.465MPa for being flowed out from choke valve 34 described in step (3) are in heat exchanger 35 All vaporized after middle heat exchange, temperature is -179.9 DEG C, then after the recovery section cold energy of main heat exchanger 15, temperature is increased to -140 DEG C, subsequently into being pressurized to 1.943MPa in nitrogen compressor 29.Circulating nitrogen gas temperature after supercharging is increased to -55.6 DEG C, so Exchanged heat afterwards in heat exchanger 30 with one 10MPa from receiving station, -150 DEG C, the high pressure LNG that flow is 248t/h, its is cold But to 8.30MPa is further pressurized to through nitrogen compressor 31 after -140 DEG C, two strands are then divided into flow divider 32, wherein one The compression circulating nitrogen gas that plume amount is 157t/h enter with being liquefied after the LNG charging heat exchange from receiving station in heat exchanger 30, temperature Degree is reduced to -148 DEG C, is then cooled to -168 DEG C through 15 further mistake of main heat exchanger again, and another plume amount is 168t/h pressure Contracting circulating nitrogen gas, which are then directly entered in main heat exchanger 15 all to liquefy and cross after heat exchange, is cooled to -168 DEG C, forms two bursts of supercoolings and follows Ring liquid nitrogen.This two strands of circulating liquid nitrogens are mixed into one in mixing valve 33, then enter after choke valve 34 is depressurized to 0.465MPa Heat exchanger 35 is exchanged heat with the high pressure nitrogen from high pressure tower top, and cold is provided for the rectifying separation of air.
High pressure LNG from receiving station is after heat exchanger 30 make use of a part of cold energy, and temperature is increased to -74.4 DEG C, still Less than its bubble point temperature, then to be sent in heat exchanger 36 with one flow from mixing valve 39 be 1141t/h, temperature is 22.8 DEG C hot glycol water (quality of glycol fraction is 30%) heat exchange.All vaporized after high pressure LNG heat exchange, temperature liter Up to 2.6 DEG C (considering that the low-temperature glycol aqueous solution has 5% cold loss caused by heat inleak during utilization), it is natural to turn into one high pressure Gas, high-pressure natural gas pipe network can be directly entered.The temperature of the glycol water flowed out from heat exchanger 36 is reduced to 0 DEG C of left side The right side, then it is divided into two strands in flow divider 38 after water pump 37 is pressurized to 0.3MPa, wherein one (flow 970t/h) enters It is used for the cooling of low-pressure air in heat exchanger 3, another stock (flow 171t/h), which is sent into heat exchanger 8, is used for air compressor 9 Inlet gas cooling.After heat exchange, the glycol water temperature flowed out from heat exchanger 3 is increased to 25.2 DEG C, and is flowed out from heat exchanger 8 Glycol water temperature be increased to 8.7 DEG C, the blended valve 39 of this two strands of ethylene glycol solutions is returned in heat exchanger 36 after mixing, Form a cold energy use circulation.
In whole air separation process, the cold energy discharged using 248t/h high pressure LNG gasification can produce 20t/h high-purity fluids Nitrogen and 218.5t/h, 1.86MPa high-pressure oxygen-enriched gas (mole fraction of oxygen is 95%), the recovery rate of oxygen exceedes 99.99%, total system power consumption is 53942kW (including water pump and circulating cooling water-cooled power consumption).The power consumption of liquid nitrogen is according to utilization 50% (about 300kWh/t) of conventional air separation unit energy consumption is calculated, then the high pressure for averagely producing 1 ton of 1.86MPa is rich The power consumption of carrier of oxygen (molar fraction 95%) is about 219.4kWh/t.And conventional method production identical state is high-pressure oxygen-enriched The power consumption of gas is about 285kWh/t, therefore one kind that this patent proposes produces high-pressure oxygen-enriched gas using cold energy of liquefied natural gas Air separating method to produce the oxygen needed for oxygen-enriched combusting when can save 23% power consumption, utilize 1 ton of LNG release Cold energy can have good energy-saving effect with using electricity wisely 82kWh.
Above-described embodiment is the preferable embodiment of the present invention, but embodiments of the present invention are not by above-described embodiment Limitation, other any Spirit Essences without departing from the present invention with made under principle change, modification, replacement, combine, simplification, Equivalent substitute mode is should be, is included within protection scope of the present invention.

Claims (8)

1. a kind of air separating method that high-pressure oxygen-enriched gas is produced using cold energy of liquefied natural gas, it is characterised in that including following Operating procedure：
(1) air compression and purification
Air initially enters self-cleaning air intake filter device (1), removes dust contained in air and other in the filter After granule foreign, low pressure is compressed to through the first air compressor (2), then low-temperature glycol water is utilized in First Heat Exchanger (3) Solution is cooled to 2~10 DEG C, and condensed water caused by Air-cooling Process is separated；Flowed from First Heat Exchanger (3) The low-pressure air gone out is divided into two strands through the first flow divider (4), and one enters in the first air purifier (11) in removing air Water, carbon dioxide and some hydrocarbons, become low pressure dry air stream；Another strand of low-pressure air then compresses through the second air Machine (5) is compressed to middle pressure, then is water-cooled in the second heat exchanger (6) using circulating cooling close to environment temperature；Changed from second The middle pressure air of hot device (6) outflow is separated into two strands through the second flow divider (7), presses air to enter the second air wherein in one net Change water, carbon dioxide and some hydrocarbons in removing air in device (12), press dry dry air stream in becoming, and another stock Middle pressure air is then first cooled further to 2~10 DEG C using the low-temperature glycol aqueous solution in the 3rd heat exchanger (8) and divided Condensate is separated out, subsequently into being compressed to high pressure in the 3rd air compressor (9), then circulation is utilized in the 4th heat exchanger (10) Cooling is water-cooled to water, the carbon dioxide and one entered close to after environment temperature in the 3rd air purifier (13) in removing air A little hydrocarbons, become high pressure dry air stream；
(2) air cools down
The middle pressure dry air obtained in step (1) is divided into two strands through the 3rd flow divider (14), then with obtaining in step (1) Low pressure dry air and high pressure dry air are fully entered in main heat exchanger (15), through with flowed out from the 5th heat exchanger (24) it is low Warm low pressure waste nitrogen, the high pressure liquid oxygen from liquid oxygen pump (28) and the low-temperature circulating nitrogen from the outflow of the 7th heat exchanger (35) are changed Heat, four strands of dry airs are cooled to the dew-point temperature close to pressure-air；It is empty from the low-temp low-pressure of main heat exchanger (15) outflow Gas enters in lower pressure column (26) after the 5th heat exchanger (24) further cools to be separated, and flowed out from main heat exchanger (15) Cryogenic high pressure air, which then enters in high-pressure tower, to be separated；Pressed from two strands of low temperature of main heat exchanger (15) outflow in air, one is straight Tap into and separated into medium pressure column (16), and then first through the 8th heat exchanger (18) to be further cooled to dew-point temperature laggard for another stock Enter the condensation liquefaction in the middle pressure aerial condenser (19) inside lower pressure column；From the middle press liquid air of condenser (19) outflow Enter after liquid-containing air air pump (20) increases to high pressure in the 8th heat exchanger (18) with pressing sky in the low temperature from main heat exchanger (15) Gas exchanges heat, and then respectively enters in medium pressure column and high-pressure tower and is separated after the 4th flow divider (21) is divided into two strands again；
(3) air rectifying
Press air and one highly pressurised liquid air respectively from bottom of towe and tower middle part enter in one low temperature obtained in step (2) Tower is pressed to carry out nitrogen, oxygen rectifying separation, the medium pressure column tower that the medium pressure nitrogen gas for therefrom pressing column overhead to obtain enters inside lower pressure column With all being liquefied after the cryogenic liquid heat exchange in lower pressure column in top condenser (17)；Therefrom press in column overhead condenser (17) and flow out A middle hydraulic fluid nitrogen part return to medium pressure column and be used to maintain rectifying operating mode as overhead reflux liquid, another part then exchanges heat through the 5th Enter the tower top of lower pressure column after device (24) supercooling, the rectifying for nitrogen, oxygen separates；
Cryogenic high pressure air and one highly pressurised liquid air are obtained in step (2) and enters high-pressure tower in the middle part of bottom of towe and tower respectively Carry out nitrogen, oxygen rectifying separation, two strands of high pressure nitrogens obtained from high pressure column overhead, one then in the 7th heat exchanger (35) with from section Liquefied after flowing the circulating liquid nitrogen heat exchange of outflow in valve (34), and be sent into condensation/reboiler (23) positioned at lower pressure column bottom, and Another strand of high pressure nitrogen also enters with all being liquefied after the low-temperature liquid oxygen heat exchange at lower pressure column bottom in condensation/reboiler (23), and low Warm liquid oxygen, which obtains, to be partly vaporized into after heat as the upflowing vapor in lower pressure column, for maintaining rectifying operating mode；From condensation/reboiler (23) high-pressure liquid nitrogen of outflow is divided into two strands in, and one returns to high-pressure tower and is used to maintain rectifying operating mode as overhead reflux liquid, Another stock is then divided into two parts through the 5th flow divider (25) again after the supercooling of the 5th heat exchanger (24), is partly into lower pressure column Tower top, the rectifying for nitrogen, oxygen separates, and remaining be then sent into low pressure liquid nitrogen tank (27) is used as liquid nitrogen product；
Obtain after two strands of oxygen-enriched liquid airs are further subcooled in the 5th heat exchanger (24) and enter from medium pressure column and high pressure tower bottom Separated in the middle part of lower pressure column, the nitrogenous higher low temperature waste nitrogen gas discharged from tower top recoverer in the 5th heat exchanger (24) Enter main heat exchanger (15) after dividing cold, and the oxygen enriched liquid extracted out from bottom of towe then also changes after liquid oxygen pump (28) supercharging into master Hot device (15), cold energy is provided for the air cooling in step (2)；In main heat exchanger (15) after recovery cold energy, high pressure liquid oxygen is complete Portion's vaporization turns into high-pressure oxygen-enriched gas products；Low temperature waste nitrogen can be used for after being heated near normal temperature in main heat exchanger (15) The regeneration of air purifier and the cooling of recirculated cooling water；
(4) LNG cold energy uses
Whole vapour after the circulating liquid nitrogen flowed out from choke valve (34) described in step (3) exchanges heat in the 7th heat exchanger (35) Change, then enter after main heat exchanger (15) recovery section cold energy in the first nitrogen compressor (29) and be pressurized；Cyclic nitrogen after supercharging Gas is in the 6th heat exchanger (30) with further increasing through the second nitrogen compressor (31) after the high pressure LNG heat exchange from receiving station Pressure, is then divided into two strands in the 6th flow divider (32), and wherein one enters in the 6th heat exchanger (30) and from receiving station Liquefy after LNG charging heat exchange, be then further subcooled through main heat exchanger (15) again, and another stock is then directly entered main heat exchanger (15) all liquefy and be subcooled after being exchanged heat in, form two strands of supercooling circulating liquid nitrogens；This two strands of circulating liquid nitrogens are in the first mixing valve (33) one is mixed into, then enters the 7th heat exchanger (35) and the elevated pressure nitrogen from high pressure tower top after choke valve (34) decompression Gas is exchanged heat, and cold is provided for the rectifying separation of air；
For high pressure LNG from receiving station after the 6th heat exchanger (30) make use of a part of cold energy, temperature is still below its bubble point temperature Degree, then be sent in the 9th heat exchanger (36) and exchanged heat with one hot glycol water from the second mixing valve (39)；It is high All vaporized after pressure LNG heat exchange, temperature is increased to more than 0 DEG C, turns into one high-pressure natural gas, can be directly entered high-pressure natural gas Pipe network；The temperature of the glycol water of outflow is reduced to 0 DEG C or so from the 9th heat exchanger (36), then is pressurized through water pump (37) It is divided into two strands in the 7th flow divider (38) afterwards, wherein one enters in First Heat Exchanger (3) cooling for being used for low-pressure air, Another strand is sent into the 3rd heat exchanger (8) inlet gas cooling for being used for the 3rd air compressor (9)；After heat exchange, from First Heat Exchanger (3) and the 3rd heat exchanger (8) outflow two strands of glycol waters through the second mixing valve (39) mixing after return the 9th heat exchanger (36) in, a cold energy use circulation is formed.
2. the air separating method according to claim 1 that high-pressure oxygen-enriched gas is produced using cold energy of liquefied natural gas, its It is characterised by：The operating pressure of low pressure column overhead described in step (3) is in 0.12~0.15MPa, the operation of medium pressure column tower top Pressure is in 0.25~0.35MPa, and the operating pressure of high pressure column overhead is in 0.5MPa.
3. the air separating method according to claim 1 that high-pressure oxygen-enriched gas is produced using cold energy of liquefied natural gas, its It is characterised by：The supercooling high-pressure liquid nitrogen from the 5th flow divider (25) described in step (3) enters lower pressure column from tower top, comes from The opening position of hydraulic fluid nitrogen 2~5 pieces of theoretical plates under tower top enters lower pressure column in the supercooling of 5th heat exchanger (24), from the 5th heat exchange The middle pressure oxygen-enriched liquid air and high-pressure oxygen-enriched liquid air of device (24) outflow enter lower pressure column from the middle part of lower pressure column, wherein high-pressure oxygen-enriched liquid air Charging aperture than high 5~10 pieces of theoretical plates of charging aperture of middle pressure oxygen-enriched liquid air, and the low pressure from the outflow of the 5th heat exchanger (24) is empty Gas enters lower pressure column between the charging aperture of high-pressure oxygen-enriched liquid air and middle pressure oxygen-enriched liquid air.
4. the air separating method according to claim 1 that high-pressure oxygen-enriched gas is produced using cold energy of liquefied natural gas, its It is characterised by：Medium pressure column overhead condenser described in step (3) is arranged in lower pressure column, positioned at the charging of middle pressure oxygen-enriched liquid air At lower 2~5 pieces of theoretical plates of mouth, middle pressure aerial condenser is also disposed in lower pressure column, positioned at medium pressure column overhead condenser and bottom of towe Between.
5. the air separating method according to claim 1 that high-pressure oxygen-enriched gas is produced using cold energy of liquefied natural gas, its It is characterised by：The high-pressure oxygen-enriched gas products from main heat exchanger discharge described in step (3), the mole fraction of wherein oxygen are less than 97%, pressure is in more than 1.0MPa.
6. the air separating method according to claim 1 that high-pressure oxygen-enriched gas is produced using cold energy of liquefied natural gas, its It is characterised by：The high-pressure liquefaction natural gas pressure from receiving station described in step (4) is 0.5~15MPa.
7. the air separating method according to claim 1 that high-pressure oxygen-enriched gas is produced using cold energy of liquefied natural gas, its It is characterised by：The intake air temperature control of the first nitrogen compressor (29) and the second nitrogen compressor (31) described in step (4) At -120~-150 DEG C, the compression ratio of described the first nitrogen compressor (29) and the second nitrogen compressor (31) is equal, and second The outlet pressure of nitrogen compressor (31) is more than 5.5MPa.
8. the air separating method according to claim 1 that high-pressure oxygen-enriched gas is produced using cold energy of liquefied natural gas, its It is characterised by：The outlet pressure higher pressure column overhead operating pressure of choke valve (34) described in step (4) is low 0.04~ 0.10MPa。
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