JP2000227216A - Vertical mill control method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote the discharge of coal from a vertical mill for reducing the amount of preserved coal in the vertical mill, and to improve a grinding property by reducing a basic speed command according to the mill differential pressure deviation when an actual mill pressure is higher than a reference differential pressure based on a coal supply command when a load increases. SOLUTION: A basic speed command 39 of a rotary classifier 21 is obtained based on a coal supply command 37 and is outputted to an adder 60, and a mill differential pressure 40 is detected by a mill differential pressure detector 41. The detected mill differential pressure 40 is outputted to a subtractor 47 as a mill differential signal 42 via a primary delay equipment 43, and a mill reference differential pressure 44 is obtained based on the coal supply command 37 and is outputted to the subtractor 47. When the coal supply command 37 rapidly increases due to the increase in a load and the mill differential pressure 40 becomes higher than the mill reference differential pressure 44 based on the coal supply command 37, the basic speed command 39 is restrained by the amount of a speed correction value 57 according to the mill differential pressure deviation 46 and the discharge of coal from a vertical mill 1 is promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vertical mill control method and apparatus.

[0002]

2. Description of the Related Art In general, a vertical mill 1 as shown in FIG. 5 has been used to pulverize granular material such as coal supplied to a coal-fired boiler to obtain fine powder such as pulverized coal. I have.

A table 5 driven by a driving device 3 such as a motor through a speed reducer 4 is disposed in a lower portion of the casing 2 of the vertical mill 1. , A pivot bracket 6 is disposed so as to be tiltable about a horizontal shaft 7 supported on the journal cover 2 a of the casing 2, and a roller 8 is provided at a tip end of the pivot bracket 6 in a direction substantially orthogonal to the horizontal shaft 7. A fluid pressure cylinder 9 using a fluid such as oil is attached to the journal cover 2a of the casing 2, and the rod 9a of the fluid pressure cylinder 9 is extended. By pressing the pressing portion 6a of the pivot bracket 6 via the plunger 11 inserted into the plunger housing 10, the roller 8 is rotated horizontally. Pressed against the table 5 top you are, to cooperate with the roller 8 and the table 5, and is able to crushed granules of coal and the like on the table 5.

In the casing 2, an annular body 12 is disposed so as to surround the table 5, and the annular body 12 has
An air port 14 is provided so that the primary air 13 introduced into the casing 2 from a position below the table 5 of the casing 2 can be blown into the upper portion of the casing 2.

A head frame 15 is provided outside the upper portion of the casing 2 so as to communicate with the inside of the casing 2, and a bearing tube 16 is fixed in the head frame 15 so as to extend vertically. Bearings 17 and 18 are fitted into the bearing cylinder 16 at a required interval vertically.
A fine powder supply pipe 19 for supplying fine powder such as pulverized coal to a burner (not shown) of the boiler is connected to a side portion of the head frame 15.

A hollow cylindrical rotary shaft 20 extending vertically is fitted into the bearings 17 and 18, and a rotary classifier 21 is mounted on a portion of the rotary shaft 20 extending into the casing 2.
A pulley 22 is fitted to a portion of the rotary shaft 20 extending above the bearing tube 16.
A pulley 25 is fitted to an output shaft 24 of a driving device 23 such as a vertical motor installed outside the upper portion of the casing 2. The pulley 25 is fitted to the pulley 22 fitted to the rotary shaft 20. An endless belt 26 is looped between them.

In the rotary classifier 21, a rotary plate 27 is fitted to the lower end of the rotary shaft 20, and an outer peripheral portion of the rotary plate 27 is
It has a configuration in which a number of flat blades 28 extending upward are arranged.

A rotary classifier 2 is provided in the casing 2.
1, a truncated inverted conical reject chute 31 is provided.
A slit 32 extending along the inclined surface is formed in the first inclined surface so that a powder obtained by pulverizing a granular material such as coal blown up by the primary air 13 can pass through.

A chute 3 of a coal feeder 34 driven by a driving device 33 such as a motor is provided inside the rotary shaft 20.
A chute tube 30 whose upper end is connected to 5 is arranged so that its lower end is opened slightly above the roller 8 in the casing 2.

In the figure, reference numeral 36 denotes a coal bunker for storing coal.

In the vertical mill 1 shown in FIG. 5, the granular material such as coal cut out from the coal bunker 36 to the coal feeder 34 is driven by the driving device 33 of the coal feeder 34 from the chute 35 to the chute pipe 30. The table 5 is dropped into the casing 5 through the, falls on the table 5, is driven by the drive unit 3 via the speed reducer 4, and contacts the table 5 rotating in the horizontal direction and rotates by contact with the table 5. Roller 8
The powder such as coal, which has been pulverized in cooperation with the above, rises in the casing 2 as shown by the arrow, accompanied by the primary air 13 blown out from the air port 14, and passes through the slit 32 of the reject chute 31. , Is blown up above the reject chute 31,
The coarse powder is classified by the rotary classifier 21 which is driven by the rotary shaft 20 and rotates together with the rotating shaft 20, and the fine powder such as the pulverized coal which has been classified into the coarse powder enters the head frame 15 through the rotary classifier 21. The coarse powder that has been sent from the head frame 15 to the fine powder feed pipe 19 and sent to a burner (not shown) of the boiler and that has been classified by the rotary classifier 21 slides down the reject chute 31. To be returned to the table 5.

By the way, the driving device 33 of the coal feeder 34
Is controlled by a coal feed command 37, while the driving device 23 of the rotary classifier 21 is controlled by a basic rotation speed command 39 output from a first function generator 38 based on the coal feed command 37. It has become.

As shown by a solid line in FIG. 6, for example, a function for outputting a basic rotation speed command 39 as a predetermined value in response to a change in the coal supply command 37 is input to the first function generator 38. ing. The function set and input to the first function generator 38 may vary slightly depending on the plant, and may be as shown by a broken line in FIG.

[0014]

However, as described above, the driving device 23 of the rotary classifier 21 is controlled simply by the basic rotation speed command 39 output from the first function generator 38 based on the coal supply command 37. In the case where the coal supply command 37 suddenly increases with the load increase, the vertical mill 1
The amount of coal in the inside increased, the grinding power of the vertical mill 1 became inadequate, the coal output decreased, and the demand for coal supply from the boiler further increased, resulting in a vicious cycle. This has the drawback of increasing the overfire amount.

Such a tendency is particularly remarkable when a high-moisture coal or hard coal is supplied to the vertical mill 1 or when the temperature of the table 5 is low because the vertical mill 1 is not sufficiently heated. .

In view of such circumstances, the present invention promotes coal removal from a vertical mill and increases the amount of coal held in the vertical mill when the coal supply command suddenly increases as the load increases. An object of the present invention is to provide a vertical mill control method and apparatus capable of reducing the amount, improving the pulverizability, suppressing the increase in the mill differential pressure and the mill current, and reducing the amount of overfire.

[0017]

According to the present invention, a rotary classifier 21 is provided, and the number of revolutions of the rotary classifier 21 is controlled by a basic rotational speed command 39 obtained based on a coal supply command 37. In the vertical mill control method, when the load is increased, the actual mill differential pressure 40 is changed to the mill reference differential pressure 4 based on the coal supply command 37.
If it is higher than 4, the basic rotational speed command 39 is reduced according to the mill differential pressure deviation 46.

Further, according to the present invention, in a vertical mill control device provided with a rotary classifier 21, a first function generator 38 for obtaining and outputting a basic rotation speed command 39 based on a coal feeding command 37 is provided.
A mill differential pressure detector 41 for detecting the mill differential pressure 40, a second function generator 45 for obtaining and outputting a mill reference differential pressure 44 based on the coal supply command 37, and detection by the mill differential pressure detector 41. The difference between the obtained mill differential pressure 40 and the mill reference differential pressure 44 output from the second function generator 45 is determined, and the mill differential pressure deviation 4
6, a third function generator 49 for obtaining and outputting a rotational speed correction value 48 of the rotary classifier 21 based on the mill differential pressure deviation 46 output from the subtractor 47, A fourth function generator 51 for obtaining and outputting a correction gain 50 for a rotation speed correction value 48 of the rotary classifier 21 based on the command 37, and a rotation speed correction value output from the third function generator 49 A multiplier 53 for multiplying 48 by a correction gain 50 output from the fourth function generator 51 to obtain and output a rotation speed correction value 52 in consideration of the coal supply command 37;
A switch 56 that outputs the rotation speed correction value 52 output from the multiplier 53 as a signal 54 when the load increases, and outputs a signal 55 of “0” as a signal 54 after the completion of the load increase and the required time has elapsed. In response to the basic rotational speed command 39 output from the first function generator 38, the switch 56
And an adder 60 that outputs a basic correction rotational speed command 59 to the driving device 23 of the rotary classifier 21 when the load rises. Is higher than the mill reference pressure 44 based on
The vertical mill control device is characterized in that the basic rotational speed command 39 is reduced in accordance with the mill differential pressure deviation 46.

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

In the vertical mill control method of the present invention, when the actual mill differential pressure 40 is higher than the mill reference differential pressure 44 based on the coal supply command 37 at the time of load increase, the mill differential pressure deviation 46 is adjusted. Thus, the basic rotational speed command 39 is reduced.

Further, in the vertical mill control device of the present invention, the first function generator 38 determines the basic rotation speed command 39 of the rotary classifier 21 based on the coal feeding command 37 and outputs it to the adder 60. At the same time, the mill differential pressure detector 41 detects the mill differential pressure 40 and outputs it to the subtractor 47.
In addition, in the second function generator 45, the mill reference differential pressure 44 is obtained based on the coal supply command 37 and output to the subtractor 47, where the mill differential pressure signal 42 and the mill reference differential pressure 44 are calculated. Is obtained, and the mill differential pressure deviation 46 is output to the third function generator 49, and the mill differential pressure deviation 46 output from the subtractor 47 in the third function generator 49 is obtained.
The rotation number correction value 48 of the rotary classifier 21 is calculated based on the following formula, and is output to the multiplier 53. In the fourth function generator 51, the rotation number correction value 48 of the rotary classifier 21 is Is obtained and output to the multiplier 53. In the multiplier 53, the rotational speed correction value 48 output from the third function generator 49 is output.
Is multiplied by a correction gain 50 output from the fourth function generator 51, and a rotation speed correction value 52 in consideration of the coal supply command 37 is obtained and output to the switch 56. From the switch 56, the rotation speed correction value 52
Is output as a signal 54 to the adder 60, and the adder 60
, The signal 54 output from the switch 56 is added to the basic rotation speed command 39 output from the first function generator 38, and the basic correction rotation speed command 59 is sent to the driving device 23 of the rotary classifier 21. Is output, and the driving device 23 of the rotary classifier 21 is controlled based on the basic correction rotation speed command 59.

Thus, in the vertical mill control method and apparatus according to the present invention, the coal supply command 37 increases sharply as the load increases, and the mill differential pressure 40 becomes higher than the mill reference differential pressure 44 based on the coal supply command 37. In such a case, the basic rotational speed command 39 is suppressed in accordance with the mill differential pressure deviation 46, and coal removal from the vertical mill 1 is promoted. The amount of coal is difficult to increase, the crushing power of the vertical mill 1 is not insufficient, the amount of coal output does not decrease, and there is no concern that the demand for coal supply from the boiler will increase further. It does not rise, which leads to a reduction in the amount of overfire.

[0023]

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

FIG. 1 is an example of an embodiment of the present invention. In the figure, the portions denoted by the same reference numerals as those in FIG. 5 represent the same components, and the basic configuration is the same as that of the conventional device shown in FIG. This is the same as the first embodiment, but the feature of the illustrated example is that a mill differential pressure detector 41 for detecting a mill differential pressure 40 as shown in FIG.
And by following the fluctuation of the mill differential pressure 40 detected by the mill differential pressure detector 41 so that a predetermined time delay occurs, the minute fluctuation of the mill differential pressure 40 is cut to reduce the mill differential pressure. A primary delay unit 43 that outputs a signal 42, a second function generator 45 that calculates and outputs a mill reference differential pressure 44 based on the coal supply command 37, and a mill differential pressure signal 42 that is output from the primary delay unit 43. A subtracter 47 for obtaining a difference from the mill reference differential pressure 44 output from the second function generator 45 and outputting a mill differential pressure deviation 46, and a mill differential pressure deviation 46 output from the subtracter 47 are used. A third function generator 49 that calculates and outputs a rotation speed correction value 48 of the rotary classifier 21;
A fourth function generator 51 for obtaining and outputting a correction gain 50 for a rotation number correction value 48 of the rotary classifier 21 based on the coal supply command 37, and a rotation number output from the third function generator 49 A multiplier 53 multiplies the correction value 48 by a correction gain 50 output from the fourth function generator 51 to obtain and output a rotation speed correction value 52 in consideration of the coal supply command 37.
When the load is increased, the rotation speed correction value 52 output from the multiplier 53 is switched to the side a in FIG. 1 and the signal 54 is output. The signal 55 of “0” is switched to the signal 54
And a change in which when the signal 54 output from the switch 56 changes, the rate of change is limited to a range equal to or less than a set value to output a rotation speed correction value 57. The rate limiting device 58 and the basic speed command 39 output from the first function generator 38 are added with the rotation speed correction value 57 output from the change rate limiting device 58 to drive the rotary classifier 21. 23 is additionally provided with an adder 60 for outputting a basic correction rotation speed command 59 to the control unit 23.

For example, as shown in FIG. 2, the second function generator 45 sets and inputs a function for increasing or decreasing the mill reference differential pressure 44 so as to be substantially proportional to the increase or decrease of the coal supply command 37. is there.

Further, as shown in FIG. 3, the third function generator 49 increases the rotation speed correction value 48 to the minus side as the mill differential pressure deviation 46 increases. If the value is equal to or more than a predetermined value, a function is set and input so that the rotation speed correction value 48 is set to the same value.

Further, as shown in FIG. 4, for example, as shown in FIG. 4, when the coal supply command 37 is in a range from 0 to a predetermined value, the correction gain 50 is set to 1.0, and In a region where the command 37 is equal to or larger than a predetermined value, a function is set and input so as to gradually decrease the correction gain 50 as the coal supply command 37 increases.

The functions set and input to each function generator are determined based on various data obtained in a test run or the like, and are the same as those shown in FIGS. 2 to 4 and FIG. It goes without saying that it is not limited.

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

During the operation of the vertical mill 1, the driving device 33 of the coal feeder 34 is controlled by the coal feed command 37, while the basic function of the rotary classifier 21 based on the coal feed command 37 in the first function generator 38. The rotational speed command 39 is obtained and the adder 6
In addition to the output to 0, the mill differential pressure detector 41 detects the mill differential pressure 40.

The mill differential pressure 40 detected by the mill differential pressure detector 41 is output to a subtractor 47 as a mill differential pressure signal 42 via a first-order lag device 43, and a coal feed is supplied to a second function generator 45. The mill reference differential pressure 44 is obtained based on the command 37 and output to the subtractor 47. The subtracter 47 outputs the mill differential pressure signal 42 output from the first-order delay unit 43 and the second function generator 45. Mill standard differential pressure 44
Is output to a third function generator 49, and the rotary classifier is operated based on the mill differential pressure deviation 46 output from the subtractor 47 in the third function generator 49. The rotation speed correction value 48 of the motor 21 is obtained and the multiplier 5
3 is output.

In the fourth function generator 51, a correction gain 50 for a rotation speed correction value 48 of the rotary classifier 21 is obtained based on the coal supply command 37, and is output to the multiplier 53. In a multiplier 53, a rotation speed correction value 48 output from the third function generator 49 is multiplied by a correction gain 50 output from the fourth function generator 51 to obtain a rotation speed in consideration of the coal supply command 37. The correction value 52 is obtained and output to the switch 56.

When the load increases, the switch 56 is switched to the position a in FIG. 1 and the rotational speed correction value 52 output from the multiplier 53 is output as a signal 54 as a change rate limiter 58.
When the signal 54 output from the switch 56 changes in the change rate limiter 58, a process for limiting the change rate to a range equal to or less than a set value is performed to perform rotation speed correction. The value 57 is output to the adder 60, and the adder 6
At 0, a rotation speed correction value 57 output from the change rate limiter 58 is added to the basic rotation speed command 39 output from the first function generator 38, and the rotary classifier 21
The basic correction rotational speed command 59 is output to the drive device 23 of
The rotary classifier 21 based on the basic correction rotational speed command 59
Is controlled.

Thus, the coking command 3
7, the mill differential pressure 40 becomes higher than the mill reference differential pressure 44 based on the coal supply command 37, and the basic rotational speed is corrected by the rotational speed correction value 57 minutes according to the mill differential pressure deviation 46. The number command 39 is suppressed, and coal removal from the vertical mill 1 is promoted.

As a result, the amount of coal held in the vertical mill 1 is less likely to increase, the crushing power of the vertical mill 1 is not insufficient, the coal output is not reduced, and the demand for coal supply from the boiler is further increased. There is no need to worry about the increase, and the mill differential pressure and the mill current do not increase, leading to a reduction in the amount of overfire.

After the required time elapses after the load rise is completed, the switch 56 is switched to the side b in FIG.
Is output to the change rate limiter 58 as the signal 54, and the driving device 23 of the rotary classifier 21 is controlled by the basic rotation speed command 39 itself.

In this manner, the coal supply command 37
When the amount of coal rapidly increases, the coal removal from the vertical mill 1 can be promoted to reduce the amount of coal held in the vertical mill 1 and the pulverizability can be improved to improve the mill differential pressure and the mill current. The rise can be suppressed, and the amount of overfire can be reduced.

Note that the vertical mill control method and apparatus of the present invention are not limited to the above-described illustrated examples, and various changes can be made without departing from the scope of the present invention. .

[0039]

As described above, according to the vertical mill control method and apparatus of the present invention, when the coal supply command 37 suddenly increases with the load increase, the vertical mill 1 Promotes coal mining and reduces the amount of coal in the vertical mill 1;
The pulverizability can be improved to suppress the increase in the mill differential pressure and the mill current, and an excellent effect that the amount of overfire can be reduced can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an embodiment of the present invention.

FIG. 2 is a diagram showing a function set and input to a second function generator shown in FIG. 1;

FIG. 3 is a diagram showing a function set and input to a third function generator shown in FIG. 1;

FIG. 4 is a diagram showing a function set and input to a fourth function generator shown in FIG. 1;

FIG. 5 is a schematic configuration diagram of a conventional example.

FIG. 6 is a diagram showing functions set and input to a first function generator shown in FIGS. 1 and 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vertical mill 21 Rotary classifier 23 Drive device 34 Coal supply machine 37 Coal supply command 38 First function generator 39 Basic rotation speed command 40 Mill differential pressure 41 Mill differential pressure detector 44 Mill reference differential pressure 45 Second function Generator 46 Mill differential pressure deviation 47 Subtractor 48 Revolution speed correction value 49 Third function generator 50 Correction gain 51 Fourth function generator 52 Revolution speed correction value 53 Multiplier 54 Signal 55 Signal 56 Switch 59 Basic correction speed Command 60 Adder

Claims (2)

[Claims] A rotary classifier (21) is provided, and the number of revolutions of the rotary classifier (21) is controlled by a basic rotational speed command (39) obtained based on a coal supply command (37). In the vertical mill control method, when the load increases, the actual mill differential pressure (40) is
If it is higher than the mill reference pressure (44) based on 7),
According to the mill differential pressure deviation (46), the basic rotational speed command (3
9) A method for controlling a vertical mill, wherein 2. A vertical mill control device provided with a rotary classifier (21), wherein a first function generator (38) for obtaining and outputting a basic rotation speed command (39) based on a coal feeding command (37). And a mill differential pressure detector (41) for detecting a mill differential pressure (40).
A second function generator (45) for obtaining and outputting a mill reference differential pressure (44) based on a coal feed command (37); and a mill differential pressure (4) detected by the mill differential pressure detector (41).
0) and the mill reference pressure difference (44) output from the second function generator (45), and the mill difference pressure deviation (46) is obtained.
Subtractor (47) that outputs the following equation; and Mill differential pressure deviation (46) that is output from the subtractor (47).
Rotation number correction value (48) of rotary classifier (21) based on
A third function generator (49) for calculating and outputting a correction gain (50) for a rotation speed correction value (48) of the rotary classifier (21) based on the coal supply command (37). A fourth function generator (51) for output, and a correction gain (48) output from the fourth function generator (51) for the rotation speed correction value (48) output from the third function generator (49). A multiplier (53) for multiplying by 50) to obtain and output a rotational speed correction value (52) in consideration of the coal supply command (37), and a rotational speed correction value output from the multiplier (53) when the load increases. (52) is output as a signal (54),
After the load rise is completed and the required time has elapsed, a signal “0” (5
A switch (56) for outputting 5) as a signal (54); and a signal output from the switch (56) in response to a basic rotational speed command (39) output from the first function generator (38). (54), and an adder (60) for outputting a basic correction rotational speed command (59) to the drive device (23) of the rotary classifier (21). 40) Coal supply command (37)
If it is higher than the mill reference differential pressure (44) based on the mill differential pressure deviation (46), the basic rotational speed command (39)
A vertical mill control device, characterized in that it is configured to reduce the temperature.