JP2000272902A - Hydrogen generator - Google Patents

Abstract

(57) [Problem] To provide a hydrogen generator that eliminates the influence of scattering of a catalyst body and operates stably for a long period of time. SOLUTION: Fuel supply unit, fuel reforming water supply unit, CO
A purification air supply unit, a reforming catalyst, and a CO conversion catalyst and / or a CO purification catalyst, and a reforming catalyst, a CO conversion catalyst toward the downstream side from the fuel supply unit,
A hydrogen generator comprising a CO purifying catalyst arranged in order, and further comprising catalyst scattering prevention means provided downstream of the reforming catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen generator for generating hydrogen used for fuel such as a fuel cell.

[0002]

2. Description of the Related Art Conventionally, hydrogen used for vehicle-mounted and household fuel cells has been developed from hydrocarbon fuels such as methane, propane, gasoline, and kerosene; alcohol fuels such as methanol;
Alternatively, ether fuels such as dimethyl ether are generated by contact with a reforming catalyst heated by adding steam. Usually, hydrocarbon-based fuel is reformed at a temperature of about 500 to 800 ° C, and alcohol and ether-based fuels are reformed at a temperature of about 200 to 400 ° C. At this time, since the concentration of carbon monoxide (CO) generated increases as the reaction proceeds at a high temperature, CO and steam are reacted using a CO shift catalyst to reduce the CO concentration to about 0.1 to 1%. ing. However, in the conventional hydrogen generator that generates hydrogen by such a mechanism, means for preventing scattering is not provided between the reforming catalyst, the CO shift catalyst, and the CO catalyst. Was.

[0003] When a means for preventing catalyst scattering is not installed, a thermal shock is applied to the catalyst when the hydrogen generator is started, and when the hydrogen generator is mounted on a vehicle, the catalyst is broken by vibration. The dropped catalyst component may be scattered downstream of the catalyst body. In this case, the scattered reforming catalyst methanizes the reformed gas, and the scattered CO shift catalyst inhibits the selective oxidation of CO, or the C shift by the reverse shift reaction.
Increasing the O concentration has been one factor that causes a reduction in the efficiency of the entire apparatus.

As described above, the conventional method performs only a steady operation in a chemical plant or the like and does not have a serious problem in applications that do not require frequent start-up operations. There were many problems in applications where the motor was repeatedly stopped and started, or where there was severe vibration.

[0005]

SUMMARY OF THE INVENTION In view of the above facts, the present invention eliminates the influence of the scattering of the catalyst and eliminates the problem of the hydrogen generator in order to solve the above-mentioned problems of the hydrogen generator. It is an object of the present invention to provide a hydrogen generator that operates at a high speed.

[0006]

According to the present invention, there is provided a fuel supply unit, a fuel reforming water supply unit, and a fuel supply unit.
An O-purifying air supply unit, a reforming catalyst, and a CO-converting catalyst and / or a CO-purifying catalyst; and a reforming catalyst, a CO-converting catalyst, and a CO-purifying catalyst that are arranged downstream from the fuel supply unit. The present invention relates to a hydrogen generator arranged in the order of media, further comprising a catalyst scattering prevention means provided downstream of the reforming catalyst body. In this case, it is preferable to provide the scattering prevention means between the reforming catalyst and the CO shift catalyst, and between the CO shift catalyst and the CO purification catalyst. Preferably, the scattering prevention means is a filter.

[0007] Examples of such a filter include a filter made of metal, ceramics, or a composite of these, or a mesh, honeycomb, or foamed filter made of metal, ceramics, or a composite of these. Preferably it is. Preferably, the temperature of the filter is higher than the temperature at which the reformed gas methanizes. Further, it is preferable to provide a pressure detecting device for detecting a pressure loss of the filter on an upstream side and a downstream side of the filter. Further, it is preferable to provide a temperature detecting device at a position close to the filter.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a schematic configuration diagram of a first embodiment of the present invention. In the hydrogen generator shown in FIG. 1, fuel is introduced from a fuel supply unit 1, and steam is added from a fuel reforming water supply unit 2. The raw material gas in which the fuel and the steam are mixed is heated through a flow path having the heat exchange fins 3.
Then, it contacts and reacts with the reforming catalyst body 4 heated by the heating burner 5 to generate a reformed gas. At this time, the combustion exhaust gas is exhausted from the exhaust port 6. Next, the amount of CO contained in the reformed gas is reduced by the CO conversion catalyst 7. Further, in order to use CO in a polymer electrolyte fuel cell, it is necessary to remove CO to a level of several ppm, so a small amount of air is introduced from the CO purification air supply unit 8,
The CO purification catalyst 9 oxidizes and removes CO. The reformed gas from which CO has been removed is supplied from the reformed gas outlet 10 to, for example, a fuel cell.

The reforming catalyst 6 and the CO shift catalyst 7
A first filter 11 and a second filter 12 are respectively installed on the downstream side of. In order to keep the reactor at a constant temperature, each part of the apparatus may be covered with a heat insulating material.
The catalyst may be a conventional one. The reforming catalyst may be a Ni catalyst, the CO conversion catalyst may be a Cu-Zn catalyst, a C
It is preferable to use a Pt catalyst as the O purification catalyst.

[0010] Fuels for generating reformed gas include city gas (natural gas), propane, kerosene, gasoline, methanol, dimethyl ether and the like. At this time, reforming methods include steam reforming by adding steam, partial reforming by adding air, and a reforming method combining both reactions. Here, a description will be given of a case where natural gas is used as fuel and steam reforming is performed. However, even if another fuel is used or the reforming method is a partial reforming or a combination of partial reforming and steam reforming, the composition of the reformed gas to be generated slightly changes, and the temperature condition at the time of the reforming is changed. The method can be applied, although it changes.

The operation and characteristics of the hydrogen generator according to the present invention will be described. Fuel is introduced from the fuel supply unit 1, and about three times as much steam as the fuel is added from the water supply unit 2. The mixed raw material gas is heated by the heating burner 4 and
The reformed catalyst body 6 heated to about 800 ° C. contacts and reacts to generate reformed gas. Since this reformed gas contains about 10% CO in addition to hydrogen, the CO shift catalyst 7 reduces carbon monoxide to several thousands ppm to about 1%. Further, since it is necessary to remove CO to a level of several ppm for use in a polymer electrolyte fuel cell, a small amount of air is introduced from the air supply unit 8 and CO is oxidized and removed by the CO purification catalyst 9. The reformed gas from which CO has been removed is supplied from the reformed gas outlet 10 to the fuel cell.

As described above, in the case of an in-vehicle or home fuel cell system, it is necessary to repeatedly start and stop the fuel cell system. At this time, a severe thermal shock is applied to each catalyst.
In particular, in the case of a vehicle, vibration is applied during traveling. If the device is operated for a long time under these conditions,
The catalyst body is gradually cracked or pulverized. At this time, there is no significant effect on the reactivity of the catalyst body itself,
The catalyst powder dropped from the catalyst body is scattered downstream. When the catalyst powder is scattered in this manner, the powder is mainly collected by the catalyst located downstream of the scattered catalyst. Specifically, the reforming catalyst is a CO shift section, and the CO shift catalyst is CO
Collected in the purification section.

Usually, a catalyst applicable as a hydrocarbon reforming catalyst functions as a methanation catalyst under a temperature condition at which a CO shift catalyst operates, and thus the catalyst powder scattered from the reforming catalyst body results in methane conversion. Rate will be reduced. Further, if the scattered powder from the CO conversion catalyst is also collected by the CO purification catalyst, the powder also has a bad effect. CO
In the purification section, air is added to selectively oxidize CO,
The CO conversion catalyst trapped on the CO purification catalyst reduces the selectivity of CO oxidation, and the CO conversion catalyst that has reached near the downstream of the CO purification catalyst reacts carbon dioxide and hydrogen by a reverse shift reaction. To increase the CO concentration.

On the other hand, as in the present embodiment, the first filter 11 is provided downstream of the reforming catalyst and the CO conversion catalyst, respectively.
When the second filter 12 and the second filter 12 are provided, the device can be operated stably for a long period of time without the catalyst powder scattered as described above being collected by the CO conversion catalyst or the CO purification catalyst.

At this time, it is preferable that the temperature of the first filter 11 downstream of the reforming catalyst body 6 is set to a temperature at which the methanation reaction does not substantially proceed. Since the methane reforming reaction is a temperature-dependent equilibrium reaction, the methanation reaction proceeds in a temperature range of about 300 to 400 ° C. For this reason,
The methane conversion will decrease. In the present embodiment, it is preferable to bring the first filter 11 close to the downstream portion of the reforming catalyst body 6 to make the temperature close to the reforming catalyst body 6. The temperature at which the methanation reaction does not substantially proceed depends on the methane conversion rate of the target apparatus, but usually refers to a temperature range in which the methane concentration does not exceed 1 to 5%.

As the first filter 11 and the second filter 12, a filter made of metal, ceramics, or a fiber made of a composite thereof, or a mesh, honeycomb, or foam made of metal, ceramics, or a composite thereof is used. It is preferable to use a body-shaped filter. As a method of manufacturing the filter, wool made of a heat-resistant material such as stainless steel, glass, quartz, etc. may be installed inside the tube so as to have a thickness of several centimeters, or compressed in advance to a thickness of several millimeters. It may be molded. These materials have a structure capable of collecting the scattered catalyst powder and are sufficiently stable under use conditions. Then, the surface is porous, and there is an effect that more than half of the catalyst scattered before passing is collected.

Further, in the present embodiment, the first filter 11 and the second filter 12 are provided in a normal narrow path, but the path of the filter section is made thicker or the size of the filter is increased so as to increase the filter area. By bending the shape, an increase in pressure loss of the filter due to clogging can be suppressed. Further, since pressure loss increases due to clogging of the filters, it is preferable to provide pressure detectors on the upstream and downstream sides of the first filter 11 and the second filter 12. When the pressure loss of the filter increases, a load is applied to a pump for sending fuel or the like, and the efficiency is reduced. Therefore, by detecting the pressure before and after the filter, the pressure loss due to the first filter 11 and the second filter 12 is obtained. The generator can be activated.

In this embodiment, a solid polymer fuel cell is used as the fuel cell, and it is necessary to remove the CO concentration to the ppm level.
Although the case where all the O purification catalysts are installed has been described,
If the fuel cell unit operates with a reformed gas containing several hundred to several thousand ppm of CO, the CO purification catalyst may not be necessary.

When a fuel such as methanol or dimethyl ether is used, reforming can be performed at a low temperature of about 300 ° C., and the CO concentration after reforming is relatively low. In some cases, it is possible to operate with only the CO purification catalyst without installing the CO. In this case, since a catalyst similar to the CO shift catalyst, for example, a copper-zinc catalyst, is used as the reforming catalyst, the scattered catalyst powder has the same effect as the scattered CO shift catalyst of the present embodiment. Preferably, a filter is provided downstream of the catalyst body.

In this embodiment, an example in which fuel is steam reformed has been described. However, when partial reforming is performed by adding air instead of steam, the proportion of hydrogen contained in the reformed gas is reduced. However, the combustion reaction occurs simultaneously with the reforming on the catalyst body, and the heating of the catalyst body becomes easy. When air and steam are added at the same time, an intermediate property between steam reforming and partial reforming is obtained. The reforming catalyst body contains N
It is preferable to use a Cu-Zn-based catalyst component as the i-based and CO-converting catalyst and a Pt-based catalyst component as the CO-purifying catalyst, but in the present invention, the reforming reaction, the CO-converting reaction, and the CO-purifying reaction The catalyst component is not particularly limited as long as it is a catalyst component having a high activity.

Although the shape of the catalyst body is a pellet shape, other shapes such as a catalyst body supported on a honeycomb may be used. In this embodiment, a filter is used as the scattering prevention means. However, if it is a means for preventing the scattering of the catalyst powder, a trap is formed in the middle of the downstream side of the catalyst body by using a flow of the reformed gas and collected. It is also possible to apply a surface treatment to the inside of the tube of the passage to adsorb the powder.

(Second Embodiment) A second embodiment of the present invention will be described. In this embodiment, as shown in FIG. 2, the first filter 31 on the downstream side of the reforming catalyst is set to a temperature at which the methanation reaction substantially proceeds, and the first filter 3
A thermocouple 33 and a measuring device 34 connected to the thermocouple 33 are installed close to the first embodiment, and most of the operation and effects are similar to those of the first embodiment. Therefore, the present embodiment will be described focusing on the different points.

FIG. 2 is a schematic configuration diagram of the present embodiment.
The first filter 31 is installed near the middle between the reforming catalyst body 26 and the CO conversion catalyst body 27, and has a temperature of 400 to 500 ° C., which is halfway between the two. First filter 31
When the scattered catalyst from the reforming catalyst body 26 is collected, heat is generated at a temperature at which the methanation reaction proceeds. This calorific value is proportional to the amount of the scattered catalyst collected by the first filter 31, and the amount of the scattered catalyst collected by the first filter is detected by detecting the temperature with the thermocouple 33 installed in close proximity. Can be estimated. When the temperature of the first filter 31 reaches a predetermined reference value,
By replacing the filter, the hydrogen generator can be operated stably for a long period of time.

In the present embodiment, as shown in FIG. 2, the thermocouple is made to approach from the downstream side of the filter. However, depending on the configuration of the device, it may be made to approach to the upstream side, the side surface, or the outside of the tube. . Further, the temperature detecting device can use a detecting means such as a thermistor or a bimetal which can detect a temperature and obtain a signal. Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.

[0025]

Example 1 Example 1 Ni-based reforming catalyst 6, Cu-
The Zn-based CO shift catalyst 7 and the Pt-based CO selective oxidation catalyst 9 were each filled in the hydrogen generator shown in FIG. A first filter 11 and a second filter 12 made of stainless steel and made of a metal fiber having a wire diameter of 0.1 μm were installed on the downstream side of the reforming catalyst 6 and the CO shift catalyst 7, respectively. 50 liters of desulfurized city gas from the fuel supply unit 1 per minute,
Steam is introduced at a rate of 150 liters per minute from the water supply unit 2, and the temperature of the reforming
The reaction was carried out by heating to ℃.

The composition of the reformed gas after passing through the reforming catalyst body 6 was measured by gas chromatography.
Hydrogen was about 80%, CO was about 11%, carbon dioxide was about 9%, and the methane concentration was 0.05%. Further, the composition of the reformed gas after passing through the CO conversion catalyst 7 is such that methane and CO are each 0.0%.
5% and 0.3%. Further, after passing through the CO purification catalyst 9, the CO concentration was 8 ppm. When the temperatures of the first filter 11 and the second filter 12 were measured, they were 700 ° C. and 150 ° C., respectively.

The hydrogen generator was once stopped and subsequently started. Further, the stop and start operations were repeated 1500 times, and the reformed gas composition was measured in the same manner. The methane concentration was 0.06% before and after passing through the first filter 11 and after passing through the CO conversion catalyst 7. there were. The CO concentration after passing through the CO purifying catalyst 9 was 9 ppm. First filter 1
The pressures before and after the first and second filters 12 were measured, and the difference in pressure loss from the initial pressure was 20 mAq and 40 mAq, respectively. The filter was taken out of the apparatus and the weight of the attached catalyst powder was measured. As a result, a weight increase of 12 g for the first filter 11 and a weight increase of 38 g for the second filter 12 were observed.

Example 2 The hydrogen generator of Example 1, a fuel cell, and a driving motor were connected and mounted on a passenger car, and a 20,000 km running test was performed. After traveling, the reformed gas composition was measured by gas chromatography in the same manner as in Example 1. As a result, the methane concentration was 0.08% before and after passing through the first filter 11 and after passing through the CO conversion catalyst 7. . The CO concentration was 10 ppm after passing through the CO purification catalyst 9.

<< Embodiment 3 >> The first filter 3 in the embodiment 1
As shown in FIG. 2, No. 1 was placed at an intermediate position between the reforming catalyst body 26 and the CO conversion catalyst body 27. First filter 31
The thermocouple 33 was set so as to be in contact with, and the signal of the thermocouple 33 was read by the measuring instrument 34. The desulfurized city gas is supplied from the fuel supply unit 21 at a rate of 50 liters per minute, and the steam is supplied to the water supply unit 2.
After reacting by introducing 150 liters per minute from 2,
Hydrogen was about 80%, CO was about 11%, carbon dioxide was about 9%, and the methane concentration was 0.05%. Further, the CO conversion catalyst 27
The composition of the reformed gas after passing was 0.1% for methane and 0.1% for CO, respectively.
05% and 0.3%. Further, after passing through the CO purification catalyst 29, the CO concentration was 8 ppm.

As in Example 1, the hydrogen generator was once stopped and subsequently started. Further stop and start operation by 150
When the composition of the reformed gas was measured 0 times, the methane concentration was 0.06% after passing through the reforming catalyst 26 and 5.5% after passing through the CO shift catalyst 27. The CO concentration was 0.3% after passing through the CO conversion catalyst 27 and 10 ppm after passing through the CO purification catalyst 29. In addition, when the temperature of the first filter 31 was compared with the initial value, the temperature increased by 15 ° C. The first filter 31 was taken out of the apparatus, and the weight of the attached catalyst powder was measured.
Showed that 12 g of catalyst powder had adhered. First filter 3
1 was replaced with a new one, and the hydrogen generator was started again. The methane concentration was 0.0% before and after passing through the first filter 31 and after passing through the CO conversion catalyst 27, respectively.
6%. The CO concentration after passing through the CO purification catalyst 29 was 9 ppm.

Comparative Example 1 First filter 1 in Example 1
The first and second filters 12 were removed, and city gas and water were reacted. Desulfurized city gas is supplied from fuel supply unit 1 at 5
When 0 liter and water vapor were introduced at 150 liters per minute from the water supply unit 2 and reacted, about 80% of hydrogen and about 1% of CO were obtained.
1%, carbon dioxide about 9%, methane concentration 0.05%. The composition of the reformed gas after passing through the CO conversion catalyst 7 is as follows:
Methane and CO were 0.05% and 0.3%, respectively. Further, after passing through the CO purification catalyst 9, the CO concentration was 8 ppm. As in Example 1, the hydrogen generator was once stopped and subsequently started. Further, the stop and start operations were repeated 1500 times and the reformed gas composition was measured. The methane concentration was 0.06% after passing through the reforming catalyst body 6,
After passing through the CO conversion catalyst 7, the content was 5.5%. The CO concentration is 0.3% after passing through the CO conversion catalyst 7 and the CO purification catalyst 9
It was 350 ppm after passing.

[0032]

As is clear from the comparison of the evaluation results of the apparatus of the above embodiment and the comparative example, according to the present invention, it is possible to prevent the operation of the apparatus from being stopped and repeated, and the effect of scattering of the catalyst due to severe vibration. In addition, it is possible to provide a hydrogen generator that operates stably for a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a hydrogen generator according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a hydrogen generator according to a second embodiment of the present invention.

[Explanation of symbols]

 1,21 Fuel supply unit 2,22 Water supply unit 3,23 Heat exchange fins 4,24 Heating burner 5,25 Exhaust port 6,26 Reforming catalyst 7,27 CO shift catalyst 8,28 Air supply 9 , 29 CO purification catalyst 10, 30 reformed gas outlet 11, 31 first filter 12, 32 second filter 33 thermocouple 34 measuring instrument

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kunihiro Ukai, Inventor 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Toshiyuki Shono 1006 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 72) Inventor Koichiro Kitagawa 6-2-61, Imafukunishi, Joto-ku, Osaka City, Osaka Prefecture F-term (reference) in Matsushita Seiko Co., Ltd. 4G040 EA03 EA06 EB18 EB23 EB33 EB43 EC08

Claims (7)

[Claims] 1. A fuel supply section, a fuel reforming water supply section, and a CO
A purification air supply unit, a reforming catalyst, and a CO conversion catalyst and / or a CO purification catalyst, and a reforming catalyst, a CO conversion catalyst toward the downstream side from the fuel supply unit,
A hydrogen generator comprising a CO purifying catalyst arranged in order, and further comprising catalyst scattering prevention means provided downstream of the reforming catalyst. 2. The scatter prevention means is provided between the reforming catalyst and the CO shift catalyst and between the CO shift catalyst and the CO purification catalyst. Hydrogen generator. 3. The hydrogen generator according to claim 1, wherein the scattering prevention means is a filter. 4. The filter according to claim 1, wherein the filter is a filter made of metal, ceramics, or a composite of these, or a mesh, honeycomb, or foamed filter made of metal, ceramics, or a composite of these. The hydrogen generator according to claim 3. 5. The hydrogen generator according to claim 3, wherein a temperature of the filter is higher than a temperature at which the reformed gas is methanated. 6. The hydrogen generator according to claim 3, wherein a pressure detector for detecting a pressure loss of the filter is provided on an upstream side and a downstream side of the filter. 7. The hydrogen generator according to claim 3, wherein a temperature detector is provided at a position close to the filter.