JP7679707B2 - Fuel Cell Power Generation Equipment - Google Patents

Description

This disclosure relates to a fuel cell power generation device.

A fuel cell power generation system is known that prevents a decrease in the amount of power generated by removing gas trapped in the coolant flow path of the fuel cell stack when the fuel cell is started (see, for example, Patent Document 1).

JP 2007-280748 A

Thermal oils such as insulating oil or water such as pure water are often used as heat transfer media to flow through the cooling system of a fuel cell. When using thermal oil as a heat transfer media, when starting up the fuel cell, in addition to removing gas trapped in the cooling system, it is also necessary to remove moisture that has condensed in the cooling system and water trapped in the cooling system. If gas and moisture are mixed into the cooling system, for example, the following problems are likely to occur:

- Damage due to cavitation in circulation pumps - Fluctuations in temperature of the thermal oil due to changes in the flow rate of the thermal oil - Abnormal pressure increases in the cooling system - Deterioration of the heat transfer performance of the thermal oil - Deterioration of the heat transfer performance and insulation properties of the thermal oil, etc.

However, with conventional technology, it is not easy to sufficiently remove the gas and moisture that cause these problems from the cooling system. Furthermore, since gas and liquid have different phase states (gas phase and liquid phase) at room temperature and different thermodynamic properties, degassing and dehydration fundamentally differ in the methods of removing substances.

The present disclosure provides a fuel cell power generation device capable of removing gas and moisture from a cooling system.

In one aspect of the present disclosure,
A fuel cell;
a cooling system for supplying thermal oil to the fuel cell;
a pump provided in the cooling system for circulating the thermal oil through the cooling system;
A tank provided at the top of the cooling system for storing the thermal oil;
a heating device for heating the thermal oil between an outlet of the fuel cell and a suction port of the pump;
a shutoff valve connected to an upper space in which gas accumulates in the tank;
a control device that opens the shutoff valve so that gas and water in the cooling system are released from the shutoff valve through the tank.

According to one aspect of the present disclosure, gas and moisture can be removed from the cooling system.

1 is a diagram showing an example of the configuration of a fuel cell power generation device according to a first embodiment; 4 is a flowchart showing an example of a start-up method for the fuel cell power generator according to the first embodiment. 10 is a flowchart showing an example of a method for calculating a time required for evaporation from the amount of condensed water. FIG. 13 is a diagram showing an example of the configuration of a fuel cell power generation device according to a second embodiment. 10 is a flowchart showing an example of a start-up method for a fuel cell power generator according to a second embodiment.

The following describes the embodiment.

Figure 1 is a diagram showing an example of the configuration of a fuel cell power generation device according to the first embodiment. The fuel cell power generation device 11 shown in Figure 1 is a device that introduces fuel gas and oxidizing gas and converts them into electrical energy. The fuel cell power generation device 11 includes, for example, a fuel cell 13, a DC-AC converter 12, a cooling system 27, a pump 28, a heater 19, a temperature sensor 17, an expansion tank 24, an oil level gauge 21, a pressure sensor 23, a shutoff valve 29, a control device 20, a temperature sensor 18, and a bypass path 26.

The fuel cell 13 is a device that electrochemically converts the chemical energy of fuels such as hydrogen and methanol into electrical energy. The fuel cell 13 has a fuel electrode 14, an air electrode 15, and a cooling plate 16. The fuel cell 13 generates electricity through an electrochemical reaction between hydrogen or hydrogen-rich gas supplied to the fuel electrode 14 and oxygen contained in the reaction air supplied to the air electrode 15 by an air blower 22. The heat generated by the power generation of the fuel cell 13 is removed by the cooling plate 16 built into the cell stack, and the temperature of the fuel cell 13 is maintained at a predetermined operating temperature.

The fuel cell 13 has an inlet 13b through which thermal oil for cooling the fuel cell 13 is introduced, and an outlet 13a through which the thermal oil is discharged after passing through the cooling plate 16 of the fuel cell 13. The heat generated in the fuel cell 13 is released together with the thermal oil discharged from the cooling plate 16 to the outlet 13a.

The DC-AC converter 12 is a DC-AC converter that converts the DC power obtained by power generation in the fuel cell 13 into AC power and supplies it to a load (not shown). The DC-AC converter 12 may be replaced with a DC-DC converter that converts the voltage of the DC power obtained by power generation in the fuel cell 13 into DC power of a different voltage and supplies it to a load (not shown).

The cooling system 27 is a cooling circuit that supplies thermal oil such as insulating oil to the fuel cell 13. The cooling system 27 includes, for example, a cooling plate 16 provided on the fuel cell 13, an outlet path 27a connecting the outlet 13a of the fuel cell 13 and the suction port 28a of the pump 28, and an inlet path 27b connecting the discharge port 28b of the pump 28 and the inlet 13b of the fuel cell 13. The thermal oil discharged from the discharge port 28b of the pump 28 to the inlet path 27b circulates through the cooling system 27.

Pump 28 is a circulation pump provided in cooling system 27, and circulates thermal oil through cooling system 27. Pump 28 has suction port 28a, which is the inlet for thermal oil, and discharge port 28b, which is the outlet for thermal oil. Pump 28 is operated by a motor (not shown) controlled by control device 20.

The heater 19 is an example of a heating device that heats the thermal oil between the outlet 13a of the fuel cell 13 and the suction port 28a of the pump 28. The heater 19 is, for example, a circulation heater provided in the outlet path 27a between the outlet 13a and the suction port 28a, and heats the thermal oil flowing in the outlet path 27a. The heating device that heats the thermal oil in the cooling system 27 is not limited to a heater such as a circulation heater, and may be other heating equipment such as a start-up burner.

The temperature sensor 17 measures the temperature T of the thermal oil between the heater 19 and the suction port 28a, and outputs a sensor signal corresponding to the measured temperature T to the control device 20. The temperature sensor 17 is provided, for example, in a path portion of the outlet path 27a between the outlet of the heater 19 and the suction port 28a of the pump 28, and measures the temperature T of the thermal oil that has passed through the outlet of the heater 19. In the example shown in FIG. 1, the temperature sensor 17 measures the temperature T between the expansion tank 24 and the heater 19.

The expansion tank 24 branches off from the outlet path 27a of the cooling system 27 and is connected to the outlet path 27a downstream of the heater 19. The expansion tank 24 has, for example, a function to absorb the expansion or contraction of the thermal oil, and a function to release gas generated in the thermal oil and release it into the atmosphere. The expansion tank 24 is provided at the top of the cooling system 27, and is installed, for example, so that the liquid level L of the thermal oil stored in the expansion tank 24 is higher than the uppermost cooling plate 16 (Figure 1 shows the position on the circuit, not the actual installation position).

The oil level gauge 21 is a level gauge that measures the liquid level L of the thermal oil in the expansion tank 24 and outputs a measurement result signal corresponding to the measured liquid level L to the control device 20.

The pressure sensor 23 measures the pressure P in the upper space where the gas accumulates in the expansion tank 24, and outputs a sensor signal corresponding to the measured pressure P to the control device 20.

Shut-off valve 29 is connected to the upper space in which gas accumulates in expansion tank 24, and is driven to open and close by control device 20. Shut-off valve 29 may be an electromagnetically driven valve or an air-driven valve.

The control device 20 is a controller that increases or decreases the flow rate of thermal oil flowing through the cooling system 27 in accordance with the temperature measured by the temperature sensor 17. The control device 20 can increase or decrease the flow rate of thermal oil passing through the heater 19 in the cooling system 27, for example, by increasing or decreasing the flow rate of thermal oil discharged from the discharge port 28b of the pump 28 to the inlet path 27b of the cooling system 27 in accordance with the temperature T measured by the temperature sensor 17. The control device 20 is, for example, a programmable logic controller (PLC).

The control device 20 energizes the heater 19 to heat the thermal oil, and deenergizes the heater 19 to stop the heater 19 from heating the thermal oil. The control device 20 controls the operation of the pump 28, and more specifically, controls an inverter that drives a motor that operates the pump 28.

The functions of the control device 20 may be realized by a processor such as a CPU (Central Processing Unit) operating according to a program stored in memory. The functions of the control device 20 may be realized by a FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

When the fuel cell power generation device 11 is started or when the temperature of the heat medium flowing through the cooling system 27 is below a predetermined temperature threshold, the control device 20 heats the heat medium flowing through the cooling system 27 using the heater 19, thereby quickly warming up the fuel cell 13.

The temperature sensor 18 measures the temperature t of the thermal oil between the discharge port 28b of the pump 28 and the inlet 13b of the fuel cell 13, and outputs a sensor signal corresponding to the measured temperature t to the control device 20. The temperature sensor 18 is provided, for example, in the path portion between the discharge port 28b of the pump 28 and the inlet 13b of the fuel cell 13 in the inlet path 27b, and measures the temperature t of the thermal oil just before it enters the inlet 13b.

The control device 20 controls the flow rate of the thermal oil flowing through the cooling system 27 according to the temperature t measured by the temperature sensor 18, and increases or decreases the lower limit of the flow rate of the thermal oil flowing through the cooling system 27 according to the temperature T measured by the temperature sensor 17. This allows the flow rate of the thermal oil flowing through the cooling system 27 to be adjusted according to the temperature t on the inlet 13b side of the fuel cell 13, and the lower limit of the flow rate of the thermal oil flowing through the cooling system 27 to be adjusted according to the temperature T on the outlet side of the heater 19.

The fuel cell power generation device 11 may include a bypass path 26 connected in parallel to the pump 28. The bypass path 26 is a circulation path whose inlet side is connected to the discharge port 28b and whose outlet side is connected to the suction port 28a. The bypass path 26 is provided with a control valve 25 and a heat exchanger 31. The cooling system 27 is formed so that a portion of the thermal oil discharged from the pump 28 is sent to the cooling plate 16 of the fuel cell 13, and the remaining thermal oil is returned to the suction port 28a side of the pump 28 via the heat exchanger 31 and the control valve 25 on the bypass path 26.

The control device 20 adjusts the temperature of the thermal oil flowing through the cooling system 27 by controlling the opening of the adjustment valve 25 according to the temperature t of the thermal oil measured by the temperature sensor 18. The control device 20 can control the temperature t of the thermal oil measured by the temperature sensor 18 to a predetermined target temperature, for example, by controlling the opening of the adjustment valve 25. In this way, the control device 20 can adjust the temperature of the fuel cell 13 to a target temperature corresponding to the power generation current of the fuel cell 13.

The heat exchanger 31 is supplied with an external heat medium such as external cooling water and exchanges heat with the heat transfer oil flowing in the bypass path 26. The external heat medium is heat exchanged by passing through the heat exchanger 36 and is supplied to the radiator 38. The radiator 38 is, for example, a cooler that air-cools the external heat medium using a fan or the like. The external heat medium whose temperature has been reduced by the radiator 38 is supplied to the heat exchanger 31.

Figure 2 is a flow chart showing an example of a method for starting up the fuel cell power generation system according to the first embodiment. When the control device 20 starts up the fuel cell power generation system 11 by turning on the main power supply (step S11), it opens the shutoff valve 29 (step S13) and operates an oil supply pump (not shown) to fill the cooling system 27 with thermal oil (step S15). In step S15, the control device 20 operates the oil supply pump (not shown) until the liquid level L of the thermal oil in the expansion tank 24 measured by the oil level gauge 21 reaches or exceeds a certain level. The oil supply pump is a pump that supplies thermal oil to the cooling system 27 from outside the cooling system 27.

In step S17, the control device 20 removes the gas contained in the thermal oil in the cooling system 27 at room temperature with the shutoff valve 29 open (room temperature degassing process). For example, the control device 20 operates the pump 28 so that the thermal oil circulates through the cooling system 27, thereby degassing the thermal oil in the cooling system 27 at room temperature for a degassing time Tg that is predetermined by a timer. In this way, the control device 20 can circulate the thermal oil in the cooling system 27 and release the gas contained in the thermal oil from the shutoff valve 29 via the expansion tank 24.

In step S19, the control device 20 removes gas contained in the thermal oil in the cooling system 27 at a high temperature with the shutoff valve 29 open (heating and degassing process). For example, the control device 20 operates the heater 19 that heats the thermal oil in the cooling system 27 to heat the thermal oil and degas it at a high temperature. This allows the control device 20 to warm up the thermal oil and release the gas contained in the thermal oil from the shutoff valve 29 via the expansion tank 24. In other words, the heating and degassing process can be used as a warm-up process for the thermal oil and the fuel cell 13, so the start-up time of the fuel cell 13 can be shortened.

In step S21, the control device 20 removes moisture contained in the thermal oil in the cooling system 27 at a high temperature with the shutoff valve 29 open (heating and dehydration process). For example, the control device 20 operates the heater 19 that heats the thermal oil in the cooling system 27 to heat the thermal oil and dehydrate it at a high temperature. As a result, the control device 20 can warm up the thermal oil and release the steam of the moisture contained in the thermal oil from the shutoff valve 29 via the expansion tank 24. In other words, the heating and dehydration process can be used as a process for warming up the thermal oil and the fuel cell 13, so the start-up time of the fuel cell 13 can be shortened.

In step S23, the control device 20 determines whether or not to continue the heating dehydration process of step S21 (dehydration continuation determination process). The control device 20 determines whether or not to continue the heating dehydration process, for example, by determining whether or not the temperature T measured by the temperature sensor 17 has risen to or above a predetermined temperature threshold.

In step S23, the control device 20 may determine whether or not to continue by judging whether the temperature T measured by the temperature sensor 17 while the thermal oil is being heated by the heater 19 has risen to or above a predetermined temperature threshold after remaining in a constant state for a predetermined time or more. A constant state for a predetermined time or more (temperature maintained state) represents a state in which the heating energy from the heater 19 is being used to dehydrate the thermal oil, and the rise in temperature T after the temperature is maintained state can be considered to mean that most of the water contained in the thermal oil has evaporated.

In step S23, the control device 20 may determine whether or not the heating and dehydration process in step S21 needs to continue by determining whether a predetermined heating time Th has elapsed since the heater 19 started heating the thermal oil. The heating time Th is counted by a timer or the like. The heating time Th is a time that is set in advance, and an example of its calculation will be described later.

If the control device 20 determines in step S23 that the heating and dehydration process needs to continue, it continues the heating and dehydration process (step S21). On the other hand, if the control device 20 determines that the heating and dehydration process does not need to continue, it closes the shutoff valve 29 (step S25) and stops heating the thermal oil by the heater 19, thereby completing the heating and dehydration process (step S27).

After completing the heating and dehydration process, the control device 20 proceeds to the power generation process in step S29 and starts power generation by the fuel cell 13.

In this way, according to the first embodiment, it is possible to remove not only gas but also moisture from the cooling system 27.

Next, we will explain an example of how to calculate the heating time Th.

Figure 3 is a flow chart showing an example of a method for calculating the time required for evaporation from the amount of condensation water. The heating time Th may be set to a time equal to or longer than the "time required for evaporation" calculated by this method. The method shown in Figure 3 may be executed by the control device 20, which may automatically set the heating time Th based on the calculated time. Alternatively, a person may calculate the "time required for evaporation" in advance according to the method shown in Figure 3, and derive the heating time Th based on the calculated time. The derived heating time Th is reflected in advance in the memory and program of the control device 20.

For example, when the temperature difference is between 40°C and 0°C, the difference in the amount of saturated water vapor in the air [g/ ^m3 ] is calculated from the relative humidity to be 46.27 (=51.12-4.85) [g/ ^m3 ]. By multiplying 46.27 [g/ ^m3 ] by the internal volume of the cooling system 27, 0.16 [ ^m3 ], the amount of condensation is calculated to be 7.4 [g] (step S31). In step S33, the amount of condensation is multiplied by the specific heat and the temperature difference K when heating to 100°C to calculate the amount of heat [kJ] required to evaporate the condensed water (0.0074 [kg] x 4.186 [kJ/kgK] x 100 [K] = 3.097 [kJ]).

On the other hand, the capacity of the heater 19 is 25 [kW], the specific heat of water is 4.186 [kJ/kgK], the specific heat of the thermal oil is 1.8 [kJ/kgK], and the mass of the thermal oil is 160 [kg]. In this case, in step S35, the amount of heat per unit time that the capacity of the heating equipment such as the heater 19 contributes to the evaporation of the water in the thermal oil is calculated to be 2.7 [J/s] (25 [kW] x (0.0074 x 4.186 / (160 x 1.8 + 0.0074 x 4.186) = 0.0027 [kW] = 2.7 [W] = 2.7 [J/s]).

Therefore, in step S37, the time required for evaporation (heating time Th) based on the amount of condensed water is calculated to be 19 minutes (3.097 [kJ] / 0.0027 [kJ/s] / 3600 = 0.32 [h] = 19 [min]).

Figure 4 is a diagram showing an example of the configuration of a fuel cell power generation device according to the second embodiment. In the second embodiment, the explanation of the configuration, action, and effect similar to those of the first embodiment will be omitted or simplified by invoking the above explanation. The fuel cell power generation device 41 shown in Figure 4 includes a suction pump 42, a moisture meter 43, and a purge valve 44.

The suction pump 42 is a pump that reduces the pressure in the cooling system 27, lowers the relative humidity, and sucks out evaporated water before the process of filling the cooling system 27 with thermal oil. The suction pump 42 is operated by a motor (not shown) controlled by the control device 20.

The moisture meter 43 measures the moisture content in the piping on the output side of the suction pump 42 and outputs a sensor signal corresponding to the measured moisture content to the control device 20. Specific examples of the moisture meter 43 include a dew point meter and a moisture analyzer.

The purge valve 44 is a shutoff valve that injects an inert dry gas (e.g., nitrogen) into the cooling system 27 to expel steam from the cooling system 27. The purge valve 44 is connected, for example, to a portion of the outlet path 27a between the heater 19 and the outlet 13a, and injects the inert dry gas into the cooling system 27 from that portion.

Figure 5 is a flow chart showing an example of a method for starting up a fuel cell power generation system according to the second embodiment. When the control device 20 starts up the fuel cell power generation system 41 by turning on the main power supply (step S41), it starts dehydrating the thermal oil in the cooling system 27 with the shutoff valve 29 closed (step S43).

In step S45, the control device 20 operates the suction pump 42 before filling the cooling system 27 with thermal oil, thereby reducing the pressure in the cooling system 27, lowering the relative humidity, and causing the suction pump 42 to suck out evaporated moisture from the cooling system 27. For example, when the pressure is reduced to one-fifth of atmospheric pressure and the volume expands five-fold, the relative humidity becomes approximately one-fifth, or 20% of the saturated state.

In step S47, the control device 20 determines whether a predetermined decompression time Tdp has elapsed since the start of decompression by the suction pump 42. The decompression time Tdp is calculated, for example, based on the difference in vapor pressure between water and thermal oil. If the predetermined decompression time Tdp has not elapsed, the control device 20 continues decompression by the suction pump 42 (step S45). On the other hand, if the predetermined decompression time Tdp has elapsed, the control device 20 performs the determination process of step S49.

In step S49, the control device 20 determines whether the moisture content measured by the moisture meter 43 is less than a predetermined allowable amount Wa. The allowable amount Wa is set, for example, to the amount of moisture that is allowable in terms of the performance of the thermal oil. If the moisture content is equal to or greater than the allowable amount Wa, the control device 20 continues reducing the pressure by the suction pump 42 (step S45). On the other hand, if the moisture content is less than the allowable amount Wa, the control device 20 performs the process of step S51.

In step S51, the control device 20 switches the purge valve 44 from closed to open to perform a purge by injecting an inert dry gas such as nitrogen into the cooling system 27 to flush out impurities from the thermal oil.

In step S53, the control device 20 determines whether a predetermined purge time Tp has elapsed since the start of purging. If the predetermined purge time Tp has not elapsed, the control device 20 continues reducing the pressure by the suction pump 42 (step S45). On the other hand, if the predetermined purge time Tp has elapsed, the control device 20 switches the purge valve 44 from open to closed (step S55), stops reducing the pressure by the suction pump 42, and completes the spin-drying process (step S57).

In step S59, the control device 20 operates the oil supply pump (not shown) to fill the cooling system 27 with thermal oil with the shutoff valve 29 open, similar to step S15 in FIG. 2. In step S61, the control device 20 degasses the thermal oil at room temperature, similar to step S17 in FIG. 2. In step S63, the control device 20 heats the thermal oil and degasses it at a high temperature, similar to step S19 in FIG. 2. After completing the heating and dehydration process, the control device 20 proceeds to the power generation process in step S65 and starts power generation by the fuel cell 13.

In this way, according to the second embodiment, it is possible to remove not only gas but also moisture from the cooling system 27.

Furthermore, in conventional fuel cell power generation systems that use thermal oil such as insulating oil, workers must visit the site during the dehydration process, and labor is required for adjustment work for the dehydration process each time. In contrast, the fuel cell power generation device and start-up method thereof according to the first and second embodiments automates dehydration and detection of completion of dehydration, making it possible to automate the dehydration process. By automating the dehydration process, for example,
The system has the following benefits: - Labor saving for dehydration adjustment work - Reduction in dehydration work mistakes (incomplete dehydration, human error) - Reduction in the labor time required to change the dehydration work setup - Realization of remote start-up - Realization of fully automatic operation in accordance with the start-up sequence.

Although the embodiments have been described above, the technology of the present disclosure is not limited to the above-described embodiments. Various modifications and improvements are possible, such as combinations or substitutions with part or all of other embodiments.

REFERENCE SIGNS LIST 11 fuel cell power generation device 12 DC-AC converter 13 fuel cell 13a outlet 13b inlet 14 fuel electrode 15 air electrode 16 cooling plate 17 temperature sensor 18 temperature sensor 19 heater 20 control device 21 oil level gauge 22 air blower 23 pressure sensor 24 expansion tank 25 control valve 26 bypass path 27 cooling system 27a outlet path 27b inlet path 28 pump 28a suction port 28b discharge port 29 shutoff valve 31 heat exchanger 36 heat exchanger 38 radiator 41 fuel cell power generation device 42 suction pump 43 moisture meter 44 purge valve

Claims (8)

A fuel cell;
a cooling system for supplying thermal oil to the fuel cell;
a pump provided in the cooling system for circulating the thermal oil through the cooling system;
A tank provided at the top of the cooling system for storing the thermal oil;
a heating device for heating the thermal oil between an outlet of the fuel cell and a suction port of the pump;
a shutoff valve connected to an upper space in which gas accumulates in the tank;
a control device that opens the shutoff valve so that gas and water in the cooling system are released from the shutoff valve through the tank. The fuel cell power generation device according to claim 1, wherein the control device operates the heating device to heat the thermal oil while the shutoff valve is open, thereby discharging the gas contained in the thermal oil from the shutoff valve via the tank and discharging the water vapor contained in the thermal oil from the shutoff valve via the tank. The fuel cell power generation device according to claim 2, wherein the control device operates the heating device after the thermal oil is poured into the cooling system. A temperature sensor is provided between the heating device and the intake port to measure the temperature of the thermal oil,
The fuel cell power generation apparatus of claim 2 or 3, wherein the control device starts heating the thermal oil by the heating equipment, and when the temperature measured by the temperature sensor rises above a predetermined temperature threshold, stops heating the thermal oil by the heating equipment. The fuel cell power generation device according to claim 2 or 3, wherein the control device starts heating the thermal oil by the heating device, and stops heating the thermal oil by the heating device after a predetermined heating time has elapsed. a suction pump for reducing the pressure in the cooling system;
2. The fuel cell power generation system according to claim 1, wherein the control device operates the suction pump before the thermal oil is poured into the cooling system, thereby causing the suction pump to suck out moisture in the cooling system. a purge valve for injecting an inert dry gas into the cooling system;
7. The fuel cell power generation system according to claim 6, wherein the control device starts depressurization by the suction pump and opens the purge valve after a predetermined depressurization time has elapsed. a moisture meter for measuring the moisture content of the piping on the output side of the suction pump;
8. The fuel cell power generation system according to claim 7, wherein the control device opens the purge valve when the amount of moisture measured by the moisture meter is lower than a predetermined allowable amount.

Images