JPH07119907A - Method and apparatus for controlling main steam pressure of coal-fired boiler - Google Patents

Abstract

PURPOSE:To enhance response of a main steam pressure of a coal fired boiler by increasing number of revolutions of a rotary classifier according to a pressure deviation when a measured value of a main steam pressure is higher than a set value, and decreasing the number of revolutions of the classifier is according to the pressure deviation when it is lower than the set value. CONSTITUTION:A signal from a second functional generator 21 is added to a signal from a high/low signal limiter 25 by a second adder 22, and output to a motor 26 of a rotary classifier 4. The number of revolutions of a rotary classifier 4 is increased in response to a pressure deviation when a measured value of a main steam pressure is higher than a set value. The number of revolutions of the classifier 4 is decreased according to the deviation when it is lower than the set value. Thus, a supply amount of pulverized coal 2' from a coal mill 3 to a coal fired boiler 5 can be immediately increased or decreased under the control of the number of revolutions of the classifier 4 preferentially to the control of a coal supply amount to the mill 3 by a coal feeder 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a main steam pressure control method and apparatus for a coal fired boiler.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a conventional main steam pressure control device for a coal-fired boiler. As shown in the figure, coal 2 supplied from a coal feeder 1 is pulverized by a coal mill 3. , The pulverized coal 2'is air-carried out to the coal-fired boiler 5 through the rotary classifier 4 mounted on the upper part of the coal mill 3 and burned. The steam 6 is led to a turbine 9 via a main steam pipe 8 having a governor 7.

Further, the steam flow rate at a required position of the main steam pipe 8 is measured by a steam flow meter 10, and a signal from the steam flow meter 10 is input to a function generator 11 to respond to the steam flow rate by a combustion program. The basic coal feed rate is converted, the steam pressure at a required position of the main steam pipe 8 is measured by a steam pressure gauge 12, and the signal from the steam pressure gauge 12 is used as a first subtractor 13 The deviation from the main steam pressure set value A is obtained, and the signal is output to the adder 15 via the first proportional integrator 14, and the adder 15 outputs the signal from the function generator 11 to the adder 15. And the signal from the adder 15 is input to the second subtractor 16 to deviate from the signal indicating the current amount of coal feeding from the coal feeding flow meter 17 provided in the coal feeding machine 1. Is required, the second subtraction Signal from 16 is output to the second proportional integrator 18 through the stoker first electric motor 19 (of the variable rotational speed), coal-fired turbine from the boiler 5 9
The amount of coal supplied is controlled so that the steam pressure introduced into the tank becomes a constant set value.

[0004]

However, in such a conventional means, there is a large time delay from the time when coal is fed to the coal mill 3 to the time when the coal is discharged as the pulverized coal 2 ', which causes a transient change in the main steam pressure. On the other hand, there is a problem that the response is low, and the actual main steam pressure follows the command for controlling the main steam pressure greatly, making it difficult to perform good control.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a main steam pressure control method and apparatus for a coal-fired boiler, which has higher response than before.

[0006]

According to the invention described in claim 1 of the present invention, the main of a coal-fired boiler 5 for controlling the main steam pressure by the coal output from a coal mill 3 equipped with a rotary classifier 4 A steam pressure control method, wherein when the measured value of the main steam pressure is higher than a set value, the rotational speed of the rotary classifier 4 is increased according to the pressure deviation, and when the measured value of the main steam pressure is lower than the set value. The rotary classifier 4 is controlled so as to reduce the rotation speed according to the deviation. The invention according to claim 2 of the present invention is a steam measuring steam flow rate of the main steam pipe 8. A flow meter 10, a first function generator 11 for converting a signal from the steam flow meter 10 into a basic coal feed rate, a steam pressure gauge 12 for measuring the steam pressure of the main steam pipe 8, and a steam pressure gauge 12 The first parameter to derive the deviation from the main steam pressure set value by deriving the signal from A vessel 13, the first proportional integrator 14 which outputs a signal to eliminate deviations obtained by said first subtracter 13
And a first adder 15 for adding the signal from the first proportional integrator 14 to the signal from the first function generator 11.
And a coal feeding flow meter 17 provided in the coal feeding machine 1 for feeding coal to the coal mill 3 and a deviation from the signal from the first adder 15 by guiding a signal from the coal feeding flow meter 17 A coal-fired boiler equipped with a second subtractor 16 to be obtained and a second proportional integrator 18 for outputting a signal for eliminating the deviation obtained by the second subtractor 16 to the electric motor 19 of the coal feeder 1. The main function of the steam pressure control device 5 is a second function generator 21 for converting a signal from the steam flow meter 10 into a basic rotation speed of a rotary classifier 4 provided in the coal mill 3, and the first function generator 21. The third function generator 23 for converting the signal from the subtractor 13 into the amount of increase / decrease in the rotation speed of the rotary classifier 4 and the rate of change of the signal from the third function generator 23 are limited. A rate-of-change limiter 24, a high-low signal limiter 25 for limiting the upper and lower limits of the signal from the rate-of-change limiter 24, and A second adder 22 for adding the signal from the high / low signal limiter 25 to the signal from the second function generator 21 and outputting the signal to the electric motor 26 of the rotary classifier 4. To do.

[0007]

Therefore, according to the first aspect of the present invention, when the rotation speed of the rotary classifier 4 is increased according to the pressure deviation when the measured value of the main steam pressure is higher than the set value, the coal mill 3
The supply amount of fine powder from the coal to the coal-fired boiler 5 is suppressed to lower the main steam pressure, while the rotation speed of the rotary classifier 4 is changed according to the pressure deviation when the measured value of the main steam pressure is lower than the set value. If it is controlled so as to lower, the amount of fine powder supplied from the coal mill 3 to the coal-fired boiler 5 is increased and the main steam pressure is increased.

According to the second aspect of the present invention, the second function generator 21 is based on the signal output from the steam flow meter 10 when the measured value of the main steam pressure is higher than the set value. The basic rotation speed of the rotary classifier 4 is converted with, and the increment of the rotation speed of the rotary classifier 4 is changed by the third function generator 23 based on the signal from the first subtractor 13. By the limiter 24 and the high / low signal limiter 25, for example, to the second adder 22 as a signal that has a rate of change such that it rapidly rises and gradually decreases, and does not exceed the upper limit that interferes with combustion in the coal-fired boiler 5. It is input and is added to the basic rotation speed by the second adder 22 to drive the electric motor 2 of the rotary classifier 4.
When output to 6, the rotation speed of the rotary classifier 4 is increased according to the pressure deviation between the measured value and the set value of the main steam pressure, so that the supply amount of fine powder from the coal mill 3 to the coal-fired boiler 5 is increased. It is suppressed and the main steam pressure is reduced.

When the measured value of the main steam pressure is lower than the set value, the basic rotation speed of the rotary classifier 4 is converted by the second function generator 21 based on the signal output from the steam flow meter 10. At the same time, based on the signal from the first subtracter 13, the third function generator 23 uses the change rate limiter 24 and the high / low signal limiter 25 to decrease the amount of rotation of the rotary classifier 4 rapidly, for example. Is input to the second adder 22 as a signal that has a rate of change that gradually decreases and gradually rises and that does not exceed the lower limit that interferes with combustion in the coal-fired boiler 5, and the second adder 22 When the rotation speed of the rotary classifier 4 is added to the basic rotation speed and output to the electric motor 26 of the rotary classifier 4, the rotation speed of the rotary classifier 4 is lowered according to the pressure deviation between the measured value of the main steam pressure and the set value. , Coal mill 3 to coal-fired boiler 5
The amount of fine powder supplied to the main steam is increased and the main steam pressure is increased.

[0010]

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

FIG. 1 shows an embodiment of the present invention, in which the same reference numerals as those in FIG. 2 represent the same parts.

In the main steam pressure control device 20 having substantially the same structure as the main steam pressure control device of FIG. 2 described above, the signal output from the steam flow meter 10 is the second function generator 21.
Is also converted into the basic rotation speed of the rotary classifier 4 according to the steam flow rate by the basic rotation speed program, and the signal from the second function generator 21 is input to the second adder 22. It is like this.

Further, the signal output from the first subtractor 13 is also led to the third function generator 23 and converted into an increase / decrease amount of the rotation speed of the rotary classifier 4 according to the pressure deviation. , The signal from the third function generator 23 is input to the rate-of-change limiter 24 to limit the rate of change, and the high-low signal limiter 25
And the upper and lower limits of the signal are limited to be guided to the second adder 22.
In, the signal from the second function generator 21 is added to the signal from the high / low signal limiter 25 and is output to the electric motor 26 (variable number of revolutions) of the rotary classifier 4,
When the measured value of the main steam pressure is higher than the set value, the rotation speed of the rotary classifier 4 is increased according to the pressure deviation, and when the measured value of the main steam pressure is lower than the set value, the rotary classification is performed according to the pressure deviation. The control for lowering the rotation speed of the machine 4 is performed.

Therefore, when the measured value of the main steam pressure is higher than the set value, the basic rotation speed of the rotary classifier 4 is increased by the second function generator 21 based on the signal output from the steam flow meter 10. And the amount of increase in the number of revolutions of the rotary classifier 4 is converted by the third function generator 23 based on the signal from the first subtractor 13, and the amount of increase in the number of revolutions is changed. Limiter 2
4. The second adder 2 as a signal that has a rate of change that rapidly increases and gradually decreases by the high / low signal limiter 25 and that does not exceed the upper limit that interferes with combustion in the coal-fired boiler 5.
2 is input to the second adder 22 and is added to the basic rotation speed by the second adder 22, and is output to the electric motor 26 of the rotary classifier 4. The rotation speed of the rotary classifier 4 is the measurement of the main steam pressure. Since it is increased according to the pressure deviation between the value and the set value, the supply amount of the pulverized coal 2 ′ from the coal mill 3 to the coal-fired boiler 5 is suppressed, and the main steam pressure is reduced.

When the measured value of the main steam pressure is lower than the set value, the second function generator 21 converts the basic rotation speed of the rotary classifier 4 based on the signal output from the steam flow meter 10. At the same time, based on the signal from the first subtractor 13, the third function generator 23 converts the reduction amount of the rotation speed of the rotary classifier 4, and the reduction amount of the rotation speed is changed by the rate-of-change limiter. Two
4. The second adder 2 as a signal having a rate of change that sharply decreases and gradually increases by the high / low signal limiter 25 and does not exceed a lower limit that hinders combustion in the coal-fired boiler 5.
2 is input to the second adder 22 and is added to the basic rotation speed by the second adder 22, and is output to the electric motor 26 of the rotary classifier 4. The rotation speed of the rotary classifier 4 is the measurement of the main steam pressure. Since it is lowered according to the pressure deviation between the value and the set value, the supply amount of the pulverized coal 2 ′ from the coal mill 3 to the coal-fired boiler 5 is increased, and the main steam pressure is increased.

Therefore, according to the above-described embodiment, prior to the control of the amount of coal fed to the coal mill 3 by the coal feeder 1, the rotation speed of the rotary classifier 4 is controlled to control the coal mill 3 to the coal-fired boiler 5.
Since the amount of pulverized coal 2'supplied to the steam generator can be immediately increased or decreased, the responsiveness to changes in the main steam pressure can be significantly improved as compared with the conventional case.

The method and apparatus for controlling the main steam pressure of the coal-fired boiler according to the present invention are not limited to the above-mentioned embodiments, and various modifications can be made without departing from the gist of the present invention. Of course.

[0018]

According to the main steam pressure control method and apparatus for a coal-fired boiler of the present invention described above, the rotary classifier 4 is operated prior to the control of the amount of coal fed to the coal mill 3 by the coal feeder 1. Since the supply amount of the pulverized coal 2 ′ from the coal mill 3 to the coal-fired boiler 5 can be immediately increased / decreased by the rotation speed control,
The excellent effect that the responsiveness to the change in the main steam pressure can be significantly improved as compared with the conventional case can be obtained.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coal feeder 3 Coal mill 4 Rotary classifier 5 Coal fired boiler 8 Main steam pipe 10 Steam flow meter 11 First function generator 12 Steam pressure gauge 13 First subtractor 14 First proportional integrator 15 First adder 16 Second subtractor 17 Coal flow meter 18 Second proportional integrator 19 Electric motor 20 Main steam pressure controller 21 Second function generator 22 Second adder 23 Third function Generator 24 Change rate limiter 25 High and low signal limiter 26 Electric motor

Claims (2)

[Claims] 1. A main steam pressure control method for a coal-fired boiler (5), wherein the main steam pressure is controlled by the coal output from a coal mill (3) equipped with a rotary classifier (4). When the measured pressure value is higher than the set value, the rotation speed of the rotary classifier (4) is increased according to the pressure deviation, and when the measured main steam pressure value is lower than the set value, the rotary classification is performed according to the pressure deviation. A main steam pressure control method for a coal-fired boiler, characterized by controlling the number of revolutions of the machine (4). 2. A steam flow meter (10) for measuring a steam flow rate of a main steam pipe (8), and a first function generator (11) for converting a signal from the steam flow meter (10) into a basic coal feed rate. )When,
Steam pressure gauge (1 to measure the steam pressure of the main steam pipe (8)
2) and a first subtractor (13) for guiding the signal from the steam pressure gauge (12) to obtain the deviation from the main steam pressure set value.
And a first proportional integrator (14) for outputting a signal for eliminating the deviation obtained by the first subtractor (13), and a signal from the first proportional integrator (14) for the first proportional integrator (14). Function generator (1
1) A first adder (15) for adding to the signal from the coal mill (3), a coal feeding flow meter (17) provided in the coal feeding machine (1) for feeding coal to the coal mill (3), and the coal feeding flow rate. A second subtractor (16) for deriving a signal from the total (17) to obtain a deviation from the signal from the first adder (15), and the second subtractor (16)
A main steam pressure controller for a coal-fired boiler (5), comprising a second proportional-integrator (18) for outputting a signal for eliminating the deviation obtained in (1) to the electric motor (19) of the coal feeder (1), A second function generator (21) for converting a signal from the steam flow meter (10) into a basic rotation speed of a rotary classifier (4) provided in a coal mill (3); A third function generator (23) for converting the signal from the calculator (13) into an increase / decrease amount of the rotation speed of the rotary classifier (4), and a signal from the third function generator (23) Rate limiter (24) for limiting the rate of change of the signal, and a high / low signal limiter (25) for limiting the upper and lower limits of the signal from the rate of change limiter (24).
And a signal from the high / low signal limiter (25) is added to the signal from the second function generator (21) and output to the electric motor (26) of the rotary classifier (4). A main steam pressure control device for a coal-fired boiler, comprising an adder (22).