JP3414045B2 - Hybrid fuel cell power generator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid polymer fuel cell having a solid polymer electrolyte, and a fuel cell for producing electricity using both hydrogen and carbon monoxide as fuel, such as a solid electrolyte fuel cell having a solid electrolyte. The present invention relates to a hybrid fuel cell power generator equipped with.

[0002]

2. Description of the Related Art Conventionally, in a phosphoric acid fuel cell power generator having a phosphoric acid electrolyte, as shown in FIG. 4, the system configuration is such that a fuel cell stack 1 composed of a unit cell stack is provided on the fuel electrode 2 side. Hydrogen-rich fuel gas is supplied from the fuel reformer 3, air as an oxidant is supplied to the oxidizer electrode 4 side, and the operating temperature is maintained at about 190 ° C. Power is generated based on the reaction. By the way, as the fuel reformer 3, LNG, LP
It is known that hydrocarbon-based raw fuels such as G and naphtha and alcohol-based raw fuels such as methanol produce a hydrogen-rich reformed gas by steam reforming, but carbon monoxide in the reformed gas is a fuel. There is a problem that the platinum catalyst in the electrode 2 acts as a catalyst poison and deteriorates. At the operating temperature, it is necessary to reduce the carbon monoxide concentration in the reformed gas to about 1%.

Therefore, in the fuel reformer 3, a carbon monoxide shift converter 6 is connected to the rear stage of the reformer 5 and the reaction of CO + H2O → CO2 + H2 in the reformed gas is caused by the action of the carbon monoxide shift catalyst. It is known that the concentration of carbon monoxide is reduced to about 1%.

However, in the fuel cell power generator using the polymer electrolyte fuel cell, the operating temperature of the fuel cell is 8
Since it is as low as about 0 ° C., it is necessary to significantly reduce the carbon monoxide concentration to about 10 ppm or less in order to prevent poisoning of the platinum catalyst.

FIG. 5 is a system configuration diagram showing an essential part of an improved conventional polymer electrolyte fuel cell power generator. A carbon monoxide shift converter 6 is provided at a stage subsequent to the reformer 5 for reforming raw fuel. Is provided to reduce the carbon monoxide concentration, and further, a carbon monoxide combustor 7 is provided at the subsequent stage, and air of several% or less is mixed into the reformed gas and brought into contact with a catalyst such as platinum to select carbon monoxide. For example, the carbon monoxide CO is converted into harmless carbon dioxide CO2 based on a chemical reaction represented by 2CO + O2 → 2CO2, and the carbon monoxide is reduced to several ppm order. 20
There is a proposal such as Japanese Patent No. 1702. Also,
Carbon monoxide, which is intended to remove carbon monoxide using a separation membrane such as palladium, or which causes an electrochemical reaction of CO and OH-ions in water like 2H2O → 2H ++ 2OH- CO + 2OH- → CO2 + H2O + 2e-. For example, a device (not shown) as disclosed in Japanese Patent Laid-Open No. 2-311302, or a device using a carbon monoxide adsorption tower is known.

[0006]

However, in the above-mentioned configuration in which the carbon monoxide combustor is provided, it is necessary to strictly control the amount of mixed air, and in the one using the separation membrane or the carbon monoxide adsorption tower, There is a problem in that a large amount of power is required to make the pressure high, and the electrochemical method also consumes electric power, resulting in a significant decrease in system efficiency.

Further, carbon monoxide contained in the gas reformed by the reformer 5 in the above fuel cell power generator has a high energy level. However, in the above-mentioned conventional configuration, even if a combination of a carbon monoxide converter and any method is used, the device becomes complicated and carbon monoxide having a high energy level is converted to carbon dioxide without effectively utilizing it. There is also a problem that the system efficiency is lowered due to separate exhaust.

On the other hand, in the polymer electrolyte fuel cell, when the polymer electrolyte membrane, which is the electrolyte, is saturated with water, the specific resistance of the membrane is lowered and the polymer electrolyte fuel cell functions as a proton conductive electrolyte. In order to maintain the power generation of the battery, various humidifiers have been proposed to keep the saturated water content without evaporating the water in the solid polymer electrolyte membrane. The conventional fuel cell power generation device also requires such a humidifying device, which causes a problem that the device becomes complicated.

The present invention solves the above-mentioned conventional problems by effectively utilizing carbon monoxide having a high energy contained in the reformed gas from the reformer and without requiring safe and large power. An object of the present invention is to provide a fuel cell power generation device capable of removing carbon to prevent poisoning of a platinum catalyst and eliminating the need for a humidifying device.

[0010]

In order to solve the above problems, the present invention has the following constitution.

That is, a reformer for reforming a hydrocarbon-based or alcohol-based raw fuel into a gas containing hydrogen and carbon monoxide, and oxygen supplied from the air as an oxidant gas
Fuel cell having an oxidizer electrode and a first fuel electrode
And oxygen in the air is supplied as an oxidant gas
Polymer fuel having an oxidant electrode and a second fuel electrode
With the battery, the gas reformed by the reformer is the first fuel electrode.
Both the supplied hydrogen and carbon monoxide and the first fuel cell for discharging the generated water and power generation as a fuel, from the first fuel electrode
The exhaust gas containing the generated water is used as the fuel gas for the second fuel electrode.
It is obtained by connecting the polymer electrolyte fuel cell which is supplied to.

[0012] supplied to the first fuel electrode of the first fuel electrode exhaust gas again first fuel cell of the first fuel cell, the carbon monoxide in the exhaust gas passed through without being utilized again Equipped with a return flow path for supply and removal, the carbon monoxide concentration detection means of the fuel gas of the polymer electrolyte fuel cell, and the flow rate of the return flow path is variable based on the output signal of the carbon monoxide concentration detection means. It is equipped with a flow rate control means.

[0013]

The present invention has the following functions due to the above construction.

That is, a reformer for reforming raw fuel, a first fuel cell for supplying reformed gas from the reformer to a first fuel electrode to generate power and discharge produced water, and a first fuel Battery first
With a configuration including a solid polymer fuel cell in which exhaust gas containing generated water from the fuel electrode is supplied to the second fuel electrode ,
The raw fuel that has passed through the reformer is supplied to the first fuel electrode of the first fuel cell as a reformed gas containing hydrogen and carbon monoxide, and is supplied to the other first oxidant electrode in the air. A cell reaction is caused by an oxidant gas such as oxygen to generate electricity, and carbon monoxide contained in the reformed gas is consumed as a fuel of the first fuel cell and converted into carbon dioxide. Further, a part of hydrogen in the reformed gas also reacts with the oxidant gas to generate water H2O. Then, this produced water and carbon dioxide in which hydrogen and carbon monoxide that have not contributed to the cell reaction have been denatured are discharged from the first fuel electrode and supplied to the second fuel electrode of the polymer electrolyte fuel cell . Type fuel cell supplies the other second oxidant electrode
Electric power is generated by an oxidizing gas such as oxygen in the air . Therefore, the high energy of carbon monoxide can be removed in the first fuel cell, and the produced polymer can operate the solid polymer fuel cell to generate electricity without a humidifier.

Further, the first fuel cell in the first fuel cell exhaust gas is constituted by the structure provided with the return passage for removing carbon monoxide of the first fuel electrode exhaust gas of the first fuel cell. The carbon monoxide that has passed through is re-supplied to the first fuel cell for more complete removal, and the carbon monoxide concentration detection means for the fuel gas of the polymer electrolyte fuel cell and the flow rate in the return flow path are adjusted. the arrangement with a variable flow control means, by varying the flow rate of the return flow path based on the output signal of the carbon monoxide density detecting means also operating conditions are changed in the device, first the first fuel cell It is possible to adjust the re-supply amount of the fuel electrode exhaust gas to be supplied to the first fuel cell again, so that the carbon monoxide concentration is reliably removed to below the platinum catalyst poisoning limit value of the polymer electrolyte fuel cell. .

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system configuration diagram showing a main part of a hybrid fuel cell power generator according to an embodiment of the present invention, in which a hydrocarbon-based raw fuel such as LNG, LPG, naphtha or an alcohol-based raw fuel such as methanol is hydrogenated. In the subsequent stage of the reformer 1 for reforming into a gas containing carbon monoxide, a stabilized zirconia-based solid electrolyte 2a having oxide ion conductivity at about 1000 ° C., a first fuel electrode 2b sandwiching the solid electrolyte 2a, and Primary acid
A solid oxide fuel cell 2 as a first fuel cell including an agent electrode 2c is provided, and a reformed gas is passed through a reformed gas passage 3 connecting the reformer 1 and the first fuel electrode 2b. It is configured to be supplied to the first fuel electrode 2b of the solid oxide fuel cell 2. Further, in the subsequent stage of the solid oxide fuel cell 2, a solid polymer electrolyte 4a having proton conductivity, a second fuel electrode 4b and a second oxidant electrode 4c sandwiching the solid polymer electrolyte 4a are sandwiched .
The polymer electrolyte fuel cell 4 is provided. The exhaust gas from the first fuel electrode 2b of the solid oxide fuel cell 2 is the second fuel electrode 4 of the solid polymer fuel cell 4 .
b , a heat exchange part 8 having a branch part 5, a hot water supply water inlet 6 and a hot water supply water outlet 7 in the middle, and a connection flow path 10 equipped with a carbon monoxide concentration detection means 9 The second fuel electrode 4b of No. 4 is supplied. Furthermore, the flow rate control means 1 electrically connected to the carbon monoxide concentration detection means 9 from the branch portion 5 of the connection flow path 10.
1 through the pressurizing device 12 and the solid oxide fuel cell 2
The return flow path 13 connected to the first fuel electrode 2b is provided.

With the above structure, the raw fuel that has passed through the reformer 1 passes through the reformed gas flow path 3 as the reformed gas containing hydrogen and carbon monoxide, and the first fuel electrode 2b of the solid oxide fuel cell 2 is formed .
And an oxidant gas such as air supplied to the other first oxidant electrode 2c causes a cell reaction to generate power. At this time, oxygen in the air on the side of the first oxidant electrode 2c becomes an oxide ion O2-, which passes through the solid electrolyte 2a and becomes the first ion.
It reacts with hydrogen and carbon monoxide in the fuel electrode 2b as represented by the following equation.

CO + O2-> CO2 + 2e- H2 + O2-> H2O + 2e- Due to the above-mentioned cell reaction, carbon monoxide CO contained in the reformed gas is used as a fuel for the solid oxide fuel cell 2 as the first fuel.
It is consumed at pole 2b and converted to carbon dioxide CO2. In addition, part of the hydrogen in the reformed gas also reacts with the oxidant gas to produce water H2O.
And hydrogen and carbon monoxide that do not contribute to the cell reaction are discharged from the first fuel electrode 2b together with the modified carbon dioxide.

The exhaust gas discharged from the first fuel electrode 2b consists of hydrogen that has not contributed to the cell reaction, water generated and carbon dioxide, and enters the heat exchange section 8 through the connection flow passage 10. In the heat exchange section 8, the water that has entered from the hot water supply water inlet 6 exchanges heat with the exhaust gas of the high-temperature solid oxide fuel cell 2, and becomes hot water and exits from the hot water supply water outlet 7. After that, the high-temperature exhaust gas of the solid oxide fuel cell 2 is lowered to the operating temperature of the solid polymer electrolyte fuel cell 4, which is about 80 ° C., by heat exchange and is supplied to the solid polymer electrolyte fuel cell 4. As a result, the heat of the high-temperature exhaust gas can be used for hot water for hot water supply, so that the system efficiency can be improved.

The solid polymer electrolyte 4a of the solid polymer electrolyte fuel cell 4 is formed of a cation exchange membrane of polystyrene type having a sulfonic acid group, a perfluorocarbon sulfonic acid membrane (Nafion, trade name of DuPont, USA), or the like. A membrane having a proton exchange group in its molecule is used, and it is possible to make it function as a proton-conducting electrolyte by containing water in the exhaust gas generated in the solid oxide fuel cell 2 to make it hydrate.

The hydrogen in the exhaust gas of the solid oxide fuel cell 2 supplied to the second fuel electrode 4b is proton H.
+ Becomes, through the solid polymer electrolyte 4a membrane, the other of the first
Electric power is generated by causing a battery reaction with an oxidant gas such as air supplied to the second oxidant electrode 4c . Second fuel at this time
In the exhaust gas supplied to the electrode 4b , carbon monoxide is consumed and removed in the solid oxide fuel cell 2 without danger of explosion, necessity of large power, and no power consumption. Since the platinum catalyst (not shown) in the fuel cell 4 is not poisoned and the high energy of carbon monoxide is effectively used for power generation, high system efficiency can be obtained. Further, the first fuel of the solid oxide fuel cell 2 is
Since the exhaust gas of the electrode 2b contains water generated by the cell reaction, the humidifying device is not required. Although the stabilized zirconia-based solid oxide fuel cell was used as the first fuel cell here, other solid oxide fuel cells and molten carbonate fuel cells, such as other solid oxide fuel cells, use both hydrogen and carbon monoxide as fuel. Other fuel cells that generate electricity may be used.

On the other hand, the first fuel of the solid oxide fuel cell 2 is
A part of the exhaust gas that has exited from the electrode 2b is responsive to the output signal of the carbon monoxide concentration detection means 9 provided in the connection flow path 10,
The first fuel of the solid oxide fuel cell 2 is pressurized from the branch portion 4 in the middle of the connection flow passage 10 through the return flow passage 13 at a predetermined flow rate controlled by the flow control means 11 and is pressurized by the pressurizing device 12.
It is configured to be supplied again to the electrode 2b . Therefore, the reforming is performed such that the carbon monoxide concentration in the exhaust gas of the first fuel electrode 2b of the solid oxide fuel cell 2 is completely removed or the supply amount of the raw fuel is changed according to the load fluctuation of the fuel cell power generator. Even if the carbon monoxide concentration in the exhaust gas of the solid oxide fuel cell 2 changes due to changes in the operating conditions of the reactor 1 and other changes in the operating conditions, the platinum catalyst of the polymer electrolyte fuel cell 4 It is possible to surely remove up to the poisoning limit value or less without exceeding the poisoning limit value.

FIG. 2 is a system configuration diagram showing a main part of a hybrid fuel cell power generator according to another embodiment of the present invention. The same reference numerals as those in FIG. 1 are corresponding components, and detailed description thereof will be omitted. To do. In the figure, together with the reformer 1 and the solid oxide fuel cell 2 is constructed adjacent integrally burner 14 is provided as a heating means for heating heating both the integral, the second polymer electrolyte fuel cell 4 An off-gas passage 15 is connected from the outlet of the fuel electrode 4b to the burner 14. A conduit 17 having a shutoff valve 16 is also provided so that the raw fuel can be supplied directly to the burner 14.

In the above structure, when the hybrid fuel cell power generator of the present invention is started, the shutoff valve 16 of the conduit 17 is closed.
Since the raw fuel can be directly supplied to the burner 14 for combustion heating, the solid oxide fuel cell 2 and the reformer 1 can be quickly heated. Then, when the temperature rises sufficiently and becomes the steady operation, the conduit 17
The closed shut-off valve 16, the polymer electrolyte fuel cell 4 second
The off gas discharged from the outlet of the fuel electrode 4b is supplied to the burner 14 through the off gas passage 15 and burned to maintain the temperature required for the first fuel cell 2. Polymer electrolyte fuel cell 4 within any part that has not contributed to cell reaction of hydrogen, the second
Since it remains in the off-gas discharged from the fuel electrode 4b of No. 4, the energy of hydrogen remaining in the off-gas is effectively used as combustion heat, and the remaining hydrogen is completely consumed, thus improving system efficiency and safety. Can be secured. Further, since the reformer 1 and the solid oxide fuel cell 2 which require substantially the same temperature are integrally formed, simultaneous heating by the burner 14 simplifies the configuration, and the reformer 1 and the solid oxide fuel cell 2 are integrated. It is possible to improve the system efficiency by effectively utilizing the heat by eliminating the heat radiation loss between the two.

FIG. 3 is a system configuration diagram showing a main part of a hybrid fuel cell power generator according to another embodiment of the present invention, and those having the same reference numerals as those in FIGS. 1 and 2 are the corresponding components and will be described in detail. The description is omitted. In the figure, methane which is a hydrocarbon fuel is used as a raw fuel, and a reformer to which this methane fuel is supplied is configured as a partial oxidation reactor 18 having a partial oxidation reaction catalyst (not shown). Also,
A preheating section 23 having a preheating gas inlet 19, a preheating gas outlet 20, and a raw fuel inlet 21 and a raw fuel outlet 22 is provided between the solid oxide fuel cell 2 and the polymer electrolyte fuel cell 4. . Further, between the solid oxide fuel cell 2 and the solid polymer fuel cell 4, a heat exchange section 8 is provided in the latter stage of the preheating section 23, and further in the latter stage, in the cooling water 25 in the container 24. A cooling unit 3 having a fuel gas inlet 27 with an opening 26 in it, a fuel gas outlet 28 located above the container 24, and a cooling water inlet 29 and a cooling water outlet 30.
1 is provided, and the fuel gas outlet 28 is connected to the second fuel electrode 4b of the polymer electrolyte fuel cell 4.

In the above structure, methane, which is the raw fuel, enters the preheating section 23 from the raw fuel inlet 21, and the first of the solid oxide fuel cell 2 that enters from the preheating gas inlet 19 there .
It is preheated by heat exchange with the exhaust gas of the fuel electrode 2b and enters the partial oxidation reactor 18 which is a reformer from the raw fuel outlet 22. The preheated and supplied methane is the partial oxidation reactor 18
A partial oxidation reaction represented by 2CH4 + O2 → 2CO + 4H2 is generated by the action of a partial oxidation reaction catalyst (not shown), and the heat of reaction associated with this reaction is used to raise the temperature of the solid oxide fuel cell 2. As a result, the heating means of the solid oxide fuel cell 2 becomes unnecessary, and the structure can be simplified. Further, in the case of methane, the steam generator is not necessary as compared with the case of using the steam reforming method of a hydrocarbon fuel, which is represented by the following formula CH4 + H2O → CO + 3H2. On the other hand, methane is the high temperature first fuel electrode 2b.
Since it is preheated by the exhaust gas, the partial oxidation reactor 1
8 is not cooled by the supplied methane, the amount of heat for maintaining the temperature required for the reaction in the reformer is reduced, and the reaction heat from the partial oxidation reaction can be used for other effective parts, thus improving the system efficiency. Can be achieved.

In the reformed gas reformed in the partial oxidation reactor 18, carbon monoxide is removed and discharged while power is generated in the solid oxide fuel cell 2. The high-temperature exhaust gas enters the preheating section 23 from the preheating gas inlet 19, is heat-exchanged with methane to be cooled, and is discharged from the preheating gas outlet 20 to the heat exchange section 8 in the latter stage.
And enters the cooling section 31 at the subsequent stage.

The exhaust gas, which enters the fuel gas inlet 27 and serves as a fuel for the polymer electrolyte fuel cell 4, is in direct contact with the cooling water 25 in the container 24 and is about 80 ° C. in the polymer electrolyte fuel cell 4. Since it is cooled to the operating temperature and is humidified to the saturated state by the evaporation of the cooling water, the humidification is performed when the amount of humidification required to keep the electrolyte 4a membrane of the polymer electrolyte fuel cell 4 in the saturated water content is insufficient. The amount can be supplemented. On the contrary, when the amount of humidification of the exhaust gas is excessive and water is condensed due to cooling, the condensed portion can be received in the container 24 and discharged from the cooling water outlet 30, so that the solid polymer fuel cell It is possible to deal with a change in operating conditions without a strict control means. Although the cooling unit having the above-described configuration is used here, if the exhaust gas and the cooling water are in direct contact with each other, any configuration such as a configuration in which moisture is sprayed into the exhaust gas (not shown) is used. You may use the thing.

[0030]

As described above, the hybrid fuel cell power generator of the present invention has the following effects.

(1) A reformer for reforming raw fuel, a first fuel cell for supplying reformed gas from the reformer to a first fuel electrode to generate power and discharge produced water, Primary fuel for fuel cells
The reformed gas generated from the raw fuel in the reformer is the first fuel by the configuration including the polymer electrolyte fuel cell in which the exhaust gas containing the generated water from the electrode is supplied to the second fuel electrode. A cell reaction occurs in the cell to generate electricity, carbon monoxide contained in the reformed gas is consumed as fuel for the first fuel cell, and some hydrogen in the reformed gas also reacts with the oxidant gas. As water H2O is generated and supplied to the polymer electrolyte fuel cell, carbon monoxide can be removed without danger of explosion, necessity of large power, and power consumption, and a platinum catalyst for polymer electrolyte fuel cell. In addition to being able to prevent the poisoning of carbon dioxide, the high energy of carbon monoxide is effectively used for power generation, so high system efficiency can be obtained. Moreover, the first of the first fuel cell
Since the fuel electrode exhaust gas contains water generated by the cell reaction, power generation can be performed by the polymer electrolyte fuel cell without a humidifying device, so that the configuration of the device can be simplified.

(2) The first fuel in the exhaust gas of the first fuel cell is constituted by the structure provided with the return passage for removing carbon monoxide of the exhaust gas of the first fuel electrode of the first fuel cell. Carbon monoxide that has passed through the cell can be re-supplied to the first fuel cell for more complete removal.

(3) The carbon monoxide concentration in the exhaust gas is completely eliminated by the structure provided with the carbon monoxide concentration detecting means for the fuel gas of the polymer electrolyte fuel cell and the flow rate controlling means for varying the flow rate in the return passage. Even if the fuel is removed or the operating conditions of the device are changed, the flow rate in the return flow path is changed based on the output signal of the carbon monoxide concentration detection means, and the first fuel of the first fuel cell is changed .
Since the re-supply amount of the electrode exhaust gas to be supplied to the first fuel cell again can be adjusted, the carbon monoxide concentration can be reliably removed to the platinum catalyst poisoning limit value of the polymer electrolyte fuel cell or less.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a main part of a hybrid fuel cell power generator according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a main part of a hybrid fuel cell power generator according to another embodiment of the present invention.

FIG. 3 is a configuration diagram showing a main part of a hybrid fuel cell power generator according to another embodiment of the present invention.

FIG. 4 is a configuration diagram showing a main part of a conventional phosphoric acid fuel cell power generator.

FIG. 5 is a configuration diagram showing a main part of a conventional polymer electrolyte fuel cell power generator.

[Explanation of symbols]

1 reformer 2 solid oxide fuel cell 2b first fuel electrode 2c first oxidant electrode 4 solid polymer fuel cell 4b second fuel electrode 4c second oxidant electrode

Continuation of the front page (56) Reference JP-A-6-89735 (JP, A) JP-A-3-149761 (JP, A) JP-A-2-160602 (JP, A) JP-A-62-274560 (JP , A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 8/00-8/24

Claims (3)

(57) [Claims] 1. A reformer for reforming a hydrocarbon-based or alcohol-based raw fuel into a gas containing hydrogen and carbon monoxide, and air.
The first oxidant that is supplied as oxygen gas in the atmosphere
A first fuel cell having a pole and a first fuel pole, and in air
Second oxidant electrode supplied with oxygen and other oxygen as oxidant gas
And a polymer electrolyte fuel cell having a second fuel electrode
For example, said first fuel cells to discharge the power to generate water both said gas reformed in the reformer is <br/> supplied to the first fuel electrode hydrogen and carbon monoxide as a fuel , The first fuel
The exhaust gas containing the generated water from the electrode is used as the fuel gas .
And the solid polymer electrolyte fuel cell which is supplied to the second fuel electrode
Connected hybrid fuel cell power generator. 2. The first fuel electrode exhaust gas of the first fuel cell is supplied again to the first fuel electrode of the first fuel cell, and the exhaust gas that has passed through without being used is supplied again. The hybrid fuel cell power generator according to claim 1, further comprising a return channel for removing carbon oxide. 3. A carbon monoxide concentration detecting means for a fuel gas of a polymer electrolyte fuel cell, and a flow rate controlling means for varying a flow rate of a return channel based on an output signal of the carbon monoxide concentration detecting means. The hybrid fuel cell power generator according to claim 2.