JPS63220001A - Controller for quantity of coal fed to coal firing boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a coal feed amount control device for a coal-fired boiler, and particularly to a coal-fired boiler suitable for conveying pulverized coal pulverized in a mill to a boiler by primary air. This invention relates to a boiler coal feed amount control device.

[Conventional technology]

FIG. 4 shows a mill used in a coal-fired boiler and its surrounding configuration. Coal is supplied to the mill 15 from a coal feeder 14,
The supplied coal is crushed and carbonized into fine powder. The mill 15 is supplied with primary air for conveying the crushed pulverized coal to the burner of the boiler.

This secondary air is supplied by a secondary air fan 16, and the primary air from this fan 16 is supplied to a primary air heater 17.
heated by. The output amount of the primary air heated by the air heater 17 is adjusted by the hot air damper 18.

On the other hand, the secondary air heater 17 is provided with a bypass passage 20, and within this bypass passage 20, a cold air damper 19 is provided to adjust the amount of air passing through the bypass passage 20. By appropriately adjusting the damper 18 and the damper 19, it is possible to supply the mill 15 with an optimum primary air temperature.

In the above configuration, the coal supplied from the coal feeder 14 is pulverized by the mill 15 into pulverized coal.

- Primary air supplied from the secondary air fan 16 is supplied to the mill 15 after being adjusted to an appropriate temperature by dampers 18 and 19. The primary air supplied to mill 15 is
It is used to dry the pulverized coal in the mill and also to transport the pulverized coal from the mill 15 to the burner.

FIG. 5 is a block diagram showing a conventional mill control device.

A PI (proportional/integral) regulator 2 is connected to a subtracter 1 that subtracts the main steam pressure (inlet pressure of a turbine (not shown)) and the main steam pressure set value. An adder 3 is connected to the PI regulator 2 for adding the boiler load command. A subtracter 4 and a differentiator 11 are connected to the adder 3, and the adder 3 performs addition with the total fuel flow rate. The output of adder 3 is Plil! It is proportional and integrated by the meter 5. A function generator 6 and a differentiator 12 are connected to the P■ controller 5, and an adder 7 is provided to add the outputs of these. Further, an adder 8 is connected to the PI adjuster 5, and addition with the output of the differentiator 11 is performed.

In the above configuration, the deviation between the actual measured value of the main steam pressure of the boiler and the main steam pressure set value is taken by the subtracter 1, the deviation value is proportional and integrated by the PI controller 2, and then added by the adder 3. Addition with the load command is performed. The output of this adder 3 becomes the combustion amount command 10.

The deviation from the total fuel flow rate is removed from the combustion amount command 10 by a subtractor 4, and the combustion amount command 10 is differentiated by a differentiator 11. The subtracted value of the subtracter 4 is proportional and integrated by the PI controller 5, and this becomes a mill master.

This mill master is used to command the coal feeder speed and control the primary air flow rate for each of the plurality of mills.

A primary air flow command signal is generated by a function generator 6 based on the output of the PI controller 5. Further, the mill master is added to the differential output of the differentiator 11 by the adder 8, and this becomes the coal feeder speed command. Furthermore, the mill master is applied to the differentiator 12, and its differential value is added by the adder 9 to the primary air flow rate command signal output from the function generator 6. The output signal of this adder 9 becomes the primary air flow rate control damper opening command.

For details on such boiler coal feed amount control, see, for example, Thermal and Nuclear Power Generation Technology Association, Vol. 33 No. 5r.
"Boiler Control", pages 59 to 86.

[Problem that the invention seeks to solve]

However, with conventional coal feeding amount control devices, mill personnel,
There is a problem in that the amount of coal fed and the amount of primary air fluctuate due to the load fluctuation that occurs when the mill is cut off, which worsens the responsiveness of the mill.

An object of the present invention is to provide a coal feed amount control device for a coal-fired boiler that improves the response delay of the mill and improves the responsiveness of the mill.

[Means for solving problems]

In order to solve the above problems, the present invention creates a mill master based on a boiler load command, total fuel flow rate, and main steam pressure deviation, and generates a coal feeder speed command and a primary air flow rate command using this mill master. In a boiler coal feed rate control device, a function generating means generates a predetermined preceding signal based on a deviation between an actual measured value of main steam pressure and a set value, and an output signal of the function generating means is used as the output of the mill master and the primary air flow rate. It is constructed by providing calculation means for outputting a coal feeder speed command and a primary air flow rate control signal for varying the primary air flow rate in addition to the command.

[Effect]

According to the above means, by generating a preceding signal according to the amount of change in the main steam pressure and increasing/decreasing the amount of coal feed and the primary air flow rate based on this signal, the amount of coal feed fed into the mill is promptly increased. Therefore, it is possible to configure a coal feed amount control device for a coal-fired boiler without causing a delay in the response of the mill.

〔Example〕

Hereinafter, one embodiment of the present invention will be briefly described with reference to the drawings.

FIG. 1 is a block diagram showing a coal feed amount control device according to the present invention, FIG. 2 is an explanatory diagram of dead zone settings set in the function generator 9 of FIG. 1, and FIG. 3 is a diagram showing responsiveness of the present invention and the conventional method. It is an explanatory diagram of improvement.

In FIG. 1, the same reference numerals are used for the same parts as in FIG. 5, so redundant explanations will be omitted. A function generator 9 for applying a preceding signal is provided, and the differentiators 11 and 12 shown in FIG. 5 are removed.

The operation up to obtaining the mill master signal has been explained with reference to FIG. 5, so redundant explanation will be omitted. When disturbances due to load changes occur, main steam pressure deviations occur extremely quickly. The present invention focuses on this point and uses the main steam pressure deviation output from the subtracter 1 as an index of the preceding signal. The function generator 9 that generates the preceding signal includes a second
As shown in the figure, a dead zone is set, and the preceding signal is not output when the main steam pressure deviation value is below this level. The preceding signal output from the function generator 9 has a faster response than the response of the signal via the PIi 14 nodes 2S2 and 5 because the main steam pressure deviation directly acts on the coal feeder and the primary air.

Note that the pulverization of coal by the mill 15 takes time until it becomes pulverized coal due to its structure. Therefore, if only the amount of coal fed is controlled, it takes, for example, 20 seconds to produce coal from the mill, resulting in a slow response. Therefore, in the present invention, a preceding signal is also applied to the adder 7, so that a response of, for example, about 5 seconds can be obtained. By controlling the primary air flow rate in advance to improve responsiveness in this way, responsiveness close to that of an oil-fired boiler can be obtained.

FIG. 3 shows a comparison of the control information of the present invention (shown by broken lines) and the conventional control information (shown by solid lines), and the state of improvement in responsiveness will be explained with reference to this figure.

As mentioned above, conventional methods have relied on correction of main steam pressure deviation by PI sub-adjustment, and the increase in the amount of coal feed and the amount of primary air relative to the load command is small.

On the other hand, according to the present invention, correction is performed using a preceding signal, and the coal feeding amount and the secondary air amount can be increased, so that the main steam pressure and the load follow-up characteristics can be improved. If the responsiveness of the mill changes due to deterioration of the mill ball over time or a change in coal type, the result will be reflected in a change in the amount of main steam pressure deviation that occurs, which is a process variable, so corrections will be made automatically. Therefore, utilizing the main steam pressure deviation as a preceding signal for the amount of coal fed and the secondary air is effective in improving the responsiveness of the mill to changes in mill characteristics over time.

〔Effect of the invention〕

As explained above, according to the present invention, the main steam pressure deviation is used as a preceding signal for the coal feeding amount and the secondary air amount, so that the responsiveness of the mill can be improved. moreover,
It is also possible to improve the response delay of the mill due to aging of the mill. This improvement in responsiveness leads to improvements in main steam pressure control and load control, which in turn makes it possible to improve power plant control.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a coal feed amount control device according to the present invention, FIG. 2 is an explanatory diagram of dead zone settings set in the function generator 9 of FIG. 1, and FIG. 3 is a diagram showing responsiveness of the present invention and the conventional method. FIG. 4 is a configuration diagram showing a mill used in a coal-fired boiler and its peripheral configuration, and FIG. 5 is a block diagram showing a conventional coal feed amount control device for a coal-fired boiler. 1.4--subtractor, 2.5--Pl adjuster, 3.
7.8--Adder, 6.9-1--Function generator, 18, 19--Damper. Figure 1 Figure 2

Claims (2)

[Claims] (1) A coal feed rate control system for a coal-fired boiler that creates a mill master based on the boiler load command, total fuel flow rate, and main steam pressure deviation, and generates a coal feeder speed command and primary air flow rate command using this mill master. a function generating means for generating a predetermined preceding signal according to the deviation between the actual measured value of the main steam pressure and the set value; and a function generating means for adding the output signal of the function generating means to the output of the mill master and the primary air flow rate command. 1. A coal feed amount control device for a coal-fired boiler, comprising a calculation means for outputting a coal feeder speed command and a primary air flow rate control signal for varying the primary air flow rate. (2) The coal-fired boiler according to claim 1, wherein the preceding signal has a dead zone with respect to the deviation value between the actual measured value of the main steam pressure and the set value. Coal feed amount control device.