JPH1026343A - Method and apparatus for calculating coal output upon purging remaining coal in mill of coal fired boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent decrease of exhaust gas and rise of a vapor temperature by accurately obtaining coal output to estimated to be discharged from a mill at the time of purging remaining coal and eliminating supply of the coal more than a required amount exceeding a fuel flow command into a furnace of a boiler. SOLUTION: The method comprises the steps of holding a coal output 11 at the time of stopping a stoker 3 at the time of mill tripping to make a remaining coal signal 12, multiplying the signal 12 by a coal output simulation gain 34 given as a function of a time based on test data previously obtained to obtain a coal output simulation signal 21, and outputting a coal output 23 estimated to be outputted from the mill at the time of purging the remaining coal.

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 during a coal residue boiler purge in a coal-fired boiler.

[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. This is the amount of coal that will 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 any abnormality occurs in one of the mills 4, the mill 4 and the corresponding coal feeder 3 are urgently stopped, but the mill 4 in which any abnormality has occurred is left as it is. In this case, since coal remaining in the mill 4 may ignite, it is necessary to perform so-called residual coal purging in which the coal remaining in the mill 4 is purged into the furnace 8 after the emergency stop of the mill 4. is there.

However, as described above, one mill 4
After the emergency stop of the mill 4, the remaining coal of the mill 4 that is emergency stopped is in a state in which the amount of coal supplied from the remaining plural (for example, five) mills 4 into the furnace 8 of the boiler 7 is balanced. If the purging is performed, unnecessarily large amount of coal exceeding the fuel flow rate command will be supplied into the furnace 8 of the boiler 7, resulting in excessive fuel and a decrease in the exhaust gas O ₂ and an increase in steam temperature. There was.

For this reason, in the prior art, FIGS.
As shown in FIG. 2, during the steady operation, the amount of coal 11 supplied to the mill 4 from the coal feeder 3 is output as it is as a signal 12 (switched to the b side in the figure). A switcher 13 that holds the coal supply amount 11 at the time and outputs it as a signal 12 representing the remaining coal amount (switched to a side in the figure) and a residual coal purge mill start command 14 after the mill trip are output. A timer 16 that outputs a signal 15 of “1” only for a required time (t [minutes] from the time) and a signal 18 of “0” output from a signal generator 17 during a steady operation are output as a signal 19 ( In the figure,
On the other hand, when the residual coal purge mill is started after the mill trip, the signal 12 output from the switch 13 is output as the signal 19 only for the time set by the timer 16 (a in the figure). Switch 20), and when the signal 19 output from the switch 20 changes, the change in the signal 19 is followed so as to cause a preset time delay, and the remaining coal is purged when the residual coal is purged. A primary delay unit 22 that outputs a coal removal amount simulation signal 21 predicted to be removed from the mill 4, and a coal removal amount simulation signal 21 output from the primary delay unit 22 is transmitted from the coal feeder 3 to the mill 4. In addition to the coal feed amount 11 fed into the furnace, an adder 24 that outputs a coal output 23 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 amount of coal 11 charged into the mill 4 from the coal feeder 3 is output to the adder 24 and the amount of coal 11
Is output as it is as a signal 12 to the switch 20 via the switch 13, and in the switch 20, a "0" signal 18 output from the signal generator 17 during the steady operation is output.
Is output as a signal 19 to the primary delay unit 22, and the coal output simulation signal 21 output from the primary delay unit 22 to the adder 24 is “0”.
1 is output as it is as the coal output 23.

On the other hand, if an abnormality occurs in the mill 4 and the mill 4 and the corresponding coal feeder 3 are urgently stopped, as shown in FIG. [Ton / h] is changed to “0”.
Holds the coal supply amount 11 at the time of stopping the coal feeder 3 and outputs the signal to the switch 20 as a signal 12 representing the remaining coal amount.

After the mill trip, when the residual coal purge mill start command 14 is output, the required time (t
[Minutes]), the signal 15 of “1” is output, and the signal 12 output from the switch 13 is changed from the switch 20 to the signal 19 only as a signal 19 during the time set by the timer 16. 22. In the first-order lag unit 22, a change in the signal 19 output from the switch 20 is
Following a preset time delay, a coal removal amount simulation signal 21 predicted to be removed from the mill 4 at the time of residual coal purge is output to an adder 24, and the primary delay is generated by the adder 24. The coal output simulation signal 21 output from the boiler 22 is supplied to the mill 4 from the coal feeder 3 to the coal feed 11
("0" after the mill trip)
It is output as the coal output 23.

Thus, after one of the mills 4 is stopped in an emergency, the remaining plurality of (for example, five) mills 4 are removed from the boiler 7.
When the residual coal purging of the mill 4 that has been emergency stopped is performed in a state where the coal output 23 of the coal supplied into the furnace 8 is balanced, the residual coal is supplied into the furnace 8 of the boiler 7 by the residual coal purging. The amount of coal output 23 of the coal supplied from the remaining plurality of mills 4 into the furnace 8 of the boiler 7 is reduced by the amount of coal output 23 of the coal.

[0013]

As described above, when coal is discharged from the mill 4 by starting the residual coal purge, the coal output 23 increases until a certain time has elapsed since the start of the residual coal purge. After that, the state of becoming substantially constant continues for a predetermined time and then decreases, but as described above, the primary delay device 22 is simply provided and the coal output simulation signal 21 is provided.
Is created, the slope of the increase in the coal output 23 and the slope of the decrease in the coal output 23 from the start of the residual coal purge until a certain time has elapsed can be set only by the same curve that is uniquely determined. , The difference from the actual coal output increases,
Viewed in precision manner not be said to be sufficient, or reduces the exhaust gas O ₂ is still fuel-excess, there is a possibility that the steam temperature is increased, room for improvement has been left.

According to the present invention, in view of such circumstances, it is possible to accurately obtain the coal removal amount 23 predicted to be removed from the mill 4 at the time of purging residual coal, and to obtain coal that exceeds the fuel flow rate command more than necessary. A method and an apparatus for calculating the amount of coal output at the time of purging remaining coal in a mill of a coal-fired boiler that can prevent the exhaust gas O ₂ from being reduced and prevent the steam temperature from increasing without being supplied into the furnace 8 of the boiler 7. Is what you do.

[0015]

According to the present invention, the amount of coal 11 at the time when the coal feeder 3 is stopped at the time of the mill trip is held as the remaining coal, and the remaining coal is given as a function of time. A coal output boiler simulated gain 34 to obtain a coal output 23 predicted to be removed from the mill 4 when the residual coal is purged. It depends on the method.

Also, according to the present invention, during steady operation, the amount of coal 11 fed from the coal feeder 3 to the mill 4 is output as a signal 12 as it is, while at the time of a mill trip, the amount of coal supplied when the coal feeder 3 is stopped. Signal 1 indicating the remaining coal amount by holding 11
The switch 13 outputs the signal as 2 and the signal 26 of “0” output from the signal generator 25 during the steady operation is output as the signal 30, while the signal generator 27 outputs the signal when the residual coal purge mill is started after the mill trip. "1" signal 2
8 as a signal 30;
9. When the signal 30 output from 9 changes from “0” to “1”, the rate-of-change limiter outputs a rate-of-change correction signal 32 by performing processing for limiting the rate of change to within a set value or less. 31, a function generator 33 for obtaining 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 output from the function generator 33 The gain 34 is multiplied by the signal 12 of the 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 coal mill, and a coal output simulation signal 21 that is output from the multiplier 35 is input from the coal feeder 3 to the mill 4. The present invention relates to an apparatus for calculating a coal output at the time of a mill residual coal purge of a coal-fired boiler, comprising an adder 24 that outputs a coal output 23 in addition to the coal feed 11.

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

In the method for calculating the amount of coal output during the purging of residual coal in a mill of a coal-fired boiler according to the present invention, the amount of supplied coal 11 at the time when the coal feeder 3 is stopped at the time of a mill trip is held as the residual coal amount. The coal output simulation gain 34 given as a function of time based on test data performed in advance for the coal output.
Is applied, and a coal removal amount 23 that is predicted to be removed from the mill 4 during the residual coal purge is obtained.

In the apparatus for calculating the amount of coal output during the purging of residual coal in a mill of a coal-fired boiler according to the present invention, the amount of coal 11 fed into the mill 4 from the coal feeder 3 is supplied to the adder 24 during steady operation. Is output and the coal supply amount 11 is
, And is output as it is to the multiplier 35 as the signal 12. The signal 35 of “0” output from the signal generator 25 during the steady operation is output to the switch 29 and the change rate limiter The coal output simulation signal 21 which is output as the coal output simulation gain 34 via the function generator 31 and the function generator 33 and output from the multiplier 35 to the adder 24 is "0". Means that the amount of coal supply 11 is the same
On the other hand, if any abnormality occurs in the mill 4 and the mill 4 and the corresponding coal feeder 3 are urgently stopped, the coal supply amount 11 becomes “0” at the time of the mill trip, The switch 13 holds the coal supply amount 11 at the time of stopping the coal feeder 3 and outputs a signal 12 representing the remaining coal amount to the multiplier 35.
After mill trip, mill 4 to purge residual coal
Is activated, “1” output from the signal generator 27 is output.
Is output from the switch 29 to the change rate limiter 31 as a signal 30. In the change rate limiter 31,
The signal 30 from the switch 29 that has changed from “0” to “1”
Is performed to limit the rate of change of the range within a set value or less, a rate-of-change correction signal 32 is output to a function generator 33,
In the function generator 33, a coal output simulation gain 34 is obtained based on the change rate correction signal 32 output from the change rate limiter 31, and is output to a multiplier 35.
In the above, the coal output simulation gain 34 output from the function generator 33 corresponds to the coal output 1 output from the switch 13.
1 is output to the adder 24, and a coal output simulation signal 21 predicted to be output from the mill 4 when the residual coal is purged is output to the adder 24.
5 is added to the coal feed 11 (to be “0” after the mill trip) fed into the mill 4 from the coal feeder 3 and output as the coal output 23. Is output.

Thus, after the emergency stop of one mill 4, the coal output 23 of the coal supplied from the remaining plurality of mills 4 into the furnace 8 of the boiler 7 is balanced.
When the residual coal is purged from the mill 4 that has been stopped urgently, the remaining plurality of mills 4 feed the boiler 7 from the remaining plurality of mills 4 by the coal output amount 23 supplied to the furnace 8 of the boiler 7 by the residual coal purge. The amount of coal output 23 of the coal supplied into the furnace 8 is reduced.

Here, as in the prior art, simply the first-order lag device 2
2 to create the coal output simulation signal 21, the gradient of the increase in the coal output 23 from the start of the residual coal purge until a certain time elapses and the gradient of the decrease in the coal output 23 are uniquely determined. However, in the case of the present invention, the combination of the change rate limiter 31 and the function generator 33 increases the coal output 23 until a certain time has elapsed since the start of the residual coal purge. The slope, the state in which the coal output 23 is substantially constant, and the slope of the decrease in the coal output 23 can be set as a function of time corresponding to test data in an actual machine. Output 2 from coal
The error between 3 and the actual coal output is minimized, so that there is no excess fuel and the exhaust gas O ₂ does not drop 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
On the other hand, at the start of the residual coal purge mill after the mill trip, a switch that outputs the signal 1 of “1” output from the signal generator 27 as the signal 30, and the signal 31 output from the switch 29 is the signal 31. When the rate of change from "0" to "1", a rate-of-change limiter that performs a process of limiting the rate of change to within a set value or less and outputs a rate-of-change correction signal 32; A function generator 35 for obtaining and outputting a coal output simulation gain 34 based on the change rate correction signal 32 output from 31, and outputs a coal output simulation gain 34 output from the function generator 33 from the switch 13. A multiplier 12 which multiplies the signal 12 of the supplied coal quantity 11 to output a coal output simulation signal 21 which is predicted to be output from the mill 4 when the residual coal is purged. Coal power simulation signal 21 In addition to the coal feed amount 11 to be introduced from the coal feeder 3 to the mill 4 in the adder 24, it is configured to output a coal output 23.

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.

During normal operation, the amount 11 of coal supplied to the mill 4 from the coal feeder 3 is output to the adder 24,
The coal supply amount 11 passes through the switch 13 and the signal 12
Is output to the multiplier 35.
At the time of steady operation, the signal 26 of “0” output from the signal generator 25 is output as the coal output simulation gain 34 via the switch 29, the change rate limiter 31, and the function generator 33,
Since the coal output simulation signal 21 output from the multiplier 35 to the adder 24 is “0”, the coal feed 11 is output from the adder 24 as it is as the coal output 23.

On the other hand, if some abnormality occurs in the mill 4 and the mill 4 and the corresponding coal feeder 3 are stopped immediately, as shown in FIG. 2, the coal supply amount 11 becomes x [ ton / h] to “0”, but the switch 13 holds the coal supply 11 at the time of stopping the coal feeder 3 and outputs it to the multiplier 35 as a signal 12 representing the remaining coal.

After the mill trip, when the mill 4 is started for purging the residual coal, a "1" signal 28 output from the signal generator 27 is output from the switch 29 to the change rate limiter 31 as a signal 30. Then, the change rate limiter 31 performs a process of limiting the change rate of the signal 30 from the switch 29 that has changed from “0” to “1” within a range equal to or less than a set value, and the change rate correction signal 32 Is output to a function generator 33, a coal output simulation gain 34 is obtained based on the change rate correction signal 32 output from the change rate limiter 31 in the function generator 33, and is output to a multiplier 35. In the multiplier 35, the coal output simulation gain 34 output from the function generator 33 is multiplied by the signal 12 of the coal feed 11 output from the switch 13, and coal is output from the mill 4 when the residual coal is purged. Expected The coal quantity simulation signal 21 is output to the adder 24, where the coal output quantity simulation signal 21 output from the multiplier 35 is supplied from the coal feeder 3 to the mill 4 in the adder 24. 11 (the value is “0” after the mill trip) and is output as the coal output 23.

Thus, after the emergency stop of one of the mills 4, the boiler 7 is removed from the remaining multiple (for example, five) mills 4.
When the residual coal purging of the mill 4 that has been emergency stopped is performed in a state where the coal output 23 of the coal supplied into the furnace 8 is balanced, the residual coal is supplied into the furnace 8 of the boiler 7 by the residual coal purging. The amount of coal output 23 of the coal supplied from the remaining plurality of mills 4 into the furnace 8 of the boiler 7 is reduced by the amount of coal output 23 of the coal.

Here, as in the conventional case, the first-order lag device 2 is simply used.
2 to create the coal output simulation signal 21, the gradient of the increase in the coal output 23 from the start of the residual coal purge until a certain time elapses and the gradient of the decrease in the coal output 23 are uniquely determined. However, in the case of the illustrated example, the combination of the change rate limiter 31 and the function generator 33 increases the coal output 23 until a certain time elapses from the start of the residual coal purge. , The state in which the coal output 23 is substantially constant, and the slope of the decrease in the coal output 23, respectively, can be set as functions of time corresponding to the test data in the actual machine. The error between the coal output 23 output from 24 and the actual coal output is kept to a minimum, and there is no excess fuel, so that the exhaust gas O ₂ does not decrease and the steam temperature does not increase.

In this way, it is possible to accurately obtain the coal removal amount 23 that is predicted to be removed from the mill 4 during the residual coal purging.
To the furnace 8 without exhaust gas O
₂ as well as an increase in steam temperature.

It should be noted that the method and apparatus for calculating the coal output at the time of purging the remaining coal in the mill of the coal-fired boiler of the present invention are not limited to the above-described illustrated examples, but may be made within the scope of the present invention. Of course, various changes can be made.

[0033]

As described above, according to the method and apparatus for calculating the amount of coal removed during the purging of residual coal in a coal-fired boiler according to the present invention, it is predicted that coal will be released from the mill 4 when purging residual coal. the coal output 23 can be accurately obtained, excessive coal above the fuel flow rate command eliminated that would be supplied to the furnace 8 of the boiler 7, to prevent deterioration and increase of the steam temperature of the exhaust gas O ₂ An excellent effect of obtaining can be achieved.

[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 showing an example of a conventional coal output amount calculation device at the time of purging remaining coal in a mill of a coal-fired boiler.

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 switch 21 coal output simulation 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 Rate-of-change correction signal 33 Function generator 34 Simulated gain of coal output 35 Multiplier

Claims (2)

[Claims] 1. A coal output (11) held at the time of a stop of a coal feeder (3) at the time of a mill trip is held as a remaining coal amount, and a coal output amount given as a function of time with respect to the remaining coal amount. Multiplying a simulated gain (34) to obtain a coal removal amount (23) predicted to be removed from the mill (4) at the time of purging residual coal; Amount calculation method. 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 (13) which outputs the signal as (2), and at the time of a mill trip, holds the coal supply (11) at the time of stopping the coal feeder (3) and outputs it as a signal (12) representing the remaining coal.
During normal operation, a signal (26) of "0" output from the signal generator (25) is output as a signal (30), while when the residual coal purge mill is started after the mill trip, the signal is output from the signal generator (27). A switch (29) that outputs the signal (28) of “1” as a signal (30), 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 amount simulation signal (2) which is predicted to be removed from the mill (4) during the residual coal purge.
A multiplier (35) that outputs 1), and a coal output simulation signal (2) that is output from the multiplier (35).
1) is provided with an adder (24) for outputting a coal output (23) in addition to the coal feed (11) fed from the coal feeder (3) to the mill (4). Output calculation device at the time of mill residual coal purge of a coal-fired boiler.