JPH01134869A - Fuel cell power generating facility and its operating method - Google Patents

Abstract

PURPOSE:To provide high performance, high reliability, and long life by controlling the inlet temp. and rate of flow of an oxidating agent gas on the basis of sensed temp. at the cell inlet and outlet, and thereby optimizing the cell temp. with respect to the load in a wider range. CONSTITUTION:When a cell is operated, the cell inlet temp. of an oxidating agent gas is sensed by a sensor 15 and sent to a controller 50, which sends a combustion gas temp. controlling signal according to the temp. and set value to a valve 42 for fuel of a combustor 40 for recirculation, to hold the gas temp. supplied to the cell constant. At the same time, the temp signal from a gas temp. sensor 16 at the cell inlet and a difference signal with the set value is passed from the controller 50 to a fuel valve 53 of a fuel modifier 20 to hold the supply temp. of the fuel gas constant. On the other hand, the temp. signal from an oxidating agent gas temp. sensor 60 at the cell outlet is sent to the controller 50, which passes a rate-of-flow signal to a flow adjusting valve 62 of a bypass flowline 63 of compressor 32, to adjust the rate of flow of the oxidating agent gas.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fuel cell power generation facility and a method of operating the same.
In particular, the present invention relates to fuel cell power generation equipment and a method of operating the same, which are suitable for operating at an optimum temperature over a wide load range, with the battery temperature not changing even during load fluctuations, maintaining high performance, high reliability, and long life.

[Conventional technology]

Conventional fuel cell power generation equipment and its operating method include means for recirculating oxidizing gas, combustion exhaust gas for a fuel reformer, and supply air oxidizing gas from a compressor, as described in JP-A No. 53-29534. The temperature of the gas at the cell inlet was controlled by mixing the gas. In addition, in Japanese Patent Application Laid-open No. 58-164157,
The temperature at the battery outlet or the battery inlet of the oxidizing gas is detected, the recirculation flow rate of the oxidizing gas is controlled, and the temperature of the oxidizing gas at the battery inlet is adjusted.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into consideration the oxidant gas temperature, gas flow rate control, or operating method for operating the battery at an optimum temperature when the battery load changes. Japanese Patent Publication No. 53-29
No. 534 does not specifically describe how to operate the battery when the battery load changes, and even if it is controlled by the battery inlet temperature of the oxidizing gas and the gas flow rate,
The operating range determined by the battery's maximum, minimum, or average temperature is not necessarily wide (although it is necessary to appropriately control the gas flow rate and gas temperature, and the battery is a type of chemical reactor, and when the temperature changes, The speed of change is very slow, and there are problems in terms of performance, reliability, and operating characteristics, such as the inability to obtain stable output and the occurrence of low-cycle thermal fatigue.

In addition, in JP-A No. 58-164157, the recirculation flow rate of the oxidizing gas is determined by detecting the oxidizing gas temperature at the outlet of the battery and, if necessary, the oxidizing gas temperature at the inlet. However, a fuel cell is a type of chemical reaction device, and when the battery temperature changes, its performance changes significantly.In other words, the amount of heat generated within the battery changes, and the battery temperature changes accordingly. do. therefore,
Controlling the recirculating oxidant gas flow rate based on the detection data of either the outlet or inlet gas temperature, or both, means that the inlet gas temperature of the cell will constantly fluctuate, and the performance will change accordingly.
Battery temperature also changes, leading to unstable output and low-cycle thermal fatigue, which poses problems in terms of performance, reliability, and operating characteristics. Also, if the battery load changes,
The above-mentioned problems are further emphasized, resulting in a control method that has serious problems in load characteristics.

The object of the present invention is to provide a fuel cell power generation equipment and method for its operation that has excellent load responsiveness, can be operated at an optimal battery temperature for a wide range of loads, and achieves high performance, high reliability, and long life. Our goal is to provide the following.

Means for Solving Problem C] The above purpose is to provide an oxidant gas temperature regulator at the battery inlet in the oxidant gas recirculation system, and to install an oxidant gas temperature regulator at the battery inlet and outlet of the oxidant gas supply and exhaust pipes. The cell outlet temperature range that is the target value of the oxidant gas is calculated from the signal from the installed gas temperature detector, the current of the load device, and the voltage signal, and based on this calculated temperature, the battery inlet temperature of the oxidant gas is set as above. By controlling the temperature at a constant level with a gas temperature regulator installed in the oxidizing gas recirculation piping system, and controlling the oxidizing gas flow rate to the battery so that the temperature at the battery outlet of the oxidizing gas falls within the above-mentioned temperature range,
achieved.

Therefore, the first invention of the present invention is "a unit composed of an electrolyte plate, an electrode, and a separator plate, and in which a flow path for fuel and oxidant gas is formed between the electrode and the separator plate. A battery stack consisting of a plurality of stacked batteries, a container for storing the stack, a piping system for supplying and exhausting fuel and oxidizing gas to the stack, a piping system for supplying and exhausting gas to the container for storing the stack, and a battery. In the fuel cell power generation equipment comprising an external load device, an acid gas supply device, and a fuel reformer, the oxidant gas supply, the battery inlet of the exhaust pipe,
An outlet gas temperature detector is provided, and an oxidizing gas recirculation piping system is provided that connects the oxidizing gas exhaust pipe and the air supply pipe.
A gas temperature regulator for controlling the battery inlet temperature of the oxidizing gas based on the battery inlet temperature detected by the detector is provided in the middle of the piping system, and the detector is further provided in the oxidizing gas supply piping system. A fuel cell power generation equipment characterized by being provided with a gas flow rate control device that controls an oxidant gas flow rate based on a cell outlet temperature detected by a fuel In battery power generation equipment, an oxidizing gas recirculation piping system is provided that connects the oxidizing gas exhaust pipe and the air supply pipe,
Calculate the battery outlet temperature range that is the target value of the oxidizing gas from the oxidizing gas supply, battery inlet of the exhaust pipe, the signal from the gas temperature detector at the outlet, the current of the load device, and the voltage signal. Based on the temperature, the cell inlet temperature of the oxidant gas is controlled to be constant by a gas temperature controller installed in the oxidant gas recirculation piping system, and the cell outlet temperature of the oxidant gas is controlled by controlling the oxidant gas flow rate to the cell. A method of operating a fuel cell power generation facility, comprising adjusting the temperature to fall within the above temperature range. ”.

[For production]

The operating temperature of a fuel cell is determined by the maximum and minimum temperatures within the cell and the average temperature of the cell. The maximum temperature of a battery is determined by the allowable evaporation amount of the electrolyte, corrosion rate, material strength, etc., and the minimum temperature is determined by the operating limit temperature of the electrolyte plate, for example, the melting point of molten carbonate. Also, since the average temperature is directly related to performance, it would be better to set it higher if possible, but due to the problems mentioned above, the average temperature should be set as high as possible so that the hot spot reaches the maximum allowable temperature. become. Battery temperature is determined by the current flowing inside the battery, operating voltage, battery circuit voltage, gas flow rate, inlet gas temperature, etc. Inside the battery, the amount of heat generated changes depending on the battery performance, and the amount of heat generated from the fuel gas inlet of the battery changes. The amount of power generated, that is, the distribution of heat generation, also changes across the outlet, creating a temperature distribution within the battery.

Therefore, in order to operate the battery at an optimal temperature, it is necessary to change the inlet gas temperature and gas flow rate depending on the load and battery performance. In addition to installing an oxidizing gas temperature controller, the oxidizing gas is supplied.

The battery outlet temperature range, which is the target value of the oxidant gas, is calculated from the signals from the gas temperature detectors installed at the battery inlet and outlet of the exhaust pipe, the current and voltage signals of the load device, and based on this calculated temperature, Controlling the cell inlet temperature of the oxidant gas to a constant value with a gas temperature controller provided in the oxidant gas recirculation piping system;
By controlling the oxidizing gas flow rate to the battery and adjusting the temperature of the oxidizing gas at the battery outlet so that it falls within the above temperature range, the battery will always be operated at the optimum temperature even when the load changes. Even under such conditions, performance instability and low-cycle thermal fatigue due to temperature fluctuations do not occur, and battery operation with good load characteristics, high performance, and high reliability can be achieved.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

Figure 1 shows a system diagram of the fuel cell power generation facility. The battery stack 10 is installed in the containment vessel 1, and an oxidant gas supply and exhaust pipe 37.11 is connected to the cathode side of the battery, and a gas temperature detector 15.16 is attached to the inlet and outlet portions. It is being The oxidizing gas exhaust pipe is branched by a valve 39 into a recirculation line 41 and an oxidizing gas line 19 for combustion gas that serves as a driving source for the turbine 31 . The oxidant gas recirculation line is equipped with a combustor 4 for controlling the oxidant gas inlet temperature.
0 is provided, and a fuel line 34 is attached via a flow rate control valve 42.

Oxidant gas is supplied to the battery by combining part of the exhaust oxidizing gas from the battery and fuel to generate high-temperature combustion gas in the turbine combustor 30, which drives the turbine 31, and uses the power to drive the compressor. 32. Air from the compressor 32 is branched by a valve 33 into oxidant gas 35 for the cell stack and combustion air 36 for the fuel reformer 20 . The oxidant gas 35 is mixed with the gas 43 from the recirculation line and the combustion gas 23 of the fuel reformer 20 before entering the cell.

Fuel gas is supplied to the battery through raw fuel 24 to fuel reformer 20.
is supplied and is carried out by the reforming action of a reforming catalyst. Here, a case is shown in which heat is required for reforming the raw fuel, and this heat source uses air 36 from the compressor to combust the fuel gas remaining in the exhaust gas 12 of the fuel gas supplied to the battery. It can be obtained by A gas temperature detector 16 is provided at the cell inlet of the fuel gas, and the gas temperature is controlled to be constant. Further, the fuel gas exhaust line 12 is provided with a valve 64 and a recirculation line 65.

Inert gas is supplied from the air supply pipe 13 at a pressure slightly higher than the gas pressure inside the battery to prevent the gas inside the battery from leaking into the inside of the battery storage container 1, and is circulated by a blower 14 to maintain a constant temperature at all times. It is adjusted so that

The load on the battery is changed by the inverter 2 installed outside the battery, and accordingly, the raw fuel 24 and the air from the compressor are adjusted by the valve 62. What passes through is supplied to the combustor 30 and used as a driving source for a turbine. Although not shown, the output of this turbine can also directly drive a generator to generate electricity.

To operate the battery, the sensor 15 sends a signal indicating the battery inlet temperature of the oxidizing gas to the controller 50, and the controller 50 sends a signal for controlling the combustion gas temperature according to the difference between the temperature based on the signal and the set value for combustion for recirculation. The temperature of the gas supplied to the battery is maintained at a constant temperature. Similarly, the temperature of the fuel gas to the battery is determined by sending a signal corresponding to the difference between the signal from the gas temperature detector 16 at the battery inlet and the installed value from the controller 50 to the combustion fuel valve 53 of the fuel reformer 20. The reformer itself can be operated at a constant temperature even when the load fluctuates, and the temperature at which fuel gas is supplied to the battery can also be kept constant.

As mentioned earlier, the battery operating conditions are such that the battery temperature is the optimum temperature.
In other words, the temperature is designed taking into consideration the maximum, minimum, average temperature, etc. Using the cell inlet temperature of the oxidant gas and the blanket gas temperature around the cell as parameters, the gas utilization rate (the value obtained by dividing the theoretically required gas flow rate determined by the load by the actual gas flow rate) is determined for the fuel and oxidation gas. FIG. 2 shows the maximum, minimum, and average temperatures of the cell when both the agent gas and the fuel gas inlet temperature were held constant. The gas utilization rate is 0.2 and 0.4 for oxidizing gas and fuel gas, respectively, and when the load is 100%, the battery operating conditions are changed from the mesh part that satisfies all the maximum, minimum, and average temperature conditions. , the position of the circle mark, that is, the blanket gas temperature is 550°C, and the oxidizing gas cell inlet temperature is 55.
If it is set to 0°C, if the utilization rate is constant (if the load changes, the gas flow rate will change), then as you can see from the results in the same figure, when the load is 50%, the battery will be kept at the optimal temperature. To achieve this, the temperature at the cell inlet of the oxidant gas must be increased to 600'C so that the operating conditions fall within the mesh area. Increasing the cell inlet temperature of the oxidant gas to 600° C. can be easily achieved by increasing the outlet gas temperature of the recirculating combustor 40 of FIG. However, changing the inlet gas temperature of the battery means that the temperature distribution of the entire battery changes, and accordingly, the amount of battery chemical reaction changes, and the heat generation distribution also changes. In a fuel cell, the flow rate of gas per unit area is very small, so when the amount of heat generated changes, the cell temperature begins to change slowly, and it takes a long time to reach a steady state. FIG. 3 shows the battery temperature change when the load is changed while the utilization rate is constant. As can be seen from these results, if the load changes and the amount of heat generated changes, the battery temperature will not become constant within 1 to 2 hours, and unless the battery temperature becomes constant, the battery performance will not become stable.

Maintains battery temperature at optimal temperature even when load changes,
In order to stabilize the performance, while keeping the battery inlet gas temperature constant, we also set the oxidizing gas utilization rate and the oxidizing gas utilization rate so that the average temperature of the battery is optimal for the load as shown in Figure 4. The relationship with the temperature rise at the oxidizing gas outlet is designed, and a signal from the oxidizing gas temperature detector at the battery outlet is sent to the controller 50 according to load fluctuations, and the bypass flow path from the compressor 32 in FIG. 63 flow control valve 62
The controller 50 sends a flow rate signal such that the average temperature of the battery becomes constant, thereby controlling the flow rate to the battery.

In this way, the cell inlet temperature of the oxidant gas is kept constant,
By detecting the oxidizing gas outlet temperature and controlling the oxidizing gas flow rate according to the load so that the battery average temperature becomes the optimum temperature, the battery temperature almost changes as shown by the broken line in Figure 3. The battery can be operated with high performance and reliability by preventing unstable performance due to load changes, thermal fatigue due to low cycles, shortened lifespan due to the occurrence of hot spots, etc. This makes it possible to achieve longer battery life.

〔Effect of the invention〕

According to the present invention, even if the battery load changes, the battery can be operated with almost no change in battery temperature, so it is possible to prevent performance instability, low cycle thermal fatigue, and the occurrence of high temperature parts due to load changes, and improve load response. This has the effect of achieving high performance, high reliability, and long-life fuel cell power generation.

[Brief explanation of the drawing]

Figure 1 shows a power generation equipment system diagram of an embodiment of the present invention, Figure 2 shows changes in battery operating range due to load fluctuations, Figure 3 shows changes in battery temperature due to load fluctuations, and Figure 4 shows battery temperature kept constant. The relationship between the load, battery temperature, and gas utilization rate is shown below. DESCRIPTION OF SYMBOLS 1... Battery storage container, 2... Load, 10... Battery stack, 11... Oxidizing gas exhaust pipe, 12... Fuel gas exhaust pipe, 13... Placket gas supply pipe, 1
5... Oxidizing gas battery inlet temperature detector, 16...
Fuel gas cell inlet temperature detector, 20... fuel reformer,
21... Reformer burner, 22... Fuel gas supply pipe,
23...Reformer burner exhaust gas, 24...Raw fuel,
30... Turbine combustor, 31... Turbine, 3
2... Compressor, 40... Recirculation combustor, 42...
・Combustor fuel valve for recirculation, 50...controller, 6
2... Compressed air bypass valve.

Claims (1)

[Claims] 1. Consisting of an electrolyte plate, an electrode, and a separator plate,
A battery stack consisting of a plurality of stacked unit cells in which a flow path for fuel and oxidant gas is formed between the electrode and the separator plate, a container for storing this stack, and supply and exhaust of fuel and oxidant gas to the stack. In a fuel cell power generation facility, which includes a piping system for supplying and exhausting gas into a container storing a stack, an external load device for the battery, an oxidizing gas supply device, and a fuel reformer, the oxidizing gas is Gas temperature detectors are provided at the battery inlet and outlet portions of the supply and exhaust pipes, and an oxidant gas recirculation piping system is provided that connects the oxidant gas exhaust pipe and the supply pipe, and the A gas temperature regulator is provided to control the battery inlet temperature of the oxidant gas based on the battery inlet temperature detected by the detector, and the battery outlet temperature detected by the detector is further provided in the oxidant gas supply piping system. A fuel cell power generation facility characterized by being provided with a gas flow rate control device that controls the gas flow rate of an oxidant gas based on. 2. The fuel cell power generation equipment according to claim 1, wherein the gas temperature regulator provided in the oxidant gas recirculation piping system is a recirculation combustor. 3. In fuel cell power generation equipment, an oxidant gas recirculation piping system is installed to connect the oxidant gas exhaust pipe and the air supply pipe, and the gas temperature is Calculate the battery outlet temperature range that is the target value of the oxidant gas from the signal from the detector, the current of the load device, and the voltage signal,
Based on this calculated temperature, the temperature at the battery inlet of the oxidant gas is controlled to be constant by a gas temperature controller installed in the oxidant gas recirculation piping system, and the oxidant gas is controlled at the battery outlet by controlling the oxidant gas flow rate to the battery. A method for operating a fuel cell power generation facility, comprising adjusting the temperature to fall within the above temperature range. 4. A gas temperature regulator installed in the oxidant gas recirculation piping system is a recirculation combustor, and supplies exhaust oxidant gas from the battery and fuel gas to the recirculation combustor, and The fuel cell power generation according to claim 3, characterized in that the rate of recirculation flow rate of the oxidizing agent gas is controlled to be constant, and the temperature at which the oxidizing agent gas is supplied to the cell is adjusted to be constant by controlling the flow rate of the fuel gas. How to operate the equipment.