Air separation device

Abstract

The present invention provides an air separation device that can reduce the risk of combustion in a heat exchanger connected to an oxygen turbine. [Solution] The air separation apparatus A1 comprises a main heat exchanger 1, an intermediate pressure rectification column 2, a low pressure rectification 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 for sending oxygen gas discharged from the gas phase of the bottom of the low pressure rectification column 4 or the refrigerant storage section of the nitrogen condenser 3 to the oxygen turbine 9 via the main heat exchanger 1 and back to the main heat exchanger 1, an oxygen bypass pipe L321 branching from the oxygen turbine inlet pipe L32, and a dilution flow pipe L42 for discharging nitrogen-containing gas with a lower oxygen concentration than the oxygen concentration in the oxygen gas discharged from the gas phase of the bottom of the low pressure rectification column 4 or the refrigerant storage section as a dilution flow and introducing it into the oxygen turbine inlet pipe L32.

Description

Technical Field

[0001] The present invention relates to an air separation device. For example, it relates to a cryogenic air separation device including an oxygen turbine and a heat exchanger.

Background Art

[0002] When separating air components into nitrogen, argon, oxygen, etc. by the cryogenic air separation method, a distillation system equipped with a plurality of distillation columns such as a medium-pressure column, a low-pressure column, and a crude argon column, an oxygen turbine for expanding oxygen, and a heat exchanger is applied. In recent years, in the semiconductor industry, while there is a large demand for nitrogen and argon, the demand for oxygen is limited, and there is a demand for an air separation device optimized for the supply of nitrogen and argon. In the semiconductor industry where the demand for nitrogen and argon is high but the demand for oxygen is limited, the pressure balance of the air separation device is enhanced to optimize the supply of nitrogen and argon, and for example, surplus oxygen obtained from a low-pressure column operating at about 3 barA is expanded to generate the required cold air. In this case, the oxygen turbine used needs to reduce the oxygen concentration to a certain extent, for example, to 80 - 95% for reasons of equipment safety. Since it is necessary to recover nitrogen and argon, the oxygen concentration from the low-pressure column is almost 100%, so it is necessary to dilute the oxygen gas. For example, nitrogen-containing gas from the low-pressure column (for example, Patent Documents 1 and 2), or evaporation gas from the crude argon column condenser (for example, Patent Document 3) is mixed with the oxygen gas for dilution.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] Diluting the oxygen gas flowing into an oxygen turbine with an inert gas results in process losses; therefore, it is desirable from an energy efficiency standpoint to use machinery that can handle high-concentration oxygen (e.g., 90% or more oxygen). From the perspective of safety and reliability of air separation equipment, high-oxygen-concentration flows carry a high risk of oxygen combustion, and this risk may increase during transient operating modes such as when the air separation equipment is started up or when the operating mode is changed. Oxygen combustion risk can occur, for example, when an oxygen flow is present in a heat exchanger made of flammable materials such as aluminum, and a flammable substance enters the heat exchanger for some reason. In large-scale air separation equipment, it is industrially very difficult to completely eliminate such risks.

[0005] This disclosure provides an air separation device that can reduce the risk of combustion in a heat exchanger connected to an oxygen turbine. [Means for solving the problem]

[0006] The air separation apparatus (A1, A2) of this disclosure comprises a main heat exchanger (1), an intermediate pressure rectification column (2), a nitrogen condenser (3), a low pressure rectification column (4), a crude argon column (5), a crude argon condenser (6), and an oxygen turbine (9). The aforementioned air separation devices (A1, A2) are An oxygen turbine inlet pipe (L32) is provided to send oxygen gas, which is discharged from the bottom of the low-pressure rectification column (4) or from the gas phase of the refrigerant storage section (32) of the nitrogen condenser (3), to the oxygen turbine (9) via the main heat exchanger (1), and then back to the main heat exchanger (1). The oxygen bypass pipe (L321) branches off from the oxygen turbine inlet pipe (L32), The system may also include dilution flow piping (L42, L621) for introducing a nitrogen-containing gas with a lower oxygen concentration than the oxygen concentration in the oxygen gas as a dilution flow into the oxygen turbine inlet piping (L32). A "dilution stream" is a fluid used to dilute the oxygen concentration in oxygen gas (oxygen-enriched gas, high-purity oxygen gas, etc.). The dilution stream may be, for example, raw air, a low-oxygen-concentration gas that can be obtained from a medium-pressure rectification column (2), a nitrogen condenser (3), a low-pressure rectification column (4), a crude argon condenser (6), etc.

[0007] The aforementioned dilution pipes (L42, L621) are The intermediate pressure rectification column (2) or the low pressure rectification column (4) may be configured to allow nitrogen-containing gas to be discharged as a dilution stream, or the crude argon condenser (6) or a portion of the raw material air may be configured to allow nitrogen-containing gas to be discharged.

[0008] The aforementioned air separation devices (A1, A2) are A gas flow meter (FIC) and a first flow control valve (V1) are provided in the oxygen turbine inlet piping (L32) upstream of the main heat exchanger (1) and the oxygen bypass piping (L321), A second flow control valve (V2) is provided in the oxygen bypass piping (L321) upstream of the main heat exchanger (1), A third flow rate adjustment / backflow prevention valve (V3) is provided in the aforementioned dilution flow piping (L42, L621), An oxygen concentration analyzer (AIC) and a fourth flow control valve (V4) are provided in the oxygen turbine inlet piping (L32) downstream from the main heat exchanger (1) for measuring the oxygen concentration. A liquid level meter (LIC) for measuring the liquid level of the refrigerant phase in the nitrogen condenser (3), It may also be equipped with.

[0009] The aforementioned air separation devices (A1, A2) are The system may also include an oxygen concentration adjustment unit (10) that sets a target oxygen concentration corresponding to the operation of the nozzle of the oxygen turbine (9), and adjusts the oxygen concentration of the oxygen gas flowing through the oxygen turbine inlet pipe by setting the dilution flow rate (the flow rate of the gas flowing through the dilution flow pipe, or the sum of that flow rate and the flow rate of the oxygen gas flowing through the oxygen turbine inlet pipe (L32)) and the oxygen bypass flow rate (the flow rate of the oxygen gas flowing through the oxygen bypass pipe) to achieve that target oxygen concentration.

[0010] The aforementioned air separation devices (A1, A2) are The oxygen turbine (9) may be equipped with an interlock (11) that stops the oxygen turbine (9) if the oxygen concentration measured by the oxygen concentration analyzer (AIC) exceeds a threshold at which it is determined that the oxygen turbine (9) is exposed to a significant combustion risk.

[0011] The aforementioned air separation devices (A1, A2) are The system may also include an oxygen gas flow shutoff control unit (12) that, when the oxygen concentration measured by the oxygen concentration analyzer (AIC) exceeds a threshold at which the oxygen turbine (9) is judged to be exposed to a significant combustion risk, closes a first flow control valve (V1) provided in the oxygen turbine inlet piping (L32) to shut off the oxygen gas flow, opens a third flow control / backflow prevention valve (V3) to introduce a diluted flow as an inert gas into the oxygen turbine inlet piping (L32) (introduced into the oxygen turbine inlet piping (L32) upstream of the main heat exchanger (1)).

[0012] The aforementioned air separation devices (A1, A2) are The system may include a dilution flow control unit (13) that controls the dilution flow rate by adjusting the mass balance of the dilution flow source (e.g., low-pressure rectification column (4), crude argon condenser (6), medium-pressure rectification column (2), raw material air). The mass balance adjustment may be performed by utilizing the fact that the adjustment target (dilution flow rate) is uniquely determined by the difference between the raw material air inflow rate and the raw material air outflow rate (including product gas and exhaust gas) of the supply source. This reduces the number of valves and other devices that cause pressure loss in the piping of the adjustment target flow rate.

[0013] The oxygen concentration adjustment unit (10) may be controlled to introduce the dilution flow into the oxygen turbine inlet piping (L32) downstream of the oxygen turbine (9). Branch dilution flow pipes that branch off from the aforementioned dilution flow pipes (L42, L621) may be connected to the oxygen turbine inlet pipe (L32) downstream of the oxygen turbine (9).

[0014] The air separation device (A1, A2) may include a subcooler (7) that cools a liquid (for example, an oxygen-enriched liquid) derived from the medium-pressure rectification column (2) with a gas derived from the low-pressure rectification column (4) or the crude argon condenser (6). The main heat exchanger (1) may have a structure divided into a plurality of parts for the optimization of the structure according to the design temperature, pressure, and flow rate and for the improvement of transportability.

[0015] The air separation device (A1, A2) of the present disclosure A main heat exchanger (1) into which feed air is introduced from the warm end and led out from the cold end, A medium-pressure rectification column (2) into which the feed air led out from the cold end of the main heat exchanger (1) is introduced at its bottom (21), A nitrogen condenser (3) into which a vapor flow is introduced from the upper part (23) of the medium-pressure rectification column (2) and condensed and led out as a reflux liquid, A low-pressure rectification column (4) into which the oxygen-enriched liquid led out from the bottom (21) of the medium-pressure rectification column (2) is introduced at its rectification section (42) and / or into which the vapor flow led out from the upper part (23) of the medium-pressure rectification column (2) is introduced at its top (43), An oxygen turbine (9) that expands and cools oxygen gas led out from the bottom of the low-pressure rectification column (4) or from the gas phase of the refrigerant storage section (32) of the nitrogen condenser (3) after heat exchange in the main heat exchanger (1), A crude argon column (5) into which the oxygen-containing fluid led out from the rectification section (42) of the low-pressure rectification column (4) is introduced at its bottom (51), A crude argon condenser (6) into which a vapor flow is introduced from the upper part of the crude argon column (5) and condensed and led out as a reflux liquid, A subcooler (7) into which the oxygen-enriched liquid led out from the bottom (21) of the medium-pressure rectification column (2) is introduced from the warm end and led out from the cold end and / or into which the liquefied nitrogen led out from the upper part (23) of the medium-pressure rectification column (2) is introduced from the warm end and led out from the cold end and / or into which the nitrogen gas led out from the top (43) of the low-pressure rectification column (4) is introduced from the cold end and led out from the warm end, may be provided.

[0016] The air separation apparatuses (A1, A2) a raw material air pipe line (L1) for introducing raw material air (Feed air) into the medium-pressure rectification column (2) through the main heat exchanger (1); an oxygen-enriched liquid pipe line (L21) for introducing the oxygen-enriched liquid derived from the bottom (21) of the medium-pressure rectification column (2) into the rectification section (42) of the low-pressure rectification column (4) through the sub-cooler (7); an oxygen-enriched liquid branch pipe line (L211) branched from downstream of the sub-cooler (7) of the oxygen-enriched liquid pipe line (L21) and introduced into the refrigerant storage section (61) of the crude argon condenser (6); a liquefied nitrogen pipe line (L23) for introducing the liquefied nitrogen derived from the upper part (23) of the medium-pressure rectification column (2) into the top (43) of the low-pressure rectification column (4) through the sub-cooler (7); a liquefied nitrogen branch pipe line (L231) branched from downstream of the sub-cooler (7) of the liquefied nitrogen pipe line (L23) and leading out a part of the liquefied nitrogen; a liquefied oxygen extraction line (L31) for taking out the refrigerant (oxygen-enriched liquid) in the refrigerant storage section (32) of the nitrogen condenser (3) as liquefied oxygen (LOX); an oxygen turbine inlet pipe (L32) which is led out from the upper gas phase of the refrigerant storage section (32) of the nitrogen condenser (3), introduced into the middle of the main heat exchanger (1) to be heated and then led out, expanded by the oxygen turbine (9), introduced again from the cold end of the main heat exchanger (1) and led out from the warm end, and taken out as oxygen gas; an oxygen-containing fluid pipe line (L421) for introducing an oxygen-containing fluid derived from the rectification section (42) of the low-pressure rectification column (4) into the bottom (51) of the crude argon column (5); a nitrogen gas pipe line (L43) which is led out from the top (43) of the low-pressure rectification column (4) and taken out as nitrogen gas (GAN) through the sub-cooler (7) and the main heat exchanger (1); A crude argon column bottom fluid piping line (L51) is provided from the bottom (51) of the crude argon column (5) and is used to introduce bottom fluid below the outlet position 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) for guiding out the vapor flow or reflux liquid from the upper part of the crude argon column (5), A crude argon condenser piping line (L62) is provided for supplying the refrigerant from the upper gas phase of the refrigerant storage section (62) of the crude argon condenser (6) and introducing it to the rectification section (42) of the low-pressure rectification column (4) above the oxygen enrichment piping line (L21), It may also be equipped with.

[0017] The fluid introduced from the rectification section (42) of the low-pressure rectification column (4) to the crude argon column (5) is called the oxygen-containing fluid, and the liquid discharged from a point lower than the raw material air introduction stage (for example, the bottom of the nitrogen rectification column) is called the oxygen-enriched liquid. The oxygen-containing fluid may be liquid or a gas-liquid mixture.

[0018] The subcooler (7) described above cools the liquid discharged from the medium-pressure rectification column (2) with gas discharged from the low-pressure rectification column (4) or the crude argon condenser (6). This reduces the amount of liquid that evaporates due to the reduced pressure when the liquid is introduced into the low-pressure rectification column (4), increasing the amount of liquid that contributes to rectification as reflux liquid, thereby improving rectification efficiency.

[0019] The aforementioned air separation devices (A1, A2) are Various measuring instruments such as flow rate meters, pressure meters, temperature meters, and liquid level meters, Control valves, gate valves and other types of valves, Piping that connects each element, It may have.

[0020] (effect) (1) The risk of combustion in the heat exchanger connected to the oxygen turbine can be reduced. (2) Under an optimized pressure balance, low temperatures can be generated by expanding excess oxygen in an oxygen turbine. (3) When diluting oxygen 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. (4) Safety can be improved by reducing the risk of combustion in air separation systems equipped with oxygen turbines. [Brief explanation of the drawing]

[0021] [Figure 1] This is a diagram showing the air separation device of Embodiment 1. [Figure 2] This is a diagram showing an air separation device according to Embodiment 2. [Modes for carrying out the invention]

[0022] Some embodiments of the present disclosure are described below. The embodiments described below illustrate examples of the present disclosure. The present disclosure is not limited to the embodiments described below and includes various modifications that do not alter the essence of the present disclosure. Not all of the configurations described below are essential to the present disclosure. Upstream and downstream are based on the flow direction of the fluid (liquid, gas).

[0023] (Embodiment 1) The first air separation device A1 of Embodiment 1 will be described with reference to Figure 1. The first air separation unit A1 comprises a main heat exchanger 1, an intermediate pressure rectification column 2, a nitrogen condenser 3, a low pressure rectification column 4, a crude argon column 5, a crude argon condenser 6, a subcooler 7, an oxygen turbine 9, an oxygen concentration adjustment unit 10, and an interlock 11.

[0024] The main heat exchanger 1 cools the raw material air introduced from the hot end and discharges it from the cold end. The cooled raw material air is introduced to the intermediate pressure rectification column 2 via the raw material air piping line L1.

[0025] The intermediate-pressure rectification column 2 comprises a bottom section 21, a rectification section 22, and a top section 23. The raw air piping line L1 is connected to the bottom section 21. The oxygen-enriched liquid stored in the bottom section 21 is sent to the rectification section 42 of the low-pressure rectification column 4 via the oxygen-enriched liquid piping line L21, after heat exchange in the subcooler 7. After heat exchange in the subcooler 7, a portion of the oxygen-enriched liquid is introduced to the refrigerant storage section 61 of the crude argon condenser 6 via the oxygen-enriched liquid branching piping line L211. A portion of the liquid nitrogen in the top section 23 is sent to the top section 43 of the low-pressure rectification column 4 via the liquid nitrogen piping line L23, after heat exchange in the subcooler 7. The liquid nitrogen branching piping line L231 branches off from the liquid nitrogen piping line L23 downstream of the subcooler 7 and is a line for extracting liquid nitrogen.

[0026] The nitrogen condenser 3 is located above the top 23 of the intermediate pressure rectification section 2. A portion of the nitrogen gas (vapor flow) discharged from the top 23 of the intermediate pressure rectification 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 refrigerant. The liquefied nitrogen returns to the top 23 of the intermediate pressure rectification column 2 as reflux liquid. The liquid level meter LIC measures the liquid level of the refrigerant phase in the nitrogen condenser 3.

[0027] The liquefied oxygen extraction line L31 is a line for extracting refrigerant (oxygen-enriched liquid) from the refrigerant storage section 32 of the nitrogen condenser 3 as liquefied oxygen (LOX).

[0028] The low-pressure rectification column 4 comprises a rectification section 42 and a top section 43. The bottom section may also serve as the refrigerant storage section 32 of the nitrogen condenser 3. The oxygen-containing fluid discharged from the rectification section 42 of the low-pressure rectification column 4 is introduced to the bottom 51 of the crude argon column 5 via the oxygen-containing fluid piping line L421. The nitrogen gas discharged from the top 43 of the low-pressure rectification column 4 is removed as low-pressure nitrogen gas (GAN) via the nitrogen gas piping line L43, through the subcooler 7 and the main heat exchanger 1.

[0029] The crude argon column 5 comprises a bottom section 51, a rectification section 52, and a top section 53. The crude argon column bottom fluid piping line L51 is led out from the bottom section 51 of the crude argon column 5 and is a line for introducing bottom fluid below the outlet position 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 a piping line for leading out the vapor flow or reflux liquid (crude argon-containing fluid) from the top of the crude argon column 5.

[0030] The crude argon condenser 6 receives the vapor flow from the upper part of the crude argon column 5, condenses it, and discharges it as reflux liquid. The crude argon condenser piping line L62 is discharged from the upper gas phase of the refrigerant storage section 62 of the crude argon condenser 6 and is a line for introducing the rectification section 42 of the low-pressure rectification column 4, which is above the oxygen enrichment liquid piping line L21.

[0031] The subcooler 7 receives oxygen-enriched liquid from the bottom 21 of the medium-pressure rectification column 2 from its warm end and discharges it from its cold end. The subcooler 7 also receives liquefied nitrogen from the top 23 of the medium-pressure rectification column 2 from its warm end and discharges it from its cold end. Furthermore, the subcooler 7 receives nitrogen gas from the top 43 of the low-pressure rectification column 4 from its cold end and discharges it from its warm end.

[0032] The oxygen turbine 9 cools the oxygen gas taken from the gas phase of the refrigerant storage section 32 of the nitrogen condenser 3 by exchanging heat in the main heat exchanger 1, and then expanding it.

[0033] The oxygen turbine inlet piping L32 is a line that leads from the upper gas phase of the refrigerant storage section 32 of the nitrogen condenser 3, is introduced to the middle of the main heat exchanger 1 (for example, an intermediate position closer to the cold end), is heated and then led out, is expanded in the oxygen turbine 9, and is again introduced from the cold end of the main heat exchanger 1 and led out from the warm end to be extracted as oxygen gas. The first flow control valve V1 is installed in the oxygen turbine inlet piping L32 upstream of the main heat exchanger 1 and the oxygen bypass piping L321. The oxygen concentration analyzer AIC and the fourth flow control valve V4 are installed in the oxygen turbine inlet piping L32 at a position beyond the middle of the main heat exchanger 1 and upstream of the oxygen turbine 9.

[0034] The oxygen bypass piping L321 branches off from the oxygen turbine inlet piping L32 and is introduced to the main heat exchanger 1, or it is reconnected to the oxygen turbine inlet piping L32 downstream of the oxygen turbine 9. The second flow control valve V2 is installed at the location where it is introduced to the main heat exchanger 1 or in the oxygen bypass piping L321 upstream of the main heat exchanger 1.

[0035] The dilution flow piping L42 leads gas (e.g., nitrogen-containing gas) as a dilution flow from the upper part of the rectification section 42 of the low-pressure rectification column 4 and connects downstream of the oxygen bypass piping L321 to the oxygen turbine inlet piping L32 upstream of the main heat exchanger 1. The third flow rate control and backflow prevention valve V3 is installed in the dilution flow piping L42.

[0036] The oxygen concentration adjustment unit 10 sets a target oxygen concentration corresponding to the operation of the nozzle of the oxygen turbine 9, and adjusts the oxygen concentration of the oxygen gas flowing through the oxygen turbine inlet pipe L32 by setting the dilution flow rate (the flow rate of gas flowing through the dilution flow pipe, or the sum of that flow rate and the flow rate of oxygen gas flowing through the oxygen turbine inlet pipe L32) and the oxygen bypass flow rate (the flow rate of oxygen gas flowing through the oxygen bypass pipe) to achieve that target oxygen concentration.

[0037] The first flow control valve V1 and the second flow control valve V2 are controlled according to the gas flow rate measured by the gas flow meter FIC, thereby controlling the oxygen gas flow rate through the oxygen bypass piping. Then, the third flow control / backflow prevention valve V3 is controlled to mix the oxygen gas flow and the dilution flow, so that the oxygen concentration after mixing becomes the target oxygen concentration.

[0038] When there is an excess of cold energy, the liquid level of the refrigerant in the nitrogen condenser 3 rises. In this case, when the liquid level of the refrigerant measured by the liquid level meter LIC exceeds a threshold, the second flow control valve V2 is opened. By increasing the flow rate of oxygen gas to the bypass, the load on the oxygen turbine 9 is reduced, and the cold balance can be restored.

[0039] The second flow control valve V2 is opened when the oxygen concentration measured by the oxygen concentration analyzer AIC exceeds a threshold. As the oxygen gas flow rate to the bypass increases, the amount of oxygen gas supplied to the oxygen turbine 9 decreases while the dilution flow gas is maintained, and consequently the oxygen concentration in the oxygen turbine 9 also decreases. Therefore, the opening degree of the second flow control valve V2 is determined by a high selector between the liquid level meter LIC and the oxygen concentration analyzer AIC. According to this embodiment, the oxygen concentration setting of the oxygen concentration analyzer AIC on the inlet side of the oxygen turbine 9 is fixed to an appropriate value during plant startup and mode switching. From the standpoint of safe operation, it is recommended to set a relatively low value during plant startup and mode switching. During plant balance adjustment, when the oxygen concentration on the inlet side of the oxygen turbine 9 approaches the target value, the oxygen concentration analyzer AIC takes over control of the second flow control valve V2 and ensures that the oxygen concentration remains below the set value. This allows for maintaining a safe operating state. Furthermore, there is an interlock 11 that, if an abnormal condition occurs such as the oxygen concentration measured by the oxygen concentration analyzer AIC reaching a high set value, will shut down the oxygen turbine 9.

[0040] The oxygen gas flow shutoff control unit 12 controls the oxygen gas flow by closing the first flow control valve V1 located in the oxygen turbine inlet piping L32 to shut off the oxygen gas flow and opening the third flow control / backflow prevention valve V3 to introduce a diluted flow as an inert gas into the oxygen turbine inlet piping L32 of the oxygen turbine 9 (introducing it into the oxygen turbine inlet piping L32 upstream of the main heat exchanger 1) when the oxygen concentration measured by the oxygen concentration analyzer AIC exceeds a threshold at which the oxygen turbine 9 is judged to be exposed to a serious combustion risk.

[0041] The dilution flow rate control unit 13 can control the dilution flow rate by adjusting the mass balance of the dilution flow source (e.g., low-pressure rectification column 4, crude argon condenser 6, medium-pressure rectification column 2, raw material air).

[0042] (Embodiment 2) The air separation device A2 of Embodiment 2 will be described with reference to Figure 2. Reference numerals that are the same as those in Embodiment 1 have the same function, and therefore their descriptions may be omitted. The dilution flow piping L621 of the air separation unit A2 is a line branched from the crude argon condenser piping line L62, which is led from the crude argon condenser 6, and introduces low-concentration oxygen gas downstream of the oxygen bypass piping L321 and upstream of the main heat exchanger 1 to the oxygen turbine inlet piping L32. The third flow rate control and backflow prevention valve V3 is installed in the dilution flow piping L621.

[0043] (Embodiment 3) In Embodiment 3, branched dilution flow pipes, which branch off from the dilution flow pipes (L42, L621), are connected to the oxygen turbine inlet pipe L32, which is downstream of the oxygen turbine 9. A fifth flow control valve is provided in the branched dilution flow pipe. The oxygen concentration adjustment unit 10 controls the fifth flow control valve to open in order to introduce a diluted flow into the oxygen turbine inlet pipe L32 downstream of the oxygen turbine 9. In Embodiment 3, the role of the second flow control valve V2 in Embodiments 1 and 2 is taken over by the fifth flow control valve on the branched dilution flow piping. When the actual oxygen concentration becomes higher than the set value of the oxygen concentration analyzer AIC, the second flow control valve V2 opens, reducing the oxygen by bypassing it. On the other hand, in Embodiment 3, the fifth flow control valve closes, increasing the dilution flow. In Embodiments 1 and 2, the second flow control valve V2 is controlled via a high selector. In contrast, in Embodiment 3, the opening degree of the fifth flow control valve can be controlled independently from the measured value of the oxygen concentration analyzer AIC.

[0044] (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) Although not specifically stated, control valves, gate valves, etc. may be installed on each 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. (4) When raw material air is used as the dilution flow, for example, it may be branched from the raw material air piping line (L1) and connected to the dilution flow piping (L42, L621), or a separate line may be provided. (5) When the dilution flow is discharged from the medium-pressure rectification column (2), it may be branched from, for example, the oxygen enrichment liquid piping line (L21) or the liquefied nitrogen piping line (L23) and connected to the dilution flow piping (L42, L621), or a separate line may be provided. [Explanation of Symbols]

[0045] 1 heat exchanger 2. Medium-pressure rectification column 3. Nitrogen condenser 4. Low-pressure rectification column 5. Crude Argon Tower 6. Crude Argon Condenser 8 Nitrogen Turbine 9. Oxygen Turbine

Claims

1. The main heat exchanger receives raw air from the hot end and discharges it from the cold end, A medium-pressure rectification column into which raw material air discharged from the main heat exchanger is introduced, A nitrogen condenser receives a vapor flow from the aforementioned medium-pressure rectification column, condenses it, and discharges it as reflux liquid. A low-pressure rectification column into which the oxygen-enriched liquid discharged from the aforementioned medium-pressure rectification column is introduced, An oxygen turbine that cools oxygen gas, which is discharged from the gas phase at the bottom of the low-pressure rectification column or the refrigerant storage section of the nitrogen condenser, after heat exchange in the main heat exchanger, expands the oxygen gas. The oxygen gas is sent to the oxygen turbine via the main heat exchanger, and then sent back to the main heat exchanger via an oxygen turbine inlet pipe, An oxygen bypass pipe branching off from the oxygen turbine inlet pipe, A dilution flow pipe is provided for introducing a nitrogen-containing gas with a lower oxygen concentration than the oxygen concentration in the oxygen gas discharged from the gas phase of the bottom of the low-pressure rectification column or the refrigerant storage section as a dilution flow, into the oxygen turbine inlet pipe. Equipped with, Air separation device.

2. A gas flow meter and a first flow control valve are provided in the oxygen turbine inlet piping upstream of the main heat exchanger and the oxygen bypass piping. A second flow control valve is provided in the oxygen bypass piping upstream of the main heat exchanger, A third flow rate adjustment and backflow prevention valve is provided in the aforementioned dilution flow piping, An oxygen concentration analyzer and a fourth flow control valve are provided in the oxygen turbine inlet piping downstream of the main heat exchanger for measuring the oxygen concentration. A liquid level meter for measuring the liquid level of the refrigerant phase in the nitrogen condenser, The air separation device according to claim 1, comprising:

3. The system includes an oxygen concentration adjustment unit that sets a target oxygen concentration corresponding to the operation of the oxygen turbine nozzle, and adjusts the oxygen concentration of the oxygen gas flowing through the oxygen turbine inlet piping by setting the dilution flow rate and oxygen bypass flow rate to achieve that target oxygen concentration. The air separation device according to claim 1.

4. The oxygen gas flow shutoff control unit controls the following: when the oxygen concentration measured by the oxygen concentration analyzer exceeds a threshold at which the oxygen turbine is judged to be exposed to a significant combustion risk, it closes the first flow control valve to shut off the oxygen gas flow, opens the third flow control / backflow prevention valve, and introduces a diluted flow as an inert gas into the oxygen turbine inlet piping. The air separation device according to claim 2.

5. The system includes an interlock that stops the oxygen turbine if the oxygen concentration measured by the oxygen concentration analyzer exceeds a threshold at which the oxygen turbine is deemed to be at significant risk of combustion. The air separation device according to claim 2.

Images