JPH088111B2 - Fuel cell automatic start control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is directed to a method for automatically starting a fuel cell, such as a phosphoric acid type or alkaline type fuel cell, which has an automatic start control device. The present invention relates to a control method that enables early detection of a failure.

[Conventional technology]

FIG. 4 shows a general system diagram of the fuel cell. Reference numeral 1 denotes a battery main body, which includes a fuel chamber 2, an oxidant chamber 3, an electrolytic solution chamber 4, and a fuel electrode 5 and an oxidant electrode 6 which are interposed in the electrolytic solution chamber 4, the fuel chamber 2 and the oxidant chamber 3, respectively. Become. A fuel supply source 7 is connected to the fuel chamber 2 via a fuel system supply valve 10 and a pressure adjusting valve 15. The fuel supply source 7, the fuel system supply valve 10, and the pressure regulating valve 15 constitute a fuel system as a whole.
An oxidant supply source 8 is communicated with the oxidant chamber 3 via the oxidant supply valve 11 and the pressure adjusting valve 16. The oxidant supply source 8, the oxidant supply valve 11, and the pressure control valve 16 constitute an oxidant system as a whole. Reference numeral 9 denotes a nitrogen supply source as a replacement gas, which is branched in two directions through a supply valve 12 and a pressure adjusting valve 17, one end of which is connected to a fuel system through a check valve 18 and the other end of which is reverse. It communicates with the oxidant system via a stop valve 19. Nitrogen supply source 9, supply valve 12, pressure regulating valve 17, and check valves 18, 19
Constitutes a nitrogen system (generally a replacement gas system) as a whole. Reference numeral 13 is a fuel chamber side discharge valve, and 14 is an oxidant chamber side discharge valve. In addition to nitrogen as the replacement gas, argon,
Although an inert gas such as helium can be used, an example using nitrogen will be described below. Here, the nitrogen-based pressure control valve 17 is a fuel-based or oxidant-based pressure control valve 1
The adjustment pressure is set to a little lower than that of 5, 16 (differential pressure 200 mm water column or less). Therefore, even when the nitrogen supply valve 12 is always open, the fuel supply valve 10 or the oxidant supply valve 11 When the valve is opened, the pressure of the fuel system or the oxidant system becomes higher than the set pressure of the nitrogen system pressure adjusting valve 17, so that nitrogen does not flow in, and conversely, the fuel supply valve 10 or the oxidant supply valve 11
Is closed, and the fuel and oxidizer are released outside the system,
When the pressure of the oxidizer system becomes equal to or lower than the set value of the nitrogen system pressure adjusting valve 17, nitrogen flows in. The role of the check valves 18 and 19 is to prevent the fuel and the oxidant from being mixed and flowing into the cell body.

Further, 21 is a sequence control unit that controls each valve based on the activation sequence, 22 is a drive circuit that controls opening and closing of the valves based on the activation sequence of the sequence control unit, 23
Is a battery voltage detector, which includes a start control circuit 21 and a drive circuit 2.
2, and the voltage detection unit 23 collectively constitute an automatic start control device. FIG. 5 is a time chart showing the startup sequence of the automatic startup control device, and the startup operation of the fuel cell will be described below with reference to FIGS. 4 and 5. When a start signal is input to the start control circuit 21 at time t ₀ , the drive voltage 12E of the nitrogen (N ₂ ) system supply valve 12 rising at time t ₀ is output as shown in FIG. 5, and the check valve is output. 18 and 19 the nitrogen is supplied to the fuel chamber 2 and the oxidizer chamber 3 via a discharge valve drive voltage 13E to t ₁ time at a somewhat time required for the internal pressure of the two chambers is stabilized,
14E is output and the fuel chamber discharge valve 13 and the oxidant chamber discharge valve 1 are output.
By opening 4, the air in the fuel system and the fuel chamber, for example, is replaced by nitrogen, and the contact between hydrogen (H ₂ ) and oxygen in the fuel that flows in later is avoided. The nitrogen replacement in the oxidant chamber is performed as needed. Fuel chamber and a predetermined time required for the fuel system is substituted with nitrogen gas to an extent no safety hazard (t ₂ -t ₁ hour) the fuel system at the time t ₂ has elapsed, the oxidant system both supply valve driving When the voltages 10E and 11E are output, the check valves 18 and 19 are closed because the pressure of the nitrogen system is low, and the fuel (H ₂ ) and the oxidant (O ₂ ) are supplied to the fuel chamber 2 and the oxidant chamber 3, respectively.
Is introduced and replacement is carried out, and along with this, the fuel cell main body 1 generates an electromotive voltage V, and the cell electromotive voltage V rises in accordance with the progress of the replacement of nitrogen with H ₂ , O ₂ . Eventually, the specified open circuit voltage V _S is reached. Therefore, the battery electromotive voltage V is detected by the detection unit 23, the detection voltage is received by the sequence control unit 21, and at the time point t ₃ when the detection voltage V exceeds the open circuit voltage V _S , the discharge valve drive voltages 13E and 14E are changed. The start-up sequence is set to stop the output, so that the fuel cell can perform the power generation movement.

[Problems to be solved by the invention]

In the conventional method, fuel and from time t ₂ to start the supply of the oxidizing agent, the nitrogen in the fuel chamber and oxidant chamber replacement time to time t ₃ when substituted to a degree no problem in performance,
Since the start-up sequence is designed to judge whether the battery voltage V has reached the specified open circuit voltage V _S ,
For example, if there is an abnormality in the device such as a blockage in the fuel system or oxidant system that reduces the flow rate of fuel or oxidant, the replacement operation continues endlessly, and power generation operation starts at time t ₃ . However, there is a problem that the switching of is significantly delayed. Also, open circuit voltage itself of the battery shows a voltage value higher in nitrogen gas mixed state, might determine whether complete replacement by slight voltage difference between the open circuit voltage of the provisions, the replacement completion t ₃ The drawback is that the decisions are likely to be inaccurate. Further, since it is considered that the output voltage of the fuel cell used for a long period of time gradually decreases, it may be difficult to determine the replacement completion time point t ₃ for such an abnormal mode.

An object of the present invention is to provide a function for detecting an abnormality of the device in the startup sequence, so that when there is no abnormality in the device, the transition from startup to power generation operation is performed stably and quickly, and the device has an abnormality. In some cases, the transition to power generation operation is interrupted to prevent the occurrence of trouble.

[Means for solving problems]

In order to solve the above problem, according to the present invention, a plurality of unit cells having an oxidant electrode and a fuel electrode sandwiching an electrolytic solution layer, and an oxidant chamber and a fuel chamber disposed on both sides of the electrode are stacked. A fuel cell body consisting of a body, a fuel system and an oxidant system for supplying fuel and an oxidant through a supply valve and a pressure regulator to the fuel chamber and the oxidant chamber, respectively, each having a discharge valve, and a supply to both chambers A replacement gas system that supplies replacement gas through a valve, a pressure regulator, and a pair of check valves, an automatic start control device that controls each of the valves based on a start sequence, and an electromotive voltage detection unit of the fuel cell. In an automatic start control method for a fuel cell comprising:
Experimentally sought to open the supply gas supply valve and at least the fuel chamber side discharge valve in response to the fuel cell start signal to lower the oxygen concentration in the exhaust gas to a sufficiently safe low concentration. The first step of performing gas replacement for a preset predetermined time is executed, and then the fuel system and oxidant system supply valves and the oxidant chamber side discharge valve are opened to set the open circuit voltage of the fuel cell to a steady value. The second step of closing the discharge valve after supplying and replacing the fuel and the oxidant for a predetermined time determined experimentally by performing the second step is performed, and immediately after the end of this step, the detected electromotive voltage of the electromotive voltage detector is detected. Is compared with a predetermined reference voltage, and when the detected electromotive voltage is less than or equal to the reference voltage, it is determined that the fuel cell is abnormal, a warning signal is issued, and at least the third valve for the fuel system is closed. The activation sequence is to be formed by braided as.

[Action]

In the above means, a first step of substituting one or both of a fuel system including a fuel chamber and an oxidant system including an oxidant chamber with nitrogen, and a second step of substituting both of them with fuel gas and oxidant gas The start-up sequence is set so that the replacement time required for the fuel cell device and the replacement time for the fuel cell device in the normal state are set to the predetermined time experimentally obtained in advance. The third step of checking whether or not the circuit voltage is reached is executed, and when the battery voltage is lower than the reference voltage, it is determined that an abnormality has occurred in the device, a warning signal is issued, and fuel gas is emitted. By shutting off and interrupting the startup, if there is no abnormality in the device, the startup operation will be completed within a predetermined time and the power generation operation will start immediately. In addition, if an abnormality occurs in the device, an abnormality is detected early by a notification signal, and a check valve is installed in the fuel system and the fuel chamber where the pressure has dropped due to the consumption of hydrogen from the high pressure nitrogen system. Since nitrogen is supplied through, the risk of damage to the battery electrodes due to the pressure difference with the oxidant system caused by interrupting the start-up and the risk of contact with both gases is avoided.

〔Example〕

 The method of the present invention will be described below based on examples.

FIG. 1 is a control and piping system diagram showing an apparatus for explaining the method of the present invention, FIG. 2 is a start sequence diagram when there is no abnormality in the apparatus, and FIG. 3 is a start sequence when there is an abnormality in the apparatus. In each case, the same parts as those of the conventional apparatus and the conventional method are denoted by the same reference numerals, and detailed description thereof will be omitted. In FIG. 1, the electromotive voltage 23E detected by the electromotive voltage detection unit 23 of the battery is input to the determination circuit 34 whose voltage comparison timing is controlled by the output signal 31E of the sequence control unit 31 and compared with the reference voltage V _S. To be done. That is, in the pulse sequence diagram shown in FIG. 2, the N ₂ supply valve drive voltage 12 that rises at time t ₀ based on the start signal
Nitrogen as a replacement gas is supplied by E, and at the time t _{1 when} the pressure in the fuel chamber and the oxidant chamber rises, the exhaust valve drive voltage 13E, 14E
Causes the exhaust valves 13 and 14 to open and the first step of replacing the air in the fuel chamber 2 and the oxidant chamber with nitrogen is carried out, the determination of the replacement time t ₂ -t _{0 in} this step being determined by the exhaust valve 13
By determining the time for the oxygen concentration to drop to a sufficiently safe low concentration by an experiment to measure the oxygen concentration in the exhaust gas emitted from and 14, the predetermined time can be determined. Next, at time t ₂ , the fuel system and oxidant system supply valves 10 and 11 are opened, nitrogen is replaced by the fuel gas and the oxidant gas, and at time t ₃ , the discharge valves 13 and 14 are closed, and the fuel cell is closed. The replacement time t ₃ -t ₂ in the second step for making the power generation operation possible is also set to a predetermined time that is determined in advance by an experiment for measuring the change with time of the battery electromotive voltage, and the time t ₃ thus determined is determined. When the output of the discharge valve drive voltages 13E and 14E is stopped at, the discharge valves 13 and 14 are closed and the fuel cell main body 1 is in the standby state for the power generation operation. Here voltage check (not shown) signal 31E to the command at decision circuit 34 from the sequence control unit 31 is output from the decision circuit 34 so if the second view V _S <V following condition is satisfied The abnormal signal 34E is not output, and the drive circuit 32
The notification signal 35E output from the device to the alarm device 35 also becomes zero, and the start-up sequence including the third step of checking the presence / absence of abnormality in the fuel cell device by its electromotive voltage is completed.

When the fuel cell device has an abnormality, the cell electromotive voltage V does not reach the reference voltage V _S , as shown in FIG. 3, and this is detected in the third step of abnormality detection. The decision circuit 34 outputs an abnormal signal 34E that rises at time t ₃ or later, and the sequence control unit 3 which receives this outputs the abnormal signal 34E.
1 is the stop of the fuel system supply valve drive voltage 10E, and the abnormality notification signal 35
Since the output of E is commanded to the drive circuit 32, the drive voltage 10E is t ₃
At the time point, it becomes zero, the supply valve 10 is closed, the supply of fuel to the fuel chamber 2 is cut off, and the alarm 35 notifies the occurrence of abnormality. Further, after the time point t ₃ when the fuel supply is cut off, the cell electromotive voltage and the gas pressure gradually decrease as the hydrogen contained in the fuel gas contained in the fuel system and the fuel chamber is consumed, and the fuel chamber 2 Since the check valve 18 senses the decrease in the gas pressure of, nitrogen is supplied from the nitrogen system to the fuel system,
The retained gas in the fuel system and the fuel chamber is deactivated to maintain safety, and the pressure difference between the fuel chamber 2 and the oxidant chamber 3 is suppressed to the pressure difference with the nitrogen system (usually 200 mm water column or less). As a result, troubles such as damage to the electrodes 5 and 6 and ejection of the electrolytic solution toward the fuel chamber can be avoided. Therefore, it becomes possible to investigate and repair the cause of the abnormality early and safely. Immediately after the second step means a prompt time within a range in which the completion delay of the startup sequence is not significantly delayed in practice, the shorter the time is, the more preferable, and the time at the time t ₃ is also included. Also, in determining the replacement time (t ₃ −t ₂ ) in the second step, it is affected by the battery temperature before startup, so it is possible to select multiple steps of replacement time in consideration of this point. It is preferable.

〔The invention's effect〕

As described above, the method of the present invention, when starting the fuel cell device having the automatic start control device, replaces the air of the fuel system including at least the fuel chamber with the inert gas, and the inert gas. And a standby state for the power generation operation by executing the replacement time with the second step of replacing the air of the oxidant system including the oxidant chamber with the fuel gas and the oxidant based on the startup sequence set to a predetermined time set in advance. Then, when the detection voltage of the electromotive voltage detection unit is lower than the reference voltage, it is determined that an abnormality has occurred in the fuel cell, at least the supply of fuel is stopped, and the third step of issuing a notification signal is executed. did. As a result, the third step functions as a means for early detection of an abnormality in the fuel cell, and an alarm voltage causes early detection of factors such as gas shortage due to blockage of the fuel system and oxidant system and aging of the fuel cell. And because safety is maintained by stopping the fuel supply,
Determining the completion of the startup sequence based on the level of the battery electromotive voltage.The drawback of the conventional technology, which is a problem with the device, in which the completion of the startup sequence is lengthened, is eliminated. It is possible to provide an automatic start-up control device for a fuel cell which has an early detection of a failure and an automatic monitoring function without requiring a device.

[Brief description of drawings]

FIG. 1 is a piping system diagram including a control circuit for explaining an embodiment method of the present invention, FIGS. 2 and 3 are start-up sequence diagrams showing the embodiment method, and FIG. 4 is a piping system showing a conventional apparatus. 5 and 5 are start-up sequence diagrams in the conventional device. 1 ... Fuel cell main body, 2 ... Fuel chamber, 3 ... Oxidant chamber,
(7,10,15,2) …… Fuel system, (8,11,16,3) …… Oxidizer system, (9,12,17,18,19) …… Substitution gas system, 10,11, 12 ……
Supply valve, 13,14 …… Discharge valve, 23 …… Electromotive voltage detector, 21,31
...... Sequence control unit, 22,32 ...... Drive circuit, 35 …… Annotator, V …… Electromotive voltage, V _S …… Reference voltage, 10E, 11E, 12E, 13
E, 14E: Drive voltage, 35E: Abnormality notification signal.

Claims (1)

[Claims] 1. A fuel cell main body comprising a stack of a plurality of unit cells each having an oxidant electrode and a fuel electrode sandwiching an electrolyte solution layer, and an oxidant chamber and a fuel chamber disposed on both sides of the electrode, respectively. A fuel system and an oxidant system for supplying fuel and an oxidant to the fuel chamber and the oxidant chamber, respectively, each having a valve via a supply valve and a pressure regulator, and a supply valve, a pressure regulator, and a pair of reverse valves for both chambers. A replacement gas system for supplying a replacement gas through a stop valve, an automatic startup control device for controlling each valve based on a startup sequence, and an automatic startup control for a fuel cell, which includes an electromotive voltage detection unit for the fuel cell. In the method, opening a supply gas supply valve and at least a fuel chamber side discharge valve in response to a fuel cell start signal,
The first step of carrying out gas replacement for a predetermined time set in advance by experimentally obtaining that the oxygen concentration in the exhaust gas is lowered to a safe low concentration is executed, and then the supply of the fuel system and the oxidant system is performed. Valve and the oxidant chamber side discharge valve are opened to experimentally determine that the open circuit voltage of the fuel cell becomes a steady value, and after the fuel and the oxidizer have been supplied and replaced for a predetermined time, the discharge valve is closed. The second step is executed, and immediately after the end of this step, the detected electromotive voltage of the electromotive voltage detection unit is compared with a predetermined reference voltage, and when the detected electromotive voltage is less than or equal to the reference voltage, it is determined that the fuel cell is abnormal. The automatic start control method for the fuel cell is characterized in that the start sequence is assembled so as to perform the third step of closing the supply valve of the fuel system at least while issuing the notification signal.