JP3085792B2 - Control device for pressurized fluidized bed boiler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control apparatus for a pressurized fluidized-bed boiler of a type that generates steam by fluidized-bed combustion to drive a steam turbine and drives a gas turbine by combustion gas.

[0002]

2. Description of the Related Art A pressurized fluidized-bed boiler forms a fluidized bed together with fuel and fluidized materials such as ash and limestone by supplying combustion air pressurized by a compressor through a large-capacity pressure vessel into the boiler. And perform fluid combustion. The pressurized fluidized-bed boiler is provided with a superheater that exchanges heat with the gas combusted in the fluidized bed.This superheater is connected to a desuperheater that controls the steam temperature at the inlet side, and is connected to the outlet side. Is connected to a steam turbine via a main steam pipe. Further, the fluidized bed boiler is provided with a reheater connected to the outlet side of the steam turbine so as to exchange heat with the combustion gas. Further, in order to control the steam temperature of the reheater, a fluidized material moving device for moving the fluidized material to raise and lower the height of the fluidized bed is also provided in the fluidized bed boiler. The pressurized fluidized bed boiler is also connected to a gas turbine powered by the combustion gas.

In such a pressurized fluidized bed boiler, FIGS. 4 and 5 show a conventional control system of a device for controlling the temperature of steam supplied to a steam turbine and controlling the amount of combustion air.

FIG. 4 shows a conventional steam temperature control system for a mechanical configuration including a final superheater 1, a spray water 2, a desuperheater 3, a main steam pipe 4 and a turbine 5 related to a pressurized fluidized-bed boiler. And adopts the following control method.
That is, the detector 6 for detecting the outlet temperature of the final superheater 1
And the output from the function generator 8 which receives the boiler input signal 7 and outputs the set value of the final superheater 1 is subtracted by the subtractor 9
Subtract with. The output signal of the subtractor 9 is input to the controller 10. The controller 10 is, for example, a proportional-integral controller, and outputs a set value of the inlet temperature of the final superheater 1. This set value is the detector 1 that detects the inlet temperature of the final superheater 1.
1 is subtracted by the subtractor 12 from the output signal. The output signal of the subtractor 12 is input to the controller 13. The controller 13 is, for example, a proportional-integral controller, and outputs a spray valve opening command 14. The spray valve opening command 14 controls the flow rate of the spray water 2 to the desuperheater 3 and controls the outlet temperature of the final superheater 1.

On the other hand, FIG. 5 shows a conventional control system for controlling the amount of combustion air in a pressurized fluidized-bed boiler, which generates a set value signal of a combustion air flow rate from a feedback signal of exhaust gas and controls the deviation from the actual air flow rate. It is a cascade control that puts vessels. That is, the required air flow rate is output from the function generator 16 which receives the boiler input command 15 as an input. On the other hand, the measured exhaust gas oxygen concentration 17 and the set exhaust gas oxygen concentration 18
The subtractor 19 having these as inputs outputs these deviations and uses them as input signals of the controller 20. The controller 20 is, for example, a proportional-integral controller and outputs a correction signal of the air flow rate. This correction signal is added by the adder 21 to a signal representing the required air flow rate from the function generator 16 and becomes a set value signal of the air flow rate. The output signal of the adder 21 becomes the input signal of the subtractor 23 together with the measured total air flow rate 22,
The subtractor 23 outputs an output signal representing the air flow deviation to the controller 24.
Give to. The controller 24 can be, for example, a proportional-integral controller, and outputs a compressor variable stator blade command 25 representing the amount of combustion air.

[0006]

In a conventional control device for a pressurized fluidized-bed boiler, there are the following problems in controlling the steam temperature. (1) In order to change the bed height of the fluidized bed, when the fluidized material moving device is operated, the fluidized bed temperature and the area of the heat transfer tube in contact with the fluidized material always change. This also changes the steam temperature, but does not compensate for such disturbances. (2) In a fluidized-bed boiler, the temperature of the fluidized-bed is controlled by another operation amount, for example, a coal supply amount. However,
Fluidized bed temperature has a significant effect on steam temperature, which varies sensitively, but has not been compensated for such disturbances.

[0007] A pressurized fluidized-bed boiler has a large-capacity pressure vessel before flowing combustion air into a fluidized-bed combustion furnace. Therefore, in order to control the amount of combustion air, it is first necessary to control the amount of air in the pressure vessel. However, the delay is very large due to the large volume. For this reason, it was necessary to set the upper limit of the flow rate of coal to be supplied to the combustion furnace according to the inflow amount of combustion air.

[0008] The present invention has been made in view of the above circumstances, and with minimal deviation between the set value of the steam temperature in the steam temperature control, the exhaust gas oxygen in the combustion air flow control
It is an object of the present invention to provide a control device in which the response of combustion air is improved in consideration of the concentration deviation .

[0009]

According to the present invention, there is provided an image forming apparatus comprising:
According to the above, a fluidized material moving device for moving the fluidized material forming the fluidized bed to raise and lower the height of the fluidized bed is provided, and a superheater for exchanging heat with gas combusted in the fluidized bed and steam to the superheater A controller for a pressurized fluidized-bed boiler, which is associated with a temperature reducer for controlling the temperature, for controlling the temperature before and after the final superheater and the flow rate of spray water supplied to the temperature reducer as input to a boiler input signal. A pressurized fluidized bed characterized by further adding a means for detecting a drive signal of the fluidized material moving device and adding a compensation signal of steam temperature due to fluidized material movement to a control system for outputting a spray valve opening degree command. A control device for a boiler is provided.

[0010]

Further, according to the present invention, a boiler input command,
The boiler input to a control system that outputs a compressor variable stationary blade command to a compressor for sending pressurized air to a pressure vessel having a large capacity for flowing combustion air into the fluidized bed with the exhaust gas and the total air flow as inputs. A control device for a pressurized fluidized-bed boiler, characterized in that a means for adding a boiler input acceleration signal obtained by differentiating a command is additionally provided.

[0012]

According to the above means, the compensation signal of the steam temperature is added to the control system of the spray valve opening command in response to the drive signal of the fluidized material moving device or in response to the temperature change of the fluidized bed. Changes in steam temperature due to movement of the fluidized material or changes in the temperature of the fluidized bed are prevented in advance.

According to the above means, by adding the boiler input acceleration signal to the combustion air flow rate control system, the compressor variable vane is operated simultaneously with the load change, and the air amount in the pressure vessel is rapidly changed. Will be done.

[0014]

FIG. 1 is a control system diagram showing an embodiment of a control device according to the present invention. In FIG. 1, the same elements as those shown in FIG. Detailed description is omitted.

According to the embodiment of FIG. 1, first, a fluidized material moving device drive signal 30 is input to a controller 31. Controller 31
Is, for example, a proportional controller, the output of which is input to the delay element 32. The delay element 32 delays the input signal by the time from when the fluidized material moving device is driven to when it affects the final superheater 1, and this output signal becomes a compensation signal for the steam temperature by driving the fluidized material moving device. . This compensation signal is input to an adder arranged at the output of the subtractor 12, and is added to the output signal of the subtractor 12.

When the fluidized bed moving device for changing the bed height of the fluidized bed is operated, a compensation signal taking into account the moving direction (vertical direction) and the strength of the fluidized bed is added to the steam temperature control system. Predictive control can be performed in consideration of the effect of the operation of the fluidized material moving device on the steam temperature, and the steam temperature control deviation width can be reduced.

FIG. 2 is a control system diagram showing another embodiment of the control device according to the present invention. In FIG. 2, the same elements as those shown in FIG. Detailed description is omitted.

According to the reference example shown in FIG. 2, a detector 35 for detecting the temperature in the fluidized bed 34 is provided, and the output of the detector 35 outputs a temperature set value by using the boiler input signal 7 as an input. The output of the function generator 36 and the output of the function generator 36 are input to the subtractor 37. The output of the subtractor 37 is supplied via a controller 38 and a delay element 39 to an adder 40 provided at the output of the subtractor 12. The controller 38 is, for example, a proportional controller, and outputs a compensation signal of the steam temperature when the fluidized bed temperature changes in response to the deviation of the temperature set value corresponding to the boiler input signal 7 from the actual value. The delay element 39 takes into account the time lag between the change of the fluidized bed temperature and the influence on the final superheater 1.

Here, the relationship between the fluidized bed temperature and the steam temperature will be described. The higher the fluidized bed temperature, the higher the steam temperature, and the lower the fluidized bed temperature, the lower the steam temperature. When the fluidized bed temperature is high, the spray flow rate is high, and when the fluidized bed temperature is low, the spray flow rate is small.However, the movement of the spray flow rate is affected by the fluidized bed temperature. become. Therefore, since the steam temperature can be predicted from the fluidized bed temperature, by adding a fluidized bed temperature correction signal to the steam temperature control system, the spray flow rate can be controlled in advance and the deviation width of the steam temperature can be reduced. become.

FIG. 3 is a control system diagram showing still another embodiment of the control device according to the present invention. 3, the same elements as those shown in FIG. 5 are denoted by the same reference numerals, and detailed description thereof will be omitted.

Referring to FIG. 3, the boiler input command 15 is input to the differentiator 41. The output signal of the differentiator 41 is
2 is input. Controller 42 may be, for example, a proportional controller, and outputs a differential signal of boiler input command 15 as a boiler input acceleration signal. This boiler input acceleration signal is input to an adder 43 provided on the output side of the controller 24, and is added to the compressor variable stator blade command 25.

Although the response of the combustion air becomes faster as the volume of the pressure vessel decreases, it is difficult to reduce the response due to the structure of the system. However, the compressor variable stator blade command 25 is corrected in advance by the boiler input acceleration signal. As a result, the compressor variable stator vane can be operated at the same time as the load changes, and the amount of air in the pressure vessel can be changed.
This speeds up the response of the combustion air.

[0023]

According to the embodiment of FIG. 1 of the present invention, it is possible to predict and control the steam temperature by driving the fluidized material moving device, and it is possible to keep the deviation of the steam temperature small.

According to the reference example shown in FIG. 2, it is possible to predict the extent to which the fluidized bed temperature affects the steam temperature, and to perform predictive control for activating the spray flow rate in advance, thereby suppressing the steam temperature deviation to a small value. it can.

According to the embodiment of FIG. 3, by incorporating the differential value of the boiler input command into the combustion air flow control signal, the variable compressor vane can be operated in advance, and the responsiveness of the combustion air can be improved. Can be improved.

[Brief description of the drawings]

FIG. 1 is a control system diagram of steam temperature control according to a first embodiment of a control device for a pressurized fluidized-bed boiler according to the present invention.

FIG. 2 is a control system diagram of steam temperature control according to a control device of a pressurized fluidized-bed boiler as a reference example.

FIG. 3 is a control system diagram for controlling the flow rate of combustion air in a control device for a pressurized fluidized-bed boiler according to the present invention.

FIG. 4 is a control system diagram of steam temperature control in a control device for a conventional pressurized fluidized-bed boiler.

FIG. 5 is a control system diagram for controlling the flow rate of combustion air in a conventional control device for a pressurized fluidized-bed boiler.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Final superheater, 2 ... Spray water, 3 ... Desuperheater, 4 ... Main steam pipe, 5 ... Turbine, 6, 11, 35 ... Temperature detector,
7 boiler input signal, 8, 16, 36 ... function generator,
9, 12, 19, 23 ... subtractor, 10, 13, 20, 2
4, 31, 38, 42: controller, 14: spray valve opening command, 15: boiler input command, 17: exhaust gas oxygen concentration ,
18: set value of exhaust gas oxygen concentration , 21, 23, 40, 4
3 ... Adder, 22 ... Total air flow, 25 ... Compressor variable stationary blade command, 30 ... Flow material moving device drive signal, 32,3
9 delay element, 34 fluidized bed, 41 differentiator.

Claims (2)

(57) [Claims] 1. A superheater for moving a fluidized material forming a fluidized bed to raise and lower the height of the fluidized bed, wherein the superheater exchanges heat with gas combusted in the fluidized bed and a superheater for the superheater. A controller for a pressurized fluidized-bed boiler, which is associated with a desuperheater for controlling steam temperature, controls the flow rate of spray water supplied to said desuperheater by inputting the temperature before and after the final superheater and a boiler input signal as input. A means for detecting a drive signal of the fluidized material moving device and adding a compensation signal for a steam temperature due to the fluidized material movement to a control system for outputting a spray valve opening command for the pressurized flow. Floor boiler control device. 2. The control device according to claim 1, wherein the boiler input command, the exhaust gas and the total air flow rate are input, and the pressurized air is supplied to a pressure vessel having a large capacity for flowing combustion air into the fluidized bed. A control system for a pressurized fluidized-bed boiler, characterized in that a means for adding a boiler input acceleration signal obtained by differentiating the boiler input command is added to a control system for outputting a compressor variable stationary blade command to the compressor.