JPH11108306A - Spray controller for superheater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a rise in the temperature of metal of a furnace wall by controlling a spray control valve to reduce the travel thereof according to a rise in the inlet pressure of a fuel economizer depending on the adhesion of scale onto the furnace wall. SOLUTION: An increase in the pressure loss of a furnace wall which is caused by scale adhering to the wall of a boiler furnace is detected and a spray control valve 17 is controlled to reduce the travel thereof by decreasing a control valve travel setting signal 23 based on the increase of an economizer inlet pressure detection signal 33. Thus, the flow rate of water to be supplied to a boiler furnace is automatically adjusted to that before the adhesion of the scale on the furnace wall to prevent possible rise in the temperature of metal of the furnace wall.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superheater spray control device.

[0002]

2. Description of the Related Art FIG. 8 is a schematic view showing an example of a once-through boiler generally used in the prior art.
Fuel 4 is supplied from a burner 3 provided with a fuel control valve 2 to perform combustion, and water 6 from a water supply pump 5 is guided to a economizer 8 through a water supply pipe 7. The hot water heated by the economizer 8 is applied to the furnace wall 1 of the boiler furnace 1.
a to be evaporated.

The steam 9 generated in the boiler furnace 1 is superheated through one or more stages of superheaters 10, the temperature of the steam 9 is adjusted by a spray nozzle 11, and guided to a final superheater 12. To generate electric power by the generator 14.

A spray pipe 15 is connected to a water supply pipe 7 at the outlet of the water supply pump 5 so that a part of the water supply 6 is branched. The spray water 16 branched by the spray pipe 15 is supplied to a spray control valve. 17 through the spray nozzle 1
1 is supplied.

In FIG. 8, reference numeral 18 denotes a controller.
Is a steam temperature detector 19 provided at the outlet of the final superheater 12.
Temperature detection signal 20 and output command (MWD) 21 from
And the control signal 22 causes the spray control valve 1
7 is controlled.

FIG. 5 is a block diagram showing an example of the controller 18 of FIG. 8. The controller 18 outputs a control valve opening setting signal 23 based on an output command 21 from a first function generator. 24. As shown in FIG. 6, when the output command 21 increases, the first function generator 24 changes the control valve opening degree setting signal 23 accordingly.

Further, the controller 18 has a second function generator 26 for outputting a steam temperature setting signal 25 based on the output command 21. As shown in FIG. 7, when the output command 21 increases, the second function generator 26 increases the steam temperature setting signal 25 in accordance with the increase of the output command 21, and from the state where the output command 21 reaches, for example, 40% of the boiler load. Thereafter, a steam temperature setting signal 25 of, for example, about 538 ° C. for setting the main steam temperature constant is output.

Further, a steam temperature setting signal 25 from the second function generator 26 and a steam temperature detection signal 20 from a steam temperature detector 19 provided at the outlet of the final superheater 12 are input and subtracted. A subtractor 27, and a proportional-integral adjuster 30 for outputting a correction signal 29 so as to eliminate a deviation signal 28 from the subtracter 27. 1 is provided with an adder 31 for adding to the control valve opening setting signal 23 from the function generator 24 of FIG.
The control signal 22 from the adder 31 is output to the spray control valve 17.

In the conventional controller 18 described above, the control valve opening setting signal 23 based on the output command 21 is set by the first function generator 24, while the output command from the second function generator 26 is set. A steam temperature setting signal 25 based on 21;
A subtractor 27 subtracts the steam temperature detection signal 20 from the steam temperature detector 19 and a correction signal 29 from a proportional-plus-integral controller 30 acting to eliminate the deviation signal 28. The spray control valve 1 is added to the control valve opening setting signal 23, and the control signal 22 obtained thereby adds
7 is controlled.

When the boiler shown in FIG. 8 is operated for a long period of time, scale adheres to the inner surface of the furnace wall 1a of the boiler furnace 1, and the pressure loss of the furnace wall 1a increases.
For this reason, a phenomenon occurs in which the discharge pressure of the water supply pump 5 that is controlled to supply the water 6 at the set flow rate gradually increases. When the discharge pressure of the water supply pump 5 increases, the differential pressure applied to the spray control valve 17 increases, and the flow rate of the spray water 16 supplied to the spray nozzle 11 increases.

At the same load, the swallowing amount of the steam 9 in the steam turbine 13 is the same, so that the flow rate of the feed water 6 supplied to the furnace wall 1a of the boiler furnace 1 decreases by the increase in the spray flow rate. This causes a problem that the metal temperature of the furnace wall 1a of the boiler furnace 1 rises.

As described above, when the metal temperature of the furnace wall 1a of the boiler furnace 1 increases, the combustion of the burner 3 is adjusted.
Alternatively, the opening degree of the spray control valve 17 is corrected.

[0013]

However, as described above, when the metal temperature of the furnace wall 1a rises due to the adhesion of the scale to the furnace wall 1a, conventionally, the combustion adjustment of the burner 3 or the spray control valve is performed. Although the adjustment is made by correcting the opening degree of 17 or the like, such adjustment work is very troublesome and has a problem that adjustment requires skill.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. By controlling the opening degree of a spray control valve based on an increase in pressure at an inlet of a economizer, the metal temperature of a furnace wall is controlled. Automatically prevent the rise of

[0015]

According to the present invention, a spray pipe is provided with a spray control valve on a spray pipe for branching a part of feed water introduced to a boiler furnace through a economizer and supplying the branch to a spray nozzle at an inlet of a final superheater. A first function generator that outputs a control valve opening setting signal based on an output command, a second function generator that outputs a steam temperature setting signal based on an output command, and the second function generator A subtractor for subtracting the steam temperature setting signal from the steam temperature detector and the steam temperature detection signal from the steam temperature detector provided at the outlet of the final superheater, and a correction signal for eliminating a deviation signal from the subtractor. A superheater spray control device comprising: a proportional-integral controller that outputs a signal; and an adder that outputs a control signal obtained by adding a correction signal of the proportional-integral controller to the control valve opening setting signal to the spray control valve. Pressure for detecting the feedwater pressure at the economizer inlet And a third function generator for outputting a economizer inlet pressure setting signal based on the output command; an economizer inlet pressure detection signal from the pressure gauge; and an economizer from the third function generator. A subtractor for subtracting an inlet pressure setting signal, a fourth function generator for receiving a pressure deviation signal from the subtractor and outputting a valve opening correction signal, and a fourth function generator And an adder for adding a valve opening correction signal from the controller to a control valve opening setting signal from the first function generator.

In the present invention, the pressure at the economizer inlet is detected by focusing on the fact that the scale adheres to the oven wall of the boiler furnace and the water supply pressure at the economizer inlet rises due to the pressure loss of the oven wall. By changing the opening of the spray control valve so as to decrease the control valve opening setting signal based on the increase in the economizer inlet pressure detection signal, the flow rate of feedwater supplied to the boiler furnace is controlled by the furnace wall. Automatically adjusts the flow rate before the scale adheres to the furnace wall to prevent the metal temperature of the furnace wall from rising.

[0017]

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

FIG. 4 shows an embodiment of the present invention applied to the conventional apparatus shown in FIG. 8. The same elements as those in FIG.

As shown in FIG. 4, a steam temperature detection signal 2 from a steam temperature detector 19 provided at the outlet of the final superheater 12 is provided.
0 and an output command (MWD) 21 as well as an economizer inlet pressure detection signal 33 from a pressure gauge 32 provided to detect the pressure of the feedwater 6 at the economizer 8 inlet. A controller 34 is provided, and the opening of the spray control valve 17 is controlled by the control signal 22 from the controller 34.

FIG. 1 is a block diagram showing an example of the controller 34. The controller 34 outputs the output command 21 as in FIG.
And a second function generator 26 that outputs a steam temperature setting signal 25 based on the output command 21. 2 and a steam temperature detector 25 provided at the outlet of the final superheater 12.
And a subtractor 27 for inputting and subtracting the steam temperature detection signal 20 from the second detector 9 and a deviation signal 2 from the subtracter 27.
And a proportional-integral adjuster 30 for outputting a correction signal 29 so as to eliminate the control signal 8 from the first function generator 24.
3 is provided, and the opening of the spray control valve 17 is controlled by a control signal 22 from the adder 31.

The controller 34 having the above configuration is provided with a third function generator 36 for outputting the economizer inlet pressure setting signal 35 based on the output command 21. As shown in FIG. 2, when the output command 21 increases, the third function generator 36 increases the inlet pressure of the economizer 8 by increasing the flow rate of the feed water 6 in FIG. Is output as a pressure-saving device pressure setting signal 35 indicating an increase in pressure with an increase in pressure.

Further, there is provided a subtractor 37 for subtracting the economizer inlet pressure setting signal 35 from the third function generator 36 and the economizer inlet pressure detection signal 33 from the pressure gauge 32. I have. Normally, the inlet pressure of the economizer 8 changes with respect to the output command 21 as shown by a solid economizer inlet pressure setting signal 35 shown by a solid line in FIG. As the feedwater pressure at the inlet 8 increases, the pressure-saving gas detector pressure detection signal 33 detected by the pressure gauge 32 is as shown in FIG.
It becomes higher than the economizer inlet pressure setting signal 35 as shown by the middle broken line.

For this reason, when the scale adheres to the furnace wall 1a, a pressure deviation signal 38 is output from the subtracter 37 which subtracts the economizer inlet pressure setting signal 35 and the economizer inlet pressure detection signal 33. The pressure deviation signal 38 is input to the fourth function generator 39.

As shown in FIG. 3, when the pressure deviation signal 38 exceeds a predetermined value X, the fourth function generator 39 outputs a minus (-) valve opening in accordance with the magnitude of the pressure deviation signal 38. A correction signal 40 is output.

Further, an adder 4 configured to add the valve opening correction signal 40 from the fourth function generator 39 to the control valve opening setting signal 23 from the first function generator 24.
1 is provided.

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

In the boiler shown in FIG. 4, when the scale adheres to the furnace wall 1a of the boiler furnace 1, the feed water pressure at the inlet of the economizer 8 increases due to the pressure loss.

Then, in response to the economizer inlet pressure setting signal 35 set by the third function generator 36 in the controller 34 of FIG. 1 based on the output command 21, as shown in FIG. 32 saver inlet pressure detection signal from 32
Is higher, and therefore the economizer inlet pressure setting signal 3
The pressure deviation signal 38 is output from a subtractor 37 that subtracts the pressure-saving signal 5 from the economizer inlet pressure detection signal 33 to a fourth function generator 39.
Will be output to

As shown in FIG. 3, the fourth function generator 39 outputs a valve opening correction signal 40 in response to the pressure deviation signal 38, and the pressure deviation signal 38 has a predetermined value. When the value exceeds X, a negative (-) valve opening correction signal 40 corresponding to the magnitude of the pressure deviation signal 38 is output to the adder 41, and the control valve opening setting signal from the first function generator 24 is output. Add to 23.

As described above, the negative valve opening correction signal 40 is added to the control valve opening setting signal 23 in response to the increase of the feed water pressure at the inlet of the economizer 8, thereby providing the control signal 2
As a result, the opening of the spray control valve 17 is controlled to be reduced.

As a result, the flow rate of the feed water 6 supplied to the boiler furnace 1 is automatically adjusted to the flow rate before the scale adheres to the furnace wall 1a, and the metal temperature of the furnace wall 1a rises. Can be prevented.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the scope of the present invention.

[0033]

According to the superheater spray control apparatus of the present invention, attention is paid to the fact that the scale is attached to the furnace wall of the boiler furnace, and the pressure of the furnace wall increases the feedwater pressure at the inlet of the economizer. By changing the opening of the spray control valve to decrease the control valve opening setting signal based on the increase in the economizer inlet pressure detection signal that is detecting the pressure at the economizer, the boiler furnace The flow rate of supplied water
An excellent effect of automatically adjusting the flow rate before the scale adheres to the furnace wall to prevent the metal temperature of the furnace wall from increasing can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a controller showing an embodiment of the present invention.

FIG. 2 is a diagram showing the operation of a third function generator of FIG. 1;

FIG. 3 is a diagram showing the operation of the fourth function generator of FIG. 1;

FIG. 4 is a block diagram showing an example of a boiler to which the present invention is applied.

FIG. 5 is a block diagram showing an example of a conventional controller.

FIG. 6 is a diagram showing the operation of the first function generator of FIG. 5;

FIG. 7 is a diagram showing the operation of the second function generator of FIG. 5;

FIG. 8 is a block diagram showing an example of a superheater spray control device provided in a conventional boiler.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 boiler furnace 6 feed water 8 economizer 11 spray nozzle 12 final superheater 15 spray pipe 17 spray control valve 19 steam temperature detector 20 steam temperature detection signal 21 output command 22 control signal 23 control valve opening setting signal 24 first function Generator 25 Steam temperature setting signal 26 Second function generator 27 Subtractor 28 Deviation signal 29 Correction signal 30 Proportional integration controller 31 Adder 32 Pressure gauge 33 Energy saving unit inlet pressure detection signal 34 Controller 35 Energy saving Unit inlet pressure setting signal 36 Third function generator 37 Subtractor 38 Pressure deviation signal 39 Fourth function generator 40 Valve opening correction signal 41 Adder

Claims (1)

[Claims] 1. A spray control valve provided in a spray pipe for branching a part of water supplied to a boiler furnace through a economizer and supplying the spray nozzle to a spray nozzle at an inlet of a final superheater, and a control valve based on an output command. A first function generator that outputs an opening degree setting signal, a second function generator that outputs a steam temperature setting signal based on an output command, a steam temperature setting signal from the second function generator, and a final function generator. A subtractor that subtracts a steam temperature detection signal from a steam temperature detector provided at the superheater outlet, and a proportional-integral controller that outputs a correction signal so as to eliminate a deviation signal from the subtractor, A superheater spray control device including an adder that outputs a control signal obtained by adding a correction signal of the proportional integration controller to the control valve opening degree setting signal to the spray control valve, wherein Pressure gauge that detects the supply water pressure of the A third function generator that outputs a coal inlet pressure setting signal, subtracts the economizer inlet pressure detection signal from the pressure gauge and the economizer inlet pressure setting signal from the third function generator. A fourth function generator that inputs a pressure deviation signal from the subtractor and outputs a valve opening correction signal, and outputs a valve opening correction signal from the fourth function generator. An adder for adding the control valve opening setting signal from the first function generator to the control valve opening setting signal.