Air separation device

Abstract

The present application addresses the problem of providing an air separation device capable of reducing the risk of combustion in a heat exchanger connected to an oxygen turbine. The air separation device (A1) is provided with a main heat exchanger (1), a medium-pressure rectifying column (2), a low-pressure rectifying column (4), a crude argon column (5), a nitrogen condenser (3), a crude argon condenser (6), an oxygen turbine (9), an oxygen turbine inlet pipe (L32), an oxygen side path pipe (L321) and a dilution flow pipe (L42). The oxygen turbine inlet pipe (L32) is used for sending oxygen led out from the bottom of the low-pressure rectifying tower (4) or the gas phase of the refrigerant storage part of the nitrogen condenser (3) to the oxygen turbine (9) through the main heat exchanger (1) and sending the oxygen to the main heat exchanger (1) again, and the oxygen side path pipe (L321) is branched from the oxygen turbine inlet pipe (L32) and is used for sending the oxygen led out from the bottom of the low-pressure rectifying tower (4) or the gas phase of the refrigerant storage part of the nitrogen condenser (3) to the oxygen turbine (9) through the main heat exchanger (1). And a dilution flow pipe (L42) for leading out, as a dilution flow, a nitrogen-containing gas having an oxygen concentration lower than the oxygen concentration in the oxygen gas led out from the bottom of the low-pressure rectifying column (4) or the gas phase of the refrigerant storage unit, and leading the nitrogen-containing gas into the oxygen turbine inlet pipe (L32).

Description

Technical Field

[0001] This invention relates to air separation devices. Specifically, it relates to cryogenic air separation devices having, for example, an oxygen turbine and a heat exchanger. Background Technology

[0002] In the case of separating air components into nitrogen, argon, oxygen, etc. by cryogenic air separation, a duplex distillation system is adopted, which has multiple distillation columns such as medium-pressure column, low-pressure column, and crude argon column, as well as an oxygen turbine for oxygen expansion and a heat exchanger.

[0003] In recent years, the semiconductor industry has required large quantities of nitrogen and argon, while the demand for oxygen is limited. This has created a need for air separation units best suited to supply nitrogen and argon. While the demand for nitrogen and argon is high, the semiconductor industry, with its limited demand for oxygen, seeks to improve the pressure balance of air separation units to make them suitable for supplying nitrogen and argon. For example, this can be achieved by expanding the residual oxygen from a low-pressure tower operating at approximately 3 barA to produce the required cool gas. In this case, for safety reasons, the oxygen concentration in the oxygen turbine used needs to be reduced to, for example, 80–95%. Since nitrogen and argon need to be recovered, and the oxygen concentration from the low-pressure tower is approximately 100%, the oxygen needs to be diluted. For example, to dilute this oxygen, nitrogen-containing gas from the low-pressure tower (e.g., Patent Documents 1, 2) or evaporated gas from the crude argon tower condenser (e.g., Patent Document 3) can be mixed with oxygen.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: U.S. Patent No. 5,129,932

[0007] Patent Document 2: U.S. Patent Publication No. 2019 / 293347

[0008] Patent Document 3: U.S. Patent Publication No. 2023 / 358468 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] Since diluting the oxygen flowing into the oxygen turbine with an inert gas results in process losses, equipment with high oxygen concentrations (e.g., 90% or higher) is preferred in terms of energy efficiency. From the viewpoint of safety and reliability of air separation units, there is a high risk of oxygen combustion under high oxygen concentration flow conditions, and the risk of oxygen combustion may increase during transitional operating modes such as air separation unit startup and changes in operating mode. Examples of oxygen combustion risks include the presence of oxygen flow within heat exchangers made of flammable materials such as aluminum, and the intrusion of flammable substances into the heat exchangers for various reasons. In large-scale air separation units, completely eliminating such risks is extremely difficult industrially.

[0011] This disclosure provides an air separation device that can mitigate the combustion risk of a heat exchanger connected to an oxygen turbine.

[0012] Methods for solving problems

[0013] The air separation apparatus (A1, A2) disclosed herein has a main heat exchanger (1), a medium-pressure distillation column (2), a nitrogen condenser (3), a low-pressure distillation column (4), a crude argon column (5), a crude argon condenser (6), and an oxygen turbine (9).

[0014] The air separation devices (A1, A2) may have an oxygen turbine inlet pipe (L32), an oxygen side pipe (L321), and a dilution flow pipe (L42, L621).

[0015] The oxygen turbine inlet piping (L32) is used to send oxygen from the bottom of the low-pressure distillation column (4) or the refrigerant storage section (32) of the nitrogen condenser (3) into the oxygen turbine (9) via the main heat exchanger (1) and back into the main heat exchanger (1).

[0016] The oxygen side piping (L321) branches off from the oxygen turbine inlet piping (L32).

[0017] The dilution flow piping (L42, L621) is used to export nitrogen-containing gas with an oxygen concentration lower than that in the oxygen as a dilution flow and introduce it into the oxygen turbine inlet piping (L32).

[0018] "Dilution stream" is a fluid used to dilute the oxygen concentration in oxygen (oxygen-enriched gas, high-purity oxygen, etc.). For example, a dilution stream can be feed air, or a low-oxygen-concentration gas that can be drawn from a medium-pressure distillation column (2), a nitrogen condenser (3), a low-pressure distillation column (4), a crude argon condenser (6), etc.

[0019] The dilution piping (L42, L621) can be configured to allow nitrogen-containing gas to be discharged as a dilution stream from the medium-pressure distillation column (2) or the low-pressure distillation column (4), or to allow nitrogen-containing gas to be discharged from the crude argon condenser (6) or a portion of the raw material air.

[0020] The air separation devices (A1, A2) may have:

[0021] A gas flow meter (FIC) and a first flow regulating valve (V1) are installed on the oxygen turbine inlet pipe (L32) upstream of the main heat exchanger (1) and the oxygen side pipe (L321).

[0022] The second flow regulating valve (V2) is installed on the oxygen side piping (L321) upstream of the main heat exchanger (1).

[0023] The third flow regulating and check valve (V3) is installed in the dilution flow piping (L42, L621).

[0024] An oxygen concentration analyzer (AIC) and a fourth flow control valve (V4) for measuring oxygen concentration are installed on the oxygen turbine inlet pipe (L32) downstream of the main heat exchanger (1).

[0025] A level gauge (LIC) for measuring the level of the refrigerant phase in the nitrogen condenser (3).

[0026] The air separation device (A1, A2) may have an oxygen concentration regulating unit (10), which is used to set a target oxygen concentration corresponding to the operation of the nozzle of the oxygen turbine (9), and to set the dilution flow rate (the gas flow rate through the dilution flow piping, or the total flow rate of the gas flow rate and the oxygen flow rate through the oxygen turbine inlet piping (L32)) and the oxygen side flow rate (the oxygen flow rate through the oxygen side piping) in a manner that achieves the target oxygen concentration, and to regulate the oxygen concentration of the oxygen flowing through the oxygen turbine inlet piping.

[0027] The air separation devices (A1, A2) may have an interlock (11) that stops the oxygen turbine (9) if the oxygen concentration measured by the oxygen concentration analyzer (AIC) exceeds a threshold for determining a significant risk of combustion in the oxygen turbine (9).

[0028] The air separation device (A1, A2) may have an oxygen flow isolation control unit (12), which controls the oxygen flow isolation in such a way that when the oxygen concentration measured by the oxygen concentration analyzer (AIC) exceeds the threshold for judging a major combustion risk in the oxygen turbine (9), the first flow regulating valve (V1) provided in the oxygen turbine inlet pipe (L32) is closed to isolate the oxygen flow, and the third flow regulating check valve (V3) is opened to introduce a dilution flow as an inactive gas into the oxygen turbine inlet pipe (L32) (introduced into the oxygen turbine inlet pipe (L32) upstream of the main heat exchanger (1)).

[0029] The air separation devices (A1, A2) may have a dilution flow control unit (13) that controls the dilution flow rate by adjusting the mass balance of the supply source of the dilution flow (e.g., low-pressure distillation column (4), crude argon condenser (6), medium-pressure distillation column (2), feed air). The mass balance adjustment can be implemented using a mechanism in which the controlled object (dilution flow rate) is uniquely determined by the difference between the feed air inflow and the feed air outflow (including product gas and waste gas) from the supply source. As a result, the number of valves, etc., that cause pressure loss in the piping of the controlled object's flow rate can be reduced.

[0030] The oxygen concentration regulating unit (10) can be controlled by introducing the dilution flow into the oxygen turbine inlet pipe (L32) downstream of the oxygen turbine (9).

[0031] Branch dilution flow lines branching from the dilution flow lines (L42, L621) can be connected to the oxygen turbine inlet line (L32) which is downstream of the oxygen turbine (9).

[0032] The air separation unit (A1, A2) may have a subcooler (7) for cooling the liquid (e.g., oxygen-enriched liquid) discharged from the medium-pressure distillation column (2) by means of the gas discharged from the low-pressure distillation column (4) or the crude argon condenser (6).

[0033] The main heat exchanger (1) can have a structure divided into multiple parts in order to optimize the structure and improve the transportability in accordance with the design temperature, pressure and flow rate.

[0034] The air separation apparatus (A1, A2) disclosed herein may include a main heat exchanger (1), a medium-pressure distillation column (2), a nitrogen condenser (3), a low-pressure distillation column (4), an oxygen turbine (9), a crude argon column (5), a crude argon condenser (6), and a subcooler (7).

[0035] Feed air is introduced from the warm end of the main heat exchanger (1) and exported from the cold end of the main heat exchanger (1).

[0036] The raw material air exported from the cold end of the main heat exchanger (1) is introduced into the bottom (21) of the medium-pressure distillation column (2).

[0037] The vapor stream from the upper part (23) of the medium-pressure distillation column (2) is introduced into the nitrogen condenser (3), condensed, and discharged from the nitrogen condenser (3) as reflux liquid.

[0038] The oxygen-enriched liquid exported from the bottom (21) of the medium-pressure distillation column (2) is introduced into the rectification section (42) of the low-pressure distillation column (4), and / or the vapor stream exported from the upper part (23) of the medium-pressure distillation column (2) is introduced into the top (43) of the low-pressure distillation column (4).

[0039] Oxygen drawn from the bottom of the low-pressure distillation column (4) or the refrigerant storage section (32) of the nitrogen condenser (3) is expanded and cooled by the oxygen turbine (9) after heat exchange through the main heat exchanger (1).

[0040] The oxygen-containing fluid drawn from the rectification section (42) of the low-pressure distillation column (4) is introduced into the bottom (51) of the crude argon column (5).

[0041] The vapor stream from the upper part of the crude argon column (5) is introduced into the crude argon condenser (6) for condensation and is discharged as reflux liquid.

[0042] Oxygen-enriched liquid exported from the bottom (21) of the medium-pressure distillation column (2) is introduced from the warm end of the subcooler (7) and exported from the cold end of the subcooler (7), and / or liquid nitrogen exported from the upper part (23) of the medium-pressure distillation column (2) is introduced from the warm end of the subcooler (7) and exported from the cold end of the subcooler (7), and / or nitrogen gas exported from the top (43) of the low-pressure distillation column (4) is introduced from the cold end of the subcooler (7) and exported from the warm end of the subcooler (7).

[0043] The air separation devices (A1, A2) may have:

[0044] The feed air piping line (L1) is used to introduce feed air into the medium-pressure distillation column (2) via the main heat exchanger (1).

[0045] The oxygen-enriched liquid piping line (L21) is used to introduce the oxygen-enriched liquid exported from the bottom (21) of the medium-pressure distillation column (2) into the rectification section (42) of the low-pressure distillation column (4) via the subcooler (7).

[0046] A branch line (L211) is formed downstream of the subcooler (7) from the oxygen-enriched liquid pipeline (L21) and is used to introduce the oxygen-enriched liquid into the refrigerant storage section (61) of the crude argon condenser (6).

[0047] Liquid nitrogen piping line (L23) for introducing liquid nitrogen from the upper part (23) of the medium-pressure distillation column (2) into the top (43) of the low-pressure distillation column (4) via the supercooler (7).

[0048] A liquid nitrogen branch line (L231) branches off downstream of the supercooler (7) from the liquid nitrogen pipeline (L23) and discharges a portion of the liquid nitrogen.

[0049] A liquid oxygen extraction line (L31) for extracting the refrigerant (oxygen-enriched liquid) from the refrigerant storage section (32) of the nitrogen condenser (3) as liquid oxygen (LOX).

[0050] It is used to extract the refrigerant from the upper gas phase of the refrigerant storage section (32) of the nitrogen condenser (3), and introduce it into the middle of the main heat exchanger (1) for heating and then out. It is then expanded by the oxygen turbine (9), and introduced again from the cold end of the main heat exchanger (1) and out from the warm end, and serves as the oxygen turbine inlet pipe (L32) for oxygen extraction.

[0051] An oxygen-containing fluid pipeline (L421) is led out from the rectification section (42) of the low-pressure distillation column (4) and introduced into the bottom (51) of the crude argon column (5).

[0052] Nitrogen piping (L43) for drawing nitrogen (GAN) from the top (43) of the low-pressure distillation column (4), via the subcooler (7) and the main heat exchanger (1).

[0053] The bottom fluid piping line (L51) of the crude argon column (5) is used to draw fluid from the bottom (51) of the crude argon column (5) and to introduce the bottom fluid below the outlet position of the oxygen-containing fluid piping line (L421) of the distillation section (42) of the low-pressure distillation column (4).

[0054] An argon extraction line (L53) for removing the vapor or reflux liquid from the upper part of the crude argon tower (5), and

[0055] The crude argon condenser piping (L62) is used to extract the refrigerant from the upper gas phase of the refrigerant storage section (62) of the crude argon condenser (6) and introduce it into the distillation section (42) of the low-pressure distillation column (4) above the oxygen-rich liquid piping (L21).

[0056] The fluid introduced from the rectification section (42) of the low-pressure distillation column (4) into the crude argon column (5) is called an oxygen-containing fluid, and the liquid exiting from a position lower than the feed air inlet section (e.g., the bottom of the nitrogen distillation column) is called an oxygen-enriched liquid. The oxygen-containing fluid can be a liquid or a gas-liquid mixture.

[0057] The aforementioned subcooler (7) cools the liquid exiting from the medium-pressure distillation column (2) using gas exiting from the low-pressure distillation column (4) or the crude argon condenser (6). As a result, when the liquid is introduced into the low-pressure distillation column (4), the amount evaporated by depressurization can be reduced, and the amount of liquid contributed to the distillation as reflux liquid can be increased, thereby improving the distillation efficiency.

[0058] The air separation devices (A1, A2) may have:

[0059] Various measuring instruments such as flow meters, pressure gauges, temperature gauges, and liquid level gauges.

[0060] Control valves, switching valves, and other types of valves, as well as

[0061] Piping that connects the various elements.

[0062] (Effect)

[0063] (1) It can reduce the risk of combustion of heat exchangers connected to oxygen turbines.

[0064] (2) Low temperature can be generated by expanding the residual oxygen in the oxygen turbine under optimal pressure balance.

[0065] (3) In the case of oxygen dilution when changing the operating mode of the oxygen turbine, the concentration of the oxygen flow can be reduced before operating the nozzle of the oxygen turbine.

[0066] (4) Safety can be improved by reducing the risk of combustion in air separation devices with oxygen turbines. Attached Figure Description

[0067] 【 Figure 1 [Illustration 1] is a diagram showing the air separation device according to Embodiment 1.

[0068] 【 Figure 2 [Illustration 1] is a diagram showing the air separation device according to Embodiment 2. Detailed Implementation

[0069] Several embodiments of this disclosure will be described below. The embodiments described below are examples used to illustrate this disclosure. This disclosure is not limited to any of the following embodiments and includes various modifications implemented without changing the spirit of this disclosure. Furthermore, all the configurations described below are not essential to this disclosure. Upstream and downstream are based on the flow direction of the fluid (liquid, gas).

[0070] (Implementation Method 1)

[0071] use Figure 1 The first air separation device A1 of Embodiment 1 will be described.

[0072] The first air separation unit A1 includes a main heat exchanger 1, a medium-pressure distillation column 2, a nitrogen condenser 3, a low-pressure distillation column 4, a crude argon column 5, a crude argon condenser 6, a subcooler 7, an oxygen turbine 9, an oxygen concentration regulating unit 10, and an interlock 11.

[0073] The main heat exchanger 1 cools the feed air introduced from the warm end and exits it from the cold end. The cooled feed air is introduced into the medium-pressure distillation column 2 via the feed air piping line L1.

[0074] The medium-pressure distillation column 2 has a bottom 21, a rectification section 22, and a top 23. The feed air piping line L1 is connected to the bottom 21. The oxygen-enriched liquid remaining at the bottom 21 undergoes heat exchange via the oxygen-enriched liquid piping line L21 through the subcooler 7, and is then fed into the rectification section 42 of the low-pressure distillation column 4. After heat exchange via the subcooler 7, a portion of the oxygen-enriched liquid is introduced into the refrigerant storage section 61 of the crude argon condenser 6 via the oxygen-enriched liquid distribution piping line L211. A portion of the liquid nitrogen at the top 23 undergoes heat exchange via the liquid nitrogen piping line L23 through the subcooler 7, and is then fed into the top 43 of the low-pressure distillation column 4. The liquid nitrogen distribution piping line L231 is a branch line downstream of the liquid nitrogen piping line L23 from the subcooler 7, allowing for the removal of liquid nitrogen.

[0075] The nitrogen condenser 3 is located above the top 23 of the intermediate-pressure distillation column 2. A portion of the nitrogen gas (vapor stream) exiting from the top 23 of the intermediate-pressure distillation column 2 is introduced into the nitrogen condenser 3 via a reflux piping line, where it is cooled (condensed) and liquefied through heat exchange with the oxygen-enriched liquid used as a refrigerant. The liquefied liquid nitrogen is returned to the top 23 of the intermediate-pressure distillation column 2 as reflux liquid. The level gauge LIC measures the refrigerant phase level in the nitrogen condenser 3.

[0076] The liquid oxygen extraction line L31 is a line used to extract refrigerant (oxygen-rich liquid) in the form of liquid oxygen (LOX) from the refrigerant storage section 32 of the nitrogen condenser 3.

[0077] The low-pressure distillation column 4 has a distillation section 42 and a top section 43. The bottom section can also serve as the refrigerant storage section 32 of the nitrogen condenser 3.

[0078] The oxygen-containing fluid exiting from the rectification section 42 of the low-pressure distillation column 4 is introduced into the bottom 51 of the crude argon column 5 via the oxygen-containing fluid piping line L421. The nitrogen gas exiting from the top 43 of the low-pressure distillation column 4 is exited as low-pressure nitrogen (GAN) via the nitrogen piping line L43 and through the supercooler 7 and the main heat exchanger 1.

[0079] The crude argon column 5 has a bottom 51, a rectification section 52, and a top 53. The bottom fluid piping line L51 of the crude argon column 5 leads from the bottom 51 and is positioned below the outlet of the oxygen-containing fluid piping line L421 of the rectification section 42 of the low-pressure rectification column 4. The argon extraction line L53 is used to extract the vapor stream or reflux liquid (fluid containing crude argon) from the upper part of the crude argon column 5.

[0080] The vapor stream from the upper part of the crude argon column 5 is introduced into the crude argon condenser 6 for condensation and is discharged as reflux liquid. The crude argon condenser piping line L62 is used to discharge the upper vapor phase from the refrigerant storage section 62 of the crude argon condenser 6 and introduce it into the rectification section 42 of the low-pressure rectification column 4, which is located above the oxygen-enriched liquid piping line L21.

[0081] Subcooler 7 introduces oxygen-enriched liquid from the bottom 21 of the medium-pressure distillation column 2 from the warm end and exits it from the cold end. Additionally, subcooler 7 introduces liquid nitrogen from the top 23 of the medium-pressure distillation column 2 from the warm end and exits it from the cold end. Furthermore, subcooler 7 introduces nitrogen gas from the top 43 of the low-pressure distillation column 4 from the cold end and exits it from the warm end.

[0082] After the oxygen extracted from the refrigerant storage section 32 of the nitrogen condenser 3 undergoes heat exchange through the main heat exchanger 1, it is expanded by the oxygen turbine 9 to cool it.

[0083] The oxygen turbine inlet pipe L32 is used to extract the upper gas phase of the refrigerant storage section 32 of the nitrogen condenser 3, introduce it into the middle of the main heat exchanger 1 (e.g., a position closer to the middle of the cold end), heat it up, and then exit it through the oxygen turbine 9 to expand it. It is then introduced again from the cold end of the main heat exchanger 1 and exited from the warm end, serving as the oxygen extraction pipeline. A first flow control valve V1 is installed on the oxygen turbine inlet pipe L32, upstream of the main heat exchanger 1 and the oxygen side pipe L321. An oxygen concentration analyzer AIC and a fourth flow control valve V4 are installed on the oxygen turbine inlet pipe L32, located at the middle of the main heat exchanger 1 and upstream of the oxygen turbine 9.

[0084] The oxygen-side piping L321 branches off from the oxygen turbine inlet piping L32 and leads to the main heat exchanger 1, or reconnects to the oxygen turbine inlet piping L32 downstream of the oxygen turbine 9. The second flow regulating valve V2 is located at a position relative to the oxygen turbine inlet piping L321 upstream of the main heat exchanger 1.

[0085] A dilution flow piping L42 draws gas (e.g., nitrogen-containing gas) from the upper part of the rectification section 42 of the low-pressure distillation column 4 as a dilution flow, and connects to the oxygen turbine inlet piping L32 downstream of the oxygen side piping L321 and upstream of the main heat exchanger 1. A third flow regulating and check valve V3 is provided on the dilution flow piping L42.

[0086] The oxygen concentration regulating unit 10 sets a target oxygen concentration corresponding to the operation of the nozzle of the oxygen turbine 9, and sets the dilution flow rate (the gas flow rate flowing through the dilution flow piping, or the total flow rate of the gas flow rate and the oxygen flow rate flowing through the oxygen turbine inlet piping L32) and the oxygen side flow rate (the oxygen flow rate flowing through the oxygen side piping) in a way that achieves the target oxygen concentration, thereby regulating the oxygen concentration flowing through the oxygen turbine inlet piping L32.

[0087] Based on the gas flow rate measured by the gas flow meter FIC, the first flow regulating valve V1 and the second flow regulating valve V2 are controlled to control the oxygen flow rate through the oxygen side piping. Furthermore, the third flow regulating and check valve V3 is controlled to mix the oxygen flow and the dilution flow, controlling the mixed oxygen concentration to the target oxygen concentration.

[0088] If there is excess cold energy, the refrigerant level in the nitrogen condenser 3 will rise. In this case, when the refrigerant level measured by the level gauge LIC exceeds the threshold, the second flow regulating valve V2 will open. By increasing the oxygen flow through the side path, the load on the oxygen turbine 9 can be reduced, restoring cold balance.

[0089] When the oxygen concentration measured by the oxygen concentration analyzer AIC exceeds a threshold, the second flow control valve V2 opens. By increasing the oxygen flow rate through the side path, the amount of oxygen supplied to the oxygen turbine 9 can be reduced while maintaining the dilution flow, thereby reducing the oxygen concentration in the oxygen turbine 9. Therefore, the opening degree of the second flow control valve V2 is determined by the high selector between the level gauge LIC and the oxygen concentration analyzer AIC.

[0090] According to this embodiment, during device startup and mode switching, the oxygen concentration setpoint of the oxygen concentration analyzer AIC on the inlet side of the oxygen turbine 9 can be fixed at a suitable value. From the viewpoint of safe operation, it is recommended to set it to a lower value during device startup and mode switching. During device balancing, if the oxygen concentration on the inlet side of the oxygen turbine 9 is close to the target value, the oxygen concentration analyzer AIC continues to be controlled by the second flow regulating valve V2 to bring the oxygen concentration below the setpoint. This allows operation to be maintained in a safe state.

[0091] Furthermore, if an abnormal situation occurs where the oxygen concentration measured by the oxygen concentration analyzer AIC reaches a high set value, the interlock 11 will stop the oxygen turbine 9.

[0092] If the oxygen concentration measured by the oxygen concentration analyzer AIC exceeds the threshold for determining a major combustion risk in the oxygen turbine 9, the oxygen flow isolation control unit 12 controls the flow by closing the first flow regulating valve V1 installed in the oxygen turbine inlet pipe L32 to isolate the oxygen flow, opening the third flow regulating and check valve V3, and introducing a dilution flow of inactive gas into the oxygen turbine inlet pipe L32 of the oxygen turbine 9 (introduced into the oxygen turbine inlet pipe L32 upstream of the main heat exchanger 1).

[0093] The dilution flow control unit 13 can control the dilution flow rate by adjusting the mass balance of the supply source of the dilution flow (e.g., low-pressure distillation column 4, crude argon condenser 6, medium-pressure distillation column 2, feed air).

[0094] (Implementation Method 2)

[0095] use Figure 2 The air separation device A2 of Embodiment 2 will be described. Reference numerals that are the same as those in Embodiment 1 have the same function, so descriptions are sometimes omitted.

[0096] The dilution flow piping L621 of the air separation unit A2 is a branch line from the crude argon condenser piping L62, which originates from the crude argon condenser 6. It guides low-concentration oxygen gas into the oxygen turbine inlet piping L32, which is downstream of the oxygen-side piping L321 and upstream of the main heat exchanger 1. A third flow regulating and check valve V3 is installed on the dilution flow piping L621.

[0097] (Implementation Method 3)

[0098] In embodiment 3, a branch dilution flow pipe branching from the dilution flow pipes (L42, L621) is connected to the oxygen turbine inlet pipe L32 downstream of the specific oxygen turbine 9. A fifth flow regulating valve is installed on the branch dilution flow pipe.

[0099] The oxygen concentration regulating unit 10 controls the flow by opening the fifth flow regulating valve and introducing a dilution flow into the oxygen turbine inlet pipe L32 downstream of the oxygen turbine 9.

[0100] In Embodiment 3, the function of the second flow regulating valve V2 in Embodiments 1 and 2 is assumed by the fifth flow regulating valve on the branch dilution flow piping. When the actual oxygen concentration is higher than the set value of the oxygen concentration analyzer AIC, the second flow regulating valve V2 is opened to divert oxygen and reduce oxygen flow. Conversely, in Embodiment 3, the fifth flow regulating valve is closed to increase the dilution flow. Furthermore, in Embodiments 1 and 2, the second flow regulating valve V2 is controlled via a high selector. However, in Embodiment 3, the opening degree of the fifth flow regulating valve can be controlled independently based on the measured value of the oxygen concentration analyzer AIC.

[0101] (Other implementation methods)

[0102] (1) Although not specifically stated, pressure regulating devices, flow control devices, etc. can be installed on each piping line to regulate pressure or flow.

[0103] (2) Although not specifically stated, control valves, switching valves, etc. can be installed on each pipeline.

[0104] (3) Although not specifically stated, pressure regulating devices, temperature measuring devices, etc. can be installed on each tower for pressure or temperature regulation.

[0105] (4) When using raw material air as a dilution flow, for example, the raw material air piping line (L1) can be branched off and connected to the dilution flow piping (L42, L621), or other lines can be installed.

[0106] (5) In the case of dilution flow being derived from medium-pressure distillation column (2), for example, it can be branched from oxygen-enriched liquid pipeline (L21) or liquid nitrogen pipeline (L23) and connected to dilution flow pipeline (L42, L621), or other pipelines can be installed.

[0107] Explanation of reference numerals in the attached figures

[0108] 1. Heat exchanger

[0109] 2. Medium-pressure distillation column

[0110] 3. Nitrogen condenser

[0111] 4. Low-pressure distillation column

[0112] 5. Crude Argon Tower

[0113] 6. Crude Argon Condenser

[0114] 8 Nitrogen Turbines

[0115] 9 Oxygen Turbines

Claims

1. An air separation device comprising: a main heat exchanger, a medium-pressure distillation column, a nitrogen condenser, a low-pressure distillation column, an oxygen turbine, oxygen turbine inlet piping, oxygen side piping, and dilution stream piping. The main heat exchanger allows raw material air to be introduced from its warm end and discharged from its cold end. The medium-pressure distillation column allows feed air exported from the main heat exchanger to be introduced into it. The nitrogen condenser allows vapor streams from the medium-pressure distillation column to be introduced into it, condensed, and then discharged as reflux liquid. The low-pressure distillation column allows the introduction of oxygen-enriched liquid from the medium-pressure distillation column. The oxygen turbine enables oxygen drawn from the bottom of the low-pressure distillation column or the refrigerant storage section of the nitrogen condenser to expand and cool after heat exchange through the main heat exchanger. The oxygen turbine inlet piping is used to feed the oxygen into the oxygen turbine via the main heat exchanger, and then back into the main heat exchanger. The oxygen side piping branches off from the oxygen turbine inlet piping. The dilution flow piping is used to export nitrogen-containing gas with a lower oxygen concentration than the oxygen in the gas phase of the low-pressure distillation column or the refrigerant storage section as a dilution flow, and introduce it into the oxygen turbine inlet piping.

2. The air separation device as claimed in claim 1, comprising: A gas flow meter and a first flow regulating valve are installed on the oxygen turbine inlet pipe upstream of the main heat exchanger and the oxygen side piping. A second flow control valve is installed on the oxygen-side piping upstream of the main heat exchanger. The third flow regulating and check valve is installed in the dilution flow piping. An oxygen concentration analyzer and a fourth flow control valve are installed in the oxygen turbine inlet piping downstream of the main heat exchanger to measure oxygen concentration. A level gauge used to determine the liquid level of the refrigerant phase in the nitrogen condenser.

3. The air separation device as claimed in claim 1, comprising an oxygen concentration regulating unit, the oxygen concentration regulating unit being used to set a target oxygen concentration corresponding to the operation of the nozzle of the oxygen turbine, to set a dilution flow rate and an oxygen side flow rate in a manner that achieves the target oxygen concentration, and to regulate the oxygen concentration of the oxygen flowing through the oxygen turbine inlet pipe.

4. The air separation device as claimed in claim 2, comprising an oxygen flow isolation control unit, wherein the oxygen flow isolation control unit controls the oxygen flow to be isolated by closing the first flow regulating valve and opening the third flow regulating and check valve when the oxygen concentration measured by the oxygen concentration analyzer exceeds the threshold for determining a major combustion risk in the oxygen turbine, thereby introducing a dilution flow as an inactive gas into the oxygen turbine inlet piping.

5. The air separation device as claimed in claim 2, comprising an interlock that stops the oxygen turbine if the oxygen concentration measured by the oxygen concentration analyzer exceeds a threshold for determining a significant risk of combustion in the oxygen turbine.

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