JPWO2018055971A1 - Hydrogen or helium purification method and hydrogen or helium purification apparatus - Google Patents

Abstract

Purification of hydrogen or helium from a raw material gas containing volatile aromatic compounds as impurities and hydrogen or helium as the main component by a PSA method using an adsorption tower (10A to 10C) packed with an adsorbent The method repeatedly performs a cycle including an adsorption step, a pressure reduction step, a desorption step, and a washing step for each of the adsorption columns (10A to 10C). Each adsorption column (10A to 10C) is divided into a first region, a second region, and a third region in order from the upstream side to the downstream side in the flow direction of the source gas in the adsorption column. The first region is filled with a silica gel-based first adsorbent 131 having a filling ratio of 15 to 75 vol% with respect to the entire adsorbent filling volume. The second region is filled with a zeolitic second adsorbent 132 having a filling ratio of 15 to 75 vol%. The third region is filled with an activated carbon-based third adsorbent 133 having a filling ratio of 5 to 30 vol%.

Description

  The present invention relates to methods and apparatus for purifying hydrogen or helium using pressure swing adsorption.

  From the viewpoint of pollution prevention, the concentration of volatile aromatic compounds in the gas released as waste gas is regulated to a low concentration. For example, in the case of a gas containing toluene as an impurity, the concentration at the ground reaching point is set to 0.7 vol ppm or less in a certain area. As a waste gas treatment method for meeting such regulations, there are an absorption method, a cooling method, an adsorption method, a combustion method and the like (see, for example, Patent Document 1). In addition, there are also cases where the gas purified by these treatments is recovered and reused. Further, with regard to waste gas treatment facilities, a space-saving and inexpensive method of installation cost and operation cost is required.

  On the other hand, when using hydrogen or helium as an industrial gas, depending on the application, it is necessary to add a purification step to obtain a high purity gas. For example, in the case of hydrogen for fuel cell vehicles, according to ISO 14687-2 (hydrogen fuel standard for FCV, 2012, Grade D), the permissible concentration of components other than hydrogen is 2 volppm or less (in terms of methane) in the case of total hydrocarbons. There is a need to. Also in this case, a space-saving and inexpensive method is required. In the removal of hydrocarbons by the absorption method, it is difficult to reduce the concentration of hydrocarbons in the diffusion gas to 1 vol% or less, and it has not been realized yet. Even in the cooling method, since impurities corresponding to the vapor pressure remain on the gas phase side, it is difficult to purify them to several ppm order in the case of volatile aromatic compounds. In the combustion method, it is necessary to mix oxygen and the like, and water and carbon dioxide and the like are generated after the combustion, so it is not suitable for obtaining a high purity gas.

  For the above reasons, adsorption is mainly used as a method for obtaining high purity hydrogen and helium. For example, in order to remove volatile aromatic compounds contained in gas, pressure swing adsorption method using synthetic zeolite or hydrophobic silica gel is employed. However, this method also has problems in cost because it uses a vacuum device for desorption and uses a hydrophobic one among silica-rich zeolite and silica gel (see, for example, Patent Document 1).

  There is also a method of treating waste gas containing volatile aromatic compounds using a pressure swing adsorption method to reduce the hydrocarbon concentration. If regeneration of the adsorbent is possible by the pressure fluctuation adsorption method, heating and cooling become unnecessary. However, in this method, a vacuum device is required at the time of desorption, and it is also necessary to pre-coat the adsorbent beforehand, and there are problems in terms of cost and complexity of operation (for example, see Patent Documents 2 and 3) ).

  In the case of purifying a gas containing a volatile aromatic compound as an impurity, a method using activated carbon as an adsorbent has conventionally been adopted. Volatile aromatic compounds that enter into the pores of activated carbon are not easily desorbed. For this reason, the method of using a heating means for desorption is adopted, and desorption is promoted by the use of a temperature fluctuation adsorption method or steam. When using a heating means, incidental facilities accompanying heating and cooling are required, and there are many problems in terms of operability such as heat transfer takes time.

  In addition, in the method using the vacuum regeneration method, the cost for vacuum regeneration is high. Moreover, in the method using a purge gas (refined product gas of high purity), the cost increases due to the use of the purge gas. Furthermore, with regard to regeneration by heating, it leads to an increase in the cost of energy required for heating as well.

JP-A-9-47635 Japanese Patent Application Laid-Open No. 11-71584 JP 2004-42013 A

  The present invention has been conceived under such circumstances, and it is possible to reduce the cost of a raw material gas containing volatile aromatic compounds as an impurity while using high pressure purity by utilizing a pressure fluctuation adsorption method. It is an object of the present invention to provide a method and apparatus suitable for obtaining hydrogen or helium.

  According to the first aspect of the present invention, a volatile aromatic compound is used as an impurity by repeating, for each adsorption column, a cycle of pressure fluctuation adsorption method using three or more adsorption columns filled with an adsorbent. A method is provided for purifying hydrogen or helium from a source gas that contains and contains hydrogen or helium as the main component. The cycle is performed by a pressure fluctuation adsorption method performed by using three or more adsorption towers filled with an adsorbent, and the raw material gas is introduced into the adsorption tower with the adsorption tower at a predetermined high pressure. An adsorption step of adsorbing the volatile aromatic compound in the raw material gas to the adsorbent and discharging a product gas having a high concentration of hydrogen or helium from the adsorption tower; and the adsorption tower after the adsorption step. The volatile aromatic compound is desorbed from the adsorbent in the adsorption tower after the depressurization step of discharging the gas remaining inside to lower the pressure in the tower and the pressure reduction step, and discharging the gas in the tower And a washing step of introducing the gas discharged from the other adsorption tower in the depressurization step into the adsorption tower after the desorption step to discharge the gas remaining in the tower. Each adsorption column is divided into a first region, a second region, and a third region in order from the upstream side to the downstream side in the flow direction of the raw material gas in the adsorption column. The first region is filled with a silica gel-based first adsorbent having a filling ratio in the range of 15 to 75 vol%. The second region is filled with a zeolitic second adsorbent having a filling ratio in the range of 15 to 75 vol%. The third region is filled with an activated carbon-based third adsorbent having a filling ratio of 5 to 30 vol%.

  Preferably, the first adsorbent comprises hydrophilic silica gel.

  According to a second aspect of the present invention, there is provided an apparatus for purifying hydrogen or helium from a source gas comprising volatile aromatic compounds as impurities and comprising hydrogen or helium as a main component. The apparatus has three or more adsorption towers, each having a first gas passage port and a second gas passage port, and being filled with an adsorbent between the first and second gas passage ports, and a product gas A storage tank for storing, a gas-liquid separation means for separating a gas discharged from the first gas passage port of the adsorption tower into a gas phase component and a liquid phase component, a main stem connected to a source gas supply source A first line having a passage and a plurality of branch passages provided for each of the adsorption towers and connected to the first gas passage port side of the adsorption towers and provided with on-off valves in each, A main trunk path provided with liquid separation means, and a plurality of branch paths provided for each of the adsorption towers and connected to the first gas passage port side of the adsorption towers and provided with on-off valves in each, And a main trunk path provided with the storage tank, and A third line having a plurality of branch paths provided for each adsorption tower and connected to the second gas passage port side of the adsorption tower and provided with on-off valves in each, and the main trunk in the third line A main trunk passage connected to the passage, and a plurality of branch passages provided for each of the adsorption towers and connected to the second gas passage port side of the adsorption towers and provided with on-off valves in each of the plurality of branch passages; 4 lines, a main trunk path connected to the main trunk path in the fourth line, and each of the adsorption towers, connected to the second gas passage port side of the adsorption tower, and provided with an on-off valve in each And a fifth line having a plurality of branched paths. Each adsorption tower is divided into a first region, a second region, and a third region in order from the first gas passage port to the second gas passage port in the adsorption tower. The first region is filled with a silica gel-based first adsorbent having a filling ratio in the range of 15 to 75 vol%. The second region is filled with a zeolitic second adsorbent having a filling ratio in the range of 15 to 75 vol%. The third region is filled with an activated carbon-based third adsorbent having a filling ratio of 5 to 30 vol%.

  Preferably, the first adsorbent comprises hydrophilic silica gel.

  The inventors of the present invention conducted intensive studies on a method of separating hydrogen or helium from a raw material gas containing volatile aromatic compounds as impurities by pressure fluctuation adsorption method. As a result, silica gel, which is an adsorbent that adsorbs volatile aromatic compounds, was examined. Zeolite and activated carbon, which are adsorbents that do not adsorb volatile aromatic compounds, are filled in the latter stage, and after completion of the adsorption step, using relatively clean gas in the layer of the zeolite and activated carbon, after completion of the desorption step By washing the adsorption column, it has been found that a product gas of high purity after purification can be obtained without using a vacuum device or heating device at the time of desorption, and the present invention has been completed.

  According to the present invention, the content of volatile aromatic compounds contained as impurities in hydrogen or helium can be purified inexpensively to 1 vol ppm or less and in a space-saving apparatus.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

FIG. 1 represents a schematic configuration of a purification apparatus used to carry out a method for purifying hydrogen according to an embodiment of the present invention. The flow state of the gas in each step of the purification method of hydrogen which concerns on embodiment of this invention is represented.

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

  FIG. 1 shows a schematic configuration of a purification apparatus X that can be used to carry out the method of purifying hydrogen or helium according to the present invention. The purification apparatus X includes adsorption towers 10A, 10B, and 10C of three towers, a raw material gas supply source 21, a product storage tank 22, an off gas tank 23, a cooler 24, a gas-liquid separator 25, and lines 31 to It has 35 and. The purification apparatus X is configured to be able to concentrate and separate hydrogen or helium from a source gas containing hydrogen or helium (crude hydrogen or crude helium) using a pressure swing adsorption method (PSA method). As an example of the source gas, there can be mentioned a gas mainly composed of hydrogen generated from organic hydride as a main component and, for example, a gas containing volatile aromatic compounds (for example, toluene, benzene, methylcyclohexane and the like) as impurities. The following description is given for the case where the main component of the source gas is hydrogen, but the present invention is not limited to this, and is applicable to the case where the main component of the source gas is helium.

  Each of the adsorption towers 10A, 10B, 10C has gas passage ports 11, 12 at both ends, and an adsorbent is filled between the gas passage ports 11, 12. Specifically, a plurality of (three) regions partitioned by, for example, perforated plates (not shown) are formed in each of the adsorption towers 10A, 10B, and 10C, and different adsorbents are respectively formed in these regions. Is filled. In the present embodiment, in the flow direction of the raw material gas in each of the adsorption towers 10A, 10B, 10C, the first adsorbent 131, the second adsorbent 131 are directed from the upstream side (gas passage port 11) to the downstream side (gas passage port 12). The adsorbent 132 and the third adsorbent 133 are laminated in order.

  As the first adsorbent 131, an adsorbent having a property of preferentially adsorbing volatile aromatic compounds is used. Examples of such an adsorbent include silica gel-based adsorbents (hydrophilic silica gel, hydrophobic silica gel and the like). Among them, hydrophilic silica gel, particularly silica gel type B is preferable. As the second and third adsorbents 132 and 133, adsorbents having relatively low adsorption ability of volatile aromatic compounds are used. Examples of the second adsorbent 132 include zeolite-based adsorbents (A-type zeolite, CaA-type zeolite, Y-type zeolite, etc.), among which CaA-type zeolite is preferable. Examples of the third adsorbent 133 include activated carbon-based ones such as coconut shell-based and coal-based. These adsorbents are generally commercially available, readily available, and do not require pretreatment. Silica gel (or silica) is inherently hydrophilic since it has hydroxyl groups on the surface, and becomes hydrophobic by carrying out hydrophobization treatment such as high temperature heating or reaction with an alkylsilylating agent. Conventionally, this hydrophobization treatment has been the cause of cost increase.

  In addition, the first to third adsorbents 131, 132, and 133 are adjusted to have a predetermined filling ratio (volume ratio) with respect to the entire filling volume of the adsorbent. Specifically, the packing ratio of the first adsorbent 131 is 15 to 75 vol%, preferably 15 to 65 vol%, and the packing ratio of the second adsorbent 132 is 15 to 75 vol%, preferably 25 to 75 vol%. The filling ratio of the third adsorbent 133 is in the range of 5 to 30 vol%, preferably 5 to 20 vol%. The total of the filling ratios of the first to third adsorbents 131, 132, and 133 is 100 vol%.

  The raw material gas supply source 21 is a pressure vessel for storing the raw material gas supplied into the adsorption towers 10A, 10B, and 10C. The concentration of the volatile aromatic compound contained in the source gas is not particularly limited, but depending on the pressure of hydrogen or helium and the concentration of the volatile aromatic compound, the volatile aromatic compound may be liquefied in the piping. Therefore, the piping from the source gas supply source 21 to the adsorption towers 10A, 10B, 10C (the main trunk path 31 'of the line 31 described later) is heated and / or before the adsorption towers 10A, 10B, 10C It is preferable to install a mist trap or the like in the main trunk path 31 ′. The pressure of the raw material gas supplied from the raw material gas supply source 21 is not particularly limited, but is preferably as high as possible, and a compressor (not shown) is installed in the main trunk path 31 'as necessary. In addition, when hydrogen or helium supplied from the source gas supply source 21 contains water as an impurity, it is preferable to install a water removing device (not shown) in the main trunk path 31 ′ of the line 31. The operating temperature by the PSA method is not particularly limited, and is, for example, about 10 to 40 ° C. However, as described above, it is preferable that the temperature is such that the volatile aromatic compound does not liquefy (about normal temperature or more).

  The product storage tank 22 is a pressure vessel for storing gas (product gas described later) discharged from the gas passage ports 12 of the adsorption towers 10A, 10B, 10C.

  The off gas tank 23 is a pressure vessel for storing the off gas discharged from the gas passage port 11 of the adsorption towers 10A, 10B, 10C.

  The cooler 24 cools the off gas. The gas-liquid separator 25 condenses the off gas passed through the cooler 24 under a predetermined pressure to separate it into a gas phase component and a liquid phase component. The term "gas-liquid separation means" includes the cooler 24 and the gas-liquid separator 25.

  The line 31 has a main trunk passage 31 'to which the raw material gas supply source 21 is connected, and branch passages 31A, 31B, and 31C connected to the respective gas passage ports 11 of the adsorption towers 10A, 10B, and 10C. Branches 31A, 31B, 31C are valves that can be automatically switched between an open state and a closed state (hereinafter, a valve having such a function is referred to as "automatic valve") 31a, 31b, 31c. Is provided.

  The line 32 is a main trunk passage 32 ′ provided with the cooler 24 and the gas-liquid separator 25, and branch passages 32A, 32B respectively connected to the respective gas passage ports 11 of the adsorption towers 10A, 10B, 10C. , 32C. Further, an off-gas tank 23 is provided on the main trunk path 32 ′ on the upstream side of the cooler 24. A pressure control valve 321 is provided between the off gas tank 23 and the cooler 24 in the main passage 32 '. The automatic valves 32a, 32b, 32c are provided in the branch passages 32A, 32B, 32C.

  The line 33 has a main trunk path 33 'provided with the product storage tank 22, and branch paths 33A, 33B, and 33C connected to the respective gas passage ports 12 of the adsorption towers 10A, 10B, and 10C. The branch valves 33A, 33B, 33C are provided with automatic valves 33a, 33b, 33c. A pressure control valve 331 is provided downstream of the product storage tank 22 in the main trunk path 33 ′.

  The line 34 is for supplying a part of the product gas flowing through the line 33 (main trunk path 33 ′) to the adsorption towers 10A, 10B, 10C, and the main trunk connected to the main trunk path 33 ′ of the line 33. A channel 34 'and branch channels 34A, 34B, 34C respectively connected to the gas passage 12 side of the adsorption towers 10A, 10B, 10C are provided. An automatic valve 341 and a flow control valve 342 are provided in the main path 34 '. The branch valves 34A, 34B, 34C are provided with automatic valves 34a, 34b, 34c.

  The line 35 is for connecting any two of the adsorption towers 10A, 10B, 10C to each other, and a main trunk path 35 'connected to the main trunk path 34' of the line 34, and the adsorption towers 10A, 10B, It has branch paths 35A, 35B, 35C each connected to the side of each gas passage port 12 of 10C. The main passage 35 ′ is provided with an automatic valve 351 and a flow rate adjustment valve 352. The branch valves 35A, 35B, 35C are provided with automatic valves 35a, 35b, 35c.

The purification method of hydrogen according to the embodiment of the present invention can be implemented using the purification apparatus X having the above configuration. During operation of the purification apparatus X, the automatic valves 31a to 31c, 32a to 32c, 33a to 33c, 34a to 34c, 35a to 35c, 341, 351, and the flow control valves 342, 352 are appropriately switched to perform in the apparatus. A desired gas flow state can be realized, and one cycle consisting of the following steps 1 to 9 can be repeated. In one cycle of this method, an adsorption step, a pressure reduction step, a pressure equalizing / decompression step, a desorption step, a washing step, a pressure equalizing pressure increase, and a pressure increase step are performed in each of the adsorption towers 10A, 10B, and 10C. FIGS. 2a to 2i schematically show the flow of gas in the purification apparatus X in steps 1 to 9. FIG. The following abbreviations are used in FIGS. 2a to 2i.
AS: adsorption step DP: depressurization step DS: desorption step RN: washing step PR: pressurization step Eq-DP: pressure equalization decompression step Eq-PR: pressure equalization pressurization step

  In step 1, the automatic valves 31a, 33a, 32b, 34b, 35c, 351 and the flow control valve 352 are opened to achieve the flow of gas as shown in FIG. 2a.

  In the adsorption tower 10A, the raw material gas is introduced from the gas passage port 11 via the line 31, and the adsorption step is performed. The inside of the adsorption tower 10A in the adsorption step is maintained at a predetermined high pressure state, and mainly volatile aromatic compounds in the raw material gas are adsorbed by the adsorbent in the adsorption tower 10A. Then, a gas (product gas) in which hydrogen is concentrated is discharged from the gas passage port 12 side of the adsorption tower 10A. The product gas is delivered to the product storage tank 22 via the branch passage 33A and the main passage 33 '. The product gas in the product storage tank 22 is appropriately taken out of the system via the pressure control valve 331 and used for a desired application.

  Here, the concentration of the volatile aromatic compound in the raw material gas introduced into the adsorption tower 10A is not particularly limited, and is, for example, about 100 vol ppm to 1 vol%. The maximum pressure (adsorption pressure) in the adsorption tower 10A in the adsorption step is, for example, 0.1 to 1.0 MPaG (G represents a gauge pressure, and the same applies to the following), preferably 0. It is 5 to 0.8 MPaG.

  In step 1, the gas passage openings 12 of the adsorption towers 10B and 10C are in communication via the lines 34 and 35, respectively. Since the adsorption step was performed first for the adsorption tower 10B and the adsorption step was performed first for the adsorption tower 10C (see step 9 shown in FIG. 2i), at the start of step 1, the adsorption tower 10C is the adsorption tower 10B. The pressure in the tower is higher than that. Then, after the start of Step 1, the pressure reduction step is performed in the adsorption tower 10C, and the gas with low impurity concentration (residual concentrated hydrogen gas) remaining in the adsorption tower 10C is discharged from the gas passage port 12, The pressure in the tower drops. The difference in pressure in the adsorption tower 10C between the start and end of Step 1 is, for example, about 300 kPa. On the other hand, in the adsorption column 10B, the cleaning step is performed, and the residual concentrated hydrogen gas discharged from the adsorption column 10C is introduced from the gas passage 12 as a cleaning gas through the line 35, the flow rate adjustment valve 352 and the line 34, Evacuate the residual gas in the tower. Here, the gas discharged from the adsorption tower 10B is a gas having a high concentration of volatile aromatic compounds, and the gas is sent to the off gas tank 23 via the line 32 as the off gas. At the end of Step 1, the pressure in the adsorption tower 10C is higher than the pressure in the adsorption tower 10B. The operation time of step 1 is, for example, about 75 seconds.

  In step 2, the automatic valves 31a, 33a, 34b, 35c, 351 and the flow control valve 352 are opened to achieve the flow of gas as shown in FIG. 2b.

  In step 2, an adsorption step is subsequently performed in the adsorption tower 10A. Also in step 2, the gas passage ports 12 and 12 of the adsorption towers 10B and 10C are in communication via the lines 34 and 35, respectively. On the other hand, the automatic valve 32b is closed about adsorption tower 10B. Then, at the start of Step 2, the pressure in the adsorption tower 10C is still higher than in the adsorption tower 10B. Therefore, pressure equalization decompression is performed in adsorption tower 10C, and pressure equalization pressurization is performed in adsorption tower 10B. More specifically, the gas in the adsorption tower 10C is introduced into the adsorption tower 10B via the lines 35 and 34, the pressure in the adsorption tower 10C is reduced, and the pressure in the adsorption tower 10B is increased. . As a result, in the adsorption towers 10B and 10C, the internal pressure becomes substantially equal. The operation time of step 2 is, for example, about 15 seconds.

  In step 3, the automatic valves 31a, 33a, 34b, 32c, 341 and the flow control valve 342 are opened to achieve the flow of gas as shown in FIG. 2c.

  In step 3, an adsorption step is subsequently performed in the adsorption tower 10A. Furthermore, in step 3, while the communication between the adsorption towers 10B and 10C is shut off, part of the product gas discharged from the gas passage port 12 of the adsorption tower 10A is transferred to the adsorption tower 10B via the line 34 and the flow control valve 342 Then, the pressure raising step of the adsorption tower 10B is performed.

  In step 3, the adsorption valve 10C is in communication with the off-gas tank 23 via the line 32 as the automatic valve 32c is opened. As a result, the desorption step is performed in the adsorption column 10C, the pressure in the column of the adsorption column 10C is reduced, and the impurities (mainly volatile aromatic compounds) are desorbed from the adsorbent, and the gas in the column (volatile aromatic compounds) Gas having a high concentration) is discharged outside the column as an off gas through the gas passage port 11. The minimum pressure (desorption pressure) inside the adsorption tower 10C in the desorption step is, for example, 0 to 50 kPaG, and preferably 0 to 20 kPaG. The off gas exhausted from the adsorption tower 10C is sent to the off gas tank 23 via the line 32. The gas in the off-gas tank 23 is appropriately sent to the cooler 24 via the pressure control valve 321, and passes through the gas-liquid separator 25 to liquefy volatile aromatic compounds and recover it as a liquid phase. Can. The operation time in step 3 is, for example, about 135 seconds. The above steps 1 to 3 correspond to 1/3 of the cycle configured by the steps 1 to 9, and the process time of these steps 1 to 3 is about 225 seconds in total.

  In the subsequent steps 4 to 6, as shown in FIGS. 2 d to 2 f, the operations performed on the adsorption tower 10A in steps 1 to 3 are performed on the adsorption tower 10B, and the operations performed on the adsorption tower 10B in steps 1 to 3 are performed The operation performed for the adsorption tower 10C and the operations performed for the adsorption tower 10C in Steps 1 to 3 are performed for the adsorption tower 10A.

  In step 4, the automatic valves 31b, 33b, 32c, 34c, 35a, 351 and the flow control valve 352 are opened to achieve the flow of gas as shown in FIG. 2d. In step 5, the automatic valves 31b, 33b, 34c, 35a, 351 and the flow control valve 352 are opened to achieve the flow of gas as shown in FIG. 2e. In step 6, the automatic valves 31b, 33b, 34c, 32a, 341 and the flow control valve 342 are opened to achieve the flow of gas as shown in FIG. 2f. Although detailed description is omitted, in steps 4, 5 and 6, the adsorption tower 10A sequentially performs the same operation as the adsorption tower 10C in steps 1, 2 and 3, and the adsorption tower 10B performs steps 1, 2 and 3 The adsorption tower 10C sequentially performs the same operation as the adsorption tower 10A, and the adsorption tower 10C sequentially performs the same operation as the adsorption tower 10B in Steps 1, 2 and 3.

  In Steps 7 to 9 below, as shown in FIGS. 2g to 2i, the operations performed on adsorption tower 10A in Steps 1 to 3 are performed on adsorption tower 10C, and the operations performed on adsorption tower 10B in Steps 1 to 3 are performed. The operation performed for the adsorption tower 10A and the operation performed for the adsorption tower 10C in Steps 1 to 3 are performed for the adsorption tower 10B.

  In step 7, the automatic valves 31c, 33c, 32a, 34a, 35b, 351 and the flow control valve 352 are opened to achieve the flow of gas as shown in FIG. 2g. In step 8, the automatic valves 31c, 33c, 34a, 35b, 351 and the flow control valve 352 are opened to achieve the flow of gas as shown in FIG. 2h. In step 9, the automatic valves 31c, 33c, 34a, 32b, 341 and the flow control valve 342 are opened to achieve the flow of gas as shown in FIG. 2i. Although detailed description is omitted, in steps 7, 8 and 9, the adsorption tower 10A sequentially performs the same operation as the adsorption tower 10B in steps 1, 2 and 3, and the adsorption tower 10B performs steps 1, 2 and 3 The adsorption tower 10C sequentially performs the same operation as the adsorption tower 10A in steps 1, 2, and 3.

  Then, the cycle consisting of the above steps 1 to 9 is repeatedly performed in each of the adsorption towers 10A, 10B, 10C, whereby the source gas is continuously introduced into any of the adsorption towers 10A, 10B, 10C, and Concentrated hydrogen gas (product gas) is continuously obtained.

  In the hydrogen purification method of the present embodiment, for one cycle by the PSA method implemented in each of the adsorption towers 10A, 10B and 10C, after the adsorption step, the residual gas in the tower is transferred to another adsorption tower after the desorption step. Introduce and perform the cleaning process. The gas in the adsorption tower after completion of the adsorption step is a gas with low impurity concentration (residual concentrated hydrogen gas), and the adsorption tower after the desorption step can be efficiently cleaned using the gas. In addition, since the product gas is not used for cleaning, it is possible to suppress a decrease in the recovery rate of hydrogen.

  The adsorbent filled in each of the adsorption towers 10A, 10B and 10C is packed with a silica gel based adsorbent as the first adsorbent 131 at the most upstream side in the flow direction of the raw material gas. The silica gel based adsorbent is excellent in the ability to adsorb impurities (volatile aromatic compounds) at high pressures of 0.1 to 1.0 MPaG (= 100 to 1000 kPaG), and has a minimum pressure at 0 to 50 kPaG (atmospheric pressure or higher) Also in the desorption step), volatile aromatic compounds can be desorbed and regenerated. The first adsorbent 131 is used in an amount of 15 to 75 vol% of the total adsorbent loading volume. As a result, volatile aromatic compounds can be efficiently adsorbed and removed, and since vacuum equipment is unnecessary, cost reduction can be achieved. In addition, if hydrophilic silica gel is used as the first adsorbent 131, volatile aromatic compounds can be appropriately adsorbed and removed without performing pretreatment, which contributes to cost reduction.

  In addition, there exists a possibility that a volatile aromatic compound can not fully be removed as the filling ratio of the 1st adsorption agent 131 is less than 15 vol%. On the other hand, when the filling ratio of the first adsorbent 131 exceeds 75 vol%, the ratio of the cleaning gas remaining in the second adsorbent 132 and the third adsorbent 133 decreases, and the amount of the cleaning gas decreases, and the amount of the cleaning gas decreases. Cleaning may be insufficient.

  In the second adsorbent 132 (zeolite adsorbent) and the third adsorbent 133 (activated carbon adsorbent) stacked downstream (downstream side) of the first adsorbent 131, volatile aromatic compounds are not adsorbed . That is, the adsorption step is completed before the first adsorbent 131 is saturated with the volatile aromatic compound, and the second adsorbent 132 and the third adsorbent 133 do not substantially adsorb the volatile aromatic compound . On the other hand, the second adsorbent 132 and the third adsorbent 133 adsorb more hydrogen than the first adsorbent 131. As a result, the adsorption step is completed and discharged from the adsorption tower in the pressure reduction step, and the desorption step is completed, and the cleaning gas used to wash other adsorption towers in the washing step remains in the column at the start of the pressure reduction step. Desorbed from the second adsorbent 132 and the third adsorbent 133 in addition to the concentrated hydrogen gas (mainly the gas in the filling region of the second adsorbent 132 and the third adsorbent 133 close to the gas passage 12) Hydrogen is added. As a result, the adsorption tower after the completion of the desorption step can be effectively cleaned using the cleaning gas having an increased hydrogen content.

  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 to the configuration of the line (piping) forming the gas flow path in the apparatus for carrying out the method for purifying hydrogen or helium according to the present invention, a configuration different from the above embodiment may be adopted. The number of adsorption towers is not limited to the three-column type shown in the above embodiment, and the same effect can be expected in the case of four or more towers.

  Moreover, although the said embodiment demonstrated the case where hydrogen was refine | purified, the adsorption capacity of the helium with respect to the adsorbent (1st adsorption agent, 2nd adsorption agent, and 3rd adsorption agent) used by the purification method which concerns on this invention It is almost the same as hydrogen. Therefore, also in the case of concentrating and purifying helium from the source gas containing helium as the main component and the volatile aromatic compound as the impurity, the same function and effect as the above embodiment can be obtained.

  Next, the utility of the present invention will be described by examples and comparative examples.

Example 1
In this example, the purification apparatus X shown in FIG. 1 is used, and the purification method using the pressure fluctuation adsorption method (PSA method) comprising the steps described with reference to FIG. The concentrated hydrogen gas as a product gas was obtained from the source gas.

  As the adsorption towers 10A, 10B, and 10C, cylindrical ones having an inner diameter of 35 mm were used, and the adsorbent filling capacity was about 1 L (liter). In each of the adsorption towers 10A, 10B and 10C, silica gel type B (Fuji silica gel B type manufactured by Fuji Silysia Chemical Ltd.) as the first adsorbent 131 from the gas passage port 11 toward the gas passage port 12, a second adsorbent A layer of CaA-type zeolite 132 (Union Showa 5AHP) and activated carbon as a third adsorbent 133 (Catarler PGAR) were stacked and packed. The packing ratio (volume ratio) of these adsorbents was 30 vol% for the first adsorbent 131, 60 vol% for the second adsorbent 132, and 10 vol% for the third adsorbent 133. As the source gas, a crude hydrogen gas containing 8500 vol ppm of toluene as an impurity was used, and the source gas was supplied at a flow rate of 5.2 NL / min. The operating conditions of the PSA method are: temperature of adsorption column etc. is 40 ° C., adsorption pressure is 0.8 MPaG, desorption pressure is 20 kPaG, washing pressure difference is 300 kPa, cycle time (time of 1 cycle consisting of steps 1 to 9) Took 675 seconds. In addition, when the impurity concentration in the obtained concentrated hydrogen gas (product gas) was measured by a hydrogen flame ion detector (FID), the toluene concentration in the product gas is less than the lower limit of determination (0.1 volppm or less), and hydrogen gas The recovery rate was 75%. The results of this example are shown in Table 1.

Example 2
In the same manner as in Example 1, except that the packing ratio of the adsorbent was 40 vol% of the first adsorbent 131, 50 vol% of the second adsorbent 132, and 10 vol% of the third adsorbent 133, hydrogen was used from the raw material gas The purification of In addition, when the impurity concentration in the obtained concentrated hydrogen gas (product gas) was measured by a hydrogen flame ion detector (FID), the toluene concentration in the product gas is less than the lower limit of determination (0.1 volppm or less), and hydrogen gas The recovery rate was 70%. The results of this example are shown in Table 1.

[Example 3]
In the same manner as in Example 1, except that the packing ratio of the adsorbent was 20 vol% of the first adsorbent 131, 70 vol% of the second adsorbent 132, and 10 vol% of the third adsorbent 133, hydrogen was used from the raw material gas The purification of In addition, when the impurity concentration in the obtained concentrated hydrogen gas (product gas) was measured by a hydrogen flame ion detector (FID), the toluene concentration in the product gas is less than the lower limit of determination (0.1 volppm or less), and hydrogen gas The recovery rate was 80%. The results of this example are shown in Table 1.

Example 4
In the same manner as in Example 1, except that the packing ratio of the adsorbent was 70 vol% for the first adsorbent 131, 20 vol% for the second adsorbent 132, and 10 vol% for the third adsorbent 133, hydrogen was used from the raw material gas The purification of In addition, when the impurity concentration in the obtained concentrated hydrogen gas (product gas) was measured by a hydrogen flame ion detector (FID), the toluene concentration in the product gas was 0.67 vol ppm, and the hydrogen gas recovery rate was 92%. there were. The results of this example are shown in Table 1.

[Example 5]
In the same manner as in Example 1, except that the packing ratio of the adsorbent was 30 vol% of the first adsorbent 131, 40 vol% of the second adsorbent 132, and 30 vol% of the third adsorbent 133, hydrogen was used from the raw material gas The purification of In addition, when the impurity concentration in the obtained concentrated hydrogen gas (product gas) is measured by a hydrogen flame ion detector (FID), the toluene concentration in the product gas is 0.43 vol ppm, and the hydrogen gas recovery rate is 85%. there were. The results of this example are shown in Table 1.

Comparative Example 1
In the same manner as in Example 1, except that the packing ratio of the adsorbent was 80 vol% for the first adsorbent 131, 10 vol% for the second adsorbent 132, and 10 vol% for the third adsorbent 133, hydrogen from the raw material gas to hydrogen was used. The purification of Further, when the impurity concentration in the obtained concentrated hydrogen gas (product gas) was measured with a hydrogen flame ion detector (FID), the toluene concentration in the product gas was 2000 vol ppm, and the hydrogen gas recovery rate was 90%. . The results of this comparative example are shown in Table 1.

Comparative Example 2
In the same manner as in Example 1 except that the packing ratio of the adsorbents was 10 vol% for the first adsorbent 131, 80 vol% for the second adsorbent 132, and 10 vol% for the third adsorbent 133, hydrogen from the raw material gas to hydrogen was used. The purification of Further, when the impurity concentration in the obtained concentrated hydrogen gas (product gas) was measured by a hydrogen flame ion detector (FID), the toluene concentration in the product gas was 3000 vol ppm, and the hydrogen gas recovery rate was 75%. . The results of this comparative example are shown in Table 1.

Comparative Example 3
In the same manner as in Example 1, except that the packing ratio of the adsorbent was 30 vol% for the first adsorbent 131, 30 vol% for the second adsorbent 132, and 40 vol% for the third adsorbent 133, hydrogen was used from the source gas The purification of The results are shown in Table 1. In addition, when the impurity concentration in the obtained concentrated hydrogen gas (product gas) was measured by a hydrogen flame ion detector (FID), the toluene concentration in the product gas was 2 vol ppm, and the hydrogen gas recovery rate was 75%. . The results of this comparative example are shown in Table 1.

  As apparent from Table 1, according to each of the above examples, it is confirmed that hydrogen gas can be purified with high purity.

X Purification devices 10A, 10B, 10C Adsorption tower 11 Gas passage port (first gas passage port)
12 gas passage (second gas passage)
131 first adsorbent 132 second adsorbent 133 third adsorbent 21 source gas supply source 22 product storage tank 23 off gas tank 24 cooler (gas-liquid separation means)
25 Gas-liquid separator (gas-liquid separation means)
31 lines (1st line)
32 lines (second line)
33 lines (third line)
34 lines (4th line)
35 lines (5th line)
31 ', 32', 33 ', 34', 35 'Main trunk roads 31A-31C, 32A-32C, 33A-33C, 34A-34C, 35A-35C
Branches 31a to 31c, 32a to 32c, 33a to 33c, 34a to 34c, 35a to 35c, 341, 351 automatic valves 321, 331 pressure control valves 342, 352 flow control valves

Claims (11)

By repeating a cycle of pressure fluctuation adsorption method performed using three or more adsorption towers packed with an adsorbent for each adsorption tower, it contains a volatile aromatic compound as an impurity and also contains hydrogen or helium as a main component A method for purifying hydrogen or helium from a source gas, said cycle comprising
With the adsorption tower at a predetermined high pressure, the raw material gas is introduced into the adsorption tower, the volatile aromatic compound in the raw material gas is adsorbed by the adsorbent, and hydrogen or helium is removed from the adsorption tower. Adsorption process to discharge product gas with high concentration of
The pressure reduction step of discharging the gas remaining in the tower from the adsorption tower after the adsorption step and reducing the pressure in the tower;
A desorption step of desorbing the volatile aromatic compound from the adsorbent in the adsorption tower after the decompression step, and discharging gas in the tower;
And a cleaning step of introducing the gas discharged from the other adsorption tower in the depressurization step into the adsorption tower after the desorption step to discharge the gas remaining in the tower.
Each adsorption column is divided into a first region, a second region, and a third region in order from the upstream side to the downstream side in the flow direction of the raw material gas in the adsorption column, and the first region is The first silica gel-based adsorbent is packed with a packing ratio in the range of 15 to 75 vol% with respect to the whole packing volume of the adsorbent, and the packing ratio is in the range of 15 to 75 vol% in the second region. A second adsorbent of the zeolite system, and the third region is filled with a third adsorbent of the activated carbon system having a filling ratio in the range of 5 to 30 vol%; Purification method.   The purification method according to claim 1, wherein the first adsorbent comprises hydrophilic silica gel.   The purification method according to claim 1, wherein the second adsorbent comprises CaA-type zeolite.   The purification method according to claim 1, wherein the third adsorbent comprises coconut shell activated carbon or coal activated carbon.   The purification method according to claim 1, further comprising a pressure raising step for raising the pressure of the adsorption tower to a predetermined adsorption pressure between the washing step and the adsorption step.   The depressurization step is carried out after the first depressurization step of introducing the residual gas discharged from the adsorption tower into the other adsorption tower in the washing step as a cleaning gas, and subsequently discharging the adsorption tower following the first depressurization step. The second depressurization step of introducing the remaining residual gas into the other adsorption tower in the pressurizing step.   The boosting step includes a first boosting step of introducing the residual gas discharged from the other adsorption tower in the first decompression step into the adsorption tower, and the other of the adsorption step subsequent to the first boosting step. The second pressurizing step of introducing a part of the product gas from the adsorption tower of the second aspect into the adsorption tower. An apparatus for purifying hydrogen or helium from a source gas comprising volatile aromatic compounds as impurities and containing hydrogen or helium as a main component,
Three or more adsorption towers, each having a first gas passage port and a second gas passage port, and wherein the adsorbent is filled between the first and second gas passage ports;
A storage tank for storing product gas,
A gas-liquid separation means for separating the gas discharged from the first gas passage port of the adsorption column into a gas phase component and a liquid phase component;
A main trunk path connected to a raw material gas supply source, and a plurality of branch paths provided for each of the adsorption towers and connected to the first gas passage port side of the adsorption towers and provided with on-off valves in each, A first line having
A main trunk path provided with the gas-liquid separation means, and a plurality of branch paths provided for each of the adsorption towers and connected to the first gas passage port side of the adsorption towers and provided with on-off valves in each , And a second line,
A main trunk path provided with the storage tank, and a plurality of branch paths provided for each of the adsorption towers and connected to the second gas passage port side of the adsorption towers and provided with on-off valves in each, With the third line,
A plurality of main trunk paths connected to the main trunk path in the third line, and a plurality of the adsorption towers provided for each of the adsorption towers and connected to the second gas passage side of the adsorption towers and provided with on-off valves in each A fourth line having a branch path,
A plurality of main trunk paths connected to the main trunk path in the fourth line, and a plurality of the adsorption towers provided for each of the adsorption towers and connected to the second gas passage port side of the adsorption towers and provided with on-off valves in each And a fifth line having a branch path,
Each adsorption column is divided into a first region, a second region, and a third region in order from the first gas passage port to the second gas passage port in the adsorption column, and the first region is A first silica gel-based adsorbent is packed with a filling ratio in the range of 15 to 75 vol% with respect to the whole packing volume of the adsorbent, and the second area has a filling ratio of 15 to 75 vol%. Hydrogen or helium filled with a zeolite-based second adsorbent and the third region is filled with a third activated carbon-based adsorbent having a filling ratio in the range of 5 to 30 vol%; Purification equipment.   The purification apparatus according to claim 8, wherein the first adsorbent comprises hydrophilic silica gel.   The purification apparatus according to claim 8, wherein the second adsorbent comprises CaA-type zeolite.   The purification apparatus according to claim 8, wherein the third adsorbent comprises coconut shell activated carbon or coal activated carbon.

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