JPH0778622A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To control the defferential pressure between a housing and a cathode in a specified value by installing a differential pressure controller to detect the pressure in the housing and the pressure of a cathode exhaust gas and to control the differential pressure. CONSTITUTION:When a system os operated, part 9 of a combustion exhaust gas is supplied to a housing 22 from a housing filling gas supply line 51. When the pressure in the housing 22 is higher to an extent exceeding a specified value than the pressure of a cathode exhaust gas 7, a differential pressure controller 56 narrows a flow control valve 52 to reduce the flow of part 9 of the combustion exhaust gas, and opens a flow control valve 54 to exhaust a gas in the housing 22 to a circulation line 21 from a three-way valve 55. When the pressure in the housing 22 is not higher to an extent exceeding a specified value than the pressure of the gas 7, the valve 54 is closed and the valve 52 is opened to control the pressure so as to obtain a specified value. A blower controller 39 controls an electric motor of a low temperature blower 35 so that the outlet pressure of the blower 35 is heightened to an extent exceeding a specified value than the pressure on cathode inlet side of a line 21 to surely supply part 9 of the combustion exhaust gas to the housing 22.

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 equipped with a differential pressure adjusting device for adjusting the pressure difference between the cathode and the internal pressure of a fuel cell container.

[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. 2 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, a power generation facility includes a reformer 10 for reforming a fuel gas 1 obtained by mixing natural gas and steam into an anode gas 2 containing hydrogen, a cathode gas 3 containing oxygen, and an anode gas 2 containing hydrogen. A fuel cell 20 for generating electricity from the fuel cell 20 is generally provided, and the anode gas 2 produced in the reformer 10 is supplied to the fuel cell 20 and consumes most of it in the fuel cell 20 to become the anode exhaust gas 4 and burns. It is supplied to the combustion chamber Co of the reformer 10 as a working gas.

In the reformer 10, combustible components (hydrogen, carbon monoxide, methane, etc.) in the anode exhaust gas 4 are burned in the combustion chamber Co to generate high-temperature combustion gas, and the combustion gas causes the reformer 10 to operate. The fuel gas 1 that is heated and passes through the reformer 10 is reformed to form the anode gas 2. The combustion exhaust gas 5 exiting the reformer 10 joins the air 6 to become the cathode gas 3, and this cathode gas 3 partially reacts in the fuel cell 20 to become the high-temperature cathode exhaust gas 7 and compresses the air 6. After recovering the power with the turbine compressor 40, the heat energy is further recovered with an exhaust heat recovery steam generator (not shown) and discharged to the outside of the system.

In the molten carbonate fuel cell, as shown in FIG. 3, a thin flat electrolyte plate (tile) 61 is sandwiched between flat electrodes of a fuel electrode (anode) 62 and an air electrode (cathode) 63. (Unit cell) 64, and this fuel cell is maintained at about 650 ° C., the anode gas containing hydrogen is supplied to the anode side, and the cathode gas containing oxygen is supplied to the cathode side, so that the anode and the cathode are connected to each other. It generates electricity. However, the voltage is low in a single cell (0.8V
Therefore, in practice, it is used as a battery (stack) in which a large number of layers are stacked via a conductive bipolar plate (separator) 65. In addition, such fuel cells are typically housed in the containment vessel 22 and operated under pressure to increase efficiency and size of the device.

The electrolyte plate 61 (tile) of the fuel cell is a ceramic powder sintered body in which the electrolytic solution is impregnated by capillary action, and when the electrolytic solution gets wet with the separator 65, the gas between the cells is changed. Sealing and gas sealing between the inside of the storage container 22 and the inside of the fuel cell 20 are performed. The performance of the seal due to such wetting (wet seal) is easily affected by the operating state of the fuel cell 20, and gas may leak even with an extremely small pressure difference (for example, 400 mmAq). When the anode gas 2 and the cathode gas 3 are mixed due to such gas leakage, the anode gas 2
Hydrogen inside may burn and damage the fuel cell.
For this reason, the containment vessel 22 is filled with an inert gas to balance the pressure with the anode gas 2 and the cathode gas 3 so as to prevent these gases from leaking into the containment vessel 22.
The purge line 15 is provided to supply the nitrogen gas 8 as shown in FIG.

In order to fill the containment vessel 22 with nitrogen gas so that it can be constantly replenished, it is necessary to provide a nitrogen generator, a nitrogen heater, a nitrogen supply line to the containment vessel, etc. If it is provided, the power generator becomes large and the amount of nitrogen gas used increases. Therefore, it is proposed to supply a part of the combustion exhaust gas 5 that has exited the reformer 10 to the storage container 22.

[0008]

In order to prevent the cathode gas 3 and the anode gas 2 from leaking from the fuel cell 20 into the storage container 22, and the cathode gas 3 and the anode gas 2 are not mixed in the storage container, the storage container is prevented. 22 and a differential pressure between the cathode or the anode and between the cathode and the anode,
Although the differential pressure control for maintaining this differential pressure is performed, conventionally, the differential pressure control between the storage container 22 and the cathode has not been appropriately performed.

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 including a differential pressure adjusting device for adjusting the pressure difference between the pressure of the storage container and the cathode. .

[0010]

In order to achieve the above object, a fuel cell for generating power from a cathode gas containing oxygen and an anode gas containing hydrogen, a storage container for storing the fuel cell, and an anode exhaust gas of the fuel cell are provided. A reformer that burns part of the cathode exhaust gas and uses the heat to reform the fuel gas containing water vapor into the anode gas, a circulation line that circulates part of the cathode exhaust gas of the fuel cell to the cathode, and the reformer combustion In a fuel cell power generator having an exhaust gas supply line for supplying exhaust gas to a circulation line, a containment vessel filling gas supply line for supplying a part of combustion exhaust gas of the exhaust gas supply line into the containment vessel, and a gas in the containment vessel To the reformer or circulation line, the pressure inside the containment vessel and the pressure inside the containment vessel and the cathode exhaust gas from the fuel cell are detected, and the differential pressure is detected. The storage container filling gas supply line and the storage container in the gas discharge line is obtained a differential pressure control device for adjusting the flow rate adjusting valve provided respectively.

The pressure on the outlet side of the blower provided in the exhaust gas supply line and the pressure on the cathode inlet side of the circulation line are detected so that the pressure on the outlet side of the blower becomes higher than the pressure on the cathode inlet side. A blower control device for controlling the blower is provided.

Also, a bypass line is provided between the outlet side and the inlet side of the blower of the exhaust gas supply line.

[0013]

A part of the combustion exhaust gas is supplied to the containment vessel from the containment vessel filling gas supply line via the flow rate adjusting valve, and is discharged from the containment vessel gas discharge line via the flow rate adjusting valve. The differential pressure adjusting device detects the pressure in the containment vessel and the pressure of the cathode exhaust gas, and adjusts the flow rate adjusting valve of the containment vessel filling gas supply line and the containment vessel gas discharge line so that the differential pressure becomes a predetermined value. . The differential pressure causes the pressure in the containment vessel to be greater than the pressure in the cathode exhaust gas, and prevents cathode gas from leaking into the containment vessel.

The blower control device controls the blower so that the outlet side pressure of the blower provided in the exhaust gas supply line is higher than the cathode inlet side pressure of the circulation line, so that it is supplied from the containment vessel filling gas supply line to the containment vessel. The pressure of the combustion exhaust gas becomes higher than the pressure of the anode gas, and the combustion exhaust gas can be supplied to the containment vessel.

By providing a bypass line between the outlet side and the inlet side of the blower of the exhaust gas supply line, the flow rate of the combustion exhaust gas on the outlet side of the blower can be adjusted.

[0016]

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 reformer 10 through the discharge line 12.
Of the cathode exhaust gas 7 and burned together with the cathode exhaust gas 7, and the combustion exhaust gas 5 is supplied to the cathode side C of the fuel cell 20 through the exhaust gas supply line 13 and the circulation line 21.

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 reforming 10 includes a combustion chamber Co that burns 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 is heated by the high temperature combustion gas generated in the combustion chamber Co to reform the fuel gas 1 into the high temperature anode gas 2 containing hydrogen, and the fuel heater 11 And is supplied to the fuel cell 20 after cooling. On the other hand, the combustion exhaust gas 5 whose temperature has decreased due to heat radiation enters the 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 is removed by the condenser 33 and the steam separator 34. Removed,
It is pressurized by the low temperature blower 35, mixed with the air 6, heated by the air preheater 32, and enters the circulation line 21. A bypass line 37 having a flow rate adjusting valve 36 is provided between the outlet side of the low temperature blower 35 and the inlet side of the condenser 33, and the discharge amount of the low temperature blower 35 is adjusted.

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 merges with the combustion exhaust gas 5 at the outlet of the low temperature blower 35. The turbine compressor 40 is provided with a backup line 41 having an electric blower 42 and is used for backup when the capacity of the turbine compressor 40 is insufficient.

The fuel cell 20 comprises 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.

A part of the cathode exhaust gas 7 is the air preheater 3
It is mixed with the combustion exhaust gas 5 heated in 2 and the air 6 to become the cathode gas 3, which is supplied to the cathode through the circulation line 21. The circulation line 21 circulates the cathode gas 3 by a high temperature blower 23.

The fuel cell 20 is stored in a storage container 22. On the outlet side of the low temperature blower 35, a containment vessel filling gas supply line 51 is provided which connects the containment vessel 22 from the connection position of the bypass line 37 and the location where the air 6 joins,
A part 9 of the combustion exhaust gas is supplied to the storage container 22 via the flow rate adjusting valve 52. The containment vessel 22 is provided with a gas discharge line 53 in the containment vessel having a flow rate adjusting valve 54 and a three-way valve 55. One of the three-way valve 55 is connected to the circulation line 21 and the other is connected to the combustion chamber Co of the reformer 10. is doing.

A differential pressure adjusting device 56 is provided which detects the pressure of the storage container 22 and the pressure of the cathode exhaust gas 7 and adjusts the flow rate adjusting valves 52 and 54 so that the differential pressure becomes a predetermined value. The differential pressure between the pressure sensor 38 provided between the bypass line 37 connection position on the outlet side of the low temperature blower 35 and the storage container filling gas supply line connection position and the pressure sensor 24 provided on the cathode inlet side of the circulation line 21 is measured. A blower controller 39 is provided which detects and controls the electric motor of the low temperature blower.

The operation of the equipment and line around the storage container 22 and the low temperature blower 35 configured as described above will be described. During operation of the fuel cell power generator, a part 9 of the combustion exhaust gas is supplied into the storage container 22 from the storage container filling gas supply line 51. Differential pressure adjusting device 5
When the pressure of the containment vessel 22 is higher than the pressure of the cathode exhaust gas 7 by a predetermined value or more, the flow control valve 6 is throttled to reduce the flow rate of a part 9 of the combustion exhaust gas, the flow control valve 54 is opened and the three-way valve 55 is used. The gas in the storage container 22 is discharged to the circulation line 21. When the pressure in the storage container 22 is not higher than the pressure of the cathode exhaust gas 7 by a predetermined value or more, the flow rate adjusting valve 54 is closed and the flow rate adjusting valve 52 is opened to adjust to a predetermined value.

The blower control device 39 controls the electric motor of the low temperature blower 35 so that the outlet side pressure of the low temperature blower 35 becomes higher than the pressure on the cathode inlet side of the circulation line 21 by a predetermined value or more, and one of the combustion exhaust gas is stored in the storage container 22. The part 9 is surely supplied.

A detector (not shown) is provided in the containment vessel 22, and the combustible gas in the containment vessel 22 is constantly monitored. When hydrogen gas, carbon monoxide gas, methane gas, etc. are detected, the three-way valve 55 is switched. The gas in the storage container 22 is guided to the combustion chamber Co of the reformer 10 and burned there. This can prevent the flammable gas from burning in the storage container 22.

[0026]

As is apparent from the above description, the present invention detects the pressure of the containment vessel and the pressure of the cathode exhaust gas by the differential pressure adjusting device and adjusts the differential pressure. The pressure difference between them can be controlled to a predetermined value. Further, since the blower control device controls the outlet pressure of the low temperature blower to be higher than the cathode inlet pressure, it is possible to reliably supply the combustion exhaust gas into the storage container.
Also, since the bypass lines are provided on the outlet side and the inlet side of the low temperature blower, it is possible to adjust the flow rate of the combustion exhaust gas to the containment vessel.

[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 an overall configuration diagram of a conventional fuel cell power generator.

FIG. 3 is a diagram showing a configuration of a molten carbonate fuel cell.

[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 9 Part of Combustion Exhaust Gas 10 Reformer 11 Fuel Heater 12 Exhaust Line 13 Exhaust Gas Supply Line 20 Fuel Cell 21 Circulation Line 22 Containment Vessel 23 High temperature blower 24,38 Pressure sensor 32 Air preheater 33 Condenser 34 Steam separator 35 Low temperature blower 36,52,54 Flow control valve 37 Bypass line 39 Blower control device 40 Turbine compressor 41 Backup line 42 Electric blower 51 Storage Container filling gas supply line 53 Containment container gas discharge line 55 Three-way valve 56 Differential pressure adjusting device Re Reforming chamber Co Combustion chamber A Anode side C Cathode side PX Pressure sensor

Claims (3)

[Claims] 1. A fuel cell for generating power from a cathode gas containing oxygen and an anode gas containing hydrogen, a containment vessel for storing the fuel cell, and the anode exhaust gas of the fuel cell is burned with a part of the cathode exhaust gas to generate heat. A reformer for reforming a fuel gas containing steam into an anode gas, a circulation line for circulating a part of the cathode exhaust gas of the fuel cell to the cathode, and an exhaust gas supply line for supplying the combustion exhaust gas of the reformer to the circulation line. In a fuel cell power generator comprising: a storage container filling gas supply line for supplying a part of the combustion exhaust gas of the exhaust gas supply line into the storage container; and a storage for discharging the gas in the storage container to a reformer or a circulation line. The gas discharge line in the container, the pressure in the containment container and the pressure of the cathode exhaust gas of the fuel cell are detected, and the differential pressure is detected in the containment container filling gas supply line and the containment. Fuel cell power plant is characterized in that a differential pressure control device for adjusting the flow control valve respectively provided vessel within the gas exhaust line. 2. The pressure on the outlet side of the blower provided in the exhaust gas supply line and the pressure on the cathode inlet side of the circulation line are detected so that the pressure on the outlet side of the blower becomes higher than the pressure on the cathode inlet side. The fuel cell power generator according to claim 1, further comprising a blower control device for controlling the blower. 3. The fuel cell power generator according to claim 2, wherein a bypass line is provided between the outlet side and the inlet side of the blower of the exhaust gas supply line.