JP6946788B2 - Fuel cell system - Google Patents

Description

The present invention relates to a fuel cell system including a reforming unit that reforms a raw material gas into a reforming gas using steam.

Conventionally, as this type of fuel cell system, a combustion part, a vaporization part, a reforming part, a tank for storing water, a supply passage for supplying water in the tank to the vaporization part, and a vaporization part in the supply passage A water sensor that detects the water level immediately before the inlet port, a pump as a water transport source, and a control unit that controls the pump have been proposed (see, for example, Patent Document 1). Before the combustion unit is ignited, the control unit of this fuel cell system rotates the pump in the reverse direction to return the water in the supply passage to the tank, empties the inside of the supply passage, and then rotates the pump in the forward direction to enter the tank. Water is supplied to the supply passage, and the water level in the supply passage is adjusted to a fixed position immediately before the inlet port of the vaporizer while monitoring the actual water level in the supply passage based on the detection signal from the water sensor. .. As a result, the timing of water supply to the vaporizer can be made more appropriate, and caulking of the reformed part (fuel carbonization phenomenon) due to insufficient reformed water and deterioration of catalyst activity (deterioration of performance) due to excessive reformed water can be suppressed. It is said that it can be done.

Japanese Unexamined Patent Publication No. 2012-133915

As described above, the fuel cell system described in Patent Document 1 is provided with a water level sensor immediately before the inlet port of the vaporization unit in order to supply water to the vaporization unit at an appropriate timing. However, even if the water level is adjusted using the water level sensor, if the discharge amount of the pump varies, excess or deficiency of water supply will occur. It is conceivable to use a high-performance pump in order to obtain a stable discharge amount, but this causes an increase in cost.

The main object of the fuel cell system of the present invention is to appropriately perform water level adjustment control and water supply control with a simple and low-cost configuration.

The fuel cell system of the present invention has adopted the following means in order to achieve the above-mentioned main object.

The fuel cell system of the present invention
A fuel cell system including a fuel cell that generates electricity based on a reforming gas containing hydrogen and an oxidant gas containing oxygen.
A reforming unit that reforms the raw material gas into the reforming gas using steam and supplies it to the fuel cell.
A vaporization unit that vaporizes water and supplies it to the reforming unit,
A water tank to store water and
A water pipe connected to the vaporization unit and the water tank,
A water pump that sends the water in the water tank to the vaporization unit through the water pipe,
A combustion part that heats the reforming part and the vaporizing part by combustion,
A flow rate sensor provided at a predetermined position on the downstream side of the water pump in the water pipe to detect the flow rate of water per unit time, and
Water level adjustment control that stops the drive of the water pump based on the change from the non-detection state in which the flow rate sensor cannot detect the flow rate to the detection state in which the flow rate is detected by driving the water pump, and detection by the flow rate sensor. A control device capable of performing water supply control for driving the water pump using feedback control so that the flow rate reaches the target flow rate.
The gist is to prepare.

The fuel cell system of the present invention includes a reforming unit, a vaporizing unit, a water tank, a water pipe, a water pump, a combustion unit, a flow rate sensor, and a control device. The vaporization section and the water tank are connected via a water pipe, and the water in the water tank is sent to the vaporization section by a water pump. The flow rate sensor is provided on the downstream side of the water pump in the water pipe and detects the flow rate of water flowing in the water pipe per unit time. The control device has water level adjustment control that drives the water pump and stops the drive of the water pump based on the change of the flow rate sensor from the non-detection state to the detection state, and the flow rate detected by the flow rate sensor becomes the target flow rate. It is possible to execute the water supply control for driving the water pump by using the feedback control. As described above, by using the flow rate sensor for the water level adjustment control and the water supply control, the water level adjustment control and the water supply control can be appropriately performed by a simple and low-cost configuration.

In such a fuel cell system of the present invention, the control device executes the water level adjustment control at the time of system startup, and then performs the water supply control at a timing when a predetermined time has elapsed from the start of ignition of the combustion unit. By starting, the water supply to the vaporization unit may be started. As a result, it is possible to suppress the excess or deficiency of the water supplied to the reforming unit when the system is started.

In the fuel cell system of the present invention of this aspect, the temperature sensor for detecting the temperature of the vaporization unit or the reforming unit is provided, and the control device starts the water supply control and then detects the temperature by the temperature sensor. The cumulative value of the flow rate detected by the flow rate sensor may be measured until the temperature reaches the peak, and the flow rate detected by the flow rate sensor may be corrected based on the cumulative value of the measured flow rate. By learning the detected value of the flow rate sensor in this way, the accuracy of water supply control can be further improved. In addition, it is possible to appropriately respond to changes over time of the flow sensor. In this case, the control device may stop the system when the cumulative value of the measured flow rate is within the abnormal value range. In this way, it is possible to determine an abnormality (failure) of the flow rate sensor and take appropriate measures.

It is a block diagram which shows the outline of the structure of the fuel cell system 10 of this embodiment. It is a flowchart which shows an example of a system control routine. It is a flowchart which shows an example of a system control routine. It is a flowchart which shows an example of the reforming water supply control routine. It is explanatory drawing which shows the state of the change of the reformer temperature at the time of system startup. It is explanatory drawing which shows an example of the map for setting the flow rate correction value.

A mode for carrying out the present invention will be described.

FIG. 1 is a configuration diagram showing an outline of the configuration of the fuel cell system 10 of the present embodiment. As shown in FIG. 1, the fuel cell system 10 of the present embodiment includes a power generation unit 20 having a fuel cell stack 36 that generates power by being supplied with a fuel gas containing hydrogen and an oxidizing agent gas (air) containing oxygen. The hot water supply unit 100 has a hot water storage tank 101 that recovers and supplies hot water generated by the power generation of the power generation unit 20, and a control device 80 that controls the entire system.

The power generation unit 20 has a vaporizer 32 that evaporates reformed water to generate water vapor and preheats a raw material fuel gas (for example, natural gas or LP gas), and a fuel gas containing hydrogen from the raw material fuel gas and water vapor (modified). A power generation module 30 including a reformer 33 for generating (quality gas), a fuel cell stack 36 for generating power by fuel gas and air, a raw fuel gas supply device 40 for supplying raw fuel gas to the vaporizer 32, and a raw fuel gas supply device 40. The air supply device 50 that supplies air to the fuel cell stack 36, the reforming water supply device 55 that supplies the reforming water in the reforming water tank 57 to the vaporizer 32, and the exhaust heat generated by the power generation module 30 are recovered. The exhaust heat recovery device 60 is provided. These are housed in a rectangular parallelepiped housing 22 that is long vertically.

The housing 22 is divided into two upper and lower chambers, a power generation module 30 is arranged in the upper chamber, and a raw fuel gas supply device 40, an air supply device 50, and a reforming water tank 57 are included in the lower chamber. A reformed water supply device 55, an exhaust heat recovery device 60, and the like are arranged. Further, the housing 22 is provided with an intake port 22a and an exhaust port 22b. A ventilation fan 24 for taking in outside air and ventilating the inside of the housing 22 is provided near the intake port 22a, and a combustible gas sensor 95 for detecting leakage of combustible gas is provided near the exhaust port 22b. There is.

The reformer 33 is configured by supporting a reforming catalyst (for example, a Ru or Ni-based catalyst) on a carrier such as ceramic, and steam reforms a mixed gas of raw fuel gas and steam supplied from the vaporizer 32. It reforms into fuel gas (reforming gas) by quality reaction. Inside the reformer 33, a temperature sensor 91 for detecting the temperature of the reformer 33 is provided.

The vaporizer 32, the reformer 33, and the fuel cell stack 36 constituting the power generation module 30 are housed in a box-shaped module case 31 formed of a heat insulating material. The vaporizer 32 and the reformer 33 are arranged above the fuel cell stack 36. The module case 31 is provided with a combustion unit 34 for starting the fuel cell stack 36, generating steam in the vaporizer 32, and supplying heat required for the steam reforming reaction in the reformer 33. Fuel off gas (anode off gas) and oxidant off gas (cathode off gas) that have passed through the fuel cell stack 36 are supplied to the combustion unit 34, and the mixed gas is ignited by the ignition heater 35 and burned to burn the fuel cell. The stack 36, the vaporizer 32, and the reformer 33 are heated. The module case 31 is provided with a temperature sensor 92 for detecting the temperature of the combustion unit 34. The combustion exhaust gas generated by the combustion of the fuel off gas and the oxidant off gas is supplied to the heat exchanger 62 via the combustion catalyst 37. The combustion catalyst 37 is an oxidation catalyst that reburns the fuel gas left unburned in the combustion unit 34 by the catalyst.

The exhaust heat recovery device 60 has a circulation pipe 61 that connects a heat exchanger 62 to which combustion exhaust gas is supplied from the power generation module 30 and a hot water storage tank 101 for storing hot water to form a circulation path for hot water. A circulation pump 63 is provided in the circulation pipe 61. By driving the circulation pump 63, the hot water is heated by heat exchange between the hot water stored by the heat exchanger 62 and the combustion exhaust gas, and the hot water is heated. Water is stored in the hot water storage tank 101. The heat exchanger 62 is connected to the reforming water tank 57 via the condensed water supply pipe 66 and is connected to the outside air via the exhaust gas discharge pipe 67. The combustion exhaust gas supplied to the heat exchanger 62 has a steam component condensed by heat exchange with the hot water, and is recovered in the reformed water tank 57 via a water purifier (not shown). Further, the remaining exhaust gas is discharged to the outside air through the exhaust gas discharge pipe 67.

The raw fuel gas supply device 40 has a raw fuel gas supply pipe 41 that connects the gas supply source 1 and the vaporizer 32. The raw fuel gas supply pipe 41 is provided with raw fuel gas supply valves (electromagnetic valves) 42, 43, orifices 44, raw fuel gas pump 45, and desulfurizer 46 in this order from the gas supply source 1 side. By driving the raw material fuel gas pump 45 with the supply valves 42 and 43 opened, the raw material fuel gas from the gas supply source 1 is passed through the desulfurizer 46 and supplied to the vaporizer 32. The raw fuel gas supplied to the vaporizer 32 is supplied to the reformer 33 via the vaporizer 32 and reformed into the fuel gas. The raw material fuel gas supply valves 42 and 43 are dual valves connected in series. The desulfurization device 46 removes the sulfur content contained in the raw material fuel gas, and for example, a room temperature desulfurization method for removing the sulfur compound by adsorbing it on an adsorbent such as zeolite can be adopted. Further, a pressure sensor 47 for detecting the pressure of the raw material gas in the raw material gas supply pipe 41 is provided between the raw material fuel gas supply valve 43 of the raw material gas supply pipe 41 and the orifice 44, and the orifice 44 and the orifice 44 are provided. A flow sensor 48 for detecting the flow rate of the raw fuel gas flowing through the raw material gas supply pipe 41 per unit time is provided between the raw material gas pump 45 and the raw material gas pump 45.

The air supply device 50 has an air supply pipe 51 that connects the filter 52 that communicates with the outside air and the fuel cell stack 36. The air supply pipe 51 is provided with an air blower 53, and by driving the air blower 53, air sucked through the filter 52 is supplied to the fuel cell stack 36. Further, the air supply pipe 51 is provided with a flow rate sensor 54 on the downstream side of the air blower 53 to detect the flow rate of air flowing through the air supply pipe 51 per unit time.

The reformed water supply device 55 has a reformed water supply pipe 56 that connects the reformed water tank 57 for storing the reformed water and the vaporizer 32. The reforming water supply pipe 56 extends upward from the reforming water tank 57 arranged in the lower chamber of the housing 22 and is connected to the vaporizer 32 arranged in the upper chamber of the housing 22. The reforming water supply pipe 56 is provided with a reforming water pump 58, and by driving the reforming pump 58, the reformed water in the reforming water tank 57 is supplied to the vaporizer 32. The reformed water supplied to the vaporizer 32 is converted into steam by the vaporizer 32 and used for the steam reforming reaction in the reformer 33.

Immediately before the inlet of the vaporizer 32 in the reforming water supply pipe 56, a flow rate sensor 59 for detecting the flow rate of the reforming water per unit time is installed. In the present embodiment, the flow rate sensor 59 is configured as a non-contact type flow meter that can detect the flow rate of reformed water in a non-contact manner, such as a thermal flow meter or an electromagnetic flow meter.

The reforming water pump 58 is configured as a motor-driven pump such as a gear pump, and can supply liquid in both forward and reverse directions by switching the rotation direction of the pump motor. That is, the reforming water pump 58 can send the water in the reforming water tank 57 toward the vaporizer 32 by driving the pump motor in the forward rotation direction, and drives the pump motor in the reverse rotation direction. As a result, the water in the reforming water supply pipe 56 can be returned to the reforming water tank 57. The reforming water pump 58 has a high sealing property, and the water above and downstream of the reforming water pump 58 (on the vaporizer 32 side) in the reforming water supply pipe 56 is below and upstream of the reforming water pump 58. It suppresses leakage to (the reformed water tank 57 side). However, when a long time has passed after the operation of the fuel cell system 10 is stopped, the water in the reforming water supply pipe 56 leaks to the reforming water tank 57 side little by little due to the influence of gravity or the like, and the reforming water supply pipe It was confirmed that the water level in 56 was lowered.

The fuel cell stack 36 includes a solid oxide fuel cell having a solid electrolyte composed of an oxygen ion conductor, an anode provided on one surface of the solid electrolyte, and a cathode provided on the other surface of the solid electrolyte. It is configured as a laminated structure, and generates electricity by an electrochemical reaction between hydrogen in the fuel gas supplied to the anode and oxygen in the air supplied to the cathode. A power line 3 from the commercial power source 2 to the load 4 is connected to the output terminal of the fuel cell stack 36 via a power conditioner 71 including a DC / DC converter and an inverter, and DC power from the fuel cell stack 36. Is added to the AC power from the commercial power source 2 through voltage conversion and DC / AC conversion by the power conditioner 71, and is supplied to the load 4. A power supply board 72 is connected to a power line branched from the power conditioner 71. The power supply board 72 includes a ventilation fan 24, a raw fuel gas supply valve 42, 43, a raw fuel gas pump 45, an air blower 53, a reforming water pump 58, a circulation pump 63, a pressure sensor 47, a flow rate sensor 48, 54, 59, and a display panel. It functions as a DC power source that supplies DC power to accessories such as the 90, temperature sensors 91, 92, and combustible gas sensor 95.

The control device 80 is configured as a microprocessor centered on the CPU 81, and in addition to the CPU 81, a ROM 82 for storing a processing program, a RAM 83 for temporarily storing data, and a flash memory as a rewritable non-volatile memory. It includes 84, a timer 85 for measuring time, and an input / output port (not shown). Various detection signals from the pressure sensor 47, the flow rate sensors 48, 54, 59, the temperature sensors 91, 92, the combustible gas sensor 95, and the like are input to the control device 80 via the input port. Further, from the control device 80, a drive signal to the fan motor of the ventilation fan 24, a drive signal to the solenoids of the raw fuel gas supply valves 42 and 43, a drive signal to the pump motor of the raw fuel gas pump 45, and a blower motor of the air blower 53. Drive signal to the pump motor of the reforming water pump 58, drive signal to the pump motor of the circulation pump 63, control signal to the inverter and DC / DC converter of the power conditioner 71, to the ignition heater 35. A drive signal, a display signal to the display panel 90 displaying various information, and the like are output via the output port.

Next, the operation of the fuel cell system 10 thus configured, particularly the operation at the time of system startup will be described. 2 and 3 are flowcharts showing an example of a system control routine executed by the CPU 81 of the control device 80. This routine runs when the system is allowed to boot.

When the system control routine is executed, the CPU 81 of the control device 80 starts the system startup process (S100). In the start-up process, for example, the corresponding auxiliary machinery is sequentially controlled, the initial operation is performed as preparation for start-up, the fuel adsorption process for adsorbing the fuel component to the desulfurizer 46 to suppress the air-fuel ratio deviation of the mixed gas, and the purging of the combustion unit 34. This is performed by sequentially executing the treatment, the off-gas ignition treatment in the combustion unit 34, the steam reforming treatment, and the like. Note that these start-up processes are examples, and the fuel adsorption process and the like may be omitted depending on the configuration of the fuel cell system 10 and the state of auxiliary machinery.

When the start-up process is started, the CPU 81 starts driving the reforming water pump 58 by rotating the pump motor at a predetermined rotation speed as one of the initial operations (S110). The reforming water pump 58 is driven by controlling the pump motor at a predetermined duty ratio in order to rotate the pump motor at a predetermined rotation speed. Subsequently, the flow rate of the reforming water (reforming water flow rate Qw) detected by the flow rate sensor 59 is repeatedly input (S120), and when the input reforming water flow rate Qw changes from the state without the flow rate to the state with the flow rate. That is, when the flow rate sensor 59 changes from the non-detection state in which the flow rate cannot be detected to the detection state in which the flow rate is detected (S130), the reforming water pump 58 is stopped (S140). The processing of S110 to S140 is a water level adjustment processing for adjusting the water level of the reforming water in the reforming water supply pipe 56 to a predetermined water level by using the flow rate sensor 59, and the state of the flow rate sensor 59 is changed from the non-detection state. By stopping the reforming water pump 58 at the timing when the detection state is changed, the water level of the reforming water can be adjusted near the installation position of the flow rate sensor 59. In the present embodiment, since the flow sensor 59 is installed immediately before the inlet of the vaporizer 32 in the reformed water supply pipe 56, the water level of the reformed water is adjusted to the inlet of the vaporizer 32 by executing the water level adjustment process. It can be adjusted to the water level immediately before.

When the CPU 81 executes the initial operation, the fuel adsorption process, and the purge process, the CPU 81 then fills the power generation module 30 with off-gas and drives the ignition heater 35 to start the off-gas ignition process (S150). Then, after waiting for a certain time elapses from the start of the ignition process (S160), the target flow rate Qw * is set to a predetermined constant flow rate Qset (S170), and the reforming water is set at the target flow rate Qw *. The reforming water supply control (water supply control) for driving the reforming water pump 58 is started (S180). The fixed time tset defines the supply timing of the reformed water, and the time determined in advance by an experiment or the like is used. The reformed water supply control controls the reformed water pump 58 by using feedback control based on the reformed water flow rate Qw and the target flow rate Qw * detected by the flow rate sensor 59, and is illustrated in FIG. This is done by executing the reformed water supply control routine. That is, first, the reformed water flow rate Qw from the flow rate sensor 59 is input (S400), and the input reformed water flow rate Qw multiplied by the flow rate correction coefficient F is obtained as a new reformed water flow rate Qw. The quality water flow rate Qw is corrected (S410). Here, the flow rate correction coefficient F is a parameter for correcting the detection error included in the flow rate sensor 59, and as an initial value, a value 1.0 in which the reformed water flow rate Qw is not substantially corrected is set. It is updated as appropriate by S270 described later in the system control routine. Next, the duty ratio (pump duty) to be executed by the reforming water pump 58 (pump motor) is set by feedback control (PID control) based on the deviation between the corrected reformed water flow rate Qw and the target flow rate Qw *. (S420). Then, the pump motor of the reforming water pump 58 is controlled based on the set pump Duty (S430).

When the CPU 81 starts the reformed water supply control in this way, after initializing the cumulative flow rate ΣQw to a value of 0 (S190), the CPU 81 inputs the reformed water flow rate Qw from the flow rate sensor 59 (S200), and then inputs the reformed water flow rate Qw. The cumulative flow rate ΣQw is calculated by integrating the water flow rate Qw (S210). Then, the reformer temperature from the temperature sensor 91 is input (S220), and it is determined whether or not the input reformer temperature has reached the peak temperature (S230). If it is determined that the reformer temperature has not reached the peak temperature, the process returns to S200 and the processes of S200 to S230 are repeated. FIG. 5 is an explanatory diagram showing a state of change in the reformer temperature when the system is started. As shown in the figure, when the off-gas is ignited, the reformer temperature rises due to the heating of the reformer 33 due to the rise in the internal temperature of the power generation module 30 due to the off-gas combustion, and the reformer water is introduced into the reformer 33. When it is done, the heat is taken away by the evaporation and it descends. Then, when the steam reforming reaction, which is an endothermic reaction, is started, each element of the steam reforming reaction, the evaporation of the reformed water, and the heating of the reformer 33 by off-gas combustion is balanced, and a stable state is reached. Therefore, the reformer temperature reaches its peak just before the off-gas is ignited and the reforming water reaches the reformer 33. In the determination of S230, for example, the average value of the reformer temperature detected by the temperature sensor 91 during a predetermined time is calculated, and the average value of the reformer temperature calculated last time is calculated two times before. When the average value of the reformer temperature calculated this time is higher than the average value of the pawnbroker temperature and less than or equal to the average value of the reformer temperature calculated last time, it is determined that the reformer temperature has reached the peak temperature. It can be done by doing.

When the CPU 81 determines that the reformer temperature has reached the peak temperature, the CPU 81 then reaches S210 from the start of supplying the reformer water to the vaporizer 32 until the reformer temperature reaches the peak temperature. It is determined whether or not the accumulated flow rate cumulative value ΣQw is within the abnormal value range including the excessive value abnormal range exceeding the upper limit value and the undervalue abnormal range below the lower limit value (S240). When it is determined that the cumulative flow rate ΣQw is within the abnormal value range, it is determined that the flow sensor 59 has failed, the fuel cell system 10 is abnormally stopped (S250), and a warning is displayed on the display panel 90. (S260), the system control routine is terminated. The cumulative flow rate ΣQw may be calculated by multiplying the target flow rate Qw * (constant flow rate Qset) by the elapsed time from the start of the water supply control until the reformer temperature reaches the peak temperature.

On the other hand, when the CPU 81 determines that the flow rate cumulative value ΣQw is not within the abnormal value range, that is, within the normal value range, the CPU 81 sets the flow rate correction coefficient F based on the flow rate cumulative value ΣQw and stores it in the flash memory 84 ( S270). In the present embodiment, the flow rate correction coefficient F is set by obtaining the relationship between the flow rate cumulative value ΣQw and the flow rate correction coefficient F in advance and storing it in the ROM 82 as a flow rate correction coefficient setting map, and the flow rate cumulative value ΣQw is given. And, it was decided to carry out by deriving the corresponding flow rate correction coefficient F from the map. FIG. 6 shows an example of a map for setting the flow rate correction coefficient. In the flow rate correction coefficient setting map, as shown in the figure, the flow rate correction coefficient F is set so that the larger the cumulative flow rate value ΣQw is, the smaller the value becomes smaller than 1.0, and the cumulative flow rate value ΣQw is within the appropriate range. On the other hand, the flow rate correction coefficient F is set so that the smaller the value, the larger the value becomes larger than 1.0. The appropriate range of the cumulative flow rate value ΣQw is a dead zone in which a value of 1.0 (substantially no correction) is set for the flow rate correction coefficient F. It should be noted that such a dead zone may not be provided. In the present embodiment, the flow rate correction coefficient F is set using the flow rate correction coefficient setting map, but it is derived by dividing the volume of the pipe downstream from the flow rate sensor 59 by the cumulative flow rate value ΣQw. It may be a thing. When the flow rate correction coefficient F is set, the detection error included in the flow rate sensor 59 is corrected by correcting the reforming water flow rate Qw detected by the flow rate sensor 59 using the set flow rate correction coefficient F thereafter. Therefore, an accurate reformed water flow rate Qw can be obtained. Therefore, it is possible to execute reformed water supply control (water supply control) with high accuracy without using a reformed water pump 58 having excessive performance.

When the steam reforming process is executed, the CPU 81 starts the power generation process (S280). When the power generation process is started, the target flow rate Qg * of the raw fuel gas, the target flow rate Qa * of the air, and the target flow rate Qw * of the reforming water are set based on the system required output (load command of the load 4) (S290). Raw fuel gas supply control and air supply control are executed based on the target flow rate Qg * and the target flow rate Qa * (S300), and reformed water supply control is executed based on the target flow rate Qw * (S310). Specifically, the raw material fuel gas supply control sets a target flow rate Qg * to be supplied by the raw material fuel gas supply device 40 based on the system required output, and is detected by the set target gas flow rate Qg * and the flow rate sensor 48. The duty ratio is set by feedback control based on the deviation from the flow rate, and the pump motor of the raw material / fuel gas pump 45 is controlled based on the set duty ratio. The air supply control sets a target flow rate to be supplied by the air supply device 50 so as to have a predetermined ratio (air-fuel ratio) to the target flow rate of the raw material fuel gas, and is detected by the set target flow rate and the flow rate sensor 54. The duty ratio is set by feedback control based on the deviation from the flow rate, and the blower motor of the air blower 53 is controlled based on the set duty ratio. The reformed water supply control is performed by setting a target flow rate Qw * based on the system required output and applying the set target flow rate Qw * to the reformed water supply control routine of FIG. 4 described above.

The CPU 81 executes the power generation process of S280 to S300, and when the system stop is requested during the execution of the power generation process (S320), the system is stopped (S330), and the reforming water pump 58 is accompanied by the stop of the system. Is stopped (S340), and the system control routine is terminated. When the system is stopped, the reforming water pump 58 (pump motor) is driven in the reverse rotation direction so that the water in the reforming water supply pipe 56 returns to the reforming water tank 57 side, and the water in the reforming water supply pipe 56 is driven. Empty the water. As a result, there is no possibility that the reforming water supply pipe 56 freezes between the time the system is stopped and the time the system is started next time, and the antifreeze heater can be eliminated.

In the fuel cell system 10 of the embodiment described above, the reforming water supply 56 connecting the reforming water tank 57 and the vaporizer 32 is provided with a flow sensor 59 for detecting the flow rate of the reforming water, and when the system is started. When the reforming water pump 58 is driven and the flow sensor 59 changes from the non-detection state in which the flow rate cannot be detected to the detection state in which the flow rate is detected, the reforming water pump 58 is stopped to raise the water level of the reforming water. Execute the water level adjustment control to be adjusted. Further, after executing the water level adjustment control, the water supply control for driving the reforming water pump 58 is executed by using the feedback control so that the flow rate detected by the flow rate sensor 59 becomes the target flow rate. As described above, by using the flow rate sensor 59 for the execution of the water level adjustment control and the execution of the water supply control, the water adjustment control and the water supply control can be appropriately performed by a simple and low-cost configuration.

Further, the fuel cell system 10 of the embodiment starts supplying water to the vaporizer 32 at a timing when a predetermined time has elapsed from the start of ignition of the combustion unit 34 after executing the water level adjustment control at the time of system startup. do. Since the water level adjustment control is accurately performed by the flow rate sensor 59, it is possible to prevent excess or deficiency of water (steam) supplied to the reforming unit 33 when the system is started.

Further, the fuel cell system 10 of the embodiment includes a temperature sensor 91 that detects the temperature of the reformer 33, and the reformer temperature detected by the temperature sensor 91 reaches the peak temperature after the water supply control is started. The cumulative value of the flow rate (cumulative flow rate ΣQw) detected by the flow rate sensor 59 is measured, and the reformed water flow rate Qw detected by the flow rate sensor 59 is corrected based on the cumulative flow rate ΣQw. By learning the detected value of the flow rate sensor 59 in this way, the accuracy of water supply control can be further improved. In addition, it is possible to appropriately respond to the secular change of the flow rate sensor 59.

Further, in the fuel cell system 10 of the embodiment, when the flow rate cumulative value ΣQw from the start of the water supply control to the time when the reformer temperature detected by the temperature sensor 91 reaches the peak temperature is within the abnormal value range. Shut down the system. As a result, it is possible to determine the failure of the flow rate sensor 59 and take appropriate measures.

In the embodiment, the fuel cell system 10 is abnormally stopped when the cumulative flow rate ΣQw of the flow rate sensor 59 from the start of water supply control to the time when the reformer temperature reaches the peak temperature is within the abnormal value range. However, the fuel cell is not limited to this, and when the peak temperature of the reformer temperature is within the abnormal temperature range including the high temperature abnormal range above the upper limit temperature and the low temperature abnormal range below the lower limit temperature. The system 10 may be abnormally stopped. Here, the high temperature abnormal range is a temperature range in which the reformer 33 may become abnormally high temperature due to insufficient supply of reformed water to the reformer 33 and coking (fuel carbonization phenomenon) may occur in the reformer 33. The low temperature abnormal range is a temperature range in which the reforming catalyst may deteriorate in activity (performance deteriorates) due to an excessive supply of reforming water to the reformer 33. Further, the flow rate correction coefficient F for correcting the reformed water flow rate Qw detected by the flow rate sensor 59 based on the peak temperature of the reformer temperature may be set. In this case, the flow rate correction coefficient F is set so that the higher the peak temperature is with respect to the appropriate temperature (insufficient supply of reformed water), the smaller the flow rate correction coefficient F is. The flow rate correction coefficient F may be set so as to be large.

In the embodiment, the fuel cell system 10 is abnormally stopped when the cumulative flow rate ΣQw is within the abnormal value range, but the present invention is not limited to this, and the reformer temperature is determined after the water supply control is started. The elapsed time until the fuel cell reaches the peak temperature (reformable water arrival time) may be measured, and the fuel cell system 10 may be abnormally stopped when the measured reformed water arrival time is within the abnormal time range. Further, the flow rate correction coefficient F for correcting the reformed water flow rate Qw detected by the flow rate sensor 59 based on the reformed water arrival time may be set. In this case, the flow rate correction coefficient F is set so that the longer the reformed water arrival time is with respect to the appropriate time (insufficient supply of reformed water), the smaller the flow rate correction coefficient F is, and the reformed water arrival time is shorter than the appropriate time (reformation). The flow rate correction coefficient F may be set so that it becomes larger as the water supply is excessive).

In the embodiment, the flow rate correction coefficient F is used to correct the reformed water flow rate Qw detected by the flow rate sensor 59, but the present invention is not limited to this, and a flow rate sensor having sufficiently high detection accuracy is used. Therefore, the reformed water flow rate Qw may not be corrected.

In the embodiment, when the system is stopped, the reforming water pump 58 (pump motor) is driven in the reverse rotation direction so that the water in the reforming water supply pipe 56 returns to the reforming water tank 57 side, and the reforming water is reformed. The water in the supply pipe 56 was emptied, but the present invention is not limited to this, and when the system is requested to start, the reforming water pump 58 (pump motor) prior to the execution of the water level adjustment control. May be driven in the reverse rotation direction to empty the water in the reforming water supply pipe 56. Further, before executing the water level adjustment control, if the flow rate sensor 59 is in a non-detection state where water cannot be detected, the reforming water pump 58 may not be driven in the reverse rotation direction.

In the embodiment, the temperature sensor 91 is provided inside the reformer 33, and the abnormality is determined based on the reformer temperature detected by the temperature sensor 91. However, the temperature sensor is provided inside the vaporizer 32. , The abnormality may be determined based on the vaporizer temperature detected by the temperature sensor. Also in this case, the reformer temperature may be replaced with the vaporizer temperature, and the processes of S220 and S230 of the system control routine may be executed.

The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem will be described. In the embodiment, the reformer 33 corresponds to the reformer, the vaporizer 32 corresponds to the vaporizer, the reformer water tank 57 corresponds to the water tank, and the reformer water supply pipe 56 corresponds to the water pipe. The reforming water pump 58 corresponds to the water pump, the combustion unit 34 corresponds to the heating unit, the flow rate sensor 59 corresponds to the flow rate sensor, and the control device 80 corresponds to the control device. Further, the temperature sensor 91 corresponds to the temperature sensor.

Regarding the correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem, the invention described in the column of means for the embodiment to solve the problem is carried out. Since it is an example for specifically explaining the form for solving the problem, the elements of the invention described in the column of means for solving the problem are not limited. That is, the interpretation of the invention described in the column of means for solving the problem should be performed based on the description in the column, and the embodiment is the invention described in the column of means for solving the problem. It is just a concrete example.

Although the embodiments for carrying out the present invention have been described above using the embodiments, the present invention is not limited to these embodiments, and various embodiments are used without departing from the gist of the present invention. Of course, it can be done.

The present invention can be used in the manufacturing industry of fuel cell systems and the like.

1 gas supply source, 2 commercial power supply, 3 power line, 4 load, 10 fuel cell system, 20 power generation unit, 22 housing, 22a intake port, 22b exhaust port, 24 ventilation fan, 30 power generation module, 31 module case, 32 Vaporizer, 33 reformer, 34 combustion part, 35 ignition heater, 36 fuel cell stack, 37 combustion catalyst, 40 raw fuel gas supply device, 41 raw fuel gas supply pipe, 42, 43 raw fuel gas supply valve, 44 orifice , 45 Raw fuel gas pump, 46 desulfurizer, 47 pressure sensor, 48 flow sensor, 50 air supply device, 51 air supply pipe, 52 filter, 53 air blower, 54 flow sensor, 55 reformed water supply device, 56 reformed water supply Pipe, 57 reformed water tank, 58 reformed water pump, 59 flow sensor, 60 exhaust heat recovery device, 61 circulation pipe, 62 heat exchanger, 63 circulation pump, 66 condensed water supply pipe, 67 exhaust gas discharge pipe, 71 Power conditioner, 72 power supply board, 80 controller, 81 CPU, 82 ROM, 83 RAM, 84 flash memory, 85 timer, 90 display panel, 91,92 temperature sensor, 95 flammable gas sensor, 100 hot water supply unit, 101 hot water storage tank.

Claims (2)

A fuel cell system including a fuel cell that generates electricity based on a reforming gas containing hydrogen and an oxidant gas containing oxygen.
A reforming unit that reforms the raw material gas into the reforming gas using steam and supplies it to the fuel cell.
A vaporization unit that vaporizes water and supplies it to the reforming unit,
A water tank to store water and
A water pipe connected to the vaporization unit and the water tank,
A water pump that sends the water in the water tank to the vaporization unit through the water pipe,
A combustion part that heats the reforming part and the vaporizing part by combustion,
A flow rate sensor provided at a predetermined position on the downstream side of the water pump in the water pipe to detect the flow rate of water per unit time, and
Water level adjustment control that stops the drive of the water pump based on the change from the non-detection state in which the flow rate sensor cannot detect the flow rate to the detection state in which the flow rate is detected by driving the water pump, and detection by the flow rate sensor. A control device capable of performing water supply control for driving the water pump using feedback control so that the flow rate reaches the target flow rate.
A temperature sensor that detects the temperature of the vaporized part or the modified part, and
Equipped with a,
When the system is started, the control device executes the water level adjustment control and then starts the water supply control at a timing when a predetermined time has elapsed from the start of ignition of the combustion unit to the vaporization unit. The cumulative value of the flow rate detected by the flow rate sensor is measured from the start of water supply and the start of the water supply control until the temperature detected by the temperature sensor reaches the peak, and the cumulative value of the measured flow rate is measured. The flow rate detected by the flow rate sensor is corrected based on the value.
Fuel cell system. The fuel cell system according to claim 1.
The control device shuts down the system when the cumulative value of the measured flow rate is within the outlier range.
Fuel cell system.

Images