JPH08180895A - Fuel cell generating device - Google Patents

Abstract

PURPOSE: To prevent the counter flow of a reformed gas by a simple means and effectively protect a generating device from a danger of ignition or explosion in a fuel cell generating device having a carbon monoxide removing device for oxidizing and removing carbon monoxide concentration in the reformed gas. CONSTITUTION: A raw fuel supplying passage and a reformed gas supplying passage for supplying fuel from a tank 10 and pump 12 as raw fuel supplying means to the hydrogen electrode of a fuel cell through a fuel reforming device 14, a carbon monoxide removing device 26 and a water supplying device 18 have check valves 31, 32, 35 for preventing the counter flow of reformed gas. An air supplying passage for supplying air from an air pump 24 as the oxidizing agent supplying means to the carbon monoxide removing device to the carbon monoxide removing device has a safety valve 33 for preventing the counter flow of the air.

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. 2, 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. 2 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 liquid fuel consisting of methanol and an excess amount of water is introduced from a tank 10 into a reforming section 15 in a fuel reforming apparatus 14 by a pump 12 and is reformed by a reforming catalyst in the reforming section. A reformed gas composed of hydrogen and carbon dioxide is generated (CH3OH (g) + H2O (g) → 3
H2 + CO2). The amount of heat required for the reforming reaction, which is an endothermic reaction, is obtained by introducing methanol gas from the methanol tank 20 and air from the air pump 24 into the combustion section 18 in the fuel reformer 14 to catalytically burn the methanol gas. The heat source gas is generated by and is introduced into the reforming section 15. A heater 17 is provided to heat the catalyst filled in the combustion section 18 to the activation temperature.

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 + H2O → H2 + CO).
2). The shift reaction in the shift conversion section 16 can reduce carbon monoxide in the reformed gas to about 1000 ppm.

The reformed gas that has passed through the shift conversion section 16 is introduced into a carbon monoxide removing device 26, and carbon monoxide in the reformed gas is oxidized and removed under the selective oxidation catalyst (CO + 1 / 2O2).
→ CO2). Thereby, the carbon monoxide concentration in the fuel gas introduced into the hydrogen electrode (-) of the fuel cell can be reduced to less than 100 ppm.

The hydrogen-rich reformed gas whose carbon monoxide concentration has been reduced in this way is introduced into the hydrogen electrode (-) of the fuel cell body 30 after being humidified by the water supply device 28.
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.

In such a fuel cell power generator,
The reformed gas remaining in the reformed gas supply line at the time of operation shutdown is flammable, and the hydrogen rich in the reformed gas may explode and react with oxygen. It is necessary to prevent the back flow of quality gas to the fuel reformer.

A conventional method of stopping a fuel cell power generator is to receive a stop command signal, disconnect the electric output system of the fuel cell, cut off the supply of the raw material gas, and instead replace it with an inert gas such as nitrogen gas. Is supplied to stop the reforming reaction in the fuel reformer. The reformed gas remaining in the reformed gas supply line on the upstream side of the fuel reformer is exhausted from the fuel cell while being gradually replaced by the inert gas, and then the combustion part or other It is supplied to a combustion device and burned.

[0010]

However, the method for stopping the fuel cell power generator in the prior art as described above is as follows.
After manual operation of the stop button or activation of the protective device built into the power generator, the controller that received the stop command signal opens and closes each flow control valve to cut off the supply of the raw material gas and start the supply of the inert gas. After outputting a control signal and opening and closing each flow control valve in response to this control signal, replacement with an inert gas gradually progresses. Therefore, during the transmission and reception of the stop command signal and the valve opening / closing control signal, the reformed gas remaining in the reformed gas supply line on the downstream side of the fuel reformer is prevented from flowing backward toward the fuel reformer. Cannot be prevented.

Further, as shown in FIG. 2, a carbon monoxide removing device 26, which oxidizes and removes carbon monoxide using air as an oxidant gas in order to reduce the carbon monoxide concentration in the reformed gas, is installed in the power generator. If included, prevent the mixed gas of the reformed gas and the oxidant gas remaining in the carbon monoxide removal device from flowing back to the air pump 24, and protect the power generation device from the risk of ignition or explosion. Is indispensable, in the above-mentioned conventional technology, until the reformed gas remaining in the reformed gas supply line on the downstream side of the carbon monoxide removing device is replaced with the inert gas, the stop command signal Since a considerable amount of time has passed since the call was sent, the danger of ignition and explosion due to backflow to the air pump cannot be eliminated.

[0012]

Therefore, the present invention solves the above-mentioned problems of the prior art and provides a fuel cell power generator equipped with a carbon monoxide removing device for oxidizing and removing the carbon monoxide concentration in the reformed gas. The purpose is to prevent the reformed gas from flowing backward by a simple means and effectively protect the power generation device from the risk of ignition or explosion.

The present invention devised to achieve the above object is a fuel reformer for reforming a raw fuel from a raw fuel supply means under a reforming catalyst to produce a hydrogen-rich reformed gas. And receiving the reformed gas generated in the fuel reformer and the oxidizing gas from the oxidizing gas supply means to oxidize and remove carbon monoxide in the reformed gas under a selective oxidation catalyst. The carbon monoxide removing device for reducing the carbon monoxide concentration in the reformed gas, and the reformed gas having the carbon monoxide concentration reduced to a predetermined value or less are supplied to the hydrogen electrode through the carbon monoxide removing device. On the other hand, in a fuel cell power generation device having a fuel cell main body in which an oxidizing gas is supplied to the oxidizing electrode to obtain a cell reaction, in an oxidizing gas supply passage from the oxidizing gas supply means to the carbon monoxide removing device. With the oxidant gas backflow prevention means Reformed gas supply passage to the reforming gas backflow prevention means from the fuel reformer to the carbon monoxide oxidizer, characterized in that is provided.

Further, a similar reformed gas is provided in the raw fuel supply passage from the raw fuel supply means to the fuel reformer and / or the reformed gas supply passage from the carbon monoxide remover to the fuel cell body. Backflow prevention means can be provided.

As these backflow preventing means, a directional control such as a lift type check valve having a valve element that moves in parallel, a swing type check valve having a valve element that makes a hinge movement, a ball valve having a spherical valve element, etc. A pressure control valve such as a pressure reducing valve, a safety valve, or a relief valve, which has a structure in which gas naturally escapes from the valve at a certain internal pressure or more, is preferably used.

Particularly, in the oxidizing gas supply passage and the reformed gas supply passage, if the stoppage of the air pump and the fuel reforming device, which are the respective gas supply sources, is delayed, the internal pressure of the reaction tube increases, which is extremely high. These channels are dangerous because
It is preferable to use a pressure control valve rather than a directional control valve.

[0017]

By providing the oxidant gas backflow prevention means and the reformed gas backflow prevention means in the respective supply flow paths, backflow that may occur when an abnormality occurs during operation or when operation is stopped is automatically and immediately prevented. It

[0018]

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. 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), which is a reforming raw material, is contained in a tank 10, and is introduced into a reforming section 15 of a fuel reforming device 14 by a pump 12. To be done. A check valve 31 is provided in the mixed liquid fuel supply line from the pump 12 to the reformer 15 to prevent the mixed liquid fuel from flowing backward from the reformer 15 to the pump 12.

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 in the vaporizing section is introduced onto the reforming catalyst of the reforming section. , Reforming reaction (CH3OH (g) + H2O (g) → 3H2 + C
The reformed gas is generated by O2). The reforming unit 15 is a carrier for the reforming catalyst, and the reforming catalyst made of, for example, Cu / Zn is supported on the reforming unit structure by impregnation, thermal spraying, electrodeposition, sputtering, coating, or the like. The reforming part structure has an activation temperature range of the reforming catalyst of 250 to 30 depending on the heat source gas.
Hold at 0 ° 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 to the adjoining shift conversion section 16, and carbon monoxide is removed by the shift reaction (CO + H2O → H2 + CO2) under the shift conversion catalyst. The carbon monoxide concentration 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 carbon monoxide removing device 26 through the check valve 32. The air pump 24 is used as the oxidant gas.
The air from the air passes through the safety valve 33 and the carbon monoxide removing device 26.
Will be introduced to. A selective oxidation catalyst (Au / α-Fe2O3 / Al2O3) is carried in the carbon monoxide removing device 26, and an oxidation reaction (CO + 1 / 2O2) by the selective oxidation catalyst is carried out.
→ CO2) oxidizes and removes carbon monoxide in the reformed gas into carbon dioxide.

The carbon monoxide removing device 26 is constructed by alternately laminating a catalyst filling layer for passing reformed gas and a cooling layer for passing cooling water controlled at 100 ° C. or lower. The quality gas is always maintained at a low temperature of 100 ° C. or lower from the inlet to the outlet of the carbon monoxide removing device 26. Therefore, the reaction of oxidizing and removing carbon monoxide to carbon dioxide is sufficiently activated by the selective oxidation catalyst, and the carbon monoxide concentration in the reformed gas can be reduced to 10 ppm or less, and further to 10 ppm or less. Become.

The surplus air supplied to the carbon monoxide removing device 26 is exhausted to the atmosphere through the safety valve 34.

The reformed gas with the carbon monoxide concentration reduced in this way passes through the check valve 35, and then passes through the water supply device 28 including a constant temperature water tank and a heater, and then the fuel cell 30.
Is supplied to the hydrogen electrode (-). Since the reformed gas is cooled and humidified in the water supply device 28, the fuel cell is maintained in the optimum operating temperature range of 50 to 100 ° C., and
The electrolyte membrane is replenished with water to maintain its wet state.

Air from the air pump 24 is supplied with oxidant gas to the oxidizing electrode (+) of the fuel cell 30, and reacts with the reformed gas supplied to the hydrogen electrode to obtain power generation. The surplus of the reformed gas supplied to the hydrogen electrode is exhausted through the check valve 36, and the surplus of the air supplied to the oxidizing electrode is exhausted through the safety valve 37.

In the fuel cell power generator configured as described above, the check valve 31 is provided in the feed passage for the raw fuel, and the check valves 32 and 35 are provided in the feed passage for the reformed gas. However, all of these are held in the open position during normal operation and do not hinder the supply of raw fuel and reformed gas. Similarly, the safety valve 33 provided in the air supply passage from the air pump 24 as the oxidant supply means to the carbon monoxide removing device 26, and the safety valve 34 provided in the surplus air discharge passage from the carbon monoxide removing device 26 are also
During normal operation, air supply and excess air discharge are allowed without any interruption. The same applies to the check valve 36 and the safety valve 37 provided in the exhaust passage from the fuel cell 30.

When the operation of the power generator is stopped or some abnormality occurs, these gases (reformed gas, air supplied to the carbon monoxide removing device, surplus air discharged from the carbon monoxide removing device, When attempting to reverse the flow of the exhaust gas (exhaust gas discharged from both electrodes of the fuel cell) through the normal flow path during normal operation, the check valve or safety valve provided in each flow path immediately responds to prevent the reverse flow. Move the valve body to. As a result, the danger of ignition and explosion in the power generator is avoided.

[0030]

According to the fuel cell power generator of the present invention, the backflow of the oxidant gas and the reformed gas at the time of the operation stop or the abnormality occurrence is automatically and immediately prevented. The danger of explosion can be completely eliminated.

Further, by using a check valve or a safety valve as the backflow prevention means, complicated control becomes unnecessary, and safety can be ensured with an extremely simple device configuration.

[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 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 30 Fuel cell 31, 32, 35, 36 Check valve 33, 34, 37 Safety valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Katsuji Tanizaki, 2-19-12 Sotokanda, Chiyoda-ku, Tokyo Equus Research Co., Ltd. (72) Inventor, Choki Ishiko, 2-chome, Sotokanda, Chiyoda-ku, Tokyo No. 12 Equus Research Co., Ltd.

Claims (4)

[Claims] 1. A fuel reformer for reforming a raw fuel from a raw fuel supply means under a reforming catalyst to produce a hydrogen-rich reformed gas, and a fuel reformer produced by the fuel reformer. The oxidizing gas is supplied from the reforming gas and the oxidizing gas supply means to oxidize and remove the carbon monoxide in the reformed gas under the selective oxidation catalyst to reduce the concentration of carbon monoxide in the reformed gas. A carbon monoxide removing device for reducing and a reforming gas having a carbon monoxide concentration reduced to a predetermined value or less through the carbon monoxide removing device is supplied to the hydrogen electrode, while an oxidizing gas is supplied to the oxidizing electrode. In a fuel cell power generation device having a fuel cell main body that obtains a cell reaction by an oxidant gas, a oxidant gas backflow prevention unit is provided in an oxidant gas supply passage from the oxidant gas supply unit to the carbon monoxide removing device. Removing the carbon monoxide from the fuel reformer A fuel cell power generation device, characterized in that reformed gas backflow prevention means is provided in a reformed gas supply flow path to the removal device. 2. A second reformed gas backflow prevention unit for preventing a backflow of reformed gas in the fuel reformer is provided in a raw fuel supply passage from the raw fuel supply unit to the fuel reformer. The fuel cell power generator according to claim 1. 3. The fuel cell power generator according to claim 1, wherein a third reformed gas backflow preventing means is provided in a reformed gas supply passage from the carbon monoxide removing device to the fuel cell main body. . 4. The fuel cell power generator according to claim 1, wherein the backflow preventing means is composed of either a directional control valve or a pressure control valve.