High-purity oxygen production method and air separation device for producing high-purity oxygen

Abstract

To provide an air separation device that suppresses energy consumption while using process gas as heat medium for liquefied oxygen so as to avoid restrictions on a production capacity of high-purity oxygen.SOLUTION: An air separation device A1 includes a main heat exchanger 1, a nitrogen rectification column 2, a nitrogen condenser 3 arranged at a top part of the nitrogen rectification column 2, a high-purity oxygen rectification column 5, and an oxygen evaporator 6 arranged at a bottom part 51 of the high-purity oxygen rectification column 5. Oxygen-containing fluid discharged from an intermediate stage of the nitrogen rectification column 2 is rectified in the high-purity oxygen rectification column 5, and concentrated at the bottom part 51 of the high-purity oxygen rectification column 5.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing high-purity oxygen and an air separation apparatus for producing high-purity oxygen.

Background Art

[0002] As a method for producing high-purity oxygen in which components having a boiling point higher or lower than oxygen are controlled to the order of ppm or less, a method using cryogenic air separation is known. As one of such production methods, there is a method in which an oxygen-containing liquid or gas is derived from a cryogenic air separation apparatus and high-purity oxygen is rectified (see, for example, Patent Document 1). For rectification of high-purity oxygen, a step of heating the liquefied oxygen as a raw material to evaporate low-boiling components such as nitrogen and argon is necessary, and as the heat medium, an oxygen-enriched liquid (Patent Document 1), raw air (Patent Document 2), recycle air (Patent Document 3), and nitrogen gas (Patent Document 4) are known to be used.

[0003] When a process liquid such as an oxygen-enriched liquid is used as a heat medium as in Patent Document 1, since the sensible heat of the process liquid is used to cover the latent heat of evaporation of the liquefied oxygen, a large molar flow rate is required, and at the same time, the heat supply amount is limited by the process balance constraint, resulting in a problem that the amount of recoverable high-purity oxygen remains small. In the methods of Patent Documents 2, 3, and 4, since the flow rates of the raw air, recycle air, or nitrogen gas used for liquefied oxygen evaporation can be increased, there is no restriction on the high-purity oxygen production capacity, but there is another problem that the energy consumption is large because it involves a gas compression process.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] The present disclosure provides a method for producing high-purity oxygen with reduced energy consumption and an air separation apparatus for producing high-purity oxygen, which use process gas as a heat medium for liquefied oxygen while avoiding constraints on high-purity oxygen production capacity. [Means for Solving the Problems]

[0006] The air separation apparatus (A1) of the present disclosure includes a main heat exchanger (1), one or more nitrogen rectification columns (2), a nitrogen condenser (3) disposed at the top (23) of each of the nitrogen rectification columns (2), a high-purity oxygen rectification column (5), and an oxygen evaporator (6) disposed at the bottom (51) of the high-purity oxygen rectification column (5). The oxygen-containing fluid derived from the intermediate stage (22, 221, 222) of the nitrogen rectification column (2) is rectified in the high-purity oxygen rectification column (5) and concentrated at the bottom (51) of the high-purity oxygen rectification column (5). As a result, the oxygen-containing fluid is concentrated into high-purity oxygen. Further, this high-purity oxygen is evaporated by indirect heat exchange with the oxygen-enriched gas evaporated in the nitrogen condenser (3) in the oxygen evaporator (6), and is supplied as a vapor flow to the rectifying section (52) of the high-purity oxygen rectification column (5).

[0007] In the present disclosure, a fluid that is derived from a rectifying stage above the introduction point of raw air, recycle air, or oxygen-enriched liquid in a rectification column and introduced into the high-purity oxygen rectification column (5) is referred to as an oxygen-containing fluid, and a liquid derived from a location lower than the raw air introduction stage (for example, the bottom of the nitrogen rectification column) is referred to as an oxygen-enriched liquid. The oxygen-containing fluid may be a liquid or a gas-liquid mixture.

[0008] In this configuration, the nitrogen gas vapor stream is heat exchanged with the oxygen-enriched liquid in the nitrogen condenser, whereby the oxygen-enriched liquid is evaporated to generate an oxygen-enriched gas. The oxygen-enriched gas used as a heat medium in the oxygen evaporator has a pressure and composition sufficient to evaporate the rectified liquefied oxygen at the bottom of the high-purity oxygen rectification column with latent heat. In particular, the oxygen-enriched gas, which contains a large amount of oxygen, can evaporate liquefied oxygen at a lower pressure than air or nitrogen, so that the liquefied oxygen can be evaporated at the supply pressure from the nitrogen evaporator without the use of a compressor.

[0009] The oxygen-containing gas condensed (reliquefied) in the oxygen evaporator (6) may be re-fed to the nitrogen condenser (3). With this configuration, the recondensed oxygen-enriched liquid obtained by condensing the oxygen-enriched gas in the oxygen evaporator is resupplied to the refrigerant side of the nitrogen condenser and evaporated by heat exchange with the vapor flow (nitrogen gas). The recondensed oxygen-enriched liquid may be sent to the nitrogen condenser (3) by head pressure utilizing the height difference between the oxygen evaporator (6) and the nitrogen condenser (3). If the oxygen evaporator (6) is located at a lower position than the nitrogen condenser (3), the liquid may be pumped through a pump.

[0010] The nitrogen rectification column (2) may have a rectification section (22) for separating components with a higher boiling point than oxygen (e.g., methane) contained in the feed air supplied thereto and for extracting an oxygen-containing liquid from the upper stage thereof. With this configuration, the high boiling point components contained in the feed air are concentrated in the liquefied oxygen. The oxygen-containing liquid that serves as a raw material for high purity oxygen is obtained by drawing out, as the oxygen-containing liquid, a portion of the reflux liquid from above the feed air inlet of the nitrogen rectification column (2), from which the high boiling point components have been sufficiently removed while still containing a sufficient amount of oxygen to serve as a raw material for high purity oxygen. A rectification section (221) is disposed between the feed air inlet and the oxygen-containing liquid outlet, and is configured so that the high boiling point components derived from the feed air are transferred into the liquefied oxygen by gas-liquid contact and are concentrated in the lower part of the rectification column. The rectifying section (22, 221, 222) may be composed of rectifying plates, regular packings, or irregular packings.

[0011] The first high-purity oxygen production method is introducing the raw material air cooled by the main heat exchanger (1) into the introduction section below the nitrogen rectifying column (2), and separating the raw material air into a nitrogen-enriched component (nitrogen-enriched fluid) and an oxygen-enriched component (oxygen-enriched fluid) in the nitrogen rectifying column (2), which is a nitrogen-oxygen separation step; a nitrogen condensation step of condensing the vapor flow (nitrogen-enriched gas) from the nitrogen rectifying column (2) in the nitrogen condenser (3); an oxygen-enriched liquid circulation step of sending the oxygen-enriched liquid derived from the bottom (21) of the nitrogen rectifying column (2) to the refrigerant side (31) of the nitrogen condenser (3); a waste gas extraction step of passing the gas derived from the top (31) of the nitrogen condenser (3) through a part of the main heat exchanger (1), then expanding and cooling it in the expansion turbine (92), and then passing it through the main heat exchanger (1) again and extracting it as waste gas; a product nitrogen gas extraction step of passing the gas derived from the top (23) of the nitrogen rectifying column (2) through the main heat exchanger (1) and extracting it as product nitrogen gas; a high-purity oxygen production step of introducing the oxygen-containing fluid derived from the intermediate stage (221) of the rectifying section (22) of the nitrogen rectifying column (2) into the top (53) of the high-purity oxygen rectifying column (5), and using the oxygen evaporator (6) provided at the bottom (51) to produce high-purity oxygen; a heat medium utilization step of using the gas (oxygen-enriched gas) derived from the top (31) of the nitrogen condenser (3) as the heat medium of the oxygen evaporator (6) for evaporating liquefied oxygen, and returning it to the refrigerant side or the top (31) of the nitrogen condenser (3); including. The nitrogen-enriched component is, for example, a fluid, including gas, liquid, and gas-liquid two-phase flow. The oxygen-enriched component is, for example, a fluid, including gas, liquid, and gas-liquid two-phase flow.

[0012] The second high-purity oxygen production method is The raw material air cooled by the main heat exchanger (1) (partially cooled after being taken out from the middle) is introduced into the lower introduction part of the nitrogen rectification column (2), and a nitrogen-oxygen separation step of separating the raw material air into a nitrogen-enriched component (nitrogen-enriched fluid) and an oxygen-enriched component (oxygen-enriched fluid) in the nitrogen rectification column (2), a nitrogen condensation step of condensing the vapor flow (nitrogen-enriched gas) from the nitrogen rectification column (2) in the first and second nitrogen condensers (3, 4), an oxygen-enriched liquid circulation step of sending the oxygen-enriched liquid derived from the bottom (21) of the nitrogen rectification column (2) to the refrigerant side (41) of the second nitrogen condenser (4) after passing through the main heat exchanger (1), a waste gas extraction step of passing the gas derived from the top (31) of the first nitrogen condenser (3) through a part of the main heat exchanger (1), then expanding and cooling it in an expansion turbine (92), and then passing it through the main heat exchanger (1) again and taking it out as waste gas, a product nitrogen gas extraction step of passing the gas derived from the top (23) of the nitrogen rectification column (2) through the main heat exchanger (1) and taking it out as product nitrogen gas, a high-purity oxygen production step of introducing the oxygen-containing fluid derived from the intermediate stage (221) of the rectification section (22) of the nitrogen rectification column (2) into the top (53) of the high-purity oxygen rectification column (5) and producing high-purity oxygen by using the oxygen evaporator (6) provided at the bottom (51), a heat medium utilization step of using the gas (oxygen-enriched gas) derived from the top (31) of the nitrogen condenser (3) as the heat medium of the oxygen evaporator (6) for evaporating liquefied oxygen and returning it to the top (31) of the nitrogen condenser (3), a recycled gas introduction step of compressing the gas derived from the top (41) of the second nitrogen condenser (4) with a compressor (91), passing it through the main heat exchanger (1), and then introducing it as recycled gas to the lower part of the nitrogen rectification column (2), is included.

[0013] The third high-purity oxygen production method is, The raw material air cooled by the main heat exchanger (1) (partially cooled and taken out from the middle) is introduced into the introduction part below the first nitrogen rectification column (2), and a nitrogen-oxygen separation step of separating the raw material air into a nitrogen-enriched component (nitrogen-enriched fluid) and an oxygen-enriched component (oxygen-enriched fluid) in the first and second nitrogen rectification columns (2, 7), a first nitrogen condensation step of condensing the vapor flow (nitrogen-enriched gas) from the first nitrogen rectification column (2) in the first nitrogen condenser (3), an oxygen-enriched liquid circulation step of sending the oxygen-enriched liquid derived from the bottom (21) of the nitrogen rectification column (2) to the rectification parts (721, 722) of the second nitrogen rectification column (7) after passing through the main heat exchanger (1), a second nitrogen condensation step of condensing the vapor flow (nitrogen-enriched gas) from the second nitrogen rectification column (7) in the second nitrogen condenser (4), a product nitrogen gas extraction step of passing the gas (nitrogen gas) derived from the top (23) of the first nitrogen rectification column (2) through the main heat exchanger (1) and taking it out as a product nitrogen gas, a waste gas extraction step of passing the gas (nitrogen gas) derived from the top (41) of the second nitrogen condenser (4) through a part of the main heat exchanger (1), then expanding and cooling it in an expansion turbine (92), and then passing it through the main heat exchanger (1) again and taking it out as a waste gas, a high-purity oxygen production step of introducing the oxygen-containing fluid derived from the rectification part (722) of the second nitrogen rectification column (7) into the top (53) of the high-purity oxygen rectification column (5) and producing high-purity oxygen by using the oxygen evaporator (6) provided at the bottom (51), a heat medium utilization step of using the gas (oxygen-enriched gas) derived from the bottom (71) of the second nitrogen rectification column (7) or the top (31) of the first nitrogen condenser (3) as a heat medium for the oxygen evaporator (6) that evaporates liquefied oxygen and returning it to the top (41) of the second nitrogen condenser (4), a recycled gas introduction step of compressing the gas derived from the rectification part (722) of the second nitrogen rectification column (7) with a compressor (91), passing it through the main heat exchanger (1), and then introducing it as a recycled gas below the first nitrogen rectification column (2), is included.

[0014] The fourth high-purity oxygen production method is, A part of the raw material air compressed by a compressor (911) is passed through a main heat exchanger (1) (derived from the middle and partially cooled), expanded in an expansion turbine (912), and introduced into a second nitrogen rectification column (7); The raw material air cooled in the main heat exchanger (1) (taken out from the middle and partially cooled) is introduced into the lower introduction part of a first nitrogen rectification column (2), and the raw material air is separated into a nitrogen-enriched component (nitrogen-enriched fluid) and an oxygen-enriched component (oxygen-enriched fluid) in the first and second nitrogen rectification columns (2, 7); A first nitrogen condensation step of condensing the vapor flow (nitrogen-enriched gas) from the first nitrogen rectification column (2) in a first nitrogen condenser (3); An oxygen-enriched liquid circulation step of sending the oxygen-enriched liquid derived from the bottom (21) of the first nitrogen rectification column (2) to the rectification parts (721, 722) of the second nitrogen rectification column (7) after passing through the main heat exchanger (1); A second nitrogen condensation step of condensing the vapor flow (nitrogen-enriched gas) from the second nitrogen rectification column (7) in a second nitrogen condenser (4); A product nitrogen gas extraction step of passing the gas (nitrogen gas) derived from the top (23) of the first nitrogen rectification column (2) through the main heat exchanger (1) and taking it out as a product nitrogen gas; A low-pressure nitrogen gas extraction step of passing the gas (nitrogen gas) derived from the top (73) of the second nitrogen rectification column (7) through the main heat exchanger (1) and taking it out as a low-pressure nitrogen gas; A waste gas extraction step of passing the gas (nitrogen gas) derived from the top (41) of the second nitrogen condenser (4) through the main heat exchanger (1) and taking it out as a waste gas; A high-purity oxygen production step of introducing the oxygen-containing fluid derived from the rectification part (722) of the second nitrogen rectification column (7) into the top (53) of a high-purity oxygen rectification column (5) and producing high-purity oxygen by using an oxygen evaporator (6) provided at the bottom (51); A heat medium utilization step of using the gas (oxygen-enriched gas) derived from the bottom (71) of the second nitrogen rectification column (7) or the top (31) of the first nitrogen condenser (3) as a heat medium for the oxygen evaporator (6) that evaporates liquefied oxygen and returning it to the top (41) of the second nitrogen condenser (4); including.

[0015] The first, second, third, and fourth high-purity oxygen production methods may include a waste gas extraction step of passing the gas derived from the top (53) of the high-purity oxygen rectification column (5) through the main heat exchanger (1) and extracting it as waste gas.

[0016] "High-purity oxygen" means that the oxygen concentration is 99.99% or higher.

[0017] The first air separation device (A1) of the present disclosure includes a main heat exchanger (1) into which raw air is introduced, a nitrogen rectification column (2) having a rectification section (22) or a bottom (21) into which the raw air heat-exchanged in the main heat exchanger (1) is introduced, at least one nitrogen condenser (3) that condenses the nitrogen-enriched gas derived from the top (23) of the nitrogen rectification column (2), an expansion turbine (92) into which the gas derived from the top or the refrigerant phase (31) of the nitrogen condenser (3) is partially passed through the main heat exchanger (1) and then introduced, a high-purity oxygen rectification column (5) having a top (53) or a purification section (52) into which the oxygen-containing fluid (which may be a gas, a liquid, or a mixed state thereof) derived from the rectification section (22) of the nitrogen rectification column (2) (at a position higher than the raw air introduction position) is introduced, an oxygen evaporator (6) disposed at the bottom (51) of the oxygen rectification column (5) that evaporates liquefied oxygen using the gas derived from the top (31) of the nitrogen condenser (3) as a heat medium, and may be provided with.

[0018] The configuration may be such that the nitrogen gas used as the heat medium is returned to the top of the nitrogen condenser (3). The high-purity oxygen production device (A1) includes a raw air piping line (L1) for introducing raw air below the nitrogen rectification column (2) through the main heat exchanger (1), and an oxygen-enriched liquid piping line (L21) for introducing the oxygen-enriched liquid derived from the bottom (21) of the nitrogen rectification column (2) into the nitrogen condenser (3). An oxygen-containing fluid pipe line (L221) for introducing an oxygen-containing fluid derived from the rectifying section (22) of the nitrogen rectifying column (2) into the high-purity oxygen rectifying column (5); A waste gas extraction pipe line (L31) for sending the gas derived from the top of the nitrogen condenser (3) through the main heat exchanger (1) partially, then sending it to the expansion turbine (92), passing it through the main heat exchanger (1) again, and taking it out as waste gas; A product nitrogen gas extraction pipe line (L23) for sending the gas derived from the top (23) of the nitrogen rectifying column (2) through the main heat exchanger (1) and taking it out as product nitrogen gas; A heat medium pipe line (L311) for sending the gas derived from the top (31) of the nitrogen condenser (3) as a heat medium to the oxygen evaporator (6), and then returning it to the top (31) of the nitrogen condenser (3) again; A waste gas extraction pipe line (L53) for sending the gas derived from the top (53) of the high-purity oxygen rectifying column (5) through the main heat exchanger (1) and taking it out as waste gas; It may be provided with. The waste gas extraction pipe line (L31) and the waste gas extraction pipe line (L53) may merge into either one. The heat medium pipe line (L311) may branch from the product nitrogen gas extraction pipe line (L31).

[0019] Also, the second air separation device (A2) Uses the nitrogen condenser (3) as the first nitrogen condenser (3), and further includes a second nitrogen condenser (4). The second air separation device (A2) An oxygen-enriched liquid pipe line (L211) for introducing the oxygen-enriched liquid derived from the bottom (21) of the nitrogen rectifying column (2) through the main heat exchanger (1) partially, and then introducing it into the second nitrogen condenser (4); A compressor (91) for compressing the gas derived from the top (41) of the second nitrogen condenser (4); A recycle gas pipeline line (L41) that is led out from the top (41) of the second nitrogen condenser (4), compressed by the compressor (91), passed through the main heat exchanger (1), and then introduced as recycle gas into the rectification section (22) of the nitrogen rectification column (2); may be provided.

[0020] Further, the third air separation device (A3) includes a second nitrogen rectification column (7) and is operated at a lower pressure than the first nitrogen rectification column (2). The second nitrogen rectification column (7) may be introduced with the oxygen-enriched gas (vapor) generated in the first nitrogen condenser (3) and / or the oxygen-enriched liquid led out from the bottom (21) of the first nitrogen rectification column (2). The third air separation device (A3) An oxygen-enriched liquid pipeline line (L212) that partially passes the oxygen-enriched liquid led out from the bottom (21) of the first nitrogen rectification column (2) through the main heat exchanger (1) and then introduces it into the rectification section of the second nitrogen rectification column (7); An oxygen-containing fluid pipeline line (L723) that introduces the oxygen-containing fluid led out from the rectification section in the middle stage of the second nitrogen rectification column (7) to the top (53) of the high-purity oxygen rectification column (5); A heat medium pipeline line (L711) that sends the gas (oxygen-enriched gas) led out from the rectification section in the lower stage of the second nitrogen rectification column (7) as a heat medium to the oxygen evaporator (6) and introduces it into the second nitrogen condenser (4); A recycle gas pipeline line (L722) that is led out from the rectification section in the middle stage of the second nitrogen rectification column (7), compressed by the compressor (91), passed through the main heat exchanger (1), and then introduced as recycle gas into the rectification section (22) of the first nitrogen rectification column (2); A waste gas extraction pipeline line (L411) that sends the gas led out from the top (41) of the second nitrogen condenser (4) to the expansion turbine (92) after partially passing it through the main heat exchanger (1), passing it through the main heat exchanger (1) again, and taking it out as waste gas; may be provided.

[0021] Further, the fourth air separation device (A4) A compressor (911) for compressing a part of the raw material air, An expansion turbine (921) that expands the compressed air compressed by the compressor (911), introduced into the main heat exchanger (1), and led out from the middle thereof, may be provided. The fourth air separation device (A4) A raw material air branch pipe line (L11) that sends the compressed air compressed by the compressor (911) to the main heat exchanger (1), leads it out from the middle, expands it through an expansion turbine (921), and sends it to the rectification section of the second nitrogen rectification column (7), A low-pressure nitrogen gas extraction pipe line (L732) for extracting the gas led out from the top (73) of the second nitrogen rectification column (7) as low-pressure nitrogen gas, A waste gas extraction pipe line (L412) for extracting the gas led out from the top (41) of the second nitrogen condenser (4) as waste gas, may be provided.

[0022] The air separation devices (A1, A2, A3, A4) May have various measuring instruments such as a flow rate measuring instrument, a pressure measuring instrument, a temperature measuring instrument, and a liquid level measuring instrument, Various valves such as a control valve and a partition valve, Pipes connecting between the respective elements, may be included.

[0023] (Function and effect) (1) While using the process gas as the heat medium for liquefied oxygen, it is possible to suppress energy consumption while avoiding the limitation of the high-purity oxygen production capacity.

Brief description of the drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0025] Some embodiments of the present disclosure will be described below. The embodiments described below illustrate an example of the present disclosure. The present disclosure is not limited to the following embodiments, and also includes various modified forms implemented within the scope of not changing the gist of the present disclosure. Note that 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 gas flow.

[0026] (Embodiment 1) The first air separation device A1 of Embodiment 1 will be described with reference to FIG. 1. The first air separation device A1 includes a main heat exchanger 1, a nitrogen rectification column 2, a nitrogen condenser 3, an expansion turbine 92, a high-purity oxygen rectification column 5, and an oxygen evaporator 6. The main heat exchanger 1 cools the raw material air introduced from the warm end and discharges it from the cold end. The cooled raw material air is introduced into the nitrogen rectification column 2 via the raw material air piping line L1. The nitrogen rectification column 2 includes a bottom 21, a rectification section 22, and a top 23. The raw material air piping line L1 is connected to the bottom 21. The oxygen-enriched liquid stored in the bottom 21 is sent to the refrigerant phase 31 of the nitrogen condenser 3 via the oxygen-enriched liquid piping line L21.

[0027] The nitrogen condenser 3 is provided above the top 23. In the nitrogen condenser 3, a part of the nitrogen gas (vapor flow) derived from the top 23 of the nitrogen rectification column 2 is introduced via the reflux piping line L231, cooled (condensed) by heat exchange with the oxygen-enriched liquid, and turned into liquefied nitrogen. The liquefied nitrogen is returned to the top 23 of the nitrogen rectification column 2 as reflux liquid.

[0028] An oxygen-containing fluid is derived from between the intermediate portions 221 and 222 of the rectification section 22 of the nitrogen rectification column 2 via the oxygen-containing fluid piping line L221 and introduced into the top 53 of the high-purity oxygen rectification column 5. The nitrogen gas derived from the top 23 of the nitrogen rectification column 2 is sent to the main heat exchanger 1 via the product nitrogen gas extraction pipe line L23 and taken out as the product nitrogen gas.

[0029] The oxygen-enriched gas (vapor of the oxygen-enriched liquid) derived from the top 31 of the nitrogen condenser 3 is introduced from the cold end of the main heat exchanger 1 via the waste gas extraction pipe line L31, and after being derived from the intermediate stage, it is expanded and cooled by the expansion turbine 92, then sent back to the main heat exchanger 1 again and taken out as the waste gas. A part of the oxygen-enriched gas (vapor of the oxygen-enriched liquid) derived from the top (refrigerant phase) 31 of the nitrogen condenser 3 is sent to the oxygen evaporator 6 as the heat medium via the heat medium pipe line L311, re-liquefied, and then returned to the top (refrigerant phase) 31 of the nitrogen condenser 3 again. The re-liquefied oxygen-enriched gas is supplied to the nitrogen condenser 3 as the recycled oxygen-enriched liquid as the refrigerant.

[0030] The high-purity oxygen rectification column 5 has a bottom 51, a purification section 52, and a top 53. The oxygen-containing liquid is introduced into the top 53 of the high-purity oxygen rectification column 5, rectified in the rectification section 52, and the liquefied oxygen is stored at the bottom 51.

[0031] An oxygen evaporator 6 is provided at the bottom 51 of the high-purity oxygen rectification column 5. The nitrogen gas of the heat medium of the oxygen evaporator 6 turns the liquid oxygen into a vapor flow (oxygen gas), and in the rectification section 52, heat and mass transfer occur, and the high-purity oxygen accumulates at the bottom 51. The gas derived from the top 53 of the high-purity oxygen rectification column 5 merges into the waste gas extraction pipe line L31 via the pipe line L53, is sent to the main heat exchanger 1, and taken out as the waste gas.

[0032] According to the air separation device A1 of Embodiment 1, it is possible to supply the cold required to maintain the heat balance of the air separation device.

[0033] (Embodiment 2) The second air separation device A2 of Embodiment 2 will be described with reference to FIG. 2. Since the same reference numerals as those in Embodiment 1 have the same functions, the description may be omitted. The second air separation device A2 includes a main heat exchanger 1, a nitrogen rectification column 2, a first nitrogen condenser 3, a second nitrogen condenser 4, a compressor 91, an expansion turbine 92, a high-purity oxygen rectification column 5, and an oxygen evaporator 6. The configuration different from that of Embodiment 1 will be mainly described.

[0034] The first nitrogen condensation section 3 is disposed above the nitrogen rectification column 2, and the second nitrogen condensation section 4 is disposed above the first nitrogen condensation section 3. In the first nitrogen condenser 3, a part of the nitrogen gas (vapor flow) derived from the top 23 of the nitrogen rectification column 2 is introduced through the first reflux piping line L231, and is cooled (condensed) by heat exchange with the oxygen-enriched liquid to become liquefied nitrogen. The liquefied nitrogen is returned as a reflux liquid to the top 23 of the nitrogen rectification column 2. In the second nitrogen condenser 4, a part of the nitrogen gas (vapor flow) derived from the top 23 of the nitrogen rectification column 2 is introduced through the second reflux piping line L232, and is cooled (condensed) by heat exchange with the oxygen-enriched liquid to become liquefied nitrogen. The liquefied nitrogen is returned as a reflux liquid to the top 23 of the nitrogen rectification column 2.

[0035] The oxygen-enriched liquid piping line L211 is a piping line that partially passes the oxygen-enriched liquid derived from the bottom 21 of the nitrogen rectification column 2 through the main heat exchanger 1 and then introduces it into the second nitrogen condenser 4. The oxygen-enriched liquid of the second nitrogen condenser 4 is sent as a refrigerant to the first nitrogen condenser 3.

[0036] The compressor 91 compresses the gas derived from the top 41 of the second nitrogen condenser 4. The recycle gas piping line L41 is a piping line that is derived from the top 41 of the second nitrogen condenser 4, compressed by the compressor 91, passed through the main heat exchanger 1, and then introduced as a recycle gas into the rectification section 22 of the nitrogen rectification column 2.

[0037] (Embodiment 3) The third air separation device A3 of Embodiment 3 will be described with reference to FIG. 3. Since the same reference numerals as those in Embodiments 1 and 2 have the same functions, the description may be omitted in some cases. The third air separation device A3 includes a main heat exchanger 1, a first nitrogen rectification column 2, a second nitrogen rectification column 7, a first nitrogen condenser 3, a second nitrogen condenser 4, a compressor 91, an expansion turbine 92, a high-purity oxygen rectification column 5, and an oxygen evaporator 6. The configuration different from that of Embodiment 2 will be mainly described.

[0038] The second nitrogen rectification column 7 is introduced with the oxygen-enriched gas (vapor) generated in the first nitrogen condenser 3 and / or the oxygen-enriched liquid derived from the bottom 21 of the first nitrogen rectification column 2. The oxygen-enriched liquid piping line L212 is a piping line that introduces the oxygen-enriched liquid derived from the bottom 21 of the first nitrogen rectification column 2 into the main heat exchanger 1, and after being derived from an intermediate stage, introduces it between the intermediate stages 221 and 222 of the rectification section of the second nitrogen rectification column 7.

[0039] The oxygen-containing liquid piping line L723 is a piping line that introduces the oxygen-containing fluid derived between the intermediate stages 722 and 723 of the rectification section of the second nitrogen rectification column 7 to the top 53 of the high-purity oxygen rectification column 5. The derivation position of the oxygen-containing fluid in the oxygen-containing fluid piping line L723 is at a position above the introduction position of the oxygen-enriched liquid in the oxygen-enriched liquid piping line L212.

[0040] The heat medium piping line L711 is a piping line that sends the gas (oxygen-enriched gas) derived from below the lower rectification section 721 of the second nitrogen rectification column 7 as the heat medium of the oxygen evaporator 6, is re-liquefied, and sent to the refrigerant phase 41 of the second nitrogen condenser 4. The recycle gas piping line L722 is a piping line that is derived between the intermediate stages 721 and 722 of the rectification section of the second nitrogen rectification column 7, compressed by the compressor 91, passes through a part of the main heat exchanger 1, and then is introduced as a recycle gas to the rectification section 22 of the first nitrogen rectification column 2. The waste gas extraction piping line L411 is a piping line that sends the gas derived from the top 41 of the second nitrogen condenser 4, partially passes it through the main heat exchanger 1, then sends it to the expansion turbine 92, expands and cools, passes through the main heat exchanger 1 again, and extracts it as waste gas.

[0041] The vapor flow pipe line L731 is a pipe line that leads out from the top 73 of the second nitrogen rectification column 7 and returns the vapor flow sent to the second nitrogen condenser 4 back to the top 73 of the second nitrogen rectification column 7. The pipe line L732 is a pipe line that branches off from the vapor flow pipe line L731 downstream of the second nitrogen condenser 4 and sends it to the top 23 of the first nitrogen rectification column 2. A liquid feed pump P1 is provided in this pipe line L732.

[0042] (Embodiment 4) The fourth air separation device A4 of Embodiment 4 will be described with reference to FIG. 4. Since the same reference numerals as those in Embodiments 2 and 3 have the same functions, the description may be omitted in some cases. The fourth air separation device A4 includes a main heat exchanger 1, a first nitrogen rectification column 2, a second nitrogen rectification column 7, a first nitrogen condenser 3, a second nitrogen condenser 4, a compressor 911, an expansion turbine 921, a high-purity oxygen rectification column 5, and an oxygen evaporator 6. The configuration different from that of Embodiment 3 will be mainly described.

[0043] The compressor 911 compresses a part of the raw material air. The expansion turbine 921 expands the compressed air that is compressed by the compressor 911, introduced into the main heat exchanger 1, and led out from the middle thereof. The raw material air branch pipe line L11 is a pipe line that branches off from the raw material air pipe line L1 upstream of the main heat exchanger 1, passes through a compressor 911 that compresses a part of the raw material air and an expansion turbine 921 that expands the compressed air compressed by the compressor 911, sends it to the main heat exchanger 1, and leads it out from the middle thereof, and then sends it to the rectification section of the second nitrogen rectification column 7. The low-pressure nitrogen gas extraction pipe line L732 is a pipe line that extracts the gas led out from the top 73 of the second nitrogen rectification column 7 as low-pressure nitrogen gas. The waste gas extraction pipe line L412 is a pipe line that extracts the gas led out from the top 41 of the second nitrogen condenser 4 as waste gas. The pipe line L53 merges into the waste gas extraction pipe line L412.

[0044] According to Embodiment 4, the cold required for heat balance is obtained by expanding a part of the raw material air or the product nitrogen gas derived from the first nitrogen rectification column 2 with an expansion turbine 921 to the pressure of the second nitrogen rectification column 7. The power obtained by the expansion turbine 921 may be applied to the power of the compressor 911 that compresses the raw material air. Note that the same applies to Embodiments 2 and 3.

[0045] (Example) Shows the result of physical simulation of the air separation device of Embodiment 2. Raw material air (1000 Nm 3 / h, 10.3 barA) is introduced from the warm end of the main heat exchanger, cooled to -163 °C, and then introduced into the first nitrogen rectification column. From the first nitrogen rectification column, nitrogen gas (531 Nm 3 / h, 10.0 barA), oxygen-enriched liquid (789 Nm 3 / h, 40.8% oxygen), and oxygen-containing fluid (120 Nm 3 / h, 20.2% oxygen) are derived. The oxygen-enriched liquid is supplied to the second nitrogen condenser 4, evaporated into recycled air (440 Nm 3 / h, 5.95 barA), compressed by the recycled air compressor 91, and then supplied to the first nitrogen rectification column 2. The oxygen-enriched liquid (349 Nm 3 / h, 53.2% oxygen) concentrated in the second nitrogen condenser 4 is supplied to the first nitrogen condenser 3 and evaporated. A part of the evaporated oxygen-enriched liquid is supplied to the main heat exchanger 1, heated, then expanded and cooled by the expansion turbine 92, and then reintroduced into the main heat exchanger 1. A part of the evaporated oxygen-enriched liquid (78.9 Nm 3 / h, 4.7 barA) is condensed in the oxygen evaporator 6 and resupplied to the first nitrogen condenser 3. The oxygen rectification column 5 is operated at 1.5 barA, and high-purity oxygen liquid (10.6 Nm 3 / h, 100% oxygen) is stored at its bottom 51.

[0046] As shown in Patent Document 2, a comparison is made with the case where raw air is used as a heat medium in the oxygen evaporator 6. In order to obtain the same nitrogen gas and high-purity oxygen liquid as in the above embodiment (Embodiment 2), in this embodiment, the required raw air is 1000 Nm 3 / h, whereas when raw air is used in the oxygen evaporator 6, 1027 Nm 3 / h of raw air is required. This is because the heat medium used in the oxygen evaporator 6 in this embodiment has a higher oxygen concentration than raw air, so condensation at a lower pressure is possible, and as a result, the compression energy required for the heat medium can be reduced. Moreover, since raw air does not need to be used as a heat medium, the amount of raw air that can be supplied to the first nitrogen rectification column 2 can also be increased, enabling an improvement in nitrogen gas recovery.

[0047] (Alternative Embodiment) (1) Although not particularly specified, a pressure regulating device, a flow control device, etc. may be installed in each piping line, and pressure regulation or flow regulation may be performed. (2) Although not particularly specified, a control valve, a partition valve, etc. may be installed in each line. (3) Although not particularly specified, a pressure regulating device, a temperature measuring device, etc. may be installed in each column, and pressure regulation or temperature regulation may be performed.

Explanation of Reference Numerals

[0048] 1 Heat exchanger 2 Nitrogen rectification column 3 Nitrogen condenser 5 Oxygen rectification column 6 Oxygen evaporator 91 Compressor 92 Expansion turbine

Claims

1. A nitrogen-oxygen separation step of introducing raw material air cooled by a main heat exchanger into an introduction part below a nitrogen rectification column and separating the raw material air into a nitrogen-enriched component and an oxygen-enriched component in at least one nitrogen rectification column; A nitrogen condensation step of condensing a vapor stream from the nitrogen rectification column with at least one nitrogen condenser; A high-purity oxygen production step of introducing an oxygen-containing fluid derived from a rectification part of the nitrogen rectification column into the high-purity oxygen rectification column and producing high-purity oxygen by using the oxygen evaporator; A heat medium utilization step of using a gas derived from at least one of the nitrogen condensers as a heat medium for the oxygen evaporator that evaporates liquefied oxygen and returning it to the nitrogen condenser; comprising A method for producing high-purity oxygen.

2. A nitrogen-oxygen separation step of introducing raw material air cooled by a main heat exchanger into an introduction part below a first nitrogen rectification column and separating the raw material air into a nitrogen-enriched component and an oxygen-enriched component in the first and second nitrogen rectification columns; A first nitrogen condensation step of condensing a vapor stream from the first nitrogen rectification column with a first nitrogen condenser; A high-purity oxygen production step of introducing an oxygen-containing fluid derived from a rectification part of the second nitrogen rectification column into the high-purity oxygen rectification column and producing high-purity oxygen by using an oxygen evaporator; A heat medium utilization step of using a gas derived from the bottom of the second nitrogen rectification column or the top of the first nitrogen condenser as a heat medium for the oxygen evaporator that evaporates liquefied oxygen and returning it to the second nitrogen condenser; comprising A method for producing high-purity oxygen.

3. A part of raw material air introduction step of passing raw material air compressed by a compressor through a main heat exchanger, expanding it with an expansion turbine, and introducing it into a second nitrogen rectification column; A nitrogen-oxygen separation step of introducing raw material air cooled by a main heat exchanger into an introduction part below a first nitrogen rectification column and separating the raw material air into a nitrogen-enriched component and an oxygen-enriched component in the first and second nitrogen rectification columns; A first nitrogen condensation step of condensing the vapor stream from the first nitrogen rectification column in a first nitrogen condenser; A second nitrogen condensation step of condensing the vapor stream from the second nitrogen rectification column in a second nitrogen condenser; A high-purity oxygen production step of introducing the oxygen-containing fluid derived from the rectifying section of the second nitrogen rectification column into a high-purity oxygen rectification column and producing high-purity oxygen using an oxygen evaporator; A heat medium utilization step of using the gas derived from the bottom of the second nitrogen rectification column or the top of the first nitrogen condenser as a heat medium for an oxygen evaporator that evaporates liquefied oxygen and returning it to the second nitrogen condenser; including A high-purity oxygen production method.

4. A main heat exchanger into which raw air is introduced; At least one nitrogen rectification column into which the raw air heat-exchanged in the main heat exchanger is introduced; At least one nitrogen condenser for condensing the gas derived from the nitrogen rectification column; A high-purity oxygen rectification column into which the oxygen-containing fluid derived from the nitrogen rectification column is introduced; An oxygen evaporator disposed at the bottom of the oxygen rectification column and using the gas derived from the nitrogen condenser as a heat medium to evaporate liquefied oxygen; An air separation apparatus comprising characterized in that it is used in the high-purity oxygen production method according to any one of claims 1 to 3; An air separation apparatus.

Images