JP3545254B2 - Fuel cell carbon monoxide remover - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is directed to a fuel cell system using hydrogen as a fuel, which removes carbon monoxide contained in a reformed gas obtained through a reformer to produce a fuel for a hydrogen-rich fuel cell. About the vessel.
[0002]
[Prior art]
The polymer electrolyte fuel cell system converts chemical energy of hydrogen into electric energy. A raw material gas (hereinafter referred to as “raw gas”) of hydrocarbons such as naphtha and alcohols such as methanol, which are relatively easily and inexpensively available from a business perspective, is mixed with steam to form a reformer and carbon monoxide conversion. A hydrogen-rich fuel gas generated by reforming in a reactor is obtained, and the hydrogen-rich fuel gas is supplied to an electrode (fuel electrode) of the fuel cell body to generate power.
[0003]
In the reformer, the reforming reaction is performed by passing the raw material gas through the reforming catalyst layer heated to a high temperature by the burner, and carbon monoxide is generated simultaneously with the reforming reaction. If the reformed gas contains carbon monoxide, the carbon monoxide poisons the fuel cell electrodes and degrades the performance. It is necessary to remove carbon monoxide in the reformed gas in the vessel. Although the concentration of carbon monoxide is reduced to about 1% in a carbon monoxide converter, it is necessary to further reduce the concentration to avoid electrode deterioration.
[0004]
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 air is supplied to the reformed gas reformed by the reformer and the carbon monoxide converter. Mixing and passing through a selective oxidation catalyst layer (hereinafter simply referred to as a catalyst layer) that selectively oxidizes only carbon monoxide to supply hydrogen gas with reduced carbon monoxide to a low level to a fuel cell. A vessel is provided.
[0005]
FIG. 4 is a side sectional view showing a conventional general carbon monoxide remover (reaction vessel). Reference numeral 1 denotes a catalyst layer, which has a structure in which a catalyst such as ruthenium or rhodium is granulated and accommodated in an elongated reaction vessel 2 (steel pipe vessel). The reaction vessel 2 has a configuration in which the reformed gas is introduced along with the air along the longitudinal direction. While the reformed gas passes through the reaction vessel 2, carbon monoxide in the reformed gas is oxidized by the action of a catalyst. By doing so, carbon monoxide is removed from the reformed gas. A mixture of the reformed gas and air enters from the inlet of the reaction vessel 2 and undergoes an oxidation reaction with the catalyst. In the reaction vessel 2, it is necessary to keep the catalyst layer 1 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 catalyst layer 1 to heat it, or a high-temperature gas is generated by a burner to generate A method of raising the temperature by sending it around is adopted. During normal operation, the reaction occurring in the catalyst layer 1 is an exothermic reaction, and the temperature of the catalyst layer 1 is raised by the heat of the exothermic reaction, so that a predetermined temperature can be maintained without externally raising the temperature.
[0006]
[Means for Solving the Problems]
The invention according to claim 1 supplies a city gas and water vapor and reforms the city gas into a reformed gas, and is connected to the reformer and supplies the city gas to the reformer. A supply pipe, which is disposed in the supply pipe, is connected to a pressure pump and a flow rate regulator for pumping city gas to the reformer, and is connected to a subsequent stage of the reformer, and converts carbon monoxide from the reformed gas. carbon monoxide shift converter and the carbon monoxide remover for removing a fuel cell body for generating electric power by the reformed gas removed carbon monoxide and oxygen in the air are reacted in the fuel cell power generation system comprising, A merging section for merging the city gas and the water vapor is provided at a subsequent stage of the flow regulator .
[0008]
As described above, when designing a carbon monoxide remover that requires temperature control, the temperature of the catalyst layer must be maintained within a predetermined range for each carbon monoxide remover with a different output, and the design in a short period of time must be performed. Development was difficult.
[0009]
Therefore, an object of the present invention is to solve the above-described problems, to maintain the catalyst layer at a uniform temperature, and to design and develop a carbon monoxide remover having a different output in a short period of time.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes mixing a fuel supplied to a fuel cell with a hydrogen-rich reformed gas containing carbon monoxide obtained through a reformer and air. In a carbon monoxide remover obtained by oxidizing and reducing the carbon monoxide by passing through a catalyst layer, a plurality of containers accommodating a catalyst and forming a catalyst layer therein and a connection connecting the plurality of containers in series A pipe, an air pipe connected to the plurality of vessels, and supplying air in parallel to the catalyst layer of each vessel; and an air pipe arranged in the air pipe, from the reformed gas inlet side of each vessel to the reformed gas outlet side. And an air hole provided to supply a large amount of air .
[0011]
According to a second aspect of the present invention, in the carbon monoxide remover according to the first aspect, the air pipe is supplied with air through an upstream header.
[0012]
According to a third aspect of the present invention, in the carbon monoxide remover according to the first or second aspect, the amount of air supplied to each catalyst layer in the plurality of containers through which the reformed gas passes is improved. The downstream catalyst layer is increased in the direction of flow of the raw gas.
[0013]
According to a fourth aspect of the present invention, in the carbon monoxide remover of the first, second or third aspect of the present invention, the temperature of the most upstream vessel or the temperature of the catalyst in the vessel is reduced in the flow of the reformed gas. At a temperature lower than the temperature of the container or the catalyst in the container.
[0014]
According to a fifth aspect of the present invention, in the carbon monoxide remover according to the fourth aspect , the container located at the uppermost stream is provided with cooling means for keeping the temperature of the catalyst in the container constant. is there.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described 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.
[0017]
FIG. 1 is an explanatory diagram of a process for obtaining a hydrogen-rich gas from a source gas. This step includes a desulfurizer 3, a reformer 4, a heat exchanger 5, a carbon monoxide converter 6, and a carbon monoxide remover 7.
[0018]
In the desulfurizer 3, the source gas is removed by contacting a sulfur compound contained as an impurity in the source gas with a desulfurization catalyst filled in the desulfurizer 3. Next, steam is added to the raw material gas desulfurized in the reformer 4, and comes into contact with the reforming catalyst filled in the reformer 4 and maintained at a high temperature to generate a hydrogen-rich reformed gas. . The reformed gas discharged from the reformer 4 is cooled by the heat exchanger 5 to the operating temperature of the carbon monoxide converter 6. In the heat exchanger 5, the reformed gas exchanges heat with cooling water and is cooled. The reformed gas cooled in the heat exchanger 5 is sent to the carbon monoxide converter 6. In the carbon monoxide converter 6, the reformed gas is converted by the carbon monoxide component contained in the reformed gas coming into contact with the conversion catalyst filled in the carbon monoxide converter 6. By the metamorphosis, the carbon monoxide concentration is reduced to 1% or less. Further, in the carbon monoxide remover 7, the reformed gas is mixed with air and brought into contact with a catalyst such as ruthenium or rhodium filled in the carbon monoxide remover 7 at a temperature of 150 to 200 ° C. Is reduced to 10 PPM or less. The gas discharged from the carbon monoxide remover 7 is supplied to the fuel electrode of the fuel cell 8, and the unreacted gas passes through a recycling line and is used as fuel for a burner.
[0019]
FIG. 2 shows a carbon monoxide remover 7 according to the first embodiment of the present invention. The carbon monoxide remover 7 is configured by connecting three reaction vessels 2, and the first, second, and third reaction vessels 2 a, 2 b, and 2 c are connected to first and second connection pipes 9, 10, respectively. Are connected in series. Each reaction vessel 2a, 2b, 2c contains a granular catalyst, and forms catalyst layers 1a, 1b, 1c. The reformed gas flows through these catalyst layers 1a, 1b, and 1c via connection pipes. Reference numeral 11 denotes air supply means for supplying air to the catalyst layer 1a, and reference numeral 12 denotes a header. Air is once collected in header 12 through an air conditioner (not shown). 13a supplies air to the catalyst layer 1a in a first air pipe extending from the header 12. A large number of air holes 14 are formed in the air pipe 13a, and the air holes 14 can distribute and supply air to the catalyst layer 1a. Reference numeral 13b denotes a second air pipe extending from the header 12, and supplies air to the catalyst layer 1b from a number of air holes 14 formed in the second air pipe 13b, similarly to the first air pipe 13a. The third air pipe 13c is similarly configured. These air holes 14 supply more air to the reformed gas outlet side of the reaction vessels 2a, 2b, 2c than to the reformed gas inlet side. Reference numeral 17 denotes a gas introduction pipe through which the reformed gas is introduced, and reference numeral 18 denotes a gas discharge pipe through which the gas processed in the reaction vessel 2 is discharged.
[0020]
In the carbon monoxide remover 7 configured as described above, during normal operation, a reformed gas containing about 1% of carbon monoxide is introduced from the gas introduction pipe 17 into the catalyst layer 1a of the first reaction vessel 2a. When air is supplied from the one air pipe 13a, an oxidation reaction is performed in the catalyst layer 1a, and carbon monoxide in the reformed gas is oxidized and reduced. At this time, the temperature of the first reaction vessel 2a is kept at 130 to 160 degrees Celsius (the temperature just before the reaction takes place), lower than the temperature of the other vessels, so that the concentration of carbon monoxide is always 0.5 to 0.1%. I keep it. A cooler is used to keep the temperature of the container constant. This gas enters the catalyst layer 1b from the first connection pipe 9, and oxidizes with the air supplied to the catalyst layer 1b to further reduce carbon monoxide. The oxidation reaction is similarly performed in the catalyst layer 1c, and the processed gas is discharged from the gas discharge pipe 18. Thus, the oxidation reaction is performed in each of the catalyst layers 1a, 1b, and 1c, so that the carbon monoxide concentration is reduced to 10 PPM or less.
[0021]
Since a plurality of catalyst layers 1a, 1b, 1c are arranged and connected in series, and air is supplied to each of the catalyst layers 1a, 1b, 1c, oxygen shortage does not occur in each of the catalyst layers 1a, 1b, 1c. An oxidation reaction can be performed.
[0022]
Further, in each of the reaction vessels 2a, 2b, and 2c, the supply of air is reduced at the inlet side where the oxidation reaction is active and increased at the outlet side, so that the oxidation reaction becomes uniform, and the respective reaction vessels 2a, 2b , 2c can be made uniform in temperature distribution in the catalyst layers 1a, 1b, 1c.
[0023]
In addition, in the reaction vessels 2a, 2b, and 2c connected in series, the amount of air supplied to the reaction vessel 2a on the upstream side where the oxidation reaction is active is reduced, and the air supplied to the downstream sides 2b and 2c is increased, so that each reaction is increased. The temperature distribution of the catalyst layer 1 between the containers 2a, 2b, 2c can be made uniform.
[0024]
In the present embodiment, three reaction vessels 2a, 2b, 2c containing the catalyst layers 1a, 1b, 1c are connected in series, and air is supplied from one side of the three catalyst layers 1a, 1b, 1c. ing. If the carbon monoxide remover 7 based on this is designed, the carbon monoxide remover 7 having a different output can be easily assembled simply by increasing or decreasing the catalyst layer 1 and the air pipe 13.
[0025]
In addition, if the basic unit is a carbon monoxide remover configured by combining one catalyst layer and air supply means for supplying air to the catalyst layer, as long as the carbon monoxide remover is designed and developed, The output can be increased simply by connecting the basic units in series.
[0026]
FIG. 3 shows a carbon monoxide remover 7 according to a second embodiment of the present invention. This carbon monoxide remover 7 is different from the first embodiment in the arrangement of the container 2 for accommodating the catalyst layer 1. In the second embodiment, as in the first embodiment, since air is supplied to each of the catalyst layers 1, there is no shortage of oxygen in each of the catalyst layers 1, and the number of the catalyst layers 1 can be easily increased and decreased. Therefore, the design and development of the carbon monoxide remover 7 having a different output can be facilitated.
[0027]
As described above, the present invention has been described based on one embodiment, but the present invention is not limited to this.
[0028]
【The invention's effect】
According to the first aspect of the present invention, if a carbon monoxide remover serving as a basic unit is designed and developed, the output can be easily increased simply by connecting a plurality of containers containing the catalyst layers in series. . Further, since air is supplied from one side of each catalyst layer, it is possible to assemble the piping without complicating the piping.
[0029]
Further, in the catalyst layer of each container, the oxidation reaction is more active on the reformed gas inlet side than on the reformed gas outlet side, and the heat generated by the oxidation reaction is larger on the reformed gas inlet side. By arranging a plurality of air holes so that more air is supplied to the reformed gas outlet side of the catalyst layer than the reformed gas inlet side of the air pipe in the container, the temperature in the catalyst layer can be kept uniform. .
[0030]
According to the second aspect of the present invention, the air pipe is provided with a header for collecting air once so as to keep the air pressure constant, so that a predetermined amount of air can be supplied to each catalyst layer without variation. . Further, by controlling the pressure of the header, the amount of air supplied to each catalyst layer can be controlled.
[0031]
According to the invention as set forth in claim 3 , the oxidation reaction is more actively performed in the catalyst layer provided on the upstream side in the direction of the flow of the reformed gas. The amount of air supplied to the catalyst layer can be increased toward the downstream catalyst layer, and the temperature difference between the catalyst layers can be reduced to keep the temperature uniform.
[0032]
According to the invention as set forth in claim 4 or 5 , the temperature of the first stage of the carbon monoxide remover is constantly reduced to a temperature just before the catalytic reaction occurs (130 to 160 degrees Celsius), and the temperature during the load increase is reduced. The concentration of carbon monoxide at the first stage outlet is always kept at 0.5 to 0.1% even when carbon monoxide is increased. When the concentration of carbon monoxide at the outlet of the carbon monoxide converter increases, the temperature of the first-stage catalyst rises, the reaction becomes active, and the increased amount of carbon monoxide reacts quickly. As a result, it is possible to prevent a temperature change in the second and subsequent stages of the carbon monoxide remover, and it is possible to always maintain the carbon monoxide concentration at 10 PPM or less including a load change.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram 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 showing 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 catalyst layer 1a first catalyst layer 1b second catalyst layer 1c third catalyst layer 2 reaction vessel 2a second catalyst layer 2b third catalyst layer 2c third catalyst layer 4 reformer 7 carbon monoxide remover 8 fuel cell 9 First connection pipe 10 Second connection pipe 11 Air supply means 12 Header 13 Air pipe 13a First air pipe 13b Second air pipe 13c Third air pipe 14 Air hole

Claims (5)

The fuel to be supplied to the fuel cell is obtained by mixing a hydrogen-rich reformed gas containing carbon monoxide obtained through a reformer with air and passing through a catalyst layer to reduce the carbon monoxide by oxidation. In the carbon monoxide remover,
A plurality of containers containing a catalyst and forming a catalyst layer inside ,
A connecting pipe for connecting said plurality of containers in series,
An air pipe connected to the plurality of containers and supplying air in parallel to the catalyst layer of each container ,
An air hole arranged in the air pipe, provided so that more air is supplied to the reformed gas outlet side than the reformed gas inlet side of each container,
Carbon monoxide remover of the fuel cell, characterized in that it comprises a. The fuel cell carbon monoxide remover according to claim 1, wherein the air pipe is supplied with air via an upstream header. The amount of air supplied to each catalyst layer in the plurality of containers through which the reformed gas passes is increased in the direction of the flow of the reformed gas toward the downstream side catalyst layer. Fuel cell carbon monoxide remover. 4. The flow of the reformed gas, wherein the temperature of the most upstream vessel or the catalyst in the vessel is lower than the temperature of the downstream vessel or the catalyst in the vessel. Fuel cell carbon monoxide remover. The carbon monoxide remover for a fuel cell according to claim 4, wherein the container located at the uppermost stream is provided with cooling means for keeping the temperature of the catalyst in the container constant .

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