Air separation method and air separation device

Abstract

Provided are an air separation method and an air separation device with which it is possible to improve the argon recovery rate while maintaining the oxygen recovery rate or suppressing a decrease in the oxygen recovery rate. The method includes a high-pressure separation step for separating high-pressure raw material air, a turbine air generation step for generating medium-pressure turbine air, a turbine air compression step for generating high-pressure turbine air, a turbine air adiabatic expansion step for generating low-pressure turbine air, and a low-pressure separation step for separating the low-pressure turbine air. An argon separation step for separating argon-rich liquefied oxygen, an argon condensation step for generating liquefied argon and low-pressure oxygen gas, a high-pressure nitrogen condensation step for generating high-pressure liquefied nitrogen and medium-pressure oxygen gas, and a product argon exporting step for extracting argon, a turbine air compression step for compressing medium-pressure turbine air using the energy generated by the turbine air adiabatic expansion step, the method further includes a raw material air bypass step in which a portion of the high-pressure raw material air is branched and decompressed and then merges with the high-pressure turbine air.

Description

Technical Field

[0001] The present invention relates to an air separation method and an air separation apparatus. Background Art

[0002] Heretofore, as a method for industrially producing oxygen or nitrogen, a method of producing by cryogenic distillation using air as a raw material (air separation method) and an apparatus for the method (air separation apparatus) have been generally known.

[0003] For example, Patent Document 1 below proposes an air separation method using an air separation apparatus, the air separation apparatus including a high-pressure column, a low-pressure column, an argon column, an indirect heat exchanger for indirectly heat-exchanging the low-pressure liquefied oxygen at the bottom of the low-pressure column and the argon gas at the top of the argon column, and an indirect heat exchanger for indirectly heat-exchanging the medium-pressure liquefied oxygen at the bottom of the argon column and the high-pressure nitrogen gas at the top of the high-pressure column. According to Patent Document 1, more product high-pressure nitrogen can be recovered while maintaining or improving the argon recovery rate, and the overall power consumption of the apparatus including the compression power of the product gas can be reduced.

[0004] In addition, in Patent Document 1 Figure 1 there is disclosed an apparatus in which the high-pressure oxygen-rich liquefied air led out from the bottom of the high-pressure column is gasified by an indirect heat exchanger after being depressurized to generate medium-pressure oxygen-rich air, which is compressed by a turbo blower and adiabatically expanded by an expansion turbine, and supplied to the low-pressure column. According to Patent Document 1, as described above, by using the oxygen-rich air for the expansion turbine, the oxygen concentration of the air supplied to the low-pressure column becomes higher than in the case of using a part of the raw material air for the expansion turbine, and thus the argon recovery rate is improved.

[0005] However, generally, in the cryogenic air separation apparatus disclosed in Patent Document 1, as described above, an expansion turbine for generating cold is required, and the more the amount of liquid product, the more cold is required, so the processing flow rate of the expansion turbine increases. On the other hand, in the case of a general air separation apparatus configured to supply the air adiabatically expanded in the expansion turbine to the low-pressure column, if the flow rate of the low-pressure turbine air increases too much, there is a tendency for the argon recovery rate to decrease due to the reduction of the ascending gas in the lower part of the low-pressure column.

[0006] As a means for suppressing the decrease in the argon recovery rate as described above, Patent Document 2 discloses that a part or all of the low-pressure turbine air is recovered by merging with the return low-temperature gas generated in the upper column, thereby optimizing the flow rate of the low-pressure turbine air supplied to the upper column.

[0007] Patent Document 1: Japanese Patent No. 6155515

[0008] Patent Document 2: Japanese Patent Publication No. 60-44587

[0009] The air separation device disclosed in Patent Document 1 can recover more high-pressure nitrogen products while maintaining or improving the argon recovery rate, and can reduce the overall power consumption of the device. On the other hand, compared with the case where raw air is used as the processing fluid in the expansion turbine in the air separation device disclosed in Patent Document 1, the inlet pressure of the expansion turbine is lower and the expansion ratio is smaller. Therefore, even when the same amount of cold is generated, the processing capacity is larger. Therefore, in the air separation device of Patent Document 1, especially when the amount of liquid products is large and the cold required for the operation of the air separation device is large, there is a problem that the amount of expansion turbines is excessive and the argon recovery rate is significantly reduced.

[0010] Here, in the case of an air separation device that uses a part of the raw air for the expansion turbine, for example, the amount of low-pressure turbine air can also be optimized by the method disclosed in Patent Document 2, and the reduction of the argon recovery rate can be suppressed. However, when oxygen-enriched air is used in the expansion turbine, since a part of the oxygen-enriched air rich in oxygen components or argon components compared with the raw air is not supplied to the low-pressure column but is recovered as a return gas (atmospheric release), there is instead a problem of becoming the main cause of reducing the oxygen recovery rate or the argon recovery rate. Summary of the Invention

[0011] The present invention has been completed in view of the above problems, and an object thereof is to provide an air separation method and an air separation device that can improve the argon recovery rate while maintaining the oxygen recovery rate or suppressing the reduction of the oxygen recovery rate.

[0012] In order to solve the above problems, the present inventors repeatedly and deeply studied the following device. The device indirectly exchanges heat to vaporize the high-pressure oxygen-enriched liquefied air derived from the bottom of the high-pressure column after depressurization, thereby generating medium-pressure turbine air as oxygen-enriched air. The medium-pressure turbine air is compressed by a turbine blower and then adiabatically expanded by an expansion turbine, and then supplied to the low-pressure column. As a result, it was found that by branching a part of the raw air and merging it with the high-pressure turbine air of the oxygen-enriched air at the inlet of the expansion turbine, it is possible to reduce the processing capacity of the expansion turbine while maintaining the generated cold, or to increase the generated cold while maintaining the processing capacity of the expansion turbine. From this, it was found that the argon recovery rate can be improved while maintaining the oxygen recovery rate or suppressing the reduction of the oxygen recovery rate, and thus the present invention was completed.

[0013] That is, in order to solve the above problems, the following air separation method and air separation device are provided.

[0014] [1]An air separation method, characterized by comprising: a high-pressure separation step of cooling and then cryogenically distilling high-pressure raw air obtained by compressing, precooling, and purifying air containing oxygen, nitrogen, and argon, so as to separate the high-pressure raw air into high-pressure nitrogen and high-pressure oxygen-rich liquefied air; a turbine air generation step of gasifying medium-pressure oxygen-rich liquefied air obtained by decompressing the high-pressure oxygen-rich liquefied air to generate medium-pressure turbine air; a turbine air compression step of heating and then compressing the medium-pressure turbine air to generate high-pressure turbine air; a turbine air adiabatic expansion step of adiabatically expanding the high-pressure turbine air to generate low-pressure turbine air, generating the cold energy required for air separation operation; a low-pressure separation step of cryogenically distilling the low-pressure turbine air to separate it into low-pressure nitrogen, low-pressure liquefied oxygen, and argon-rich liquefied oxygen; an argon separation step of pressurizing the argon-rich liquefied oxygen and then cryogenically distilling it at a pressure higher than that of the low-pressure separation step, so as to separate the argon-rich liquefied oxygen into argon gas and medium-pressure liquefied oxygen; an argon condensation step of indirectly exchanging heat between the argon gas and the low-pressure liquefied oxygen to liquefy the argon gas to generate liquefied argon, and to gasify the low-pressure liquefied oxygen to generate low-pressure oxygen; a high-pressure nitrogen condensation step of indirectly exchanging heat between the high-pressure nitrogen and the medium-pressure liquefied oxygen, so as to liquefy the high-pressure nitrogen to generate high-pressure liquefied nitrogen, and to gasify the medium-pressure liquefied oxygen to generate medium-pressure oxygen; and a product argon extraction step of extracting at least one of a part of the argon gas, the argon gas not liquefied in the argon condensation step, and a part of the liquefied argon as a product. The turbine air compression step uses the energy generated by the turbine air adiabatic expansion step to compress the medium-pressure turbine air. The air separation method further includes a raw air bypass step, and the raw air bypass step branches a part of the high-pressure raw air, decompresses it, and then merges it with the high-pressure turbine air.

[0015] [2]According to the air separation method described in [1] above, characterized in that in the turbine air generation step, the high-pressure nitrogen is liquefied to generate high-pressure liquefied nitrogen by indirectly exchanging heat between the high-pressure nitrogen and the medium-pressure oxygen-rich liquefied air, and the medium-pressure oxygen-rich liquefied air is gasified to generate the medium-pressure turbine air.

[0016] [3]According to the air separation method described in [1] above, characterized in that in the turbine air generation step, the high-pressure nitrogen-rich air generated in the intermediate stage of the high-pressure separation step is liquefied to generate high-pressure nitrogen-rich liquefied air by indirectly exchanging heat between the high-pressure nitrogen-rich air and the medium-pressure oxygen-rich liquefied air, and the medium-pressure oxygen-rich liquefied air is gasified to generate the medium-pressure turbine air.

[0017] [4]According to the air separation method described in [1] above, it is characterized in that in the turbine air generation process, through the indirect heat exchange between the high-pressure raw material air and the medium-pressure oxygen-rich liquefied air, the high-pressure raw material air is liquefied to generate high-pressure liquefied air, and the medium-pressure oxygen-rich liquefied air is vaporized to generate the medium-pressure turbine air.

[0018] [5]According to the air separation method described in any one of [1] to [4] above, it is characterized in that in the raw material air bypass process, the flow rate of the high-pressure raw material air branched from the high-pressure raw material air is indirectly adjusted by controlling the pressure after decompression.

[0019] [6]An air separation device, comprising: a high-pressure tower for cooling and then cryogenically distilling the high-pressure raw material air obtained by compressing, precooling, and purifying air containing oxygen, nitrogen, and argon, so as to separate the high-pressure raw material air into high-pressure nitrogen and high-pressure oxygen-rich liquefied air; a turbine air evaporator for vaporizing the medium-pressure oxygen-rich liquefied air obtained by decompressing the high-pressure oxygen-rich liquefied air to generate medium-pressure turbine air; a turbine blower for heating and then compressing the medium-pressure turbine air to generate high-pressure turbine air; an expansion turbine for adiabatically expanding the high-pressure turbine air to generate low-pressure turbine air and generating the cold quantity required for air separation operation; a low-pressure tower for cryogenically distilling the low-pressure turbine air to separate it into low-pressure nitrogen, low-pressure liquefied oxygen, and argon-rich liquefied oxygen; an argon tower for pressurizing the argon-rich liquefied oxygen and cryogenically distilling it at a pressure higher than that of the low-pressure tower, so as to separate the argon-rich liquefied oxygen into argon and medium-pressure liquefied oxygen; an argon condenser for liquefying the argon to generate liquefied argon through the indirect heat exchange between the argon and the low-pressure liquefied oxygen, and vaporizing the low-pressure liquefied oxygen to generate low-pressure oxygen; a high-pressure nitrogen condenser for liquefying the high-pressure nitrogen to generate high-pressure liquefied nitrogen through the indirect heat exchange between the high-pressure nitrogen and the medium-pressure liquefied oxygen, and vaporizing the medium-pressure liquefied oxygen to generate medium-pressure oxygen; and a product argon export pipeline for extracting at least one of a part of the argon, the argon not liquefied in the argon condenser, and a part of the liquefied argon as a product. Regarding the turbine blower, the turbine blower is driven to rotate by using the rotational energy generated by the expansion turbine. The air separation device further includes a raw material air bypass pipeline for branching a part of the high-pressure raw material air, decompressing it, and then converging it with the high-pressure turbine air.

[0020] [7]According to the air separation device described in [6] above, it is characterized in that in the turbine air evaporator, through the indirect heat exchange between the high-pressure nitrogen and the medium-pressure oxygen-rich liquefied air, the high-pressure nitrogen is liquefied to generate high-pressure liquefied nitrogen, and the medium-pressure oxygen-rich liquefied air is vaporized to generate the medium-pressure turbine air.

[0021] [8] The air separation device according to [6] above is characterized in that the turbo air evaporator liquefies the high-pressure nitrogen-rich air generated in the intermediate stage of the treatment in the high-pressure column through indirect heat exchange with the medium-pressure oxygen-rich liquefied air, thereby generating high-pressure nitrogen-rich liquefied air, and vaporizes the medium-pressure oxygen-rich liquefied air to generate the medium-pressure turbo air.

[0022] [9] The air separation device according to [6] above is characterized in that the turbo air evaporator liquefies the high-pressure raw material air through indirect heat exchange with the medium-pressure oxygen-rich liquefied air, thereby generating high-pressure liquefied air, and vaporizes the medium-pressure oxygen-rich liquefied air to generate the medium-pressure turbo air.

[0023]

[10] The air separation device according to any one of [6] to [9] above is characterized in that a raw material air bypass valve is further provided on the raw material air bypass pipeline, and the raw material air bypass valve can indirectly adjust the flow rate of the high-pressure raw material air branched from the high-pressure raw material air by controlling the pressure after decompression.

[0024] According to the air separation method of the present invention, the following method is adopted as described above. The method includes: a turbo air generation step of generating medium-pressure turbo air and a turbo air compression step of generating high-pressure turbo air, and further includes a raw material air bypass step of decompressing a part of the high-pressure raw material air and then merging it with the high-pressure turbo air. In this way, by branching a part of the high-pressure raw material air and then merging it with the high-pressure turbo air as oxygen-rich air, it is possible to reduce the processing amount of the expansion turbine while maintaining the generated cold amount, or to increase the generated cold amount while maintaining the processing amount of the expansion turbine.

[0025] Therefore, it is possible to improve the argon recovery rate while maintaining the oxygen recovery rate or suppressing the decrease in the oxygen recovery rate.

[0026] In addition, according to the air separation device of the present invention, the following structure is adopted as described above. In this structure, the high-pressure oxygen-rich liquefied air led out from the bottom of the high-pressure column is decompressed and then gasified through indirect heat exchange to generate medium-pressure turbo air as oxygen-rich air. The medium-pressure turbo air is compressed by a turbo blower and then adiabatically expanded by an expansion turbine and supplied to the low-pressure column. The device structure further includes a raw material air bypass pipeline for decompressing a part of the high-pressure raw material air and then merging it with the high-pressure turbo air. By providing such a raw material air bypass pipeline, similarly to the above, it is possible to reduce the processing amount of the expansion turbine while maintaining the generated cold amount, or to increase the generated cold amount while maintaining the processing amount of the expansion turbine.

[0027] Therefore, in the same manner as described above, it is possible to improve the argon recovery rate while maintaining the oxygen recovery rate or suppressing a decrease in the oxygen recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 FIG. is a diagram schematically illustrating an air separation method and an air separation apparatus according to an embodiment of the present invention, and is a system diagram showing a schematic structure of the entire air separation apparatus. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] Hereinafter, with reference to Figure 1 an air separation method and an air separation apparatus according to an embodiment to which the present invention is applied will be described.

[0030] In addition, for easy understanding of the features, for convenience, in the following description, the drawings sometimes magnify or simplify the representation of the feature portions. In addition, the materials and the like illustrated in the following description are examples, and the present invention is not limited to these, and can be appropriately changed within the scope of not changing the gist thereof.

[0031] <Air Separation Apparatus>

[0032] Hereinafter, an air separation apparatus that can be used for the operation of the air separation method according to the present embodiment will be described in detail.

[0033] Figure 1 FIG. is a system diagram showing a schematic structure of the entire air separation apparatus 10 according to the present embodiment.

[0034] In addition, in the description of the present embodiment, "low pressure" means a pressure equal to or lower than the operating pressure of the low-pressure column 18 described in detail later and 400 kPaA or lower. In addition, "medium pressure" means a pressure equal to or lower than the pressure of the fluid having the highest pressure among the medium-pressure oxygen gasified in the high-pressure nitrogen condenser H2 and the medium-pressure turbine air gasified in the turbine air evaporator H3 and higher than the operating pressure of the low-pressure column 18. In addition, "high pressure" means a pressure higher than the pressure of the fluid having the highest pressure among the medium-pressure oxygen gasified in the high-pressure nitrogen condenser H2 and the medium-pressure turbine air gasified in the turbine air evaporator H3.

[0035] As Figure 1As shown, the air separation device 10 of the present embodiment includes: an air compressor 11, an air precooler 12, an air purifier 13, an air booster 14, a post-cooler 15 for the air booster, a main heat exchanger 16, a high-pressure column 17, a low-pressure column 18, an argon column 19, an outer cylinder 20 of a turbo air evaporator, a subcooler 21, a turbo blower 22, a post-cooler 23 for the turbo blower, an expansion turbine 24, a liquefied oxygen pump 25, a rich argon liquefied oxygen pump 26, an argon condenser H1, a high-pressure nitrogen condenser H2, a turbo air evaporator H3, pipelines L1, L2, L4 to L6, L8 to L18, L20 to L24, L31 to L35, L51, L52, L71, L72, L191, L192, and valves V1 to V8. Moreover, the air separation device 10 of the present embodiment is generally configured by further including a raw material air bypass pipeline L25 and a raw material air bypass valve V9.

[0036] The air compressor 11 is provided on the pipeline L1 and is connected to a raw material air supply source (not shown) that supplies air (raw material air) containing oxygen, nitrogen, and argon and the air precooler 12 through the pipeline L1. The air compressor 11 compresses the air containing oxygen, nitrogen, and argon. The air (raw material air) compressed by the air compressor 11 is transported to the air precooler 12 via the pipeline L1.

[0037] One end side of the pipeline L1 is connected to a raw material air supply source (not shown), and the other end side is connected to the bottom of the high-pressure column 17. A part of the pipeline L1 passes through the main heat exchanger 16. The pipeline L1 compresses the air from the raw material air supply source (not shown) by the air compressor 11, precools it by the air precooler 12, purifies it by the air purifier 13 to generate high-pressure raw material air, and supplies it to the high-pressure column 17 after cooling by the main heat exchanger 16.

[0038] The air precooler 12 is provided on the pipeline L1 between the air compressor 11 and the air purifier 13. The air precooler 12 is connected to the air compressor 11 and the air purifier 13 through the pipeline L1. The air precooler 12 removes the compression heat of the air compressed by the air compressor 11. The air from which the compression heat has been removed by the air precooler 12 is supplied to the air purifier 13 via the pipeline L1.

[0039] The air purifier 13 is provided on the pipeline L1 between the air precooler 12 and the branch position of the pipeline L2. The air purifier 13 is connected to the air precooler 12 and the main heat exchanger 16 through the pipeline L1. The air purifier 13 removes impurities contained in the air from which the compression heat has been removed by the air precooler 12. Specifically, for example, it removes water or carbon dioxide, etc., to generate high-pressure raw air. The high-pressure raw air after removing impurities by the air purifier 13 is supplied to the bottom of the high-pressure column 17 via the pipeline L1 and the main heat exchanger 16, and is supplied to the air booster 14 via the pipeline L2 branched from the pipeline L1, and further supplied to the pipeline L51 via the raw air bypass pipeline L25 branched from the pipeline L1.

[0040] The pipeline L2 branches from the pipeline L1 between the air purifier 13 and the main heat exchanger 16, and one end side is connected to the lower part of the high-pressure column 17. A part of the pipeline L2 passes through the main heat exchanger 16. In addition, a valve V4 is provided on the pipeline L2. The pipeline L2 compresses a part of the high-pressure raw air purified by the air purifier 13 with the air booster 14, precools it with the air booster aftercooler 15, cools it with the main heat exchanger 16, and supplies it to the high-pressure column 17 after decompression by the valve V4.

[0041] The air booster 14 is provided on the pipeline L2 between the position where the pipeline L2 branches from the pipeline L1 and the air booster aftercooler 15. The air booster 14 further compresses a part of the high-pressure raw air from which impurities have been removed to generate boosted raw air. The boosted raw air compressed by the air booster 14 is transported to the air booster aftercooler 15 via the pipeline L2.

[0042] The air booster aftercooler 15 is provided on the pipeline L2 on the downstream side of the air booster 14. The air booster aftercooler 15 removes the compression heat of the boosted raw air compressed by the air booster 14. The boosted raw air cooled by the air booster aftercooler 15 becomes high-pressure raw liquefied air via the pipeline L2, the main heat exchanger 16 and the valve V4, and is supplied to the lower part of the high-pressure column 17.

[0043] The valve V4 is provided on the pipeline L2 between the main heat exchanger 16 and the high-pressure column 17. The valve V4 decompresses the boosted raw air cooled by the air booster aftercooler 15 and the main heat exchanger 16 to generate high-pressure raw liquefied air.

[0044] The main heat exchanger 16 is configured to allow a part of the pipelines L1, L2, L5, L51, L8, L13, L14, L16, L20 to pass through. The main heat exchanger 16 indirectly exchanges heat between the high-temperature fluid flowing through the pipelines L1, L2, L51 and the low-temperature fluid flowing through the pipelines L5, L8, L13, L14, L16, L20 to cool each high-temperature fluid and heat each low-temperature fluid.

[0045] The high-pressure tower 17 is connected to pipelines L1, L2, and L72. In addition to a part of the high-pressure raw air obtained by compressing, precooling, purifying, and cooling the air containing oxygen, nitrogen, and argon, the high-pressure tower 17 also performs cryogenic distillation on the high-pressure raw liquefied air supplied from pipeline L2 and the high-pressure liquefied nitrogen supplied from pipeline L72, thereby separating them into high-pressure nitrogen and high-pressure oxygen-rich liquefied air.

[0046] In the high-pressure tower 17, through the above-mentioned cryogenic distillation, high-pressure nitrogen is concentrated in the upper part of the high-pressure tower 17, and high-pressure oxygen-rich liquefied air is concentrated in the lower part of the high-pressure tower 17.

[0047] One end side of pipeline L71 is connected to the top of the high-pressure tower 17, and the other end side is connected to the liquefaction passage inlet of the high-pressure nitrogen condenser H2. Pipeline L71 supplies the high-pressure nitrogen concentrated in the upper part of the high-pressure tower 17 to the high-pressure nitrogen condenser H2.

[0048] The high-pressure nitrogen condenser H2 is housed at the bottom of the argon tower 19. The liquefaction passage inlet is connected to pipeline L71, and the liquefaction passage outlet is connected to pipeline L72. The high-pressure nitrogen condenser H2 indirectly exchanges heat between the high-pressure nitrogen supplied from pipeline L71 and the medium-pressure liquefied oxygen located at the bottom of the argon tower 19, thereby liquefying the high-pressure nitrogen to generate high-pressure liquefied nitrogen, and vaporizing the medium-pressure liquefied oxygen to generate medium-pressure oxygen.

[0049] Pipeline L8 is a pipeline branched from pipeline L71. A part of pipeline L8 passes through the main heat exchanger 16. Pipeline L8 is a pipeline for recovering a part of the high-pressure nitrogen after heat recovery in the main heat exchanger 16 as product high-pressure nitrogen (HPGN2).

[0050] One end side of pipeline L72 is connected to the liquefaction passage outlet of the high-pressure nitrogen condenser H2, and the other end side is connected to the top of the high-pressure tower 17. Pipeline L72 supplies the high-pressure liquefied nitrogen generated by the high-pressure nitrogen condenser H2 to the high-pressure tower 17.

[0051] Pipeline L9 is a pipeline branched from pipeline L72 and is connected to the top of the low-pressure tower 18. A part of pipeline L9 passes through the subcooler 21, and a valve V6 is provided in the path. Pipeline L9 cools a part of the high-pressure liquefied nitrogen generated by the high-pressure nitrogen condenser H2 by the subcooler 21, and after reducing the pressure by the valve V6, supplies it to the low-pressure tower 18.

[0052] The valve V6 is provided on pipeline L9 located between the low-pressure tower 18 and the subcooler 21. The valve V6 reduces the pressure of the high-pressure liquefied nitrogen flowing through pipeline L9.

[0053] Pipeline L10 is a pipeline branched from pipeline L9. Pipeline L10 is a pipeline for recovering a part of the high-pressure liquefied nitrogen as product high-pressure liquefied nitrogen (HPLN2).

[0054] One end side of pipeline L11 is connected to the middle part or the lower part of high-pressure tower 17, and the other end side is connected to the middle part or the upper part of low-pressure tower 18. A part of pipeline L11 passes through subcooler 21. In addition, a valve V7 is provided on the path of pipeline L11. Pipeline L11 extracts a part of the fluid descending in the middle part or the lower part of high-pressure tower 17, cools it with subcooler 21, and supplies it to low-pressure tower 18 after reducing the pressure with valve V7.

[0055] Valve V7 is provided on pipeline L11 between low-pressure tower 18 and subcooler 21. Valve V7 reduces the pressure of the fluid flowing through pipeline L11.

[0056] One end side of pipeline L4 is connected to the bottom of high-pressure tower 17, and the other end side is connected to the outer cylinder 20 of the turbine air evaporator. A valve V1 is provided on the path of pipeline L4. Pipeline L4 reduces the pressure of the high-pressure oxygen-rich liquefied air extracted from high-pressure tower 17 with valve V1, generates medium-pressure oxygen-rich liquefied air, and supplies it to the outer cylinder 20 of the turbine air evaporator.

[0057] Valve V1 is provided on pipeline L4. Valve V1 reduces the pressure of the high-pressure oxygen-rich liquefied air flowing through pipeline L4 to generate medium-pressure oxygen-rich liquefied air.

[0058] In addition, as Figure 1 shown by the dotted line in the figure, a part of the high-pressure oxygen-rich liquefied air can also be extracted from pipeline L12 branched from pipeline L4, cooled by subcooler 21, and supplied to low-pressure tower 18 after reducing the pressure with valve V3.

[0059] One end side of pipeline L31 is connected to the upper part of high-pressure tower 17, and the other end is connected to the liquefaction passage inlet of turbine air evaporator H3. Pipeline L31 extracts the high-pressure nitrogen gas concentrated in the upper part of high-pressure tower 17 and supplies it to turbine air evaporator H3.

[0060] In addition, instead of extracting high-pressure nitrogen gas from the upper part of high-pressure tower 17 through pipeline L31, as Figure 1 shown by the dotted line in the figure, a part of the high-pressure raw material air can also be extracted from pipeline L33 branched from pipeline L1 and supplied to turbine air evaporator H3, or high-pressure nitrogen-rich air ascending in the middle part or the lower part of high-pressure tower 17 can be extracted through pipeline L34 with one end side connected to the middle part or the lower part of high-pressure tower 17 and supplied to turbine air evaporator H3.

[0061] The outer cylinder 20 of the turbine air evaporator is connected to one end side of pipeline L4, and the turbine air evaporator H3 is housed inside it. The outer cylinder 20 of the turbine air evaporator can store the medium-pressure oxygen-rich liquefied air supplied from pipeline L4.

[0062] The turbine air evaporator H3 is housed in the outer cylinder 20 of the turbine air evaporator. The liquefaction passage inlet thereof is connected to one end side of the pipeline L31. The turbine air evaporator H3 indirectly exchanges heat between the high-pressure nitrogen supplied from the pipeline L31 and the medium-pressure oxygen liquefied air supplied from the pipeline L4, thereby liquefying the high-pressure nitrogen supplied from the pipeline L31 to generate high-pressure liquefied nitrogen, and gasifying the medium-pressure oxygen-rich liquefied air supplied from the pipeline L4 and stored inside the outer cylinder 20 of the turbine air evaporator to generate medium-pressure turbine air.

[0063] One end side of the pipeline L32 is connected to the liquefaction passage outlet of the turbine air evaporator H3, and the other end side is connected to the upper part of the low-pressure tower 18. A part of the pipeline L32 passes through the subcooler 21, and a valve V5 is provided in its path. The pipeline L32 cools the high-pressure liquefied nitrogen generated by the turbine air evaporator H3 by the subcooler 21, and supplies it to the low-pressure tower 18 after reducing the pressure by the valve V5.

[0064] In addition, in the present embodiment, as Figure 1 shown by the dotted line, a pipeline L35 can also be provided. The pipeline L35 branches from the pipeline L32 located between the liquefaction passage outlet of the turbine air evaporator H3 and the subcooler 21, and one end side is connected to the upper part of the high-pressure tower 17. The pipeline L35 supplies all or part of the high-pressure liquefied nitrogen flowing through the pipeline L32 to the high-pressure tower 17.

[0065] The valve V5 is provided in the path of the pipeline L32 located between the low-pressure tower 18 and the subcooler 21. The valve V5 reduces the pressure of the high-pressure liquefied nitrogen flowing through the pipeline L32.

[0066] One end side of the pipeline L5 is connected to the gas outlet of the outer cylinder 20 of the turbine air evaporator, and the other end side is connected to the turbine blower 22. A part of the pipeline L5 passes through the main heat exchanger 16.

[0067] The pipeline L5 supplies the medium-pressure turbine air generated by the turbine air evaporator H3 housed inside the outer cylinder 20 of the turbine air evaporator to the turbine blower 22 after heat recovery by the main heat exchanger 16.

[0068] The turbine blower 22 is connected to one end side of the pipeline L5. The turbine blower 22 further compresses the medium-pressure turbine air conveyed through the pipeline L5 to generate high-pressure turbine air. The turbine blower 22 is driven to rotate by using the rotational energy generated by the expansion turbine 24 described later.

[0069] One end of pipeline L51 is connected to the turbo blower 22, and the other end is connected to the expansion turbine 24. A turbo blower aftercooler 23 is provided on the pipeline L51 in the illustrated figure, and a part of the pipeline L51 passes through the main heat exchanger 16. The pipeline L51 cools the high-pressure turbine air compressed by the turbo blower 22 by the turbo blower aftercooler 23 and the main heat exchanger 16 and then supplies it to the expansion turbine 24.

[0070] The turbo blower aftercooler 23 is provided on the path of the pipeline L51 between the turbo blower 22 and the main heat exchanger 16. The turbo blower aftercooler 23 is a component that removes the compression heat of the high-pressure turbine air compressed by the turbo blower 22.

[0071] The expansion turbine 24 is connected to one end of the pipeline L51. The expansion turbine 24 adiabatically expands the high-pressure turbine air passing through the turbo blower aftercooler 23 and the main heat exchanger 16 to generate the cooling capacity required for the operation of the device and generate low-pressure turbine air.

[0072] The expansion turbine 24 uses the rotational energy generated by the expansion turbine 24 to drive the turbo blower 22 to rotate.

[0073] One end of the pipeline L52 is connected to the outlet of the expansion turbine 24, and the other end is connected to the middle part of the low-pressure tower 18. The pipeline L52 supplies the low-pressure turbine air generated by the expansion turbine 24 to the middle part of the low-pressure tower 18.

[0074] One end of the pipeline L6 is connected to the liquid outlet of the turbo air evaporator outer cylinder 20, and the other end is connected to the middle part of the low-pressure tower 18. A valve V2 is provided in the path of the pipeline L6. The pipeline L6 supplies the medium-pressure oxygen-enriched liquefied air gasified by the turbo air evaporator H3 that is not contained inside the turbo air evaporator outer cylinder 20 to the low-pressure tower 18 after reducing the pressure by the valve V2.

[0075] The valve V2 is provided in the path of the pipeline L6. The valve V2 reduces the pressure of the fluid flowing through the pipeline L6.

[0076] The low-pressure tower 18 is connected to one end of the pipeline L9, one end of the pipeline L32, one end of the pipeline L11, one end of the pipeline L52, and one end of the pipeline L6, and an argon condenser H1 is accommodated at the bottom of the low-pressure tower 18. In addition to the fluid reduced in pressure by the valve V5, the fluid reduced in pressure by the valve V6, the fluid reduced in pressure by the valve V2, the fluid reduced in pressure by the valve V7, and the low-pressure turbine air obtained by adiabatic expansion of the expansion turbine 24, the low-pressure tower 18 also separates the low-pressure oxygen gasified by the argon condenser H1 by low-temperature distillation into low-pressure nitrogen, low-pressure liquefied oxygen, and argon-enriched liquefied oxygen.

[0077] One end side of pipeline L13 is connected to the top of low-pressure tower 18, and a part of it passes through subcooler 21 and main heat exchanger 16. Pipeline L13 is a pipeline for recovering the low-pressure nitrogen concentrated in the upper part of low-pressure tower 18 as product low-pressure nitrogen (LPGN2) after heat recovery through subcooler 21 and main heat exchanger 16.

[0078] An argon condenser H1 is provided at the bottom of low-pressure tower 18, and the liquefaction passage inlet is connected to pipeline L191. Argon condenser H1 indirectly exchanges heat between the argon gas supplied from pipeline L191 and the low-pressure liquefied oxygen at the bottom of low-pressure tower 18, thereby liquefying the argon gas to generate liquefied argon and vaporizing the low-pressure liquefied oxygen to generate low-pressure oxygen.

[0079] One end side of pipeline L18 is connected to the middle part of low-pressure tower 18, and the other end side is connected to the middle or lower part of argon tower 19. A rich-argon liquefied oxygen pump 26 is provided on pipeline L18. Pipeline L18 supplies the rich-argon liquefied oxygen concentrated in the middle part of low-pressure tower 18 to argon tower 19 after being pressurized by rich-argon liquefied oxygen pump 26.

[0080] Rich-argon liquefied oxygen pump 26 is provided in the path of pipeline L18. Rich-argon liquefied oxygen pump 26 pressurizes the rich-argon liquefied oxygen led from low-pressure tower 18 to pipeline L18.

[0081] Argon tower 19 is connected to one end of pipelines L18 and L192, and a high-pressure nitrogen condenser H2 is housed at the bottom of argon tower 19. Argon tower 19 separates the rich-argon liquefied oxygen and liquefied argon into argon gas and medium-pressure liquefied oxygen by low-temperature distillation at a pressure higher than that of low-pressure tower 18 for the rich-argon liquefied oxygen pressurized by rich-argon liquefied oxygen pump 26 and the liquefied argon supplied from pipeline L192.

[0082] One end side of pipeline L191 is connected to the top of argon tower 19, and the other end side is connected to the liquefaction passage inlet of argon condenser H1. Pipeline L191 supplies the argon gas concentrated in the upper part of argon tower 19 to argon condenser H1.

[0083] One end side of pipeline L192 is connected to the liquefaction passage outlet of argon condenser H1, and the other end side is connected to the top of argon tower 19. Pipeline L192 supplies the liquefied argon generated by argon condenser H1 to argon tower 19.

[0084] One end side of pipeline L15 is connected to the bottom of low-pressure tower 18, and the other end side is connected to one end side of pipeline L23 and one end side of pipeline L16. Pipeline L15 is a pipeline for supplying the low-pressure liquefied oxygen at the bottom of low-pressure tower 18 to pipeline L16.

[0085] Pipeline L17 is a pipeline branched from pipeline L15. Pipeline L17 is a pipeline for recovering a part of the low-pressure liquefied oxygen flowing through pipeline L15 as product low-pressure liquefied oxygen (LPLO2).

[0086] One end side of pipeline L23 is connected to the bottom of the argon column 19, and the other end side is connected to one end side of pipeline L15 and one end of pipeline L16. A valve V8 is provided in the path of pipeline L23. Pipeline L23 is a pipeline for supplying medium-pressure liquefied oxygen at the bottom of the argon column 19 to pipeline L16.

[0087] The valve V8 is provided on pipeline L23. The valve V8 reduces the pressure of the medium-pressure liquefied oxygen flowing through pipeline L23.

[0088] Pipeline L24 is a pipeline branched from pipeline L23. Pipeline L24 is a pipeline for recovering a part of the medium-pressure liquefied oxygen flowing through pipeline L23 as product medium-pressure liquefied oxygen (MPLO2).

[0089] One end side of pipeline L16 is connected to one end side of pipeline L15 and one end side of pipeline L23. A part of pipeline L16 passes through the main heat exchanger 16. In addition, a liquefied oxygen pump 25 is provided in the path of pipeline L16. Pipeline L16 is a pipeline for pressurizing the fluid supplied to pipeline L16 by the liquefied oxygen pump 25 and recovering it as product high-pressure oxygen (HPGO2) after heat recovery by the main heat exchanger 16.

[0090] The liquefied oxygen pump 25 is provided on pipeline L16 on the upstream side of the main heat exchanger 16. The liquefied oxygen pump 25 pressurizes the fluid supplied to pipeline L16.

[0091] Pipeline L20 is a pipeline branched from pipeline L191, and a part of it passes through the main heat exchanger 16. Pipeline L20 is a pipeline for recovering a part of the argon gas flowing through pipeline L191 as product argon gas (GAR) after heat recovery by the main heat exchanger 16.

[0092] In addition, as Figure 1 shown by the dashed line in the figure, sometimes one end side of pipeline L21 is connected to the liquefaction path outlet of the argon condenser H1. In this case, pipeline L21 converges with pipeline L20, and the argon gas not liquefied in the argon condenser H1 is recovered as product argon gas (GAR) after heat recovery by the main heat exchanger 16.

[0093] Pipeline L22 is a pipeline branched from pipeline L192. Pipeline L22 is a pipeline for recovering a part of the liquefied argon flowing through pipeline L192 as product liquefied argon (LAR).

[0094] The subcooler 21 is configured to allow a portion of the pipeline L14, a portion of the pipeline L13, a portion of the pipeline L11, a portion of the pipeline L32, and a portion of the pipeline L9 to pass through. The subcooler 21 allows the low-temperature fluid flowing through the pipeline L13 to indirectly exchange heat with the high-temperature fluids flowing through the pipeline L11, the pipeline L32, and the pipeline L9, thereby warming the low-temperature fluid and cooling each high-temperature fluid.

[0095] In addition, the combination of the low-temperature fluid and the high-temperature fluid in the supercooler 21 is not limited thereto.

[0096] One end of the pipeline L14 is connected to the upper part of the low-pressure tower 18, and a part of the pipeline L14 passes through the subcooler 21 and the main heat exchanger 16. The pipeline L14 is a pipeline for recovering the low-purity low-pressure nitrogen gas concentrated in the upper part of the low-pressure tower 18 as waste nitrogen gas WGN2 after heat recovery through the subcooler 21 and the main heat exchanger 16.

[0097] One end of the raw air bypass line L25 is connected to the downstream side of the air purifier 13 in the line L1, and the other end is connected to the upstream side of the main heat exchanger 16 in the line L51, and a raw air bypass valve V9 is provided in the path. The raw air bypass line L25 branches a part of the high-pressure raw air from the line L1, and after being decompressed by the raw air bypass valve V9, it merges with the high-pressure turbine air flowing in the line L51.

[0098] The raw air bypass valve V9 is provided on a path of the raw air bypass line L25 on the upstream side of the main heat exchanger 16. The raw air bypass valve V9 decompresses the high-pressure raw air flowing in the raw air bypass line L25. More specifically, the raw air bypass valve V9 is configured to indirectly adjust the flow rate of the high-pressure raw air in the raw air bypass line L25 by controlling the decompressed pressure of the high-pressure raw air branched from the line L1.

[0099] In the present embodiment, the raw air bypass valve V9 may be set as an automatic valve, and a flow regulator (not shown) may be used to operate the raw air bypass valve V9 so that the flow meter (not shown) provided on the raw air bypass line L25 matches the set value. On this basis, a pressure regulator (not shown) may be used to operate the set value of the flow regulator, and the flow rate may be indirectly controlled so that the indicated value of the pressure gauge (not shown) provided in the inlet system of the expansion turbine 24 matches the target value.

[0100] In the air separation device 10 of this embodiment, as an example, the case where the pipelines L20 and L22 for exporting product argon gas (GAR) or product liquefied argon (LAR) are provided is described, but it is sufficient to have at least one of the pipelines L20 and L22.

[0101] Although inFigure 1 The drawings are omitted. However, for example, in the case of recovering the low-pressure oxygen (LPGO2) of the product, a product outlet pipeline is provided with one end connected to the bottom of the low-pressure column 18 and a part passing through the main heat exchanger 16. In this case, after the low-pressure oxygen of the low-pressure column 18 is heat-recovered by the main heat exchanger 16, the omitted product outlet pipeline recovers the heat-recovered low-pressure oxygen as the product low-pressure oxygen (LPGO2).

[0102] In addition, for example, in the case of recovering the medium-pressure oxygen (MPGO2) of the product, a product outlet pipeline (drawings omitted) is provided with one end side connected to the bottom of the argon column 19 and a part passing through the main heat exchanger 16. In this case, after the medium-pressure oxygen of the argon column 19 is heat-recovered by the main heat exchanger 16, this product outlet pipeline recovers the heat-recovered medium-pressure oxygen as the product medium-pressure oxygen (MPGO2).

[0103] In addition, in the case of recovering the product low-pressure oxygen (LPGO2), product medium-pressure oxygen (MPGO2), product medium-pressure liquefied oxygen (MPLO2), product low-pressure liquefied oxygen (LPLO2), etc., and instead not recovering the product high-pressure oxygen (HPGO2), the pipeline L16, liquefied oxygen pump 25, air booster 14, after-cooler 15 of the air booster, pipeline L2, and valves V4, V8 can be removed from the structural elements.

[0104] The air separation apparatus 10 of the present embodiment includes: a high-pressure column 17 for subjecting high-pressure raw air obtained by compressing, precooling, and purifying air containing oxygen, nitrogen, and argon to low-temperature distillation after cooling, thereby separating the high-pressure raw air into high-pressure nitrogen and high-pressure oxygen-rich liquefied air; a turbo air evaporator H3 for vaporizing medium-pressure oxygen-rich liquefied air obtained by reducing the pressure of the high-pressure oxygen-rich liquefied air to generate medium-pressure turbo air; a turbo blower 22 for compressing the medium-pressure turbo air after heating to generate high-pressure turbo air; an expansion turbine 24 for adiabatically expanding the high-pressure turbo air to generate low-pressure turbo air and generating the cold amount required for air separation operation; a low-pressure column 18 for subjecting the low-pressure turbo air to low-temperature distillation to separate it into low-pressure nitrogen, low-pressure liquefied oxygen, and argon-rich liquefied oxygen; an argon column 19 for subjecting the argon-rich liquefied oxygen to pressurization and low-temperature distillation at a pressure higher than that of the low-pressure column 18, thereby separating the argon-rich liquefied oxygen into argon and medium-pressure liquefied oxygen; an argon condenser H1 for indirectly exchanging heat between argon and low-pressure liquefied oxygen to liquefy argon to generate liquefied argon and vaporize the low-pressure liquefied oxygen to generate low-pressure oxygen; a high-pressure nitrogen condenser H2 for indirectly exchanging heat between high-pressure nitrogen and medium-pressure liquefied oxygen to liquefy the high-pressure nitrogen to generate high-pressure liquefied nitrogen and vaporize the medium-pressure liquefied oxygen to generate medium-pressure oxygen; and pipelines L20, L21 as product argon export pipelines for extracting at least one of a part of argon, unliquefied argon in the argon condenser, and a part of liquefied argon as product argon gas (GAR) or product liquefied argon (LAR). Moreover, the air separation apparatus 10 of the present embodiment uses the rotational energy generated by the expansion turbine 24 to drive the turbo blower 22 to rotate. The air separation apparatus 10 further includes a raw air bypass pipeline L25 for branching off a part of the high-pressure raw air, reducing its pressure, and then merging it with the high-pressure turbo air.

[0105] According to the air separation apparatus 10 of the present embodiment, by having the above structure, for example, even when the flow rates of product medium-pressure liquefied oxygen (MPLO2), product low-pressure liquefied oxygen (LPLO2), product high-pressure liquefied nitrogen (HPLN2), etc. are large and the cold amount required for operation is large, by bypassing a part of the high-pressure raw air to the pipeline L51 which is the inlet of the expansion turbine 24, it is possible to relatively suppress the flow rate of the turbo blower 22 and increase the compression ratio, increase the expansion ratio of the expansion turbine 24, and suppress the increase in the throughput. As a result, it is possible to reduce the flow rate of the low-pressure turbo air supplied to the low-pressure column 18, and thus improve the argon recovery rate.

[0106] On the other hand, in the case of a structure in which a part or all of the low-pressure turbine air is not supplied to the low-pressure column but recovered (released to the atmosphere) as described in Patent Document 2 above, although the flow rate of the low-pressure turbine air supplied to the low-pressure column is optimized, thereby improving the argon recovery rate, the oxygen recovery rate decreases because the oxygen component contained in the low-pressure turbine air not supplied to the low-pressure column cannot be recovered as a product. In contrast, by using the air separation device 10 of the present embodiment, all of the low-pressure turbine air can be supplied to the low-pressure column 18 as a raw material for the low-pressure column 18, so that a decrease in the oxygen recovery rate can be suppressed.

[0107] <Air separation method>

[0108] Next, for the air separation method of the present embodiment, a method of separating air using the Figure 1 illustrated air separation device 10 will be exemplified and described in detail.

[0109] In addition, in the following description, the same reference is made as in the description of the air separation device 10 of the present embodiment above Figure 1 for the description, and the detailed description of the structure of the air separation device 10 that has already been described is omitted.

[0110] Air containing oxygen, nitrogen, and argon is supplied to pipeline L1. This air is compressed by the air compressor 11, the compression heat is removed by the air precooler 12, and impurities (specifically, for example, water or carbon dioxide, etc.) contained in the air are removed by the air purifier 13, becoming high-pressure raw material air.

[0111] A part of the high-pressure raw material air from which the impurities have been removed in the air purifier 13 is cooled by the main heat exchanger 16 and supplied to the high-pressure column 17.

[0112] The remaining part of the high-pressure raw material air from which the impurities have been removed in the air purifier 13 is further pressurized by the air booster 14 provided on the pipeline L2 branched from the pipeline L1 to become boosted raw material air. The boosted raw material air removes the compression heat through the aftercooler 15 of the air booster, is cooled by the main heat exchanger 16, and then is depressurized by the valve V4 to become high-pressure raw material liquefied air, which is supplied to the high-pressure column 17.

[0113] In the main heat exchanger 16, the high-temperature fluid flowing through the pipelines L1, L2, and L51 is indirectly heat-exchanged with the low-temperature fluid flowing through the pipelines L5, L8, L13, L14, L16, and L20, thereby cooling each high-temperature fluid and heating each low-temperature fluid.

[0114] In the high-pressure column 17, the high-pressure raw material air introduced via pipeline L1, the high-pressure raw material liquefied air introduced via pipeline L2, and the high-pressure liquefied nitrogen introduced via pipeline L72 are separated by cryogenic distillation into high-pressure nitrogen gas located in the upper part of the high-pressure column 17 and high-pressure oxygen-rich liquefied air located in the lower part of the high-pressure column 17 (high-pressure separation process).

[0115] The high-pressure nitrogen gas located at the top of the high-pressure column 17 is introduced via pipeline L71 into the high-pressure nitrogen condenser H2 housed at the bottom of the argon column 19.

[0116] The high-pressure nitrogen gas supplied to the high-pressure nitrogen condenser H2 via pipeline L71 is liquefied into high-pressure liquefied nitrogen through indirect heat exchange with the medium-pressure liquefied oxygen located at the bottom of the argon column 19, and the medium-pressure liquefied oxygen located at the bottom of the argon column 19 is vaporized to generate medium-pressure oxygen gas (high-pressure nitrogen condensation process).

[0117] A part of the high-pressure nitrogen gas exported to pipeline L71 is exported to pipeline L8 branched from pipeline L71, and after heat recovery by the main heat exchanger 16, it is recovered as product high-pressure nitrogen gas (HPGN2).

[0118] The high-pressure liquefied nitrogen generated by the high-pressure nitrogen condenser H2 is introduced into the top of the high-pressure column 17 via pipeline L72.

[0119] A part of the high-pressure liquefied nitrogen exported to pipeline L72 is exported to pipeline L9, cooled by the subcooler 21, and after being depressurized by valve V6, it is introduced into the top of the low-pressure column 18.

[0120] A part of the high-pressure liquefied nitrogen in pipeline L9 is exported to pipeline L10 and recovered as product high-pressure liquefied nitrogen (HPLN2).

[0121] The high-pressure oxygen-rich liquefied air located at the bottom of the high-pressure column 17 is exported to pipeline L4, depressurized by valve V1 to become medium-pressure oxygen-rich liquefied air, and supplied to the outer cylinder 20 of the turbo air evaporator.

[0122] A part of the high-pressure nitrogen gas concentrated in the upper part of the high-pressure column 17 is exported from the upper part of the high-pressure column 17 to pipeline L31 and introduced into the turbo air evaporator H3.

[0123] The high-pressure nitrogen gas supplied to the turbo air evaporator H3 via pipeline L31 is liquefied into high-pressure liquefied nitrogen through indirect heat exchange with the medium-pressure oxygen-rich liquefied air supplied to the outer cylinder 20 of the turbo air evaporator via pipeline L4, and the medium-pressure oxygen-rich liquefied air supplied to the outer cylinder 20 of the turbo air evaporator via pipeline L4 is vaporized to generate medium-pressure turbo air (turbo air generation process).

[0124] In addition, the fluid introduced into the turbo air evaporator H3 via pipeline L31 can be as Figure 1A part of the high-pressure raw material air (line L33) or a part of the high-pressure nitrogen-rich air (line L34) rising in the middle or lower part of the high-pressure column 17, as shown by the dashed line in the figure, is used to replace the high-pressure nitrogen concentrated in the upper part of the high-pressure column 17.

[0125] In this case, a part of the high-pressure raw material air or a part of the high-pressure nitrogen-rich air is also liquefied by the turbo air evaporator H3 to become high-pressure liquefied air or high-pressure nitrogen-rich liquefied air respectively.

[0126] By the above change of the fluid, the temperature of the fluid on the condensation side in the turbo air evaporator H3 rises, and the temperature of the fluid on the evaporation side also rises. Therefore, the pressure of the medium-pressure turbo air generated by the turbo air evaporator H3 becomes higher, and as a result, it has the advantage of being able to increase the expansion ratio in the expansion turbine 24 described later.

[0127] In addition, in the present embodiment, as Figure 1 shown by the dashed line in the figure, all or a part of the fluid liquefied by the turbo air evaporator H3 can also be led out to the line L35 branched from the line L32 and supplied to the high-pressure column 17.

[0128] The high-pressure liquefied nitrogen generated in the turbo air evaporator H3 is led out to the line L32, cooled by the subcooler 21, and decompressed by the valve V5 and then introduced into the upper part of the low-pressure column 18.

[0129] The medium-pressure turbo air generated in the turbo air evaporator H3 is led out to the line L5, heat-recovered to room temperature by the main heat exchanger 16, and then compressed by the turbo blower 22 (turbo air compression process).

[0130] In addition, in the turbo air compression process, the energy generated by the turbo air adiabatic expansion process described later is used to compress the medium-pressure turbo air. That is, in the turbo air compression process, the expansion turbine 24 drives the turbo blower 22 to rotate to compress the medium-pressure turbo air.

[0131] The high-pressure turbo air generated by the compression of the turbo blower 22 is led out to the line L51, the compression heat is removed by the turbo blower aftercooler 23, and it is further cooled by the main heat exchanger 16 and then introduced into the expansion turbine 24.

[0132] The high-pressure turbo air introduced into the expansion turbine 24 is adiabatically expanded to near the operating pressure of the low-pressure column 18, and after generating the cooling capacity required for the operation of the plant, it becomes low-pressure turbo air and is led out to the line L52 (turbo air adiabatic expansion process).

[0133] In addition, the energy generated by the turbo air adiabatic expansion process is used for the above-mentioned turbo air compression process to compress the medium-pressure turbo air.

[0134] Here, in the air separation method of the present embodiment, a part of the high-pressure feed air branches from pipeline L1 through the feed air bypass pipeline L25, and after being decompressed by the feed air bypass valve V9, it converges with the high-pressure turbine air flowing in pipeline L51 (feed air bypass process). According to the above process, the flow rate of the turbo blower 22 is relatively reduced compared to the flow rate of the expansion turbine 24, and the outlet pressure of the turbo blower 22 rises. Therefore, the expansion ratio of the expansion turbine 24 becomes larger. Thereby, the cold quantity generated per unit throughput in the expansion turbine 24 can be increased.

[0135] In addition, since the pressure of the high-pressure turbine air rises with the increase in the flow rate of the feed air bypass pipeline L25, the pressure of the high-pressure turbine air can be adjusted by the flow rate of the feed air bypass pipeline L25. The pressure of the high-pressure turbine air is equal to or lower than the pressure of the high-pressure feed air or the pressure of the high-pressure column 17.

[0136] In the feed air bypass process, for example, the pressure of the high-pressure feed air branched from pipeline L1 after decompression can be controlled by the feed air bypass valve V9, thereby indirectly adjusting the flow rate of the high-pressure feed air in the feed air bypass pipeline L25.

[0137] Furthermore, the feed air bypass pipeline L25 and the feed air bypass valve V9 can also be used when starting the air separation device 10. In this case, when starting the air separation device 10 to cool each device such as the high-pressure column 17, the low-pressure column 18, and the argon column 19 from the normal-temperature initial state to the low-temperature stable state, the high-pressure feed air in pipeline L1 can be supplied to the expansion turbine 24 via the feed air bypass pipeline L25 without passing through the high-pressure column 17. Thereby, a low-temperature fluid can be generated by the adiabatic expansion of the expansion turbine 24, and thus the device can be effectively cooled.

[0138] The low-pressure turbine air led out to pipeline L52 is introduced into the middle part of the low-pressure column 18 as the feed of the low-pressure column 18.

[0139] The medium-pressure oxygen-rich liquefied air supplied to the outer cylinder 20 of the turbine air evaporator and not vaporized by the turbine air evaporator H3 is led out to pipeline L6, and after being decompressed by the valve V2, it is introduced into the middle part of the low-pressure column 18 as the feed of the low-pressure column 18.

[0140] In the low-pressure column 18, in addition to the fluid decompressed by the valve V5, the fluid decompressed by the valve V7, the fluid decompressed by the valve V6, the fluid decompressed by the valve V2, and the low-pressure turbine air obtained by the adiabatic expansion of the expansion turbine 24, there is also low-pressure oxygen gasified by the argon condenser H1. Through low-temperature distillation, it is separated into low-pressure nitrogen gas located in the upper part of the low-pressure column 18, low-pressure liquefied oxygen located in the lower part of the low-pressure column 18, and argon-rich liquefied oxygen located in the middle part of the low-pressure column 18 (low-pressure separation process).

[0141] The low-pressure nitrogen gas at the top of the low-pressure tower 18 is led out into pipeline L13. After heat recovery by the subcooler 21 and the main heat exchanger 16, it is recovered as the product low-pressure nitrogen gas (LPGN2).

[0142] The low-purity low-pressure nitrogen gas rising in the upper part of the low-pressure tower 18 is led out into pipeline L14. After heat recovery by the subcooler 21 and the main heat exchanger 16, it is recovered as waste nitrogen gas WGN2. In the subcooler 21, through the indirect heat exchange between the high-temperature fluid flowing through pipelines L11, L32, and L9 and the low-temperature fluid flowing through pipelines L13 and L14, each high-temperature fluid is cooled and each low-temperature fluid is heated, but the combination of the high-temperature fluid and the low-temperature fluid is not limited thereto. The low-pressure liquefied oxygen at the bottom of the low-pressure tower 18 is contained in the argon condenser H1 at the bottom of the low-pressure tower 18. Through indirect heat exchange with the argon gas at the top of the argon tower 19, it vaporizes itself to become low-pressure oxygen gas, and the argon gas is liquefied to generate liquefied argon (argon condensation process).

[0143] The low-pressure liquefied oxygen that has not been vaporized by the argon condenser H1 is led out into pipeline L15, converges with the medium-pressure liquefied oxygen decompressed by valve V8, and then is introduced into pipeline L16.

[0144] The fluid introduced into pipeline L16 is pressurized by the liquefied oxygen pump 25 to the necessary pressure corresponding to the product specifications to become high-pressure liquefied oxygen. The high-pressure liquefied oxygen is completely vaporized by the main heat exchanger 16, and after heat recovery to normal temperature, it is recovered as the product high-pressure oxygen gas (HPGO2).

[0145] A part of the low-pressure liquefied oxygen led out into pipeline L15 is led out into pipeline L17 branched from pipeline L15 and is recovered as the product low-pressure liquefied oxygen (LPLO2).

[0146] The argon-rich liquefied oxygen concentrated in the middle part of the low-pressure tower 18 is led out into pipeline L18. After being pressurized by the argon-rich liquefied oxygen pump 26 to the pressure required for transporting it to the argon tower 19 with an operating pressure higher than that of the low-pressure tower 18, it is introduced into the middle part or the lower part of the argon tower 19.

[0147] In addition, according to the positional relationship between the low-pressure tower 18 and the argon tower 19, sometimes it is also possible not to use the argon-rich liquefied oxygen pump 26, but to use the liquid head based on the liquid level height difference to transport the argon-rich liquefied oxygen of the low-pressure tower 18 to the argon tower 19. At this time, the argon-rich liquefied oxygen pump 26 is not required.

[0148] In the argon tower 19, the argon-rich liquefied oxygen supplied via pipeline L18, the liquefied argon supplied via pipeline L192, and the medium-pressure oxygen gas obtained by vaporizing the high-pressure nitrogen condenser H2 are separated by low-temperature distillation into argon gas at the upper part of the argon tower 19 and medium-pressure liquefied oxygen at the lower part of the argon tower 19 (argon separation process).

[0149] The argon gas located in the upper part of the argon column 19 is introduced into the argon condenser H1 via the pipeline L191.

[0150] The argon gas introduced into the argon condenser H1 is indirectly heat-exchanged with the low-pressure liquefied oxygen at the bottom of the low-pressure column 18, and is liquefied into liquefied argon by itself, and the low-pressure liquefied oxygen is vaporized to generate low-pressure oxygen (argon condensation process).

[0151] The liquefied argon generated by the argon condensation process is introduced into the top of the argon column 19 via the pipeline L192.

[0152] A part of the argon gas in the pipeline L191 is led out to the pipeline L20 branched from the pipeline L191, and after being heat-recovered to normal temperature by the main heat exchanger 16, it is recovered as product argon gas (GAR) (product argon gas leading-out process).

[0153] In addition, as Figure 1 shown by the dotted line in, sometimes the argon gas not liquefied in the argon condenser H1 is led out to the pipeline L21, and after being heat-recovered to normal temperature by the main heat exchanger 16 via the pipeline L20, it is recovered as product argon gas (GAR).

[0154] A part of the liquefied argon flowing through the pipeline L192 is led out to the pipeline L22 branched from the pipeline L192, and is recovered as product liquefied argon (LAR) (product argon leading-out process).

[0155] The medium-pressure liquefied oxygen at the bottom of the argon column 19 is in the high-pressure nitrogen condenser H2 housed at the bottom of the argon column 19, and is indirectly heat-exchanged with the high-pressure nitrogen gas supplied from the top of the high-pressure column 17, and is vaporized by itself to become medium-pressure oxygen, and the high-pressure nitrogen gas is liquefied to generate high-pressure liquefied nitrogen (high-pressure nitrogen condensation process).

[0156] The medium-pressure liquefied oxygen not vaporized by the high-pressure nitrogen condenser H2 is led out to the pipeline L23, and after being decompressed by the valve V8, it converges with the low-pressure liquefied oxygen in the pipeline L15.

[0157] A part of the medium-pressure liquefied oxygen led out to the pipeline L23 is led out to the pipeline L24 branched from the pipeline L23, and is recovered as product medium-pressure liquefied oxygen (MPLO2).

[0158] In addition, although in Figure 1The drawings are omitted, but sometimes the other end of the pipeline L15 connected to the bottom of the low-pressure column 18 is connected to the lower part of the argon column 19. In this case, the pipeline L15 pressurizes the low-pressure liquefied oxygen discharged from the bottom of the low-pressure column 18 through a liquid head based on the liquid level height difference or a pump (omitted in the drawings) provided on the pipeline L15, etc., to generate pressurized liquefied oxygen, and supplies it to the lower part of the argon column 19. The pressurized liquefied oxygen supplied from the pipeline L15 converges with the medium-pressure liquefied oxygen at the bottom of the argon column 19, is discharged to the pipeline L23, and is recovered as product high-pressure oxygen (HPGO2) via the pipeline L16. In this case, the valve V8 provided on the pipeline L23 is not required.

[0159] In addition, although Figure 1 the drawings are omitted, but sometimes the other end of the pipeline L23 connected to the bottom of the argon column 19 is connected to the lower part of the low-pressure column 18. In this case, the pipeline L23 reduces the pressure of the medium-pressure liquefied oxygen discharged from the bottom of the argon column 19 through the valve V8 to generate depressurized liquefied oxygen, and supplies it to the lower part of the low-pressure column 18. The depressurized liquefied oxygen supplied from the pipeline L23 converges with the low-pressure liquefied oxygen at the bottom of the low-pressure column 18, is discharged to the pipeline L15, and is recovered as product high-pressure oxygen (HPGO2) via the pipeline L16.

[0160] In addition, although Figure 1 the drawings are omitted, but sometimes a part or all of the high-pressure raw material liquefied air introduced into the high-pressure column 17 via the pipeline L2 is supplied to the middle part or the upper part of the low-pressure column 18.

[0161] In addition, sometimes the raw material air bypass pipeline L25 branches from the middle of the main heat exchanger 16 of the pipeline L1 or from the outlet of the main heat exchanger 16 of the pipeline L1, and converges with the inlet of the expansion turbine 24 of the pipeline L51. In this case, a part of the high-pressure raw material air cooled by the main heat exchanger 16 of the pipeline L1 can be bypassed to the inlet of the expansion turbine 24 and supplied.

[0162] The concentration of argon contained in the product argon (GAR) and the concentration of argon contained in the product liquefied argon (LAR) are preferably 50% or more, and more preferably 95% or more, for example.

[0163] In addition to the case where argon or liquefied argon is directly recovered as a product as described above, sometimes an argon purification device (omitted in the drawings) is provided in the subsequent stage to remove impurities such as oxygen components or nitrogen components.

[0164] Even when the product argon (GAR) or the product liquefied argon (LAR) is not required, when the purity of the product high-pressure oxygen (HPGO2) or the product liquefied oxygen (LPLO2 or MPLO2, etc.) is high, for example, when the oxygen concentration is 98% or more, argon is sometimes recovered to improve the oxygen recovery rate.

[0165] Although the illustration is omitted in Figure 1 in the case of recovering the low-pressure oxygen (LPGO2) of the product, the low-pressure oxygen is led out from the bottom of the low-pressure column 18, heat-recovered to normal temperature by the main heat exchanger 16, and then recovered as a product.

[0166] In addition, in the case of recovering the medium-pressure oxygen (MPGO2) of the product, the medium-pressure oxygen is led out from the bottom of the argon column 19, heat-recovered to normal temperature by the main heat exchanger 16, and then recovered as a product.

[0167] In the case of recovering the low-pressure oxygen (LPGO2) and / or the medium-pressure oxygen (MPGO2) of the product, the low-pressure liquefied oxygen at the bottom of the low-pressure column 18 is introduced into the bottom of the argon column 19 via a pipeline with the illustration omitted, or the medium-pressure liquefied oxygen at the bottom of the argon column 19 is introduced into the bottom of the low-pressure column 18 via a pipeline with the illustration omitted, whereby the flow rate balance can be adjusted.

[0168] The air separation method of the present embodiment includes: a high-pressure separation step of cooling and then cryogenically distilling the high-pressure raw material air obtained by compressing, precooling, and purifying the air containing oxygen, nitrogen, and argon, so as to separate the high-pressure raw material air into high-pressure nitrogen and high-pressure oxygen-rich liquefied air; a turbine air generation step of gasifying the medium-pressure oxygen-rich liquefied air obtained by decompressing the high-pressure oxygen-rich liquefied air to generate medium-pressure turbine air; a turbine air compression step of heating and then compressing the medium-pressure turbine air to generate high-pressure turbine air; a turbine air adiabatic expansion step of adiabatically expanding the high-pressure turbine air to generate low-pressure turbine air, generating the cold quantity required for air separation operation; a low-pressure separation step of cryogenically distilling the low-pressure turbine air to separate it into low-pressure nitrogen, low-pressure liquefied oxygen, and argon-rich liquefied oxygen; an argon separation step of pressurizing the argon-rich liquefied oxygen and cryogenically distilling it at a pressure higher than that of the low-pressure separation step, so as to separate the argon-rich liquefied oxygen into argon and medium-pressure liquefied oxygen; an argon condensation step of indirectly exchanging heat between argon and low-pressure liquefied oxygen to liquefy argon to generate liquefied argon, and at the same time gasifying the low-pressure liquefied oxygen to generate low-pressure oxygen; a high-pressure nitrogen condensation step of indirectly exchanging heat between high-pressure nitrogen and medium-pressure liquefied oxygen, so as to liquefy the high-pressure nitrogen to generate high-pressure liquefied nitrogen, and at the same time gasify the medium-pressure liquefied oxygen to generate medium-pressure oxygen; and a product argon extraction step of extracting at least one of a part of argon, the argon not liquefied in the argon condensation step, and a part of the liquefied argon as a product, the turbine air compression step uses the energy generated by the turbine air adiabatic expansion step to compress the medium-pressure turbine air, and the air separation method further includes a raw material air bypass step, and the raw material air bypass step branches a part of the high-pressure raw material air, decompresses it, and then merges it with the high-pressure turbine air.

[0169] According to the air separation method of the present embodiment, by adopting the method including the above respective processes, similarly to the above content, for example, when the flow rates of product medium-pressure liquefied oxygen (MPLO2), product low-pressure liquefied oxygen (LPLO2), product high-pressure liquefied nitrogen (HPLN2), etc. are large and the amount of cold required for operation is large, by bypassing a part of the high-pressure raw air to the pipeline L51 which is the inlet of the expansion turbine 24, the flow rate of the turbo blower 22 can be relatively suppressed to increase the compression ratio, the expansion ratio of the expansion turbine 24 can be increased, and the increase in the throughput can be suppressed. Thereby, the flow rate of the low-pressure turbine air supplied to the low-pressure column 18 can be reduced, so that the argon recovery rate can be improved.

[0170] In addition, as in the above-mentioned Patent Document 2, when a part or all of the low-pressure turbine air is not supplied to the low-pressure column but recovered (released to the atmosphere), although the flow rate of the low-pressure turbine air supplied to the low-pressure column is optimized, thereby the argon recovery rate can be improved, the oxygen recovery rate is reduced because the oxygen component contained in the low-pressure turbine air not supplied to the low-pressure column cannot be recovered as a product. In contrast, by using the air separation apparatus 10 of the present embodiment, all of the low-pressure turbine air can be supplied to the low-pressure column 18 as a raw material of the low-pressure column 18, so that the reduction in the oxygen recovery rate can be suppressed.

[0171] Furthermore, as described above, since the high-pressure column 17, the low-pressure column 18, and the argon column 19 are thermally integrated through the respective processes, the operating pressures of the respective distillation columns increase in the order of the low-pressure column 18, the argon column 19, and the high-pressure column 17.

[0172] <Other Embodiments>

[0173] As described above, an example of the air separation method and the air separation apparatus of the present invention has been described by way of the embodiments, but the present invention is not limited to the above embodiments. Each structure and its combination in the above embodiments are examples, and additions, omissions, replacements, and other changes of the structure can be made without departing from the gist of the present invention.

[0174] <Function and Effect>

[0175] As described above, according to the air separation method of the present embodiment, the following method is adopted, which includes: a turbine air generation process for generating medium-pressure turbine air and a turbine air compression process for generating high-pressure turbine air, and further includes a raw air bypass process for reducing the pressure of a part of the high-pressure raw air and then merging it with the high-pressure turbine air. In this way, by branching a part of the high-pressure raw air and then merging it with the high-pressure turbine air as oxygen-enriched air, the throughput of the expansion turbine 24 can be reduced while maintaining the generated cold amount, or the generated cold amount can be increased while maintaining the throughput of the expansion turbine 24.

[0176] Therefore, it is possible to improve the argon recovery rate while maintaining the oxygen recovery rate or suppressing the decrease in the oxygen recovery rate.

[0177] In addition, the air separation apparatus 10 according to the present embodiment has the above-described structure: the structure indirectly exchanges heat with the high-pressure oxygen-rich liquefied air led out from the bottom of the high-pressure column 17 after depressurization to vaporize it, thereby generating medium-pressure turbine air as oxygen-rich air, compresses the medium-pressure turbine air by the turbine blower 22, adiabatically expands it by the expansion turbine 24, and supplies it to the low-pressure column 18. The apparatus further includes a raw material air bypass line L25 that depressurizes a part of the high-pressure raw material air and merges it with the high-pressure turbine air. By providing such a raw material air bypass line L25, similarly to the above, it is possible to reduce the throughput of the expansion turbine 24 while maintaining the generated cooling capacity, or to increase the generated cooling capacity while maintaining the throughput of the expansion turbine 24.

[0178] Therefore, similarly to the above, it is possible to improve the argon recovery rate while maintaining the oxygen recovery rate or suppressing the decrease in the oxygen recovery rate.

[0179] Example

[0180] Hereinafter, examples will be shown to more specifically describe the air separation method and the air separation apparatus of the present invention. However, the present invention is not limited to the following examples and can be appropriately modified and implemented within the scope of not changing its gist.

[0181] <Example>

[0182] In the example, using a simulator manufactured by Taiyo Nippon Sanso Corporation (this simulator is the same as the simulator used in actual design of an air separation apparatus), a simulation was performed using Figure 1 the air separation apparatus 10 shown.

[0183] In the simulation of this example, the following conditions were set: when the flow rate of the high-pressure raw material air was set to 100, the recovery flow rate was 24.1, the pressure was 117 kPaA, the product low-pressure nitrogen (LPGN2) with an oxygen concentration of 0.1 ppm or less, the flow rate was 9.8, the pressure was 800 kPaA or more, the product high-pressure nitrogen (HPGN2) with an oxygen concentration of 0.1 ppm or less, and the flow rate was 2.2, the product low-pressure liquefied nitrogen (LPLN2) with an oxygen concentration of 0.1 ppm or less, the recoverable flow rates of the product high-pressure oxygen (HPGO2) with a pressure of 3120 kPaA and an oxygen concentration of 99.6% or more and the product argon (GAR) with an oxygen concentration of 1.5% or less were calculated. In addition, the condition was set such that the flow rate of the high-pressure raw material air flowing through the raw material air bypass line L25 was 6.1.

[0184] The simulation conditions and results of the above-mentioned examples are shown in the following Table 1. The following Table 1 is a list showing the simulation conditions and simulation results of the examples and comparative examples described later. In the following Table 1, the values ​​in parentheses are calculated values ​​based on the simulation.

[0185] [Table 1]

[0186] Simulation input conditions and calculation results

[0187]

[0188]

[0189] <Comparative Example>

[0190] In the comparative example, for Figure 1 The case of the raw air bypass line L25 shown (i.e., the case where the flow rate of the high-pressure raw air in the raw air bypass line L25 is 0 (zero)) was simulated under the same conditions as the above-mentioned embodiment, and the results are shown in the above-mentioned Table 1.

[0191] <Evaluation Results of Examples and Comparative Examples>

[0192] As shown in the simulation results in Table 1, Figure 1 In the example of the simulation conducted under the condition that a part of the high-pressure raw air is made to flow through the raw air bypass line L25 at a flow rate of 6.1, the outlet pressure of the turbo blower 22 driven by the expansion turbine 24, that is, the inlet pressure of the expansion turbine 24, increases, the expansion ratio of the expansion turbine 24 increases, and the processing capacity of the expansion turbine 24 decreases. It can be confirmed that in the example, the amount of low-pressure turbine air supplied to the low-pressure column 18 is reduced, and on the contrary, the flow rates of the medium-pressure oxygen and low-pressure oxygen generated by the high-pressure nitrogen condenser and the argon condenser are increased, and as a result, the flow rate of the product high-pressure oxygen (HPGO2) is maintained, and the flow rate of the product argon (GAR) is increased. Specifically, the result of the example is that the flow rate of the product high-pressure oxygen (HPGO2) is maintained at 19.2, and the flow rate of the product argon (GAR) is 0.62.

[0193] On the other hand, in the comparative example of the simulation carried out under the condition that the high-pressure raw air does not flow through the raw air bypass line L25, compared with the example, the outlet pressure of the turbo blower 22 driven by the expansion turbine 24, that is, the inlet pressure of the expansion turbine 24, decreases. From this, it can be confirmed that the expansion ratio of the expansion turbine 24 also decreases and the throughput increases. Thus, in the comparative example, compared with the example, the amount of low-pressure turbine air supplied to the low-pressure column 18 increases to 30.0. Therefore, on the one hand, the flow rate of the product high-pressure oxygen (HPGO2) is maintained at 19.2, and on the other hand, the flow rate of the product argon (GAR) decreases to 0.50.

[0194] Based on the results of the examples described above, it can be confirmed that the air separation method of the present invention having a raw air bypass process and the air separation apparatus 10 of the present invention having a raw air bypass line L25 can maintain the oxygen recovery rate or suppress the decrease in the oxygen recovery rate, and can improve the argon recovery rate.

[0195] The air separation method and air separation apparatus of the present invention can improve the argon recovery rate while maintaining the oxygen recovery rate or suppressing the decrease in the oxygen recovery rate, and are therefore very suitable for various uses in industrial oxygen or nitrogen production.

[0196] Description of Reference Numerals

[0197] 10 Air separation apparatus

[0198] 11 Air compressor

[0199] 12 Air pre-cooler

[0200] 13 Air purifier

[0201] 14 Air booster

[0202] 15 After-cooler for air booster

[0203] 16 Main heat exchanger

[0204] 17 High-pressure column

[0205] 18 Low-pressure column

[0206] 19 Argon column

[0207] 20 Outer cylinder of turbo air evaporator

[0208] 21 Sub-cooler

[0209] 22 Turbo blower

[0210] 23 After-cooler for turbo blower

[0211] 24 Expansion turbine

[0212] 25 Liquid oxygen pump

[0213] 26 Argon-rich Liquid Oxygen Pump

[0214] H1 Argon Condenser

[0215] H2 High-pressure Nitrogen Condenser

[0216] H3 Turbine Air Evaporator

[0217] Pipelines L1, L2, L4 - L6, L8 - L18, L20 - L24, L31 - L35, L51, L52, L71, L72, L191, L192

[0218] L25 Raw Air Bypass Pipeline

[0219] Valves V1 - V8

[0220] V9 Raw Air Bypass Valve

Claims

1. An air separation method, characterized in that, Comprising: A high-pressure separation process, in which the high-pressure raw air obtained by compressing, precooling and purifying air containing oxygen, nitrogen and argon is cooled and then cryogenically distilled, so as to separate the high-pressure raw air into high-pressure nitrogen and high-pressure oxygen-rich liquefied air; A turbine air generation process, in which the medium-pressure oxygen-rich liquefied air obtained by decompressing the high-pressure oxygen-rich liquefied air is vaporized to generate medium-pressure turbine air; A turbine air compression process, in which the medium-pressure turbine air is heated and then compressed to generate high-pressure turbine air; A turbine air adiabatic expansion process, in which the high-pressure turbine air is adiabatically expanded to generate low-pressure turbine air, generating the cooling capacity required for air separation operation; A low-pressure separation process, in which the low-pressure turbine air is cryogenically distilled and separated into low-pressure nitrogen, low-pressure liquefied oxygen and argon-rich liquefied oxygen; An argon separation process, in which the argon-rich liquefied oxygen is pressurized and then cryogenically distilled at a pressure higher than that of the low-pressure separation process, so as to separate the argon-rich liquefied oxygen into argon and medium-pressure liquefied oxygen; An argon condensation process, through the indirect heat exchange between the argon and the low-pressure liquefied oxygen, liquefying the argon to generate liquefied argon, and vaporizing the low-pressure liquefied oxygen to generate low-pressure oxygen; A high-pressure nitrogen condensation process, through the indirect heat exchange between the high-pressure nitrogen and the medium-pressure liquefied oxygen, liquefying the high-pressure nitrogen to generate high-pressure liquefied nitrogen, and vaporizing the medium-pressure liquefied oxygen to generate medium-pressure oxygen; And A product argon extraction process, in which at least one of a part of the argon, the argon not liquefied in the argon condensation process and a part of the liquefied argon is extracted as a product; The turbine air compression process uses the energy generated by the turbine air adiabatic expansion process to compress the medium-pressure turbine air; The air separation method further includes a raw air bypass process, in which a part of the high-pressure raw air branches off, is decompressed and then merges with the high-pressure turbine air.

2. The air separation method according to claim 1, wherein In the turbine air generation process, through the indirect heat exchange between the high-pressure nitrogen and the medium-pressure oxygen-rich liquefied air, the high-pressure nitrogen is liquefied to generate high-pressure liquefied nitrogen, and the medium-pressure oxygen-rich liquefied air is vaporized to generate the medium-pressure turbine air.

3. The air separation method according to claim 1, characterized in that, In the turbine air generation process, through the indirect heat exchange between the high-pressure nitrogen-rich air generated in the middle stage of the high-pressure separation process and the medium-pressure oxygen-rich liquefied air, the high-pressure nitrogen-rich air is liquefied to generate high-pressure nitrogen-rich liquefied air, and the medium-pressure oxygen-rich liquefied air is vaporized to generate the medium-pressure turbine air.

4. The air separation method according to claim 1, wherein, In the turbine air generation process, through the indirect heat exchange between the high-pressure raw air and the medium-pressure oxygen-rich liquefied air, the high-pressure raw air is liquefied to generate high-pressure liquefied air, and the medium-pressure oxygen-rich liquefied air is vaporized to generate the medium-pressure turbine air.

5. The air separation method according to any one of claims 1 to 4, characterized in that, The raw air bypass process indirectly adjusts the flow rate of the high-pressure raw air branched off from the high-pressure raw air by controlling the pressure after decompression.

6. An air separation device, characterized in that, Comprising: A high-pressure tower, which is used to cool and then cryogenically distill the high-pressure raw air obtained by compressing, precooling and purifying air containing oxygen, nitrogen and argon, so as to separate the high-pressure raw air into high-pressure nitrogen and high-pressure oxygen-rich liquefied air; A turbo air evaporator for vaporizing medium-pressure oxygen-rich liquefied air obtained by reducing the pressure of the high-pressure oxygen-rich liquefied air to generate medium-pressure turbo air; A turbo blower for heating and compressing the medium-pressure turbo air to generate high-pressure turbo air; An expansion turbine for adiabatically expanding the high-pressure turbo air to generate low-pressure turbo air and producing the cold energy required for air separation operation; A low-pressure column for cryogenically distilling the low-pressure turbo air to separate it into low-pressure nitrogen, low-pressure liquefied oxygen, and argon-rich liquefied oxygen; An argon column for pressurizing the argon-rich liquefied oxygen and cryogenically distilling it at a pressure higher than that of the low-pressure column to separate the argon-rich liquefied oxygen into argon gas and medium-pressure liquefied oxygen; An argon condenser for indirectly exchanging heat between the argon gas and the low-pressure liquefied oxygen to liquefy the argon gas to generate liquefied argon and vaporize the low-pressure liquefied oxygen to generate low-pressure oxygen; A high-pressure nitrogen condenser for indirectly exchanging heat between the high-pressure nitrogen and the medium-pressure liquefied oxygen to liquefy the high-pressure nitrogen to generate high-pressure liquefied nitrogen and vaporize the medium-pressure liquefied oxygen to generate medium-pressure oxygen; And A product argon export pipeline for extracting at least one of a part of the argon gas, the argon gas not liquefied in the argon condenser, and a part of the liquefied argon as a product; Regarding the turbo blower, the rotational energy generated by the expansion turbine is used to drive the turbo blower to rotate; The air separation device further includes a raw material air bypass pipeline for branching and reducing the pressure of a part of the high-pressure raw material air and then merging it with the high-pressure turbo air.

7. The air separation device according to claim 6, wherein The turbo air evaporator indirectly exchanges heat between the high-pressure nitrogen and the medium-pressure oxygen-rich liquefied air to liquefy the high-pressure nitrogen to generate high-pressure liquefied nitrogen and vaporize the medium-pressure oxygen-rich liquefied air to generate the medium-pressure turbo air.

8. The air separation device according to claim 6, characterized in that, The turbo air evaporator indirectly exchanges heat between the high-pressure nitrogen-rich air generated in the intermediate stage of the treatment in the high-pressure column and the medium-pressure oxygen-rich liquefied air to liquefy the high-pressure nitrogen-rich air to generate high-pressure nitrogen-rich liquefied air and vaporize the medium-pressure oxygen-rich liquefied air to generate the medium-pressure turbo air.

9. The air separation device according to claim 6, wherein The turbo air evaporator indirectly exchanges heat between the high-pressure raw material air and the medium-pressure oxygen-rich liquefied air to liquefy the high-pressure raw material air to generate high-pressure liquefied air and vaporize the medium-pressure oxygen-rich liquefied air to generate the medium-pressure turbo air.

10. The air separation device according to any one of claims 6 to 9, characterized in that, A raw material air bypass valve is further provided on the raw material air bypass pipeline, and the raw material air bypass valve can indirectly adjust the flow rate of the high-pressure raw material air branched from the high-pressure raw material air by controlling the pressure after pressure reduction.

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