JP6905534B2 - Hydrogen or helium purification method, and hydrogen or helium purification equipment - Google Patents

Description

The present invention relates to a method and an apparatus for purifying hydrogen or helium using a pressure fluctuation adsorption method.

From the viewpoint of pollution prevention, the concentration of volatile aromatic compounds in the gas released as waste gas is regulated to be low. 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 volppm or less in some areas. Examples of the waste gas treatment method for complying with such regulations include an absorption method, a cooling method, an adsorption method, a combustion method, and the like (see, for example, Patent Document 1). In addition, the gas after purification by these treatments may be recovered and reused. Further, for waste gas treatment equipment, a method that saves space and has low introduction cost and operating cost is required.

On the other hand, when hydrogen or helium is used as an industrial gas, it is necessary to add a purification step in order to obtain a high-purity gas depending on the application. For example, in the case of hydrogen for fuel cell vehicles, according to ISO14687-2 (hydrogen fuel standard for FCV, 2012, Grade D), the permissible concentration of components other than hydrogen is 2 volppm or less (methane equivalent) for total hydrocarbons. There is a need to. Even 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 hydrocarbon concentration in the diffusion gas to 1 vol% or less, and this has not been realized yet. Even in the cooling method, impurities of vapor pressure remain on the vapor phase side, so that it is difficult to purify volatile aromatic compounds to the order of several ppm. In the combustion method, it is necessary to mix oxygen and the like, and water and carbon dioxide are generated after combustion, so that it is not suitable for obtaining a high-purity gas.

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

There is also a method of reducing the hydrocarbon concentration by treating the waste gas containing the volatile aromatic compound by using the pressure fluctuation adsorption method. If the adsorbent can be regenerated by the pressure fluctuation adsorption method, heating and cooling are not required. However, in this method, a vacuum device is required at the time of desorption, and it is also necessary to precoat the adsorbent in advance, which causes problems in terms of cost and complexity of operation (see, for example, Patent Documents 2 and 3). ).

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

In addition, the method using the vacuum regeneration method requires a cost for vacuum regeneration. In addition, the method using purge gas (purified high-purity product gas) leads to cost increase due to the use of purge gas. Furthermore, regeneration by heating also leads to an increase in cost due to the energy required for heating.

Japanese Unexamined Patent Publication No. 9-47635 Japanese Unexamined Patent Publication No. 11-71584 Japanese Unexamined Patent Publication No. 2004-42013

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

According to the first aspect of the present invention, by repeating the cycle of the pressure fluctuation adsorption method performed using three or more adsorption towers filled with an adsorbent for each adsorption tower, a volatile aromatic compound is produced as an impurity. A method for purifying hydrogen or helium from a raw material gas containing hydrogen or helium as a main component is provided. In the cycle, the raw material gas is introduced into the adsorption tower while the adsorption tower is at a predetermined high pressure by a pressure fluctuation adsorption method performed using three or more adsorption towers filled with an adsorbent. 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 a tower from the adsorption tower after the adsorption step is completed. The volatile aromatic compound is desorbed from the adsorbent in the adsorption tower after the decompression step of discharging the gas remaining in the tower to reduce the pressure in the tower and the gas in the tower is discharged. The desorption step includes a cleaning step of introducing the gas discharged from another adsorption tower in the decompression step into the adsorption tower that has completed the desorption step and discharging the gas remaining in the tower. Each of the adsorption towers 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 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 zeolite-based 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 in the range of 5 to 30 vol%.

Preferably, the first adsorbent is made of hydrophilic silica gel.

According to the second aspect of the present invention, there is provided an apparatus for purifying hydrogen or helium from a raw material gas containing a volatile aromatic compound as an impurity and containing hydrogen or helium as a main component. The device has three or more adsorption towers, each of which has a first gas passage port and a second gas passage port, and is filled with an adsorbent between the first and second gas passage ports, and a product gas. A storage tank for storage, a gas-liquid separation means for separating the gas discharged from the first gas passage port of the adsorption tower into a gas phase component and a liquid phase component, and a main trunk connected to a raw material gas supply source. A first line having a path 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 tower and each of which is provided with an on-off valve, and the above-mentioned gas. A main trunk path provided with a 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 tower and each of which is provided with an on-off valve. A second line having a second line, a main trunk path provided with the storage tank, and a plurality of suction towers provided for each of the suction towers, which are connected to the second gas passage port side of the suction tower and each of which is provided with an on-off valve. A third line having a branch path, a main trunk path connected to the main trunk path in the third line, and a main trunk path provided for each adsorption tower and connected to the second gas passage port side of the adsorption tower. A fourth line having a plurality of branch paths each provided with an on-off valve, a main trunk path connected to the main trunk path in the fourth line, and the suction tower provided for each of the suction towers. It is provided with a fifth line which is connected to the second gas passage port side of the tower and has a plurality of branch paths, each of which is provided with an on-off valve. Each of the adsorption towers 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 zeolite-based 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 in the range of 5 to 30 vol%.

Preferably, the first adsorbent is made of hydrophilic silica gel.

The present inventors diligently studied a method for separating hydrogen or helium from a raw material gas containing a volatile aromatic compound as an impurity by a pressure fluctuation adsorption method, and found that silica gel, which is an adsorbent for adsorbing a volatile aromatic compound, was found. The latter stage is filled with zeolite and activated charcoal, which are adsorbents that do not adsorb volatile aromatic compounds, and after the adsorption step is completed, a relatively clean gas in the layer of the zeolite and activated charcoal is used to complete the desorption step. We have found that by cleaning the adsorption tower, it is possible to obtain a high-purity product gas after purification without using a vacuum device or a heating device at the time of desorption, and have completed the present invention.

According to the present invention, the content of a volatile aromatic compound contained as an impurity in hydrogen or helium can be purified to 1 volppm or less at low cost and in a space-saving device.

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

A schematic configuration of a purification apparatus used for carrying out the method for purifying hydrogen according to an embodiment of the present invention is shown. The gas flow state in each step of the hydrogen purification method according to the embodiment of the present invention is shown.

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 for purifying hydrogen or helium according to the present invention. The purification apparatus X includes three adsorption towers 10A, 10B, 10C, 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 31. 35 and. The purification apparatus X is configured to be capable of concentrating and separating hydrogen or helium from a raw material gas containing hydrogen or helium (crude hydrogen or crude helium) by using a pressure fluctuation adsorption method (PSA method). Examples of the raw material gas include a gas containing hydrogen generated from an organic hydride as a main component and containing, for example, a volatile aromatic compound (for example, toluene, benzene, methylcyclohexane, etc.) as an impurity. The following description will be given for the case where the main component of the raw material gas is hydrogen, but the present invention is not limited to this, and is applicable to the case where the main component of the raw material gas is helium.

Each of the adsorption towers 10A, 10B, and 10C has gas passage ports 11 and 12 at both ends, and an adsorbent is filled between the gas passage ports 11 and 12. Specifically, a plurality of (three) regions defined by, for example, a perforated plate (not shown) are formed inside each of the adsorption towers 10A, 10B, and 10C, and different adsorbents are 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, the second 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 this order.

As the first adsorbent 131, an adsorbent having a property of preferentially adsorbing a volatile aromatic compound is used. Examples of such an adsorbent include silica gel-based adsorbents (hydrophilic silica gel, hydrophobic silica gel, etc.), and among them, hydrophilic silica gel, particularly silica gel B type, is preferable. For the second and third adsorbents 132 and 133, adsorbents having a relatively low adsorbing 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.), and CaA-type zeolite is particularly preferable. Examples of the third adsorbent 133 include activated carbon-based ones such as coconut shell-based and coal-based ones. These adsorbents are generally commercially available and readily available and do not require pretreatment. Since silica gel (or silica) has a hydroxyl group on its surface, it is originally hydrophilic, and becomes hydrophobic by performing a hydrophobizing treatment such as high-temperature heating or a reaction with an alkylsilylating agent. Conventionally, this hydrophobization treatment has been a cause of cost increase.

Further, the first to third adsorbents 131, 132, and 133 are adjusted so as to have a predetermined filling ratio (volume ratio) with respect to the entire filling capacity of the adsorbent. Specifically, the filling ratio of the first adsorbent 131 is in the range of 15 to 75 vol%, preferably 15 to 65 vol%, and the filling 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 filling ratio of each 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 to be supplied into the adsorption towers 10A, 10B, and 10C. The concentration of the volatile aromatic compound contained in the raw material gas is not particularly limited, but the volatile aromatic compound may be liquefied in the pipe depending on the pressure of hydrogen or helium and the concentration of the volatile aromatic compound. Therefore, the piping from the raw material gas supply source 21 to the adsorption towers 10A, 10B, 10C (main trunk road 31'of the line 31, which will be described later) is heated and / or before the adsorption towers 10A, 10B, 10C. It is preferable to install a mist trap or the like on the main trunk road 31'. The pressure of the raw material gas supplied from the raw material gas supply source 21 is not particularly limited, but a higher pressure is preferable, and a compressor (not shown) is installed in the main trunk road 31'if necessary. When hydrogen or helium supplied from the raw material gas supply source 21 contains water as an impurity, it is preferable to install a water removing device (not shown) in the main trunk road 31'of the line 31. The operating temperature according to 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 room temperature or higher).

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

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

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

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

The line 32 is a main trunk road 32'provided with a cooler 24 and a gas-liquid separator 25, and branch roads 32A, 32B connected to each gas passage port 11 side of the adsorption towers 10A, 10B, 10C. , 32C. Further, the main trunk road 32'is provided with an off-gas tank 23 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 trunk road 32'. The branch paths 32A, 32B, 32C are provided with automatic valves 32a, 32b, 32c.

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

The line 34 is for supplying a part of the product gas flowing through the line 33 (main trunk road 33') to the adsorption towers 10A, 10B, 10C, and is connected to the main trunk road 33'of the line 33. It has a road 34'and a branch road 34A, 34B, 34C connected to each gas passage port 12 side of the adsorption towers 10A, 10B, 10C. The main trunk road 34'is provided with an automatic valve 341 and a flow rate adjusting valve 342. The branch paths 34A, 34B, 34C are provided with automatic valves 34a, 34b, 34c.

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

The hydrogen purification method according to the embodiment of the present invention can be carried out by using the purification apparatus X having the above configuration. When the purification device X is in operation, the automatic valves 31a to 31c, 32a to 32c, 33a to 33c, 34a to 34c, 35a to 35c, 341,351, and the flow rate control valves 342,352 are appropriately switched in the device. A desired gas flow state can be achieved, and one cycle consisting of the following steps 1 to 9 can be repeated. In one cycle of this method, the adsorption step, the pressure reducing step, the pressure equalizing pressure reducing step, the desorption step, the cleaning step, the pressure equalizing pressure increasing step, and the pressure increasing step are performed in each of the suction towers 10A, 10B, and 10C. 2a to 2i schematically show the gas flow state in the purification apparatus X in steps 1 to 9. In addition, in FIGS. 2a-2i, the following abbreviations are used.
AS: Adsorption process DP: Decompression process DS: Desorption process RN: Cleaning process PR: Pressurization process Eq-DP: Equalizing pressure depressurizing process Eq-PR: Equalizing pressure increasing process

In step 1, the automatic valves 31a, 33a, 32b, 34b, 35c, 351 and the flow rate adjusting valve 352 are opened, and the gas flow state as shown in FIG. 2a is achieved.

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 in 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, the hydrogen-concentrated gas (product gas) 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 road 33A and the main trunk road 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 purpose.

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

Further, in step 1, the gas passage ports 12 of the adsorption towers 10B and 10C communicate with each other via the lines 34 and 35. Since the adsorption tower 10B was first desorbed and the adsorption tower 10C was first subjected to the adsorption step (see step 9 shown in FIG. 2i), the adsorption tower 10C was the adsorption tower 10B at the start of step 1. The pressure inside the tower is higher than that. Then, after the start of step 1, a decompression step is performed in the adsorption tower 10C, and the gas having a low impurity concentration (residual concentrated hydrogen gas) remaining in the adsorption tower 10C is discharged from the gas passage port 12. The pressure inside the tower drops. The difference in pressure inside the suction tower 10C at the start and end of step 1 is, for example, about 300 kPa. On the other hand, in the adsorption tower 10B, a cleaning step is performed, and the residual concentrated hydrogen gas discharged from the adsorption tower 10C is introduced from the gas passage port 12 as cleaning gas via the line 35, the flow rate adjusting valve 352 and the line 34, and Discharge the gas remaining in the tower. Here, the gas discharged from the adsorption tower 10B is a gas having a high concentration of a volatile aromatic compound, and the gas is sent as an off gas to the off gas tank 23 via the line 32. At the end of step 1, the pressure inside the suction tower 10C is higher than the pressure inside the suction 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 rate adjusting valve 352 are opened, and the gas flow state as shown in FIG. 2b is achieved.

In step 2, the adsorption step is continuously performed in the adsorption tower 10A. Further, also in step 2, the gas passage ports 12 and 12 of the adsorption towers 10B and 10C communicate with each other via the lines 34 and 35. On the other hand, the automatic valve 32b of the suction tower 10B is closed. Then, at the start of step 2, the pressure inside the suction tower 10C is still higher than that inside the suction tower 10B. Therefore, the pressure equalizing pressure is reduced in the adsorption tower 10C, and the pressure equalizing pressure is increased in the suction tower 10B. More specifically, the gas inside the adsorption tower 10C is introduced into the adsorption tower 10B via the lines 35 and 34, the inside of the adsorption tower 10C is depressurized, and the inside of the adsorption tower 10B is boosted. .. As a result, in the adsorption towers 10B and 10C, the internal pressures are 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 rate adjusting valve 342 are opened, and the gas flow state as shown in FIG. 2c is achieved.

In step 3, the adsorption step is continuously performed in the adsorption tower 10A. Further, in step 3, while blocking the communication between the suction towers 10B and 10C, a part of the product gas discharged from the gas passage port 12 of the suction tower 10A is sent to the suction tower 10B via the line 34 and the flow rate adjusting valve 342. After the introduction, the step of increasing the pressure of the adsorption tower 10B is performed.

Further, in step 3, the suction tower 10C communicates with the off-gas tank 23 via the line 32 by opening the automatic valve 32c. As a result, the desorption step is performed in the adsorption tower 10C, the inside of the adsorption tower 10C is depressurized, impurities (mainly volatile aromatic compounds) are desorbed from the adsorbent, and the gas in the tower (volatile aromatic compounds) is desorbed. Gas having a high concentration of gas) is discharged to the outside of the tower as 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, preferably 0 to 20 kPaG. The off-gas discharged 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 further passed through the gas-liquid separator 25 to liquefy the volatile aromatic compound and recover it as a liquid phase. Can be done. 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 composed of 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. 2d to 2f, the operation performed on the suction tower 10A in steps 1 to 3 is performed on the suction tower 10B, and the operation performed on the suction tower 10B in steps 1 to 3 is performed. The operation performed on the suction tower 10C is performed, and the operation performed on the suction tower 10C in steps 1 to 3 is performed on the suction tower 10A.

In step 4, the automatic valves 31b, 33b, 32c, 34c, 35a, 351 and the flow rate adjusting valve 352 are opened, and the gas flow state as shown in FIG. 2d is achieved. In step 5, the automatic valves 31b, 33b, 34c, 35a, 351 and the flow rate adjusting valve 352 are opened, and the gas flow state as shown in FIG. 2e is achieved. In step 6, the automatic valves 31b, 33b, 34c, 32a, 341 and the flow rate adjusting valve 342 are opened, and the gas flow state as shown in FIG. 2f is achieved. Although detailed description will be omitted, in steps 4, 5 and 6, the suction tower 10A sequentially performs the same operations as the suction tower 10C in steps 1, 2 and 3, and the suction tower 10B performs the same operations as in steps 1, 2 and 3. The same operation as the suction tower 10A in the above is sequentially performed, and the suction tower 10C sequentially carries out the same operation as the suction tower 10B in steps 1, 2 and 3.

In the subsequent steps 7 to 9, as shown in FIGS. 2g to 2i, the operation performed on the suction tower 10A in steps 1 to 3 is performed on the suction tower 10C, and the operation performed on the suction tower 10B in steps 1 to 3 is performed. The operation performed on the suction tower 10A is performed, and the operation performed on the suction tower 10C in steps 1 to 3 is performed on the suction tower 10B.

In step 7, the automatic valves 31c, 33c, 32a, 34a, 35b, 351 and the flow rate adjusting valve 352 are opened, and the gas flow state as shown in FIG. 2g is achieved. In step 8, the automatic valves 31c, 33c, 34a, 35b, 351 and the flow rate adjusting valve 352 are opened, and the gas flow state as shown in FIG. 2h is achieved. In step 9, the automatic valves 31c, 33c, 34a, 32b, 341 and the flow control valve 342 are opened, and the gas flow state as shown in FIG. 2i is achieved. Although detailed description is omitted, in steps 7, 8 and 9, the suction tower 10A sequentially performs the same operations as the suction tower 10B in steps 1, 2 and 3, and the suction tower 10B performs the same operations as the suction tower 10B in steps 1, 2 and 3. The same operation as the suction tower 10C in the above is sequentially performed, and the suction tower 10C sequentially carries out the same operation as the suction tower 10A in steps 1, 2 and 3.

Then, by repeating the cycle consisting of the above steps 1 to 9 in each of the adsorption towers 10A, 10B, and 10C, the raw material gas is continuously introduced into any of the adsorption towers 10A, 10B, and 10C, and the raw material gas is continuously introduced. Concentrated hydrogen gas (product gas) is continuously acquired.

In the hydrogen purification method of the present embodiment, for one cycle by the PSA method carried out 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 the adsorption step is a gas having a low impurity concentration (residual concentrated hydrogen gas), and the adsorption tower after the desorption step can be efficiently cleaned using the gas. Moreover, since the product gas is not used for cleaning, it is possible to suppress a decrease in the hydrogen recovery rate.

Regarding the adsorbents to be filled in the adsorption towers 10A, 10B, and 10C, the silica gel-based adsorbent as the first adsorbent 131 is filled on the most upstream side in the flow direction of the raw material gas. The silica gel-based adsorbent has an excellent ability to adsorb impurities (volatile aromatic compounds) at a high pressure of 0.1 to 1.0 MPaG (= 100 to 1000 kPaG), and has a minimum pressure (0 to 50 kPaG) above atmospheric pressure. The volatile aromatic compound can be desorbed and regenerated even in the desorption step). The first adsorbent 131 is used in an amount of 15 to 75 vol% of the total adsorbent filling capacity. As a result, the volatile aromatic compound can be efficiently adsorbed and removed, and the vacuum equipment is not required, so that the cost can be reduced. Further, if hydrophilic silica gel is used as the first adsorbent 131, the volatile aromatic compound can be appropriately adsorbed and removed without pretreatment, which contributes to cost reduction.

If the filling ratio of the first adsorbent 131 is less than 15 vol%, the volatile aromatic compound may not be sufficiently removed. On the other hand, when the filling ratio of the first adsorbent 131 exceeds 75 vol%, the proportion of the cleaning gas remaining in the second adsorbent 132 and the third adsorbent 133 decreases, and the amount of the cleaning gas decreases in the cleaning step. Insufficient cleaning may occur.

The second adsorbent 132 (zeolite-based adsorbent) and the third adsorbent 133 (activated carbon-based adsorbent) laminated on the subsequent stage (downstream side) of the first adsorbent 131 do not adsorb volatile aromatic compounds. .. 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 cleaning gas that is discharged from the adsorption tower in the decompression process after the adsorption process is completed and is used for cleaning the other adsorption towers in the cleaning process after the desorption process is completed remains in the tower at the start of the decompression process. Desorbs 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 near the gas passage port 12). Hydrogen is added. As a result, the adsorption tower after the desorption step can be effectively cleaned using the cleaning gas having an increased hydrogen content.

Although the specific embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made without departing from the idea of the invention. For example, as for 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 that of the above embodiment may be adopted. The number of adsorption towers is not limited to the three-tower type shown in the above embodiment, and the same effect can be expected even in the case of four or more towers.

Further, in the above embodiment, the case of purifying hydrogen has been described, but the ability to adsorb helium to the adsorbents (first adsorbent, second adsorbent, and third adsorbent) used in the purification method according to the present invention has been described. It is almost the same as hydrogen. Therefore, even when helium is concentrated and purified from a raw material gas containing helium as a main component and a volatile aromatic compound as an impurity, the same action and effect as those in the above-described embodiment can be obtained.

Next, the usefulness of the present invention will be described with reference to Examples and Comparative Examples.

[Example 1]
In this embodiment, the purification apparatus X shown in FIG. 1 is used, and the purification method using the pressure fluctuation adsorption method (PSA method) consisting of each step described with reference to FIG. 2 is performed under the conditions shown below. , Obtained concentrated hydrogen gas as a product gas from the raw material 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, 10C, silica gel B type (Fuji Silysia Chemical Ltd. Fuji silica gel B type) as the first adsorbent 131 and the second adsorbent from the gas passage port 11 to the gas passage port 12 CaA-type zeolite (5AHP manufactured by Union Showa Co., Ltd.) as 132 and activated carbon (PGAR manufactured by Cataler Co., Ltd.) as the third adsorbent 133 were laminated and filled. The filling 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 raw material gas, crude hydrogen gas containing 8500 volppm of toluene as an impurity was used, and the raw material gas was supplied at a flow rate of 5.2 NL / min. The operating conditions according to the PSA method are that the temperature of the adsorption tower, etc. is 40 ° C, the adsorption pressure is 0.8 MPaG, the desorption pressure is 20 kPaG, the cleaning pressure difference is 300 kPa, and the cycle time (the time of one cycle composed of steps 1 to 9). Was set to 675 seconds. Moreover, 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 below the lower limit of quantification (0.1 volppm or less), and the hydrogen gas. The recovery rate was 75%. The results of this example are shown in Table 1.

[Example 2]
Hydrogen from the raw material gas was charged in the same manner as in Example 1 except that the filling ratio of the adsorbent was 40 vol% for the first adsorbent 131, 50 vol% for the second adsorbent 132, and 10 vol% for the third adsorbent 133. Was purified. Moreover, 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 below the lower limit of quantification (0.1 volppm or less), and the hydrogen gas. The recovery rate was 70%. The results of this example are shown in Table 1.

[Example 3]
Hydrogen from the raw material gas was charged in the same manner as in Example 1 except that the filling ratio of the adsorbent was 20 vol% for the first adsorbent 131, 70 vol% for the second adsorbent 132, and 10 vol% for the third adsorbent 133. Was purified. Moreover, 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 below the lower limit of quantification (0.1 volppm or less), and the hydrogen gas. The recovery rate was 80%. The results of this example are shown in Table 1.

[Example 4]
Hydrogen from the raw material gas was charged in the same manner as in Example 1 except that the filling 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. Was purified. Moreover, 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 volppm, and the hydrogen gas recovery rate was 92%. there were. The results of this example are shown in Table 1.

[Example 5]
Hydrogen from the raw material gas was charged in the same manner as in Example 1 except that the filling ratio of the adsorbent was 30 vol% for the first adsorbent 131, 40 vol% for the second adsorbent 132, and 30 vol% for the third adsorbent 133. Was purified. Moreover, 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 0.43 volppm, and the hydrogen gas recovery rate was 85%. there were. The results of this example are shown in Table 1.

[Comparative Example 1]
Hydrogen from the raw material gas was charged in the same manner as in Example 1 except that the filling 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. Was purified. Moreover, 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 2000 volppm, and the hydrogen gas recovery rate was 90%. .. The results of this comparative example are shown in Table 1.

[Comparative Example 2]
Hydrogen from the raw material gas was charged in the same manner as in Example 1 except that the filling ratio of the adsorbent was 10 vol% for the first adsorbent 131, 80 vol% for the second adsorbent 132, and 10 vol% for the third adsorbent 133. Was purified. Moreover, 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 volppm, and the hydrogen gas recovery rate was 75%. .. The results of this comparative example are shown in Table 1.

[Comparative Example 3]
Hydrogen from the raw material gas was charged in the same manner as in Example 1 except that the filling 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. Was purified. The results are shown in Table 1. Moreover, 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 volppm, and the hydrogen gas recovery rate was 75%. .. The results of this comparative example are shown in Table 1.

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

X Purifier 10A, 10B, 10C Adsorption tower 11 Gas passage port (first gas passage port)
12 Gas passage port (second gas passage port)
131 1st Adsorbent 132 2nd Adsorbent 133 3rd Adsorbent 21 Raw Material 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 (2nd line)
33 lines (3rd 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
Branch paths 31a to 31c, 32a to 32c, 33a to 33c, 34a to 34c, 35a to 35c, 341,351 Automatic valve 3211,331 Pressure control valve 342,352 Flow rate control valve

Claims (11)

By repeating the cycle of the pressure fluctuation adsorption method performed using three or more adsorption towers filled with an adsorbent for each adsorption tower, a volatile aromatic compound is contained as an impurity and hydrogen or helium is contained as a main component. A method for purifying hydrogen or helium from a source gas, wherein the cycle is:
In a state where the adsorption tower is at a predetermined high pressure, the raw material gas is introduced into the adsorption tower to adsorb the volatile aromatic compound in the raw material gas to the adsorbent, and hydrogen or helium is adsorbed from the adsorption tower. Adsorption process that discharges product gas with high concentration of
A decompression step of discharging the gas remaining in the tower from the suction tower after the adsorption step to reduce the pressure in the tower, and a decompression step.
A desorption step of desorbing the volatile aromatic compound from the adsorbent in the adsorption tower after the depressurization step and discharging the gas in the tower.
It includes a cleaning step of introducing the gas discharged from another adsorption tower in the decompression step into the adsorption tower which has completed the desorption step and discharging the gas remaining in the tower.
Each of the adsorption towers 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 tower. A silica gel-based first adsorbent having a filling ratio in the range of 15 to 75 vol% is filled with respect to the entire filling capacity of the adsorbent, and the second region is filled with a filling ratio in the range of 15 to 75 vol%. Is filled with a zeolite-based second adsorbent, and the third region is filled with an activated carbon-based third adsorbent having a filling ratio in the range of 5 to 30 vol%, of hydrogen or helium. Purification method. The purification method according to claim 1, wherein the first adsorbent contains hydrophilic silica gel. The purification method according to claim 1, wherein the second adsorbent contains a CaA-type zeolite. The refining method according to claim 1, wherein the third adsorbent contains coconut shell activated carbon or coal activated carbon. The purification method according to claim 1, further comprising a step of increasing the pressure of the adsorption tower to a predetermined adsorption pressure between the cleaning step and the adsorption step. In the decompression step, the residual gas discharged from the adsorption tower is introduced as a cleaning gas into another adsorption tower in the cleaning step, and the first decompression step is followed by discharge from the adsorption tower. The purification method according to claim 5, further comprising a second depressurization step of introducing the residual gas to another adsorption tower in the pressurization step. The boosting step includes the first boosting step of introducing the residual gas discharged from the other adsorption tower in the first depressurizing step into the adsorption tower, and the adsorption step following the first boosting step. The purification method according to claim 6, further comprising a second step-up step of introducing a part of the product gas from the adsorption tower into the adsorption tower. A device for purifying hydrogen or helium from a raw material gas containing a volatile aromatic compound as an impurity and hydrogen or helium as a main component.
Three or more adsorption towers, each of which has a first gas passage port and a second gas passage port, and is filled with an adsorbent between the first and second gas passage ports, and
A storage tank for storing product gas and
A gas-liquid separation means for separating the gas discharged from the first gas passage port of the adsorption tower into a gas phase component and a liquid phase component,
A main trunk road connected to a raw material gas supply source, and a plurality of branch roads provided for each of the adsorption towers and connected to the first gas passage port side of the adsorption tower and each of which is provided with an on-off valve. The first line with
A main trunk road provided with the gas-liquid separation means, and a plurality of branch roads provided for each of the adsorption towers and connected to the first gas passage port side of the adsorption tower and each of which is provided with an on-off valve. The second line with,
A main trunk road provided with the storage tank, and a plurality of branch roads provided for each suction tower and connected to the second gas passage port side of the suction tower and each of which is provided with an on-off valve. With the third line to have
A plurality of main trunk roads connected to the main trunk road in the third line, and a plurality of suction towers provided for each of the suction towers and connected to the second gas passage port side of the suction tower and each provided with an on-off valve. The fourth line, which has a branch road, and
A plurality of main trunk roads connected to the main trunk road in the fourth line, and a plurality of suction towers provided for each of the suction towers and connected to the second gas passage port side of the suction tower and each provided with an on-off valve. With a fifth line, which has a branch road,
Each of the adsorption towers 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, and the first region includes the first region. , The silica gel-based first adsorbent having a filling ratio in the range of 15 to 75 vol% is filled with respect to the entire filling capacity of the adsorbent, and the second region is filled with a filling ratio of 15 to 75 vol%. Hydrogen or helium, which is filled with a zeolite-based second adsorbent in the range, and the above-mentioned third region is filled with an activated carbon-based third 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 is made of hydrophilic silica gel. The purification apparatus according to claim 8, wherein the second adsorbent contains CaA-type zeolite. The refining apparatus according to claim 8, wherein the third adsorbent contains coconut shell activated carbon or coal activated carbon.

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