JP5644406B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system having a cell unit using, for example, a polymer electrolyte cell.

Conventionally, as this type of fuel cell system, there is a configuration disclosed in Patent Document 1 under the name of a hydrogen supply system for a vehicle-mounted fuel cell.
A conventional hydrogen supply system for a vehicle-mounted fuel cell disclosed in Patent Document 1 is an ejector for returning hydrogen that has not been used for power generation in the fuel cell to a path for supplying hydrogen from a hydrogen supply source to the fuel cell. And a bypass path for bypassing the ejector and supplying hydrogen from the hydrogen supply source to the fuel cell.

Japanese Patent Laid-Open No. 2001-210342

  The hydrogen supply system for a vehicle-mounted fuel cell disclosed in the above-mentioned Patent Document 1 performs a non-circulating dead-end operation without causing the ejector to recirculate hydrogen that has not been used for power generation under certain conditions. In addition, hydrogen gas flows back through the reflux pipe (to the ejector return portion), and there is a problem that the generated water flows back into the cell stack and power generation becomes unstable.

  In addition, when reflux by the ejector is performed below the freezing point, a phenomenon called icing occurs in which the water vapor being refluxed from the cell stack is cooled by the hydrogen gas supplied from the hydrogen supply tank below the freezing point, and the ejector nozzle is frozen and blocked. There is also a problem that the generated hydrogen gas cannot be recirculated.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fuel cell system capable of preventing backflow of exhaust hydrogen-containing gas and preventing icing of an ejector due to recirculation when the temperature is below freezing.

The present invention for solving the above problems is as follows.
A cell unit that generates power by separating and bringing a hydrogen-containing gas and an oxygen-containing gas into contact with each other, and refluxing means for refluxing the exhausted hydrogen-containing gas discharged from the cell unit to the cell unit in the fuel cell system which arranged the road, the return means is a so Awa pairs et injector and HRB, a hydrogen-containing gas flows towards the cell unit and bypass for bypassing the Ezeku data, to the cell unit A three-way valve for switching the hydrogen-containing gas fed toward the detour to a detour ,
Cell temperature of Ruyunitto or ejector provided cell temperature determination means for determining whether or not within a predetermined temperature range including the freezing temperature,
When it is determined that the temperature of the cell unit or the ejector has entered a predetermined temperature range including the freezing point temperature, the recirculation is stopped and the supply hydrogen gas is switched to the bypass by the three-way valve.

  ADVANTAGE OF THE INVENTION According to this invention, while preventing the back flow of exhaust hydrogen containing gas, the icing of the ejector which is a recirculation | reflux means or the three-way pipe | tube installed instead of the ejector can be prevented.

(A) is explanatory drawing which shows schematic structure of the fuel cell system which concerns on 1st embodiment of this invention, (B) is a flowchart which shows the operation | movement at the time of starting. It is a flowchart which shows the operation | movement based on the temperature detection at the time of starting of the fuel cell system which concerns on 1st embodiment same as the above. (A) is explanatory drawing which shows schematic structure of the fuel cell system which concerns on 2nd embodiment of this invention, (B) is a flowchart which shows the operation | movement at the time of starting. It is a flowchart which shows the operation | movement based on the temperature detection at the time of starting of the fuel cell system which concerns on 2nd embodiment same as the above.

EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated with reference to drawings. FIG. 1A is an explanatory diagram showing a schematic configuration of the fuel cell system according to the first embodiment of the present invention, and FIG. 1B is a flowchart showing an operation at the time of startup.
In FIG. 1 and FIGS. 2 to 4 shown below, among the hydrogen-containing gas and the oxygen-containing gas, only the hydrogen-containing gas distribution system is illustrated, and the illustration of the oxygen-containing gas distribution system is omitted. It is simplified.

  In addition to the cell stack 10, the fuel cell system A1 according to the first embodiment of the present invention includes a fuel tank 20, a pressure regulating valve 21, an ejector 22, a pressure sensor 23, an ON-OFF valve 25, a temperature sensor 28, and a nitrogen purge valve. 24, a separate tank 30, a drain valve 31 and the like, and a control unit C.

The cell stack 10 is formed by polymerizing a plurality of cell units 11 with a gap between each other, and generates electric power by allowing a hydrogen-containing gas and an oxygen-containing gas to flow separately inside and outside the cell units 11. It is what I do.
In the present embodiment, “hydrogen gas” as “hydrogen-containing gas” and “air” as “oxygen-containing gas” will be described as examples, but the present invention is not limited thereto.

  Each of the cell units 11... Is a unit in which a solid polymer cell in which an anode and a cathode are disposed on both sides of an electrolyte is accommodated between separators (none of which is shown).

  The fuel tank 20 stores a required amount of hydrogen gas to be supplied to the cell stack 10, and a supply pipe 20 a is connected between the fuel tank 20 and the receiving portion of the cell stack 10. .

  The above-described pressure regulating valve 21 has a function of steplessly increasing / decreasing the pressure of hydrogen gas fed from the fuel tank 20, and is disposed at an intermediate portion of the feed pipe 20a. It is connected to the output side of a control unit C, which will be described later, and the supply pressure is controlled to increase or decrease.

  In the present embodiment, the pressure regulating valve 21 increases or decreases the pressure of the hydrogen gas supplied from the fuel tank 20 which is a hydrogen gas supply source to the receiving portion of the cell stack 10 and thus to the anode of each cell unit 11. It is the pressure regulation part for doing.

A separation tank 30 (to be described later) is connected to the discharge portion of the cell stack 10 via a discharge pipe 10a, and a return pipe 30a as a return path is connected between the separator tank 30 and the ejector 22. Yes.
That is, the exhausted hydrogen gas discharged from the anode of the cell stack 10 is made to recirculate to the cell stack 10 via the ejector 22.

The ejector 22 is a supply pipe 20 a and is disposed on the downstream side of the pressure regulating valve 21.
The ejector 22 has a function of returning the exhausted hydrogen gas discharged from the cell stack 10 to the anode through the return pipe 30a by the entrainment action of the hydrogen gas flowing through the supply pipe 20a.
Instead of the ejector 22 as the reflux means, an HRB (Hydrogen recirculation blower, abbreviated as hydrogen circulation pump, hereinafter referred to as “HRB”) is provided in the reflux pipe 30a, and a three-way pipe is provided instead of the ejector 22. It may be a means. That is, only the ejector 22 serves as the reflux means, and the HRB and the three-way pipe together serve as the reflux means. Of course, the ejector 22 may be provided, and the reflux pipe 30a may be provided with the HRB as the reflux means.

The pressure sensor 23 measures the pressure of the hydrogen gas discharged from the ejector 22.
The feed pipe 20a is disposed on the downstream side of the ejector 22 and is connected to the input side of the control unit C so as to detect pressure.

The ON-OFF valve 25 is used to open and shut off the exhaust hydrogen gas flowing through the reflux pipe 30a.
That is, by opening the ON-OFF valve 25 during the pressure increase during intermittent operation, pressure is applied to the reflux pipe 30a side to prevent the exhaust hydrogen gas from flowing back through the cell stack 10. By providing such an ON-OFF valve 25 in the reflux pipe 30a, more stable power generation can be performed.
In the present embodiment, the ON-OFF valve 25 is a flow control unit for preventing the backflow of exhaust hydrogen gas (exhaust hydrogen-containing gas) to the cell unit 11. As will be described later, this flow control unit performs or stops reflux according to the temperature.
The temperature sensor 28 is for measuring the temperature of the cell stack 10, and hence also the cell unit 11, and is connected to the input side of the control unit C.

The separation tank 30 separates and stores the water w contained in the exhausted hydrogen gas discharged from the anode, and the water w stored in the separation tank 30 is discharged to the outside through the drain valve 31. I am doing so.
The drain valve 31 is connected to the output side of the control unit C and is appropriately controlled to open and close.
The nitrogen purge valve 24 is for discharging the nitrogen gas staying in the separation tank 30 and is connected to the output side of the control unit C so as to be controlled for opening and closing.

The controller C includes a CPU (Central Processing Unit), an interface circuit, and the like, and exhibits the following functions by executing a required program.
(1) A function of determining whether or not the flow rate of the hydrogen-containing gas supplied to the cell unit 11 necessary for generating electric power (current) for responding to the load is smaller than a predetermined flow rate. This function is referred to as “flow rate determination means C1”.
“Determining whether or not the flow rate of the hydrogen-containing gas to be delivered is smaller than a predetermined flow rate” depends on whether or not it is smaller than the flow rate of hydrogen-containing gas to cope with a low load of 10% or less of the maximum output. In addition, it has been experimentally confirmed that a general ejector designed with the required maximum output power has a low load of 10% or less (cannot be recirculated in a low flow rate region).
Further, even when an HRB is provided in the reflux pipe 30a as the reflux means, for example, it depends on whether the flow rate is smaller than the hydrogen-containing gas flow rate to cope with a low load of 10% or less of the maximum output.
That is, the “predetermined flow rate” is a flow rate at which the exhaust hydrogen-containing gas is not recirculated to the cell unit 11. In other words, this is the flow rate of hydrogen gas at which the exhaust hydrogen gas cannot be recirculated to the cell unit 11 through the recirculation pipe 30a.

(2) When it is determined that the flow rate of hydrogen-containing gas supplied to the cell unit 11 necessary for generating electric power (current) to cope with the load is less than a predetermined flow rate, the hydrogen-containing gas A function that fluctuates the pressure of the gas intermittently. This function is referred to as “gas supply pressure fluctuation means C2.”
In the present embodiment, the pressure of the hydrogen gas supplied to the anode of the cell unit 11 is intermittently increased or decreased through the pressure regulating valve 21 that is the pressure regulating unit.
When the flow rate of the hydrogen gas exceeds a predetermined flow rate, the hydrogen gas is supplied at a constant pressure.

“Intermittently” includes irregular intervals in addition to equal intervals.
The value of the pressure fluctuation is set so that the impurities in the solid polymer cell can be discharged. Specifically, it can be set to two values: a relatively high pressure value at which water is discharged and a relatively low pressure value at which nitrogen gas or the like is discharged.

  For example, a normal pressure fluctuation is set to a relatively low pressure value at which nitrogen gas or the like can be discharged, and after repeating the pressure fluctuation a predetermined number of times, the pressure fluctuation is performed at a relatively high pressure value at which water can be discharged. You may do it.

  That is, when the exhausted hydrogen gas cannot be recirculated, impurities (water, nitrogen, etc.) in the solid polymer cell are discharged by intermittently increasing / decreasing the anode pressure. Thereby, the hydrogen gas concentration from the anode upstream to the downstream of the solid polymer cell can be improved as a whole, and thus stable power generation can be performed.

(3) When it is determined that the flow rate of the hydrogen-containing gas supplied to the cell unit 11 necessary for generating electric power (current) to cope with the load is smaller than a predetermined flow rate, the flow control unit 25 A function to prevent the backflow of exhaust hydrogen gas through This function is called “backflow prevention means C3”.

(4) A function of detecting the temperature of the cell unit 11. This function is referred to as “cell temperature detection means C4”.
In the present embodiment, the temperature of the cell unit 11 is detected based on the temperature sensor 28.

(5) Whether or not the temperature of the cell unit 11 measured via the temperature sensor 28 has entered a predetermined temperature range including the freezing point temperature, that is, the temperature of the cell unit 11 is lowered to a predetermined temperature range including the freezing point temperature. A function to determine whether or not This function is referred to as “cell temperature determination means C5”.
The “predetermined temperature range including the freezing point temperature” increases the amount of nitrogen permeated from the cathode, making dead-end operation difficult, and the ejector temperature takes into account sensor errors and the heat capacity of the ejector 22. Is a temperature range of about 20 ° C. or less, which is the upper limit temperature that does not cause icing.
Further, even when HRB is provided in the reflux pipe 30a as the reflux means, the temperature range is about 20 ° C. or less, which is the upper limit temperature that does not cause icing.
“Icing” means that the water vapor being refluxed from the cell stack 10 is cooled by the hydrogen supplied below the freezing point from the fuel tank 20 and frozen and closed by the ejector nozzle portion.
Further, even when an HRB is provided in the reflux pipe 30 a as a reflux means and a three-way pipe is provided in place of the ejector 22, “icing” means that the water vapor being refluxed from the cell stack 10 is supplied below the freezing point from the fuel tank 20. It is cooled with hydrogen and frozen and blocked with a three-way tube.

(6) When it is determined that the detected temperature of the cell unit 11 has entered a predetermined temperature region including the freezing point temperature (decreased to a predetermined temperature region including the freezing point temperature), Function to stop reflux. This function is referred to as “reflux stop means C6”.
The “predetermined temperature range including the freezing point temperature” is as described above.

The startup operation of the fuel cell system A1 having the above-described configuration will be described with reference to FIG.
Step 1: In FIG. 1B, abbreviated as “Sa1”. The same applies hereinafter.
The pressure of the hydrogen gas supplied from the fuel tank 20 is intermittently increased or decreased and supplied to the anode.

Step 2: Determine whether the flow rate of hydrogen gas required to generate power (current) for responding to the load is greater than a predetermined flow rate, and generate power (current) for responding to the load If it is determined that the flow rate of the hydrogen gas necessary to make the flow is larger than the predetermined flow rate, the process proceeds to step 3; otherwise, the process returns to step 1.
Step 3: Hydrogen gas is continuously fed so that the anode pressure becomes constant, and the process returns to Step 2.

  An operation based on temperature detection at the start-up time of the fuel cell system A1 having the above-described configuration will be described with reference to FIG. FIG. 2 is a flowchart showing an operation based on temperature detection at the time of startup of the fuel cell system A1.

Step 1: In FIG. 2, abbreviated as “Sb1”. The same applies hereinafter.
The temperature of the cell stack 11 is detected.
Step 2: It is determined whether or not the temperature of the cell unit 11 has entered a predetermined temperature range including the freezing point temperature (whether or not it has fallen to a predetermined temperature range including the freezing point temperature), and the temperature includes the freezing point temperature. If it is determined that the temperature has entered the predetermined temperature range (decreased to a predetermined temperature range including the freezing point temperature), the process proceeds to step 4; otherwise, the process proceeds to step 3.
Step 3: The ON-OFF valve 25 is opened to recirculate the exhaust hydrogen gas via the ejector 22.
Step 4: The ON-OFF valve 25 is driven to close, and the pressure of the hydrogen gas supplied from the fuel tank 20 is intermittently increased or decreased to supply it to the anode (stopping the reflux).

According to the present embodiment, the following effects can be obtained.
-Stops the reflux of water vapor when the temperature is below freezing, and prevents icing in the ejector.
-Since the nitrogen permeation amount is low at low temperatures, dead-end operation can be performed more easily. Even if the temperature is not below the freezing point, the ejector may be below the freezing point depending on the arrangement of the temperature sensor. In this case, icing can be effectively prevented.

  Next, a fuel cell system according to a second embodiment of the invention will be described with reference to FIGS. FIG. 3A is an explanatory diagram showing a schematic configuration of a fuel cell system according to the second embodiment of the present invention, and FIG. 3B is a flowchart showing an operation at the time of startup.

  The hardware configuration of the fuel cell system A2 according to the second embodiment is the same as that described in the fuel cell system A1 according to the first embodiment described above, except for the detour 27a, the three-way valve 27, and the reflux pipe 30a. Since the check valve 26 is provided, in the present embodiment, the same components as those described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Here, the difference will be described.

The three-way valve 27 is provided on the upstream side of the ejector 22 disposed on the feed pipe 20a, and a bypass pipe 27a serving as a bypass is disposed between the ejector 22 and the feed pipe 20a on the downstream side of the ejector 22. Yes.
In this embodiment, instead of the ejector 22 as the reflux means, an HRB may be provided in the reflux pipe 30a and a three-way pipe may be provided in place of the ejector 22 as the reflux means. That is, only the ejector 22 serves as the reflux means, and the HRB and the three-way pipe together serve as the reflux means. Of course, the ejector 22 may be provided, and the reflux pipe 30a may be provided with the HRB as the reflux means.
The three-way valve 27 is connected to the output side of the control unit C and is appropriately controlled to be switched.

That is, in the present embodiment, the control unit C has the following functions in addition to the functions described above.
(7) When it is determined that the temperature of the cell unit 11 has entered a predetermined temperature range including the freezing point temperature (decreased to a predetermined temperature range including the freezing point temperature), hydrogen supplied toward the cell unit 11 A function of switching and feeding the contained gas to the bypass 27a via the three-way valve 27. This function is referred to as “detour feeding means C7”.
Thereby, at the time of intermittent operation, the ejector 22 can be bypassed, pressure loss of the ejector 22 can be avoided, and more stable intermittent operation can be performed.

The operation of the fuel cell system A2 having the above configuration will be described with reference to FIG.
Step 1: In FIG. 3B, abbreviated as “Sc1”. The same applies hereinafter.
The three-way valve 27 is switched so that the hydrogen gas flows through the bypass pipe 27a, and the hydrogen gas is intermittently supplied to the anode.

Step 2: Determine whether the flow rate of hydrogen gas required to generate power (current) for the load is greater than the required flow rate, and generate power (current) for the load If it is determined that the flow rate of the hydrogen gas necessary for making the flow is larger than the required flow rate, the process proceeds to step 3; otherwise, the process returns to step 1.
Step 3: The three-way valve 27 is switched so that the hydrogen gas flows through the ejector 22, the hydrogen gas is continuously fed so that the anode pressure becomes constant, and the process returns to Step 2.

An operation based on temperature detection at the start-up of the fuel cell system A2 having the above-described configuration will be described with reference to FIG. FIG. 4 is a flowchart showing an operation based on temperature detection at the time of startup of the fuel cell system A2.
Step 1: In FIG. 4, abbreviated as “Sd1”. The same applies hereinafter.
The temperature of the cell stack 11 and therefore also the cell unit 11 is detected.
Step 2: It is determined whether or not the temperature of the cell unit 11 has entered a predetermined temperature range including the freezing point temperature (whether or not the temperature has decreased to a predetermined temperature range including the freezing point temperature). If it is determined that a predetermined temperature range including the temperature has been entered (decreased to a predetermined temperature range including the freezing point temperature), the process proceeds to step 4. Otherwise, the process proceeds to step 3.
Step 3: Switch the three-way valve 27 to the ejector 22 side and return to Step 1.
Step 4: The three-way valve 27 is switched to the bypass pipe 27a side, and the pressure of the hydrogen gas supplied from the fuel tank 20 is intermittently increased / decreased and supplied to the anode (return is stopped).
In FIG. 4, “intermittent increase / decrease in the hydrogen gas pressure” is referred to as “non-circulating dead-end operation”.

The present invention is not limited to the above-described embodiments, and the following modifications can be made.
-Although the above temperature sensor illustrated what was arrange | positioned so that the temperature of a cell unit may be measured, it is not restricted to the form, For example, the temperature of an ejector is measured separately from the temperature sensor which measures the temperature of the said cell unit. A temperature sensor for measurement may be provided.

Although described in detail above, in any case, the configuration described in each of the above-described embodiments is not limited to being applied only to each of the embodiments, and the configuration described in one embodiment is not limited to other embodiments. In addition, they can be applied mutatis mutandis or applied to them, and they can be arbitrarily combined.

11 Cell unit 22 Ejector 25 Flow control unit (ON-OFF valve)
27 Three-way valve 27a Detour (bypass pipe)
28 Temperature Sensor 30a Reflux Path (Reflux Pipe)
C1 Flow rate determination means C2 Gas supply pressure fluctuation means C3 Backflow prevention means C6 Reflux stop means C4, 5 Cell temperature determination means C7 Detour supply means

Claims (6)

A cell unit that generates power by separating and bringing a hydrogen-containing gas and an oxygen-containing gas into contact with each other, and refluxing means for refluxing the exhausted hydrogen-containing gas discharged from the cell unit to the cell unit In the fuel cell system arranged on the road,
The return means is a so Awa pairs et injector and HRB, and bypass for the hydrogen-containing gas flows towards the cell unit bypass the Ezeku data, the hydrogen-containing gas fed towards the cell unit A three-way valve for switching to a detour ,
Cell temperature of Ruyunitto or ejector provided cell temperature determination means for determining whether or not within a predetermined temperature range including the freezing temperature,
When it is determined that the temperature of the cell unit or the ejector has entered a predetermined temperature range including a freezing point temperature, the recirculation is stopped and the supplied hydrogen gas is switched to a bypass by the three-way valve. A cell unit that generates power by separating and bringing a hydrogen-containing gas and an oxygen-containing gas into contact with each other, and refluxing means for refluxing the exhausted hydrogen-containing gas discharged from the cell unit to the cell unit In the fuel cell system arranged on the road,
The return means is a combination of HRB and three-way pipe, a bypass for bypassing the three sides tube a hydrogen-containing gas flows towards the cell unit and the hydrogen content fed towards the cell unit A three-way valve for switching gas to a bypass ,
Cell temperature of Ruyuni' bets is provided a cell temperature determination means for determining whether or not within a predetermined temperature range including the freezing temperature,
When the temperature of Seruyuni' bets is determined to have entered the predetermined temperature range including the freezing point temperature, it stops the reflux, the fuel cell system and switches the supply of hydrogen gas to the bypass passage by the three-way valve. A cell unit that generates power by separating and bringing a hydrogen-containing gas and an oxygen-containing gas into contact with each other, and refluxing means for refluxing the exhausted hydrogen-containing gas discharged from the cell unit to the cell unit In the fuel cell system arranged on the road,
The recirculation means is an ejector, and bypasses the hydrogen-containing gas flowing toward the cell unit to bypass the ejector, and switches the hydrogen-containing gas supplied toward the cell unit to the bypass. A three-way valve ,
Cell temperature of Ruyunitto or ejector provided cell temperature determination means for determining whether or not within a predetermined temperature range including the freezing temperature,
A fuel cell system characterized in that when it is determined that the temperature of a cell unit or ejector has entered a predetermined temperature range including a freezing point temperature, the supply hydrogen gas is switched to a bypass by the three-way valve. A cell unit that generates power by separating and bringing a hydrogen-containing gas and an oxygen-containing gas into contact with each other, and refluxing means for refluxing the exhausted hydrogen-containing gas discharged from the cell unit to the cell unit In the fuel cell system arranged on the road,
The return means, the ejector is any combination of the combination or the ejector and HRB of HRB and three-way pipe, a bypass for bypassing the ejector or three-way tube a hydrogen-containing gas flows towards the cell unit, A three-way valve for switching the hydrogen-containing gas supplied to the cell unit to a bypass,
A flow rate determining means for determining whether or not the hydrogen-containing gas flow rate supplied to the cell unit is smaller than a predetermined flow rate;
When it is determined that the flow rate of the hydrogen-containing gas supplied to the cell unit is less than a predetermined flow rate, gas supply pressure fluctuation means for intermittently increasing or decreasing the pressure of the hydrogen-containing gas;
When it is determined that the flow rate of hydrogen-containing gas sent to the cell unit is less than the predetermined flow rate, the detour sending is performed by switching the hydrogen-containing gas sent toward the cell unit to the cell unit via the three-way valve. And a fuel supply system. The reflux means is either an ejector or a combination of an ejector and an HRB;
A temperature sensor is provided to measure the temperature of the cell unit or ejector .
Cell temperature determination means for determining whether or not the temperature of the cell unit or ejector measured via the temperature sensor has entered a predetermined temperature range including the freezing point temperature,
When the bypass feeding means determines that the temperature of the cell unit or ejector has entered a predetermined temperature range including the freezing point temperature, the hydrogen-containing gas fed toward the cell unit via the three-way valve is bypassed. The fuel cell system according to claim 4 , wherein the fuel cell system is switched and fed. The reflux means is a combination of HRB and a three-way pipe,
Together they are arranged a temperature sensor for measuring the temperature of Seruyuni' bets,
Includes a cell temperature determination means for determining whether the temperature of Seruyuni' bets measured through the temperature sensor is within a predetermined temperature range including the freezing temperature,
The bypass feed means, when the temperature of Seruyuni' bets is determined to have entered the predetermined temperature range including the freezing temperature is sent to switch the hydrogen-containing gas fed towards the cell unit via a three-way valve to the bypass path The fuel cell system according to claim 4 , wherein the fuel cell system is supplied.

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