JP2000026105A - CO selective oxidizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CO selective oxidizer in which air is uniformly mixed into a flow of a reformed gas so that the temperature of the reformed gas can be maintained within a predetermined range. SOLUTION: A first cylinder 11, a second cylinder 12 provided in the first cylinder 11 and formed of a porous material, and a third cylinder 13 provided in the second cylinder 12 are provided. Air flows between the first cylinder 11 and the second cylinder 12, a CO selective oxidation catalyst 15 is filled between the second cylinder 12 and the third cylinder 13 and a reformed gas flows, and a heat transfer medium is supplied into the third cylinder 13. Let it flow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a CO for selectively oxidizing CO of a reformed gas generated by a reformer of a fuel cell.
It relates to a selective oxidizer.

[0002]

2. Description of the Related Art A polymer electrolyte fuel cell (PEFC) is expected to be used as a small stationary type, a portable power source and a power source for an electric vehicle because it can generate power even at room temperature and can obtain a high output density. 2. Description of the Related Art In a fuel cell, a main body includes a cell main body and a reformer that supplies a gas mainly containing hydrogen to the cell main body, and methanol or the like is used as a fuel. The reformer reforms the fuel into a reformed gas mainly composed of hydrogen by causing a fuel to react with steam in the presence of a reforming catalyst.

The reaction formula of methanol and steam is as follows. CH ₃ OH + H ₂ O → 3H ₂ + CO ₂ (1) This reaction is performed at 250 to 300 ° C. and is an endothermic reaction. A Cu or Zn system is used as the reforming catalyst.

CO ₂ + H ₂ → CO + H ₂ O (2) At the same time as the reaction of the formula (1), the reverse shift reaction of the formula (2) also occurs, and a small amount of CO is generated. Since PEFC operates at low temperature, even if the amount of CO contained in the reformed gas is small, the platinum catalyst of the fuel cell is poisoned by CO (the action of strongly adsorbing platinum and inhibiting the reaction of hydrogen), and the battery Power generation. In PEFC, this countermeasure against CO poisoning is the biggest problem when using reformed gas. Therefore, a method of selectively oxidizing CO by mixing a small amount of air into the reformed gas, a method of removing CO with a thin palladium film, a method of removing Pt-R
Although measures such as a method of using a u-alloy catalyst for a fuel electrode have been studied, a simple and definitive solution has not yet been found.

FIG. 6 schematically shows the structure of a conventional CO selective oxidizer. A plurality of containers filled with a selective oxidation catalyst are arranged in series, and a reformed gas and a small amount of air for selective oxidation are supplied to each container. Oxidation of CO is an exothermic reaction, and if the temperature in the container rises, hydrogen gas, which is the main component of the reformed gas, will burn, so the temperature of each container is maintained at a temperature at which hydrogen gas does not burn, for example, around 150 ° C. Therefore, cooling air is caused to flow to the outer surface of each container to adjust the temperature of the container.

[0006]

In the case of the above-mentioned CO selective oxidizer, it is difficult to maintain the temperature in the vessel in a temperature range suitable for the selective oxidation of CO, and the hot spot where the temperature is locally high becomes difficult. And the case where hydrogen gas other than CO is burned occurs, and the power generation efficiency of the fuel cell is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-described problems. The purpose is to provide.

[0008]

In order to achieve the above object, according to the present invention, a first cylinder, a second cylinder made of a porous material provided in the first cylinder, and a second cylinder are provided. And a third cylinder provided in the first cylinder, air flows between the first cylinder and the second cylinder, and C flows between the second cylinder and the third cylinder.
The reforming gas is supplied by filling the O selective oxidation catalyst, and the heat transfer medium is supplied into the third cylinder.

The reformed gas flows through the space between the second cylinder and the third cylinder filled with the CO selective oxidation catalyst, and is dispersed through the porous material of the second cylinder and mixed with the inflowing air.
The CO gas contained in the reformed gas is oxidized to carbon dioxide gas by the action of the selective oxidation catalyst. At this time, heat is generated, and the temperature of the reformed gas rises, but the reformed gas and the CO selective catalyst are absorbed by the heat transfer medium flowing in the third cylinder, and are kept in a temperature range suitable for performing CO selective oxidation. it can. Thereby, the selective oxidation of CO is appropriately performed.

According to the second aspect of the present invention, a fourth cylinder is provided in the third cylinder, and the heat transfer medium flows only between the third cylinder and the fourth cylinder.

When the outer shape of the first cylinder is constant, the outer shapes of the second cylinder and the third cylinder are made as large as possible, so that the contact area between the porous material and the reformed gas and the contact area between the heat transfer medium and the reformed gas are increased. Is increased, the selective oxidation is performed efficiently. However, when the diameter of the third cylinder is increased, the amount of the heat transfer medium flowing inside becomes considerably larger than necessary. Therefore, the fourth cylinder is provided, and the heat transfer medium flows only between the third cylinder and the fourth cylinder. Less. In addition, the space inside the fourth cylinder can be effectively used.

According to a third aspect of the present invention, there is provided a first cylinder, a second cylinder provided in the first cylinder, and a third cylinder made of a porous material provided in the second cylinder. The first
A heat transfer medium flows between the cylinder and the second cylinder, a CO selective oxidation catalyst is filled between the second cylinder and the third cylinder, a reformed gas flows, and air flows into the third cylinder.

The reformed gas flows through the space between the second cylinder and the third cylinder filled with the CO selective oxidation catalyst, and is dispersed through the porous material of the third cylinder and mixed with the incoming air to form CO 2.
The CO gas contained in the reformed gas is oxidized to carbon dioxide gas by the action of the selective oxidation catalyst. At this time, heat is generated, and the temperature of the reformed gas rises. However, the reformed gas and the CO selective catalyst are absorbed by the heat transfer medium flowing in contact with the second cylinder, and are brought into a temperature range suitable for performing the CO selective oxidation. Can hold. Thereby, the selective oxidation of CO is appropriately performed.

According to a fourth aspect of the present invention, a fourth cylinder is provided in the third cylinder, and the air flows only between the third cylinder and the fourth cylinder.

When the outer shape of the first cylinder is constant, the outer shapes of the second cylinder and the third cylinder are made as large as possible, so that the contact area between the porous material and the reformed gas and the contact area between the heat transfer medium and the reformed gas are increased. Is increased, the selective oxidation is performed efficiently. However, when the diameter of the third cylinder is increased, the amount of air flowing inside becomes considerably larger than necessary. Therefore, a fourth cylinder is provided, and air flows only between the third cylinder and the fourth cylinder to reduce the air flow rate. In addition, the space inside the fourth cylinder can be effectively used.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a fuel cell system using a CO selective oxidizer. The fuel cell system includes a reformer 1 for generating a reformed gas from fuel gas and water, a selective oxidizer 2 for selectively oxidizing a CO gas contained in the reformed gas, and a reformed gas from which the CO gas has been removed. And a fuel cell 3 that performs a cell reaction with air to generate power. In the selective oxidizer 2,
A reformed gas, air for selectively oxidizing a small amount of CO contained in the reformed gas, and a heat transfer medium are supplied. The heat transfer medium is at a temperature suitable for performing the CO selective oxidation of the reformed gas. This temperature varies depending on the CO selective oxidation catalyst used.
It is used to maintain the temperature of the reformed gas at +/- 10 ° C. For this purpose, the selective oxidizer 2 is provided with a heat medium circulating line 4. The heat medium circulating line 4 includes a pump 5 for circulating the heat transfer medium, a cooler for maintaining the heat transfer medium at a predetermined temperature, and the like. A temperature controller 6 with a heater is provided. Steam or the like may be used instead of the heat transfer medium.

FIG. 2 shows the structure of the CO selective oxidizer of the first embodiment, and FIG. 3 is a sectional view taken along line XX of FIG. The first cylinder 11 is made of metal, but may be made of a synthetic resin because air passes through the inside. The second cylinder 12 is provided in the first cylinder 11 and is made of a porous material obtained by sintering metal powder or ceramics. The third cylinder 13 is provided in the second cylinder 12 and is made of a metal having good heat conductivity. The fourth cylinder 14 is provided in the third cylinder 13 and is made of a metal material or a synthetic resin.

Air flows between the first cylinder 11 and the second cylinder 12 and flows out through the porous material of the second cylinder 12. A space between the second cylinder 12 and the third cylinder 13 is filled with a CO selective oxidation catalyst, and a reformed gas containing CO flows between the catalysts. A heat transfer medium flows between the third cylinder 13 and the fourth cylinder 14. Steam may be used instead of the heat transfer medium. The amount of air flowing into the third cylinder 13 through the second cylinder 12 can be controlled by the porous material and the air pressure. The temperatures of the reformed gas and the CO selective oxidation catalyst 15 are adjusted to a temperature range suitable for performing CO selective oxidation by the heat transfer medium, for example, a range of 150 ± 10 ° C. Under these conditions, air and CO contained in the reformed gas undergo an oxidation reaction,
To carbon dioxide. When the outer diameter of the first cylinder 11 is constant, the outer diameters of the second and third cylinders 12 and 13 are made as large as possible in consideration of the air flow rate and the reformed gas flow rate.
The porous area of the cylinder 12 and the heat transfer area of the third cylinder 13 are increased.

The operation of the selective oxidizer thus configured will be described. The reformed gas is supplied to the second cylinder 12 and the third cylinder 1
The temperature is adjusted to a temperature range suitable for carrying out the selective oxidation of CO by the heat transfer medium flowing through the space filled with the three CO selective oxidation catalysts 15 and flowing through the third cylinder 13, for example, 150 ± 10 ° C. Air is dispersed and flows out of the porous material of the second cylinder 12 to the extent necessary for selective oxidation, mixes with the reformed gas, and under the CO selective oxidation catalyst 15, CO is oxidized and harmless CO ₂
Becomes Since the temperature of the reformed gas is controlled, the selective oxidation of CO is high, and the combustion of hydrogen gas can be minimized.

Next, a second embodiment will be described. FIG. 4 shows the second
FIG. 5 is a sectional view taken along line YY of FIG. The first cylinder 21 is made of metal, but may be made of a synthetic resin having good heat insulating properties because a heat transfer medium passes through the inside. The second cylinder 22 is provided in the first cylinder 21 and is made of a metal having good heat conductivity because it performs heat transfer. The third cylinder 23 is provided in the second cylinder 22 and is made of a metal powder capable of flowing out air or a porous material obtained by sintering ceramics. The fourth cylinder 24 is provided in the third cylinder 23, and is made of a metal material or a synthetic resin because air flows between the fourth cylinder 24 and the third cylinder 23.

A heat transfer medium flows between the first cylinder 21 and the second cylinder 22, and the temperature of the reformed gas is adjusted through the second cylinder 22. Steam may be used instead of the heat transfer medium. A space between the second cylinder 22 and the third cylinder 23 is filled with a CO selective oxidation catalyst, and a reformed gas containing CO flows between the catalysts. Air flows between the third cylinder 23 and the fourth cylinder 24,
Air flows into the reformed gas through the porous material of the third cylinder 23. The amount of air flowing into the second cylinder 22 through the third cylinder 23 can be controlled by the porous material and the air pressure. The temperatures of the reformed gas and the CO selective oxidation catalyst 15 are adjusted to a temperature range suitable for performing CO selective oxidation by the heat transfer medium, for example, a range of 150 ± 10 ° C. Under these conditions, air and CO contained in the reformed gas perform an oxidation reaction,
CO is converted to carbon dioxide. When the outer diameter of the first cylinder 21 is constant, the outer diameters of the second and third cylinders 22 and 23 are made as large as possible in consideration of the air flow rate and the reformed gas flow rate. In addition, the porous area of the third cylinder 23 is increased.

In the second embodiment, the second cylinder 12 and the third cylinder 13 of the first embodiment are replaced with the third cylinder 23 and the second cylinder 22 of the second embodiment, and the first cylinder 21 and the second cylinder 22 are replaced. A heat transfer medium is passed between the third cylinder 23 and the fourth cylinder 24, and the operation is the same as that of the first embodiment.

[0023]

As is apparent from the above description, according to the present invention, a second cylinder made of a porous material is provided inside a first cylinder, and air is caused to flow between the first cylinder and the third cylinder from the porous material. A third cylinder is provided inside the second cylinder, and a CO selective oxidation catalyst is filled between the second cylinder and the reformed gas to flow therethrough. A heat transfer medium is passed through the third cylinder, and a reforming is performed in the second cylinder. Although the CO contained in the reformed gas is selectively oxidized and the temperature of the reformed gas rises, the heat is absorbed by the heat transfer medium in the third cylinder, and the reformed gas can be maintained at a temperature suitable for the selective oxidation. Also,
Air can be dispersed and supplied, and CO gas can be selectively oxidized reliably. A similar effect can be obtained by passing a heat transfer medium between the first cylinder and the second cylinder, passing air through the third cylinder, and using the third cylinder as a porous material.

[Brief description of the drawings]

FIG. 1 is a diagram showing a fuel cell system including a CO selective oxidizer.

FIG. 2 is a diagram illustrating a configuration of a first exemplary embodiment of the present invention.

FIG. 3 is a sectional view taken along line XX of FIG. 2;

FIG. 4 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 5 is a sectional view taken along line YY of FIG. 4;

FIG. 6 is a diagram showing a configuration of a conventional CO selective oxidizer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reformer 2 Selective oxidizer 3 Fuel cell 4 Heat transfer medium circulation line 5 Pump 6 Temperature controller 11, 21 1st cylinder 12, 22 2nd cylinder 13, 23 3rd cylinder 14, 24 4th cylinder 15 CO selection Oxidation catalyst

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takenori Watanabe 3-1-1, Toyosu, Koto-ku, Tokyo

Claims (4)

[Claims] 1. A first cylinder, a second cylinder provided in the first cylinder and formed of a porous material, and a third cylinder provided in the second cylinder. Air is flowed between the second cylinders, a CO selective oxidation catalyst is filled between the second and third cylinders, a reformed gas is flowed, and a heat transfer medium is flowed into the third cylinders. CO selective oxidizer. 2. The CO selective oxidizer according to claim 1, wherein a fourth cylinder is provided in the third cylinder, and the heat transfer medium flows only between the third cylinder and the fourth cylinder. . 3. A first cylinder, a second cylinder provided in the first cylinder, and a third cylinder made of a porous material provided in the second cylinder. A heat transfer medium is caused to flow between the second cylinders, a CO selective oxidation catalyst is filled between the second cylinder and the third cylinder, a reformed gas is caused to flow, and air is caused to flow into the third cylinder. CO selective oxidizer. 4. The CO selective oxidizer according to claim 3, wherein a fourth cylinder is provided inside the third cylinder, and the air is caused to flow only between the third cylinder and the fourth cylinder.