Gas separation facility and gas separation method

Abstract

The present invention suggests a gas separation facility capable of performing gas separation processing that does not increase loss in power or pressure of a vacuum pump and that does not involve a cleaning step. The present invention comprises: two or more adsorbent filling layers 21a, 21b which are disposed in series in a flowing direction of a raw material gas; adsorption columns 22a, 22b which respectively accommodate the adsorbent filling layers 21a, 21b in a separated manner; desorbed gas discharge lines 15 which discharge, as desorbed gases, gas components desorbed from an adsorbent and which are provided to the respective adsorbent filling layers 21a, 21b at raw material gas supply sides and / or discharge sides of the adsorbent filling layers 21a, 21b; open / close valves V1, V2 which are provided to the desorbed gas discharge lines; a vacuum pump VP which is connected to the desorbed gas discharge lines 15 and which sucks the gases from the adsorption columns 22a, 22b; a desorbed gas recovery line 17 which is connected to the downstream side of the vacuum pump VP and which branches into a plurality of gas recovery lines 17a, 17b; and open / close valves V4, V5 which are provided to the gas recovery lines 17a, 17b.

Description

Gas separation equipment and gas separation method

[0001] The present invention relates to a gas separation facility and a gas separation method.

[0002] Pressure Swing Adsorption (PSA) has been used as a method for separating predetermined gas components contained in a feed gas (see, for example, Patent Document 1). The PSA method is a separation method that utilizes the fact that the amount of gas components adsorbed onto an adsorbent varies depending on the gas type and its partial pressure, and typically includes a step of adsorbing the gas components onto the adsorbent (adsorption step), a step of supplying a portion of the desorbed gas desorbed in another adsorption tower as a cleaning gas in order to increase the adsorption rate of the gas components onto the adsorbent (cleaning step), and a step of desorbing the adsorbed gas components from the adsorbent to recover the gas (desorption step).

[0003] The PSA method is applied in various fields, but is often used as a method for producing highly concentrated gas by adsorbing one component contained in a raw gas. There are two types of PSA methods: a pressurization method using a pressure difference between pressurized and atmospheric pressure, and a suction method using a pressure difference between atmospheric pressure (or slightly pressurized) and reduced pressure; the latter is sometimes called a VSA method (Vacuum Swing Adsorption method). Since the PSA method uses a gas compressor and a vacuum pump to perform pressure swings, a large amount of power is required for gas separation. Therefore, methods that do not involve a cleaning process have been proposed with the aim of reducing the amount of power consumed (see, for example, Patent Document 2).

[0004] Fig. 1 shows a gas separation facility for performing gas separation by a suction-type PSA method without a cleaning process. The gas separation facility 100 shown in Fig. 1 includes an adsorbent packed bed 11 filled with an adsorbent that adsorbs gas components contained in a feed gas, an adsorption tower 12 containing the adsorbent packed bed 11, a feed gas inlet line 13 for introducing the feed gas into the adsorption tower 12, an off-gas exhaust line 14 for exhausting non-adsorbed gas components that were not adsorbed by the adsorbent in the adsorption process as off-gas, a desorption gas exhaust line 15 for exhausting desorbed gas components desorbed from the adsorbent in the desorption process as desorbed gas, a pressure release line 16 for reducing the pressure inside the adsorption tower 12, a vacuum pump VP connected to the desorption gas exhaust line 15 and for sucking gas from the adsorption tower 12 to reduce the pressure inside the adsorption tower 12, and a desorption gas recovery line 17 connected downstream of the vacuum pump VP. The desorbed gas recovery line 17 branches into a plurality of (two in the example of FIG. 1) gas recovery lines 17a and 17b.

[0005] The raw material gas introduction line 13, the off-gas exhaust line 14, and the desorption gas exhaust line 15 are provided with on-off valves V0, V6, and V1, respectively. The gas recovery lines 17a and 17b are provided with on-off valves V4 and V5, respectively. The pressure release line 16 is also provided with a pressure release valve B1.

[0006] 1 , gas separation is performed using a suction-type PSA process without a cleaning process. First, in the adsorption process, only on-off valves V0 and V6 are opened, and all other on-off valves are closed. A raw gas is introduced into adsorption tower 12 via raw gas inlet line 13. The gas components of the raw gas are adsorbed onto the adsorbent, and non-adsorbed gas components not adsorbed onto the adsorbent are exhausted as off-gas via off-gas exhaust line 14. After the adsorption process, and prior to the desorption process, on-off valves V0 and V6 are closed, and pressure release valve B1 is opened to reduce the pressure inside adsorption tower 12. The desorbed gas components desorbed from the adsorbent are then released as a release gas (pressure release process). Subsequently, pressure release valve B1 is closed, and the desorption process is performed. Specifically, the desorption process is divided into multiple time periods. First, during the first time period, on-off valves V1 and V4 are opened, and gas is sucked from the adsorption tower 12 by the vacuum pump VP to reduce the pressure inside the adsorption tower 12, and impurity gas components other than the target gas component are desorbed from the adsorbent. The desorbed impurity gas components are exhausted from the adsorption tower 12 as impurity gas, and the impurity gas is recovered from the gas recovery line 17a. Next, during the second time period, on-off valve V4 is closed and on-off valve V5 is opened, and the target gas component is desorbed from the adsorbent and exhausted from the adsorption tower 12 as target gas, and the target gas is recovered from the gas recovery line 17b.

[0007] The PSA method uses a suction method without a cleaning process. ２ and N ２ The target gas component (e.g., CO ２ ) to adsorb the target gas (e.g., CO ２ In the case of separating and recovering impurity gas components (e.g., N ２ ) is separated and recovered in the gas recovery line 17a, and then the target gas component (e.g., CO ２ ) is separated and recovered through the gas recovery line 17b. ２ (For example, N ２ gas) and target gas (e.g., CO ２ The gas can be effectively separated from the gas.

[0008] In the gas separation equipment 100 shown in FIG. 1, two adsorption towers 12 are arranged in parallel, and while an adsorption process is being performed in one adsorption tower 12 (e.g., the left adsorption tower), a desorption process can be performed in the other adsorption tower 12 (e.g., the right adsorption tower), thereby enabling efficient gas separation.

[0009] JP-A-6-144818 Patent No. 6677181

[0010] Using the gas separation equipment shown in Figure 1, a raw material gas (e.g., CO) is separated by a suction-type PSA method without a cleaning process. ２ and N ２ The target gas component (e.g., CO ２ ) to adsorb the target gas (e.g., CO ２ In the case of separating and recovering impurity gas components (e.g., N) that have a low adsorption power to the adsorbent, as described above, in the desorption step, ２ ) is separated and recovered in the gas recovery line 17a, and then the target gas component (e.g., CO ２ ) is separated and recovered from the gas recovery line 17b, thereby ２ (For example, N ２ gas) and target gas (e.g., CO ２ The gas can be effectively separated from the gas.

[0011] On the other hand, when the target gas is separated and recovered using the above-mentioned operation method, the target gas components (e.g., CO ２ ) are adsorbed in large amounts by the adsorbent in the upper part of the adsorbent packed bed 11. ２ When the target gas component is separated and recovered after the separation and recovery of the target gas component, the desorbed target gas component is re-adsorbed by the adsorbent in the lower part of the adsorbent packed bed, as shown in Figure 2. As a result, the power of the vacuum pump VP required to separate the target gas component increases.

[0012] Furthermore, as the height of the adsorbent packed bed 11 increases, the pressure loss increases when the target gas component adsorbed in large amounts by the adsorbent in the upper part of the adsorbent packed bed 11 is desorbed and flows through the adsorbent. As a result, the PSA operation is performed without the target gas component being sufficiently desorbed, and the target gas recovery efficiency decreases.

[0013] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to propose a gas separation facility that can perform gas separation treatment without a cleaning step, without increasing the power and pressure loss of the vacuum pump.

[0014] The present invention, which solves the above problems, is as follows.

[0015] [1] A gas separation facility comprising: two or more adsorbent packed beds filled with an adsorbent that adsorbs specific components contained in a raw material gas and arranged in series in a flow direction of the raw material gas; one adsorption tower accommodating all of the two or more adsorbent packed beds, or two or more adsorption towers accommodating the two or more adsorbent packed beds separately; a desorption gas exhaust line provided for each of the two or more adsorbent packed beds on at least one of the raw material gas supply side or discharge side of the two or more adsorbent packed beds, for exhausting gas components desorbed from the adsorbent in the adsorbent packed bed as desorbed gas; a first on-off valve provided in the desorption gas exhaust line; a vacuum pump connected to the desorption gas exhaust line and for sucking gas from the adsorption tower to reduce the pressure inside the adsorption tower; a desorption gas recovery line connected downstream of the vacuum pump and branching into a plurality of gas recovery lines; and a second on-off valve provided in the gas recovery line.

[0016] [2] The gas separation facility according to [1], further comprising a pressure relief line connected downstream of an adsorption tower containing the most downstream adsorbent packed bed among the two or more adsorbent packed beds, the pressure relief line having a pressure relief valve for reducing the pressure inside the adsorption tower.

[0017] [3] A method for separating and recovering target gas components from a raw gas by pressure swing adsorption using the gas separation equipment described in [1] or [2] above, the method comprising: an adsorption step of adsorbing gas components onto the adsorbents in the two or more adsorbent packed layers; and a desorption step of desorbing the gas components adsorbed onto the adsorbents in the adsorption step to recover desorbed gases; and no cleaning step of supplying a portion of desorbed gas from another adsorption tower as cleaning gas to the adsorption tower, characterized in that the desorption step is divided into a plurality of time zones, and the plurality of gas recovery lines are switched by the second on-off valve for each of the plurality of time zones to recover the desorbed gas.

[0018] [4] The gas separation method according to [3], wherein the desorption step is started in a state in which a first on-off valve provided in a desorption gas exhaust line connected to an adsorption tower accommodating an adsorbent packed bed that is not the most downstream of the two or more adsorbent packed beds is opened and a first on-off valve provided in an off-gas exhaust line connected to an adsorption tower accommodating an adsorbent packed bed that is not the most downstream of the two or more adsorbent packed beds is closed, and then at least one of the first on-off valves that is closed is opened to recover the desorbed gas.

[0019] According to the present invention, gas separation treatment without a cleaning step can be carried out without increasing the power and pressure loss of the vacuum pump.

[0020] FIG. 5 is a diagram illustrating the equipment configuration of an example of a PSA gas separation equipment that does not have a cleaning process. FIG. 6 is a diagram illustrating the readsorption behavior of a target gas component desorbed in an adsorbent-packed tank in a PSA gas separation equipment that does not have a cleaning process. FIG. 7 is a diagram illustrating a first example of a gas separation equipment according to the present invention. FIG. 8 is a diagram illustrating a second example of a gas separation equipment according to the present invention. FIG. 9 is a diagram illustrating a third example of a gas separation equipment according to the present invention. FIG. 10 is a diagram illustrating an adsorption step and a pressure step in a gas separation method using the gas separation equipment shown in FIG. 3. FIG. 11 is a diagram illustrating the first half of a desorption step in a gas separation method using the gas separation equipment shown in FIG. 3. FIG. 12 is a diagram illustrating the second half of a desorption step in a gas separation method using the gas separation equipment shown in FIG.

[0021] (Gas Separation Equipment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A gas separation equipment according to the present invention is characterized by comprising two or more adsorbent packed beds filled with an adsorbent that adsorbs specific components contained in a raw material gas and arranged in series in the flow direction of the raw material gas, one adsorption tower accommodating all of the two or more adsorbent packed beds or two or more adsorption towers accommodating the two or more adsorbent packed beds separately, a desorption gas exhaust line provided for each of the two or more adsorbent packed beds on at least one of the raw material gas supply side or discharge side of the two or more adsorbent packed beds, for exhausting gas components desorbed from the adsorbent in the adsorbent packed bed as desorbed gas, a first on-off valve provided in the desorption gas exhaust line, a vacuum pump connected to the desorption gas exhaust line and for sucking gas from the adsorption tower to reduce the pressure inside the adsorption tower, a desorption gas recovery line connected downstream of the vacuum pump and branching into multiple gas recovery lines, and a second on-off valve provided in the gas recovery line.

[0022] FIG. 3 shows a first example of a gas separation system according to the present invention. Components identical to those shown in FIG. 1 are designated by the same reference numerals. The gas separation system 1 shown in FIG. 3 differs from the gas separation system 100 shown in FIG. 1 in that the gas separation system 1 shown in FIG. 3 includes two or more (two in the example shown in FIG. 3) adsorbent packed beds 21a, 21b arranged in series (i.e., along the flow direction of the raw gas) in the direction of flow of the raw gas, and two or more (two in the example shown in FIG. 3) adsorption towers 22a, 22b that individually accommodate the two or more adsorbent packed beds 21a, 21b. Accordingly, a desorption gas exhaust line 15 for exhausting gas components desorbed from the adsorbents in the adsorbent packed beds 21a, 21b as desorbed gas is provided for each of the two or more adsorbent packed beds 21a, 21b on at least one of the raw gas supply side or discharge side of the two or more adsorbent packed beds 21a, 21b. In addition, on-off valves (first on-off valves) V1 and V2 are also provided on each desorption gas exhaust line 15. Furthermore, on-off valves V7 and V8 are provided in the off-gas exhaust line 14 between the two adsorption towers 22a and 22b. The on-off valves V7 and V8 enable the exhaust of desorbed gas from the adsorption tower 22a and the exhaust of desorbed gas from the adsorption tower 22b to be carried out independently in the desorption step. This makes it possible to appropriately select whether to exhaust desorbed gas from only one of the adsorption towers 22a and 22b or to simultaneously exhaust desorbed gas from both adsorption towers 22a and 22b, depending on the amount of impurity gas remaining in the adsorption towers 22a and 22b.

[0023] In the gas separation equipment 1 illustrated in FIG. 3, the adsorbent packed bed 21a (adsorption tower 22a) arranged on the upstream side is used to adsorb a target gas (e.g., CO ２ The adsorbent packed bed 21b (adsorption tower 22b) on the downstream side has a height at which breakthrough of the target gas occurs during the adsorption step, and the adsorbent packed bed 21b (adsorption tower 22b) on the downstream side has a height at which breakthrough of the target gas does not occur during the adsorption step.

[0024] In the gas separation equipment 1 shown in Figure 3, during the second time period of the desorption step, the on-off valves V1, V5, V7, and V8 are opened, and the target gas components adsorbed to the adsorbent in the adsorbent packed bed 21a packed in the adsorption tower 22a are desorbed by the vacuum pump VP, and the desorbed gas is exhausted. This suppresses re-adsorption of the target gas components as shown in Figure 2, and allows the target gas to be recovered without increasing the power and pressure loss of the vacuum pump VP. Note that during the desorption step, in addition to the on-off valves V1, V5, V7, and V8, V2 may also be opened; however, closing V2 is more effective in suppressing re-adsorption of the target gas components.

[0025] 3, the gas separation equipment 1 preferably further includes a pressure release line 16 having a pressure release valve B1 for reducing the pressure inside the adsorption towers 22a and 22b, the pressure release line 16 being connected downstream of the adsorption tower 22b that houses the most downstream adsorbent packed bed 21b of the two or more adsorbent packed beds 21a and 21b. This allows the pressure inside the adsorption tower 22b to be reduced simply by releasing the pressure when the adsorption pressure in the adsorption step is high, thereby reducing the power required for suction by the vacuum pump VP.

[0026] In FIG. 3, the pressure release valve B1 and the pressure release line 16 are provided as an exhaust line independent of the off-gas exhaust line 14, but they may be configured to bypass the off-gas exhaust line 14.

[0027] Although the number of adsorbent packed beds (i.e., adsorption towers) arranged in series is two in FIG. 3 , it may be three or more. In this case, the number of adsorption towers may be determined, for example, by designing the most downstream adsorption tower to have a height at which breakthrough of the target gas does not occur during the adsorption process, and the adsorption towers other than the most downstream adsorption tower to have heights at which breakthrough of the target gas occurs during the adsorption process. Furthermore, although the two adsorbent packed beds 21 a, 21 b (i.e., adsorption towers 22 a, 22 b) are arranged vertically in FIG. 3 , they may also be arranged horizontally in series.

[0028] Figure 4 shows a second example of a gas separation system according to the present invention. Components identical to those shown in Figure 3 are designated by the same reference numerals. The gas separation system 2 shown in Figure 4 differs from the gas separation system 1 shown in Figure 3 in that a single adsorption tower 32 accommodates two or more (two in Figure 4) adsorbent packed beds 31a, 31b. The two or more (two in Figure 4) adsorbent packed beds 31a, 32b accommodated in the adsorption tower 32 are spaced apart from each other, and a desorbed gas exhaust line 15 equipped with an on-off valve V1 is connected between the two adjacent adsorbent packed beds 31a, 31b in the adsorption tower 32.

[0029] In the gas separation equipment 2 shown in Fig. 4, in the desorption step, only the on-off valves V1 and V5 are opened, and the target gas components adsorbed by the adsorbent in the adsorbent packed layer 31a packed in the adsorption tower 32 are desorbed by the vacuum pump VP, and the desorbed gas is exhausted. This suppresses re-adsorption of the target gas components as shown in Fig. 2, and allows the target gas to be recovered without increasing the power consumption and pressure loss of the vacuum pump VP.

[0030] FIG. 5 shows a third example of a gas separation system according to the present invention. Components identical to those shown in FIG. 3 are designated by the same reference numerals. The difference between the gas separation system 3 shown in FIG. 5 and the gas separation system 1 shown in FIG. 3 is that the gas separation system 3 shown in FIG. 5 additionally includes a desorbed gas exhaust line 15 equipped with an on-off valve V3 on the raw gas supply side of the most upstream adsorbent bed 21a among the two or more adsorbent beds. This configuration allows the target gas component to be desorbed from the adsorbent in the adsorption tower 22a more efficiently than the gas separation system 1 shown in FIG. 3 by driving the vacuum pump VP with only the on-off valves V1, V3, V5, V7, and V8 open during the desorption process. As with the gas separation system 1 shown in FIG. 3, the on-off valve V2 may be opened in addition to the on-off valves V1, V3, V5, V7, and V8 during the desorption process. However, closing V2 is more effective in suppressing re-adsorption of the target gas component.

[0031] Next, the operation of a gas separation system according to the present invention will be described using the gas separation system 1 shown in Figure 3 as an example. Here, the gas separation system 1 has two adsorbent packed beds 21a, 21b (i.e., adsorption towers 22a, 22b) arranged in series, each housed in an adsorption tower 22a, 22b. Two rows of the serially arranged adsorbent packed beds 21a, 21b (i.e., adsorption towers 22a, 22b) are provided. The left-hand row of adsorption towers in Figure 3 performs the adsorption process, while the right-hand row of adsorption towers performs the processes subsequent to the adsorption process (pressure release process and desorption process).

[0032] First, as shown in FIG. 6, in order to perform the adsorption step in the left adsorption towers 22a and 22b, the on-off valves V0, V7, V8, and V6 are opened, and a raw material gas (e.g., CO ２ and N ２ The target gas component (e.g., CO ２ ) are adsorbed by the adsorbent (e.g., zeolite) in the adsorbent packed layers 21a and 21b. Non-adsorbed gas components (e.g., N ２ ) is exhausted as off-gas.

[0033] 6, in the right-side adsorption towers 22a and 22b, the pressure release valve B1 and the on-off valves V7 and V8 are opened to reduce the internal pressure of the adsorption towers 22a and 22b, thereby desorbing impurity gas components from the adsorbent in the adsorbent packed bed 21b packed in the adsorption towers 22a and 22b (pressure release step). The desorbed impurity gas components are exhausted from the adsorption tower 22b as a release gas through the pressure release line 16.

[0034] Next, as shown in FIG. 7 , the adsorption process continues in the left adsorption towers 22a and 22b, while the desorption process is performed in the right adsorption towers 22a and 22b. The desorption process is divided into two time periods. In the first time period, the on-off valves V2, V4, V7, and V8 are opened, and the other on-off valves are closed. The vacuum pump VP is driven to suck gas from the adsorption tower 22b, reducing the internal pressure of the adsorption tower 22b and desorbing impurity gas components from the adsorbent in the adsorbent packed bed 21b packed in the adsorption tower 22b. The desorbed impurity gas components are exhausted as impurity gas from the adsorption tower 22b via the desorption gas exhaust line 15 and recovered via the gas recovery line 17a of the desorption gas recovery line 17.

[0035] Next, as shown in FIG. 8 , the adsorption process continues in the left adsorption towers 22a and 22b, while the desorption process is performed in the right adsorption towers 22a and 22b. Specifically, during the second time period, the on-off valve V4 is closed and the on-off valves V1 and V5 are opened to switch the gas recovery line 17 from 17a to 17b. The vacuum pump VP is then driven to suck gas from the adsorption towers 22a and 22b, reducing the internal pressure of the adsorption towers 22a and 22b and desorbing the target gas component from the adsorbent in the adsorbent packed beds 21a and 21b packed in the adsorption towers 22a and 22b. The desorbed target gas component is exhausted as the target gas from the adsorption towers 22a and 22b via the desorption gas exhaust line 15 and recovered via the gas recovery line 17b of the desorption gas recovery line 17.

[0036] In this way, the adsorption step can be performed in the left adsorption towers 22 a, 22 b, and the depressurization step and adsorption step can be performed in the right adsorption towers 22 a, 22 b. When the gas separation equipment 3 shown in Fig. 5 is used as the gas separation equipment, as shown in Fig. 9, the on-off valve V3 can be opened during the second time period of the desorption step to desorb the target gas component from the raw gas supply side of the adsorption tower 22 a as well, thereby recovering the target gas.

[0037] After the desorption step in the left adsorption towers 22 a, 22 b and the pressure release step and adsorption step in the right adsorption towers 22 a, 22 b are completed, the pressure release step and desorption step are performed in the left adsorption towers 22 a, 22 b, and the adsorption step is performed in the right adsorption towers 22 a, 22 b. By alternately repeating the adsorption step and the pressure release step and desorption step in the left and right adsorption towers 22 a, 22 b, the target gas can be efficiently separated and recovered from the raw material gas.

[0038] The above-described operation of the gas separation equipment is merely an example. By providing on-off valves V7 and V8 on each of the gas lines from the adsorption towers upstream of on-off valve V1, operation (driving) can be flexibly adjusted depending on the components of the raw gas, the type of target gas, and the like. For example, when desorbing the target gas component from the adsorbent during the second time period of the desorption step, both on-off valves V7 and V8 are open in FIG. 8 . Alternatively, only one of the on-off valves (e.g., on-off valve V7) can be opened to desorb the target gas component from the adsorbent in one adsorption tower (e.g., adsorption tower 22a), and then only the other (e.g., on-off valve V8) can be opened to desorb the target gas component from the adsorbent in the other adsorption tower (e.g., adsorption tower 22b). Also, although on-off valve V2 is open in FIG. 8 , it may be closed.

[0039] (Gas Separation Method) The gas separation method according to the present invention is a method for separating and recovering target gas components from a raw material gas by pressure swing adsorption using the gas separation equipment according to the present invention described above, and includes an adsorption step of adsorbing the gas components onto the adsorbents in two or more adsorbent packed layers, and a desorption step of desorbing the gas components adsorbed onto the adsorbents in the adsorption step and recovering the desorbed gas, and does not include a cleaning step of supplying a portion of the desorbed gas from another adsorption tower to the adsorption tower as a cleaning gas, characterized in that the desorption step is divided into a plurality of time zones, and the desorbed gas is recovered by switching between a plurality of gas recovery lines using a second on-off valve for each of the plurality of time zones.

[0040] As described above, the gas separation equipment according to the present invention is a gas separation system for separating raw gas (e.g., CO ２ and N ２The system includes two or more adsorbent packed beds arranged in series in the flow direction of a gas mixture (gas mixture with the target gas), one adsorption tower accommodating all of the two or more adsorbent packed beds, or two or more adsorption towers accommodating the two or more adsorbent packed beds separately, and a desorbed gas exhaust line provided for each of the two or more adsorbent packed beds on at least one of the feed gas supply side or discharge side of the two or more adsorbent packed beds, for exhausting the gas components desorbed from the adsorbent in the adsorbent packed beds as desorbed gas. This suppresses re-adsorption of the target gas components as shown in Figure 2, and enables the target gas to be recovered without increasing the power and pressure loss of the vacuum pump VP.

[0041] In the present invention, it is preferable to start the desorption step in a state in which the on-off valve (V2 in FIG. 3 ) provided in the desorption gas exhaust line 15 connected to the adsorption tower (adsorption tower 22b in FIG. 3 ) accommodating the most downstream adsorbent packed bed (adsorbent packed bed 21b in FIG. 3 ) of two or more adsorbent packed beds (adsorbent packed beds 21a and 21b in FIG. 3 ) is opened, and the on-off valve (V1 in FIG. 3 ) provided in the desorption gas exhaust line 15 connected to the adsorption tower (adsorption tower 22a in FIG. 3 ) accommodating the adsorbent packed bed that is not the most downstream adsorbent packed bed (adsorbent packed bed 21a in FIG. 3 ) of the two or more adsorbent packed beds is closed, and then open at least one of the closed on-off valves (V1, V7, and V8 in FIG. 3 ) to recover the desorbed gas.

[0042] If the on-off valves (V1, V7, and V8 in Figure 3) installed in the desorption gas exhaust line 15 connected between adjacent adsorbent packed beds 21a and 21b are left open from the start of the desorption process, some of the target gas will be desorbed along with the impurity gas, resulting in a decrease in the recovery rate of the target gas. Therefore, the desorption step is started in a state in which an on-off valve (V2 in FIG. 3 ) provided in the desorption gas exhaust line 15 connected to the adsorption tower (adsorption tower 22b in FIG. 3 ) accommodating the most downstream adsorbent packed bed (adsorbent packed bed 21b in FIG. 3 ) of two or more adsorbent packed beds (adsorbent packed beds 21a and 21b in FIG. 3 ) is opened, and an on-off valve (V1 in FIG. 3 ) provided in the desorption gas exhaust line 15 connected to the adsorption tower (adsorption tower 22a in FIG. 3 ) accommodating the non-most downstream adsorbent packed bed (adsorbent packed bed 21a in FIG. 3 ) of the two or more adsorbent packed beds is closed, and then at least one of the closed on-off valves (V1, V7, and V8 in FIG. 3 ) is opened to recover the desorbed gas. This operating method can suppress a decrease in the recovery rate of the target gas.

[0043] The opening and closing operation of the on-off valve does not necessarily have to coincide with the switching timing of the gas recovery lines 17a, 17b downstream of the vacuum pump. For example, after the gas recovery lines 17a, 17b downstream of the vacuum pump VP are switched, the on-off valve V1 provided in the desorption gas exhaust line 15 connected between adjacent adsorbent packed beds may be opened after a predetermined time has elapsed.

[0044] According to the present invention, gas separation treatment without a cleaning step can be carried out without increasing the power and pressure loss of the vacuum pump.

[0045] 1, 2, 3, 100 Gas separation equipment 11, 21a, 21b, 31a, 31b Adsorbent packed bed 12, 22a, 22b, 32 Adsorption tower 13 Raw material gas introduction line 14 Off-gas exhaust line 15 Desorption gas exhaust line 16 Pressure release line 17 Desorption gas recovery line 17a, 17b Gas recovery line B1 Pressure release valve V0, V1, V2, V3, V4, V5, V6, V7, V8 On-off valve VP Vacuum pump

Claims

1. A gas separation facility comprising: two or more adsorbent packed beds filled with an adsorbent that adsorbs gas components contained in a raw material gas and arranged in series in the flow direction of the raw material gas; one adsorption tower accommodating all of the two or more adsorbent packed beds, or two or more adsorption towers accommodating the two or more adsorbent packed beds separately; a desorption gas exhaust line provided for each of the two or more adsorbent packed beds on at least one of the raw material gas supply side or discharge side of the two or more adsorbent packed beds, for exhausting gas components desorbed from the adsorbent in the adsorbent packed beds as desorbed gas; a first on-off valve provided in the desorption gas exhaust line; a vacuum pump connected to the desorption gas exhaust line and for sucking gas from the adsorption tower to reduce the pressure inside the adsorption tower; a desorption gas recovery line connected downstream of the vacuum pump and branching into a plurality of gas recovery lines; and a second on-off valve provided in the gas recovery line.

2. The gas separation facility according to claim 1, further comprising a pressure relief line connected downstream of the adsorption tower containing the most downstream adsorbent packed bed among the two or more adsorbent packed beds, the pressure relief line having a pressure relief valve for reducing the pressure inside the adsorption tower.

3. A method for separating and recovering target gas components from a raw gas by pressure swing adsorption using the gas separation equipment described in claim 1 or 2, comprising an adsorption step in which the gas components are adsorbed onto the adsorbent in the two or more adsorbent packed layers, and a desorption step in which the gas components adsorbed onto the adsorbent in the adsorption step are desorbed and the desorbed gas is recovered, but no cleaning step in which a portion of the desorbed gas from another adsorption tower is supplied to the adsorption tower as cleaning gas, characterized in that the desorption step is divided into a plurality of time periods, and the desorbed gas is recovered by switching the plurality of gas recovery lines using the second on-off valve for each of the plurality of time periods.

4. The gas separation method according to claim 3, wherein the desorption step is initiated with a first on-off valve provided in a desorption gas exhaust line connected to an adsorption tower accommodating an adsorbent layer that is not the most downstream of the two or more adsorbent layers being opened and a first on-off valve provided in an off-gas exhaust line connected to an adsorption tower accommodating an adsorbent layer that is not the most downstream of the two or more adsorbent layers being closed, and then at least one of the closed first on-off valves is opened to recover the desorbed gas.

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