JPH1038258A - Method and apparatus for calculating coal output during normal shutdown of coal-fired boiler mill - Google Patents

Abstract

(57) [Summary] [Problem] To accurately obtain the coal output expected to be discharged from the mill when the mill is normally stopped, and supply more coal than necessary to the fuel flow rate command into the furnace of the boiler. Provided is a method and an apparatus for calculating the amount of coal output during a normal stop of a mill of a coal-fired boiler, which can prevent a decrease in exhaust gas and an increase in steam temperature while preventing the exhaust gas from being lost. SOLUTION: When a coal gate is closed, a coal supply amount 11 at a time when a coal feeder is stopped is held as a residual coal amount signal 12, and the residual coal amount signal 12 is timed based on test data previously performed. Coal output simulation gain 34 given as a function of
Is multiplied to obtain a coal output simulation signal 21 and output as a coal output 23 predicted to be output from the mill when the mill is normally stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for calculating a coal output when a coal-fired boiler is normally stopped at a mill.

[0002]

2. Description of the Related Art Generally, in the case of a coal-fired boiler, as shown in FIG. 3, coal stored in a coal bunker 1 is supplied to a coal feeder 3 driven by a drive device 2 such as a motor.
The pulverized coal pulverized in the mill 4 for coal pulverization is pneumatically conveyed to the burner 6 through the pulverized coal pipe 5 and burned in the furnace 8 of the boiler 7.

In FIG. 1, reference numeral 9 denotes a coal gate which is opened and closed by a driving device 10 such as a motor.

Since the amount of coal (pulverized coal) supplied from the mill 4 into the furnace 8 of the boiler 7 cannot be directly measured, the weight of the coal present on the coal feeder 3 is shown. In addition to the measurement using a load cell or the like, the number of revolutions of the driving device 2 of the coal feeder 3 is measured, and the product of these is defined as the coal feed supplied from the coal feeder 3 to the mill 4. The coal output is estimated to be supplied from the mill 4 to the furnace 8 of the boiler 7.

In general, a plurality of (for example, six) mills 4 are provided for one boiler 7, and when the boiler 7 is in a normal operation, the amount of coal output of each mill 4 is reduced. The sum is compared with a fuel flow rate command based on a boiler load command (MWD), and based on the comparison result, a coal feed command to each coal feeder 3 is obtained. The device 3 is controlled.

On the other hand, for example, when one mill 4 is normally stopped, first, the coal gate 9 of the coal bunker 1 corresponding to the mill 4 is closed, and the coal remaining on the coal feeder 3 is removed from the mill 4.
After charging into the mill, the coal feeder 3 is stopped. However, if the coal is left in the mill 4, the coal remaining in the mill 4 may ignite. After the stop of 3, the operation of the mill 4 needs to be continued for a required time, and a process of discharging the coal remaining in the mill 4 into the furnace 8 needs to be performed.

However, as described above, one mill 4
When the coal feeder 3 is stopped by closing the coal gate 9 in order to normally stop the coal supply, the coal supply amount becomes zero at that time, but actually, the coal output from the mill 4 has a pulverization delay. After stopping the coal feeder 3, the mill 4 is emptied to empty the mill 4.
Since coal is continuously output from the inside, unnecessarily large amount of coal exceeding the fuel flow rate command is supplied into the furnace 8 of the boiler 7, resulting in excessive fuel and a decrease in exhaust gas O ₂ , There was a risk that the temperature would rise.

For this reason, conventionally, as shown in FIG. 4, during normal operation, the amount of coal 11 charged into the mill 4 from the coal feeder 3 is output as it is as a signal 11 '(to the b side in the figure). On the other hand, when the coal gate 9 is closed when the mill is normally stopped, a signal 38 of "0" output from the signal generator 37 is output as a signal 11 '(switched to the a side in the figure). During normal operation, the signal 11 'output from the switch 36 is output as it is as a signal 12 (switched to the b side in the figure), while when the coal gate 9 is closed when the mill is normally stopped, the switch is A switch 13 which holds a signal 11 'of the coal supply amount 11 immediately before it becomes "0" output from 36 and outputs it as a signal 12 indicating the remaining coal amount (switched to a side in the figure) A timer 16 that outputs a signal 1 of “1” after a lapse of a required time (t [minutes] from the time when the coal gate switching command 14 for closing the coal gate 9 is output during the normal stop of the mill; During operation, the signal 12 output from the switch 13 is used as the signal 19 as it is.
(Switched to the b side in the figure)
When the coal gate 9 is closed when the mill is normally stopped, a signal 18 of "0" output from the signal generator 17 is output as a signal 19 after the elapse of the time set by the timer 16 (switched to the a side in the figure). When the switch 19 and the signal 19 output from the switch 20 change, the change in the signal 19 is followed so as to cause a preset time delay, and the coal is discharged from the mill 4 during the normal stop of the mill. A primary delay unit 22 that outputs a coal output simulation signal 21 predicted to be produced, and a signal 11 ′ output from the switch 36 during normal operation is output as the coal output 23 as it is (b side in the figure). On the other hand, when the coal gate 9 is closed during the normal stop of the mill, the coal output simulation signal 21 output from the primary delay unit 22 is output as the coal output 23 (cut to the a side in the figure). And the switching unit 39) constitutes a coal output calculation device.

In the case of the conventional coal output calculation device as described above,
At the time of steady operation, the coal feed amount 11 to be fed into the mill 4 from the coal feeder 3 is output as it is to the switch 39 via the switch 36 as a signal 11 ', and the signal 11' of the coal feed 11 is output to the switch Via 39, the coal output 23 is output as it is.

On the other hand, in order to normally stop the mill 4, a coal gate switching command 14 for closing the coal gate 9 of the coal bunker 1 corresponding to the mill 4 is output, and the coal gate 9
Is closed, the switch 36 outputs the signal 38 of "0" outputted from the signal generator 37 as the signal 11 ', and as shown in FIG. When the gate 9 is closed, x [ton / h] changes from "0" to "0". However, when the coal gate 9 is closed when the mill is normally stopped, the switch 13 immediately before the output from the switch 36 at that time immediately becomes "0". Is held and output to the switch 20 as a signal 12 indicating the remaining coal amount.

When the coal gate switch command 14 is output, a signal 15 of "1" is output from the timer 16 after a required time (t [minutes]), and the signal 12 output from the switch 13 is switched. After the time set by the timer 16 elapses from the state of being output as the signal 19 via the device 20, the switch 20 is switched to a signal 18 of “0” output from the signal generator 17. 19 is output to the first-order lag unit 22. The first-order lag unit 22 follows a change in the signal 19 output from the switching unit 20 so that a predetermined time delay occurs. Is output to the switch 39, and the switch 39
Thus, the coal output simulation signal 21 is output as the coal output 23.

Thus, when one of the mills 4 is normally stopped, the amount of coal output 2 predicted to be removed from the mill 4 is calculated.
By three, the coal output 23 of the coal supplied from the remaining plurality of mills 4 into the furnace 8 of the boiler 7 is reduced.

[0013]

As described above, the mill 4 is
When coal is discharged from mill 4 to shut down normally,
The coal output 23 becomes substantially constant after the coal gate 9 is closed.
The state continues for a predetermined time and then decreases
However, as described above, coal removal is performed simply by providing the first-order delay unit 22.
When the simulation signal 21 is generated, the coal output 23 tends to decrease.
Can only be set with a curve that uniquely determines
The difference between the actual coal output and the actual
It is not enough to look at, and there is still too much fuel
Exhaust gas O 2 may decrease or the steam temperature may increase.
There was room for improvement.

According to the present invention, in view of such circumstances, it is possible to accurately obtain the coal output 23 predicted to be discharged from the mill 4 when the mill is normally stopped, and to obtain coal that exceeds the fuel flow rate command more than necessary. It is intended to provide a method and an apparatus for calculating the amount of coal output during a normal stop of a mill of a coal-fired boiler, which can prevent the exhaust gas O ₂ from being reduced and prevent the steam temperature from rising due to being prevented from being supplied into the furnace 8 of the boiler 7. Things.

[0015]

According to the present invention, when the mill is normally stopped, the coal supply amount 11 at the time of closing the coal gate 9 is held as the residual coal amount, and the residual coal amount is subjected to a test data set in advance. Multiplying a coal output simulation gain 34 given as a function of time based on the above, to obtain a coal output 23 predicted to be output from the mill 4 when the mill is normally stopped. It relates to a method of calculating the amount of coal output at the time.

Also, according to the present invention, during a steady operation, the amount of coal 11 fed from the coal feeder 3 to the mill 4 is directly changed to a signal 11 '.
On the other hand, when the coal gate 9 is closed when the mill is normally stopped, a switch 38 that outputs a signal "0" 38 output from the signal generator 37 as the signal 11 ', and an output from the switch 36 during normal operation. Signal 11 '
Is output as a signal 12 as it is, and when the coal gate 9 is closed during the normal stop of the mill, the signal 11 'of the coal supply 11 immediately before becoming "0" output from the switch 36 at that time is held and retained. A switch 13 for outputting as a signal 12 representing the amount of coal, and a signal generator 2 for steady operation.
The signal 26 of "0" output from 5 is output as the signal 30, while the signal 28 of "1" output from the signal generator 27 when the coal gate 9 is closed when the mill is normally stopped.
29 as a signal 30, and the switch 29
Rate changer 31 that outputs a rate-of-change correction signal 32 by performing a process of limiting the rate of change to a range equal to or less than a set value when the signal 30 output from the controller 30 changes from “0” to “1”. A function generator 33 for calculating and outputting a coal output simulation gain 34 based on a change rate correction signal 32 output from the change rate limiter 31; and a coal output simulation gain output from the function generator 33. 34 is multiplied by the signal 12 indicating the amount of coal supply 11 output from the switch 13, and the mill 4
A multiplier 35 that outputs a coal output simulation signal 21 that is predicted to be output from the reactor, and a signal 41 of “0” output from a signal generator 40 during a steady operation is output as a signal 21 ′. A switch 42 that outputs the coal output simulation signal 21 output from the multiplier 35 as a signal 21 ′ when the coal gate 9 is closed during a normal stop;
Is added to the signal 11 ′ output from the switch 36 to output the coal output 23.
4. A coal output calculation device for a coal-fired boiler at the time of a normal stop of a mill, comprising:

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

In the method for calculating the coal output during the normal stop of the mill of the coal-fired boiler according to the present invention, the coal feed 11 at the time of closing the coal gate 9 at the time of the normal stop of the mill is held as the remaining coal, and the remaining coal is calculated. Simulated coal output gain 3 given as a function of time based on test data
4 and the coal output 23 predicted to be discharged from the mill 4 when the mill is normally stopped is obtained.

In the apparatus for calculating coal output during the normal stop of the mill of the coal-fired boiler according to the present invention, the coal feed 11 supplied from the coal feeder 3 to the mill 4 is switched via the switch 36 during the steady operation. Signal 11 'is output to the adder 24 as a signal 11', and the signal 11 'of the coal supply 11 is output to the multiplier 35 as it is via the switch 13 as the signal 12, but is output from the signal generator 40. Since the signal 41 of “0” is output from the switch 42 to the adder 24 as a signal 21 ′, the coal feed 11 is output from the adder 24 as it is as the coal output 23 while the mill 4 is When the coal gate 9 of the coal bunker 1 corresponding to the mill 4 is closed for normal stop, the switch 36 outputs the signal 38 of "0" output from the signal generator 37 as the signal 11 '. , Coal supply signal 11 Is set to "0" when the coal gate 9 is closed, but the switch 13 is used when the coal gate 9 is closed when the mill is normally stopped. 11 signals 1
1 'is held and output to the multiplier 35 as the signal 12 representing the remaining coal amount. When the coal gate 9 is closed, the signal 1 of "1" output from the signal generator 27 is output from the switch 29. Output to the rate-of-change limiter 31 as a signal 30;
The change rate limiter 31 performs a process of limiting the rate of change of the signal 30 from the switch 29 that has changed from “0” to “1” to within a range equal to or less than a set value. The change rate correction signal 3 output to the generator 33 and output from the change rate limiter 31 in the function generator 33
And a multiplier 3 for calculating a coal output simulation gain 34 based on
5 and the multiplier 35 multiplies the coal output simulation signal 34 output from the function generator 33 by the signal 12 of the coal output 11 output from the switch 13,
The coal removal amount simulation signal 21 predicted to be removed from the mill 4 when the mill is normally stopped is sent to the adder 2 via a switch 42.
4 as a signal 21 ′, and in the adder 24, a signal 21 ′ (coal removal amount simulation signal 21 output from the multiplier 35) output from the switch 42 is output from the switch 36. The signal is added to the signal 11 ′ (“0” after the coal gate 9 is closed) and output as the coal output 23.

As a result, when one of the mills 4 is normally stopped, the coal output amount 2 which is predicted to be discharged from the mill 4
By three, the coal output 23 of the coal supplied from the remaining plurality of mills 4 into the furnace 8 of the boiler 7 is reduced.

Here, as in the prior art, simply the first-order lag device 2
2 is used to generate the coal output simulation signal 21, only the curve that uniquely determines the slope of the reduction of the coal output 23 when the coal is discharged from the mill 4 to normally stop the mill 4. Although it cannot be set, in the case of the present invention, the combination of the change rate limiter 31 and the function generator 33 causes the slope of the reduction of the coal output 23 to be a function of the time corresponding to the test data in the actual machine. , The error between the coal output 23 output from the adder 24 and the actual coal output is minimized, and the fuel becomes excessive and the exhaust gas O ₂
And the steam temperature does not rise.

[0022]

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

FIGS. 1 and 2 show an example of an embodiment of the present invention. In the figures, the parts denoted by the same reference numerals as those in FIGS. 3 to 5 represent the same parts. The signal 26 of “0” output from the signal generator 25 is
While the coal gate 9 is closed when the mill is normally stopped, the switch 31 outputs the signal 28 of "1" output from the signal generator 27 as the signal 30. The signal 31 is the signal 30 output from the switch 29. Is "0" to "1"
When the change rate is changed to a change rate limiter that performs a process of limiting the change rate to a range equal to or less than a set value and outputs a change rate correction signal 32, a change rate limiter 33 outputs the change rate output from the change rate limiter 31. A function generator 35 for calculating and outputting a coal output simulation gain 34 based on the correction signal 32;
Is multiplied by the coal output simulation signal 34 output from the switch 13 to output the coal output simulation signal 21 predicted to be output from the mill 4 during normal mill stop. The output multiplier 42 outputs the signal 41 of "0" output from the signal generator 40 as a signal 21 'during normal operation, while output from the multiplier 35 when the coal gate 9 is closed during normal mill stop. The switch 24 outputs the coal output simulation signal 21 as a signal 21 ′. The switch 24 outputs the signal 21 ′ output from the switch 42 to the switch 3.
This is an adder that outputs the coal output 23 in addition to the signal 11 ′ output from 6.

The change rate of the change rate limiter 31 and the function of the function generator 33 are set based on test data previously performed.

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

At the time of steady operation, the amount 11 of coal fed into the mill 4 from the coal feeder 3 is output to the adder 24 as a signal 11 ′ through the switch 36, and the signal 11 Is output as it is to the multiplier 35 as the signal 12 via the switch 13, but the signal 41 of "0" output from the signal generator 40 is output from the switch 42 to the adder 24 as the signal 21 '. Therefore, the adder 24 outputs the coal supply amount 11 as it is as the coal output amount 23.

On the other hand, when the coal gate 9 of the coal bunker 1 corresponding to the mill 4 is closed in order to normally stop the mill 4, the switch 36 outputs a “0” signal 38 output from the signal generator 37. Is output as a signal 11 ′,
As shown in FIG. 2, when the coal gate 9 is closed, the signal 11 ′ of the coal supply changes from x [ton / h] to “0”.
Reference numeral 3 denotes a signal 12 'indicating the residual coal quantity by holding the signal 11' of the coal supply quantity 11 immediately before it becomes "0" output from the switch 36 at the time when the coal gate 9 is closed when the mill is normally stopped. To the multiplier 35.

When the coal gate 9 is closed, a "1" signal 28 output from the signal generator 27 is switched to a switch 29.
Is output to the rate-of-change limiter 31 as a signal 30. The rate-of-change limiter 31 limits the rate of change of the signal 30 from the switch 29 that has changed from "0" to "1" to be within a set value or less. Is performed, a change rate correction signal 32 is output to a function generator 33, and in the function generator 33, based on the change rate correction signal 32 output from the change rate limiter 31, a coal output simulation gain 34 is calculated. It is obtained and output to a multiplier 35, where the function generator 33
The output coal simulation gain 34 output from the switch 13
Is supplied to the adder 24 via the switching unit 42. The simulation signal 21 is multiplied by the signal 12 indicating the amount of coal supply 11 output from the milling unit. 21 ', and in the adder 24, the signal 21' output from the switch 42 (the coal output simulation signal 21 output from the multiplier 35) is output as the signal 11 'output from the switch 36. ("0" after the closing of coal gate 9)
And output as a coal output 23.

As a result, when one of the mills 4 is normally stopped, the amount of coal output 2 predicted to be removed from the mill 4
By three, the coal output 23 of the coal supplied from the remaining plurality of mills 4 into the furnace 8 of the boiler 7 is reduced.

Here, as in the conventional case, the first-order lag device 2 is simply used.
2 is used to generate the coal output simulation signal 21, only the curve that uniquely determines the slope of the reduction of the coal output 23 when the coal is discharged from the mill 4 to normally stop the mill 4. Although it cannot be set, in the case of the illustrated example, the inclination of the reduction of the coal output 23 is reduced by the combination of the change rate limiter 31 and the function generator 33 in the time corresponding to the test data in the actual machine. Since it can be set as a function, the error between the coal output 23 output from the adder 24 and the actual coal output is minimized, and the fuel becomes excessive and the exhaust gas O
₂ does not drop or the steam temperature does not rise.

In this way, it is possible to accurately obtain the coal removal amount 23 predicted to be removed from the mill 4 when the mill is normally stopped, and to supply unnecessarily more coal exceeding the fuel flow rate command into the furnace 8 of the boiler 7. It is possible to prevent a decrease in exhaust gas O ₂ and an increase in steam temperature.

It should be noted that the method and apparatus for calculating the coal output at the time of the normal stop of the mill of the coal-fired boiler according to the present invention are not limited to the illustrated examples described above, and various methods may be used without departing from the scope of the present invention. Of course, changes can be made.

[0033]

As described above, according to the method and apparatus for calculating the coal output during the normal stop of the mill of the coal-fired boiler according to the present invention, the output expected to be discharged from the mill 4 during the normal stop of the mill. it is possible to obtain the coal amount 23 accurately, excessive coal above the fuel flow rate command eliminated that would be supplied to the furnace 8 of the boiler 7 can prevent the deterioration and increase of the steam temperature of the exhaust gas O ₂ This can provide an excellent effect.

[Brief description of the drawings]

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

FIG. 2 is a time chart of an example of an embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a coal supply system of a general coal-fired boiler.

FIG. 4 is a block diagram illustrating an example of a conventional coal output calculation device when a mill of a coal-fired boiler is normally stopped.

FIG. 5 is a time chart of the conventional example shown in FIG.

[Explanation of symbols]

 Reference Signs List 3 coal feeder 4 mill 11 coal feed 12 signal 13 switcher 21 coal output simulation signal 21 'signal 23 coal output 24 adder 25 signal generator 26 signal 27 signal generator 28 signal 29 switch 30 signal 31 change Rate limiter 32 Change rate correction signal 33 Function generator 34 Simulated coal output gain 35 Multiplier 36 Switch 37 Signal generator 38 Signal 40 Signal generator 41 Signal 42 Switch

Claims (2)

[Claims] 1. When the mill is normally stopped, the coal supply (11) at the time of closing the coal gate (9) is held as a residual coal amount, and the residual coal amount is determined based on test data conducted in advance. A coal-fired boiler mill characterized in that a coal output simulation gain (34) given as a function is multiplied to obtain a coal output (23) that is predicted to be output from the mill (4) when the mill is normally stopped. Calculation method for coal output during normal shutdown. 2. In a steady operation, the amount (11) of coal supplied from the coal feeder (3) to the mill (4) is directly changed to a signal (1).
A switch (1 ') which outputs a signal (38) of "0" output from the signal generator (37) as a signal (11') when the coal gate (9) is closed when the mill is normally stopped. 36), the signal (11 ') output from the switch (36) during normal operation is output as it is as a signal (12), while the coal gate (9) when the mill is normally stopped is closed at the time when the coal gate (9) is closed. "0" output from the container (36)
A switch (13) that holds the signal (11 ′) of the coal supply amount (11 ′) immediately before and outputs it as a signal (12) representing the remaining coal amount, and outputs the signal from the signal generator (25) during steady operation. The signal (26) of "0" is output as the signal (30), while the signal (2) of "1" output from the signal generator (27) when the coal gate (9) is closed when the mill is normally stopped.
8) as a signal (30), a switch (29), and a signal (30) output from the switch (29) is "0".
Is changed from "1" to "1", the rate of change is limited to a range equal to or less than a set value, and the rate-of-change correction signal (3
A rate-of-change limiter (31) for outputting 2) and a function for obtaining and outputting a coal output simulation gain (34) based on a rate-of-change correction signal (32) output from the rate-of-change limiter (31) Multiplying the coal output simulation signal (34) output from the function generator (33) by the coal output (11) signal (12) output from the switch (13); Coal removal simulation signal (2) which is predicted to be removed from mill (4) during normal mill stop
A multiplier (35) that outputs 1) and a signal (41) of “0” output from the signal generator (40) during a steady operation is output as a signal (21 ′), while coal during normal mill stop is output. When the gate (9) is closed, the switch (4) that outputs the coal output simulation signal (21) output from the multiplier (35) as a signal (21 ′).
2) and adding the signal (21 ′) output from the switch (42) to the signal (11 ′) output from the switch (36),
An apparatus for calculating a coal output during a normal stop of a mill of a coal-fired boiler, comprising an adder (24) for outputting a coal output (23).