JP2761066B2 - Solid polymer electrolyte fuel cell device and power generation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel cell device using a solid polymer electrolyte membrane and a power generation method thereof.

(Prior Art) FIG. 2 is a conceptual diagram of a conventional solid polymer electrolyte fuel cell device. The fuel cell body 4 has a structure in which a solid polymer electrolyte membrane is sandwiched between two glass diffusion electrodes, and each fuel cell is separated by a gas separator. First, a methanol raw material is introduced from a tank into a methanol decomposition apparatus 8 to generate a decomposition gas composed of hydrogen and carbon monoxide, and is introduced into a carbon monoxide shift contacting reaction apparatus 9 together with water from a water tank 6, thereby forming Hydrogen and carbon dioxide are generated from carbon and water vapor, and a hydrogen-rich generated gas is introduced into the hydrogen electrode of the fuel cell body 4 through the humidifier 10 to generate power. The cooling water supplied to the reaction device 9 and the fuel cell main body 4 is introduced into the steam expander 12 to expand and recover energy, and at the same time, the coaxial compressor is driven to inhale and pressurize air, and the fuel cell main body 4 is cooled. Pump to oxygen electrode.

The cracked gas flowing out of the above methanol cracker is
Although containing nearly 20% of multiple carbon monoxide, carbon monoxide is considerably removed in a carbon monoxide shift catalytic reactor, but the carbon monoxide shift reaction requires a molar ratio of water vapor to carbon monoxide, for example. , Even if the reaction is carried out under the condition of excess steam such as 3: 1, the limit is to reduce the concentration of carbon monoxide to about 0.2% (2000 ppm). This gas is supplied to the hydrogen electrode of the fuel cell body, Power was being generated at operating temperatures exceeding 200 ° C.

(Problems to be Solved by the Invention) In a fuel cell using a solid polymer electrolyte membrane operated at about 100 ° C., the power generation performance is reduced because the gas diffusion electrode is poisoned by carbon monoxide in hydrogen gas. Although there is a problem, as long as the above carbon monoxide shift reaction is used,
It is difficult to further reduce the concentration of carbon monoxide in hydrogen gas from the above value. Therefore, in order to generate power while minimizing the effect of poisoning, the fuel cell must be operated at a temperature of 200 ° C or higher, generating power.Therefore, it is important to select a solid polymer electrolyte membrane that can withstand this operating temperature. There were restrictions. Also,
At such operating temperatures, the life of the film is necessarily shortened.

According to the study of the present inventors, in order to operate a solid polymer electrolyte fuel cell stably under high power generation performance at 100 ° C. or less, the concentration of carbon monoxide in hydrogen gas supplied to a fuel electrode must be reduced. Although it is necessary to keep the concentration below 10 ppm, there is no carbon monoxide removal apparatus suitable for this purpose.

On the other hand, a solid polymer electrolyte membrane to be incorporated in a conventional fuel cell body must always be kept in a wet state. For this purpose, cooling water has been supplied from the water tank to the fuel cell main body, and water has been supplied to the humidifier to supply water to the hydrogen gas immediately before supply to the fuel cell main body.

However, since the calorific value of the fuel cell greatly fluctuates due to the load fluctuation of the fuel cell, it has been very difficult to adjust the amount of steam to be added.

Therefore, the present invention solves the above problems, and a carbon monoxide removing device for suppressing the carbon monoxide concentration in hydrogen gas to 10 ppm or less, and almost saturated steam at a varying operating temperature is constantly applied to the surface of the electrolyte membrane. A solid polymer electrolyte fuel cell device capable of maintaining a constant wet state of the solid polymer electrolyte membrane even when the load fluctuates and providing stable power generation by providing a humidity control means for holding It seeks to provide a way.

(Means for Solving the Problems) The present invention provides: (1) a fuel cell device that generates hydrogen by supplying hydrogen generated from methanol to a fuel cell body in which a solid polymer electrolyte membrane is sandwiched between two glass diffusion electrodes. , A methanol steam reformer, a carbon monoxide remover, a humidity controller, and the fuel cell main body are sequentially connected to enable supply of hydrogen to a hydrogen electrode of the fuel cell main body, and The wet device is provided with a hydrophobic gas diffusion film, so that the cooling water flowing out of the fuel cell body and the reformed gas flowing out of the carbon monoxide removing device can be contacted via the hydrophobic gas diffusion film. (2) a device for selectively oxidizing and removing carbon monoxide by introducing a small amount of oxygen, and / or
Or a fuel cell device according to the above (1), wherein an electrolytic oxidation device provided with a catalyst electrode having carbon monoxide adsorption performance is used; and (3) methanol is added to the solid polymer electrolyte fuel cell device. In a method of supplying a raw material and generating power, a steam reforming reaction of a methanol raw material is used to generate a reformed gas containing hydrogen as a main component, and reduce the carbon monoxide concentration of the reformed gas to 10 ppm or less. A power generation method characterized by adding steam substantially equilibrium with the cooling water flowing out of the fuel cell main body, supplying the water vapor to the hydrogen electrode of the fuel cell main body, and generating power at an operating temperature in the range of 50 to 100 ° C. is there.

(Operation) FIG. 1 is a conceptual diagram of a solid polymer electrolyte fuel cell of the present invention.

The reformed gas generated by the methanol steam reformer 1 is introduced into a carbon monoxide remover 2 such as a selective oxidizer or an electrolytic oxidizer to reduce the carbon monoxide concentration to 10 ppm or less. The power is adjusted and supplied to the fuel cell main body 4 to generate power. The cooling water is supplied from the water tank 6 to the fuel cell body 4 by the pump 7 to indirectly cool the fuel cell body 4 or provided on the hydrogen electrode side and / or the oxygen side of the gas separator of the fuel cell body 4. It is introduced into the water supply groove to cool the fuel cell body 4 and supply water to the solid polymer electrolyte membrane. The cooling water flowing out of the fuel cell main body 4 is introduced into the humidity control device 3, and substantially saturated steam at the temperature of the cooling water is added to the hydrogen gas. The cooling water flowing out of the humidity controller 3 removes dissolved ions in the ion exchanger 5 and returns to the water tank 6 to prevent the equipment from being corroded by being circulated.

As the carbon monoxide removing device 2, a selective oxidizing device for selectively oxidizing and removing carbon monoxide by introducing a small amount of oxygen, an electrolytic oxidizing device using a catalyst electrode having carbon monoxide adsorption performance, or the like may be used. it can.

In the above selective oxidation apparatus, a catalyst containing 0.1 to 50% by weight, preferably 1 to 10% by weight of gold is used, and the O ₂ / CO molar ratio is adjusted to 0.5 to 5, preferably 1 to 3, and 100 Selectively oxidize below ℃. The catalyst is Fe ₂ O ₃ , CoO, NiO, Al
One or more oxide carriers of the group consisting of ₂ O ₃ , TiO ₂ , ZrO ₂ , SiO ₂ are impregnated with an aqueous solution of chloroauric acid, dried and calcined, or nitrates of the above oxide constituent elements and chloroauric acid Is co-precipitated by neutralizing with an aqueous alkali solution, washed with water, dried and calcined. (See Japanese Patent Application No. 63-304053.) In place of the above catalyst, a carrier such as Al ₂ O ₃
Also, a catalyst supporting an oxide such as Fe, Mn, and Co can be used.

Further, as a catalyst electrode used in the electrolytic oxidation device, a gas diffusion electrode for a fuel cell can be used as it is,
The material may be a platinum group metal, an alloy of a platinum group metal, an oxide of a platinum group metal, or the like. The catalyst electrode is provided with an intermittent energization to electrolytically oxidize adsorbed carbon monoxide and desorb as carbon dioxide.

As the apparatus for removing carbon monoxide of the present invention, a combination of the above apparatuses is preferable. That is, with the restriction of thermodynamic equilibrium, by combining a selective oxidation device suitable for processing high concentration gas of carbon monoxide and an electrolytic oxidation device suitable for processing low concentration gas of carbon monoxide, 10 ppm or less Hydrogen gas having a carbon monoxide concentration can be easily obtained. By incorporating these carbon monoxide removal devices into a solid polymer electrolyte fuel cell, the supply of air to the selective oxidation device can be increased even when the supply amount of hydrogen gas is increased in response to an increase in the load on the fuel cell. By increasing the amount or shortening the regeneration cycle of the electrolytic oxidation apparatus, the amount of carbon monoxide to be removed can be increased, and the hydrogen gas having the above-mentioned carbon monoxide concentration can be supplied stably.

In addition, all of the above carbon monoxide removal devices are 100 ° C.
It can be operated at the following relatively low temperatures, so that purified hydrogen gas can be supplied to the fuel cell without heat exchange without heat exchange, and a solid polymer electrolyte fuel cell that generates power in the temperature range of 50 to 100 ° C And the apparatus can be compactly assembled.

Further, the humidity control device is composed of a gas diffusion film having hydrophobic pores and a base supporting the gas diffusion film. On both sides of the gas diffusion film, the hydrogen gas flowing out of the carbon monoxide removing device and the hydrogen gas flowing out of the fuel cell main body. Cooling water is caused to flow, and the water vapor in the hydrogen gas is adjusted by moving the water vapor through the pores of the gas diffusion film according to the water vapor pressure difference at the temperature of the cooling water.

The solid polymer electrolyte fuel cell of the present invention adopts such a device configuration to reduce the carbon monoxide concentration to 10 pp.
m to the fuel cell body,
Power generation can be performed at an operating temperature of 00 ° C., and even when the load fluctuates, the power generation can be performed with excellent load response, which can cool the fuel cell body and maintain a constant wet state of the solid polymer electrolyte membrane. Made it possible.

(Example) Using the fuel cell device shown in Fig. 1, power was generated from a methanol raw material.

The catalyst used in the selective oxidation device has an atomic ratio of Au to Fe of 5:95.
The mixture of iron nitrate and chloroauric acid is neutralized with an aqueous alkali solution to coprecipitate, and the coprecipitate is washed with water and dried.
It was obtained by firing at ℃. A platinum electrode was used for the electrolytic oxidation device. Further, a water supply groove is provided on the hydrogen electrode side of the gas separator of the fuel cell body to enable cooling and adjustment of moisture.

First, the methanol reformer has a methanol concentration of 160 mol / h.
A mixture of r and 320 mol / hr of water is supplied, H ₂ : 59%, CO ₂ : 19
%, H ₂ O: 21%, CO: 1%, 2 kg of reformed gas at 270 ℃
/ cm ² G. This reformed gas is cooled by a water-cooled cooler to 50
Cooled to ° C. Thereafter, the selective oxidation apparatus filled with the selective oxidation catalyst was cooled at 50 ml of warm water at 50 ° C. at 10 ml / min, and the reformed gas and about 1 Nm ³ / hr of air were introduced to selectively oxidize carbon monoxide. The carbon monoxide concentration was reduced to 100 ppm. This gas was introduced into an electrolytic oxidation apparatus equipped with the following carbon monoxide-adsorbing catalyst electrode to lower the carbon monoxide concentration to 10 ppm or less. The electrodes were regenerated by applying a constant current of 6.0 A and 0.8 V alternately for two seconds at 10 minute intervals. The purified hydrogen gas thus obtained was passed through a humidity control device at a temperature of 70 ° C., a supply rate of 7.2 Nm ³ / hr, and a partial pressure of steam of 0.0
Introduced into the fuel cell at 75 kg / m ² G, and the hot water for cooling
Power generation was performed at 90 ° C. at a supply rate of 5 ml / min. In addition,
The cooling water flowing out of the fuel cell body was introduced into the humidity control device.

(Effect of the Invention) According to the present invention, by employing the above configuration, it is possible to control the humidity of hydrogen gas having a residual carbon monoxide concentration of 10 ppm or less and supply it to the fuel cell main body. It has become possible to operate fuel cells at relatively low temperatures. In addition, even when the load fluctuated, the cooling of the fuel cell body and the replenishment of water to the solid polymer electrolyte membrane could be rapidly performed, and the responsiveness to the load fluctuation could be greatly improved. Further, since the carbon monoxide removing device can be operated at substantially the same temperature as that of the fuel cell body, the compatibility between the two is good, and this greatly contributes to downsizing of the fuel cell device.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a fuel cell device of the present invention, and FIG. 2 is a configuration diagram of a conventional device.

──────────────────────────────────────────────────続 き Continued on the front page (72) Yoshiyuki Takeuchi, Inventor 4-62-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (72) Inventor Masaaki Yanagi 4-chome, Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture No. 6-22 Mitsubishi Heavy Industries, Ltd. Hiroshima Laboratory (56) References Patent 2670146 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 8/04 H01M 8/10 H01M 8 / 06

Claims (3)

(57) [Claims] 1. A fuel cell apparatus for generating electricity by supplying hydrogen generated from methanol to a fuel cell body having a solid polymer electrolyte membrane sandwiched between two gas diffusion electrodes, comprising: a methanol steam reformer; The carbon removing device, the humidity control device, and the fuel cell main body are sequentially connected to enable supply of hydrogen to the hydrogen electrode of the fuel cell main body, and the humidity control device is provided with a hydrophobic gas diffusion film. A cooling water flowing out of the fuel cell main body and a reformed gas flowing out of the carbon monoxide removing device can be contacted via the hydrophobic gas diffusion membrane. 2. An apparatus for selectively oxidizing and removing carbon monoxide by introducing a small amount of oxygen as said carbon monoxide removing apparatus,
The fuel cell device according to claim 1, wherein an electrode oxidizing device provided with a catalyst electrode having a performance of adsorbing carbon monoxide is used. 3. A method for generating electricity by supplying a methanol raw material to a polymer electrolyte fuel cell device, wherein the methanol raw material is subjected to a steam reforming reaction to produce a reformed gas containing hydrogen as a main component. After reducing the concentration of gaseous carbon monoxide to 10 ppm or less, water vapor substantially equilibrium with the cooling water flowing out of the fuel cell body is added, and then supplied to the hydrogen electrode of the fuel cell body, in a temperature range of 50 to 100 ° C. A power generation method, wherein power is generated at an operating temperature.