JP2000335904A - Co-remover and fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CO-remover enabling a selective oxidation catalyst over the whole region in a reaction vessel to be maintained within an optimum temperature range, and having improved performance for removing carbon monoxide, and further to provide a fuel cell system having improved cell characteristics. SOLUTION: This CO-remover has plural reaction vessels 11A and 11B storing selective oxidation catalyst and connected to each other, and selectively oxidizes carbon monoxide in a CO-containing gas by the selective oxidation reaction caused by the selective oxidation catalyst by passing the CO-containing gas and air through the reaction vessel 11A and 11B. The upstream part and the downstream part of one reaction vessel 11A of the plural reaction vessels 11A and 11B arranged in series are arranged so as to be able to carry out the heat exchange with the downstream part and the upstream part of the other reaction vessel 11B, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for removing carbon monoxide from a CO-containing gas containing carbon monoxide.
The present invention relates to a removing device and a fuel cell system including the same.
In particular, the present invention relates to a technique for improving the performance of removing carbon monoxide in a CO removal device and improving the power generation performance of a fuel cell system.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of environmental protection, it has been required to replace an engine using combustion energy such as gasoline or light oil, and it has been studied to obtain driving energy of a vehicle or the like from a fuel cell. In this fuel cell, power is generated by supplying an oxidizing agent such as air to the cathode and supplying a hydrogen-rich fuel gas to the anode.

FIG. 4 is a system configuration diagram showing a schematic configuration of a normal fuel cell system. A hydrocarbon source gas such as methane or propane gas supplied from a source gas supply system (not shown) is first supplied to a desulfurizer 1, and a sulfur component added as an odorant to the source gas by the desulfurizer 1. Is removed and introduced into the reformer 2. Steam is supplied to the reformer 2 from a steam supply system (not shown) together with the raw material gas, and the steam reforming reaction (CH ₄ + H ₂ O → CO +
3H ₂ ) generates a hydrogen-rich fuel gas having a hydrogen concentration of about 75 to 80%.

[0004] The fuel gas immediately after leaving the reformer 2 contains carbon monoxide at a concentration of about 10 to 15%. When the fuel gas immediately after leaving the reformer 2 is directly supplied to the anode of the fuel cell body to reduce the performance of the catalyst used for the anode, the carbon monoxide deteriorates the power generation performance of the fuel cell body. Let it.

[0005] Therefore, the fuel gas discharged from the conventional reformer 2 is passed through a CO converter 3 and a CO remover 4 to a fuel cell main body 5.
Is supplied to the anode 51. C in the CO transformer 3
The carbon monoxide is shifted to carbon dioxide by the O shift reaction (CO + H ₂ O → CO ₂ + H ₂ ), and the carbon monoxide concentration becomes 1
%. Further, a selective oxidation reaction (CO + 1 / 2O ₂ → CO ₂ ) occurs in the CO removing device 4, and carbon monoxide is selectively oxidized and its concentration is reduced to about 10 ppm. And thus, carbon monoxide is 10
The hydrogen-rich fuel gas reduced to about ppm
It is supplied to the anode 51 of the fuel cell body 5. Air is supplied to the cathode 52 of the fuel cell main body 5 by an air supply means such as a blower (not shown), and as a result, power is generated in the fuel cell main body 5.

The above-mentioned CO removing device 4 is usually made of ruthenium,
It comprises an elongated steel tube container (reaction container) in which a selective oxidation catalyst such as rhodium is accommodated, and is configured such that fuel gas is introduced into the reaction container along with its longitudinal direction together with air. . Then, when the fuel gas passes through the inside of the reaction vessel, carbon monoxide in the fuel gas is selectively oxidized by the selective oxidation catalyst to carbon dioxide, and the carbon monoxide concentration is reduced (Japanese Patent Laid-Open No. −20170
No. 2).

[0007] In such a CO removal device, when fuel gas and air are introduced into the reaction vessel, a selective oxidation reaction proceeds from the inlet side, and the mono-oxidation in the fuel gas proceeds along the gas flow direction. The carbon and oxygen in the air reach the outlet side while being consumed by the selective oxidation reaction. For this reason, the concentrations of carbon monoxide and oxygen are high on the inlet side and low on the outlet side, and accordingly, the selective oxidation reaction occurring in the reaction vessel is high on the inlet side and low on the outlet side. Further, since such a selective oxidation reaction is an exothermic reaction, the amount of heat generated in the reaction vessel is large at the inlet side and reduced at the outlet side. high temperature,
A temperature distribution of low temperature occurs at the outlet side.

On the other hand, in order to selectively oxidize carbon monoxide using a selective oxidation catalyst such as ruthenium or rhodium, it is necessary to maintain the temperature of these selective oxidation catalysts in an optimum temperature range. For example, when a ruthenium-based selective oxidation catalyst is used, it is necessary to maintain the temperature of the catalyst in a temperature range of 130 ° C. to 190 ° C. in order to sufficiently selectively oxidize carbon monoxide. If the temperature of the selective oxidation catalyst is higher than this temperature range, carbon monoxide or carbon dioxide is combined with hydrogen to produce methane, so that hydrogen as fuel is consumed and supplied to the fuel cell body. As a result, the amount of generated hydrogen decreases, and the amount of power generation decreases. On the other hand, at a temperature lower than the above temperature range, a selective oxidation reaction that can sufficiently remove carbon monoxide does not occur.

Therefore, in the conventional CO removing apparatus, as described above, a temperature distribution of a high temperature at the inlet side and a low temperature at the outlet side occurs, so that the selective oxidation catalyst in the reaction vessel is set to an optimum temperature range over the entire range. It becomes difficult to maintain, and the efficiency of the selective oxidation reaction is reduced, so that carbon monoxide cannot be sufficiently removed or the amount of hydrogen supplied as fuel may be reduced.

In order to solve such a problem, there has been proposed a CO removal apparatus including a plurality of reaction vessels and introducing oxygen into the upstream side of each of the reaction vessels (Japanese Patent Application Laid-Open No. 8-47621). issue).

[0011]

However, even in such an apparatus, the problem that a temperature distribution at the inlet side becomes high and a temperature at the outlet side becomes low in each of the reaction vessels along the gas flow direction is fundamentally solved. Therefore, it becomes difficult to adjust the selective oxidation catalyst to the optimum temperature range, and the efficiency of the selective oxidation reaction is reduced, so that carbon monoxide cannot be sufficiently removed or the amount of hydrogen as fuel decreases. The problem still remained.

The present invention solves the above-mentioned conventional problems, makes the temperature distribution generated in the gas flow direction of the reaction vessel close to a uniform distribution, and makes the selective oxidation catalyst in the reaction vessel an optimum temperature range over the entire range. It is an object of the present invention to provide a CO removal device capable of maintaining the same and having improved carbon monoxide removal performance, and to provide a fuel cell system having improved cell performance using the CO removal device.

[0013]

Means for Solving the Problems In order to solve such a conventional problem, a CO removing apparatus according to the present invention has a plurality of reaction vessels accommodating a selective oxidation catalyst and connected to each other,
A CO removal device that passes a CO-containing gas and air containing carbon monoxide through the plurality of reaction vessels and selectively oxidizes carbon monoxide in the CO-containing gas by a selective oxidation reaction generated by the selective oxidation catalyst. The upstream part and the downstream part of one of the reaction vessels in the consecutively arranged reaction vessels among the plurality of reaction vessels are arranged so as to be able to transfer heat to the downstream part and the upstream part of the other reaction vessel, respectively. It is characterized by the following.

The upstream and downstream portions of one of the plurality of reaction vessels are arranged close to the downstream and upstream portions of the other reaction vessel. It is characterized by having.

Further, the one reaction vessel and the other reaction vessel are connected close to each other by a connection member having good thermal conductivity.

In addition, an air inlet for introducing air is provided in at least one of a plurality of communicating portions that communicate the plurality of reaction vessels with each other.

Further, the reaction vessels in which the plurality of reaction vessels have a flat shape and are arranged continuously are characterized in that the surfaces having the largest areas are arranged to face each other. A serpentine gas flow path is formed in a plurality of reaction vessels.

Further, the fuel cell system of the present invention
An O removing device is provided in a fuel gas supply path.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a CO removing apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view for explaining a schematic configuration of a CO removing apparatus according to the present embodiment, and FIG. 2 is a front view taken along line AA in FIG.

In the figure, reference numerals 11A and 11B denote reaction vessels made of stainless steel, for example, each having a flat shape. The inside of each of the reaction vessels 11A and 11B is filled with a granular or pellet-shaped selective oxidation catalyst such as ruthenium or rhodium for selectively oxidizing carbon monoxide. As shown in FIG. 2, a plurality of gas flow path partition plates 16 are provided in the reaction vessel 11A, and the gas flow path has a meandering (serpentine) configuration. Also, the reaction vessel 11B
Similarly, a plurality of gas flow path partition plates are provided inside,
The gas channel has a serpentine configuration.

The direction in which the partition plate 16 is provided is preferably a vertical direction as shown in FIG. Partition plate 16
Is provided in the horizontal direction, the selective oxidation catalyst filled in the reaction vessel accumulates under the influence of gravity, and a gap is formed in the upper portion, and the CO-containing gas flows through this gap.

Reference numeral 12 denotes a gas introduction pipe for introducing a CO-containing gas containing carbon monoxide into one reaction vessel 11A, and reference numeral 13 denotes an air introduction pipe for introducing air.

The CO-containing gas and air are respectively supplied to the gas introduction pipe 1
2 and one of the reaction vessels 11 through the air introduction pipe 13.
A is introduced into the reaction vessel 11A from the supply port 21 of A.
The outlet 2 is selectively oxidized by the selective oxidation catalyst filled in the reaction vessel 11A along the gas flow direction.
Then, the gas having a reduced concentration of carbon monoxide is discharged from the outlet 22.

The discharge port 22 is connected to the supply port 2 in the other reaction vessel 11B by a gas pipe constituting the communication section 14.
3 and the outlet 22 of one reaction vessel 11A.
Is discharged into the reaction vessel 11B from the supply port 23 of the other reaction vessel 11B via the communication portion 14. Then, the reaction vessel 11 is moved along the gas flow direction.
The gas reaches the outlet 24 while being selectively oxidized by the selective oxidation catalyst filled in B, and the gas having a further reduced carbon monoxide concentration is discharged from the outlet 24 through the gas discharge pipe 15 to the outside. .

As described above, the carbon-containing C-containing carbon monoxide
The O gas is introduced into one reaction vessel 11A together with air, and after the concentration of carbon monoxide in the gas is reduced by the selective oxidation reaction by the selective oxidation catalyst filled in the reaction vessel 11A, the other reaction is performed again. The gas is introduced into the vessel 11B, and is discharged to the outside in a state where the concentration of carbon monoxide in the gas is further reduced by the selective oxidation reaction by the selective oxidation catalyst filled in the reaction vessel 11B.

Here, as described above, the reaction vessels 11A and 1A
Within 1B, there is a temperature distribution in which the temperature is higher on the upstream side where the supply ports 21 and 23 are arranged, and lower on the downstream side where the discharge ports 22 and 24 are arranged. However, in the present invention, the reaction vessels 11A and 11B are arranged so that the upstream and downstream of one reaction vessel 11A can conduct heat with the downstream and upstream of the other reaction vessel 11B, respectively. I have. More specifically, as shown in FIG. 1, flat reaction vessels 11A and 11B are arranged such that their surfaces having the largest areas are close to each other. At this time, the upstream side of one of the reaction vessels 11A, that is, the side where the supply port 21 is arranged, and the downstream side of the other reaction vessel 11B, that is, the side where the discharge port 24 is arranged, are brought close to each other. The downstream side of 11A, that is, the side where the discharge port 22 is arranged, and the upstream side of the other reaction vessel 11B, that is, the side where the supply port 23 is arranged, are arranged close to each other.

According to such a configuration, one of the reaction vessels 11
On the upstream side, which is the high temperature part in FIG.
The amount of heat generated on the downstream side, which is the low temperature part in 1B, is transferred. Further, the amount of heat generated on the downstream side, which is the high-temperature part, in the other reaction vessel 11B is transferred to the downstream side, which is the low-temperature part in one reaction vessel 11A. Thus, the amount of heat transferred from the reaction vessel 11B to the reaction vessel 11A is small on the upstream side, which is a high temperature part, and large on the downstream side, which is a low temperature part. For this reason, the temperature difference generated between the upstream side and the downstream side can be made smaller than before. Also,
Similarly, the temperature difference between the upstream side and the downstream side in the reaction vessel 11B can be reduced as compared with the conventional case. Therefore, it is possible to maintain the temperature of the selective oxidation catalyst in the reaction vessel in the optimum temperature range over the gas flow direction,
It becomes possible to improve the carbon monoxide removal performance of the removal device.

Further, according to the CO removing apparatus of the present embodiment, a serpentine (meandering) gas flow path is formed inside the reaction vessel, and the length of the gas flow path is smaller than the size of the reaction vessel. And extremely large. For this reason, the size of the reaction vessel can be made smaller than the amount of the selective oxidation reaction generated in the reaction vessel, and the apparatus can be made compact.

(Example) The dimensions are 1.2 cm × 15 cm ×
At 20 cm, the catalyst filling length (length in the gas flow direction) is 1.
Reaction containers A and B in which a pellet-shaped catalyst in which ruthenium as a selective oxidation catalyst is supported on an alumina surface in a 2 m stainless steel container are disposed in the configuration of FIG. 1 to remove CO of the present invention. The device was prepared. And this CO
A gas containing 79% of hydrogen, 20% of carbon dioxide, and 1% of carbon monoxide was introduced into the removing device at a flow rate of 20 NL / min. At the same time, [O ₂ ] / [CO] = 0.
3 air was introduced. Then, the temperature distribution along the gas flow direction in the reaction vessel A in the CO removal apparatus of this example was measured. The result is shown in FIG. Further, for comparison, a case where a CO removal device of a comparative example having the same configuration as that of the example was used except that the reaction vessels A and B were arranged so as to be separated from each other so that heat exchange did not occur between them. Is also shown in FIG.

As shown in the figure, in the case of the embodiment shown by the solid line, the temperature difference between the upstream side and the downstream side of the reaction vessel is reduced by 6%.
The temperature can be about 0 ° C., and the temperature of the selective oxidation catalyst can be maintained in an optimal temperature range of 130 ° C. to 190 ° C. over the entire gas flow direction. On the other hand, in the case of the comparative example device indicated by the broken line, a temperature difference of about 100 ° C. has occurred, the temperature on the downstream side has become lower than the optimum temperature range, and the temperature of the selective oxidation catalyst has been reduced over the entire gas flow direction. The optimum temperature range cannot be maintained over the entire temperature range. Therefore, according to the present invention, it has been found that the temperature difference generated between the upstream side and the downstream side of the reaction vessel can be reduced, and the temperature of the selective oxidation catalyst can be maintained in an optimum temperature range throughout the gas flow direction. .

As a result, according to the CO removing apparatus of this embodiment, the selective oxidation reaction can be sufficiently advanced, and the concentration of carbon monoxide in the gas discharged from the reaction vessel B is 9 pp.
m. On the other hand, in the case of the comparative example device, the progress of the selective oxidation reaction was insufficient, and the carbon monoxide concentration was reduced to 30 p.
pm only.

As described above, according to the CO removing apparatus of the present invention, the temperature difference generated in the reaction vessel can be made smaller than before, and the temperature difference can be selected over the range along the gas flow direction in the reaction vessel. The temperature of the oxidation catalyst can be kept in an appropriate range. For this reason, the performance of removing carbon monoxide can be improved more than before, and the concentration of carbon monoxide can be lower than before.

Further, since the two continuous reaction vessels are arranged close to each other as described above, the size of the CO removing device can be made smaller than before, and the size can be reduced.

In the above embodiment, the configuration including two reaction vessels has been described. However, the number of reaction vessels is not limited to two, and may be three or more. Even when three or more reaction vessels are provided, of the two reaction vessels arranged continuously, the upstream side and the downstream side in one of the reaction vessels are in heat transfer with the downstream side and the upstream side in the other reaction vessel, respectively. By arranging as much as possible, the effects of the present invention can be achieved.

It is not necessary to arrange two reaction vessels that are continuously arranged close as long as heat can be transferred. For example, when the amount of heat generated on the upstream side in one of the reaction vessels is too large, it may be arranged with a gap provided between one of the reaction vessels and the other. According to such an embodiment, the amount of heat transferred between the respective reaction vessels can be reduced, and heat is also released in the gap, so that the temperature can be prevented from rising too much. Thus, it is sufficient that one reaction vessel and the other reaction vessel are arranged so as to be able to transfer heat, and when an interval is provided between them, the temperature distribution generated in the reaction vessel falls within an appropriate temperature range. It may be determined appropriately so as to fall within the range.

In order to arrange one reaction vessel and the other reaction vessel close to each other with a gap provided therebetween, it is preferable to connect the two by a connection member having good thermal conductivity. For example, when disposing the reaction vessels 1A and 1B having the flat shape shown in FIG. 1 close to each other, the surfaces having the largest areas are opposed to each other, and a good thermal conductivity such as stainless steel is provided therebetween. The connection is preferably performed with a plate-shaped connection member made of a material having the material interposed therebetween. According to such an embodiment, heat can be exchanged between the reaction vessels via a connection member having good thermal conductivity, and heat can be released via the connection member.

Further, the air inlet for introducing air into the reaction vessel is provided not only on the upstream side of the reaction vessel located at the most upstream side as in the above-described embodiment, but also for connecting a plurality of reaction vessels to each other. May be provided in the communication part of the. With such a configuration, even if the air is consumed in the reaction vessel located on the upstream side of the communication part and the amount of air supplied to the reaction vessel on the downstream side is insufficient, the air provided in the communication part Since air is newly introduced from the inlet, the selective oxidation reaction in the reaction vessel arranged on the downstream side can sufficiently proceed. In addition, the position of the communication part in which the air inlet is provided and the number of the air inlets may be appropriately determined as needed.

In addition, by applying the above-described CO removing device to a fuel cell system and providing the CO removing device in a fuel gas supply path, the fuel gas in which carbon monoxide is sufficiently reduced can be supplied to the fuel cell system. It can be supplied to the anode of the main body, and battery performance and life can be improved. Further, the whole fuel cell system can be made compact.

[0040]

As described above, according to the CO removing apparatus of the present invention, the temperature difference generated in the reaction vessel can be made smaller than in the prior art, and the temperature difference can be reduced over the range along the gas flow direction in the reaction vessel. The temperature of the catalyst can be kept in an appropriate range. For this reason, the performance of removing carbon monoxide can be improved more than before, and the concentration of carbon monoxide can be lower than before.

Further, since the two consecutive reaction vessels are arranged close to each other as described above, the size of the CO removing device can be made smaller than before, and the size can be reduced.

Further, according to the fuel cell system of the present invention using such a CO removing device, the fuel gas whose carbon monoxide is sufficiently reduced is supplied to the anode of the fuel cell main body, so that the power generation is performed. It is possible to improve the performance and the service life.

[Brief description of the drawings]

FIG. 1 is a perspective view for explaining a schematic configuration of a CO removal device according to an embodiment of the present invention.

FIG. 2 is a front view taken along the line AA in FIG.

FIG. 3 is a characteristic diagram illustrating a temperature distribution along a gas flow direction in the CO removing devices of the example and the comparative example.

FIG. 4 is a system configuration diagram showing a schematic configuration of a fuel cell system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Desulfurizer, 2 ... Reformer, 3 ... CO converter, 4 ... CO removal apparatus, 5 ... Fuel cell main body, 11A, 11B ... Reaction vessel, 12 ... Gas introduction piping, 13 ... Air introduction piping, 14 ...
Communication section, 15: gas discharge pipe, 21, 23 ... supply port, 2
2, 24 ... outlet

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G040 EA03 EA07 EB31 FA06 FB04 FC07 FE03 4G069 AA03 BA01B BA41A BC70B CC32 EA02Y 5H027 AA02 BA01 BA17

Claims (7)

[Claims] 1. A selective oxidation catalyst comprising: a plurality of reaction vessels accommodating a selective oxidation catalyst and connected to each other, wherein a CO-containing gas containing carbon monoxide and air are passed through the plurality of reaction vessels. A CO removal device that selectively oxidizes carbon monoxide in the CO-containing gas by a selective oxidation reaction caused by the upstream part of one of the plurality of reaction vessels and one of the reaction vessels arranged continuously. A CO removal device, wherein a downstream portion is arranged so as to be able to transfer heat to a downstream portion and an upstream portion of the other reaction vessel, respectively. 2. An upstream part and a downstream part of one of the plurality of reaction vessels which are arranged continuously are arranged close to a downstream part and an upstream part of the other reaction vessel, respectively. The CO removal device according to claim 1, wherein 3. The C according to claim 2, wherein the one reaction vessel and the other reaction vessel are connected close to each other by a connecting member having good thermal conductivity.
O removal device. 4. An air inlet for introducing air is provided in at least one of a plurality of communication portions connecting the plurality of reaction vessels to each other. A CO removal device according to any one of the above. 5. The plurality of reaction vessels have a flat shape,
The CO removal apparatus according to any one of claims 1 to 4, wherein the reaction vessels arranged continuously have the surfaces having the largest areas facing each other. 6. The CO removal device according to claim 1, wherein a serpentine gas flow path is formed in each of the plurality of reaction vessels. 7. The CO according to any one of claims 1 to 6,
A fuel cell system comprising a removal device in a fuel gas supply path.