JP2009196893A - Method for driving hydrogen generating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide method for driving a hydrogen generating device in which, regarding a hydrogen generating device by steam reforming, in the case it is stopped and is cooled, the intrusion of air into the device is evaded without introducing an inert gas, and deterioration (oxidation) in a reforming catalyst or a shift catalyst is prevented. <P>SOLUTION: Regarding the method for driving a hydrogen generating device, in the hydrogen generating device comprising: a reforming section having a reforming catalyst for steam-reforming fuel; a raw material feeding section feeding the fuel and water to the reforming section; a heating section for the reforming catalyst; and a modification section having a catalyst at least including copper, and where a gas generated in the reforming section is fed to the modification section, the method comprises: a stage (a) where the heating operation in the heating section is stopped; a stage (b) where the amounts of the fuel and water to be fed are gradually reduced; a stage (c) where the feed of the water is stopped; and a stage (d) where the feed of the fuel is stopped. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a method of operating a hydrogen generator that generates steam by steam reforming, for example, a hydrocarbon-based fuel.

Conventionally, as a method for generating hydrogen, for example, a steam reforming method using a fuel such as a hydrocarbon such as natural gas, LPG, naphtha, or an alcohol such as methanol as a raw material has been performed. For this steam reforming, a noble metal catalyst such as nickel or white metal is used.
In such a steam reforming method, carbon monoxide is generated in addition to hydrogen and carbon dioxide by the reforming reaction. In order to increase the amount of hydrogen generated, hydrogen is further obtained by a shift reaction with water. A copper-based catalyst is often used for this shift reaction.

  As the shift catalyst used for the shift reaction of carbon monoxide and water, a copper-based catalyst mainly composed of copper having higher catalytic activity than other catalysts is generally used. This catalyst can obtain catalytic activity by reducing copper in an oxidized state. Therefore, it is necessary to start the hydrogen generator having the shift portion after reducing the copper catalyst in advance. When the apparatus is operated continuously, the catalytic activity is maintained because the gas passing through the shift zone is a reducing gas containing hydrogen.

  However, when air is mixed into the apparatus for some reason when the apparatus is stopped, the copper-based catalyst is oxidized and the catalytic activity is reduced. In addition, when the apparatus is stopped frequently and the chance of air mixing increases, the catalyst may be sintered due to heat generated during oxidation-reduction of the copper-based catalyst, and the catalyst activity may be significantly reduced. In particular, when the apparatus is stopped, the temperature inside the apparatus is high, and as the apparatus cools, the inside of the apparatus is in a reduced pressure state, and the possibility of sucking air from the outside increases.

  Therefore, when the apparatus is stopped, a method is generally used in which an inert gas such as nitrogen gas is purged with air to cool the apparatus to prevent air from entering. However, in a hydrogen generator that needs to be frequently started and stopped, it is necessary to always prepare an inert gas. Therefore, when the apparatus is stopped, a method of cooling by introducing an inert gas such as nitrogen into the apparatus is generally used.

Certainly, in a hydrogen generator used in a plant or the like that operates continuously and stops the apparatus for a certain period of time, it is not a big problem to introduce an inert gas into the apparatus and cool it.
However, in a hydrogen generator that repeatedly starts and stops on a daily basis, there is a problem that it is relatively difficult to always prepare an inert gas.

  Accordingly, the present invention provides a hydrogen generation apparatus using steam reforming that avoids air mixing into the apparatus without introducing an inert gas when the apparatus is stopped and cooled, The purpose is to prevent oxidation (deterioration).

The present invention includes a reforming unit having a reforming catalyst for steam reforming a fuel, a raw material supply unit for supplying the fuel and water to the reforming unit, a heating unit for the reforming catalyst, and at least copper. A hydrogen generation apparatus comprising a shift section having a catalyst containing and supplying gas generated in the reforming section to the shift section; (a) stopping the heating operation of the heating section; (b) the fuel and Provided is a method for operating a hydrogen generator, which includes a step of gradually reducing the amount of water supply, (c) a step of stopping the supply of water, and (d) a step of stopping the supply of fuel.
In this case, the reforming temperature in step (b) is preferably a temperature that does not exceed the heat resistance temperature of the reforming catalyst.
In the step (b), when the supply amount of the fuel and water is decreased, it is preferable that the supply amount of water is smaller than the supply amount of fuel.
Moreover, it is preferable that the reforming temperature in the step (c) is a temperature at which carbon is not deposited on the reforming catalyst.
Moreover, it is preferable that the shift catalyst temperature in the step (d) is a temperature at which the catalytic activity of the shift catalyst is not lowered by air oxidation.
Furthermore, when the fuel is liquid at normal temperature, it is preferable to include a step (e) of operating and stopping the heating unit again between the step (c) and the step (d).
Further, it is preferable that an opening / closing valve is provided at the outlet of the transformation section, and the opening / closing valve is closed in the step (d).

  The present invention also includes a reforming section having a reforming catalyst for steam reforming fuel, a raw material supply section for supplying the fuel and water to the reforming section, a heating section for the reforming catalyst, and at least In a hydrogen generator comprising a shift section having a catalyst containing copper and supplying gas generated in the reforming section to the shift section, (a ′) heating operation of the heating section is stopped, Provided is a method of operating a hydrogen generator that supplies at least an amount of fuel corresponding to a volume reduction amount into the hydrogen generator when the inside of the generator is depressurized.

According to the present invention, it is possible to solve the problem at the time of stopping the conventional hydrogen generator, avoid air mixing into the apparatus at the time of cooling the apparatus stopped, and prevent oxidation of the steam reforming catalyst or the shift catalyst. Can do. In addition, it is possible to provide a hydrogen generator that can be used for routine startup and stop by not using an inert gas.
As described above, the present invention stops the heating operation of the heating unit when the hydrogen supply of the hydrogen generator is stopped, then reduces the supply amount of fuel and water, then stops the supply of water, and finally Stop supplying hydrocarbon components. If the fuel is liquid at room temperature, the heating unit is activated once more, and finally the supply of fuel is stopped.
In particular, when the fuel and water supply amounts are reduced, the water supply amount in the apparatus can be prevented from dew condensation by reducing the water supply amount from the fuel. Also, after the heating operation of the heating unit is stopped, when the inside of the device is in a depressurized state, the amount of air mixed into the device is reduced by supplying at least an amount of fuel corresponding to the volume reduction amount. Can be made. Further, by closing the on-off valve when the fuel supply is stopped, external air suction during the cooling of the apparatus can be minimized and catalyst deterioration can be prevented.

It is a schematic longitudinal cross-sectional view of the hydrogen generator in one embodiment of this invention. It is a schematic longitudinal cross-sectional view of the hydrogen generator in other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings for easy understanding.

First Embodiment FIG. 1 is a schematic longitudinal sectional view of a hydrogen generator according to a first embodiment of the present invention. In FIG. 1, for example, a fuel such as hydrocarbons and water, which are raw materials for the steam reforming reaction, are supplied from a raw material supply unit 1. In the reforming unit 2, the reforming catalyst 2b used for the steam reforming reaction is accommodated in the catalyst unit 2a. Here, a catalyst prepared from a white metal noble metal was used as the reforming catalyst 2b.
In 3, the reforming catalyst temperature measuring unit 3 detects the temperature of the reforming catalyst 2 a, and heats the reforming unit 2 by a heating unit 4 having heating means such as a flame burner. The shift unit 6 accommodates the shift catalyst 6a and is provided with a shift catalyst temperature measuring unit 7 that detects the temperature of the shift catalyst 6a. Here, a catalyst containing at least copper as a component was used as the shift catalyst 6a.
In the raw material supply path 5, the raw material is supplied from the raw material supply section 1 to the reforming section 2, and the reformed gas is supplied from the reforming section 2 to the shift section 6 through the gas supply path 8. Further, the hydrogen generated in the shift unit 6 is exhausted from the hydrogen exhaust path 9.

In such a hydrogen generator to which the method of the present invention can be applied, the operation in the case of supplying hydrogen constantly will be described.
First, the heating unit 4 is operated to heat the reforming catalyst 2a of the reforming unit 2. The raw material fuel and water are supplied from the raw material supply unit 1 to the reforming catalyst 2a being heated through the raw material supply path 5, and the steam reforming reaction proceeds. The reformed gas passes through the gas supply path 8 to the shift section 6 and supplies hydrogen generated by converting carbon monoxide from the hydrogen exhaust path 9 to the outside.
And when stopping an apparatus, while stopping the heating operation by the heating part 4 (process (a)), the supply amount of fuel and water is gradually reduced (process (b)), and then the supply of water is stopped. (Step (c)), and finally the supply of fuel is stopped (Step (d)).

  When stopping the hydrogen supply, first, the heating operation by the heating unit 4 is stopped as a step (a). This is because when the supply of raw materials is stopped at the same time as the heating is stopped, the inside of the apparatus such as the reforming catalyst and the shift catalyst is at a high temperature. Because.

Immediately after the heating operation is stopped, the reforming section and the shift section are at temperatures corresponding to respective catalytic reactions, and are in a high temperature state of 800 deg or more as compared with the outside air temperature. When the supply of fuel and water is stopped in this state, the pressure in the apparatus is reduced as the temperature of the hydrogen generator decreases. If the inside of the apparatus is kept in a completely sealed state, there is no problem. Otherwise, air enters the apparatus from the outside.
Therefore, fuel and water are supplied even after the step (a), and the temperature of the reforming section is lowered by an endothermic reaction during the steam reforming reaction.

  At this time, the supply amount of fuel and water may be constant, but the steam reforming reactivity decreases as the catalyst temperature of the reforming unit decreases, so the supply amount of fuel and water is reduced in the reforming unit. It is preferable to decrease as the catalyst temperature decreases.

  Next, when the supply of water is stopped after the inside of the apparatus is sufficiently cooled, water may be collected in the apparatus. Therefore, the supply of water is stopped before the supply of fuel is stopped.

Finally, after sufficiently purging the inside of the apparatus, particularly the reforming section and the transformation section, and purging the inside of the apparatus with fuel so that the intrusion of air caused by the decompression of the inside of the cooled apparatus is minimized, Stop supplying fuel. In particular, when the fuel is a gas at normal temperature, the fuel purge effect is increased.
As a result, the operation method of the hydrogen generator of the present invention can suppress the mixing of air into the apparatus to the minimum and prevent oxidation of the catalyst, particularly oxidation of the shift catalyst.

  In the step (b), when the supply of fuel and water is drastically reduced, the endothermic amount due to the steam reforming reaction is reduced, the reforming catalyst temperature becomes high, and the reforming catalyst may exceed the heat-resistant use temperature. Therefore, it is preferable to lower the temperature while taking into consideration the heat resistant temperature of the reforming catalyst.

  In step (c), when the supply of water is stopped when the reforming catalyst is at a certain high temperature, carbon deposition may occur on the reforming catalyst. Further, stopping the supply of water after the inside of the apparatus is sufficiently cooled causes water to accumulate in the apparatus. Therefore, it is preferable to perform the step (c) after the reforming temperature is lowered to a temperature at which carbon is not deposited on the reforming catalyst.

  Finally, in step (d), the fuel supply is stopped. The process (( It is preferred to carry out d). By the above operation, the air suction probability due to the apparatus cooling is reduced, and catalytic oxidation by the suction air is prevented.

Here, an operation example of the hydrogen generator in this embodiment will be described.
The hydrocarbon component methane gas was used as the raw material fuel. 2 mol or more of water was added to 1 mol of methane gas, and the water was supplied to the reforming catalyst 2a of the reforming unit 2 to advance the steam reforming reaction.
The reforming catalyst temperature at this time was maintained at about 700 ° C. by the heating operation of the heating unit 4. The gas after the reforming section was supplied to the shift section 6 filled with a copper-based shift catalyst, and the carbon monoxide in the gas after the reforming section was lowered by a shift reaction with water. The shift catalyst at this time was used at a temperature of about 300 ° C. or lower. In this apparatus, when the supply of raw materials is stopped together with the stop of heating, the reduced pressure state is reduced to about 1/4 in the reforming catalyst portion and about 1/2 in the shift catalyst portion as compared to the open air portion with temperature cooling. Unless the device is hermetically sealed, the reduced pressure dependence results in the suction of external air.

  Therefore, first, as the step (a), the heating unit is stopped, and during the period in which the reforming catalyst temperature is maintained at a temperature at which the steam reforming reaction can proceed, the raw material is supplied to lower the reforming catalyst temperature. It was. Next, in step (b), the reforming catalyst temperature was detected by the reforming catalyst temperature measuring section, and it was confirmed that this temperature reached 650 ° C., which is a temperature at which the reforming catalyst does not rub the heat-resistant temperature. After that, the supply of methane gas and water was reduced.

  Next, as a step (c), it was confirmed that the temperature of the reforming catalyst became 400 ° C. or less at which the methane gas decomposition reaction proceeded on the reforming catalyst and no carbon deposition occurred, and the water supply was stopped.

Finally, as a step (d), after confirming that the detected temperature in the shift catalyst temperature measurement unit has reached 50 ° C., which is a temperature that can prevent the catalytic activity from being reduced due to catalytic oxidation of the mixed air, fuel supply Stopped. At this time, it is necessary to confirm that the temperature of the reforming catalyst portion is also sufficiently lowered.
The temperature of the reforming catalyst and the temperature of the shift catalyst may be determined according to the type and characteristics of the catalyst, the type of fuel to be supplied, and the like.

  It was confirmed that by performing the above operation, water vapor generation characteristics that remain unchanged even when the apparatus is repeatedly started and stopped are obtained. When the apparatus is stopped without executing the method of the present invention, the catalyst is oxidized by external air suction, and the shift reaction cannot be sufficiently maintained when the apparatus is started next time, and carbon monoxide at the outlet of the hydrogen generator It has also been confirmed that the concentration is considerably higher than that in the case of stopping the apparatus according to the present invention.

In the above operation example, the supply amount of fuel and water is reduced based on the detection results of the reforming catalyst temperature and the shift catalyst temperature, then the water supply is stopped, and finally the fuel supply is stopped. Although the operation has been performed, if the type and supply amount of fuel to be supplied and the operating conditions of the apparatus are known, the period for performing steps (b), (c) and (d) may be set in terms of time.
Further, although the white metal-based noble metal catalyst is used as the reforming catalyst, it is also possible to use a nickel-based catalyst whose main component is nickel. Since the nickel-based catalyst can obtain a high catalytic activity in the reduced state like the copper-based catalyst, the oxidation can be prevented by stopping the hydrogen generator by the method of the present invention.

Furthermore, although methane gas, which is a hydrocarbon, was used as the fuel, it goes without saying that similar results can be obtained with other hydrocarbon components or mixtures thereof.
Moreover, when reducing the supply of hydrocarbons and water, it is not necessary to reduce them at the same ratio. By reducing the water supply ratio to be smaller, the water vapor partial pressure can be reduced, and the risk of water condensation in the apparatus can be reduced. Moreover, although the flame burner was used as a heating part, as long as it is the structure which can heat a reforming catalyst, what kind of heating form may be sufficient.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. The hydrogen generator in this embodiment has almost the same configuration as that shown in FIG. 1, and only the differences will be described below. The difference is that 10 on-off valves are provided at the outlet of the hydrogen exhaust passage 9.

In the second embodiment, hydrogen is generated by performing substantially the same operation as in the first embodiment. The difference is that, in the step (d) of stopping the supply of fuel, when the hydrocarbon is stopped, the on-off valve is closed to make the inside of the device a sealed space. By providing the on-off valve in this manner and closing the on-off valve when the fuel supply is stopped, the inside of the apparatus is made a sealed space, so that air mixing due to diffusion can be prevented in the apparatus after the fuel purge.
In particular, when the apparatus is stopped for a long period of time, the degree of catalytic oxidation by the diffusion air can be greatly reduced. In the apparatus configuration according to the present invention, one operation was performed in which the on-off valve 10 was left open for a long period of time after the apparatus was stopped. As a result, the oxidation state of the shift catalyst left in the closed state was analyzed. As a result, it was confirmed that the progress of oxidation could be clearly prevented as compared with the open state.

Third Embodiment Next, a third embodiment of the present invention will be described. The configuration of the hydrogen generator used here is the same as that of the first embodiment shown in FIG.
In the present embodiment, the apparatus is stopped by performing substantially the same operation as in the first embodiment. The difference is that in step (d), the fuel supply is stopped after the heating unit stopped in step (a) is actuated again. This is a preferred embodiment when a fuel that is liquid at room temperature is used as the raw material fuel.

An example of operation in the method for stopping the hydrogen generator in this embodiment will be shown. Naphtha, which is liquid at room temperature, was used as a raw material fuel. The operation is the same as that shown in the operation example of the first embodiment until the raw material is stopped.
When naphtha that is liquid at room temperature is used, if the supply of the raw material is stopped after the inside of the apparatus is cooled to near room temperature, there is a high possibility that a large amount of hydrocarbon components remain in the apparatus as a liquid. This is not preferable from the viewpoint of ensuring the safety of the apparatus in addition to preventing the catalyst oxidation.
Therefore, it is preferable to perform the step (e) before stopping the fuel supply in the step (d). After operating the heating unit to thermally decompose naphtha on the reforming catalyst to purge the inside of the apparatus as a gas component, the heating unit is stopped and the fuel supply is stopped. As a result, the amount of naphtha remaining as a liquid in the apparatus can be greatly reduced.

Also in this case, as in the first embodiment, in the step (b), when the feed of the fuel and water is drastically reduced, the endothermic amount due to the steam reforming reaction is reduced and the reforming catalyst temperature is high. Therefore, since the reforming catalyst may exceed the heat-resistant use temperature, it is preferable to lower it while considering the heat-resistant temperature of the reforming catalyst.
In step (c), when the supply of water is stopped when the reforming catalyst is at a certain high temperature, carbon deposition may occur on the reforming catalyst. Further, stopping the supply of water after the inside of the apparatus is sufficiently cooled causes water to accumulate in the apparatus. Therefore, it is preferable to perform the step (c) after the reforming temperature is lowered to a temperature at which carbon is not deposited on the reforming catalyst.

  In addition, carbon deposition may occur on the reforming catalyst during fuel decomposition, but by using a white metal noble metal catalyst as the reforming catalyst, it is possible to suppress a decrease in catalyst activity due to carbon deposition to a minimum. Also, as in the second embodiment, an on-off valve is provided, and when the fuel supply is stopped, the on-off valve is closed to make the inside of the device a sealed space, thereby preventing air from being mixed into the device after hydrocarbon purge. it can.

  In the present invention, the reforming section and the shift section are provided in order to steam reform the fuel and supply hydrogen. However, when alcohol such as methanol is steam reformed as the fuel, only the reforming section may be used. Since many alcohol components also become liquid at room temperature, after stopping the heating unit, after the reforming unit reaches a predetermined temperature, the stopping method shown in this embodiment is performed again before the raw material is stopped. Thus, the possibility that alcohol exists in liquid form in the apparatus can be reduced.

Fourth Embodiment Next, a fourth embodiment of the present invention will be described. The apparatus configuration is the same as that shown in FIG.
In the present embodiment, after the heating operation of the heating unit is stopped, when the inside of the hydrogen generator is in a reduced pressure state due to a temperature drop, at least an amount of hydrocarbon components corresponding to the volume reduction amount is supplied to the hydrogen generator. To do. This operation can reduce the probability of air mixing during the cooling process when the apparatus is stopped.

  When only the fuel is supplied at a high temperature of the reforming catalyst, the fuel is decomposed and carbon is deposited on the catalyst. However, when a white metal-based noble metal catalyst is used as the reforming catalyst, the decrease in catalytic activity due to carbon deposition is reduced. Moreover, it can be made to react with the deposited carbon component by supplying an excessive amount of water during the steady operation of the apparatus, and the carbon component can be reduced. Therefore, after the heating operation of the heating unit is stopped, when the inside of the hydrogen generator is in a reduced pressure state due to a temperature drop, at least an amount of fuel corresponding to the volume reduction is supplied to the hydrogen generator. By this operation, it is possible to reduce the proportion of air mixed in the cooling process when the apparatus is stopped.

  Next, an operation example in the operation method of the hydrogen generator in the present embodiment will be shown. Note that a white metal-based noble metal catalyst was used as the reforming catalyst. After the heating operation of the heating section is stopped, when the inside of the hydrogen generator is in a reduced pressure state due to a temperature drop, the operation of supplying at least an amount of fuel corresponding to the volume reduction amount to the hydrogen generator is repeated 100 times or more. As a result, it was confirmed that almost the same characteristics as those of the initial hydrogen generator were obtained.

DESCRIPTION OF SYMBOLS 1 Raw material supply part 2 Reforming part 2a Catalyst part 2b Reforming catalyst 3 Reforming catalyst temperature measurement part 4 Heating part 5 Raw material supply path 6 Transformation part 6a Transformation catalyst 7 Transformation catalyst temperature measurement part 8 Gas supply path 9 Hydrogen exhaust path 10 On-off valve

Claims (7)

A reforming unit having a reforming catalyst for steam reforming fuel, a raw material supply unit for supplying the fuel and water to the reforming unit, a heating unit for the reforming catalyst, and a catalyst containing at least copper In a hydrogen generator comprising a shift section and supplying gas generated in the reforming section to the shift section,
(A) a step of stopping the heating operation of the heating unit, (b) a step of gradually decreasing the supply amount of the fuel and water, (c) a step of stopping the supply of water, and (d) supply of the fuel The operation method of the hydrogen generator which includes the process of stopping this in order of process (a), (b), (c) and (d).   The method for operating a hydrogen generator according to claim 1, wherein the reforming temperature in step (b) is a temperature not exceeding the heat resistance temperature of the reforming catalyst.   The method for operating a hydrogen generator according to claim 1, wherein the reforming temperature in step (c) is a temperature at which carbon is not deposited on the reforming catalyst.   The method for operating a hydrogen generator according to claim 1, wherein the shift catalyst temperature in step (d) is a temperature at which the catalytic activity of the shift catalyst is not reduced by air oxidation.   The operation method of the hydrogen generator of Claim 1 including the process (e) of starting and stopping the said heating part again between a process (c) and a process (d) when a fuel is liquid at normal temperature.   The method for stopping a hydrogen generator according to any one of claims 1 to 5, wherein when the supply amounts of fuel and water are reduced in step (b), the supply amount of water is made smaller than the supply amount of fuel.   The operation method of the hydrogen generator according to any one of claims 1 to 6, wherein an opening / closing valve is provided at the outlet of the shift section, and the opening / closing valve is closed in the step (d).

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