JPH06212909A - Compound electric power plant - Google Patents

Abstract

PURPOSE:To reduce the charge of fuel required to obtain a specified electric energy, namely specified gas turbine output or boiler output. CONSTITUTION:In a compound electric power plant in which the exhaust gas 2 from a gas turbine 1 is fed into a boiler 3 as a combustion gas, a heat exchanger 31 for heating at least either one of the air 8 and the fuel 6 fed into a combustor 5 located at the entrance of the gas turbine, by using the heat of the boiler exhaust gas 14, is provided. Otherwise, a heat exchanger for heating at least either one of the fuel 10 and the gas turbine exhaust gas 2 fed into the boiler 3, by using the heat of the boiler exhaust gas 14 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combined cycle power plant for introducing exhaust gas from a gas turbine into a boiler as combustion air.

[0002]

2. Description of the Related Art A combined cycle power plant that puts gas turbine exhaust into a boiler as combustion air is an existing boiler
This is often done with the aim of increasing the output and increasing the efficiency of steam power plants using turbines. In this case, in the combined cycle power plant, as shown in FIG. 5, the exhaust gas 2 of the gas turbine 1 is fed into the boiler 3 as the whole or a part of the combustion air, as shown in FIG. Since the amount of passing gas increases and the temperature of the exhaust gas from the boiler rises, a stack gas cooler 4 is installed on the downstream side of the boiler 3 to recover exhaust heat.

The other components will be described below.
The gas turbine 1 is supplied with gas generated by burning the fuel 6 in the combustor 5 with the air 8 from the compressor 7, and the generator 9 is driven. Further, the fuel 10 is injected into the boiler 3, and in addition to the gas turbine exhaust 2 described above, the boiler 3 is passed through the pushing fan 11 and the air preheater 12.
It is burned by the air 13 introduced into. Then, after the combustion exhaust gas 14 passes through the superheater 15, the reheater 16 and the economizer 17, a part thereof is supplied to the stack gas cooler 4 described above, and the rest is supplied to the air preheater 12 described above. After that, the two merge and are discharged from the chimney 18 into the atmosphere.

On the other hand, the steam 19 superheated by the superheater 15 in the boiler 3 is supplied to the high-pressure turbine 20 for work, and then supplied to the reheater 16 and then reheated and then the intermediate-pressure (or low-pressure) turbine. Powered by 21 to work, generator 22
To drive. Then, the steam 19 that has finished its work in the turbine 21 is cooled by the condenser 23 to become water 24. Part of this water 24 is medium pressure (or low pressure) in the low-pressure feed water heater 25.
After being heated by the bleed air 26 from the turbine 21 and the rest being heated by the boiler exhaust gas 14 in the stack gas cooler 4 described above, they merge and are deaerated by the deaerator 27. A part of the degassed water 24 is a high pressure feed water heater 28.
Is heated by the extraction air 26 from the high-pressure turbine 20 and the rest is heated by the boiler exhaust gas 14 in the stack gas cooler 4 described above, and then combined and supplied to the economizer 17 to be heated.

[0005]

In the above-described conventional combined cycle power plant, the amount of fuel 6 injected into the combustor 5 at the inlet of the gas turbine 1 is increased in order to obtain a predetermined gas turbine output. The amount of heat that the gas turbine exhaust 2 brings into the boiler 3 also increases. Therefore, boiler exhaust gas 1
Since the heat quantity of No. 4 also increases, it is designed to be recovered by the stack gas cooler 4. In this case, in order to obtain a predetermined boiler inlet feed water temperature, the steam turbine extraction air 26 is reduced or no extraction is performed. Disappear. Then, along with the decrease in the extraction amount, the steam turbines 20, 2
The amount of swallowed steam of 1 decreases, and the steam turbine output decreases accordingly. In addition, as the steam amount at the steam turbine inlet decreases, the amount of steam 19 injected into the condenser 23 relatively increases, and the ratio of condenser loss (heat amount discarded in the condenser) increases. .

The present invention has been made in order to solve the problems of the prior art, and can reduce the amount of fuel input required to obtain a predetermined amount of power generation, that is, a predetermined gas turbine output or boiler output. Another object of the present invention is to provide a combined power generation plant that can reduce the feed water heating amount in the stack gas cooler, increase the extraction amount from the steam turbine to increase the steam turbine output, and further reduce the condenser loss. .

[0007]

In order to achieve the above-mentioned object, the present invention according to claim 1 is a combined cycle power plant in which exhaust gas of a gas turbine is injected into a boiler as combustion air. Is used to provide a heat exchanger for heating at least one of air and fuel introduced into the combustor at the inlet of the gas turbine.

Further, in order to achieve the above-mentioned object, the present invention according to claim 2 uses the exhaust gas heat of the boiler in a combined cycle power plant in which the exhaust gas of a gas turbine is introduced into a boiler as combustion air. A heat exchanger for heating at least one of fuel injected into the boiler and gas turbine exhaust is provided.

[0009]

According to the first aspect of the present invention, the combustion air and / or fuel of the gas turbine is heated (preheated) by using the heat held in the boiler exhaust gas, and then is introduced into the combustor at the gas turbine inlet. By doing so, it is possible to reduce the amount of fuel input required to obtain a predetermined gas turbine inlet gas temperature, that is, a predetermined gas turbine output, and it is possible to increase the efficiency of the gas turbine cycle.

According to the second aspect of the present invention, the gas turbine exhaust serving as the fuel and / or the combustion air of the boiler is heated (preheated) by using the heat held in the boiler exhaust gas, and then is introduced into the boiler. By doing so, it is possible to reduce the boiler fuel input amount for giving a predetermined boiler output, that is, the required amount of heat that steam or the like should obtain in the boiler, and it is possible to increase the efficiency of the steam turbine cycle.

Further, according to the present invention as defined in any one of claims 1 and 2, the heat quantity for heating the gas turbine exhaust serving as combustion air and / or fuel for the gas turbine or fuel and / or combustion air for the boiler. Is taken from the boiler exhaust gas, the temperature of the boiler exhaust gas is lowered, which reduces the amount of heat to be recovered by the stack gas cooler. Therefore, the amount of feed water heated by the stack gas cooler decreases, and it is necessary to increase the amount of bleed air from the steam turbine to compensate for this. As a result, the amount of steam extracted from the steam turbine is increased, so that the amount of steam that can be injected into the turbine is increased and the output of the steam turbine, that is, the output of the generator is increased. Furthermore, as the steam turbine extraction amount increases, the turbine outlet steam amount with respect to the turbine inlet steam amount decreases, so the loss of the condenser decreases. Further, since the amount of heat absorbed by the steam in the boiler increases due to the increase in the steam amount at the steam turbine inlet, the amount of heat discharged from the boiler decreases and the boiler efficiency also increases. From the above, the plant efficiency can be increased.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 and FIG. 2 show two different embodiments of the present invention according to claim 1, and the same parts as those shown in FIG. Omit it.

First, the embodiment shown in FIG. 1 is a gas turbine 1
In a combined cycle power plant in which the exhaust gas 2 of the above is input to the boiler 3 as combustion air, the heat of the boiler exhaust gas 14 is used,
A heat exchanger 31 is provided for heating the air 8 introduced into the combustor 5 at the inlet of the gas turbine 1.

In this embodiment, the heat exchanger 31 is a heat pipe type heat exchanger, and the heat extracted from the boiler exhaust gas 14 using the heat pipe causes air at the outlet of the compressor 7, that is, at the inlet of the gas turbine 1. Although the air 8 fed into the combustor 5 is heated, the heat exchanger of another type such as a steel pipe type in which the air 8 is directly heated by the boiler exhaust gas 14 can be used. Further, the heat transfer surface of the heat exchanger 31 on the boiler exhaust gas 14 side is provided in the duct connecting the boiler 3 and the stack gas cooler 4 in the present embodiment, but may be provided in the boiler 3.

By providing such a heat exchanger 31 to heat the air 8 introduced into the combustor 5 at the inlet of the gas turbine 1, the temperature of the combustion air 8 rises, so that the gas temperature at the predetermined gas turbine inlet is increased. That is, it is possible to reduce the input amount of the fuel 6 required to obtain a predetermined gas turbine output.

Further, since a large amount of heat of the boiler outlet exhaust gas 14 is recovered by the heat exchanger 31, the amount of heat to be recovered by the stack gas cooler 4 is reduced. Therefore, the heating of the feed water 24 to obtain the predetermined boiler inlet feed water temperature is performed by the high pressure feed water heater 28 and the low pressure feed water heater 25 using the extraction air 26 of the high pressure turbine 20 and the intermediate pressure turbine 21. Therefore, as compared with the case of the conventional example shown in FIG. 5, the extraction air 26 from the steam turbines 20 and 21 is increased, and the amount of steam that can be swallowed by the turbine is increased accordingly.
Steam turbine output increases. Further, as the steam turbine inlet steam amount and the turbine extraction amount increase, the condenser 23
The amount of steam 19 injected into the device relatively decreases, and the rate of condenser loss decreases. Furthermore, since the amount of heat absorbed by the steam 19 in the boiler 3 increases due to the increase in the amount of steam at the steam turbine inlet, the amount of heat discharged from the boiler decreases and the boiler efficiency also increases.

Next, in the embodiment shown in FIG. 2, in the combined power generation plant in which the exhaust gas 2 of the gas turbine 1 is injected into the boiler 3 as combustion air, the heat of the boiler exhaust gas 14 is used to perform combustion at the inlet of the gas turbine 1. Fuel 6 thrown into vessel 5
A heat exchanger that heats the gas turbine, in this embodiment, a heat pipe type heat exchanger 32 is provided to heat the gas turbine fuel 6. Therefore, according to this embodiment, the same operational effect as that of the embodiment shown in FIG. 1 can be obtained.

Although not shown, the two embodiments shown in FIGS. 1 and 2 are combined to heat both the air 8 and the fuel 3 introduced into the combustor 5 at the inlet of the gas turbine 1 with a heat exchanger. Even if it does so, the same effect as described above can be obtained.

Next, FIGS. 3 and 4 show two different embodiments of the present invention according to claim 2, and the same parts as those shown in FIG. The description will be omitted.

First, the embodiment shown in FIG. 3 is a gas turbine 1.
In a combined cycle power plant in which the exhaust gas 2 of the above is input to the boiler 3 as combustion air, the heat of the boiler exhaust gas 14 is used,
A heat exchanger for heating the fuel 10 charged into the boiler 3, that is, a heat pipe type heat exchanger 33 in this embodiment is provided.

By heating the boiler fuel 10 with the boiler exhaust gas 14 by providing such a heat exchanger 33, the temperature of the fuel 10 charged into the boiler 3 rises, so that a predetermined boiler output, that is, a predetermined boiler output is obtained. The input amount of the fuel 10 required to obtain the heat input to the boiler is reduced. Further, since the amount of heat to be recovered by the stack gas cooler 4 is also reduced, it is possible to obtain the same effect as that of the embodiment shown in FIG.

Next, in the embodiment shown in FIG. 4, in a combined power plant in which the exhaust gas 2 of the gas turbine 1 is injected into the boiler 3 as combustion air, the heat of the boiler exhaust gas 14 is used to supply the combustion air to the boiler 3. A heat exchanger for heating the gas turbine exhaust 2 that is input as the heat exchanger, in this embodiment, a heat pipe type heat exchanger 34 is provided.

The boiler 3 is provided with such a heat exchanger 34.
By heating the gas turbine exhaust 2 that is input as combustion air to the boiler exhaust gas 14, the temperature of the combustion air that is input to the boiler 3 rises. Therefore, as in the embodiment shown in FIG. The boiler output, that is, the input amount of the fuel 10 required to obtain a predetermined boiler heat input is reduced. Further, since the amount of heat to be recovered by the stack gas cooler 4 is also reduced, it is possible to obtain the same effect as that of the embodiment shown in FIG.

[0025]

As described above, according to the first aspect of the present invention, the combustion air and / or the fuel of the gas turbine is heated by using the heat of the boiler exhaust gas, and then the gas turbine inlet is used. By injecting the gas into the combustor, it is possible to reduce the fuel injection amount required to obtain a predetermined gas turbine inlet gas temperature, that is, a predetermined gas turbine output, and it is possible to increase the efficiency of the gas turbine cycle. .

According to the second aspect of the present invention, by heating the gas turbine exhaust serving as the fuel and / or the combustion air of the boiler by using the heat held in the boiler exhaust gas, it is introduced into the boiler. It is possible to reduce the boiler fuel input amount for giving a predetermined boiler output, that is, the required amount of heat that steam or the like should obtain in the boiler, and it is possible to increase the efficiency of the steam turbine cycle.

Further, according to the present invention as set forth in any one of claims 1 and 2, the amount of steam that can be injected into the steam turbine is increased due to an increase in the steam turbine extraction amount, the steam turbine output is increased, and the condenser loss is increased. The rate can be reduced and the efficiency of the steam turbine cycle can be increased.

As described above, according to the present invention, it is possible to increase the efficiency of the combined power generation plant and increase the plant output, and it is possible to reduce the amount of fuel used to obtain a predetermined amount of power generation.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a combined cycle power plant according to the present invention according to claim 1.

FIG. 2 is a system diagram showing another embodiment of the combined cycle power plant according to the present invention as defined in claim 1;

FIG. 3 is a system diagram showing an embodiment of a combined cycle power plant according to the present invention as set forth in claim 2.

FIG. 4 is a system diagram showing another embodiment of the combined power generation plant according to the present invention as defined in claim 2;

FIG. 5 is a system diagram showing a conventional combined cycle power plant.

[Explanation of symbols]

 1 Gas Turbine 2 Exhaust 3 Boiler 5 Combustor 6 Fuel 7 Compressor 8 Air 10 Fuel 14 Exhaust Gas 31 Heat Exchanger 32 Heat Exchanger 33 Heat Exchanger 34 Heat Exchanger

Claims (2)

[Claims] 1. In a combined cycle power plant in which exhaust gas of a gas turbine is supplied to a boiler as combustion air, the exhaust gas heat of the boiler is used to heat at least one of air and fuel injected into a combustor at the gas turbine inlet. A combined cycle power plant having a heat exchanger that operates. 2. A heat exchange for heating at least one of fuel injected into a boiler and gas turbine exhaust by using exhaust gas heat of the boiler in a combined cycle power plant that inputs the exhaust of a gas turbine to a boiler as combustion air. Combined power plant characterized by having a power supply.