KR102382274B1 - Hydrogen or helium purification method and hydrogen or helium purification apparatus - Google Patents

Abstract

A method of purifying hydrogen or helium by the PSA method performed from a raw material gas containing a volatile aromatic compound as an impurity and containing hydrogen or helium as a main component by the PSA method using an adsorption tower (10A to 10C) filled with an adsorbent, For each of the adsorption towers 10A to 10C, a cycle including an adsorption step, a pressure reduction step, a desorption step, and a washing step is repeatedly performed. Each adsorption tower 10A-10C is divided into a 1st area|region, a 2nd area|region, and a 3rd area|region sequentially toward a downstream from an upstream in the flow direction of the source gas in an adsorption tower. The first region is filled with the silica gel-based first adsorbent 131 having a filling ratio of 15 to 75 vol% with respect to the total filling capacity of the adsorbent. The second region is filled with the zeolite-based second adsorbent 132 having a filling ratio of 15 to 75 vol%. The third region is filled with the third adsorbent 133 of activated carbon having a filling ratio of 5 to 30 vol%.

Description

Hydrogen or helium purification method and hydrogen or helium purification apparatus

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

From the viewpoint of pollution prevention, the concentration of the volatile aromatic compound in the gas emitted as waste gas is regulated so as to be low in concentration. For example, in the case of a gas containing toluene as an impurity, in some regions, the ground reaching point concentration is set to 0.7 volppm or less. As a treatment method of waste gas for responding to such a regulation, there exist an absorption method, a cooling method, an adsorption method, a combustion method, etc. (refer patent document 1, for example). Moreover, the gas after refinement|purification by those processes may be collect|recovered and reused. Moreover, about the waste gas processing facility, the method which saves space and is low in introduction cost and operation cost is calculated|required.

On the other hand, when using hydrogen or helium as an industrial gas, it is necessary to add a purification process in order to obtain a highly purified gas depending on a use. For example, in the case of hydrogen for fuel cell vehicles, according to ISO14687-2 (hydrogen fuel standard for FCV, 2012, GradeD), the allowable concentration of components other than hydrogen is 2 volppm or less (in terms of methane) for total hydrocarbons. there is Also in this case, the space-saving and inexpensive method is calculated|required. In the removal of hydrocarbons by the absorption method, it is difficult to set the hydrocarbon concentration in the diffusion gas to 1 vol% or less, and has not yet been realized. Also in the cooling method, since impurities of vapor pressure remain on the gas phase side, it is difficult to purify volatile aromatic compounds to the order of several ppm. In the combustion method, it is necessary to mix oxygen etc., and since water, carbon dioxide, etc. are produced after combustion, 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 volatile aromatic compounds contained in gas, a pressure swing adsorption method using synthetic zeolite or hydrophobic silica gel is employed. However, in this method as well, since a vacuum device is used for desorption and hydrophobic ones are used among silica-rich zeolite and silica gel, there is a problem in terms of cost (see, for example, Patent Document 1).

There is also a method in which a waste gas containing a volatile aromatic compound is treated using a pressure swing adsorption method to reduce the hydrocarbon concentration. If the adsorbent can be regenerated by the pressure swing adsorption method, heating or cooling becomes 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, and there is a problem 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 employed. The volatile aromatic compound introduced into the pores of the activated carbon is not easily desorbed. For this reason, the method of using a heating means for desorption is employ|adopted and desorption is accelerated|stimulated by the temperature fluctuation adsorption method or use of steam. In the case of using a heating means, there are many problems in terms of operability, such as requiring additional equipment for heating and cooling, and taking time for heat transfer.

In addition, in the method using the vacuum regeneration method, the cost for vacuum regeneration is increased. In addition, in the method using the purge gas (purified high-purity product gas), the cost increases as much as the purge gas is used. Moreover, also with respect to regeneration by heating, it leads to an increase in cost by the amount of energy required for heating similarly.

JPH9-47635A JPH11-71584 A JP 2004-42013 A

The present invention has been devised under these circumstances, and it is to provide a method and apparatus suitable for obtaining high-purity hydrogen or helium from a raw material gas containing volatile aromatic compounds as impurities using a pressure swing adsorption method while reducing costs doing it as a task

According to the first aspect of the present invention, the cycle of the pressure swing adsorption method performed using three or more adsorption towers filled with adsorbents is repeated for each adsorption tower to contain volatile aromatic compounds as impurities, and hydrogen or helium as a main component A method for purifying hydrogen or helium from a source gas comprising

In the cycle, the source gas is introduced into the adsorption tower under a predetermined high pressure by a pressure swing adsorption method performed using three or more adsorption towers filled with an adsorbent, and the volatile aromatic compound in the source gas is an adsorption step of adsorbing the adsorbent and discharging a product gas having a high concentration of hydrogen or helium from the adsorption tower; and a desorption process of desorbing the volatile aromatic compound from the adsorbent in the adsorption tower after the decompression process is completed and discharging gas in the tower, and the desorption process of gas discharged from another adsorption tower in the depressurization process and a cleaning step of introducing into the finished adsorption tower and discharging the gas remaining in the tower. Each of said adsorption towers is divided into 1st area|region, 2nd area|region, and 3rd area|region sequentially from an upstream to a downstream in the flow direction of the said source gas in the said 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 a 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 also containing hydrogen or helium as a main component. The device includes three or more adsorption towers each having a first gas passage port and a second gas passage port, and filled with an adsorbent between the first gas passage port and the second gas passage port, and for storing product gas a storage tank for, gas-liquid separation means for separating the gas discharged from the first gas passage port of the adsorption tower into a gaseous component and a liquid phase component, a main path connected to a source gas supply source, and each of the adsorption towers A first line connected to the first gas passage side of the adsorption tower and having a plurality of branch passages each provided with an on/off valve, a main passage in which the gas-liquid separation means is installed, and each of the adsorption towers are installed in the adsorption tower A second line connected to the first gas passage side and having a plurality of branch passages each provided with on/off valves; A third line connected to the old side and having a plurality of branch passages each provided with an on/off valve, a main passage connected to the main passage in the third line, and each of the adsorption towers are provided for the second line of the adsorption tower 2 A fourth line connected to the gas passage side and having a plurality of branch passages each provided with an on/off valve, a main passage connected to the main passage in the fourth line, and an adsorption tower provided for each of the adsorption towers and a fifth line connected to the second gas passage side and having a plurality of branch passages each provided with an on-off valve. Each of the adsorption towers is sequentially divided into a first region, a second region and a third region from the first gas passage port in the adsorption tower toward the second gas passage port. 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 have intensively studied a method of separating hydrogen or helium from a raw material gas containing volatile aromatic compounds as impurities by pressure swing adsorption. After the adsorption process is completed, after the adsorption process is completed, the adsorption tower after the desorption process is cleaned using a relatively clean gas in the layer of the zeolite and activated carbon, so that a vacuum device or heating is performed during desorption. It was found that a product gas of high purity after purification can be obtained without using an apparatus, and the present invention has been completed.

ADVANTAGE OF THE INVENTION According to this invention, the content rate of the volatile aromatic compound contained as an impurity in hydrogen or helium can be purified to 1 volppm or less at low cost and space-saving apparatus.

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

1 shows a schematic configuration of a purification apparatus used for carrying out a method for purifying hydrogen according to an embodiment of the present invention.
2 shows the flow state of gas in each step of the hydrogen purification method according to the embodiment of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of this invention is concretely described with reference to drawings.

Fig. 1 shows a schematic configuration of a purification apparatus X that can be used for carrying out the method for purifying hydrogen or helium according to the present invention. The purification device (X) includes three adsorption towers (10A, 10B, 10C), a source 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 35 are provided. The refiner|purifier X is comprised so that it can concentrate and separate hydrogen or helium using the pressure swing adsorption method (PSA method) from the source gas (crude hydrogen or crude helium) containing hydrogen or helium. Examples of the source gas include a gas containing, as a main component, hydrogen generated from organic hydride, and containing, for example, a volatile aromatic compound (for example, toluene, benzene, methylcyclohexane, etc.) as an impurity. can Although the following description is made with respect to the case where the main component of the source gas is hydrogen, the present invention is not limited to this, and it is also applicable to the case where the main component of the source gas is helium.

Each of the adsorption towers 10A, 10B, and 10C is provided with gas passage ports 11 and 12 at both ends, and an adsorbent is filled between the gas passage ports 11 and 12 . Specifically, in each of the adsorption towers 10A, 10B, and 10C, a plurality (three) regions partitioned by, for example, a perforated plate (not shown) are formed, and different adsorbents are formed in these regions. is charged In the present embodiment, in the flow direction of the source gas in each of the adsorption towers 10A, 10B, and 10C, from the upstream side (gas passage port 11) to the downstream side (gas passage port 12) A first adsorbent 131 , a second adsorbent 132 , and a third adsorbent 133 are sequentially stacked.

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

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 total 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%, and the filling ratio of the third adsorbent 133 is in the range of 5 to 30 vol%, preferably 5 to 20 vol%. The sum of the respective filling ratios of the first to third adsorbents 131 , 132 and 133 is 100 vol%.

The source gas supply source 21 is a pressure vessel for storing the source gas 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 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 pipe. Accordingly, the piping from the source gas supply source 21 to the adsorption towers 10A, 10B, and 10C (the main path 31' of the line 31 to be described later) is heated and/or the adsorption towers 10A, 10B, 10C ) It is preferable to install a mist trap etc. in the main path 31' in front. Although the pressure of the source gas supplied from the source gas supply source 21 is not specifically limited, Higher pressure is preferable, and a compressor (not shown) is installed in the main path 31' as needed. In addition, when the hydrogen or helium supplied from the source gas supply source 21 contains water as an impurity, it is preferable to install a water removal device (not shown) in the main 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 mentioned above, it is preferable that it is a temperature (at least about room temperature) at which a volatile aromatic compound does not liquefy.

The product storage tank 22 is a pressure vessel for storing gas (a product gas to be 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 offgas. The gas-liquid separator 25 condenses the off-gas that has passed through the cooler 24 under a predetermined pressure to separate the gas-phase component and the liquid-phase component. The term "gas-liquid separation means" includes the cooler 24 and the gas-liquid separator 25 .

The line 31 is a main path 31' to which the source gas supply source 21 is connected, and a branch path 31A respectively connected to the gas passage ports 11 side of the adsorption towers 10A, 10B, and 10C. 31B, 31C). In the branch passages 31A, 31B, and 31C, valves 31a, 3lb, and 31c that can be automatically switched between an open state and a closed state (hereinafter, a valve having such a function is referred to as an "automatic valve") are provided. .

The line 32 is a branch connected to the main path 32' in which the cooler 24 and the gas-liquid separator 25 are installed, and to the gas passage port 11 side of the adsorption towers 10A, 10B, and 10C, respectively. furnaces 32A, 32B, and 32C are provided. Moreover, the off-gas tank 23 is provided in the main path 32' on the upstream side of the cooler 24. As shown in FIG. A pressure regulating valve 321 is provided between the off-gas tank 23 and the cooler 24 in the main path 32'. Automatic valves 32a, 32b, and 32c are installed in the branch furnaces 32A, 32B, and 32C.

The line 33 is a main furnace 33' in which the product storage tank 22 is installed, and branch furnaces 33A and 33B respectively connected to the gas passage ports 12 sides of the adsorption towers 10A, 10B, and 10C. , 33C) is provided. Automatic valves 33a, 33b, 33c are installed in the branch furnaces 33A, 33B, and 33C. A pressure regulating valve 331 is provided on the downstream side of the product storage tank 22 in the main path 33'.

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

The line 35 is for connecting any two of the adsorption towers 10A, 10B, and 10C to each other, and the main path 35' connected to the main path 34' of the line 34, and the adsorption tower 10A , 10B, and 10C are provided with branch furnaces 35A, 35B, and 35C respectively connected to the gas passage port 12 side. An automatic valve 351 and a flow rate control valve 352 are installed in the main path 35'. Automatic valves 35a, 35b, 35c are installed in the branch furnaces 35A, 35B, and 35C.

The hydrogen purification method 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 rate control valves 342 and 352 are appropriately switched. By doing so, a desired gas flow state in the device is realized, and one cycle consisting of the following steps 1 to 9 can be repeated. In one cycle of this method, in each of the adsorption towers 10A, 10B, and 10C, an adsorption step, a pressure reduction step, a pressure equalization pressure reduction, a desorption step, a washing step, a pressure equalization step, and a pressure increase step are performed. 2A to 2I schematically show the flow state of the gas in the purification apparatus X in steps 1 to 9. FIG. In addition, in FIGS. 2A-2I, the following abbreviations are used.

AS: adsorption process

DP: decompression process

DS: Desorption process

RN: cleaning process

PR: step-up process

Eq-DP: Equal pressure decompression process

Eq-PR: Equalization and Step-Up Process

In step 1, the automatic valves 31a, 33a, 32b, 34b, 35c, 351 and the flow control valve 352 are opened, so that the gas flow state as shown in Fig. 2A is achieved.

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

Here, although there is no restriction|limiting in particular about the density|concentration of the volatile aromatic compound in the source gas introduce|transduced into 10 A of adsorption towers, For example, it is set to about 100 volppm - 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 represents a gauge pressure, the same applies below), preferably 0.5 to 0.8 MPa It is G.

In addition, in step 1, the gas passage ports 12 of each of the adsorption towers 10B and 10C are connected via the lines 34 and 35. As shown in FIG. Since the adsorption tower 10B was first subjected to a desorption step, and the adsorption tower 10C was first subjected to an adsorption step (see step 9 shown in Fig. 2i), at the start of step 1, the adsorption tower 10C was The pressure in the tower is higher than that of 10B). Then, after the start of step 1, a decompression process is performed in the adsorption tower 10C, and the gas (residual concentrated hydrogen gas) with a low impurity concentration remaining in the tower of the adsorption tower 10C is discharged from the gas passage port 12 . As a result, the pressure in the tower decreases. The difference between the pressure in the tower of the adsorption tower 10C at the start and the end of step 1 is, for example, about 300 kPa. On the other hand, in the adsorption tower 10B, a washing process is performed, and the residual concentrated hydrogen gas discharged from the adsorption tower 10C is discharged as a washing gas through a line 35, a flow rate adjustment valve 352 and a line 34 through the gas passage port. The gas introduced from (12) and remaining in the tower is discharged. Here, the gas discharged|emitted from the adsorption tower 10B is a gas with a high concentration of a volatile aromatic compound, and this gas is sent to the off-gas tank 23 via the line 32 as an off-gas. At the end of step 1, the pressure in the tower of the adsorption tower 10C is higher than the pressure in the tower of 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, so that the flow state of the gas as shown in Fig. 2B is achieved.

In step 2, an adsorption process is performed continuously in 10 A of adsorption towers. Also in step 2, the gas passage ports 12 and 12 of the adsorption towers 10B and 10C are connected through the lines 34 and 35 respectively. On the other hand, the automatic valve 32b is closed with respect to the adsorption tower 10B. And at the time of the start of Step 2, the inside of the tower of the adsorption tower 10C is still higher pressure than the inside of the tower of the adsorption tower 10B. Therefore, pressure equalization and pressure reduction are performed in the adsorption tower 10C, and pressure equalization pressure increase is performed in the adsorption tower 10B. More specifically, the gas in the tower of the adsorption tower 10C is introduced into the adsorption tower 10B via the lines 35 and 34, and the pressure in the tower of the adsorption tower 10C is reduced while the pressure in the tower of the adsorption tower 10B is increased. do. As a result, in the adsorption towers 10B, 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, so that the gas flow state as shown in Fig. 2C is achieved.

In step 3, the adsorption process is performed continuously in 10 A of adsorption towers. In addition, in step 3, while blocking the communication between the adsorption towers 10B and 10C, a part of the product gas discharged from the gas passage port 12 of the adsorption tower 10A is connected to the line 34 and the flow rate control valve 342. It introduces into the adsorption tower 10B through the intervening, and the pressure-increasing process of the adsorption tower 10B is performed.

In addition, in step 3, about 10 C of adsorption towers, the automatic valve 32c is opened and it is communicating with the off-gas tank 23 via the line 32. As shown in FIG. Thereby, the desorption process is performed in the adsorption tower 10C, the pressure inside the tower of the adsorption tower 10C is decompressed, impurities (mainly volatile aromatic compounds) are desorbed from the adsorbent, and the gas in the tower (gas with a high concentration of volatile aromatic compounds) is It is discharged out of the tower as off-gas through the gas passage 11 . The minimum pressure (desorption pressure) inside the adsorption tower 10C in a desorption process is 0-50 kPaG, for example, Preferably it is 0-20 kPaG. The off-gas discharged|emitted from 10 C of adsorption towers is sent to the off-gas tank 23 via the line 32. As shown in FIG. The gas in the off-gas tank 23 is appropriately sent to the cooler 24 via the pressure regulating valve 321, and passes through the gas-liquid separator 25 to liquefy the volatile aromatic compound and recover it as a liquid. 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 constituted by steps 1 to 9, and the process time of these steps 1 to 3 is about 225 seconds in total.

In subsequent steps 4 to 6, as shown in FIGS. 2D to 2F, the operation performed for the adsorption tower 10A in steps 1 to 3 is performed to the adsorption tower 10B, and the adsorption tower 10B in steps 1 to 3 The operation performed with respect to 10 C of adsorption towers is performed with respect to 10 C of adsorption towers, and the operation performed with respect to 10 C of adsorption towers in steps 1 to 3 is performed with respect to 10 A of adsorption towers.

In step 4, the automatic valves 31b, 33b, 32c, 34c, 35a, 351 and the flow control valve 352 are opened, so that 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 control valve 352 are opened, so that 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 control valve 342 are opened, so that the gas flow state as shown in Fig. 2F is achieved. Although detailed description is omitted, in steps 4, 5, and 6, the adsorption tower 10A sequentially performs the same operations as the adsorption tower 10C in steps 1, 2, and 3, and the adsorption tower 10B performs steps 1, 2, The same operations as in the adsorption tower 10A in step 3 are sequentially performed, and the adsorption tower 10C sequentially performs the same operations as in the adsorption 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 for the adsorption tower 10A in steps 1 to 3 is performed to the adsorption tower 10C, and the adsorption tower 10B in steps 1 to 3 The operation performed with respect to the adsorption tower 10A is performed with respect to the adsorption tower 10A, and the operation performed with respect to the adsorption tower 10C in steps 1-3 is performed with respect to the adsorption tower 10B.

In step 7, the automatic valves 31c, 33c, 32a, 34a, 35b, 351 and the flow control valve 352 are opened, so that the flow state of the gas as shown in Fig. 2G is achieved. In step 8, the automatic valves 31c, 33c, 34a, 35b, 351 and the flow control valve 352 are opened, so that 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, so that the flow state of the gas as shown in Fig. 2I is achieved. Although detailed description is omitted, in steps 7, 8, and 9, the adsorption tower 10A sequentially performs the same operations as the adsorption tower 10B in steps 1, 2, and 3, and the adsorption tower 10B performs steps 1, 2, The same operations as in the adsorption tower 10C in step 3 are sequentially performed, and the adsorption tower 10C sequentially performs the same operations as in the adsorption tower 10A in steps 1, 2 and 3.

And, by repeatedly performing the cycle consisting of the above steps 1 to 9 in each of the adsorption towers 10A, 10B, 10C, the source gas is continuously introduced into any one of the adsorption towers 10A, 10B, 10C, Concentrated hydrogen gas (product gas) is continuously acquired.

In the hydrogen purification method of this embodiment, for one cycle by the PSA method performed in each of the adsorption towers 10A, 10B, and 10C, after the adsorption step, the residual gas in the tower is introduced into another adsorption tower after the desorption step. Then, a washing process is performed. The gas in the adsorption tower after completion of 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 washed using the gas. In addition, since the product gas is not used for cleaning, a decrease in the recovery rate of hydrogen can be suppressed.

With respect to the adsorbent charged in each of the adsorption towers 10A, 10B, and 10C, the silica gel adsorbent as the first adsorbent 131 is filled on the most upstream side in the flow direction of the raw material gas. Silica gel-based adsorbents have excellent adsorption capacity of impurities (volatile aromatic compounds) at a high pressure of 0.1 to 1.0 MPaG (= 100 to 1000 kPaG), and even at the lowest pressure (desorption process) at 0 to 50 kPaG above atmospheric pressure. 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 filling capacity. As a result, volatile aromatic compounds can be efficiently adsorbed and removed, and since a vacuum installation is not required, cost reduction can be achieved. In addition, when hydrophilic silica gel is used as the first adsorbent 131, volatile aromatic compounds can be appropriately adsorbed and removed without pretreatment, which contributes to cost reduction.

Moreover, when the filling ratio of the 1st adsorbent 131 is less than 15 vol%, there exists a possibility that a volatile aromatic compound may become unable to be fully removed. 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 is lowered, and the amount of the cleaning gas is reduced to perform cleaning. There exists a possibility that washing|cleaning in a process may become inadequate.

The second adsorbent 132 (zeolite-based adsorbent) and the third adsorbent 133 (activated carbon-based adsorbent) laminated on the rear end (downstream side) of the first adsorbent 131 do not adsorb volatile aromatic compounds. That is, the adsorption process is terminated 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 process is completed and discharged from the adsorption tower in the depressurization step, and the cleaning gas used for cleaning the other adsorption towers in the cleaning step after the desorption step is completed is concentrated hydrogen gas remaining in the tower at the start of the decompression step. Hydrogen desorbed from the second adsorbent 132 and the third adsorbent 133 in addition to (mainly the gas in the filling region of the second adsorbent 132 and the third adsorbent 133, close to the gas passage 12) is applied As a result, the adsorption tower after completion of the desorption process can be effectively washed using the cleaning gas having a high hydrogen content.

As mentioned above, although specific embodiment of this invention was described, this invention is not limited to this, Various changes are possible within the range which does not deviate from the idea of invention. For example, as for the configuration of the line (pipe) forming the gas flow path in the apparatus for performing the hydrogen or helium purification method 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 only 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.

In the above embodiment, the case of purifying hydrogen has been described, but the adsorption capacity of helium to the adsorbents (first adsorbent, second adsorbent, and third adsorbent) used in the purification method according to the present invention is substantially the same as that of 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 effects as in the above embodiment are exhibited.

Example

Next, the usefulness of this invention is demonstrated by an Example and a comparative example.

[Example 1]

In this embodiment, the raw material gas is used under the conditions shown below by the purification method using the pressure swing adsorption method (PSA method) consisting of each step described with reference to FIG. 2 using the purification apparatus X shown in FIG. Concentrated hydrogen gas was obtained as a product gas from

As the adsorption towers 10A, 10B, and 10C, a cylindrical one having an inner diameter of 35 mm was used, and the adsorbent filling capacity was about 1 L (liter). In each of the adsorption towers 10A, 10B, and 10C, from the gas passage port 11 toward the gas passage port 12, the silica gel type B (Fuji SILYSIACHEMICAL LTD.) product as the first adsorbent 131 is Fuji silica gel type B), CaA type zeolite (5AHP manufactured by UNION SHOWA KK) as the second adsorbent 132, and activated carbon (PGAR manufactured by Cataler Corporation) as the third adsorbent 133. , stacked and filled. As for the filling ratio (volume ratio) of these adsorbents, the first adsorbent 131 was 30 vol%, the second adsorbent 132 was 60 vol%, and the third adsorbent 133 was 10 vol%. As for the source gas, crude hydrogen gas containing 8500 volppm toluene as an impurity was used, and the source gas was supplied at a flow rate of 5.2 Nl/min. The operating conditions by the PSA method are: the temperature of the adsorption tower etc. is 40°C, the adsorption pressure is 0.8 MPaG, the desorption pressure is 20 kPaG, the washing pressure difference is 300 kPa, the cycle time (time of one cycle consisting of steps 1 to 9) ) became 675 seconds. In addition, when the concentration of impurities 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 below the lower limit of quantification (0.1 volppm or less), and the hydrogen gas recovery rate was 75% it was Table 1 shows the results of this example.

[Example 2]

Purification of hydrogen from the raw material gas was carried out in the same manner as in Example 1, except that the filling ratio of the adsorbent was set to 40 vol% of the first adsorbent 131, 50 vol% of the second adsorbent 132, and 10 vol% of the third adsorbent 133. was done. In addition, 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 below the lower limit of quantification (0.1 volppm or less), and the hydrogen gas recovery rate was 70% it was Table 1 shows the results of this example.

[Example 3]

Purification of hydrogen from the source gas was carried out in the same manner as in Example 1, except that the filling 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. was done. In addition, when the concentration of impurities 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 below the lower limit of quantification (0.1 volppm or less), and the hydrogen gas recovery rate was 80% it was Table 1 shows the results of this example.

[Example 4]

Purification of hydrogen from the source gas was carried out in the same manner as in Example 1, except that the filling ratio of the adsorbent was 70 vol% of the first adsorbent 131, 20 vol% of the second adsorbent 132, and 10 vol% of the third adsorbent 133. was done. Further, when the concentration of impurities 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 0.67 volppm, and the hydrogen gas recovery rate was 92%. Table 1 shows the results of this example.

[Example 5]

Purification of hydrogen from the source gas was carried out in the same manner as in Example 1, except that the filling 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. was done. In addition, when the concentration of impurities 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 0.43 volppm, and the hydrogen gas recovery rate was 85%. Table 1 shows the results of this example.

[Comparative Example 1]

Purification of hydrogen from the source gas was carried out in the same manner as in Example 1, except that the filling ratio of the adsorbent was 80 vol% of the first adsorbent 131, 10 vol% of the second adsorbent 132, and 10 vol% of the third adsorbent 133. was done. Further, when the concentration of impurities 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 volppm, and the hydrogen gas recovery rate was 90%. Table 1 shows the results of this comparative example.

[Comparative Example 2]

Purification of hydrogen from the source gas was carried out in the same manner as in Example 1, except that the filling ratio of the adsorbent was 10 vol% of the first adsorbent 131, 80 vol% of the second adsorbent 132, and 10 vol% of the third adsorbent 133. was done. In addition, when the concentration of impurities 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 3000 volppm, and the hydrogen gas recovery rate was 75%. Table 1 shows the results of this comparative example.

[Comparative Example 3]

Purification of hydrogen from the source gas was carried out in the same manner as in Example 1, except that the filling ratio of the adsorbent was 30 vol% of the first adsorbent 131, 30 vol% of the second adsorbent 132, and 40 vol% of the third adsorbent 133. was done. The results are shown in Table 1. Further, when the concentration of impurities 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 2 volppm, and the hydrogen gas recovery rate was 75%. Table 1 shows the results of this comparative example.

Adsorbent filling rate hydrogen gas
recovery rate
[%] Toluene concentration in product gas first adsorbent second adsorbent tertiary adsorbent Example 1 60 30 10 75 0.1 volppm or less Example 2 40 50 10 70 0.1 volppm or less Example 3 20 70 10 80 0.1 volppm or less Example 4 70 20 10 92 0.67 volppm Example 5 30 40 30 85 0.43 volppm Comparative Example 1 80 10 10 90 2000 volppm Comparative Example 2 10 80 10 75 3000 volppm Comparative Example 3 30 30 40 75 2 volppm

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: refiner
10A, 10B, 10C: adsorption tower
11: gas passage port (first gas passage port)
12: gas passage port (second gas passage port)
131: first adsorbent
132: second adsorbent
133: third adsorbent
21: source gas source
22: product storage tank
23: off-gas tank
24: cooler (gas-liquid separation means)
25: gas-liquid separator (gas-liquid separation means)
31: line (first line)
32: line (second line)
33: line (third line)
34: line (fourth line)
35: line (fifth line)
31', 32', 33', 34', 35': weekly
31A-31C, 32A-32C, 33A-33C, 34A-34C, 35A-35C: branched
31a to 31c, 32a to 32c, 33a to 33c, 34a to 34c, 35a to 35c, 341, 351: automatic valve
321, 331: pressure control valve
342, 352: flow control valve

Claims (11)

By repeating the cycle of the pressure swing adsorption method performed using three or more adsorption towers filled with adsorbents for each adsorption tower, hydrogen or helium is produced from crude hydrogen gas or crude helium gas as a source gas containing volatile aromatic compounds as impurities. A method for purifying hydrogen or helium for purification, wherein the cycle comprises:
In a state where the adsorption tower is at a predetermined high pressure, the source gas is introduced into the adsorption tower to adsorb the volatile aromatic compound in the source gas to the adsorbent, and a product gas having a high concentration of hydrogen or helium is discharged from the adsorption tower. fair;
a decompression step of lowering the pressure in the tower by discharging the gas remaining in the tower from the adsorption tower having completed the adsorption step;
a desorption step of desorbing the volatile aromatic compound from the adsorbent in the adsorption tower after the decompression step has been completed, and discharging gas in the tower; and
a cleaning process of introducing the gas discharged from another adsorption tower in the depressurization process into the adsorption tower where the desorption process has been completed and discharging the gas remaining in the tower,
Each of the adsorption towers is divided into a first area, a second area and a third area sequentially from an upstream side to a downstream side in the flow direction of the source gas in the adsorption tower, and in the first area, the adsorbent Based on the total filling capacity of is filled, 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%. The method of claim 1, wherein the second adsorbent comprises hydrophilic silica gel. The method of claim 1, wherein the second adsorbent comprises a CaA-type zeolite. The method of claim 1 , wherein the third adsorbent comprises coconut shell activated carbon or coal activated carbon. The method for purifying hydrogen or helium according to claim 1, further comprising a pressure increasing step for increasing the pressure of the adsorption tower to a predetermined adsorption pressure between the washing step and the adsorption step. 6. The method of claim 5, wherein the decompression step comprises a first decompression step of introducing the residual gas discharged from the adsorption tower as a cleaning gas to another adsorption tower in the cleaning step, and discharge from the adsorption tower following the first decompression step. A method for purifying hydrogen or helium, comprising a second reduced pressure step of introducing the remaining residual gas to another adsorption tower in the pressure boosting process. The method according to claim 6, wherein the pressure-increasing process comprises a first pressure-increasing step of introducing the residual gas discharged from another adsorption tower in the first pressure-reducing step into the adsorption tower, and following the first pressure-rising step, in the adsorption process A method for purifying hydrogen or helium, comprising a second pressure-increasing step of introducing a portion of product gas from another adsorption tower into the adsorption tower. An apparatus for purifying hydrogen or helium from crude hydrogen gas or crude helium gas as a raw material gas containing volatile aromatic compounds as impurities, comprising:
three or more adsorption towers each having a first gas passage port and a second gas passage port, and filled with an adsorbent between the first gas passage port and the second gas passage port;
a storage tank for storing product gas;
gas-liquid separation means for separating the gas discharged from the first gas passage port of the adsorption tower into a gaseous component and a liquid phase component;
a first line having a main path connected to a source gas supply source, and a plurality of branch paths provided for each of the adsorption towers and connected to the first gas passage side of the adsorption tower and provided with an on/off valve, respectively;
a second line having a main path in which the gas-liquid separation means is installed, and a plurality of branch paths installed in each of the adsorption towers, connected to the first gas passage side of the adsorption tower, and provided with an on/off valve, respectively;
a third line having a main path in which the storage tank is installed, and a plurality of branch paths installed in each of the adsorption towers, connected to the second gas passage side of the adsorption tower, and provided with an on/off valve, respectively;
a main path connected to the main path in the third line, and a fourth branch path provided for each adsorption tower and connected to the second gas passage side of the adsorption tower and provided with an on/off valve, respectively line; and
A fifth line comprising a main path connected to the main path in the fourth line, and a plurality of branch paths provided for each adsorption tower and connected to the second gas passage side of the adsorption tower and provided with an on/off valve, respectively. including the line,
Each of the adsorption towers is divided into a first region, a second region and a third region sequentially from the first gas passage port in the adsorption tower toward the second gas passage port, and in the first region, the adsorbent Based on the total filling capacity of is filled, 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%. The apparatus of claim 8, wherein the first adsorbent is made of hydrophilic silica gel. The apparatus of claim 8, wherein the second adsorbent comprises a CaA-type zeolite. 9. The apparatus of claim 8, wherein the third adsorbent comprises coconut shell activated carbon or coal activated carbon.

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