Air separation device

Abstract

The objective is to provide an air separation system that reduces the number of pieces of equipment by operating an ultra-high purity oxygen rectification column (UPO column) and an oxygen rectification column at equivalent pressures and using a common recycled gas compressor, thereby producing product oxygen of different purities as well as product nitrogen. [Solution] The air separation apparatus A1 comprises a main heat exchanger E1, a nitrogen rectification column 2, a first nitrogen condenser 3, a second nitrogen condenser 4, an ultra-high purity oxygen rectification column 5, an ultra-high purity oxygen evaporator 6, an oxygen rectification column 7, an oxygen evaporator 8, a turbine 91, a booster 92, a recycle gas compressor 10, and a liquefied oxygen pump 11. By operating the ultra-high purity oxygen rectification column 6 and the oxygen rectification column 7 at equivalent pressure and using a common recycle gas compressor 10, ultra-high purity oxygen (UPO) and oxygen (GOX) can be produced at low cost.

Description

[Technical Field]

[0001] This invention relates to an air separation apparatus capable of producing product nitrogen gas along with product oxygen gas of different purities. [Background technology]

[0002] An air separation unit removes impurities (water and carbon dioxide) from compressed raw air using a purification unit, cools it, and then performs rectification in a rectification column to obtain product gases of nitrogen, argon, and oxygen.

[0003] Prior art includes methods for producing product oxygen gas (GOX) by integrating a nitrogen rectification column and an oxygen rectification column (Patent Document 1), and a process in which an ultra-high purity oxygen rectification column operates at a lower pressure (e.g., 1.5 barA) than an oxygen rectification column when supplying nitrogen (N2), ultra-high purity oxygen (UPO), and oxygen (GOX) (Patent Document 2). Furthermore, there is a high-purity oxygen and nitrogen production system that can produce large quantities of high-purity oxygen without impairing the nitrogen recovery rate relative to the amount of raw air (Patent Document 3). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] China Public Gazette No. 108120226 [Patent Document 2] China Public Gazette No. 108036584 [Patent Document 3] Japanese Patent Publication No. 2020173041

[0005] When producing ultra-high purity oxygen (UPO) and oxygen (GOX), a recycle gas compressor is required for the air separation unit to achieve sufficient distillation capacity. However, until now, ultra-high purity oxygen (UPO) and oxygen (GOX) each required separate compressors corresponding to the pressure of the rectification column. [Overview of the project] [Problems that the invention aims to solve]

[0006] This invention provides an air separation apparatus that reduces the number of pieces of equipment by operating the ultra-high purity oxygen (UPO) process and the oxygen (GOX) production process at equivalent pressure and using a common recycled gas compressor, thereby producing product oxygen of different purities as well as product nitrogen. [Means for solving the problem]

[0007] The inventor discovered that ultra-high purity oxygen (UPO) and oxygen (GOX) can be produced at low cost by operating an ultra-high purity oxygen rectification column and an oxygen rectification column at equivalent pressure and using a common recycled gas compressor. This disclosure includes, for example, the following aspects: [1] A main heat exchanger that exchanges heat with the raw air, A nitrogen rectification column into which the raw material air that has passed through the main heat exchanger is introduced, A first nitrogen condenser that condenses the vapor flow introduced from the nitrogen rectification column and returns the resulting reflux liquid to the top of the nitrogen rectification column, An ultra-high purity oxygen rectification column into which an oxygen-containing fluid, which has been drawn out from the intermediate part of the rectification section of the aforementioned nitrogen rectification column, An ultra-high purity oxygen evaporator is provided at the bottom of the ultra-high purity oxygen rectification column, An oxygen rectification column into which the first oxygen-enriched liquid from the refrigerant storage section of the first nitrogen condenser is introduced, An oxygen evaporator is provided at the lower part of the oxygen rectification column, The system includes a recycle gas compressor that compresses a mixed recycle gas obtained by mixing a first recycle gas discharged from the top of the ultra-high purity oxygen rectification column with a second recycle gas discharged from the top of the oxygen rectification column, An air separation device configured such that the mixed recycled gas compressed by the recycled gas compressor is sent to the ultra-high purity oxygen evaporator and / or the oxygen evaporator as a heat transfer medium. [2] The air separation apparatus according to [1], wherein the mixed recycled gas is heated in the main heat exchanger, compressed in the recycled gas compressor, introduced into the main heat exchanger for cooling, and then sent to the ultra-high purity oxygen evaporator and / or the oxygen evaporator as a heat transfer medium. [3] The air separation apparatus according to [1], wherein the mixed recycled gas is heated in the main heat exchanger, then compressed in the recycled gas compressor, then combined with the raw air, introduced into the main heat exchanger for cooling, and then sent to the ultra-high purity oxygen evaporator and / or the oxygen evaporator as a heat transfer medium. [4] A second nitrogen condenser is installed above the first nitrogen condenser, An oxygen enrichment line for introducing the oxygen enrichment liquid at the bottom of the nitrogen rectification column into the second nitrogen condenser, Turbine and A booster, which is driven by the rotational power of the turbine, is connected coaxially to the turbine, The system further comprises piping for supplying the second oxygen-enriched liquid stored in the refrigerant storage section of the second nitrogen condenser to the refrigerant storage section of the first nitrogen condenser as the first oxygen-enriched liquid, In the first nitrogen condenser, the vapor flow introduced from the nitrogen rectification column and the first oxygen-enriched liquid stored in the refrigerant storage section of the first nitrogen condenser are subjected to heat exchange, and a portion of the first oxygen-enriched liquid is evaporated to obtain the first oxygen-enriched gas, which is then discharged, heated in the main heat exchanger, and expanded by the turbine. An air separation apparatus according to any one of [1] to [3], wherein the second oxygen-enriched gas obtained by exchanging heat between the vapor flow introduced from the nitrogen rectification column and the second oxygen-enriched liquid in the second nitrogen condenser to evaporate a portion of the second oxygen-enriched liquid is compressed by the booster, and the second oxygen-enriched gas compressed by the booster is cooled in the main heat exchanger before being introduced into the nitrogen rectification column.

[0008] (effect) (1) By operating the ultra-high purity oxygen rectification column and the oxygen rectification column at the same pressure and using a common recycle gas compressor, the number of equipment can be reduced, and product oxygen (UPO and GOX) with different purities can be produced. (2) By using compressed mixed recycle gas (a gas obtained by compressing a mixed gas of the gas derived from the top of the ultra-high purity oxygen rectification column and the gas derived from the top of the oxygen rectification column with a recycle gas compressor) as the heat source of the ultra-high purity oxygen evaporator and / or the oxygen evaporator, the nitrogen production amount can be maintained without increasing the feed air amount as compared with the case of using the oxygen-enriched liquid of the nitrogen rectification column or the feed air as the heat source. (3) By recovering the cold of the first oxygen-enriched gas expanded and cooled by the turbine in the main heat exchanger, it is possible to contribute to maintaining the cold balance of the entire apparatus. In addition, since the second oxygen-enriched gas compressed by the booster can be recycled and reused as a raw material for the nitrogen rectification column, it can also contribute to the nitrogen recovery rate. Furthermore, by mechanically connecting the turbine and the booster, the power obtained by the turbine can be used to drive the booster, and the power consumption can be suppressed.

Brief Description of the Drawings

[0009] [Figure 1] It is a diagram showing an example of the air separation apparatus A1 of Embodiment 1.

Modes for Carrying Out the Invention

[0010] Hereinafter, the apparatus in one embodiment will be described with reference to the embodiment shown in FIG. 1. However, this is to explain an example of the present disclosure. The present disclosure is not limited to the following embodiments, and includes various modified forms implemented within the scope of not changing the gist of the present disclosure. Also, not all of the configurations described below are essential configurations of the present disclosure. Upstream and downstream are based on the flow direction of the fluid (liquid, gas).

[0011] (Embodiment 1) The air separation apparatus A1 of Embodiment 1 will be described with reference to FIG. 1. The air separation unit A1 comprises a main heat exchanger E1, a nitrogen rectification column 2, a primary nitrogen condenser 3, a secondary nitrogen condenser 4, an ultra-high purity oxygen rectification column 5, an ultra-high purity oxygen evaporator 6, an oxygen rectification column 7, an oxygen evaporator 8, a turbine 91, a booster 92, a recycle gas compressor 10, and a liquefied oxygen pump 11.

[0012] The feed air is pressurized to a predetermined pressure by a feed air compressor (not shown), and moisture and carbon dioxide are removed by a feed air purification device (not shown). The feed air purification device employs a series of well-known techniques, such as temperature swing adsorption and filters. The purified feed air is then introduced into the main heat exchanger E1 at the hot end via the feed air line L1, cooled, and then discharged from the cold end to be introduced into the lower part of the nitrogen rectification column 2.

[0013] (Nitrogen rectification column) In the nitrogen rectification column 2, cooled raw material air comes into countercurrent contact with the reflux liquid and is separated into nitrogen and oxygen components by rectification. Oxygen and components with higher boiling points than oxygen in the raw material air dissolve in the reflux liquid, while components with lower boiling points than oxygen are released into the gas phase to form a vapor flow. The nitrogen rectification column 2 comprises a column bottom 21, rectification sections (lower rectification section 22, middle rectification section 23, upper rectification section 24), and a column top 25. The raw material air line L1 is connected to the lower part of the nitrogen rectification column 2, preferably between the lower rectification section 22 and the middle rectification section 23.

[0014] The oxygen enrichment liquid line L21 sends the oxygen enrichment liquid stored at the bottom of the tower 21 to the refrigerant storage section 40 of the second nitrogen condenser 4. Alternatively, the oxygen enrichment liquid may be cooled in a subcooler (not shown) before being introduced into the second nitrogen condenser 4. Furthermore, a first valve V1 may be provided in the oxygen enrichment liquid line L21.

[0015] Pipe L26 sends the nitrogen gas (vapor flow) from the top of the tower 25 to the second nitrogen condenser 4, which will be described later, and the cooled and condensed liquid nitrogen is returned to the top of the tower 25 as reflux liquid. Also, pipe L25 sends the nitrogen gas (vapor flow) from the top of the tower 25 to the first nitrogen condenser 3, which will be described later, and the condensed liquid nitrogen is returned to the top of the tower 25 as reflux liquid. Furthermore, the product nitrogen gas line L27 draws nitrogen gas from the top of the tower 25, sends it to the cold end of the main heat exchanger E1, and extracts the heated product nitrogen gas (GAN) from the hot end. As an alternative, the product nitrogen gas may also be extracted from piping L25 or piping L26.

[0016] (Second nitrogen condenser) The second nitrogen condenser 4 is located above the first nitrogen condenser 3, which will be described later. The oxygen-enriched liquid stored in the second nitrogen condenser 4, which is sent from the bottom 21 of the nitrogen rectification column 2, becomes the second oxygen-enriched liquid. The second nitrogen condenser 4 comprises a refrigerant storage section 40 where the second oxygen-enriched liquid is stored, and a gas phase section 41. Piping L26 introduces nitrogen gas (vapor flow) into the second nitrogen condenser 4 from the top 25 of the nitrogen rectification column 2. The introduced nitrogen gas is cooled and liquefied by heat exchange with the second oxygen-enriched liquid stored in the refrigerant storage section 40, and returns to the top 25 of the nitrogen rectification column 2 as reflux liquid.

[0017] The second oxygen-enriched gas line L41 extracts the second oxygen-enriched gas, which is the result of the evaporation of the second oxygen-enriched liquid, from the gas phase section 41 of the second nitrogen condenser 4 and introduces it into the booster 92. The second oxygen-enriched gas, pressurized in the booster 92, is introduced into the middle section of the main heat exchanger E1 where it is cooled, and is discharged from the cold end and introduced into the lower part of the nitrogen rectification column 2, preferably below the inlet of the raw material air line L1, and between the bottom section 21 and the lower rectification section 22.

[0018] (First Nitrogen Condenser) The first nitrogen condenser 3 is located above the nitrogen rectification column 2 and below the second nitrogen condenser 4. Piping L40 leads the second oxygen-enriched liquid from the second nitrogen condenser 4 and sends it as the first oxygen-enriched liquid to the refrigerant storage section 30 of the first nitrogen condenser 3. In other words, the second oxygen-enriched liquid led from the second nitrogen condenser 4 is sent to the first nitrogen condenser 3 and stored as the first oxygen-enriched liquid. The first nitrogen condenser 3 comprises a refrigerant storage section 30 where the first oxygen-enriched liquid is stored and a gas phase section 31. A valve V4 may be installed in piping L40 to adjust the flow rate of the second oxygen-enriched liquid sent to the first nitrogen condenser 3.

[0019] Nitrogen gas discharged from the top 25 of the nitrogen rectification column 2 via piping L25 exchanges heat with the primary oxygen-enriched liquid stored in the refrigerant storage unit 30, is cooled, and liquefied. The resulting liquefied nitrogen returns to the top 25 of the nitrogen rectification column 2 as reflux liquid via piping L25. The first oxygen-enriched gas line L31 discharges the first oxygen-enriched gas, which is the result of the evaporation of the first oxygen-enriched liquid, from the gas phase section 31 and introduces it to the cold end of the main heat exchanger E1. The first oxygen-enriched gas, which is heated in the main heat exchanger E1 and discharged from the intermediate section, is then expanded in the turbine 91. After being expanded and cooled, the first oxygen-enriched gas is again introduced to the cold end of the main heat exchanger E1, supplying cooling to the main heat exchanger E1, and is then removed as waste gas from the hot end. Before being discharged as waste gas, it may be used as regenerating gas for the adsorbent in an air purification device (not shown). Alternatively, the turbine 91 may be connected to a booster 92, and the resulting power may be used to drive the booster 92.

[0020] (Ultra-high purity oxygen rectification column) The ultra-high purity oxygen rectification column 5 comprises a top section 52, a rectification section 51, and a bottom section 61. An ultra-high purity oxygen evaporator 6 is also provided at the bottom section 61 of the ultra-high purity oxygen rectification column 5. Piping L23 leads oxygen-containing fluid from the intermediate section of the rectification section of the nitrogen rectification column 2, preferably between the middle rectification section 23 and the upper rectification section 24, and introduces it into the top section 52 of the ultra-high purity oxygen rectification column 5. The oxygen-containing fluid introduced into the top section 52 and the vapor flow of ultra-high purity liquefied oxygen stored in the bottom section 61 come into countercurrent contact in the rectification section 51, and a fluid with a high oxygen content is stored in the bottom section 61. A valve V2 may be provided in piping L23 to expand the oxygen-containing fluid.

[0021] The first recycle gas line L52 leads to the top 52 of the ultra-high purity oxygen rectification column 5 and merges with the second recycle gas line L74, which leads to the top 74 of the oxygen rectification column 7 (described later). The piping after the second recycle gas line L74 and the first recycle gas line L52 merge is designated as the recycle gas confluence line L75. The recycle gas confluence line L75 sends the mixed gas of the first and second recycle gases as "mixed recycle gas" to the cold end of the main heat exchanger E1, and after being led out from the hot end, it is sent to the recycle gas compressor 10. The first recycled gas is a gas mainly composed of oxygen and nitrogen, discharged from the top 52 of the ultra-high purity oxygen rectification column 5 when the vapor flow of the oxygen-containing fluid and the ultra-high purity oxygen solution come into countercurrent contact. The second recycled gas is a gas mainly composed of oxygen and nitrogen, discharged from the top 74 of the oxygen rectification column 7, which will be described later. Preferably, the first and second recycled gases have an oxygen concentration of 10% to 25% and a nitrogen concentration of 75% to 90%. The mixed gas of the first and second recycled gases (mixed recycled gas), compressed by the recycled gas compressor 10, may be combined and mixed with raw material air in the raw material air line L1 upstream of the main heat exchanger E1 before being sent to the ultra-high purity oxygen evaporator 6 and the oxygen evaporator 8 (described later) as a heat transfer medium. The mixed fluid of the mixed recycled gas and raw material air may then be introduced into the main heat exchanger E1 for cooling, and then introduced into the nitrogen rectification column 2.

[0022] The raw air branch line L11 branches off from the raw air line L1 between the main heat exchanger E1 and the nitrogen rectification column 2, and delivers a portion of the mixed fluid of mixed recycled gas and raw air. The raw air branch line L11 then branches into the first raw air branch line L111 and the second raw air branch line L121. The piping L11 sends a portion of the mixed fluid of mixed recycled gas and raw air as a heat transfer medium to the ultra-high purity oxygen evaporator 6. The heat transfer medium (mixed fluid of mixed recycled gas and raw air) introduced into the ultra-high purity oxygen evaporator 6 heats the high-oxygen-content fluid stored at the bottom of the column 61 to produce ultra-high purity liquefied oxygen (UPO). The ultra-high purity liquefied oxygen (UPO) can be extracted in the ultra-high purity liquefied oxygen line L61, which is connected to the bottom of the column 61. Furthermore, the first raw material air branch line L111, downstream of the ultra-high-purity oxygen evaporator 6, delivers a mixed fluid of cooled mixed recycled gas and raw material air, merges with the oxygen enrichment liquid line L21, and introduces the mixed fluid into the refrigerant storage section 40 of the second nitrogen condenser 4. A valve V5 may also be provided in the first raw material air branch line L111 downstream of the ultra-high-purity oxygen evaporator 6.

[0023] (Oxygen rectification column) The oxygen rectification column 7 comprises a column base 71, a lower rectification section 72, an upper rectification section 73, and a column top 74. An oxygen evaporator 8 is also provided below the oxygen rectification column 7. Liquefied air is stored in the column base 71, and a space is provided between the oxygen evaporator 8 and the column base 71. The first oxygen enrichment line L33 draws the first oxygen enrichment from the refrigerant storage section 30 of the first nitrogen condenser 3 and introduces it into the rectification section of the oxygen rectification column 7, preferably between the lower rectification section 72 and the upper rectification section 73. The first oxygen enrichment line L33 may be equipped with a valve V3, which may adjust the flow rate of the first oxygen enrichment before supplying it to the rectification section of the oxygen rectification column 7.

[0024] The second raw material air branch line L121 branches off from the raw material air branch line L11 and introduces a portion of the mixed fluid of mixed recycled gas and raw material air to the heat transfer medium side of the oxygen evaporator 8. The mixed fluid cooled in the oxygen evaporator 8 becomes liquefied air and is stored at the bottom of the tower 71. Alternatively, a high-pressure air line L2 may be provided, in which purified high-pressure air (HP air) is cooled in the main heat exchanger E1, and the pressure is reduced by valve V8 to create a gas-liquid mixture. This high-pressure air is then introduced between the bottom of the tower 71 and the oxygen evaporator 8, allowing the gaseous component to be used as the heat transfer medium for the oxygen evaporator 8 while the liquid component is stored at the bottom of the tower 71.

[0025] Piping L81 introduces the vapor flow of liquefied air from the bottom of the tower 71 into the oxygen evaporator 8 using it as a heat transfer medium. The liquefied air, cooled by heat exchange with the liquefied oxygen stored in the liquid phase section 81, is returned to the bottom of the tower 71.

[0026] The liquefied oxygen line L82 outputs the liquefied oxygen from the liquid phase section 81. The outputted liquefied oxygen may be compressed by the liquefied oxygen pump 11 provided in the liquefied oxygen line L82, sent to the main heat exchanger E1 where it is heated, and then extracted from the hot end as product oxygen gas (GOX).

[0027] The first liquefied air line L71 introduces liquefied air stored at the bottom of the column 71 into the gas phase section 41 of the second nitrogen condenser 4. A valve V6 may be provided in the first liquefied air line L71 to adjust the amount of liquefied air. The second liquefied air line L72 introduces liquefied air from the bottom of the column 71 into the top section 74 of the oxygen rectification column 7. A valve V7 may be provided in the second liquefied air line L72 to adjust the amount of liquefied air.

[0028] The second recycle gas line L74 leads out the second recycle gas from the top 74 of the oxygen rectification column 7, merges with the first recycle gas line L52, and connects to the recycle gas confluence line L75. The recycle gas confluence line L75 sends the mixed gas of the first and second recycle gases as "mixed recycle gas" to the cold end of the main heat exchanger E1, leads out from the hot end, and then sends it to the recycle gas compressor 10. The mixed recycled gas compressed by the recycled gas compressor 10 may be mixed with the raw air in the raw air line L1, cooled in the main heat exchanger E1, and then introduced into the nitrogen rectification column 2.

[0029] The air separation device A1 of this disclosure may further include a second main heat exchanger E2 (not shown) separate from the main heat exchanger E1. In that case, heat exchange may be performed indirectly by introducing the mixed recycled gas from the recycled gas confluence line L75 and the liquefied oxygen from the liquefied oxygen line L82 to the cold end of the second main heat exchanger E2, and the high-pressure air from the high-pressure air line L2 to the hot end.

[0030] (Another embodiment) (1) Unless otherwise specified, pressure regulators, flow rate control devices, etc. may be installed in each piping line, and pressure regulation or flow rate regulation may be performed. (2) Unless otherwise specified, control valves, gate valves, etc. may be installed in each piping line. (3) Unless otherwise specified, each tower may be equipped with a pressure regulator, a temperature measuring device, etc., and pressure regulation or temperature regulation may be performed.

[0031] (Examples) A simulation was performed using the configuration of Embodiment 1 (Figure 1). 20℃, 9.9 barA, 1071 Nm 3 The dried and purified raw material air at a rate of / h is cooled to -164°C in the main heat exchanger E1 before being introduced into the nitrogen rectification column 2. 864 Nm from the bottom 21 of nitrogen rectification column 2 3 A 2 / h oxygen-enriched solution is drawn out, its flow rate is adjusted by valve V1, and then it is sent to the second nitrogen condenser 4. 455 Nm³ of the second oxygen-enriched liquid stored in the refrigerant storage section 40 of the second nitrogen condenser 4 3 The value of / h is derived and sent to the first nitrogen condenser 3 as the first oxygen enrichment solution via L40.

[0032] From the second nitrogen condenser 4, a 6.0 barA second oxygen-enriched gas is released at a rate of 435 Nm³. 3Derived from / h, it is compressed to 9.8 barA in the booster 92. Then, it is cooled in the main heat exchanger E1 and sent to the lower part of the nitrogen rectification column 2.

[0033] The first oxygen-enriched gas derived from the first nitrogen condenser 3 is heated in the main heat exchanger E1 and then expanded in the turbine 91. Then, it is heated again in the main heat exchanger, and 526 Nm 3 The waste gas of / h is discharged.

[0034] The nitrogen gas derived from the top 25 of the nitrogen rectification column 2 is heated in the main heat exchanger E1 through the product nitrogen line L27 and taken out as the product nitrogen gas (GAN) at 18°C, 9.6 barA, 545 Nm 3 / h.

[0035] From the middle part of the rectification section of the nitrogen rectification column 2, an oxygen-containing fluid without high-boiling components at -168°C, 9.7 barA, 103 Nm 3 / h is derived from L23, expanded by the valve V2, and sent to the top 52 of the ultra-high purity oxygen rectification column 5.

[0036] At the bottom 61 of the ultra-high purity oxygen rectification column 5, ultra-high purity liquefied oxygen at -171°C, 3.1 barA, 7 Nm 3 / h is output as the product (UPO). From the top 52 of the ultra-high purity oxygen rectification column 5, at 3.0 barA, 96 Nm 3 The first recycle gas is derived from the first recycle gas line L52.

[0037] The first oxygen-enriched liquid stored in the first condenser 3 is taken out at 4.7 barA, 24 Nm 3 / h from the first enriched oxygen liquid line L33, the flow rate is adjusted by the valve V3, and it is sent to the rectification section of the oxygen rectification column 7.

[0038] At the top 74 of the oxygen rectification column 7, the second recycle gas at -182°C, 3.0 barA, 58 Nm 3 / h is taken out from the second recycle gas line L74 and merges with the first recycle gas in L52. The recycle gas confluence line L75 produces 154 Nm³ 3 The mixed recycled gas at a rate of / h is heated in the main heat exchanger E1, compressed to 9.6 barA by the recycled gas compressor 10, and then merged with the raw air in the raw air line L1. The mixed fluid of raw air and mixed recycled gas is introduced into the main heat exchanger E1, cooled, and then introduced into the nitrogen rectification column 2.

[0039] Furthermore, the mixed fluid of raw air and mixed recycled gas is supplied from the raw air branch line L11, which branches off from the raw air line L1, at -164°C, 9.7 barA, and 138 Nm³. 3 It is derived at / h and sent as a heat transfer medium to the ultra-high purity oxygen evaporator 6 at the bottom of the ultra-high purity oxygen rectification column 5 and the oxygen evaporator 8 at the bottom of the oxygen rectification column 7 via the first raw material air branch line L111 and the second raw material air branch line L121.

[0040] 20℃, 21 barA, 24 Nm 3 A purified high-pressure air stream (HP Air) of 1 / h is introduced from the high-pressure air line L2 to the main heat exchanger E1, where it is cooled and then introduced between the oxygen evaporator 8 and the bottom 71 of the oxygen rectification column 7.

[0041] Oxygen evaporator 8: -171°C, 3.1 barA, 17 Nm 3 Liquid oxygen at a rate of / h is extracted via L82, pressurized to 7.7 barA by the liquid oxygen pump 11, then heated in the main heat exchanger E1, and extracted as product oxygen gas (GOX) at 18°C ​​and 7.5 barA.

[0042] Since the pressures of the first recycled gas from the ultra-high-purity oxygen rectification column 5 and the second recycled gas from the oxygen rectification column 7 are equivalent, a single recycled gas compressor 10 can be used, resulting in a reduction in the number of pieces of equipment. [Explanation of Symbols]

[0043] E1 Main heat exchanger 2. Nitrogen rectification column 3. First Nitrogen Condenser 4. Second Nitrogen Condenser 5. Ultra-high purity oxygen rectification column 6. Ultra-high purity oxygen evaporator 7. Oxygen rectification column 8. Oxygen evaporator 91 Turbine 92 Booster 10. Recycle gas compressor 11. Liquefied oxygen pump

Claims

1. A main heat exchanger that exchanges heat with the raw air, A nitrogen rectification column into which the raw material air that has passed through the main heat exchanger is introduced, A first nitrogen condenser that condenses the vapor flow introduced from the nitrogen rectification column and returns the resulting reflux liquid to the top of the nitrogen rectification column, An ultra-high purity oxygen rectification column into which an oxygen-containing fluid, which has been drawn out from the intermediate part of the rectification section of the aforementioned nitrogen rectification column, An ultra-high purity oxygen evaporator is provided at the bottom of the ultra-high purity oxygen rectification column, An oxygen rectification column into which the first oxygen-enriched liquid from the refrigerant storage section of the first nitrogen condenser is introduced, An oxygen evaporator is provided at the lower part of the oxygen rectification column, The system includes a recycle gas compressor that compresses a mixed recycle gas obtained by mixing a first recycle gas discharged from the top of the ultra-high purity oxygen rectification column with a second recycle gas discharged from the top of the oxygen rectification column, An air separation device configured such that the mixed recycled gas compressed by the recycled gas compressor is sent to the ultra-high purity oxygen evaporator and / or the oxygen evaporator as a heat transfer medium.

2. The air separation apparatus according to claim 1, wherein the mixed recycled gas is heated in the main heat exchanger, compressed in the recycled gas compressor, introduced into the main heat exchanger for cooling, and then sent to the ultra-high purity oxygen evaporator and / or the oxygen evaporator as a heat transfer medium.

3. The air separation apparatus according to claim 1, wherein the mixed recycled gas is heated in the main heat exchanger, compressed in the recycled gas compressor, then combined with the raw air, introduced into the main heat exchanger for cooling, and then sent to the ultra-high purity oxygen evaporator and / or the oxygen evaporator as a heat transfer medium.

4. A second nitrogen condenser is installed above the first nitrogen condenser, An oxygen enrichment line for introducing the oxygen enriched liquid at the bottom of the nitrogen rectification column into the second nitrogen condenser, Turbine and, A booster, which is driven by the rotational power of the turbine, is connected coaxially to the turbine, The system further comprises piping for supplying the second oxygen-enriched liquid stored in the refrigerant storage section of the second nitrogen condenser to the refrigerant storage section of the first nitrogen condenser as the first oxygen-enriched liquid, In the first nitrogen condenser, the vapor flow introduced from the nitrogen rectification column and the first oxygen-enriched liquid stored in the refrigerant storage section of the first nitrogen condenser are subjected to heat exchange, and a portion of the first oxygen-enriched liquid is evaporated to obtain the first oxygen-enriched gas, which is then discharged, heated in the main heat exchanger, and expanded by the turbine. An air separation apparatus according to any one of claims 1 to 3, wherein the second nitrogen condenser is configured to exchange heat with the vapor flow introduced from the nitrogen rectification column and the second oxygen enrichment liquid to evaporate a portion of the second oxygen enrichment liquid, thereby obtaining a second oxygen enriched gas, which is then compressed by the booster, and the second oxygen enriched gas compressed by the booster is cooled in the main heat exchanger before being introduced into the nitrogen rectification column.

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