JPH0650107A - Pressurized fluidized bed boiler power generation plant - Google Patents

Abstract

PURPOSE:To stably stop a plant at the time of failure in a pressurized fluidized bed boiler power generation plant and prevent overspeed of a gas turbine at the time of no-load failure. CONSTITUTION:A boiler bypass pipeline 21 is installed between air supply piping 7 from a compressor 1 to a boiler 4 and combustion gas supply piping 8 from the boiler 4 to a gas turbine 2. A gas turbine bypass pipeline 23 is installed between the confluence of the combustion gas supply piping 8 with the boiler bypass piping 21 and an inlet of the gas turbine 2. At the time of failure, air and combustion gas are flowed in the boiler bypass pipeline 21 and the gas turbine bypass pipeline 23. Consequently, by flowing of the air and combustion gas in the boiler bypass pipeline 21 and the gas turbine bypass pipeline 23, temperature at the inlet of the gas turbine 2 can be decreased without increasing a flow-rate at the inlet of the gas turbine 2 and also variation of flow velocity in the boiler 4 is decreased so as to stably stop a plant in the case of failure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressurized fluidized bed boiler power plant composed of a pressurized fluidized bed boiler, an air compressor, a gas turbine and the like, and particularly to a plant for a failure in the plant. The present invention relates to an improved pressurized fluidized bed boiler power plant capable of being safely stopped.

[0002]

2. Description of the Related Art A pressurized fluidized bed boiler power plant is under development as a coal utilization plant which should replace the conventional pulverized coal burning steam plant. In a pressurized fluidized bed boiler power plant, a fluidized medium such as lime or sand is supplied into the pressurized boiler together with granular coal having a diameter of several millimeters as a fuel, and high-pressure air is supplied thereto. Combustion and coal desulfurization take place at the same time as the flow. In order to carry out these reactions stably in the pressurized boiler, it is required to keep the fluid state in the boiler constant, and therefore the power plant is installed in the boiler so as not to change the flow velocity in the boiler. It is controlled and operated so that the ratio of the flow rate of air to be supplied (mass flow rate) and the pressure in the boiler is kept substantially constant.

In order to stop the pressurized fluidized bed boiler power generation plant due to some trouble or the like, it is necessary to stop the boiler. In the pressurized fluidized bed boiler, the fluidized bed is placed in a large pressure vessel. Since the boiler is arranged, it is not always easy to safely stop its operation, and some proposals have been made so far. For example, Japanese Patent Laid-Open No. 1-1
Japanese Patent No. 95928 discloses an example of a method of completely shutting off the air sent to the boiler and stopping the combustion, and the flow in the boiler is completely stopped only by the shutoff valve due to a valve leak, a pressure difference between the containers and the like. Since this is not possible, a method is disclosed in which, after the gas turbine and the boiler are insulated by the two shutoff valves and the one bypass valve, the hot combustion gas is released to the atmosphere by the discharge valve.

[0004]

An emergency shutoff valve is installed in the air supply pipe and the combustion gas supply pipe, the gas turbine and the boiler are shut off by the shutoff valve, and the hot combustion gas is discharged to the atmosphere by the discharge valve. The discharging method has a complicated structure, and the coal remaining in the boiler may be incompletely burned to discharge carbon monoxide, which is a harmful gas.

As a method for avoiding this, a method has been proposed in which the combustion air is gradually reduced to completely burn the coal remaining in the boiler. However, when the air is passed through the boiler and released to the outside. In order to stably burn the coal remaining in the boiler, it is necessary not to change the flow velocity as in the steady operation, and if the air flow rate is insufficient, incomplete combustion will occur and combustible Carbon oxide is generated. In addition, when the flow velocity decreases, uneven flow of air occurs in the boiler, local combustion proceeds, the combustion temperature of that part rises, coal and fluid medium melt and solidify, and melt and solidify to restart the operation. You will have to remove the coal and fluid media. On the other hand, if the air flow rate becomes excessive and the flow rate increases, coal and fluid media inside the boiler will be scattered outside the boiler and damage downstream equipment. Therefore, the method of gradually reducing the combustion air has been extremely difficult to control.

Further, when the gas turbine becomes unloaded due to some trouble, unless the flow rate of the combustion gas supplied to the gas turbine is properly controlled, the rotational speed of the turbine greatly exceeds the rated speed and there is a risk of damage. Since there is a possibility that the outlet pressure of the air compressor will rise and the air compressor will enter the surging area while existing, the gas flow rate is controlled independently or in conjunction with the boiler operation when the turbine is unloaded. A means capable of doing this was desired.

An object of the present invention is to obtain a pressurized fluidized bed boiler power generation plant that can safely stop the pressurized fluidized bed boiler power generation plant in the event of a failure. Another object of the present invention is to obtain a pressurized fluidized bed boiler power plant that does not damage the turbine even if the gas turbine becomes unloaded due to some trouble.

[0008]

[Means for Solving the Problems]
Pressurized fluidized bed boiler, compressor for supplying air to the pressurized fluidized bed boiler, gas turbine for driving the compressor by receiving combustion gas from the pressurized fluidized bed boiler, and the pressurized fluidized bed In a pressurized fluidized bed boiler power plant equipped with a generator driven by the heat source generated by the boiler, an air supply pipe that supplies compressed air from the compressor to the pressurized fluidized bed boiler and combustion from the pressurized fluidized bed boiler to a gas turbine A boiler bypass pipe line provided with a control valve for connecting to a combustion gas supply pipe for supplying gas is provided, and a control valve is further provided between a joint between the boiler bypass pipe line and the combustion gas supply pipe and the gas turbine inlet. This is achieved by providing a gas turbine bypass line provided with.

A check valve is installed at a position downstream of the joint between the air supply pipe and the boiler bypass pipe line, and means for performing heat exchange between the combustion gas supply pipe line and the gas turbine bypass pipe line is provided. Further provision, and further provision of means for performing heat exchange between the boiler bypass line and the gas turbine bypass line are particularly preferable modes for achieving the object.

[0010]

In the pressurized fluidized bed boiler power plant of the present invention, high pressure air is supplied to the boiler from the compressor through the air supply pipe during normal operation. In a boiler, coal is burned, and the burned combustion gas is supplied to a gas turbine through a combustion gas pipe, and the gas turbine generates power to drive a compressor and a generator.

When a failure occurs in the plant, the boiler bypass pipeline control valve installed in the boiler bypass pipeline is opened, and a part of the air at the compressor outlet is diverted to the boiler bypass pipeline to the combustion gas pipeline. While supplying the gas, the gas turbine bypass pipe control valve installed in the gas turbine bypass pipe is opened to discharge the combustion gas from the combustion gas pipe to the outside through the gas turbine bypass pipe.

In the prior art, an emergency shutoff valve was installed in the air supply pipe and the combustion gas supply pipe and operated. However, in the present invention, since both shutoff valves are not installed, an emergency shutoff valve is provided. It is also possible to supply air from the compressor to the boiler, and by discharging combustion gas from the boiler, the combustion of the boiler is continued without significantly changing the flow velocity in the boiler from the steady state, and It is possible to stably burn and consume the remaining coal.

That is, even in an emergency, the air from the compressor and the residual air in the pressure vessel are supplied into the boiler by flowing the air and the combustion gas into the air supply pipe and the combustion gas supply pipe, and the flow velocity in the boiler is increased. Can be secured.
Further, in the pressurized fluidized bed boiler power generation plant of the present invention, relatively low temperature air is supplied to the combustion gas pipe from the boiler bypass pipe line, and the temperature of the combustion gas decreases due to the mixing of the air and the combustion gas.

In general gas turbine characteristics, the corrected flow rate at the inlet (weight flow rate × √temperature / pressure) is constant. Therefore, as the temperature of the combustion gas decreases, the weight flow rate flowing through the turbine increases correspondingly. This means that the output of the gas turbine decreases as the temperature decreases, but increases as the weight flow rate increases, and air is passed from the boiler bypass pipe to the turbine inlet to reduce the temperature of the combustion gas. As a result, the output of the turbine decreases, but the rate of decrease decreases. For this reason, when the gas turbine generator is disconnected from the system and the load disappears, the rotation speed of the gas turbine system is rated at 11% by using only the boiler bypass pipeline.
It has been found that there are cases where it cannot be reduced within 0%.

Therefore, in the present invention, the gas turbine bypass pipe having a control valve is further installed, and a part of the combustion gas mixed with the air from the boiler bypass pipe is passed through the gas turbine as necessary. By discharging the gas to the outside of the system, the flow rate of the gas passing through the gas turbine can be reduced, the output of the gas turbine can be reduced, and the rotational speed of the gas turbine system can be suppressed within 110% of the rated value.

[0016]

EXAMPLES The present invention will now be described in more detail based on an example. FIG. 1 shows a first embodiment of a pressurized fluidized bed boiler power plant according to the present invention. The air compressor 1 is connected to the gas turbine 2 and the gas turbine generator 15,
The air supply pipe 7 is connected to the pressure vessel 3 from the outlet of the air compressor 1. A fluidized bed boiler 4 is installed inside the pressure vessel 3, and a combustion gas supply pipe 8 is connected from the outlet of the pressure vessel 3 to the inlet of the gas turbine 2. In the combustion gas supply pipe 8,
Cyclone 9, precision dedusting device 10 and gas mixing device 1
1 is installed.

An exhaust gas supply pipe 1 is provided at the outlet of the gas turbine 2.
2 is connected, the exhaust gas supply pipe 12 is connected to an exhaust heat recovery feed water heater 13, and a chimney 14 is installed at the tip thereof.
The steam system includes a steam turbine 16 and a steam turbine generator 17 connected to the steam turbine 16. In addition, a steam pipe is connected from the outlet of the steam turbine 16 to the condenser 18, and the steam pipe further passes from the condenser 18 through the deaerator 19, the feed water pump 20, and the exhaust heat recovery feed water heater 13. It is connected to a steam heat transfer tube 6 located in the fluidized bed boiler 4. The other end of the steam heat transfer tube 6 is connected to the steam turbine 1 via a steam pipe.
6 is connected.

A boiler bypass pipe 21 is branched from an air supply pipe 7 connecting the air compressor 1 and the pressure vessel 3. A control valve 22 is installed in the boiler bypass pipe 21 and the other end is It is connected to the gas mixing device 11. A gas turbine bypass pipe line 23 having a control valve 24 installed is connected to the gas mixing device 11, and the other end of the gas turbine bypass pipe line 23 supplies exhaust gas downstream of the exhaust heat recovery feed water heater 13. It is connected to the pipe 12.

A signal from the emergency controller 25 is input to the control valve 22 provided in the boiler bypass line and the control valve 24 provided in the turbine bypass line. The operation of this pressurized fluidized bed boiler power plant is as follows. The air compressor 1 compresses the atmosphere and supplies compressed air into the pressure vessel 3 through the air supply pipe 7. The air that has entered the pressure vessel 3 is supplied from the lower part of the fluidized bed boiler 4 into the fluidized bed boiler 4 to cause the fluidized medium 5 in the fluidized bed boiler 4 to flow and at the same time to burn coal, which is the fuel in the fluidized medium 5. Although not shown, a supply and discharge device for coal, fluidized medium and the like is further provided as in the known pressurized fluidized bed boiler. In the fluidized bed boiler 4, combustion heat is given to the steam heat transfer pipe 6, and combustion gas is discharged from the fluidized bed boiler 4 through the combustion gas supply pipe 8 and supplied to the cyclone 9.

In the cyclone 9, the solid particles scattered from the fluidized bed boiler 4 are separated simultaneously with the combustion gas. The precision dust removal device 10 is provided as needed for the purpose of performing more precise dust removal with a filter or the like, and the combustion gas generated from the cyclone 9 further passes through the precision dust removal device 10 to further remove impurities. To be done. By passing through such a dust collector, the combustion gas is converted into the gas turbine 2
Can be supplied to.

The combustion gas passes through the gas mixing device 11 and is supplied to the gas turbine 2 to generate power. The gas turbine 2 drives the air compressor 1 and the gas turbine generator 15, and the gas turbine generator 15 Generate electricity. The combustion exhaust gas discharged from the gas turbine 2 is the exhaust gas supply pipe 1
It is supplied to the exhaust heat recovery feed water heater 13 through 2 to heat the feed water of the steam turbine system, and then is discharged from the chimney 14 to the outside.

The feed water heated by the exhaust heat recovery feed water heater 13 is supplied to the fluidized bed boiler 4, and is heated by the fluidized medium 5 in the fluidized bed boiler 4 to become steam and become a steam turbine 16
To generate steam and drive the steam turbine generator 17 to generate electric power. The steam exiting the steam turbine 16 is condensed in a condenser 18, deaerated by extraction steam in a deaerator 19, further pressurized by a water supply pump 20, and then supplied to an exhaust heat recovery feed water heater 13.

When some trouble occurs in the power generation plant or the power transmission system, the plant promptly stops the supply of fuel (coal) to be supplied to the boiler and stops the operation so as not to leave a trouble in the next operation start. There is a need. At this time, the biggest concern is that the flow velocity in the boiler fluctuates greatly as described above, causing the fluidized medium in the boiler to scatter, and the combustion in the boiler to become non-uniform, resulting in local combustion and temperature increase. Is to rise.

Further, the load of the gas turbine generator 15 disappears and the number of revolutions of the gas turbine system exceeds 110% (general upper limit value), or the outlet pressure of the air compressor 1 becomes high and the air compressor 1 Is to enter the surging area. In the present invention, when a failure occurs in the plant, a necessary signal is input to the emergency control device 25 to install the boiler bypass pipe control valve 22 and the gas turbine bypass pipe 2 installed in the boiler bypass pipe 21 from the emergency control device 25.
A signal for opening the gas turbine bypass line control valve 24 installed in No. 3 is generated and input to each valve. When the boiler bypass pipeline control valve 22 on the boiler bypass pipeline 21 is opened, a part of the air supplied from the air supply pipeline 7 to the pressure vessel 3 passes through the boiler bypass pipeline 21 and the gas mixing device 11 In the gas mixing device 11, the gas is mixed with the high temperature combustion gas supplied from the precision dust removal device 10 through the combustion gas supply pipe 8 to become a low temperature combustion gas. This low-temperature combustion gas is supplied to the gas turbine 2, and at the same time, the turbine bypass pipeline control valve 24 is opened to flow through the gas turbine bypass pipeline 23 and be released to the outside through the gas turbine 2 bypass pipeline.

As a result, the temperature of the combustion gas at the inlet of the gas turbine 2 is lowered and the flow rate is also lowered, so that the power generated by the gas turbine 2 is lowered and the rise of the gas turbine rotation speed can be suppressed. Further, since the air supply pipe 7 and the combustion gas supply pipe 8 are not cut off, a flow rate is secured in the fluidized medium 5, and since the operation can be performed without a large change from the steady-state flow velocity, the residual coal combustion of the boiler is stably continued. You can stop driving while

For one model of the pressurized fluidized bed boiler power plant having the configuration shown in FIG. 1, the operating characteristics at the time of failure were subjected to simulation analysis using a computer. The results are shown below. FIG. 2 is a plot of the time-dependent change of the operating state of the air compressor 1 on the characteristic diagram of the air compressor 1, which is operated from the point A of 100% load, and a signal is generated in the fault 5 seconds after the start of the simulation The result is that the gas turbine generator 15 is unloaded, and the open signal is given to the boiler bypass pipeline control valve 22 and the gas turbine bypass pipeline control valve 24, and point B represents a point after 120 seconds have elapsed. It can be seen that the pressure gradually decreases and separates from the surging line, and the corrected rotation speed also temporarily increases, but decreases with time.

FIG. 3 shows the temperature T4 inside the fluidized bed boiler 4, the outlet temperature T7 of the air compressor 1, and the temperature T inside the gas mixing device 11.
11 shows the change over time. It can be seen that the temperature of the gas mixing device 11 sharply drops due to the introduction of the low-temperature air compressor 1 outlet air. FIG. 4 shows the pressure P4 in the fluidized bed boiler 4, the outlet pressure P7 of the air compressor 1, and the gas mixing device 1.
1 shows a temporal change of the internal pressure P11. Although P11 is rapidly reduced by opening the gas turbine bypass line control valve 24, air is supplied from the boiler bypass line 21 by opening the boiler bypass line control valve 22, so that the decrease is suppressed. The air compressor 1 outlet pressure P7 decreases because air flows to the boiler bypass pipe line 21, but the pressure inside the fluidized bed boiler 4 changes little because the volume of the pressure vessel 3 is large.

FIG. 5 shows the change over time in the weight flow rate of each part. G7 is the flow rate of the air supplied from the air supply pipe 7 to the pressure vessel 3, G2 is the flow rate through the gas turbine 2, and G36 is the flow rate. G21 indicates the flow rate of air flowing from the pressure vessel 3 into the fluidized bed boiler 4, G21 indicates the flow rate of air flowing through the boiler bypass pipeline 21, and G23 indicates the flow rate of combustion gas flowing through the gas turbine bypass pipeline 23. Although the flow rate of gas flowing through the gas turbine 2 is once decreased by opening the gas turbine bypass line control valve 24, the decrease is suppressed by the inflow of air in the boiler bypass line 21, and the flow rate is suppressed to a state where the flow rate is slightly higher than in the steady state. In this simulation, the maximum flow rate characteristic of the gas turbine bypass line control valve 24 is set to be the same as that of the gas turbine 2, so G2 and G23 have the same flow rate.

The change in the number of revolutions of the gas turbine system (actual number of revolutions / actual number of revolutions at the design point) is as shown in FIG. 6, which shows that an increase in the number of revolutions can be suppressed. Further, the corrected flow velocity ((weight flow rate / pressure) / (weight flow rate / pressure) design) showing the change in the flow rate in the fluidized bed boiler 4 becomes as shown in FIG. 7 and can be suppressed within about 20% increase. It is shown that.

Although it is clear that the simulation results shown here are the results under certain conditions and show different results under other conditions, as shown here, the pressurized fluidized bed boiler according to the present invention. It will be apparent that in a power plant, the plant can be stably stopped when a failure occurs. Further, it can be easily inferred that the plant can be further stabilized and stopped by optimizing the setting conditions according to the operating conditions of the actual machine.

According to the embodiment of the present invention, the air supply pipe 7 and the combustion gas supply pipe 8 which have been considered necessary in the past in an emergency.
The effect is that the plant can be shut down without installing the above expensive shutoff valve. In the above description, the boiler bypass pipeline control valve 22 installed in the boiler bypass pipeline 21 and the gas turbine bypass pipeline control valve 2 installed in the gas turbine bypass pipeline 23 from the emergency control device 25.
The example in which a signal for simultaneously opening 4 is generated and input to each valve has been described. However, the boiler bypass line control valve 22 or the gas turbine bypass line control may be performed depending on the scale of the entire plant or each component or its operating environment. It may be appropriate to send a signal to open only one of the valves 24, and furthermore it may happen that it may be appropriate to open each control valve partially. Be understood by.

Another embodiment of the present invention is shown in FIG. In the embodiment of FIG. 8, in addition to the embodiment of FIG. 1, an air check valve 30 is installed on the air supply pipe 7. In the steady state, the air from the air compressor 1 flows through the air supply pipe 7 from the air compressor 1 to the pressure vessel 3, but in an emergency, the pressure P7 at the outlet of the air compressor 1 as shown in the simulation result of FIG. And the pressure P4 of the fluidized bed boiler 4 is reduced, and it is expected that the pressure will reverse and the air will flow from the pressure vessel 3 to the air compressor 1 depending on the conditions. When this flow occurs, the pressure in the air supply pipe 7 fluctuates, and the outlet pressure of the air compressor 1 also fluctuates, so that the operation of the air compressor 1 becomes unstable.

In this embodiment, by installing the air check valve 30, there is an effect that the flow from the pressure vessel 3 to the air compressor 1 can be suppressed and the air compressor 1 can be operated stably. Another embodiment of the present invention is shown in FIG. In the embodiment of FIG. 9, in addition to the embodiment of FIG. 1, the combustion gas cooling device 3 is provided between the precision dust removing device 10 and the gas mixing device 11 of the combustion gas supply pipe 8.
1 is installed and the gas turbine bypass line 23 downstream of the gas turbine bypass line control valve 24 is connected to the combustion gas cooling device 3
Connected to 1.

From the gas mixing device 11 through the gas turbine bypass line 23, the gas turbine bypass line control valve 2
The combustion gas supplied to No. 4 has a high pressure, and this gas undergoes adiabatic expansion in the gas turbine bypass line control valve 24, and the temperature decreases as the pressure decreases. The combustion gas whose temperature has been reduced can be guided to the combustion gas cooling device 31 to cool the high temperature gas in the combustion gas supply pipe 8, the combustion gas temperature at the inlet of the gas turbine 2 is further reduced, and the rotation speed of the gas turbine system can be reduced. It has the effect of further suppressing the rise.

Another embodiment of the present invention is shown in FIG. Figure 1
In the embodiment of No. 0, the gas turbine bypass pipeline 23 is replaced with the gas turbine bypass pipeline control valve 24 of the embodiment of FIG.
A gas turbine bypass conduit control valve 32 having a heat exchanging means is installed on the top of the boiler bypass conduit 21 so that part or all of the air passing through the boiler bypass conduit 21 passes through the heat exchanging means. Although not particularly shown, a part of the air that has passed through the heat exchanger and cooled the gas turbine bypass line control valve 32 may be mixed with the gas turbine bypass line 23 as it is. According to this embodiment, since the gas turbine bypass line control valve 32 can be cooled, it is possible to reduce the amount of expensive heat-resistant material used for the gas turbine bypass line 23 and to use an inexpensive valve. There is.

[0036]

According to the present invention, in addition to being able to stably stop the pressurized fluidized bed boiler power plant at the time of a failure, it is possible to prevent the occurrence of turbine destruction and surging at the time of no-load failure of the gas turbine. You can

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an embodiment of a pressurized fluidized bed boiler power generation plant according to the present invention.

FIG. 2 is a graph showing characteristic values in one example of the present invention.

FIG. 3 is a graph showing other characteristic values in one example of the present invention.

FIG. 4 is a graph showing another characteristic value according to the embodiment of the present invention.

FIG. 5 is a graph showing another characteristic value according to an embodiment of the present invention.

FIG. 6 is a graph showing another characteristic value according to the embodiment of the present invention.

FIG. 7 is a graph showing another characteristic value according to an embodiment of the present invention.

FIG. 8 is a schematic explanatory view showing another embodiment of the pressurized fluidized bed boiler power plant according to the present invention.

FIG. 9 is a schematic explanatory view showing still another embodiment of the pressurized fluidized bed boiler power generation plant according to the present invention.

FIG. 10 is a schematic explanatory view showing still another embodiment of the pressurized fluidized bed boiler power generation plant according to the present invention.

[Explanation of symbols]

 1 ... Air compressor 2 ... Gas turbine 3 ... Pressure vessel 4 ... Fluidized bed boiler 5 ... Fluid medium 7 ... Air supply pipe 8 ... Combustion gas supply pipe 11 ... -Gas mixing device 21 ... Boiler bypass pipeline 22 ... Boiler bypass pipeline control valve 23 ... Turbine bypass pipeline 24 ... Turbine bypass pipeline control valve

Front page continuation (72) Inventor Takeshi Suzumura 3-1-1, Sachimachi, Hitachi, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Kanzo Sato 3-1-1, Sachimachi, Hitachi, Ibaraki No. Stock Company Hitachi, Ltd. Hitachi factory (72) Inventor Takashi Asao 3-2-1, Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi Engineering Co., Ltd.

Claims (4)

[Claims] 1. A pressurized fluidized bed boiler, a compressor that supplies air to the pressurized fluidized bed boiler, a gas turbine that receives combustion gas supplied from the pressurized fluidized bed boiler and drives the compressor, In a pressurized fluidized bed boiler power plant including a generator driven by a heat source generated by the pressurized fluidized bed boiler, an air supply pipe for supplying compressed air from the compressor to the pressurized fluidized bed boiler and the heating unit. A boiler bypass pipe line provided with a control valve for connecting a combustion gas supply pipe for supplying combustion gas from a pressure fluidized bed boiler to a gas turbine is provided, and a joint portion between the boiler bypass pipe line and the combustion gas supply pipe is further provided. A pressurized fluidized bed boiler power plant comprising a gas turbine bypass pipe provided with a control valve between the gas turbine inlets. 2. The pressurized fluidized bed boiler power plant according to claim 1, wherein a check valve is installed at a position downstream of a joint between the air supply pipe and the boiler bypass pipe line. 3. The pressurized fluidized bed boiler power generation according to claim 1, further comprising means for performing heat exchange between the combustion gas supply pipe and the gas turbine bypass pipe line. plant. 4. The pressurized fluidized bed boiler power plant according to claim 1, further comprising means for performing heat exchange between the boiler bypass line and the gas turbine bypass line.