JPH07161371A - Method and apparatus for controlling temperature of fuel cell - Google Patents

Abstract

PURPOSE:To keep the temperature at the inlet of a cathode gas within a prescribed range and suppress the difference of the temperature at the inlet and the temperature at the outlet of the cathode gas within a prescribed range even if the function of a fuel cell is gradually degraded due to operation for a long duration. CONSTITUTION:A temperature controlling apparatus for a fuel cell is provided with an air supplying line 32 to supply low temperature air to a cathode 5 and a recirculating line 38 to mix a part of the cathode waste gas 9 which passes a fuel cell 20 with a cathode gas in the upper stream side of the fuel cell. The flow rate in the recirculating line 38 is controlled so as to keep the temperature Ti of the cathode gas at the inlet of the fuel cell within a prescribed range and also the flow rate in the air supplying line 32 is controlled so as to keep the temperature To of the cathode waste gas at the outlet of the fuel cell within a prescribed range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control method and apparatus for a fuel cell, and more particularly to a temperature control method and apparatus for a molten carbonate fuel cell.

[0002]

2. Description of the Related Art Molten carbonate fuel cells have characteristics that conventional power generators do not have, such as high efficiency and little impact on the environment, and they are attracting attention as a power generation system following hydropower, thermal power, and nuclear power. Is currently being researched and developed all over the world. In particular, in a power generation facility using a molten carbonate fuel cell using natural gas as a fuel, a fuel gas 3 obtained by mixing natural gas 1 and water vapor 2 is converted to an anode gas 4 containing hydrogen as shown in FIG. A reformer 10 that produces a reforming gas and a fuel cell 20 that generates electric power from an anode gas 4 and a cathode gas 5 containing oxygen are generally provided. The anode gas 4 produced by the reformer 10 is supplied to the fuel cell 20. It is supplied and consumes most (for example, 80%) of it in the fuel cell to become the anode exhaust gas 6, and after separating its water content, it is supplied to the combustor of the reformer 10 as the combustion gas 7. In the reformer, combustible components (hydrogen, carbon monoxide, methane, etc.) in the combustion gas 7 are burned in the combustor to generate high temperature combustion gas, and the high temperature combustion gas heats the reforming pipe 10a. The fuel gas 3 flowing in the reforming pipe is reformed. The flue gas 8 exiting the reformer joins with the air 11 to become the cathode gas 5, and a part of this cathode gas 5 reacts in the fuel cell 20 to become the hot cathode exhaust gas 9 and a part thereof is recycled. The remaining power is recovered by the turbine 31 of the power recovery device 30, the heat is recovered by the boiler 35, and the heat is discharged to the outside of the system.

[0003]

In the above-described power generation equipment, if the inlet gas temperature of the fuel cell is too low, the electrolyte constituting the fuel cell may be partially solidified and the fuel cell may be essentially damaged. Also, since the heat generated by the fuel cell is removed (cooled) by the cathode gas,
If the flow rate of the cathode gas is too low, the electrolyte near the outlet becomes hot and evaporates, resulting in a problem of extremely shortening the battery life. Therefore, the inlet gas temperature Ti of the cathode gas
Must be maintained within a predetermined range (for example, 550 to 600 ° C.), and the difference ΔT between the outlet temperature To of the cathode exhaust gas and the inlet temperature must be suppressed within a predetermined range (for example, 100 to 150 ° C. or less).

In order to meet such a demand, in the conventional power generation equipment, a relatively large amount of cathode exhaust gas (To = about 700 ° C.) is recirculated to the cathode inlet side by the cathode circulation blower 16, and low temperature (Ta = 150 to 200 ° C.). ) Air and mixed with this gas temperature (inlet gas temperature T in FIG. 3).
i) is detected and the flow rate by the cathode circulation blower 16 is controlled so that this temperature falls within a predetermined temperature range.

However, as illustrated in FIG. 2, the performance of the fuel cell gradually deteriorates due to long-term operation. Therefore, even if the same current is taken out, the output voltage thereof gradually decreases, and the same output (= voltage × current) is obtained. In order to maintain, the current needs to be increased. Therefore, the amount of heat generated in the fuel cell 20 gradually increases due to an increase in internal resistance due to deterioration,
There is a problem that the temperature To of the cathode exhaust gas gradually increases. In particular, in the temperature control means of the fuel cell described above, when the temperature To of the cathode exhaust gas becomes high, the temperature Ti of the cathode gas after being mixed with air is maintained within a predetermined range.
Since the gas flow rate of the cathode circulation blower 16 is controlled to be decreased, the total flow rate of the cathode gas 3 is decreased, the temperature To of the cathode exhaust gas 7 is further increased, and the temperature of the electrolyte solution near the outlet is quickly increased. Therefore, there is a problem that the battery life is shortened.

The present invention was devised to solve such problems. That is, the object of the present invention is to improve the performance of a fuel cell even if it gradually deteriorates due to long-term operation.
The inlet gas temperature Ti of the cathode gas can be maintained within a predetermined range, and the outlet temperature To and the inlet temperature T of the cathode gas can be maintained.
An object of the present invention is to provide a temperature control method and apparatus for a fuel cell, which can suppress the difference ΔT from i within a predetermined range.

[0007]

According to the present invention, there is provided a fuel cell temperature control method for generating power from an anode gas containing hydrogen and a cathode gas containing oxygen, wherein air for supplying low temperature air to the cathode gas is used. A supply line and a recirculation line for mixing a part of the cathode exhaust gas that has passed through the fuel cell with the cathode gas on the upstream side of the fuel cell are provided so that the temperature of the cathode gas at the inlet of the fuel cell falls within a predetermined range. To control the flow rate of the recirculation line, and to control the flow rate of the air supply line so that the temperature of the cathode exhaust gas at the outlet of the fuel cell is within a predetermined range. Provided.

Further, according to the present invention, there is provided a temperature control device for a fuel cell for generating electric power from an anode gas containing hydrogen and a cathode gas containing oxygen, which has an air flow rate control valve to supply low temperature air to the cathode gas. The air supply line for supplying, the recirculation line for mixing a part of the cathode exhaust gas passing through the fuel cell with the cathode gas on the upstream side of the fuel cell, which has a cathode circulation blower, and the temperature of the cathode gas at the inlet of the fuel cell Adjust the flow rate of the recirculation line so that the cathode gas temperature detector to measure, the cathode exhaust gas temperature detector to measure the temperature of the cathode exhaust gas at the outlet of the fuel cell, and the measured value by the cathode gas temperature detector are within the specified range. A control device for controlling and controlling the flow rate of the air supply line so that the measurement value by the cathode exhaust gas temperature detector falls within a predetermined range, Temperature control apparatus for a fuel cell characterized by comprising is provided.

[0009]

According to the above method and apparatus of the present invention, the flow rate of the air supply line is controlled so that the temperature To of the cathode exhaust gas at the outlet of the fuel cell falls within a predetermined range.
As illustrated in FIG. 2, the performance of the fuel cell gradually deteriorates due to long-term operation, and in order to maintain the same output (= voltage × current), the current is increased and the calorific value of the fuel cell is increased to increase the temperature of the cathode exhaust gas. When To increases, the flow rate of the air supply line, that is, the amount of low temperature air flowing into the cathode gas increases so that this temperature falls within a predetermined range. As a result, the temperature Ti of the cathode gas at the inlet of the fuel cell decreases and the total amount of the cathode gas increases, so the temperature To of the cathode exhaust gas also decreases.

On the other hand, since the flow rate of the recirculation line is controlled so that the temperature Ti of the cathode gas at the inlet of the fuel cell is within a predetermined range, the amount of heat generated in the fuel cell increases and the temperature of the cathode exhaust gas rises. Since the temperature Ti of the cathode gas at the inlet of the fuel cell is lowered by the above-mentioned control, the cathode exhaust gas flowing into the cathode gas from the recirculation line is increased, which increases the total amount of the cathode gas. The temperature To further decreases.

Therefore, since the control of the air supply line and the control of the recirculation line act synergistically to suppress the temperature rise of the cathode exhaust gas, it is effective even when the performance of the fuel cell gradually deteriorates due to long-term operation. In addition, the inlet gas temperature Ti of the cathode gas can be maintained within a predetermined range, and the difference ΔT between the outlet temperature and the inlet temperature of the cathode gas can be suppressed within a predetermined range.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. In addition, in each figure, the same parts are denoted by the same reference numerals. FIG. 1 is an overall configuration diagram of a temperature control device for a fuel cell according to the present invention. In this figure, a fuel cell 20 is a molten carbonate fuel cell similar to that in FIG. 3, which generates electric power from an anode gas 4 containing hydrogen and a cathode gas 5 containing oxygen.

The temperature control device of the present invention has an air flow control valve 32, an air supply line 34 for supplying low-temperature air to the cathode gas 5, and a cathode circulation blower 36. The cathode exhaust gas passes through the fuel cell 20. A recirculation line 38 for mixing a part of 9 into the cathode gas on the upstream side of the fuel cell 20, a cathode gas temperature detector 40 for measuring the temperature Ti of the cathode gas 5 at the inlet of the fuel cell 20, and an outlet for the fuel cell. A cathode exhaust gas temperature detector 42 for measuring the temperature To of the cathode exhaust gas 9 at
It has and.

The controller 44 controls the flow rate of the recirculation line 38 so that the value measured by the cathode gas temperature detector 40 falls within a predetermined range, and the value measured by the cathode exhaust gas temperature detector 42 falls within a predetermined range. The flow rate of the air supply line 34 is controlled so that That is, the cathode circulation blower 36 is controlled by the controller 44 so that the temperature Ti of the cathode gas 5 at the inlet of the fuel cell 20 falls within a predetermined range.
Thus, the flow rate of the recirculation line 38 is controlled, and the flow rate of the air supply line 34 is controlled by the air flow rate control valve 32 so that the temperature To of the cathode exhaust gas 9 at the outlet of the fuel cell 20 falls within a predetermined range.

The operation of the temperature control device of the present invention will be described below. The temperature To of the cathode exhaust gas 9 at the outlet of the fuel cell is within a predetermined range (for example, 650 to 700 ° C.)
The flow rate of the air supply line is controlled so that the fuel cell performance gradually deteriorates due to long-term operation as illustrated in FIG. 2, and the current is increased to maintain the same output (= voltage × current). As a result, the amount of heat generated in the fuel cell increases and the temperature To of the cathode exhaust gas 9 rises (for example, 7
When the temperature is 00 ° C. or higher, the flow rate of the air supply line 34, that is, the low-temperature (for example, Ta = 150 to 200 ° C.) air amount flowing into the cathode gas increases so that this temperature falls within a predetermined range. As a result, the temperature Ti of the cathode gas 5 at the inlet of the fuel cell decreases and the total amount of the cathode gas increases, so the temperature To of the cathode exhaust gas decreases.
It becomes a predetermined range (for example, 650 to 700 ° C.).

On the other hand, the temperature Ti of the cathode gas at the inlet of the fuel cell is in a predetermined range (for example, 550 to 600 ° C.).
By controlling the flow rate of the recirculation line 38 so that the amount of heat generation in the fuel cell 20 increases and the temperature To of the cathode exhaust gas rises, the temperature Ti of the cathode gas at the inlet of the fuel cell is increased by the above control. Since the temperature of the cathode exhaust gas decreases, the amount of cathode exhaust gas flowing into the cathode gas 5 from the recirculation line 38 increases, which increases the total amount of cathode gas, and thus the temperature To of the cathode exhaust gas further decreases.

Therefore, since the control of the air supply line 34 and the control of the recirculation line 38 synergistically act to suppress the temperature rise of the cathode exhaust gas, even when the performance of the fuel cell gradually deteriorates due to long-term operation, It is possible to effectively maintain the inlet gas temperature Ti of the cathode gas within a predetermined range and suppress the difference ΔT between the outlet temperature and the inlet temperature of the cathode gas within a predetermined range.

The present invention is not limited to the above-described embodiments, and it goes without saying that the present invention can be freely modified without departing from the gist of the present invention.

[0019]

As described above, in the method and apparatus of the present invention, the control of the air supply line and the control of the recirculation line act synergistically to suppress the temperature rise of the cathode exhaust gas, so that the performance of the fuel cell is improved. Even when the temperature gradually deteriorates due to long-term operation, it is possible to effectively maintain the cathode gas inlet gas temperature Ti within a predetermined range and suppress the difference ΔT between the cathode gas outlet temperature and the inlet temperature within a predetermined range. ,
Has excellent effect.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a temperature control device for a fuel cell according to the present invention.

FIG. 2 is a performance characteristic of a fuel cell before and after deterioration.

FIG. 3 is an overall configuration diagram of a conventional fuel cell power generator.

[Explanation of symbols]

 1 Natural Gas 2 Water Vapor 3 Fuel Gas 4 Anode Gas 5 Cathode Gas 6 Anode Exhaust Gas 7 Combustion Gas 8 Combustion Exhaust Gas 9 Cathode Exhaust Gas 10 Reformer 10a Reformer Tube 11 Air 20 Fuel Cell 30 Power Recovery Device 31 Turbine 32 Air Flow Control Valve 34 Air supply line 35 Boiler 36 Cathode circulation blower 38 Recirculation line 40 Cathode gas temperature detector 42 Cathode exhaust gas temperature detector 44 Control device A Anode side C Cathode side Re Reforming chamber Co Combustion chamber

Claims (2)

[Claims] 1. A method for controlling a temperature of a fuel cell for generating power from an anode gas containing hydrogen and a cathode gas containing oxygen, comprising: an air supply line for supplying low temperature air to the cathode gas; and a cathode passing through the fuel cell. A recirculation line for mixing a part of the exhaust gas into the cathode gas on the upstream side of the fuel cell, and controlling the flow rate of the recirculation line so that the temperature of the cathode gas at the inlet of the fuel cell falls within a predetermined range, Moreover, the temperature control method of the fuel cell, wherein the flow rate of the air supply line is controlled so that the temperature of the cathode exhaust gas at the outlet of the fuel cell falls within a predetermined range. 2. A temperature control device for a fuel cell, which generates electric power from an anode gas containing hydrogen and a cathode gas containing oxygen, comprising an air supply line having an air flow rate control valve and supplying low temperature air to the cathode gas. , A recirculation line that has a cathode circulation blower and mixes a part of the cathode exhaust gas that has passed through the fuel cell with the cathode gas on the upstream side of the fuel cell, and the cathode gas temperature detection that measures the temperature of the cathode gas at the inlet of the fuel cell And a cathode exhaust gas temperature detector that measures the temperature of the cathode exhaust gas at the outlet of the fuel cell,
Control to control the flow rate of the recirculation line so that the value measured by the cathode gas temperature detector falls within a predetermined range and to control the flow rate of the air supply line so that the value measured by the cathode exhaust gas temperature detector falls within a predetermined range. A device for controlling a temperature of a fuel cell.