JP2008117780A - Fuel cell device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell device with an exhausting way of fuel exhaust gas improved, free from draining exhaust gas containing a fuel gas component such as hydrogen gas outside a fuel cell device system and free from risk of causing undesirable reaction of hydrogen gas outside a system of a fuel cell. <P>SOLUTION: An exhaust port 36 of fuel exhaust gas directly exhausted from a fuel electrode 13 of a fuel cell body 10 is positioned at a place where air flow exists generated from either a radiator fan 39 for cooling the fuel cell body, a fan of a condenser for separating moisture from air exhaust gas, or a rotating wheel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell device. More specifically, the present invention relates to an improvement in the manner of exhausting fuel exhaust gas.

  A normal fuel cell has an electrolyte membrane sandwiched between a fuel electrode and an air electrode. Hydrogen gas is supplied to the fuel electrode as a fuel gas, while air is supplied to the air electrode to react with each other through the electrolyte membrane. Power is obtained as the electrochemical reaction proceeds.

The fuel gas supplied to the fuel electrode is preferably completely consumed at the fuel electrode. However, even if pure hydrogen is supplied from a hydrogen cylinder as a fuel gas, the output of the battery becomes unstable due to N 2, O 2 or generated water that permeates from the air electrode as the cell reaction proceeds.
Therefore, conventionally, fuel gas has been discharged continuously or at regular intervals outside the fuel cell system.

  However, since hydrogen gas has high activity, if the hydrogen gas is allowed to flow in this manner, the hydrogen gas may cause an undesirable reaction outside the fuel cell system.

The present invention has been made to solve such problems. The invention described in claim 1 is as follows. That is,
The exhaust port of the fuel exhaust gas that is exhausted directly from the fuel electrode of the fuel cell main body is one of a radiator fan that cools the fuel cell main body, a condenser fan that separates moisture from the air exhaust gas, and a rotating wheel. The fuel cell device is located where the generated air flow is.
The fuel cell device according to the second aspect of the present invention is as follows. That is,
2. The fuel cell device as defined in claim 1, wherein the exhaust port faces a radiator fan.
The fuel cell device defined in claim 3 is as follows. That is,
A fuel exhaust gas path for exhausting fuel exhaust gas directly exhausted from the fuel electrode of the fuel cell body;
An air introduction path for supplying air to the air electrode of the fuel cell main body,
The fuel cell apparatus is characterized in that the fuel exhaust gas is supplied to the air introduction path through the fuel exhaust gas path and mixed with air.
The fuel cell device defined in claim 4 is as follows. That is,
In the fuel cell device defined in claim 3, a hydrogen concentration sensor for detecting a concentration of a hydrogen gas component in the fuel exhaust gas,
A flow meter for detecting a flow rate of the fuel exhaust gas;
And a control device that controls the amount of air introduced into the air introduction path based on detection results of the hydrogen concentration sensor and the flow meter.

  According to the first aspect of the present invention, it is not necessary to provide the mechanical airflow generating means exclusively for the exhaust port. Therefore, the number of parts of the device can be reduced.
  According to invention of Claim 2, there exists an effect similar to the invention of Claim 1.
  According to the third aspect of the present invention, the hydrogen gas contained in the fuel exhaust gas is diffused along the air flow, and the abnormal reaction caused by the hydrogen gas contained in the fuel exhaust gas does not occur.
  According to the fourth aspect of the present invention, when the hydrogen gas concentration is high or the flow rate of the fuel exhaust gas is large, and as a result, a large amount of hydrogen gas can be mixed with the air, the amount of air introduced is increased, so that in the air introduction path Increase the air flow rate. This promotes premixing of air and hydrogen gas.

  In the above, exhaust gas containing a fuel gas component includes fuel exhaust gas exhausted directly from the fuel electrode and air exhaust gas exhausted from the air electrode. The latter is the case of a fuel cell device of a type in which fuel exhaust gas is once introduced into the air electrode.

  The air flow is generated mechanically by a fan or the like. Although this mechanical airflow generating means can be provided exclusively for generating an airflow to the exhaust port, it is preferable to use a radiator fan of a cooling system from the viewpoint of reducing the number of parts of the apparatus. In addition, a condenser fan that separates moisture from the air exhaust gas, a rotating wheel, or the like can be used.

  Airflow is also generated as air convection due to temperature differences. Therefore, if an exhaust port is arranged toward or near a component having a temperature difference from the atmosphere, such as a humidifier, the air discharged from the exhaust port is caught in the convection air and diffused. .

Next, an embodiment of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 shows a schematic configuration of a fuel cell device 1 of an embodiment. FIG. 2 shows a basic unit of the fuel cell main body 10.

  As shown in FIG. 1, the apparatus 1 includes a fuel cell body 10, a hydrogen gas supply system 20 as a fuel gas, an air supply system 30, and a water supply system 40.

  The unit unit of the fuel cell main body 10 has a configuration in which a solid polymer electrolyte membrane 12 is sandwiched between an air electrode 11 and a fuel electrode 13. In an actual apparatus, a plurality of these unit units are stacked (fuel cell stack). Air manifolds 14 and 15 are formed above and below the air electrode 11. An attachment hole for attaching the nozzle 41 is formed in the upper manifold 14. On the other hand, the lower air manifold 15 is capable of efficiently discharging the dropped water.

As shown in FIG. 2, the unit unit of the air electrode 11 -the solid polymer electrolyte membrane 12 -the fuel electrode 13 is sandwiched between a pair of carbon connector plates 16 and 17. A plurality of grooves 18 are formed on the surface of the connector plate 16 facing the air electrode 11 for circulating air. Each groove 18 is formed in the vertical direction and communicates with the manifolds 14 and 15. As a result, the mist-like water supplied from the nozzle 41 reaches the lower part of the air electrode 11 along the groove 18.
Similarly, a groove 19 for flowing hydrogen gas is formed on the surface of the connector plate 17 facing the fuel electrode 13. In the embodiment, a plurality of the grooves 19 are formed in the horizontal direction.

Since water is supplied to the air electrode 11, it is made of a water-resistant material. Moreover, since the effective area of the air electrode 11 will decrease if a water film is formed there, the material of the air electrode 11 is also required to have high water repellency. As such a material, a gas diffusion layer coated with (C + PTFE) using carbon cloth as a base material was used.
A thin film of general-purpose Nafion (trade name: DuPont) was used for the solid polymer electrolyte membrane 12.
The thickness of the membrane is not particularly limited as long as reverse osmosis of generated water is possible from the air electrode side.
The fuel electrode 13 is made of the same material as the air electrode 11. This is for sharing parts.
On the surface of the air electrode 11 and the fuel electrode 13 that are in contact with the electrolyte membrane 12, a well-known platinum-based catalyst used to promote the reaction between oxygen and hydrogen with a certain thickness is uniformly dispersed. Thus, it is formed as a catalyst layer in the air electrode 11 and the fuel electrode 13.

In this embodiment, a hydrogen cylinder made of a hydrogen storage alloy was used as the hydrogen source 21 of the hydrogen gas supply system 20. In addition, a reforming raw material such as a water / methanol mixture is reformed in a reformer to generate a hydrogen-rich reformed gas, which is stored in a tank and used as a hydrogen source. You can also Of course, when the fuel cell device 1 is used in a room, the hydrogen pipe can be used as a hydrogen source.
The hydrogen source 21 and the fuel electrode 13 are connected by a hydrogen gas supply path 22 via a hydrogen supply pressure regulating valve 23. The pressure regulating valve 23 adjusts the pressure of the hydrogen gas supplied to the fuel electrode 13, and a general-purpose configuration can be used.

Exhaust gas from the fuel electrode 13 is supplied to the air introduction path 31 through the fuel exhaust gas path 24 and is mixed therewith with air. The fuel exhaust gas introduced into the air introduction path 31 is further mixed at a portion where the air exhaust gas circulation path 35 joins the air introduction path 31. A hydrogen exhaust valve 25 for opening and closing the fuel exhaust gas passage 24 is disposed in the fuel exhaust gas passage 24. Reference numeral 27 in the drawing is a sensor that detects the concentration of the hydrogen gas component in the fuel exhaust gas, and reference numeral 29 is a flow meter that detects the flow rate of the fuel exhaust gas.
If the outlet of the fuel exhaust gas passage 24 is directed to the outlet of the nozzle 41 or the outlet of the air introduction passage 31, stirring and mixing are performed there. In this case, the fuel exhaust gas is directly supplied to the air manifold 14. It becomes possible to introduce.

The hydrogen gas supplied to the fuel electrode 13 is used for the power generation reaction and most of it is consumed. However, the remaining surplus hydrogen gas flows through the exhaust gas passage 24 and enters the air introduction passage 31 via the exhaust valve 25. be introduced. Here, the air electrode 11 reaches the air electrode 11 in a premixed and highly dispersed state.
Thus, the surplus hydrogen gas supplied to the air electrode 11 burns on the catalyst and is converted into water. This water is supplied to the electrolyte membrane 12. In this way, in the fuel cell device 1 in which the generated water by the normal cell reaction and the recovered water by the combustion of the surplus hydrogen gas can be used, there are no conventional humidifiers in the gas paths of the hydrogen gas system 20 and the air system 30. Not needed.

Air is supplied to the air electrode 11 from the atmosphere by the blower 37. The blower 37 is driven and controlled by a motor 38. Reference numeral 31 in the figure denotes an air introduction path, which is connected to the manifold 14 of the air electrode 11. An air exhaust gas passage 32 for exhausting air that has passed through the air electrode 11 is connected to the lower manifold 15, and the air exhaust gas is sent to the circulation passage 35 and the exhaust port 36 through a separator 33 that separates water. It is done. The ratio of the air exhaust gas distributed to the circulation path 35 and the exhaust port 36 is adjusted by the opening degree of the air exhaust pressure regulating valve 34. The reason why the air exhaust gas is circulated is to completely burn the surplus hydrogen gas introduced into the air electrode 11.
The circulation path 35 and the valve 34 may be omitted, and the air exhaust gas may be discharged to the atmosphere as it is.

  The air exhaust gas is exhausted toward the radiator fan 39, and is diffused into the atmosphere. Thus, the air exhaust gas is caught in the air flow generated by the radiator fan 39 and diffuses along this air flow. Therefore, the air exhaust gas does not stay in one place, so that the concentration of the hydrogen gas component contained therein becomes as small as possible, and this hardly causes an undesirable reaction.

The water separated by the aggregator 33 is sent to the tank 42. A water level sensor 43 is attached to the tank 42. When the water level of the tank 42 becomes a predetermined value or less by the water level sensor 43, an alarm 44 blinks to notify the operator of water shortage.
In the water supply system 40 of the embodiment, a water supply path 45 is connected from the tank 42 to the nozzle 41 via a pump 46, a water pressure sensor 47 and a pressure regulating valve 48. The water adjusted to a desired water pressure by the pressure regulating valve 48 blows out from the nozzle 41 and becomes mist in the air manifold 14. Then, mist-like water is supplied to the substantially entire surface of the air electrode 11 by the momentum (initial speed) at the time of blowing, the weight of the mist, the air flow, and the like.

In this way, the water supplied to the surface of the air electrode 11 evaporates by removing latent heat from the surrounding air. Thereby, evaporation of the water | moisture content of the electrolyte membrane 12 is prevented.
Further, since the water supplied to the air electrode 11 also takes away latent heat from the air electrode 11, it also has an action of cooling it. In particular, when water is supplied at the time of starting, heat exceeding the rating of a cooler (not shown) that may be generated due to an abnormal reaction is cooled, and damage to the fuel cell body can be prevented.

  Reference numeral 50 in the figure denotes a voltmeter that measures the voltage between the air electrode 11 and the fuel electrode 13.

Next, the operation of the fuel cell device 1 of the embodiment will be described with reference to FIG. 3 and the subsequent drawings.
The control device 70 and the memory 73 are housed in a control box (not shown in FIG. 1) of the fuel cell device 1. The memory 73 stores a control program that defines the operation of the control device 70 that is a computer, parameters for executing various controls, and a lookup table.

First, the operation of the hydrogen gas supply system 20 will be described.
At startup, the hydrogen exhaust valve 25 is kept closed, and the hydrogen supply pressure regulating valve 23 is adjusted so that hydrogen gas is supplied to the fuel electrode 13 at a predetermined concentration below the explosion limit.
When the fuel cell device 1 is operated with the exhaust valve 25 closed, the partial pressure of hydrogen consumed at the fuel electrode 13 gradually decreases due to the influence of N2, O2 or generated water that permeates from the air electrode. As a result, the output voltage also decreases, and a stable voltage cannot be obtained.

Therefore, based on a predetermined rule, the valve 25 is released to exhaust the gas whose hydrogen partial pressure has decreased, and the atmosphere gas in the fuel electrode 13 is refreshed.
The predetermined rule is stored in the memory 73, and the control device 70 reads the rule from the memory 73 and executes the opening / closing of the exhaust valve 25 and the adjustment of the pressure regulating valve 23.

In this embodiment, the voltmeter 50 monitors the output voltage, and when the output voltage drops below a predetermined threshold, the valve 25 is released for a predetermined time (for example, 1 second).
Alternatively, the time interval at which the output voltage starts to decrease when the fuel cell device 1 is operated with the valve 25 closed is measured in advance, and the exhaust valve 25 is substantially the same as or slightly shorter than the time interval. The exhaust valve 25 is intermittently controlled to open and close.

Next, the operation of the air supply system 30 will be described.
The motor 38 normally rotates at a constant output, and outside air is supplied to the air manifold 14 by the blower 37 at a constant pressure. On the other hand, a part of the air exhaust gas is discharged out of the system according to the opening degree of the air exhaust pressure regulating valve 34, and the remaining part is circulated through the circulation path 35. That is, since the air exhaust gas contains hydrogen, the moisture generated by burning the hydrogen is appropriate for maintaining the electrolyte membrane 12 in a wet state. The opening degree of the pressure regulating valve 34 is adjusted so that the balance is optimal.

The adjustment of the opening degree of the air exhaust pressure regulating valve 34 is also controlled by the control device 70 based on a predetermined rule. The predetermined rule is stored in the memory 73.
In this embodiment, the moisture balance of the fuel cell main body 10 is mainly adjusted by a water supply system 40 described later, so the opening of the pressure regulating valve 34 may be fixed.

  When the hydrogen exhaust valve 25 is opened, the air supply system 30 operates as shown in FIG. First, in step 1, the concentration of the hydrogen gas component in the fuel exhaust gas is detected by the hydrogen concentration sensor 27. Next, in step 3, the flow rate of the fuel exhaust gas is detected by the flow meter 29. Based on the detection results obtained in these steps 1 and 3, the optimum air introduction amount is calculated (step 5). That is, when the hydrogen gas concentration is high or the flow rate of the fuel exhaust gas is large and as a result, a large amount of hydrogen gas can be mixed with the air, the output of the motor 38 is increased to increase the amount of air introduced, and thus the air introduction path 31 Increase the air flow rate. Thereby, premixing of air and hydrogen gas is promoted (step 7).

  Note that the calculation in step 5 is executed by the calculation device 70 based on rules stored in advance in the memory 73. As an example of this rule, there is an equation in which the amount of air introduced is defined using the hydrogen gas concentration and the flow rate of the fuel exhaust gas as parameters. Alternatively, the air introduction amount can be obtained from a lookup table of these parameters.

  In this embodiment, the air introduction amount is calculated based on the concentration of the hydrogen gas component in the fuel exhaust gas and the flow rate of the fuel exhaust gas. However, only one of the values is detected, and the air introduction amount is calculated from the detection result. May be.

Next, the operation of the water supply system 40 will be described.
Water in the tank 42 is pumped by a pump 46. Then, the pressure is adjusted by the injection pressure adjusting valve 48 and sprayed from the nozzle 41. Thereby, water will be supplied to the air electrode 11 in a liquid state (fog state).

The supply amount of water is controlled by the control device 70 based on a predetermined rule. The predetermined rule is stored in the memory 73.
In this embodiment, as shown in FIG. 5, the output voltage between the air electrode 11 and the fuel electrode 13 is first monitored (step 11). Then, the optimum water injection amount is calculated based on the output voltage (step 13). This calculation can be obtained by using a predetermined equation or preparing a predetermined look-up table (stored in the memory 73). Normally, when the output voltage becomes smaller than a predetermined threshold voltage or when the fluctuation range of the output voltage exceeds a predetermined threshold, the water supply system 40 starts its operation.

Next, in step 15, the optimum water pressure corresponding to the optimum water injection amount is calculated. For example, since the water injection amount and the water pressure have the relationship shown in FIG. 6, this relationship is stored in advance in the memory 73 in the form of an equation or a lookup table.
In this embodiment, the water pressure of the nozzle 41 is adjusted by the opening of the pressure regulating valve 48 in the circulation path 49 while the pump 46 is operated at a constant power. That is, if the opening degree of the pressure regulating valve 48 is large (small), the water pressure of the nozzle 41 is small (large).

  Accordingly, in step 17, the water pressure applied to the nozzle 41 is detected by the water pressure sensor 47, and the pressure regulating valve 48 is adjusted by feedback control so that the water pressure becomes a desired value (optimum water pressure) (step 19).

  In addition, the water supply system 40 may be operated at a constant water pressure every predetermined time (for example, 5 to 10 seconds).

(Second embodiment)
A fuel cell device 101 of this embodiment is shown in FIG. In this apparatus 101, the fuel exhaust gas path 24 does not merge with the air introduction path 31, but is directly discharged out of the system of the apparatus 101. The discharge port 103 faces the radiator fan 39.
According to the fuel cell device 101 configured as described above, the fuel exhaust gas discharged from the discharge port 103 is entrained in the air flow generated by the radiator fan 39 and diffuses along the air flow. Therefore, the air exhaust gas does not stay in one place, so that the concentration of the hydrogen gas component contained therein becomes as small as possible, and this hardly causes an undesirable reaction.

  The present invention is not limited to the description of the embodiments and examples of the invention described above. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims.

It is a schematic diagram which shows the structure of the fuel cell apparatus of the Example of this invention. It is sectional drawing which similarly shows the basic composition of a fuel cell main body. It is a schematic diagram which similarly shows the control system of a fuel cell apparatus. It is a flowchart which similarly shows operation | movement of an air supply system. It is a flowchart which similarly shows operation | movement of a water supply system. It is a graph which similarly shows the relationship between water injection quantity and water pressure. It is a schematic diagram which shows the structure of the fuel cell apparatus of the other Example of this invention.

Explanation of symbols

1, 101 Fuel cell device
10 Fuel cell body
11 Air electrode
12 Electrolyte membrane
13 Fuel electrode
20 Hydrogen supply system
25 Hydrogen exhaust gas passage
30 Air supply system
35 Air exhaust gas circuit
36, 103 Exhaust port
39 radiator fan
40 Water supply system

Claims (4)

The exhaust port of the fuel exhaust gas that is exhausted directly from the fuel electrode of the fuel cell main body is one of a radiator fan that cools the fuel cell main body, a condenser fan that separates moisture from the air exhaust gas, and a rotating wheel. A fuel cell device, wherein the fuel cell device is located where the generated air flow is. The fuel cell apparatus according to claim 1, wherein the exhaust port faces a radiator fan. A fuel exhaust gas path for exhausting fuel exhaust gas directly exhausted from the fuel electrode of the fuel cell body;
  An air introduction path for supplying air to the air electrode of the fuel cell main body,
  The fuel cell apparatus, wherein the fuel exhaust gas is supplied to the air introduction path through the fuel exhaust gas path and mixed with air. A hydrogen concentration sensor for detecting a concentration of a hydrogen gas component in the fuel exhaust gas;
  A flow meter for detecting a flow rate of the fuel exhaust gas;
  The fuel cell apparatus according to claim 3, further comprising: a control device that controls an air introduction amount into the air introduction path based on detection results of the hydrogen concentration sensor and the flow meter.

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