JP2005085534A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell which is started promptly at the time of starting a fuel cell system. <P>SOLUTION: The fuel cell system is equipped with an air compressor 6 for supplying air to an oxygen electrode of a fuel cell stack 7, a carbon monoxide accumulation container 16 for supplying carbon monoxide, and a means which supplies the air and carbon monoxide respectively to the oxygen electrode of the fuel cell stack 7 from the air compressor 6 and the carbon accumulation container 16 at the starting of the fuel cell system and warms up the fuel cell stack by oxidation reaction heat of the carbon monoxide. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polymer electrolyte fuel cell system, and more particularly to a fuel cell system that can be started quickly when starting below freezing.

Conventionally, Patent Document 1 discloses a technique in which hydrogen is supplied to an air electrode of a fuel cell to react with oxygen in order to warm up the fuel cell at startup, and the reaction heat is used to warm up the fuel cell. .
JP 2001-189164 A

  However, in the above invention, water is generated in the air electrode by the reaction of hydrogen and oxygen at the air electrode of the fuel cell, the surface of the catalyst is covered with water or ice, and oxygen does not contact the catalyst. As a result, the fuel cell cannot generate power or the output of the fuel cell is reduced.

  The present invention has been invented to solve such problems, and it is an object of the present invention to suppress the generation of water at the oxygen electrode of the fuel cell when the fuel cell is warmed up and to quickly start up the fuel cell.

  In the present invention, in the fuel cell system, air supply means for supplying air to the oxygen electrode, carbon monoxide supply means for supplying carbon monoxide to the oxygen electrode, and air from the air supply means when the fuel cell system is started. In addition, there is provided means for supplying carbon monoxide also from the carbon monoxide supply means and for warming up the fuel cell stack by reaction heat due to an oxidation reaction between air and carbon monoxide.

  According to the present invention, carbon monoxide and air are supplied to the oxygen electrode of the fuel cell at the time of starting the fuel cell system, and the fuel cell stack is warmed up by the oxidation reaction heat of carbon monoxide. Even at the time of starting below freezing, the fuel cell stack can be started quickly and efficiently.

  The configuration of the first embodiment of the present invention will be described with reference to FIG.

  The fuel cell system according to the first embodiment of the present invention includes a methanol tank 1 that stores methanol, which is a raw material for generating power in the fuel cell stack 7, a water tank 2 that similarly stores water, and heats methanol and water. An evaporator 3 to be evaporated, a steam reforming reactor 4 for reforming methanol and water evaporated in the evaporator 3 into a reformed gas containing hydrogen, and a steam reformer 4 provided downstream of the steam reforming reactor 4 A hydrogen separator / purifier 5 that selectively separates hydrogen in the reformed gas reformed by the reforming reactor 4, and a hydrogen-rich reformed gas by the hydrogen separator / purifier 5 and the air compressor 6 supply the hydrogen gas. Fuel cell stack 7 that generates electric power with the generated air, a carbon monoxide adsorber 14 that adsorbs carbon monoxide contained in the reformed gas separated from hydrogen by the hydrogen separator / purifier 5, and the fuel cell stack 7 Acid A carbon monoxide storage container 16 which is a carbon monoxide storage means for supplying carbon monoxide to the pole, a carbon monoxide sensor 20 which is provided downstream of the carbon monoxide storage container 16 and measures the concentration of carbon monoxide, The combustor 8 supplies heat to the evaporator 3.

  The steam reforming reactor 4 generates reformed gas containing hydrogen by the steam reforming reaction of the methanol and water evaporated by the evaporator 3.

  The hydrogen separator / purifier 5 is provided with a hydrogen separation membrane made of a palladium-silver alloy on the outer surface of a porous alumina substrate tube, and the reformed gas generated in the steam reforming reactor 4 is passed through the hydrogen separation membrane. And a hydrogen separator through which hydrogen selectively permeates from the primary side to the secondary side. The reformed gas containing hydrogen monoxide, carbon monoxide, carbon dioxide, water (steam), and unreacted methanol is discharged from the primary outlet 5a, and is separated from the hydrogen rich material containing a very small amount of carbon monoxide. The reformed gas is discharged from the secondary side outlet 5b.

  In the fuel cell stack 7, air containing oxygen is adjusted to a temperature suitable for reaction by a cooler 9 by an air compressor 6, which is an air supply means for supplying air to the oxygen electrode, and then is supplied to the air electrode via a valve 22. The reformed gas supplied and hydrogen-rich by the hydrogen separator / purifier 5 is adjusted to a temperature suitable for the reaction by the cooler 10 and then supplied to the fuel electrode through the valve 23 to generate electricity.

  The carbon monoxide adsorber 14 adsorbs carbon monoxide in the reformed gas discharged from the primary outlet 5a of the hydrogen separator / purifier 5 and absorbed moisture by the dehumidifier 11 with an adsorbent, that is, absorbs carbon monoxide. This is a carbon monoxide collector to be recovered. As the adsorbent, copper halide, diamine compound, pyridine or a derivative thereof, activated carbon, silica alumina, silica gel and the like are used.

  The combustor 8 is a reformed gas discharged from the primary side outlet 5 a of the hydrogen separator / purifier 5, exhausted hydrogen supplied from the fuel cell stack 7 via the capacitor 26, or the cooler 10 to the fuel electrode of the fuel cell 7. A part of the supplied hydrogen is adjusted by the valve 27 and burned by exhaust air from the fuel cell stack 7. The combustion heat is used to evaporate methanol and water in the evaporator 3.

  In the evaporator 3, the methanol supplied from the methanol tank 1 and the water supplied from the water tank 2 are converted into steam by the heat from the combustor 8, and the methanol and water converted into steam are converted into the steam reforming reactor 4. Is reformed to a hydrogen-rich reformed gas.

  The reformed gas is separated into a gas containing hydrogen and other substances in the hydrogen separator / purifier 5, and the hydrogen is adjusted to a temperature suitable for power generation in the fuel cell stack 7 through the cooler 10 from the secondary side outlet 5b. Thereafter, the fuel is supplied to the fuel electrode of the fuel cell stack 7 through the valve 23. Part of the hydrogen that has passed through the cooler 10 is supplied to the combustor 8 by the valve 27 and burned. The air compressed by the air compressor 6 is adjusted to a temperature suitable for the reaction of the fuel cell stack 7 by the cooler 9 and then supplied to the fuel electrode of the fuel cell stack 7 through the valve 22.

  A part of the reformed gas separated by the hydrogen separator / purifier 5 and discharged from the primary outlet 5a and separated from the hydrogen is absorbed by the dehumidifier 11 and then introduced into the carbon monoxide adsorber 14 through the valve 12. Then, carbon monoxide is adsorbed by the carbon monoxide adsorbent provided in the carbon monoxide adsorber 14. When a certain predetermined carbon monoxide is adsorbed to the carbon monoxide adsorbent during the operation of the fuel cell system, the valves 12 and 13 are closed, the carbon monoxide adsorber 14 and the fuel cell system are shut off, and the valve 25 is opened to the outside. And the suction pump 15 is operated to suck the carbon monoxide adsorbed on the adsorbent, send the carbon monoxide to the carbon monoxide storage container 16, and store the carbon monoxide in the carbon monoxide storage container 16. At this time, the valve 21 is closed, and the pressure in the carbon monoxide storage container 16 becomes high. Thereafter, the valves 12 and 13 are opened, and the remaining reformed gas having adsorbed carbon monoxide is sent to the combustor 8 and burned.

  The valve 21 is opened at the next start-up, particularly at sub-zero temperature start, carbon monoxide stored in the carbon monoxide storage container 16 is mixed into the air supplied from the air compressor 6, and carbon monoxide is obtained by oxygen in the air. Is oxidized in the fuel cell 7. The heat generated at this time is used to warm up the fuel cell stack 7. At this time, the concentration of carbon monoxide is measured by the carbon monoxide concentration sensor 20 provided upstream of the valve 21, the carbon monoxide concentration stored in advance in the controller 24, the amount of air supplied from the air compressor 6, and the fuel cell. The carbon monoxide poisoning of the air electrode of the fuel cell stack 7 can be suppressed and a predetermined output voltage (for example, 0.4 V) or more can be obtained by a relational expression with the stack 7 or a map, and further, the fuel cell stack 7 The amount of air supplied from the air compressor 6 is adjusted so as to warm up the engine.

  Shutoff valves 22 and 23 are provided in the upstream flow paths of the fuel cell stack 7, respectively. By simultaneously opening the shutoff valves 22 and 23, hydrogen and air are simultaneously supplied to the fuel electrode and the oxygen electrode of the fuel cell stack 7. . In the case where hydrogen and air are not supplied to the fuel electrode and the oxygen electrode of the fuel cell stack 7 at the same time, when hydrogen is supplied to the fuel electrode and then air is supplied to the oxygen electrode, hydrogen moves from the fuel electrode to the oxygen electrode. Over occurs and water is produced during the reaction. Further, when hydrogen is supplied to the fuel electrode after air is supplied to the oxygen electrode, the fuel electrode is deteriorated due to lack of hydrogen. Therefore, by providing the shut-off valves 22 and 23 and simultaneously opening the shut-off valves 22 and 23, it is possible to suppress the generation of water in the oxygen electrode and the deterioration of the fuel electrode.

  The effect of 1st Embodiment of this invention is demonstrated.

  Carbon monoxide in the reformed gas generated by the raw material reforming during operation is stored in the carbon monoxide storage container 16, and the carbon monoxide stored from the carbon monoxide storage container 16 at the start-up, especially at the start of below freezing point. Is supplied to the air electrode of the fuel cell stack 7 and the heat generated by the oxidation reaction with the air supplied by the air compressor 6 is used for warming up the fuel cell stack 7, so that the fuel cell system is quickly started up. be able to.

  Oxidation of carbon monoxide can suppress generation of water that causes freezing. Further, since the gas introduced into the carbon monoxide adsorber 14 is removed of moisture in the gas by the dehumidifier 11, the carbon monoxide supplied to the fuel cell stack 7 is sufficiently dry, and further suppresses the generation of water. be able to. Further, valves 22 and 23 are provided upstream of the fuel electrode and the oxygen electrode of the fuel cell stack 7, respectively, and hydrogen and air as fuel gas are simultaneously supplied to the respective electrodes of the fuel cell stack 7 by opening the valves simultaneously. Thus, hydrogen crossover can be prevented, water production at the oxygen electrode can be suppressed, and deterioration of the fuel electrode can be suppressed.

  Since the concentration of carbon monoxide is measured by the carbon monoxide concentration sensor 20 and the amount of air from the air compressor 6 is adjusted according to the concentration, it is possible to prevent the oxygen electrode from being poisoned by carbon monoxide. The voltage drop of the fuel cell stack 7 can be prevented.

  Next, a second embodiment of the present invention will be described with reference to FIG.

  The second embodiment will be described with respect to parts different from FIG.

  In the second embodiment, the carbon monoxide adsorber 30 is provided immediately downstream of the cooler 10, and the methanol sensor 31 is provided downstream of the primary side outlet 5 a of the hydrogen separator / purifier 5.

  The carbon monoxide adsorber 30 adsorbs and removes carbon monoxide slightly contained in the hydrogen-rich reformed gas separated in the hydrogen separator / purifier 5, and the reformed gas having a higher hydrogen concentration is removed from the fuel cell stack. 7 is supplied to the fuel electrode. The adsorbed carbon monoxide is supplied to the air electrode of the fuel cell stack 7 via the suction pump 15 at the next startup.

  The unreacted methanol concentration in the reformed gas discharged from the primary side outlet 5a of the hydrogen separator / purifier 5 is measured by the methanol sensor 31, and when the methanol concentration is stabilized at a predetermined value, the valves 12 and 13 are opened to monoxide. The reformed gas discharged from the primary outlet 5a of the hydrogen separator / purifier 5 is continuously introduced into the carbon adsorber 14 to adsorb carbon monoxide contained in the reformed gas.

  The effect of 2nd Embodiment of this invention is demonstrated.

  The carbon monoxide adsorber 30 removes carbon monoxide in the reformed gas that is discharged from the secondary outlet 5b of the hydrogen separator / purifier 5 and is supplied to the fuel electrode of the fuel cell stack 7. The fuel cell stack 7 can be started efficiently. In addition, the fuel cell stack 7 can be warmed up more quickly by reacting the adsorbed carbon monoxide with air at the time of start-up, in particular at the time of start below freezing.

  The methanol concentration in the reformed gas from which hydrogen discharged from the primary outlet 5a of the hydrogen separator / purifier 5 is separated by the methanol sensor 31 is measured, and the reformed gas is supplied to the carbon monoxide adsorber 14 after the methanol concentration is stabilized. Since carbon monoxide is introduced and the carbon monoxide is adsorbed, the reformed gas having a high methanol concentration is not mixed into the carbon monoxide adsorber 14, and a gas containing hydrogen is mixed into the oxygen electrode of the fuel cell stack 7 at the start-up. Can be prevented.

  Next, a third embodiment of the present invention will be described with reference to FIG.

  The third embodiment will be described with respect to the differences from FIG.

  In the third embodiment, a high-pressure hydrogen cylinder 33 and a carbon monoxide cylinder 32 are provided, and pure hydrogen is supplied to the fuel electrode of the fuel cell without performing fuel reforming.

  Pure hydrogen is supplied from the high-pressure hydrogen cylinder 33 to the fuel electrode of the fuel cell stack 7, and air is supplied from the air compressor 6 to the fuel cell stack 7 to perform a reaction.

  At startup, particularly at below freezing, carbon monoxide is supplied from the carbon monoxide cylinder 32 to the oxygen electrode of the fuel cell stack 7 and is oxidized and heated by the air supplied from the air compressor 6 to warm up the fuel cell stack 7. To do.

  The effect of the third embodiment of the present invention will be described.

  Since carbon monoxide is supplied to the fuel cell stack 7 from the carbon monoxide cylinder 32 at the time of start-up, the carbon monoxide can be supplied quickly and stably, and the fuel cell can be heated and warmed up without generating water. It can be carried out.

  It goes without saying that the present invention is not limited to the above-described embodiments, and includes various modifications and improvements that can be made within the scope of the technical idea.

  The present invention can be used for a fuel reforming type fuel cell system, and can be used for, for example, a fuel cell vehicle that requires particularly quick start performance.

It is a block diagram of 1st Embodiment of this invention. It is a block diagram of 2nd Embodiment of this invention. It is a block diagram of 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Evaporator 4 Steam reforming reactor 5 Hydrogen separation refiner 6 Air compressor 7 Fuel cell stack 8 Combustor 11 Dehumidifier 14 Carbon monoxide adsorber 15 Suction pump 16 Carbon monoxide accumulation container 20 Carbon monoxide concentration sensor 30 Carbon monoxide adsorber 31 Methanol sensor

Claims (5)

In a fuel cell system including a fuel cell stack in which hydrogen is supplied to the fuel electrode and air is supplied to the oxygen electrode,
Air supply means for supplying air to the oxygen electrode; carbon monoxide storage means for storing carbon monoxide supplied to the oxygen electrode;
Means for supplying carbon monoxide from the carbon monoxide accumulating means to the oxygen electrode together with air from the air supply means when starting the fuel cell system, and for warming up the fuel cell stack by heat of oxidation reaction of carbon monoxide; A fuel cell system comprising: A reforming reactor for reforming the raw material into a reformed gas containing hydrogen and carbon monoxide;
A hydrogen separation and purification device that is located downstream of the reforming reactor and separates hydrogen supplied from the reformed gas to the fuel electrode of the fuel cell stack;
A carbon monoxide recovery unit that recovers a part of carbon monoxide contained in the reformed gas separated from hydrogen by the hydrogen separation and purification device,
2. The fuel cell system according to claim 1, wherein carbon monoxide recovered by the carbon monoxide recovery device is stored in the carbon monoxide storage means. A carbon monoxide concentration sensor for detecting a carbon monoxide concentration downstream of the carbon monoxide accumulation means;
3. The fuel cell system according to claim 2, wherein the amount of air supplied from the air supply means for oxidizing carbon monoxide is adjusted based on the detected concentration of monoxide. A detection means for detecting a remaining raw material concentration of the raw material in the remaining reformed gas from which hydrogen has been separated by the hydrogen separation and purification device;
4. The fuel cell system according to claim 2, wherein when the remaining raw material concentration falls below a predetermined concentration, carbon monoxide is recovered by the carbon monoxide recovery device. 5.   5. The fuel cell system according to claim 1, wherein when the fuel cell stack is started, supply of air and hydrogen to the oxygen electrode and the fuel electrode is started at the same time. 6.

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