JP2002117881A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a humidifying amount demanded in case discharge gas discharged from a fuel cell is used as humidifying gas to reaction gas supplied for the fuel cell. SOLUTION: A fuel cell system 10 is constituted with a fuel cell 11, an ejector 15, which mixes the discharge gas discharged from the fuel cell 11 and a fuel gas, and makes it re-circulate to the fuel cell 11, a humidifying part 18 which humidifies the fuel gas with the moisture contained in the discharge gas, a gas-liquid separation part 17 which recovers condensation water from the discharge gas which flows out from the humidifying part 18, a fuel gas flow-way branching part 20 which branches the flow way of the fuel gas by an upstream side of the ejector 15, an water absorbing ejector 16 which mixes the condensation water recovered collected by the gas-liquid separation part 17, with the other one of the branched fuel gas, and a fuel gas flow-way junction part 24 which mixes the fuel gas which flows out of water absorbing ejector 16 into the fuel gas which flows out of the humidifying part 18, and supplies it to the fuel cell 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel cell system using, for example, a solid polymer membrane as an electrolyte membrane, and more particularly to a technique for humidifying a solid polymer membrane.

[0002]

2. Description of the Related Art Conventionally, a solid polymer membrane fuel cell has a stack (stacked) in which a plurality of cells are stacked on a cell formed by sandwiching a solid polymer electrolyte membrane between an anode and a cathode from both sides. In the following, the fuel cell stack,
Alternatively, it is simply called a fuel cell. ), Hydrogen is supplied as fuel to the anode, air is supplied to the cathode as an oxidant, and hydrogen ions generated by a catalytic reaction at the anode move through the solid polymer electrolyte membrane to the cathode. Thus, an electrochemical reaction occurs with oxygen at the cathode to generate power.

Here, in order to maintain high power generation efficiency, it is necessary to secure the function as an ion-conductive electrolyte membrane by maintaining the solid polymer electrolyte membrane in a saturated water-containing state. For this reason, water is added to a reaction gas such as hydrogen or oxygen supplied to the fuel cell, for example, as in a polymer electrolyte membrane fuel cell disclosed in Japanese Patent Application Laid-Open No. 8-273687.
2. Description of the Related Art A fuel cell equipped with a humidifier that sets a high steam concentration (steam partial pressure) in a reaction gas is known. In this fuel cell, exhaust gas (off gas) discharged from the fuel cell
When the reactant gas and the exhaust gas are brought into contact with each other through the hollow fiber membrane as a humidifying gas, the moisture contained in the exhaust gas passes through the membrane hole of the hollow fiber membrane and diffuses as water vapor into the reaction gas. Thus, the reaction gas is humidified.

[0004]

In the case where the exhaust gas discharged from the fuel cell is used as a humidified gas, as in the case of the polymer electrolyte membrane fuel cell according to one example of the prior art, the exhaust gas is Must be set high. Here, when a reaction gas humidified to a predetermined wet state, for example, hydrogen as a fuel gas is supplied to the fuel cell, hydrogen is consumed in the fuel cell,
The amount of water vapor that can be contained in the fuel gas is reduced, and condensed water is generated in an amount corresponding to the reduced amount. Thus, the exhaust gas discharged from the fuel cell contains a mixture of gaseous water vapor and liquid condensed water. For this reason, for example, when the reaction gas is humidified by using water vapor in the exhaust gas, the humidification amount of the reaction gas supplied to the fuel cell can ensure the humidification amount required for the fuel cell stack. Even if it is set to a value of the order, it is not possible to use the portion of the water content in the reaction gas that has been changed from water vapor to condensed water in the exhaust gas, and this is required for the fuel cell stack. There is a possibility that the humidification amount cannot be secured. The present invention has been made in view of the above circumstances, and is required for a fuel cell stack even when exhaust gas discharged from a fuel cell is used as a humidifying gas for a reaction gas supplied to the fuel cell. It is an object of the present invention to provide a fuel cell system capable of securing a humidification amount.

[0005]

In order to solve the above-mentioned problems and to achieve the above object, a fuel cell system according to the present invention according to the first aspect of the present invention provides a fuel cell system in which a fuel gas and an oxidizing gas are supplied to perform an electrochemical reaction. (E.g., fuel cell 11 in an embodiment described later) and an ejector that mixes exhaust gas discharged from the fuel cell with the fuel gas and recirculates the fuel gas to the fuel cell (e.g., an embodiment described below). Ejector 15) and the exhaust gas discharged from the fuel cell and the fuel gas discharged from the ejector through a water-permeable membrane (for example, a hollow fiber membrane in an embodiment described later). A humidifying unit (for example, a humidifying unit 18 in an embodiment to be described later) for humidifying the fuel gas with moisture contained in the exhaust gas, and flowing out of the humidifying unit. A water recovery unit (for example, a gas-liquid separation unit 17 in an embodiment described later) for recovering condensed water from the exhaust gas to be discharged, and a flow path branching unit (for example, a flow path branching unit) that branches a flow path of the fuel gas upstream of the ejector. A condensed water supply for mixing the condensed water collected by the water collecting means with one of the fuel gases branched by the flow path branching means, and a fuel gas flow branching part 20 in an embodiment described later. Means (for example, a water absorption ejector 16 in an embodiment to be described later) and the fuel gas flowing out of the humidifying means and the fuel gas flowing out of the condensed water supply means are mixed and supplied to the fuel cell. And a fuel gas supply means (for example, a fuel gas flow path merging portion 24 in an embodiment described later).

[0006] According to the fuel cell system having the above structure, when the exhaust gas discharged from the fuel cell is used as a humidifying gas for the fuel gas supplied to the fuel cell, first, the humidification required for the fuel cell is used. The amount of water vapor in the fuel gas is set to a predetermined amount (for example, 80 to 100% relative humidity) so as to satisfy the amount. Since the fuel gas is consumed and reduced in the fuel cell, the amount of water vapor that can be contained in the fuel gas is reduced and condensed water is generated. Thus, the exhaust gas discharged from the fuel cell contains a mixture of gaseous water vapor and liquid condensed water.

In the humidifying means for utilizing the exhaust gas as a humidifying gas for the fuel gas, when the fuel gas and the exhaust gas are brought into contact via a water permeable membrane such as a hollow fiber membrane, the moisture contained in the exhaust gas is reduced. After passing through the membrane holes of the hollow fiber membrane, it is supplied to the fuel gas as water vapor. At this time, when steam and condensed water are mixed in the exhaust gas that is the humidified gas, a state occurs in which the condensed water does not contribute to the humidification of the fuel gas but only the water vapor contributes to the humidification. Therefore, for example, condensed water that has not contributed to humidification remains in the exhaust gas that has passed through the humidifying means by flowing inside the hollow fiber membrane, but the condensed water in this exhaust gas is removed by the water collecting means. After being recovered, it is mixed with the fuel gas by the condensed water supply means. This makes it possible to effectively use the condensed water that does not contribute to the humidification of the fuel gas, for example, in a hollow fiber membrane or the like when the water vapor and the condensed water are mixed.

Further, the fuel gas flow path is branched in advance, the condensed water from the condensed water supply means is mixed with one of the branched fuel gases, and the other fuel gas is supplied to the humidifying means. The fuel gas mixed with the condensed water is combined with the fuel gas humidified by the humidifying means. In this case, for example, the other fuel gas in which the condensed water is mixed is combined with the one fuel gas and then introduced into the humidifying means, or the condensed water supplied from the condensed water supplying means can be supplied without branching the fuel gas. In comparison with the method of introducing the fuel gas obtained by mixing water into the humidifying means, the fuel gas in a dry state is introduced into the humidifying means, so to speak, the action of the humidifying means, that is, the fuel contained in the exhaust gas contains water vapor. The effect of humidifying gas can be used more effectively, and both steam and condensed water can be used for humidifying fuel gas regardless of the form of moisture contained in exhaust gas. The amount of humidification to be performed can be reliably ensured.

Further, in the fuel cell system according to the present invention, the condensed water supply means comprises an ejector for condensed water suction (for example, a water absorption ejector 16 in an embodiment described later), and By introducing the fuel gas, the condensed water is sucked from the water recovery means and merged with the one fuel gas.

According to the fuel cell system having the above-described structure, when the fuel gas is supplied to the fluid supply port of the ejector for sucking condensed water, the fuel gas is accelerated in the process of passing through the nozzle of the ejector, and the fuel gas flows from the tip of the nozzle. In the vicinity of the high-speed fuel gas flow discharged into the sub-flow chamber toward the discharge pipe, the condensed water introduced into the sub-flow chamber from the sub-flow introduction pipe is drawn into the high-speed fuel gas flow so as to be inside the fluid discharge pipe. Taken to. Along with this, a negative pressure is generated in the sub-flow chamber, and condensed water recovered by the water recovery means is sucked through the sub-flow introduction pipe so as to compensate for the negative pressure. For this reason, for example, the condensed water recovered from the exhaust gas can be mixed with the fuel gas without having to additionally input electric or mechanical energy.

Further, in the fuel cell system according to the present invention, the water recovery means includes a water tank (for example, a gas-liquid separation housing 41 in an embodiment described later) for storing the condensed water, It is characterized by having a water delivery pipe (for example, a water delivery pipe 46 in an embodiment described later) for connecting a tank and the condensed water supply means. According to the fuel cell system having the above-described configuration, the condensed water contained in the exhaust gas that has passed through the humidifying unit is collected by the water collecting unit such as a gas-liquid separator and stored in the water tank. Then, the condensed water stored in the water tank is sent out to the condensed water supply means via a water sending pipe. Thereby, the fuel gas can be humidified by using the condensed water contained in the exhaust gas reliably and effectively.

Further, in the fuel cell system according to the present invention as set forth in claim 4, the flow path branching means transfers the fuel gas to one or both of the ejector and the condensed water suction ejector. It is characterized by comprising switching means (for example, first and second switching valves 71 and 72 in an embodiment to be described later) that can be selectively switched so as to circulate.
According to the fuel cell system having the above-described configuration, the passage switching means including, for example, a plurality of valves and the like capable of opening and closing the fuel gas passage is provided downstream of the passage branching unit. In particular, by controlling the opening and closing of the flow path of the fuel gas supplied to the condensed water suction ejector, for example, when the fuel cell becomes over-humidified, the fuel gas is supplied to the condensed water suction ejector. By stopping the supply, it is possible to prevent, for example, the accumulation of water in the gas flow path inside the fuel cell and the reduction of the flow rate of the fuel gas, and the reduction of the output voltage of the fuel cell.

Further, in the fuel cell system according to the present invention as set forth in claim 5, the switching means includes an output state quantity of the fuel cell (for example, a cell voltage in an embodiment described later).
The flow path of the fuel gas is selected based on the following. According to the fuel cell system having the above configuration, the flow path of the fuel gas is selected based on the output state quantity of the fuel cell, for example, the output voltage, the current value, the power value, and the like. Thus, for example, when the fuel gas becomes excessively humidified and the output voltage of the fuel cell may decrease, the supply of the fuel gas to the condensed water supply unit is stopped, and the humidification amount for the fuel gas is reduced. , A desired output can be secured.

Further, in the fuel cell system according to the present invention, the switching means may include a moisture state quantity of the fuel cell (for example, a dew point or humidity of a fuel gas, a humidification rate, or a water vapor in an embodiment described later). Pressure) is selected based on the pressure of the fuel gas. According to the fuel cell system having the above-described structure, the flow path of the fuel gas is determined based on the moisture state amount of the fuel cell, for example, the dew point and humidity of the fuel gas immediately before the fuel gas inlet of the fuel cell, the humidification amount, the water vapor pressure, and the like. select. Thus, a desired humidification amount for the fuel gas can be secured.

Further, in the fuel cell system according to the present invention, a cathode-side water collecting means for collecting condensed water from an exhaust gas discharged from a cathode side of the fuel cell to which the oxidizing gas is supplied. (For example, an air electrode gas-liquid separation unit 82 in an embodiment to be described later), and the condensed water supply unit is provided with one of the fuel gas branched by the flow path branching unit and the cathode side water collection unit. And mixing the condensed water collected by the method.

According to the fuel cell system having the above structure, the exhaust gas discharged from the cathode side of the fuel cell passes through the inside of a water permeable membrane such as a hollow fiber membrane and then passes through a gas-liquid separator or the like. To collect the liquid condensed water contained in the exhaust gas.
Then, the condensed water recovered by the cathode-side water recovery means can be mixed with the fuel gas by the condensed water supply means when the humidification amount for the fuel gas is insufficient on the anode side, for example. Can be prevented from lowering the power generation efficiency.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuel cell system according to one embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram of a fuel cell system 10 according to an embodiment of the present invention. FIG. 2A is a side sectional view of an ejector 15, and FIG. 2B is a side sectional view of a water absorption ejector 16. FIG. 3 is a longitudinal sectional view of the gas-liquid separation unit 17. The fuel cell system 10 according to the present embodiment is mounted on a vehicle such as an electric vehicle, for example, and includes a fuel cell 11, a fuel supply unit 12, an oxidant supply unit 13, and an oxidant humidifier 1.
4, an ejector 15, a water absorption ejector 16, a gas-liquid separator 17, and a humidifier 18.

The fuel cell 11 has a structure in which a solid polymer electrolyte membrane such as a solid polymer ion exchange membrane is sandwiched between an anode and a cathode from both sides.
A plurality of cells are stacked and provided with a fuel electrode to which, for example, hydrogen is supplied as a fuel gas, and an air electrode to which, for example, air containing oxygen is supplied as an oxidant gas. The air electrode has an air supply port 11a to which air is supplied from the oxidant supply unit 13 and an air discharge port 1 provided with an air discharge valve 19 for discharging air in the air electrode to the outside.
1b is provided. On the other hand, the fuel electrode is provided with a fuel supply port 11c to which hydrogen is supplied from the fuel supply unit 12, and a fuel discharge port 11d for discharging hydrogen in the fuel electrode to the outside.

The oxidant supply unit 13 is, for example, an air compressor, and is controlled in accordance with the load of the fuel cell 11 and an input signal from an accelerator pedal (not shown). Air is supplied to the air electrode of the fuel cell 11. The oxidizing agent humidifying unit 14 mixes water vapor with the air supplied from the oxidizing agent supplying unit 13 and humidifies the air before supplying it to the fuel cell 11 to ensure the ionic conductivity of the solid molecular electrolyte membrane.

The fuel gas supplied from the fuel supply section 12 is supplied to, for example, two first
And the fuel gas in the first fuel gas flow path 21 is sequentially passed through the ejector 15 and the humidifying section 18 and then the fuel cell 11
Is supplied to Further, the other second fuel gas flow path 22
Is supplied to the fuel cell 11 after flowing through the water absorption ejector 16.

As shown in FIGS. 1 and 2, the ejector 15
Is provided with, for example, a fluid supply port 31, a sub-flow introduction pipe 32, a fluid discharge pipe 33, a nozzle 34, and a sub-flow chamber 35. Inside the ejector main body 15a, for example, a sub-flow chamber 35 formed of a substantially columnar space coaxially with the axis O is formed, and a sub-flow introduction pipe extending in a direction orthogonal to the axis O is formed in the sub-flow chamber 35. The sub flow introduction pipe 32 has one end opened on the inner peripheral surface of the sub flow chamber 35 and the other end opened on the outer surface of the ejector body 15a.

In the direction along the axis O of the ejector 15, a substantially cylindrical nozzle 34 protrudes coaxially with the axis O from one of the inner wall surfaces of the subflow chamber 35. It is arranged so as to be close to the other inner wall surface of the chamber 35. At the base end of the nozzle 34, a fluid supply port 31 opened on the outer surface of the ejector body 15a is provided.
The nozzle 34 has a tapered inner peripheral surface whose diameter gradually decreases from the base end to the tip. Then, on the other inner wall surface of the sub-flow chamber 35, the ejector main body 1 extends along the axis O direction.
One end of a fluid discharge pipe 33 passing through 5a is open,
The other end of the fluid discharge pipe 33 opens on the outer surface of the ejector body 15a.

The fuel gas is supplied from the fuel supply unit 12 to the fluid supply port 31 of the ejector 15, and the humidification unit 18 is discharged from the fuel discharge port 11 d of the fuel cell 11 to the substream introduction pipe 32. Exhaust gas branch 2 after being circulated
One of the exhaust gases branched at 3 is introduced.
Here, the fuel gas supplied from the fluid supply port 31 is accelerated while passing through the nozzle 34. And nozzle 3
In the vicinity of the high-speed fuel flow discharged into the sub-flow chamber 35 from the distal end portion of the sub-flow introduction pipe 32 toward the fluid discharge pipe 33,
The exhaust gas introduced into the sub-flow chamber 35 from above is drawn into the fluid discharge pipe 33 so as to be drawn into the high-speed fuel flow. Accordingly, a negative pressure is generated in the sub-flow chamber 35, and the exhaust gas is sucked from the sub-flow introduction pipe 32 so as to compensate for the negative pressure.

The fuel gas and the exhaust gas mixed by the ejector 15 are discharged from the fluid discharge pipe 33 and supplied to the humidifying section 18. That is, the exhaust gas discharged from the fuel cell 11 is circulated through the ejector 15.

In this embodiment, the water absorption ejector 1
6 has, for example, the structure shown in FIG. That is, the water absorption ejector 16 is connected to the fuel flow supply port 36, for example.
, A water introduction pipe 37, a fuel flow discharge pipe 38, and a nozzle 39.
It is comprised including. For example, the nozzle 39 connected to the fuel flow supply port 36 along the axis O has a tapered inner peripheral surface whose diameter gradually decreases from the base end to the front end, and the base end of the nozzle 39 is A substantially cylindrical fuel flow discharge pipe 38
The nozzle 39 is provided so as to protrude toward the inside of the fuel flow discharge pipe 38 coaxially with the axis O. Further, the fuel flow discharge pipe 38 has a water introduction pipe 3 extending through the pipe wall in a direction orthogonal to the axis O.
7 is connected, one end 37a of a water introduction pipe 37 that opens inside the fuel flow discharge pipe 38 is disposed near the tip end opening 39a of the nozzle 39, and the other end of the water introduction pipe 37 is connected to the fuel flow discharge pipe. 38, and are arranged so as to protrude toward the outside.

The water introduction pipe 37 of the water absorption ejector 16 has
The water collected in the gas-liquid separation unit 17 is introduced. That is, the fuel gas supplied from the fuel flow supply port 36 of the water absorption ejector 16 is accelerated while passing through the nozzle 39. Then, the fuel flow discharge pipe 3 extends from the tip of the nozzle 39.
8 near the high-speed fuel flow discharged into the
The water introduced into the fuel flow discharge pipe 38 from 7 is drawn toward the tip of the fuel flow discharge pipe 38 so as to be drawn into the high-speed fuel flow. Accordingly, the fuel flow discharge pipe 3
Negative pressure is generated in 8, and water is sucked from water introduction pipe 37 so as to compensate for the negative pressure. In addition, the water absorption ejector 16 is not limited to the structure shown in FIG.
For example, as shown in FIG. 2A, it may have a structure equivalent to the ejector 15, or may have another structure. In short, any structure may be used as long as water is entrained so as to be drawn into the high-speed fuel flow.

The fuel gas and water mixed by the water absorption ejector 16 are discharged from the fluid discharge pipe 33 and
Supplied to That is, the liquid water recovered in the gas-liquid separation unit 17 of the water contained in the exhaust gas discharged from the fuel cell 11 is circulated through the water absorption ejector 16.

The gas-liquid separation unit 17 includes a gas-liquid separation housing 41 and a gas-liquid separation housing 4 as shown in FIG.
A plurality of partition plates 43 forming a flow path 42 meandering upward from below in the vertical direction, an exhaust gas inlet 44 provided at a lower part of the gas-liquid separation housing 41 and communicating with the flow path 42; An exhaust gas outlet 45 provided at an upper portion of the gas-liquid separation housing 41 and communicating with the flow path 42;
6 and one end 46 of the water delivery pipe 46.
a is configured to be immersed in water stored at the bottom of the gas-liquid separation housing 41. Further, the other end 46b is provided so as to protrude toward the outside of the gas-liquid separation housing 41, and the other end 46b is connected to the substream introduction pipe 32 of the water absorption ejector 16.

In the gas-liquid separation section 17, liquid liquid water as water or exhaust gas containing gaseous water vapor and liquid liquid water as moisture is introduced into the gas-liquid separation housing 41 from the exhaust gas inlet 44. It is supplied and rises while meandering in the flow path 42. When the exhaust gas flows through the flow path 42, moisture (mainly, liquid water) in the exhaust gas collides with and adheres to the wall surface of the partition plate 43 and the wall surface of the gas-liquid separation housing 41. And
The water adhering to these wall surfaces becomes a liquid, falls along the wall surface due to gravity, reaches the bottom of the gas-liquid separation housing 41, and is stored as liquid water. On the other hand, the exhaust gas from which water (mainly liquid water) has been removed is discharged from the exhaust gas outlet 45. That is, the gas-liquid separation unit 17
By passing the exhaust gas discharged from the fuel cell 11 shown in FIG. 1 and circulated through the humidifying section 18, the exhaust gas is separated into gas and liquid, and for example, liquid moisture is removed.
Only the exhaust gas in which the dried or gaseous water vapor is left flows out from the exhaust gas outlet 45, and excess moisture (mainly liquid water) in the exhaust gas flows from the water delivery pipe 46 to the side stream of the water absorption ejector 16. It is sent out to the introduction tube 32.

The humidifying section 18 is provided with a water permeable membrane such as a hollow fiber membrane, and uses the exhaust gas discharged from the fuel cell 11 as a humidifying gas for the fuel gas discharged from the ejector 15. We are using. That is, for example, when the fuel gas and the exhaust gas are brought into contact with each other through a water permeable membrane such as a hollow fiber membrane, the moisture (particularly, water vapor) contained in the exhaust gas is converted into water vapor after passing through the membrane hole of the hollow fiber membrane. It is supplied to fuel gas. The fuel gas humidified by the humidifying unit 18 is supplied to the fuel cell 11 after being combined with the fuel gas discharged from the water absorption ejector 16 by the fuel gas combining unit 24. Thereby, the ionic conductivity of the solid molecular electrolyte membrane is ensured. A dew point meter 51 for detecting the dew point of the fuel gas is provided near the fuel supply port 11c of the fuel cell 11.

The fuel cell system 10 according to the present embodiment
Has the above-described configuration. Next, the operation of the fuel cell system 10 will be described with reference to the accompanying drawings.
FIG. 4 is a graph showing a change in the amount of water contained in the exhaust gas introduced as a humidifying gas into the humidifying unit 18 and a change in the amount of water collected from the exhaust gas in the humidifying unit 18. First, the amount of water vapor in the fuel gas is adjusted to a predetermined amount (for example, a relative humidity of 8 to satisfy the humidification amount required for the fuel cell 11).
0-100%). Since the fuel gas is consumed and reduced in the fuel cell 11, the amount of water vapor that can be contained in the fuel gas is reduced and condensed water is generated. As a result, the exhaust gas discharged from the fuel cell 11 contains a mixture of gaseous water vapor and liquid water such as liquid condensed water.

Here, when the exhaust gas is supplied as a humidifying gas to the fuel gas to the humidifying section 18 using, for example, a hollow fiber membrane as the water permeable membrane, as shown in FIG. 4, for example, the liquid water contained in the exhaust gas becomes It has the property of not contributing to the humidification of fuel gas. In other words, as a property with respect to the hollow fiber membrane, in a state in which water vapor and liquid water are mixed in the humidified gas, for example, water vapor having a higher moving speed than liquid water has a property of being easily transmitted through the membrane hole of the hollow fiber membrane, Most liquid water, which is heavier and slower in moving speed than water vapor, is suppressed from permeating through the membrane holes of the hollow fiber membrane and contributing to humidification of the fuel gas. For example, as shown in FIG. 4, of the moisture contained in the humidified gas flowing inside the hollow fiber membrane,
Regarding the amount of water that can be recovered through the pores of the hollow fiber membrane,
The amount of recovered water when the humidified gas contains only a predetermined amount of water vapor (for example, the recovered amount α shown in FIG. 4), and the recovery when the humidified gas contains liquid water in addition to the predetermined amount of water vapor The amount of water (for example, the recovered amount β shown in FIG. 4) is the same. Then, the liquid water mixed and contained in the water vapor is the unrecovered portion (for example, the unrecovered portion (liquid) shown in FIG. 4).
γ) remains in the humidified gas. It should be noted that humidification with 100% liquid water is more effective than humidification of fuel gas with humidification gas in which steam and liquid water are mixed.
It goes without saying that the humidification efficiency is better.

That is, the exhaust gas flowing out of the humidifying section 18 contains liquid water that has not contributed to the humidification of the fuel gas. This exhaust gas is mixed with the fuel gas via the ejector 15 and is recirculated to the fuel cell 11, and is introduced into the gas-liquid separation unit 17, where the moisture (mainly liquid water) contained in the exhaust gas is converted into a liquid. Collected as water. Then, the water collected in the gas-liquid separation unit 17 is mixed with the fuel gas through the water absorption ejector 16 and then mixed with the fuel gas.
The fuel gas flows out of the humidifier 18 and is humidified by the humidifier 18 so as to be combined with the fuel gas and supplied to the fuel cell 11.

As described above, according to the fuel cell system 10 of the present embodiment, for example, the exhaust gas that has passed through the humidifying section 18 by flowing inside the hollow fiber membrane does not contribute to the humidification of the fuel gas. Liquid water will remain,
The liquid water in the exhaust gas is mixed with the fuel gas by the water absorption ejector 16 after being collected by the gas-liquid separation unit 17. Thereby, the humidifying unit 1 made of a hollow fiber membrane or the like, for example.
8, liquid water which did not contribute to the humidification of the fuel gas in a state where water vapor and condensed water were mixed (for example, as shown in FIG. 4,
The unrecovered portion (liquid) γ) can be recovered and effectively used in the gas-liquid separation unit 17 provided downstream of the humidification unit 18.

In addition, the fuel gas flow path is branched in advance into first and second fuel gas flow paths 21 and 22, and the water recovered by the gas-liquid separation unit 17 is added to the other fuel gas. The fuel gas is mixed, and one fuel gas is supplied to the humidifying unit 18 via the ejector 15. Then, since the other fuel gas mixed with water is combined with the fuel gas humidified by the humidifying unit 18, the humidification of the fuel gas can be performed efficiently. That is, for example, the other fuel gas mixed with water in the water absorption ejector 16 is merged with the one fuel gas and then introduced into the humidifying section 18 or, for example, the fuel gas is branched without branching. The fuel gas in a dry state is introduced into the humidifying unit 18 as compared with a method of introducing the fuel gas obtained by mixing the water collected in the liquid separating unit 17 into the humidifying unit 18. , Ie, the function of humidifying the fuel gas by the water vapor contained in the exhaust gas, can be effectively exerted. Therefore, regardless of the form of moisture contained in the exhaust gas, both steam and liquid water can be effectively used for humidifying the fuel gas, and the amount of humidification required for the fuel cell 11 can be ensured. Can be.

In the above-described embodiment, the gas-liquid separation section 17 is provided downstream of the exhaust gas branch section 23. However, the present invention is not limited to this. For example, a first modification of the embodiment shown in FIG. As shown in the configuration diagram of the fuel cell system 60 according to the example, the exhaust gas branch section 23 may be provided downstream of the gas-liquid separation section 17. In the following, the same parts as those of the above-described embodiment are denoted by the same reference numerals, and are simplified or omitted to describe a fuel cell system 60 according to a first modification of the present embodiment. Fuel cell system 6 according to a first modification of the present embodiment
At 0, the exhaust gas that has flowed out including the liquid water that has not contributed to the humidification of the fuel gas in the humidifier 18 is
The water (mainly liquid water) contained in the exhaust gas introduced into the gas-liquid separation unit 17 is collected as liquid water. Then, the recovered water is mixed with the fuel gas via the water absorption ejector 16. On the other hand, only the exhaust gas from which water (mainly liquid water) has been removed and in which the dried or gaseous water vapor has remained is discharged from the exhaust gas outlet 45 of the gas-liquid separation unit 17, and the exhaust gas branch unit 23 is discharged. Through the auxiliary flow introduction pipe 32 of the ejector 15.

As described above, according to the fuel cell system 60 according to the first modified example of the present embodiment, the auxiliary flow introduction pipe 32 of the ejector 15 from which the fuel gas humidified in the humidification section 18 flows out is provided. Since only the relatively dried exhaust gas is supplied, the function of the humidifying unit 18, that is, the function of humidifying the fuel gas by the water vapor contained in the exhaust gas, can be more effectively exerted, and the fuel cell 11 The required humidification amount can be surely secured. In addition, when the exhaust gas is introduced into the sub-flow introduction pipe 32 of the ejector 15 in the exhaust gas branching section 23, for example, liquid moisture contained in the exhaust gas is sucked up together with the exhaust gas, so that the circulation amount of the exhaust gas itself is increased. And the occurrence of problems such as a decrease in the flow rate and the blocking of the flow path by liquid water can be prevented.

In the above-described embodiment, the fuel gas flow path branching section 20 branches into, for example, two first and second fuel gas flow paths 21 and 22. However, the present invention is not limited to this. For example, FIG. As shown in a configuration diagram of a fuel cell system 70 according to a second modified example of the present embodiment, a first and second switching valve 71 serving as switching means in each of the first and second fuel gas flow paths 21 and 22. , 72 may be provided. In the following, the same parts as those of the above-described embodiment are denoted by the same reference numerals, and are simplified or omitted to describe a fuel cell system 70 according to a second modification of the present embodiment. FIG. 7 is a flowchart showing the operation of the fuel cell system 70 according to the second modification of the present embodiment.

First, in step S01 shown in FIG. 7, the cell voltage of the fuel cell 11 is detected by a voltage detector (not shown). Next, in step S02, it is determined whether the detected cell voltage is within a predetermined range.
If the result of this determination is "YES", the process proceeds to step S01.
Proceed to. On the other hand, if the result of this determination is "NO", the flow proceeds to step S03. In step S03, the second
The switching valve 72 is set to the “closed” state.

That is, when the cell voltage of the fuel cell 11 deviates from within a predetermined range, all the fuel gas supplied from the fuel supply unit 12 flows through the first fuel gas flow branching unit 20 via the fuel gas flow path branching unit 20. It is set so as to circulate on the road 21.
Then, after being mixed with the relatively dry exhaust gas in the ejector 15, it is humidified by the wet exhaust gas in the humidifying section 18 and supplied to the fuel cell 11.
That is, the fuel gas is not supplied to the water-absorbing ejector 16 that humidifies the fuel gas by the water collected by the gas-liquid separation unit 17, and the humidifying unit 18 that humidifies the fuel gas by the water vapor contained in the exhaust gas. Only the fuel gas is supplied. Therefore, when the cell voltage of the fuel cell 11 deviates from within a predetermined range, for example, when the fuel gas becomes excessively humidified and the output voltage of the fuel cell 11 decreases, the fuel gas supplied to the fuel cell 11 By reducing the amount of wetting, it is possible to prevent problems such as the accumulation of water in the gas flow path inside the fuel cell 11 and the reduction of the flow rate of the fuel gas.

As described above, according to the fuel cell system 70 according to the second modification of the present embodiment, for example, when the fuel gas becomes excessively humidified and the output voltage of the fuel cell 11 is likely to decrease, The supply of the fuel gas to the water recovery ejector 16 is stopped to reduce the humidification amount of the fuel gas,
A desired output can be secured. Thus, it is possible to prevent a situation where water is accumulated in the gas flow path inside the fuel cell 11 and the flow rate of the fuel gas is reduced. In this case, the output voltage is not limited to the cell voltage of the fuel cell 11, but may be other output state quantities (for example, current value, power value, etc.) of the fuel cell 11 or moisture state quantity of the fuel cell 11, for example, The opening and closing operations of the first and second switching valves 71 and 72 may be controlled based on the dew point, humidity, humidification amount, water vapor pressure, and the like of the fuel gas immediately before the gas inlet. Further, the first switching valve 71 may be omitted. Also in these cases, it is possible to secure the above-described output and prevent a decrease in the flow amount.

In the above-described embodiment, the humidifying section 18 and the gas-liquid separating section 17 for passing the exhaust gas discharged from the fuel electrode side of the fuel cell 11 are provided. However, the present invention is not limited to this. 8, an air electrode humidifying unit 81 and an air electrode gas-liquid that allow exhaust gas discharged from the air electrode side of the fuel cell 11 to flow, as shown in the configuration diagram of the fuel cell system 80 according to the third modification of the present embodiment shown in FIG. A separation unit 82 may be further provided. Hereinafter, the same parts as those of the above-described embodiment will be denoted by the same reference numerals and simplified or omitted, and a description will be given of a fuel cell system 80 according to a third modification of the present embodiment. FIG. 9 is a configuration diagram of the air electrode gas-liquid separation unit 82, and FIG.
0 indicates the operation of the fuel cell system 80 shown in FIG.
FIGS. 11A to 11C are flowcharts showing the opening and closing operation of the switching valve 84, and FIGS. 11A to 11C are main part enlarged views showing a flow path of a reaction gas in the fuel cell system 80. In the fuel cell system 80 according to the third modified example of the present embodiment, the exhaust gas discharged from the air electrode side of the fuel cell 11 is first introduced into the air electrode humidifier 81 and supplied from the oxidant supply unit 13. It is used as a humidifying gas for the oxidizing gas.

The exhaust gas flowing out of the air electrode humidifying section 81 contains liquid water that has not contributed to the humidification of the oxidizing gas, and this exhaust gas is introduced into the air electrode gas-liquid separating section 82 and is added to the exhaust gas. The contained water (mainly liquid water) is recovered as liquid water. Here, the air electrode gas-liquid separation unit 82
For example, as shown in FIG. 9, the gas-liquid separation unit 17 has substantially the same configuration as that of the above-described gas-liquid separation unit 17, and differs from the above-described gas-liquid separation unit 17 in that the water stored in the gas-liquid separation housing 41 is different. The point is that a water level sensor 83 for detecting the water level is provided.
Further, as shown in FIG. 8, the fuel cell system 80
One end is connected to the water delivery pipe 46 of the air electrode gas-liquid separation unit 82 with respect to the fuel electrode side water flow passage 84 connecting the water delivery pipe 46 of the gas-liquid separation unit 17 and the water introduction pipe 37 of the water absorption ejector 16. And an air electrode-side water flow passage 85 having the other end connected to merge with the fuel electrode-side water flow passage 84; a third switching valve 86 provided in the air electrode-side water flow passage 85; For example, it is provided with a branch part 87 and a discharge valve 88 which are provided between the fuel cell 23 and the gas-liquid separation part 17, for example, a three-way valve or the like.

The fuel cell system 80 according to the third modification of the present embodiment has the above-described configuration. Next, the operation of the fuel cell system 80, in particular, the opening / closing operation of the third switching valve 86 and the branch portion 87, and The switching operation will be described with reference to the accompanying drawings. First, in step S11 shown in FIG. 10, the water level sensor 83 detects the water level of the water stored in the gas-liquid separation housing 41 of the air electrode gas-liquid separation unit 82. Next, in step S12, it is determined whether the detected water level is lower than a predetermined lower limit water level.
If this determination is "NO", the flow proceeds to step S13. On the other hand, if the result of the determination is "YES", the flow proceeds to step S14.

In step S13, the third switching valve 86 is opened, and the flow advances to step S11. In step S14, the third switching valve 86 is closed, and the process proceeds to step S11. That is, when water exceeding a predetermined lower limit water level is stored in the gas-liquid separation housing 41 of the air electrode gas-liquid separation unit 82,
The third switching valve 86 is opened to set a state in which water can be supplied to the water absorption ejector 16. On the other hand, when the water stored in the air electrode gas-liquid separator 82 is less than the predetermined lower limit water level, the third switching valve 86 is closed, and the exhaust gas on the air electrode side, that is, the air is discharged to the water absorption ejector 16. Is prevented from flowing, and for example, it is possible to prevent the fuel cell 11 from being damaged by supplying the oxidant gas to the fuel electrode side of the fuel cell 11.

Further, a description will be given of a combination of a switching operation of the above-described third switching valve 86 and a branching portion 87 forming, for example, a three-way valve, with reference to the accompanying drawings. First, FIG.
As shown in FIG. 1A, when the water recovered from the exhaust gas on the cathode side is supplied to the water absorption ejector 16 without using the water recovered from the exhaust gas on the anode side, the third switching is performed. The valve 86 is opened, and the flow path in the branch portion 87 is switched to the discharge valve 88. Thereby, the exhaust gas branch 2
Exhaust gas with liquid water remaining therethrough is discharged to the outside via the branch 87 and the discharge valve 88, and only the water collected in the air electrode gas-liquid separator 82 is supplied to the water absorption ejector 16. You. That is, the fuel gas supplied to the fuel electrode side of the fuel cell 11 is humidified by the water collected from the exhaust gas on the air electrode side and the water vapor contained in the exhaust gas on the fuel electrode side.

On the other hand, as shown in FIG. 11 (b), the water recovered from the exhaust gas on the fuel electrode side is supplied to the water absorbing ejector 16 without using the water recovered from the exhaust gas on the air electrode side. Then, the third switching valve 86 is closed, and the flow path in the branch portion 87 is switched to the gas-liquid separation portion 17. As a result, the exhaust gas in which the liquid water remains flowing from the exhaust gas branch portion 23 passes through the branch portion 87 to the gas-liquid separation portion 1.
7 and only the water collected in the gas-liquid separation unit 17 is supplied to the water absorption ejector 16. That is,
The fuel gas supplied to the fuel electrode side of the fuel cell 11 is humidified by the water collected from the exhaust gas on the fuel electrode side and the water vapor contained in the exhaust gas on the fuel electrode side.

Further, as shown in FIG. 11C, when water collected from the exhaust gas on the air electrode side and water collected from the exhaust gas on the fuel electrode side are supplied to the water absorption ejector 16, , The third switching valve 86 is opened, and the branch portion 87 is opened.
Is switched to the gas-liquid separator 17. As a result, the exhaust gas flowing from the exhaust gas branching section 23 and remaining with liquid water is supplied to the gas-liquid separating section 17 through the branching section 87, and the water collected in the gas-liquid separating section 17 is subjected to water absorption. It is supplied to the ejector 16. In addition, the water collected in the air electrode gas-liquid separation unit 82 is supplied to the water absorption ejector 16 via the opened third switching valve 86. That is, the fuel gas supplied to the fuel electrode side of the fuel cell 11 includes water recovered from the exhaust gas on the air electrode side, water recovered from the exhaust gas on the fuel electrode side, and exhaust gas on the fuel electrode side. It is humidified by the contained water vapor.

As described above, according to the fuel cell system 80 according to the third modification of the present embodiment, for example, when there is a possibility that the humidification amount for the fuel gas is insufficient on the fuel electrode side, the discharge on the air electrode side is performed. The fuel gas can be humidified by the gas, and the power generation efficiency of the fuel cell 11 can be prevented from lowering. Moreover, the air electrode gas-liquid separation unit 8
By providing the water level sensor 83 for detecting the water level of the water stored in the second gas-liquid separation housing 41, the exhaust gas on the air electrode side, that is, the oxidizing gas composed of air, flows into the water absorption ejector 16 on the fuel electrode side. For example, it is possible to prevent the fuel cell 11 from being damaged by supplying the oxidizing gas to the fuel electrode side of the fuel cell 11. Furthermore, the humidification amount of the fuel gas supplied to the fuel cell 11 can be adjusted only by changing the combination of the opening / closing operation and the switching operation of the third switching valve 86, the branch portion 87, and the discharge valve 88. Although the configuration is simple, it is possible to easily perform detailed humidification amount control.

[0050]

As described above, according to the fuel cell system of the first aspect of the present invention, when water vapor and condensed water are mixed, for example, the hollow fiber membrane does not contribute to the humidification of the fuel gas. Condensed water can be used effectively. Moreover, by introducing the relatively dry fuel gas into the humidifying means, the action of the humidifying means, that is, the action of humidifying the fuel gas by the water vapor contained in the exhaust gas, can be effectively utilized, and Regardless of the form of water contained, both steam and condensed water can be used for humidifying the fuel gas, and the humidification amount required for the fuel cell stack can be reliably ensured. Further, claim 2
According to the fuel cell system of the present invention described in, for example, without the need to additionally input electrical or mechanical energy,
The condensed water recovered from the exhaust gas can be mixed with the fuel gas. Further, according to the fuel cell system of the present invention, the fuel gas can be humidified by effectively utilizing the condensed water contained in the exhaust gas.

Further, according to the fuel cell system of the present invention, when the fuel cell stack is over-humidified, for example, the supply of the fuel gas to the condensed water suction ejector is performed. By stopping, for example, it is possible to prevent water from accumulating in the gas flow path inside the fuel cell and reduce the flow rate of the fuel gas, and prevent the output voltage of the fuel cell from decreasing. Further, according to the fuel cell system of the present invention, when the fuel gas becomes excessively humidified and the output voltage of the fuel cell may decrease, the fuel gas is supplied to the condensed water supply means. Is stopped, the amount of humidification to the fuel gas is reduced, and a desired output can be secured. Further, according to the fuel cell system of the present invention, a desired humidification amount for the fuel gas can be secured. Furthermore, according to the fuel cell system of the present invention as set forth in claim 7, the condensed water collected by the cathode-side water collecting means may be insufficient when the humidification amount of the fuel gas on the anode side is insufficient. Moisture can be further mixed with the fuel gas by the condensed water supply means, so that the power generation efficiency of the fuel cell can be prevented from lowering.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention.

FIG. 2A is a side sectional view of an ejector, and FIG. 2B is a side sectional view of a water absorbing ejector.

FIG. 3 is a longitudinal sectional view of the gas-liquid separation unit shown in FIG.

FIG. 4 is a graph showing changes in the amount of moisture contained in exhaust gas introduced as a humidifying gas into the humidifying section and the amount of moisture recovered from the exhaust gas in the humidifying section.

FIG. 5 is a configuration diagram of a fuel cell system according to a first modification of the present embodiment.

FIG. 6 is a configuration diagram of a fuel cell system according to a second modification of the present embodiment.

FIG. 7 is a flowchart showing an operation of a fuel cell system according to a second modified example of the embodiment.

FIG. 8 is a configuration diagram of a fuel cell system according to a third modification of the present embodiment.

9 is a configuration diagram of an air electrode gas-liquid separation unit shown in FIG.

10 is a flowchart showing the operation of the fuel cell system according to a third modification of the present embodiment shown in FIG. 8, particularly the switching operation of the third switching valve.

11 (a) to 11 (c) are enlarged views of a main part showing a flow path of a reaction gas in the fuel cell system shown in FIG.

[Explanation of symbols]

Reference Signs List 10, 60, 70, 80 Fuel cell system 11 Fuel cell 15 Ejector 16 Water absorption ejector (Condensed water supply unit, Ejector for condensed water suction) 17 Gas-liquid separation unit (Water recovery unit) 18 Humidification unit (Humidification unit) 20 Fuel gas flow path branching section (flow path branching means) 24 Fuel gas flow path joining section (fuel gas supply means) 41 Gas-liquid separation housing (water tank) 46 Water delivery pipe 71 First switching valve (switching means) 72 Second Switching valve (switching means) 82 Air electrode gas-liquid separation unit (cathode side water recovery means)

Continued on the front page (72) Inventor Toshikatsu Katagiri 1-4-1 Chuo, Wako-shi, Saitama Pref. Inside of Honda R & D Co., Ltd. (72) Mikihiro Suzuki 1-4-1 Chuo, Wako-shi, Saitama Co., Ltd. Honda R & D F-term (reference) 5H026 AA06 5H027 AA06 BA19 KK52 MM01

Claims (7)

[Claims] 1. A fuel cell which is supplied with a fuel gas and an oxidizing gas to generate power by an electrochemical reaction, and an ejector which mixes exhaust gas discharged from the fuel cell with the fuel gas and recirculates the fuel gas to the fuel cell. Humidifying means for bringing the exhaust gas discharged from the fuel cell into contact with the fuel gas flowing out of the ejector via a water-permeable membrane, and humidifying the fuel gas with moisture contained in the exhaust gas. Water collecting means for collecting condensed water from the exhaust gas flowing out of the humidifying means, flow path branching means for branching the flow path of the fuel gas on the upstream side of the ejector, A condensed water supply means for mixing the condensed water recovered by the water recovery means with one of the fuel gases branched and branched, and the fuel gas flowing out of the humidifying means, A fuel cell system, comprising: fuel gas supply means for mixing the fuel gas flowing out of the condensed water supply means and supplying the mixed fuel gas to the fuel cell. 2. The condensed water supply means forms an ejector for condensed water suction, and by introducing the one fuel gas, sucks the condensed water from the water recovery means and merges with the one fuel gas. 2. The method according to claim 1, wherein
3. The fuel cell system according to item 1. 3. The water collecting means according to claim 1, wherein the water collecting means includes a water tank for storing the condensed water, and a water delivery pipe connecting the water tank and the condensed water supplying means. 3. The fuel cell system according to any one of 2. 4. The fuel cell system according to claim 1, wherein the flow path branching means includes a switching means capable of selectively switching the fuel gas to flow to one or both of the ejector and the condensed water suction ejector. The fuel cell system according to claim 2, wherein the fuel cell system comprises: 5. The fuel cell system according to claim 4, wherein the switching means selects the flow path of the fuel gas based on an output state quantity of the fuel cell. 6. The fuel cell system according to claim 4, wherein the switching unit selects the flow path of the fuel gas based on a water state amount of the fuel cell. 7. A condensed water supply means for collecting condensed water from exhaust gas discharged from a cathode side of the fuel cell to which the oxidant gas is supplied, wherein the condensed water supply means is provided with the flow path branch. The fuel cell system according to any one of claims 1 to 6, wherein the condensed water recovered by the cathode-side water recovery means is mixed with one of the fuel gases branched by the means. .