JP2002255509A - Hydrogen production apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen production apparatus capable of stably supplying hydrogen with a low carbon monoxide concentration, and to keep a catalyst activity in the low temperature of a noble metal modified catalyst strong against a repetition of redox, concerning the hydrogen production apparatus which supplies hydrogen to fuel cells, or the like. SOLUTION: A modifying part 3 having a modified catalyst 3a composed of a noble metal catalyst and a metal oxide which reacts carbon monoxide with steam is provided, and a reforming part 1 which supplies hydrogen containing at least carbon monoxide and steam to the modifying part 3 and a modified air supplying part 8 which supplies a oxidizing gas to the modifying part 3 are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen generator which needs to reduce the concentration of carbon monoxide generated simultaneously when reforming a hydrocarbon component and water as raw materials to generate hydrogen gas. .

[0002]

2. Description of the Related Art A cogeneration system using a fuel cell with high power generation efficiency has attracted attention as a distributed power generation device that effectively uses heat and electricity.

[0003] Most fuel cells generate power using hydrogen as fuel. The hydrogen is produced by reacting a raw material such as natural gas, a hydrocarbon component such as LPG, an alcohol such as methanol, or a naphtha component with water in a reforming section provided with a reforming catalyst to generate hydrogen, It is produced by an autothermal method using a steam reforming reaction and a partial oxidation reaction of raw materials in combination.

In the reforming reaction for producing hydrogen from water and the above-mentioned raw materials, carbon monoxide is produced as a secondary component. This carbon monoxide becomes a poisoning component of a fuel cell electrode catalyst particularly in a polymer fuel cell operating at a low temperature. Therefore, a hydrogen generator for a polymer fuel cell uses a shift unit that shifts water and carbon monoxide to hydrogen and carbon dioxide (shift reaction), and a purifier that oxidizes or methanates carbon monoxide. You. In the metamorphic section, a Fe—Cr-based catalyst or a Cu—Zn-based catalyst is used to reduce carbon monoxide to a concentration of about 0.5%. In the purification unit, Pt, which is a precious metal-based noble metal, is used.
Alternatively, a configuration is adopted in which carbon monoxide is selectively oxidized or methanated using a Ru-based catalyst, and finally carbon monoxide is reduced to a level of about 100 ppm.

In order to stably reduce carbon monoxide,
It is important that carbon monoxide and water vapor undergo a sufficient shift reaction in the shift section. Because this transformation reaction is exothermic,
It is desirable to make the reaction at a temperature as low as possible. But,
At a low temperature, the reaction rate decreases, and the metamorphic portion becomes large. If hydrogen gas is supplied beyond the maximum capacity of the shift unit (shift unit) in order to reduce the size of the shift unit, an oxidizing gas is supplied to the shift unit in accordance with the supply amount, and in addition to the shift reaction, A method of performing an oxidation reaction of carbon oxide has also been devised.

[0006]

The Cu-Zn-based catalyst generally used in the shift section has a high activity at a low temperature, and the ability to reduce carbon monoxide is greater than other shift catalysts. This catalyst exhibits catalytic activity in a reduced state, but the catalytic activity is significantly reduced by repeated oxidation and reduction. Therefore, supplying an oxidizing gas to a Cu—Zn-based catalyst even when supplying hydrogen gas is not desirable from the viewpoint of catalyst durability.

On the other hand, Pt, Pd, Ru, P
A shift catalyst composed of a noble metal such as h and a metal oxide has been devised. However, this noble metal shift catalyst is
Low activity at low temperature compared to Cu-Zn catalyst. Therefore, it has been desired to effectively reduce carbon monoxide by using a noble metal-based shift catalyst that is resistant to oxidation and reduction.

An object of the present invention is to solve the above-mentioned problems relating to the conventional hydrogen generating apparatus shift section, and an object of the present invention is to provide a hydrogen generating apparatus capable of stably supplying hydrogen gas having a low carbon monoxide concentration.

[0009]

In order to solve the above-mentioned problems, a first present invention (corresponding to claim 1) comprises a noble metal-based catalyst and a metal oxide for reacting carbon monoxide with water vapor. A shift section having a shift catalyst body, a gas supply section for supplying a hydrogen gas containing at least carbon monoxide and water vapor to the shift section, and an oxidizing gas supply section for feeding an oxidizing gas to the shift section. It is a hydrogen generator provided with.

According to a second aspect of the present invention (corresponding to claim 2), the shift catalyst has a structure having a number of passages through which gas flows, and the oxidizing gas supply unit is provided downstream of the structure. The hydrogen generator according to the first aspect of the present invention for supplying the oxidizing gas.

According to a third aspect of the present invention (corresponding to claim 3), the shift unit has a temperature detecting unit for detecting the temperature of the shift catalyst, and the temperature detected by the temperature detecting unit is set within a set temperature range. The hydrogen generator according to the first aspect of the present invention, wherein a supply amount of the oxidizing gas from the oxidizing gas supply unit to the shift unit is controlled such that:

According to a fourth aspect of the present invention (corresponding to claim 4), the shift section is constituted by a plurality of shift mechanisms, each of which has the shift catalyst body, and The hydrogen generator according to the first aspect of the present invention, wherein a gas supply unit supplies the oxidizing gas to the shift mechanism located downstream of a gas flow.

According to a fifth aspect of the present invention (corresponding to claim 5), the plurality of stages means two stages, the oxidizing gas is not supplied to the former shift mechanism, and the second shift mechanism is not shifted to the latter shift mechanism. The hydrogen generator according to a fourth aspect of the present invention for supplying the oxidizing gas.

According to a sixth aspect of the present invention (corresponding to claim 6), the rear-stage shift mechanism has a temperature detector for detecting the temperature of the shift catalyst body in the shift mechanism, and the temperature is detected by the temperature detector. The hydrogen generator according to the fifth aspect of the present invention, wherein a supply amount of the oxidizing gas from the oxidizing gas supply unit to the subsequent shift mechanism is controlled such that a temperature to be performed is within a set temperature range.

According to a seventh aspect of the present invention (corresponding to claim 7), the plurality of stages means two stages, the oxidizing gas is not supplied to the former shift mechanism, and the second shift mechanism is The oxidizing gas is supplied, and is disposed between the preceding metamorphic mechanism and the subsequent metamorphic mechanism, and the temperature of the gas flowing from the former metamorphic mechanism to the latter metamorphic mechanism is controlled within a predetermined range. The hydrogen generator according to the fourth aspect of the present invention, further comprising a temperature adjustment unit that adjusts the temperature so that the temperature falls within the range.

According to an eighth aspect of the present invention (corresponding to claim 8), a purifying section having a purifying catalyst body to which hydrogen gas is supplied from the shift section and oxidizing carbon monoxide; And a second oxidizing gas supply unit for supplying hydrogen.

According to the present invention described above, it is possible to effectively and stably reduce carbon monoxide in hydrogen gas by using a noble metal-based conversion catalyst which is resistant to oxidation and reduction, thereby solving the problems of the conventional hydrogen generator. I do.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a configuration diagram of a hydrogen generator according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 1 denotes a reformation of a steam reforming reaction serving as a hydrogen gas supply unit. This is a reforming section provided with a high quality catalyst section 1a. Reforming catalyst unit 1
As the catalyst body a, a noble metal supported on an alumina substrate was used. Reference numeral 2 denotes a flame burner (details not shown), which serves as heating means for the reforming catalyst section 1a. Reference numeral 5 denotes a raw material supply unit for supplying a hydrocarbon component as a raw material, and reference numeral 6 denotes a water supply unit for water for reacting with the raw material, which is configured to supply the water to the reforming catalyst unit 1a.

Reference numeral 3 denotes a shift section containing a shift catalyst body 3a. As the shift catalyst 3a, a noble metal (P in this embodiment)
t catalyst) and a catalyst prepared using Ce oxide were dipped in cordierite honeycomb. A first conversion temperature measuring section 9 for measuring the gas temperature before the shift catalyst 3a, and a second shift temperature measuring section 9 for measuring the gas temperature after the shift catalyst 3a.
A temperature measurement unit 10 is provided.

Reference numeral 4 denotes a purifying section containing the purifying catalyst 4a. As the purification catalyst 4a, a noble metal (in this embodiment, P
t) was carried on an alumina substrate, and cordierite honeycomb was subjected to a dipping treatment. Further, the purification catalyst 4a
A first purification temperature measuring unit 12 for measuring the temperature of the gas before and a second temperature measuring unit 13 for purification measuring the gas temperature after the purification catalyst 4a are provided.

Reference numeral 7 denotes a reforming section 1, a shift section 3, and a purification section 4.
And a gas ventilation path having an outlet in the purification section 4 through which the gas flows. Reference numeral 8 denotes a modified air supply unit that supplies air as an oxidizing gas to the gas after the reforming unit 1 through the gas ventilation path 7. Reference numeral 11 denotes a purified air supply unit that supplies air as an oxidizing gas to the gas after the shift unit 3 through the gas ventilation path 7. An air pump was used for both the modified air supply unit 8 and the purified air supply unit 11.

In the first embodiment, in the hydrogen generator of the present invention, the shift unit 3 as an example of a shift unit, the reforming unit 1 as an example of a gas supply unit, and the shift unit as an example of an oxidizing gas supply unit. Each of the air supply units 8 is used.

The operation of the hydrogen generator when supplying hydrogen will be described below.

During a steady operation for supplying hydrogen, the heating section 2 is operated to heat the catalyst of the reforming catalyst section 1a to a temperature of 700 to 750.degree. The hydrocarbon component as the raw material is supplied from the raw material supply unit 5 and the water is supplied from the water supply unit 6 to the reforming catalyst unit 1a being heated, so that the steam reforming reaction proceeds. The gas after the reforming unit 1 is ventilated to the shift unit 3 through the gas venting path 7,
At the same time, air is added from the modified air supply unit 8.

In the shift unit 3, the shift catalyst 3a mainly shifts carbon monoxide and steam in the gas after the reforming unit 1 to carbon dioxide and hydrogen. At this time, the gas temperature at the inlet of the shift unit 3 is measured by the shift first temperature measuring unit 9, and the gas temperature at the outlet is measured by the shift second temperature measuring unit 10. The gas after the shift unit 3 is supplied to the purification unit 4 through the gas ventilation path 7, and at the same time, air is supplied from the purified air supply unit 11.

In the purifying section 4, carbon monoxide is oxidized and reduced by the purifying catalyst 4a. At this time, the gas temperature at the inlet of the purification unit 4 is measured by the first purification temperature measurement unit 12, and the gas temperature at the outlet is measured by the second purification temperature measurement unit 13. The hydrogen gas purified by the purifier 4 is supplied to the outside of the hydrogen generator from the gas passage 7.

Next, the structural features of the present embodiment will be described. In the present embodiment, Pt is used as the shift catalyst body 3a.
While using a catalyst prepared using a catalyst and Ce oxide,
It is characterized in that air as an oxidizing gas is supplied to the gas after the reforming section 1 from the shift air supply section 8 and the shift reaction proceeds in the shift section 3.

Next, differences between the features of this embodiment and the conventional configuration will be described. As a conventional configuration of a general metamorphic unit, a hydrogen generator of a phosphoric acid type fuel cell will be described as an example. The shift unit has a structure in which the gas body after the reforming unit is simply supplied in many cases, and as a shift catalyst, a Cu-Zn-based material having relatively low-temperature activity and a characteristic of effectively reducing carbon monoxide. Catalysts are widely used. However, since the Cu—Zn-based catalyst has a low heat-resistant temperature of 300 to 350 ° C. and is limited to use under a low reaction rate, a large catalyst volume is required.

In order to reduce the size of the shift section (shift section), if hydrogen gas is supplied beyond the maximum capacity of the shift section, an oxidizing gas is supplied to the shift section in accordance with the supply amount.
A configuration has been devised in which an oxidation reaction of carbon monoxide is performed in addition to the metamorphic reaction to reduce carbon monoxide. However, Cu-
The Zn-based catalyst exhibits high catalytic properties when used in a reduced state, but has a problem that the dispersion state and the like of the catalyst are changed due to rapid oxidation and the characteristics are deteriorated. Therefore, supplying an oxidizing gas to the Cu—Zn-based catalyst is not so desirable from the viewpoint of preventing a decrease in catalytic activity.

Therefore, in the present embodiment, an oxidizing gas is supplied to the shift unit, and a shift catalyst adjusted using a Pt catalyst and Ce oxide is used. This is a major difference from the conventional configuration. This catalyst has excellent heat resistance and oxidation resistance as compared with the Cu-Zn-based catalyst, and has a characteristic that the metamorphic reactivity hardly decreases by repeated oxidation-reduction. Therefore, the present embodiment has a configuration in which the effect of introducing the oxidizing gas into the shift portion can be maximized as compared with the conventional configuration.

Next, the specific effects of the present embodiment will be described. In the Pt-based shift catalyst used in the present embodiment, the shift reaction proceeds because the carbon monoxide adsorbed on the Pt catalyst reacts with oxygen atoms of water vapor to form carbon dioxide by the action of Ce oxide. Although this Pt-based shift catalyst is excellent in oxidation resistance, the activity of the shift catalyst at low temperatures tends to be slightly lower than that of the Cu-Zn shift catalyst. This is due to the temperature dependence of the adsorption of carbon monoxide on the Pt-based catalyst, which indicates that the lower the temperature of the adsorbed carbon monoxide, the more difficult it is to desorb from the Pt catalyst. That is, even in the shift catalyst, the desorption property of carbon monoxide is lowered at low temperature, so that the shift reaction is inhibited.

However, the temperature dependence of the Pt catalyst in adsorbing carbon monoxide changes depending on the presence of an oxidizing gas. For example, when oxygen is present as an oxidizing gas, P
The carbon monoxide adsorbed on the t catalyst has a characteristic of being desorbed even at a lower temperature. In this embodiment, utilizing this characteristic, an oxidizing gas is supplied to the Pt-based shift catalyst to desorb carbon monoxide adsorbed on the Pt catalyst, thereby ensuring shift reaction at lower temperature, Can be reduced. In other words, by supplying the oxidizing gas to the shift section, the reactivity of the shift catalyst, particularly at low temperatures, can be improved as described above, so that the concentration of carbon monoxide at the outlet of the shift section is greatly reduced. What you can do is a unique effect.

When a large amount of oxidizing gas is supplied, hydrogen is oxidized and consumed. Therefore, it is desirable to set the upper limit of the amount that completely oxidizes carbon monoxide in hydrogen gas. From the viewpoint of ensuring the conversion reactivity at low temperature, it is not necessary to add the equivalent amount of carbon monoxide oxidation, and the amount that can effectively reduce carbon monoxide in consideration of the amount of supplied hydrogen gas, the operating temperature of the conversion catalyst, etc. It is desirable to increase or decrease with.

Further, since the calorific value can be changed by the amount of supplied air, the temperature of the shift catalyst can be controlled. The shift catalyst temperature may be set based on the shift catalyst characteristics, for example, the upper limit is based on the heat-resistant temperature, and the lower limit is set based on the catalyst reaction maintaining temperature. The catalyst used in this embodiment depends on the adjustment conditions (5
Considering that the temperature is about calcination at 00 ° C.), about 500 ° C. was set as the heat resistance limit.
The lower limit temperature corresponds to a high concentration of carbon monoxide (about 1
0% concentration) 150 ° C. as the temperature at which the catalyst activity can be maintained
Was used as a guide. By setting the catalyst operating temperature range at the upper and lower temperatures and controlling the catalyst temperature with the supplied air amount, it is possible to maintain high shift reactivity in the shift section.

Next, the difference between the object and the effect of the present embodiment and the conventional structure will be compared. The main purpose of supplying the oxidizing gas to the metamorphic section in the conventional configuration is to oxidize and reduce a portion of carbon monoxide in the hydrogen gas by introducing air, thereby obtaining an effect of reducing the load on the metamorphic section. . On the other hand, in the present embodiment, the purpose is to activate the shift catalyst as described above, and as a result, the shift reaction proceeds at a low temperature and the effect of reducing carbon monoxide is obtained. That is, it can be seen that the purpose and the effect are greatly different.

Next, the detailed effects of the present invention will be described based on one embodiment in which hydrogen is generated using methane gas as a raw material. First, the heating unit 2 is operated, and the raw material supply unit 5
And supplied methane gas as a raw material to the reforming catalyst section 1a. About 3 mol of water was added to the reforming catalyst section 1a from the water supply section 6 with respect to 1 mol of the methane gas. Reforming catalyst section 1a
Is heated to a temperature of 700 to 750 ° C., steam reforming proceeds, and 97 to 99% of supplied methane is reacted. Due to this reaction, the hydrogen gas at the outlet of the reforming section 1 contains about 10% of carbon dioxide and about 10% of carbon monoxide (dry gas basis).

The post-reforming section 1 gas is supplied to the shift section 3,
The metamorphic reaction proceeds to reduce the concentration of carbon monoxide. At this time, air was supplied to the gas as an oxidizing gas from the modified air supply unit 8. The amount of supplied air was supplied with an upper limit of an amount containing half of the amount of carbon monoxide in the gas after the reforming section 1. The amount of air to be supplied was controlled so that the temperature of the second temperature measurement unit 10 detected by the shift second conversion temperature measuring unit 10, which was the gas temperature after the shift catalyst 3a of the shift shift unit 3, became 300 ° C. At this time, the concentration of carbon monoxide at the outlet of the shift section 3 was about 0.6%. For comparison, an operation was performed in which no air was supplied and control was performed so that the temperature detected by the second metamorphic second temperature measurement unit 10 was 300 ° C. At this time, the concentration of carbon monoxide at the outlet of the shift part 3 was about 0.7%. In addition, it is also possible to control the amount of supplied air and adjust the temperature of the shift catalyst body in the range of 150 to 500 ° C.

Next, air containing twice the amount of carbon monoxide as the amount of oxygen was supplied from the purified air supply unit 11 to the gas after the shift unit 3 assuming a steady operation. In the purification unit 4, carbon monoxide is oxidized by the purification catalyst to reduce its concentration. In order to effectively reduce carbon monoxide, the temperature of the purification first temperature measurement unit 12 is 100 to 150 ° C., and the purification second temperature measurement unit 1
The purifying unit 4 was operated so that the temperature of the sample No. 3 was 120 to 200 ° C. Thereby, the concentration of carbon monoxide (dry gas base) in the hydrogen gas after the purification unit 4 was reduced to 20 ppm or less. Although the example using methane gas as a raw material is shown,
Hydrocarbon gas such as natural gas and LPG, or naphtha,
A liquid fuel such as kerosene may be used as a raw material.

It should be noted that the Pt used in the metamorphic unit 3 of this embodiment
A Pt-based shift catalyst in which a catalyst and a Ce oxide are adjusted exhibits a shift reaction without supplying an oxidizing gas, and a shift section conventionally provided for the purpose of oxidizing and reducing carbon monoxide is referred to as a shift section. It is completely different. Although Pt was used as the noble metal of the shift catalyst, the catalyst activity is exhibited when at least one of Pt, Pd, Rh, and Ru is included. As with Pt, those noble metals tend to be less likely to desorb as the temperature of the adsorbed carbon monoxide decreases, and in the presence of an oxidizing gas, carbon monoxide has the property of desorbing even at lower temperatures. Therefore, when a shift catalyst containing at least one of Pt, Pd, Rh, and Ru is used, it goes without saying that the configuration shown in the present embodiment can improve the catalytic activity at a low temperature. Further, as the metal oxide, not only Ce oxide but also Zr oxide, a solid solution of Zr and Ce oxide, or Re oxide shows catalytic activity.

In the present embodiment, a flame burner is used as the heating unit 2, but any structure may be used as long as the reforming catalyst can be heated. Further, the reforming catalyst is not limited to a noble metal-based catalyst, and a nickel-based catalyst or the like may be used. Further, the air pump is used as the modified air supply unit 8 and the purified air supply unit 11, but the air pump is not limited to the air pump as long as it can supply air, such as an air blower. Further, the oxidizing gas is not limited to air, and any gas containing oxygen, such as a gas from an oxygen cylinder, can be supplied.

The purification catalyst used here was Al ₂
The purification catalyst was prepared by dispersing and supporting Pt on Al ₂ O ₃ using O ₃ and a Pt salt solution and sintering the coating, and coating the cordierite honeycomb to prepare a purification catalyst. It is not limited to.

(Embodiment 2) FIG. 2 is a configuration diagram of a hydrogen generator according to Embodiment 2 of the present invention, which has almost the same configuration as the hydrogen generator shown in Embodiment 1 of FIG. The description of the same parts will be omitted, and only different points will be described.
The difference is that the shift catalyst 3a of the shift unit 3 is divided into two parts, one located upstream and the other located downstream with respect to the hydrogen gas flow inside the shift unit 3, and the air supplied to the shift unit 3 The supply unit outlet is provided in the shift unit 3 to supply air, which is an oxidizing gas, to the shift catalyst 3a located downstream of the hydrogen gas flow. The shift catalyst 3
Although the outlet of the metamorphic air supply unit 8 is provided at a position that substantially divides a into two, it is needless to say that the position of the outlet needs to be determined in consideration of operating conditions such as the supply amount of hydrogen gas.

The operation is substantially the same as that of the hydrogen generator described in the first embodiment, and carbon monoxide is more effectively reduced.

Next, features of the present embodiment will be described in comparison with those of the first embodiment. In the hydrogen generator according to Embodiment 1, the oxidizing gas is supplied from the upstream of the shift section. When the temperature of the shift catalyst is high, the supplied oxidizing gas may be consumed upstream of the shift catalyst. As a result, the oxidizing gas does not spread downstream of the shift catalyst body, and the effect of activating the shift reaction downstream of the shift catalyst body is reduced. Further, since the temperature of the shift catalyst body rises due to the heat generated by the oxidation, conditions for operating the shift catalyst body at a low temperature are restricted, and there is a possibility that carbon monoxide cannot be reduced effectively. Therefore, the second embodiment is characterized in that air, which is an oxidizing gas, is supplied to the shift catalyst 3a located downstream of the hydrogen gas flow.

Next, effects of the present embodiment will be described. In the present embodiment, the shift reaction proceeds first in the upstream portion of the shift catalyst body 3a to reduce carbon monoxide. An oxidizing gas is supplied to the gas from the modified air supply unit 8. Since the concentration of carbon monoxide is reduced before the shift catalyst 3a located downstream, the amount of oxidizing gas corresponding to the concentration can be reduced as compared with the case where the gas is supplied before the shift unit 3. As a result, heat generated by the supplied oxidizing gas is reduced, and the shift catalyst can be operated at a low temperature. In the metabolic reaction between carbon monoxide and water vapor, which is an exothermic reaction, the equilibrium shifts toward lower carbon monoxide at a low temperature, so that carbon monoxide can be further reduced.

Next, detailed effects of the present invention will be described based on one example in which methane gas is used as a raw material to generate hydrogen, as in the example performed in the first embodiment. Since the operations in the reforming section and the purification section are almost the same, the description will be omitted, and only the operation in the shift section will be described.

In the same manner as in the first embodiment, methane is subjected to steam reforming in the reforming section 1 so that carbon dioxide is reduced to about 10%.
%, And about 10% of carbon monoxide (dry gas basis) was supplied to the shift converter 3 as hydrogen gas. In the shift part 3, the shift reaction proceeds with the shift catalyst body 3a located upstream. Here, the detected temperature of the first metamorphic temperature measuring section 9 is 30
By operating at 0 ° C., the amount was reduced to about 2% before the shift catalyst body located downstream. Next, air was supplied from the modified air supply unit 8 with an upper limit of an amount containing twice the amount of carbon monoxide.

As compared with the embodiment of the first embodiment, since the concentration of carbon monoxide is about 1/5, the calorific value of the oxidizing gas can be reduced to 1/5 at the maximum. Compared with the example in the first embodiment, the temperature detected by the shift second temperature measurement unit 10 which is the gas temperature after the shift catalyst body 3a could be lowered by about 50 ° C. at the maximum. That is, since the temperature at the downstream portion of the shift catalytic converter 3a could be lowered, the concentration of carbon monoxide at the outlet of the shift converter 3 could be reduced to about 0.5%.

Note that the temperature of the shift catalyst needs to be determined based on the operating conditions of the hydrogen generator such as the amount of hydrogen to be generated and the amount of water to be supplied. For example, under the condition that the amount of hydrogen to be generated is large, the amount of carbon monoxide contained in the hydrogen also increases.
In that case, it is desirable to make the temperature of the shift catalyst high. However, when the temperature of the shift catalyst is increased, methane is generated from hydrogen and carbon dioxide in the gas, and the amount of hydrogen decreases. Further, when the shift catalyst is operated at a low temperature, the reaction rate becomes slow, and the carbon monoxide cannot be reduced effectively.
Therefore, it is desirable to use the shift catalyst body temperature in the range of 150 to 500 ° C. The temperature of the shift catalyst body can be adjusted by increasing or decreasing the supply amount of the oxidizing gas from the oxidizing gas supply unit to the shift unit.

(Embodiment 3) FIG. 3 is a diagram showing a configuration of a hydrogen generator according to Embodiment 3 of the present invention, which has almost the same configuration as the hydrogen generator shown in Embodiment 2 shown in FIG. The description of the same parts will be omitted, and only different points will be described. The difference is that the shift unit 3 is composed of a first shift unit 3b containing a first shift catalyst unit 3c and a second shift unit 3d containing a second shift catalyst unit 3e. The first shift unit 3b and the second shift unit The point that an air-cooling fan that is a shift cooling unit 14 that adjusts the temperature of the gas after the first shift unit 3b is provided between the shift units 3d. The shift first temperature measuring unit 9 is provided at the gas inlet of the first shift unit 3b, the shift second temperature measuring unit 10 is provided at the gas outlet of the second shift unit 3d, and the gas after the first shift catalyst 3c is provided. A point that the oxidizing gas is supplied from the modified air supply unit 8. And an outlet of the reforming section 1 is provided with a pre-reformation temperature adjusting section 15 for the post-reforming gas temperature.
Is provided to adjust the temperature of the second shift catalyst body 3e of the second shift unit 3d. In addition, the temperature adjustment part 15 before denaturation was an air cooling fan.

The operation is substantially the same as that of the hydrogen generator described in the second embodiment, and carbon monoxide is more effectively reduced. The difference is that the gas temperature is adjusted by the pre-denaturation temperature adjustment unit 15 after the reforming unit 1. Further, the gas temperature raised by the heat generated by the metamorphic reaction in the first metamorphic section 3b is
Is to cool down.

Next, features of the present embodiment will be described in comparison with those of the second embodiment. In the hydrogen generator according to the second embodiment, the temperature of the portion of the shift section 3 located downstream of the shift catalyst body 3a depends on the upstream temperature. For example, the reforming unit 1
Large amount of hydrogen gas supplied from the
When the amount of carbon monoxide to be subjected to the shift reaction in step a increases, the temperature of the downstream shift catalyst 3a rises due to the heat generated by the shift reaction, and the carbon monoxide may not be reduced effectively. Therefore, in the third embodiment, the shift unit 3 is replaced by the first shift unit 3
b and a second shift unit 3d, and an air-cooling fan as the shift cooling unit 14 is provided between the first shift unit 3b and the second shift unit 3d to adjust the temperature of the gas after the first shift unit 3b. It is characterized by.

Next, effects of the present embodiment will be described. In the present embodiment, first, the metamorphic reaction proceeds to some extent in the first metamorphic section 3b. Denatured air supply unit 8
The oxidizing gas is supplied more, but the amount of oxidizing gas corresponding to the carbon monoxide concentration is changed as in the second embodiment because the concentration of carbon monoxide before the second shift part 3d located downstream is reduced. It can be less than the oxidizing gas supplied before the part 3. Further, as the shift reaction proceeds, the gas temperature after the first shift section 3b increases. In particular, when the amount of hydrogen gas supplied to the shift unit 3 is large, the amount of carbon monoxide that undergoes shift reaction increases, and the temperature rise increases.

Therefore, the shift cooling section 14 is operated to adjust the temperature of the gas after the first shift section 3b. In consideration of the temperature equilibrium of the metamorphic reaction, it is desirable to operate the metamorphic unit at a temperature as low as possible, but it is necessary to set the operating conditions in relation to the reaction speed. However, by providing the shift cooling unit 14 as in the present embodiment, the temperature of the shift catalyst body 3e of the second shift unit 3d can be operated under the optimal condition at a low temperature, and the carbon monoxide can be more stably formed. The effect of reduction can be obtained.

Next, the detailed effects of the present invention will be described based on an example in which methane gas is used as a raw material to generate hydrogen, as in the example performed in the second embodiment. Since the operations in the reforming section and the purification section are almost the same, the description will be omitted, and only the operation in the shift section will be described.

As in the example of the second embodiment, methane is subjected to steam reforming in the reforming section 1 and carbon dioxide is reduced to about 10%.
%, And about 10% of carbon monoxide (dry gas basis) was supplied to the shift converter 3 as hydrogen gas. First, the metamorphic reaction proceeded in the first metamorphic section 3b. Pre-transformation temperature controller 15
Was operated, the gas after the reforming section at about 700 to 750 ° C. was cooled, and the temperature was detected at 300 ° C. in the first conversion temperature measuring section 9. In the first metamorphosis section, carbon monoxide was reduced to about 2%. Next, as in Embodiment 2, air was supplied from the modified air supply unit 8 with the upper limit of the amount containing oxygen twice the amount of carbon monoxide.

Compared with the embodiment of the first embodiment, since the concentration of carbon monoxide is about 1/5, the calorific value due to the oxidizing gas can be reduced to 1/5 at the maximum. Compared with the example of the first embodiment, the temperature detected by the shift second temperature measuring unit 10 which is the gas temperature after the shift catalyst 3a could be lowered by about 50 ° C. at the maximum. As a result, the second metamorphosis unit 3
Since d could be operated at a low temperature, the concentration of carbon monoxide at the outlet of the shift section 3 could be reduced to about 0.5%.

Next, an operation result when the amount of methane supplied to the reforming section 1 is increased about 1.5 times as described above will be described. In the first metamorphic unit 3b, the amount of heat generated by the metamorphic reaction increases. Therefore, if the cooling capacity in the metamorphic cooling unit 14 is made the same as before the increase in the amount of methane, the metamorphic second temperature measuring unit 10 that becomes the outlet temperature of the metamorphic unit 3 The detection temperature at about 50 ° C. increased. As a result, the outlet carbon monoxide concentration also increased. Next, when the metamorphic cooling unit 14 is operated and the temperature detected by the metamorphic second temperature measuring unit 10 is made the same as before the increase in the amount of methane, the second metamorphic unit 3
It was possible to reduce the concentration of carbon monoxide at the outlet e to almost the same concentration as before the increase in the amount of methane. This is because when the flow rate of the hydrogen gas fluctuates, the second shift unit can be effectively operated by controlling the temperature of the second shift catalyst body 3e. In addition, the 1st metamorphosis part 3b was made to operate on the same conditions as the above,
Since the operating load on the catalyst increased, the concentration of carbon monoxide at the outlet of the first shift section 3b was about 2.5%.

It is desirable that the temperature of the second shift catalyst in the second shift section be as low as possible in order to reduce carbon monoxide. It is necessary to determine the temperature in consideration of the amount of hydrogen gas supplied to the shift section and the water vapor in the gas.

In this embodiment, the lower limit temperature is 150 ° C. and the upper limit temperature is 1 as a temperature at which the catalyst activity can be maintained.
300 ° C., at which the concentration of carbon monoxide was equal to that when the reaction was performed at 50 ° C., was used as a standard of the operating temperature of the catalyst. This temperature range needs to be set according to the type of catalyst used and the operating conditions. Also, by controlling the temperature of the shift catalyst in this temperature range by the amount of supplied air, high shift reactivity can be maintained in the shift section.

By providing the pre-reformation temperature control unit 15 for the post-reforming gas temperature at the outlet of the reforming unit 1, the first conversion unit 3b
The temperature of the inlet can be adjusted, so that the metamorphic section can be operated more stably. From the viewpoint of preventing methanation in the metamorphic section, the standard of the temperature in the first metamorphic section 3b is 5
It is necessary to determine the temperature within a temperature range of not higher than 00 ° C. and at least 150 ° C. in order to effectively advance the shift reaction, in consideration of the amount of hydrogen gas to be supplied to the shift unit and the steam in the gas. In addition, although the air cooling by the fan is configured to adjust the temperature, water cooling that circulates water may be used.

Further, it is needless to say that the size and the ratio of the first shift unit and the second shift unit need to be determined in consideration of operating conditions such as the supply amount of hydrogen gas.

In the above-described third embodiment, as an example of the case where the shift unit of the hydrogen generator of the present invention is constituted by a plurality of shift mechanisms, the first shift unit 3b and the second shift unit 3d In the third embodiment, one of the plurality of stages of the metamorphic mechanism means the first metamorphic unit 3b, and the other means the second metamorphic unit 3d.
Further, the multi-stage shift mechanism is not limited to two stages.

As described above, according to the present embodiment, in the hydrogen generator for supplying hydrogen by steam reforming a hydrocarbon component, the shift catalyst in the shift section is made of a noble metal catalyst and a metal oxide. By supplying the oxidizing gas from the oxidizing gas supply unit to the metamorphic unit when hydrogen gas is supplied, P
Desorption of carbon monoxide adsorbed on the t catalyst is promoted. As a result, the reactivity of the shift catalyst, particularly at low temperatures, can be improved, so that the concentration of carbon monoxide at the outlet of the shift section can be significantly reduced. That is, it is possible to provide a hydrogen generator capable of stably supplying hydrogen gas having a low carbon monoxide concentration.

[0066]

As is apparent from the above description, the present invention can provide a hydrogen generator capable of stably supplying hydrogen gas having a low carbon monoxide concentration.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a hydrogen generator according to Embodiment 1 of the present invention.

FIG. 2 is a configuration diagram of a hydrogen generator according to Embodiment 2 of the present invention.

FIG. 3 is a configuration diagram of a hydrogen generator according to Embodiment 3 of the present invention.

[Explanation of symbols]

 Reference Signs List 1 reforming section 1a reforming catalyst section 2 heating section 3 transformation section 3a transformation catalyst body 3b first transformation section 3c first transformation catalyst body 3d second transformation section 3e second transformation catalyst body 4 purification section 4a purification catalyst body 5 Supply unit 6 Water supply unit 7 Gas ventilation path 8 Metamorphic air supply unit 9 Metamorphosis first temperature measurement unit 10 Metamorphosis second temperature measurement unit 11 Purified air supply unit 12 Purification first temperature measurement unit 13 Purification second temperature measurement unit 14 Metamorphosis Cooling unit 15 Temperature adjustment unit before denaturation

Continued on the front page (72) Inventor Takeshi Tomizawa 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 4G040 EB31 EB32 EB43 4G140 EB31 EB32 EB34 EB43 5H027 AA02 BA01 BA17 KK48 MM12

Claims (8)

[Claims] 1. A shift section having a shift catalyst body composed of a noble metal-based catalyst and a metal oxide for reacting carbon monoxide with steam, and a hydrogen gas containing at least carbon monoxide and steam in the shift section. And a oxidizing gas supply unit that supplies an oxidizing gas to the shift unit. 2. The oxidizing gas supply unit according to claim 1, wherein the shift catalyst has a structure having a plurality of passages through which gas flows, and the oxidizing gas supply unit supplies the oxidizing gas downstream of the structure. Hydrogen generator. 3. The shift unit has a temperature detection unit for detecting a temperature of the shift catalyst body, and the oxidizing gas supply unit controls the temperature detected by the temperature detection unit to be within a set temperature range. The hydrogen generator according to claim 1, wherein a supply amount of the oxidizing gas to the shift unit is controlled. 4. The shift unit comprises a plurality of shift mechanisms, each of which includes the shift catalyst, wherein the oxidizing gas supply unit is located downstream with respect to the gas flow. The hydrogen generator according to claim 1, wherein the oxidizing gas is supplied to the shift mechanism that performs the conversion. 5. The multi-stage means two stages, wherein the oxidizing gas is not supplied to the metamorphic mechanism of the preceding stage, and the oxidizing gas is supplied to the metamorphic mechanism of the subsequent stage. Hydrogen generator. 6. The post-transformation mechanism has a temperature detection unit for detecting the temperature of the transformation catalyst in the transformation mechanism, and the temperature detected by the temperature detection unit is within a set temperature range. The hydrogen generator according to claim 5, wherein a supply amount of the oxidizing gas from the oxidizing gas supply unit to the subsequent shift mechanism is controlled. 7. The plurality of stages means two stages, wherein the oxidizing gas is not supplied to the upstream metamorphic mechanism, but the oxidizing gas is supplied to the succeeding metamorphic mechanism, A temperature adjusting unit disposed between the mechanism and the subsequent metamorphic mechanism, for adjusting the temperature of gas flowing from the former metamorphic mechanism to the latter metamorphic mechanism so that the temperature falls within a predetermined range. The hydrogen generator according to claim 4. 8. A hydrogen gas is supplied from the shift unit,
A purification unit having a purification catalyst for oxidizing carbon monoxide,
The hydrogen generator according to claim 1, further comprising a second oxidizing gas supply unit that supplies an oxidizing gas to the purification unit.