Rectification separation method of oxygen-argon-nitrogen ternary system in air

Abstract

The invention discloses a rectification separation method for an oxygen-argon-nitrogen ternary system in air. The method comprises the following steps: carrying out multi-stage compression and molecular sieve purification on raw material air to remove impurities so as to obtain dry air; purified air is divided into two streams, one stream is pressurized through air critical pressure, liquefied through a main heat exchanger, throttled, depressurized and fed into the bottom of the air separation tower, the other stream is subjected to turbocharging through a turbocharger and expansion refrigeration through an expansion machine, and expansion work drives supercharging equipment; liquid oxygen / gaseous oxygen is led out from the bottom of the air separation tower, and top nitrogen is compressed and shunted to serve as air separation tower top reflux liquid and a pure argon tower cold source respectively; a crude argon-refined argon double-tower structure is adopted, internal circulation reflux is formed by compressing and liquefying process argon, a high-purity argon product is led out from the bottom of a refined argon tower, and uncondensed waste gas and waste nitrogen are cooperatively discharged. Low-energy-consumption production of high-purity oxygen, nitrogen and argon is achieved through linkage of multiple stages of heat pumps.

Description

Technical Field

[0001] The present invention relates to the technical field of air separation processes, and particularly to a rectification separation method for an air oxygen-argon-nitrogen ternary system. Background Art

[0002] Air separation uses air as the feed gas to produce gas products such as oxygen, nitrogen, argon, helium, neon, krypton, and xenon, and has wide applications in industries such as petrochemical, metallurgy, and electronic information. It is a large-scale basic industry.

[0003] Existing air separation technologies mainly rely on cryogenic rectification processes. However, traditional solutions regard air as an oxygen-nitrogen binary system and ignore the significant impact of argon (0.9%) on product purity. As a high-value gas, the separation requirements of argon and its interference with the purity of oxygen and nitrogen require that air be regarded as an oxygen-argon-nitrogen ternary system for rectification.

[0004] As Figure 5 shown, the current rectification process for the air oxygen-argon-nitrogen ternary system is also known as the air rectification separation double-tower process. In fact, from the perspective of the rectification body part (sub-system), it is an optimized sequential rectification organization plan for the air oxygen-argon-nitrogen ternary system through a partition model. Above the argon fraction extraction port of the upper tower 6 is a nitrogen-argon-oxygen rectification tower approximated as an oxygen-nitrogen rectification tower, and the crude argon condenser plus the part below the argon fraction extraction port of the upper tower 6 is a nitrogen-argon-oxygen rectification tower approximated as an oxygen-argon rectification tower. In order to ensure the purity of the argon product, generally, a pure argon tower nitrogen-argon-oxygen rectification tower approximated as a nitrogen-argon rectification tower is also required. In fact, it is a three-tower process or a four-tower process (plus the lower tower 7). In terms of the cooling and heating supply scheme part (sub-system), it is a one-to-many open-type heat pump cooling and heating supply scheme with rectification raw dry air as the circulating working medium. The specific description is as follows.

[0005] Dry air is compressed to 5.0 - 6.0 bar in two stages by an air compressor (the pressure varies according to the actual engineering conditions, the heat transfer temperature difference of the condenser, the heat transfer resistance of the main heat exchanger, and the resistance of the rectification column). After purification, 15% of the pressurized air exchanges heat with the return gas in the main heat exchanger and then enters the expander for expansion refrigeration. The air after expansion refrigeration enters the upper column 6 to participate in rectification, and the work output by the expander is used for the turbocharging of the air for expansion refrigeration. The remaining 85% of the pressurized air exchanges heat with the return gas in the main heat exchanger and then partially enters the bottom of the lower column 7 with liquid carried. The upper column 6 and the lower column 7 are connected by the main condenser. The pressurized air is condensed and separated in the lower column 7. The pressurized nitrogen at the top of the lower column 7 is condensed into liquid nitrogen in the main condenser. Part of the liquid nitrogen is subcooled in the subcooler and then throttled and depressurized to be sent to the top of the air separation column as reflux liquid, and part of the liquid nitrogen is used as the reflux liquid nitrogen of the lower column 7. The oxygen-enriched liquid air is obtained at the bottom of the lower column 7. The oxygen-enriched liquid air is subcooled by heat exchange in the subcooler and then divided into two parts. One part is throttled and depressurized and sent to the middle of the air separation column as reflux liquid. One part is throttled and depressurized and sent to the crude argon condenser arranged at the top of the crude argon condensation column to evaporate and gasify. The oxygen-enriched air after evaporation and gasification converges with the air for expansion refrigeration (in a superheated state) and then enters the upper column 6 to participate in rectification. The evaporation and gasification of the oxygen-enriched liquid air in the crude argon condenser condenses the process argon gas at the top of the crude argon condensation column as the reflux liquid of the crude argon condensation column. The process argon gas is led out from the top of the crude argon condensation column and enters the middle of the fine argon column for rectification and separation. The pressurized nitrogen led out from the top of the lower column 7 is condensed into liquid nitrogen in the pressurized nitrogen condenser arranged at the bottom of the fine argon column, subcooled, and then throttled and depressurized to be sent to the liquid nitrogen evaporation-condenser arranged at the top of the fine argon column to evaporate and gasify and absorb heat to condense the nitrogen-argon mixed gas at the top of the fine argon column as the reflux liquid of the fine argon column. The uncondensed nitrogen-argon mixed gas (referred to as waste gas) is discharged into the atmosphere through the waste gas discharge valve. The gasified nitrogen converges with the nitrogen at the top of the air separation column.

[0006] A small amount of liquid oxygen is led out from the bottom of the upper column 6. The oxygen (with a purity of over 99.5% and an argon content of less than 0.5%) is reheated to room temperature by heat exchange in the main heat exchanger and used as the product oxygen. The argon fraction is led out from about 25 theoretical plate numbers above the bottom of the upper column 6 and enters the crude argon condensation column for condensation and separation. The dirty nitrogen led out from the middle of the upper column 6 is reheated to room temperature by heat exchange in the subcooler and the main heat exchanger and used as the regeneration gas of the purifier and for the air cooling tower. The nitrogen with qualified purity led out from the top of the air separation column is reheated to room temperature by heat exchange in the subcooler and the main heat exchanger and used as the product nitrogen. The fine argon gas with qualified purity led out from the bottom of the fine argon column is reheated to room temperature by heat exchange in the main heat exchanger and used as the product argon.

[0007] The above distillation process scheme for the oxygen-argon-nitrogen ternary system is, in terms of the distillation body, a sequential distillation organization scheme optimized by the partition model for the air-oxygen-argon-nitrogen ternary system. Above the argon fraction extraction outlet 6 in the upper column is a nitrogen-argon-oxygen distillation column approximated as an oxygen-nitrogen distillation column. The crude argon condenser plus the part below the argon fraction extraction outlet 6 in the upper column is a nitrogen-argon-oxygen distillation column approximated as an oxygen-argon distillation column. The crude argon condenser is the rectifying section of the nitrogen-argon-oxygen distillation column approximated as an oxygen-argon distillation column, and the part below the argon fraction extraction outlet 6 in the upper column is the stripping section of the nitrogen-argon-oxygen distillation column approximated as an oxygen-argon distillation column. The pure argon column is a nitrogen-argon-oxygen distillation column approximated as a nitrogen-argon distillation column. In terms of the cooling and heating supply scheme, it is a one-to-many open-type heat pump cooling and heating supply scheme with dry air of the distillation raw material as the circulating working medium. Among them, the so-called lower column 7 is a one-to-many open-type heat pump conversion column, which converts the open-type heat pump with dry air of the distillation raw material as the circulating working medium into an open-type heat pump for cooling and heating with nitrogen as the circulating working medium and an open-type heat pump for cooling and heating with oxygen-enriched air as the circulating working medium.

[0008] The existing distillation process for the ternary system has the following problems: High energy consumption: The compression power consumption of traditional single heat pump or one-to-many heat pump schemes is large, and the liquefaction efficiency is low (especially when below the critical pressure of air). Complex equipment: It requires multi-stage distillation columns (three towers or four towers) and complex cooling and heating supply systems, resulting in redundant processes. Poor flexibility: The production of liquid nitrogen and the process of nitrogen internal compression are restricted, making it difficult to flexibly adjust the product ratio. Summary of the Invention

[0009] The purpose of the present invention is to provide a distillation separation method for the air-oxygen-argon-nitrogen ternary system.

[0010] The technical solution adopted by the present invention is: A distillation separation method for the air-oxygen-argon-nitrogen ternary system, which includes the following steps: Step 1, air pretreatment: Compress the raw air through an air compressor, and remove moisture, carbon dioxide, and hydrocarbons through a purifier to obtain dry air; Step 2, pressure air shunt and liquefaction: Divide the purified dry air into two streams. The first stream of dry air is used for normal flow liquefaction, pressurize it to the critical pressure of air through a pressure air booster, completely liquefy it after heat exchange with the return gas in the main heat exchanger, and enter the bottom pressure air condenser of the air separation tower to be condensed into liquid air after throttling and decompression or after liquid expansion and decompression. The liquid air after liquefaction in the pressure air condenser is subcooled and then throttled and decompressed to the middle of the air separation tower as reflux liquid; The second stream of dry air enters an expander after being turbocharged for expansion refrigeration, and the expanded air is sent to the air separation tower to participate in distillation. Step 3: Liquid oxygen and oxygen are drawn from the bottom of the air separation column; nitrogen is drawn from the top of the air separation column, reheated to room temperature after heat exchange in the subcooler and the main heat exchanger, compressed to 5.0 - 6.0 bar, and then part of the pressurized nitrogen after heat exchange with the reverse flow gas in the main heat exchanger is used to produce liquid nitrogen in the pressurized nitrogen condenser at the bottom of the air separation column, and after being subcooled in the subcooler, it is sent to the top of the air separation column as reflux liquid; another part of the pressurized nitrogen is used to produce liquid nitrogen in the pressurized nitrogen condenser at the bottom or middle of the argon purification column, and after being subcooled in the subcooler, it is sent to the top of the argon purification column as reflux liquid; Specifically, part of the pressurized nitrogen after compression and heat exchange enters the pressurized nitrogen condenser of the air separation column and is condensed into liquid nitrogen. The liquid nitrogen is throttled and depressurized after being subcooled and sent to the top of the air separation column as reflux liquid; another part of the pressurized nitrogen enters the pressurized nitrogen condenser in the middle of the argon purification column and is condensed into liquid nitrogen, which is throttled and depressurized after being subcooled and sent to the top of the argon purification column as reflux liquid; Further, the pressurized nitrogen condenser is arranged at the liquid air inlet.

[0011] Specifically, in Step 3, part of the nitrogen drawn from the top of the air separation column is drawn out as product nitrogen, part of the nitrogen is compressed to 5.0 - 6.0 bar by a nitrogen compressor to obtain pressurized nitrogen, part of the pressurized nitrogen is condensed into liquid nitrogen in the pressurized nitrogen condenser at the bottom of the air separation column after heat exchange with the reverse flow gas in the main heat exchanger, and part or all of the liquid nitrogen is throttled and depressurized after being subcooled and sent to the top of the air separation column as reflux liquid; part of the pressurized nitrogen enters the pressurized nitrogen condenser in the argon purification column and is condensed into liquid nitrogen, which is throttled and depressurized after being subcooled and sent to the top of the argon purification column as reflux liquid; the waste nitrogen is throttled and depressurized to the top of the air separation column as reflux liquid after being subcooled in the main heat exchanger; the reheated waste nitrogen is used as the purification gas regenerating gas and for the air cooling tower.

[0012] Step 4: An argon fraction containing argon at a specified ratio is drawn from the argon fraction outlet above the bottom end of the air separation column to the rough argon column. The liquid at the bottom of the rough argon column returns to the air separation column as the descending liquid; the process argon gas drawn from the top of the rough argon column is compressed, heat-exchanged with the reverse flow gas in the main heat exchanger, and then enters the process argon gas condenser at the bottom of the air separation column and is condensed into liquid process argon gas. The liquid process argon gas is subcooled and sent to the top of the rough argon column as reflux liquid; the refined argon gas with a purity greater than the set purity is drawn from the bottom of the argon purification column; Part of the pressurized process argon gas is drawn from before the process argon gas condenser at the bottom of the air separation column and sent to the pressurized process argon gas condenser at the bottom of the argon purification column to be condensed into liquid process argon gas, which is subcooled and sent to the middle of the argon purification column as reflux liquid; Part of the pressurized nitrogen is drawn from before the pressurized nitrogen condenser of the air separation column and condensed into liquid nitrogen in the pressurized nitrogen condenser at the bottom or middle of the argon purification column, and after being subcooled, it is sent to the top of the argon purification column as reflux liquid; the non-condensable gas at the top of the argon purification column is drawn out, combined with the waste nitrogen drawn from the upper part of the air separation column, and after passing through the subcooler and the main heat exchanger to recover the cold energy, it is used as the regenerating gas for the purifier and for the air cooling tower.

[0013] Specifically, argon fraction is drawn from the bottom of the air separation column and enters the crude argon column for rectification separation; the argon gas drawn from the top of the crude argon column is cryogenically compressed to 2.2 bar, and after heat exchange in the main heat exchanger, part of the pressurized process argon gas enters the pressurized process argon condenser arranged at the bottom of the air separation column and is condensed into liquid process argon, and after subcooling, it is throttled and depressurized to the top of the crude argon column as reflux liquid; another part of the pressurized process argon gas is condensed into liquid process argon in the pressurized process argon condenser at the bottom of the pure argon column, and after subcooling, it is throttled and depressurized and sent to the middle of the pure argon column as reflux liquid (which is also the raw material transportation of the pure argon column).

[0014] Further, in step 1, the air is compressed to 4.0 - 4.4 bar.

[0015] Further, in step 2, the total proportion of the first stream of dry air is 5% - 30%, the critical pressure of the air is 38 bar; the proportion of the second stream of dry air is 70% - 95%.

[0016] Further, in step 2, the expansion output work of the second stream of dry air in the expander is used for the turbocharging of the expansion refrigerated air.

[0017] Further, part of the pressurized dry air is separated from the second stream of dry air as the third stream of dry air, and the pressurized air of the third stream of dry air without turbocharging enters the pressurized air condenser arranged at the bottom or middle of the air separation column after heat exchange with the return gas in the main heat exchanger and is condensed into liquid air.

[0018] Specifically, in step 2, part of the pressurized air is pressurized to the critical pressure of the air (38 bar), liquefied through the main heat exchanger, throttled and depressurized, and enters the bottom condenser of the air separation column to improve the liquefaction efficiency. The remaining air participates in rectification after turbocharging and expansion refrigeration.

[0019] Specifically, in step 3, air, nitrogen, and process argon are used as circulating working fluids, and the following condensers are respectively set; the pressurized air condenser is located at the bottom of the air separation column, and the liquefied liquid air is subcooled and then throttled and depressurized to the middle of the air separation column as reflux liquid; the pressurized nitrogen condenser: the pressurized process argon condenser: the process argon is compressed to 2.0 - 2.5 bar, condensed in the pressurized process argon condenser after heat exchange in the main heat exchanger, and throttled and depressurized to the top of the crude argon column as reflux liquid; Further, in step 4, the process argon at the top of the crude argon column is cryogenically compressed or reheated and compressed at normal temperature.

[0020] Further, in step 4, the specified proportion of argon in the argon fraction drawn from the air separation column is 10 - 12%; the process argon drawn from the top of the crude argon column is cryogenically compressed or reheated and compressed at normal temperature to 2.0 - 2.5 bar.

[0021] Specifically, the air separation column separates oxygen and nitrogen. The argon fraction (containing 10% argon) is drawn from the middle of the column to the crude argon column; the crude argon column further separates argon and oxygen, and the process argon gas at the top is compressed and then condensed and refluxed. The pure argon column purifies the argon gas to a qualified purity, and the product argon gas is drawn from the bottom.

[0022] Furthermore, in step 4, structured packings are used in the air separation column, the crude argon column, and the pure argon column; the air separation column has 85 theoretical plates; the crude argon column has 200 theoretical plates; the pure argon column has 20 - 30 theoretical plates.

[0023] Furthermore, the oxygen drawn in step 3 is reheated to room temperature by heat exchange with the positive-flow air in the main heat exchanger and then used as the product oxygen. The purity of the oxygen product is not less than 99.5% and the argon content is below 0.5%; part of the nitrogen drawn from the top of the air separation column is used as the product nitrogen after being reheated to room temperature by heat exchange in the subcooler and the main heat exchanger. The purity of the pure argon gas drawn from the bottom of the pure argon column is not less than 99.5%, and the pure argon gas is used as the product pure argon gas after being reheated by heat exchange in the main heat exchanger.

[0024] Furthermore, in step 4, the argon fraction with an argon content reaching a specified ratio of 10 - 12% is drawn from the argon fraction outlet above the bottom end of the air separation column, directly cryogenically compressed to 1.5 - 2.0 bar, heated by heat exchange in the main heat exchanger, and then condensed into a liquid oxygen-argon mixture in the pressure oxygen-argon mixture condenser arranged at the bottom of the air separation column. After subcooling, it is throttled and depressurized and sent to the 30th theoretical plate above the bottom of the air separation column to participate in rectification.

[0025] The present invention adopts the above technical solutions and has the following technical effects compared with the prior art: A complete air separation device consists of two relatively independent parts: air liquefaction and air rectification separation. For the air liquefaction part, breaking through the concept constraints of the so-called all-low-pressure and ultra-low-pressure cryogenic air separation process schemes, the process parameters of the air liquefaction part are optimized, and the optimal pressure for liquefying air is determined to be 38 bar, the critical pressure of air, thereby steadily improving the air liquefaction efficiency and laying a solid theoretical foundation for the energy consumption accounting of the air separation device. For the air rectification separation part, the basic scheme of a three-open-type heat pump for cooling and heating with raw air, nitrogen, and process argon as the circulating working medium replaces the existing one-drag-multiple-open-type heat pump for cooling and heating scheme with raw air as the circulating working medium (where the so-called lower tower in the double towers is actually a one-drag-multiple cooling and heating open-type heat pump conversion tower), and the compression power consumption of the heat pump circulating working medium is reduced by more than 20%. At the same time, the flexibility of the product scheme is increased. It is beneficial to produce high-purity products, beneficial to produce high-proportion liquid nitrogen products and nitrogen internal compression. It creates the possibility for further reducing the energy consumption of air rectification. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The following further elaborates on the present invention in detail in conjunction with the drawings and specific embodiments; Figure 1 Schematic diagram of the architecture of Embodiment 1 of the rectification separation method for an air oxygen-argon-nitrogen ternary system according to the present invention; Figure 2 Schematic diagram of the architecture of Embodiment 2 of the rectification separation method for an air oxygen-argon-nitrogen ternary system according to the present invention; Figure 3 Schematic diagram of the architecture of Embodiment 3 of the rectification separation method for an air oxygen-argon-nitrogen ternary system according to the present invention; Figure 4 Schematic diagram of the architecture of Embodiment 4 of the rectification separation method for an air oxygen-argon-nitrogen ternary system according to the present invention; Figure 5 Schematic diagram of the architecture of rectifying an air oxygen-argon-nitrogen ternary system in the prior art; Reference numerals: 1 is an air compressor, 2 is a temperature-variable and pressure-variable purifier, 3 is a turbocharger, 4 is a main heat exchanger, 5 is a low-temperature expander, 6 is an air separation column or an upper column, 7 is a lower column, 8 is a crude argon column, 9 is a pure argon column, 10 is a subcooler, 11 is a pressurized air booster, 12 is a cryogenic compressor for process argon or oxygen-argon mixed gas. 13 is a nitrogen compressor, and 15 is a nitrogen cryogenic compressor. Detailed implementation manners

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application.

[0028] In terms of the rectification body, the new rectification process scheme for the air oxygen-argon-nitrogen ternary system is exactly the same as the current rectification process scheme for the air oxygen-argon-nitrogen ternary system, and both are the rectification organization schemes optimized by the partition model. Above the argon fraction extraction port of the air separation column 6 is a nitrogen-argon-oxygen rectification column approximated as an oxygen-nitrogen rectification column, and below the crude argon column 8 plus the argon fraction extraction port of the air separation column 6 is a nitrogen-argon-oxygen rectification column approximated as an oxygen-argon rectification column. The pure argon column 9 is a nitrogen-argon-oxygen rectification column approximated as a nitrogen-argon rectification column. In terms of the cooling and heating supply scheme, a three-open heat pump basic cooling and heating supply scheme with air, nitrogen, and process argon (or oxygen-argon mixed gas) as circulating working fluids and pressure air condensers, pressure nitrogen condensers, and pressure process argon condensers arranged at the bottom of the air separation column 6 is adopted.

[0029] Such as Figures 1 to 4As shown in one of the figures, the present invention discloses a rectification separation method for an air oxygen-argon-nitrogen ternary system. Dry air is compressed in two stages by an air compressor 1 to 2.1 - 5.3 bar (generally taken as 4.2 bar, which varies according to the resistance of the main heat exchanger 4, the resistance of the air separation column 6, and the heat exchange temperature difference of the condenser). After being purified by a purifier 2, the pressurized air for normal flow liquefaction is further pressurized by a pressurized air booster 11 to the critical pressure of air (38 bar). After being fully liquefied by heat exchange with the return gas in the main heat exchanger 4, it is throttled and depressurized or expanded and depressurized by a liquid expander 5 and enters the pressurized air condenser arranged at the bottom of the air separation column 6. At the same time, part of the purified pressurized air at 2.1 - 5.3 bar (generally taken as 4.1 bar) enters the pressurized air condenser arranged at the bottom of the air separation column 6 after heat exchange with the return flow device in the main heat exchanger 4 and is condensed into liquid air. The liquid air is subcooled and then throttled and depressurized and sent to the middle of the air separation column 6 as reflux liquid. The remaining pressurized air is turbocharged and then enters an expander 5 after heat exchange with the return gas in the main heat exchanger 4 for expansion refrigeration. The air after expansion refrigeration enters the air separation column 6 to participate in rectification, and the work output by the expansion of the expander 5 is used for the turbocharging of the air for expansion refrigeration.

[0030] After the reflux nitrogen is reheated to room temperature by heat exchange in the subcooler 10 and the main heat exchanger 4, part of it is used as product nitrogen, and part of the nitrogen is compressed by a nitrogen compressor 13 to 2.0 - 6.0 bar (generally taken as 5.4 bar). After heat exchange in the main heat exchanger 4, it enters the pressurized nitrogen condenser arranged at the bottom of the air separation column 6 and is condensed into liquid nitrogen. After being subcooled, it is throttled and depressurized and sent to the top of the air separation column 6 as reflux liquid. A small amount of pressurized nitrogen is led to the pressurized nitrogen condenser arranged at the bottom of the argon purification column 9 before the pressurized nitrogen condenser and is condensed into liquid nitrogen. After being subcooled, it is throttled and depressurized and sent to the top of the argon purification column 9 as reflux liquid.

[0031] An argon fraction (containing about 10% argon, a small amount of nitrogen, and the rest oxygen) is led from about 25 theoretical plate numbers above the bottom of the air separation column 6 into the crude argon column 8 for condensation separation. The descending liquid at the bottom of the crude argon column 8 (at the argon fraction extraction port) returns to the air separation column 6 to participate in rectification. Process argon gas is led from the top of the crude argon column 8 and directly deep-cooled and compressed by a process argon or oxygen-argon mixed gas deep-cooling compressor 12 to 1.5 - 2.5 bar (generally taken as 2.2 bar). After heat exchange in the main heat exchanger 4, it enters the pressurized process argon condenser arranged at the bottom of the air separation column 6 and is condensed into liquid process argon. After being subcooled, it is sent to the top of the crude argon column 8 as reflux liquid. Part of the pressurized process argon is led before the pressurized process argon condenser and is condensed into liquid process argon in the pressurized process argon condenser arranged at the bottom of the argon purification column 9. After being subcooled, it is sent to the middle of the argon purification column 9 as reflux liquid (which is also the raw material transportation of the argon purification column 9). The top gas of the argon purification column is combined with the waste nitrogen.

[0032] The number of theoretical plates of the air separation column 6 is about 85, including about 25 below the argon fraction extraction outlet and 60 above the argon fraction extraction outlet. The number of theoretical plates of the crude argon column 8 is about 200, and the number of theoretical plates of the pure argon column 9 is about 30. Liquid oxygen is drawn from the bottom of the air separation column 6, and the oxygen is reheated to room temperature in the main heat exchanger 4 and then used as the product oxygen. Nitrogen is drawn from the top of the air separation column 6, and in the subcooler 10 and the main heat exchanger 4, after being reheated to room temperature, part of it is used as the product nitrogen, and part is compressed by the nitrogen compressor 13 to 2.0 - 6.0 bar (usually taken as 5.4 bar), and then enters the pressure nitrogen condenser arranged at the bottom of the air separation column 6 after heat exchange in the main heat exchanger 4. The waste nitrogen drawn from the middle of the air separation column 6 is reheated to room temperature in the subcooler 10 and the main heat exchanger 4, and is used as the regeneration gas of the purifier 2 and for the air cooling tower. The pure argon gas drawn from the bottom of the pure argon column 9 is reheated to room temperature in the main heat exchanger 4 and then used as the product argon.

[0033] The following will make a detailed description of the specific embodiments of the present invention: Embodiment 1: As Figure 1 shown, 50000 NM3 of dry air is compressed to 4.2 bar by the air compressor 1, and after purification, 5000 NM3 of it is boosted to 38 bar by the pressurized air booster 11. After heat exchange with the return gas in the main heat exchanger 4, it is all liquefied and throttled and depressurized to enter the pressure air condenser arranged at the bottom of the air separation column 6. The liquid air is subcooled by heat exchange with the return nitrogen and waste nitrogen in the subcooler 10, and then throttled and depressurized and sent to the middle of the air separation column 6 as the reflux liquid. The remaining 45000 NM3 of pressurized air is turbocharged by the turbocharger 3 and then enters the main heat exchanger 4 to exchange heat with the return gas and then enters the expander 5 for expansion refrigeration. The air after expansion refrigeration enters the air separation column 6 to participate in rectification. 45000 NM3 of nitrogen and 20000 NM3 of waste nitrogen are drawn from the top and the upper middle part of the air separation column 6. 45000 NM3 of nitrogen reheated to room temperature in the subcooler 10 and the main heat exchanger 4, among which 20000 NM3 is used as the product nitrogen, and 25000 NM3 is compressed by the nitrogen compressor 13 to 5.4 bar, and after heat exchange with the return gas in the main heat exchanger 4, it enters the pressure nitrogen condenser arranged at the bottom of the air separation column 6 and is condensed into liquid nitrogen. After being subcooled by heat exchange with the return nitrogen and waste nitrogen in the subcooler 10, it is throttled and depressurized and sent to the top of the air separation column 6 as the reflux liquid. The 20000 NM3 of reheated waste nitrogen is used as the regeneration gas of the purifier and for the air cooling tower. 300 NM3 of pressurized nitrogen is drawn before the pressure nitrogen condenser and condensed into liquid nitrogen in the pressure nitrogen condenser arranged at the bottom of the pure argon column 9, and after being subcooled, it is throttled and depressurized and sent to the top of the pure argon column 9 as the reflux liquid. The gas at the top of the pure argon column 9 is combined with the waste nitrogen.

[0034] Process argon gas (14,000 NM3) is drawn from the top of the crude argon column 8 and deeply cooled and compressed to 2.2 bar by the process argon or oxygen-argon mixed gas cryogenic compressor 12. After heat exchange in the main heat exchanger 4, it enters the pressure process argon condenser at the bottom of the air separation column 6 and is condensed into liquid process argon. After subcooling, it is throttled and depressurized and sent to the top of the crude argon column 8 as reflux liquid. 400 NM3 of pressure process argon drawn before the pressure process argon condenser is condensed into liquid process argon in the pressure process argon condenser at the bottom of the pure argon column 9. After subcooling, it is throttled and depressurized and sent to the middle of the pure argon column 9 as reflux liquid (also the raw material transportation of the pure argon column 9).

[0035] The air separation column 6 has 85 theoretical plates, the crude argon column 8 has 200 theoretical plates, and the pure argon column 9 has 20 - 30 theoretical plates.

[0036] Argon fraction is drawn from 25 theoretical plates above the bottom of the air separation column 6 and enters the crude argon column 8 for rectification separation (the argon content in the argon fraction is about 10% and the nitrogen content is below 0.5%). The descending liquid at the bottom of the crude argon column 8 returns to the air separation column 6 to participate in rectification.

[0037] 3,500 - 4,000 NM3 of liquid oxygen and 6,000 - 6,500 NM3 of oxygen are drawn from the bottom of the air separation column 6. After heat exchange and reheating to normal temperature in the main heat exchanger 4, they are used as product oxygen with an oxygen product purity of 99.5% (with an argon content of below 0.5%). 45,000 NM3 of nitrogen is drawn from the top of the air separation column 6. After heat exchange and reheating to normal temperature in the subcooler 10 and the main heat exchanger 4, 20,000 NM3 of it is used as product nitrogen. 400 NM3 of pure argon gas is drawn from the bottom of the pure argon column 9 and after heat exchange and reheating to normal temperature in the main heat exchanger 4, it is used as product argon.

[0038] Implementation case two of the new air oxygen-argon-nitrogen ternary system rectification process plan: As Figure 2 shown, 50,000 NM3 of dry air is compressed to 4.2 bar by the air compressor 1. After purification, 2,000 NM3 of it is pressurized to 38 bar by the pressure air booster 11 and after complete liquefaction by heat exchange with the reverse flow gas in the main heat exchanger 4, it is throttled and depressurized and enters the pressure air condenser at the bottom of the air separation column 6. 28,000 NM3 of 4.1 bar pressure air enters the pressure air condenser at the bottom of the air separation column 6 after heat exchange with the reverse flow gas in the main heat exchanger 4 and is condensed into liquid air. 30,000 NM3 of liquid air is subcooled after heat exchange with the reverse flow nitrogen and waste nitrogen in the subcooler 10 and then throttled and depressurized and sent to the middle of the air separation column 6 as reflux liquid. 20,000 NM3 of 4.1 bar pressure air is turbocharged by the turbocharger 3 and after heat exchange with the reverse flow gas in the main heat exchanger 4, it enters the expander 5 for expansion refrigeration. The air after expansion refrigeration enters the air separation column 6 to participate in rectification. The work output by the expansion of the expander 5 is used for the turbocharging of the turbocharger 3 for the air of expansion refrigeration.

[0039] From the top of the air separation column 6, 22,000 NM3 of nitrogen is deeply cooled and compressed to 2.0 bar by the nitrogen deep-cooling compressor 15. After heat exchange in the main heat exchanger 4 and the subcooler 10, it enters the pressure nitrogen condenser set at the liquid air inlet and is condensed into liquid nitrogen. The liquid nitrogen is subcooled in the subcooler 10 and then throttled and depressurized to the top of the air separation column 6 as reflux liquid. 300 NM3 of pressured nitrogen is led before the pressure nitrogen condenser and condensed into liquid nitrogen in the pressure nitrogen condenser set in the middle of the argon purification column 9 (where the argon content in the descending liquid is 20%). After subcooling, it is sent to the top of the argon purification column 9 as reflux liquid.

[0040] 16,000 NM3 of process argon is led from the top of the crude argon column 8 and deeply cooled and compressed to 2.2 bar by the process argon or oxygen-argon mixed gas deep-cooling compressor 12. After heat exchange in the main heat exchanger 4, it enters the pressure process argon condenser set at the bottom of the air separation column 6 and is condensed into liquid process argon. After subcooling in the subcooler 10, it is sent to the top of the crude argon column 8 as reflux liquid. 400 NM3 of pressured process argon is led before the pressure process argon condenser and condensed into liquid process argon in the pressure process argon condenser set at the bottom of the argon purification column 9. After subcooling, it is throttled and depressurized to the middle of the argon purification column 9 as reflux liquid.

[0041] The air separation column 6 has 85 theoretical plates, the crude argon column 8 has 200 theoretical plates, and the argon purification column 9 has 20 - 30 theoretical plates.

[0042] Argon fraction (containing 10% argon and less than 0.5% nitrogen) is led from 25 theoretical plates above the bottom of the air separation column 6 and enters the crude argon column 8 for condensation and separation.

[0043] 1,000 - 1,500 NM3 of liquid oxygen and 8,500 - 9,000 NM3 of gaseous oxygen (purity 99.8%, containing less than 0.2% argon) are led from the bottom of the air separation column 6. After heat exchange and reheating to normal temperature in the main heat exchanger 4, they are used as product oxygen. 20,000 NM3 of nitrogen is led from the top of the air separation column 6. After heat exchange and reheating to normal temperature in the subcooler 10 and the main heat exchanger 4, it is used as product nitrogen. 400 NM3 of refined argon is led from the bottom of the argon purification column 9. After heat exchange and reheating to normal temperature in the main heat exchanger 4, it is used as product argon.

[0044] Case Three of the New Air Oxygen-Argon-Nitrogen Ternary System Rectification Process Argon: As Figure 3As shown in the figure, 50,000 NM3 of dry air is compressed by the air compressor 1 to 4.2 bar. After purification, 2,000 NM3 of it is boosted to 38 bar by the pressurized air booster 11, and then exchanges heat with the return gas in the main heat exchanger 4 and is completely liquefied, and then throttled and depressurized to enter the pressurized air condenser at the bottom of the air separation column 6. 5,000 NM3 of 4.1 bar pressurized air exchanges heat with the return gas in the main heat exchanger 4 and then enters the pressurized air condenser at the bottom of the air separation column 6 and is condensed into liquid air. The liquid air exchanges heat with the return nitrogen and waste nitrogen in the subcooler 10, is subcooled, and then throttled and depressurized to be sent to the middle of the air separation column 6 as reflux liquid. The remaining 43,000 NM3 of 4.1 bar pressurized air is turbocharged by the turbocharger 3, exchanges heat with the return gas in the main heat exchanger 4, and then enters the expander 5 for expansion refrigeration. The air after expansion refrigeration enters the air separation column 6 to participate in rectification. The work output by the expansion of the expander 5 is used for the turbocharging of the turbocharger 3 for the air of expansion refrigeration.

[0045] 42,000 NM3 of return nitrogen exchanges heat and reheats to normal temperature in the subcooler 10 and the main heat exchanger 4. Among them, 20,000 NM3 is used as product nitrogen, and 22,000 NM3 is compressed to 5.4 bar by the nitrogen compressor 13, exchanges heat with the return gas in the main heat exchanger 4, and then enters the pressurized nitrogen condenser at the bottom of the air separation column 6 and is condensed into liquid nitrogen. The liquid nitrogen is subcooled and then throttled and depressurized to be sent to the top of the air separation column 6 as reflux liquid.

[0046] About 16,000 NM3 of oxygen-argon mixed gas (argon fraction, containing 10% argon and less than 0.5% nitrogen) is drawn from about 25 theoretical plates above the bottom of the air separation column 6, deeply compressed to 1.6 bar by the cryogenic compressor 12 for process argon or oxygen-argon mixed gas, exchanges heat in the main heat exchanger 4, and then enters the pressurized oxygen-argon mixed gas condenser at the bottom of the air separation column 6 and is condensed into liquid oxygen-argon mixed gas, and after subcooling, it is throttled and depressurized to be sent to the 30th theoretical plate above the air separation column 6 to participate in rectification.

[0047] The air separation column 6 has 85 theoretical plates. 3,500 - 4,000 NM3 of liquid oxygen and 6,000 - 6,500 NM3 of oxygen with a purity of 99.8% and less than 0.2% argon are drawn from the bottom of the air separation column 6, exchange heat and reheat to normal temperature in the main heat exchanger 4, and are used as product oxygen. 42,000 NM3 of nitrogen is drawn from the top of the air separation column 6, exchanges heat and reheats to normal temperature in the subcooler 10 and the main heat exchanger 4, and among them, 20,000 NM3 is used as product nitrogen. 20,000 NM3 of waste nitrogen is drawn from the middle of the air separation column 6, exchanges heat and reheats to normal temperature in the subcooler 10 and the main heat exchanger 4, and is used as the regeneration gas of the purifier 2 and for the air cooling tower.

[0048] Implementation case four of the new air oxygen-argon-nitrogen ternary system rectification process plan: As Figure 4As shown in the figure, dry air of 50,000 NM3 is compressed by air compressor 1 to 4.2 bar. Among them, 5,000 NM3 is further compressed to 38 bar by pressure air booster 11, exchanges heat with the return gas in main heat exchanger 4, is fully liquefied, and then throttled and depressurized to enter the pressure air condenser at the bottom of air separation column 6. The liquid air exchanges heat with the return nitrogen and waste nitrogen in subcooler 10 to be subcooled, and then throttled and depressurized to be sent to the middle of air separation column 6 as reflux liquid. The remaining pressure air is turbocharged by turbocharger 3, enters main heat exchanger 4 to exchange heat with the return gas, and then enters expander 5 for expansion refrigeration. The air after expansion refrigeration enters air separation column 6 to participate in rectification.

[0049] 48,000 NM3 of return nitrogen exchanges heat and is reheated to normal temperature in subcooler 10 and main heat exchanger 4. Among them, 20,000 NM3 is used as product nitrogen, and 30,000 NM3 is compressed to 5.4 bar by nitrogen compressor 13. After exchanging heat with the return gas in main heat exchanger 4, it enters the pressure nitrogen condenser at the bottom of air separation column 6 and is condensed into liquid nitrogen. After exchanging heat with the return nitrogen and waste nitrogen in subcooler 10 to be subcooled, 3,500 - 4,000 NM3 of it is led out as product liquid nitrogen. 25,700 - 26,200 NM3 is throttled and depressurized and sent to the top of air separation column 6 as reflux liquid. 300 NM3 of pressure nitrogen is led before the pressure nitrogen condenser and condensed into liquid nitrogen in the pressure nitrogen condenser at the bottom of argon purification column 9, and after being subcooled, it is throttled and depressurized and sent to the top of argon purification column 9 as reflux liquid. The gas at the top of argon purification column 9 converges with the waste nitrogen.

[0050] 14,000 NM3 of process argon is led from the top of crude argon column 8 and deeply compressed to 2.2 bar by the deep cryogenic compressor 12 for process argon or oxygen-argon mixed gas. After exchanging heat in main heat exchanger 4, it enters the pressure process argon condenser at the bottom of air separation column 6 and is condensed into liquid process argon. After being subcooled, it is throttled and depressurized and sent to the top of crude argon column 8 as reflux liquid. About 400 NM3 of pressure process argon is led before the pressure process argon condenser and condensed into liquid process argon in the pressure process argon condenser at the bottom of argon purification column 9. After being subcooled, it is throttled and depressurized and sent to the middle of argon purification column 9 as reflux liquid (which is also the raw material transportation of argon purification column 9).

[0051] The number of theoretical plates of air separation column 6 is 85, the number of theoretical plates of crude argon column 8 is 200, and the number of theoretical plates of argon purification column 9 is 20 - 30! Argon fraction (containing about 10% argon and less than 0.5% nitrogen) is led from the 25th theoretical plate above the bottom of air separation column 6 and enters crude argon column 8.

[0052] Draw 10,000 NM3 of oxygen gas from the bottom of the air separation column 6. After heat exchange and reheating to normal temperature in the main heat exchanger 4, it is used as the product oxygen. Draw about 400 NM3 of refined argon from the bottom of the refined argon column 9. After heat exchange and reheating to normal temperature in the main heat exchanger 4, it is used as the product argon. Draw 3,500 - 4,000 NM3 of liquid nitrogen from behind the subcooler 10 as the liquid nitrogen product. Draw 50,000 NM3 of nitrogen from the top of the air separation column 6. After heat exchange and reheating to normal temperature in the subcooler 10 and the main heat exchanger 4, 20,000 NM3 of it is used as the product nitrogen.

[0053] The technical solution of the present invention has the following technical characteristics: 1) For the pressurized air used for normal-flow liquefaction in the air liquefaction part, a pressurized air booster 11 is added to boost the pressure of the pressurized air for liquefying the normal-flow air to 38 bar (the critical pressure of air), so as to ensure that no matter how the rectification cooling and heating supply scheme of the air oxygen-argon-nitrogen ternary system changes, and no matter whether the so-called double-expansion refrigeration scheme is adopted or not, the air liquefaction efficiency can reach the highest under the same equipment performance parameters and the same engineering conditions! The quantity of liquid products in the air separation unit is adjusted by whether to adopt deep cooling compression, the oxygen-nitrogen internal compression scheme and the rectification cooling and heating supply scheme. 2) The new rectification process scheme for the air oxygen-argon-nitrogen ternary system adopts a three-open heat pump cooling and heating supply scheme with air, nitrogen, and process argon (or oxygen-argon mixed gas) as the circulating working medium. Compared with the current one-drive-multiple-open heat pump cooling and heating supply scheme with air as the circulating working medium, the cooling and heating power consumption (i.e., the compression power consumption of the open heat pump circulating working medium) is reduced by 25% - 30%. At the same time, according to the product purity and actual engineering conditions, an open heat pump for cooling and heating with the rectification intermediate product as the circulating working medium is added to further reduce the energy consumption. 3) Based on the basic three-open heat pump cooling and heating supply scheme with air, nitrogen, and process argon as the circulating working medium, by adding a suitable open heat pump cooling and heating supply scheme, high-purity oxygen, argon, and nitrogen products can be produced with low power consumption under the same engineering conditions (theoretical number of trays). 4) For the new rectification process scheme of the air oxygen-argon-nitrogen ternary system, as long as the compression amount of the nitrogen compressor 13 is increased, the liquid nitrogen product can be very conveniently drawn out and a large quantity of nitrogen internal compression process scheme can be adopted, while the current rectification process scheme of the air oxygen-argon-nitrogen ternary system cannot achieve this.

[0054] The present invention adopts the above technical solutions and has the following technical effects compared with the prior art: A complete air separation unit consists of two relatively independent parts: air liquefaction and air rectification separation. For the air liquefaction part, it breaks through the conceptual constraints of the so-called full low-pressure and ultra-low-pressure cryogenic air separation process solutions, optimizes the process parameters of the air liquefaction part, and determines that the optimal pressure for liquefying air is the air critical pressure of 38 bar, thereby steadily improving the air liquefaction efficiency and laying a solid theoretical foundation for the energy consumption accounting of the air separation unit. For the air rectification separation part, the basic scheme of a three-open heat pump for cooling and heating with raw air, nitrogen, and process argon as the circulating working medium replaces the existing one-drag-multiple-open heat pump for cooling and heating scheme with raw air as the circulating working medium (where the so-called lower column 7 in the double towers is actually a one-drag-multiple cooling and heating open heat pump conversion tower), and the compression power consumption of the heat pump circulating working medium is reduced by more than 20%. At the same time, the flexibility of the product scheme is increased. It is beneficial to produce high-purity products, and it is beneficial to produce high-proportion liquid nitrogen products and nitrogen internal compression. It creates the possibility for further reducing the energy consumption of air rectification..

[0055] Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. Usually, the components of the embodiments of the present application described and illustrated in the drawings here can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present application is not intended to limit the scope of the present application claimed, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

Claims

1. A method for the distillation separation of an air oxygen, argon and nitrogen ternary system, characterized in that: It includes the following steps: Step 1, compressing the raw air through an air compressor, removing moisture, carbon dioxide and hydrocarbons through a purifier to obtain dry air; Step 2, the purified dry air is divided into two streams, the first stream of dry air is used for positive flow liquefaction, is pressurized to the critical pressure of air by a pressure air booster, is completely liquefied after heat exchange with reflux gas in a main heat exchanger, enters the pressure air condenser at the bottom of the air separation tower after throttling and reducing pressure or after expansion and reducing pressure by a liquid expander, and the liquid air after liquefaction in the pressure air condenser is throttled and reduced pressure after supercooling to the middle of the air separation tower as reflux liquid; The second stream of dry air enters the main heat exchanger after being turbocharged, exchanges heat with the reflux gas, and then enters the expander for expansion and refrigeration. The expanded air is sent to the air separation tower for distillation, and the expansion output work of the expander is used for turbocharging of the expanded refrigeration air. Step 3, liquid oxygen and oxygen are drawn out from the bottom of the air separation tower; nitrogen is drawn out from the top of the air separation tower, and after heat exchange with the main heat exchanger to room temperature, it is compressed to 5.0-6.0 bar, and then heat exchanged with the reflux gas in the main heat exchanger. A part of the pressure nitrogen passes through the pressure nitrogen condenser at the bottom of the air separation tower to produce liquid nitrogen, and is sent to the top of the air separation tower as reflux liquid after being supercooled in the subcooler; another part of the pressure nitrogen passes through the pressure nitrogen condenser at the bottom or middle of the refined argon tower to produce liquid nitrogen, and is sent to the top of the refined argon tower as reflux liquid after being supercooled in the subcooler; Step 4, an argon fraction outlet above the bottom of the air separation tower draws out an argon fraction containing a specified proportion of argon to a crude argon tower, and the liquid at the bottom of the crude argon tower returns to the air separation tower as descending liquid; the process argon gas drawn out from the top of the crude argon tower is compressed, and then heat-exchanged with the reflux gas in the main heat exchanger before entering the bottom pressure process argon condenser of the air separation tower to be condensed into process argon liquid, and the process argon liquid is supercooled and sent to the top of the crude argon tower as reflux liquid; The bottom of the refined argon tower draws out refined argon gas with a purity greater than the set purity; Lead part of the pressure process argon gas from the pressure process argon gas condenser at the bottom of the air separation tower to the pressure process argon gas condenser at the bottom of the refined argon tower to be condensed into process argon gas liquid, and then sent to the middle of the refined argon tower as reflux liquid after being supercooled; Part of the pressure nitrogen introduced from the pressure nitrogen condenser of the air separation tower is condensed into liquid nitrogen in the pressure nitrogen condenser set at the bottom or middle of the refined argon tower, and is sent to the top of the refined argon tower as reflux liquid after supercooling; the non-condensable gas at the top of the refined argon tower is introduced and merged with the dirty nitrogen gas introduced from the upper part of the air separation tower, and then passes through the cooler, the main heat exchanger reheats and recovers the cold energy, and is used as the regeneration gas of the purifier and the air cooling tower.

2. The distillation separation method of the air oxygen, argon and nitrogen ternary system according to claim 1, characterized in that: In step 1, the air is compressed to 4.0-4.4 bar.

3. The distillation separation method of the air oxygen, argon and nitrogen ternary system according to claim 1 is characterized in that: In step 2, the total proportion of the first stream of dry air is 5%-30%, and the critical air pressure is 38 bar; the proportion of the second stream of dry air is 70%-95%.

4. The distillation separation method of the air oxygen, argon and nitrogen ternary system according to claim 1 is characterized in that: In step 2, part of the pressurized dry air is separated from the second dry air as the third dry air. The third dry air, which is the pressurized air without turbocharging, enters the pressurized air condenser arranged at the bottom or middle of the air separation tower to be condensed into liquid air after heat exchange with the reflux air in the main heat exchanger.

5. The distillation separation method of the air oxygen, argon and nitrogen ternary system according to claim 1, characterized in that: Part of the nitrogen drawn from the top of the air separation tower in step 3 is drawn out as product nitrogen.

6. The distillation separation method of the air oxygen, argon and nitrogen ternary system according to claim 1, characterized in that: In step 4, the argon fraction drawn out from the air separation tower contains a specified proportion of argon of 10-12%; the process argon gas drawn out from the top of the crude argon tower is compressed to 2.0-2.5 bar by cryogenic compression or reheating at room temperature.

7. The distillation separation method of the air oxygen, argon and nitrogen ternary system according to claim 1 is characterized by: In step 4, the air separation tower, crude argon tower and refined argon tower all use structured packing; the air separation tower uses 85 theoretical plates; the crude argon tower uses 200 theoretical plates; and the refined argon tower uses 20-30 theoretical plates.

8. The method for fractionation and separation of an air oxygen, argon and nitrogen ternary system according to claim 1, characterized in that: The oxygen drawn out in step 3 is heat exchanged with the positive flow air in the main heat exchanger and reheated to room temperature as product oxygen, and the purity of the oxygen product is not less than 99.5% and contains less than 0.5% argon; the nitrogen drawn out from the top of the air separation tower is heat exchanged with the main heat exchanger and reheated to room temperature, and part of the nitrogen is used as product nitrogen; The purity of the refined argon gas drawn out from the bottom of the refined argon tower is not less than 99.5%, and the refined argon gas is used as the product refined argon gas after heat exchange and reheating in the main heat exchanger.

9. The method for fractionation and separation of an air oxygen, argon and nitrogen ternary system according to claim 1, characterized in that: In step 4, an argon fraction outlet above the bottom of the air separation tower draws out an argon fraction containing a specified proportion of argon, which is directly cryogenically compressed to 1.5-2.0 bar and enters a pressure oxygen-argon mixed gas condenser arranged at the bottom of the air separation tower after heat exchange in the main heat exchanger to be condensed into liquid oxygen-argon mixed gas. After supercooling, the argon fraction is throttled and decompressed and sent to 30 theoretical plates above the bottom of the air separation tower to participate in distillation.

Images