JP2000264604A - Carbon monoxide remover for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon monoxide remover that can retain the catalyst layer at a uniform temperature as much as possible, when the oxidation reaction is carried out for removing the carbon monoxide in the gas in the catalyst layer. SOLUTION: In the carbon monoxide remover where hydrogen-rich gas including carbon monoxide is mixed with air and the mixture is allowed to pass through the elements 11, 12, 13 to reduce carbon monoxide in the gas, the catalyst layer is divided into a plurality of the catalyst layer elements 11, 12, 13 and spaces are provided between the catalyst layer elements 11, 12, 13. In the catalyst layers elements, the catalyst pass 28, 29 is formed so that the mixed gas may oxidatively reacts with the catalyst and pass through and the passing holes 25, 26 are formed so that the mixed gas pass through without contact with the catalyst where the cross section of these passing holes 25, 26 are made smaller at the catalyst elements toward the downstream.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte fuel cell system, which removes carbon monoxide contained in a reformed gas obtained from a raw material gas through a reformer to produce a hydrogen-rich gas as a fuel. The present invention relates to a carbon monoxide remover provided in the middle of a supply line to supply a battery.

[0002]

2. Description of the Related Art A polymer electrolyte fuel cell system converts chemical energy of hydrogen into electric energy. A raw material gas (hereinafter referred to as a raw material gas) of natural gas, hydrocarbons such as naphtha, and alcohols such as methanol, which can be obtained relatively easily and inexpensively, is mixed with steam to reformer and carbon monoxide conversion. A hydrogen-rich reformed gas generated by reforming in a reactor is obtained, and the hydrogen-rich gas is supplied to an electrode (fuel electrode) of the fuel cell body to generate power.

In a reformer, a raw material gas is passed through a reforming catalyst layer heated to a high temperature by a burner to perform a reforming reaction. However, the reforming reaction may cause deterioration of a fuel cell catalyst. Carbon oxides are also generated. If the reformed gas contains carbon monoxide, this carbon monoxide will poison the fuel cell electrodes and reduce the performance.Before supplying the hydrogen-rich gas to the fuel cell anode, It is necessary to remove carbon monoxide in the gas reformed by the reformer. Although the concentration of carbon monoxide is reduced to about 1% in the carbon monoxide converter, it is necessary to further reduce the concentration to avoid electrode deterioration.

In particular, in the case of a polymer electrolyte fuel cell system, it is necessary to reduce carbon monoxide to a level of about 10 PPM, and the reformed gas reformed by a reformer and a carbon monoxide converter is required. Is provided with a carbon monoxide remover for supplying hydrogen gas to a fuel cell in which carbon monoxide has been reduced to a low level by mixing air with air and passing through a selective oxidation catalyst layer that selectively oxidizes carbon monoxide. .

A method and an apparatus for selectively removing carbon monoxide from a hydrogen-rich gas stream containing hydrogen and carbon monoxide and supplying the same to a fuel cell are disclosed, for example, in Japanese Patent Application Laid-Open No. 5-201770.
No. 2 discloses this. In this embodiment, carbon monoxide is oxidized to carbon dioxide by a specific catalyst such as ruthenium and rhodium, and carbon monoxide is removed from the reformed gas. In this case, the catalyst is accommodated in an elongated reaction vessel (steel tube vessel), and the reformed gas is introduced along with the air along the longitudinal direction of the reaction vessel. Carbon monoxide in the reformed gas is oxidized by a catalyst and oxygen in the air into carbon dioxide while passing through the gas to remove carbon monoxide from the reformed gas.

FIG. 4 is a side sectional view showing a conventional general carbon monoxide remover (reaction vessel). Reference numeral 5 denotes a catalyst layer, and a mixture of reformed gas and air enters through an inlet 7 of the reaction vessel 6 and undergoes an oxidation reaction with the catalyst. When the mixture and the catalyst undergo an oxidation reaction, the selective oxidation catalyst layer 5 needs to be maintained at a predetermined operating temperature in order to obtain good selectivity (selectively oxidize only carbon monoxide). This operating temperature is usually about 150 to 200 degrees Celsius, and at the time of startup, a heater is installed around the selective oxidation catalyst layer 5 to heat or
A method is used in which a high-temperature gas is generated by a burner and sent around the reaction vessel 6 to raise the temperature. During normal operation, the oxidation reaction occurring in the catalyst layer 5 is an exothermic reaction, and the temperature of the catalyst layer 5 is increased by the heat of the exothermic reaction. Can be kept.

[0007]

However, if the oxidation reaction of the catalyst layer 5 is not uniform, a temperature difference occurs in the catalyst layer 5,
The temperature in the catalyst layer 5 may partially reach 200 degrees Celsius or more. At temperatures above 200 degrees Celsius, catalyst degradation may occur, or the reaction may shift to a methanation reaction, reducing the hydrogen in the reformed gas.

In the reaction vessel 6, the reaction vessel 6
Since the length of the catalyst layer 5 is long, the temperature difference of the catalyst layer 5 in the flow direction of the reformed gas increases. If the temperature difference of the catalyst layer 5 is large, the mixture introduced from the inlet 7 of the reaction vessel 6 does not uniformly oxidize with the carbon monoxide in the gas flow direction, so that a uniform reaction temperature cannot be obtained. Was. In such a reaction vessel 6, an active oxidation reaction occurs only on the inlet 7 side and the temperature rises to 200 ° C. or more, and the predetermined temperature of the catalyst layer 5 is insufficient on the outlet 8 side, so that a favorable oxidation reaction cannot be performed. was there.

Therefore, the present invention solves the above-mentioned problems and provides a catalyst layer having a reaction temperature as uniform as possible when an oxidation reaction for removing carbon monoxide in a reformed gas is performed. It is intended to provide a carbon remover.

[0010]

In order to achieve the above-mentioned object, the invention according to claim 1 provides a hydrogen-rich reformed gas containing carbon monoxide obtained by reforming a raw material gas by a reformer. In a carbon monoxide remover that oxidizes and reduces carbon monoxide in the reformed gas by mixing with a gas containing oxygen and passing through the catalyst layer, the catalyst layer is divided into a plurality of catalyst layer elements, A space is provided between the catalyst layer elements, and a catalyst passage is provided in the most downstream catalyst layer element through which a mixture of a reformed gas and a gas containing oxygen undergoes an oxidation reaction with the catalyst. The catalyst layer element is provided with a catalyst passage through which the air-fuel mixture oxidizes and reacts with the catalyst and a through-hole through which the air-fuel mixture does not come into contact with the catalyst of the catalyst layer element, and the cross-sectional area of the through-hole is arranged on the downstream side. Catalyst layer Are those formed smaller as placement of apertures.

According to a second aspect of the present invention, a hydrogen-rich reformed gas containing carbon monoxide obtained by reforming a raw material gas with a reformer is mixed with a gas containing oxygen and passed through a catalyst layer. In a carbon monoxide remover that oxidizes and reduces carbon monoxide in the reformed gas, the catalyst layer is divided into a plurality of catalyst layer elements, and a space is provided before and after each catalyst layer element, Except for the most downstream catalyst layer element, each catalyst layer element is provided with a bypass pipe connecting the space before and after each catalyst layer element.

According to a third aspect of the present invention, the number of the catalyst layer elements is increased or decreased according to the amount of the air-fuel mixture.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. Note that the same components as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is an explanatory diagram of a process for obtaining a hydrogen-rich gas from a source gas. This step includes a desulfurizer 9, a reformer 1, a heat exchanger 10, a carbon monoxide converter 2, and a carbon monoxide remover 3.

In the desulfurizer 9, the raw material gas is removed by contacting a sulfur compound contained as an impurity in the raw material gas with a desulfurization catalyst filled in the desulfurizer 9. Steam is added to the raw material gas desulfurized in the reformer 1, and the raw material gas comes into contact with the reforming catalyst filled inside the reformer 1 and maintained at a high temperature to generate a hydrogen-rich reformed gas. The reformed gas discharged from the reformer 1 is sent to the heat exchanger 10 for cooling to the operating temperature of the carbon monoxide converter 2. In the heat exchanger 10, the reformed gas undergoes heat exchange with cooling water to be cooled. The reformed gas cooled in the heat exchanger 10 is sent to the carbon monoxide converter 2. In the carbon monoxide converter 2, the reformed gas is converted by a carbon monoxide component contained in the reformed gas coming into contact with a conversion catalyst filled in the carbon monoxide converter 2. 1% carbon monoxide concentration
It is reduced below. Further, in the carbon monoxide remover 3, the reformed gas is mixed with air and brought into contact with a catalyst 15 such as ruthenium or rhodium filled in the carbon monoxide remover 3 at a temperature of 150 to 200 degrees C. 10 PPM concentration
It is reduced below. The gas discharged from the carbon monoxide remover 3 is supplied to the fuel electrode of the fuel cell 4, and a part of the gas passes through a recycling line and is used as fuel for a burner.

FIG. 2 is a side sectional view of a carbon monoxide remover according to a first embodiment of the present invention. As shown in this figure,
The carbon monoxide remover 3 divides the catalyst layer in the container 6 into three catalyst layer elements, and is provided with a space before and after each catalyst layer element. The first, second, and third catalyst layer elements 11, 12, from upstream in the direction of flow
Thirteen. Each of the catalyst layer elements 11, 12, and 13 is formed by being filled with a specific catalyst 15, such as granular ruthenium or rhodium, surrounded by an inner wall of the container 6 and a perforated plate. The size of the particles of the catalyst 15 is
The catalyst 15 does not spill out of the perforated plate 14 larger than 6. Spaces are provided before and after each of the catalyst layer elements 11, 12, and 13, and first, second, third, and fourth spaces 21, 22, 23, and 24 are provided, respectively. Reference numeral 25 denotes a first passage hole formed by providing a cylindrical tube at the center of the first catalyst layer element 11, and a mixture of the reformed gas and air entered from the gas introduction tube 27 which is an inlet of the container is used as a first passage hole. The first catalyst layer element 11 flows downstream without contacting the catalyst 15. Reference numeral 26 denotes a second passage hole formed in the second catalyst layer element 12 and a first passage hole 25.
In the same manner as described above, the air-fuel mixture
5 and can pass downstream without contact. The cross-sectional area of the second passage hole 26 is smaller than the cross-sectional area of the first passage hole 25. The third catalyst layer element 13 has no passage hole, and the entire amount of the air-fuel mixture passing through the upstream catalyst passages 28 and 29 and the passage holes 25 and 26 passes through the catalyst layer element 13. Third catalyst layer element 1
Downstream of the third space 24 and the gas discharge pipe 32
Is provided.

During normal operation, the carbon monoxide concentration is about 1
% Mixed gas of reformed gas and air
When the air-fuel mixture enters the space 21, the air-fuel mixture spreads into the first space 21. The air-fuel mixture that has spread into the first space 21 passes through the holes 16 of the perforated plate 14 through the catalyst passages 2 of the catalyst layer element 11.
8 and those passing through the passage holes 25 and flow into the second space 22. At this time, in the gaseous mixture that has passed through the first catalyst layer element 11, carbon monoxide and oxygen in the gaseous mixture are oxidized by the catalyst 15 to reduce carbon monoxide. Heat is generated by this oxidation reaction, and the temperature rise is particularly large on the upstream side of the catalyst layer element 11.
Next, the air-fuel mixture that has entered the second space 22 flows into the third space 23 after being divided into the catalyst passage 29 and the passage hole 26 of the second catalyst layer element 12. At this time, the oxidation reaction that occurs in the second catalyst layer element 12 is smaller than the oxidation reaction that occurs in the first catalyst layer element 11 because the carbon monoxide concentration and the oxygen concentration in the air-fuel mixture are reduced, and heat is generated. Less. The mixture, which has entered the third space 23 and spreads, contacts the catalyst 15 of the third catalyst layer element 13 in its entirety and undergoes an oxidation reaction, and is sent from the fourth space 24 to the gas discharge pipe 32. Is discharged. As described above, the concentration of carbon monoxide is reduced to 10 PPM or less by the oxidation reaction in each of the catalyst layer elements 11, 12, and 13.

As described above, the air-fuel mixture that has entered the carbon monoxide remover 3 from the gas introduction pipe 27 is removed from each catalyst layer element 1
Since the mixture is dispersed by passing through the passage holes 25 and 26 provided in the catalyst layers 1 and 12, a part of the mixture is prevented from coming into contact with the catalyst.
Oxidation reaction and exothermic reaction are reduced by that amount, and active temperature rise can be suppressed.

Since the cross-sectional area of the passage hole is larger in the upstream passage hole, the amount of the air-fuel mixture in contact with the catalyst is larger in the downstream catalyst layer element than in the upstream catalyst layer element. In the exothermic reaction, the concentration of carbon monoxide and oxygen in the air-fuel mixture becomes higher toward the upstream side, so that the upstream catalyst layer element is more actively performed, and the temperature rise can be made substantially uniform throughout the catalyst layer.

A part of the air-fuel mixture flows from the gas introduction pipe 27 through the through holes 25 and 26, respectively, into the second and third spaces 2 and 3.
2 and 23, the second and third catalyst layer elements 1
The oxygen deficiency in 2 and 13 can be compensated. In this way, while preventing active oxidation only in the upstream catalyst layer elements 11 and 12 and preventing oxygen deficiency in the downstream side, the temperature distribution of the entire catalyst layer elements 11, 12 and 13 is made uniform. By maintaining a good temperature state, a good carbon monoxide removing effect can be obtained.

FIG. 3 is a side sectional view of a carbon monoxide remover according to a second embodiment of the present invention. First space 21 and second space
Between the second space and the third space,
The bypass pipes 33 and 34 are provided, respectively.

When the mixed gas of the reformed gas and the air enters the first space 21 from the gas introduction pipe 27, the first space 2
Spread in one. The air-fuel mixture spread in the first space 21
The gas passing through the catalyst passage 28 of the catalyst layer element 11 and the gas passing through the bypass pipe 33 flow from the holes 16 of the perforated plate 14 into the second space 22. Since the air-fuel mixture is dispersed in the first space, the oxidation reaction and the exothermic reaction in the first catalyst layer element 11 are reduced by that amount, and the temperature rise can be suppressed. Second catalyst layer element 1
2, the temperature rise can be similarly suppressed. In this way, a part of the air-fuel mixture is reduced so that the air-fuel mixture and the catalyst are gradually oxidized, so that the temperature is not excessively increased, and the good temperature of the entire carbon monoxide remover 3 can be maintained.

Although the present invention has been described based on the embodiments, the present invention is not limited to these embodiments. In the first embodiment, the passage holes 25, 2, 2 are provided at the center positions of the catalyst layer elements 11, 12 except for the most downstream catalyst layer element 13.
6 is provided, but may not be at the center position as long as the air-fuel mixture can be dispersed and flow into the catalyst passage and the passage hole.

[0024]

According to the first or second aspect of the present invention, the catalyst layer is divided into a plurality of catalyst layer elements, a space is provided between each catalyst layer element, and the catalyst layer is mixed with each catalyst layer element. By providing a catalyst passage through which gas oxidizes and reacts with the catalyst and a through hole through which the air-fuel mixture does not come into contact with the catalyst of the catalyst layer element, the air-fuel mixture entering from the gas introduction pipe flows into the catalyst passage and the through-hole. Will be sorted out.
Due to the distribution of the air-fuel mixture, the oxidation reaction in each catalyst element is reduced accordingly. The mixture passing through the through-holes is dispersed to each catalyst layer element and the oxidation reaction is gradually performed, so the exothermic reaction accompanying the oxidation reaction is also dispersed and the temperature of the entire catalyst layer becomes uniform and the temperature of the catalyst layer is kept in a good state Can be held.

According to the third aspect of the present invention, by designing the carbon monoxide remover by increasing or decreasing the number of each catalyst layer element in accordance with the amount of air-fuel mixture entering the carbon monoxide remover, The temperature can be controlled more finely, a good temperature state can be maintained in the catalyst layer, and an efficient carbon monoxide remover can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a system of a raw material gas reforming apparatus.

FIG. 2 is a side sectional view of the carbon monoxide remover showing the first embodiment of the present invention.

FIG. 3 is a side sectional view of a carbon monoxide remover according to a second embodiment of the present invention.

FIG. 4 is a side sectional view showing a conventional carbon monoxide remover.

[Explanation of symbols]

 Reference Signs List 1 reformer 3 carbon monoxide remover 4 fuel cell 5 catalyst layer 11 first catalyst layer element 12 second catalyst layer element 13 third catalyst layer element 15 catalyst 21 first space 22 second space 23 Third space 24 Fourth space 25 First passage hole 26 Second passage hole 28 Catalyst passage of first catalyst layer element 29 Catalyst passage of second catalyst layer element 30 Catalyst passage of third catalyst layer element 33 1st bypass pipe 34 2nd bypass pipe

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Taketoshi Koki 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Osamu Tajima 2-chome Keihanhondori, Moriguchi-shi, Osaka No. 5-5 Sanyo Electric Co., Ltd. F term (reference) 4G040 FA01 FB04 FC07 4G069 AA15 BC70A BC71A CC17 CC32 DA05 EA02X EE06 FB79

Claims (3)

[Claims] 1. A hydrogen-rich reformed gas containing carbon monoxide obtained by reforming a raw material gas by a reformer is mixed with a gas containing oxygen, and the mixed gas is passed through a catalyst layer. In a carbon monoxide remover for oxidizing and reducing carbon monoxide, the catalyst layer is divided into a plurality of catalyst layer elements, a space is provided between each catalyst layer element, and a catalyst layer element at the most downstream position is provided. A catalyst passage through which an air-fuel mixture of a reformed gas and a gas containing oxygen oxidizes and reacts with the catalyst is provided. Fuel, wherein a passage hole through which the air-fuel mixture passes without contacting the catalyst of the catalyst layer element is provided, and a cross-sectional area of this passage hole is formed smaller as the passage hole of the catalyst layer element arranged on the downstream side. Electric Of the carbon monoxide remover. 2. A hydrogen-rich reformed gas containing carbon monoxide, obtained by reforming a raw material gas by a reformer, is mixed with a gas containing oxygen and passed through a catalyst layer, so that In a carbon monoxide remover for oxidizing and reducing carbon monoxide, the catalyst layer is divided into a plurality of catalyst layer elements, and a space is provided before and after each catalyst layer element, and the most downstream catalyst layer element is provided. A carbon monoxide remover for a fuel cell, characterized in that a bypass pipe is provided in each of the catalyst layer elements except for the one connected to the space before and after each catalyst layer element. 3. The catalyst layer element according to claim 1, wherein the number of the catalyst layer elements is increased or decreased according to the amount of the air-fuel mixture.
Or a carbon monoxide remover according to claim 2.