JPH0773894A - Fuel cell power generator - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] A solid polymer electrolyte membrane for a fuel cell with a simple structure that does not use a pump to supply water to a fuel cell or a reformer, and that simplifies and reduces the weight of the entire device. Can be humidified, and at the same time, the reformed fuel gas supplied to the fuel electrode of the fuel cell can be lowered to a suitable temperature. In a fuel cell power generator 10 having a fuel cell in which a fuel electrode and an oxidizing electrode are arranged on both sides of an electrolyte, a condenser 24 for condensing water vapor contained in exhaust gas from the oxidizing electrode of the fuel cell 10. And the control means 25 for forcibly discharging the condensed water collected from the condenser 24 in accordance with the rise in the room pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell, particularly a solid polymer type fuel cell, that is, a solid polymer type fuel cell having a solid polymer membrane such as perfluorocarbon sulfonic acid (trade name Nafion manufactured by DuPont, USA) as an electrolyte. The present invention relates to a power generator using a fuel cell.

[0002]

2. Description of the Related Art A polymer electrolyte fuel cell using a solid polymer membrane such as Nafion as an electrolyte has recently attracted attention as a fuel cell particularly suitable for mounting on a vehicle because of its small size and light weight and high output density. Has been done.

A gas containing generated steam and unreacted air is discharged from the oxidizing electrode of the fuel cell. A steam separator for supplying the exhaust gas to the condenser to recover the condensed water and further separating the condensed water into gas and water is provided. The gas and water separated by the steam separator are supplied to the reformer and the fuel cell via a pump.

Further, in order to exhibit ionic conductivity suitable for use as an electrolyte, it is necessary that the solid polymer membrane is not dried. A method described in JP-A-3-269955 is known as a method for humidifying a solid polymer film. According to this conventional technique, the carburetor a and the humidifier b are provided in the fuel supply system that supplies the reformed fuel gas that has passed through the reformer to the fuel electrode of the fuel cell, and the air pressurized by the compressor is used as the fuel. A vaporizer c and a humidifier d are provided in the air supply system that supplies the oxidizing electrode of the battery. The water sent to the vaporizer c from the tank that stores the water generated in the oxidizing electrode of the fuel cell is vaporized by using the high temperature air as a heat source by pressurization, and this water vapor is further fed to the vaporizer a. , Is sufficiently vaporized using the exhaust gas from the reformer and the reformed fuel gas as heat sources. By introducing the steam from the vaporizer a into the humidifiers b and d, both the reformed fuel gas and the air supplied to the fuel cell are made to contain a sufficient amount of steam, and the solid polymer membrane is humidified. It

The advantage of this prior art is that, at the same time as humidifying the solid polymer membrane, the reformed fuel gas and air, which are at a considerably high temperature at the beginning of the supply system, are supplied to the operating temperature of the fuel cell (about 80 to 100 ° C.). It is possible to supply to the fuel cell in a state of being lowered to a temperature close to). That is, the high-temperature reformed fuel gas obtained through the reformer has a temperature of about 100 ° C. + α due to heat exchange in the vaporizer a, and the air that has been compressed by the compressor and has a high temperature is heat exchange in the vaporizer c. Since the temperature is lowered, the ionic conductivity of the solid polymer membrane in the operated fuel cell is exhibited well, and the power generation efficiency is improved.

[0006]

Since a large amount of water is required in a power generator having a fuel cell and a reformer, it is necessary to consider the water balance of the system as a whole. As described above, it is possible to condense the exhaust gas from the oxidizing electrode of the fuel cell with the condenser and supply the condensed water to the fuel cell and the reformer using the steam separator and the pump. However, this leads to a complicated and heavy device.

Although the above-mentioned prior art disclosed in Japanese Patent Laid-Open No. 3-269955 has a great advantage, on the other hand, a vaporizer and a humidifier are provided in both the reformed fuel gas supply system and the air supply system. It is necessary to provide a complicated circulation system between the carburetor, the humidifier, and related devices, which also causes a problem that the entire fuel cell system is complicated.

[0008]

According to the present invention, water is supplied to a fuel cell or a reformer in a fuel cell power generation apparatus without using a pump, and the configuration of the entire apparatus is simplified and the weight is reduced. With the goal.

Another object of the present invention is to humidify a solid polymer electrolyte membrane of a fuel cell with a simple structure,
At the same time, it is an object of the present invention to provide a polymer electrolyte fuel cell power generator having a novel structure, which can lower the temperature of the reformed fuel gas supplied to the fuel electrode of the fuel cell to a suitable temperature.

That is, according to the present invention, a fuel cell in which a fuel electrode and an oxidizing electrode are arranged on both sides of an electrolyte, and a hydrogen rich gas to be supplied to the fuel electrode of the fuel cell by a reforming reaction using a liquid fuel as a raw material In a fuel cell power generator having a reformer that generates various reformed gases, a condenser that condenses water vapor contained in the exhaust gas from the oxidizing electrode of the fuel cell and condensed water that is collected from the condenser are compressed to room pressure. And a control means for forcibly discharging in accordance with the rise of the temperature.

The control means includes a water storage chamber for storing the condensed water recovered from the condenser, a float that moves up and down according to the water surface level in the water storage chamber, and a float when the water surface level in the water storage chamber exceeds a certain level. It is preferable to have an exhaust valve that is closed by means of a water discharge valve and a drain valve that forcibly discharges water by increasing the gas internal pressure of the water storage chamber when the exhaust valve is closed by the float.

The present invention also provides a fuel cell in which a fuel electrode and an oxidation electrode are joined on both sides of a solid polymer electrolyte membrane and a reforming reaction using a liquid fuel as a raw material to supply it to the fuel electrode of the fuel cell. In a solid polymer electrolyte fuel cell power generation device having a reformer that generates a hydrogen-rich reformed gas that should be, a bubbling chamber is interposed in the reformed gas supply path from the reformer to the fuel electrode of the fuel cell. While passing the reformed gas from the reformer in the bubble state into the water in the bubbling chamber, heat is exchanged between the reformed gas and water to cool the reformed gas and heat the water to generate steam. A condenser configured to supply a cooled mixture of reformed gas and steam to a fuel electrode of a fuel cell and condensing steam contained in exhaust gas from an oxidizing electrode of the fuel cell; Condensed water recovered from the chamber Characterized in that a control means for forcibly discharged in response to an increase in pressure.

The water discharged from the control means can be supplied to the bubbling chamber.

The control means includes a water storage chamber for storing condensed water recovered from the condenser, a float that moves up and down according to the water surface level in the water storage chamber, and a float when the water surface level in the water storage chamber exceeds a certain level. It is preferable that the exhaust valve is configured to include an exhaust valve that is closed by a water discharge valve and a drain valve that forcibly discharges water by increasing the gas internal pressure of the water storage chamber when the exhaust valve is closed by the float. is there.

In this case, the gas discharged through the exhaust valve can be supplied to the reformer, and the water discharged through the drain valve can be supplied to the bubbling chamber.

In order to further improve the efficiency of heat exchange in the bubbling chamber, heating means for heating water in the bubbling chamber can be provided. This heating means can use the combustion exhaust gas and the generated steam from the combustion section used for the reforming reaction in the reformer as heat sources. Preferably, a second bubbling chamber that is partitioned adjacent to the bubbling chamber is provided,
The water in the bubbling chamber is heated via the water that is heated by the combustion exhaust gas from the combustion section passing through the water in the second bubbling chamber in a bubble state. Further, the water vapor generated from the combustion section is liquefied by passing through the second bubbling chamber and heats the water in the bubbling chamber through the water that is heat-recovered.

By supplying unreacted reformed gas discharged from the fuel electrode of the fuel cell and air discharged from the oxidizing electrode to the combusting section and combusting, combustion exhaust gas used as a heat source of the heating means is generated. You can

Further, a water amount adjusting means for controlling the amount of water in the bubbling chamber can be provided.

[0019]

The exhaust gas from the oxidizing electrode of the fuel cell is fed into the condenser, and the condensed water is recovered from the steam contained in the exhaust gas. The condensed water is then supplied to the control means, is forcibly discharged according to the rise in the room pressure, and is supplied to the fuel cell, the reformer and other necessary parts.

The control means has a water storage chamber, a float, an exhaust valve, and a drain valve, and the exhaust valve is closed by the float when the condensed water level in the water storage chamber becomes a certain level or higher. When the exhaust valve is closed, the gas internal pressure in the water storage chamber rises and the water is forcibly drained through the drain valve.

The reformed gas from the reformer has a high temperature of about 250 ° C. at the reformer outlet, and the high temperature reformed gas passes through the water in the bubble state in the bubbling chamber, so that the temperature near 100 ° C. And is supplied to the fuel electrode as having a suitable temperature close to the operating temperature of the polymer electrolyte fuel cell. At the same time, the water in the bubbling chamber is heated to generate steam, and this steam is supplied to the fuel electrode together with the reformed gas, so that the solid polymer membrane electrolyte is humidified and exhibits good ionic conductivity.

[0022]

1 shows a power generator according to an embodiment of the present invention. This power generator is based on the above-mentioned Nafion or PSSA-P.
Ion-exchangeable solid polymer resin membranes such as VA (polystyrene sulfonic acid-polyvinyl alcohol copolymer) and PSAA-EVOH (polystyrene sulfonic acid-ethylene vinyl alcohol copolymer) are used as electrolytes, and fuel electrodes are provided on both sides of this electrolyte. A unit cell formed by joining an oxidizing electrode has a polymer electrolyte fuel cell 10 having a structure in which a plurality of unit cells are stacked with a separator interposed therebetween. Hydrogen gas and water vapor are supplied to the fuel electrode of the fuel cell 10 through a reformer and a bubbling chamber 18, which will be described later, and air is supplied to the oxidizing electrode.

The reformer 12 includes a reforming section for producing a hydrogen-rich reformed gas (mainly hydrogen gas containing carbon dioxide gas and other contaminants) to be supplied to the fuel electrode of the fuel cell 10. 14 and a combustion unit 16 that generates combustion exhaust gas as a heat source for the reforming reaction in the reforming unit 14. A liquid fuel such as methanol is supplied to the reforming unit 14, is vaporized by a vaporizer provided in the reforming unit 14 as required, and is then steam reformed under a known catalytic action.

The reformed gas obtained by the reforming reaction in the reforming section 14 is sent from the reformer 12 to the water storage bubbling chamber 18. The reformed gas at the outlet of the reformer 12 has about 25
Although it has a high temperature of about 0 ° C., heat is exchanged while passing through the water in the bubbling chamber 18 while rising as bubbles.
It is cooled to about 0 ° C. On the contrary, the water in the bubbling chamber 18 is heated by the hot reformed gas to generate steam. That is, the reformed gas and steam at a temperature of about 100 ° C. are delivered from the bubbling chamber 18 and supplied to the fuel electrode of the fuel cell 10.

Unreacted reformed gas and steam are discharged from the fuel electrode of the fuel cell 10, and unreacted air is discharged from the oxidizing electrode together with the generated steam. The reformed gas and steam discharged from the fuel electrode are traps 2 having a water tank.
2 to the reformer 12 after the steam is separated therefrom.
Is supplied to the combustion section 16. The water in the trap 22 is supplied to the reforming section 14 of the reformer 12 to generate the steam necessary for the reforming reaction, and the second bubbling chamber 2 to be described later.
Used to replenish water to zero. On the other hand, the exhaust gas from the oxidizing electrode is condensed into water and high temperature air by the control means 25 after the condensed water is recovered from the steam in the exhaust gas by the condenser 24, and the water is bubbling chamber 18 through the water supply line 26. Is supplied to the combustion section 16 of the reformer 12 through the air supply line 27 and is consumed as combustion fuel.

The control means 25 has the structure shown in FIG. 2, and has a water storage chamber 28 for storing the condensed water W from the condenser 24. A float 29 that moves up and down according to the water level of the condensed water W is provided in the water storage chamber 28, a drain valve 30 that communicates with the water supply line 26 is located below, and an exhaust valve 31 that communicates with the air supply line 27 is located above. It is provided.

When a large amount of condensed water W is stored in the water storage chamber 28 beyond a predetermined water level, the float 29 closes the exhaust valve 31. When the exhaust valve 31 is closed, exhaust to the exhaust line 27 is stopped, so the condenser 24
The internal pressure of the water storage chamber 28 rises due to the gas sent from
As a result, the drain valve 30 is opened, and drainage is performed through the drain line 26. When the water level in the water storage chamber 28 drops below a predetermined level due to drainage, the exhaust valve 31 is opened again and exhaust to the exhaust line 27 is performed. This reduces the internal pressure and closes the drain valve 30 again.

In the illustrated embodiment, water is supplied to the bubbling chamber 18 through the drainage line 26, but instead of or together with this, another place requiring water, for example, the reformer 12 is used. It may be configured to supply to the reforming unit 14 of.

As described above, the unreacted reformed gas in the exhaust gas from the fuel electrode of the fuel cell 10 is supplied to the combustion section 16 of the reformer 12 through the trap 22 and discharged from the oxidizing electrode. The air to be supplied is supplied via the condenser 24 and the control means 25. The combustion exhaust gas obtained by burning the mixture of the unreacted reformed gas and air in the combustion section 16 is given to the reforming section 14 and used as a heat source for the reforming reaction as is well known. However, part of it is also used as a heat source for raising the temperature of the water in the bubbling chamber 18 to near 100 ° C.

In the illustrated embodiment, a second bubbling chamber 20 is provided in contact with the bubbling chamber 18 in order to efficiently heat the water in the bubbling chamber 18 to such a temperature, and the combustion section 1
Part of the combustion exhaust gas from 6 is in this second bubbling chamber 2
Supplied to zero. Similar to the bubbling action in the bubbling chamber 18, the water temperature efficiently rises while the combustion exhaust gas rises in water in the second bubbling chamber 20 in a bubble state, and the water temperature changes to the water in the bubbling chamber 18. Heat is transferred. The combustion exhaust gas passing through the water in the second bubbling chamber 20 is exhausted to the outside. Second bubbling chamber 2
The water in the trap 22 is mainly used for supplying water to 0, but the water vapor contained in the combustion exhaust gas is also liquefied while passing through the water in the second bubbling chamber 20. The overflow water from the second bubbling chamber 20 is trapped in the trap 22.
It is sent to the reforming section 14 together with the water from.

As described above, the bubbling chamber 1 is provided between the fuel electrode of the fuel cell 10 and the reforming section 14 of the reformer 12.
8 is provided and the reformed gas obtained from the reforming section 14 is allowed to pass through the water in the bubbling chamber 18 as bubbles, so that the heat exchange between the high temperature reformed gas and the water in the bubbling chamber is efficiently performed. Then, the water vapor obtained by heating the water in the bubbling chamber and the reformed gas lowered to an appropriate temperature near 100 ° C. are supplied to the fuel electrode. The water vapor humidifies the electrolyte of the fuel cell through the fuel electrode.

Efficient heat exchange is demonstrated by passing gas bubbles into water by the following calculation.

The gas bubbles in the water are subject to buoyancy due to the density difference, and the floating speed of the gas (3H ₂ + CO ₂ ) bubbles can be calculated from the Stokes resistance equation as shown in the following formula 1.

[Equation 1] Here, assuming that the water temperature is 300 K and the water pressure is 0.1 MPa (condition 1), the water temperature is 380 K, the water pressure is 0.1 MPa (condition 2) and the water temperature is 380 K and the water pressure is 0.2 MPa (condition 3). Then ρw (kg / m ³ ) = 1
000, ρg (kg / m ³ ) = 0.505, ηw (Pa
・ S) = 854, and in condition 2 ρw = 100
0, ρg = 0.398, ηw = 263, and under condition 3, ρw = 1000, ρg = 0.696, ηw = 26.
Therefore, when these numerical values are applied to the equation 1 with the bubble diameter of 2 mm, the floating speed V1 = 2.5 m / s under the condition 1 and the floating speed V2 = 8.3 m / s under the condition 2 At that time, the levitation speed V3 = 8.3 m / s. From this result, it is understood that the gas bubble velocity increases as the water temperature increases, but is not affected by the pressure change. Next, since the amount of heat per gas sphere having a bubble diameter of 2 mm is calculated by the following mathematical formula 2, 450K, 0.1M
Physical properties ρg (kg / m ³ ) = 0.3351 of mixed gas (3H2 + CO2) under Pa condition, Cp (KJ / k)
When g · K) = 11.12 is applied to Equation 2, the gas carry-in heat quantity Qg = 1.87 × 10 ⁻⁵ KJ.

[Equation 2] Further, the heat radiation amount per one gas sphere is obtained by the following mathematical formula 3.

[Equation 3] Here, the heat transfer coefficient when the gas sphere at a temperature of 450 K passes through water at 373 K under a pressure of 0.1 MPa is represented by Whi
The heat transfer coefficient h = 90700 w / m ² · K is obtained by the Taker's empirical formula. Therefore, from the equation Qg = Q′g · t, it is understood that the heat dissipation time t of the gas sphere is t = 2.2 × 10 ⁻⁴ sec, and the gas sphere is instantly cooled in water. Also, the required liquid level height h = V required for heat dissipation
T = 1.83 × 10 ⁻³ m, and it is understood that a very small amount of water is sufficient. As described above, a small amount of water may be present in the bubbling chamber 18, but in order to control the temperature of the reformed gas and the amount of water vapor supplied to the fuel electrode of the fuel cell 10 within a suitable range, a certain fixed range is required. It is desirable that the amount of water is always maintained. For this reason, although the float 19 is provided in the bubbling chamber 18 in the illustrated embodiment, in consideration of the water balance of the entire system, it is necessary to collect the reaction product water contained in the exhaust gas from the oxidizing electrode. . Therefore, the recovered water is guided to the bubbling chamber 18 via the condenser 24, and the liquid level difference between the bubbling chambers 18 and 20 is adjusted by the float 19. Regarding the buoyancy of the float 19, the diameter of the conducting pipe, that is, the float volume is determined in consideration of the fact that the pressure in the bubbling chamber 18 is higher than that in the second bubbling chamber 20. The second bubbling chamber 2
Although it is conceivable to install a float on the 0 side, since the atmosphere exists on the second bubbling chamber 20 side and this atmosphere may enter the bubbling chamber 18, it may enter the combustion range of hydrogen. 19 is preferably installed on the side of the bubbling chamber 18.

According to the present invention, by providing the control means, it is possible to perform the action of combining the conventional steam-water separator and the pump, and it is possible to simplify and reduce the weight of the entire apparatus. Further, by providing the bubbling chamber, the reformed gas is cooled to an appropriate temperature and at the same time water vapor is obtained, so that the solid polymer electrolyte membrane of the fuel cell can be humidified.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a polymer electrolyte fuel cell power generator according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of control means in FIG.

[Explanation of symbols]

 10 Solid Polymer Fuel Cell 12 Reformer 14 Reforming Section 16 Combustion Section 18 Bubbling Chamber 20 Second Bubbling Chamber 22 Trap 24 Condenser 25 Control Means 28 Water Storage Chamber 29 Float 30 Drain Valve 31 Exhaust Valve

Claims (12)

[Claims] 1. A fuel cell power generator having a fuel cell in which a fuel electrode and an oxidizing electrode are arranged on both sides of an electrolyte, and a condenser for condensing water vapor contained in exhaust gas from the oxidizing electrode of the fuel cell. And a control means for forcibly discharging the condensed water collected from the condenser in accordance with an increase in the room pressure. 2. A water storage chamber for storing condensed water recovered from the condenser, a float that moves up and down according to a water surface level in the water storage chamber, and a water surface level in the water storage chamber above a certain level. When the exhaust valve is closed by the float, an exhaust valve, and when the exhaust valve is closed by the float, a drain valve forcibly discharging water by increasing the gas internal pressure of the water storage chamber is included. The fuel cell power generator according to claim 1, wherein 3. A fuel cell in which a fuel electrode and an oxidation electrode are joined to both sides of a solid polymer electrolyte membrane, and hydrogen to be supplied to the fuel electrode of the fuel cell by a reforming reaction using a liquid fuel as a raw material. In a solid polymer electrolyte fuel cell power generator having a reformer that produces a rich reformed gas, a bubbling chamber is interposed in a reformed gas supply path from the reformer to a fuel electrode of the fuel cell, While passing the reformed gas from the reformer into water in the bubbling chamber in a bubble state, heat is exchanged between the reformed gas and water to cool the reformed gas and heat the water to generate steam. A condenser configured to supply the produced and cooled mixture of reformed gas and steam to the fuel electrode of the fuel cell, and to condense steam contained in the exhaust gas from the oxidizing electrode of the fuel cell. And the condenser A solid polymer fuel cell power generator comprising: a control means for forcibly discharging the collected condensed water according to an increase in the room pressure. 4. The polymer electrolyte fuel cell power generator according to claim 3, wherein the water discharged from the control means is supplied to the bubbling chamber. 5. The water storage chamber for storing condensed water recovered from the condenser, the float that moves up and down according to the water surface level in the water storage chamber, and the water surface level in the water storage chamber above a certain level. When the exhaust valve is closed by the float, an exhaust valve, and when the exhaust valve is closed by the float, a drain valve forcibly discharging water by increasing the gas internal pressure of the water storage chamber is included. The polymer electrolyte fuel cell power generator according to claim 3, wherein 6. The gas discharged through the exhaust valve is supplied to the reformer, and the water discharged through the drain valve is supplied to the bubbling chamber. Polymer electrolyte fuel cell power generator. 7. A heating means for heating water in the bubbling chamber is provided.
The polymer electrolyte fuel cell power generator of any one of. 8. The solid polymer fuel cell power generation according to claim 7, wherein the heating means uses combustion exhaust gas and steam generated from a combustion section used for a reforming reaction in the reformer as heat sources. apparatus. 9. The heating means comprises a second bubbling chamber which is partitioned adjacent to the bubbling chamber,
9. The solid polymer according to claim 8, wherein the combustion exhaust gas from the combustion unit heats the water in the bubbling chamber through the water that is heated by passing through the water in the second bubbling chamber in the form of bubbles. Type fuel cell power generator. 10. The heating means heats the water in the bubbling chamber through the water which is liquefied by the steam generated from the combustion section passing through the second bubbling chamber and is heat-recovered. The polymer electrolyte fuel cell power generator according to claim 9. 11. An unreacted reformed gas discharged from a fuel electrode of the fuel cell and air discharged from an oxidizing electrode are supplied to the combustion section and burned in the combustion section to generate combustion exhaust gas. 11. The polymer electrolyte fuel cell power generator according to claim 10. 12. The polymer electrolyte fuel cell power generator according to claim 11, further comprising water amount adjusting means for controlling the amount of water in the bubbling chamber.