JPH05190191A - Fuel cell type power generation plant - Google Patents

Abstract

PURPOSE:To improve the plant efficiency by reducing the rated discharged air quantity of a turbine compressor or the fuel flow rate to an auxiliary burner by mixing the plant exhaust gas into the auxiliary burner combustion air. CONSTITUTION:A plant exhaust gas system C is branched to a plant exhaust gas system 30 for directly feeding the plant exhaust gas 22 into an auxiliary burner 6 and a plant exhaust gas branched system 31, and a portion of the exhaust gas 22 is mixed into the auxiliary burner combustion air 27. Accordingly, the oxygen left in the exhaust gas 22 can be effectively utilized for the combustion in the auxiliary burner 6, and the rated discharged air quantity of a turbine compressor 7 can be reduced by reducing supply of fresh air into the burner 6 from a compressor 14. Accordingly, the combustion quantity in the burner 6 can be reduced, and the plant efficiency is improved.

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 generation plant, and more particularly to a fuel cell power generation plant designed to further improve plant efficiency.

[0002]

2. Description of the Related Art FIG. 7 shows a schematic flow of a conventional general fuel cell power plant.

In this fuel cell power plant, 1 is a fuel cell main body, 2 is a reformer, 3 is a high temperature carbon monoxide shift converter, 4 is a low temperature carbon monoxide shift converter, and 5 is a heat exchanger having a water separation function. , 6 are auxiliary burners, and 7 is a turbine compressor.

The fuel cell power plant is equipped with a reformed gas system A, which produces a raw material gas 10 in which natural gas 8 as a raw fuel and steam 9 are mixed at a specific ratio. The raw material gas 10 undergoes a chemical reaction while sequentially passing through a reformer 2, a high temperature carbon monoxide shift converter 3, a low temperature carbon monoxide shift converter 4, etc., and a reformed gas containing hydrogen, carbon dioxide and steam as main components. It will be 11. This reformed gas 11 is
Excess water is removed by the heat exchanger 5 having a water separation function to form the cell fuel gas 12, which is supplied to the fuel electrode 13 of the fuel cell body 1.

On the other hand, the air system B provided in the fuel cell power plant is sucked from the atmosphere by the compressor 14 of the turbine compressor 7 and compressed, and a part of the compressed air is used as the cell air 15 in the fuel cell main body. 1 is supplied to the air electrode 16 and oxygen contained in the cell air 15 and hydrogen contained in the cell fuel gas 12 chemically react with each other in the fuel cell main body 1 to generate water. Be done.

Further, the fuel cell power generation plant is provided with a plant exhaust gas system C, and the plant exhaust gas system C converts the fuel electrode exhaust gas 17 having a relatively low water content by the reaction in the fuel cell main body 1 from the fuel electrode 13. The reformer burner 21 is discharged to the reformer burner 21, while the reformer burner 21 consumes oxygen in the fuel cell main body 1 and exhausts the air electrode 18 and the turbine compressor 1.
The reformer burner air 20 mixed with the air 19 supplied from the fuel cell 4 is guided, and the anode exhaust gas 17 is mixed with the reformer burner air 20 and burned in the reformer burner 21. The heat supplies the thermal energy required for the reforming reaction in the reformer 2.

The plant exhaust gas 22 after the thermal energy is supplied to the reformer 2 in this way is still a considerably high temperature gas and is recovered as thermal energy as the power of the turbine compressor 7. It is sent to the burner 6 and mixed with the combustion gas of the auxiliary burner 6 to form the auxiliary burner exhaust gas 23 as the turbine 2 of the turbine compressor 7.
4 is supplied. The thermal energy of the auxiliary burner exhaust gas 23 is converted into mechanical energy by the turbine 24 to become the power of the compressor 14, and finally discharged outside the fuel cell power plant.

On the other hand, when the plant load of the fuel cell power plant decreases, the flow rates of the cell fuel gas 12 and the cell air 15 consumed in the fuel cell body 1 decrease, and the raw material reformed in the reformer 2 The flow rate of gas 10 also decreases. Due to this decrease in the flow rate, the thermal energy required for reforming the raw material gas 10 also decreases, so the reformer burner 21
The amount of combustion at is also reduced. Therefore, when the plant load decreases, the flow rate of the plant exhaust gas 22 and the plant exhaust gas 2
Since the heat energy of 2 also decreases, the power of the compressor 14 cannot be supplied by itself.

The thermal energy which is insufficient at this time is supplemented by burning the natural gas 25 or the fuel gas 26 obtained by branching the cell fuel gas in the auxiliary burner 6 by the auxiliary burner combustion air 27 from the compressor 14. At this time, the fuel cell body 1 and the reformer burner 21
The air in the compressor 14 becomes surplus as much as the amount of battery air 15 and air 19 supplied to the auxiliary burner 6 bypasses the fuel cell power plant as bypass air 28 and is supplied to the turbine 24. Is recovered as power.

In such a fuel cell power plant, the fuel gas 26 to the auxiliary burner 6 and the fuel electrode exhaust gas 17 to the reformer burner 21 have not yet been generated at the time of plant startup or temperature rise. 6 and the reformer burner 21 use natural gas 2 which is the raw fuel for the plant, respectively.
By burning 5 and 29, the heat energy required for temperature rise and reforming in the turbine compressor 7 and the reformer 2 is supplied.

[0011]

In the conventional fuel cell power plant, when the auxiliary gas burner 6 burns the fuel gas 26 branched from the natural gas 25 or the cell fuel gas 12, the fresh air 27 is used. I was doing this. Therefore, all the air required for combustion is supplied from the turbine compressor 7. For this reason, it was necessary to increase the rated discharge air amount of the turbine compressor 7 by the amount of air flow required, so that the driving power of the turbine compressor 7 was increased, which was an obstacle for improving the plant efficiency. It was

Further, as in the conventional fuel cell power plant, the fuel gas 2 obtained by branching the cell fuel gas 12 from which excess water has been removed in the heat exchanger 5 having a water separating function.
When 6 is burned by the auxiliary burner 6, an extra fuel gas is required by the amount of energy of the removed water, so that there is a problem that the plant efficiency is reduced accordingly.

The present invention has been made in consideration of the above-mentioned circumstances, and the thermal energy required to reduce the rated discharge air amount of the turbine compressor for supplying air to the plant or to drive the turbine compressor. An object of the present invention is to provide a fuel cell power plant in which the plant efficiency is improved by reducing the fuel flow rate to the auxiliary burner for replenishing the fuel.

[0014]

In order to achieve the above object, a fuel cell power plant according to the present invention comprises a turbine compressor driven by thermal energy of plant exhaust gas, and the turbine only by the thermal energy of this plant exhaust gas. In a fuel cell power plant comprising an auxiliary burner for replenishing the turbine compressor with insufficient thermal energy when the thermal energy required to drive the compressor cannot be covered, the plant exhaust gas is wholly or partially supplemented. A plant exhaust gas branch system for mixing with burner combustion air is provided, and an air supply means for forcibly mixing the auxiliary burner combustion air with the plant exhaust gas is provided in the plant exhaust gas branch system. You can also do so.

Further, in the same fuel cell power generation plant as described above, a reformed gas branch system for guiding the reformed gas before water separation to the auxiliary burner may be provided, or in addition to this reformed gas branch system, the plant exhaust gas branch system. It is also possible to provide a system, and it is also possible to interpose, in the same manner as described above, an air supply means for forcibly mixing the plant exhaust gas with the auxiliary burner combustion air in the plant exhaust gas branch system. ..

[0016]

According to the present invention configured as described above, by providing the plant exhaust gas branching system for mixing all or part of the plant exhaust gas with the auxiliary burner combustion air,
It is possible to positively utilize the oxygen remaining in the plant exhaust gas and effectively utilize the oxygen remaining in the plant exhaust gas for combustion in the auxiliary burner. By effectively utilizing the residual oxygen, it is possible to reduce the supply of fresh air from the turbine compressor to the auxiliary burner by an amount commensurate with this oxygen, and to reduce the rated discharge air amount of the turbine compressor. You can

Further, by providing the reformed gas branch system for guiding the reformed gas before water separation to the auxiliary burner, the reformed gas before water separation containing a considerable amount of steam is supplied to the auxiliary burner as fuel gas. As a result, the turbine compressor is used to recover energy by the amount of energy contained in the steam contained in the reformed gas (fuel gas), and the combustion amount in the auxiliary burner is converted into fuel gas. The amount of vapor contained can be reduced.

[0018]

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

FIG. 1 is a schematic flow chart showing a first embodiment of a fuel cell power generation plant according to the present invention. The same components as those of the conventional fuel cell power generation plant shown in FIG. Is omitted. Differences are as follows.

In the fuel cell power plant of this embodiment, the plant exhaust gas system C is branched into a plant exhaust gas system 30 and a plant exhaust gas branch system 31 in which the plant exhaust gas 22 is directly supplied to the auxiliary burner 6, and this plant exhaust gas branch system is used. 31 is connected to the auxiliary burner combustion air 27 on the upstream side of the auxiliary burner 6 so that a part of the plant exhaust gas 22 is mixed into the auxiliary burner combustion air 27.

The plant exhaust gas system 30 directly supplied to the auxiliary burner 6 is not always necessary, and all the plant exhaust gas 22 can be supplied to the auxiliary burner combustion air 27 through the plant exhaust gas branch system 30.

In this embodiment, by mixing a part or all of the plant exhaust gas 22 of the plant exhaust gas system C with the auxiliary burner combustion air 27, the oxygen remaining in the exhaust gas 22 is burned in the auxiliary burner 6. Can be used effectively. By effectively utilizing the oxygen remaining in the exhaust gas 22, the compressor 1 is commensurate with this oxygen.
It is possible to reduce the supply of fresh air from the auxiliary burner 6 to the rated discharge air amount of the turbine compressor 7.

As described above, by reducing the rated discharge air amount of the turbine compressor 7, the required power of the compressor 14 can also be reduced, whereby the combustion required for driving the turbine compressor 7 by the auxiliary burner 6 is reduced. The amount can be reduced to improve plant efficiency.

FIG. 2 shows a modification of the first embodiment of the fuel cell power generation plant shown in FIG. 1, in which the plant exhaust gas 22 is supplemented with the auxiliary burner combustion in the plant exhaust gas branch system 31 of the plant exhaust gas system C. A plant exhaust gas pressurizing blower 32 is interposed as an air feeding means for forcibly mixing with the working air 27.

By thus interposing the booster blower 32, when the pressure of the plant exhaust gas 22 is lower than the pressure of the auxiliary burner combustion air 27, the plant exhaust gas 22 is discharged.
Can be forcibly mixed with the auxiliary burner combustion air 27.

As shown in FIG. 3, an ejector 34 is provided in place of the booster blower 32 in FIG. 2, and the ejector effect of the ejector 34 positively attracts the plant exhaust gas 22 into the auxiliary burner combustion air 27. It is also possible to mix the plant exhaust gas 22 with the combustion air 27.

FIG. 4 is a schematic flow chart showing a second embodiment of the fuel cell power plant. In this embodiment, steam is provided upstream of the heat exchanger 5 having a water separation function of the reformed gas system A. The reformed gas branch system 34 for branching the reformed gas 11 containing a large amount and supplying it as fuel for the auxiliary burner 6 is provided.

In the case of this embodiment, the reformed gas 11 upstream of the heat exchanger 5 having a moisture separating function for removing steam is guided to the reformed gas branch system 34, and the reformed gas 11 containing a large amount of steam is introduced. Since it can be supplied to the auxiliary burner 6 as fuel, the energy contained in the steam contained in the reformed gas 11 (fuel gas) is utilized as compared with the conventional case of burning the fuel gas from which steam has been removed, It is possible to recover energy in the turbine in excess of this energy.

As described above, the reformed gas containing a large amount of steam is supplied as the fuel of the auxiliary burner 6 and the energy of the steam contained in the reformed gas (fuel gas) is excessively recovered by the turbine. By doing so, the amount of combustion in the auxiliary burner 6 can be reduced by the amount of vapor contained in the fuel gas, leading to an improvement in plant efficiency.

In addition to the branching of the reformed gas branch system 34 from the reformed gas system A immediately before the heat exchanger 5, as shown in FIG. The reformed gas branching system 3 from any desired position on either the inlet side or the outlet side of the reactor 3 or the inlet side of the low temperature carbon monoxide shift converter 4.
It is also possible to branch 5, 36, 37 or 38 and connect the branched reformed gas branch system to the auxiliary burner 6. Also in this case, the reformed gas containing a large amount of steam can be supplied to the auxiliary burner 6 as the reformed gas fuel 39.

FIG. 6 is a schematic flow chart showing a third embodiment of the fuel cell power plant. In this embodiment, the first embodiment of the fuel cell power plant shown in FIG. 1 and the second embodiment shown in FIG. This is a combination of examples.

In this fuel cell power plant, the plant exhaust gas 22 of the plant exhaust gas system C is branched into a plant exhaust gas system 30 and a plant exhaust gas branch system 31 which are directly supplied to the auxiliary burner 6, and this plant exhaust gas branch system 31 is used as an auxiliary burner. 6 is connected to the auxiliary burner combustion air 27 on the upstream side so that a part or all of the plant exhaust gas 22 is mixed into the auxiliary burner combustion air 27, and the heat exchanger 5 of the reformed gas system A is used. The reformed gas branch system 34 is connected upstream of the reformed gas branch system 34, and a part of the reformed gas 11 is guided to the reformed gas branch system 34 to be supplied as fuel for the auxiliary burner 6.

In the case of this embodiment, both the effects of the first embodiment and the effects of the second embodiment can be obtained. That is, the flow rate of the fresh air from the compressor 14 to the auxiliary burner 6 can be reduced, and the energy can be recovered by the turbine in excess of the energy of the steam contained in the reformed gas.

In this fuel cell power plant, the effects of both the first and second embodiments are summed up to obtain the auxiliary burner 6
In this case, the combustion amount required to drive the turbine compressor 7 can be significantly reduced, and the plant efficiency can be further improved.

In the embodiments of the present invention, some equipments and process flows that are not directly related to the present invention are omitted, but the equipments and process flows that should be present in a fuel cell power plant are shown. If not, it does not mean that the fuel cell power plant is not equipped with these devices. For example, in a fuel cell power plant, various heat exchangers are required for temperature control, but it is natural that these heat exchangers are provided in the fuel cell power plant.

Further, as the fuel cell power generation plant, the fuel cell power generation plant using natural gas has been described as an example, but other fuels can be replaced as they are. In the fuel cell power plant of the present invention, various fuels such as natural gas, naphtha, and methanol can be used as the plant raw fuel, and it goes without saying that the plant raw fuel is not limited to natural gas.

[0037]

Since the present invention has the above-mentioned structure,
By mixing part or all of the plant exhaust gas with the auxiliary burner combustion air on the upstream side of the auxiliary burner, the rated discharge air amount of the turbine compressor can be reduced to reduce the required power of the compressor, or the steam can be reduced. By supplying a large amount of reformed gas as fuel for the auxiliary burner, it is possible to recover the energy in the turbine in excess of the energy of the steam contained in the reformed gas, and drive the turbine compressor in the auxiliary burner. It is possible to improve the plant efficiency by reducing the amount of combustion required for the above compared to the conventional one.

[Brief description of drawings]

FIG. 1 is a schematic flow chart showing a first embodiment of a fuel cell power plant according to the present invention.

FIG. 2 is a schematic flowchart showing a modified example of FIG.

FIG. 3 is a schematic flowchart showing another modification of FIG.

FIG. 4 is a schematic flow chart showing a second embodiment of the fuel cell power plant according to the present invention.

5 is a schematic flow chart showing a modified example of FIG.

FIG. 6 is a schematic flow chart showing a third embodiment of the fuel cell power plant according to the present invention.

FIG. 7 is a schematic flow diagram showing a conventional fuel cell power plant.

[Explanation of symbols]

 1 Fuel cell main body 2 Reformer 3 High temperature carbon monoxide shifter 4 Low temperature carbon monoxide shifter 5 Heat exchanger having water separation function 6 Turbine compressor 10 Raw material gas 11 Reformed gas 12 Battery fuel gas 14 Compressor 15 Battery Air 21 Reformer burner 22 Plant exhaust gas 24 Turbine 27 Auxiliary burner combustion air 30 Plant exhaust gas system 31 Plant exhaust gas branch system 32 Booster blower (air supply means) 33 Ejector (air supply means) 34, 35, 36, 37, 38 Reformed gas branch system A Reformed gas system B Air system C Plant exhaust system

Claims (5)

[Claims] 1. A turbine compressor driven by the thermal energy of a plant exhaust gas, and a thermal energy shortage when the thermal energy required to drive the turbine compressor cannot be covered only by the thermal energy of the plant exhaust gas. In a fuel cell power plant including an auxiliary burner for supplying the turbine compressor, a fuel cell comprising a plant exhaust gas branching system for mixing all or part of the plant exhaust gas with auxiliary burner combustion air. Power plant. 2. The fuel cell power plant according to claim 1, wherein an air supply unit for forcibly mixing the auxiliary burner combustion air with the plant exhaust gas is provided in the plant exhaust gas branching system. .. 3. A turbine compressor driven by the thermal energy of the plant exhaust gas, and a thermal energy shortage when the thermal energy required to drive the turbine compressor cannot be covered by the thermal energy of the plant exhaust gas alone. In a fuel cell power plant equipped with an auxiliary burner for replenishing the turbine compressor, a reformed gas system for reforming raw fuel and supplying it to a fuel electrode of a fuel cell body is provided, while water separation of the reformed gas system is performed. A fuel cell power plant comprising a reformed gas branch system for guiding the former reformed gas to the auxiliary burner. 4. A turbine compressor driven by the thermal energy of plant exhaust gas, and a thermal energy shortage when the thermal energy required to drive the turbine compressor cannot be covered only by the thermal energy of this plant exhaust gas. In a fuel cell power plant including an auxiliary burner for replenishing the turbine compressor, a reformed gas system that reforms raw fuel and supplies it to a fuel electrode of a fuel cell main body is provided, while all or one of the plant exhaust gas is provided. A plant exhaust gas branching system that mixes a part with auxiliary burner combustion air,
A reformed gas branching system for guiding the reformed gas before water separation of the reformed gas system to the auxiliary burner, a fuel cell power plant. 5. The fuel cell power plant according to claim 4, wherein an air supply means for forcibly mixing the plant exhaust gas with the auxiliary burner combustion air is provided in the plant exhaust gas branch system. ..