Air separation apparatus and air separation method

Abstract

The present invention provides an air separation apparatus and air separation method that achieve a high argon yield without increasing the heat transfer area of ​​the deoxidized argon condenser that generates reflux liquid in an argon column that produces deoxidized argon, which is the raw material for a high-purity argon column. [Solution] The system comprises an argon column 700 that distills argon-containing oxygen extracted from a low-pressure column 600 to produce deoxidized argon from which oxygen has been removed, a deoxidized argon condenser 400 that produces reflux liquid for the argon column 700, a high-purity argon column 800 that distills the deoxidized argon to collect pure argon from which nitrogen has been removed, a high-purity argon condenser 900 for producing reflux liquid for the top of the high-purity argon column 800, a high-purity argon evaporator 910 for producing rising gas for the bottom of the high-purity argon column 800, a pipeline 622 for supplying liquid nitrogen as a cooling medium to the high-purity argon condenser 900, and a pipeline 42 for supplying liquid generated from the high-pressure column 500 as a heating medium to the high-purity argon evaporator 910.

Description

Technical Field

[0005] , , , ,

[0001] The present invention relates to an air separation apparatus and an air separation method for separating and collecting nitrogen, argon, and oxygen by low-temperature distillation using air as a raw material.

Background Art

[0002] The high-purity argon column of an air separation apparatus is a distillation column equipped with a high-purity argon condenser for generating reflux liquid at the top and a high-purity argon evaporator for generating rising gas at the bottom. The high-purity argon column uses deoxidized argon (argon from which oxygen has been removed) generated in the argon column as a raw material, and separates it into argon gas containing nitrogen gas at the top and pure argon containing almost no nitrogen at the bottom.

[0003] Generally, nitrogen gas supplied from the top of the high-pressure column is used as the heating source of the high-purity argon evaporator. Patent Document 1 discloses that liquid nitrogen liquefied by taking latent heat from nitrogen gas in the high-purity argon evaporator is used as a cooling source for the high-purity argon condenser after being depressurized and its temperature is lowered.

[0004] In addition, in order to prevent argon solidification and blockage in the high-purity argon condenser without loss of the argon collection amount in the air separation apparatus, Patent Document 2 discloses using liquefied air supplied from the bottom of the high-pressure column as the heating source of the high-purity argon evaporator, and using it as a cooling source for the high-purity argon condenser after depressurization.

[0005] In any of the conventional high-purity argon columns, cooling in the high-purity argon condenser and heating in the high-purity argon evaporator are integrated by a heat pump through one heat medium, and heat has been effectively utilized. However, although there are differences in the heat medium between the two conventional technologies, there is no difference in the argon collection amount, and the problem has been to improve the efficiency of heat utilization as an air separation apparatus and increase the argon yield.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2-247484 [Patent Document 2] Japanese Patent Application Publication No. 7-243759 [Overview of the project] [Problems that the invention aims to solve]

[0007] The objective of the present invention is to provide an air separation apparatus and air separation method that achieve a high argon yield without increasing the heat transfer area of ​​the deoxidized argon condenser that generates reflux liquid in an argon column that produces deoxidized argon, which is the raw material for a high-purity argon column. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides the following means.

[0009] [1] An air separation apparatus comprising: a double rectification column for collecting oxygen and nitrogen by low-temperature distillation of air; a main condenser for generating reflux liquid nitrogen for the high-pressure and low-pressure columns of the double rectification column; a subcooler for cooling liquid nitrogen supplied to the low-pressure column and liquid air from the high-pressure column; an argon column for distilling argon-containing oxygen extracted from the low-pressure column to produce deoxidized argon from which oxygen has been removed; a deoxidized argon condenser for generating reflux liquid for the argon column; a high-purity argon column for collecting pure argon from which nitrogen has been removed by distilling the deoxidized argon; a high-purity argon condenser for generating reflux liquid for the top of the high-purity argon column; a high-purity argon evaporator for generating rising gas for the bottom of the high-purity argon column; a pipeline for supplying liquid nitrogen as a cooling medium to the high-purity argon condenser; and a pipeline for supplying liquid generated from the high-pressure column as a heating medium to the high-purity argon evaporator. [2] The air separation apparatus according to [1], characterized in that the pipeline for supplying liquid nitrogen as a cooling medium to the high-purity argon condenser is a pipeline for supplying a portion of the liquid nitrogen supplied to the low-pressure tower. [3] The air separation apparatus according to [1] or [2], characterized in that the pipeline for supplying the liquid generated from the high-pressure tower as a heating medium to the high-purity argon evaporator is a pipeline for supplying liquid air cooled by the supercooler. [4] The air separation apparatus according to [3], characterized in that it includes a pipeline for sending liquid air, which has been cooled in the high-purity argon evaporator and then depressurized, as a cooling medium to the deoxidizing argon condenser, and a pipeline for sending the gas evaporated in the deoxidizing argon condenser and some of the liquid that did not evaporate to the low-pressure tower. [5] The air separation apparatus according to [3], characterized in that it includes a pipeline for sending the liquid separated in the gas-liquid separator as a cooling medium to the deoxidizing argon condenser, via a gas-liquid separator that separates the depressurized liquid air into gas and liquid after it has been cooled in the high-purity argon evaporator, and a pipeline for sending the gas separated in the gas-liquid separator to a position in the low-pressure tower above the position from which the evaporated gas and liquid from the deoxidizing argon condenser are sent to the low-pressure tower. [6] The air separation apparatus according to [2], characterized in that the pipeline for supplying the liquid generated from the high-pressure tower as a heating medium to the high-purity argon evaporator is a pipeline for supplying liquid nitrogen generated in the main condenser. [7] The air separation apparatus according to [1], characterized in that the pipeline for supplying the liquid generated from the high-pressure tower as a heating medium to the high-purity argon evaporator is a pipeline for supplying liquid nitrogen generated in the main condenser, and the pipeline for supplying liquid nitrogen as a cooling medium to the high-purity argon condenser is a pipeline for supplying liquid nitrogen from which sensible heat has been removed as a heating medium in the high-purity argon evaporator as a cooling medium to the high-purity argon condenser. [8] The air separation apparatus according to [6] or [7], characterized by comprising a pipeline for sending liquid air taken from the lower part of the high-pressure tower, cooled in the supercooler, and then depressurized, as a cooling medium to the deoxidizing argon condenser, and a pipeline for sending the gas evaporated in the deoxidizing argon condenser and some of the liquid that did not evaporate to the low-pressure tower. [9] The air separation apparatus according to [6] or [7], characterized in that it includes a pipeline for sending the liquid separated in a gas-liquid separator as a cooling medium to the deoxidizing argon condenser, via a gas-liquid separator that takes out liquid air from the lower part of the high-pressure tower, cools it in the supercooler, and then separates the depressurized liquid air into gas and liquid, and a pipeline for sending the gas separated in the gas-liquid separator to a position in the low-pressure tower above the position from which evaporated gas and liquid from the deoxidizing argon condenser are sent to the low-pressure tower.

[0010]

[10] An air separation method for separating oxygen, nitrogen, and argon by low-temperature distillation of air, comprising the steps of: separating supplied raw material air into oxygen and nitrogen in a compound rectification column; generating reflux liquid nitrogen in a main condenser from the high-pressure and low-pressure columns of the compound rectification column; cooling the liquid nitrogen supplied to the low-pressure column and the liquid air from the high-pressure column in a supercooler; distilling the argon-containing oxygen extracted from the low-pressure column to generate deoxidized argon from which oxygen has been removed in an argon column; and deoxidizing the reflux liquid from the argon column An air separation method characterized by comprising the steps of: generating in an argon condenser; distilling the deoxidized argon to obtain pure argon from which nitrogen has been removed in a high-purity argon column; generating reflux liquid to the top of the high-purity argon column in a high-purity argon condenser; generating rising gas to the bottom of the high-purity argon column in a high-purity argon evaporator; supplying liquid nitrogen to the high-purity argon condenser as a cooling medium; and supplying liquid generated from the high-pressure column to the high-purity argon evaporator as a heating medium.

[11] The air separation method according to

[10] , characterized in that the step of supplying liquid nitrogen as a cooling medium to the high-purity argon condenser is a step of supplying a portion of the liquid nitrogen supplied to the low-pressure tower.

[12] The air separation method according to

[10] or

[11] , characterized in that the step of supplying liquid generated from the high-pressure tower as a heating medium to the high-purity argon evaporator is the step of supplying liquid air cooled in the supercooler.

[13] The air separation method according to

[12] , characterized by comprising the steps of sending liquid air that has been cooled in the high-purity argon evaporator and then depressurized as a cooling medium to the deoxidizing argon condenser, and sending the gas evaporated in the deoxidizing argon condenser and some of the liquid that did not evaporate to the low-pressure tower.

[14] The air separation method according to

[12] , characterized by comprising the steps of: sending the liquid separated in the gas-liquid separator as a cooling medium for the deoxidizing argon condenser via a gas-liquid separator that separates the depressurized liquid air into gas and liquid after it has been cooled in the high-purity argon evaporator; and sending the gas separated in the gas-liquid separator to a position in the low-pressure tower above the position from which the evaporated gas and liquid from the deoxidizing argon condenser are sent to the low-pressure tower.

[15] The air separation method according to

[11] , characterized in that the step of supplying liquid generated from the high-pressure tower as a heating medium to the high-purity argon evaporator is the step of supplying liquid nitrogen generated in the main condenser.

[16] The air separation method according to

[10] , characterized in that the step of supplying liquid generated from the high-pressure tower to the high-purity argon evaporator as a heating medium is a step of supplying liquid nitrogen generated in the main condenser, and the step of supplying liquid nitrogen to the high-purity argon condenser as a cooling medium is a step of supplying liquid nitrogen from which sensible heat has been removed as a heating medium in the high-purity argon evaporator as a cooling medium to the high-purity argon condenser.

[17] The air separation method according to

[15] or

[16] , characterized by comprising the steps of: taking liquid air from the lower part of the high-pressure tower, cooling it in the supercooler, and then sending the depressurized liquid air as a cooling medium to the deoxidizing argon condenser; and sending the gas evaporated in the deoxidizing argon condenser and some of the liquid that did not evaporate to the low-pressure tower.

[18] A step of taking out from the lower part of the high-pressure column, cooling with the subcooler, and then sending the depressurized liquid air through a gas-liquid separator that separates it into gas and liquid, and sending the liquid separated by the gas-liquid separator as a cooling medium to the deoxidized argon condenser; and a step of sending the gas separated by the gas-liquid separator to a position above the position where the evaporation gas and liquid from the deoxidized argon condenser are sent to the low-pressure column in the low-pressure column. The air separation method according to

[15] or

[16] , characterized by comprising the above steps.

Advantages of the Invention

[0011] According to the present invention, the argon yield can be increased without increasing the heat transfer area of the deoxidized argon condenser that generates the reflux liquid in the argon column that produces deoxidized argon as the raw material for the high-purity argon column.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic diagram showing the air separation apparatus of the first embodiment. [Figure 2] It is a schematic diagram showing the air separation apparatus of the second embodiment. [Figure 3] It is a schematic diagram showing the air separation apparatus of the third embodiment. [Figure 4] It is a schematic diagram showing the air separation apparatus of the fourth embodiment. [Figure 5] It is a schematic diagram showing the air separation apparatus of the fifth embodiment. [Figure 6] It is a schematic diagram showing the air separation apparatus of the comparative example.

Modes for Carrying Out the Invention

[0013] Hereinafter, the present invention will be described based on preferred embodiments. The air separation apparatus and air separation method of the present invention separate air by low-temperature distillation to separate oxygen, nitrogen, and argon.

[0014] FIG. 1 is a schematic diagram showing an air separation apparatus according to the first embodiment. The air separation apparatus 101 of the first embodiment includes a high-pressure column 500, a low-pressure column 600, an argon column 700, and a high-purity argon column 800. The high-pressure column 500, the low-pressure column 600, the argon column 700, and the high-purity argon column 800 are housed in a cold box 100. The argon column 700 in the illustrated example consists of a crude argon column 710 and a deoxidation column 720.

[0015] The high-pressure column 500 and the low-pressure column 600 constitute a dual rectification column 140. The dual rectification column 140 performs a process of cryogenic distillation of air to separate it into oxygen and nitrogen. The dual rectification column 140 includes a main condenser 300. The main condenser 300 performs a process of generating reflux liquid nitrogen for the high-pressure column 500 and the low-pressure column 600.

[0016] The air separation apparatus 101 includes a subcooler 202 for cooling the liquid nitrogen supplied to the low-pressure column 600 and the liquid air from the high-pressure column 500. The subcooler 202 performs a process of cooling the liquid nitrogen supplied to the low-pressure column 600 via a pipeline 62 and cooling the liquid air taken out from the high-pressure column 500 via pipelines 41 and 51.

[0017] The raw air supplied to the air separation apparatus 101 is compressed by a compressor 111 and purified by a purification device 112. In the purification device 112, carbon dioxide, water vapor, etc. are removed from the raw air. Then, a part of the raw air is sent to a turbine 122 via a booster 121 through a pipeline 21. The raw air sent to the turbine 122 is adiabatically expanded and then supplied to the middle part of the low-pressure column 600 through a pipeline 123.

[0018] The remaining raw air is supplied to the bottom of the high-pressure tower 500 via pipeline 22, and as it rises through the high-pressure tower 500, nitrogen, a low-boiling point component, is concentrated through gas-liquid contact with the reflux liquid flowing down the tower. This generates nitrogen gas at the top of the high-pressure tower 500. In addition, as the reflux liquid flows down the high-pressure tower 500, oxygen, a high-boiling point component, is enriched. This generates oxygen-enriched liquid air at the bottom of the high-pressure tower 500. The liquid air taken out from the bottom of the high-pressure tower 500 is cooled in the supercooler 202 via pipeline 51, then depressurized and supplied to the low-pressure tower 600 via pipeline 52.

[0019] As the liquid air supplied to the low-pressure tower 600 flows down through gas-liquid contact with the rising gas within the tower, the high-boiling-point component, oxygen, is concentrated. This generates liquid oxygen at the bottom of the low-pressure tower 600. Additionally, as the rising gas within the low-pressure tower 600 rises, the low-boiling-point component, nitrogen, is concentrated. This generates nitrogen gas at the top of the low-pressure tower 600. The nitrogen gas 161 extracted from the top of the low-pressure tower 600 is heated in the supercooler 202 and the main heat exchanger 201 before being recovered as product nitrogen gas 162.

[0020] Argon-enriched oxygen is extracted from the bottom of the low-pressure column 600 and supplied to the argon column 700 via the pipeline 31. Examples of the composition of the argon-enriched oxygen include 0.01-0.05% nitrogen and 5-15% argon. The argon column 700 performs a process of distilling the argon-containing oxygen extracted from the low-pressure column 600 to produce deoxidized argon from which the oxygen has been removed. Argon-containing oxygen is oxygen enriched with argon.

[0021] The argon column 700 in the illustrated example is divided into a crude argon column 710 and a deoxidation column 720. The crude argon column 710 and the deoxidation column 720 are connected by pipes 71 and 72. The argon column 700 may consist of a single column, but it is preferable to divide it into two columns so that the height of the cold box 100 can be reduced.

[0022] If the argon column 700 is divided into a crude argon column 710 and a deoxidation column 720, the pressure in the deoxidation column 720 may be adjusted using a valve 70 installed in a pipeline 71 connecting the top of the crude argon column 710 to the bottom of the deoxidation column 720. A pressure reducing valve is an example of the valve 70. A pump 73 is provided in a pipeline 72 connecting the bottom of the deoxidation column 720 to the top of the crude argon column 710.

[0023] As the argon-enriched oxygen supplied to the argon column 700 rises within the column, the low-boiling-point component, argon, is concentrated through gas-liquid contact with the reflux liquid flowing down within the argon column 700. As a result, deoxidized argon is generated at the top of the deoxidation column 720. Deoxidized argon is argon from which oxygen has been removed, and its composition is exemplified by 0.3-1.5% nitrogen and 0.1-10 ppm oxygen. In addition, as the reflux liquid flows down within the argon column 700, the high-boiling-point component, oxygen, is concentrated. The oxygen-concentrated component is returned from the bottom of the crude argon column 710 to the position where the argon-enriched oxygen was extracted from the low-pressure column 600, via the pipeline 32.

[0024] The liquid oxygen generated at the bottom of the low-pressure tower 600 is supplied to the main condenser 300, where it exchanges heat with nitrogen gas supplied to the main condenser 300 from the top of the high-pressure tower 500 via pipeline 301 to produce oxygen gas, which becomes the rising gas in the low-pressure tower 600. Liquid oxygen that does not evaporate in the main condenser 300 is removed from the bottom of the low-pressure tower 600 and recovered as product liquid oxygen 163. Furthermore, a portion of the liquid oxygen is pressurized by pump 164, then evaporated in the main heat exchanger 201 and recovered as product oxygen gas 165.

[0025] Meanwhile, the liquid nitrogen generated by heat exchange in the main condenser 300 is returned to the high-pressure tower 500 as reflux liquid via pipeline 61, and a portion of the liquid nitrogen is cooled in the supercooler 202. A portion of the liquid nitrogen cooled in the supercooler 202 is supplied as reflux liquid to the low-pressure tower 600 via pipelines 62 and 621, and the remainder is supplied as a cooling medium to the high-purity argon condenser 900 via pipeline 622.

[0026] The deoxidized argon generated at the top of the deoxidation column 720 is supplied to the deoxidized argon condenser 400 via pipeline 721, where it exchanges heat with oxygen-enriched liquid air supplied from the bottom of the high-pressure column 500 via pipelines 41, 42, and 43. Of the deoxidized liquid argon generated by the heat exchange, a portion is returned to the deoxidation column 720 via pipeline 722, while the remainder is supplied to the high-purity argon column 800 via pipeline 723. The deoxidized argon supplied to the high-purity argon column 800 may be deoxidized argon gas that did not condense in the deoxidized argon condenser 400, but deoxidized liquid argon is preferred.

[0027] The deoxidizing argon condenser 400 performs the process of generating reflux liquid for the argon column 700. In the illustrated example, the deoxidizing argon condenser 400 is located at the top of the deoxidizing column 720. If the crude argon column 710 and the deoxidizing column 720 are not separated, the deoxidizing argon condenser 400 is located at the top of the argon column 700.

[0028] The high-purity argon column 800 performs a process of distilling deoxidized argon to obtain pure argon from which nitrogen has been removed. The high-purity argon column 800 is equipped with a high-purity argon condenser 900 for generating reflux liquid to the top of the column and a high-purity argon evaporator 910 for generating rising gas to the bottom of the column.

[0029] The deoxidized liquid argon supplied to the high-purity argon column 800 becomes concentrated as it flows down through gas-liquid contact with the rising gas within the column, resulting in the formation of argon, which is a high-boiling-point component. As a result, liquid pure argon from which nitrogen has been removed is produced at the bottom of the high-purity argon column 800. Of the liquid pure argon, some is supplied to the high-purity argon evaporator 910 via pipeline 911, while the remainder is recovered as product liquid argon via pipeline 920. The high-purity argon evaporator 910 performs the process of generating rising gas at the bottom of the high-purity argon column 800.

[0030] Furthermore, as the rising gas in the high-purity argon column 800 ascends, nitrogen, a low-boiling-point component, becomes concentrated. As a result, argon gas containing nitrogen gas is generated at the top of the high-purity argon column 800 and supplied to the high-purity argon condenser 900 via the pipeline 901. In the illustrated example, the high-purity argon condenser 900 is located at the top of the high-purity argon column 800. The high-purity argon condenser 900 performs the process of generating reflux liquid at the top of the high-purity argon column 800.

[0031] The nitrogen-containing argon gas supplied to the high-purity argon condenser 900 exchanges heat with liquid nitrogen supplied from pipeline 622 as a cooling medium to produce liquid argon. The liquid nitrogen supplied from pipeline 622 is part of the liquid nitrogen supplied to the low-pressure tower 600 from pipelines 62 and 621.

[0032] The liquid argon produced in the high-purity argon condenser 900 is returned to the high-purity argon column 800 via pipeline 902. Nitrogen-containing argon gas that does not condense in the high-purity argon condenser 900 is released into the atmosphere via pipeline 905. The nitrogen content in the nitrogen-containing argon gas is, for example, around 50%.

[0033] The pipeline 903 for extracting exhaust gas from the high-purity argon condenser 900 may merge with the pipeline 904 for extracting exhaust gas from the low-pressure tower 600. These exhaust gases, after passing through the supercooler 202, are used together with nitrogen gas 161 and liquid oxygen pressurized by the pump 164 to cool the raw material air by heat exchange in the main heat exchanger 201.

[0034] The air separation apparatus 101 of the first embodiment includes a pipeline 42 that carries liquid air cooled in a supercooler 202 as a heating medium supplied to a high-purity argon evaporator 910. In the illustrated example, liquid air supplied from the high-pressure tower 500 via pipeline 41 is cooled in the supercooler 202 and then supplied to the high-purity argon evaporator 910 via pipeline 42.

[0035] The liquid pure argon supplied to the high-purity argon evaporator 910 exchanges heat with liquid air supplied from the high-pressure tower 500 via pipelines 41 and 42 to produce pure argon gas. The pure argon gas produced in the high-purity argon evaporator 910 is returned to the high-purity argon tower 800 via pipeline 913 and becomes rising gas.

[0036] In the illustrated example, a gas-liquid separator 912 is provided between the bottom of the high-purity argon column 800 and the high-purity argon evaporator 910. Liquid pure argon extracted from the bottom of the high-purity argon column 800 is supplied to the high-purity argon evaporator 910 via the gas-liquid separator 912. In addition, the gaseous component of the pure argon coming out of the high-purity argon evaporator 910, which has been separated from the liquid component by the gas-liquid separator 912, is supplied to the high-purity argon column 800 via a pipe 913.

[0037] In the illustrated example, the liquid air used as the heating medium for the high-purity argon evaporator 910 is the oxygen-enriched liquid air at the bottom of the high-pressure tower 500, which is cooled in the supercooler 202 before being supplied to the high-purity argon evaporator 910. The oxygen-enriched liquid air, from which sensible heat has been removed in the high-purity argon evaporator 910, is depressurized and supplied as a cooling medium to the deoxidized argon condenser 400 via the pipeline 43.

[0038] A portion of the liquid air supplied to the deoxidizing argon condenser 400 evaporates and is supplied to the low-pressure tower 600 via pipeline 401. In addition, the oxygen-enriched liquid air that did not evaporate in the deoxidizing argon condenser 400 is further enriched with oxygen and supplied to the low-pressure tower 600 via pipeline 402.

[0039] Figure 2 is a schematic diagram showing an air separation apparatus of the second embodiment. The air separation apparatus 102 of the second embodiment is the same as the first embodiment in that it includes a high-pressure tower 500, a low-pressure tower 600, an argon tower 700, a high-purity argon tower 800, etc.

[0040] In the air separation apparatus 102 of the second embodiment, the oxygen-enriched liquid air from which sensible heat has been removed in the high-purity argon evaporator 910 is depressurized and supplied to the gas-liquid separator 404 via the pipeline 43. The liquid separated in the gas-liquid separator 404 is supplied to the deoxidizing argon condenser 400 as a cooling medium. On the other hand, the gas separated in the gas-liquid separator 404 is supplied to the low-pressure tower 600 via the pipeline 403. The position at which this gas is supplied to the low-pressure tower 600 via the pipeline 403 (height in the low-pressure tower 600) is higher than the position at which the evaporated gas and liquid from the deoxidizing argon condenser 400 are supplied to the low-pressure tower 600 via the pipelines 401 and 402.

[0041] Figure 3 is a schematic diagram showing an air separation apparatus of the third embodiment. The air separation apparatus 103 of the third embodiment is the same as the first embodiment in that it includes a high-pressure tower 500, a low-pressure tower 600, an argon tower 700, a high-purity argon tower 800, etc.

[0042] In the air separation apparatus 103 of the third embodiment, liquid nitrogen produced in the main condenser 300 is used as the heating medium for the high-purity argon evaporator 910. In this case, the liquid nitrogen generated from the high-pressure tower 500 is sent to the high-purity argon evaporator 910 via the pipeline 631. The liquid nitrogen used as the heating medium is cooled in the supercooler 202 via the pipeline 63 and supplied to the low-pressure tower 600 via pipelines 62 and 621.

[0043] Furthermore, in the third embodiment, the liquid air, which has been cooled in the subcooler 202 via the pipeline 41 from the lower part of the high-pressure tower 500 and then depressurized, is supplied as a cooling medium to the deoxidized argon condenser 400 via the pipeline 42, without passing through the high-purity argon evaporator 910.

[0044] As in the first embodiment, the liquid nitrogen used as the cooling medium for the high-purity argon condenser 900 is a portion of the liquid nitrogen cooled in the supercooler 202, as in the third embodiment. The pipeline 62 through which the liquid nitrogen cooled in the supercooler 202 is delivered is branched into pipeline 621, which supplies liquid nitrogen as reflux liquid for the low-pressure tower 600, and pipeline 622, which supplies liquid nitrogen as the cooling medium for the high-purity argon condenser 900.

[0045] Figure 4 is a schematic diagram showing an air separation apparatus of the fourth embodiment. The air separation apparatus 104 of the fourth embodiment is the same as the first and third embodiments in that it includes a high-pressure tower 500, a low-pressure tower 600, an argon tower 700, a high-purity argon tower 800, etc.

[0046] Furthermore, in the fourth embodiment, as in the third embodiment, the reduced-pressure liquid air is supplied to the deoxidized argon condenser 400 via pipeline 42 after being cooled in the supercooler 202 from the lower part of the high-pressure tower 500 via pipeline 41. Furthermore, although not specifically shown in the figures, in the fourth embodiment, as in the fifth embodiment described later, a gas-liquid separator 404 may be provided in the pipeline 42, and only the separated liquid may be supplied to the deoxidizing argon condenser 400. In this case, as in the fifth embodiment, the gas separated in the gas-liquid separator 404 is supplied to a position above the supply position of pipelines 401 and 402 in the low-pressure tower 600 via pipeline 403, which is separate from pipelines 401 and 402, without passing through the deoxidizing argon condenser 400.

[0047] Furthermore, the fourth embodiment is similar to the third embodiment in that it includes a pipeline 631 for supplying liquid nitrogen produced in the main condenser 300 as a heating medium to the high-purity argon evaporator 910. The liquid nitrogen used as a heating medium is cooled in the supercooler 202 via pipeline 63 and supplied to the low-pressure tower 600 via pipeline 62.

[0048] In the fourth embodiment, the air separation device 104 utilizes a portion of the liquid nitrogen used as the heating medium for the high-purity argon evaporator 910 as a cooling source for the high-purity argon condenser 900. Therefore, a pipeline 64 branches off from pipeline 63, which carries liquid nitrogen from which sensible heat has been removed as a heating medium, to carry a portion of the liquid nitrogen to the high-purity argon condenser 900.

[0049] Figure 5 is a schematic diagram showing an air separation apparatus of the fifth embodiment. The air separation apparatus 105 of the fifth embodiment is the same as the first and third embodiments in that it includes a high-pressure tower 500, a low-pressure tower 600, an argon tower 700, a high-purity argon tower 800, etc.

[0050] In the air separation apparatus 105 of the fifth embodiment, the depressurized liquid air, cooled in the subcooler 202 via pipe 41 from the lower part of the high-pressure tower 500, is supplied to the gas-liquid separator 404 via pipe 42. The liquid separated in the gas-liquid separator 404 is supplied to the deoxidizing argon condenser 400 as a cooling medium. On the other hand, the gas separated in the gas-liquid separator 404 is supplied to the low-pressure tower 600 via pipe 403. The position at which this gas is supplied to the low-pressure tower 600 via pipe 403 (height in the low-pressure tower 600) is higher than the position at which the evaporated gas and liquid from the deoxidizing argon condenser 400 are supplied to the low-pressure tower 600 via pipes 401 and 402.

[0051] The air separation devices 101, 102, 103, 104, and 105 of the first to fifth embodiments include pipelines (pipelines 622 in Figures 1-3 and 5, and pipeline 64 in Figure 4) that supply liquid nitrogen as a cooling medium to the high-purity argon condenser 900, and pipelines (pipelines 42 in Figures 1-2, and pipeline 631 in Figures 3-5) that supply liquid generated from the high-pressure tower 500 as a heating medium to the high-purity argon evaporator 910.

[0052] The high-purity argon condenser 900 generates reflux liquid for the high-purity argon column 800, which collects pure argon, and the high-purity argon evaporator 910 generates rising gas for the high-purity argon column 800. By using liquid nitrogen as the cooling medium for the high-purity argon condenser 900 and the liquid produced from the high-pressure column 500 as the heating medium for the high-purity argon evaporator 910, the argon yield can be increased without increasing the heat transfer area of ​​the deoxidation argon condenser 400, which is the top condenser of the argon column 700 that produces the raw materials for the high-purity argon column 800.

[0053] If the heating medium for the high-purity argon evaporator 910 is liquid nitrogen produced from the high-pressure tower 500, a portion of the supplied liquid nitrogen may be used as the cooling medium for the high-purity argon condenser 900. If the heating medium for the high-purity argon evaporator 910 is liquid air produced from the high-pressure tower 500, a portion of the liquid nitrogen produced from the high-pressure tower 500 can be used as the cooling medium for the high-purity argon condenser 900. The liquid air produced from the high-pressure tower 500 may have a different composition from the purified raw material air; for example, it may be oxygen-enriched liquid air.

[0054] Although the air separation apparatus and air separation method of the present invention have been described above based on preferred embodiments, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. Modifications include adding, substituting, omitting, or otherwise changing the components in each embodiment. It is also possible to combine components used in two or more embodiments as appropriate. [Examples]

[0055] The present invention will be specifically described below with reference to examples.

[0056] <Comparison of Example 1 and Comparative Example> In Example 1, the air separation device 101 shown in Figure 1 was used. In the comparative example, the air separation device 106 shown in Figure 6 was used.

[0057] In the comparative example air separation apparatus 106, a portion of the nitrogen gas at the top of the high-pressure tower 500 is used as a heating medium for the high-purity argon evaporator 910. Therefore, a pipeline 302 is arranged to supply nitrogen gas to the high-purity argon evaporator 910 from a pipeline 301 that sends nitrogen gas from the top of the high-pressure tower 500 to the main condenser 300. The nitrogen gas supplied to the high-purity argon evaporator 910 condenses with liquid pure argon through heat exchange to produce liquid nitrogen. The liquid nitrogen produced in the high-purity argon evaporator 910 is depressurized to lower its temperature and then supplied to the high-purity argon condenser 900 via pipeline 64, where it is used as a cooling source.

[0058] [Table 1]

[0059] The meanings of the quantities shown in Table 1 are as follows: "Product oxygen quantity" represents the total amount of product liquid oxygen 163 and product oxygen gas 165 extracted from the bottom of the low-pressure tower 600. "Amount of raw material air" represents the total amount of raw material air supplied into the cold box 100 via the compressor 111 and the purification device 112, and then through the pipelines 21 and 22. "Amount of oxygen gas produced in the main condenser" represents the amount of oxygen gas produced in the main condenser 300 when liquid oxygen generated at the bottom of the low-pressure tower 600 exchanges heat with nitrogen gas supplied from the top of the high-pressure tower 500. "Amount of nitrogen at the top of the low-pressure tower" represents the amount of nitrogen gas generated at the top of the low-pressure tower 600. "Amount of refluxed liquid nitrogen supplied to the low-pressure tower" refers to the amount of liquid nitrogen supplied from pipelines 62 and 621 as reflux liquid to the low-pressure tower 600. "Feed argon amount" represents the amount of argon-enriched oxygen supplied to the argon column 700 via pipeline 31. "Product argon amount" refers to the amount of liquid product argon recovered from the bottom of the high-purity argon column 800 via pipeline 920. "Amount of cooling medium supplied to the deoxidizing argon condenser" refers to the amount of cooling medium supplied to the deoxidizing argon condenser 400. "Amount of cooling medium supplied to the high-purity argon condenser" refers to the amount of cooling medium supplied to the high-purity argon condenser 900. The values ​​shown in Table 1 and above are relative values ​​with the raw air amount set to 100. "L / V at the bottom of the low-pressure tower" refers to the gas-liquid flow rate ratio (L / V) at the bottom of the low-pressure tower 600. "Argon concentration in feed argon" is the argon concentration [%] contained in argon-enriched oxygen supplied to the argon column 700 via pipeline 31.

[0060] As shown in Table 1, the amount of product argon increases in Example 1 (Figure 1) compared to the Comparative Example (Figure 6). In the Comparative Example, a portion of the nitrogen gas at the top of the high-pressure tower 500 is used in the high-purity argon evaporator 910, whereas in Example 1, the nitrogen gas is not extracted and the entire amount is supplied to the main condenser 300. As a result, the amount of oxygen gas produced in the main condenser 300 increases, the amount of rising gas in the low-pressure tower 600 increases, and the argon concentration in the feed argon increases. This is considered to be the reason for the increase in argon yield in Example 1.

[0061] On the other hand, in the air separation apparatus (not shown) described in Figure 1 of Patent Document 2, a portion of the oxygen-enriched liquid air used as the heating medium for the high-purity argon evaporator 910 is separated, depressurized, and then used as the cooling medium for the high-purity argon condenser 900. As a result, the amount supplied to the deoxidized argon condenser 400 decreases, so the evaporation rate must be reduced so that the temperature difference in the deoxidized argon condenser 400 does not become small. In other words, the amount of argon-enriched oxygen, which is the raw material for deoxidized argon in the argon column 700, cannot be increased, and therefore the amount of product argon cannot be increased.

[0062] <Comparison of Examples 1-3 and Comparative Examples> Table 2 shows the amount of product argon and the heat transfer area of ​​the deoxidizing argon condenser 400 in each process. In Example 1, the air separation apparatus 101 shown in Figure 1 was used. In Example 2, the air separation apparatus 103 shown in Figure 3 was used. In Example 3, the air separation apparatus 105 shown in Figure 5 was used. In the comparative example, the air separation apparatus 106 shown in Figure 6 was used.

[0063] [Table 2]

[0064] In Table 2, the amount of product argon and the heat transfer area of ​​the deoxidizing argon condenser 400 are relative values ​​with Comparative Example 1 (Figure 6) set to 100. The amount of product argon in the Comparative Example and Example 1 corresponds to 0.66 and 0.68 in Table 1, respectively, but each includes errors due to rounding. For the reasons stated above, in Examples 1 to 3 (Figures 1, 3, and 5), the heat transfer area of ​​the deoxidizing argon condenser 400 is about the same as in the Comparative Example (Figure 6), but the amount of product argon increases. Therefore, in each example, it was possible to increase the argon yield (the ratio of product argon amount to raw material air amount) without increasing the heat transfer area of ​​the deoxidizing argon condenser. [Industrial applicability]

[0065] According to the present invention, when separating oxygen, nitrogen, and argon by low-temperature distillation of air, the argon yield can be increased without increasing the heat transfer area of ​​the deoxidizing argon condenser. [Explanation of Symbols]

[0066] 21,22,31,32,41,42,43,51,52,61,62,63,64…Pipelines, 70…Valves, 71,72…Pipelines, 73…Pumps, 100…Cold boxes, 101,102,103,104,105,106…Air separation units, 111…Compressors, 112…Purification units, 121…Step-up pumps, 122…Turbines, 123…Pipelines, 140…Double rectification columns, 161…Nitrogen gas, 162…Product nitrogen gas, 163…Product liquid oxygen, 164…Pumps, 165…Product oxygen gas, 201…Main heat exchangers, 202…Supercooling Equipment, 300... Main condenser, 301, 302... Pipeline, 400... Deoxidation argon condenser, 401, 402, 403... Pipeline, 404... Gas-liquid separator, 500... High-pressure tower, 600... Low-pressure tower, 621, 622, 631... Pipeline, 700... Argon tower, 710... Crude argon tower, 720... Deoxidation tower, 721, 722, 723... Pipeline, 800... High-purity argon tower, 900... High-purity argon condenser, 901, 902, 903, 904, 905... Pipeline, 910... High-purity argon evaporator, 911... Pipeline, 912... Gas-liquid separator, 913, 920... Pipeline.

Claims

1. A compound rectification column for extracting oxygen and nitrogen by low-temperature distillation of air, The main condenser that generates reflux liquid nitrogen in the high-pressure column and low-pressure column of the aforementioned compound rectification column, A supercooler for cooling liquid nitrogen supplied to the low-pressure tower and liquid air from the high-pressure tower, An argon column that distills argon-containing oxygen extracted from the low-pressure column to produce deoxidized argon from which oxygen has been removed, A deoxidizing argon condenser that generates reflux liquid from the argon column, A high-purity argon column for distilling the deoxidized argon to obtain pure argon from which nitrogen has been removed, A high-purity argon condenser for generating reflux liquid to the top of the high-purity argon column, A high-purity argon evaporator for generating rising gas to the bottom of the high-purity argon tower, A pipeline for supplying liquid nitrogen as a cooling medium to the aforementioned high-purity argon condenser, A pipeline for supplying the liquid generated from the high-pressure tower as a heating medium to the high-purity argon evaporator, An air separation device characterized by comprising:

2. The air separation apparatus according to claim 1, characterized in that the pipeline for supplying liquid nitrogen as a cooling medium to the high-purity argon condenser is a pipeline for supplying a portion of the liquid nitrogen supplied to the low-pressure tower.

3. The air separation apparatus according to claim 1 or 2, characterized in that the pipeline that supplies the liquid generated from the high-pressure tower as a heating medium to the high-purity argon evaporator is a pipeline that supplies liquid air cooled by the supercooler.

4. The air separation apparatus according to claim 3, further comprising a pipeline for sending the depressurized liquid air, which has been cooled in the high-purity argon evaporator, as a cooling medium to the deoxidizing argon condenser, and a pipeline for sending the gas evaporated in the deoxidizing argon condenser and some of the unevaporated liquid to the low-pressure tower.

5. The air separation apparatus according to claim 3, further comprising: a pipeline for sending the liquid separated in the gas-liquid separator as a cooling medium to the deoxidizing argon condenser, via a gas-liquid separator that separates the depressurized liquid air into gas and liquid after it has been cooled in the high-purity argon evaporator; and a pipeline for sending the gas separated in the gas-liquid separator to a position in the low-pressure tower above the position from which the evaporated gas and liquid from the deoxidizing argon condenser are sent to the low-pressure tower.

6. The air separation apparatus according to claim 2, characterized in that the pipeline that supplies the liquid generated from the high-pressure tower as a heating medium to the high-purity argon evaporator is a pipeline that supplies liquid nitrogen generated in the main condenser.

7. The pipeline that supplies the liquid generated from the high-pressure tower as a heating medium to the high-purity argon evaporator is the pipeline that supplies the liquid nitrogen produced in the main condenser. The air separation apparatus according to claim 1, characterized in that the pipeline for supplying liquid nitrogen as a cooling medium to the high-purity argon condenser is a pipeline for supplying liquid nitrogen, from which sensible heat has been removed as a heating medium in the high-purity argon evaporator, as a cooling medium to the high-purity argon condenser.

8. The air separation apparatus according to claim 6 or 7, further comprising: a pipeline for sending liquid air, which is taken from the lower part of the high-pressure tower, cooled in the supercooler, and then depressurized, as a cooling medium to the deoxidizing argon condenser; and a pipeline for sending the gas evaporated in the deoxidizing argon condenser and some of the unevaporated liquid to the low-pressure tower.

9. The air separation apparatus according to claim 6 or 7, further comprising: a pipeline for sending the liquid separated in the gas-liquid separator as a cooling medium to the deoxidizing argon condenser, via a gas-liquid separator that extracts liquid air from the lower part of the high-pressure tower, cools it in the supercooler, and then separates the depressurized liquid air into gas and liquid; and a pipeline for sending the gas separated in the gas-liquid separator to a position in the low-pressure tower above the position from which evaporated gas and liquid from the deoxidizing argon condenser are sent to the low-pressure tower.

10. An air separation method that separates oxygen, nitrogen, and argon by low-temperature distillation of air, The process involves separating the supplied raw material air into oxygen and nitrogen in a compound rectification column, The process involves generating reflux liquid nitrogen in the high-pressure and low-pressure columns of the aforementioned compound rectification column using the main condenser, A step of cooling the liquid nitrogen supplied to the low-pressure tower and the liquid air from the high-pressure tower with a supercooler, The process involves distilling the argon-containing oxygen extracted from the low-pressure column to remove the oxygen, thereby generating deoxidized argon in an argon column. The process involves generating reflux liquid from the argon column in a deoxidized argon condenser, The process involves distilling the deoxidized argon to remove nitrogen and collecting pure argon in a high-purity argon column, The process involves generating reflux liquid to the top of the aforementioned high-purity argon column using a high-purity argon condenser, The process involves generating the rising gas at the bottom of the aforementioned high-purity argon tower using a high-purity argon evaporator, The process of supplying liquid nitrogen as a cooling medium to the aforementioned high-purity argon condenser, The process of supplying the liquid generated from the high-pressure tower as a heating medium to the high-purity argon evaporator, An air separation method characterized by comprising the following:

11. The air separation method according to claim 10, characterized in that the step of supplying liquid nitrogen as a cooling medium to the high-purity argon condenser is a step of supplying a portion of the liquid nitrogen to be supplied to the low-pressure tower.

12. The air separation method according to claim 10 or 11, characterized in that the step of supplying liquid generated from the high-pressure tower as a heating medium to the high-purity argon evaporator is a step of supplying liquid air cooled in the supercooler.

13. The air separation method according to claim 12, further comprising the steps of: sending the depressurized liquid air, after being cooled in the high-purity argon evaporator, as a cooling medium for the deoxidizing argon condenser; and sending the gas evaporated in the deoxidizing argon condenser and some of the unevaporated liquid to the low-pressure tower.

14. The air separation method according to claim 12, further comprising the steps of: sending the liquid separated in the gas-liquid separator as a cooling medium for the deoxidizing argon condenser via a gas-liquid separator that separates the depressurized liquid air into gas and liquid after it has been cooled in the high-purity argon evaporator; and sending the gas separated in the gas-liquid separator to a position in the low-pressure tower above the position from which the evaporated gas and liquid from the deoxidizing argon condenser are sent to the low-pressure tower.

15. The air separation method according to claim 11, characterized in that the step of supplying liquid generated from the high-pressure tower as a heating medium to the high-purity argon evaporator is a step of supplying liquid nitrogen generated in the main condenser.

16. The step of supplying the liquid generated from the high-pressure tower as a heating medium to the high-purity argon evaporator is the step of supplying the liquid nitrogen generated in the main condenser. The air separation method according to claim 10, characterized in that the step of supplying liquid nitrogen as a cooling medium to the high-purity argon condenser is a step of supplying liquid nitrogen from which sensible heat has been removed as a heating medium in the high-purity argon evaporator as a cooling medium to the high-purity argon condenser.

17. The air separation method according to claim 15 or 16, further comprising the steps of: taking liquid air from the lower part of the high-pressure tower, cooling it in the supercooler, and then sending the depressurized liquid air as a cooling medium to the deoxidizing argon condenser; and sending the gas evaporated in the deoxidizing argon condenser and some of the liquid that did not evaporate to the low-pressure tower.

18. The air separation method according to claim 15 or 16, comprising the steps of: taking liquid air from the lower part of the high-pressure tower, cooling it in the supercooler, and then sending the liquid separated in the gas-liquid separator as a cooling medium for the deoxidizing argon condenser via a gas-liquid separator; and sending the gas separated in the gas-liquid separator to a position in the low-pressure tower above the position from which evaporated gas and liquid from the deoxidizing argon condenser are sent to the low-pressure tower.

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