JPH10332104A - Coal-fired boiler mill feed control method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A temporary increase in main steam pressure accompanying the operation of a soot blower can be suppressed, the main steam pressure can be maintained at a main steam pressure set value, and the amount of power generation in a generator can be reduced. Provided is a method for controlling the amount of coal supplied to a mill of a coal-fired boiler that can control the required amount of power generation. SOLUTION: When operating a soot blower 29, a coal supply command 25a is temporarily reduced to reduce a coal supply 23a by a required amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the amount of coal supplied to a mill of a coal-fired boiler.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 4, a coal-fired boiler in a thermal power plant includes a pulverized coal F as a fuel supplied from a mill 4 in a furnace 1a of a boiler body 1 and a plurality of burners 2 as shown in FIG. The combustion gas G2 is injected into the boiler body 1 to heat water and steam flowing through the heat transfer tube, and the inside of the superheater 5 disposed in the sub-side wall 1b of the boiler body 1. The flowing main steam is superheated, the combustion gas G2 deprived of heat is discharged from the lower end of the rear heat transfer section 1c to the exhaust gas duct 3 as boiler exhaust gas G3, and the superheated steam V superheated by the superheater 5 is superheated steam pipe. The steam turbine 7 is guided to the steam turbine 7, and the steam turbine 7 is driven to drive the generator 8 to generate power.

[0003] Coal from a coal bunker 9 installed above the mill 4 is fed by a coal feeder 11 driven by a driving device 10 such as a motor. The charcoal F is pneumatically conveyed to the burner 2 via the pulverized coal pipe 12.

The amount of power generated by the generator 8 is controlled by controlling the pressure (main steam pressure) and the flow rate (main steam flow rate) of the superheated steam V introduced into the steam turbine 7 to obtain the required power generation amount. The control of the main steam pressure is performed by controlling the amount (coal feed amount) of coal supplied from the coal feeder 11 to the mill 4, and the control of the main steam flow rate is performed. Is performed by adjusting the opening of the main steam flow control valve 13 provided at the inlet of the steam turbine 7 of the superheated steam pipe 6.

In FIG. 4, reference numeral 14 denotes a pressure detector for detecting a main steam pressure 14a. Reference numeral 15 denotes a difference between a main steam pressure set value 16 and a main steam pressure 14a detected by the pressure detector 14, thereby obtaining a main steam pressure. A subtractor that outputs the deviation 15a, and 17 is a subtractor 1
5 is a proportional-integral controller that outputs a megawatt-based signal 17a required to eliminate the main steam pressure deviation 15a by performing a proportional integral process on the main steam pressure deviation 15a output from the main steam pressure deviation 15a. The signal 17a output from the integration controller 17 is added to the boiler master command 1
The adder 20 outputs the set value 20a of the coal supply based on the boiler master command 18a output from the adder 18.
A function generator 21 for detecting and outputting the rotation speed 21a of the driving device 10 of the coal feeder 11; a load cell 22 for detecting the weight 22a of the coal present on the coal feeder 11; The weight detector 23 calculates the product of the number of revolutions 21a of the driving device 10 detected by the rotation detector 21 and the weight 22a of the coal detected by the weight detector 22, and outputs the actual coal supply 23a. , 24 is a subtractor for calculating the difference between the coal supply set value 20a output from the function generator 20 and the coal supply 23a output from the multiplier 23, and outputting a coal supply deviation 24a. Integral control for outputting a coal feed command 25a as a mill master for eliminating the coal feed deviation 24a to the drive unit 10 of the coal feeder 11 by proportionally integrating the coal feed amount deviation 24a output from the boiler 24. It is a vessel.

A function as shown in FIG. 5 is set in the function generator 20, and this function increases and decreases the coal supply amount set value 20a substantially in proportion to the increase and decrease of the boiler master command 18a. It means to make it.

In FIG. 4, reference numeral 26 denotes a generator output detector for detecting the actual generator output 26a of the generator 8, and 27 denotes a boiler load command 19 and the generator output detected by the generator output detector 26. 26a is a subtractor for obtaining a difference from the output 26a and outputting a generator output deviation 27a. 28 is an opening for eliminating the generator output deviation 27a by performing a proportional integral process on the generator output deviation 27a output from the subtractor 27. This is a proportional-integral controller that outputs a command 28a to the main steam flow control valve 13.

In operation of the coal-fired boiler shown in FIG. 4, the main steam pressure 14a is detected by the pressure detector 14, and the main steam pressure set value 16 and the main steam pressure detected by the pressure detector 14 are detected by the subtractor 15. The difference from the pressure 14a is obtained, and the main steam pressure deviation 15a is output to the proportional-integral controller 17, where the subtracter 1
5, the main steam pressure deviation 15a is proportionally integrated, and a megawatt-based signal 17a required for eliminating the main steam pressure deviation 15a is output to the adder 18. The adder 18 outputs a boiler load command. 19 is added to the signal 17a output from the proportional-integral controller 17, and a boiler master command 18a is output to the function generator 20. The function generator 20 supplies power based on the boiler master command 18a output from the adder 18. Coal quantity set value 2
0a is calculated and output to the subtractor 24, while the rotation detector 21 detects the rotation speed 2 of the driving device 10 of the coal feeder 11.
1a, the weight 22a of the coal currently present on the coal feeder 11 is detected by the weight detector 22, and the rotation speed 21a of the driving device 10 detected by the rotation The product of the coal and the weight 22a of the coal detected by the weight detector 22 is obtained, and the actual coal supply amount 2
3a is output to the subtractor 24, and the difference between the coal supply set value 20a output from the function generator 20 and the coal supply 23a output from the multiplier 23 is calculated in the subtracter 24. The coal amount deviation 24a is output to a proportional integral controller 25. The proportional integral controller 25 performs a proportional integration process on the coal amount deviation 24a output from the subtracter 24 to eliminate the coal amount deviation 24a. The coal feed command 25a as a mill master is output to the driving device 10 of the coal feeder 11, whereby the actual coal feed 23 supplied to the mill 4 is output.
is controlled so as to be a coal feed set value 20a set based on the boiler master command 18a, and a required amount of the pulverized coal F is supplied from the mill 4 into the furnace 1a of the boiler body 1,
Main steam pressure 14 a introduced into steam turbine 7 is maintained at main steam pressure set value 16.

At the same time, the actual generator output 26a of the generator 8 is detected by the generator output detector 26, and the subtractor 2
In 7, the difference between the boiler load command 19 and the generator output 26a detected by the generator output detector 26 is determined,
The generator output deviation 27a is output to the proportional-integral controller 28. In the proportional-integral controller 28, the generator output deviation 27a output from the subtracter 27 is subjected to proportional integration processing to eliminate the generator output deviation 27a. Opening command 28a
Is output to the main steam flow control valve 13, the opening degree of the main steam flow control valve 13 is adjusted, and the main steam flow introduced into the steam turbine 7 is maintained at a required value.
Is adjusted so that the power generation amount at the required power generation amount becomes the required power generation amount.

Meanwhile, in the case of the coal-fired boiler as described above, as the operation is continued, soot adheres to the inner wall of the furnace wall of the boiler main body 1 and the surface of the heat transfer tube such as the superheater 5 and the like.
The soot blower 29 is inserted and arranged at a required position in the boiler main body 1 and the soot blower 29 is periodically or in accordance with the state of adhering soot from the outside of the boiler main body 1. While gradually inserting in the width direction of the boiler main body 1 (a direction perpendicular to the plane of the paper in FIG. 4), it is rotated around an axis, and the inner surface of the furnace wall of the boiler main body 1 and the surface of the heat transfer tube such as the superheater 5 are rotated. , Etc., and the attached soot is blown off and removed.

In the example of FIG. 4, only the soot blower 29 inserted under the nose portion 1d of the boiler main body 1 is shown, and the soot blower inserted at other places is omitted.

[0012]

However, as described above, when soot is blown from the soot blower 29 onto the inner wall of the furnace wall of the boiler main body 1 or the surface of the heat transfer tube such as the superheater 5 to remove attached soot. The heat absorption rate of the boiler body 1 is improved, and the improvement in the heat absorption rate is a temporary disturbance in the control of the main steam pressure 14a, and as if the coal supply 23a was increased and exceeded the coal supply set value 20a. Is operated as if the coal were put into the mill 4, the main steam pressure 14a temporarily increased, the power generation in the generator 8 exceeded the required power generation, and the control was not performed as desired. was there.

The present invention has been made in view of the above circumstances, and can suppress a temporary increase in main steam pressure due to operation of a soot blower.
An object of the present invention is to provide a method for controlling a mill coal feed rate of a coal-fired boiler, which can maintain the main steam pressure at a set value of the main steam pressure and can control a power generation amount in a power generator to a required power generation amount. .

[0014]

SUMMARY OF THE INVENTION According to the present invention, a coal feed amount is supplied to a coal feeder such that an actual coal feed amount supplied to a mill becomes a set value based on a boiler master command. In the method for controlling the amount of coal supplied to a mill of a coal-fired boiler that outputs
The present invention relates to a method for controlling the amount of coal supplied to a mill of a coal-fired boiler, wherein the operation of the soot blower temporarily reduces the amount of supplied coal to reduce the amount of supplied coal by a required amount.

According to the above means, the following effects can be obtained.

When the soot blower is operated, the heat collection rate of the boiler body is improved, and this improvement in the heat collection rate becomes a temporary disturbance in the control of the main steam pressure introduced into the steam turbine. Is increased and the amount of coal exceeding the set coal supply value acts as if it were fed into the mill, and the main steam pressure attempts to temporarily increase.However, when the soot blower is operating, the When the coal supply is reduced by the required amount by reducing the main steam pressure, the main steam pressure introduced to the steam turbine is maintained at the main steam pressure set value, a temporary increase is avoided, and the power generation amount in the generator is required. The amount of generated power will not be exceeded.

[0017]

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

FIGS. 1 to 3 show an embodiment of the present invention. In the drawings, the same reference numerals as those in FIGS. 4 and 5 denote the same parts. This is similar to the conventional one shown in FIGS. 4 and 5, but the feature of this example is that, as shown in FIGS.
, A signal generator 33 that outputs a signal 32 of α%, a signal 30 of 0% output from the signal generator 31, and a signal generator 33 of α% output from the signal generator 33. A switching relay 35 that outputs one of the signals 32 as a signal 34, and a process of limiting the rate of change to a set value or less when the signal 34 output from the switching relay 35 changes. A rate-of-change limiter 37 that outputs a signal 36, a signal 36 output from the rate-of-change limiter 37, and a signal 3 output from the switching relay 35.
Subtracter 39 for obtaining a difference from the output signal 4 and outputting a deviation signal 38
0% signal 30 output from the signal generator 31
And a switching relay 41 for outputting any one of the deviation signal 38 output from the subtractor 39 as a signal 40.
And the coal feed command 25 output from the proportional-integral controller 25
a is added to the signal 40 output from the switching relay 41, and an adder 42 for outputting a coal supply command 25a 'to the drive unit 10 of the coal feeder 11 is additionally provided.
During the operation, the coal supply command 25a is temporarily reduced to reduce the coal supply 23a by a required amount.

As shown in FIGS. 2 and 3, a circuit for switching the switching relays 35 and 41 is a soot blower 2.
When the operation signal 43 that becomes “1” is input during the operation of No. 9 and the operation signal 43 changes from “0” to “1”, a predetermined time delay T1 is caused to change to “1”. An on-delay timer 45 that outputs a delay signal 44 and a delay signal 44 that is output from the on-delay timer 45 are input, and when the delay signal 44 changes from “0” to “1”, a predetermined time An on-delay timer 47 that outputs a delay signal 46 that changes to "1" by causing a delay T2, and a delay signal 44 output from the on-delay timer 45, the signal 4 of "1"
8 to switch the switching relays 35 and 41 from the b → c side to the a → c side.
7 is reset by the delay signal 46 output from
A signal 48 of "0" is output to output the switching relays 35 and 41.
And a single flip-flop 49 for switching from a → c side to b → c side. The time delay T1 set in the on-delay timer 45 is:
Since there is a slight time lag from when the operation signal 43 of the soot blower 29 is output to when the operation of the soot blower 29 is actually started, this time lag is assumed. On the other hand, the on-delay timer 47 is set. The time delay T2 is set to correspond to the time from when the operation of the soot blower 29 is actually started until immediately before it ends. In FIG. 2, reference numeral 50 denotes a NOT circuit.

Next, the operation of the illustrated example will be described.

During normal operation of the coal-fired boiler in a state where the soot blower 29 is not operated, the switching relays 35 and 41 are switched from b to c, respectively.
0% signal 30 output from signal generator 31 is signal 4
Since it is output to the adder 42 as 0, the coal feed command 25a as a mill master for eliminating the coal feed deviation 24a output from the proportional-integral controller 25 passes through the adder 42 as it is. Is output to the driving device 10 of the coal feeder 11 so that the actual coal feed 23a supplied to the mill 4 becomes the coal feed set value 20a set based on the boiler master command 18a. Then, a required amount of pulverized coal F is supplied from the mill 4 into the furnace 1a of the boiler body 1, and the main steam pressure 14a introduced into the steam turbine 7 is maintained at the main steam pressure set value 16.

On the other hand, when the operation of the coal-fired boiler is continued and soot adheres to the inner surface of the furnace wall of the boiler main body 1 or the surface of the heat transfer tube such as the superheater 5, the operation signal 43 of the soot blower 29 is sent to the on-delay timer 45. The on-delay timer 45 inputs the operation signal 4 of the soot blower 29.
After the elapse of a time delay T1 corresponding to the time from when 3 is output to when the operation of the soot blower 29 is actually started,
The delay signal 44 of “1” is a single flip-flop 49
The single flip-flop 49 is set and the signal 48 of "1" is output to the switching relays 35 and 4
1 is switched from the b → c side to the a → c side.

When the switching relays 35 and 41 are switched from the b → c side to the a → c side, the α% signal 32 output from the signal generator 33 is transmitted to the signal 3 via the switching relay 35.
4 is output to the subtractor 39 and the change rate limiter 37, and the change rate limiter 37 performs a process of limiting the change rate of the signal 34 output from the switching relay 35 to within a set value or less. A signal 36 is output to the subtractor 39, and a difference between the signal 36 output from the change rate limiter 37 and the signal 34 output from the switching relay 35 is obtained in the subtracter 39. The signal 40 is output to the adder 42 via the switching relay 41 as a signal 40. In the adder 42, the minus signal 40 output from the switching relay 41 is added to the coal feed command 25a output from the proportional-integral controller 25. It is added and the amount of coal supply 25
is output to the drive unit 10 of the coal feeder 11 as a ', whereby the actual coal feed amount 23a supplied to the mill 4 is calculated from the soot blower set value 20a set based on the boiler master command 18a. The pulverized coal F is controlled by the mill 4 into the furnace 1a of the boiler main body 1 by a required amount smaller than usual by a required amount, so that the pulverized coal F is controlled to be slightly lower by an amount corresponding to the improvement of the heat collection rate of the boiler main body 1 accompanying the operation of the 29 The main steam pressure 14a introduced into the steam turbine 7 is maintained at the main steam pressure set value 16 to avoid a temporary rise,
The amount of power generated by the generator 8 does not exceed the required amount of power generation, and control is performed as desired.

The reason why the decrease in the coal feed amount command 25a is gradually reduced from α% is that the main steam pressure 14 due to the improvement of the heat collection rate of the boiler main body 1 due to the operation of the soot blower 29.
This is because the rise of “a” is only temporary, and stops and stabilizes over time.

The delay signal 44 output from the on-delay timer 45 is applied to the single flip-flop 49
The delay signal 47 is also input to the on-delay timer 47,
When the time delay T2 set in advance from the change of the state of the soot blower 29 from “0” to “1”, that is, the time from when the operation of the soot blower 29 is actually started to immediately before the end thereof has elapsed, the on-delay timer 47 sets “1” Is output to the single flip-flop 49, the single flip-flop 49 is reset and a signal 48 of "0" is output, and the switching relays 35 and 41 are switched from a → c side to b →
Switch to c side.

When the switching relays 35 and 41 are switched from the a → c side to the b → c side, the 0% output from the signal generator 31 is output in the same manner as in the normal operation of the coal-fired boiler described above.
Is output to the adder 42 as a signal 40, and the coal feed command 25a as a mill master for eliminating the coal feed deviation 24a output from the proportional-integral controller 25 is supplied through the adder 42 as it is. It is output to the drive unit 10 of the coal feeder 11 as the quantity command 25a '.
The actual amount of coal supplied to the boiler master command 18a
Is controlled so as to be a coal feed set value 20a set based on the above-described formula, a required amount of pulverized coal F is supplied from the mill 4 into the furnace 1a of the boiler body 1, and the main steam pressure 14a introduced into the steam turbine 7 Is maintained at the main steam pressure set value 16.

In this manner, a temporary increase in the main steam pressure 14a due to the operation of the soot blower 29 can be suppressed, and the main steam pressure 14a can be maintained at the main steam pressure set value 16, and the power generation in the generator 8 Can be controlled to the required power generation.

It should be noted that the method for controlling the amount of supplied coal in a mill of a coal-fired boiler of the present invention is not limited to the above-described illustrated example, and various changes can be made without departing from the scope of the present invention. Of course.

[0029]

As described above, according to the method for controlling the amount of coal supplied to a coal-fired boiler according to the present invention, it is possible to suppress a temporary increase in the main steam pressure accompanying the operation of a soot blower. Can be maintained at the set value of the main steam pressure, and the power generation amount in the power generator can be controlled to the required power generation amount.

[Brief description of the drawings]

FIG. 1 is an overall schematic configuration diagram of an example of an embodiment of the present invention.

FIG. 2 is a switching circuit diagram of the switching relay shown in FIG.

FIG. 3 is a time chart illustrating output signals of respective devices according to an example of an embodiment of the present invention.

FIG. 4 is an overall schematic configuration diagram of a conventional example.

FIG. 5 is a diagram showing functions set in function generator 20 shown in FIGS. 1 and 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boiler main body 4 Mill 5 Superheater 7 Steam turbine 8 Generator 11 Coal supply machine 14 Pressure detector 14a Main steam pressure 18a Boiler master command 20a Coal supply amount set value 23a Coal supply amount 25a Coal supply amount command 29 Soot blower 30 Signal 31 Signal Generator 32 Signal 33 Signal Generator 34 Signal 35 Switching Relay 36 Signal 37 Rate-of-Change Limiter 38 Deviation Signal 39 Subtractor 40 Signal 41 Switching Relay 42 Adder 43 Operation Signal 44 Delay Signal 45 On Delay Timer 46 Delay Signal 47 On Delay Timer 48 signal 49 Single flip-flop V Superheated steam

Claims (1)

[Claims] 1. A coal-fired boiler mill for outputting a coal feed amount command to a coal feeder so that the actual coal feed amount supplied to the mill becomes a coal feed amount set value set based on a boiler master command. A method for controlling the amount of coal supplied to a mill of a coal-fired boiler, wherein the amount of supplied coal is reduced by a required amount during the operation of the soot blower.