JPH08106913A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE: To reduce the concentration of carbon monoxide in a hydrogen-rich fuel gas supplied to a fuel cell to 10ppm or less. CONSTITUTION: A reformed gas from a fuel reformer 14 is introduced into a carbon monoxide removing unit 26 through a water recovery unit 32, cooling water is circulated to cooling layers of the unit 32 and the unit 26, and a sensor 27 for measuring the temperature of the reformed gas exhausted from the unit 26 is installed. When the temperature of the reformed gas is increased above an activation temperature region of a selected oxidation catalyst carried to the unit 26, a controller 36 controls operation of a circulation pump 34 so as to increase the circulation velocity of cooling water. The reformed gas is cooled by the cooling layers of the unit 32 and the unit 26, and the selected activation catalyst is always kept in the activation temperature region. Excess steam contained in the reformed gas by reaction in a reformer 15 and a modifier 16 is recovered and removed with the water recovery unit 32, and the reformed gas whose carbon monoxide concentration is reduced is humidified with a water supply unit 28, then supplied to a hydrogen electrode of a fuel cell 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generator.

[0002]

2. Description of the Related Art A schematic system configuration diagram of a conventional solid polymer electrolyte fuel cell power generator is shown in FIG. Here, as is well known, the fuel cell main body 30 has a structure in which a solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes and each fuel cell is isolated by a gas separator. Platinum is generally used for the gas diffusion electrode. However, if carbon monoxide is contained in the fuel gas introduced to the hydrogen electrode, the poisoning of platinum may lower the power generation efficiency or make it unstable. Are known. Therefore, in the configuration shown in FIG. 6, the carbon monoxide content in the reformed gas is reduced through the shift reaction in the shift conversion section 16 of the fuel reformer 14 and the oxidation reaction in the carbon monoxide remover 26. I am supposed to.

The structure shown in FIG. 6 will be described below centering on the flow until the reformed gas is introduced into the hydrogen electrode (-) of the fuel cell 30.

A mixed fuel consisting of methanol and an excess amount of water is supplied to a fuel reformer 14 from a tank 10 by a pump 12.
Is introduced into the reforming section 15 inside and is reformed by the reforming catalyst in the reforming section to generate a reformed gas composed of hydrogen and carbon dioxide (CH ₃ OH (g) + H ₂ O (g) → 3H ₂
+ _CO 2). The amount of heat required for the reforming reaction, which is an endothermic reaction, is
The methanol tank 2 is installed in the combustion section 18 in the fuel reformer 14.
Methanol gas from 0 and air from the air pump 24 are introduced to catalytically burn the methanol gas to generate a heat source gas.
Given by introducing to. In order to heat the catalyst filled in the combustion section 18 to the activation temperature, the heater 17
Is provided.

The reformed gas obtained by undergoing the reforming reaction in the reforming section 15 contains a large amount of carbon monoxide of about 1%. Therefore, next, the reformed gas is introduced into the shift conversion section 16 provided in the fuel reforming apparatus adjacent to the reforming section.
In the shift conversion section, the shift reaction by the shift conversion catalyst is performed to generate hydrogen and carbon dioxide from carbon monoxide in the reformed gas and excess steam in the reforming section (CO + H ₂ O → H ₂ + CO).
₂ ).

Although carbon monoxide in the reformed gas is considerably removed by the shift reaction in the shift conversion section 16, the shift reaction is performed under the condition of excess steam such as a molar ratio of steam to carbon monoxide of 3: 1. Even if done below, carbon monoxide concentration of 100
The limit is to reduce it to about 0 ppm.

Therefore, the reformed gas that has passed through the shift conversion unit 16 is introduced into the carbon monoxide removing device 26, and the carbon monoxide in the reformed gas is oxidized and removed under the selective oxidation catalyst, and the hydrogen electrode ( The concentration of carbon monoxide in the fuel gas introduced into
Reduction to less than 0 ppm has been proposed, for example, in Japanese Patent Laid-Open No. 3-203165.

The hydrogen-rich reformed gas with the carbon monoxide concentration reduced in this way is humidified by the water supply device 28 and then introduced into the hydrogen electrode (-) of the fuel cell main body 30,
The electric power is generated by causing a battery reaction with the oxidant gas (air) introduced from the air pump 24 to the oxygen electrode (+). The humidification of the reformed gas maintains the solid polymer electrolyte membrane in the fuel cell main body 30 in a wet state and controls the temperature of the fuel cell to a predetermined operating temperature (around 100 ° C.) to maximize power generation efficiency. It is done to bring out.

[0009]

Carbon monoxide removing device 2
The selective oxidation catalyst supported in 6 means a catalyst in which an activated oxidation reaction selectively acts on constituent molecules according to the activation temperature range. Au / α-Fe ₂ O ₃ / Al ₂ O ₃ is known as a catalyst that selectively promotes the oxidation reaction with carbon monoxide and has excellent reaction efficiency. According to this catalyst, the reformed gas, which is a mixed gas containing hydrogen, carbon dioxide, carbon monoxide, and water, is mixed with 10
In the high temperature range of 0 ° C or higher, the reaction of selectively oxidizing hydrogen to produce water is promoted, but in the low temperature range of 50 to 100 ° C, the reaction of selectively oxidizing carbon monoxide to produce carbon dioxide is promoted. To be done.

Therefore, when utilizing this selective oxidation catalyst for the oxidation removal of carbon monoxide, it is essential to maintain the carbon monoxide removal device 26 carrying the catalyst in a low temperature range of 50 to 100 ° C. However, since the temperature control is not sufficiently performed in the prior art, the carbon monoxide concentration in the reformed gas is reduced to 100 ppm or less, more preferably to about 10 ppm or less, which is a satisfactory low level. It was difficult to do.

Further, the reformed gas contains a large amount of surplus steam in the reforming reaction and shift reaction in the fuel reforming device 14, and this is directly introduced into the carbon monoxide removing device 26. Therefore, there has been a problem that the catalyst surface is wetted and clogging occurs. Furthermore, since the catalyst temperature is maintained at a low temperature as described above, the water vapor once attached to the catalyst surface does not easily evaporate, and the catalyst deterioration is caused to prevent the selective oxidation reaction of carbon monoxide.

[0012]

Therefore, the present invention solves the above-mentioned problems of the prior art and ensures that the carbon monoxide concentration in the hydrogen-rich fuel gas supplied to the fuel cell is 100 p.
It is an object of the present invention to provide a fuel cell power generation device that can be reduced to pm or less, more preferably 10 ppm or less, and thus can improve and stabilize power generation performance.

The present invention, which was devised to achieve such an object, provides a fuel reforming means for reforming a raw fuel gas under a reforming catalyst to produce a hydrogen-rich reformed gas, and the fuel reforming means. The carbon monoxide concentration in the reformed gas is temporarily reduced by reacting carbon monoxide in the reformed gas with water under a shift catalyst to generate hydrogen and carbon dioxide. And a carbon monoxide concentration in the reformed gas secondarily reduced by oxidizing and removing carbon monoxide in the reformed gas after passing through the reforming means under a selective oxidation catalyst. Carbon oxide oxidation removal means, humidification means for humidifying the reformed gas whose carbon monoxide concentration is reduced to a predetermined value or less through these shift conversion means and carbon monoxide oxidation removal means, and reforming humidified by the humidification means Gas is supplied to the hydrogen electrode while oxidizer is present at the oxidizing electrode In a fuel cell power generator having a fuel cell main body that is supplied with gas to obtain a cell reaction, a water recovery means is provided between the shift conversion means and the carbon monoxide oxidation removal means to reform the water recovery means. Circulating means for circulating the gas and circulating the cooling water used for the water collecting means is provided between the water collecting means and the carbon monoxide oxidation removing means.

Temperature control means may be provided to maintain the temperature of the cooling water in the active temperature range of the selective oxidation catalyst used in the carbon monoxide oxidation removal means. The temperature control means includes a temperature sensor that measures the temperature of the reformed gas discharged from the carbon monoxide oxidation removal means, and a controller that receives the measurement result of the temperature sensor and controls the circulation speed of the cooling water by the circulation means. Can be configured as having

[0015]

The carbon monoxide in the reformed gas is 100 ppm or less, particularly preferably 10 pp, due to the shift reaction in the shift conversion means and the oxidation reaction in the carbon monoxide oxidation removal means.
Since the concentration is reduced to m or less and the hydrogen is supplied to the hydrogen electrode of the fuel cell, the desired cell performance can be stably exhibited without poisoning platinum used as an electrode catalyst.

The reformed gas discharged from the shift conversion means contains a large amount of excess steam in the reforming reaction and shift conversion reaction, but must pass through the water recovery means before being introduced into the carbon monoxide oxidation removal means. As a result, the excess water vapor is condensed and recovered, so that it is possible to prevent the surface of the selective oxidation catalyst used in the carbon monoxide oxidation removing means from being wet and causing clogging.

In the water recovery means, since the water recovery layer through which the reformed gas passes is cooled by the cooling layer through which the cooling water passes, surplus steam in the reformed gas is condensed in the water recovery layer and reformed. It is recovered in a drain part provided in the gas downstream part or directly in a cooling water tank in which the cooling water after passing through the cooling layer is recovered. The temperature of this cooling water is adjusted to the activation temperature of the selective oxidation catalyst (100 ° C. or lower),
Since it circulates between the cooling layer of the water recovery means and the cooling layer of the carbon monoxide oxidation removal means, the reformed gas is always maintained at the temperature or less inside the carbon monoxide oxidation removal means, The action of the selective oxidation catalyst is maximally activated.

On the other hand, the reformed gas discharged from the shift conversion means contains a small amount of unreacted methanol in the reforming reaction. This methanol adheres to the selective oxidation catalyst used in the carbon monoxide removing means to cause poisoning, and when supplied to the fuel cell main body, adheres to the electrode components to cause poisoning here as well. Conventionally, this methanol was removed only in the water supply device installed immediately before the fuel gas was supplied to the fuel cell body, but in the present invention,
When the reformed gas passes through the water recovery means, the water and methanol are removed together with the water, so that the amount of residual methanol is reliably reduced to an allowable range after passing through the water supply device.

[0019]

EXAMPLE A system configuration of a solid polymer electrolyte fuel cell power generator according to the present invention will be described with reference to FIG. In addition, the same device as the conventional configuration shown in FIG.
The parts have the same reference numerals.

The liquid methanol from the methanol tank 20 is introduced into the combustion section 18 of the fuel reformer 14 by the pump 22 and the air from the air pump 24 is introduced into the combustion section 18 of the combustion catalyst. The heat source gas is generated by being burned at. The heater 17 is provided to heat the combustion catalyst to the activation temperature.
The heat source is not limited to the above, and for example, the heat source gas may be generated by burning hydrogen gas or liquid methanol with a burner using air as a combustion aid. The heat source gas is used as a heat source for a reforming reaction and a shift reaction in the reforming section 15 and the shift conversion section 16 described later.

A mixed liquid fuel of methanol and water (mixing ratio 1: 1 to 1: 4) as a reforming raw material is contained in a tank 10 and introduced into a reforming section 15 of a fuel reforming device 14 by a pump 12. To be done. Although not shown, the reforming section 15 is provided with a vaporizing section for vaporizing the reforming raw material, and the reforming fuel gas sequentially vaporized by the vaporizing section is introduced onto the reforming catalyst of the reforming section to reform the reforming catalyst. Reaction (CH ₃ OH (g) + H ₂ O (g) → 3
A reformed gas is generated by H ₂ + CO ₂ . Reformer 1
Reference numeral 5 denotes a reforming catalyst carrier, and a reforming catalyst made of Cu / Zn, for example, is carried on the reforming structure by impregnation, thermal spraying, electrodeposition, sputtering, coating or the like. The reforming part structure is within the activation temperature range of the reforming catalyst by the heat source gas.
Hold at 0-300 ° C. The reformed gas produced by the reforming reaction under the reforming catalyst is rich in hydrogen, but contains surplus steam, carbon dioxide, and a trace amount (about 1%) of carbon monoxide.

The reformed gas produced by the reforming reaction is introduced from the reforming section 15 into the adjoining shift conversion section 16 and is monoxidized by the shift reaction (CO + H ₂ O → H ₂ + CO ₂ ) under the shift conversion catalyst. Carbon is removed, and the concentration of carbon monoxide in the reformed gas is reduced to about 1000 ppm. The active temperature range of the shift reaction is 150 to 200 ° C., and the heat source gas is used as the heat source in the shift conversion section.

The reformed gas that has undergone the shift reaction in the shift conversion section 16 is introduced into the water recovery device 32. Water recovery device 32
As shown in FIG. 2, a water recovery layer 39 that allows the reformed gas to pass therethrough and a cooling layer 40 that allows the cooling water at room temperature or lower to pass therethrough are alternately laminated. A cooling water tank 41 for storing the cooling water after passing through the cooling layer 40 is provided at the bottom. The reformed gas is cooled by the cooling water passing through the adjacent cooling layer 40 while passing through the water recovery layer 39, and the excess steam in the reformed gas is condensed into water, and the reformed gas reaches the bottom of the water recovery layer 39. It collects in the cooling water tank 41 from the formed drainage hole 42.

Water recovery layer 3 in the water recovery device 32 of FIG.
9 is formed as a mere space, but as shown in FIG. 3, a thin layer 43 of a water absorbing agent such as silica gel is placed in the cooling layer 4.
It may be formed on the boundary wall surface with 0 by impregnation, coating, or the like.
Alternatively, the water absorbing agent may be filled entirely or partially in the space of the water recovery layer 39. By using the water absorbing agent in this way, the efficiency of condensing and collecting the excess water in the reformed gas can be improved.

Further, as shown in FIG. 4, instead of directly collecting the water obtained by condensing by cooling the reformed gas in the cooling water tank 41 as shown in FIG. 2 or 3, A drain part 44 may be provided adjacent to the bottom of the laminated structure of the water recovery device 32, and the condensed water collected at the bottom of the water recovery layer 39 may be recovered by the drain part 44. In the embodiment shown in FIG. 4, the water absorbing agent 45 is filled in the entire space of the water collecting layer 39, but the water absorbing agent 45 is partially (for example, only in the lower space portion in contact with the drain portion 44) in the water collecting layer 39. It may be filled, or the water recovery layer may be formed as a mere space as shown in FIG. 2, or a thin layer of a water absorbing agent may be formed on the wall surface of the water recovery layer as shown in FIG. Of course.

The cooling water is circulated by the circulation pump 34 between the cooling layer 40 of the water recovery device 32, the cooling water tank 41 and the cooling layer 38 (FIG. 5) in the carbon monoxide removing device 26. A temperature sensor 27 is attached to the reformed gas outlet of the carbon monoxide removing device 26 to constantly measure the reformed gas temperature at the outlet, and the measurement signal is sent to the controller 36. When it is detected that the reformed gas temperature at the outlet has risen to, for example, 100 ° C. or more, the controller 36 controls the circulation pump 34 to increase the circulation speed of the cooling water and improve the cooling effect. In this way, the reformed gas that has passed through the shift conversion unit 16 of the fuel reformer 14 is cooled by the cooling water circulating in the water recovery unit 32, and excess water and unreacted methanol are removed.

The reformed gas cooled by the water recovery device 32 is then introduced into the carbon monoxide removing device 26 and carried by the selective oxidation catalyst (Au / α-Fe2O3).
/ Al2O3) oxidation reaction (CO + 1 / 2O2 → C
O2) oxidizes and removes carbon monoxide in the reformed gas to carbon dioxide. As shown in FIG. 5, the carbon monoxide removing device 26 has a catalyst packed bed 37 that allows the reformed gas to pass through.
And cooling layers 38 that allow cooling water to pass therethrough are alternately laminated. As described above, the cooling water whose temperature is controlled to 100 ° C. or lower by the controller 36 is circulated by the circulation pump 34.
Since the tank of the water recovery device 32 and the cooling layer 38 of the carbon monoxide removing device 26 are circulated through the reforming gas, the reformed gas is always 100 ° C. or less from the inlet to the outlet of the carbon monoxide removing device 26. Maintained at low temperature. Therefore, the reaction of oxidizing and removing carbon monoxide into carbon dioxide is sufficiently activated by the selective oxidation catalyst, and the concentration of carbon monoxide in the reformed gas is 10 ppm or less, further 10 ppm.
It becomes possible to reduce to the following.

The reformed gas with the carbon monoxide concentration reduced in this way is supplied to the hydrogen electrode (-) of the fuel cell 30 via the water supply device 28 consisting of a constant temperature water tank and a heater. Since the reformed gas is cooled and humidified in the water supply device 28, the fuel cell is kept in the optimum operating temperature range of 50 to 100 ° C., and the electrolyte membrane is rehydrated to maintain its wet state. It

[0029]

According to the present invention, the water recovery device is provided between the fuel reforming device and the carbon monoxide removing device by the selective oxidation catalyst in the reformed gas supply path to the hydrogen electrode of the fuel cell. Since the reformed gas discharged from the reformer is cooled to the active temperature range of the selective oxidation catalyst by the water recovery device, the carbon monoxide is efficiently removed by oxidation in the carbon monoxide removing device. It can be supplied to the fuel cell hydrogen electrode with a low concentration of 10 ppm or less.

In addition, since the reformed gas that has undergone the reforming reaction and the shift reaction in the fuel reforming apparatus contains excess steam, the surplus steam is removed by passing through the water recovery apparatus. The surface of the selective oxidation catalyst carried by the carbon monoxide removing device is prevented from being wetted and clogged, and the catalyst is not deteriorated.

Furthermore, since unreacted methanol in the reformed gas is also removed while passing through the water recovery device, the selective oxidation catalyst of the carbon monoxide removal device and the electrode components of the fuel cell are not poisoned.

[Brief description of drawings]

FIG. 1 is a schematic system configuration diagram of a solid polymer electrolyte fuel cell power generator according to the present invention.

FIG. 2 is a perspective view schematically showing a configuration example of the water recovery device in FIG.

FIG. 3 is a perspective view schematically showing another configuration example of the water recovery device.

FIG. 4 is a perspective view schematically showing still another configuration example of the water recovery device.

5 is a perspective view schematically showing a configuration example of a carbon monoxide removing device in FIG.

FIG. 6 is a schematic system configuration diagram of a solid polymer electrolyte fuel cell power generator according to a conventional technique.

[Explanation of symbols]

 14 Fuel reforming device 15 Reforming unit 16 Metamorphic unit 26 Carbon monoxide removing device 27 Temperature sensor 30 Fuel cell 32 Water recovery device 34 Circulation pump 36 Controller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuji Tanizaki 2-19-12 Sotokanda, Chiyoda-ku, Tokyo Within Equus Research Co., Ltd. (72) Inventor Shinya Ohara 2-19, Sotokanda, Chiyoda-ku, Tokyo No. 12 Stock company Equus Research

Claims (5)

[Claims] 1. A fuel reforming means for reforming a raw fuel gas under a reforming catalyst to produce a hydrogen-rich reformed gas, and a reformed gas in the reformed gas produced by the fuel reforming means. A conversion means for temporarily reducing the carbon monoxide concentration in the reformed gas by reacting carbon monoxide with water under a conversion catalyst to generate hydrogen and carbon dioxide, and after passing through the conversion means Of carbon monoxide in the reformed gas by oxidizing and removing the carbon monoxide in the reformed gas under a selective oxidation catalyst to secondarily reduce the carbon monoxide concentration in the reformed gas; Humidifying means for humidifying the reformed gas in which the carbon monoxide concentration is reduced to a predetermined value or less via the carbon oxide oxidation removing means,
In the fuel cell power generator, the reforming gas humidified by the humidifying means is supplied to the hydrogen electrode while the oxidizing electrode is supplied with the oxidant gas to obtain a cell reaction. Water recovery means is provided between the carbon monoxide oxidation removal means and the reformed gas is circulated through the water recovery means, and cooling water is provided between the water recovery means and the carbon monoxide oxidation removal means. A fuel cell power generation device comprising a circulation means for circulation. 2. The fuel cell according to claim 1, further comprising temperature control means for maintaining the temperature of the cooling water in the active temperature range of the selective oxidation catalyst used in the carbon monoxide oxidation removal means. Power generator. 3. The temperature control means measures the temperature of the reformed gas discharged from the carbon monoxide oxidation removal means, and the cooling water cooled by the circulation means in response to the measurement result of the temperature sensor. The fuel cell power generator according to claim 2, further comprising a controller that controls a circulation speed. 4. The fuel cell power generator according to claim 3, wherein the operating temperature of the carbon monoxide oxidation removal device is maintained at 100 ° C. or lower by the temperature control means. 5. The fuel cell power generator according to claim 1, wherein excess water vapor and unreacted methanol in the reformed gas are removed by the water recovery means.