Gas separation equipment and gas separation method

Abstract

The present invention proposes gas separation equipment capable of performing a gas separation process that does not have a cleaning step, without increasing vacuum pump power and pressure loss. The present invention comprises an adsorbent filler layer 11 that is filled with an adsorbent, an adsorption tower 12 that houses the adsorbent filler layer 11, a starting material gas supply line 13 that is for introducing a starting material gas into the adsorption tower 12, an off-gas exhaust line that is for discharging, from the adsorption tower 12, a non-adsorbed gas component, which has not been adsorbed to the adsorbent in an adsorption step, a target gas recovery line that is for discharging, from the adsorption tower 12, a target gas component which has been desorbed from the adsorbent or discharging an impurity gas component from the adsorption tower 12, a purge gas supply line 21 that is for introducing, into the adsorption tower 12, purge gas which is for desorbing the target gas component having been adsorbed to the adsorbent, a purge gas exhaust line 22 that is for discharging, from the adsorption tower 12, the purge gas which contains the target gas, and a vacuum pump VP that aspirates gas from the adsorption tower 12 to reduce the internal pressure.

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 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. The PSA typically includes a step of adsorbing the gas components onto an 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 a highly concentrated gas by adsorbing one component contained in a raw material gas. There are two types of PSA methods: a pressurization method that uses a pressure difference between pressurized and atmospheric pressure, and a suction method that uses a pressure difference between atmospheric pressure (or slightly pressurized) and reduced pressure; the latter is sometimes called the VPSA method (Vacuum Pressure Swing Adsorption).

[0004] In the VPSA method, a large amount of power is required for gas separation because a vacuum pump is used for pressure swing. Therefore, in order to reduce the amount of power required, a method without a cleaning step, such as that described in Patent Document 2, has been proposed. This method is efficient because it can omit the step of circulating the target gas desorbed by the vacuum pump back into the adsorbent packed bed as a cleaning gas.

[0005] FIG. 1 shows a gas separation facility that performs gas separation using a VPSA 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 a target gas component contained in a raw gas, an adsorption tower 12 that houses the adsorbent packed bed 11, a raw gas supply line 13 that introduces the raw gas into the adsorption tower 12, and a gas exhaust line 14 that exhausts non-adsorbed gas components that were not adsorbed by the adsorbent during the adsorption process from the adsorption tower 12 as off-gas or exhausts the target gas component desorbed from the adsorbent as target gas from the adsorption tower 12. The gas exhaust line 14 branches into an off-gas exhaust line 15 and a target gas recovery line 16. A vacuum pump VP is connected to the target gas recovery line 16, which draws gas from the adsorption tower 12 and reduces the pressure inside the adsorption tower 12. Furthermore, downstream of the vacuum pump VP, the target gas recovery line 16 branches into multiple (two in the example of Figure 1) gas separation lines (a first gas separation line 16a and a second gas separation line 16b).

[0006] The raw gas supply line 13, the off-gas exhaust line 15, and the target gas recovery line 16 are provided with on-off valves V1, V2, and V3, respectively. The first gas separation line 16a and the second gas separation line 16b are provided with on-off valves V4 and V5, respectively.

[0007] Here, a method for gas separation using the VPSA method without a cleaning step using the gas separation equipment 100 shown in Figure 1 will be described. First, as shown in Figure 1(a), in the adsorption step, only on-off valves V1 and V2 are opened, and all other on-off valves are closed. A raw material gas is introduced into the adsorption tower 12 via the raw material gas supply line 13. The target gas component contained in the raw material gas is adsorbed onto the adsorbent, and non-adsorbed gas components not adsorbed onto the adsorbent are exhausted as off-gas from the off-gas exhaust line 15 (adsorption step). Next, the desorption step is divided into several time periods. As shown in Figure 1(b), in the first time period, on-off valves V3 and V4 are opened, and gas is sucked from the adsorption tower 12 using the vacuum pump VP to reduce the pressure inside the adsorption tower 12. Impurity gas components other than the target gas component are desorbed from the adsorbent and exhausted from the adsorption tower 12 as impurity gas. The impurity gas is then recovered from the first gas collection line 16a (impurity gas removal step). 1(c), during a second time period, the on-off valve V4 is closed and the on-off valve V5 is opened to desorb the target gas component from the adsorbent, which is then exhausted from the adsorption tower 12 as the target gas, and the target gas is recovered from the second gas collection line 16b (target gas component desorption step). The desorption step is comprised of an impurity gas removal step and a target gas component desorption step.

[0008] The VPSA method does not require 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 collected in the first gas collection line 16a, and then the target gas component (e.g., CO ２ ) is separated and recovered from the second gas separation line 16b. ２ (For example, N ２ gas) and target gas (e.g., CO ２ The gas can be effectively separated from the gas.

[0009] 1 shows only one adsorption tower 12 of the gas separation facility 100, it is also possible to arrange two adsorption towers 12 in parallel, and while an adsorption step is being performed in one adsorption tower 12, a desorption step can be performed in the other adsorption tower 12. This allows for efficient gas separation.

[0010] JP-A-6-144818 Patent No. 6677181

[0011] In the VPSA method without a cleaning step disclosed in Patent Document 2, impurity gases and target gases are separated and recovered by utilizing the time-dependent change in the composition of the desorbed gas. That is, as shown in FIG. 1(a), a gas separation facility 100 is used, which has multiple branched gas separation lines 16a and 16b provided downstream of a vacuum pump VP. The gas separation lines 16a and 16b are switched over time to separate and recover impurity gases (e.g., N ２ ) and the target gas (e.g., CO ２ ) are separated and recovered. In order to effectively separate the impurity gas and the target gas in this operating mode, it is desirable to use a vacuum pump VP to suck from the off-gas discharge side where the concentration of the impurity gas increases. For example, when separating and recovering the target gas from a raw material gas that is a mixed gas of the target gas and the impurity gas using an adsorbent, the impurity gas with a low adsorption force is first separated and recovered in the first gas separation line 16a, and then the target gas is separated and recovered from the first gas separation line 16b.

[0012] On the other hand, when the target gas is separated and recovered using this operating method, a large amount of the target gas is adsorbed to the upper part (the raw material gas supply line 13 side) of the adsorbent packed bed 11. Therefore, when the target gas is separated and recovered after the impurity gas is separated and recovered, as shown in FIG. 1( b), a portion of the desorbed target gas is re-adsorbed to the lower part of the adsorbent packed bed 11. As a result, the target gas needs to be desorbed again, and the power of the vacuum pump VP required to separate the target gas increases.

[0013] Furthermore, as the height of the adsorbent packed bed 11 increases, the pressure loss increases when the target gas component adsorbed in large amounts in the upper part of the adsorbent packed bed 11 is desorbed and flows through the adsorbent packed bed 11. As a result, the target gas component in the upper part of the adsorbent packed bed 11 is not fully desorbed and the VPSA operation is performed with some of the target gas component remaining adsorbed, resulting in a decrease in the target gas recovery efficiency.

[0014] 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.

[0015] The present invention, which solves the above problems, is as follows.

[0016] an adsorption tower containing the adsorbent bed; a raw material gas supply line for introducing the raw material gas into the adsorption tower; an off-gas exhaust line for exhausting non-adsorbed gas components not adsorbed by the adsorbent in an adsorption step from the adsorption tower as off-gas; a target gas recovery line for exhausting the target gas component desorbed from the adsorbent from the adsorption tower as the target gas or exhausting impurity gas components from the adsorption tower as impurity gas; a purge gas supply line for introducing a purge gas that desorbs the target gas component adsorbed to the adsorbent into the adsorption tower; a purge gas exhaust line for exhausting the purge gas containing the target gas from the adsorption tower; and a vacuum pump connected to the gas exhaust line, which draws gas from the adsorption tower and reduces the pressure inside the adsorption tower. The term "gas separation equipment comprising the off-gas exhaust line and the target gas recovery line" includes not only a gas separation equipment in which the off-gas exhaust line and the target gas recovery line are each directly connected to the adsorption tower, but also a gas separation equipment in which the off-gas exhaust line and the target gas recovery line are partially shared, the shared portion is connected to the adsorption tower, and the off-gas exhaust line and the target gas recovery line branch off from the shared portion. The term "gas separation equipment comprising the raw gas supply line and the purge gas exhaust line" includes not only a gas separation equipment in which the raw gas supply line and the purge gas exhaust line are each directly connected to the adsorption tower, but also a gas separation equipment in which the raw gas supply line and the purge gas exhaust line are partially shared, the shared portion is connected to the adsorption tower, and the raw gas supply line and the purge gas exhaust line branch off from the shared portion.

[0017] [2] The off-gas exhaust line and the target gas recovery line are partially shared, the shared portion is connected to the adsorption tower, and the off-gas exhaust line and the target gas recovery line branch off from the shared portion. The gas separation equipment described in [1].

[0018] [3] The gas separation facility according to [1] or [2], further comprising a plurality of branched gas separation lines connected downstream of the vacuum pump, and an on-off valve provided in each of the gas separation lines.

[0019] [4] The gas separation facility according to any one of [1] to [3], further comprising a temperature regulator provided in the purge gas supply line for adjusting the temperature of the purge gas.

[0020] [5] The gas separation equipment described in [4], wherein the adsorption tower has a plurality of gas supply ports for introducing purge gas whose temperature is adjusted by the temperature regulator, and the purge gas supply line is connected to each of the plurality of gas supply ports.

[0021] [6] A gas separation method using a gas separation facility, wherein the gas separation facility comprises: an adsorbent packed bed filled with an adsorbent that adsorbs a target gas component contained in a raw material gas; an adsorption tower accommodating the adsorbent packed bed; a raw material gas supply line that introduces the raw material gas into the adsorption tower; an off-gas exhaust line that exhausts non-adsorbed gas components that were not adsorbed by the adsorbent in the adsorption step from the adsorption tower as off-gas; a target gas recovery line that exhausts the target gas component desorbed from the adsorbent from the adsorption tower as the target gas or exhausts impurity gas components from the adsorption tower as impurity gas; a purge gas supply line that introduces a purge gas that desorbs the target gas component adsorbed to the adsorbent into the adsorption tower; a purge gas exhaust line that exhausts the purge gas containing the target gas from the adsorption tower; and a vacuum pump connected to the gas exhaust line that sucks gas from the adsorption tower and reduces the pressure inside the adsorption tower. a target gas component desorption step of desorbing the target gas component adsorbed to the adsorbent, wherein the target gas component desorption step includes a purging step of circulating the purge gas from the purge gas supply line through the adsorption tower to desorb the target gas component adsorbed to the adsorbent during at least a portion of the target gas component desorption step;

[0022] [7] The gas separation method according to [6], wherein the gas separation equipment further comprises a plurality of branched gas separation lines provided downstream of the vacuum pump, and an on-off valve provided in each of the gas separation lines, wherein in the impurity gas removal step, the impurity gas is discharged from a first gas separation line among the plurality of gas separation lines, and the target gas and / or purge gas remaining in the adsorption tower are discharged from a second gas separation line among the plurality of gas separation lines during a time period other than the target gas component desorption step in the desorption step.

[0023] [8] The gas separation method according to [6] or [7], wherein the gas separation facility further includes a temperature regulator provided in the purge gas supply line for adjusting the temperature of the purge gas, and the purge gas whose temperature has been adjusted by the temperature regulator is supplied to the adsorption tower.

[0024] [9] The gas separation method according to [8], wherein the adsorption tower has a plurality of gas supply ports for introducing purge gas whose temperature has been adjusted by the temperature regulator, the purge gas supply line is connected to each of the plurality of gas supply ports, and the purge gas whose temperature has been adjusted by the temperature regulator is supplied to the adsorption tower from each of the plurality of gas supply ports.

[0025]

[10] The gas separation method according to any one of [6] to [9], wherein the target gas is carbon dioxide gas and the purge gas is hydrogen gas.

[0026] 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.

[0027] 5 is a diagram illustrating the equipment configuration of an example of a VPSA gas separation equipment that does not have a cleaning step. FIG. 6 is a diagram illustrating a first example of a gas separation equipment according to the present invention. FIG. 7 is a diagram illustrating a second example of a gas separation equipment according to the present invention. FIG. 8 is a diagram illustrating a case where the second target gas exhaust line 23 is also used for exhausting purge gas remaining in the adsorbent packed layer 11 before the adsorption step of the next cycle. 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 a fourth example of a gas separation equipment according to the present invention. FIG. 11 is a diagram illustrating a modified example of a gas separation equipment according to the present invention. FIG. 12 is a diagram illustrating a gas separation method using the gas separation equipment shown in FIG. 5 as an example.

[0028] (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: an adsorbent packed bed filled with an adsorbent that adsorbs a target gas component contained in a raw material gas; an adsorption tower containing the adsorbent packed bed; a raw material gas supply line that introduces the raw material gas into the adsorption tower; an off-gas exhaust line that exhausts non-adsorbed gas components that were not adsorbed by the adsorbent in the adsorption step from the adsorption tower as off-gas; a target gas recovery line that exhausts the target gas component desorbed from the adsorbent from the adsorption tower as the target gas or exhausts impurity gas components from the adsorption tower as impurity gas; a purge gas supply line that introduces a purge gas that desorbs the target gas component adsorbed on the adsorbent into the adsorption tower; a purge gas exhaust line that exhausts purge gas containing the target gas from the adsorption tower; and a vacuum pump connected to the gas exhaust line that sucks gas from the adsorption tower and reduces the pressure inside the adsorption tower.

[0029] Figure 2 shows a first example of a gas separation system according to the present invention. Components identical to those shown in Figure 1 are designated by the same reference numerals. The gas separation system 1 shown in Figure 2 differs from the gas separation system 100 shown in Figure 1 in that the gas separation system 1 shown in Figure 2 is provided with a purge gas supply line 21 that introduces a purge gas into the adsorption tower 12 to desorb the target gas component adsorbed on the adsorbent, and a purge gas exhaust line 22 that exhausts the purge gas containing the target gas from the adsorption tower 12. In the example shown in Figure 2, the purge gas supply line 21 is connected to the side of the middle stage of the adsorption tower 12, and the purge gas exhaust line 22 is connected to the upper part of the adsorption tower 12.

[0030] By using a gas separation equipment 1 having such a configuration, during at least a portion of the desorption process, a purge gas that desorbs the target gas components adsorbed to the adsorbent is introduced into the adsorption tower 12 from the purge gas supply line 21, thereby lowering the partial pressure of the target gas and promoting desorption of the target gas components, and purge gas containing the target gas can be exhausted from the adsorption tower 12 through the purge gas exhaust line 22, thereby reducing the power and pressure loss of the vacuum pump VP.

[0031] Next, the operation of the gas separation equipment 1 will be described. ２ and the impurity gas is N ２ Here, the case where the target gas component is CO ２ and the impurity gas is N ２ 2A, in the adsorption step, the on-off valves V1 and V2 are opened and the remaining on-off valves are closed, and CO is supplied from the raw material gas supply line 13. ２ and N ２ A raw material gas containing CO (for example, a by-product gas such as a blast furnace gas discharged from a steelworks) is introduced into the adsorption tower 12 and passed through the adsorption tower, and the non-adsorbed gas components that are not adsorbed by the adsorbent are exhausted as off-gas from the gas exhaust line 14 and the off-gas exhaust line 15. ２ is adsorbed to the upper part of the adsorbent packed layer 11, and N ２is partly adsorbed in the lower part of the adsorbent packed bed 11 or remains in the gaps between the adsorbents (adsorption step).

[0032] Next, as shown in FIG. 2( b), during the first time period of the desorption step, the on-off valves V1 and V2 are closed, and the on-off valves V3 and V8 are opened. The vacuum pump VP is used to suck gas from the adsorption tower 12, reducing the pressure inside the adsorption tower 12. The N ２ The impurity gas is desorbed from the adsorbent and discharged from the adsorption tower 12 as an impurity gas, and the impurity gas is recovered from the target gas recovery line 16 (impurity gas removal step). ２ is characterized by being discharged relatively early during suction by the vacuum pump VP. ２ The gas is vented.

[0033] Subsequently, as shown in FIG. 2( c), in the second time period of the desorption step (target gas component desorption step), the on-off valves V3 and V8 are closed, and the on-off valves V6 and V7 are opened, so that the target gas component CO 2 is supplied from the purge gas supply line 21. ２ A purge gas (e.g., H ２ The purge gas is introduced into the adsorption tower 12 through the purge gas supply line 21, and the CO ２ This reduces the partial pressure of CO from the adsorbent. ２ The desorption of the desorbed CO ２ The gas is exhausted together with the purge gas from the purge gas exhaust line 22 (purge gas treatment process). The type of purge gas is not particularly limited as long as it is a gas containing components that have a lower adsorption force to the adsorbent than the target gas components. In the example shown in Figure 2, the entire target gas component desorption process is composed of the purge gas treatment process.

[0034] Figure 3 shows a second example of a gas separation system according to the present invention. Components identical to those shown in Figure 2 are designated by the same reference numerals. The gas separation system 2 shown in Figure 3 differs from the gas separation system 1 shown in Figure 2 in that the gas separation system 2 shown in Figure 3 has multiple (two in Figure 3) branched gas separation lines (a first gas separation line 16a and a second gas separation line 16b) connected downstream of the vacuum pump VP, with on-off valves V4 and V5 provided on each of the gas separation lines 16a and 16b, and a second target gas recovery line 23 connected to the vacuum pump VP on the upper and middle sides of the adsorption column 12.

[0035] By using the gas separation equipment 2, in the desorption step, CO, which is a target gas component, is separated using a purge gas. ２ Even during periods when desorption of N is not being performed, the composition of the gas sucked by the vacuum pump VP varies with time. This allows the first gas separation line 16a and the second gas separation line 16b to be switched over at regular intervals to separate the impurity gas N. ２ gas and the target gas, CO ２ The gas can be recovered separately.

[0036] Specifically, the desorption process is divided into a plurality of time periods. As shown in FIG. 3( a), in the first time period, the on-off valves V3 and V4 are opened, the other on-off valves are closed, and the vacuum pump VP is used to suck gas from the adsorption tower 12 to reduce the pressure inside the adsorption tower 12. Then, the impurity gas component N ２ is desorbed from the adsorbent and discharged from the adsorption tower 12 as an impurity gas, and N ２ Next, as shown in FIG. 3B, in the second time period, the on-off valves V3 and V4 are closed and the on-off valves V5, V9, V10, and V11 are opened to remove CO 2 , which is a target gas component. ２ is desorbed from the adsorbent, and the target gas, CO ２ The gas is exhausted from the adsorption tower 12 and recovered through the second gas separation line 16b. Subsequently, as shown in FIG. 3(c), in a third time period, a purge gas (e.g., H ２The CO ２ The partial pressure of CO ２ The target gas is desorbed from the adsorbent, and a purge gas containing the target gas is exhausted from a purge gas exhaust line 22 (purge gas treatment step). In the example shown in FIG. 3, the target gas desorption step is partly constituted by the purge gas treatment step.

[0037] The second target gas exhaust line 23 in the gas separation equipment 2 shown in Fig. 3 can also be used as a line for discharging the purge gas remaining in the adsorbent packed bed 11 before the adsorption step of the next cycle, as shown in Fig. 4. Note that if the height of the adsorbent packed bed 11 (i.e., the adsorption tower 12) is not particularly large, the second target gas exhaust line 23 does not necessarily need to be provided.

[0038] Figure 5 shows a third example of a gas separation system according to the present invention. The same components as those shown in Figure 3 are denoted by the same reference numerals. The gas separation system 3 shown in Figure 5 differs from the gas separation system 2 shown in Figure 3 in that the purge gas supply line 21 is provided with a temperature regulator 31 for regulating the temperature of the purge gas.

[0039] For example, if the target gas component is CO ２ When CO is absorbed in the pores of 13X zeolite, ２ When using an adsorbent that adsorbs CO, all of the CO can be removed by simply reducing the pressure with the vacuum pump VP. ２ It is difficult to desorb the purge gas H ２ circulating CO ２ Even if the partial pressure is lowered, CO ２ The desorption of CO ２ The partial pressure of CO increases ２ In order to promote the desorption of CO, it is necessary to circulate a large amount of purge gas H2. ２ Another effective method for promoting desorption is to blow in a temperature-adjusted purge gas.

[0040] That is, as shown in FIG. 5, the purge gas H ２The temperature of the adsorbent increases by heating the adsorbent to a high temperature and then passing the adsorbent through the adsorption tower 12. Generally, when the temperature of the adsorbent increases, the amount of gas components adsorbed to the adsorbent decreases, so that CO 2 can be adsorbed with less vacuum pump power or a smaller purge gas flow rate. ２ Furthermore, if the adsorption step of the next cycle is started while the temperature of the adsorbent is kept elevated, the CO ２ Therefore, before proceeding to the adsorption process, the purge gas H ２ It is preferable to lower the temperature of the adsorbent by cooling the adsorbent at a low temperature and circulating the adsorbent through the adsorption tower 12. A single temperature regulator may be used both for heating the purge gas and for cooling the purge gas, or two temperature regulators may be installed side by side.

[0041] Figure 6 shows a fourth example of a gas separation system according to the present invention. Components that are the same as those shown in Figure 5 are designated by the same reference numerals. The gas separation system 4 shown in Figure 6 differs from the gas separation system 3 shown in Figure 5 in that the adsorption tower 12 is provided with a plurality of gas supply ports 32 (five in Figure 6) for introducing purge gas whose temperature has been adjusted by a temperature adjuster 31, and the purge gas supply line 21 is connected to each of the plurality of gas supply ports 32.

[0042] If the height of the adsorption tower 12 is large, the time required to heat and cool the adsorbent may become a problem in the process. Therefore, by adopting a configuration in which temperature-adjusted purge gas can be supplied from multiple gas supply ports 32 as shown in Figure 6, the time required to heat and cool the adsorbent can be significantly reduced.

[0043] (Gas Separation Method) The gas separation method according to the present invention is a method for separating and recovering a target gas component from a raw material gas by a pressure swing adsorption method using the gas separation equipment according to the present invention described above. The gas separation method according to the present invention includes: an adsorption step of circulating the raw material gas from the raw material gas supply line into the adsorption tower to adsorb the target gas component onto the adsorbent; an impurity gas removal step of exhausting the impurity gas components in the adsorption tower as the impurity gas from the target gas exhaust line; and a target gas component desorption step of desorbing the target gas component adsorbed onto the adsorbent. The target gas component desorption step is characterized in that, during at least a portion of the target gas component desorption step, the purge treatment step includes circulating the purge gas from the purge gas supply line through the adsorption tower to desorb the target gas component adsorbed onto the adsorbent, and exhausting the purge gas containing the target gas from the purge gas exhaust line.

[0044] As described above, the gas separation systems 1 to 4 according to the present invention shown in FIGS. 2, 3, 5, and 6 are provided with a purge gas supply line 21 for introducing a purge gas that desorbs the target gas component adsorbed on the adsorbent into the adsorption tower 12, and a purge gas exhaust line 22 for exhausting the purge gas containing the target gas from the adsorption tower 12.

[0045] Using gas separation equipment 1 having such a configuration, a purge treatment process is provided in which, during at least a portion of the target gas component desorption process, purge gas is circulated from the purge gas supply line 21 through the adsorption tower 12 to desorb the target gas components adsorbed to the adsorbent and the purge gas containing the target gas is exhausted from the purge gas exhaust line.This reduces the partial pressure of the target gas, promotes desorption of the target gas components, and allows the purge gas containing the target gas to be exhausted from the adsorption tower 12 from the purge gas exhaust line 22, thereby reducing the power and pressure loss of the vacuum pump VP.

[0046] As the purge gas, a non-adsorbable gas that is not adsorbed by the adsorbent (for example, a gas whose adsorption amount at the gas pressure is 1 / 10 or less of the amount of the target gas adsorbed) can be used. ２ , impurity gas is N２ and when the adsorbent is zeolite, H ２ In the target gas component desorption step, during the time period when the purge gas is flowing, the vacuum pump VP can be designed and operated in a manner appropriate to the scale of the facility, such as by stopping the vacuum pump VP or by operating it at a low load with reduced output to be on standby, or by providing a plurality of adsorbent packed beds 11 in the gas separation facility 1 shown in Figure 2 and using them also for suction of adsorbent packed beds in other target gas component desorption steps.

[0047] Furthermore, it is preferable to use the gas separation equipment 2 shown in Figure 4, which further includes multiple branched gas separation lines 16a, 16b provided downstream of the vacuum pump VP and on-off valves V4, V5 provided on the gas separation lines 16a, 16b, and to discharge the impurity gas from a first gas separation line of the multiple gas separation lines in the impurity gas removal step, and to discharge both the target gas and the purge gas remaining in the adsorption tower 12 from a second gas separation line of the multiple gas separation lines in the target gas component desorption step during a time period other than the target gas component desorption step in the desorption step.

[0048] In FIG. 3, the impurity gas N ２ After the gas is collected from the first gas collection line 16a, the target gas, CO ２ is recovered from the second gas separation line 16b, and finally, purge gas H ２ is passed through the adsorption tower 12, and the target gas CO ２ and purge gas H ２ The procedure for recovering the mixed gas of N and N from the purge gas exhaust line 22 has been exemplified, but the time for which the purge gas is passed can be selected appropriately by the practitioner. ２ is collected from the first gas collection line 16a, and then a purge gas H is supplied from the purge gas supply line 21. ２ is passed through the adsorption tower 12 to produce the target gas CO ２ and purge gas H ２ The mixed gas is recovered from the purge gas exhaust line 22, and finally the target gas CO ２Alternatively, the remaining purge gas H in the adsorbent packed bed 11 may be recovered from the second gas separation line 16b before the adsorption step of the next cycle, as shown in FIG. ２ is exhausted from the purge gas exhaust line 22, the raw material gas and the remaining purge gas H ２ Purge gas H by mixing with ２ This can avoid a decrease in utilization efficiency.

[0049] Furthermore, it is preferable to use the gas separation equipment 5 shown in FIG. 5 which further includes a temperature regulator 31 provided in the purge gas supply line 21 for adjusting the temperature of the purge gas, and to supply the purge gas whose temperature has been adjusted by the temperature regulator 31 to the adsorption tower 12.

[0050] The temperature regulator 31 controls the purge gas H ２ The temperature of the adsorbent increases by heating the adsorbent to a high temperature and then passing the adsorbent through the adsorption tower 12. Generally, when the temperature of the adsorbent increases, the amount of gas components adsorbed to the adsorbent decreases, so that CO 2 can be adsorbed with less vacuum pump power or a smaller purge gas flow rate. ２ Furthermore, if the adsorption step of the next cycle is started while the temperature of the adsorbent is kept elevated, the CO ２ Therefore, before proceeding to the adsorption process, the purge gas H ２ It is preferable to lower the temperature of the adsorbent by cooling it and passing it through the adsorption tower 12 at a low temperature.

[0051] When the purge gas is heated by the temperature regulator 31, a heat source with a relatively low temperature of about 200° C. or less can be used. ２ Since this method is effective in promoting desorption, unused waste heat from steel mills, for example, can be effectively used. Also, cold energy from liquefied natural gas or liquefied hydrogen can be used as a heat source for cooling the purge gas.

[0052] It is also preferable to provide the adsorption tower 12 with a plurality of gas supply ports 32 for introducing purge gas whose temperature has been adjusted by a temperature regulator 31, connect the purge gas supply line 21 to each of the plurality of gas supply ports 32, and supply the purge gas whose temperature has been adjusted by the temperature regulator 31 to the adsorption tower 12 from each of the plurality of gas supply ports 32.

[0053] If the height of the adsorption tower 12 is large, the time required to heat and cool the adsorbent may become a process issue. However, by supplying temperature-adjusted purge gas from multiple gas supply ports 32, the time required to heat and cool the adsorbent can be significantly reduced.

[0054] The raw material gas used in the above method is not particularly limited, but by-product gases such as those discharged from blast furnaces in steelworks can be suitably used. Since the gas discharged from the purge gas exhaust line 22 is a mixed gas of the purge gas and the target gas, it is particularly preferred that the purge gas be a gas that can be mixed with the target gas and reused. For example, as shown in FIG. 2(c), the target gas may be CO ２ gas, H ２ When gas is used as a purge gas, the gas discharged is H ２ Gas and CO ２ Therefore, the discharged mixed gas contains CO ２ It can be reused as a raw material gas in chemical plants where it is converted into methane, methanol, etc. through hydrogenation reactions. ２ The CO diffusion rate in the pores of the adsorbent is also fast, so the CO ２ This is also preferable from the viewpoint of promoting the desorption of the material.

[0055] 2 to 6, the off-gas exhaust line 15 and the target gas recovery line 16 are partially shared, and the shared portion (gas exhaust line 14) is connected to the adsorption tower 12. The off-gas exhaust line 15 and the target gas recovery line 16 branch off from the shared portion (gas exhaust line 14). This is preferable in terms of strength when the adsorption tower 12 has a pressure-resistant structure. However, if the adsorption tower 12 has sufficient structural strength, the off-gas exhaust line 15 and the target gas recovery line 16 may be directly connected to the adsorption tower 12 without providing the gas exhaust line 14.

[0056] In the gas separation systems 1 to 4 shown in Figures 2 to 6, the purge gas supply line 21 is connected to the side of the middle stage of the adsorption tower 12, and the purge gas exhaust line 22 is connected to the top of the adsorption tower 12. However, as long as the purge gas can be circulated through the region where the target gas component is adsorbed by the adsorbent, their connection positions are not limited and can be any position. For example, as shown in Figure 7(a), the purge gas supply line 21 can be connected to the side of the upper stage of the adsorption tower 12, and the purge gas exhaust line 22 can be branched off from the gas exhaust line 14 connected to the adsorption tower 12. Furthermore, as shown in Figure 7(b), if the adsorption tower 12 has sufficient structural strength, the purge gas exhaust line 22 can be connected directly to the adsorption tower 12 without the gas exhaust line 14. Furthermore, a configuration in which the purge gas is circulated through an internal tube inserted into the adsorption tower 12 can also achieve similar effects.

[0057] 2 to 6, the purge gas exhaust line 22 is directly connected to the adsorption tower 12, but as shown in Fig. 7(c), the purge gas exhaust line 22 may be connected to the raw material gas supply line 13, and one gas line may branch into the raw material gas supply line 13 and the purge gas exhaust line 22. In other words, the raw material gas supply line 13 and the purge gas exhaust line 22 may be partially shared, the shared portion may be connected to the adsorption tower 12, and the raw material gas supply line 13 and the purge gas exhaust line 22 may branch from the shared portion.

[0058] In the above explanation, it is assumed that a gas separation method without a cleaning step is carried out, and a case has been described in which two adsorption towers 12 are arranged in parallel, and an adsorption step is carried out in one adsorption tower 12 while a desorption step is carried out in the other adsorption tower 12. However, this is not limited to this, and the gas separation equipment and gas separation method according to the present invention can also be applied to a case in which a cleaning step is included.

[0059] Using the gas separation equipment 3 shown in FIG. 5, the target gas is separated into CO ２ , impurities N ２ Gas, purge gas H ２ The raw material gas is impurity gas N ２ and target gas CO ２ As a mixed gas of CO ２ First, as shown in FIG. 8( a), the raw material gas was passed through the upper part of the adsorption tower 12 to adsorb CO ２ The impurity gas component N ２ Although some of the CO was adsorbed by the adsorbent, most of it remained in the gas phase between the adsorbent gaps. Next, as shown in FIG. 8(b), the impurity gas was discharged using a vacuum pump VP and a first gas separation line 16a. After the impurity gas was sufficiently discharged, the target gas CO was extracted from the adsorbent using a vacuum pump VP and a second gas separation line 16b, as shown in FIG. 8(c). ２ Subsequently, as shown in FIG. 8( d ), purge gas H ２ By circulating the gas in the adsorption tower 12, CO of the target gas component that was not desorbed from the adsorbent after suction by the vacuum pump VP is removed. ２ Desorb the purge gas H ２ Finally, as shown in FIG. 8( e), the remaining purge gas H ２ The purge gas H was again sucked by the vacuum pump VP and discharged from the second gas separation line 16b. ２ is CO ２ Since the gas is hardly adsorbed to the adsorbent, it can be discharged in a short time without placing a large load on the vacuum pump VP.

[0060] By operating in the above manner, CO２ The remaining purge gas H ２ After exhausting the CO gas, the process returned to the step shown in FIG. ２ The adsorbent that has been fully desorbed is CO ２ There are many adsorption sites, so more CO ２ In addition, the remaining purge gas H ２ and the impurity gas N in the source gas ２ Since the H supplied as a purge gas does not mix with the ２ The target gas, discharge purge gas, and residual purge gas obtained by the gas separation method of FIG. ２ and H ２ These are gases whose main components are, for example, CO ２ It can be supplied as a raw material gas to chemical plants that synthesize methane, methanol, etc. through hydrogenation treatment.

[0061] 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.

[0062] 1, 2, 3, 4, 100 Gas separation equipment 11 Catalyst packed bed 12 Adsorption tower 13 Raw material gas supply line 14 Gas exhaust line 15 Off-gas exhaust line 16 Target gas recovery line 16a First gas separation line 16b Second gas separation line 21 Purge gas supply line 22 Purge gas exhaust line 23 Second target gas supply line 31 Temperature regulator 32 Gas inlet V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11 On-off valve VP Vacuum pump

Claims

an adsorbent packed bed filled with an adsorbent that adsorbs a target gas component contained in a raw material gas; an adsorption tower containing the adsorbent packed bed; a raw material gas supply line that introduces the raw material gas into the adsorption tower; an off-gas exhaust line that discharges non-adsorbed gas components that were not adsorbed by the adsorbent in the adsorption step from the adsorption tower as off-gas; a target gas recovery line that discharges the target gas component desorbed from the adsorbent as the target gas from the adsorption tower, or discharges impurity gas components desorbed from the adsorbent as impurity gas from the adsorption tower; a purge gas supply line that introduces a purge gas that desorbs the target gas component adsorbed to the adsorbent into the adsorption tower; a purge gas exhaust line that exhausts the purge gas containing the target gas from the adsorption tower; and a vacuum pump connected to the gas exhaust line that sucks gas from the adsorption tower and reduces the pressure inside the adsorption tower.

2. The gas separation equipment described in claim 1, wherein the off-gas exhaust line and the target gas recovery line are partially shared, the shared portion is connected to the adsorption tower, and the off-gas exhaust line and the target gas recovery line branch off from the shared portion.

3. The gas separation facility according to claim 1 or 2, further comprising a plurality of branched gas separation lines connected downstream of the vacuum pump, and an on-off valve provided on each of the gas separation lines.

4. A gas separation facility according to any one of claims 1 to 3, further comprising a temperature regulator provided in the purge gas supply line for adjusting the temperature of the purge gas.

5. The gas separation equipment described in claim 4, wherein the adsorption tower has a plurality of gas supply ports for introducing purge gas whose temperature is adjusted by the temperature regulator, and the purge gas supply line is connected to each of the plurality of gas supply ports.

6. A gas separation method using gas separation equipment, the gas separation equipment comprising: an adsorbent packed bed filled with an adsorbent that adsorbs a target gas component contained in a raw material gas; an adsorption tower accommodating the adsorbent packed bed; a raw material gas supply line that introduces the raw material gas into the adsorption tower; an off-gas exhaust line that exhausts non-adsorbed gas components that were not adsorbed by the adsorbent in the adsorption step from the adsorption tower as off-gas; a target gas recovery line that exhausts the target gas component desorbed from the adsorbent from the adsorption tower as the target gas or exhausts impurity gas components from the adsorption tower as impurity gas; a purge gas supply line that introduces a purge gas that desorbs the target gas component adsorbed to the adsorbent into the adsorption tower; a purge gas exhaust line that exhausts the purge gas containing the target gas from the adsorption tower; and a vacuum pump connected to the gas exhaust line that sucks gas from the adsorption tower and reduces the pressure inside the adsorption tower, the gas separation method comprising: a target gas component desorption step of desorbing the target gas component adsorbed to the adsorbent, wherein the target gas component desorption step includes a purging step of circulating the purge gas from the purge gas supply line through the adsorption tower to desorb the target gas component adsorbed to the adsorbent during at least a portion of the target gas component desorption step; 7. The gas separation method according to claim 6, wherein the gas separation equipment further comprises a plurality of branched gas separation lines provided downstream of the vacuum pump, and an on-off valve provided on each of the gas separation lines, wherein in the impurity gas removal step, the impurity gas is discharged from a first gas separation line of the plurality of gas separation lines, and the target gas and / or purge gas remaining in the adsorption tower are discharged from a second gas separation line of the plurality of gas separation lines during a time period other than the target gas component desorption step in the desorption step.

8. A gas separation method according to claim 6 or 7, wherein the gas separation equipment further comprises a temperature regulator provided in the purge gas supply line for adjusting the temperature of the purge gas, and the purge gas whose temperature has been adjusted by the temperature regulator is supplied to the adsorption tower.

9. The gas separation method according to claim 8, wherein the adsorption tower has a plurality of gas supply ports for introducing purge gas whose temperature has been adjusted by the temperature regulator, the purge gas supply line is connected to each of the plurality of gas supply ports, and the purge gas whose temperature has been adjusted by the temperature regulator is supplied to the adsorption tower from each of the plurality of gas supply ports.

10. A gas separation method according to any one of claims 6 to 9, wherein the target gas is carbon dioxide gas and the purge gas is hydrogen gas.

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