JP6801331B2 - Fuel cell system - Google Patents

Description

The present invention relates to a fuel cell system including a fuel cell that generates electricity based on a fuel gas and an oxidant gas.

Conventionally, as this type of fuel cell system, one that measures the flow rate of the fluid used in the fuel cell system is known. For example, Patent Document 1 describes a fuel cell, a reformer that supplies fuel gas to the fuel cell by steam reforming, a shot pump that intermittently supplies water to the reformer, and water from the shot pump. In a fuel cell system equipped with a flow rate switch that detects intermittent flow, it is based on the product of the set value of the discharge amount per shot by the shot pump and the number of signals output from the flow rate switch per unit time. Those that calculate the amount of water supplied per unit time are disclosed.

Japanese Unexamined Patent Publication No. 2008-159466

By the way, in the flow rate control of the fluid used in the fuel cell system, a flow meter (flow rate sensor) for detecting the flow rate (discharge amount) of the fluid discharged from the pump or the blower is provided, and the flow rate from the flow meter and the target flow rate are set. It is generally performed by feedback control in which a control DUTY (duty ratio) is set and drive control is performed based on the deviation of. This is because if the flow rate is controlled using a map in which the target flow rate and the control DUTY are associated with each other without using a flow meter, the flow rate error becomes large due to the variation in pressure loss of the equipment, and the operation of the fuel cell system operates. This is because there is a risk of instability (a risk of insufficient supply of fuel gas or instability of combustion). According to the technique described in Patent Document 1 described above, it is possible to measure the discharge amount of the pump without using a flow meter, but the discharge amount per shot is limited to a constant intermittent type pump, and the intermittent type It cannot be applied to non-pumps and blowers.

The main object of the fuel cell system of the present invention is to accurately control the flow rate of the fluid used in the system without using a flow meter.

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 fuel gas and an oxidant gas.
A fluid supply device that supplies the fluid used in the system,
A flow rate switch that operates when a set flow rate of fluid is supplied from the fluid supply device,
A control device that determines the operation amount corresponding to the required flow rate required by the system using the correspondence information between the flow rate and the operation amount, and controls the fluid supply device based on the determined operation amount.
With
The control device updates the correspondence information based on the amount of operation of the fluid supply device when the flow rate switch is activated.
The gist is that.

In the fuel cell system of the present invention, the operation amount corresponding to the required flow rate required by the system is determined by using the correspondence information between the flow rate and the operation amount, and the fluid supply device is controlled based on the operation amount. Is. In this fuel cell system, a flow rate switch that operates when a set flow rate of fluid is supplied from the fluid supply device is provided, and correspondence information is updated based on the operation amount of the fluid supply device when the flow rate switch operates. That is, when the flow rate switch is activated, the flow rate of the fluid supplied from the fluid supply device is the set flow rate, so the relationship between the operation amount of the fluid supply device and the set flow rate at that time should be reflected in the correspondence information. Therefore, it is possible to deal with pressure loss changes due to variations in equipment, installation environment, changes over time, and the like. As a result, it is possible to accurately control the flow rate of the fluid used in the system without using a flow meter.

In such a fuel cell system of the present invention, the flow rate switch may be configured to operate at a flow rate within a flow rate range required by the system as the fuel cell operates as the set flow rate. By doing so, it is possible to update the correspondence information during the operation of the fuel cell, and it is possible to improve the control accuracy of the flow rate control. In particular, if the set flow rate is defined as the flow rate at the time of starting, which is a point where the combustibility of the fuel cell is severe, the control accuracy of the flow rate control at the time of starting can be improved and the combustibility can be improved. ..

Further, in the fuel cell system of the present invention, the control device controls the fluid supply device so that the flow rate switch operates according to a load fluctuation during operation of the fuel cell, and updates the correspondence information. May be. By doing so, it is possible to update the correspondence information during the operation of the fuel cell, and it is possible to improve the accuracy of the flow rate control.

Further, in the fuel cell system of the present invention, the control device may control the fluid supply device so that the flow rate switch operates before the start of the fuel cell to update the correspondence information. By doing so, by updating the correspondence information before starting the fuel cell, it is possible to further improve the control accuracy at the time of starting or operating.

Further, in the fuel cell system of the present invention, the control device may determine that an abnormality has occurred in the flow rate switch when the operation amount when the flow rate switch is operated is not within the predetermined operation amount range. Good. In this way, it is possible to determine whether or not there is an abnormality in the flow rate switch when updating the correspondence information.

It is a block diagram which shows the outline of the structure of the fuel cell system 10 as one Example of this invention. It is explanatory drawing which shows an example of a map. It is a flowchart which shows an example of a map update processing routine. It is explanatory drawing which shows the state of updating a map. It is explanatory drawing which shows the state of the control DUTY, the flow rate switch output, and the flow rate change with time.

A mode for carrying out the present invention will be described with reference to examples.

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

The power generation unit 20 receives the supply of reformed water and raw fuel gas (for example, natural gas or LP gas) and heats them to evaporate the reformed water to generate steam and preheat the raw fuel gas. The vaporizer 32, the reformer 33 that reforms the raw fuel gas from the vaporizer 32 by a steam reforming reaction to generate fuel gas, and the fuel cell 36 that generates power by receiving the supply of fuel gas and air. A power generation module 30 including the above, a raw fuel gas supply device 40 for supplying raw fuel gas to the vaporizer 32, an air supply device 50 for supplying air to the fuel cell 36, and a reformer for supplying reformed water to the vaporizer 32. It includes a quality water supply device 55 and an exhaust heat recovery device 60 that recovers the exhaust heat generated by the power generation module 30. The power generation unit 20 is housed in the housing 22, and the inside is ventilated by the ventilation fan 24 provided in the intake port 22a of the housing 22.

The vaporizer 32, the reformer 33, and the fuel cell 36 are housed in a box-shaped module case 31 formed of a heat insulating material. The module case 31 is provided with a combustion unit 34 for starting the fuel cell 36, generating steam in the vaporizer 32, and supplying heat required for the steam reforming reaction in the reformer 33. Anode off gas (fuel off gas) and cathode off gas (oxidizer off gas) from the fuel cell 36 are supplied to the combustion unit 34, and these mixed gases are ignited by the ignition heater 35 and burned to burn the fuel cell 36 and the fuel cell 36. The vaporizer 32 and the reformer 33 are heated.

In the raw fuel gas supply device 40, the fuel supply device 1 and the vaporizer 32 are connected by a raw fuel gas supply pipe 41, and the raw fuel gas from the fuel supply device 1 is supplied by the raw fuel gas supply valve 45 by driving the raw fuel gas pump 45. It is supplied to the vaporizer 32 via the (electromagnetic valve) 42, 43 and the desulfurizer 46. The raw material 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 configured as double valves connected in series. The desulfurization device 46 removes the sulfur content contained in the raw material fuel gas. 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, in the raw material gas supply pipe 41, a pressure sensor 47 that detects the pressure of the raw material gas in the raw material gas supply pipe 41 and a flow rate that detects the flow rate of the raw material fuel gas flowing through the raw material gas supply pipe 41 per unit time. A sensor 48 is provided.

In the air supply device 50, the filter 52 communicating with the outside air and the fuel cell 36 are connected by the air supply pipe 51, and the outside air is driven to the fuel cell 36 via the filter 52 by driving the air blower 53 provided in the air supply pipe 51. Supply. The air supply pipe 51 is provided with a flow rate switch 54 that operates when the flow rate of air flowing through the air supply pipe 51 per unit time exceeds the set flow rate NLM_s and outputs an on signal. Here, as the flow rate switch 54, an electromagnetic flow rate switch, a mechanical flow rate switch, or the like can be adopted, and as compared with the flow rate sensor, the structure is simple, there are few failures, and it is advantageous in terms of cost. Further, in the present embodiment, the flow rate switch 54 is designed so that the set flow rate NLM_s is within the flow rate range that can be supplied to the air supply device 50 during the normal operation of the fuel cell 36.

In the reforming water supply device 55, the reforming water tank 57 for storing the reforming water and the vaporizer 32 are connected by the reforming water supply pipe 56, and the reforming water pump 58 provided in the reforming water supply pipe 56 is provided. The reformed water in the reformed water tank 57 is supplied to the vaporizer 32 by the drive of. 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. The reformed water tank 57 is provided with a water purifier (not shown) for purifying the reformed water to be stored.

In the exhaust heat recovery device 60, the heat exchanger 62 to which the combustion exhaust gas in the power generation module 30 is supplied and the hot water storage tank 101 for storing hot water are connected by a circulation pipe 61, and the circulation pump 63 provided in the circulation pipe 61. In the heat exchanger 62, the hot water stored in the hot water storage tank 101 is heated by heat exchange with the combustion exhaust gas and 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, and the combustion exhaust gas supplied to the heat exchanger 62 is stored in hot water. By heat exchange with water, the water vapor component is condensed and recovered in the reformed water tank 57, and the remaining exhaust gas is discharged to the outside air through the exhaust gas discharge pipe 67.

The fuel cell 36 is configured as a solid oxide fuel cell in which a plurality of single cells including an electrolyte and an anode electrode and a cathode electrode sandwiching the electrolyte are laminated, and is composed of hydrogen in the fuel gas and oxygen in the air. It generates electricity by an electrochemical reaction. A power line 3 from the commercial power source 2 to the load 4 is connected to the output terminal of the fuel cell 36 via a power conditioner 71 including an inverter and a DC / DC converter, and DC power from the fuel cell 36 is AC. It is converted into electric power and added to the AC electric power from the commercial power source 2 so that it can be 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 supplements the raw fuel gas supply valves 42 and 43, the air blower 53, the raw fuel gas pump 45, the reforming water pump 58, the circulation pump 63, the combustible gas sensor 91, the pressure sensor 47, the flow sensor 48, the flow switch 54, and the like. It functions as a DC power supply that supplies DC power to the machine.

The control device 80 is configured as a microprocessor centered on a CPU 81, and includes a ROM 82 for storing a processing program, a RAM 83 for temporarily storing data, and an input / output port (not shown) in addition to the CPU 81. Various detection signals from the pressure sensor 47, the flow rate sensor 48, the flow rate switch 54, the combustible gas sensor 91 provided near the exhaust port 22b of the housing 22, 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 provided in the intake port 22a of the housing 22, a drive signal to the inverters of the raw fuel gas supply valves 42 and 43, and a raw fuel gas pump 45. Drive signal to the pump motor, drive signal to the 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, inverter of the power conditioner 71 and DC / DC A control signal to the converter, a drive signal to the ignition heater 35, a display signal to the display panel 90, and the like are output via the output port.

The control device 80 inputs a load command accompanying the load fluctuation of the load 4, and the raw fuel gas supply device 40, the air supply device 50, etc. are supplied so that the raw fuel gas, air, and the like are supplied by the flow rate according to the input load command. To control. Here, in the present embodiment, the control of the raw material fuel gas supply device 40 is performed by setting a target flow rate to be supplied by the raw material fuel gas supply device 40 based on the input load command, and using the set target flow rate and the flow rate sensor 48. The control DUTY is set by feedback control based on the deviation from the detected flow rate, and the pump motor of the raw material fuel gas pump 45 is driven and controlled by the set control DUTY. Further, in the control of the air supply device 50, the target flow rate to be supplied by the air supply device 50 is set based on the input load command, and the corresponding control duty is set and set from the map based on the set target flow rate. It is performed by driving and controlling the blower motor of the air blower 53 by the control DUTY. FIG. 2 shows an example of a map. In the map, as shown, the flow rate and the control duty have a proportional relationship.

Next, the operation of the fuel cell system 10 configured in this way, particularly the process of updating the map for controlling the air supply device 50 will be described. FIG. 3 is a flowchart showing an example of a map update processing routine executed by the CPU 81 of the control device 80. This routine is executed when a load command with an increase in load is input.

When the map update processing routine is executed, the CPU 81 of the control device 80 first gradually raises the control DUTY so that the flow rate of the air supplied to the fuel cell 36 increases in response to the input load command to supply the air. While controlling the device 50 (air blower 53) (step S100), it waits for the output signal of the flow rate switch 54 to change from an off signal to an on signal (step S110). When the output signal of the flow rate switch 54 changes from the off signal to the on signal, the control DUTY set at that time is stored in the RAM 83 as the control DUTY_a (step S120), and the stored control DUTY_a is larger than the lower limit value DUTY_L and It is determined whether or not it is smaller than the upper limit value DUTY_H (steps S130 and S140). Here, the lower limit value DUTY_L and the upper limit value DUTY_H indicate the lower limit value and the upper limit value of the control DUTY range that can be taken when the flow rate switch 54 operates normally. If it is determined that the control DUTY_a is larger than the lower limit value DUTY_L and smaller than the upper limit value DUTY_H, the map is updated based on the control DUTY_a (step S150), and the map update processing routine is terminated. FIG. 4 shows how the map is updated. As shown in the figure, the map is updated by making the relationship between the flow rate and the control DUTY a proportional relationship on a straight line passing through the intersection and the origin of the set flow rate NLM_s and the control DUTY_a. As described above, since the flow rate switch 54 is designed so that the set flow rate NLM_s is within the air flow rate range required for the air supply device 50 during the normal operation of the fuel cell 36, the operation of the fuel cell 36 is performed. You can update the map inside.

If it is determined in step S130 that the control DUTY_a is equal to or less than the lower limit value DUTY_L, or if it is determined in step S140 that the control DUTY_a is equal to or greater than the upper limit value DUTY_H, it is determined that the flow rate switch 54 has failed (step S160), and the map update processing routine is performed. To finish. In this case, the CPU 81 displays a warning display on the display panel 90 prompting maintenance or replacement of the flow rate switch 54.

FIG. 5 is an explanatory diagram showing a state of time change of the control DUTY, the flow rate switch output, and the flow rate. As shown in the figure, when the control DUTY of the air blower 53 (blower motor) controlled using the map rises and the flow rate of the air flowing through the air supply pipe 51 becomes equal to or higher than the set flow rate NLM_s, the output of the flow rate switch 54 is output from the off signal. It becomes an on signal. Since the control DUTY_a at this time corresponds to the set flow rate NLM_s, it is possible to deal with the pressure loss change due to the variation of the equipment, the installation environment, the change with time, etc. by reflecting the correspondence relationship on the map.

The fuel cell system 10 of the present embodiment described above is provided with a flow rate switch 54 that outputs an on signal when the flow rate of air flowing through the air supply pipe 51 exceeds the set flow rate NLM_s, and the output signal of the flow rate switch 54 is When the off signal changes to the on signal, the map is updated by reflecting the relationship between the control DUTY_a and the set flow rate NLM_s at that time in the map. As a result, it is possible to deal with pressure loss changes due to variations in equipment, installation environment, changes over time, and the like. As a result, it is possible to accurately control the flow rate of air without using a flow meter.

Further, in the fuel cell system 10 of the present embodiment, the flow rate switch 54 is designed so that the set flow rate NLM_s is within the flow rate range of the air required for the air supply device 50 during the normal operation of the fuel cell 36. To. As a result, the map can be updated during the operation of the fuel cell 36, and the control accuracy of the flow rate control can be further improved.

Further, in the fuel cell system 10 of the present embodiment, when the control DUTY_a when the output signal of the flow rate switch 54 changes from the off signal to the on signal is not within the DUTY range determined by the lower limit value DUTY_L and the upper limit value DUTY_H, It is determined that the flow rate switch 54 has a failure. As a result, it is possible to determine whether or not there is an abnormality in the flow rate switch 54 when updating the map.

In the embodiment, the flow rate switch 54 is designed so that the set flow rate NLM_s is within the flow rate range of the air required for the air supply device 50 during the normal operation of the fuel cell 36, but when the fuel cell 36 is started, the flow rate switch 54 is designed. The flow rate switch 54 may be designed so that the flow rate is within the flow rate range of air required for the air supply device 50. In this case, the map update processing routine may be executed at the time of starting the fuel cell 36. As a result, it is possible to improve the control accuracy of the flow rate control at the time of starting, which is a severe point of combustibility of the fuel cell 36, and improve the combustibility.

In the embodiment, the map update process is executed when the load command accompanied by the load fluctuation is input during the operation of the fuel cell 36, but the map update process may be executed before the start of the fuel cell 36. .. As a result, by updating the map before starting the fuel cell 36, it is possible to accurately execute the flow rate control at the time of starting or operating the fuel cell 36.

In the embodiment, the control DUTY when driving and controlling the air blower 53 is increased by inputting a load command accompanied by an increase in load, and the map is updated when the output signal of the flow rate switch 54 changes from an off signal to an on signal. However, the map may be updated when the output signal of the flow rate switch 54 changes from an on signal to an off signal by lowering the control DUTY when driving and controlling the air blower 53 by inputting a load command accompanied by a load reduction. ..

In the embodiment, the flow rate sensor 48 is provided in the raw material fuel gas supply pipe 41, and the raw material fuel gas pump 45 is controlled by feedback control based on the deviation between the target flow rate and the flow rate detected by the flow rate sensor 48. It may be controlled by setting the corresponding control DUTY from the target flow rate using the map. In this case, instead of the flow rate sensor 48, a flow rate switch that operates when the flow rate of the raw fuel gas flowing through the raw material fuel gas supply pipe 41 exceeds the set flow rate is provided, and the control DUTY_a and the set flow rate when the flow rate switch operates are provided. You can update the map based on the relationship. Further, the reforming water pump 58 of the reforming water supply device 55 may be controlled by setting the corresponding control DUTY from the target flow rate using the map. In this case as well, a flow rate switch may be provided in the reforming water supply pipe 56, and the map may be updated based on the relationship between the control DUTY_a when the flow rate switch is activated and the set flow rate. As described above, it can be applied to any fluid supply device as long as the flow rate of the fluid used in the system can be controlled by using a map.

In the embodiment, the control DUTY corresponding to the target flow rate is set by using the map, but the control DUTY corresponding to the target flow rate may be set by using a calculation formula instead of the map. In this case, when updating the calculation formula, the proportional relational expression of the straight line passing through the intersection and the origin of the set flow rate NLM_s and the control DUTY_a may be obtained as the calculation formula.

In the embodiment and its modification, the map and the calculation formula are defined as the relationship between the control DUTY and the flow rate. For example, the motor is defined as the relationship between the rotation speed and the flow rate of the blower motor or the pump motor, and the motor is determined by the rotation speed. Anything may be used as long as it determines the relationship between the operation amount and the flow rate, such as by controlling.

In the embodiment, when the control DUTY_a is not within the DUTY range determined by the lower limit value DUTY_L and the upper limit value DUTY_H, it is determined that the flow rate switch 54 has a failure, but such a determination may not be performed.

The correspondence between the main elements of the examples and the main elements of the invention described in the column of means for solving the problem will be described. In the embodiment, the air blower 53 corresponds to the "fluid supply device", the flow rate switch 54 corresponds to the "flow rate switch", and the control device 80 corresponds to the "control device".

As for the correspondence between the main elements of the examples 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 solving the problem in the examples 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 examples are the inventions 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 with reference to examples, the present invention is not limited to these examples, 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 fuel supply device, 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 Combustor, 35 Ignition heater, 36 Fuel cell, 40 Raw fuel gas supply device, 41 Raw fuel gas supply pipe, 42, 43 Raw fuel gas supply valve, 45 Raw fuel gas pump, 46 Desulfurization Vessel, 47 pressure sensor, 48 flow sensor, 50 air supply device, 51 air supply pipe, 52 filter, 53 air blower, 54 flow switch, 55 reformed water supply device, 56 reformed water supply pipe, 57 reformed water tank, 58 reformed water pump, 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 control device, 81 CPU, 82 ROM, 83 RAM, 90 display panel, 91 combustible gas sensor, 100 hot water supply unit, 101 hot water storage tank.

Claims (6)

A fuel cell system including a fuel cell that generates electricity based on a fuel gas and an oxidant gas.
A fluid supply device that supplies the fluid used in the system,
A flow rate switch that outputs an output signal of an on signal or an off signal and changes the output signal when the flow rate of the fluid supplied from the fluid supply device changes over a set flow rate.
A control device that determines the operation amount corresponding to the required flow rate required by the system using the correspondence information between the flow rate and the operation amount, and controls the fluid supply device based on the determined operation amount.
With
The control device updates the correspondence information by reflecting the correspondence between the operation amount of the fluid supply device and the set flow rate when the output signal of the flow switch changes in the correspondence information.
A fuel cell system characterized by that. The fuel cell system according to claim 1.
The flow rate switch is configured so that the output signal changes at a flow rate within the flow rate range required by the system as the fuel cell operates as the set flow rate.
A fuel cell system characterized by that. The fuel cell system according to claim 1 or 2.
The control device controls the fluid supply device so that the output signal of the flow rate switch changes according to the load fluctuation during the operation of the fuel cell, and updates the correspondence information.
A fuel cell system characterized by that. The fuel cell system according to any one of claims 1 to 3.
The control device controls the fluid supply device so that the output signal of the flow rate switch changes before the start of the fuel cell, and updates the correspondence information.
A fuel cell system characterized by that. The fuel cell system according to any one of claims 1 to 4.
The control device determines that an abnormality has occurred in the flow rate switch when the operation amount when the output signal of the flow rate switch changes is not within the predetermined operation amount range.
A fuel cell system characterized by that. The fuel cell system according to any one of claims 1 to 5.
The control device corresponds to the control device so that the relationship between the flow rate and the operation amount is a proportional relationship on a straight line passing through the intersection and the origin of the operation amount when the output signal of the flow rate switch changes and the set flow rate. Update related information,
A fuel cell system characterized by that.

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