JP6646526B2 - Hydrogen gas production method and hydrogen gas production device - Google Patents

Description

  The present invention relates to a hydrogen gas production method and a hydrogen gas production device.

  2. Description of the Related Art In recent years, expectations for hydrogen as a fuel for fuel cells leading to improvement of the global environment have increased. As a typical hydrogen production method, impurities other than hydrogen contained in a hydrogen-rich gas obtained by reforming a hydrocarbon (natural gas) or dehydrogenating an organic hydride containing hydrogen are removed by a hydrogen purifier. There is a method (see JP-A-2014-73922). As such a hydrogen purifier, there is an adsorption tower using a TSA (Temperature Swing Adsorption) method and a PSA (Pressure Swing Adsorption) method.

  The above-described hydrogen production apparatus is generally operated such that hydrogen is supplied to a hydrogen vehicle or the like during the day and the supply (purification) of hydrogen is stopped at night. Therefore, the purification of the hydrogen-rich gas by the adsorption tower is stopped at night. In the adsorption tower, when the purification is stopped, that is, when the supply of the hydrogen-rich gas is stopped, the impurities adsorbed by the adsorbent diffuse into the adsorption tower, and a residual gas containing a large amount of impurities is generated in the adsorption tower. Therefore, when the purification is restarted after the purification of the hydrogen-rich gas is stopped, the residual gas in the adsorption tower is mixed with the purified gas, and the purity of the obtained hydrogen gas becomes insufficient, so that it is necessary to treat the hydrogen gas as an off-gas. As a result, there is a disadvantage that the recovery rate of the hydrogen gas is reduced, and it takes time to start up the supply of the hydrogen gas.

JP 2014-73922 A

  The present invention has been made in view of the above circumstances, and a method for producing a hydrogen gas capable of suppressing a decrease in the recovery rate of hydrogen gas and shortening the startup time when repeatedly stopping and restarting hydrogen gas purification. And an apparatus for producing hydrogen gas.

  The present invention made in order to solve the above-mentioned problems is a hydrogen gas production method for producing high-purity hydrogen gas from a hydrogen-rich gas containing an impurity gas other than hydrogen gas and hydrogen by purification using an adsorption tower, The method is characterized by comprising a step of purifying an exhaust gas containing residual gas discharged from the adsorption tower by using a residual gas adsorption tower from the time when the purification is stopped to the time when the purification is restarted.

  According to the hydrogen gas production method, the residual gas contained in the exhaust gas is exhausted by discharging the residual gas in the adsorption tower and refining the gas containing the residual gas by the adsorption tower before the refining of the hydrogen-rich gas is restarted. And hydrogen gas can be recovered as high-purity hydrogen gas. As a result, the hydrogen gas producing method can suppress a decrease in the recovery rate of the hydrogen gas and can shorten the startup time until the supply of the hydrogen gas.

  The method for producing hydrogen gas may further include a step of performing a dehydrogenation reaction of the organic hydride by heating in the presence of a catalyst, and the hydrogen-rich gas may be a gas discharged in the dehydrogenation reaction step. By using the organic hydride for transporting the hydrogen-rich gas, the transport efficiency of hydrogen can be increased.

  The residual gas adsorption tower is preferably of the TSA type. Since the residual gas adsorption tower is mainly used only when refining is resumed, the heat regeneration can be performed over time. Therefore, by using a TSA type adsorption tower for the residual gas, it is possible to reduce the flow rate of the purge gas required at the time of regeneration of the adsorption tower for the residual gas, thereby suppressing a decrease in production efficiency.

  It is preferable to regenerate the adsorption tower for residual gas using the heat of the dehydrogenation reaction. By thus regenerating the TSA type residual gas adsorption tower using the heat of the dehydrogenation reaction, the operating cost can be further reduced.

  In the exhaust gas refining step, the supply of the exhaust gas to the residual gas adsorption tower may be stopped depending on the concentration of the exhaust gas other than the hydrogen gas. By performing such control, the minimum necessary purification can be performed in the residual gas adsorption tower, so that the operating cost can be further reduced.

  The adsorbent filled in the adsorption tower is preferably zeolite, activated carbon, porous silica, porous alumina, or a metal organic structure. By using such an adsorbent, the quality of high-purity hydrogen gas obtained from the adsorption tower can be improved.

  Another invention made in order to solve the above-mentioned problem is a hydrogen gas production method for producing high-purity hydrogen gas from a hydrogen-rich gas containing an impurity gas other than hydrogen gas and hydrogen by purification using an adsorption tower, It is characterized by comprising a residual gas adsorption tower for purifying an exhaust gas containing a residual gas discharged from the inside of the adsorption tower after stopping the purification of the hydrogen-rich gas.

  According to the hydrogen gas producing apparatus, the residual gas contained in the exhaust gas is exhausted by discharging the residual gas in the adsorption tower and refining the gas containing the residual gas by the adsorption tower before the refining of the hydrogen-rich gas is restarted. And hydrogen gas can be recovered as high-purity hydrogen gas. As a result, the hydrogen gas producing apparatus can suppress a decrease in the recovery rate of the hydrogen gas and shorten the startup time until the supply of the hydrogen gas.

  As described above, according to the hydrogen gas production method and the hydrogen gas production apparatus of the present invention, when the stop and restart of the hydrogen gas purification are repeated, it is possible to suppress the decrease in the recovery rate of the hydrogen gas and to shorten the startup time. .

It is a schematic diagram showing the hydrogen gas production device of one embodiment of the present invention.

  Hereinafter, embodiments of a hydrogen gas production apparatus and a hydrogen gas production method of the present invention will be described in detail with reference to the drawings as appropriate.

[Hydrogen gas production equipment]
The hydrogen gas producing apparatus shown in FIG. 1 includes a reactor 1 for performing a dehydrogenation reaction of an organic hydride A by heating in the presence of a catalyst, and an aromatic compound by cooling from a mixed gas of an aromatic compound and hydrogen discharged from the reactor 1. A separator 2 for gas-liquid separation of the compound, a main adsorption tower 3 for purifying the mixed gas (hydrogen-rich gas B) separated by the separator 2, and a gas discharged from the main adsorption tower 3 after the purification of the hydrogen-rich gas B is stopped. It is mainly provided with a residual gas adsorption tower 4 for purifying exhaust gas C containing residual gas to obtain high-purity hydrogen gas. In addition, the hydrogen gas producing apparatus includes a hydrogen-rich gas buffer tank 5 for storing the hydrogen-rich gas B discharged from the separator 2 and an adsorption tower 4 for the residual gas of the exhaust gas C depending on the concentration of the exhaust gas C other than the hydrogen gas. And a control mechanism (not shown) for stopping the supply to the apparatus.

  Examples of the organic hydride A used in the hydrogen gas production device include hydrogenated aromatic compounds such as methylcyclohexane (hereinafter also referred to as MCH), cyclohexane, dimethylcyclohexane, ethylcyclohexane, decalin, methyldecalin, dimethyldecalin, and ethyldecalin. Can be For example, when MCH is used as the organic hydride A, it is converted to toluene as an aromatic compound by a dehydrogenation reaction.

  The hydrogen gas production apparatus is used for supplying hydrogen to vehicles using hydrogen as fuel, such as hydrogen vehicles and fuel cell vehicles, and for medium- to large-scale power generation using fuel cells.

<Reactor>
The reactor 1 is a dehydrogenation reactor that performs a dehydrogenation reaction of the organic hydride A by heating in the presence of a catalyst. Specifically, the reactor 1 has a dehydrogenation catalyst that promotes the dehydrogenation reaction of the organic hydride A, and heats the organic hydride A and brings the organic hydride A into contact with the dehydrogenation reaction catalyst, so that hydrogen is converted from the organic hydride A An oxidation reaction that separates Thereby, a mixed gas of the aromatic compound and hydrogen is generated. When MCH is used as the organic hydride A, the mixed gas may contain unreacted MCH and by-products such as methane and benzene.

  As the dehydrogenation catalyst used in the reactor 1, for example, sulfur, selenium, alumina carrying fine platinum particles, and the like are known.

  The lower limit of the heating temperature of the organic hydride A in the reactor 1 is preferably 150 ° C, more preferably 200 ° C. On the other hand, the upper limit of the heating temperature of the organic hydride A is preferably 400 ° C., and more preferably 350 ° C. If the heating temperature of the organic hydride A is less than the above lower limit, the reaction rate of the organic hydride A and the yield of hydrogen gas may be insufficient. Conversely, if the heating temperature of the organic hydride A exceeds the above upper limit, the energy cost required for heating may unnecessarily increase.

<Separator>
The separator 2 gas-liquid separates the mixed gas of the aromatic compound and the hydrogen discharged from the reactor 1 into a mixed gas of the aromatic compound and the hydrogen by cooling to obtain a hydrogen-rich gas B. The separator 2 has a cooling mechanism for cooling gas flowing inside. By cooling the gas inside the separator 2, MCH and aromatic compounds having a relatively high boiling point are easily separated from the mixed gas, and the concentration of the aromatic compound including toluene in the separated gas is reduced. You. The aromatic compound separated as a liquid is discharged from the separator 2 as a drain D.

  The lower limit of the temperature of the mixed gas at the outlet of the separator 2 is preferably −40 ° C., and more preferably −35 ° C. On the other hand, the upper limit of the temperature of the mixed gas at the outlet of the separator 2 is preferably -10C, more preferably -15C. If the temperature of the mixed gas at the outlet of the separator 2 falls below the lower limit, the energy required for cooling the mixed gas may be excessive. Conversely, when the temperature of the mixed gas at the outlet of the separator 2 exceeds the upper limit, the concentration of the aromatic compound in the mixed gas after separation is not sufficiently reduced, and the adsorption load in the subsequent adsorption tower increases, There is a possibility that the life of the adsorbent may be reduced, and a recovery rate of hydrogen gas may be reduced.

  The lower limit of the concentration of the aromatic compound in the mixed gas after separation by the separator 2 is preferably 50 ppm, more preferably 100 ppm. On the other hand, the upper limit of the concentration of the aromatic compound in the mixed gas is preferably 800 ppm, more preferably 600 ppm. If the concentration of the aromatic compound in the mixed gas is less than the lower limit, the cooling cost in the separator 2 may be significantly increased. Conversely, when the concentration of the aromatic compound in the mixed gas exceeds the upper limit, the adsorption load in the subsequent adsorption tower increases, and the life of the adsorbent may decrease, and the recovery rate of hydrogen gas may decrease. is there. The “concentration” in this specification is a ratio on a volume basis.

<Hydrogen-rich gas buffer tank>
The hydrogen-rich gas buffer tank 5 is provided in the hydrogen-rich gas supply line 101 in order to temporarily store the hydrogen-rich gas B discharged from the separator 2 to absorb fluctuations in the flow rate and to supply the hydrogen-rich gas B to the main adsorption tower 3 stably. Specifically, the hydrogen-rich gas B discharged from the separator 2 is compressed by a compressor (not shown) and stored in the hydrogen-rich gas buffer tank 5. The lower limit of the pressure in the hydrogen-rich gas buffer tank 5 is preferably 5 atm in absolute pressure, more preferably 8 atm. On the other hand, the upper limit of the pressure in the hydrogen-rich gas buffer tank 5 is preferably 20 atm, more preferably 10 atm. If the pressure is lower than the lower limit, supply of the hydrogen-rich gas B to the main adsorption tower 3 may not be easy. Conversely, if the pressure exceeds the upper limit, the equipment and operating costs may be excessive.

<Main adsorption tower>
The main adsorption tower 3 purifies the mixed gas (hydrogen-rich gas B) separated by the separator 2 and obtains a high-purity hydrogen gas having a higher purity than the hydrogen-rich gas B as a product gas E. Specifically, the main adsorption tower 3 is filled with an adsorbent that can be regenerated by the TSA method or the PSA method, and contains a hydrogen-rich gas B such as a hydrocarbon gas as a by-product generated in a dehydrogenation reaction from an organic hydride. The impurities contained therein are removed by adsorption. Further, from the viewpoint of reducing the size of the apparatus, the main adsorption tower 3 is preferably of a PSA type.

  Specifically, the hydrogen gas producing apparatus includes a plurality of (four in the figure) main adsorption towers 3a, 3b, 3c, 3d, and a hydrogen-rich gas supply communicating with the plurality of main adsorption towers 3a, 3b, 3c, 3d. A line 101, a product gas discharge line 102, and an off-gas discharge line 103 are provided. The number of the main adsorption towers 3 is arbitrary.

  The hydrogen-rich gas B is supplied to the plurality of main adsorption towers 3a, 3b, 3c, 3d through a hydrogen-rich gas supply line 101.

  The main adsorption tower 3 is filled with an adsorbent for adsorbing the above impurities in the hydrogen-rich gas B, and discharges the high-purity product gas E from the product gas discharge line 102. These main adsorption towers 3 are operated by sequentially switching a series of steps of adsorption, pressure reduction, washing and pressure equalization, pressure increase, and adsorption. Specifically, after the end of the adsorption step, the adsorbed impurities are removed and the adsorbent is regenerated by a step of reducing the pressure in the adsorption tower and a step of purging with a hydrogen gas as the product gas E. . Thereafter, the pressure of the adsorption tower in which the adsorbent has been regenerated is increased again, and the pressure is again applied to hydrogen purification. During the operation of the hydrogen gas producing apparatus, the timing of the series of steps is shifted in each adsorption tower so that at least one adsorption tower is an adsorption step, so that adsorption and regeneration are simultaneously performed in different adsorption towers. And the product gas E can be continuously produced.

  The main adsorption tower 3 is filled with an adsorbent capable of adsorbing MCH, toluene, methane, moisture and the like, which are main impurities in the hydrogen-rich gas B. The adsorbent is not particularly limited as long as it can adsorb each impurity and can be regenerated by the TSA method or the PSA method. As such an adsorbent, X-type or A-type zeolite, activated carbon, porous silica, porous alumina, and a metal organic structure can be particularly preferably used.

  In the case of removing a plurality of types of impurities, it is possible to respond by filling the corresponding adsorbents in order. Specifically, it is preferable to fill the aromatic compound adsorbent and the lower hydrocarbon adsorbent sequentially from the introduction direction (inlet side) of the hydrogen-rich gas B.

  The hydrogen-rich gas supply line 101 is a line for introducing the hydrogen-rich gas B into the main adsorption tower 3. The hydrogen-rich gas supply line 101 and the main adsorption tower 3 are connected via hydrogen-rich gas supply valves V1a, V1b, V1c, and V1d, respectively.

  The product gas discharge line 102 is a recovery line for the product gas E, which is a high-purity hydrogen gas obtained by removing impurities of the hydrogen-rich gas B in the main adsorption tower 3, and includes a plurality of main adsorption towers 3a, 3b, 3c, 3d. Are connected via product gas discharge valves V2a, V2b, V2c, V2d, respectively. The recovered product gas E is temporarily stored in the product gas buffer tank 6 and supplied as appropriate. This product gas E is also used as a purge gas (cleaning gas) for the main adsorption tower 3.

  A discharge line of the main adsorption tower 3 is connected to a pressure equalizing line 104 and a washing line 105 in addition to the product gas discharge line 102. The equalizing line 104 is connected to the main adsorption towers 3a, 3b, 3c, 3d via equalizing valves V4a, V4b, V4c, V4d, respectively, and the washing line 105 is connected to the main adsorption towers 3a, 3b, 3c, 3d, respectively. The cleaning valves V5a, V5b, V5c, and V5d are connected. While recovering the product gas E from at least one main adsorption tower 3 by the product gas discharge line 102, the pressure equalizing line 104, and the cleaning line 105, the product gas buffer tank 6 or the remaining The product gas E is supplied from the main adsorption tower 3 to perform the pressure increasing and cleaning steps.

Specifically, the above steps can be performed in each main adsorption tower 3 by performing the following steps cyclically as shown in Table 1.
(1) An adsorption step of producing a high-purity hydrogen gas by adsorbing and removing impurities by supplying a hydrogen-rich gas B to one of the four main adsorption towers 3 (main adsorption tower 3a). (2) Adsorption step A part of the gas remaining in the main adsorption tower 3a which has been completed is transferred to the main adsorption tower 3c which has been subjected to a second equalization step described later, and the internal pressure between the main adsorption tower 3a and the main adsorption tower 3c is equalized. (3) Holding step for maintaining the pressure equalization state in the first pressure equalizing step (4) Part of the gas remaining in the main adsorption tower 3a after the holding step is completed is transferred to the main adsorption tower 3d. To equalize the internal pressures of the main adsorption tower 3a and the main adsorption tower 3d. (5) The gas remaining in the main adsorption tower 3a after the second equalization step is removed from the off-gas buffer tank 7 and a first pressure reducing step for reducing the internal pressure to the atmospheric pressure. (6) A second depressurizing step in which the main adsorption tower 3a, which has been depressurized to the atmospheric pressure in the first depressurizing step, is further depressurized to below the atmospheric pressure using the vacuum pump P1. An adsorbent regeneration step (8) in which the high-purity gas E is supplied from the product gas buffer tank 6 or another main adsorption tower 3 in a state where the pressure is reduced to less than 10 to desorb impurities adsorbed on the adsorbent of the main adsorption tower 3a. ) A part of the gas remaining in the main adsorption tower 3b for which the holding step has been completed is transferred to the main adsorption tower 3a for which the regeneration of the adsorbent has been completed in the adsorbent regeneration step, and the main adsorption tower 3a and the main adsorption tower 3b have to be separated from each other. Second pressure equalization step for equalizing the internal pressure (9) A part of the gas remaining in the main adsorption tower 3c after the adsorption step is transferred to equalize the internal pressure between the main adsorption tower 3a and the main adsorption tower 3c. First pressure equalization step (10) Main adsorption Boosting step of the high-purity hydrogen gas E was introduced into the 3a, to boost the pressure of the main adsorption tower 3a to a pressure for performing adsorption step

When there are three main adsorption towers 3, the following steps can be performed cyclically as shown in Table 2 to perform the above-described process in each of the main adsorption towers 3.
(1) An adsorption step of producing a high-purity hydrogen gas by supplying and removing impurities by supplying a hydrogen-rich gas B to one of the three main adsorption towers 3 (main adsorption tower 3a). (2) Adsorption step A part of the gas remaining in the main adsorption tower 3a after the transfer is transferred to the main adsorption tower 3c after the regeneration step described below, and the internal pressure between the main adsorption tower 3a and the main adsorption tower 3c is equalized. Step (3) Transfer the gas remaining in the main adsorption tower 3a after the pressure equalization step to the off-gas buffer tank 7 and reduce the internal pressure to the atmospheric pressure. (4) First pressure reduction step to the atmospheric pressure The second depressurization step (5) in which the pressure of the main adsorption tower 3a is further reduced to less than the atmospheric pressure by using the vacuum pump P1 (5). 6 or Adsorbent regeneration step of supplying high-purity gas E from the main adsorption tower 3 to desorb impurities adsorbed on the adsorbent of the main adsorption tower 3a (6) the adsorbent regeneration step completed in the adsorbent regeneration step Part of the gas remaining in the main adsorption tower 3b after the adsorption step is transferred to the adsorption tower 3a, and the internal pressure between the main adsorption tower 3a and the main adsorption tower 3b is equalized. Step of introducing high-purity hydrogen gas E into the tower 3a and increasing the pressure in the main adsorption tower 3a to a pressure at which the adsorption step is performed.

  The off-gas discharge line 103 is a line used to reduce the pressure inside the adsorption tower during the regeneration of the main adsorption tower 3 and discharge off-gas. The off-gas discharge line 103 is connected to the main adsorption towers 3a, 3b, 3c, 3d via off-gas discharge valves V3a, V3b, V3c, V3d, respectively. The suction side of a vacuum pump P1 for reducing the pressure to below the atmospheric pressure during regeneration of the main adsorption tower 3 is connected to the off-gas discharge line 103. The off gas buffer tank 7 is connected to the off gas discharge line 103. The off-gas buffer tank 7 temporarily stores the off-gas F discharged when the main adsorption tower 3 and the residual gas adsorption tower 4 are regenerated.

<Adsorption tower for residual gas>
The residual gas adsorption tower 4 purifies the exhaust gas C including the residual gas discharged from the main adsorption tower 3 after stopping the purification of the hydrogen-rich gas, and obtains high-purity hydrogen gas E. Specifically, the adsorbent 4 for residual gas is filled with an adsorbent that can be regenerated by the TSA method or the PSA method, and other than the hydrogen gas contained in the exhaust gas C supplied through the exhaust gas supply line 201. The impurities are absorbed and removed. Since the residual gas adsorption tower 4 is mainly used only when refining is resumed (for example, 1 hour or more and 2 hours or less per day), regeneration may be performed at other times (for example, 22 hours or more and 23 hours or less per day). it can. Therefore, the number of the residual gas adsorption towers 4 may be one, but may be plural.

  By using a TSA type for the residual gas adsorption tower 4, heating and regeneration can be performed over a long period of time, and operation costs can be reduced. Further, by using the TSA type, the residual gas adsorption tower 4 can be regenerated by using the heat of the dehydrogenation reaction generated in the reactor 1, and the operation cost can be further reduced.

  The same adsorbent as the main adsorption tower 3 can be used as the adsorbent to be filled in the residual gas adsorption tower 4. However, the amount of the exhaust gas C processed by the residual gas adsorption tower 4 depends on the amount of hydrogen Since it is smaller than the rich gas B, the residual gas adsorption tower 4 can be made smaller than the main adsorption tower 3.

  The gas purified in the residual gas adsorption tower 4 is stored in the product gas buffer tank 6 via the second product gas discharge line 202. That is, the high-purity hydrogen gas discharged from the residual gas adsorption tower 4 is mixed with the high-purity hydrogen gas discharged from the main adsorption tower 3 and supplied as the product gas E.

  Further, off-gas generated during regeneration of the residual gas adsorption tower 4 is stored in the off-gas buffer tank 7 via the second off-gas discharge line 203, and is appropriately processed.

<Control mechanism>
The control mechanism provided in the hydrogen gas producing apparatus sends the exhaust gas C including the residual gas discharged from the main adsorption tower 3 to the residual gas adsorption tower 4 after the purification of the hydrogen-rich gas B is stopped and before the purification is restarted. The control is performed to stop the supply of the exhaust gas C to the residual gas adsorption tower 4 according to the gas concentration other than the hydrogen gas of the exhaust gas C. This control can be performed, for example, by opening and closing the exhaust gas control valve V6 provided in the exhaust gas supply line 201. This control may be performed immediately before resuming the purification of the hydrogen-rich gas B.

  By such control, the minimum necessary purification can be performed in the residual gas adsorption tower 4 while suppressing a decrease in the hydrogen recovery rate, so that the operating cost can be further reduced. The gas concentration can be measured, for example, by gas chromatography.

[Hydrogen gas production method]
Next, the hydrogen gas producing method will be described using the hydrogen gas producing apparatus of FIG.

  The method for producing hydrogen gas produces high-purity hydrogen gas from a hydrogen-rich gas containing hydrogen gas and an impurity gas other than hydrogen by purification using an adsorption tower. The method for producing hydrogen gas includes a step of performing a dehydrogenation reaction of organic hydride A by heating in the presence of a catalyst (dehydrogenation reaction step), and a step of cooling from a mixed gas of an aromatic compound and hydrogen discharged in the dehydrogenation reaction step. A gas-liquid separation of an aromatic compound (gas-liquid separation step), a step of purifying the hydrogen-rich gas B obtained in the gas-liquid separation step in the main adsorption tower 3 (a hydrogen-rich gas purification step), (A main adsorption tower regeneration step). Further, in the hydrogen gas production method, the exhaust gas C including the residual gas discharged from the main adsorption tower 3 is purified by the residual gas adsorption tower 4 from the time when the purification of the hydrogen-rich gas B is stopped to the time when it is restarted. The method includes a step of obtaining high-purity hydrogen gas (an exhaust gas purification step) and a step of regenerating the residual gas adsorption tower 4 (a residual gas adsorption tower regeneration step).

<Dehydrogenation reaction step>
In the dehydrogenation reaction step, the organic hydride A is dehydrogenated by heating in the presence of a catalyst using the reactor 1.

<Gas-liquid separation process>
In the gas-liquid separation step, a mixed gas of an aromatic compound and hydrogen discharged from the reactor 1 is separated into a mixed gas containing an aromatic compound and hydrogen using the separator 2 to obtain a hydrogen-rich gas B. . This gas-liquid separation is performed while cooling the gas flowing inside the separator 2 with a refrigerant. By cooling the gas flowing inside the separator 2 in the gas-liquid separation step, the aromatic compound and the hydrogen are easily separated, and the concentration of the aromatic compound in the gas after the separation is reduced.

<Hydrogen-rich gas purification process>
In the hydrogen-rich gas purification step, the hydrogen-rich gas B is purified using the main adsorption tower 3 to obtain high-purity hydrogen gas. In the hydrogen-rich gas purification step, the hydrogen gas may be purified while cooling the gas flowing through the main adsorption tower 3 with a refrigerant. By cooling the gas flowing inside the main adsorption tower 3 at the time of adsorption, the effective amount of impurities adsorbed by the adsorbent is increased, the required amount of the adsorbent is reduced, and the apparatus can be downsized.

  In the adsorption tower, the impurities in the hydrogen-rich gas B are adsorbed by the adsorbent, and the saturated adsorption portion of the adsorbent increases. Therefore, in order to prevent impurities from being mixed into the product gas E, it is necessary to stop the adsorption operation in a state where the unadsorbed portion of the adsorbent remains.

<Main adsorption tower regeneration process>
In the main adsorption tower regeneration step, the main adsorption tower 3 is regenerated using the above-described pressure equalizing line 104, washing line 105, and off-gas discharge line 103, and high-purity hydrogen gas as a purge gas, and the off-gas F is discharged. The hydrogen gas used as the purge gas may be obtained by the hydrogen gas producing method or may be a previously prepared hydrogen gas.

  Specifically, in the regeneration of the adsorption tower, the gas in the adsorption tower is discharged from the off-gas discharge line 103, and the pressure is reduced to normal pressure. At this time, by providing a void on the product gas outlet side of the adsorption tower, hydrogen existing in the void is used for purging the adsorbent, and contributes to desorption of impurities such as aromatic hydrocarbons.

  After the pressure is reduced to normal pressure, the gas in the adsorption tower is sucked through the off-gas discharge line 103 by the vacuum pump P1, and the pressure in the adsorption tower is reduced to a negative pressure. Thereafter, the vacuum pump P1 is further operated, and the adsorbent is further regenerated by introducing a purge gas into the adsorption tower through the cleaning line 105 while maintaining the inside of the adsorption tower at a negative pressure. By suctioning with the vacuum pump P1, some of the impurities in the gas existing in the gap between the adsorbents are removed, and the partial pressure is reduced, so that the adsorption equilibrium shifts to the attachment / detachment side. It becomes easier to regenerate the agent. In addition, in this reduced pressure suction operation, the hydrogen gas present in the gap between the adsorbents and the hydrogen present in the voids move to the exhaust side to act as a purge gas, thereby contributing to the progress of attachment and detachment of impurities. After the regeneration of the adsorbent, a pressure equalizing operation is performed, and then the product gas E is introduced into the adsorption tower to repressurize the adsorbent, and then the adsorption operation is performed again.

  At the end of the purge, the adsorbent has not been completely regenerated, and some of the adsorbed impurities remain, but the unsaturated adsorbent portion of the adsorbent has increased compared to the end of adsorption. Even if the process shifts to the adsorption step again, a sufficient adsorption capacity can be recovered. In addition, with respect to the decrease in the adsorption capacity of the adsorbent due to repeated adsorption, depressurization, decompression, and purging, the adsorption time is set to a shorter value in accordance with the decrease in the adsorption capacity, so that the purity of the product gas during adsorption is reduced. Can be secured. Also, instead of setting the adsorption time short, the purity of the product gas can be ensured by reducing the amount of hydrogen-rich gas introduced into the adsorption tower and lowering the linear velocity LV of the gas in the adsorption tower. is there.

  The hydrogen-rich gas purification step and the main adsorption tower regeneration step are alternately performed in the plurality of main adsorption towers 3a, 3b, 3c, 3d while shifting their periods.

<Exhaust gas purification process>
In the exhaust gas purification step, after stopping the purification of the hydrogen-rich gas B, the exhaust gas C containing the residual gas discharged from the main adsorption tower 3 is purified by the residual gas adsorption tower 4 until the purification is restarted, Obtain high-purity hydrogen gas. The exhaust gas refining step may be performed immediately before refining of the hydrogen-rich gas B is restarted.

  Specifically, the hydrogen-rich gas B is first supplied to the main adsorption tower 3 before the refining of the hydrogen-rich gas B is resumed. At this time, the exhaust gas C discharged from the main adsorption tower 3 contains a large amount of residual gas remaining in the main adsorption tower 3 at the time of stoppage. Next, the exhaust gas C is supplied to the residual gas adsorption tower 4 through an exhaust gas supply line 201 for purification. The high-purity hydrogen gas purified by the residual gas adsorption tower 4 is supplied to the product gas buffer tank 6 via the second product gas discharge line 202.

  Thereafter, when the concentration of the gas other than the hydrogen gas of the exhaust gas C becomes equal to or less than the threshold value, the supply of the gas discharged from the main adsorption tower 3 to the residual gas adsorption tower 4 is stopped, and the main adsorption tower 3 The discharged gas is supplied directly to the product gas buffer tank 6 through the product gas discharge line 102 as high-purity hydrogen gas. Thus, the purification of the hydrogen-rich gas B is restarted.

  The threshold value of the concentration of the gas other than the hydrogen gas is, for example, preferably 300 ppm, more preferably 100 ppm, for the entire gas other than the hydrogen gas. When a concentration threshold is provided for each component of the exhaust gas C, water is preferably 5 ppm, hydrocarbon is preferably 2 ppm, oxygen is preferably 5 ppm, helium is preferably 300 ppm, and the total of nitrogen and argon is 100 ppm. Preferably, carbon dioxide is preferably 2 ppm and carbon monoxide is preferably 0.2 ppm.

<Residual gas adsorption tower regeneration process>
In the residual gas adsorption tower regeneration step, the residual gas adsorption tower 4 is regenerated and the off-gas is discharged in the same procedure as the main adsorption tower 3. The off-gas is stored in the off-gas buffer tank 7 by suction of the vacuum pump P1, and is appropriately processed.

  When the TSA type is used as the residual gas adsorption tower 4, as a method of utilizing the heat generated in the reactor 1, for example, steam is exchanged with high-temperature exhaust gas when fuel such as kerosene is burned in the reactor 1. A method is used in which the generated gas is supplied to a jacket provided outside the residual gas adsorption tower 4 and circulated as necessary. Note that a heat medium other than steam may be used as the fluid supplied to the jacket.

  When the residual gas adsorption tower 4 is heated and regenerated, the pressure may be reduced by a vacuum pump at the same time. As a result, some of the impurities in the gas that are freely present in the gap between the adsorbents are removed, the partial pressure is reduced, and the adsorption equilibrium shifts to the detachable side. Therefore, the regeneration of the adsorbent can be promoted by further purging after this. The amount of gas used for purging can be reduced by heating and reducing the pressure.

<Advantages>
According to the hydrogen gas producing method and the hydrogen gas producing apparatus, the exhaust gas is discharged by discharging the residual gas in the adsorption tower and refining the gas containing the residual gas by the adsorption tower before the refining of the hydrogen-rich gas is restarted. Gas and hydrogen gas contained in the gas can be recovered as high-purity hydrogen gas. As a result, the hydrogen gas production method and the hydrogen gas production apparatus can suppress a decrease in the recovery rate of the hydrogen gas and can shorten the startup time until the supply of the hydrogen gas.

[Other Embodiments]
The hydrogen gas production method and the hydrogen gas production apparatus of the present invention are not limited to the above embodiment.

  In the above embodiment, the gas mixture after the dehydrogenation reaction is separated into gas and liquid. However, this gas and liquid separation is not essential and can be omitted. That is, the mixed gas discharged by the dehydrogenation reaction may be directly supplied to the main adsorption tower as a hydrogen-rich gas.

  Further, in the above embodiment, as the hydrogen-rich gas, one obtained by gas-liquid separation of an aromatic compound from an organic hydride was used. However, the hydrogen-rich gas is produced by steam reforming, autothermal reforming, or partial oxidation reforming of a hydrocarbon gas as a hydrogen-rich gas. It is also possible to use a reformed gas to be produced or off-gas of a plant having a high hydrogen content. When a reformed gas is used as the hydrogen-rich gas, a reformer for reforming the raw material gas is used instead of the reactor and the separator of the above embodiment, and a heat source is supplied to the reformer as necessary. You.

  As the raw material gas used for the reforming reaction, a compound containing carbon and hydrogen in a molecule or a mixture thereof can be appropriately selected and used. Examples of the compound include methane, ethane, propane, butane, natural gas, LPG (liquefied petroleum gas), gasoline, naphtha, hydrocarbon fuels such as kerosene and light oil, alcohols such as methanol and ethanol, and ethers such as dimethyl ether. Can be mentioned.

  Further, the hydrogen-rich gas buffer tank and the off-gas buffer tank in the above embodiment are not essential components, and can be omitted. Further, a vacuum pump is an optional component.

  As a condition for stopping the supply of the exhaust gas from the main adsorption tower to the residual gas adsorption tower, a predetermined time may be used instead of the gas concentration of the exhaust gas other than hydrogen gas. For example, the hydrogen gas production apparatus may be configured to automatically stop the supply after a certain time has elapsed. This can simplify the device.

  As described above, the hydrogen gas production method and the hydrogen gas production apparatus can suppress a decrease in the recovery rate of the hydrogen gas and shorten the start-up time when repeatedly stopping and restarting the hydrogen gas purification. Used for supplying hydrogen.

DESCRIPTION OF SYMBOLS 1 Reactor 2 Separator 3, 3a, 3b, 3c, 3d Main adsorption tower 4 Residual gas adsorption tower 5 Hydrogen rich gas buffer tank 6 Product gas buffer tank 7 Off gas buffer tank 101 Hydrogen rich gas supply line 102 Product gas discharge line 103 Off gas Discharge line 104 Equalizing line 105 Cleaning line 201 Exhaust gas supply line 202 Second product gas discharge line 203 Second offgas discharge line A Organic hydride B Hydrogen rich gas C Exhaust gas D Drain E Product gas F Offgas V1a, V1b, V1c, V1d Hydrogen rich gas supply valve V2a, V2b, V2c, V2d Product gas discharge valve V3a, V3b, V3c, V3d Off gas discharge valve V4a, V4b, V4c, V4d Equalizing valve V5a, V5b, V5c, V5d Cleaning valve V6 Exhaust gas Valve P1 vacuum pump

Claims (4)

A hydrogen gas production method for producing high-purity hydrogen gas from hydrogen-rich gas containing hydrogen gas and an impurity gas other than hydrogen by purification using an adsorption tower,
Before stopping and restarting the purification of the hydrogen-rich gas, comprises a step of purifying an exhaust gas containing residual gas discharged from the adsorption tower by a residual gas adsorption tower ,
Further comprising a step of performing a dehydrogenation reaction of the organic hydride by heating in the presence of a catalyst,
The hydrogen-rich gas is discharged in the dehydrogenation reaction step,
The above-mentioned residual gas adsorption tower is a TSA type,
A method for producing hydrogen gas , comprising regenerating the adsorption tower for residual gas using heat of the dehydrogenation reaction . 2. The hydrogen gas production method according to claim 1, wherein in the exhaust gas purification step, supply of the exhaust gas to the residual gas adsorption tower is stopped depending on a gas concentration of the exhaust gas other than hydrogen gas. 3. The method for producing hydrogen gas according to claim 1 , wherein the adsorbent filled in the adsorption tower is zeolite, activated carbon, porous silica, porous alumina, or a metal organic structure. A hydrogen gas production apparatus for producing high-purity hydrogen gas from a hydrogen-rich gas containing an impurity gas other than hydrogen gas and hydrogen by purification using an adsorption tower,
A residual gas adsorption tower for purifying exhaust gas containing residual gas discharged from the adsorption tower after the purification of the hydrogen-rich gas is stopped ,
A reactor for performing a dehydrogenation reaction of the organic hydride by heating in the presence of a catalyst ,
The above-mentioned residual gas adsorption tower is a TSA type,
A hydrogen gas production apparatus further comprising a heat circulating unit for circulating heat of the dehydrogenation reaction in the reactor and the residual gas adsorption tower .

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