JPH06251789A - Temperature control for fuel cell power generation equipment - Google Patents

Abstract

PURPOSE:To prevent a circulating quantity of cathode gas and motive power consumption of a blower from becoming excessive when a partial load is applied to a fuel cell by arranging an air preheater, a bypass line and an air adjusting valve, and adjusting an air quantity flowing in the bypass line so that a combustion exhaust gas temperature can coincide with a control setting temperature. CONSTITUTION:An air preheater 22 is arranged in an exhaust gas line 12, and air supplied to a combustion chamber 10a of a reformer is heated indirectly by combustion exhaust gas 4 coming out from the reformer 10. A bypass line 24 supplies the air 6 to the combustion chamber 10a of the reformer by bypassing the air preheater 22, and an air adjusting valve 26 adjusts an air quantity flowing in the bypass line. A control setting value of a combustion exhaust gas temperature at an outlet of the air preheater 22 is set high in a low load according to a load of a fuel cell, and is set low in a high load, and the air quantity flowing in the bypass line is adjusted so that the combustion exhaust gas temperature can coincide with the control setting temperature.

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 for fuel cell power generation equipment, and more particularly to a method for controlling the operating temperature of a molten carbonate fuel cell by circulating a cathode gas.

[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. Particularly, in a power generation facility using a molten carbonate fuel cell using natural gas as a fuel, as shown in FIG. 5, a reformer 10 for reforming a fuel gas 1 such as natural gas into an anode gas 2 containing hydrogen, A fuel cell 20 for generating electric power from an anode gas and a cathode gas 3 containing oxygen is generally provided, and the anode gas 2 produced by the reformer is supplied to the fuel cell, and most of the fuel gas in the fuel cell ( (For example, 80%), it is supplied to the combustion chamber 10a of the reformer as anode exhaust gas. In the reformer, combustible components (hydrogen, carbon monoxide, methane, etc.) in the anode exhaust gas are burned in the combustion chamber 10a, and the high-temperature combustion gas heats the reforming pipe in the reforming chamber to remove the fuel passing through the reforming pipe. Reform. Exhaust gas from the reforming chamber 4
Joins with the air 6 to become the cathode gas 3, and supplies necessary carbon dioxide to the cathode side of the fuel cell. A part of the cathode gas, a part of which has reacted in the fuel cell, is circulated on the upstream side of the fuel cell and the rest is discharged to the outside of the system.

[0003]

In the above-mentioned fuel cell power generation facility, a method of controlling the circulation amount of the cathode gas has been conventionally used to control the operating temperature of the fuel cell. That is, the operating temperature of the fuel cell is about 650 ° C. on average, and it is generated in the fuel cell by controlling the circulating amount of the cathode gas so that the inlet temperature of the cathode gas is about 550 ° C. and the outlet temperature is about 700 ° C. The heat generated was removed and the temperature of the fuel cell was controlled to be constant. But,
In such a fuel cell facility, at the time of partial load, the gas temperature of the combustion exhaust gas that has exited the reformer decreases due to the characteristics of the reformer and the heat radiation loss of the pipe between the reformer and the fuel cell. To maintain the same constant value (for example, 550 ° C.) as at 100% load, it is necessary to remarkably increase the circulation amount of the cathode gas, which increases the blower consumption power and causes a problem of insufficient blower capacity. there were. Further, in order to solve this problem, if the blower capacity is increased and the circulation flow rate of the cathode gas is increased, the gas flow rate flowing through the cell is increased and the outlet temperature of the cathode gas is lowered. To be constant,
There is no choice but to further increase the circulation amount of cathode gas,
Blower consumption power increases more and more. In addition, the battery characteristics are
Since the voltage rises when the output current decreases due to partial load, the amount of heat generated in the battery decreases, which further lowers the temperature of the cathode gas at the battery outlet, forcing the circulation flow rate of the cathode gas to increase. There was a point. As a result, there is a problem that the blower consumption power becomes excessive at the time of partial load, the thermal efficiency at the power transmission end is reduced, and the blower capacity becomes excessive.

The present invention was created to solve such problems. That is, an object of the present invention is to provide a temperature control method for a fuel cell power generation facility in which the circulation amount of cathode gas and the blower consumption power do not become excessive when the fuel cell is partially loaded.

[0005]

According to the present invention, a reformer for reforming a fuel gas into an anode gas containing hydrogen, a fuel cell for generating electricity from a cathode gas containing oxygen and the anode gas, Temperature of fuel cell power generation equipment equipped with an exhaust gas line that joins the combustion exhaust gas that has exited the quality chamber with the cathode gas, and a cathode gas circulation line that returns part of the cathode gas that has passed through the fuel cell to the upstream side of the fuel cell In the control method, provided in the exhaust gas line, provided in the exhaust gas line, an air preheater for indirectly heating the air supplied to the combustion chamber of the reformer by the combustion exhaust gas exiting the reformer,
A bypass line for bypassing the air preheater to supply air to the combustion chamber of the reformer; and an air control valve for adjusting the amount of air flowing through the bypass line, and controlling the temperature of the combustion exhaust gas at the outlet of the air preheater. The set value is set to be high at low load and low at high load according to the load of the fuel cell, and the amount of air flowing through the bypass line is adjusted so that the combustion exhaust gas temperature matches the control set temperature. A method for controlling the temperature of a fuel cell power generation facility is provided. Further, according to the present invention, a reformer for reforming a fuel gas into an anode gas containing hydrogen, a fuel cell for generating power from the anode gas and a cathode gas containing oxygen, and a combustion exhaust gas leaving the reformer. In a temperature control method of a fuel cell power generation facility, comprising: an exhaust gas line for joining the cathode gas to the cathode gas; and a cathode gas circulation line for returning a part of the cathode gas that has passed through the fuel cell to the upstream side of the fuel cell. The flow rate of the cathode gas flowing through the cathode gas circulation line so that the inlet temperature set value of the cathode gas fuel cell is reduced according to the decrease in the load, and the inlet temperature of the fuel cell inlet of the cathode gas matches the inlet temperature set value. A temperature control method for a fuel cell power generation facility is provided.

[0006]

According to the configuration of the first aspect of the invention, the air preheater is provided in the exhaust gas line, and the air supplied to the combustion chamber of the reformer can be indirectly heated by the combustion exhaust gas discharged from the reformer. it can. Further, a bypass line that bypasses the air preheater and supplies air to the combustion chamber of the reformer, and an air control valve that adjusts the amount of air flowing through the bypass line are provided, and the amount of air flowing through the bypass line is provided. Is adjusted to adjust the amount of decrease in the temperature of the combustion exhaust gas in the air preheater so that the temperature of the combustion exhaust gas at the outlet of the air preheater matches the control set temperature.
Furthermore, since the control set temperature is set to be high at low load and low at high load according to the load of the fuel cell, even if the gas temperature of the combustion exhaust gas leaving the reformer drops, air and the circulated cathode The temperature of the cathode gas combined with the gas does not decrease, and therefore, the circulation amount of the cathode gas and the blower consumption power do not increase when the fuel cell is partially loaded. In addition, the second
According to the configuration of the invention of (1), the inlet temperature set value of the cathode gas of the fuel cell is reduced according to the reduction of the load of the fuel cell,
Moreover, since the flow rate of the cathode gas flowing through the cathode gas circulation line is controlled so that the inlet temperature of the cathode gas of the fuel cell matches the inlet temperature set value, the inlet temperature of the cathode gas of the fuel cell is kept at a constant value (for example, 550 ° C.). Compared with the case of, the circulation amount of the cathode gas is small and the blower consumption power hardly increases.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a fuel cell power generation facility for carrying out the first method of the present invention. In this figure, this power generation facility includes a reformer 10 for reforming a fuel gas 1 into an anode gas 2 containing hydrogen, and a fuel cell 20 for generating power from a cathode gas 3 containing oxygen and an anode gas 2.
An exhaust gas line 12 that joins the combustion exhaust gas 4 that has exited the reformer 10 with the cathode gas 3, and a cathode gas circulation line 14 that returns a part 5 of the cathode gas that has passed through the fuel cell 20 to the upstream side of the fuel cell. Is equipped with. The cathode gas circulation line 14 is provided with a blower 16 driven by an inverter motor 15 so that the flow rate of the circulating cathode gas can be controlled. Further, a temperature sensor 17 is provided at the fuel cell inlet of the cathode gas 3, and the temperature controller 18 controls the inverter 19 according to the output signal of the temperature sensor 17 and the load command 7 to supply power to the inverter motor 15. It is designed to control the frequency. Such a configuration is similar to the conventional fuel cell power generation facility shown in FIG. The fuel cell power generation facility shown in FIG. 1 is further provided in the exhaust gas line 12, and the combustion chamber 10 of the reformer is constituted by the combustion exhaust gas 4 discharged from the reformer 10.
an air preheater 22 for indirectly heating the air 6 supplied to a;
A bypass line 24 that bypasses the air preheater 22 and supplies the air 6 to the combustion chamber 10a of the reformer, and an air control valve 2 that adjusts the amount of air flowing through the bypass line 24.
6 and. In FIG. 1, the air control valve 2
6 is a three-way valve, but a two-way valve may be used by separating the valve attached to the line to the air preheater and the valve attached to the bypass line, or a two-way valve only on the bypass line with a small piping resistance. May be used. Furthermore, this power generation facility
A temperature sensor 27 provided at the outlet of the air preheater 22 of the exhaust gas line 12, and a temperature controller that receives the output signal of the temperature sensor 27 and the load command 7 of the fuel cell power generation facility and adjusts the air control valve 26. 28 is provided.
In the fuel cell power generation facility having such a configuration, when the load on the fuel cell is reduced, as shown in FIG. 2, the control set value of the combustion exhaust gas temperature at the outlet of the air preheater 22 is increased at a low load according to the load on the fuel cell. , It is set low at high load, and the amount of air flowing through the bypass line is adjusted so that the combustion exhaust gas temperature matches the control set temperature. The control set value of the combustion exhaust gas temperature at the outlet of the air preheater may be a constant value regardless of the load of the fuel cell. As a result, even if the gas temperature of the flue gas discharged from the reformer decreases, the temperature of the cathode gas combined with the air and the circulated cathode gas does not decrease, and therefore the cathode gas of the cathode gas during partial load of the fuel cell is reduced. Circulation amount and blower consumption power do not increase.

FIG. 3 is another configuration diagram showing a fuel cell power generation facility for carrying out the second method of the present invention. In this figure, this power generation facility is similar to the fuel cell power generation facility of FIG. 1 and includes a reformer 10, a fuel cell 20, and an exhaust gas line 1.
2 and a cathode gas circulation line 14, a blower 16 driven by an inverter motor 15 is provided in the cathode gas circulation line 14, and a temperature sensor 17 is provided at the fuel cell inlet of the cathode gas 3. The temperature control device 18 controls the inverter 19 according to the output signal of the temperature sensor 17 and the load command 7 to control the frequency of the power supply supplied to the inverter motor 15. In the fuel cell power generation facility having such a configuration, when the load on the fuel cell is reduced, as shown in FIG. 4, the inlet temperature set value of the fuel cell for the cathode gas is reduced in accordance with the reduction in the load on the fuel cell, and The flow rate of the cathode gas flowing through the cathode gas circulation line is controlled so that the inlet temperature of the fuel cell matches the inlet temperature set value. As a result, compared to the case where the fuel cell inlet temperature of the cathode gas is set to a constant value (for example, 550 ° C.), the circulation amount of the cathode gas is small, the blower consumption power hardly increases, and the operating temperature of the fuel cell decreases. Therefore, the battery performance is slightly reduced, but the power consumption of the blower does not increase significantly, so that the thermal efficiency at the transmission end can be improved.

[0009]

As described above, according to the configuration of the first invention, the air preheater is provided in the exhaust gas line, and the air supplied to the combustion chamber of the reformer by the combustion exhaust gas discharged from the reformer is supplied. Indirect heating is possible. Further, a bypass line that bypasses the air preheater and supplies air to the combustion chamber of the reformer, and an air control valve that adjusts the amount of air flowing through the bypass line are provided, and the amount of air flowing through the bypass line is provided. Is adjusted to adjust the amount of decrease in the temperature of the combustion exhaust gas in the air preheater so that the temperature of the combustion exhaust gas at the outlet of the air preheater matches the control set temperature. Furthermore, since the control set temperature is set to be high at low load and low at high load according to the load of the fuel cell, even if the gas temperature of the combustion exhaust gas leaving the reformer drops, air and the circulated cathode The temperature of the cathode gas combined with the gas does not decrease, and therefore, the circulation amount of the cathode gas and the blower consumption power do not increase when the fuel cell is partially loaded. Further, according to the configuration of the second aspect of the invention, the inlet temperature set value of the cathode gas of the fuel cell is reduced according to the reduction of the load of the fuel cell, and the inlet temperature of the cathode gas of the fuel cell is set to the inlet temperature setting. Since the flow rate of the cathode gas flowing through the cathode gas circulation line is controlled so as to match the value, the circulation amount of the cathode gas is smaller than that when the temperature of the fuel cell inlet of the cathode gas is a constant value (for example, 550 ° C.). Low, blower power consumption hardly increases.

Therefore, it is possible to obtain an excellent effect that the circulation amount of the cathode gas and the power consumption of the blower do not increase and the thermal efficiency at the power transmission end does not decrease when the fuel cell is partially loaded.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a fuel cell power generation facility for carrying out a first method of the present invention.

FIG. 2 is a diagram showing a relationship between a power generation output and a control set value of temperature.

FIG. 3 is a configuration diagram showing a fuel cell power generation facility for carrying out a second method of the present invention.

FIG. 4 is a diagram showing a relationship between a power generation output and a cathode gas inlet temperature set value.

FIG. 5 is an overall configuration diagram showing a conventional power generation facility.

[Explanation of symbols]

 1 Fuel Gas 2 Anode Gas 3 Cathode Gas 4 Combustion Exhaust Gas 5 Circulation Cathode Gas 6 Air 7 Load Command 10 Reformer 10a Combustion Chamber 12 Exhaust Gas Line 14 Cathode Gas Circulation Line 15 Inverter Motor 16 Blower 17 Temperature Sensor 18 Temperature Control Device 19 Inverter 20 Fuel Cell 22 Air Preheater 24 Bypass Line 26 Air Control Valve 27 Temperature Sensor 28 Temperature Controller

Claims (2)

[Claims] 1. A reformer for reforming a fuel gas into an anode gas containing hydrogen, a fuel cell for generating electricity from a cathode gas containing oxygen and the anode gas, and a combustion exhaust gas discharged from the reformer as a cathode gas. In the temperature control method of the fuel cell power generation facility, comprising: an exhaust gas line that joins the fuel cell, and a cathode gas circulation line that returns a part of the cathode gas that has passed through the fuel cell to the upstream side of the fuel cell. An air preheater that indirectly heats air supplied to the combustion chamber of the reformer by the combustion exhaust gas that has exited the reformer; and a bypass line that bypasses the air preheater and supplies air to the combustion chamber of the reformer. And an air control valve for adjusting the amount of air flowing through the bypass line, and the control set value of the combustion exhaust gas temperature at the outlet of the air preheater is high at low load according to the load of the fuel cell, Set low in the load, and the flue gas temperature to adjust the amount of air flowing through the bypass line so as to coincide with the control set temperature, the temperature control method for a fuel cell, characterized in that. 2. A reformer for reforming a fuel gas into an anode gas containing hydrogen, a fuel cell for generating electricity from the anode gas and a cathode gas containing oxygen, and a combustion exhaust gas discharged from the reformer as a cathode gas. In the temperature control method of the fuel cell power generation facility, which comprises an exhaust gas line that joins the fuel cell and a cathode gas circulation line that returns a part of the cathode gas that has passed through the fuel cell to the upstream side of the fuel cell, the load of the fuel cell is reduced. In accordance with the above, the fuel cell inlet temperature set value of the cathode gas is lowered, and the flow rate of the cathode gas flowing through the cathode gas circulation line is controlled so that the cathode gas fuel cell inlet temperature matches the inlet temperature set value. A method for controlling temperature of a fuel cell power generation facility, comprising: