High-purity oxygen production equipment

Abstract

To provide a high-purity oxygen production device that can be effectively controlled to produce high-purity oxygen having a desired quality. [Solution] A high-purity oxygen production apparatus comprising: a heat exchanger 1 for cooling feed air; a first fractionator 2 having an inlet section for introducing cooled feed air and an outlet section for discharging an oxygen-containing liquid, and reducing the concentration of high-boiling-point impurities having a boiling point higher than that of oxygen in the oxygen-containing liquid compared to the concentration of the high-boiling-point impurities in the feed air; a second fractionator 4 having an inlet section for introducing an oxygen-containing liquid and an outlet section for discharging high-purity oxygen, and reducing the concentration of low-boiling-point impurities having a boiling point lower than that of oxygen in the high-purity oxygen compared to the concentration of the low-boiling-point impurities in the oxygen-containing liquid; a first pipe having a branch section and a first valve V1 for introducing the oxygen-containing liquid discharged from the first fractionator into the second fractionator; and a second pipe branching from the branch section and having a second valve V2, the first valve adjusting the flow rate of the oxygen-containing liquid introduced into the second fractionator.

Description

[Technical Field]

[0001] The present invention relates to a high-purity oxygen production apparatus and also to a method for producing high-purity oxygen using the high-purity oxygen production apparatus. [Background technology]

[0002] High-purity oxygen is liquid oxygen with a very low content (e.g., less than 1 ppm by volume) of impurities (e.g., nitrogen, argon, neon, helium, methane). High-purity oxygen is particularly important in the semiconductor manufacturing process in the semiconductor industry. To produce high-purity oxygen, atmospheric air is usually used as a raw material. High-purity oxygen can be produced by reducing the concentration of impurities contained in atmospheric air.

[0003] For example, Patent Document 1 discloses a high-purity oxygen production apparatus equipped with a rectification column that reduces the concentration of impurities in the feed air. High-purity oxygen production apparatuses must be appropriately controlled so that high-purity oxygen of the desired quality is produced. In conventional high-purity oxygen production apparatuses, the quality of the produced high-purity oxygen is controlled by analyzing the concentration of impurities in the produced high-purity oxygen using means such as a Fourier transform infrared spectrometer (FTIR) or atmospheric pressure ionization mass spectrometer (API-MS), which are capable of detecting impurities at the ppb level. Then, based on the results of this quality control, the operation of the high-purity oxygen production apparatus is controlled so that high-purity oxygen of the desired quality is produced. However, such conventional apparatuses and methods require expensive means such as FTIR and API-MS, which impose a heavy burden in terms of cost. In addition, it is difficult to control the high-purity oxygen production apparatus in real time according to the quality of the high-purity oxygen currently being produced. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-204825 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a high-purity oxygen production device that can be effectively controlled so that high-purity oxygen having a desired quality is produced. [Means for solving the problem]

[0006] The present inventors have discovered that in a high-purity oxygen production apparatus that uses a first fractionator that reduces the concentration of high-boiling-point impurities in the feed air to produce an oxygen-containing liquid, and a second fractionator that reduces the concentration of low-boiling-point impurities in the oxygen-containing liquid to produce high-purity oxygen, the high-purity oxygen production apparatus can be effectively controlled by adjusting the oxygen concentration in the oxygen-containing liquid and the flow rate of the oxygen-containing liquid introduced into the second fractionator, and have completed the present invention. That is, the present disclosure provides, for example, the following high-purity oxygen production apparatus. [1] A heat exchanger for cooling the raw air; a first rectification column having an inlet for introducing the cooled feed air and an outlet for discharging an oxygen-containing liquid, the first rectification column reducing the concentration of high-boiling-point impurities having a boiling point higher than that of oxygen in the oxygen-containing liquid compared to the concentration of high-boiling-point impurities in the feed air; a vessel having a nitrogen condenser therein, the vessel being located at an upper portion of the first rectification column; a second rectification column having an inlet for introducing the oxygen-containing liquid and an outlet for discharging high-purity oxygen, the second rectification column reducing the concentration of low-boiling-point impurities having a boiling point lower than that of oxygen in the high-purity oxygen compared to the concentration of low-boiling-point impurities in the oxygen-containing liquid; a first pipe for introducing the oxygen-containing liquid discharged from the first rectification column into the second rectification column, the first pipe including a branch portion and a first valve; a second pipe branching from the branching portion and having a second valve; a pipe for extracting an oxygen-enriched liquid from the bottom of the first rectification column and introducing the liquid into a vessel equipped with the nitrogen condenser therein; Equipped with the first valve adjusts the flow rate of the oxygen-containing liquid introduced into the second rectification column; High-purity oxygen production equipment. [Effects of the Invention]

[0007] The high-purity oxygen production device of the present disclosure can be effectively controlled so that high-purity oxygen having the desired quality is produced. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows an example of the configuration of a high-purity oxygen production apparatus according to the present disclosure. [Figure 2] FIG. 2 shows an example of the relationship between the oxygen concentration in the oxygen-containing liquid discharged from the first fractionator and the methane concentration in the oxygen-containing liquid in the high-purity oxygen production apparatus of the present disclosure, and an example of the relationship between the oxygen concentration in the oxygen-containing liquid discharged from the first fractionator and the methane concentration in the high-purity oxygen discharged from the second fractionator. [Figure 3] FIG. 3 shows another example of the configuration of the high-purity oxygen production apparatus of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail, but the scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without departing from the spirit of the present invention. The embodiments may be implemented alone or in combination with one another. When a specific description given for one embodiment also applies to other embodiments, that description is omitted in the other embodiments. It should be noted that each numerical range in the present disclosure includes the upper and lower limit values ​​indicated by "to" and "from." For example, the description "A to B" or "A to B" using numerical values ​​A and B means A or more and B or less. Furthermore, the descriptions "A to B," "A to B," or "A or more and B or less" in the numerical ranges described in stages in the present disclosure independently include both "preferably A or more" and "preferably B or less," and these lower or upper limit values ​​may be replaced with the upper or lower limit value of another numerical range. Furthermore, the lower or upper limit value of a numerical range described in the present disclosure may be replaced with a numerical value within that numerical range that is shown in the examples or drawings.

[0010] <High-purity oxygen production equipment> In one embodiment, a heat exchanger for cooling the feed air; a first rectification column having an inlet for introducing the cooled feed air and an outlet for discharging an oxygen-containing liquid, the first rectification column reducing the concentration of high-boiling-point impurities having a boiling point higher than that of oxygen in the oxygen-containing liquid compared to the concentration of high-boiling-point impurities in the feed air; a vessel having a nitrogen condenser therein, the vessel being located at an upper portion of the first rectification column; a second rectification column having an inlet for introducing the oxygen-containing liquid and an outlet for discharging high-purity oxygen, the second rectification column reducing the concentration of low-boiling-point impurities having a boiling point lower than that of oxygen in the high-purity oxygen compared to the concentration of low-boiling-point impurities in the oxygen-containing liquid; a first pipe for introducing the oxygen-containing liquid discharged from the first rectification column into the second rectification column, the first pipe including a branch portion and a first valve; a second pipe branching from the branching portion and having a second valve; a pipe for extracting an oxygen-enriched liquid from the bottom of the first rectification column and introducing the liquid into a vessel equipped with the nitrogen condenser therein; Equipped with the first valve adjusts the flow rate of the oxygen-containing liquid introduced into the second rectification column; High-purity oxygen production equipment is disclosed.

[0011] Also disclosed is a method for producing high-purity oxygen, which includes controlling the content of impurities in the produced high-purity oxygen by adjusting the oxygen concentration of the oxygen-containing liquid introduced into the second fractionator in the above-mentioned high-purity oxygen production apparatus.

[0012] In conventional high-purity oxygen production apparatuses, the quality of the produced high-purity oxygen is controlled by analyzing the concentration of impurities in the produced high-purity oxygen using means such as a Fourier transform infrared spectrometer (FTIR) or atmospheric pressure ionization mass spectrometer (API-MS), which are capable of detecting impurities at the ppb level. Based on the results of this quality control, the operation of the high-purity oxygen production apparatus is controlled so that high-purity oxygen of the desired quality is produced. Therefore, when using conventional high-purity oxygen production apparatuses, the use of the above means requires high costs, and it is difficult to appropriately control the operation of the high-purity oxygen production apparatus in real time. On the other hand, the high-purity oxygen production apparatus of the present disclosure can effectively produce high-purity oxygen of the desired quality without performing quality control using such expensive means. Furthermore, it is easy to appropriately control the operation of the high-purity oxygen production apparatus in real time so that high-purity oxygen of the desired quality is effectively produced.

[0013] (High-purity oxygen production apparatus further equipped with a flow meter) The high-purity oxygen producing apparatus according to one embodiment may further include a flow meter for measuring the flow rate of the oxygen-containing liquid introduced into the second rectification column through the first pipe. In this case, preferably, when the flow rate of the oxygen-containing liquid measured by the flow meter is lower than a predetermined flow rate, the opening of the first valve is increased, and when the flow rate of the oxygen-containing liquid measured by the flow meter is higher than the predetermined flow rate, the opening of the first valve is decreased. A high-purity oxygen producing apparatus further including a flow meter can more effectively control the operation of the high-purity oxygen producing apparatus based on the flow rate of the oxygen-containing liquid measured by the flow meter.

[0014] The above-mentioned predetermined flow rate is preferably 1 to 30%, more preferably 1 to 25%, and particularly preferably 1 to 20% of the flow rate of the feed air.

[0015] The flow meter can be installed at any position as long as the effects of the present invention can be obtained, but is preferably installed in the first pipe between the branching portion of the first pipe and the introduction portion of the second rectification column.

[0016] (High-purity oxygen production device further equipped with an oxygen concentration meter) The high-purity oxygen producing apparatus according to one embodiment may further include an oxygen concentration meter that measures the oxygen concentration of the oxygen-containing liquid or the oxygen concentration of the vapor at the outlet of the first rectification column. In this case, preferably, when the oxygen concentration of the oxygen-containing liquid measured by the oxygen concentration meter is lower than a predetermined concentration, the aperture of the second valve is increased, and when the oxygen concentration of the oxygen-containing liquid measured by the oxygen concentration meter is higher than the predetermined concentration, the aperture of the second valve is decreased. A high-purity oxygen production apparatus equipped with an oxygen concentration meter can more effectively control the operation of the high-purity oxygen production apparatus based on the oxygen concentration of the oxygen-containing liquid or the oxygen concentration of the vapor at the outlet of the first fractionator, measured by the oxygen concentration meter.

[0017] The above-mentioned predetermined concentration is preferably in the range of 1 to 50%, more preferably 1 to 40%, and particularly preferably 1 to 30%.

[0018] The oxygen concentration meter can be provided at any position as long as the effects of the present invention can be obtained, but is preferably provided in the first pipe between the outlet of the first rectification column and the branching portion of the first pipe, or in the outlet of the first rectification column.

[0019] Hereinafter, with reference to FIG. 1, a high-purity oxygen production apparatus according to one embodiment and a method for producing high-purity oxygen using this high-purity oxygen production apparatus will be described in more detail.

[0020] The high-purity oxygen production apparatus shown in FIG. 1 is an apparatus for producing high-purity oxygen from raw air, and is equipped with a heat exchanger 1, a first fractionator 2, a second fractionator 4, a pipe L2 (first pipe), a valve V1 (first valve), a pipe L3 (second pipe), a valve V2 (second valve), an oxygen concentration meter 3, and a flow meter 10. However, the configuration of the high-purity oxygen production apparatus of the present disclosure is not limited to the configuration shown in Fig. 1. For example, although the high-purity oxygen production apparatus shown in Fig. 1 includes an oxygen concentration meter 3 and a flow meter 10, the high-purity oxygen production apparatus of the present disclosure may include only one of the oxygen concentration meter 3 and the flow meter 10, or may not include both the oxygen concentration meter 3 and the flow meter 10.

[0021] <Feed air> The feed air is typically air obtained from the atmosphere surrounding the apparatus, and preferably air that has been obtained from the atmosphere surrounding the apparatus and then has had particulates, moisture, carbon dioxide, etc. removed by known methods (e.g., filters, dryers, carbon dioxide removers, adsorbers) and / or has been compressed. The feed air preferably contains components contained in atmospheric air, such as nitrogen, oxygen, argon, neon, helium, and methane, in the same proportions as atmospheric air. The feed air contains oxygen (boiling point -183°C), high-boiling impurities having a higher boiling point than oxygen, and low-boiling impurities having a lower boiling point than oxygen. Non-limiting examples of high-boiling impurities include methane (boiling point -161.6°C). Non-limiting examples of low-boiling impurities include nitrogen (boiling point -195.8°C), argon (boiling point -185.8°C), neon (-246.08°C), and helium (boiling point -268.9°C).

[0022] <Heat exchanger> The heat exchanger 1 cools the feed air to generate low-temperature gas, which is sent to the first fractionator 2 through a pipe L1. The cooling of the feed air in the heat exchanger 1 can be carried out by heat exchange between the feed air and the fluid in each pipe passing through the heat exchanger 1.

[0023] <First rectification column> The first rectification column 2 has an inlet for introducing a low-temperature gas and an outlet for discharging an oxygen-containing liquid. The first rectification column 2 reduces the concentration of high-boiling-point impurities in the oxygen-containing liquid compared to the concentration of high-boiling-point impurities in the feed air.

[0024] More specifically, low-temperature gas is introduced into the first rectification column 2 through a pipe L1 connected to the inlet. The introduced low-temperature gas rises as vapor within the first rectification column 2. Rectification is carried out by gas-liquid contact between the rising vapor and reflux liquid, which is supplied from L7 and L10 (described below) and flows down within the first rectification column 2. That is, the first rectification column 2 produces oxygen-enriched liquid flowing down to the bottom, and separates nitrogen gas (nitrogen components) from the top.

[0025] The outlet for discharging the oxygen-containing liquid is provided in the central portion of the first rectification column 2. In the outlet, the oxygen-containing liquid and the vapor are preferably in a state of vapor-liquid equilibrium. Therefore, the oxygen-containing liquid is preferably a part of the reflux liquid that is in a state of vapor-liquid equilibrium with the vapor in the outlet. High-boiling impurities (e.g., methane) contained in the feed air are concentrated in the oxygen-enriched liquid that flows down to the bottom of the first fractionator 2. Therefore, the concentration of high-boiling impurities in the oxygen-containing liquid at the outlet is reduced compared to the concentration of high-boiling impurities in the feed air.

[0026] The oxygen-enriched liquid in which high-boiling impurities are concentrated can be taken out from the bottom of the first fractionator 2 through a pipe L4. The oxygen-enriched liquid withdrawn through pipe L4 is introduced through pipe L5 via heat exchanger 1 or oxygen evaporator 7 into a vessel located at the top of the first rectification column and equipped with a nitrogen condenser 6 inside. In this vessel, heat exchange takes place between the oxygen-enriched liquid and nitrogen gas passing through the nitrogen condenser 6 in pipe L7. Due to the heat exchange, part of the oxygen-enriched liquid evaporates, and nitrogen gas in pipe L7 passing through the nitrogen condenser 6 is liquefied. The gas produced by evaporation can be taken out from pipe L6 connected to the top of the first rectification column 2. The liquefied nitrogen gas in pipe L7 is returned to the first rectification column 2 as part of the reflux liquid. Another portion of the oxygen-enriched liquid is introduced through pipe L9, which has valve V3, into a vessel containing nitrogen condenser 5, which is located below the vessel containing nitrogen condenser 6. Heat exchange is performed in the vessel containing nitrogen condenser 5 in the same way as in the vessel containing nitrogen condenser 6, but gas produced by evaporation in the vessel containing nitrogen condenser 5 is discharged as waste gas to the outside of the high-purity oxygen production apparatus through pipe L13.

[0027] The first rectification column 2 can have any configuration as long as the effects of the present invention can be obtained. The first rectification column 2 may be a known rectification column, for example, a type packed with packing or a type having trays arranged therein. Furthermore, the first rectification column 2 may consist of a single rectification column or a plurality of rectification columns. Non-limiting examples of the first rectification column 2 include rectification columns consisting of one or more of a high-pressure column, a medium-pressure column, a low-pressure column, a crude argon column, and a pure argon column.

[0028] <Second rectification column> The second fractionator 4 has an inlet for introducing the oxygen-containing liquid through a pipe L2 and an outlet for discharging the high-purity oxygen. The second fractionator 4 reduces the concentration of low-boiling-point impurities in the high-purity oxygen compared to the concentration of low-boiling-point impurities in the oxygen-containing liquid.

[0029] More specifically, the second rectification column 4 introduces an oxygen-containing liquid through a pipe L2 connected to the inlet. Within the second rectification column 4, rectification is carried out by gas-liquid contact between the ascending vapor and the reflux liquid, which is supplied from L2 and described below and descends within the second rectification column 4. That is, the second rectification column 4 produces high-purity oxygen and flows down to the bottom. The high-purity oxygen thus produced can be extracted from the bottom of the second rectification column 4. Furthermore, low-boiling-point impurities contained in the ascending vapor are extracted from the second rectification column 4 through a pipe L11 connected to the top of the second rectification column 4 and discharged to the outside of the apparatus.

[0030] The second rectification column 4 may have any configuration as long as the effects of the present invention can be obtained. The second rectification column 4 may be a known rectification column, for example, a type packed with packing or a type arranged with trays. The second rectification column 4 may consist of one rectification column or multiple columns.

[0031] <First and second pipes and first and second valves> The pipe L2 (first pipe) introduces the oxygen-containing liquid discharged from the first fractionator 2 into the second fractionator 4. The pipe L2 has a branch portion. Pipe L3 (second pipe) branches off from the branch point of pipe L2. Pipe L3 supplies the oxygen-containing liquid supplied from pipe L2 to pipe L4. In pipe L4, the supplied oxygen-containing liquid merges with the oxygen-enriched liquid extracted from the bottom of first fractionator 2. Valve V1 (first valve) is provided in pipe L2. In the apparatus shown in Fig. 1, valve V1 is provided between the branching section and second rectification column 4, but this is not limitative and valve V1 may be provided, for example, between first rectification column 2 and the branching section. A valve V2 (second valve) is provided in the pipe L3.

[0032] The valve V1 can control the device by adjusting the flow rate of the oxygen-containing liquid in the pipe L2 according to the flow rate measured by the flow meter 10. Details of the control will be described later.

[0033] Valve V2 adjusts the flow rate of the oxygen-containing liquid in pipe L2 in accordance with the oxygen concentration measured by oxygen concentration meter 3, thereby adjusting the oxygen concentration in the oxygen-containing liquid introduced into the second rectification column, thereby controlling the apparatus. Details of this control will be described later.

[0034] <Flowmeter> The flow meter 10 measures the flow rate of the oxygen-containing liquid introduced into the second fractionator 4 through the pipe L2.

[0035] In the high-purity oxygen production apparatus shown in FIG. 1, the flow meter 10 is provided in the pipe L2 between the branch point with the pipe L3 and the valve V1. However, the location where the flow meter 10 is provided is not limited to this, and it may be provided in any location within the range where the effects of the present invention can be obtained.

[0036] As long as the effects of the present invention can be obtained, any flow meter can be used as the flow meter 10. For example, the flow meter 10 may be an orifice type flow meter.

[0037] <Oxygen concentration meter> The oxygen concentration meter 3 measures the oxygen concentration of the oxygen-containing liquid discharged from the first rectification column 2 described below, or the oxygen concentration of the vapor in the discharge section of the first rectification column 2 from which the oxygen-containing liquid is discharged.

[0038] 1, the oxygen concentration meter 3 is provided in the pipe L2 between the outlet portion from which the first rectification column 2 outputs the oxygen-containing liquid and the branch portion to the pipe L3. However, the location where the oxygen concentration meter 3 is provided is not limited thereto, and the oxygen concentration meter 3 may be provided in any position as long as the effects of the present invention can be obtained. For example, the oxygen concentration meter 3 may be provided directly in the outlet portion, in which case the oxygen concentration meter 3 can measure the oxygen concentration of the vapor in the outlet portion. The oxygen-containing liquid is preferably in a state of vapor-liquid equilibrium with the vapor in the outlet portion. Therefore, the oxygen concentration of the oxygen-containing liquid discharged from the first rectification column 2 and the oxygen concentration of the vapor in the outlet portion of the first rectification column 2 from which the oxygen-containing liquid is discharged preferably coincide with each other.

[0039] Any oxygen concentration meter can be used as long as the effects of the present invention can be obtained as the oxygen concentration meter 3. The oxygen concentration meter 3 may be, for example, a relatively inexpensive oxygen concentration meter used for detecting oxygen concentrations of 0.01 to 100 by volume, such as a zirconia type oxygen concentration meter.

[0040] <Operation of high-purity oxygen production equipment> The high-purity oxygen production apparatus shown in FIG. 1 operates as follows.

[0041] (Production of high-purity oxygen) First, feed air is introduced into the apparatus through pipe L1 and cooled by heat exchanger 1, and the cooled feed air is supplied to first fractionator 2. In the first fractionator 2, the concentration of high boiling impurities (eg, methane) is reduced and an oxygen-containing liquid is produced. The oxygen-containing liquid is supplied to the second fractionator 4 through a pipe L2. In the second fractionator 4, the concentration of low boiling point impurities is reduced and high purity oxygen is produced, which is taken out from the bottom of the second fractionator 4 to produce high purity oxygen.

[0042] (Control of high-purity oxygen production equipment using a flow meter) When the flow rate of the oxygen-containing liquid measured by the flow meter 10 is lower than a predetermined flow rate, the opening of the valve V1 is increased, and when the flow rate of the oxygen-containing liquid measured by the flow meter 10 is higher than the predetermined flow rate, the opening of the valve V1 is decreased. The predetermined flow rate is preferably 1 to 30%, more preferably 1 to 25%, and particularly preferably 1 to 20% of the flow rate of the feed air. This allows the high purity oxygen production apparatus to control the amount of oxygen-containing liquid introduced into the second fractionator 4 to be constant.

[0043] In the high-purity oxygen production apparatus shown in FIG. 1, the flow meter 10 is provided between the branch point of the pipes L2 and L3 and the valve V1, but this is not limited thereto, and the flow meter 10 can be provided at any position as long as the effects of the present invention can be obtained.

[0044] (Control of high-purity oxygen production equipment using an oxygen meter) When the oxygen concentration of the oxygen-containing liquid measured by the oxygen concentration meter 3 is lower than a predetermined concentration, the opening of the valve V2 is increased, and when the oxygen concentration of the oxygen-containing liquid measured by the oxygen concentration meter 3 is higher than the predetermined concentration, the opening of the valve V2 is decreased. The predetermined concentration is preferably in the range of 1 to 50%, more preferably 1 to 40%, and particularly preferably 1 to 30%. When the oxygen concentration of the oxygen-containing liquid is decreasing based on the oxygen concentration measured by the oxygen concentration meter 3, the valve V2 increases the flow rate of the oxygen-containing liquid supplied to the pipe L4. As a result, the amount of liquid (reflux liquid) being rectified in the first rectification column 2 decreases, thereby reducing the efficiency of rectification. In other words, the efficiency of separation between the oxygen-enriched liquid and nitrogen gas (nitrogen component) in the first rectification column 2 decreases, causing the oxygen concentration of the oxygen-containing liquid to increase. Conversely, when the oxygen concentration of the oxygen-containing liquid is increasing, the valve V2 reduces the flow rate of the oxygen-containing liquid supplied to the pipe L4, thereby reducing the oxygen concentration of the oxygen-containing liquid.

[0045] The impurities in the high-purity oxygen produced in the second rectification column 4 originate from the impurities in the oxygen-containing liquid produced in the first rectification column 2, and the concentration of the impurities in the oxygen-containing liquid is positively correlated with the oxygen concentration of the oxygen-containing liquid. In other words, the concentration of the impurities in the high-purity oxygen is positively correlated with the oxygen concentration of the oxygen-containing liquid. Therefore, the high-purity oxygen producing apparatus equipped with the oxygen concentration meter 3 can appropriately control the concentration of impurities in the produced high-purity oxygen based on the oxygen concentration of the oxygen-containing liquid measured by the oxygen concentration meter 3. Furthermore, as described above, the oxygen concentration of the oxygen-containing liquid and the oxygen concentration of the steam in the outlet part of the first rectification column 2 preferably coincide with each other, so the high-purity oxygen producing apparatus equipped with the oxygen concentration meter 3 can appropriately control the concentration of impurities in the produced high-purity oxygen based on the oxygen concentration of the steam in the outlet part of the first rectification column 2 measured by the oxygen concentration meter 3.

[0046] The correlation equation between the oxygen concentration of the oxygen-containing liquid and the concentration of impurities in the oxygen-containing liquid or high-purity oxygen can be obtained by simulating the configuration of the apparatus and the components of the feed air, and / or by actually measuring the oxygen concentration of the oxygen-containing liquid and the concentration of impurities in the high-purity oxygen in a high-purity oxygen production apparatus operating in a steady state. Furthermore, since the composition of impurities in the produced high-purity oxygen is usually constant, when the concentration of a specific component (e.g., methane) of the impurities in the high-purity oxygen is evaluated based on the oxygen concentration of the oxygen-containing liquid, it is possible to calculate the total concentration of impurities in the high-purity oxygen from the concentration of the specific component.

[0047] For example, using the production apparatus shown in Figure 1, the relational expression of the correlation between the oxygen concentration of the oxygen-containing liquid and the methane concentration in the oxygen-containing liquid or high-purity oxygen can be obtained by simulation from the configuration of the apparatus and the components of the feed air. Figure 2 shows a plot of the relationship between the oxygen concentration in the oxygen-containing liquid or high-purity oxygen and the methane concentration in the oxygen-containing liquid or high-purity oxygen obtained by the simulation. The plot shown in FIG. 2 shows that the oxygen concentration of the oxygen-containing liquid is positively correlated with the methane concentration of the oxygen-containing liquid, and that the oxygen concentration of the oxygen-containing liquid is positively correlated with the methane concentration of the high purity oxygen.

[0048] Therefore, in a high-purity oxygen production apparatus equipped with the oxygen concentration meter of the present disclosure, it is possible to appropriately determine a relational expression of the correlation between the oxygen concentration of the oxygen-containing liquid measured by the oxygen concentration meter 3 and the concentration of impurities (or specific components of impurities) in the high-purity oxygen. Furthermore, by using this relational expression, it is possible to evaluate the concentration of impurities (or specific components of impurities) in the high-purity oxygen based on the oxygen concentration of the oxygen-containing liquid.

[0049] Another example of the configuration of a high-purity oxygen production apparatus is shown in Figure 3. The same reference numerals as in Figure 1 have the same functions, and therefore their explanations will be omitted. The high-purity oxygen production apparatus in Figure 3 has the same configuration as in Figure 1, except for the pipe L3 (second pipe), and operates in the same way. The pipe L3 (second pipe) branches off from a branching point provided on the pipe L2. The pipe L3 directly supplies the oxygen-containing liquid supplied from the pipe L2 to a container equipped therein with a nitrogen condenser 6. The pipe L3 (second pipe) may also supply the oxygen-containing liquid to the container through a subcooler. When the oxygen concentration of the oxygen-containing liquid is decreasing based on the oxygen concentration measured by the oxygen concentration meter 3, the valve V2 increases the flow rate of the oxygen-containing liquid supplied to the vessel. As a result, the amount of liquid (reflux liquid) being rectified in the first rectification column 2 decreases, and the efficiency of rectification decreases. In other words, the efficiency of separation of the oxygen-enriched liquid and nitrogen gas (nitrogen component) in the first rectification column 2 decreases, and the oxygen concentration of the oxygen-containing liquid increases. Conversely, when the oxygen concentration of the oxygen-containing liquid is increasing, valve V2 reduces the flow rate of the oxygen-containing liquid supplied to the vessel, thereby decreasing the oxygen concentration of the oxygen-containing liquid. In this way, the production apparatus of Figure 3 can be effectively controlled to produce high-purity oxygen having the desired quality. Note that oxygen concentration meter 3 may measure the oxygen concentration of the vapor at the outlet of first rectification column 2.

[0050] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of the present disclosure are disclosed below. [1] A heat exchanger for cooling the raw air; a first rectification column having an inlet for introducing the cooled feed air and an outlet for discharging an oxygen-containing liquid, the first rectification column reducing the concentration of high-boiling-point impurities having a boiling point higher than that of oxygen in the oxygen-containing liquid compared to the concentration of high-boiling-point impurities in the feed air; a vessel having a nitrogen condenser therein, the vessel being located at an upper portion of the first rectification column; a second rectification column having an inlet for introducing the oxygen-containing liquid and an outlet for discharging high-purity oxygen, the second rectification column reducing the concentration of low-boiling-point impurities having a boiling point lower than that of oxygen in the high-purity oxygen compared to the concentration of low-boiling-point impurities in the oxygen-containing liquid; a first pipe for introducing the oxygen-containing liquid discharged from the first rectification column into the second rectification column, the first pipe including a branch portion and a first valve; a second pipe branching from the branching portion and having a second valve; a pipe for extracting an oxygen-enriched liquid from the bottom of the first rectification column and introducing the liquid into a vessel equipped with the nitrogen condenser therein; Equipped with the first valve adjusts the flow rate of the oxygen-containing liquid introduced into the second rectification column; High-purity oxygen production equipment. [2] The high-purity oxygen production apparatus according to [1], wherein the second pipe extracts oxygen-enriched liquid from the bottom of the first rectification column, joins with a pipe that introduces the oxygen-enriched liquid into a vessel equipped with the nitrogen condenser therein, and supplies the oxygen-containing liquid. [3] The high-purity oxygen production apparatus according to [1], wherein the second pipe supplies the oxygen-containing liquid to a container having the nitrogen condenser therein. [4] further comprising a flow meter for measuring the flow rate of the oxygen-containing liquid introduced into the second rectification column through the first pipe; A high-purity oxygen production apparatus according to [1] to [3], wherein when the flow rate of the oxygen-containing liquid measured by the flow meter is lower than a predetermined flow rate, the opening degree of the first valve is increased, and when the flow rate of the oxygen-containing liquid measured by the flow meter is higher than the predetermined flow rate, the opening degree of the first valve is decreased. [5] The high-purity oxygen production apparatus according to [4], wherein the predetermined flow rate is 1 to 30% of the flow rate of the feed air. [6] The high-purity oxygen production apparatus according to [4] or [5], wherein the flow meter is provided in the first pipe between the branching portion of the first pipe and the introduction portion of the second rectification column. [7] An oxygen concentration meter is further provided to measure the oxygen concentration of the oxygen-containing liquid or the oxygen concentration of the vapor at the outlet portion of the first rectification column, A high-purity oxygen production apparatus according to any one of [1] to [6], wherein when the oxygen concentration of the oxygen-containing liquid measured by the oxygen concentration meter is lower than a predetermined concentration, the opening degree of the second valve is increased, and when the oxygen concentration of the oxygen-containing liquid measured by the oxygen concentration meter is higher than the predetermined concentration, the opening degree of the second valve is decreased. [8] The high-purity oxygen production apparatus according to [7], wherein the predetermined concentration is in the range of 1 to 50%. [9] The high-purity oxygen production apparatus according to [7] or [8], wherein the oxygen concentration meter is provided in the first piping between the outlet of the first rectification column and the branch of the first piping, or is provided in the outlet of the first rectification column.

[10] The high-purity oxygen generating apparatus according to any one of [1] to [9], further comprising at least one container equipped with a nitrogen condenser therein below the container equipped with the nitrogen condenser therein.

[11] A method for producing high-purity oxygen, comprising controlling the content of impurities in the high-purity oxygen produced by adjusting the oxygen concentration of the oxygen-containing liquid introduced into the second fractionator in the high-purity oxygen production apparatus described in any one of [1] to

[10] . The configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible as appropriate within the scope that does not deviate from the gist of this disclosure. [Explanation of symbols]

[0051] 1 heat exchanger 2. First rectification column 3. Oxygen concentration meter 4. Second rectification column 5 Nitrogen condenser 6 Nitrogen condenser 7. Oxygen evaporator 8. Recycled Air Compressor 9. Expansion turbine 10 Flow meter L1~L14 piping V1~V4 valves

Claims

1. a heat exchanger for cooling the feed air; a first rectification column having an inlet for introducing the cooled feed air and an outlet for discharging an oxygen-containing liquid, the first rectification column reducing the concentration of high-boiling-point impurities having a boiling point higher than that of oxygen in the oxygen-containing liquid compared to the concentration of high-boiling-point impurities in the feed air; a vessel having a nitrogen condenser therein, the vessel being located at an upper portion of the first rectification column; a second rectification column having an inlet for introducing the oxygen-containing liquid and an outlet for discharging high-purity oxygen, the second rectification column reducing the concentration of low-boiling-point impurities having a boiling point lower than that of oxygen in the high-purity oxygen compared to the concentration of low-boiling-point impurities in the oxygen-containing liquid; a first pipe for introducing the oxygen-containing liquid discharged from the first rectification column into the second rectification column, the first pipe including a branch portion and a first valve; a second pipe branching from the branching portion and having a second valve; a pipe for extracting an oxygen-enriched liquid from the bottom of the first rectification column and introducing the liquid into a vessel equipped with the nitrogen condenser therein; Equipped with the first valve adjusts the flow rate of the oxygen-containing liquid introduced into the second rectification column; High-purity oxygen production equipment.

2. 2. The high-purity oxygen production apparatus according to claim 1, wherein the second pipe takes out an oxygen-enriched liquid from the bottom of the first rectification column, joins a pipe that introduces the oxygen-enriched liquid into a vessel equipped with the nitrogen condenser therein, and supplies the oxygen-containing liquid.

3. 2. The high-purity oxygen production system according to claim 1, wherein the second pipe supplies the oxygen-containing liquid to a vessel containing the nitrogen condenser.

4. a flow meter for measuring a flow rate of the oxygen-containing liquid introduced into the second rectification column through the first pipe; 2. The high-purity oxygen production apparatus of claim 1, wherein when the flow rate of the oxygen-containing liquid measured by the flow meter is lower than a predetermined flow rate, the opening degree of the first valve is increased, and when the flow rate of the oxygen-containing liquid measured by the flow meter is higher than the predetermined flow rate, the opening degree of the first valve is decreased.

5. 5. The high purity oxygen production system according to claim 4, wherein the predetermined flow rate is 1 to 30% of the flow rate of the feed air.

6. 5. The high-purity oxygen production apparatus according to claim 4, wherein the flow meter is provided in the first pipe between the branching portion of the first pipe and the introduction portion of the second rectification column.

7. an oxygen concentration meter for measuring the oxygen concentration of the oxygen-containing liquid or the oxygen concentration of the vapor at the outlet portion of the first rectification column; 5. A high-purity oxygen production apparatus as described in claim 4, wherein when the oxygen concentration of the oxygen-containing liquid measured by the oxygen concentration meter is lower than a predetermined concentration, the opening degree of the second valve is increased, and when the oxygen concentration of the oxygen-containing liquid measured by the oxygen concentration meter is higher than the predetermined concentration, the opening degree of the second valve is decreased.

8. 8. The high-purity oxygen production system according to claim 7, wherein the predetermined concentration is in the range of 1 to 50%.

9. 8. The high-purity oxygen production apparatus according to claim 7, wherein the oxygen concentration meter is provided in the first pipe between the outlet of the first rectification column and the branch portion of the first pipe, or is provided in the outlet of the first rectification column.

10. 2. The high-purity oxygen production system according to claim 1, further comprising at least one vessel equipped with a nitrogen condenser therein, located below the vessel equipped with a nitrogen condenser therein and positioned at an upper portion of the first rectification column.

11. 11. A method for producing high-purity oxygen, comprising: controlling the content of impurities in the produced high-purity oxygen by adjusting the oxygen concentration of the oxygen-containing liquid introduced into the second rectification column in the high-purity oxygen production apparatus according to any one of claims 1 to 10.

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