JPH0729587A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To provide a low cost circulation means of a cathode circulation line by installing an ejector in the cathode circulation line, by inhaling a cathode gas with a mixture of a combustion exhaust gas and air, and by circulating a mixture of them. CONSTITUTION:An ejector 24 is installed in a cathode circulation line 21 to circulate a cathode gas 3. The ejector 24 ejects a suction gas from a nozzle, and inhales a gas from an inhaling hole with the accompanying flow, then they are mixed and discharged from a discharge hole. As the suction gas, a mixture of a combustion gas 5 and air, and as an inhaling gas, a cathode exhaust gas 7 is used, then these mixture, which is the gas 3, is discharged to the cathode circulation line 20 to circulate. The ejector 24 has no rotating parts, simple structure, and resists to a high temperature of 600-700 deg.C by selecting a suitable material. The ejector 24 is low cost compared with a circulation blower, needs no cooling air, and is easy to maintain.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generator having an ejector in a cathode circulation line.

[0002]

2. Description of the Related Art Molten carbonate fuel cells have characteristics that conventional power generators do not have, such as high efficiency and little impact on the environment. Collected, and researches are now underway all over the world.

FIG. 3 is a diagram showing an example of power generation equipment using a molten carbonate fuel cell using natural gas as a fuel. In the figure, the power generation facility includes a reformer 10 for reforming a fuel gas 1 obtained by mixing natural gas and water vapor into an anode gas 2 containing hydrogen, a cathode gas 3 containing oxygen, and an anode gas 2.
And a fuel cell 20 for generating electricity from the fuel cell 20. The anode gas 2 produced in the reformer 10 is supplied to the fuel cell 20, and most of it is consumed in the fuel cell 20 to become the anode exhaust gas 4. It is supplied to the combustion chamber Co of the reformer 10 as a combustion gas.

In the reformer 10, combustible components (hydrogen, carbon monoxide, methane, etc.) in the anode exhaust gas 4 are combusted in a combustion chamber to generate high temperature combustion gas, and the high temperature combustion gas is used to reform the reformer 10. Is heated to reform the fuel gas 1 passing through the reformer 10. The combustion exhaust gas 5 exiting the reformer 10 joins with the air 6 to become a cathode gas 3, and this cathode gas 3 is
A part of the fuel cell 20 reacts to become the high-temperature cathode exhaust gas 7, and power is recovered by the turbine compressor 40 that compresses the air 6, and then power is recovered by an exhaust heat recovery steam generator (not shown). It is discharged outside.

The combustion exhaust gas 5 passes through the exhaust gas supply line 13, merges with the air 6, and enters the cathode circulation line 21.
A circulation blower 23 is provided in the cathode circulation line 21 to circulate the cathode gas 3. The cathode gas 3 reacts in the fuel cell 20 to become the cathode exhaust gas 7, which is mixed with the combustion exhaust gas 5 and the air 6 and circulated, and the temperature thereof is 500 to 600 ° C.

[0006]

In the above conventional power generation equipment, the temperature of the cathode gas 3 is as high as 500 to 600 ° C. Therefore, the circulation blower 23 for circulating the cathode gas 3 to the cathode inlet side has a high temperature special specification, and is manufactured. There was a problem that it was difficult. That is, the blower 3 for high temperature of 600 to 700 ° C. needs special design, uses expensive heat-resistant metal, has poor workability, and has a problem of high manufacturing cost. In addition, the bearings of the blower also become extremely hot, so a large amount of cooling air is required.To obtain this air, it is necessary to significantly increase the capacity of the indoor air compressor used for controlling the control valve and other components. It was Further, since the power of the on-site compressor also increases in accordance with the increase in capacity, there is a problem that the cost of the entire system increases and the efficiency decreases.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell power generator having a low-cost circulating means in the cathode circulation line.

[0008]

To achieve the above object, a reformer for reforming a fuel gas containing water vapor into an anode gas containing hydrogen, and a fuel cell for generating electricity from a cathode gas containing oxygen and an anode gas. A cathode circulation line for circulating the cathode exhaust gas of the fuel cell to the cathode; an exhaust line for discharging the anode exhaust gas of the fuel cell to the combustion chamber of the reformer; and a combustion exhaust gas of the reformer mixed with air. In the fuel cell power generator including the exhaust gas supply line that supplies the cathode circulation line and the air line that supplies the air, an ejector is provided in the cathode circulation line to mix the combustion exhaust gas and the air. The gas exhausts the cathode exhaust gas, mixes it, and circulates it.

[0009]

The ejector injects suction gas from the nozzle, sucks the gas from the suction port by its accompanying flow, mixes it, and discharges it from the discharge port. By using a mixed gas of combustion exhaust gas and air as the suction gas and using cathode exhaust gas as the suction gas, the cathode gas as the mixed gas is discharged to the cathode circulation line. Thereby, the cathode gas can be circulated. The ejector has no rotating part and its structure is simple.
The structure can withstand a high temperature of 0 to 700 ° C.
Ejectors are less expensive to manufacture than circulating blowers, require no cooling air, and are easy to maintain, thus reducing overall plant costs.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a fuel cell power generator according to the present invention. In this figure, the same parts as those in FIG. 2 are represented by the same reference numerals. The fuel cell power generation facility includes a reformer 10 for reforming a fuel gas 1 containing water vapor into an anode gas 2 containing hydrogen, and a fuel cell 20 generating electricity from the anode gas 2 and a cathode gas 3 containing oxygen. The anode exhaust gas 4 discharged from the fuel cell 20 is supplied to the combustion chamber Co of the reformer 10 through the discharge line 12 and burned, and the combustion exhaust gas 5 passes through the exhaust gas supply line 13 and the cathode circulation line 21 and is discharged from the fuel cell 20. It is supplied to the cathode side C.

In FIG. 1, the fuel gas 1 is a fuel heater 11
After being heated at 1, it is supplied to the reformer 10. The reformer 10 includes a combustion chamber Co that combusts with the anode exhaust gas 4 and the cathode exhaust gas 7 that have exited the fuel cell 20, and a reforming chamber Re that reforms the fuel gas 1 by heat transfer from the combustion chamber Co. The reforming chamber Re is filled with a reforming catalyst, and the combustion chamber C
The fuel gas 1 is reformed into the high-temperature anode gas 2 containing hydrogen by the high-temperature combustion gas generated in o
And is supplied to the fuel cell 20 after being cooled. On the other hand, the combustion exhaust gas 5 whose temperature has decreased due to heat radiation enters the cathode circulation line 21 through the exhaust gas supply line 13, but is cooled in the exhaust gas supply line 13 by the air preheater 32, and the moisture by the condenser 33 and the steam separator 34. Is removed, pressurized by the low temperature blower 35, mixed with the air 6, heated by the air preheater 32, and enters the cathode circulation line 21. The low temperature blower 35 is a roots type blower and the gauge pressure is about 1
About 1 Kg / cm of combustion exhaust gas coming in at Kg / cm ^2
2 Pressurize and discharge at about 2 Kg / cm ² . Temperature sensor 2 provided on the cathode inlet side of the cathode circulation line 21
The discharge pressure is controlled by the measured value of 5.

A part of the cathode exhaust gas 7 drives the turbine of the turbine compressor 40 and is supplied to an exhaust heat recovery steam generator (not shown). The air 6 compressed by the turbine compressor 40 is further pressurized by the electric blower 42, and about 2 Kg /
It is discharged from the air line 14 at a pressure of cm ² . The air line 14 is the outlet of the low temperature blower 35 and the exhaust gas supply line 1
Merge into 3. A roots type is used for the electric blower 42, and the air 6 pressurized by the turbine compressor 40 to about 1 Kg / cm ² is further pressurized by about 1 Kg / cm ² .

The fuel cell 20 is composed of an anode side A through which the anode gas 2 passes and a cathode side C through which the cathode gas 3 passes, and hydrogen and carbon monoxide in the anode gas, oxygen in the cathode gas, and dioxide. Electricity is generated from carbon by a chemical reaction. The fuel cell 20 includes a storage container 22.
Stored in, it prevents combustible gas from leaking to the outside and enhances safety.

A part of the cathode exhaust gas 7 is a part of the air preheater 3.
It is mixed with the combustion exhaust gas 5 and the air 6 heated in 2, becomes the cathode gas 3, and is supplied to the cathode by the cathode circulation line 21. An ejector 24 is provided in the cathode circulation line 21 and circulates the cathode gas 3.

FIG. 2 is a view showing the structure of the ejector 24, in which the ejector 24 has a constricted cross section, and the nozzle 51 is expanded subsequently.
And a cylindrical suction portion 52 surrounding the nozzle 51, and a discharge portion 53 that spreads toward the end following the suction portion 52. The nozzle 51 has a suction port 54, the suction portion 52 has a suction port 55, and the discharge portion 53 has a discharge port 53. Is provided with a discharge port 56. Suction port 54
The sucked gas that has entered into the nozzle 51 becomes a high-speed jet flow by passing through the nozzle 51. The suction gas entering from the suction port 55 is sucked as an accompanying flow of this high-speed jet flow, the suction gas and the suction gas are mixed, and the velocity energy is converted into the pressure energy through the discharge portion 53 which spreads toward the end. Is discharged.

In the embodiment, the mixed gas of the combustion exhaust gas 5 and the air 6 is used as the suction gas, the cathode exhaust gas 7 is used as the suction gas, and these mixed gases are discharged from the discharge port 56 as the cathode gas 3. .

In the cathode circulation line 21, the temperature of the fuel cell 20 is controlled by controlling the flow rate of the cathode gas 3 supplied to the cathode. Therefore, by providing the temperature sensor 25 on the cathode inlet side of the cathode circulation line 21 and controlling the discharge pressure of the low temperature blower 35, the flow rate of the mixed gas of the combustion exhaust gas 5 and the air 6 flowing from the suction port 54 of the ejector 24. Is controlled to control the flow rate of the cathode gas 3. Since the temperature of the mixed gas of the combustion exhaust gas 5 and the air 6 is lower than that of the cathode gas 3, the temperature of the cathode gas 3 is lowered by increasing the flow rate of the mixed gas.

[0018]

As is apparent from the above description, according to the present invention, the cost of the equipment itself is reduced by using the circulation blower of the cathode circulation line as the ejector, and further the axial cooling is unnecessary, so that the cooling air compressor The power becomes unnecessary. However, although the pressure of the suction gas that drives the ejector is set to be slightly high in consideration of the ejector efficiency, the system configuration is inexpensive as a whole and the system cost can be reduced.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a fuel cell power generator according to the present invention.

FIG. 2 is a diagram illustrating a configuration of an ejector.

FIG. 3 is an overall configuration diagram of a conventional fuel cell power generator.

[Explanation of symbols]

 1 Fuel Gas 2 Anode Gas 3 Cathode Gas 4 Anode Exhaust Gas 5 Combustion Exhaust Gas 6 Air 7 Cathode Exhaust Gas 10 Reformer 11 Fuel Heater 12 Exhaust Line 13 Exhaust Gas Supply Line 14 Air Line 20 Fuel Cell 21 Cathode Circulation Line 22 Containment Container 24 Ejector 25 Temperature Sensor 32 Air Preheater 33 Condenser 34 Steam Separator 35 Low Temperature Blower 40 Turbine Compressor 42 Electric Blower 51 Nozzle 52 Suction Portion 53 Discharge Port 54 Suction Port 55 Suction Port 56 Discharge Port Re Reforming Chamber Co Combustion Chamber A Anode side C Cathode side

Claims (1)

[Claims] 1. A reformer for reforming a fuel gas containing water vapor into an anode gas containing hydrogen, a fuel cell for generating electricity from a cathode gas containing oxygen and an anode gas, and a cathode exhaust gas of the fuel cell as a cathode. A circulating cathode circulation line, an exhaust line for discharging the anode exhaust gas of the fuel cell to the combustion chamber of the reformer, and an exhaust gas supply for mixing the combustion exhaust gas of the reformer with air and supplying the mixture to the cathode circulation line. In a fuel cell power generator including a line and an air line for supplying the air, an ejector is provided in the cathode circulation line, and the cathode exhaust gas is sucked and mixed by the mixed gas of the combustion exhaust gas and the air. A fuel cell power generator characterized in that it is adapted to circulate.