JP3010910B2 - How to protect pressurized fluidized bed boilers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying combustion air to a pressurized fluidized-bed boiler having a fluidized-bed boiler housed in a pressure vessel.

[0002]

2. Description of the Related Art FIG. 2 shows the principle of a conventional combined power generation system using a pressurized fluidized bed boiler. As shown in the figure, this pressurized fluidized bed boiler combined cycle system stores a fluidized bed boiler c provided with a cyclone b in a pressure vessel a, and a fuel such as coal and desulfurization of limestone and the like inside the fluidized bed boiler c. The agent is made to flow with a fluid medium (bed material) and burned efficiently, and the generated steam causes the generator d
Is to be driven. That is, in order to improve the combustion efficiency, high-pressure combustion air is required. However, since the fluidized-bed boiler c has a structure that is weak against high pressure, it is stored in the pressure vessel a so that the boiler The differential pressure inside and outside the building was reduced.

[0003] The pressurized fluidized-bed boiler combined power generation system will be briefly described. Coal is pulverized to 6 mm or less, supplied to a fluidized-bed boiler c together with a desulfurizing agent, and is a bed made of a mixture of coal, a desulfurizing agent, and ash. Due to the material, a fluidized bed f having a high bed height (about 4 m) is formed by the high-pressure air from the compressor e. The coal is agitated with air in the fluidized bed f.
It burns efficiently under a pressure of about ^{2 to} 1.6 MPa (12 to 16 kgf / cm ² ). In addition, S generated during combustion
O ₂ is absorbed by the desulfurizing material in the layer f, and generation of NOx can be suppressed because the combustion temperature is low. The heat generated in the layer f is recovered as steam by the heat transfer tube g in the fluidized bed having high heat transfer characteristics, and drives the steam turbine h. Thereafter, the combustion exhaust gas is supplied from the boiler c to about 860 to 870.
° C, 1.1 to 1.5 MPa (11 to 15 kgf / c
After being exhausted at m ² ) and dedusted by the cyclone b, the gas turbine i is driven. The gas turbine i drives the combustion air compressor e and also drives the generator j with surplus power, so that the exhaust gas from the gas turbine i is reduced as required to reduce soot and dust below the emission regulation. After the heat is recovered at k, it is discharged from the chimney l. Also, the load adjustment of the boiler c depends on the amount of air supplied within the pressure,
By moving the bed material in and out between the bed material storage container m and the boiler, the height of the fluidized bed f is changed. For example, when the load is reduced, the pressure of the combustion air is increased, the valve n is opened to release the pressure in the bed material storage container m to the outside, and the bed material is sucked from the boiler c through the suction pipe o to reduce the bed height. Conversely, when the load is increased, the combustion air is reduced, and the amount of air in the L valve p of the supply pipe is adjusted to feed the bed material from the bed material storage container m to the boiler c, thereby increasing the bed height. It is achieved by doing.

[0004]

If the gas turbine i that drives the compressor e for supplying high-pressure air suddenly stops due to a failure or the like, the supply of high-pressure air to the boiler c also stops. However, due to the volume chamber effect, ignitable combustion occurs such that air in the pressure vessel a flows into the boiler c for a while, and unburned components burn in a state in which the fluidized bed f does not flow. An undesired clinker was generated at the time of restart, and rapid restart was difficult. Therefore, when the gas turbine i is suddenly stopped, the pressure in the pressure vessel a is extracted to the outside so as to prevent the air from flowing into the boiler c and the pressure is reduced. It is conceivable to extract the gas inside the boiler c to the outside in order to eliminate the pressure,
The withdrawal work must be performed carefully so that the pressure difference between the inside and outside of the boiler c does not increase, and the work is difficult.

Accordingly, the present invention has been devised to effectively solve the above-mentioned problems, and its main purpose is to eliminate the differential pressure between the inside and outside of the boiler when the gas turbine is suddenly stopped. It is an object of the present invention to provide a method for protecting a pressurized fluidized-bed boiler, which can facilitate restarting and prevent a boiler from being damaged.

[0006]

According to the present invention, there is provided a pressure vessel to which high-pressure combustion air is supplied, wherein the combustion air supplied to the pressure vessel is introduced from below. A fluidized-bed boiler for burning while forming a fluidized bed is housed, and a gas turbine and a compressor are driven by combustion exhaust gas from the fluidized-bed boiler, and pressurized air for supplying high-pressure combustion air from the compressor into the pressure vessel. In the fluidized-bed boiler, the inside of the pressure vessel and the upper part of the fluidized-bed of the fluidized-bed boiler are communicated by a bypass pipe, and a shutoff valve for shutting off the flow of combustion air is provided in the bypass pipe, so that the gas turbine stops suddenly. When you do
The shut-off valve is opened to supply the combustion air inside the pressure vessel to the upper part of the fluidized bed of the fluidized bed boiler to balance the upper and lower pressures of the fluidized bed.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The present invention as described above, when the gas turbine for driving the compressor is stopped abruptly, the flow of the fluidized bed boiler combustion air inside the pressure vessel by opening the shut-off valve
Since the gas flows in the upper part of the bed, the pressure difference between the upper and lower parts of the fluidized bed is reduced, and the combustion air in the pressure vessel does not flow from the lower part of the fluidized bed boiler to the fluidized bed due to the volume chamber effect. This can be prevented, and restart can be easily performed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a pressurized fluidized-bed boiler power generation system according to the present invention. As shown in the figure, the pressurized fluidized-bed boiler has a fluidized-bed boiler 2 housed in a pressure vessel 1 and performs efficient combustion with high-pressure combustion air.

The fluidized-bed boiler 2 is provided with a vertical boiler frame 3 and a cyclone 4 and a bed material storage container 5. The bed material supplied from the bed material storage container 5 is provided at the bottom of the boiler frame 3. A fluidized bed 6 in which a fuel such as coal or a desulfurizing material such as limestone is mixed is formed, and the fluidized bed 6 is caused to flow by high-pressure combustion air supplied from a combustion air inlet 8 below the boiler body 3 to perform combustion. It has become. In the generated combustion exhaust gas, ash dust is roughly removed by a cyclone 4 and then sent to a gas turbine 18, which is turned to drive a compressor 13 that supplies high-pressure combustion air to the fluidized-bed boiler 2. It is converted into clean gas by the denitration process 19 and discharged.

The bed material storage container 5 is connected to the bottom of the boiler body 3 via a suction pipe 7 having an L valve, and sucks or supplies the bed material according to a load change to form a bed of the fluidized bed 6. The height can be adjusted freely.

Further, a heat transfer pipe 9 through which cooling water flows is provided on a side wall of the boiler body 3, and steam generated by heat generated by combustion in the boiler body 3 is generated.
By turning 0, the generator 11 is driven.

As shown in the figure, the inside of the pressure vessel 1 and the inside of the boiler frame 3 are communicated by a bypass pipe 12, and the high-pressure combustion air inside the pressure vessel 1 flows to the upper part 14 of the fluidized bed in the boiler frame 3. It flows directly. The bypass pipe 12 is provided with a shutoff valve 15 for shutting off the flow of combustion air, and is closed during normal operation to shut off the flow of air.
Is opened, the combustion air inside the pressure vessel 1 is opened to flow to the upper part 14 of the fluidized bed of the boiler frame 3.

An air discharge valve 1 is provided on a side wall of the pressure vessel 1.
An air discharge pipe 17 provided with the pressure vessel 6 is connected to the pressure vessel 1 so that the high-pressure combustion air in the pressure vessel 1 can escape to the outside of the pressure vessel 1.

Next, the operation of the present invention will be described.

During normal operation, the flow of combustion air is
First, after flowing from the compressor 13 into the pressure vessel 1 and staying there, it flows from the air inlet 8 of the boiler frame 3 into the boiler frame 3 and is used as combustion air while flowing through the fluidized bed 6. At this time, the shutoff valve 15 of the bypass pipe 12 is in a closed state, and the air in the pressure vessel 1 does not flow from the bypass pipe 12 into the boiler frame 3. Then, the combustion gas generated in the upper portion 14 of the fluidized bed of the boiler frame 3 is sent to the gas turbine 18 after passing through the cyclone 4, and after being driven, is discharged through the denitration treatment 19 and the like.

Next, in this state, the gas turbine 1
When the compressor 8 stops due to a failure, the compressor 13 driven thereby also stops at the same time, and the supply of the combustion air into the pressure vessel 1 stops. At the same time, the shut-off valve 15 of the bypass pipe 12 is opened and By flowing a part of the combustion air in the pressure vessel 1 to the fluidized bed upper portion 14 side of the boiler frame 3, the pressure is balanced above and below the fluidized bed 6. Therefore, the combustion air does not flow from the lower part of the fluidized bed 6 due to the volume chamber effect, and the occurrence of clinker due to the unburned ignited combustion is prevented. The flow
To restart the pressure of Doso top 14 can be the same as the pressure in the pressure vessel 1, that the pressure in the pressure container 1 is activated to remain open the shut-off valve 15 to a high pressure, flow
Since the pressure in the layer upper portion 14 can be increased, restart can be easily performed.

Then, the internal pressure of the pressure vessel 1 and the boiler frame 3
When the flow of combustion air in the bypass pipe 12 stops due to the same condition, the air release valve 16 may be opened in some cases,
The combustion air in the pressure vessel 1 is discharged to the outside from the air discharge pipe 17 to reduce the pressure in the pressure vessel 1 and the boiler frame 3. Further, at this time, the combustion gas in the boiler body 3 flows into the pressure vessel 1 through the bypass pipe 12, so that a large pressure difference does not occur inside and outside the boiler body 3.

That is, as described above, in the conventional pressurized fluidized bed boiler, when the gas turbine 18 is stopped and the supply of the combustion air is stopped, the inside of the pressure vessel 1 is moved from the boiler frame 3 side by the volume chamber effect. Is a high pressure, a small amount of combustion air in the pressure vessel 1 passes through the air inlet 8 and flows into the fluidized bed 6 for a while, and clinker is generated in the fluidized bed 6 due to insufficient combustion air. However, in the present invention, the provision of the bypass pipe 12 between the boiler body 3 and the pressure vessel 1 makes it possible to quickly reduce the differential pressure between the boiler body 3 and the pressure vessel 1, and It is possible to prevent the occurrence of clinker and damage to the boiler frame 3 due to the differential pressure.

[0020]

According to the above summary the present invention, when the gas turbine is abruptly stopped by malfunction, the flow of the fluidized bed boiler combustion air inside the pressure vessel by opening the shut-off valve
Because the fluid flows to the upper part of the fluidized bed, the pressure difference between the upper and lower parts of the fluidized bed is reduced, and the combustion air in the pressure vessel does not flow from the lower part of the fluidized-bed boiler to the fluidized bed due to the volume chamber effect. And restart can be easily performed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a conventional example of a pressurized fluidized-bed boiler combined cycle system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure vessel 2 Fluidized-bed boiler 12 Bypass pipe 13 Compressor 15 Shut-off valve 18 Gas turbine

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F22B 1/02

Claims (1)

(57) [Claims] 1. A fluidized-bed boiler for storing combustion air supplied into the pressure vessel from below into a pressure vessel to which high-pressure combustion air is supplied and burning the fluidized bed while forming a fluidized bed. In a pressurized fluidized-bed boiler that drives a gas turbine and a compressor by combustion exhaust gas from a fluidized-bed boiler and supplies high-pressure combustion air from the compressor into the pressure vessel, the fluidized bed of the fluidized-bed boiler and the inside of the fluidized-bed boiler The upper part is communicated with a bypass pipe, and a shutoff valve for shutting off the flow of combustion air is provided in the bypass pipe, and when the gas turbine is suddenly stopped,
A method for protecting a pressurized fluidized-bed boiler, comprising opening the shut-off valve and supplying combustion air in the pressure vessel to an upper portion of the fluidized-bed of the fluidized-bed boiler to balance pressures above and below the fluidized-bed.