Purified gas production apparatus and method for producing purified gas

Abstract

To provide an apparatus and a method for producing a purified gas containing high-concentration nitrogen gas with reduced oxygen gas concentration.SOLUTION: An apparatus for producing a purified gas containing nitrogen gas by pressure swing adsorption comprises: a first adsorption tower having a first adsorbent and configured to obtain an intermediate gas having a higher nitrogen gas content than a raw material gas from the raw material gas containing nitrogen gas and oxygen gas; a pair of second adsorption towers each having a second adsorbent and configured to obtain the purified gas having a higher nitrogen gas content than the raw material gas and the intermediate gas from at least one selected from the group consisting of the raw material gas and the intermediate gas; a raw material gas introduction passage for introducing the raw material gas into the pair of second adsorption towers; and an intermediate gas introduction passage for introducing the intermediate gas from the first adsorption tower into the pair of second adsorption towers.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to an apparatus for producing a purified gas and a method for producing a purified gas. [Background technology]

[0002] Nitrogen gas is used in a wide range of applications, including the semiconductor, chemical, and food industries. Nitrogen gas can be obtained, for example, by separating oxygen gas from air, which is the raw material, using cryogenic separation, membrane separation, adsorption separation, and other methods. However, since cryogenic separation requires large-scale equipment, it is limited to users who require large amounts of nitrogen from the viewpoint of initial equipment costs. In addition, although the initial cost of separating nitrogen gas using membrane separation is relatively low, it is used to purify low-purity nitrogen gas, and the driving energy is large in separating high-purity nitrogen gas, which causes problems with running costs. On the other hand, separation of nitrogen gas using adsorption separation does not require large-scale equipment, and is relatively easy to introduce from the viewpoint of driving energy and equipment costs.

[0003] Among the adsorption separation methods, equipment using the Pressure Swing Adsorption (PSA) method is widely used to produce high-purity nitrogen gas. In addition, nitrogen gas users require nitrogen gas with a purity appropriate for their application and the energy required to drive the equipment, and in order to meet these demands, the performance of PSA equipment is being improved.

[0004] Patent Document 1 (JP Patent Publication No. 10-192636) discloses a method for improving the recovery rate of nitrogen gas in nitrogen gas separation by a PSA process using two adsorption towers by moving the gas so that the pressure is equalized in the middle part of the two adsorption towers. Patent Document 2 (JP Patent Publication No. 2017-160079) discloses a method for increasing the amount of nitrogen gas generated by providing a storage tank for temporarily collecting the product gas in addition to the adsorption towers and sending a part of the product gas to the adsorption towers during regeneration of the adsorption towers. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-192636 [Patent Document 2] JP 2017-160079 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the methods described in Patent Documents 1 and 2 have room for improvement in terms of reducing the concentration of oxygen gas that is not completely separated from the nitrogen gas. In addition, from the standpoint of rising electricity costs and reducing carbon dioxide emissions (reducing driving energy), there is a demand for improved cost-performance devices.

[0007] An object of the present disclosure is to provide an apparatus and method for producing a purified gas containing high-concentration nitrogen gas with a reduced concentration of oxygen gas. [Means for solving the problem]

[0008] [1] An apparatus for producing a purified gas containing nitrogen gas by a pressure swing adsorption method, comprising: a first adsorption tower having a first adsorbent for obtaining an intermediate gas having a higher nitrogen gas content than a raw material gas containing nitrogen gas and oxygen gas from the raw material gas; a pair of second adsorption towers having a second adsorbent and configured to obtain a purified gas having a higher nitrogen gas content than the raw gas and the intermediate gas from at least one gas selected from the group consisting of the raw gas and the intermediate gas; a raw material gas inlet passage for introducing the raw material gas into the pair of second adsorption towers; an intermediate gas introduction passage for introducing the intermediate gas from the first adsorption tower into the pair of second adsorption towers.

[0009] [2] The apparatus for producing a refined gas according to [1], wherein the volume of the first adsorption tower is smaller than the volume of one of the pair of second adsorption towers.

[0010] [3] The apparatus for producing a refined gas according to [1] or [2], wherein the first adsorbent has a higher adsorption rate of oxygen gas than the second adsorbent.

[0011] [4] A method for producing a purified gas using the purified gas production apparatus according to any one of [1] to [3], a first step of introducing the raw material gas into the first adsorption tower to obtain the intermediate gas; a second step of introducing at least the intermediate gas into one of the pair of second adsorption towers to obtain the purified gas.

[0012] [5] The method for producing a purified gas according to [4], wherein the second step includes a step of introducing only the intermediate gas into one of the pair of second adsorption towers, and a step of introducing only the raw material gas into one of the pair of second adsorption towers.

[0013] [6] a first regeneration step of regenerating the first adsorbent after the first step; The method for producing a purified gas according to [4] or [5], further comprising a second regeneration step of regenerating the second adsorbent after the second step.

[0014] [7] The method for producing a purified gas according to [6], further comprising a first purge regeneration step of promoting regeneration of the first adsorbent by introducing exhaust gas after the second regeneration step into the first adsorption tower after the first regeneration step. Effect of the Invention

[0015] According to the present disclosure, it is possible to provide an apparatus and a method for producing a purified gas containing high-concentration nitrogen gas with a reduced concentration of oxygen gas. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a production apparatus for purified gas in this embodiment. [Diagram 2]FIG. 2 is a schematic diagram showing another example of the configuration of the purified gas production apparatus according to the present embodiment. [Diagram 3] FIG. 3 is a schematic diagram showing yet another example of the configuration of the purified gas production apparatus according to the present embodiment. [Figure 4] FIG. 4 is a schematic diagram showing the gas flow state in step 1 in the method for producing a purified gas according to this embodiment. [Diagram 5] FIG. 5 is a schematic diagram showing the gas flow state in step 2 in the method for producing a purified gas according to this embodiment. [Figure 6] FIG. 6 is a schematic diagram showing the gas flow state in step 3 in the method for producing a purified gas according to this embodiment. [Figure 7] FIG. 7 is a schematic diagram showing the gas flow state in step 4 in the method for producing a purified gas according to this embodiment. [Figure 8] FIG. 8 is a schematic diagram showing the gas flow state in step 5 in the method for producing a purified gas according to this embodiment. [Figure 9] FIG. 9 is a schematic diagram showing the gas flow state in step 6 in the method for producing a purified gas according to this embodiment. [Figure 10] FIG. 10 is a schematic diagram showing the gas flow state in step 7 in the method for producing a purified gas according to this embodiment. [Figure 11] FIG. 11 is a schematic diagram showing the gas flow state in step 8 in the method for producing a purified gas according to this embodiment. [Figure 12] FIG. 12 is a schematic diagram showing an example of the configuration of a conventional purified gas production apparatus. [Figure 13] FIG. 13 is a schematic diagram showing another example of the configuration of a conventional purified gas production apparatus. [Figure 14] FIG. 14 is a schematic diagram showing yet another example of the configuration of a conventional purified gas production apparatus. [Figure 15] FIG. 15 is a graph showing the relationship between the ratio of the amount of raw material gas used to the amount of purified gas recovered in Test Example 1 and the concentration of oxygen gas in the purified gas. [Figure 16] FIG. 16 is a graph showing the relationship between the flow rate of the purified gas per unit mass of the adsorbent and the concentration of oxygen gas in the purified gas in Test Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, embodiments of the present disclosure will be described. However, the following description does not limit the scope of the claims.

[0018] <Refined gas production equipment> 1 to 3, the purified gas production apparatus 30 in this embodiment is a PSA apparatus for producing a purified gas containing nitrogen gas by a pressure swing adsorption (PSA) method, and includes a first adsorption tower 1 having a first adsorbent for obtaining an intermediate gas having a higher nitrogen gas content than the raw gas from a raw gas containing nitrogen gas and oxygen gas, a pair of second adsorption towers 10 having a second adsorbent for obtaining a purified gas having a higher nitrogen gas content than the raw gas and the intermediate gas from at least one gas selected from the group consisting of the raw gas and the intermediate gas, a raw gas introduction passage 2 for introducing the raw gas into the pair of second adsorption towers 10, and an intermediate gas introduction passage 4 for introducing the intermediate gas from the first adsorption tower 1 to the pair of second adsorption towers 10. The purified gas production apparatus 30 according to this embodiment will be described below.

[0019] <<Raw material gas>> In this embodiment, the term "raw material gas" refers to a gas containing at least nitrogen gas and oxygen gas. The concentration of nitrogen gas in the raw material gas is preferably 70% by volume or more and 90% by volume or less, more preferably 75% by volume or more and 85% by volume or less. The concentration of oxygen gas in the raw material gas is preferably 10% by volume or more and 30% by volume or less, more preferably 15% by volume or more and 25% by volume or less. The raw material gas may contain other gases (e.g., carbon dioxide, argon, etc.) so long as it contains nitrogen gas and oxygen gas. The raw material gas is preferably substantially composed of nitrogen gas and oxygen gas, and more preferably air. Here, "substantially composed of nitrogen gas and oxygen gas" means that the concentration of nitrogen gas and oxygen gas in the raw material gas is 98% by volume or more.

[0020] "Intermediate Gas" In this embodiment, the "intermediate gas" refers to a gas having a higher nitrogen gas content than the raw material gas. The nitrogen gas concentration in the intermediate gas is preferably 75 vol% or more and 98 vol% or less, and more preferably 78 vol% or more and 95 vol% or less. The oxygen gas concentration in the intermediate gas is preferably 2 vol% or more and 25 vol% or less, and more preferably 5 vol% or more and 22 vol% or less. The intermediate gas may contain other gases as long as it contains nitrogen gas and oxygen gas.

[0021] Refined Gas In this embodiment, the term "purified gas" refers to a gas having a higher nitrogen gas content than the raw gas and the intermediate gas. The concentration of nitrogen gas in the purified gas is preferably 98% by volume or more, and more preferably 98.5% by volume or more. The concentration of oxygen gas in the purified gas is preferably 1000 ppm by volume or less, more preferably 500 ppm by volume or less, more preferably 300 ppm by volume or less, even more preferably 100 ppm by volume or less, even more preferably 50 ppm by volume or less, and even more preferably 10 ppm by volume or less.

[0022] 《First adsorption tower》 The first adsorption tower 1 is an apparatus having a first adsorbent for obtaining an intermediate gas having a higher nitrogen gas content than the raw gas from a raw gas containing nitrogen gas and oxygen gas. In the first adsorption tower 1, the intermediate gas is obtained by adsorbing mainly oxygen gas in the raw gas onto the first adsorbent. The first adsorption tower 1 may be composed of multiple adsorption towers, but is preferably composed of a single adsorption tower.

[0023] The first adsorption tower 1 has an inlet side and an outlet side. An inlet nozzle 1D is provided on the inlet side, and an outlet nozzle 1E is provided on the outlet side. The first adsorption tower 1 has a packed section 1C packed with a first adsorbent. The first adsorption tower 1 is provided with an inlet region 1A provided on the inlet side of the packed section 1C, and an outlet region 1B provided on the outlet side of the packed section 1C. The first adsorption tower 1 may be provided with a pressure gauge (not shown) for detecting the pressure inside the first adsorption tower 1.

[0024] (First adsorbent) The first adsorbent is an adsorbent for adsorbing and removing at least oxygen gas in the raw gas. For example, a speed-separation type adsorbent can be used as the first adsorbent. Here, the speed-separation type adsorbent refers to an adsorbent whose adsorption amount in a short time differs due to the difference in the diffusion speed of nitrogen gas and oxygen gas toward the adsorption point. In the present disclosure, this time difference is utilized to introduce the unadsorbed gas as an intermediate gas into the second adsorption tower described later. For example, a speed-separation type adsorbent can be used as carbon molecular sieves (CMS). As the CMS, a conventionally known one can be used. As the CMS, for example, Bellfine MG405L, Bellfine MG407S, Bellfine MG81A, etc., manufactured by Air Water Inc. can be used.

[0025] One type of first adsorbent may be filled alone in the first adsorption tower 1, or a combination of multiple types of first adsorbents may be filled in the first adsorption tower 1. Note that the first adsorption tower 1 may be mixed with other adsorbents for the purpose of adsorbing and removing moisture, other gases, and the like contained in the raw material gas.

[0026] 《Second adsorption tower》 The second adsorption tower 10 has a second adsorbent and is an apparatus for obtaining a purified gas having a higher nitrogen gas content than the raw gas and the intermediate gas from at least one gas selected from the group consisting of the raw gas and the intermediate gas. In the second adsorption tower 10, oxygen gas in the at least one gas selected from the group consisting of the raw gas and the intermediate gas is adsorbed by the second adsorbent to obtain a purified gas. The second adsorption tower 10 is composed of a pair of towers (second adsorption towers 10A, 10a).

[0027] The pair of second adsorption towers 10A, 10a has an inlet side and an outlet side. Inlet nozzles 10E, 10e are provided on the inlet side, and outlet nozzles 10F, 10f are provided on the outlet side. The pair of second adsorption towers 10A, 10a has packed sections 10D, 10d filled with a second adsorbent. The pair of second adsorption towers 10A, 10a has inlet regions 10B, 10b provided on the inlet side of the packed sections 10D, 10d, and outlet regions 10C, 10c provided on the outlet side of the packed sections 10D, 10d, respectively. The pair of second adsorption towers 10A, 10a may each be provided with a pressure gauge (not shown) for detecting the pressure inside the pair of second adsorption towers 10A, 10a.

[0028] The volume of the first adsorption tower 1 is preferably smaller than the volume of one of the pair of second adsorption towers 10 (the second adsorption tower 10A or 10a). In this way, a compact and inexpensive device configuration can be achieved, and a purified gas with higher purity can be obtained. The volume of the first adsorption tower 1 is preferably 50% or less of the volume of one of the pair of second adsorption towers 10, and may be 25% or less, 15% or less, 10% or less, or 5% or less. However, if the volume of the first adsorption tower 1 is too smaller than the volume of one of the pair of second adsorption towers 10, there is a risk that oxygen gas will not be adsorbed even if the raw material gas passes through the first adsorption tower 1. Therefore, the volume of the first adsorption tower 1 may be, for example, 1% or more, or 3% or more of the volume of one of the pair of second adsorption towers 10. The pair of second adsorption towers 10A and 10a have the same volume.

[0029] The second adsorbent is an adsorbent for adsorbing and removing oxygen gas in at least one selected from the group consisting of raw gas and intermediate gas. The second adsorbent may be, for example, a velocity separation type adsorbent. The velocity separation type adsorbent may be, for example, CMS. The second adsorbent is preferably a velocity separation type adsorbent, and more preferably CMS. As the CMS, for example, Bellfine MG407H, Bellfine MG407S, Bellfine MG81A, etc., manufactured by Air Water Co., Ltd., may be used.

[0030] The first adsorbent and the second adsorbent may be the same adsorbent or different adsorbents. When the first adsorbent and the second adsorbent are different adsorbents, it is preferable that the adsorption rate of oxygen gas of the first adsorbent is higher than that of the second adsorbent. Here, an adsorbent having a high adsorption rate of oxygen gas refers to an adsorbent that can adsorb oxygen gas to near the upper limit of the adsorption amount in a short time. For example, Bellfine MG405L can adsorb oxygen gas to the upper limit of the adsorption amount in about 5 seconds, and Bellfine MG407H can adsorb oxygen gas to the upper limit of the adsorption amount in about 40 seconds.

[0031] A single type of second adsorbent may be filled into the pair of second adsorption towers 10, or a combination of multiple second adsorbents may be filled into the pair of second adsorption towers 10. Note that other adsorbents may be mixed into the pair of second adsorption towers 10 for the purpose of adsorbing and removing moisture and other gases contained in the raw material gas and the intermediate gas.

[0032] <<Inlet for raw gas>> A raw material gas inlet passage 2 is provided as an inlet passage for introducing the raw material gas into the pair of second adsorption towers 10. The raw material gas inlet passage 2 is connected to the inlet nozzles 10E, 10e of the pair of second adsorption towers 10A, 10a, respectively. An on-off valve 6A is provided in the raw material gas inlet passage 2, and the supply and stop of the raw material gas to the pair of second adsorption towers 10 is controlled by controlling the opening and closing of the valve 6A.

[0033] 《First adsorption tower introduction path》 The raw material gas inlet passage 2 has a first adsorption tower inlet passage 3 as a branch passage for introducing the raw material gas into the first adsorption tower 1. The first adsorption tower inlet passage 3 branching off from the raw material gas inlet passage 2 is connected to an inlet nozzle 1D of the first adsorption tower 1. An on-off valve 6B is provided in the first adsorption tower inlet passage 3, and the supply and stop of the raw material gas to the first adsorption tower 1 is controlled by controlling the opening and closing of this valve.

[0034] <Intermediate gas inlet> An intermediate gas inlet passage 4 is provided as an inlet passage for introducing the intermediate gas from the first adsorption tower 1 to the pair of second adsorption towers 10. The intermediate gas inlet passage 4 is connected to the outlet nozzle 1E of the first adsorption tower 1. The intermediate gas inlet passage 4 merges with the raw material gas inlet passage 2 downstream of the first adsorption tower inlet passage 3 (see FIGS. 1 to 3). An on-off valve 7 is provided in the intermediate gas inlet passage 4, and by controlling the opening and closing of this valve, the supply of the intermediate gas from the first adsorption tower 1 and its stop are controlled.

[0035] As described above, the raw material gas inlet passage 2 and the intermediate gas inlet passage 4 partially overlap on the downstream side. The raw material gas inlet passage 2 (intermediate gas inlet passage 4) is provided with on-off valves 9A and 9B, and by controlling the opening and closing of these valves, the supply and stop of the raw material gas to the pair of second adsorption towers 10A and 10a is controlled.

[0036] Refined Gas Tank The purified gas is stored in the purified gas tank 12. The purified gas tank 12 may be provided with a pressure gauge for detecting the pressure of the purified gas in the purified gas tank 12.

[0037] 《Refined gas inlet》 A purified gas inlet passage 11 is provided as an inlet passage for introducing the purified gas from the pair of second adsorption towers 10 to the purified gas tank 12. The purified gas inlet passage 11 is connected to outlet nozzles 10F, 10f of the pair of second adsorption towers 10A, 10a, respectively. On-off valves 16A, 16B are provided in the purified gas inlet passage 11, and the supply and stop of the purified gas to the purified gas tank 12 is controlled by controlling the opening and closing of these valves.

[0038] Exhaust gas exhaust passage A first exhaust gas discharge passage 5 is provided as a discharge passage for discharging exhaust gas containing oxygen gas adsorbed in the first adsorption tower 1 (hereinafter also referred to as "first exhaust gas"). The first exhaust gas discharge passage 5 is connected to an inlet nozzle 1D of the first adsorption tower 1. An on-off valve 8 is provided in the first exhaust gas discharge passage 5, and by controlling the opening and closing of this valve, exhaust of the first exhaust gas from the first adsorption tower 1 and its stop are controlled.

[0039] A second exhaust gas discharge passage 14 is provided as a discharge passage for discharging exhaust gas (hereinafter also referred to as "second exhaust gas") containing oxygen gas adsorbed in the pair of second adsorption towers 10. The second exhaust gas discharge passage 14 is connected to the inlet nozzles 10E, 10e of the pair of second adsorption towers 10A, 10a, respectively. The second exhaust gas discharge passage 14 may partially overlap with the raw material gas introduction passage 2 (see FIGS. 1 to 3). An on-off valve 18B is provided in the second exhaust gas discharge passage 14, and by controlling the opening and closing of this valve, the release of the second exhaust gas from the pair of second adsorption towers 10A, 10a to the atmosphere and the supply to the first adsorption tower 1 are controlled.

[0040] In addition, an adsorption tower connecting passage 15 may be provided as an introduction passage for introducing the second exhaust gas discharged from the pair of second adsorption towers 10A, 10a into the first adsorption tower 1. By introducing the second exhaust gas into the first adsorption tower 1 in which oxygen gas has been adsorbed, regeneration of the first adsorbent can be promoted. The adsorption tower connecting passage 15 connects the outlet nozzle 1E of the first adsorption tower 1 to the inlet nozzles 10E, 10e of the pair of second adsorption towers 10A, 10a. The adsorption tower connecting passage 15 may partially overlap with the raw material gas introduction passage 2, or may partially overlap with the second exhaust gas discharge passage 14 (see Figures 1 to 3). The adsorption tower connecting passage 15 is provided with an on-off valve 18A, and by controlling the opening and closing of the valve, the introduction and stop of the second exhaust gas from the pair of second adsorption towers 10A, 10a into the first adsorption tower 1 is controlled.

[0041] As described above, the second exhaust gas discharge passage 14 and the adsorption tower connecting passage 15 partially overlap on the upstream side. The second exhaust gas discharge passage 14 (adsorption tower connecting passage 15) is provided with on-off valves 17A and 17B, and by controlling the opening and closing of these valves, the release of the second exhaust gas from the pair of second adsorption towers 10A and 10a to the atmosphere and the supply of the second exhaust gas to the first adsorption tower 1 are controlled.

[0042] 《Equal Pressure Path》 The purified gas production apparatus 30 may have a pressure equalization path as a path for equalizing the pressure of the pair of second adsorption towers 10A, 10a. Gas can be transferred from one high-pressure second adsorption tower to the other low-pressure second adsorption tower via the pressure equalization path.

[0043] Examples of the pressure equalization path include an outlet pressure equalization path 20 (see Figs. 2 and 3) for connecting the outlet nozzles 10F, 10f of the pair of second adsorption towers 10A, 10a, an inlet pressure equalization path 21 (see Fig. 2) for connecting the inlet nozzles 10E, 10e of the pair of second adsorption towers 10A, 10a, and an intermediate pressure equalization path 22 (see Fig. 3) for connecting the packed sections 10D, 10d, which are the intermediate sections of the pair of second adsorption towers 10, and the inlet nozzles 10E, 10e. One or more pressure equalization paths may be provided. It is preferable that more than one pressure equalization path is provided. The pressure equalization paths are preferably provided with the outlet pressure equalization path 20 and the inlet pressure equalization path 21, preferably provided with the outlet pressure equalization path 20 and the intermediate pressure equalization path 22, and preferably provided with the inlet pressure equalization path 21 and the intermediate pressure equalization path 22. It is more preferable that the pressure equalization paths are provided with the outlet pressure equalization path 20 and the intermediate pressure equalization path 22. An on-off valve 23 is provided in the outlet pressure equalizing passage 20, an on-off valve 24 is provided in the inlet pressure equalizing passage 21, and an on-off valve 25 is provided in the intermediate pressure equalizing passage 22. By controlling the opening and closing of these, the movement of gas between the pair of second adsorption towers 10A, 10a is controlled.

[0044] 《Second Adsorption Tower Connection》 A second adsorption tower connecting path 13 may be provided as a path for connecting the pair of second adsorption towers 10. A portion of the purified gas obtained in one of the pair of second adsorption towers 10 is introduced into the other of the pair of second adsorption towers 10 via the second adsorption tower connecting path 13, thereby promoting desorption of oxygen gas adsorbed by the second adsorbent. A needle valve 19 is provided in the second adsorption tower connecting path 13, and by opening this, a portion of the purified gas is used as a gas for promoting desorption of oxygen gas due to the pressure difference between the pair of second adsorption towers 10A, 10a.

[0045] <Method of producing purified gas> The method for producing a purified gas in this embodiment is carried out by using the above-mentioned purified gas production apparatus 30, and includes a first step of introducing a raw material gas into the first adsorption tower 1 to obtain an intermediate gas, and a second step of introducing at least the intermediate gas into one of a pair of second adsorption towers 10 to obtain a purified gas. The method for producing a purified gas according to this embodiment will be described below. Note that descriptions similar to those described in the above-mentioned <Purified gas production apparatus> will be omitted.

[0046] 《1st process》 The first step is a step of obtaining an intermediate gas from a raw material gas by pressure swing adsorption in the first adsorption tower 1. This step includes (1) a first adsorption step and (2) a first regeneration step.

[0047] (1st adsorption step) In this process, a raw material gas is introduced into the first adsorption tower 1 to adsorb oxygen gas. The first adsorption tower 1 is filled with a first adsorbent for adsorbing oxygen gas. The raw material gas is introduced from an inlet nozzle 1D of the first adsorption tower 1 and brought into contact with the first adsorbent, thereby adsorbing mainly oxygen gas.

[0048] (1st regeneration process) This step is a step of desorbing the oxygen gas adsorbed in the first adsorbent after the first adsorption step. This step may be performed, for example, by opening the first adsorption tower 1 to the atmosphere and reducing the pressure in the first adsorption tower 1 to approximately atmospheric pressure.

[0049] [First purge regeneration process] The first regeneration step may be carried out, for example, by introducing (purging) a gas that promotes regeneration of the first adsorbent (hereinafter also referred to as "first regeneration gas") into the first adsorption tower 1. An example of the first regeneration gas is the second exhaust gas. By using the second exhaust gas as the regeneration gas, the exhausted gas can be effectively utilized. The first regeneration step may be carried out by both opening the first adsorption tower 1 to the atmosphere and introducing the first regeneration gas into the first adsorption tower 1.

[0050] 《Second process》 The second step is a step of obtaining a purified gas from at least the intermediate gas by pressure swing adsorption in one of the pair of second adsorption towers 10. The second step may include a step of obtaining a purified gas from the raw material gas in one of the pair of second adsorption towers 10. That is, the second step may include a step of introducing only the intermediate gas into one of the pair of second adsorption towers 10, and a step of introducing only the raw material gas into one of the pair of second adsorption towers 10. This step includes (1) a second adsorption step, (2) a pressure equalization step, and (3) a second regeneration step.

[0051] (Second adsorption step) In this process, at least the intermediate gas is introduced into one of the pair of second adsorption towers 10 to adsorb oxygen gas. The pair of second adsorption towers 10 is filled with a second adsorbent for adsorbing oxygen gas. The intermediate gas is introduced from an inlet of one of the pair of second adsorption towers 10 and brought into contact with the second adsorbent, thereby mainly adsorbing oxygen gas.

[0052] This process may further include a process of introducing the raw material gas into one of the pair of second adsorption towers 10. While the raw material gas is being introduced into one of the pair of second adsorption towers 10, a first regeneration process may be carried out in the first adsorption tower 1. In this manner, by changing the gas introduced into one of the pair of second adsorption towers 10 in this process, a purified gas in which the concentration of oxygen gas is efficiently reduced can be obtained.

[0053] (Pressure equalization process) This step is a step of equalizing the pressure in the pair of second adsorption towers 10 by communicating the pair of second adsorption towers 10. In this step, the second adsorption tower after the second regeneration step and the second adsorption tower after the second adsorption step are communicated with each other of the pair of second adsorption towers 10, and gas is transferred from the second adsorption tower after the second adsorption step to the second adsorption tower after the second regeneration step, thereby equalizing the pressure in the pair of second adsorption towers 10.

[0054] The second adsorption tower after the second adsorption process is at high pressure, and the second adsorption tower after the second regeneration process is at low pressure (approximately atmospheric pressure). When pressure equalization is performed in this state, gas moves from the high-pressure second adsorption tower after the second adsorption process to the low-pressure second adsorption tower after the second regeneration process. Depressurization equalization is performed in the high-pressure second adsorption tower, and pressurization equalization is performed in the low-pressure second adsorption tower.

[0055] This process is carried out through the movement of gas using the outlet pressure equalizing passage 20, the movement of gas using the inlet pressure equalizing passage 21, or the movement of gas using the intermediate pressure equalizing passage 22. When the outlet pressure equalizing passage 20 is used, gas with a high nitrogen gas content is moved. When the inlet pressure equalizing passage 21 is used, gas with a low nitrogen gas content is moved. When the intermediate pressure equalizing passage 22 is used, gas with a lower nitrogen gas content than the gas used in the outlet pressure equalizing passage 20 and a higher nitrogen gas content than the gas used in the inlet pressure equalizing passage 21 gas is moved.

[0056] This step is preferably carried out via a plurality of pressure equalization paths. That is, it is preferably carried out via any one of gas movement using the outlet pressure equalization path 20 and the inlet pressure equalization path 21, gas movement using the outlet pressure equalization path 20 and the intermediate pressure equalization path 22, and gas movement using the inlet pressure equalization path 21 and the intermediate pressure equalization path 22. In this manner, the pressures in the pair of second adsorption towers 10 become more uniform. This step is more preferably carried out by gas movement using the outlet pressure equalization path 20 and gas movement using the intermediate pressure equalization path 22.

[0057] (Second regeneration process) This step is a step of desorbing the oxygen gas adsorbed in the second adsorbent after the second adsorption step. This step may be performed, for example, by opening the second adsorption tower of the pair of second adsorption towers 10 after the second adsorption step to the atmosphere and reducing the pressure in the second adsorption tower to approximately atmospheric pressure.

[0058] [Second purge regeneration process] The second regeneration step may be carried out, for example, by introducing a gas (hereinafter also referred to as "second regeneration gas") that promotes regeneration of the second adsorbent into the second adsorption tower of the pair of second adsorption towers 10 after the second adsorption step. An example of the second regeneration gas is a purified gas. By introducing the second regeneration gas into the second adsorption tower of the pair of second adsorption towers 10 after the second adsorption step, the oxygen gas adsorbed to the second adsorbent can be efficiently desorbed. The second regeneration step may be carried out by both opening the second adsorption tower of the pair of second adsorption towers 10 after the second adsorption step to the atmosphere and introducing the second regeneration gas into the second adsorption tower of the pair of second adsorption towers 10 after the second adsorption step.

[0059] (Time for each process) The times required for the first step (first adsorption step, first regeneration step) and the second step (second adsorption step, pressure equalization step, second regeneration step) are set appropriately. The time required for the first step is preferably shorter than the time required for the second step. This is because, while the first step is being carried out in the first adsorption tower 1, the second adsorption step and pressure equalization step are carried out in one of the pair of second adsorption towers 10, and the second regeneration step and pressure equalization step are carried out in the other of the pair of second adsorption towers 10, thereby enabling efficient production of purified gas (see steps 1 to 4 and steps 5 to 8 in the production process of purified gas described below).

[0060] <Production steps of purified gas> Each step in the above-mentioned method for producing purified gas and the operation of the above-mentioned production apparatus 30 for purified gas will be further described below with reference to Table 1 and Figures 4 to 11, which use the same production apparatus 30 for purified gas as in Figure 3. As shown in Table 1, the first adsorption tower 1 and the pair of second adsorption towers 10 perform one of the above-mentioned steps at each stage of steps 1 to 8. Note that the following steps are merely examples and are not limited to these. In addition, in the following steps, it is assumed that one of the pair of second adsorption towers 10 (second adsorption tower 10A) has completed the second regeneration step, the other of the pair of second adsorption towers 10 (second adsorption tower 10a) has completed the second adsorption step, and the pressure equalization step is performed via the outlet pressure equalization path 20 and the intermediate pressure equalization path 22.

[0061] [Table 1]

[0062] (Step 1) As shown in Table 1 and Fig. 4, the first adsorption step is carried out in the first adsorption tower 1. That is, the on-off valve 6B is opened, and the raw material gas is introduced into the first adsorption tower 1 via the first adsorption tower inlet path 3. In the first adsorption tower 1, mainly oxygen gas is adsorbed and separated by the first adsorbent from the raw material gas, and becomes an intermediate gas.

[0063] Meanwhile, a pressure equalization step is carried out in the pair of second adsorption towers 10. That is, the on-off valves 23, 25 are opened, and gas moves from second adsorption tower 10a to second adsorption tower 10A through the outlet pressure equalization path 20 and the intermediate pressure equalization path 22.

[0064] (Step 2) As shown in Table 1 and FIG. 5, the first adsorption step is subsequently carried out in the first adsorption tower 1.

[0065] Meanwhile, in the second adsorption tower 10A, the second adsorption step is carried out. That is, the on-off valves 7 and 9A are opened, and the intermediate gas is introduced into the second adsorption tower 10A via the intermediate gas inlet passage 4 and the raw gas inlet passage 2. In the second adsorption tower 10A, mainly oxygen gas is adsorbed and separated by the second adsorbent to become a purified gas. The purified gas is introduced into the purified gas tank 12 via the purified gas inlet passage 11 by opening the on-off valve 16A.

[0066] Furthermore, in the second adsorption tower 10a, a second regeneration step is carried out. That is, the needle valve 19 is opened, and a part of the purified gas is introduced from the second adsorption tower 10A to the second adsorption tower 10a via the second adsorption tower connecting line 13. This purges the second adsorption tower 10a and promotes desorption of the oxygen gas adsorbed by the second adsorbent, and at the same time, the on-off valves 17B and 18B are opened to open the inside of the second adsorption tower 10a to the atmosphere and the pressure in the second adsorption tower 10a is reduced to approximately atmospheric pressure, thereby desorbing the oxygen gas adsorbed by the second adsorbent.

[0067] (Step 3) As shown in Table 1 and Fig. 6, the first regeneration step is carried out in the first adsorption tower 1. That is, the on-off valve 8 is opened to open the inside of the first adsorption tower 1 to the atmosphere, and the pressure in the first adsorption tower 1 is reduced to approximately atmospheric pressure, thereby accelerating the desorption of the oxygen gas adsorbed by the first adsorbent. In this case, the on-off valves 6B and 7 are closed.

[0068] Meanwhile, in the second adsorption tower 10A, the second adsorption step continues. That is, the on-off valves 6A and 9A are opened, and the raw material gas is introduced into the second adsorption tower 10A through the raw material gas inlet passage 2. In the second adsorption tower 10A, oxygen gas is adsorbed and separated by the second adsorbent from the raw material gas, and the raw material gas becomes a purified gas. The purified gas is introduced into the purified gas tank 12 through the purified gas inlet passage 11 by opening the on-off valve 16A.

[0069] In addition, in the second adsorption tower 10a, the second regeneration step is subsequently carried out.

[0070] (Step 4) As shown in Table 1 and Fig. 7, the first regeneration step is subsequently performed in the first adsorption tower 1. The first regeneration step in this step includes a first purge regeneration step. That is, the first regeneration step is performed by opening the on-off valve 18A and introducing the second exhaust gas, which is the first regeneration gas, into the first adsorption tower 1, in addition to exhausting to the atmosphere. In this case, the on-off valve 18B is closed.

[0071] Meanwhile, in the second adsorption tower 10A, the second adsorption step continues to be carried out.

[0072] In addition, the second regeneration step is subsequently carried out in the second adsorption tower 10a. As described above, the second exhaust gas discharged from the second adsorption tower 10a is introduced into the first adsorption tower 1 as the first regeneration gas.

[0073] (Step 5) As shown in Table 1 and FIG. 8, in the first adsorption tower 1, the first adsorption step is carried out in the same manner as in step 1.

[0074] Meanwhile, a pressure equalization step is carried out in the pair of second adsorption towers 10. However, the gas flow differs from that in step 1. That is, the on-off valves 23 and 25 are opened, and gas moves from the second adsorption tower 10A to the second adsorption tower 10a via the outlet pressure equalization path 20 and the intermediate pressure equalization path 22.

[0075] (Step 6) As shown in Table 1 and FIG. 9, the first adsorption step is subsequently carried out in the first adsorption tower 1.

[0076] Meanwhile, in the second adsorption tower 10a, the second adsorption step is carried out. That is, the on-off valves 7 and 9B are opened, and the intermediate gas is introduced into the second adsorption tower 10a via the intermediate gas inlet passage 4 and the raw gas inlet passage 2. In the second adsorption tower 10a, oxygen gas is adsorbed and separated by the second adsorbent to become a purified gas. The purified gas is introduced into the purified gas tank 12 via the purified gas inlet passage 11 by opening the on-off valve 16B.

[0077] Furthermore, a second regeneration step is carried out in the second adsorption tower 10A. That is, needle valve 19 is opened to introduce a portion of the purified gas from the second adsorption tower 10a into the second adsorption tower 10A and promote desorption of the oxygen gas adsorbed by the second adsorbent, and at the same time, on-off valves 17A and 18B are opened to open the inside of the second adsorption tower 10A to the atmosphere and reduce the pressure in the second adsorption tower 10A to approximately atmospheric pressure, thereby promoting desorption of the oxygen gas adsorbed by the second adsorbent.

[0078] (Step 7) As shown in Table 1 and FIG. 10, in the first adsorption tower 1, the first regeneration step is carried out in the same manner as in step 3.

[0079] Meanwhile, in the second adsorption tower 10a, the second adsorption step continues to be performed. That is, the on-off valves 6A and 9B are opened, and the raw material gas is introduced into the second adsorption tower 10a through the raw material gas inlet passage 2. In the second adsorption tower 10a, oxygen gas is adsorbed and separated by the second adsorbent from the raw material gas, and the raw material gas becomes a purified gas. The purified gas is introduced into the purified gas tank 12 through the purified gas inlet passage 11 by opening the on-off valve 16B.

[0080] Furthermore, in the second adsorption tower 10A, the second regeneration step is subsequently carried out.

[0081] (Step 8) 11, the first regeneration step is subsequently performed in the first adsorption tower 1. The first regeneration step in this step includes a first purge regeneration step, similar to step 4.

[0082] Meanwhile, in the second adsorption tower 10a, the second adsorption step continues to be carried out.

[0083] In addition, the second regeneration step is subsequently carried out in the second adsorption tower 10A. The second exhaust gas discharged from the second adsorption tower 10A is introduced into the first adsorption tower 1 as a first regeneration gas. EXAMPLES

[0084] The following examples are provided to illustrate, but not to limit, the scope of the claims.

[0085] <Test Example 1> (No. A) Using the purified gas production apparatus 30 shown in FIG. 3, purified gas was produced from raw gas through the adsorption cycle shown in Table 2. Air was used as the raw gas. During one adsorption cycle, the amount of air supplied (flow rate) was kept constant, and purified gas was produced from air several times while the amount of air supplied was changed. Note that in Nos. B to E described below, the amount of air supplied (flow rate) was kept constant during one adsorption cycle, and purified gas was produced from air several times while the amount of air supplied was changed.

[0086] [Table 2]

[0087] The specific device configuration is as follows.

[0088] [Device configuration] First adsorbent: CMS (MG405L, manufactured by Air Water Inc.) Second adsorbent: CMS (MG407H, manufactured by Air Water Inc.) First adsorption tower volume: 0.5L (CMS filling amount: 0.34kg) Second adsorption tower volume: 15.7L (CMS filling amount: 11.5kg) (No.B) Except for changing the volume of the first adsorption tower to 1.0 L (CMS loading amount: 0.75 kg), the same equipment configuration as No. A was used to produce purified gas from raw gas using the adsorption cycle shown in Table 2.

[0089] (No.C) Except for changing the volume of the first adsorption tower to 2.0 L (CMS filling amount: 1.49 kg), the same equipment configuration as No. A was used to produce purified gas from raw gas using the adsorption cycle shown in Table 2.

[0090] (No.D) Except for changing the volume of the first adsorption tower to 4.0 L (CMS packing amount: 3.21 kg), the same equipment configuration as No. A was used to produce purified gas from raw material gas using the adsorption cycle shown in Table 2.

[0091] (No. E) A purified gas was produced from a raw material gas using the adsorption cycle shown in Table 3, using the purified gas production apparatus 60 shown in Fig. 14. This purified gas production apparatus is the same as the purified gas production apparatuses No. A to D except for the first adsorption tower and the paths connected to the first adsorption tower. The second adsorbent and the volume of the second adsorption tower are the same as those of the apparatuses No. A to D.

[0092] [Table 3]

[0093] [evaluation] (Nitrogen and oxygen gas concentrations in intermediate and refined gases) In Nos. A to D, the concentration of oxygen gas in the intermediate gas was measured near the outlet nozzle 1E of the first adsorption tower 1. An oxygen concentration sensor (LC-450F, manufactured by Toray Engineering Co., Ltd.) was used to measure the oxygen gas concentration in the intermediate gas. Also, in Nos. A to E, the concentration of oxygen gas in the purified gas was measured in the purified gas tank 12. An oxygen concentration sensor (LC-450L, manufactured by Toray Engineering Co., Ltd.) was used to measure the oxygen gas concentration in the purified gas. Note that the sum of nitrogen gas and oxygen gas in the intermediate gas and purified gas is taken as 100% by volume.

[0094] (Ratio of raw gas supply volume to refined gas recovery volume) For Nos. A to E, the relationship between the ratio of the feed gas (air) supply rate to the recovered amount of purified gas (nitrogen gas) (Air Nitrogen ratio: AN ratio) and the concentration of oxygen gas in the purified gas was calculated. The results are shown in FIG. 15. The smaller the AN ratio, the better the recovery rate of the purified gas, and the lower the oxygen concentration in the purified gas at the same or similar AN ratio, the better the performance of the purified gas production equipment. In addition, the AN ratio value of No. E was calculated relative to the AN ratios of Nos. A to D when the oxygen concentration of the purified gas was 100 ppm. The results are shown in Table 4. The larger the value, the better the performance of the purified gas production equipment.

[0095] (Amount of purified gas recovered per unit mass of adsorbent) For Nos. A to E, the relationship between the flow rate (recovery amount) of purified gas (nitrogen gas) per unit mass of adsorbent (CMS) (Nitrogen Velocity divided by CMS Mass: MV) and the concentration of oxygen gas in the purified gas was calculated. The results are shown in FIG. 16. The higher the MV, the better the recovery rate of the purified gas, and the lower the oxygen concentration in the purified gas at the same or similar MV, the better the performance of the purified gas production equipment. The MV is calculated from the sum of the CMS contained in the first adsorption tower and the CMS contained in the second adsorption tower. In addition, the MV values ​​of Nos. A to D were calculated relative to the MV of No. E when the oxygen concentration of the purified gas was 100 ppm. The results are shown in Table 4. The higher the value, the better the performance of the purified gas production equipment.

[0096] [Table 4]

[0097] [result] The oxygen gas concentration in the intermediate gas obtained in Nos. A to D was 3 vol. % or more and 21 vol. % or less (nitrogen gas concentration: 79 vol. % or more and 97 vol. % or less). The oxygen gas concentration in the intermediate gas differs depending on the adsorption state of the first adsorbent in the first adsorption tower 1. That is, in the early stage of the first adsorption step, the first adsorbent is not saturated, so a large amount of oxygen gas is adsorbed, and the oxygen gas concentration in the intermediate gas is low. On the other hand, in the final stage of the first adsorption step, the first adsorbent is close to saturation, so the amount of oxygen gas adsorbed is small, and the oxygen gas concentration in the intermediate gas is high.

[0098] The oxygen gas concentration in the refined gas obtained in Nos. A to E was 10 ppm by volume or more and 1000 ppm by volume or less (nitrogen gas concentration: 99.9% by volume or more).

[0099] As shown in FIG. 15, compared to No. E, which produced purified gas using a purified gas production apparatus 60 not equipped with a first adsorption tower, Nos. A to D, which produced purified gas using a purified gas production apparatus 30 equipped with a first adsorption tower, had a lower oxygen concentration in the purified gas at a similar AN ratio. Also, in Table 4, the AN ratio value of No. E compared to the AN ratios of Nos. A to D was a value exceeding 1.0. Furthermore, among Nos. A to D, Nos. B and C had lower oxygen concentrations in the purified gas at similar AN ratios, and the AN ratio value of No. E was higher than the AN ratios of Nos. B and C. From these results, it is considered that there is an optimal first adsorption tower volume from the viewpoint of the AN ratio.

[0100] As shown in Fig. 16, compared to No. E, in which purified gas was produced using a purified gas production apparatus 60 not equipped with a first adsorption tower, Nos. A to D, in which purified gas was produced using a purified gas production apparatus 30 equipped with a first adsorption tower, had lower oxygen concentrations in the purified gas at similar MVs. Also, in Table 4, the MV values ​​of Nos. A to D relative to the MV of No. E were values ​​exceeding 1.0. Furthermore, among Nos. A to D, Nos. C and D had lower oxygen concentrations in the purified gas at similar MVs, and the MV values ​​of Nos. C and D relative to the MV of No. E were higher.

[0101] <Test Example 2> (No.1) Using the purified gas production apparatus 30 shown in Figure 1, purified gas was produced from raw material gas by the adsorption cycle shown in Table 2. Air was used as the raw material gas, and the average flow rate was 177.0 NL / min. The specific apparatus configuration is the same as that of the purified gas production apparatus 30 No. C in Test Example 1, and is also the same for the purified gas production apparatuses 30 Nos. 2 to 6 described below.

[0102] (No.2) Using the refined gas production apparatus 40 shown in Fig. 12, refined gas was produced from raw material gas by the adsorption cycle shown in Table 3. The refined gas production apparatus was the refined gas production apparatus No. 1 except for the first adsorption tower and each path connected to the first adsorption tower. The flow rate of the raw material gas was 175.6 NL / min on average.

[0103] (No.3) Using the purified gas production apparatus 30 shown in Fig. 2, a purified gas was produced from a raw material gas by the adsorption cycle shown in Table 2. The flow rate of the raw material gas was 148.2 NL / min on average.

[0104] (No.4) Using the refined gas production apparatus 50 shown in Fig. 13, refined gas was produced from raw gas by the adsorption cycle shown in Table 3. The refined gas production apparatus was the refined gas production apparatus No. 3 except for the first adsorption tower and each path connected to the first adsorption tower. The flow rate of the raw gas was 145.4 NL / min on average.

[0105] (No.5) Using the purified gas production apparatus 30 shown in Fig. 3, a purified gas was produced from a raw material gas by the adsorption cycle shown in Table 2. The flow rate of the raw material gas was 147.4 NL / min on average.

[0106] (No.6) Using the refined gas production apparatus 60 shown in Fig. 14, refined gas was produced from raw material gas by the adsorption cycle shown in Table 3. The refined gas production apparatus was the refined gas production apparatus No. 5 except for the first adsorption tower and each path connected to the first adsorption tower. The flow rate of the raw material gas was 144.7 NL / min on average.

[0107] (evaluation) The oxygen gas concentrations in the intermediate gases obtained in Nos. 1, 3, and 5, and the oxygen gas concentrations in the refined gases obtained in Nos. 1 to 6 were measured. The oxygen concentration sensor used in Test Example 1 was used for the measurements. The reduction ratio of the oxygen gas concentration with and without the first adsorption tower was calculated. The results are shown in Table 5. Here, the "reduction ratio of oxygen gas concentration" refers to the ratio of the oxygen gas concentration in the refined gas of No. 1 to the oxygen gas concentration in the refined gas of No. 2 in No. 1, the ratio of the oxygen gas concentration in the refined gas of No. 2 to the oxygen gas concentration in the refined gas of No. 4 in No. 3, and the ratio of the oxygen gas concentration in the refined gas of No. 5 to the oxygen gas concentration in the refined gas of No. 6 in No. 5. In this test example, the sum of the nitrogen gas and the oxygen gas in the intermediate gas and the refined gas was set to 100% by volume.

[0108] [Table 5]

[0109] The oxygen gas concentration in the intermediate gas obtained in Nos. 1, 3 and 5 was 3 vol% or more and 21 vol% or less (nitrogen gas concentration: 79 vol% or more and 97 vol% or less). The oxygen gas concentration in the refined gas obtained in Nos. 1 to 6 was as shown in Table 5 (nitrogen gas concentration: 99.9 vol% or more).

[0110] As shown in Table 5, the oxygen concentration in the purified gas obtained in No. 1 was confirmed to be 59.7% lower than that in the purified gas obtained in No. 2. The oxygen concentration in the purified gas obtained in No. 3 was confirmed to be 63.2% lower than that in the purified gas obtained in No. 4. The oxygen concentration in the purified gas obtained in No. 5 was confirmed to be 54.4% lower than that in the purified gas obtained in No. 6.

[0111] In this way, by using the purified gas production apparatus and production method described in the present disclosure, it is possible to produce a purified gas containing high-concentration nitrogen gas with a reduced oxygen gas concentration from a raw gas containing oxygen gas and nitrogen gas, particularly air. In addition, since the present disclosure efficiently produces purified gas from air, it is possible to contribute to some of the activities of the Sustainable Development Goals (SDGs).

[0112] The embodiments and examples disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0113] 1 first adsorption tower, 1A inlet region, 1B outlet region, 1C filling section, 1D inlet nozzle, 1E outlet nozzle, 2 raw gas inlet passage, 3 first adsorption tower inlet passage, 4 intermediate gas inlet passage, 5 first exhaust gas exhaust passage, 6A, 6B, 7, 8, 9A, 9B on-off valve, 10, 10A, 10a second adsorption tower, 10B, 10b inlet region, 10C, 10c outlet region, 10D, 10d filling section, 10E, 10e inlet nozzle, 10F, 10f outlet nozzle, 11 purified gas inlet passage, 12 purified gas tank, 13 second adsorption tower connecting passage, 14 second exhaust gas exhaust passage, 15 adsorption tower connecting passage, 16A, 16B, 17A, 17B, 18, 18A, 18B on-off valve, 19 needle valve, 20 outlet equalizing passage, 21 Inlet pressure equalizing passage, 22 intermediate pressure equalizing passage, 23, 24, 25 on-off valve, 30, 40, 50, 60 refined gas production equipment.

Claims

1. An apparatus for producing a purified gas containing nitrogen gas by pressure swing adsorption, comprising: a first adsorption tower having a first adsorbent for obtaining an intermediate gas having a higher nitrogen gas content than a raw material gas containing nitrogen gas and oxygen gas from the raw material gas; a pair of second adsorption towers having a second adsorbent for obtaining a purified gas having a higher nitrogen gas content than the raw gas and the intermediate gas from at least one gas selected from the group consisting of the raw gas and the intermediate gas; a raw material gas inlet passage for introducing the raw material gas into the pair of second adsorption towers; an intermediate gas inlet passage for introducing the intermediate gas from the first adsorption tower into the pair of second adsorption towers.

2. 2 . The apparatus for producing a refined gas according to claim 1 , wherein a volume of the first adsorption tower is smaller than a volume of one of the pair of second adsorption towers.

3. 2. The apparatus for producing a refined gas according to claim 1, wherein the first adsorbent has a higher adsorption rate of oxygen gas than the second adsorbent.

4. A method for producing a purified gas using the apparatus for producing a purified gas according to any one of claims 1 to 3, a first step of introducing the raw material gas into the first adsorption tower to obtain the intermediate gas; a second step of introducing at least the intermediate gas into one of the pair of second adsorption towers to obtain the purified gas.

5. 5. The method for producing a refined gas according to claim 4, wherein the second step includes: introducing only the intermediate gas into one of the pair of second adsorption towers; and introducing only the raw material gas into one of the pair of second adsorption towers.

6. a first regeneration step of regenerating the first adsorbent after the first step; The method for producing a purified gas according to claim 4 , further comprising a second regeneration step of regenerating the second adsorbent after the second step.

7. 7. The method for producing a purified gas according to claim 6, further comprising a first purge regeneration step of promoting regeneration of the first adsorbent by introducing exhaust gas after the second regeneration step into the first adsorption tower after the first regeneration step.

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