JPH04334563A - Control device for coal feed amount from coal mill - Google Patents

Abstract

PURPOSE:To reduce delay is responsiveness to variations in the load on a control device for the amt. of coal fed from a coal mill in a coal-fired boiler. CONSTITUTION:A control device for the amt. of coal fed from a coal mill which comprises a constant generator 31 for setting at a predetermined value the revolution number of a rotary separator in the coal mill; a subtracter 35 for producing a corrected signal by subtracting the signal generated through a primary retardation operator 34 from an output demand signal 33 fed thereinto; a limiter 41 and an integrator 42 for processing the corrected signal to generate a revolution number correcting signal; and an adder 43 for adding the revolution number correcting signal to an output from the constant generator 31, whereby the rotary separator is rotated at a speed of the revolution number corresponding to the load condition to enhance fuel responsiveness to variations in the load.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coal mill coal feeding amount control device applied to a coal-fired boiler.

0002

2. Description of the Related Art Conventionally, in coal mills, mill journal oil pressure has been controlled by a roll lift program method shown in FIG. 2 and a coal feed amount program method shown in FIG. The mill air volume was determined according to the amount of coal fed, and the rotation speed of the rotary separator was maintained at a constant value by a constant generator 31, as shown in FIG. FIG. 2 shows a journal hydraulic control device using a mill roll lift program method.

[0003] The mill journal oil pressure setting value 0 is set by the function generator 02 which receives the measured value 01 of the mill roll lift as input.
3 is output. The mill journal oil pressure setting value 03 and the journal oil pressure measurement value 04 are input to a subtracter 05, and an output signal (deviation signal) from the subtracter 05 is input to a controller 06. The output signal 07 of the controller 06 becomes a mill journal oil pressure command.

In addition, in the coal feeding amount program method, as shown in FIG. 3, a measured value 11 of the actual coal feeding amount is input. It has function generators 12, 13, 14, and 15. The function generators 12, 13, 14, and 15 have switches 16 programmed with functions of actual coal feed amount and mill load for various coal types.
The type of coal currently being burned in the boiler is selected, and a mill load signal 17 suitable for the type of coal is output.

The function generator 18 receives the mill load signal 17 and outputs the mill journal oil pressure setting signal 19. The mill journal oil pressure setting signal 19 is input to the subtractor 21 together with the measured value 20 of the journal oil pressure. The output signal (deviation signal) from the subtractor 21 becomes an input signal to the controller 22 (for example, a PI controller, etc.), and the output signal from the controller 22 is directly transmitted to the mill journal oil pressure command 23.
becomes. On the other hand, as shown in FIG. 4, the rotary separator rotational speed is determined by using the output of the constant generator 31 as the rotational speed command 32.

[0006]

[Problem to be solved by the invention] In conventional mill journal hydraulic control, mill air volume, and rotary separator rotation speed control, the mill coal discharge amount responded with a certain delay to the coal feed amount command. . Considering rapid load fluctuations in coal-fired boilers, in order to improve controllability, it is desirable for the mill coal discharge amount to have a small response delay and quick response to the coal feed amount command. The present invention aims to speed up the response of the amount of coal discharged from the mill.

[0007]

[Means for Solving the Problems] In the conventional system, the number of rotations of the rotary separator is maintained at a constant value (see FIG. 4). The rotational speed of the rotary separator has a great effect on the fineness of the mill waste coal, but in the present invention, by varying the rotational speed of the rotary separator during load fluctuations, the fineness changes transiently. This makes it possible to better follow the coal feed amount command.

[0008]

[Operation] By improving the followability of the mill coal discharge amount to the coal feed amount command, it becomes possible to improve controllability even in response to disturbances in the load change rate. This is an important point for coal-fired boilers to achieve control performance equivalent to oil/gas-fired boilers.

[0009]

[Embodiment] An embodiment of rotary separator rotation speed control according to the present invention is shown in FIG. The output demand signal 33 and the output signal of the first-order lag operator 34 which receives the output demand signal 33 as inputs are input to a subtracter 35 . The output of the subtracter 35 and the output signal of the constant generator 36 are input to the integrator 37, and the output of the integrator 37 and the output signal of the integrator 42 are input to the subtracter 38.

The output of the subtracter 38 and the output signal of the constant generator 39 are multiplied by an integrator 40, and the output signal of the integrator 40 is input to an upper/lower limiter 41. The output signal of the upper/lower limiter 41 is input to the integrator 42, and the integrator 42
The output signal is input to the adder 43 as a correction signal for the rotary separator rotation speed command with respect to the output demand. The adder 43 outputs the output signal of the constant generator 31 and the integrator 4.
2 is added as an input signal, and a rotation speed command value of the rotary separator is output as an output.

[0011]

Effects of the Invention By controlling the rotational speed of the rotary separator according to the present invention, it is possible to improve the responsiveness of the amount of discharged coal from the mill when the load changes. For example, when the load increases, the rotary separator rotation speed command value according to the present invention is outputted as a value smaller than the output from the constant generator.

[0012] This method takes advantage of the fact that when the rotational speed of the rotary separator is lowered, the fineness deteriorates (the particle size increases) but the amount of emitted coal temporarily increases, and this increases the responsiveness of the fuel to an increase in load. The purpose is to

On the other hand, when the load decreases, the rotational speed of the rotary separator is temporarily increased to make it difficult to discharge pulverized coal. The fineness of the discharged coal at this time is better (the particle size is smaller) than when the rotation speed is constant. As a result, it is expected that the followability of the coal discharge response when the load decreases will be better than that of the conventional system.

[Brief explanation of the drawing]

FIG. 1 is a diagram of rotation speed control of a rotary separator according to an embodiment of the present invention.

FIG. 2 is a diagram of a journal hydraulic control device using a mill roll lift program method.

FIG. 3 is a diagram of a journal hydraulic control device using a coal feeding amount program method.

FIG. 4 is a diagram showing rotation speed control of a conventional rotary separator.

[Explanation of symbols]

02, 12, 13, 14, 15, 18...Function generator, 0
5, 21, 35, 32...subtractor, 06,22...controller,
16... Switch, 31, 36, 39... Constant generator, 37
, 40... Integrator, 41... Upper/lower limiter, 42... Integrator,
43...Adder.

Claims (1)

[Claims] [Claim 1] A coal feeding amount control device for a coal mill having a rotary separator as a classifier in a coal crusher, comprising a constant generator for setting the rotation speed of the rotary separator and a correction signal generated based on an output demand signal. What is claimed is: 1. A coal feeding amount control device comprising: a means for controlling the amount of coal fed; and a device for controlling the amount of coal feeding by changing the rotational speed of a rotary separator based on the correction signal to follow changes in load.