JPH02132770A - Device for cooling reforming device of fuel cell - Google Patents

Abstract

PURPOSE:To prevent catalysts for reforming from being oxidized, without the structure of the device becoming complicated, by providing a heating passage with an air blowing device capable of blowing a larger amount of air than the required amount of air blowed for operating a fuel cell, and providing means for controlling the air blowing device so that the amount of air blowed is decreased when the air blowing device is operated, whereas it is increased when the device is stopped and cooled. CONSTITUTION:A heating passage B which allows heated gas heated by a burner 9 to pass therethrough is provided with an air blowing device 15 capable of blowing a larger amount of air than the required amount of air blowed for operating a fuel cell 16, and controlling means C are provided for controlling the air blowing device 15 so that the amount of air blowed is decreased when the air blowing device 15 is operated, whereas it is increased when the device is stopped and cooled; i.e., a larger amount of air than the amount of air blowed during operation is forced to pass through the heating passage B, so that a catalyst layer 2 in a raw material passage A is forcibly cooled to enable the temperature of the catalyst layer 2 to be lowered less than its active temperature region. The catalyst can thus be cooled promptly and be preserved when the air blowing device is stopped, and therefore the reforming capability of the catalyst can be prevented from deteriorating without the structure of the device becoming complicated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cooling device for a fuel cell reformer.

[Conventional technology]

A fuel cell system includes, for example, a reformer that reforms a raw material that is a mixture of methanol and water into hydrogen gas, and an electrochemical reaction between the hydrogen gas generated by this reformer and oxygen in the air to generate electricity. It consists of a fuel cell body that converts energy into energy.

By the way, in such a fuel cell system, after the operation is stopped, the temperature of the reformer gradually decreases due to heat radiation. Therefore, methanol and water in the gaseous state in the reformer condense and become liquid, resulting in a high negative pressure level in the reformer system. As a result, if the valves are not tightened enough or the sealing of piping etc. is insufficient, outside air may be sucked in, and the reforming catalyst in the reformer may be included in the outside air. It is oxidized by oxygen and its reforming ability decreases. This catalyst generally has poor heat resistance, and if it is oxidized at high temperatures, it will deteriorate significantly due to the heat.

For this reason, conventionally, when the fuel cell system is stopped, inert gas such as nitrogen gas is continuously purged into the reformer system until the catalyst temperature drops to prevent the catalyst from oxidizing. .

[Problem to be solved by the invention]

However, such a structure requires special equipment such as a cylinder for storing inert gas, making the equipment complex. The present invention was made in view of these circumstances, and provides a cooling device for a fuel cell reformer that can prevent oxidation of a reforming catalyst without complicating the structure. .

[Means to solve the problem]

A cooling device for a reformer according to the present invention includes a heating passage through which heated gas heated by a burner flows, and a blower device capable of blowing a larger amount of air than that required for operating a fuel cell. The system is equipped with a control means that controls the amount of air blown to be small when the system is in operation, and to increase the amount of air blown when the system is stopped and cooled.

[Function] In the present invention, the amount of air blown during stop cooling is larger than during normal operation, and the raw material passage is forcibly cooled by this air, so that the catalyst is quickly cooled.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing a fuel cell system equipped with a first embodiment of a cooling device for a fuel cell reformer according to the present invention, and FIG. 2 is an enlarged sectional view of the reformer. In the figure, the reference numeral 1 indicates a reforming device, which includes an inner case 1a and an outer case 1b each having a cylindrical inner space with a bottom and a cylindrical shape with a bottom, and covers the outside of the outer case 1b. It is composed of a cover 1c and the like. Outer case 1b
are covered with an inner case 1a with the opening facing downward, and the internal spaces of these members are communicated with each other near the edge of the opening. Further, in the internal space of these cases, a catalyst layer 2 made of a catalyst for chemically reacting raw materials, which will be described later, is provided. As the catalyst, for example, copper-based, copper-zinc-based, copper-chromium-based catalysts, etc. can be used.

Reference numeral 3 designates a carburetor disposed below the inner and outer cases, and the central portion thereof is wound into a coil shape so as to face into the opening of the inner case 1a. The inlet side of the vaporizer 3 is connected via a raw material supply pipe 6 equipped with a reformer population valve 4 and a supply bomb 5 to a raw material tank 7 containing a raw material mixed with methanol and water at a predetermined ratio. The outlet side is connected to the top of the internal space of the inner case 1a, which corresponds to the inlet side of the catalyst layer 2.

The top of the internal space of the outer case 1b, which corresponds to the outlet side of the catalyst layer 2, is connected to the fuel cell main body 16 through a hydrogen supply pipe, which will be described later. That is, the raw material is vaporized by the vaporizer 3 and the inner and outer cases, guided to the catalyst layer 2, and reformed into hydrogen gas, and the raw material passage A connected to the fuel cell main body 16.
is formed.

A hydrogen burner 8 and a methanol burner 9 are arranged below the vaporizer 3. The methanol burner 9 is connected via a fuel supply line 13 having a burner inlet valve 11 and a burner pump 12 to a fuel tank 14 storing methanol.

Here, the space above the burner and the space formed between the inner and outer cases are communicated by a communication pipe 1d penetrating the top of the inner case 1a, and the space formed between the inner and outer cases is connected to the outer part by the cover 10. The space formed outside the case 1b communicates with the space near the opening edge of the outer case 1b. Therefore, the heated gas heated by the methanol burner 9 or the like flows from the inside of the inner case 1a through the space between the inner and outer cases, and then flows to the outside of the outer case 1b, and then is discharged to the outside. That is, the inner and outer cases la, lb and the cover IC
Thus, a heating passage B is formed through which heating gas flows to heat the raw material passage A.

A burner blower 15 is provided in the heating passage B and supplies outside air to the heating passage B. This burner blower 15
The air blower is capable of blowing a larger amount of air than that required to operate the fuel cell. A variable throttle C is provided on the outlet side of the burner blower 15 as a control means for controlling the amount of air blown by the burner blower 15. The variable throttle C is composed of a throttle valve or the like, and by changing the cross-sectional area of the passage, the variable throttle C is controlled so that the amount of air blown is decreased when the fuel cell is in operation, and increased when the fuel cell is stopped and cooled. Note that the amount of air blown by the burner blower 15 can also be controlled by changing the rotational speed of the burner blower 15.

Reference numeral 16 denotes a fuel cell main body, which is constructed by stacking a large number of battery cells with an electrolyte interposed between an anode and a cathode, and an oxygen population valve 17, a cell blower l8, and a four-way valve 19 are installed on the inlet side of the anode. It is connected to the combustion air outlet of the reformer 1 with an oxygen supply line 20 provided. As shown in an enlarged view in FIG. 3, the four-way valve 19 supplies the heated gas heated by the reformer 1 to the cell blower 18 as shown by the broken line when raising the temperature of the fuel cell main body 16, and when cooling the fuel cell main body 16, it supplies the heated gas heated by the reformer 1 to the cell blower 18. The oxygen supply line 20 is switched so that the oxygen supply line 20 is supplied to the cell blower 18. On the other hand, the inlet side of the cathode is connected to the outlet side of the catalyst layer 2 through a hydrogen supply pipe 23 equipped with a hydrogen population valve 21 and a reserve tank 22. Reference numeral 24 denotes an exhaust pipe connected to the outlet side of the anode, which is opened to the atmosphere via an oxygen outlet valve 25. A hydrogen recovery pipe 26 is connected to the outlet side of the cathode, and is used to return hydrogen that has not reacted in the fuel cell main body 16 to the reformer 1 for use as a heat source. and hydrogen outlet valve 2
It is connected to the hydrogen burner 8 via 8. 29 is a bypass pipe line having a bypass valve 30, and a hydrogen outlet valve 2
8 and the reserve tank 22 are communicated with each other.

Note that 31 is a diode 3 on the output side of the fuel cell main body 16.
A motor as a load is connected through 2, and 33 is a battery connected in the same way as the motor 31.

In the fuel cell system configured in this manner, methanol pressurized by the burner bomb 12 is supplied to the methanol burner 9, and is combusted by outside air supplied by the burner blower 15. Therefore, heating gas is generated by this combustion, and the heating gas flows through the heating passage B while heating the vaporizer 3 and the catalyst layer 2, and is supplied to the fuel cell main body 16.

On the other hand, the raw material in which methanol and water are mixed in the raw material tank 7 is supplied to the vaporizer 3, where it is vaporized and placed in the catalyst layer 2.
The fuel is sent to the fuel cell main body 16 after being chemically reacted by a catalyst and reformed into a gas whose main components are hydrogen and carbon dioxide. And the fuel cell body l6
In this step, hydrogen gas in the reformed gas and oxygen in the air supplied by the cell block 18 undergo an electrochemical reaction by a catalyst, and electrical energy is generated.

When stopping the fuel cell system, first, at a first point in time, the operation to stop the supply pump 5 and the burner pump 12 is started, and the pump output is stepped so that these pumps are stopped after a certain period of time has elapsed after the start of the stop operation. The amount of raw material supplied to the vaporizer 3 and the amount of methanol supplied to the methanol burner 9 are gradually decreased by gradually decreasing the amount of the raw material supplied to the vaporizer 3 and the amount of methanol supplied to the methanol burner 9. At this time, while suppressing the amount of heat generated by the methanol burner 9 to a small value, the catalyst N2 is cooled by utilizing the endothermic action that occurs when the vaporized raw material gas undergoes a chemical reaction as shown in the following equation.

C■30H +H20 -3Hz+COz -11.8
Kcal At the same time as this operation, the variable throttle C is controlled so that the cross-sectional area of the passage is maximized, and the burner blower 15 continues to supply a larger amount of air into the heating passage B than during operation.

Note that the four-way valve 19 is on the cooling side and supplies outside air to cool the fuel cell main body 16.

At a second point in time when a certain period of time has elapsed while cooling by the burner blower 15, the bypass valve 3o is opened and the hydrogen population valve 2 is opened.
1 and the hydrogen outlet valve 28 are closed to supply reformed gas to the hydrogen burner 8.

Then, at a third point in time after a certain amount of time has elapsed,
Completely stop the supply pump 5 and burner bomb 12,
Close the reformer population valve 4 and burner inlet valve l1. The time up to the third point is at most the time required for the temperature of the catalyst layer 2 to drop to a temperature at which almost no chemical reaction occurs with the raw materials. This temperature is usually about 110 to 180'C. In other words, even if air enters the reformer 1 for some reason and the catalyst layer 2 undergoes an oxidative exothermic reaction, the catalyst layer 2 will exceed the critical temperature at the upper limit of the operating temperature range and deteriorate significantly. It is a safe temperature that will not cause any damage. To be more specific, the maximum safe temperature is 20 to 20 degrees higher than the normal operating temperature (near the upper limit of efficient operating temperature).
The temperature is 50° C. lower, and the minimum value is about 20° C. lower than the lower limit of the operating temperature. Furthermore, at a fourth point in time when hydrogen is no longer generated from the reformer 1, the bypass valve 3
Close 0. In this state, the burner blower 15 continues to operate, and at the fifth point in time when the temperature of the catalyst layer 2 becomes lower than the catalyst activation temperature range, the burner blower 15 is stopped, and when the cell temperature drops to a predetermined temperature, the burner blower 15 is stopped. The cell blower 18 is stopped, and the fuel cell system stopping operation is completed. After the stop operation is completed, the reformer 1 is sealed by the reformer population valve 4, the hydrogen population valve 21, and the bypass valve 30, so that no air flows in, or at least a very small amount of air flows into the reformer 1. There is no deterioration caused by oxidative heat generation, and there is no problem with storage after completion.

Therefore, by flowing air in the heating passage B in an amount larger than the amount of air blown during operation, the catalyst layer 2 in the raw material passage A is forcedly air-cooled, and the temperature of the catalyst layer 2 is quickly lowered to below the activation temperature range. be able to.

In this embodiment, since the endothermic action that occurs when the raw material undergoes a chemical reaction in the catalyst layer 2 is also utilized for cooling, the catalyst layer 2 can be cooled more effectively.

In this way, the present invention is designed to enhance the cooling effect by blowing more air into the heating passage B during stop cooling than during operation, so the blowing device is
The present invention is not limited to a stand having a large air blowing capacity, and the means for controlling the blower is not limited to the variable diaphragm C. That is, FIGS. 4 to 8 are configuration diagrams of a reformer showing other embodiments of the cooling device for a fuel cell reformer according to the present invention, and FIGS. A third example is shown. In both of these embodiments, two burner blowers 15.15 are installed on the inlet side of the heating passage B.
It has been established. In the second embodiment, when the fuel cell system is operated, one burner blower 1 is
5 and both burner blowers 15 when stopped and cooled.
．． 15 at the same time to control the amount of air blown. On the other hand, in the third embodiment, the amount of air blown is controlled by the number of burner blowers 15 being operated and the operation of the throttle valve 41.

FIG. 6 shows a fourth embodiment, in which two burner blowers 15 having a forward/reverse function and heat resistance are used, and one of these burner blowers 15 is connected to the outlet side of the heating passage B with a three-way switching valve 4.
2.

In the figure, solid lines indicate air flow during operation, and broken lines and chain lines indicate air flow during stop cooling.

FIG. 7 shows a fifth embodiment in which a burner blower 15 is connected to each side of the heating passage B via a three-way switching valve 4'2.42.
．． 15 is provided, and the blowing capacity of the burner blower 15 on the outlet side is increased. In the figure, the solid line indicates the air flow during operation, and the broken line indicates the air flow during stop cooling. According to this embodiment, the cooling air can flow from the outlet side to the inlet side of the heating passage B without imparting heat resistance to the burner blower 15.

FIG. 8 shows a sixth embodiment, in which two burner blowers 15
One of them is provided on the exit side of the heating passage B via a three-way switching valve 42, and an exhaust port 43 is provided in the center of the heating passage B to be used only during stop cooling. In this way, the catalyst layer 2 can be cooled from both sides, as the solid line in the drawing shows the air flow during operation, and the broken line shows the air flow during stop cooling.

〔Effect of the invention〕

As explained above, according to the present invention, a blower device capable of blowing a larger amount of air than that required for operation of a fuel cell system is provided in a heating passage through which heated gas heated by a burner flows, and the blower device When driving, the amount of airflow is low,
Since a control means is provided to control the amount of air blown to increase during stop cooling, a larger amount of air is blown into the heating passage during stop cooling than during normal operation, and this air can quickly cool the catalyst. .

Therefore, by making a simple modification to a conventional fuel cell system, the catalyst can be quickly cooled and stored during shutdown, thereby preventing the catalyst's reforming ability from decreasing without complicating the structure. can do.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a fuel cell system equipped with a first embodiment of a cooling device for a fuel cell reformer according to the present invention, FIG. 2 is an enlarged sectional view of the reformer, and FIG. 1 is a block diagram showing a four-way valve, and FIGS. 4 to 8 are block diagrams of reforming apparatuses showing second to sixth embodiments. DESCRIPTION OF SYMBOLS 1... Reformer, 2... Catalyst layer, 3... Vaporizer, 5... Supply pump, 9... Methanol burner, 12... Burner pump, 15 ... Burner blower, 16... Fuel cell main body, A... Raw material passage, B... Heating passage, C... Variable throttle. Patent applicant Yamaha Motor Co., Ltd.

Claims (1)

[Claims] a raw material passage that vaporizes the raw material and guides it to a catalyst to be reformed into hydrogen gas and is also connected to the fuel cell main body; a heating passage that allows heating gas introduced from the outside and heated by a burner to flow through the raw material passage so as to heat the raw material passage; In a fuel cell equipped with a reformer having a reformer, a blower device capable of blowing a larger amount of air than that required for operation of the fuel cell is provided in the heating passage, and when the blower device is in operation, the amount of air blows is small; A cooling device for a fuel cell reformer, which is provided with a control means for controlling the amount of air blown to be increased during stop cooling.