JPH07213936A - Control method for correcting coal output characteristics of vertical mill - Google Patents

Abstract

PURPOSE:To prevent coal outputting characteristics from becoming worse by increasing the amt. of circulation in a mill caused by change in properties of a coal raw material. CONSTITUTION:When a standard coal is fed on a grinding table 4 of a vertical mill and pulverization is performed while a mill roller 7 is pressed by a basic pressing force control command 30, the change in the differential pressure between the upper part and the lower part in the mill when the amt. of coal feeding is changed is detected and standard coal outputtng characteristics 41 is obtd. in advance and the differential pressure 36 of the mill is detected when the vertical mill is worked. Then, when the differential pressure of the mill becomes large to the same amt. of coal feeding as the standard coal outputting characteristics, the additional pressure of the mill roller 7 is increased and the degree of pulverization of a coal raw material 6 is improved and, as a result, the amt. of circulation in the mill is decreased and the coal outputting characteristics is prevented from becoming worse.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the coal output characteristics of a vertical mill.

[0002]

2. Description of the Related Art In order to supply pulverized coal fuel to a pulverized coal burning boiler or the like, a vertical mill for pulverizing and guiding coal raw material has been conventionally used.

FIG. 5 shows an example thereof, in which a crushing table 4 horizontally rotated by a motor 2 driven by a motor 2 is provided at a lower position inside a mill casing 1.
Grinding grooves 5 are formed on the outer peripheral portion of the upper surface of the crushing table 4, and a plurality of (three) mill rollers 7 for pressing the crushing grooves 5 to crush the coal raw material 6 are provided on the crushing table 4. It is arranged.

The mill roller 7 has a support shaft 8 for rotatably supporting the roller body 7a, the outer end side of which is attached to the mill casing 1 by a fulcrum pin 9 so as to be rotatable up and down. The pressurizing force of the mill roller 7 to the crushing table 4 can be adjusted by pressing the bracket 10 provided on the upper side of the intermediate part by the pressurizing force adjusting device 11 attached to the inner surface of the mill casing 1.

The pressurizing force adjusting device 11 includes a cylinder body 12, a pressure piece 13 which is installed in one end of the cylinder body 12 and has one end protruding so as to abut against the bracket 10, and the cylinder body 1
A movable piece 15 that is internally installed inside the second body 2 and can move toward and away from the pressure piece 13 along a fixed shaft 14 provided at the axis of the cylinder body 12; A compression spring 16 interposed therebetween and a pusher 17 which is fitted to the fixed shaft 14 and pushes the moving piece 15 toward the pressing piece 13.
And the pusher 1 screwed onto the outer end of the fixed shaft 14.
7 and an adjusting screw 18 for adjusting the pushing amount.

A raw material supply pipe 19 for supplying the coal raw material 6 from the outside of the mill casing 1 onto the pulverization table 4 is provided above the axis of the pulverization table 4. As shown in the drawing, a constant rotation classifier 22 in which a rotary blade 20 is rotated at a constant rotation speed by a motor 21 is provided on the outer periphery, and the inside of the constant rotation classifier 22 is connected to a pulverized coal extraction pipe 23. ing.
Further, as the conventional classifier, a fixed classifier in which a plurality of fixed blades extending in the radial direction are fixed on the circumference is also used.

A plurality of mill ports 2 for blowing air are provided outside the crushing groove 5 in the crushing table 4.
4 is formed, and further, an air introduction space 25 communicating with the mill port 24 is formed below the crushing table 4, and the air 26 is supplied from the outside to the air introduction space 25. There is.

The coal raw material 6 supplied onto the crushing table 4 from the raw material supply pipe 19 is crushed by the crushing grooves 5 of the crushing table 4.
The mill roller 7 is crushed by being pressed against it and air 26 is blown out from the mill port 24 at this time, so that the crushed crushed product rides on the air flow from the mill port 24 and rises in the mill casing 1. The coarse powder in the air flow is generated by the rotating blade 20 of the constant rotation classifier 22.
The fine powder falls downward by colliding with, and is passed between the rotary blades 20 of the constant rotation classifier 22 to be guided to the fine powder take-out pipe 23 to be guided to a burner such as a pulverized coal burning boiler (not shown). The coarse powder separated by colliding with the rotating blade 20 of the constant rotation classifier 22 is the crushing table 4 described above.
It falls on and is crushed again.

Due to changes in the load of the pulverized coal burning boiler,
When the amount of pulverized coal supplied to the boiler is adjusted, the amount of pulverized coal supplied from the raw material supply pipe 19 and the flow rate of air 26 supplied to the air introduction space 25 are changed to change the amount of pulverized coal. The amount of pulverized coal taken out from the take-out pipe 23 and guided to the burner or the like is controlled.

In the vertical mill described above, the crushed material is conveyed by the air 26 blown up from the mill port 24, and the crushed particles circulate in the space inside the mill casing 1 as indicated by A and stay therein. However, when the properties of the coal raw material 6 change such that the water content of the coal raw material 6 increases or the hardness of the coal raw material 6 increases, the mill internal circulation amount that remains in the mill casing 1 due to deterioration of the crushability Has a problem that the coal output characteristics are deteriorated and the responsiveness of fuel flow rate control (pulverized coal flow rate control) changes (is delayed).

[0011]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems in the above-mentioned conventional method, and the internal circulation amount of the mill increases due to changes in the properties of the coal raw material, etc., and the coal output characteristics deteriorate. It is an object of the present invention to provide a method for controlling the coal output characteristics correction of a vertical mill that prevents the occurrence of the above.

[0012]

SUMMARY OF THE INVENTION The present invention is directed to a mill in which the amount of coal supplied is changed when the reference coal is supplied to a pulverizing table of a vertical mill to pulverize the mill roller while pressurizing it with a basic pressing force. Detecting changes in the differential pressure between the upper and lower parts of the inner part, the standard coal output characteristics were obtained in advance, and when the vertical mill was in operation, the mill differential pressure increased with the same supply amount as the reference coal output characteristics. A method for controlling coal output characteristics of a vertical mill characterized by preventing the deterioration of coal output characteristics by decreasing the internal circulation amount of the mill by increasing the pressing force of the mill roller to increase the fineness of the coal raw material. , And, when the standard coal is supplied to the grinding table of the vertical mill, it is pulverized by the pressure of the mill roller, and the pulverized pulverized coal is fed through the variable speed rotary classifier that rotates at the basic rotation speed. Detects changes in the differential pressure between the upper and lower parts of the mill when the amount is changed Obtain the coal output characteristics in advance, and reduce the rotation speed of the variable-speed rotary classifier when the vertical mill is in operation and the mill differential pressure increases with the same coal supply amount as the reference coal output characteristics. The present invention relates to a method for controlling coal output characteristic correction of a vertical mill, characterized in that the internal circulation amount of the mill is reduced by increasing the passability to prevent deterioration of carbon output characteristics.

[0013]

According to the first aspect of the present invention, when the vertical mill is in operation, the previously determined standard coal discharge characteristics and the mill differential pressure at the same feed amount are compared, and when the mill differential pressure becomes large. When the pressing force of the mill roller is increased, coal raw material with poor pulverizability becomes finely pulverized by a large pressing force, which facilitates coal production, and therefore the internal circulation amount of the mill decreases and the coal production characteristics are improved. It

According to the invention of claim 2, when the vertical mill is in operation,
By comparing the previously-calculated standard coal discharge characteristics with the mill differential pressure at the same feed rate, when the mill differential pressure becomes large, if the number of rotations of the variable speed rotary classifier is reduced, it will circulate. The pulverized coal existing in the mill easily passes through the variable speed rotary classifier to be discharged, so that the internal circulation amount of the mill is reduced and the coal discharge characteristics are improved.

[0015]

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

FIG. 1 shows an embodiment of the invention of claim 1, in which the same reference numerals as those in FIG. 5 represent the same components.

As shown in the figure, in order to automatically control the pressing force of the mill roller 7 provided on the grinding table 4 of the vertical mill, the pressing force adjusting device 1 for the mill roller 7 shown in FIG.
1 instead of the hydraulic cylinder type mill roller hydraulic device 27
Is provided to the mill roller hydraulic device 27.
Connect 8.

The pressure control device 28 is a function generator 31 which outputs a basic pressure control command 30 based on the coal supply amount command 29.
Further, the basic pressure control command 30 is added to the adder 32.
Further, the pressure is introduced into the pressure adjusting device 34 via the subtractor 33 and the pressure applied by the mill roller hydraulic device 27 is controlled.

The basic pressing force control command 30 is based on a set constant value or a change value programmed to increase the pressing force by increasing the coal supply amount command 29.

Further, a differential pressure gauge 35 for detecting a differential pressure between two points, that is, an upper required position inside the mill casing 1 and a lower position near the crushing table 4, is provided, and the mill differential pressure detected by the differential pressure gauge 35 is provided. 36 is introduced into a coefficient computing unit 37 to obtain a mill coal output characteristic determination coefficient α, and the mill output characteristic determination coefficient α is put into a function generator 38 to obtain a correction bias 39, and the correction bias 39 is added to the above. The basic pressing force control command 30 is corrected by putting it in the device 32.

The mill roller load 40 is input to the subtractor 33, and the mill roller load 40 is subtracted from the basic pressurizing force control command 30 from the adder 32, so that the mill roller load 40 is not included. Only the pressure applied by the pressing of the hydraulic device 27 is input to the pressure adjusting device 34.

The operation of the above embodiment will be described.

An average coal type is selected from the properties of the coal raw material used for the vertical mill to form a standard coal (adjusted coal), and the standard coal is supplied onto the crushing table 4, and a basic value based on a constant value or a variable value is added. The mill roller 7 is pressed by the pressure control command 30 to be pulverized.

At this time, the reference coal shown in FIG. 2 is changed by changing the feed amount of the reference coal and performing a plurality of operations for detecting the change in the differential pressure between the upper and lower parts inside the mill casing 1 by the differential pressure gauge 35. The coal output characteristic 41 is obtained in advance.

Subsequently, when the vertical mill is operated to supply pulverized coal to the target location, the differential pressure gauge 35 newly detects the differential pressure between the upper and lower parts of the mill casing 1, and the detected differential pressure 36 of the mill. (ΔP ₁ ) is entered into the coefficient calculation device 37, and compared with the mill differential pressure ΔP ₂ at the same amount of coal supply in the standard coal coal discharge characteristic 41 which is obtained in advance, the mill coal discharge characteristic determination coefficient α
Ask for.

[0026]

[Formula 1] Mill coal output characteristic determination coefficient α = ΔP ₁ / ΔP ₂ (Equation (I)

When the newly detected mill differential pressure 36 becomes larger than the reference coal discharge characteristic 41, α becomes a numerical value of 1 or more and is input to the function generator 38.

The function generator 38 has an output of 0 when the mill coal output characteristic judgment coefficient α is 1, and when the mill coal output characteristic judgment coefficient α is larger than 1, a correction bias 39 corresponding to the magnitude is set. It is output to the adder 32 and added to the basic pressing force control command 30. An upper limit value is set for the correction bias 39 to prevent the pressing force of the mill roller 7 from being excessively increased.

The differential pressure between the mill and the pressure applied to the mill roller have a relationship as shown in FIG. 3. When the pressure applied to the mill roller is increased, the differential pressure of the mill can be decreased, that is, the internal circulation amount of the mill can be decreased. Correction bias 3 for control command 30
By adding 9, the mill roller hydraulic device 27 is actuated via the pressure adjusting device 34, and the pressure of the mill roller 7 is increased.

When the pressing force of the mill roller 7 is increased, the coal raw material 6 having poor pulverizability is also finely pulverized, so that the coal is easily discharged from the vertical mill. The characteristics are improved.

The correction bias 39 from the function generator 38 is reset by stopping the vertical mill, and the vertical mill is repeatedly started and stopped due to fluctuations in boiler load and the like. It is rare that 39 is accumulated up to the upper limit value.

FIG. 4 shows an embodiment of an apparatus for carrying out the invention of claim 2, which is a pulverized coal take-out pipe 23 of a vertical mill.
Constant rotation classifier 2 rotating at a constant rotation speed shown in FIG. 5 so that the fineness of the pulverized coal discharged from
Instead of 2, the variable speed rotary classifier 42 is provided, and the rotary speed control device 43 is connected to the variable speed rotary classifier 42.

The rotation speed control device 43 uses the coal supply amount command 29.
Function generator 4 which issues a basic rotational speed control command 44 based on
5, the basic rotation speed control command 44 is sent via the adder 46 to the motor 21 of the variable speed rotary classifier 42.
It is put in.

Further, the mill differential pressure 36 from the differential pressure gauge 35 for detecting the differential pressure between the upper and lower parts in the mill casing 1 is introduced into the coefficient calculating device 47 to obtain the mill coal output characteristic determination coefficient α, and the mill output characteristic is determined. A correction bias 49 is obtained by inserting the charcoal characteristic determination coefficient α into the function generator 48, and the correction bias 49 is inserted into the adder 46 to correct the basic rotation speed control command 44. In this case, the correction bias 49 has a negative value.

The operation of the above embodiment will be described.

Similar to the above-mentioned example, an average coal type is selected from the properties of the coal raw material used in the vertical mill to form a reference coal (adjusted coal), and the reference coal is supplied onto the crushing table 4 to a predetermined size. The mill roller 7 is pressed by the pressing force of 1.

At this time, the reference coal shown in FIG. 2 is changed by changing the amount of the reference coal supplied and performing a plurality of operations for detecting the change in the differential pressure between the upper and lower parts of the mill casing 1 by the differential pressure gauge 35. The coal output characteristic 41 is obtained in advance.

Subsequently, when the vertical mill is operated to supply pulverized coal to the target location, the differential pressure gauge 35 newly detects the differential pressure between the upper and lower parts of the mill casing 1, and the detected differential pressure 36 of the mill. (ΔP ₁ ) is input to the coefficient calculation device 47, and compared with the mill differential pressure ΔP ₂ at the same coal supply amount in the standard coal coal discharge characteristic 41, which is obtained in advance, and is compared with the mill coal discharge characteristic by the above formula (I). The determination coefficient α is obtained.

When the newly detected mill differential pressure 36 becomes larger than the reference coal discharge characteristic 41, α becomes a numerical value of 1 or more and is input to the function generator 48.

The output of the function generator 48 is zero when the mill coal output characteristic determination coefficient α is 1, and when the mill coal output characteristic determination coefficient α is larger than 1, it is negative (minus) according to the magnitude. The correction bias 49 is output to the adder 46 and added to the basic rotation speed control command 44. The lower limit value of the correction bias 49 is set to prevent the rotational speed of the variable speed rotary classifier 42 from being excessively reduced.

As a result, the number of revolutions of the variable speed rotary classifier 42 is reduced, and the pulverized coal circulating in the vertical mill easily passes through the variable speed rotary classifier 42 to be coal-fired. The internal circulation amount of the mill is reduced and the coal output characteristics are improved.

It should be noted that the present invention is not limited to the above-mentioned embodiment, and various configurations such as a mill roller hydraulic device and a variable speed type rotary classifier can be adopted, and the scope does not deviate from the gist of the present invention. Of course, various changes can be made within.

[0043]

According to the invention of claim 1, when the vertical differential mill is in operation, the differential pressure of the mill is detected, and when the differential pressure of the mill increases with the same coal feeding amount as the previously determined standard coal output characteristic. Since the pressing force of the mill roller is increased, coal raw material with poor grindability is easily pulverized by a large pressing force to facilitate coal production, thus reducing the internal circulation amount of the mill and improving coal production characteristics. It

According to the second aspect of the present invention, the mill differential pressure is detected when the vertical mill is in operation, and when the mill differential pressure becomes large when the same coal feeding amount as the reference coal output characteristic previously obtained, becomes possible. Since the rotation speed of the variable speed rotary classifier is reduced, the circulating pulverized coal easily passes through the variable speed rotary classifier to be discharged, which reduces the internal circulation amount of the mill Charcoal characteristics are improved.

[Brief description of drawings]

FIG. 1 is a cut front view showing an embodiment of the invention of claim 1;

FIG. 2 is a graph showing a relationship between a mill differential pressure and a coal supply amount command and a reference coal coal discharge characteristic.

FIG. 3 is a graph showing the relationship between mill differential pressure and mill roller pressure.

FIG. 4 is a cut front view showing an embodiment of the invention of claim 2;

FIG. 5 is a cut front view showing an example of a conventional vertical mill.

[Explanation of symbols]

 4 Grinding table 6 Coal raw material 7 Mill roller 30 Basic pressure control command (basic pressure) 36 Mill differential pressure 41 Standard coal output characteristics 42 Variable speed rotary classifier 44 Basic speed control command (basic speed)

Claims (2)

[Claims] 1. When the reference coal is supplied to the pulverizing table of the vertical mill to pulverize the mill roller while pressurizing it with a basic pressing force, the change in the differential pressure between the upper and lower parts of the mill when the amount of coal supplied is changed. Is detected in advance and the standard coal output characteristics are obtained in advance, and when the vertical mill is in operation, the pressing force of the mill roller is increased when the mill differential pressure increases with the same coal supply amount as the reference coal output characteristics. A method for correcting coal output characteristics of a vertical mill, characterized in that the internal circulation amount of the mill is reduced by increasing the fineness of the coal raw material to prevent deterioration of coal output characteristics. 2. When the standard coal is supplied to the pulverizing table of the vertical mill to be pulverized by the pressure of the mill roller, and the pulverized pulverized coal is taken out through a variable speed rotary classifier rotating at a basic rotation speed, The change in the differential pressure between the upper and lower parts of the mill when the coal feed rate is changed is detected to obtain the reference coal output characteristics in advance, and when the vertical mill is in operation, the same supply amount as the reference coal output characteristics is set. When the differential pressure in the mill becomes large, the rotation speed of the variable-speed rotary classifier is reduced to improve the passage, thereby reducing the internal circulation amount of the mill and preventing the deterioration of coal output characteristics. Control method for correcting coal output characteristics of vertical mill.