JPH03171563A - Solid electrolyte fuel cell power generating system - Google Patents

Abstract

PURPOSE:To make use in an isolated island or during moving possible and to make the control of reaction air supply amount in response to the load change of a cell possible by preheating the air to be supplied to a cathode to high temperature when system operation is started. CONSTITUTION:When system operation is started, raw fuel and air for combustion are supplied to an exhaust heat recovery boiler 9, and they are burned there, and water from a pipeline 13 is converted into steam. The steam is supplied to a steam turbine 10 through a pipeline 14 to turn it. Reaction air is supplied to a preheater 12 with an air compressor 11, and the air is heated to high temperature by heat exchange with exhaust gas from the exhaust heat recovery boiler 9. The high temperature preheated air is supplied to a cathode of a fuel cell 1 to raise its temperature. When the cell 1 is heated to around 1000 deg.C, fuel is supplied to an anode, and power generation is started. When power load 17 is varied, revolutions per minute of the turbine 10 is controlled with a signal from a power load detecting system 18.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to improvements in solid oxide fuel cell (SOFC) power generation systems.

[Conventional technology] In a power generation system using a solid oxide fuel cell (SOFC), from the viewpoint of power generation efficiency, it is necessary to raise the temperature of the solid oxide fuel cell to approximately 1000°C to generate electricity.
Therefore, the temperature of the solid oxide fuel cell body is increased by the following method.

(1) The solid oxide fuel cell body is placed in an electric furnace and heated to a predetermined temperature.

{2} Air to be supplied to the solid oxide fuel cell is sent to the solid oxide fuel cell in advance by an external power source, and the temperature is raised to a predetermined temperature.

[Problems to be Solved by the Invention] However, the conventional temperature raising method has the following problems.

(1) The method of ripening in an electric cell is good on a laboratory scale, but when solid oxide fuel cells are used industrially, a large heating furnace is required, resulting in a slow process. .

2) The method of raising temperature with an electric heater using an external power source is simple, but requires an external power circuit, so it is difficult to apply to solid oxide fuel cell power generation systems used for remote islands or for transportation. .

This invention solves the above-mentioned problems of the prior art,
Power generation using a solid oxide fuel cell that is inexpensive and can be used for remote islands or for transportation, has a temperature raising function, and controls the amount of reaction air supplied according to fluctuations in the load on the fuel cell. The purpose is to provide a system. [Means for Solving the Problems] A power generation system using a solid oxide fuel cell according to the present invention is a power generation system using a solid oxide fuel cell, in which surplus fuel and raw fuel that are not used in the power generation reaction of the fuel cell are used. an air preheater that preheats the air supplied to the cathode side of the fuel cell with the combustion exhaust gas discharged by the waste heat recovery boiler; and an air compressor driven by a steam turbine rotated by steam generated by the exhaust heat recovery boiler, and when the power generation system is started, raw fuel and combustion air are supplied to the exhaust heat recovery boiler and burned. , generating steam and supplying the generated steam to the steam turbine to drive the 11 pneumatic machines to supply air to the cathode side of the fuel cell, and the air preheater is provided with the exhaust heat recovery boiler. By supplying the generated combustion exhaust gas and preheating the air supplied to the cathode side, the temperature of the fuel cell is gradually raised,
After the start of power generation, the solid oxide fuel cell power generation system uses the surplus fuel as part of the fuel for the exhaust heat recovery boiler.

In addition, in the above-mentioned solid oxide fuel cell power generation system, the amount of steam supplied to the steam turbine is varied according to fluctuations in the load on the fuel cell, and the rotational speed of the air compressor is changed to generate a fuel P:l battery. This is a solid oxide fuel cell power generation system that varies the amount of air supplied and also varies the amount of fuel supplied to the fuel cell. [Effect]. A power generation system using a solid oxide fuel cell according to the present invention is a power generation system using a solid oxide fuel cell, in which surplus fuel and raw fuel that are not used in the power generation reaction of the fuel cell are combusted with combustion air. an air preheater that preheats the air supplied to the cathode side of the fuel cell using the combustion exhaust gas discharged by the exhaust heat recovery boiler; and an air compressor driven by a rotating steam turbine, and when the power generation system is started, raw fuel and combustion air are supplied to the exhaust heat recovery boiler and combusted to generate steam and generate Supplying steam to the steam turbine to drive the air compressor to supply air to the cathode side of the fuel cell, and supplying the air preheater with combustion exhaust gas generated in the exhaust heat recovery boiler, The air supplied to the cathode side is preheated. At the time of starting the fuel cell, the air supplied to the power source side is preheated to a high temperature by the air preheater, so as the air is supplied, the temperature of the fuel cell increases until it reaches almost the optimum operating condition. It becomes 1000″C.
Once this state is reached, fuel is supplied to the anode and power generation begins. When power generation starts, surplus fuel that is not used in the power generation reaction is supplied to the exhaust heat recovery boiler, and the exhaust heat recovery boiler is operated using this surplus fuel as part of its fuel. Therefore, when the fuel cell is started, the temperature of the fuel cell can be easily raised, and surplus fuel is used as fuel for the exhaust heat recovery boiler, and exhaust gas from the exhaust heat recovery boiler is used for air preheating, so the overall Power generation efficiency increases. Furthermore, in the above-mentioned solid oxide fuel cell power generation system, a power generation system that varies the amount of fuel and air supplied to the fuel cell according to changes in the load on the fuel cell will further increase the overall power generation efficiency. be.

As a method of varying the supply amount of fuel and air, the supply amount of fuel can be easily changed using a flow rate adjustment valve, but in the case of air, the flow rate adjustment valve cannot control it correctly, so air compression By changing the rotational speed of the machine, the supply amount was changed. [Example] A power generation system using a solid oxide fuel cell according to an example of the present invention will be explained with reference to FIG. FIG. 1 is an explanatory diagram showing the configuration of an apparatus for implementing a solid electrolyte fuel cell power generation system according to an embodiment of the present invention. This power generation system operates by burning exhaust air 3 discharged from the cathode 2 of the fuel cell 1 and exhaust fuel 5 discharged from the anode 4 on the downstream side of the fuel cell 1. An exhaust heat recovery boiler 9 operates by burning raw fuel branched from a raw fuel pipe 6 separately supplied to the anode 4 with combustion air supplied through a combustion air pipe 8 by a blower 7; An air compressor 1 driven by a turbine 10 rotated by steam generated in a recovery boiler 9
1, and an air preheater 12 that preheats the air supplied by the air compressor 11 with the exhaust gas of the exhaust heat recovery boiler 9.
is provided. To explain how this power generation system operates, when starting up the power generation system, raw fuel and combustion air are supplied to the exhaust heat recovery boiler 9 for combustion, and water is supplied through the water supply pipe 13 to generate steam. ．． This steam is steam pipe 1
4 to the steam turbine 10;
Rotate. This steam turbine 10 includes an air compressor 1
1 is connected, and this air compressor 11 supplies reaction air to an air preconditioner 12. The air preheater 12 is supplied with exhaust gas from the exhaust heat recovery boiler 9, and the supplied air exchanges heat with the exhaust gas and becomes high temperature. The preheated air is then supplied to the cathode 2 side of the fuel cell 1, raising the temperature of the fuel cell 1. When the temperature of the fuel cell 1 reaches approximately 1000°C, which is the optimum temperature for operation, fuel is supplied to the anode side and power generation begins. When power generation starts, surplus fuel (exhaust fuel) and exhaust air that are not used in the power generation reaction are generated, which are supplied to the exhaust recovery boiler 9 and used to generate steam. When the temperature increases, the amount of fuel burned in the exhaust heat recovery boiler 9 increases, and the amount of steam generated increases more than necessary. When a predetermined temperature is detected, the temperature signal is used to throttle the flow rate regulating valve 16 provided in the raw fuel pipe 6 to reduce the amount of raw fuel supplied. It is equipped with an electric power load detection system 18 that detects the load 17, and when the electric power load fluctuates (when the load decreases since normal rated operation is performed), the fuel flow rate is adjusted based on the signal from the electric power load detection system 18. The valve 19 is throttled to reduce the amount of fuel supplied to the anode 4, and the steam flow rate regulating valve 20 provided in the steam pipe 14 is throttled to reduce the rotational speed of the steam turbine 10. The amount of air supplied to the cathode 2 is reduced to maintain an appropriate amount of air supplied depending on the load.

Since the power generation system using a solid oxide fuel cell according to one embodiment of the present invention is performed as described above, the temperature of the fuel cell can be raised inexpensively and reliably at the time of startup of the power generation system, and the power generation system can withstand load fluctuations. Accordingly, appropriate fuel and air can be supplied, resulting in high total power generation efficiency. Note that it is also possible to generate electricity by rotating a generator using the exhaust gas 2L from the air preheater 12.

[Effects of the invention] According to this invention, the temperature of the fuel cell can be raised inexpensively and reliably at the time of startup of the power generation system, and appropriate fuel and air supply can be made according to load fluctuations. Power generation efficiency increases.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an apparatus for implementing a solid oxide fuel cell power generation system according to a first embodiment of the present invention.

Claims (2)

[Claims] (1) In a power generation system using a solid oxide fuel cell, an exhaust heat recovery boiler that generates steam by burning excess fuel and raw fuel that are not used in the power generation reaction of the fuel cell with combustion air; an air preheater that preheats the air supplied to the cathode side of the fuel cell using combustion exhaust gas discharged by the exhaust heat recovery boiler; and an air compressor driven by a steam turbine rotated by steam generated by the exhaust heat recovery boiler. When starting up the power generation system,
Raw fuel and combustion air are supplied to the exhaust heat recovery boiler and combusted to generate steam, and the generated steam is supplied to the steam turbine to drive the air compressor to drive the cathode side of the fuel cell. and supplying air to the air preheater, and supplying combustion exhaust gas generated in the exhaust heat recovery boiler to the air preheater to preheat the air supplied to the cathode side, thereby gradually increasing the temperature of the fuel cell. ,
A solid oxide fuel cell power generation system characterized in that after the start of power generation, the surplus fuel is used as part of the fuel for the exhaust heat recovery boiler. (2) Varying the amount of steam supplied to the steam turbine in accordance with fluctuations in the load on the fuel cell, and varying the number of revolutions of the air compressor to vary the amount of air supplied to the fuel cell,
2. The solid oxide fuel cell power generation system according to claim 1, wherein the amount of fuel supplied to the fuel cell is also varied.