Gas separation method and gas separation device

Abstract

To provide a gas separation method and a gas separation apparatus capable of easily continuing the separation of target gas from raw material gas even when concentration of the target gas in the raw material gas fluctuates.SOLUTION: A gas separation method according to the present invention is a gas separation method for separating a target gas from raw material gas by a pressure fluctuation adsorption, includes a separation cycle which repeats the steps of, in this order, an adsorption step of supplying the raw material gas to an adsorption unit and adsorbing the target gas in the raw material gas on the adsorption unit, a purge step of supplying the target gas stored in a target gas storage tank to the adsorption unit, and a separation step of desorbing the target gas adsorbed on the adsorption unit from the adsorption unit and supplying and storing the desorbed target gas in the target gas storage tank, where a target gas supply amount, which is an amount of the target gas supplied to the adsorption unit in the purge step, is adjusted according to target gas concentration, which is concentration of the target gas in the raw material gas supplied to the adsorption unit in the adsorption step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas separation method and a gas separation apparatus. [Background technology]

[0002] In the manufacturing process of semiconductor products such as semiconductor integrated circuits or display devices such as liquid crystal panels, plasma generated by high-frequency discharge in a rare gas atmosphere is used. While argon has traditionally been used as the rare gas in such processes, krypton and xenon have recently attracted attention for more advanced processing. In the lighting field, while argon has traditionally been used as the fill gas in light bulbs, high-value-added products using krypton or xenon have recently been manufactured to reduce power consumption and improve brightness. Similarly, in the glass field, while argon has traditionally been used as the fill gas in double-glazed glass, high-value-added products using krypton have recently been manufactured to improve thermal insulation performance.

[0003] However, krypton and xenon are extremely rare and expensive gases due to their abundance in the air used as raw materials and the complexity of the separation process, and their use has led to problems such as an imbalance in supply and demand and a significant increase in costs. To make the use of such gases economically viable, it is extremely important to separate and recover used rare gases at a high recovery rate and reuse them.

[0004] A known method for separating and recovering krypton or xenon at a high concentration and with a high recovery rate is one that uses pressure swing adsorption (PSA). Patent Document 1 discloses this type of gas separation method. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-61831 Summary of the Invention [Problem to be solved by the invention]

[0006] According to the gas separation method of Patent Document 1, the target gas can be adsorbed onto an adsorption unit and separated from the raw gas. In such a gas separation method, a raw gas containing a gas discharged from a facility as an introduced gas may be used. In this case, the concentration of the target gas in the introduced gas may vary depending on the operating state of the facility, which may in turn cause the concentration of the target gas in the raw gas to vary. If the concentration of the target gas in the raw gas varies, the amount of target gas separated from the raw gas may also vary.

[0007] In the gas separation method of Patent Document 1, the target gas separated from the raw material gas is stored in a target gas storage tank for use in the separation cycle. Therefore, if the amount of target gas separated from the raw material gas fluctuates, the amount of target gas stored in the target gas storage tank may become insufficient or excessive, which may make it impossible to continue separating the target gas from the raw material gas.

[0008] An object of the present invention is to provide a gas separation method and gas separation apparatus that can easily continue to separate a target gas from a raw material gas even when the concentration of the target gas in the raw material gas fluctuates. [Means for solving the problem]

[0009] A gas separation method according to a first aspect of the present invention comprises: (1) A gas separation method for separating a target gas from a raw material gas by pressure swing adsorption, an adsorption step of supplying the raw material gas to an adsorption section and adsorbing the target gas in the raw material gas into the adsorption section; a purging step of supplying the target gas stored in a target gas storage tank to the adsorption section; a separation step of desorbing the target gas adsorbed in the adsorption section from the adsorption section and supplying the target gas to the target gas storage tank for storage; and A gas separation method, wherein a target gas supply amount, which is the amount of the target gas supplied to the adsorption section in the purging step, is adjusted according to a target gas concentration, which is the concentration of the target gas in the raw gas supplied to the adsorption section in the adsorption step.

[0010] A gas separation method according to one embodiment of the present invention includes: (2) This is a gas separation method described in (1) above, wherein, when the target gas concentration in the adsorption step is greater than the target gas concentration in the adsorption step performed in the previous separation cycle, the target gas supply amount in the purge step is made smaller than the target gas supply amount in the purge step of the previous separation cycle.

[0011] A gas separation method according to one embodiment of the present invention includes: (3) This is a gas separation method according to (1) or (2) above, wherein, when the target gas concentration in the adsorption step is lower than the target gas concentration in the adsorption step performed in the previous separation cycle, the target gas supply amount in the purge step is made larger than the target gas supply amount in the purge step of the previous separation cycle.

[0012] A gas separation method according to one embodiment of the present invention includes: (4) The gas separation method according to any one of (1) to (3) above, wherein the target gas concentration is an average value of the target gas concentration in the raw gas at two or more points in time during the adsorption step.

[0013] A gas separation method according to one embodiment of the present invention includes: (5) In the gas separation method according to (4) above, the target gas concentration is an average value of the target gas concentration in the raw gas obtained at predetermined time intervals in the adsorption step.

[0014] A gas separation apparatus according to a second aspect of the present invention comprises: (6) A gas separation apparatus that separates a target gas from a raw material gas by a pressure swing adsorption method, an adsorption unit capable of adsorbing the target gas; a target gas storage tank capable of storing the target gas; a control unit that controls a separation cycle that repeats in this order the following steps: an adsorption step of supplying the raw material gas containing the target gas to the adsorption unit and adsorbing the target gas to the adsorption unit; a purging step of supplying the target gas stored in the target gas storage tank to the adsorption unit; and a separation step of desorbing the target gas adsorbed in the adsorption unit from the adsorption unit and supplying it to the target gas storage tank for storage; a concentration meter capable of measuring a target gas concentration, which is the concentration of the target gas in the raw material gas supplied to the adsorption section in the adsorption step; The control unit is a gas separation apparatus that adjusts a target gas supply amount, which is the amount of the target gas supplied to the adsorption unit in the purging step, according to the measurement value of the concentration meter.

[0015] A gas separation apparatus according to one embodiment of the present invention comprises: (7) The gas separation device is described in (6) above, wherein the control unit reduces the target gas supply amount in the purge step to be less than the target gas supply amount in the purge step of the separation cycle immediately preceding the target gas concentration in the adsorption step, if the target gas concentration in the adsorption step is greater than the target gas concentration in the adsorption step performed in the separation cycle immediately preceding the target gas concentration in the adsorption step.

[0016] A gas separation apparatus according to one embodiment of the present invention comprises: (8) The gas separation device is described in (6) or (7) above, wherein the control unit increases the target gas supply amount in the purge step to be greater than the target gas supply amount in the purge step of the separation cycle immediately preceding the adsorption step if the target gas concentration in the adsorption step is smaller than the target gas concentration in the adsorption step performed in the separation cycle immediately preceding the adsorption step.

[0017] A gas separation apparatus according to one embodiment of the present invention comprises: (9) The gas separation apparatus according to any one of (6) to (8) above, wherein the target gas concentration is an average value of the target gas concentration in the raw gas at two or more points in time during the adsorption step.

[0018] A gas separation apparatus according to one embodiment of the present invention comprises: (10) The gas separation apparatus according to (9) above, wherein the target gas concentration is an average value of the target gas concentration in the raw gas obtained at predetermined time intervals in the adsorption step. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a gas separation method and a gas separation apparatus that can easily continue to separate a target gas from a raw material gas even when the concentration of the target gas in the raw material gas fluctuates. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing a gas separation apparatus according to one embodiment of the present invention, illustrating the gas separation apparatus in a state in which the adsorption process of one of two separation cycles and the separation process of the other separation cycle are being performed. [Figure 2] 2 is a diagram showing the gas separation apparatus in a state following the state shown in FIG. 1, in which the recovery step is being carried out while the adsorption step of one separation cycle is continuing. [Figure 3] 3 is a diagram showing the gas separation apparatus in a state following the state shown in FIG. 2, in which the adsorption step of one separation cycle is continuing while the rinsing step of the other separation cycle is being carried out. [Figure 4] 4 is a diagram showing the gas separation apparatus in a state in which a purge step in one separation cycle and a pressure equalization step in the other separation cycle are being performed, following the state shown in FIG. 3. FIG. [Figure 5]5 is a diagram showing the gas separation apparatus in a state in which the separation step of one separation cycle and the adsorption step of the other separation cycle are being performed, following the state shown in FIG. 4. FIG. [Figure 6] FIG. 6 is a diagram showing the gas separation apparatus in a state following the state shown in FIG. 5, in which the recovery step in one separation cycle is being carried out and the adsorption step in the other separation cycle is continuing. [Figure 7] FIG. 7 is a diagram showing the gas separation apparatus in a state following the state shown in FIG. 6, in which the rinse step of one separation cycle has been carried out and the adsorption step of the other separation cycle has continued. [Figure 8] FIG. 8 is a diagram showing the gas separation apparatus in a state in which the pressure equalization step of one separation cycle and the purge step of the other separation cycle are being performed, following the state shown in FIG. 7. [Figure 9] FIG. 1 is a diagram illustrating two separation cycles included in a gas separation method according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the gas separation method and gas separation apparatus according to the present invention will be described with reference to the drawings. In each drawing, the same components are designated by the same reference numerals. Note that the embodiments described below are merely examples, and the present invention is not necessarily limited thereto. Appropriate modifications can be made without departing from the technical spirit of the present invention.

[0022] <Gas separation device 100> 1 to 8 are diagrams showing a gas separation apparatus 100 as one embodiment of the gas separation apparatus according to the present invention. The gas separation apparatus 100 shown in Figures 1 to 8 is a pressure swing adsorption gas separation apparatus that uses an adsorbent and a feed gas containing an adsorbent component that is easily adsorbed to the adsorbent and a weakly adsorbable component that is poorly adsorbed to the adsorbent, separates the adsorbent component from the weakly adsorbable component in the feed gas, and recovers each of the adsorbent component and the weakly adsorbable component.

[0023] A pressure swing adsorption gas separation device is a device for performing pressure swing adsorption (PSA) separation, which utilizes the selectivity of an adsorbent for adsorbed gases. The selectivity of an adsorbent for adsorbed gases can be determined by differences in equilibrium adsorption capacity or differences in adsorption rate. Activated carbon, an example of an adsorbent with selectivity due to differences in equilibrium adsorption capacity (equilibrium separation adsorbent), adsorbs xenon at least 10 times more than nitrogen and argon (298 K, 100 kPa (abs)). Molecular sieve carbon (MSC), an example of an adsorbent with selectivity due to differences in adsorption rate (rate separation adsorbent), adsorbs oxygen at a rate approximately 15 times faster than nitrogen. In the case of activated carbon, easily adsorbed components include, for example, xenon, carbon dioxide, and sulfur hexafluoride, and poorly adsorbed components include, for example, nitrogen, oxygen, helium, argon, neon, and hydrogen. In the case of MSC, the easily adsorbed component is, for example, oxygen or carbon dioxide, and the less easily adsorbed component is, for example, nitrogen.

[0024] The types of readily adsorbable and poorly adsorbable components vary depending on the adsorbent used. Therefore, a component that is readily adsorbable to one adsorbent may be poorly adsorbable to another. Conversely, a component that is poorly adsorbable to one adsorbent may be readily adsorbable to another adsorbent. For example, when the adsorbent is an equilibrium separation adsorbent such as activated carbon, Na-X zeolite, Ca-X zeolite, Ca-A zeolite, or Li-X zeolite, examples of readily adsorbable components include xenon, krypton, and sulfur hexafluoride, while examples of poorly adsorbable components include nitrogen, oxygen, hydrogen, helium, neon, and argon. When the adsorbent is a rate separation adsorbent such as Na-A zeolite or MSC, examples of readily adsorbable components include nitrogen, oxygen, and argon, while examples of poorly adsorbable components include krypton, xenon, and sulfur hexafluoride.

[0025] As shown in Figures 1 to 8, the gas separation apparatus 100 of this embodiment includes adsorption sections 10A and 10B, auxiliary adsorption sections 11A and 11B, a raw material gas storage tank 1, a target gas storage tank 2, a non-adsorbed gas storage tank 3, and compressors 4 and 5.

[0026] [Adsorption sections 10A, 10B and auxiliary adsorption sections 11A, 11B] The adsorption units 10A, 10B and auxiliary adsorption units 11A, 11B of this embodiment each include a container and an adsorbent filled in the container. More specifically, the adsorption units 10A, 10B of this embodiment each are so-called "lower columns" filled with an adsorbent. The auxiliary adsorption units 11A, 11B of this embodiment each are so-called "upper columns" filled with an adsorbent. However, the shape of the container is not particularly limited. The adsorbent is highly adsorbent for the target gas in the raw gas and poorly adsorbent for non-adsorbed gases, which are components other than the target gas. It is desirable that the adsorbent filled in the lower column and the upper column be the same, but different adsorbents may be filled as long as they have the above-mentioned properties.

[0027] [Source gas storage tank 1, target gas storage tank 2, and non-adsorbed gas storage tank 3] The raw material gas storage tank 1, the target gas storage tank 2, and the non-adsorption gas storage tank 3 are tanks capable of storing gas. There are no limitations on the configurations of the raw material gas storage tank 1, the target gas storage tank 2, and the non-adsorption gas storage tank 3, but it is particularly preferable that the raw material gas storage tank 1 and the target gas storage tank 2 are gas bags. A gas bag is a tank that can expand and contract like a balloon depending on the amount of storage. Furthermore, the raw material gas storage tank 1 may be filled with an adsorbent capable of adsorbing at least one component contained in the raw material gas, the target gas storage tank 2 with an adsorbent capable of adsorbing the target gas, and the non-adsorption gas storage tank 3 with an adsorbent capable of adsorbing the non-adsorption gas.

[0028] [Compressor 4] The compressor 4 is capable of pumping the raw gas from the raw gas storage tank 1 to the adsorption units 10A and 10B. The compressor 4 is also capable of pumping the target gas from the target gas storage tank 2 to the adsorption units 10A and 10B. That is, the compressor 4 of this embodiment serves both as a compressor that pumps the raw gas from the raw gas storage tank 1 to the adsorption units 10A and 10B and a compressor that pumps the target gas from the target gas storage tank 2 to the adsorption units 10A and 10B. However, the gas separation apparatus 100 may be configured to separately include a compressor that pumps the raw gas from the raw gas storage tank 1 to the adsorption units 10A and 10B and a compressor that pumps the target gas from the target gas storage tank 2 to the adsorption units 10A and 10B.

[0029] The configuration of the compressor 4 is not particularly limited, but it is preferable that the configuration does not allow components other than the raw material gas to be mixed into the gas being pumped when pumping the raw material gas from the raw material gas storage tank 1, and does not allow components other than the target gas to be mixed into the gas being pumped when pumping the target gas from the target gas storage tank 2. Furthermore, the compressor 4 is preferably highly airtight and oil-free (does not use lubricating oil or has a structure in which lubricating oil does not come into contact with the gas being pumped).

[0030] [Compressor 5] The compressor 5 is capable of pumping the target gas in the target gas storage tank 2 to the outside of the gas separation apparatus 100. The configuration of the compressor 5 is not particularly limited, but it is preferable that the compressor 5 is configured so that components other than the target gas are not mixed into the gas being pumped when pumping the target gas in the target gas storage tank 2. Furthermore, the compressor 5 is preferably highly airtight and oil-free (does not use lubricating oil or is configured so that lubricating oil does not come into contact with the gas being pumped).

[0031] The gas separation apparatus 100 of this embodiment is provided with paths L1 to L16 through which gas can flow.

[0032] The path L1 can supply an introduction gas from outside the gas separation apparatus 100 to the raw material gas storage tank 1. The path L2 connects the raw material gas storage tank 1 and the compressor 4. The path L3 connects the target gas storage tank 2 and the compressor 4. The path L4 connects the compressor 4 and the adsorption unit 10A. The path L5 connects the compressor 4 and the adsorption unit 10B. The path L6A connects the auxiliary adsorption section 11A and the non-adsorbed gas reservoir 3. The path L6B connects the auxiliary adsorption section 11B and the non-adsorbed gas reservoir 3. The path L7 can discharge the non-adsorbed gas in the non-adsorbed gas reservoir 3 to the outside of the gas separation apparatus 100. The path L8A connects the non-adsorbed gas reservoir 3 and the auxiliary adsorption section 11A. The path L8B connects the non-adsorbed gas reservoir 3 and the auxiliary adsorption section 11B. The path L9 connects the adsorption unit 10B and the target gas storage tank 2 without the compressor 4 intervening. The path L10 connects the adsorption unit 10A and the target gas storage tank 2 without the compressor 4 intervening. The path L11 connects the adsorption unit 10A and the raw material gas storage tank 1 without the compressor 4 intervening. The path L12 connects the adsorption unit 10B and the raw material gas storage tank 1 without the compressor 4 intervening. The path L13 allows the target gas in the target gas storage tank 2 to be discharged to the outside of the gas separation apparatus 100. The path L14 connects the auxiliary suction portion 11A and the auxiliary suction portion 11B. The path L15 connects the suction unit 10A and the auxiliary suction unit 11A. The path 16 connects the suction portion 10B and the auxiliary suction portion 11B.

[0033] The valves V1 to V15 are opening and closing devices that can open and close the paths.

[0034] A valve V1 is provided in the path L2. A valve V2 is provided on the path L3. A valve V3 is provided on the path L4. A valve V4 is provided on the path L5. A valve V5 is provided on the path L15. A valve V6 is provided in the path L16. A valve V7 is provided on the path L8A. A valve V8 is provided on the path L8B. A valve V9 is provided in the path L14. A valve V10 is provided in the path L10. A valve V11 is provided on the path L9. A valve V12 is provided in the path L11. A valve V13 is provided on the path L12. A valve V14 is provided on the path L6A. A valve V15 is provided on the path L6B.

[0035] The gas separation apparatus 100 of this embodiment further includes a concentration meter 6 , pressure gauges 7 and 8 , a sensor 9 , and a control unit 20 .

[0036] [Densitometer 6] The concentration meter 6 of this embodiment can measure the concentration of the target gas in the raw material gas in the raw material gas storage tank 1. The concentration meter 6 may be configured to directly measure the concentration of the target gas in the raw material gas, or may be configured to indirectly derive the concentration of the target gas in the raw material gas from the measurement results of the concentrations of components other than the target gas in the raw material gas.

[0037] The configuration of the concentration meter 6 is not particularly limited as long as it can measure the concentration of the target gas in the raw material gas in the raw material gas storage tank 1, and may be, for example, a mass spectrometer, a gas chromatograph analyzer, a zirconia oxygen meter, a galvanic cell oxygen meter, an infrared spectrophotometer, an ultrasonic concentration meter, or a thermal conduction concentration meter. Although the concentration meter 6 in this embodiment is provided on paths L4 and L5, the installation location is not limited as long as it can measure the concentration of the target gas in the raw material gas. The concentration meter 6 may be provided, for example, on path L2.

[0038] [Pressure gauges 7 and 8] The pressure gauge 7 is provided on the path L6A and can measure the pressure in the adsorption unit 10A and the auxiliary adsorption unit 11A in the adsorption step A1 described later. The pressure gauge 8 is provided on the path L6B and can measure the pressure in the adsorption unit 10B and the auxiliary adsorption unit 11B in the adsorption step B5 described later.

[0039] [Sensor 9] The sensor 9 is provided in the target gas storage tank 2 and is capable of measuring the amount of target gas stored in the target gas storage tank 2. The configuration of the sensor 9 is not particularly limited as long as it is capable of measuring the amount of target gas stored in the target gas storage tank 2, and may be, for example, a weight sensor that measures a change in weight of the target gas storage tank 2. Furthermore, if the target gas storage tank 2 is a gas bag, the sensor 9 may be a level sensor that measures a change in height of the gas bag. If the target gas storage tank 2 is a tank with a fixed volume, the sensor 9 may be a pressure sensor that measures the pressure of the target gas storage tank 2. Furthermore, the sensor 9 may be configured by combining two or more of a level sensor, a weight sensor, and a pressure sensor.

[0040] [Control unit 20] The control unit 20 of this embodiment controls two separation cycles CA and CB, which will be described later. More specifically, the control unit 20 of this embodiment controls the two separation cycles CA and CB, which will be described later, by sequentially controlling the opening and closing of valves V1 to V15 and the operation and stopping of compressors 4 and 5. The control unit 20 includes a processor, such as a general-purpose processor such as a CPU (central processing unit) or an MPU (micro processing unit), or a dedicated processor specialized for a specific process. The control unit 20 may further include a storage unit, such as a ROM (read only memory) or a RAM (random access memory).

[0041] <Gas separation method> Next, a gas separation method using the above-described gas separation apparatus 100 will be described as one embodiment of the gas separation method according to the present invention. In this embodiment, an example will be described in which a mixed gas containing two components, a target gas and a non-adsorbable gas other than the target gas, is used as the raw gas. Therefore, in this embodiment, an adsorbent that is highly adsorbable to the target gas and poorly adsorbable to the non-adsorbable gas is used as the adsorbent for the adsorption sections 10A, 10B and the auxiliary adsorption sections 11A, 11B. The target gas may be, for example, xenon. The non-adsorbable gas may be, for example, argon. When the target gas is xenon and the non-adsorbable gas is argon, the adsorbent may be, for example, activated carbon.

[0042] 9 is a diagram illustrating two separation cycles CA and CB included in the gas separation method of this embodiment. As shown in FIG. 9, the gas separation method of this embodiment includes two separation cycles CA and CB, which are executed in parallel. More specifically, in the gas separation method of this embodiment, while separation cycle CA is executed using adsorption unit 10A and auxiliary adsorption unit 11A, separation cycle CB is executed using adsorption unit 10B and auxiliary adsorption unit 11B.

[0043] The separation cycle CA of this embodiment includes an adsorption step A1, a purging step A2, a separation step A3, a recovery step A4, a rinsing step A5, and a pressure equalization step A6, which are repeatedly performed in this order. The separation cycle CB of this embodiment includes a separation step B1, a recovery step B2, a rinsing step B3, a pressure equalization step B4, an adsorption step B5, and a purging step B6, which are repeatedly performed in this order. While the following mainly describes the steps of the separation cycle CA, the same applies to the steps of the separation cycle CB.

[0044] [Adsorption process A1] 1 to 3 show the gas separation apparatus 100 in a state in which the adsorption step A1 is being performed. As shown in FIGS. 1 to 3, in the adsorption step A1, valves V2, V4, V7, V9, V10, V12, and V15 are closed, and valves V1, V3, V5, and V14 are opened. In this state, the raw material gas in the raw material gas storage tank 1 is supplied to the adsorption unit 10A via paths L2 and L4 by the compressor 4. At this time, the pressures in the adsorption unit 10A and the auxiliary adsorption unit 11A increase at approximately the same rate because valve V5 is open.

[0045] The raw material gas supplied from the raw material gas storage tank 1 to the adsorption section 10A is a mixed gas of the introduction gas supplied to the raw material gas storage tank 1 via the path L1 and the gas supplied to the raw material gas storage tank 1 in the recovery process and rinsing process described below.

[0046] In the raw gas supplied to the adsorption unit 10A, the target gas is preferentially adsorbed by the adsorbent in the adsorption unit 10A, and the non-adsorbed gas is concentrated. The gas in which the non-adsorbed gas has been concentrated in the adsorption unit 10A passes through the adsorption unit 10A and is then supplied to the auxiliary adsorption unit 11A. In the gas supplied to the auxiliary adsorption unit 11A, the target gas is further adsorbed by the adsorbent in the auxiliary adsorption unit 11A, and the non-adsorbed gas is further concentrated. The gas in which the non-adsorbed gas has been further concentrated in the auxiliary adsorption unit 11A passes through the auxiliary adsorption unit 11A and is then supplied to the non-adsorbed gas storage tank 3 via path L6A.

[0047] Here, if the target gas concentration in the raw gas supplied to the adsorption section 10A in the adsorption step A1 (hereinafter sometimes referred to simply as "target gas concentration") is higher than the target gas concentration in the adsorption step A1 of the previous separation cycle CA, the amount of target gas adsorbed by the adsorbent in the adsorption section 10A and auxiliary adsorption section 11A increases, while the amount of non-adsorbed gas concentrated in the adsorption section 10A and auxiliary adsorption section 11A decreases, compared to the case of the previous separation cycle CA. As a result, the pressure in the adsorption section 10A and auxiliary adsorption section 11A decreases.

[0048] Conversely, if the target gas concentration in the adsorption step A1 is lower than that in the adsorption step A1 of the previous separation cycle CA, the amount of target gas adsorbed by the adsorbent in the adsorption section 10A and the auxiliary adsorption section 11A decreases, while the amount of non-adsorbed gas concentrated in the adsorption section 10A and the auxiliary adsorption section 11A increases, compared to the case of the previous separation cycle CA. As a result, the pressure in the adsorption section 10A and the auxiliary adsorption section 11A increases.

[0049] In the gas separation method of this embodiment, the target gas concentration is measured by the concentration meter 6, and the measured value is stored in the control unit 20. This makes it possible to adjust the amount of target gas supplied to the adsorption unit 10A in the purge step A2 described below based on the stored measured value.

[0050] [Purge process A2] FIG. 4 shows the gas separation apparatus 100 in a state in which the purge step A2 is being performed. As shown in FIG. 4, in the purge step A2, valve V1 is closed and valve V2 is opened, while adsorption step A1 is being performed (see FIGS. 1 to 3). In this state, the target gas in the target gas storage tank 2 is supplied as a purge gas to the adsorption unit 10A via paths L3 and L4 by the compressor 4. This pushes the non-adsorbed gas in the adsorption unit 10A into the auxiliary adsorption unit 11A, and the adsorption unit 10A is saturated with the target gas. The non-adsorbed gas in the adsorption unit 10A refers to the non-adsorbed gas co-adsorbed in the packed bed of adsorbent in the adsorption unit 10A and the non-adsorbed gas present in the voids of the adsorbent.

[0051] 4, in the purge step A2, in addition to the above-described valve operations, valves V7, V8, V14, and V15 may be closed and valve V9 may be opened. This allows the gas in auxiliary adsorption section 11A to be supplied to auxiliary adsorption section 11B via path L14. This reduces the pressure in adsorption section 10A and auxiliary adsorption section 11A, making it easier to push the non-adsorbed gas in adsorption section 10A to auxiliary adsorption section 11A. This also allows the pressure in adsorption section 10B and auxiliary adsorption section 11B to be equalized with that of adsorption section 10A and auxiliary adsorption section 11A.

[0052] Here, if the target gas concentration in the adsorption step A1 is greater than the target gas concentration in the adsorption step A1 of the previous separation cycle CA, the amount of target gas required to push the non-adsorbed gas in the adsorption section 10A to the auxiliary adsorption section 11A in the purge step A2 will be smaller than in the case of the previous separation cycle CA.

[0053] Conversely, if the target gas concentration in the adsorption step A1 is lower than the target gas concentration in the adsorption step A1 of the previous separation cycle CA, the amount of target gas required to push the non-adsorbed gas in the adsorption section 10A to the auxiliary adsorption section 11A in the purge step A2 will be greater than in the case of the previous separation cycle CA.

[0054] Based on the above, in the purge step A2 of the gas separation method of this embodiment, the amount of target gas supplied to the adsorption section 10A (hereinafter, sometimes simply referred to as the "target gas supply amount") is adjusted according to the target gas concentration, which is the concentration of the target gas in the raw gas supplied to the adsorption section 10A in the adsorption step A1.

[0055] More specifically, if the target gas concentration in the adsorption process A1 is greater than the target gas concentration in the adsorption process A1 performed in the previous separation cycle CA, the target gas supply amount in the purge process A2 is made smaller than the target gas supply amount in the purge process A2 of the previous separation cycle CA.

[0056] Conversely, if the target gas concentration in the adsorption process A1 is lower than the target gas concentration in the adsorption process A1 performed in the previous separation cycle CA, the target gas supply amount in the purge process A2 is made larger than the target gas supply amount in the purge process A2 of the previous separation cycle CA.

[0057] For example, if the measured target gas concentration in the adsorption step A1 of the previous separation cycle CA is 50% and the measured target gas concentration in the adsorption step A1 of the current separation cycle CA is 51 to 90%, the target gas supply rate in the purge step A2 of the current separation cycle CA may be reduced by 1 to 90% compared to the target gas supply rate in the purge step A2 of the previous separation cycle CA.Also, if the measured target gas concentration in the adsorption step A1 of the previous separation cycle CA is 50% and the measured target gas concentration in the adsorption step A1 of the current separation cycle CA is 51 to 60%, the target gas supply rate in the purge step A2 of the current separation cycle CA may be reduced by 1 to 20% compared to the target gas supply rate in the purge step A2 of the previous separation cycle CA.

[0058] Conversely, for example, if the measured target gas concentration in the adsorption step A1 of the previous separation cycle CA is 50% and the measured target gas concentration in the adsorption step A1 of the current separation cycle CA is 10 to 49%, the target gas supply rate in the purge step A2 of the current separation cycle CA may be increased by 1 to 90% compared to the target gas supply rate in the purge step A2 of the previous separation cycle CA.Furthermore, for example, if the measured target gas concentration in the adsorption step A1 of the previous separation cycle CA is 50% and the measured target gas concentration in the adsorption step A1 of the current separation cycle CA is 40 to 49%, the target gas supply rate in the purge step A2 of the current separation cycle CA may be increased by 1 to 20% compared to the target gas supply rate in the purge step A2 of the previous separation cycle CA.

[0059] For example, when the supply flow rate of the target gas is constant, the supply amount of the target gas may be controlled by the purge step time during which the target gas is supplied. In other words, when the supply flow rate of the target gas in the purge step A2 is constant, the purge step time may be adjusted depending on the target gas concentration.

[0060] The target gas supply amount may be determined using an arithmetic expression that is automatically determined depending on the target gas concentration in the adsorption step A1 of the immediately preceding separation cycle CA.

[0061] The target gas concentration used to adjust the target gas supply rate is preferably the average value of the target gas concentration in the feed gas at two or more time points in the adsorption step A1. Furthermore, the target gas concentration used to adjust the target gas supply rate is more preferably the average value of the target gas concentration in the feed gas obtained at predetermined time intervals in the adsorption step A1. Specifically, the target gas concentration is more preferably the average value of the target gas concentration in the feed gas obtained at predetermined time intervals between 1 and 10 seconds in the adsorption step A1. Furthermore, the target gas concentration is even more preferably the average value of the target gas concentration in the feed gas obtained at predetermined time intervals between 1 and 5 seconds in the adsorption step A1.

[0062] [Separation process A3] Fig. 5 shows the gas separation apparatus 100 in a state in which the separation step A3 is being performed. As shown in Fig. 5, in the separation step A3, valves V2, V3, and V5 are closed and valve V10 is opened, in a state in which the purge step A2 is being performed (see Fig. 4). As a result, the target gas adsorbed in the adsorption unit 10A in the adsorption step A1 and the purge step A2 is supplied to the target gas storage tank 2 via path L10 due to the pressure difference between the adsorption unit 10A and the target gas storage tank 2.

[0063] The target gas supplied to and stored in the target gas storage tank 2 is appropriately discharged to the outside of the gas separation apparatus 100 through a path L13 by a compressor 5. The target gas remaining in the target gas storage tank 2 without being discharged to the outside of the gas separation apparatus 100 is used as a purge gas in the above-mentioned purge steps A2 and B2.

[0064] In the separation step A3, in addition to the above-mentioned valve operations, the valves V7, V9, and V14 are closed, and the auxiliary adsorption unit 11A is in a resting state.

[0065] As described above, if the target gas concentration in the adsorption step A1 of the current separation cycle CA is higher than the target gas concentration in the adsorption step A1 of the previous separation cycle CA, the pressure in the adsorption section 10A and the auxiliary adsorption section 11A will be lower than in the previous separation cycle CA, resulting in a decrease in the amount of target gas recovered from the adsorption section 10A to the target gas storage tank 2 in the separation step A3.

[0066] Furthermore, as described above, if the target gas concentration in the adsorption step A1 of the current separation cycle CA is lower than the target gas concentration in the adsorption step A1 of the previous separation cycle CA, the pressure in the adsorption section 10A and the auxiliary adsorption section 11A increases compared to that in the previous separation cycle CA, which increases the amount of target gas recovered from the adsorption section 10A to the target gas storage tank 2 in the separation step A3.

[0067] As described above, in the gas separation method of this embodiment, the target gas supply amount in the purge step A2 is adjusted according to the target gas concentration in the adsorption step A1. Therefore, even if the target gas concentration in the adsorption step A1 of the current separation cycle CA is higher than the target gas concentration in the adsorption step A1 executed in the immediately previous separation cycle CA and the amount of target gas recovered from the adsorption section 10A to the target gas storage tank 2 in the separation step A3 of the current separation cycle CA is reduced compared to that in the immediately previous separation cycle CA, the target gas supply amount in the purge step A2 of the current separation cycle CA can be reduced compared to the target gas supply amount in the purge step A2 of the immediately previous separation cycle CA, thereby preventing a shortage of the target gas stored in the target gas storage tank 2. Conversely, even if the target gas concentration in the adsorption step A1 of the current separation cycle CA is lower than the target gas concentration in the adsorption step A1 executed in the previous separation cycle CA and the amount of target gas recovered from the adsorption section 10A to the target gas storage tank 2 in the separation step A3 of the current separation cycle CA is increased compared to that in the previous separation cycle CA, the target gas supply amount in the purge step A2 of the current separation cycle CA can be made larger than the target gas supply amount in the purge step A2 of the previous separation cycle CA, thereby preventing the amount of target gas stored in the target gas storage tank 2 from becoming excessive. This makes it easy to continue separating the target gas from the raw material gas even if the target gas concentration in the raw material gas fluctuates.

[0068] The time for performing the separation step A3 may be adjusted in accordance with the time for performing the rinsing step A5.

[0069] [Recovery process A4] FIG. 6 shows the gas separation apparatus 100 in a state in which the recovery step A4 is being performed. As shown in FIG. 6, in the recovery step A4, valve V10 is closed and valves V5 and V12 are opened, while the separation step A3 is being performed (see FIG. 5). As a result, the gas in auxiliary adsorption section 11A, which was paused during the separation step S3, is supplied to adsorption section 10A due to the pressure difference between auxiliary adsorption section 11A and adsorption section 10A. The gas supplied to adsorption section 10A purges adsorption section 10A, is discharged from adsorption section 10A, and is recovered in the raw material gas storage tank 1 via path L11. The gas recovered in the raw material gas storage tank 1 is mixed with the introduced gas supplied from path L1 and then used as the raw material gas in the subsequent adsorption steps A1 and B5.

[0070] [Rinse process A5] FIG. 7 shows the gas separation apparatus 100 in a state in which the rinsing step A5 is being performed. As shown in FIG. 7, in the rinsing step, valve V7 is opened from the state in which the recovery step is being performed (see FIG. 6). As a result, the non-adsorbed gas stored in the non-adsorbed gas storage tank 3 is supplied to the auxiliary adsorption unit 11A via path L8A as a countercurrent purge gas. The non-adsorbed gas supplied to the auxiliary adsorption unit 11A replaces and desorbs the target gas adsorbed by the adsorbent in the auxiliary adsorption unit 11A. The gas containing the non-adsorbed gas and the target gas replaced and desorbed from the adsorbent passes through the auxiliary adsorption unit 11A and is recovered in the source gas storage tank 1 via the adsorption unit 10A and path L11.

[0071] In the rinsing step A5 of this embodiment, the non-adsorbed gas stored in the non-adsorbed gas storage tank 3 is supplied to the auxiliary adsorption section 11A via path L8A as a countercurrent purge gas, but the non-adsorbed gas discharged from the auxiliary adsorption section 11B in the adsorption step B5, which is performed in parallel with the rinsing step A5, may also be supplied directly to the auxiliary adsorption section 11A as a countercurrent purge gas.

[0072] As described above, in the separation cycle CA of the gas separation method of this embodiment, the target gas and non-adsorbed gases as components other than the target gas can be continuously separated from the source gas by repeatedly performing the adsorption step A1, purging step A2, separation step A3, recovery step A4, and rinsing step A5 in this order. However, in the gas separation method of this embodiment, it is preferable to perform the pressure equalization step A6 after the rinsing step A5.

[0073] [Equal pressure pressurization process A6] Fig. 8 shows the gas separation apparatus 100 in a state in which the pressure equalization step A6 is being performed. As shown in Fig. 8, in the pressure equalization step A6, valves V7 and V12 are closed and valve V9 is opened, from the state in which the rinsing step A5 is being performed (see Fig. 7). As a result, the non-adsorbed gas discharged from auxiliary adsorption section 11B is supplied to auxiliary adsorption section 11A and adsorption section 10A via path L14.

[0074] In the separation cycle CA, when returning from the pressure equalization step A6 to the adsorption step A1, the valve V9 is closed and the valves V1, V3, and V14 are opened. In this state, the raw material gas in the raw material gas storage tank 1 is supplied by the compressor 4 to the adsorption section 10A via the paths L2 and L4.

[0075] As described above, in the gas separation method of this embodiment, two separation cycles CA and CB (see FIG. 9) are performed in parallel. Specifically, in the gas separation method of this embodiment, while the adsorption step A1 is being performed, the separation step B1, the recovery step B2, and the rinsing step B3 are performed (see FIGS. 1 to 3 and 9). In addition, in the gas separation method of this embodiment, while the purging step A2 is being performed, the pressure equalization step B4 is performed (see FIGS. 4 and 9). Furthermore, in the gas separation method of this embodiment, while the separation step A3, the recovery step A4, and the rinsing step A5 are being performed, the adsorption step B5 is performed (see FIGS. 5 to 7 and 9). Furthermore, in the gas separation method of this embodiment, while the pressure equalization step A6 is being performed, the purging step B6 is performed (see FIGS. 8 and 9).

[0076] In this way, in the gas separation method of this embodiment, separation cycle CA is performed in adsorption section 10A and auxiliary adsorption section 11A, and separation cycle CB is performed in adsorption section 10B and auxiliary adsorption section 11B in parallel, thereby continuously separating non-adsorbed gas and target gas from the raw material gas.

[0077] In the gas separation method of this embodiment, the supply of the introduction gas to the raw material gas storage tank 1 via path L1, the discharge of the non-adsorbed gas from the non-adsorbed gas storage tank 3 via path L7, and the discharge of the target gas from the target gas storage tank 2 via path L13 may be performed continuously regardless of the above-mentioned steps. [Example]

[0078] <Test Example 1> Using the gas separation apparatus 100 of this embodiment, separation cycles CA and CB were performed using the valve control shown in Table 1. The conditions were as follows. In each step in Table 1, valves marked "open" are in an open state, and valves marked "-" are in a closed state.

[0079] Inlet gas: Mixture of xenon and argon (xenon concentration 10%) 2.0L / min (All the following data are at 0°C and atmospheric pressure.) Highly adsorbed component (target gas): Xenon 0.2L / min Hardly adsorbed components (non-adsorbed gas): Argon 1.8L / min Adsorption section 10A, adsorption section 10B, auxiliary adsorption section 11A, auxiliary adsorption section 11B: Stainless steel pipe 80A (inner diameter 83.1 mm) filled with 1.5 kg of activated carbon as an adsorbent to a height of 500 mm Raw gas storage tank 1: Membrane gas holder, volume 100L Target gas storage tank 2: Membrane gas holder, volume 100L Compressor 4: Diaphragm compressor 20L / min Compressor 5: Diaphragm compressor 0.2L / min Concentration meter 6: Ultrasonic gas concentration meter Sensor 9: Laser level sensor

[0080] [Table 1]

[0081] When the system was operated under the above conditions, the argon concentration discharged from the non-adsorbed gas reservoir 3 and the xenon concentration discharged from the target gas reservoir 2 settled almost constant. The results at this time are as follows: Argon concentration in xenon: 443 ppm Product xenon concentration: 99.95% Xenon concentration in argon: 387 ppm Xenon recovery rate: 99.65% Gas concentration supplied to the adsorption section during the adsorption process: Xenon 50% Adsorption pressure: 520kPa Gas volume in the target gas storage tank at the end of the purge process / pressure equalization process: 15L

[0082] Example 1 During operation under the operating conditions of Test Example 1, the conditions of the introduced gas were changed as follows. Inlet gas: Mixture of xenon and argon (xenon concentration 20%) 2.0 L / min (All the following data are at 0°C and atmospheric pressure.) Highly adsorbed component: Xenon 0.4L / min Hardly adsorbed components: Argon 1.6L / min

[0083] During operation, the gas concentration supplied to the adsorption section during the adsorption process was measured every second, and the average xenon concentration was 55%, and the average argon concentration was 45%, so the purge process / pressure equalization process was changed to 80 seconds. As a result, the amount of gas stored in target gas storage tank 2 was kept constant, and the argon concentration discharged from non-adsorbed gas storage tank 3 and the xenon concentration discharged from target gas storage tank 2 settled at an almost constant level. The results at this time are as follows. Argon concentration in xenon: 407 ppm Product xenon concentration: 99.96% Xenon concentration in argon: 523 ppm Xenon recovery rate: 99.79% Average concentration of xenon supplied to the adsorption section during the adsorption process: 55% Average argon concentration supplied to the adsorption section during the adsorption process: 45% Adsorption pressure: 490kPa Gas volume in the target gas storage tank at the end of the purge process / pressure equalization process: 15L

[0084] <Example 2> During operation under the operating conditions of Test Example 1, the conditions of the introduced gas were changed as follows. Inlet gas: Mixture of xenon and argon (xenon concentration 5%) 2.0L / min Highly adsorbed component: Xenon 0.1L / min Hardly adsorbed components: Argon 1.9L / min

[0085] During operation, the gas concentration supplied to the adsorption section during the adsorption process was measured every second, and the average xenon concentration was 45%, and the average argon concentration was 55%, so the purge process / pressure equalization process was changed to 106 seconds. As a result, the amount of gas stored in the target gas storage tank was maintained constant, and the argon concentration discharged from non-adsorbed gas storage tank 3 and the xenon concentration extracted from target gas storage tank 2 settled at an almost constant level. The results at this time are as follows. Argon concentration in xenon: 390 ppm Product xenon concentration: 99.95% Xenon concentration in argon: 297 ppm Xenon recovery rate: 99.43% Average concentration of xenon supplied to the adsorption section during the adsorption process: 45% Average argon concentration supplied to the adsorption section during the adsorption process: 55% Adsorption pressure: 550kPa Gas volume in the target gas storage tank at the end of the purge process / pressure equalization process: 15L

[0086] <Comparative Example 1> During operation under the operating conditions of Test Example 1, the conditions of introduced gas and the like were changed as follows. Inlet gas: Mixture of xenon and argon (xenon concentration 20%) 2.0L / min (All the following data are at 0°C and atmospheric pressure.) Highly adsorbed component: Xenon 0.4L / min Hardly adsorbed components: Argon 1.6L / min

[0087] During operation, the amount of gas stored in the target gas storage tank gradually decreased to zero, and operation could no longer be continued. At this time, the gas concentration supplied to the adsorption section in the adsorption process was 55% xenon, and the adsorption pressure was 490 kPa.

[0088] <Comparative Example 2> During operation under the operating conditions of Test Example 1, the conditions of the introduced gas, etc. were changed as follows: Inlet gas: Mixture of xenon and argon (xenon concentration 5%) 2.0L / min Highly adsorbed component: Xenon 0.1L / min Hardly adsorbed components: Argon 1.9L / min

[0089] During operation, the amount of gas stored in the target gas storage tank gradually increased and exceeded the storage capacity, making it impossible to continue operation. At this time, the gas concentration supplied to the adsorption section in the adsorption process was 45% xenon, and the adsorption pressure was 550 kPa. [Industrial Applicability]

[0090] The present invention relates to a gas separation method and a gas separation apparatus. [Explanation of symbols]

[0091] 1: Raw material gas storage tank 2: Target gas storage tank 3: Non-adsorbed gas storage tank 4, 5: Compressor 6: Densitometer 7: Pressure gauge 8: Pressure gauge 9: Sensor 10A, 10B: Adsorption part 11A, 11B: Auxiliary suction part L1~L16: Route V1~V15: Valves

Claims

1. A gas separation method for separating a target gas from a raw material gas by pressure swing adsorption, an adsorption step of supplying the raw material gas to an adsorption section and adsorbing the target gas in the raw material gas into the adsorption section; a purging step of supplying the target gas stored in a target gas storage tank to the adsorption section; a separation step of desorbing the target gas adsorbed in the adsorption section from the adsorption section and supplying the target gas to the target gas storage tank for storage; and a target gas supply amount, which is the amount of the target gas supplied to the adsorption section in the purging step, is adjusted according to a target gas concentration, which is the concentration of the target gas in the raw material gas supplied to the adsorption section in the adsorption step; When the target gas concentration in the adsorption step is greater than the target gas concentration in the adsorption step executed in the previous separation cycle, the target gas supply amount in the purge step is made smaller than the target gas supply amount in the purge step of the previous separation cycle, thereby maintaining the amount of the target gas stored in the target gas storage tank at a predetermined amount or more.

2. A gas separation method for separating a target gas from a raw material gas by pressure swing adsorption, comprising: an adsorption step of supplying the raw material gas to an adsorption section and adsorbing the target gas in the raw material gas into the adsorption section; a purging step of supplying the target gas stored in a target gas storage tank to the adsorption section; a separation step of desorbing the target gas adsorbed in the adsorption section from the adsorption section and supplying the target gas to the target gas storage tank for storage; and a target gas supply amount, which is the amount of the target gas supplied to the adsorption section in the purging step, is adjusted according to a target gas concentration, which is the concentration of the target gas in the raw material gas supplied to the adsorption section in the adsorption step; When the target gas concentration in the adsorption step is lower than the target gas concentration in the adsorption step executed in the previous separation cycle, the target gas supply amount in the purge step is made larger than the target gas supply amount in the purge step of the previous separation cycle, and the amount of the target gas stored in the target gas storage tank is maintained at or below a predetermined amount.

3. The gas separation method according to claim 1 or 2, wherein the target gas concentration is an average value of the concentrations of the target gas in the feed gas at two or more points in time during the adsorption step.

4. The gas separation method according to claim 3 , wherein the target gas concentration is an average value of the target gas concentration in the raw gas obtained at predetermined time intervals in the adsorption step.

5. A gas separation apparatus that separates a target gas from a raw material gas by a pressure swing adsorption method, an adsorption unit capable of adsorbing the target gas; a target gas storage tank capable of storing the target gas; a control unit that controls a separation cycle that repeats in this order the following steps: an adsorption step of supplying the raw material gas containing the target gas to the adsorption unit and adsorbing the target gas to the adsorption unit; a purging step of supplying the target gas stored in the target gas storage tank to the adsorption unit; and a separation step of desorbing the target gas adsorbed in the adsorption unit from the adsorption unit and supplying it to the target gas storage tank for storage; a concentration meter capable of measuring a target gas concentration, which is the concentration of the target gas in the raw material gas supplied to the adsorption section in the adsorption step; The control unit adjusts a target gas supply amount, which is the amount of the target gas supplied to the adsorption unit in the purging step, according to the measurement value of the concentration meter; When the target gas concentration in the adsorption process is greater than the target gas concentration in the adsorption process performed in the previous separation cycle, the control unit reduces the target gas supply amount in the purge process to be less than the target gas supply amount in the purge process of the previous separation cycle, thereby maintaining the amount of the target gas stored in the target gas storage tank at a predetermined amount or more.

6. A gas separation apparatus for separating a target gas from a raw material gas by a pressure swing adsorption method, comprising: an adsorption unit capable of adsorbing the target gas; a target gas storage tank capable of storing the target gas; a control unit that controls a separation cycle that repeats in this order the following steps: an adsorption step of supplying the raw material gas containing the target gas to the adsorption unit and adsorbing the target gas to the adsorption unit; a purging step of supplying the target gas stored in the target gas storage tank to the adsorption unit; and a separation step of desorbing the target gas adsorbed in the adsorption unit from the adsorption unit and supplying it to the target gas storage tank for storage; a concentration meter capable of measuring a target gas concentration, which is the concentration of the target gas in the raw material gas supplied to the adsorption section in the adsorption step; The control unit adjusts a target gas supply amount, which is the amount of the target gas supplied to the adsorption unit in the purging step, according to the measurement value of the concentration meter; When the target gas concentration in the adsorption process is lower than the target gas concentration in the adsorption process performed in the previous separation cycle, the control unit increases the target gas supply amount in the purge process to be greater than the target gas supply amount in the purge process of the previous separation cycle, thereby maintaining the amount of the target gas stored in the target gas storage tank at a predetermined amount or less.

7. The gas separation apparatus according to claim 5 or 6, wherein the target gas concentration is an average value of the target gas concentrations in the feed gas at two or more points in time during the adsorption step.

8. The gas separation apparatus according to claim 7 , wherein the target gas concentration is an average value of the target gas concentration in the raw material gas obtained at predetermined time intervals in the adsorption step.

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