JPH08247441A - Controller for separate damper of coal firing boiler - Google Patents

Abstract

PURPOSE: To properly regulate secondary air flow rate so as not to carry out the combustion of excessive amount of air during starting of a powdered coal mill and prevent the temporary rise of NOx value. CONSTITUTION: A function generator 25, is provided, to which a coal feed command signal 24 for correcting and computing a coal feed delay is inputted and which calculates and outputs the opening command signal 26 of a separate damper 17 so as to correspond to the amount of coal feed of a mill. Thus, the opening of the separate damper 17 can be controlled in accordance with the opening command signal 26 corresponding to the amount of coal feed of the mill from the function generator 25, during the operation of the mill. In such a way. during the operation of the powdered coal mill, since the opening of the separate damper 17 is controlled so as to correspond to the amount of coal feed of the mill, the opening of the separate damper 17 can be controlled so that secondary air flow rate does not become excessive even when the amount of coal feed of the mill is low in the mill-actuation time, and the temporary rise of NOx value can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separate damper control device for a coal fired boiler.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a burner structure of a general coal-fired boiler. In the figure, 1 is a coal-fired boiler, 2 is a burner throat section opened in a furnace wall 3, and 4 is pulverized coal not shown. A pulverized coal nozzle for injecting the fine powder 6 carried by the primary air 5 from the mill to the furnace side (right side in the figure) through the burner throat section 2 is shown.
An oil burner 7 for heating the boiler at the time of starting the boiler is housed in a burner inner cylinder 8 and arranged concentrically, and the secondary air supplied to the wind box 9 is provided around the tip end of the pulverized coal nozzle 4. A secondary air flow path 13 in which 10 is introduced into the burner throat section 2 as a swirling flow by passing an air register 12 whose opening can be adjusted by an opening / closing drive device 11.
Are formed.

The burner 14 having such a structure is provided in a plurality of stages, each of which is a set of a plurality arranged in the horizontal direction, and the wind box 9 is provided for the plurality of burners 14 arranged in the same stage.
Is shared, and the opening / closing drive unit 1 is installed in the secondary air inlet 15 for introducing the secondary air 10 into the wind box 9 of each stage.
A separate damper 17 whose opening degree can be adjusted by 6 is provided.

The opening control of the separate damper 17 is as follows.
As shown in FIG. 5, a power generation output command signal (MWD) 1 that is a request command from the power generation side that uses the steam of the coal-fired boiler 1.
8 is input to the function generator 19, the function generator 19 calculates an opening command signal 20 based on the power generation output command signal 18, and the opening command signal 20 is passed through the change rate limiter 21 to separate the signal. The damper 17 is output to the opening / closing drive device 16 for output.

That is, when the load of the coal-fired boiler 1 is changed based on the power generation output command, the burner 14 is ignited or extinguished for each stage, and the magnitude of the power generation output command is changed. Since it is almost decided which stage of the burner 14 should be ignited or extinguished, a function generator 19 for inputting a different function for each stage of the burner 14 is provided and the power generation output command signal 18 to the opening command signal 20. Is calculated.

[0006]

However, in the above conventional control method, the function generator 19 of each stage has a function as shown in FIG. 6 (the function indicated by the chain double-dashed line in FIG. Since the separate damper 17 is opened at a stroke at a time when the power generation output command reaches a predetermined magnitude, the pulverized coal mill corresponding to each stage is input. When starting up, there was a problem that the NOx (nitrogen oxide) value temporarily rises due to an excess air amount relative to the mill coal output.

That is, as shown in the time schedule table of FIG. 7, when the pulverized coal mill corresponding to the burner 14 of a predetermined stage is started, the secondary air flow rate indicated by the curve X is immediately after the start of the mill. However, the start of the coal feeder for supplying coal to the pulverized coal mill is started after the primary air flow rate indicated by the curve Y has sufficiently risen. The amount of coal output from the mill, indicated by Z, is gradually increased by gradually being conveyed to the primary air after the pulverized coal mill has begun to be pulverized and pulverized by the coal feeder. Then, on the side of the burner 14, a small amount of fine powder 6 (mill coal output) is supplied to the place where the secondary air 10 is flowing at a sufficient flow rate and is burned, resulting in combustion with an excessive amount of air. I am temporarily NOx
The value will rise.

The present invention has been made in view of the above situation, and the secondary air flow rate is appropriately adjusted so as to prevent combustion with an excessive amount of air when the pulverized coal mill is started, and the temporary N is temporarily set.
The purpose is to prevent the rise of Ox value.

[0009]

The present invention provides an opening command signal 23 for oil burner combustion of a separate damper 17 which receives a power generation output command signal 18 and adjusts the secondary air flow rate for each stage burner 14. Function generator 2 for calculating and outputting
2 and the coal feed command signal 24 in which the coal output delay is corrected and calculated, and the separate damper 17 is provided so as to correspond to the mill output.
Generator 25 for calculating and outputting the opening command signal 26 of
And the opening command signal 23 for oil burner combustion from the function generator 22 when the mill is stopped to select the separate damper 1
7 and outputs to the function generator 25 during mill operation.
Related to a separate damper control device for a coal-fired boiler, which is provided with a switch 27 that selects an opening degree instruction signal 26 corresponding to the amount of coal output from the mill and outputs it to the separate damper 17. Is.

Further, a signal generator 29 for outputting an opening command signal 30 which defines the minimum opening of the separate damper 17.
And the switch 27 when the burner air register 12 is not fully closed.
The opening command signal 23 or 26 is output to the separate damper 17, and when the burner air register 12 is fully closed, the opening command signal 30 from the signal generator 29 is selected to select the separate damper. It is preferable to provide a switch 28 for outputting toward 17,
In addition, it is preferable to include a change rate limiter 33 that limits the rate of change of the opening degree command signal 23, 26, or 30 output to the separate damper 17.

[0011]

Therefore, in the present invention, when controlling the opening of the separate damper 17 provided in the burner 14 of a predetermined stage, if the pulverized coal mill corresponding to the burner 14 of this stage is stopped, the power generation output command signal The opening degree command signal 23 from the function generator 22 is selected by the switch 27 in accordance with 18, and is output to the separate damper 17, and the separate damper 1
The opening degree of 7 is controlled.

That is, the separate damper 17 is controlled to the opening for burning the oil burner according to the power generation output command signal 18.

When the pulverized coal mill corresponding to the burner 14 in the predetermined stage is stopped, the pulverized coal mill is started, and the switch 27 is switched to generate a function generator based on the coal feeding command signal 24. The opening command signal 26 from 25 is selected and output to the separate damper 17, and the opening of the separate damper 17 is controlled based on the coal supply command signal 24 so as to correspond to the mill coal output.

That is, the separate damper 17 is suppressed to a small opening so that the secondary air flow rate does not become excessive while the mill coal output is small, and the secondary air flow rate follows the increase in the mill coal output. The opening of the separate damper 17 is controlled so as to be increased appropriately.

Further, a signal generator 29 which outputs an opening degree instruction signal 30 which defines the minimum opening degree of the separate damper 17.
And the switch 27 when the burner air register 12 is not fully closed.
The opening command signal 23 or 26 is output to the separate damper 17, and when the burner air register 12 is fully closed, the opening command signal 30 from the signal generator 29 is selected to select the separate damper. When the air register 12 is fully closed, the switch 28 can be switched to secure the minimum opening degree of the separate damper 17 when the air register 12 is fully closed.

Further, if the change rate limiter 33 for limiting the change rate of the opening command signal 23, 26 or 30 output to the separate damper 17 is provided, the separate damper 17 is provided.
It is possible to avoid a situation in which the opening degree of is rapidly changed and the secondary air flow rate is significantly changed.

[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 which parts designated by the same reference numerals as those in FIGS. 4 and 5 represent the same parts.

As shown in FIG. 1, the coal-fired boiler 1 (see FIG.
The power generation output command signal (MWD) 18, which is a request command from the power generation side using the steam (see the above), is input to the function generator 22, and the function generator 22 responds to the power generation output command signal 18 The opening command signal 23 for oil burner combustion of the separate damper 17 is calculated.

A function (program) similar to that shown in FIG. 6 is input to the function generator 22, but in the case of the function generator 22, the separate damper is generated according to the power generation output command. 17 is controlled to the opening for burning the oil burner.

Further, a coal feed command signal 24 for correcting the coal output delay is input from a control system of a pulverized coal mill (not shown) to a function generator 25. Based on the charcoal command signal 24, the opening degree command signal 26 of the separate damper 17 is calculated so as to correspond to the mill coal output.

A function (program) as shown in FIG. 2 is input to the function generator 25, and the mill coal output amount is adjusted until the coal supply command corrected and calculated for the coal output delay reaches a predetermined value. In order to prevent the secondary air flow rate from becoming excessive, the opening amount of the separate damper 17 is suppressed to a small opening amount, and when the coal feeding command reaches a predetermined size, the mill coal output amount is increased to a sufficient amount. As a matter of fact, the opening of the separate damper 17 is opened to a predetermined opening.

The coal supply command signal 24 in which the coal production delay is corrected and calculated is the instructed coal supply amount and the amount of the fine powder 6 (see FIG. 4) which is actually crushed by the pulverized coal mill and discharged. (Mill coal output) Considering that there is a time delay with the coal output, this is a signal obtained by correcting and calculating the coal supply command so that it approximates the actual mill output, and this type of signal is a pulverized coal mill. Since it has been conventionally used in the control system of 1), it may be diverted.

The opening command signals 23 and 26 from the function generators 22 and 25 are input to the switch 27, respectively.
In the switch 27, when the mill operation signal 34 derived from the control system of the pulverized coal mill is input as the switch signal, the opening degree instruction signal 23 from the function generator 22 is selected and output, When the mill operation signal 34 is not input, the opening instruction signal 26 corresponding to the mill coal output from the function generator 25 is selected and output.

Here, the mill operation signal 34 may be any signal as long as it can determine whether or not the pulverized coal mill is in an operating state, and various signals can be substituted.

Further, in the present embodiment, the switching device 2
The opening command signal 23 or 26 selected and output at 7 is input to another switch 28, and the switch 28 is
An opening degree command signal 30 that defines the minimum opening degree of the separate damper 17 that is output from the signal generator 29 is also input, and in this switch 28, the burner 14 of the relevant stage guided from the burner control device 31 (Fig. 4)) is inputted as a switching signal, the opening degree command signal 23 from the upstream side switching device 27.
Or 26 is selected and output, and when the air register full-close signal 32 is not input, the opening degree instruction signal 30 from the signal generator 29 is selected and output.

The opening command signal 23, 26 or 30 selected and output by the switch 28 on the downstream side is
Separate damper 17 provided in the burner 14 of the relevant stage
Is output to the opening / closing drive device 16 via the change rate limiter 33.

Thus, when controlling the opening of the separate damper 17 provided in the burner 14 of a predetermined stage, if the pulverized coal mill corresponding to the burner 14 of this stage is stopped, the mill operation signal 34 Since there is no input to the switch 27, the switch 27 selects the opening command signal 23 from the function generator 22 based on the power generation output command signal 18.

However, at this time, if the air register full-close signal 32 from the burner controller 31 is input to the switch 28, the switch 28 selects and outputs the opening command signal from the signal generator 29. Therefore, the separate damper 17 is controlled to the minimum opening degree.

On the other hand, if the pulverized coal mill corresponding to the burner 14 at the predetermined stage is stopped and the burner 14 at the predetermined stage opens the air register 12 (see FIG. 4), the boiler is started at the time of starting. Oil burner 7 for raising etc. (see Fig. 4)
Is generated in many cases, so the power generation output command signal 18
The opening command signal 2 output from the function generator 22 according to
3 is selected by each of the switching devices 27 and 28, and the separate damper 17 is controlled to the opening degree for oil burner combustion.

When the burner 14 of the predetermined stage fully closes the air register 12 and the pulverized coal mill corresponding to the burner 14 of the predetermined stage is stopped, the mill operation signal 34 is started. By the upstream switch 27
Is switched to select the opening degree instruction signal 26 from the function generator 25 based on the coal feeding instruction signal 24, and at the time of starting the pulverized coal mill, the air register 12 of the burner 14 at the predetermined stage is opened to open the air. Since the register full-closed signal 32 is also eliminated, the switch 28 on the downstream side is also switched, and the opening command signal 26 is transmitted to the separate damper 1
7 is output to the open / close drive device 16 via the change rate limiter 33.

Since this opening command signal 26 is calculated so as to correspond to the mill coal output based on the coal supply command signal 24 in which the coal delay is corrected and calculated, as shown in the time schedule table of FIG. The secondary air flow rate indicated by the curve X changes in accordance with the mill coal output indicated by the curve Z, and while the mill output is small, the secondary air flow rate is prevented from becoming excessive. The opening of the separate damper 17 is opened so that the damper 17 is suppressed to a small opening and the secondary air flow rate is appropriately increased in accordance with the increase in the coal output of the mill. The curve Y in FIG. 3 shows the transition of the primary air flow rate.

When the pulverized coal mill is stopped, contrary to the above, in response to the decrease in the coal supply command signal 24, the separate dump damper is used in response to the decreasing mill coal output. The opening degree of 17 is appropriately adjusted to reduce the secondary air flow rate.

At this time, when the coal supply command signal 24 finally disappears, the separate damper 17 is fully closed, but the air register 12 is also fully closed when the pulverized coal combustion in the burner 14 at the predetermined stage is completed. As described above, the burner control device 31 outputs the air register full-close signal 32 to the switch 28, and the signal generator 29 switches to the opening command signal 30 that defines the minimum opening. Therefore, the separate damper 17 is used. Will be kept at the minimum opening.

When the pulverized coal mill is stopped, the power generation output command is reduced prior to this. Therefore, in the conventional case, the mill coal output is reduced and the air amount is excessive. Before that, there was a tendency that the separate damper 17 was closed and the air amount was reduced, and the NOx value dropped rather greatly, but in controlling the NOx value with the denitration device on the downstream side, do not change the NOx value greatly. Is preferred, so
From the start to the stop of the pulverized coal mill as in this embodiment, the separate damper 17 is opened so that the mill coal output and the secondary air flow rate are balanced based on the coal supply command signal 24 for which the coal output delay is corrected and calculated. If controlled, the NOx value can be suppressed to a gradual change, and the NOx value can be controlled well by the denitration device.

Therefore, according to the above-described embodiment, the secondary air flow rate can be appropriately adjusted so that combustion with an excessive air amount is not performed at the time of starting the pulverized coal mill, so that a temporary increase in the NOx value can be prevented. You can

Further, as in this embodiment, the air register 12
When the switch is fully closed, the switch 28 is switched to separate the damper 1
If the minimum opening degree of 7 is secured, it is possible to prevent the phenomenon in which the flame and the exhaust gas from the furnace side flow backward to the burner 14 in the extinguished state.

Further, as in this embodiment, the opening command signal 23, 26 or 30 output to the separate damper 17 is output.
If the change rate limiter 33 that limits the change rate is provided, it is possible to avoid a situation in which the opening degree of the separate damper 17 is suddenly changed and the secondary air flow rate is significantly changed.

The separate damper control device for a coal-fired boiler according to the present invention is not limited to the above-mentioned embodiment, and various modifications can be made without departing from the scope of the present invention. is there.

[0040]

The separate damper control device for a coal-fired boiler according to the present invention described above can achieve various excellent effects as described below.

(I) Since the secondary air flow rate can be appropriately adjusted so that combustion with an excessive air amount is not performed at the time of starting the pulverized coal mill, it is possible to prevent a temporary increase in the NOx value.

(II) If the switch 28 is switched when the air register 12 is fully closed to secure the minimum opening of the separate damper 17, flames and exhaust gas from the furnace side with respect to the burner 14 in a fire extinguishing state are provided. The phenomenon of backflow can be prevented.

(III) If the change rate limiter 33 for limiting the change rate of the opening command signal 23, 26 or 30 output to the separate damper 17 is provided, the opening degree of the separate damper 17 is rapidly changed. It is possible to avoid a situation where the secondary air flow rate fluctuates significantly.

[Brief description of drawings]

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

FIG. 2 is a graph showing an example of a function (program) for calculating an opening degree instruction signal corresponding to a mill coal output based on a coal supply instruction signal in which a coal output delay is corrected and calculated.

FIG. 3 is a time schedule table for explaining the transition of the secondary air flow rate in the embodiment of the present invention.

FIG. 4 is a cross-sectional view showing an example of a burner structure of a general coal-fired boiler.

FIG. 5 is a system diagram showing a conventional example.

FIG. 6 is a graph showing an example of a function (program) for calculating an opening degree instruction signal based on a power generation output instruction signal in a conventional example.

FIG. 7 is a time schedule table for explaining the transition of the secondary air flow rate in the conventional example.

[Explanation of symbols]

 1 Coal Fired Boiler 6 Fine Powder (Coal) 10 Secondary Air 12 Air Register 14 Burner 17 Separate Damper 18 Power Generation Output Command Signal 22 Function Generator 23 Opening Command Signal 23 Opening Command Signal 24 Charging Command Signal 25 Function Generator 26 Opening Command Signal 27 Switcher 28 Switcher 29 Signal Generator 30 Opening Command Signal 31 Burner Controller 33 Change Rate Limiter

Claims (3)

[Claims] 1. An opening command signal (23) for oil burner combustion of a separate damper (17) for inputting a power generation output command signal (18) and adjusting a secondary air flow rate for each stage burner (14). Function generator for calculating and outputting (22)
And a separate dumper (1) to input the coal supply command signal (24) that corrects and calculates the coal output delay and to correspond to the mill output.
7) Select the function generator (25) that calculates and outputs the opening command signal (26) and the oil burner combustion opening command signal (23) from the function generator (22) when the mill is stopped. Output to the separate damper (17) and at the time of mill operation, the opening command signal (26) corresponding to the mill coal output from the function generator (25) is selected and directed to the separate damper (17). A separate damper control device for a coal-fired boiler, comprising a switching device (27) for outputting. 2. A signal generator (29) that outputs an opening command signal (30) that defines the minimum opening of the separate damper (17) and a switch (when the air register (12) for burner is not fully closed. Two
The opening command signal (23) or (26) from 7) is selected and output to the separate damper (17), and when the burner air register (12) is fully closed, the signal generator (29) outputs the signal. Switching device (28) for selecting the opening command signal (30) and outputting it to the separate damper (17)
The separate damper control device for the coal-fired boiler according to claim 1, further comprising: 3. A change rate limiter (33) for limiting the rate of change of the opening command signals (23), (26) or (30) output to the separate damper (17). A separate damper control device for a coal-fired boiler according to claim 1 or 2.