JPH0771717A - Method of removing bed after occurrence of boiler trip in pressurized fluidized bed type boiler - Google Patents

Abstract

PURPOSE:To enable a stable and positive removal of bed material to be carried out by a method wherein a removal pressure dropping valve is opened to remove the bed material after a pressure within a pressure container is made stable during a trip of a boiler. CONSTITUTION:A pressure variation rate monitoring switch 45 outputs a signal 44 to an AND circuit 47 when a pressure in a pressure container 2 is stabled and a pressure variation rate is lower than a variation rate set value 43 during a trip of a boiler. The AND circuit 47 and an OR circuit 49 are turned ON by inputting the signal 44 and a boiler trip signal 46. An instruction signal 51 is outputted after the ON signal obtained from the OR circuit 49 and a bed height reducing instruction 39 obtained from a bed height monitor switch 38 are inputted to an AND circuit 50 and then the AND circuit 50 becomes ON, a removal pressure reducing valve 20 is opened and the bed material in a main body of the boiler is removed into a bed material storing container. With such an arrangement as above, it is possible to perform a stable and positive removal of the bed material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bed material withdrawal method after a boiler trip occurs in a pressurized fluidized bed boiler.

[0002]

2 shows a pressurized fluidized bed boiler, which comprises a pressure vessel 2, a fluidized bed type boiler main body 3 housed in the pressure vessel 2, and Boiler body 3
Fuel 4 such as coal is placed on the side of the
A fuel supply nozzle 5 for supplying the fuel is supplied to the fuel supply nozzle 5. A fuel supply pipe 7 having a fuel flow rate control valve 6 is connected to the fuel supply nozzle 5. A bed material 8 is housed in the boiler body 3, and the bed material 8 is fluidized by compressed air 9 introduced into the boiler body 3 from the pressure vessel 2 to form a fluidized bed 10. Fuel 4 by heat of 10
Is designed to burn.

At the top of the boiler body 3, the combustion gas generated in the boiler body 3 is used as an exhaust gas 11 for a gas turbine 12
An exhaust gas duct 13 that feeds the gas is passed through the top of the pressure vessel 2 and is connected to drive the gas turbine 12 with the exhaust gas 11. In addition, the gas turbine 12
The air compressor 14 and the generator 15 are connected, and the compressed air 9 compressed by the air compressor 14 is compressed air feed pipe 1
It is adapted to be guided to the pressure vessel 2 via 6. Further, an air flow rate control valve 25 is provided on the air intake side of the air compressor 14 so that the compressed air pressure by the air compressor 14 can be adjusted. 26 is the exhaust gas duct 1
3 shows an exhaust gas cutoff valve provided in FIG.

A bed material storage container 1 is provided in the pressure container 2.
7 is provided, the upper end of the bed material storage container 17 and the inside of the fluidized bed 10 by the bed material 8 in the boiler body 3 are connected by a bed material return pipe 18, and the bed material storage container The lower part of 17 and the inside of the fluidized bed 10 of the boiler body 3 are connected by a bed material supply pipe 19.

To the upper portion of the bed material storage container 17, a pressure reducing pipe 21 for extraction is connected which penetrates the pressure container 2 and has a pressure reducing valve 20 for discharge to the outside. Further, the bed material supply pipe 19 has a bent shape at a right angle by a vertical portion 19a and a horizontal portion 19b, and a compressed air pipe 22 penetrating the pressure vessel 2 from the lateral direction is connected to the right bent portion. A compressed air control valve 23 is provided outside the compressed air pipe 22, and the compressed air 24 is regulated by the compressed air control valve 23 to supply the bed material 8 in the bed material storage container 17 to the bed material. It can be arbitrarily supplied into the boiler main body 3 through the pipe 19.

Further, the pressure vessel 2 is provided with a pressure vessel pressure reducing valve 27 for reducing the pressure in the pressure vessel 2 when a boiler trip described later occurs.

In the boiler body 3, the fluidized bed 1 is detected by detecting the differential pressure between the fluidized bed 10 and the upper space thereof.
A bed height detector 28 for detecting a bed height of 0 is provided, and a detection signal 29 of the bed height detector 28 is input to a control device 30 and a pressure vessel for detecting the pressure in the pressure vessel 2 is provided. The detection signal 32 of the pressure detector 31 is input to the control device 30.

The controller 30 outputs an output command (MWD) 33.
Based on the control signal 34, the fuel flow rate of the fuel flow rate control valve 6 is adjusted, and the air flow rate control valve 25 and the air flow rate control valve 25 and The entire pressurized fluidized bed boiler 1 is adjusted by adjusting the opening of the pressure vessel pressure reducing valve 27 to adjust the pressure in the pressure vessel 2 and further adjusting the amount of water supplied to the evaporator of the boiler body 3 (not shown). I'm trying to control the driving.

Further, the control device 30 opens the extracting pressure reducing valve 20 based on the detection signal 29 from the bed height detector 28 so that the bed height corresponding to the output command 33 is held, and the inside of the boiler body 3 is opened. The bed material 8 in the boiler main body 3 is pulled out into the bed material storage container 17 or the compressed air control valve 23 by generating a pressure difference between the bed material storage container 17 and the bed material storage container 17.
Bed material 8 in the bed material storage container 17 by opening
Is supplied to the boiler main body 3.

Further, the control device 30 detects the flow rate of the feed water to the boiler body 3, the pressure of steam generated by the boiler body 3, the output of the steam turbine connected to the boiler body 3, and the like, and the detected values thereof. When the value indicates an abnormal value, the fuel flow rate control valve 6 is shut off by the control signal 34, the supply amount of supply water is rapidly narrowed down, and the pressure vessel pressure reducing valve 27 is opened to reduce the pressure in the pressure vessel 2. Therefore, the boiler is tripped.

Further, the control device 30 includes a gas turbine 12
When the output of the generator 15 connected to the, the vibration of the gas turbine 12 and the like are detected, and the detected values show an abnormal value, the control signal 34 shuts off the exhaust gas shutoff valve 26,
The air flow control valve 25 is shut off to trip the gas turbine (GT trip). Further, at the time of this gas turbine trip, the fluidized bed 10 cannot be formed in the boiler body 3, so the boiler side is also made to trip at the same time.

As described above, at the time of boiler trip, the gas turbine 12 side keeps the operation as it is to keep the formation of the fluidized bed 10. The fluidized bed 10 is formed by the boiler main body 3 after the boiler trip occurs.
It has the effect of reducing the internal temperature to eliminate the boiler trip, and when the pressurized fluidized bed boiler 1 is restarted after the boiler trip, the bed material 8 in the boiler main body 3 is temporarily placed in the bed material storage container 17. It is necessary to extract the bed material 8 to start it after making it to a required small layer thickness, and the work of extracting the bed material 8 is very difficult.
When the pressure reducing valve 20 for extraction is opened to reduce the pressure inside the bed material storage container 17 in the state where 0 is formed, the bed material 8 inside the boiler body 3 can be easily stored inside the bed material storage container 17 by utilizing the differential pressure. It has the effect that it can be extracted.

When the gas turbine trip occurs, the fluidized bed 10 is not formed and the bed material 8 is immediately deposited on the lower portion of the boiler main body 3, so that the differential pressure is used to generate the inside of the boiler main body 3. The bed material 8 cannot be extracted into the bed material storage container 17, and thus a separate extraction operation is performed. However, since the fluidized bed 10 is formed at least at the time of boiler trip, this is used. The work is simplified by pulling out the bed material 8 by differential pressure.

In the conventional extraction of the bed material 8 at the time of the boiler trip described above, the output command 33 disappears due to the boiler trip, so that the control signal 34 from the control device 30 opens the extraction pressure reducing valve 20 immediately after the boiler trip occurs. Then, the bed material 8 in the boiler body 3 is pulled out.

[0015]

However, as described above, since the bed material 8 is conventionally extracted immediately after the boiler trip occurs, the bed material 8 is extracted as described above. There was a problem that could not be improved.

That is, when a boiler trip occurs, the pressure vessel pressure reducing valve 27 is opened, and the pressure in the pressure vessel 2 is reduced due to the decrease in the amount of heat due to the stop of the fuel 4. At this time, the pressure fluctuates unstablely. However, the pressure inside the boiler main body 3 also fluctuates in an unstable manner, and the pressure inside the bed material storage container 17 connected to the boiler main body 3 via the extraction pipe 18 also fluctuates in an unstable manner. To do.

Therefore, in this state, the pressure reducing valve 20 for extraction
Is opened to reduce the pressure in the bed material storage container 17 to extract the bed material 8 in the boiler body 3 into the bed material storage container 17, the pressure in the boiler body 3 and the bed material storage container 17 Since a stable differential pressure cannot be maintained between the pressure and the pressure, the bed material 8 pulsates in the extraction pipe 18 and the extraction pipe 18 is closed.

The present invention has been made in order to solve the above-mentioned conventional problems, and enables the bed material in the boiler main body to be stably and surely extracted into the bed material storage container after a boiler trip occurs. An object of the present invention is to provide a bed material withdrawal method after a boiler trip occurs in a pressurized fluidized bed boiler.

[0019]

According to the present invention, the bed material in the boiler body is placed in the bed material storage container in a state where the supply of fuel to the boiler body is stopped and the pressure vessel is decompressed due to the occurrence of a boiler trip. A method of extracting bed material after a boiler trip occurs in a pressurized fluidized bed boiler that detects the pressure inside the pressure vessel, and after the boiler trip occurs, the rate of change in pressure inside the pressure vessel stabilizes below a prescribed value. After that, the bed material in the pressure vessel is extracted into the bed material storage container by opening the pressure reducing valve for extraction to reduce the pressure in the bed material storage container. The bed material withdrawing method of No.

[0020]

In the present invention, when a boiler trip occurs, the pressure in the pressure vessel is detected, and when the rate of change in the pressure in the pressure vessel stabilizes below a predetermined value, the pressure reducing valve for extraction is opened to open the bed material storage vessel. Reduce the internal pressure. As a result, a stable differential pressure is generated between the inside of the boiler main body and the inside of the bed material storage container, and the bed material within the pressure container can be stably and reliably extracted into the bed material storage container.

[0021]

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

FIG. 1 shows an example of the bed material withdrawal control circuit 35 provided in the control device 30 of FIG. 2, in which the detection signal 29 from the bed height detector 28 of FIG. The floor height set value 37 according to the command 33 is subtracted and the floor height monitor switch 38 is turned on. The bed height monitor switch 38 issues a bed height reduction command 39 for pulling out the bed material 8 when the detection signal 29 is larger than the bed height setting value 37, and the detection signal 29 shows the bed height setting value 3
When it is smaller than 7, a bed height increase command 40 for supplying the bed material 8 is issued.

Further, a change rate calculator 41 for obtaining a change rate by taking the detection signal 32 from the pressure vessel internal pressure detector 31 and differentiating the detection signal 32 is provided, and the signal from the change rate calculator 41 is provided. 42 is a small rate of change (close to zero)
There is provided a pressure change rate monitor switch 45 which outputs a signal 44 when the change rate set value 43 set in step 1 becomes smaller.

Further, the pressure change rate monitor switch 45.
And an AND circuit 47 for taking in a signal 44 from the boiler and a boiler trip signal 46 when a boiler trip occurs.
The output of the ND circuit 47 is taken in one side, and the boiler trip signal 46 is taken in through the NOT circuit 48 to the other side O
An R circuit 49 is provided, and an AND circuit 50 that receives the output of the OR circuit 49 on one side and the layer height decrease command 39 of the layer height monitor switch 38 on the other side is provided.
A switching circuit 52 that sends a command signal 51 of the D circuit 50 to the pressure reducing valve 20 for extraction provided in the bed material storage container 17 is configured.

Next, the operation of the above embodiment will be described.

When the pressurized fluidized bed boiler 1 is operating stably, there is no boiler trip signal 46, so AN
Although the D circuit 47 is OFF, the ON signal from the NOT circuit 48 is output to the OR circuit 49, so that O
The R circuit 49 is turned on and a signal is output to the AND circuit 50. Therefore, when the detection signal 29 of the bed height detector 28 is larger than the bed height set value 37, the bed height decrease command 39 from the bed height monitor switch 38 is issued to the AND circuit 50, and the AND circuit 50 is turned on. As a result, the command signal 51 is output to the extraction pressure reducing valve 20, the extraction pressure reducing valve 20 is opened, the inside of the bed material storage container 17 is decompressed, and the bed material 8 in the boiler body 3 is extracted into the bed material storage container 17. The bed height of the fluidized bed 10 is adjusted in such a manner as to take it out.

When a boiler trip occurs, the output command 33 disappears, so that the bed height monitor switch 38 is released.
Outputs the height reduction command 39 to the AND circuit 50.

On the other hand, when a boiler trip occurs, the boiler trip signal 46 is taken into the AND circuit 47. However, at this time, the rate of change of the detection signal 32 detected by the pressure detector 31 in the pressure vessel is obtained by the rate-of-change calculator 41, and the rate-of-change signal 42 falls below the required rate-of-change set value 43. Unless it becomes smaller, the pressure change rate monitor switch 45 does not output the signal 44.
The D circuit 47 remains off. That is, after the boiler trip occurs, the pressure in the pressure vessel 2 is unstable and fluctuates and decreases. Therefore, the pressure change rate monitor switch 45 does not operate in this state. Therefore, AND
Since the circuit 47 is turned off and the NOT circuit 48 is also turned off, the AND circuit 49 is also turned off, and thus the AND circuit 50 is also turned off, so that the extraction pressure reducing valve 20 is not operated and is kept in the closed state.

The pressure in the pressure vessel 2 becomes stable,
When the change rate becomes smaller than the change rate set value 43, the pressure change rate monitor switch 45 outputs the signal 44 to the AND circuit 47.
When the signal 44 and the boiler trip signal 46 are input, the AND circuit 47 is turned on and the OR circuit 49 is also turned on.

Then, the ON signal from the OR circuit 49 and the layer height decrease command 39 from the layer height monitor switch 38 are A
When the AND circuit 50 is put into the ND circuit 50 and the AND circuit 50 is turned ON, the command signal 51 is output, the pressure reducing valve 20 for extraction is opened, and the bed material 8 in the boiler body 3 is extracted into the bed material storage container 17. Will be issued.

As described above, at the time of a boiler trip, the pressure reducing valve 20 for withdrawal is opened and the bed material is withdrawn after the fluctuation in the pressure in the pressure vessel 2 is stabilized and is stabilized. Inner and bed material storage container 17
A stable differential pressure is generated between the inside and the inside, and the bed material 8 can be extracted stably and reliably.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

[0033]

According to the bed material withdrawal method of the pressurized fluidized bed boiler according to the present invention after the occurrence of the boiler trip, the pressure reduction in the withdrawal is stabilized after the fluctuation of the pressure in the pressure vessel is stabilized after the occurrence of the boiler trip. Since the valve is opened and the bed material inside the boiler body is pulled out into the bed material storage container,
A stable differential pressure is generated between the inside of the boiler main body and the inside of the bed material storage container, and the excellent effect that the bed material can be extracted stably and surely can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a bed material extraction control circuit for carrying out the method of the present invention.

FIG. 2 is an overall side view showing an outline of a pressurized fluidized bed boiler.

[Explanation of symbols]

 1 Pressurized fluidized bed boiler 2 Pressure vessel 3 Boiler body 4 Fuel 8 Bed material 17 Bed material storage container 20 Pressure reducing valve for extraction

Claims (1)

[Claims] 1. A pressurized fluidized bed boiler for extracting the bed material in the boiler body into the bed material storage container in a state where the supply of fuel to the boiler body is stopped and the pressure container is decompressed due to the occurrence of a boiler trip. A method for extracting bed material after a boiler trip occurs, detecting the pressure in the pressure vessel, and opening the pressure reducing valve for extraction after the boiler trip occurs and the rate of change in pressure in the pressure vessel stabilizes below a predetermined value. A bed material withdrawal method after a boiler trip occurs in a pressurized fluidized bed boiler, characterized in that the bed material in the pressure vessel is extracted into the bed material storage vessel by reducing the pressure in the bed material storage vessel.