JP2017226562A - Hydrogen gas manufacturing method and hydrogen gas manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen gas manufacturing method capable of suppressing recovery rate reduction of hydrogen gas when stop and resumption of hydrogen gas purification are repeated.SOLUTION: The hydrogen gas manufacturing method is a hydrogen gas manufacturing method for manufacturing a high purity hydrogen gas by purification of a hydrogen rich gas containing hydrogen gas and an impurity gas other than hydrogen by an adsorption tower, having a process for mixing a discharge gas containing a residual gas discharged from the adsorption tower with the hydrogen rich gas before purification with the absorption tower by resumption after the purification of the hydrogen rich gas is stopped. A process for conducting dehydrogenation of organic halide by heating in the presence of a catalyst is included and preferably the hydrogen rich gas is a gas discharged in the dehydrogenation process. The hydrogen gas manufacturing device has a line for mixing the discharge gas containing the residual gas discharged from inside of the adsorption tower after stopping purification of the hydrogen rich gas with the hydrogen rich gas before purification by the adsorption tower.SELECTED DRAWING: Figure 1

Description

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

  In recent years, there is an increasing expectation for hydrogen as a fuel for fuel cells that leads to improvement of the global environment. 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 (refer to JP 2014-73922 A). As this hydrogen purifier, there are adsorption towers using TSA (Temperature swing adsorption) method and PSA (Pressure swing adsorption) method.

  The above-described hydrogen production apparatus is generally operated so as to supply hydrogen to a hydrogen automobile during the day and stop the supply (purification) of hydrogen at night. Therefore, the purification of the hydrogen rich gas by the adsorption tower is stopped at night. When the purification is stopped in the adsorption tower, that is, 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 refining is resumed after the purification of the hydrogen-rich gas is stopped, the residual gas in the adsorption tower is mixed into the purified gas, and the resulting hydrogen gas becomes insufficiently pure and needs to be treated as an off-gas. As a result, there is a disadvantage that the recovery rate of hydrogen gas decreases.

JP 2014-73922 A

  The present invention has been made based on the above circumstances, and provides a hydrogen gas production method and a hydrogen gas production apparatus that can suppress a decrease in the recovery rate of hydrogen gas when repeatedly stopping and restarting hydrogen gas purification. With the goal.

  The present invention made to solve the above problems is a hydrogen gas production method for producing high-purity hydrogen gas by purification using an adsorption tower from a hydrogen-rich gas containing an impurity gas other than hydrogen gas and hydrogen. The method includes a step of mixing exhaust gas containing residual gas discharged from the inside of the adsorption tower with the hydrogen rich gas before purification by the adsorption tower before the refining is stopped and restarted.

  According to the method for producing hydrogen gas, before the refining of the hydrogen rich gas is resumed, the residual gas in the adsorption tower is discharged, and the gas containing the residual gas is mixed with the hydrogen rich gas and purified by the adsorption tower, thereby being discharged. Residual gas and hydrogen gas contained in the gas can be recovered as high-purity hydrogen gas. As a result, the hydrogen gas production method can suppress a decrease in the recovery rate of hydrogen gas.

  The hydrogen gas production method 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. As described above, by using the organic hydride for transport of the hydrogen-rich gas, the transport efficiency of hydrogen can be increased.

  In the exhaust gas mixing step, mixing of the exhaust gas into the hydrogen rich gas may be stopped depending on the gas concentration of the exhaust gas other than hydrogen gas. By performing such control, it is possible to prevent the rise time (time until the supply of high purity hydrogen gas starts) from being unnecessarily long.

  In the mixing step, the exhaust gas and the hydrogen rich gas may be supplied to the buffer tank. By supplying the exhaust gas and the hydrogen rich gas to the buffer tank in this way, these mixed gases can be stably supplied to the adsorption tower.

  Before the mixing step, it is preferable to further include a step of removing the impurity gas in the exhaust gas by a residual gas adsorption tower. Thus, by removing the impurity gas in the exhaust gas with a dedicated adsorption tower, the load on the adsorption tower for the hydrogen-rich gas can be reduced, and as a result, the hydrogen gas recovery rate can be improved.

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

  Another invention made to solve the above-mentioned problems is a hydrogen gas production method for producing high-purity hydrogen gas by purification with an adsorption tower from hydrogen-rich gas containing hydrogen gas and impurity gas other than hydrogen, It is characterized by comprising a line for mixing exhaust gas containing residual gas exhausted from the inside of the adsorption tower after stopping purification of the hydrogen rich gas into the hydrogen rich gas before purification by the adsorption tower.

  According to the hydrogen gas production apparatus, before the refining of the hydrogen rich gas is resumed, the residual gas in the adsorption tower is discharged, and the gas containing the residual gas is mixed with the hydrogen rich gas and purified by the adsorption tower, thereby being discharged. Residual gas and hydrogen gas contained in the gas can be recovered as high-purity hydrogen gas. As a result, the hydrogen gas production apparatus can suppress a decrease in the recovery rate of hydrogen gas.

  As described above, according to the hydrogen gas production method and the hydrogen gas production apparatus of the present invention, it is possible to suppress a decrease in the recovery rate of hydrogen gas when repeatedly stopping and restarting the hydrogen gas purification.

It is the schematic which shows the hydrogen gas manufacturing apparatus of one Embodiment of this invention. It is the schematic which shows the hydrogen gas manufacturing apparatus of embodiment different from FIG.

[First embodiment]
Hereinafter, embodiments of the hydrogen gas production apparatus and the 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 production apparatus of FIG. 1 includes a reactor 1 that performs a dehydrogenation reaction of 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. Separator 2 for gas-liquid separation of the compound, main adsorption tower 3 for purifying the mixed gas (hydrogen rich gas B) separated by the separator 2, and residual exhausted from the main adsorption tower 3 after the purification of hydrogen rich gas is stopped An exhaust gas mixing line 4 that mainly mixes the exhaust gas C containing gas with the hydrogen rich gas B before being purified by the main adsorption tower 3 is provided. The hydrogen gas production apparatus also includes a hydrogen rich gas buffer tank 5 that stores the hydrogen rich gas B discharged from the separator 2 and the exhaust gas C supplied from the exhaust gas mixing line 4, and a hydrogen gas other than the hydrogen gas of the exhaust gas C. A control mechanism (not shown) that stops mixing the exhaust gas C into the hydrogen-rich gas B according to the gas concentration is further provided.

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

  The hydrogen gas production apparatus is used for supplying hydrogen to hydrogen-powered vehicles such as hydrogen automobiles and fuel cell automobiles, and for medium- and 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 reaction catalyst that promotes the dehydrogenation reaction of the organic hydride A. The reactor 1 is heated from the organic hydride A and brought into contact with the dehydrogenation reaction catalyst to generate hydrogen from the organic hydride A. Causes an oxidation reaction to separate Thereby, a mixed gas of an aromatic compound and hydrogen is generated. In addition, when MCH is used as the organic hydride A, there is a possibility that unreacted MCH and by-products such as methane and benzene are included in the mixed gas.

  As the dehydrogenation reaction catalyst used in the reactor 1, for example, alumina carrying sulfur, selenium, fine particle platinum or the like is known.

  As a minimum of heating temperature of organic hydride A in reactor 1, 150 ° C is preferred and 200 ° C is more preferred. On the other hand, the upper limit of the heating temperature of the organic hydride A is preferably 400 ° C., more preferably 350 ° C. If the heating temperature of the organic hydride A is less than the 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 upper limit, the energy cost required for heating may be unnecessarily increased.

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

  As a minimum of the temperature of the mixed gas in the exit of the separator 2, -40 degreeC is preferable and -35 degreeC is more preferable. On the other hand, the upper limit of the temperature of the mixed gas at the outlet of the separator 2 is preferably −10 ° C., more preferably −15 ° C. If the temperature of the mixed gas at the outlet of the separator 2 is lower than the lower limit, the energy required for cooling the mixed gas may be excessive. Conversely, if the temperature of the mixed gas at the outlet of the separator 2 exceeds the above 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 exists a possibility that the lifetime of adsorbent may fall and the recovery rate of hydrogen gas may fall.

  The lower limit of the aromatic compound concentration in the mixed gas after separation by the separator 2 is preferably 50 ppm and more preferably 100 ppm. On the other hand, the upper limit of the aromatic compound concentration in the mixed gas is preferably 800 ppm and more preferably 600 ppm. If the aromatic compound concentration in the mixed gas is less than the lower limit, the cooling cost in the separator 2 may be significantly increased. On the other hand, if 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 be reduced or the hydrogen gas recovery rate may be reduced. is there. The “concentration” in this specification is a volume-based ratio.

<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 primarily store the hydrogen-rich gas B discharged from the separator 2 to absorb flow rate fluctuations and stably supply it to the main adsorption tower 3. 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 hydrogen rich gas buffer tank 5 also stores the exhaust gas C supplied from the exhaust gas mixing line 4. The exhaust gas C is compressed by the compressor 6 provided in the exhaust gas mixing line 4 and mixed with the hydrogen rich gas B 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, and 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, and more preferably 10 atm. If the pressure is smaller than the lower limit, the supply of the hydrogen rich gas B to the main adsorption tower 3 may not be easy. On the contrary, if the pressure exceeds the upper limit, the apparatus and the operating cost may be excessive.

<Main adsorption tower>
The main adsorption tower 3 purifies the mixed gas (hydrogen rich gas B) and the exhaust gas C separated by the separator 2, and obtains a high purity hydrogen gas having a higher purity than the hydrogen rich gas B as the 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 in a hydrogen-rich gas such as a hydrocarbon gas as a by-product generated in the dehydrogenation reaction from the organic hydride. To remove impurities contained in In view of reducing the size of the apparatus, the main adsorption tower 3 is preferably a PSA type.

  Specifically, the hydrogen gas production apparatus includes a plurality (4 in the figure) of main adsorption towers 3a, 3b, 3c, 3d and a supply of hydrogen-rich gas that communicates 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. The number of 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 the hydrogen rich gas supply line 101.

  The main adsorption tower 3 is filled with an adsorbent that adsorbs the impurities in the hydrogen-rich gas B, and discharges a 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, decompression, washing and pressure equalization, pressure increase, and adsorption. Specifically, after the adsorption step is completed, the adsorbed impurities are removed and the adsorbent is regenerated by reducing the pressure in the adsorption tower and cleaning (purging) with hydrogen gas, which is the product gas E. . Thereafter, the adsorption tower in which the adsorbent has been regenerated is pressurized again and subjected to hydrogen purification again. During operation of the hydrogen gas production apparatus, adsorption and regeneration are simultaneously performed in different adsorption towers by shifting the timing of the above series of steps in each adsorption tower so that at least one adsorption tower becomes an adsorption process. The product gas E can be produced continuously.

  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 impurities 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 addition, when removing multiple types of impurities, it is possible to respond by sequentially filling adsorbents adapted to each. Specifically, the aromatic compound adsorbent and the lower hydrocarbon adsorbent are preferably filled 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 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 and V2d, respectively. The recovered product gas E is temporarily stored in the product gas buffer tank 7 and supplied as appropriate. The product gas E is also used as a purge gas (cleaning gas) for the main adsorption tower 3.

  In addition to the product gas discharge line 102, a pressure equalization line 104 and a cleaning line 105 are connected to the discharge side of the main adsorption tower 3, respectively. The pressure equalization line 104 is connected to the main adsorption towers 3a, 3b, 3c, 3d via pressure equalization valves V4a, V4b, V4c, V4d, respectively, and the cleaning line 105 is connected to the main adsorption towers 3a, 3b, 3c, 3d, respectively. It is connected via cleaning valves V5a, V5b, V5c, V5d. While recovering product gas E from at least one main adsorption tower 3 by these product gas discharge line 102, pressure equalization line 104 and washing line 105, the product gas buffer tank 7 or the remaining is recovered from the other main adsorption tower 3. The product gas E can be supplied from the main adsorption tower 3 to perform the pressurization and cleaning steps.

Specifically, the above steps can be performed in each main adsorption tower 3 by cyclically performing the following steps as shown in Table 1.
(1) Adsorption step for producing high-purity hydrogen gas by adsorbing and removing impurities by supplying the hydrogen-rich gas B to one of the four main adsorption towers 3 (main adsorption tower 3a) (2) Adsorption step Part of the gas remaining in the main adsorption tower 3a that has finished the above is transferred to the main adsorption tower 3c that has finished the second pressure equalizing step described later, and the internal pressures of the main adsorption tower 3a and the main adsorption tower 3c are made equal. The first pressure equalizing step (3) The holding step for holding the pressure equalization state in the first pressure equalizing step (4) The part of the gas remaining in the main adsorption tower 3a after the holding step is removed, and the main adsorption tower 3d The second pressure equalizing step (5) for equalizing the internal pressure 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 pressure equalization step is removed from the off-gas buffer tank The first decompression step is carried out to reduce the internal pressure to atmospheric pressure. (6) The main adsorption tower 3a depressurized to atmospheric pressure in the first depressurization step is further depressurized to less than atmospheric pressure using the vacuum pump P1. (7) The main adsorption tower 3a is atmospheric pressure in the second depressurization step. An adsorbent regeneration step (8) in which the high-purity gas E is supplied from the product gas buffer tank 7 or other main adsorption tower 3 in a state where the pressure is reduced to less than 8 to desorb impurities adsorbed on the adsorbent in the main adsorption tower 3a. ) A part of the gas remaining in the main adsorption tower 3b in which the holding step is completed is transferred to the main adsorption tower 3a in which the regeneration of the adsorbent is completed in the adsorbent regeneration step, and the main adsorption tower 3a and the main adsorption tower 3b 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, and the internal pressures of the main adsorption tower 3a and the main adsorption tower 3c are equalized. 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

In addition, when there are three main adsorption towers 3, the above steps can be performed in each main adsorption tower 3 by cyclically performing the following steps as shown in Table 2.
(1) An adsorption step for producing high-purity hydrogen gas by adsorbing and removing impurities by supplying hydrogen-rich gas B to one of the three main adsorption towers 3 (main adsorption tower 3a) (2) Adsorption step Part of the gas remaining in the main adsorption tower 3a after completion of the transfer is transferred to the main adsorption tower 3c after the regeneration step, which will be described later, to equalize the internal pressure of the main adsorption tower 3a and the main adsorption tower 3c. Step (3) A gas remaining in the main adsorption tower 3a that has finished the pressure equalization step is transferred to the off-gas buffer tank 8, and a first pressure reduction step (4) in which the internal pressure is reduced to atmospheric pressure. Second decompression step (5) in which the decompressed main adsorption tower 3a is further decompressed to less than atmospheric pressure using the vacuum pump P1. In the second decompression step, the main adsorption tower 3a is decompressed to less than atmospheric pressure, and the product gas buffer tank 7 or The high-purity gas E is supplied from the main adsorption tower 3 and the adsorbent regeneration step for desorbing the impurities adsorbed on the adsorbent in the main adsorption tower 3a is performed. A pressure equalization step for transferring a part of the gas remaining in the main adsorption tower 3b after the adsorption step to the adsorption tower 3a and equalizing the internal pressure of the main adsorption tower 3a and the main adsorption tower 3b. (7) Main adsorption Step of increasing pressure by introducing high-purity hydrogen gas E into the tower 3a and increasing the pressure in the main adsorption tower 3a to the pressure for performing the adsorption step

  The off-gas discharge line 103 is a line used for depressurizing the inside of the adsorption tower and discharging off-gas when the main adsorption tower 3 is regenerated. The off gas discharge line 103 is connected to the main adsorption towers 3a, 3b, 3c, and 3d and the off gas discharge valves V3a, V3b, V3c, and V3d, respectively. The off-gas discharge line 103 is connected to the suction side of a vacuum pump P1 for reducing the pressure to below atmospheric pressure when the main adsorption tower 3 is regenerated. An offgas buffer tank 8 is connected to the offgas discharge line 103. The offgas buffer tank 8 temporarily stores offgas F discharged when the main adsorption tower 3 is regenerated.

<Exhaust gas mixing line>
The exhaust gas mixing line 4 is configured so that the hydrogen rich gas B before the purification of the exhaust gas C including the residual gas discharged from the main adsorption tower 3 before the refining of the hydrogen rich gas B is restarted in the main adsorption tower 3. The gas outlet after purification of the main adsorption tower 3 and the hydrogen rich gas supply line 101 are connected to each other. Specifically, the exhaust gas mixing line 4 connects the main adsorption tower 3 and the hydrogen rich gas buffer tank 5.

  The exhaust gas mixing line 4 has an exhaust gas control valve V6, and a second off-gas exhaust line 203 for exhausting the exhaust gas C as off-gas upstream from the exhaust gas control valve V6 is connected via an off-gas control valve V7. Is done. The second off gas discharge line 203 is connected to the off gas buffer tank 8.

<Control mechanism>
The control mechanism provided in the hydrogen gas production apparatus before the purification of the hydrogen rich gas is stopped and restarted before the exhaust gas C containing the residual gas exhausted from the main adsorption tower 3 is purified by the main adsorption tower 3. Then, the control is performed to stop the mixing of the exhaust gas C into the hydrogen rich gas B according to the gas concentration of the exhaust gas C other than the hydrogen gas. This control can be performed by opening and closing an exhaust gas control valve V6 provided in the exhaust gas mixing line 4, for example.

  By such control, it is possible to prevent the rise time (time until the start of high-purity hydrogen gas supply) from being unnecessarily prolonged while suppressing a decrease in the recovery rate of hydrogen. The gas concentration can be measured by, for example, gas chromatography.

  Moreover, the said control mechanism may perform control which discharges | emits exhaust gas C as off-gas according to gas concentrations other than hydrogen gas of exhaust gas C. FIG. This control can be performed, for example, by opening and closing an exhaust gas control valve V6 and an offgas control valve V7 provided in the second offgas exhaust line 203.

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

  The hydrogen gas production method produces 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 hydrogen gas production method includes a step of performing a dehydrogenation reaction of the organic hydride A by heating in the presence of a catalyst (dehydrogenation reaction step), and cooling from a mixed gas of the aromatic compound and hydrogen discharged in the dehydrogenation reaction step. Gas-liquid separation step (gas-liquid separation step), the step of purifying the hydrogen-rich gas B obtained in the gas-liquid separation step in the main adsorption tower 3 (hydrogen-rich gas purification step), and the main adsorption tower 3 (main adsorption tower regeneration step). In addition, the hydrogen gas production method before the purification of the hydrogen rich gas B is stopped and restarted before the exhaust gas C containing residual gas discharged from the main adsorption tower 3 is purified by the main adsorption tower 3. A step of mixing with the hydrogen rich gas B (exhaust gas mixing step) is provided.

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

<Gas-liquid separation process>
In the gas-liquid separation step, the separator 2 is used to gas-liquid separate the mixed gas of the aromatic compound and hydrogen discharged from the reactor 1 into a mixed gas containing the aromatic compound and hydrogen to obtain a hydrogen rich gas B. . This gas-liquid separation is performed while the gas flowing through the separator 2 is cooled by the refrigerant. In this way, by cooling the gas flowing inside the separator 2 in the gas-liquid separation step, the aromatic compound and hydrogen are easily separated, and the concentration of the aromatic compound in the separated gas is reduced.

<Hydrogen rich gas purification process>
In the hydrogen rich gas purification step, the main adsorption tower 3 is used to purify the hydrogen rich gas B to obtain high purity hydrogen gas. In the hydrogen rich gas purification step, it is preferable to purify the hydrogen gas while cooling the gas flowing through the main adsorption tower 3 with a refrigerant. Thus, by cooling the gas flowing through the main adsorption tower 3 during adsorption, the effective adsorption amount of impurities by the adsorbent increases, the necessary amount of adsorbent is reduced, and the apparatus can be miniaturized.

  In the adsorption tower, 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 while 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 pressure equalization line 104, the cleaning line 105, the off-gas discharge line 103, and the high-purity hydrogen gas as the purge gas, and the off-gas F is discharged. The hydrogen gas used as the purge gas may be obtained by the hydrogen gas production method or may be a hydrogen gas prepared in advance.

  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 present in the void is used for purging the adsorbent, contributing to desorption of impurities such as aromatic hydrocarbons.

  After depressurization 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 adsorption tower is depressurized to a negative pressure. Thereafter, the vacuum pump P1 is further operated, and the adsorbent is further regenerated by introducing the 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 of the adsorbent are removed and the partial pressure is lowered, so that the adsorption equilibrium shifts to the detachable side. It becomes easy to regenerate the agent. In this vacuum suction operation, the hydrogen gas present in the gap between the adsorbents and the hydrogen present in the voids move to the exhaust side, thereby acting as purge gas, contributing to the progress of attachment / detachment of impurities. After regeneration of the adsorbent, a pressure equalizing operation is performed, and after that, after repressurization by introducing the product gas E into the adsorption tower, the adsorption operation is performed again.

  At the end of the purge, the adsorbent is not completely regenerated and some of the adsorbed impurities remain, but the unsaturated adsorbed portion of the adsorbent increases compared to the end of adsorption. Even if the process moves to the adsorption process again, a sufficient adsorption capacity is recovered. In addition, to reduce the adsorption capacity of the adsorbent due to repeated adsorption, depressurization, decompression, and purge, the product gas purity at the time of adsorption can be reduced by setting a shorter adsorption time corresponding to the decrease in the adsorption capacity. Can be secured. It is also possible to ensure the purity of the product gas 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, rather than setting the adsorption time short. is there.

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

<Exhaust gas mixing process>
The exhaust gas mixing step is performed after the purification of the hydrogen rich gas B is stopped. In the exhaust gas mixing step, the exhaust gas C containing residual gas discharged from the main adsorption tower 3 is mixed with the hydrogen rich gas B before the refining of the hydrogen rich gas B is stopped and restarted. The mixed exhaust gas C is purified by the main adsorption tower 3 as a part of the hydrogen rich gas B, and becomes high purity hydrogen gas.

  Specifically, the hydrogen rich gas B is first supplied to the main adsorption tower 3 before resuming the purification of the hydrogen rich gas B. 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 hydrogen rich gas buffer tank 5 while being compressed by the compressor 6 by the exhaust gas mixing line 4 and mixed with the hydrogen rich gas B. This hydrogen-rich gas B is purified by the main adsorption tower 3 as described above and supplied as the product gas E. The mixing of the exhaust gas C and the hydrogen rich gas B may be performed in the buffer tank as described above or in the pipe.

  Thereafter, when the gas concentration of the exhaust gas C other than hydrogen gas becomes equal to or lower than the threshold value, the supply of the gas discharged from the main adsorption tower 3 to the exhaust gas mixing line 4 (mixing with the hydrogen rich gas B) is stopped. At the same time, the gas discharged from the main adsorption tower 3 is directly supplied to the product gas buffer tank 7 through the product gas discharge line 102 as high-purity hydrogen gas. Thereby, purification of the hydrogen rich gas B is resumed.

  As a threshold value of the gas concentration other than the hydrogen gas, for example, 300 ppm is preferable in the whole gas other than hydrogen gas, and 100 ppm is more preferable. Further, when setting a concentration threshold 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. Carbon dioxide is preferably 2 ppm, and carbon monoxide is preferably 0.2 ppm.

  Further, in the exhaust gas mixing step, the exhaust gas C may be discharged as off-gas from the second off-gas discharge line 203 when the gas concentration of the exhaust gas C other than hydrogen gas exceeds the second threshold value. Thereby, it is possible to prevent a residual gas having a high concentration of impurities (particularly a component that does not condense such as methane) from entering the hydrogen-rich gas B and deteriorating the quality of the product gas obtained.

  As a 2nd threshold value of gas concentrations other than the said hydrogen gas, 10000 ppm is preferable in the whole gas other than hydrogen gas, for example, and 9000 ppm is more preferable.

<Advantages>
According to the hydrogen gas production method and the hydrogen gas production apparatus, the residual gas in the adsorption tower is discharged by the resumption of the purification of the hydrogen rich gas, and the gas containing the residual gas is mixed with the hydrogen rich gas and purified by the adsorption tower. As a result, the residual gas and hydrogen gas contained in the exhaust 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 hydrogen gas.

[Second Embodiment]
Next, a hydrogen gas production method and a hydrogen gas production apparatus according to another embodiment of the present invention will be described.

[Hydrogen gas production equipment]
The hydrogen gas production apparatus of FIG. 2 includes a reactor 1, a separator 2, a main adsorption tower 3, an exhaust gas mixing line 4, a hydrogen rich gas buffer tank 5, and a gas concentration of exhaust gas C other than hydrogen gas. Mainly includes a control mechanism (not shown) for stopping the mixing of the exhaust gas C into the hydrogen-rich gas B, and a residual gas adsorption tower 9 for removing the impurity gas in the exhaust gas C.

  The hydrogen gas production apparatus is the same as the hydrogen gas production apparatus shown in FIG. 1 except that the residual gas adsorption tower 9 is provided. Therefore, the same components are denoted by the same reference numerals and description thereof is omitted.

<Adsorption tower for residual gas>
The residual gas adsorption tower 9 is disposed in the exhaust gas mixing line 4 to purify the exhaust gas C containing the residual gas discharged from the main adsorption tower 3 after the purification of the hydrogen-rich gas is stopped, and remove impurities. Specifically, the residual gas adsorption tower 9 is filled with an adsorbent that can be regenerated by the TSA method or the PSA method, and other than hydrogen gas contained in the exhaust gas C supplied by the exhaust gas mixing line 4. Impurities are removed by adsorption. Since the residual gas adsorption tower 9 is mainly used only when refining is resumed (for example, 1 hour to 2 hours per day), regeneration can be performed at other times (for example, 22 hours to 23 hours per day). it can. For this reason, the number of the residual gas adsorption towers 9 may be one, but may be plural.

  By making the adsorption tower 9 for residual gas into the TSA type, heating regeneration can be performed over time, and the operating cost can be reduced. Furthermore, by using the TSA type, the residual gas adsorption tower 9 can be regenerated using the heat of the dehydrogenation reaction generated in the reactor 1, and the operating cost can be further reduced.

  The adsorbent charged in the residual gas adsorption tower 9 can be the same as that used in the main adsorption tower 3, but the amount of the exhaust gas C processed by the residual gas adsorption tower 9 is the hydrogen processed by the main adsorption tower 3. Since it is smaller than the rich gas B, the residual gas adsorption tower 9 can be made smaller than the main adsorption tower 3.

  The gas purified by the residual gas adsorption tower 9 is supplied to the hydrogen rich gas buffer tank 5 through the exhaust gas mixing line 4 and mixed with the hydrogen rich gas B.

[Method for producing hydrogen gas]
The hydrogen gas production method using the hydrogen gas production apparatus of FIG. 2 includes an exhaust gas purification step and a residual gas adsorption tower regeneration step in addition to the hydrogen gas production method of the first embodiment.

<Exhaust gas purification process>
In the exhaust gas purification step, the exhaust gas C containing the residual gas discharged from the main adsorption tower 3 after the purification of the hydrogen-rich gas is purified by the residual gas adsorption tower 9 to remove impurities.

<Adsorption tower regeneration process for residual gas>
In the residual gas adsorption tower regeneration step, the residual gas adsorption tower 9 is regenerated in the same procedure as the main adsorption tower 3 and the off-gas is discharged.

<Advantages>
According to the hydrogen gas production method and the hydrogen gas production apparatus, since the exhaust gas is purified and mixed with the hydrogen rich gas, the regeneration frequency of the main adsorption tower can be reduced, and as a result, the hydrogen gas recovery rate can be improved.

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

  In the above embodiment, the hydrogen-rich gas is obtained by gas-liquid separation of an aromatic compound from organic hydride, but the hydrogen-rich gas is generated by steam reforming, autothermal reforming or partial oxidation reforming of hydrocarbon gas. It is also possible to use a reformed gas or a plant off-gas having a high hydrogen content. When reformed gas is used as the hydrogen-rich gas, a reformer that reforms the raw material gas is used instead of the reactor and separator of the above embodiment, and a heat source is supplied to the reformer as necessary. The

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

  Further, as a condition for stopping the mixing of the exhaust gas from the main adsorption tower with the hydrogen rich gas, a predetermined time may be used instead of the gas concentration of the exhaust gas other than the hydrogen gas. For example, the hydrogen gas production apparatus may be configured to automatically stop the mixing after a predetermined time has elapsed. Thereby, the apparatus can be simplified.

  As described above, the hydrogen gas production method and the hydrogen gas production apparatus can suppress a decrease in the recovery rate of hydrogen gas when repeatedly stopping and restarting hydrogen gas purification, so that the hydrogen gas production method and the hydrogen gas production apparatus can be used for supplying high-purity hydrogen. Preferably used.

DESCRIPTION OF SYMBOLS 1 Reactor 2 Separator 3, 3a, 3b, 3c, 3d Main adsorption tower 4 Exhaust gas mixing line 5 Hydrogen rich gas buffer tank 6 Compressor 7 Product gas buffer tank 8 Off gas buffer tank 9 Adsorption tower for residual gas 101 Hydrogen rich gas supply line 102 Product gas discharge line 103 Off gas discharge line 104 Pressure equalization line 105 Cleaning line 203 Second off gas discharge line A Organic hydride B Hydrogen rich gas C Exhaust gas D Drain E Product gas F Off gas 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 Pressure equalizing valve V5a, V5b, V5c, V5d Cleaning valve V6 Exhaust gas control valve V7 Off-gas Control valve P1 Vacuum pump

Claims (7)

A hydrogen gas production method for producing high-purity hydrogen gas by purification with an adsorption tower from hydrogen-rich gas containing impurity gas other than hydrogen gas and hydrogen,
A step of mixing exhaust gas containing residual gas discharged from the inside of the adsorption tower with the hydrogen rich gas before being purified by the adsorption tower before the refining of the hydrogen rich gas is stopped and restarted. To produce hydrogen gas. Further comprising a step of dehydrogenating the organic hydride by heating in the presence of a catalyst,
The method for producing hydrogen gas according to claim 1, wherein the hydrogen-rich gas is a gas discharged in the dehydrogenation reaction step.   The method for producing hydrogen gas according to claim 1 or 2, wherein in the exhaust gas mixing step, mixing of the exhaust gas into the hydrogen rich gas is stopped depending on a gas concentration of the exhaust gas other than hydrogen gas.   The method for producing hydrogen gas according to claim 1, wherein the exhaust gas and the hydrogen rich gas are supplied to the buffer tank in the mixing step.   The method for producing hydrogen gas according to any one of claims 1 to 4, further comprising a step of removing the impurity gas in the exhaust gas with an adsorption tower for residual gas before the mixing step.   The method for producing hydrogen gas according to any one of claims 1 to 5, wherein the adsorbent packed in the adsorption tower is zeolite, activated carbon, porous silica, porous alumina, or a metal organic structure. A hydrogen gas production method for producing high-purity hydrogen gas by purification with an adsorption tower from hydrogen-rich gas containing impurity gas other than hydrogen gas and hydrogen,
An apparatus for producing hydrogen gas, comprising: a line for mixing exhaust gas containing residual gas exhausted from the inside of the adsorption tower after the purification of the hydrogen rich gas is mixed with the hydrogen rich gas before purification by the adsorption tower.

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