JPH11267535A - Variable-speed driven type coal mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the mill function and suppress the roller wear in a variable-speed driven type coal mill controlling the rotation speed of a mill table to be optimum corresponding to the load quantity and type of coal and controlling the gap between a roller of the mill and the table to be constant. SOLUTION: A table 14 of a mill main body 15 is rotated by a motor 22 through a gear connection apparatus 16. A load instructing signal (the load quantity and the type of coal) 31, a coal layer signal 32 from an angle detector 23 for detecting the angle θ of a roller 5, and a rotation speed feedback signal 35 of the motor 22 are transmitted to a control apparatus 20. The data of the optimum rotation speed of the motor 22 corresponding to the load and the type of coal and the optimum angle θ are previously stored in the memory part 24 in the control apparatus 20 and those signals are compared with the data in the memory part 24 by a computing part 25 and a frequency instructing signal 33 to give the optimum values to the load and the coal layer and to keep the gap (t) constant is transmitted to an inverter 21. The inverter 22 converts the signal into a rotation speed instructing signal 34 to rotate a motor 22 and drive the table 4 at the rotation speed suitable for the load quantity and the type of coal with which the table is loaded at the time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable speed drive type coal mill, which controls the number of rotations of a motor in accordance with a load command and the type of coal, improves crushing performance, reduces power, and wears rollers. Is also to be reduced.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing the configuration of a typical conventional coal mill. Reference numeral 1 denotes a supply pipe for a material to be ground, 2 a fine powder outlet pipe, 3 a separator, 4 a rotating table, 5 a roller, 6 Is a crushed material supplied from the crushed material supply pipe 1, 7 is a crushed material,
Reference numeral 8 denotes hot air for conveyance and drying. Reference numeral 11 denotes a roller mill top plate, and reference numerals 12a and 12b denote sealing rings provided on the separator 3 and the roller mill top plate 11, respectively.

[0003] In the coal mill composed of the above-described parts, the material 6 to be pulverized such as the raw material of coal is supplied to the supply pipe 1 for the material to be pulverized.
Through to the table 4. Pulverized object 6 carried
Is moved to the lower part of the roller 5 by the centrifugal force of the rotating table 4 and is pulverized into a pulverized material 7. The pulverized material 7 is conveyed through a blow-up block and a primary classification block attached to the inner wall of the roller mill on the outer peripheral surface of the table 4, conveyed by a hot air 8 for drying, and conveyed into the separator 3.

The pulverized material 7 entering the separator 3 is classified into fine powder and coarse powder by the rotation of the separator 3. The fine powder passes through the separator 3 and is conveyed from the fine powder outlet pipe 2 to a burner or the like of the boiler. On the other hand, the coarse powder falls again on the table 4 and is reground.

FIG. 2 is a control system diagram of the conventional coal mill described above. In the figure, reference numeral 15 denotes a mill main body;
The table 4 which rotates as described above and the roller 5 above the table 4 are provided inside. The table 4 is connected to the rotation shaft of a motor 17 via a gear connecting device 16. The start and stop of the motor 17 are controlled by a control panel 18. In the current control of the coal mill, the start and stop of a motor 17 are controlled by a control panel 18, and the table 4 in the mill main body 15 is rotationally driven at a constant rotation speed by a motor 17 via a gear coupling device, and the table periphery is controlled. The vehicle is operated so that the speed becomes a constant speed determined for performance.

[0006]

As described above, in the operation of the conventional coal mill, the rotation of the motor 17 is constant, and the peripheral speed of the table 4 is rotated at a predetermined constant speed at which the pulverization is optimal. doing. In recent coal mills, not only the operation of the table 4 at a constant peripheral speed, but also a method in which the number of rotations of the motor is controlled in two stages according to the load and the type of coal is controlled. This is performed by switching the speed in two stages by converting the number of poles using an induction motor as a motor.

[0007] In the above-mentioned control method of the constant peripheral speed of the table, when the load is small, excessive grinding occurs, the roller wear is large, the power consumption is large, and power is wasted. In the case where the load is small or the coal is a relatively soft coal type, it is preferable to perform a low-load operation by reducing the number of revolutions, but such an operation is not possible. Further, if control at a constant peripheral speed is performed when such low-load operation is required, the vibration increases, and the wear of the roller increases.

In the operation method in which the peripheral speed is kept constant, when the diameter of the table 4 is modified by modifying the table 4, the peripheral speed is made constant and the rotation speed of the motor is changed. In order to set the values to the same values, the operation must be stopped, and the gear coupling device 16 and the like must be repaired, resulting in a large maintenance cost.

In order to solve the above problem, the two-speed control system based on the number of poles of the motor, which has been recently adopted, is a very effective means for solving the above problem. Only, and the switching is rapid and discontinuous, which is not preferable in terms of the pulverizing performance.

Accordingly, the present invention provides a method for controlling the rotational speed of a motor so that the peripheral speed of a table of a coal mill becomes an optimum peripheral speed depending on the load amount and the type of coal, and improves the grindability of the mill. An object of the present invention is to provide a variable speed drive type coal mill capable of controlling the number of rotations of a motor so that the coal seam has a predetermined constant value.

[0011]

The present invention provides the following means for solving the above-mentioned problems.

A table which is rotated by a motor in the mill body and has a plurality of rollers pressed on the table; coal for charging coal from above the mill body and pulverizing the coal between the rollers and the table; In the mill, a detector that outputs a signal corresponding to the gap between the table and the roller, and an inverter that controls the number of rotations of the motor,
A control device for outputting a frequency signal to the inverter, the control device having data of an optimum motor rotation speed and an optimum gap between the table and the rollers corresponding to a load amount and a type of coal to be input. A frequency signal corresponding to an optimal motor rotation speed corresponding to at least one of the load amount, coal type, and each signal of the detector which are input by referring to data in the storage unit. To the inverter.

In the variable speed drive type coal mill of the present invention, the control device stores in advance the load amount of the coal to be charged, the optimal number of rotations of the motor corresponding to the type of the coal, and the preferable gap between the table and the rollers. Stored in the department. The control device inputs a load amount command signal, a coal type identification signal, a detector signal, and a motor rotation speed feedback signal,
By referring to the data in the storage unit, the optimum motor speed corresponding to each of these signals is compared with the actual speed, and a frequency signal for setting the actual speed to the optimum speed is instructed to the inverter. The inverter converts this frequency signal into a motor speed command signal, controls the motor speed, and the motor rotates the table at the optimum speed under the current conditions.
Crush coal.

Further, the control device refers to the data in the storage section based on the input signal from the detector, compares the optimum gap between the table and the roller under predetermined conditions with the current gap, It is possible to set the rotation speed of the motor so that this gap becomes an optimum constant gap, and output a frequency signal corresponding to this. According to the present invention, it is also possible to control the rotation speed of the motor which is optimal for all of the load amount signal, the coal type identification signal, and the signal from the detector. One or two
It is possible to set the most suitable number of rotations of the motor in correspondence with these signals.

According to the above-mentioned variable speed drive type coal mill of the present invention, even when pulverizing coal of a high coal type, the load response is improved, the pulverization performance is optimized, over-pulverization is eliminated, and power is reduced. Reduction is made. Further, since the operation is performed while keeping the gap between the roller and the table constant at an optimum value, the wear of the roller is reduced and the quiet operation becomes possible.

[0016]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a control system diagram of a variable speed drive type coal mill according to one embodiment of the present invention. In this control system diagram, reference numerals 4, 5, 15, 16
Has the same functions as those of the conventional system diagram shown in FIG. 2, and features of the present invention are characterized by devices denoted by reference numerals 20 to 22 and various signals denoted by reference numerals 31 to 35. Will be described in detail.

In FIG. 1, a table 4 and rollers 5 are provided in a mill body 15, and the table 4 is connected to a motor 22 via a gear connecting device 16. Motor 22
Is controlled by a command from an inverter 21 controlled by the control device 20, and controls the number of rotations of the table 4 according to the load condition as described later.

Reference numeral 23 denotes an angle detector.
Detects the inclination angle θ of the roller 5 in order to set the gap t between the roller 5 and the table 4 to a constant value which is optimal for pulverizing coal.
This is for inputting to the control device 20 and controlling the angle to be constant. Reference numeral 24 denotes a storage unit in the control device 20, which stores an optimal motor rotation speed (or a peripheral speed of the table 4) corresponding to the type of coal used in advance, as described later.

In the coal mill having the above configuration, a load command (coal supply amount, coal type, etc.) signal 31 is given, and the motor 2
2 and the supplied coal is pulverized between the table 4 and the roller 5 as described in the conventional example. The control device is used as the angle detection signal of the detector 23 or the coal seam signal 32 together with the load command signal 31. 20. Also, the motor 22
The feedback signal 35 of the number of rotations is also given to the control device 20.

On the other hand, in the storage unit 24 of the control device 20,
The amount of load to be input as a load in advance, the type of coal and the optimal motor speed (or table peripheral speed) suitable for the type of load and type of coal, or the optimal rotation based on a combination of a typical load amount pattern and type of coal The number and the like are stored. These data can be input or modified from the terminal 26 as appropriate. In the arithmetic unit 25 of the control device 20, the load command (load amount, coal type) signal 3
1. A frequency command signal 33 for comparing the feedback signal 35 of the rotation speed with the optimum data in the storage unit 24 to obtain a difference from the current rotation speed of the motor and correcting the current rotation speed to the optimum rotation speed. Is output.

The frequency command signal 33 is input to the inverter 21. The inverter 21 converts the frequency command signal 33 into a rotation speed command signal 34 to rotate the rotation speed of the motor 22 at a predetermined optimum rotation speed. Motor 22
Rotates the table 4 via the gear connecting device 16 at an optimum rotational speed corresponding to the load and the type of coal currently being fed into the mill, and crushes the type of coal.

Further, the control device 20 receives from the detector 23 a coal seam signal 32 which is a signal of the angle θ of the roller 4 corresponding to the gap between the table 4 and the roller 5 currently in operation. The rotation speed of the motor 22 can be controlled so that the coal seam signal 32 has a preset angle (the angle of the roller corresponding to the optimum gap t). The optimum roller angle in this case is determined in advance by the terminal 2.
6 and stored in the storage device 24. or,
The control of the rotation speed of the motor 22 is performed by outputting the frequency command signal 33 to the inverter 21 and using the rotation speed command signal 24 from the inverter 21 as described above.

The rotation speed control of the motor 22 based on the load amount signal, the coal type identification signal, and the coal seam signal individually controls the rotation speed of the motor 22 only by changing the load amount, for example. A control method in which control is not performed by a signal of the coal seam, a method in which only the gap between the table 4 and the roller 5 is made constant only by the coal seam signal 32, and a method in which the control is not performed by other load amounts and coal type signals, or The signals of the load amount, the coal type and the coal seam may be controlled in combination. Of course, the rotation speed of the motor 22 may be controlled based on all the signals of the load amount, the coal type and the coal seam.

According to the variable speed drive type coal mill of the embodiment described above, the control device 20, the inverter 21, and the detector 23 are provided, and the load command signal (load amount, coal type) 31, the coal seam signal 32, Motor speed feedback signal 35
Is input, and the motor 22 is controlled so that the table 4 in the mill body 15 has an optimum rotation speed according to these signals. Therefore, load response is improved, and pulverization is performed by fine control according to the type of coal. The performance is improved, over-crushing is eliminated, and power is reduced. Further, by controlling the coal bed constant, the wear of the roller 4 is reduced, and a quiet operation becomes possible.

[0025]

The variable speed drive type coal mill of the present invention has a table rotated by a motor in the mill body, and a plurality of rollers pressed on the table, and coal is charged from the upper part of the mill body. In a coal mill that pulverizes the coal between the roller and the table, a detector that outputs a signal corresponding to a gap between the table and the roller, an inverter that controls the number of rotations of the motor, and a frequency signal to the inverter A control unit that outputs data of an optimum motor rotation speed and an optimum gap between the table and the roller corresponding to the load amount and coal type of the coal to be input. Then, a frequency signal corresponding to an optimum motor speed corresponding to at least one of the load amount, coal type, and each signal of the detector with reference to the data of the storage unit is input. It is characterized in that the command to the serial inverter.

With this configuration, even when pulverizing coal of a high coal type, the load response is improved, the pulverizing performance is optimized, over-pulverization is eliminated, and power is reduced.
Further, since the operation is performed while keeping the gap between the roller and the table constant at an optimum value, the wear of the roller is reduced and the quiet operation becomes possible.

[Brief description of the drawings]

FIG. 1 is a control system diagram of a variable speed drive type coal mill according to an embodiment of the present invention.

FIG. 2 is a control system diagram of a conventional coal mill.

FIG. 3 is a configuration diagram of a conventional coal mill.

[Explanation of symbols]

 4 Table 5 Roller 15 Mill body 16 Gear coupling device 20 Controller 21 Inverter 22 Motor 23 Angle detector 24 Storage unit 25 Operation unit 26 Terminal 31 Load command signal 32 Coal seam signal 33 Frequency command signal 34 Revolution command signal 35 Revolution speed feedback signal

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Osamu Kawabata 1-1-1 Wadasakicho, Hyogo-ku, Kobe-shi Inside the Kobe Shipyard, Mitsubishi Heavy Industries, Ltd.

Claims (1)

[Claims] 1. A mill having a table rotated by a motor in a mill main body, and a plurality of rollers pressed on the table, coal is charged from an upper portion of the mill main body, and the coal is pulverized between the roller and the table. In a coal mill, a detector that outputs a signal corresponding to the gap between the table and the roller, and an inverter that controls the number of rotations of the motor,
A control device for outputting a frequency signal to the inverter, the control device having data of an optimum motor rotation speed and an optimum gap between the table and the rollers corresponding to a load amount and a type of coal to be input. A frequency signal corresponding to an optimal motor rotation speed corresponding to at least one of the load amount, coal type, and each signal of the detector which are input by referring to data in the storage unit. To the inverter.