JPH0658501A - Pressurized fluidized bed boiler and operation method thereof - Google Patents

Abstract

PURPOSE:To provide a fluidized bed boiler capable of easily controlling a load and a method thereof. CONSTITUTION:A plurality of air dispersing members 2a-2d are disposed at a predetermined interval in the direction of the height of a fluidized bed, and a group of heat transfer pipes 6a-6c are disposed between adjacent air dispersing members 2a-2d, and further fuel supply nozzles 4a-4d are provided upwardly of the respective air dispersing members 2a-2d and at locations in the fluidized layer 103. Upon an increase of a load rate, an air supply location is moved from the uppermost stage to lower stage locations of the air dispersing members 2a-2d in succession without changing the height of the fluidized layer surface 10 and in conformity with the increase of the load rate, and a fluid medium 100 existent at the upper portions of the air dispersing members 2a-2d is fluidized stepwise to substantially increase a heat transfer area of the group of the heat transfer pipes 6a-6c contributing to vapor production. Additionally thereto, a fuel supporting location is also moved from the uppermost stage to lower stage locations of the fuel supply nozzles 4a-4d in succession to increase the amount of fuel supply in conformity with increases of the heat transfer area and the amount of heat absorption. Temperature of fuel gas is prevented from being lowered even upon a decrease of the load, and hence a pressurized container 101 is prevented from being excessively large-sized for accommodation of a fluidized medium tank.

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, and more particularly, it is used in a combined cycle power plant for burning coal in a pressurized fluidized bed combustion furnace to drive a steam turbine and a gas turbine to obtain electric power. In a pressurized fluidized bed boiler, a pressurized fluidized bed boiler whose load is easily controlled and an operating method thereof are provided.

[0002]

2. Description of the Related Art Due to the demand for higher efficiency of coal-fired power plants, the development of a pressurized fluidized bed boiler combined cycle power plant capable of not only conventional steam turbine power generation but also gas turbine power generation has been promoted. ing. FIG. 2 shows a conventional pressurized fluidized bed boiler.
A fluidized bed combustion furnace 102 is housed in a pressure vessel 101 pressurized to a predetermined pressure up to about kg / cm ² g, and the fluidized bed combustion furnace 102 mainly contains limestone particles as a desulfurizing agent. The fluidized medium 100 is filled. This fluid medium 1
00 is fluidized by the combustion air 31 supplied from the air disperser 2 provided at the bottom of the furnace to form the fluidized bed 103.

The coal particles of the fuel 104 are fed to the fuel supply nozzle 4
Is blown into the fluidized bed 103 from the above and is burned in the fluidized bed 103 by the above-mentioned combustion air 31. Fluidized bed 103
A heat transfer tube group 6 is arranged in almost the entire area inside, and combustion heat of coal is removed by heating the boiler feed water 106 and generation of steam through the heat transfer tube group 6. As a result, the fluidized bed 103 is maintained at a predetermined temperature, typically 860 ° C.

The generated steam 105 is supplied to a steam turbine (not shown) to obtain electric power. On the other hand, the combustion gas 32 from the fluidized bed combustion furnace 102 passes through the space above the fluidized bed 103, a so-called freeboard 107, and is discharged from the outlet of the fluidized bed combustion furnace 102 to remove the dust 109 by the cyclone 108. After dedusting, it is supplied to a gas turbine (not shown) to obtain electric power.

As described above, the control of the steam generation amount, that is, the electric power generation amount in the conventional pressurized fluidized bed boiler has been performed as follows. For example, the method disclosed in Japanese Unexamined Patent Publication No. 1-217108 will be described with reference to the boiler shown in FIG. 2. As the supply amount of the fuel 104 changes, the bed height of the fluidized bed 103 is raised and lowered and immersed in the fluidized bed 103. The heat transfer area of the heat transfer tube group 6 is changed. Fluidized bed 10
The operation of raising and lowering the bed height of 3 is performed by the fluidized medium 1 from the fluidized bed 103.
00 is withdrawn and re-supplied. Therefore, in the pressurized container 101, a separate fluid medium tank 110 is installed.
Is provided and the fluid medium 100 in the fluidized bed 103 is withdrawn and re-supplied through the extraction conduit 111 and the supply conduit 112.

When the load is reduced in the prior art, the fluidized medium 100 is moved from the fluidized bed 103 to the fluidized medium tank 110.
However, the heat transfer tube group 6 immersed in the fluidized bed 103 due to the decrease in the bed height of the fluidized bed 103 is partially removed from the freeboard 10.
Exposed to 7. As a result, the combustion gas 32 released at 860 ° C., which is the same as the temperature of the fluidized bed 103, becomes freeboard 10.
The heat transfer tube group 6 exposed at 7 cools and the temperature decreases. Therefore, the temperature of the inlet gas of a gas turbine (not shown) arranged at the outlet of the fluidized bed combustion furnace 102 is lowered, and the output of the gas turbine is lowered to lower the power generation efficiency as the pressurized fluidized bed boiler combined cycle power plant. .

On the contrary, when the load is increased, the fluid medium 100 in the fluid medium tank 110 is supplied from the fluid medium tank 110 to the fluidized bed 103 through the feed conduit 112, and the fluidized bed 1
Increase the bed height of 03. By increasing the bed height of the fluidized bed 103, the heat transfer tube group 6 exposed on the freeboard 107 is immersed in the fluidized medium 100. As a result, the fluidized medium 1 at 860 ° C. which is the same as the temperature of the fluidized bed 103
00 and the heat transfer tube group 6 have a large contact area, and steam 1
05 can also be increased to increase the load.

On the other hand, as a method for changing the load in a normal pressure fluidized bed boiler, there is a method described in Japanese Patent Publication No. 1-28585. In this method, in a fluidized bed boiler having a heat transfer tube and a plurality of vertically arranged air dispersers in the fluidized bed, and a fuel supply conduit provided on the side wall above the fluidized bed surface, the height of the fluidized bed is changed. Instead, the vertical air introduction height of the air disperser is changed according to the load, and the contact area between the fluid medium and the heat transfer tube group in a substantially flowing state is changed to change the load.

[0009]

[Patent Document 1] Japanese Laid-Open Patent Publication No. 1-21 which employs the above-described load control method by changing the bed height of the fluidized bed 103.
Although the method described in Japanese Patent No. 17108 realizes a smooth load change, it has the following problems. That is, the fluidized medium 100 is withdrawn from the fluidized bed combustion furnace 102 to the fluidized medium tank 110 to reduce the load, and the bed height of the fluidized bed 103 is reduced. The heat transfer tube group 6 arranged on the upper part of the additional unit 103 is exposed to the freeboard 107. as a result,
The combustion gas 32 released at 860 ° C., which is the same as the temperature of the fluidized bed 103, is cooled by the exposed heat transfer tube group 6 and the temperature is lowered. As a result, the gas temperature at the inlet of the gas turbine is lowered, the output of the gas turbine is lowered, and the power generation efficiency of the pressurized fluidized bed boiler combined cycle power plant is lowered.

Further, since the fluidized medium tank 110 is required, the pressure vessel 101 for accommodating the fluidized medium tank 110 becomes large, and a large number of man-hours are required for its production and inspection. On the other hand
When the load changing method in the atmospheric fluidized bed boiler described in Japanese Patent No. 28285 is directly applied to the pressurized fluidized bed boiler,
Since coal is supplied in the form of a mixed slurry of coal and water, which is a preferable form of supply to the pressurized fluidized bed boiler, part of the water content in the slurry evaporates in the freeboard section on the fluidized bed surface and burns due to its latent heat. Reduce gas temperature. Therefore, even if the coal is supplied by compressed air in the air flow method, unless the pressurized air for transportation is heated to the freeboard temperature, the combustion gas temperature is similarly lowered, and as a result, the gas turbine inlet gas temperature is reduced. Will lower it.

Further, since coal is supplied from the fuel supply conduit provided above the fluidized bed surface, it is discharged from the coal fine powder and coal discharged outside the furnace while riding on the upward flow of the combustion gas. The proportion of volatile components increases, which lowers combustion efficiency. Further, they increase the load of the dust removing equipment provided at the gas turbine inlet.

The object of the present invention is the above-mentioned drawbacks of the prior art, that is, the temperature of the combustion gas is reduced when the load is reduced, and the pressurized container is excessively large to accommodate the fluidized medium tank.
Another object of the present invention is to provide a pressurized fluidized bed boiler with easy load control and an operating method thereof, excluding the problem of reduction in combustion efficiency.

[0013]

The above object of the present invention is achieved by the following constitutions. That is, in a pressurized fluidized bed boiler in which a plurality of air dispersers are arranged at predetermined intervals in the height direction of the fluidized bed, and a heat transfer tube group is further arranged between the air dispersers, each air disperser Above, and a pressurized fluidized bed boiler provided with fuel supply nozzles at a position in the fluidized bed, or a plurality of air dispersers are arranged at predetermined intervals in the heightwise direction of the fluidized bed. In a pressurized fluidized bed boiler in which a heat transfer tube group is arranged between air dispersers, the height of the fuel supply position is limited to within the fluidized bed, and the height of the dispersed air supply position for fluidized bed fluidization and the fuel supply position This is a method of operating a pressurized fluidized bed boiler that responds to load changes by changing the height.

Here, at least one of the installation intervals and the number of arrangements of the respective air dispersers and fuel supply nozzles is determined by the desired change interval and the number of change steps of the load factor. Further, the upper surface of the fluidized bed is set at a position at least 0.5 m above the uppermost fuel supply nozzle, and the fluidized bed between the uppermost air disperser and the fluidized bed surface is an area for starting and raising the temperature. Yes No heat transfer tube group is installed.

Further, in order to prevent the medium particles to be fluidized by the air from the air disperser at the lower position from being obstructed by the air disperser at the upper position, the air disperser has a pipe grid type and is disposed between the upper and lower parts of the disperser. It is preferable to use an air disperser in which particles can easily flow. Further, the supply method of fuel such as coal is not limited to the air flow transfer method using pressurized air or the pump supply method using slurry.

[0016]

In the above fluidized bed combustion furnace of the present invention, when the load factor is increased, the height of the fluidized bed surface is not changed,
In order to increase the load factor, the air supply position is sequentially moved from the uppermost stage to the air disperser at the lower stage position, and the fluidized medium existing in the upper part of the air disperser is fluidized stepwise to form a fluidized layer. To increase the heat transfer area of the heat transfer tube group that is inside and substantially contributes to steam generation. Further, as the air supply position moves, the fuel supply position also sequentially moves from the uppermost stage to the lower position fuel supply nozzle. The fuel supply amount is increased in proportion to the increase in the heat transfer area and the heat absorption amount.

On the contrary, when air and coal are supplied from the air disperser and the fuel supply nozzle in the lowermost stage and the load factor is gradually reduced from the combustion state with a load factor of 100%, the lowermost stage is sequentially moved to the upper stage position. The air disperser and the fuel supply port used for the thing are moved, fluidization of a lower area | region is stopped, and the heat transfer area of a combustion area and the heat transfer tube group which is working substantially is reduced.

As described above, the present invention copes with a change in load by raising or lowering the supply height of combustion air and the fuel supply height without changing the fluidized bed height. In this way, since the bed height of the fluidized bed is not changed, the heat transfer tube group immersed in the fluidized medium is not exposed to the freeboard, and further, since fuel is not supplied to the freeboard, neither moisture nor transport air is supplied. Therefore, the temperature of the combustion gas released from the fluidized bed does not drop on the freeboard.

Therefore, the gas temperature at the gas turbine inlet, which is a typical application example of the pressurized fluidized bed boiler of the present invention, becomes high, and the output of the gas turbine is not reduced. Further, since it is not necessary to change the amount of the fluid medium in the fluidized bed, a separate fluid medium tank for storing and re-supplying the fluid medium can be omitted or its capacity can be reduced.

[0020]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows a pressurized fluidized bed boiler according to an embodiment of the present invention, in which a fluidized bed combustion furnace 102 and a cyclone 108 are housed in a pressure vessel 101 pressurized to a predetermined pressure, and a fluidized bed combustion furnace 102 is provided. A fluidized medium 100 mainly composed of limestone particles as a desulfurizing agent is filled therein to form a fluidized bed 103. In addition, the fluidized bed combustion furnace 102 has a plurality of stages of air dispersers 2 a to 2 in the bottom portion thereof and in the height direction of the fluidized bed 103.
d, fuel supply nozzles 4a to 4d are provided. One end of each of the air dispersers 2a to 2d is in the pressure vessel 101.
Air valves 3a to 3d that can be opened are connected to the respective air valves.

Each of the air dispersers 2a-2d is itself
Also, a type that does not hinder the upward and downward flow of the fluidized medium 100 particles that are fluidized by the air that rises from the lower air disperser 2 is used. The air dispersers 2a to 2d of this embodiment adopt a pipe grid type that satisfies the above conditions. Fuel supply nozzles 4a to 4d are provided above the dispersers 2a to 2d in a pair with the air dispersers 2a to 2d, penetrating through the combustion furnace wall, and each fuel supply nozzle 4 has a switching valve 5a to. 5c is connected to a fuel supply conduit to supply coal of fuel 104. Further, in order to facilitate the supply of coal to the pressurized condition, a pumping system using a mixed slurry of coal and water is adopted in this embodiment. At this time, particles of dolomite or limestone as an in-furnace desulfurizing agent are added to the above-mentioned coal / water mixed slurry and supplied. In addition,
The initially filled fluid medium 100 is fed from a media hopper 115 through conduit 116.

Heat transfer tube groups 6a to 6c are installed in the regions between the air distributors 2a to 2d, respectively, and the feed water 106 introduced into the lowermost heat transfer tube group 6a receives heat transfer tube groups 6b and 6b.
The steam 105 is generated through 6c. Further, the furnace bottom 9 below the lowermost air disperser 2a is appropriately reduced in cross section to become the discharge conduit 7 for the fluidized medium 100. The discharge conduit 7 is provided with a discharge mechanism 8 for the fluidized medium 100. Also,
The top of the fluidized bed combustion furnace 102 has a discharge conduit for the combustion gas 32 and is connected to a cyclone 108.

The space above the fluidized bed surface 10 in the fluidized bed combustion furnace 102 is called a freeboard 107, and the combustion gas 32 released from the fluidized bed 103 moves up the freeboard 107 and is introduced into the cyclone 108. Cyclone 108
The dust 109 is discharged to the outside of the pressure vessel 101, and the cyclone 108 on the side opposite to the outlet of the dust 109.
Although not shown, a precision dust remover and a gas turbine are connected downstream of the outlet of the exhaust gas, and the combustion gas 32 from which dust has been removed is introduced into the gas turbine (not shown). Around the flow path of the combustion gas 32 discharged from the cyclone 108 is an introduction path for the combustion air 31 introduced into the pressure vessel 101, and the combustion air 3 introduced into the pressure vessel 101 from here.
1 is supplied to the fluidized bed combustion furnace 102 through the air valves 3a to 3d and the air dispersers 2a to 2d, respectively.

A fluidized medium 100 is placed in the fluidized bed combustion furnace 102.
However, the fluidized medium 100 covers the uppermost air disperser 2d and the fuel supply nozzle 4d, and the fluidized bed surface 10 is positioned 0.5 m or more above the uppermost fuel supply nozzle 4d. The fluidized medium 100 is filled. The upper area of the air dispersion plate 2d is the fluidized bed area at startup,
The height of the fluidized bed 103 which is 0.5 m or more above the fuel supply nozzle 4d is a height required to prevent the coal supplied from the nozzle 4d from blowing through the freeboard 107 without being burned. Further, a startup burner 11 is installed right above the uppermost air disperser 2d so as to penetrate through the wall of the combustion furnace 102, and a high temperature combustion gas is supplied to the fluidized bed 10 to raise the temperature at startup.
It is designed to be supplied within 3. The burner 11 is provided between the uppermost air disperser 2d and the uppermost air valve 3d so as to pass the high temperature gas through the air disperser 2d in the fluidized bed 103.
You may make it supply inside.

In the pressurized fluidized bed boiler having the above structure, first, the fluidized bed combustion furnace 102 is started, that is, the fluidized bed 1
The temperature of 03 is raised from the upper region of the uppermost air disperser 2d. The fluidized medium 100 in the upper region of the disperser 2d is fluidized by the air from the air disperser 2d, and the high temperature combustion furnace gas is introduced from the starting burner 11 to raise the fluidized bed 103 in the upper region of the disperser 2d. Let it warm. further,
When the temperature of the region reaches a temperature sufficient to ignite and maintain the combustion of coal, coal is supplied from the uppermost fuel supply nozzle 4d to raise the temperature of the coal to the target fluidized bed temperature.

Next, the air supply is switched from the air valve 3d to the air valve 3c and moved to the air disperser 2c to fluidize the upper region of the air disperser 2c. Fuel 10
The switching valve 5c of No. 4 is switched to switch the supply of the fuel 104 from the fuel supply nozzle 4d to the fuel supply nozzle 4c. As a result, the upper region of the air disperser 2c including the upper region of the air disperser 2d is kept in a fluidized state, and the supplied coal is burned to raise and maintain the temperature to a predetermined temperature. Due to the fluidization of the upper region of the air disperser 2c, heat is absorbed from the heat transfer tube group 6c in that region, and the amount of steam 105 commensurate with the heat transfer area is generated.

Further, when the amount of generated steam 105 is increased, that is, the load is increased, the air disperser 2 and the fuel supply nozzle 4 are sequentially moved to the lower order in the same manner as above, and the fluidized state of the fluidized bed 103 is increased. Increase the area at
That is, the heat transfer area of the heat transfer tube 6 which is substantially operating is increased to increase the heat absorption amount. Further, the temperature of the fluidized bed 103 is maintained by increasing the coal supply amount corresponding to the increase in the heat absorption amount.

FIG. 1 is a diagram showing a state in which air is supplied from the air disperser 2b and coal is supplied from the fuel supply nozzle 4b, and the fluidized medium 100 in a region below the air disperser 2b is a non-fluidized region. (Hatched portion) 117, and the heat transfer tube group 6 a is in a state of not substantially contributing to the generation of the steam 105. On the other hand, the fluid medium 100 in the upper region of the air disperser 2b is in a fluidized state, and the heat transfer tube groups 6b and 6c.
Is absorbing heat from. Further, when the load factor of 100% is achieved, the air disperser 2 and the fuel supply nozzle 4 in the steady operation state are the lowest air disperser 2 respectively.
a, at the position of the fuel supply nozzle 4a, at this time, the entire amount region of the fluidized bed 103 is in a fluidized state, and all the heat transfer tube groups 6
The steam 105 is generated by a, 6b, and 6c.

As described above, this embodiment has the three heat transfer tube groups 6a, 6b, 6c, and the air disperser 2a as described above.
.About.2d, the positions at which the fuel supply nozzles 4a to 4d are used can be changed to change the load in three stages. That is, the number of heat transfer tube groups 6 to be installed is determined by the desired number of load change stages, and a pair of the air disperser 2 and the fuel supply nozzle 4 corresponding to the number of load change stages is provided. Further, instead of the number of the air dispersers 2, the fuel supply nozzles 4, and the heat transfer tube groups 6 installed, or together with the number of the installed air dispersers 2, the fuel supply nozzles 4, the heat transfer tube groups 6 are installed at desired intervals. It can be determined by the interval of change stages of the load factor and / or the number of change stages of the load factor.

In the operation of the pressurized fluidized bed boiler of this embodiment, the pressure of the combustion furnace 102 is 10 to 20 atm and the temperature is 800.
~ 950 ° C, the superficial gas velocity of the fluidized bed 103 is 0.5 ~
A range of 1.5 m / s is adopted. Also, the fluid medium 10
Dolomite or limestone particles are used as particles of 0. Even if the load is changed by the above configuration and action, the fluidized bed surface 10 is formed in a state of always covering the uppermost heat transfer tube group 6c, so that the combustion gas 32 released from the fluidized bed 103 is as in the conventional case. The free boat 107 is introduced into the gas turbine through the cyclone 108 and the precision dust remover without lowering the temperature due to heat exchange.

[0031]

According to the present invention, since the combustion gas temperature does not decrease in the free boat section even under the operating condition where the load factor is low, the output of the gas turbine is not decreased. Further, since the fuel supply nozzle is in the fluidized bed, the combustion efficiency can be kept high. Therefore, high efficiency of the coal-fired power plant can be achieved, the coal consumption per output power can be reduced, and the emission amount of carbon dioxide gas can be reduced.

Further, since a separate fluid medium tank for storing and delivering the fluid medium can be omitted or its capacity can be reduced, the pressure vessel for accommodating the fluid medium tank can be made small, and the number of manufacturing and inspection steps thereof can be reduced. Can be reduced. Moreover, a compact pressurized fluidized bed boiler can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a pressurized fluidized bed combustion boiler of the present invention.

FIG. 2 is a diagram showing a conventional pressurized fluidized bed combustion boiler.

[Explanation of symbols]

2 ... Air disperser, 3 ... Air valve, 4 ... Fuel supply nozzle, 5
... switching valve, 6 ... heat transfer tube group, 7 ... exhaust conduit, 9 ... furnace bottom, 10 ... fluidized bed surface, 11 ... starter burner, 31 ... combustion air, 32 ... combustion gas, 101 ... pressurized container, 102 ...
Fluidized bed combustion furnace, 103 ... Fluidized bed, 104 ... Fuel, 105
... Steam, 106 ... Boiler water supply, 107 ... Freeboard, 108 ... Cyclone, 109 ... Dust, 110 ... Fluid medium tank, 115 ... Medium hopper, 117 ... Non-fluidization area

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Ueda 3-36 Takaracho, Kure-shi, Hiroshima Babcock Hitachi Ltd. Kure Research Institute (72) Inventor Taro Sakata 6-9 Takaracho, Kure-shi, Hiroshima Babcock Hitachi Ltd. Kure Factory

Claims (4)

[Claims] 1. A pressurized fluidized bed boiler in which a plurality of air dispersers are arranged at predetermined intervals in the height direction of the fluidized bed, and a group of heat transfer tubes is arranged between the respective air dispersers. A pressurized fluidized bed boiler characterized in that a fuel supply nozzle is provided above the air disperser and at a position within the fluidized bed. 2. The at least one of the intervals and the number of installed air dispersers and fuel supply nozzles is determined by at least one of the desired load factor change step interval and / or the change step number. Pressurized fluidized bed boiler. 3. The pressurized fluidized bed boiler according to claim 1, wherein the upper surface of the fluidized bed is set at a position at least 0.5 m above the uppermost fuel supply nozzle. 4. A pressurized fluidized bed boiler in which a plurality of air dispersers are arranged at predetermined intervals in the height direction of the fluidized bed, and a heat transfer tube group is arranged between the air dispersers. Pressurized fluidized bed characterized in that the height of the position is limited to the inside of the fluidized bed, and the height of the dispersed air supply position for fluidized bed fluidization and the height of the fuel supply position are changed to respond to load changes. How to operate the boiler.