JP6502921B2 - Purification method of target gas - Google Patents

Description

  The present invention relates to a method and apparatus for purifying a target component gas by removing impurity components from a mixed gas containing the target component such as hydrogen by using a pressure fluctuation adsorption method.

  In recent years, hydrogen has attracted attention as an energy source to replace hydrocarbons, such as a fuel cell raw material, and as an energy storage medium of energy having a large output fluctuation such as wind power generation and solar power generation. As a method of producing hydrogen, for example, a method of separating from hydrogen-containing gas such as coke oven gas (hereinafter referred to as "COG" appropriately) and a method of obtaining it by reforming a hydrocarbon-based material such as natural gas or methanol are known. There is. Coke oven gas contains light hydrocarbons such as carbon monoxide, carbon dioxide and methane as impurities in addition to hydrogen as the main component, and further heavy hydrocarbons, BTX (benzene, toluene, xylene), sulfur compounds Includes a small amount of etc. A pressure fluctuation adsorption method (hereinafter referred to as "PSA method") is known as a representative method for purifying such hydrogen-containing gas to obtain high purity hydrogen gas. For purification of hydrogen gas by PSA method, for example, a mixed gas containing hydrogen is introduced into an adsorption tank filled with an adsorbent under high pressure to adsorb impurities to the adsorbent, and hydrogen-enriched hydrogen-enriched gas And a step of depressurizing the inside of the adsorption tank to desorb the impurities from the adsorbent and discharging the gas from the adsorption tank.

  When purifying hydrogen from COG by the PSA method, impurities such as heavy hydrocarbons, BTX, and sulfur compounds contained in the COG may be removed before purification by the PSA method in order to reduce the purification ability of the PSA. desirable. As a method of removing these specific impurities, for example, there is a pre-adsorption method (hereinafter referred to as "pre-adsorption"). In pre-adsorption, an adsorption tank (hereinafter referred to as "pre-adsorption tank") filled with an adsorbent for adsorbing impurities is placed prior to the PSA method to adsorb and remove impurities from COG. In this pre-adsorption, a method of flowing COG in one direction in the pre-adsorption tank to remove these impurities and replacing it with a new adsorption tank before the impurities break through the pre-adsorption tank (Patent Document 1), a PSA method There is a method (Patent Document 2) of regenerating the pre-adsorption tank by desorbing impurities from the pre-adsorption tank (pre-filter) in conjunction with the main adsorption tank which performs

  However, in the case where the adsorption tank is replaced before the impurities are breakthrough as in Patent Document 1, it is necessary to make the adsorption tank larger in order to reduce the replacement frequency. In addition, when the pre-adsorption tank is regenerated in conjunction with the PSA method as in Patent Document 2, the life of the pre-adsorption tank becomes longer than in the method of replacing the pre-adsorption tank, and the cost can be reduced. Impurities removed by adsorption are more likely to enter the main adsorption tank of the PSA method.

Japanese Examined Patent Publication 3-9391 Japanese Examined Patent Publication 8-32549

  The present invention has been conceived under such circumstances, and in purifying the target gas from the mixed gas containing the target component, the high purity target gas is efficiently recovered by using the PSA method. It is an object of the present invention to provide a method and apparatus suitable for preventing the influence of the impurity component on the adsorbent, among the impurities, among the components that reduce the purification ability of the PSA adsorbent.

  The method for purifying a target gas provided by the first aspect of the present invention is a method for purifying a target gas from a mixed gas containing a target component and a plurality of impurity components, wherein the impurity components are selectively adsorbed. The mixed gas is introduced into the adsorption unit while the adsorption unit is at a relatively high pressure by a pressure fluctuation adsorption method performed using a plurality of adsorption units filled with the adsorbent to An adsorption step of adsorbing the above-mentioned impurity component of the above to the adsorbent and discharging the target component-enriched gas enriched from the target component from the adsorption unit, and decompressing the adsorption unit to discharge the gas from the adsorption unit In the target gas purification method in which the cycle including the pressure reduction step is repeated in each of the adsorption units, the adsorption units are connected in series. And a second adsorption tank, and in the decompression step, the on-off valve provided between the first and second adsorption tanks does not communicate with the state in which the first and second adsorption tanks are in communication It is characterized by switching to the state.

  The inventor conducted the following factor analysis to solve the above-mentioned problems. First, in order to extend the life of the pre-adsorption tank (reduce the frequency of replacement of the adsorbent in the tank), regeneration of the pre-adsorption tank by synchronizing the adsorption / desorption of the pre-adsorption tank with the purification cycle by the PSA method is necessary. Also, for example, when the source gas is COG, in order to recover more hydrogen (target gas) from the COG, it is desirable that the hydrogen contained in the pre-adsorption tank can also be recovered before the regeneration step. However, when trying to recover hydrogen in the pre-adsorption tank, there is a possibility that the impurities removed by the pre-adsorption are also recovered at the same time. Once these impurities are recovered, these impurities are difficult to be desorbed, so the hydrogen purification ability in the PSA method is significantly degraded. Therefore, even if the pre-adsorption tank is synchronized with the PSA method, it has been necessary to use an excessive pre-adsorption tank so that the above-mentioned impurities are not recovered to the main adsorption tank.

  The inventors of the present invention have conducted intensive studies to solve the above problems, and have found that an automatic valve (open / close valve) is provided between the pre-adsorption tank (first adsorption tank) and the main adsorption tank (second adsorption tank) performing PSA. The system is based on the installation and recovery of the gas in the pre-adsorption tank only during the process in which the pre-adsorbed impurities are difficult to flow to the main adsorption tank. It has been found that it is possible to reduce the possibility of impurity inflow from the pre-adsorption tank to the main adsorption tank while improving the recovery rate. Further, as described above, by reducing the possibility of the inflow of impurities from the pre-adsorption tank to the main adsorption tank, the pre-adsorption tank can be made compact to an appropriate size.

  Preferably, the depressurizing step includes a step of introducing a gas mainly composed of a target component in the first adsorption tank into the second adsorption tank while communicating the first and second adsorption tanks with each other. Discharging the gas mainly containing the impurity component in the first adsorption tank to the outside without communicating the first and second adsorption tanks.

  Preferably, in the step of introducing the gas mainly containing the target component into the second adsorption tank, the gas in the second adsorption tank is introduced into the other second adsorption tank, and the impurity component is introduced. The step of discharging the main gas to the outside is performed after the step of introducing the gas mainly containing the target component into the second adsorption tank.

  Preferably, a plurality of the first adsorption vessels are provided in parallel with each other with respect to the corresponding second adsorption vessels in series, and the second adsorption of the gas mainly composed of the target component is performed. In the step of introducing into the tank and the step of discharging the gas mainly containing the above-mentioned impurity component, the gas flow so as to allow the gas to enter and exit in any one of the plurality of first adsorption tanks provided in a plurality. Switch the state.

  Preferably, the first adsorption tank is filled with a first adsorbent which selectively adsorbs at least one of the plurality of impurity components, and the second adsorption tank contains the plurality of impurity components. And a second adsorbent that selectively adsorbs at least one of the other.

  Preferably, the target component is hydrogen.

  The apparatus for purifying target gas provided by the second aspect of the present invention is an apparatus for purifying a target gas from a mixed gas containing a target component and a plurality of impurity components, wherein one ends thereof are connected via a communication passage. A plurality of adsorbents which are in fluid communication with each other and which are provided with a first gas passage port and a second gas passage port and which are filled with an adsorbent which selectively adsorbs an impurity component are internally connected in series A set of first and second adsorption vessels, an on-off valve attached to the communication passage, a main trunk passage having a gas introduction end, and the set of first and second adsorption vessels are provided A first pipe having a plurality of branch paths connected to the first gas passage port side of the first adsorption tank and provided with an on-off valve; a main trunk path having a gas outlet end; Provided for each second set of adsorption tanks A second pipe having a plurality of branch paths connected to the second gas passage port side of the second adsorption tank and provided with an on-off valve, and connected to the main trunk path of the second pipe and flow rate adjusting means And a plurality of main passages provided with each of the first and second adsorption vessels, connected to the second gas passage side of the second adsorption vessel, and provided with an on-off valve. And a main trunk path provided with a flow control valve, and one end and the other end of the main trunk path, for each set of the first and second adsorption vessels A fourth pipe having a plurality of branch paths provided and connected to the second gas passage side of the second adsorption tank and having a plurality of branch valves attached thereto; a main trunk path having a gas discharge end; And each of the first and second adsorption vessels is provided for each of the first and second adsorption vessels. A plurality of branch passage connected to and closing valve on the passage port side is attached, a fifth pipe having, characterized in that it comprises a.

  Preferably, a plurality of the first adsorption vessels are provided in parallel with each other with respect to the corresponding second adsorption vessels in series, and any one of the plurality of provided first adsorption vessels is provided. A switching means is provided to switch the gas flow conditions to allow gas in and out in one.

  Preferably, the first adsorption tank is filled with a first adsorbent which selectively adsorbs at least one of the plurality of impurity components, and the second adsorption tank contains the plurality of impurity components. And a second adsorbent that selectively adsorbs at least one of the other.

The schematic structure of the gas purification apparatus which can be used for enforcing the purification method of the target gas based on this invention is represented. The gas flow state in steps 1 to 5 of the purification method of the target gas according to the present invention is shown. The gas flow state in steps 6 to 10 of the purification method of the target gas according to the present invention is shown. The gas flow state in steps 11-15 of the purification method of the target gas which concerns on this invention is represented. The gas flow state in steps 16-20 of the purification method of the target gas which concerns on this invention is represented. It is a figure which shows the principal part of the modification of the gas purification apparatus which can be used to perform the purification method of the target gas which concerns on this invention.

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

  FIG. 1 shows a schematic configuration of an example of a gas purification apparatus X1 that can be used to carry out a method for purifying a target gas according to an embodiment of the present invention. The gas purification apparatus X1 includes, for example, a first adsorption tank 10A, 10B, 10C, 10D functioning as a pre-adsorption tank, a second adsorption tank 20A, 20B, 20C, 20D functioning as a main adsorption tank, and a communication passage 16 And pipes 31 to 35, and is configured to concentrate and purify the target gas from a mixed gas containing the target gas using a pressure fluctuation adsorption method (PSA method). The mixed gas is, for example, coke oven gas (COG) when the target gas is hydrogen. COG contains, for example, carbon dioxide, carbon monoxide, methane, etc. as impurities in addition to hydrogen as the main component, and further, heavy hydrocarbons, BTX (benzene, toluene, xylene), sulfur compounds, etc. by the PSA method. It contains impurities that adversely affect hydrogen purification. The composition of the mixed gas is not particularly limited. For example, 54.0 mol% of hydrogen, 30.0 mol% of methane, 7.0 mol% of carbon monoxide, 3.0 mol% of carbon dioxide, and other light The amount of hydrocarbon is 4.0 mol%, and heavy hydrocarbon, BTX, sulfur compound, etc. is 2.0 mol%. Although the following description will be made on the assumption that the mixed gas is COG, the present invention is not limited thereto.

  The first adsorption tank 10A to 10D and the second adsorption tank 20A to 20D correspond to each other so as to form a pair, and in the present embodiment, four pairs (4 pairs) of the first and second adsorption tanks Is provided. Each pair of first and second adsorption vessels (for example, the first and second adsorption vessels 10A and 20A) are connected in series in the flow direction of the gas through the communication passage 16, and It constitutes an adsorption unit.

  Each of the first adsorption tanks 10A to 10D has gas passage ports 11 and 12 at both ends. Each of the second adsorption tanks 20A to 20D has gas passage ports 21 and 22 at both ends. Each communication passage 16 connects the first and second adsorption tanks forming the respective sets, one end of the communication passage 16 is connected to the gas passage 12, and the other end is connected to the gas passage 21. . The communication passage 16 is provided with an automatic valve 16a (16b, 16c, 16d) for switching between an open state and a closed state.

  Each of the first adsorption tanks 10A to 10D is filled with an adsorbent (first adsorbent) for selectively adsorbing heavy hydrocarbons, BTX and sulfur compounds contained in the mixed gas (COG). There is. Examples of the first adsorbent include activated carbon. In each of the second adsorption vessels 20A to 20D, an adsorbent (second adsorbent) for selectively adsorbing methane, carbon monoxide, carbon dioxide, and other light hydrocarbons contained in the mixed gas It is filled. Examples of the second adsorbent include carbon molecular sieve (CMS) and zeolite molecular sieve (ZMS). These may be used alone or in combination of two or more. In addition, when the mixed gas contains water, the second adsorbent may additionally contain alumina.

  The pipe 31 is for supplying mixed gas (raw material gas) to the first adsorption tank 10A to 10D, and a main trunk path 31 'having the raw material gas introduction end E1, and the first adsorption tank 10A to 10D The branch passages 31A to 31D are respectively connected to the gas passage openings 11 of The branch paths 31A to 31D are respectively provided with automatic valves 31a, 31b, 31c, and 31d for switching between the open state and the closed state. In addition, in the main trunk passage 31 ′ of the pipe 31, a compressor (not shown) may be provided to pressure-feed the mixed gas to the first adsorption tanks 10A to 10D.

  The pipe 32 is a flow path for taking out the product gas (target component-enriched gas) from the second adsorption tank 20A to 20D, and the main trunk path 32 ′ having the product gas outlet end E2 and the second adsorption tank 20A to 20D have branch passages 32A, 32B, 32C, 32D connected to the gas passage openings 22 respectively. The branch paths 32A to 32D are provided with automatic valves 32a, 32b, 32c and 32d for switching between the open state and the closed state, respectively. The product gas outlet end E2 of the pipe 32 is connected to, for example, a buffer tank (not shown) for temporarily storing the product gas.

  The pipe 33 is for supplying a part of the product gas flowing through the pipe 32 (main trunk path 32 ′) to the second adsorption tanks 20A to 20D, and is connected to the main trunk path 32 ′ of the pipe 32. It has a branch passage 33A, 33B, 33C, 33D connected to the gas passage 22 of each of the main adsorption passage 33 'and the second adsorption tanks 20A to 20D. The main passage 33 ′ is provided with an automatic valve 331 for switching between an open state and a closed state, and a flow control valve 332. The branch paths 33A to 33D are provided with automatic valves 33a, 33b, 33c, and 33d, respectively, for switching between the open state and the closed state.

  The pipe 34 is for connecting any two of the second adsorption tanks 20A to 20D to each other, and is connected to the main trunk path 34 'and one leg of this main trunk path 34', and the second adsorption The branch channels 34A, 34B, 34C, 34D connected to the gas passage ports 22 of the tanks 20A to 20D, respectively, and the other leg of the main trunk channel 34 'are connected to the second adsorption tanks 20A to 20D, respectively. It has branch passages 34A ', 34B', 34C ', 34D' connected to the gas passage 22. A flow control valve 341 is provided in the main passage 34 '. In the branch paths 34A to 34D and 34A 'to 34D', automatic valves 34a, 34b, 34c, 34d and 34a ', 34b', 34c ', 34d' for switching between the open state and the closed state, respectively It is provided.

  The pipe 35 is a flow path of gas (mainly desorbed gas) discharged from each of the first adsorption vessels 10A to 10D, and a main trunk path 35 'having a gas discharge end E3 and the first adsorption vessels 10A to 10D. There are branch passages 35A, 35B, 35C, 35D connected to the respective gas passage ports 11 of 10D. The branch paths 35A to 35D are provided with automatic valves 35a, 35b, 35c, 35d for switching between the open state and the closed state.

  In the present embodiment, the target gas purification method according to the present invention can be performed using the gas purification device X1 having the above configuration. Specifically, during operation of the gas purification apparatus X1, the automatic valves 16a-16d, 31a-31d, 32a-32d, 33a-33d, 34a-34d, 34a'-34d ', 35a-35d, 331, and flow rate control By appropriately switching the valves 332 and 341, a desired gas flow state is realized in the apparatus, and one cycle consisting of the following steps 1 to 20 is repeated. In one cycle of this method, in each of the first adsorption tanks 10A to 10D, an adsorption step, a pressure equalization (first pressure equalization / decompression) step, a standby step, a countercurrent pressure reduction step, a countercurrent washing step, equalization A pressure (first pressure equalization boosting) process, a standby process, a pressure equalization (second pressure equalization boosting) process, and a product gas pressure boosting process are performed. In each of the second adsorption tanks 20A to 20D, an adsorption step, a pressure equalization (first pressure equalization depressurization) step, a cocurrent pressure reduction step, a pressure equalization (second pressure equalization depressurization) step, a standby step, A countercurrent pressure reduction process, a countercurrent cleaning process, a pressure equalization (first pressure equalization and pressure increase) process, a standby process, a pressure equalization (second pressure equalization and pressure increase) process, and a product gas pressure pressurization process are performed. In the present embodiment, each of the first adsorption tanks 10A to 10D is filled with activated carbon as a first adsorbent, and the lower part (closer to the gas passage port 21) and the upper part in each of the second adsorption tanks 20A to 20D The CMS and ZMS as the second adsorbent are stacked and filled in equal amounts in the vicinity of the gas passage port 22. FIGS. 2 to 5 schematically show the flow of gas in the gas purification apparatus X1 in steps 1 to 20. FIG.

  In step 1, the gas flow state as shown in FIG. 2a is achieved, and the adsorption step is performed in the first adsorption tank 10A and the second adsorption tank 20A, the first adsorption tank 10B and the second adsorption tank 20B. In the pressure equalizing (second pressure equalizing and pressurizing) step, in the first adsorption tank 10C and the second adsorption tank 20C, the countercurrent pressure reduction step is performed in the first adsorption tank 10D and the second adsorption tank 20D. A pressure equalization (first pressure equalization) step is performed. In this step, the automatic valves 16a to 16d are opened to synchronize the first adsorption tanks 10A to 10D and the second adsorption tanks 20A to 20D. Therefore, in the first adsorption tank 10A to 10D and the second adsorption tank 20A to 20D, the first adsorption tank 10A (10B, 10C, 10D) and the second adsorption tank 20A (20B, 20C) are combined. , 20D) are in communication. The process time of step 1 is, for example, 20 seconds.

  As well understood by referring to FIGS. 1 and 2a together, in step 1, a raw material gas (mixed gas) is introduced into the first adsorption tank 10A via the pipe 31 and the gas passage port 11. The first and second adsorption vessels 10A and 20A in the adsorption step are maintained at a predetermined high pressure state, and impurities (for example, heavy hydrocarbons, BTX, sulfur compounds, etc.) in the mixed gas are absorbed by the first adsorption. It is adsorbed by the first adsorbent in the tank 10A. In addition, the gas (pre-adsorbed permeating gas) after pre-adsorption which is discharged through the gas passage port 12 of the first adsorption tank 10A (secondary adsorption tank) is transmitted through the communication passage 16 and the gas passage port 21. It will be introduced at 20A. As a result, impurities (for example, carbon monoxide, carbon dioxide, methane, etc.) in the pre-adsorbed permeation gas are adsorbed by the second adsorbent in the second adsorption tank 20A, and a product gas with high hydrogen gas concentration (hydrogen The enrichment gas is exhausted through the gas passage port 22 of the second adsorption tank 20A. The product gas is recovered from the product gas outlet E2 via the pipe 32, for example, to an external buffer tank (not shown). In the following, in order to simplify the description, the reference to the gas passage ports 11, 12, 21 and 22 which are merely the gas inlet and outlet ports will be omitted.

  The gas in the second adsorption tank 20D discharged from the second adsorption tank 20D is introduced into the second adsorption tank 20B and the first adsorption tank 10B through the pipe 34. Since the second adsorption tank 20D and the first adsorption tank 10D have previously performed the adsorption step (see step 20 shown in FIG. 5e), the second adsorption tank 20D and the inside of the first adsorption tank 10D Is higher than the pressure in the second adsorption tank 20B and the first adsorption tank 10B. Therefore, the pressure in the second adsorption tank 20D and the first adsorption tank 10D is reduced by introducing the in-tank gas from the second adsorption tank 20D into the second adsorption tank 20B and the first adsorption tank 10B. The pressure inside the second adsorption tank 20B and the first adsorption tank 10B is raised. Further, the in-tank gas from the first adsorption tank 10D is introduced into the second adsorption tank 20D via the communication passage 16. As described above, since the first adsorption tank 10D has previously performed the adsorption step, the impurity component (heavy hydrocarbon, BTX, sulfur compound, etc.) is adsorbed predominantly by the adsorbent in the first adsorption tank 10D. The gas in the tank has a high concentration of hydrogen gas which is the target gas. Such hydrogen-rich gas moves from the first adsorption tank 10D to the second adsorption tank 20D.

  In the second adsorption tank 20C and the first adsorption tank 10C, the impurities are desorbed from the first adsorbent and the second adsorbent by reducing the pressure in the countercurrent direction following step 20 (FIG. 5e). The generated desorbed gas is discharged together with the gas remaining in the second adsorption tank 20C and the first adsorption tank 10C (hereinafter, the desorption gas and the residual gas are collectively referred to as “in-tank gas”). The gas in the tank passes through the pipe 35 and is discharged from the gas discharge end E3 to the outside. In addition, an off gas tank (not shown) may be installed in the main trunk passage 35 'of the pipe 35, and the exhaust gas from the first adsorption tank may be temporarily stored in the off gas tank.

  In step 2, the gas flow state as shown in FIG. 2b is achieved, and the adsorption step continues in the first adsorption tank 10A and the second adsorption tank 20A, the second adsorption tank 20B and the first adsorption tank The product gas boosting step in 10B, the countercurrent cleaning step in the second adsorption tank 20C and the first adsorption tank 10C, the cocurrent pressure reduction step in the second adsorption tank 20D, the first adsorption tank 10D Standby process is performed. In this step, the automatic valves 16a to 16c are opened to synchronize the first adsorption tanks 10A to 10C and the second adsorption tanks 20A to 20C. On the other hand, the automatic valve 16d is in the closed state, and the first adsorption tank 10D and the second adsorption tank 20D are not in communication (in synchronization) with each other. The process time of step 2 is, for example, 70 seconds.

  As well as referring to FIGS. 1 and 2b in combination, in step 2, the mixed gas is introduced into the first adsorption tank 10A via the pipe 31 and the second adsorption tank is continued from step 1 Product gas is discharged from 20A. The product gas is recovered in the same manner as in step 1, but a portion thereof is introduced into the second adsorption tank 20B and the first adsorption tank 10B through the piping 33, and the product gas of these adsorption tanks 20B and 10B Boosting is performed. At the same time, in step 2, the gas in the adsorption tank 20D derived from the second adsorption tank 20D is introduced into the second adsorption tank 20C via the pipe 34, and the second adsorption tank 20C and the first The gas (mainly desorption gas) in the adsorption tank 10C is discharged from the gas passage port 11 side. The gas in the tank is discharged from the gas discharge end E3 to the outside through the pipe 35.

  Further, in step 2, while the cocurrent flow depressurizing step is performed in the second adsorption tank 20D, the first adsorption tank 10D is not synchronized with the second adsorption tank 20D, and a standby state in which gas does not enter or leave It is a process. If the cocurrent flow depressurizing step is performed also in the first adsorption tank 10D, the impurities adsorbed in the first adsorption tank 10D may flow into the second adsorption tank 20D through the communication passage 16. Due to this reason, the first adsorption tank 10D is a standby process without being synchronized with the cocurrent flow depressurization process of the second adsorption tank 20D.

  In step 3, a gas flow state as shown in FIG. 2c is achieved, and the adsorption step continues in the first adsorption tank 10A and the second adsorption tank 20A, the second adsorption tank 20B and the first adsorption tank The product gas boosting step continues at 10 B, the pressure equalization (first pressure equalization boosting) step at the second adsorption tank 20 C and the first adsorption tank 10 C, the pressure equalization at the second adsorption tank 20 D 2 equalization pressure reduction) step is performed. On the other hand, as in step 2, the first adsorption tank 10D is a standby process. The automatic valves 16a to 16c are open, and the automatic valve 16d is closed. The process time of step 3 is, for example, 20 seconds.

  As can be better understood by referring to FIGS. 1 and 2c together, in step 3, the mixed gas is introduced into the first adsorption tank 10A via the pipe 31 and the second adsorption tank is continued from step 2 Product gas is discharged from 20A. Part of the product gas is introduced into the second adsorption tank 20B and the first adsorption tank 10B through the pipe 33, and the pressure increase by the product gas of these adsorption tanks 20B and 10B is subsequently performed. At the same time, in step 3, the gas derived from the second adsorption tank 20D is introduced into the second adsorption tank 20C through the pipe 34, and also through the communication passage 16 to the first adsorption tank 10C. be introduced.

  In step 4, a gas flow state as shown in FIG. 2d is achieved, and the adsorption step continues in the first adsorption tank 10A and the second adsorption tank 20A, the second adsorption tank 20B and the first adsorption tank A product gas boosting step is subsequently performed at 10 B, and a standby step is performed at the second adsorption tank 20 C and the first adsorption tank 10 C. Further, the standby process is performed in the second adsorption tank 20D, and the countercurrent pressure reduction process is performed in the first adsorption tank 10D. The automatic valves 16a to 16c are open, and the automatic valve 16d is closed. The process time of step 4 is, for example, 10 seconds.

  In steps 2 and 3, while the cocurrent flow depressurization step and the pressure equalization (second pressure equalization depressurization) step are performed in the second adsorption tank 20D, the first adsorption tank 10D is the standby step, The first adsorption tank 10D has a relatively high pressure as compared to the second adsorption tank 20D. Therefore, when the second adsorption tank 20D and the first adsorption tank 10D are synchronized and the countercurrent pressure reduction process is started, a gas flow from the first adsorption tank 10D to the second adsorption tank 20D is generated, and the first adsorption tank 20D is generated. Impurities present in the adsorption tank 10D may flow into the second adsorption tank 20D via the communication passage 16. In order to prevent such a situation, only the first adsorption tank 10D is subjected to the countercurrent pressure reduction process until the pressure of the first adsorption tank 10D becomes approximately the same as that of the second adsorption tank 20D.

  As well understood by referring to FIGS. 1 and 2d together, in step 4, the mixed gas is introduced into the first adsorption tank 10A through the pipe 31 and the second adsorption tank is continued from step 3 Product gas is discharged from 20A. Part of the product gas is introduced into the second adsorption tank 20B and the first adsorption tank 10B through the pipe 33, and the pressure increase by the product gas of these adsorption tanks 20B and 10B is subsequently performed. The second adsorption tank 20C and the first adsorption tank 10C are subjected to the first pressure equalization (first pressure equalization pressurization) in the previous step 3, but in the subsequent step 6 (FIG. 3a) Wait to receive a second equalization (second equalization boosting). In the first adsorption tank 10D, impurities are desorbed from the adsorbent by reducing the pressure in the countercurrent direction, and gas in the tank (mainly desorption gas) is discharged from the first adsorption tank 10D. With regard to the second adsorption tank 20D, the internal pressure of the first adsorption tank 10D is the second adsorption tank 20D in order to carry out countercurrent pressure reduction with the first adsorption tank 10D in the later step 5 (FIG. 2e) Wait until the pressure is reduced to the same degree as the internal pressure of.

  In step 5, a gas flow state as shown in FIG. 2e is achieved, and the adsorption step continues in the first adsorption tank 10A and the second adsorption tank 20A, the second adsorption tank 20B and the first adsorption tank A product gas boosting step is continued at 10 B, and a standby step is performed at the second adsorption tank 20 C and the first adsorption tank 10 C. Further, the countercurrent pressure reduction step is performed in the second adsorption tank 20D and the first adsorption tank 10D. The automatic valves 16a to 16d are in the open state. The process time of step 5 is, for example, 80 seconds.

  As well as referring to FIGS. 1 and 2e in combination, in step 5, the mixed gas is introduced into the first adsorption tank 10A through the pipe 31 and the second adsorption tank continues from step 4 Product gas is discharged from 20A. Part of the product gas is introduced into the second adsorption tank 20B and the first adsorption tank 10B through the pipe 33, and the pressure increase by the product gas of these adsorption tanks 20B and 10B is subsequently performed. The second adsorption tank 20C and the first adsorption tank 10C continue to stand by to receive a second pressure equalization (second pressure equalization and pressure increase) in the subsequent step 6 (FIG. 3a). In the second adsorption tank 20D, impurities are desorbed from the adsorbent by reducing the pressure in the countercurrent direction, and the gas in the tank (mainly desorption gas) is discharged. The discharged gas is introduced into the first adsorption tank 10D through the communication passage 16. In the first adsorption tank 10D, the pressure in the countercurrent direction is continuously reduced to desorb the impurities from the adsorbent, and the gas in the tank (mainly desorption gas) is discharged from the first adsorption tank 10D.

  In steps 1 to 5, the pressure (adsorption pressure) in the first and second adsorption tanks 10A and 20A in the adsorption step is, for example, 0.6 to 4.0 MPaG. In Steps 1 to 5, the minimum pressure (desorption pressure) inside the first and second adsorption tanks (10C, 10D, 20C, 20D) in the countercurrent pressure reduction step is, for example, 30 to 50 kPaG, and is preferably Is the atmospheric pressure.

  Steps 1 to 5 correspond to 1⁄4 of one cycle configured by steps 1 to 20, and the process time of the steps 1 to 5 is, for example, a total of 200 seconds. The internal temperatures of the first and second adsorption tanks 10A to 10D and 20A to 20D when one cycle consisting of steps 1 to 20 is repeated are not particularly limited, but considering the temperature change according to the season, There is no problem if it is about 0 to 40 ° C.

  In steps 6 to 10, the gas flow state as shown in FIGS. 3a to 3e is achieved, and in the first adsorption tank 10A, pressure equalization (the first adsorption tank 10D in the same manner as the first adsorption tank 10D in steps 1 to 5) 1 pressure equalization), standby process, and countercurrent pressure reduction process are performed, and in the second adsorption tank 20A, pressure equalization (first pressure equalization) is performed in the same manner as the second adsorption tank 20D in steps 1 to 5 A pressure reduction step, a cocurrent flow reduction step, a pressure equalization (second pressure equalization pressure reduction) step, a standby step, and a countercurrent pressure reduction step are performed. In the first adsorption tank 10B and the second adsorption tank 20B, the adsorption step is performed in the same manner as the first adsorption tank 10A and the second adsorption tank 20A in Steps 1 to 5. In the first adsorption tank 10C and the second adsorption tank 20C, in the same manner as the first adsorption tank 10B and the second adsorption tank 20B in Steps 1 to 5, the pressure equalization (second pressure equalization and pressure increase) process, the product A gas boosting step is performed. In the first adsorption tank 10D and the second adsorption tank 20D, in the same manner as the first adsorption tank 10C and the second adsorption tank 20C in Steps 1 to 5, a countercurrent pressure reduction process, a countercurrent washing process, pressure equalization ( The first equalization pressure increase step) and the standby step are performed.

  In Steps 11 to 15, the gas flow state as shown in FIGS. 4a to 4e is achieved, and in the first adsorption tank 10A and the second adsorption tank 20A, the first adsorption tank 10C and Steps 1 to 5 in Steps 1 to 5 are obtained. Similarly to the second adsorption tank 20C, a countercurrent pressure reduction step, a countercurrent washing step, a pressure equalization (first pressure equalization pressure increase) step, and a standby step are performed. In the first adsorption tank 10B, in the same manner as the first adsorption tank 10D in Steps 1 to 5, the pressure equalization (first pressure equalization pressure reduction) process, the standby process, and the countercurrent pressure reduction process are performed, and the second adsorption In tank 20B, in the same manner as in the second adsorption tank 20D in steps 1 to 5, pressure equalization (first pressure equalization depressurization) process, cocurrent pressure reduction process, pressure equalization (second pressure equalization depressurization) process, standby process , A countercurrent depressurization step is performed. In the first adsorption tank 10C and the second adsorption tank 20C, the adsorption step is performed in the same manner as the first adsorption tank 10A and the second adsorption tank 20A in Steps 1 to 5. In the first adsorption tank 10D and the second adsorption tank 20D, in the same manner as the first adsorption tank 10B and the second adsorption tank 20B in Steps 1 to 5, the pressure equalization (second pressure equalization and pressure increase) process, the product A gas boosting step is performed.

  In steps 16 to 20, the gas flow state as shown in FIGS. 5a to 5e is achieved, and in the first adsorption tank 10A and the second adsorption tank 20A, the first adsorption tank 10B and steps 1 to 5 in steps 1 to 5 are obtained. Similar to the second adsorption tank 20B, the pressure equalization (second pressure equalization and pressure increase) process and the product gas pressure increase process are performed. In the first adsorption tank 10B and the second adsorption tank 20B, in the same manner as the first adsorption tank 10C and the second adsorption tank 20C in Steps 1 to 5, a countercurrent pressure reduction process, a countercurrent washing process, pressure equalization ( The first equalization pressure increase step) and the standby step are performed. In the first adsorption tank 10C, in the same manner as the first adsorption tank 10D in Steps 1 to 5, the pressure equalization (first pressure equalization pressure reduction) process, the standby process, and the countercurrent pressure reduction process are performed, and the second adsorption In tank 20C, in the same manner as in the second adsorption tank 20D in steps 1 to 5, pressure equalization (first pressure equalization depressurization) process, cocurrent pressure reduction process, pressure equalization (second pressure equalization depressurization) process, standby process , A countercurrent depressurization step is performed. In the first adsorption tank 10D and the second adsorption tank 20D, the adsorption step is performed in the same manner as the first adsorption tank 10A and the second adsorption tank 20A in Steps 1 to 5.

  Then, steps 1 to 20 described above are repeatedly performed in each of the first adsorption tank 10A to 10D and the second adsorption tank 20A to 20D, whereby the first and second adsorption tanks 10A, 20A to 10D are performed. The mixed gas is continuously introduced into any of the sets 20D and 20D, and a product gas with a high concentration of hydrogen gas is continuously obtained.

  In the purification method of the target gas of the present embodiment, gas separation by the PSA method is performed using a plurality of sets of first and second adsorption tanks 10A to 10D and 20A to 20D arranged in series. The first and second adsorption vessels 10A, 20A (10B, 20B, 10C, 20C, 10D, 20D) of each set are in communication via the communication passage 16, and the automatic passage 16a (16b) is connected to the communication passage 16 , 16c, 16d) are provided. Thereby, in the pressure reduction step in the gas separation by the PSA method, the first adsorption tank 10A (10B, 10C, 10D) and the second adsorption tank are closed by closing the automatic valves 16a (16b, 16c, 16d) appropriately. It becomes possible to carry out different processes without synchronization with 20A (20B, 20C, 20D). Therefore, for example, with respect to the first and second adsorption tanks 10A and 20A (10B, 20B, 10C, 20C, 10D, and 20D) to be subjected to the depressurization operation, the first adsorption step is performed as in steps 1, 6, 11, and 16. The automatic valves 16a to 16d are opened to connect the corresponding first and second adsorption tanks only in the process in which the impurities in the adsorption tanks 10A to 10D do not flow into the second adsorption tanks 20A to 20D. On the other hand, as in steps 2, 3, 4, 7, 8, 9, 12, 13, 14, 17, 18, and 19, the impurities in the first adsorption tank 10A to 10D are the second adsorption tank 20A to 20D. The automatic valves 16a to 16d are closed to prevent communication between the corresponding first and second adsorption tanks. As a result, while the recovery rate of hydrogen gas (target gas) in the product gas to be recovered is enhanced, the second adsorption tank 20A to 20D is caused by the impurities selectively adsorbed by the adsorbents in the first adsorption tank 10A to 10D. It is possible to prevent the adsorption capacity of the inner adsorbent from decreasing.

  Unlike the present embodiment, the automatic valves 16a to 16d are not provided in the communication passage 16, and the first and second adsorption tanks are communicated also in steps 2, 3, 7, 8, 12, 13, 13, 17 In the cocurrent flow depressurization step and the pressure equalization (second pressure equalization depressurization) step, the impurities adsorbed in the first adsorption tank flow into the second adsorption tank, and the adsorption capacity of the second adsorption tank is The possibility of deterioration is increased. In order to prevent this, it is necessary to increase the size of the first adsorption tank.

  The first adsorption tank 10D in step 3, the first adsorption tank 10A in step 8, the first adsorption tank 10B in step 13, and the first adsorption tank 10C in step 18 are standby steps, but these steps The automatic valves 35d, 35a, 35b and 35c may be opened to make a countercurrent pressure reduction step. Here, if the internal pressure of the first adsorption tank 10A to 10D is reduced to a pressure equal to or lower than the internal pressure of the corresponding second adsorption tank 20A to 20D, steps 4, 9, 14 and 19 are omitted. It is also good.

  As mentioned above, although specific embodiment of this invention was described, this invention is not limited to this, A various change is possible within the range which does not deviate from the thought of invention. For example, as for the configuration of the pipe forming the gas flow path in the apparatus for executing the method of purifying the target gas according to the present invention, a configuration different from the above embodiment may be adopted. The number of adsorption units (units consisting of a pair of first and second adsorption tanks) is not limited to the four-unit type shown in the above embodiment, and in the case of three or less units or five or more units But the same effect can be expected.

  The first adsorption tank 10D in steps 2 and 3, the first adsorption tank 10A in steps 7 and 8, the first adsorption tank 10B in steps 12 and 13, and the first adsorption tank 10C in steps 17 and 18 are waiting processes. However, due to conditions such as the composition of the source gas and the operating pressure, there is no risk that the impurities pre-adsorbed in the first adsorption tank (pre-adsorption tank) will flow into the second adsorption tank It is possible to freely select a process to be synchronized according to the conditions, such as a cocurrent flow depressurization process or a pressure equalization (second pressure equalization depressurization) process in synchronization with the second adsorption tank.

  Furthermore, a plurality of small-sized first adsorption tanks arranged in parallel can be connected to each of the second adsorption tanks, and it can be switched with a manual valve etc. to which first adsorption tank the gas flows. A configuration may be adopted. FIG. 6 shows the case where two first adsorption vessels (10A, 10A) are provided in parallel, and in the example shown in the figure, two first adsorption vessels (10A, 10A) are provided in the parallel branch passage 161. Three-way valves 17 and 18 for allowing the flow of gas into one of the adsorption vessels 10A and 10A are provided at the branch portion. By doing this, the replacement frequency of each pre-adsorption tank (the first adsorption tank) increases, but the volume of the first adsorption tank can be reduced, so the gas discharged at the time of pressure reduction (pressure reduction step) The amount of accompanying hydrogen gas (target gas) decreases, and it is possible to suppress a decrease in target gas recovery rate due to attaching a pre-adsorption tank in the previous step.

  Further, the target gas is not limited to the hydrogen of the above embodiment. Other than the above embodiment, the target component is a poorly adsorbed component (for example, argon) which is hardly adsorbed by the adsorbent by gas separation using the PSA method, and the easily adsorbed component selectively adsorbed by the adsorbent is the impurity component. It is possible to apply the present invention by using such a poorly adsorbed component as a target gas, as long as purification is possible in the following manner.

X1 Gas purification device 10A, 10B, 10C, 10D first adsorption tank 11 gas passage port (first gas passage port)
12 Gas passage port 16 Communication passages 16a, 16b, 16c, 16d Automatic valve 161 Branching passages 17, 18 Three-way valve (switching means)
20A, 20B, 20C, 20D second adsorption tank 21 gas passage port 22 gas passage port (second gas passage port)
31 to 35 Piping 31 ', 32', 33 ', 34', 35 'Main trunk path 31A to 31D, 32A to 32D, 33A to 33D, 34A to 34D, 34A' to 34D ', 35A to 35D Branching path 31a to 31d, 32a to 32d, 33a to 33d, 34a to 34d, 34a 'to 34d', 35a to 35d, 331 automatic valves 332, 341 flow control valves

Claims (4)

A method for purifying a target gas from a mixed gas containing a target component and a plurality of impurity components, comprising:
By the pressure fluctuation adsorption method performed by using a plurality of adsorption units filled with an adsorbent which selectively adsorbs the above-mentioned impurity component, the above-mentioned mixed gas is made to the above-mentioned adsorption unit in a state where the above-mentioned adsorption unit is relatively high pressure. And adsorb the impurity component in the mixed gas to the adsorbent, and discharge the target component-enriched gas enriched in the target component from the adsorption unit, and decompressing the adsorption unit In each of the adsorption units, a cycle including a pressure reduction step of discharging the gas from the adsorption unit and a pressure-up step of introducing the gas discharged from the other adsorption unit at a relatively high pressure to the adsorption unit In the purification method of the target gas to be repeated,
Each adsorption unit includes first and second adsorption vessels connected in series;
In the pressure reduction step, the on-off valve provided between the first and second adsorption vessels switches the state in which the first and second adsorption vessels are in communication and the state in which the first and second adsorption vessels are in communication ,
The depressurizing step includes the steps of: introducing a gas mainly composed of a target component in the first adsorption tank into the second adsorption tank while communicating the first and second adsorption tanks; Introducing the gas in the second adsorption tank into the other second adsorption tank without connecting the second adsorption tank, and the step of connecting the first and second adsorption tanks without communication Discharging the gas mainly containing the impurity component in the adsorption tank 1;
In the step of introducing the gas mainly composed of the target component into the second adsorption tank, the gas in the second adsorption tank is introduced into the other second adsorption tank,
The step of introducing the gas in the second adsorption tank into the other second adsorption tank is performed after the step of introducing the gas mainly composed of the target component into the second adsorption tank, and the second In the step of introducing the gas in the adsorption tank into the other second adsorption tank, the gas in the second adsorption tank is introduced into the other second adsorption tank in the pressure raising step,
In the step of discharging the gas mainly containing the impurity component to the outside, the step of introducing the gas mainly containing the target component into the second adsorption tank, and the gas in the second adsorption tank are other than the above A method for purifying a target gas, which is performed after the step of introducing into the second adsorption tank . A plurality of the first adsorption vessels are provided in parallel with each other in relation to the corresponding second adsorption vessels in series;
In the step of introducing the gas mainly containing the target component into the second adsorption tank and the step of discharging the gas mainly containing the impurity component, any one of the plurality of first adsorption tanks provided in plurality switching the gas flow conditions to allow entry and exit of gas in one process for purifying target gas according to claim 1. The first adsorption tank is filled with a first adsorbent which selectively adsorbs at least one of the plurality of impurity components,
The method for purifying target gas according to claim 1, wherein the second adsorption tank is filled with a second adsorbent which selectively adsorbs at least one other of the plurality of impurity components. The purification method of a target gas according to claim 1, wherein the target component is hydrogen.

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