JPH0317350B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a turbo compressor system that is incorporated into a fuel cell power generation system.

(b) Conventional technology Fuel cell power generation systems can achieve higher thermal efficiency than steam power generation systems that use oil, coal, etc. as fuel, and are also environmentally friendly and have flexibility in terms of location. are doing. Therefore, in recent years, not only power supplies for special purposes such as space exploration, but also
Various uses are being considered for use as a commercial power source for installation in buildings, etc., and development is intensifying with the aim of putting it into practical use.

A fuel cell power generation system consists of a fuel cell that has an electrolyte layer interposed between an air electrode and a hydrogen electrode, and a hydrocarbon fuel such as natural gas that is reformed to supply hydrogen gas as fuel to the hydrogen electrode. A reformer for supplying air, and an air supply means for supplying air to the air electrode and the reformer. The performance of the fuel cell tends to improve as the pressure of each reaction gas increases. Therefore, the operating pressure of each of the reaction gases is set to a value of about 3 to 6 kg/cm ² g, for example. At this time, compressing the air requires a large amount of power, amounting to about 20% of the energy generated by the battery. On the other hand, the reforming reaction for producing fuel gas for the battery is carried out at a high temperature of about 800° C., and high temperature exhaust gas is discharged from the reformer. Therefore, if the exhaust gas energy of a power system for compressing air can be calculated, it will have a significant effect on improving the efficiency of the system.

Under these circumstances, in recent fuel cell power generation systems, it has become common to employ a turbo compressor as the air supply means. That is,
The turbo compressor has a compressor interposed in an air supply line connected to the air electrode of the fuel cell and the inlet of the reformer, and a turbine installed in the exhaust line connected to the air electrode and the outlet of the reformer. The turbine is used to drive the compressor so that the supplied air pressure is approximately constant, and the energy contained in the exhaust gas, etc. is recovered by the turbine and used for the work of compressing the air. This aims to improve system efficiency.

Incidentally, relatively small fuel cell power generation systems that are installed individually in buildings and the like have a characteristic in that their power demand changes significantly during specific time periods such as lunch breaks. Therefore, in such systems, there is a desire to be able to vary the amount of air supplied to the fuel cell and the reformer over a wide range, for example, from about 25% to 100%. However, on the other hand, there is a desire to maintain the pressure of the air supplied to the fuel cell at a relatively high constant value in view of the performance of the cell and the control of the fuel cell system. Therefore, simply applying a normal turbo compressor to compress air in a fuel cell cannot satisfy the above requirements because of its limited characteristics. In other words, the turbo compressor used in such a system must have a variable turbine nozzle to control the discharge pressure of the compressor so that it always exhibits a substantially constant value.
If the flow rate is reduced while the discharge pressure of the compressor is held constant, the compressor will cause surging and the operation will become unstable.
In extreme cases, the compressor may be damaged. In other words, when the preset discharge pressure is high, the operating conditions of the compressor easily enter the surging generation region A shown by diagonal lines in Fig. 1 when the flow rate is low, resulting in normal supply air compression. It becomes difficult to run a business.
Therefore, it is difficult to vary the air flow rate supplied to the fuel cell over a wide range of 25% to 100% with just this type of device.

(C) Purpose The present invention has been made in view of the above circumstances, and is designed to freely control the flow rate of air supplied to the compressor over a wide range while maintaining the discharge pressure at a constant value. The present invention provides a turbo compressor system for fuel cell power generation that does not cause inconveniences such as surging even when the power is used, and can therefore be suitably adopted for fuel cell power generation systems used under conditions where power demand varies widely. The purpose is to provide.

(D) Structure In order to achieve the above object, the present invention provides an air supply line compressor connected to the air electrode of the fuel cell and the inlet of the reformer, and also provides a compressor connected to the air electrode and the outlet of the reformer. In a turbo compressor system for fuel cell power generation, a variable nozzle type turbine is interposed in an exhaust system path connected to the compressor, and the turbine drives the compressor so that the supplied air pressure is approximately constant. The outlet of the turbine and the inlet are communicated via a bypass line, and the bypass line is provided with a flow control valve that is opened in an operating region where the amount of air supplied to the fuel cell and the reformer is small; It is characterized by being equipped with a flow control valve and an auxiliary combustion furnace.

(e) Examples Examples of the present invention will be described below with reference to the drawings.

Embodiment 1 (FIG. 2) FIG. 2 shows the turbo compressor system for fuel cell power generation, in which 1 is a fuel cell, 2 is a reformer, and 3 is a turbo compressor. fuel cell 1
As schematically shown in the drawing, a hydrogen electrode 6 has a hydrogen chamber 5 formed on one side of a porous electrode 4, and an air electrode has an air chamber 8 formed on one side of a porous electrode 7. 9, an electrolyte 11 is interposed between the hydrogen chamber 5 and the hydrogen chamber 5, so that power can be generated by sequentially supplying hydrogen gas as fuel to the hydrogen chamber 5 and compressed air to the air chamber 8. It's summery. The reformer 2 is configured to reform a hydrocarbon fuel such as natural gas to generate hydrogen gas, and to sequentially supply this hydrogen gas to the hydrogen electrode 6 of the fuel cell 1. Fuel and compressed air are introduced through the inlet 2a, and high-temperature exhaust gas is discharged through the exhaust port 2b. Further, the turbo compressor 3 connects the compressor 12 to the variable nozzle 1.
It is designed to be driven by a turbine 14 having a turbine 3. The compressor 12 is interposed in the middle of an air supply line 15 whose starting end is open to the atmosphere and whose terminal end is connected to the inlet 8a of the air chamber 8 of the fuel cell and the inlet 2a of the reformer 2. The turbine 14 is interposed in the middle of an exhaust line 16 which is connected to the outlet 8b of the air quality 8 and the outlet 2b of the reformed gas 2 and whose terminal end is open to the atmosphere. Further, the outlet of the compressor 12 and the inlet of the turbine 14 are communicated via a bypass line 17, and a flow rate regulating valve 18 is interposed in the bypass line 17. This flow rate control valve 18 is
It is designed to open in an operating region where the amount of air supplied to the fuel cell 1 and the reformer 2 is small, and for example, the flow rate of air flowing through the air supply line 15 and the rotation speed of the turbo compressor are input. Opening/closing is controlled by an actuator (not shown) that operates as a signal.

Note that 20 and 21 are flow rate control valves for adjusting the amount of air supplied to the fuel cell 1 and the reformer 2.

With such a configuration, the turbine 14 is operated by excess air at the air electrode outlet of the fuel cell 1 and the exhaust gas from the reformer 2, and the compressor 12
is driven. As a result, the air flowing through the feed system path 15 is compressed to a required pressure, and is sequentially supplied to the air chamber 8 of the fuel cell 1 and the reformer 2 to generate electricity. In this system, by adjusting the opening degree of the variable nozzle 13 of the turbine 14, the pressure of the compressed air discharged from the compressor 12 is kept constant, and the fuel cell 1 and the reformer 2 can be controlled within a range of, for example, about 25% to 100%, making it possible to respond to a wide range of changes in power demand. In carrying out such control, if the operating conditions of the compressor 12 fall into the surging occurrence region A shown in FIG. 1, the flow control valve 18 is opened appropriately. As a result, a portion of the air discharged from the compressor 12 is guided to the turbine side through the bypass line 17. Therefore, the flow rate of air passing through the compressor 12 increases, and the operating conditions of the compressor 12 are returned to the normal operating region B on the right side of the surge line 1, thereby effectively preventing the occurrence of surging. Therefore, if it is like this,
It is possible to easily respond to a wide range of changes in power demand without causing instability in operation or damage to the compressor.

Embodiment 2 (FIG. 3) In a system similar to that of Embodiment 1 described above (the same symbols are attached to the same or corresponding parts and the explanation is omitted), an auxiliary combustion furnace 22 is provided in the middle of the bypass line 17. It is set up. The auxiliary combustion furnace 22 burns fuel sequentially supplied from the outside to add heat energy to the air flowing through the bypass line 17.

If it has such a configuration, the above-mentioned Example 1
Not only can you obtain the same effect as the auxiliary combustion furnace 2.
2 has the advantage of being able to compensate for the lack of output of the turbine 14 and ensuring stable operation. In other words, when the demand for electricity suddenly increases and the temperature of the reformer etc. does not rise in time, resulting in a temporary shortage of turbine power, or due to the characteristics of the turbo compressor, or when there is always a shortage of turbine power in the operating range. By supplying fuel to the auxiliary combustion furnace 22 and adding heat energy to the air flowing through the bypass system, it is possible to compensate for the lack of power, and it is possible to ensure proper operation over a wide range of operation.

It goes without saying that the means for opening and closing the flow control valve of the bypass system is not limited to the one described above, and various modifications can be made without departing from the spirit of the present invention.

(F) Effect Since the present invention has the above-described configuration, even if the flow rate of air supplied to the compressor is freely controlled over a wide range while maintaining the discharge pressure at a constant value, surging etc. will not occur. It is possible to provide a turbo compressor system for fuel cell power generation that does not cause any inconvenience, and can therefore be suitably adopted in fuel cell power generation systems used under conditions where power demand varies widely. be.

[Brief explanation of the drawing]

FIG. 1 is a characteristic explanatory diagram showing the characteristics of a compressor, FIG. 2 is a system explanatory diagram showing one embodiment of the present invention, and FIG. 3 is a system explanatory diagram showing another embodiment of the present invention. 1... Fuel cell, 2... Reformer, 3... Turbo compressor, 9... Air electrode, 12... Compressor, 13... Variable nozzle, 14... Turbine,
17...Bypass system line, 18...Flow rate control valve, 2
2... auxiliary combustion furnace.

Claims (1)

[Claims] 1. A compressor is interposed in the air supply line connected to the air electrode of the fuel cell and the inlet of the reformer, and a compressor is installed in the exhaust line connected to the air electrode and the outlet of the reformer. In a turbo compressor system for fuel cell power generation in which a nozzle-type turbine is provided and the turbine drives the compressor so that the supplied air pressure is substantially constant, an outlet of the compressor and an inlet of the turbine are connected. A turbo for fuel cell power generation, characterized in that the bypass system is provided with a flow control valve that opens in an operating region where the amount of air supplied to the fuel cell and the reformer is small. compressor system. 2 A compressor is interposed in the air supply line connected to the air electrode of the fuel cell and the inlet of the reformer, and a variable nozzle type turbine is interposed in the exhaust line connected to the air electrode and the outlet of the reformer. In a turbo compressor system for fuel cell power generation, the compressor is driven by the turbine so that the supplied air pressure is substantially constant, and the outlet of the compressor and the inlet of the turbine are connected via a bypass line. a flow control valve that is opened in an operating region where the amount of air supplied to the fuel cell and the reformer is small; and a reheating furnace that imparts thermal energy to the air flowing through the bypass system. A turbo compressor system for fuel cell power generation, characterized by being provided with.