JPH09206614A - Control method of pressing force of roller mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of self-exciting vibration without discharging matter to be ground as coarse particles. SOLUTION: In the case of a coal grinding roller mill, when coal supply stopping operation is performed at time t1 from a low load region, the supply quantity of coal lowers as shown by (a) of a drawing and the pressing force acting on a grinding roller is also reduced as shown by (b) of the drawing. The supply quantity of coal becomes lowest at time t2 and, when a coal supply stopping command is outputted at time t3, the roller mill increases the pressing force of the grinding roller as shown by (c) of the drawing within the residual coat treatment region up to a stop time of time t4. By this constitution, coal in the roller mill can be rapidly finely ground to be rapidly discharged out of the roller mill and can be rapidly passed, through the residual coal treatment region having the possibility of the generation of self-exciting vibration and the generation of self-exciting vibration can be suppressed. Further, since coal is finely ground to the end, coarse particles are not discharged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller mill pressure control method for controlling the pressure applied to a crushing section of a roller mill for crushing coal, cement clinker, raw materials for chemical products and the like.

[0002]

2. Description of the Related Art As one of pulverizers for finely pulverizing lumps such as coal, cement raw materials and raw material raw materials, there is a roller mill having a rotating pulverizing table and a pulverizing roller which rotates on the pulverizing table. Such a roller mill will be described with reference to FIG.

FIG. 2 is a diagram showing a schematic structure of a vertical roller mill for crushing coal. In this figure, 1 is a casing,
Reference numeral 2 is a rotary shaft of a motor (not shown), 3 is a speed reducer for reducing the rotation of the rotary shaft 2, 4 is a crushing table which is fixedly rotated on a vertical rotary shaft (not shown) connected to the speed reducer 3, and 41 is a crushing table 4. Is a crushing race surface formed on the circumference of the upper surface of. A crushing roller 5 is in contact with the crushing race surface 41 and rotates by the rotation of the crushing table. 6 is a roller bracket for rotatably supporting the crushing roller 5, 7 is a lower pressure frame, 8 is an upper pressure frame, 9 is a spring interposed between the lower pressure frame and the upper pressure frame, 10
Is a roller pivot. The roller bracket 6 is supported by the lower pressing frame 7 via the roller pivot 10.

Reference numeral 12 is a hydraulic cylinder, 13 is a rod of the hydraulic cylinder, 14 is a link, 15 is a pin for connecting the upper pressurizing frame 8 and the link 14, and 16 is a pin for connecting the rod 13 and the link 14. By expanding and contracting the rod 13 of the hydraulic cylinder 12, the upper pressure frame 8, the spring 9, the lower pressure frame 7, the roller pivot 10,
The pressure applied to the crushing roller 5 via the roller bracket 6 is adjusted. 18 is a rotary classifier, 19 is a coal feeder, 20
Is a supply pipe for guiding the coal supplied from the coal feeder 19 to the crushing table 4.

When the coal from the coal feeder 19 is supplied to the center of the crushing table 4 through the supply pipe 20, the supplied coal is rotated by the centrifugal force of the rotation of the crushing table 4 and the outer periphery of the crushing table 4 is rotated. And is crushed by being caught between the crushing race surface 41 and the crushing roller. On the other hand, hot air is guided to the bottom of the casing 1 by a duct (not shown), and this hot air is, as shown by an arrow W, the crushing table 4
Is blown upward from between the outside of the casing and the inside of the casing 1, and the pulverized coal is dried and transported to the upper part.
Coarse of the transported coal powder falls on the way (primary classification), and other coal powder further rises to the rotary classifier 1.
No. 8 is reached and the particles are classified again (secondary classification), and the coal powder having a predetermined particle size or less is sent to, for example, a pulverized coal burner of a boiler or a differential storage bin, and the coal powder having a predetermined particle size or more is crushed on a crushing table. It is made to fall to No. 4, and is crushed again with the newly supplied coal. In this way, crushing and classification are repeated.

[0006]

By the way, in the above roller mill, when the coal supply is stopped, the crushing roller 5
Since the thickness of the coal layer underneath becomes smaller and the particles of the coal layer become finer than when the coal is being fed, the friction resistance becomes small and the crushing roller 5 becomes slippery, so that the crushing roller 5 does not roll. It becomes stable, which may cause self-excited vibration. In order to avoid such self-excited vibration, conventionally,
For example, as disclosed in Japanese Utility Model Laid-Open No. 62-95742, a means for stabilizing the rolling by reducing the load on the crushing roller, or rolling the coal in the roller mill by discharging it to the outside of the roller mill even in a coarse particle state. In order to stabilize the, the method of reducing the classification ability was adopted.

However, in all of these means, since coal is discharged in the state of coarse particles, the amount of pyrite increases and N
An increase in the O _X and unburned had caused the problem arises.
Further, not only in the case of crushing coal but also in the case of crushing other objects to be crushed, it is not preferable that the objects to be crushed should be discharged in the form of fine powder and coarse particles.

An object of the present invention is to solve the above-mentioned problems in the prior art and to provide a method for controlling the pressure of a roller mill which can prevent the occurrence of self-excited vibration without discharging the crushed material in coarse particles. Especially.

[0009]

To achieve the above object, the present invention comprises a rotating crushing table, a crushing roller facing the crushing table, and a pressing means for applying pressure to the crushing roller. In a roller mill for crushing an object to be crushed between the crushing table and the crushing roller in a state where pressure is applied to the crushing roller by the pressurizing means, a residual coal treatment area after the supply of the object to be crushed is stopped. so,
It is characterized in that the pressure applying means makes the pressure applied to the crushing roller higher than the pressure when the supply of the object to be crushed is stopped to operate the roller mill.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a diagram illustrating a method for controlling a pressing force of a roller mill according to an embodiment of the present invention. FIG.
(A) is a diagram showing the amount of coal supplied to the roll mill, in which the horizontal axis represents time and the vertical axis represents the coal supply amount. FIG. 1B is a diagram showing changes in the pressing force applied to the crushing roller 5, where the horizontal axis represents time and the vertical axis represents the pressing force. When the roller mill is operating in the low load region, the amount of coal supplied is small and the pressure applied to the crushing roller 5 is also low. From this operating state, when the operation is performed to stop the coal supply at time t ₁ , the coal supply amount decreases with time as shown in (a) of FIG. 1 and the coal supply amount decreases. Therefore, the pressing force of the crushing roller 5 also decreases as shown in FIG. 1 (b), and the supply amount of coal becomes the minimum (minimum coal supply amount) at time t ₂ and the pressing force also becomes the minimum. Becomes continue,
When the coal supply stop command is output at time t ₃ , the supply of coal becomes 0, and the operation of the roller mill enters the residual coal treatment area.

As described above, in the conventional roller mill, in the operation of the residual coal treatment area, the pressing force of the pulverizing roller 5 is reduced or the classification ability is reduced to stabilize the rolling of the pulverizing roller 5. Try. However, in the present embodiment,
In the operation of the residual coal treatment area from the time the coal supply stop command is output at time t ₃ to the time the roller mill is stopped at time t ₄ , as shown in FIG.
The pressing force of is increased almost in proportion to time.

The upper limit of the pressing force in the residual coal treatment region is preferably 30% to 300% of the pressing force during crushing (pressing force adjusted according to the amount of coal to be crushed). That is, 30
If it is less than 100%, the required crushing ability cannot be obtained, and if it exceeds 300%, the crushing ability becomes too large and the fine powder becomes too fine, and the coal bed becomes too thin, and vibration easily occurs. is there.

As described above, by increasing the pressure in the residual coal treatment area, the crushing ability of the crushing roller 5 is increased, the coal in the roller mill is quickly pulverized, and the coal is pulverized by the hot air W to the outside of the roller mill. Can be discharged quickly. That is, since it is possible to quickly pass through the residual coal treatment region where self-excited vibration may occur, it is possible to suppress the occurrence of self-excited vibration. Further, unlike the conventional method, the pressing force of the crushing roller 5 is not reduced or the classification ability is not reduced, so that the particle size of the coal discharged to the outside of the roller mill can be increased, and the pyrite is compared to the conventional method. Increase in quantity, N
O _X and the increase of unburned fuel can be suppressed significantly.

Here, it was predicted that by increasing the pressure in the residual coal treatment region as described above, the coal milling characteristics of the roller mill would rapidly increase during the treatment period in that region. When the coal is supplied to the boiler, there is almost no influence on the boiler side (boiler main steam pressure deviation, etc.), and further, mechanical vibration when the crushing roller 5 and the crushing table 4 are in a metal touch state. It was confirmed that it can be ignored.

In the above description of the embodiment, coal was used as an example of the object to be crushed by the roller mill, but it goes without saying that it can be applied to objects other than coal. Further, the mode of increase of the pressing force in the residual coal treatment area is not limited to the linear increase, and may be set to an appropriate mode in consideration of the structural conditions of the roller mill, the physical properties of the material to be ground, and the like. it can.

[0016]

As described above, in the present invention, the pressure applied to the crushing roller in the residual coal treatment area of the roller mill is set to be higher than the pressure when the supply of the material to be crushed is stopped. Can be quickly finely pulverized and quickly discharged to the outside of the roller mill, can quickly pass through the residual coal treatment region where self-excited vibration may occur, and suppress the occurrence of self-excited vibration. Further, since the pressing force of the crushing roller or the classification ability is not reduced unlike the conventional method, coarse particles are not discharged. In the case of a roller mill for use in a boiler, the coal is discharged to the outside of the roller mill is because it is fine, can be compared with the conventional method increases and pyrite amount, remarkably suppressed the increase of the NO _X and unburned combustibles .

[Brief description of drawings]

FIG. 1 is a diagram illustrating a method for controlling a pressing force of a roller mill according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a vertical roller mill for crushing coal.

[Explanation of symbols]

 4 Grinding Table 5 Grinding Roller 6 Roller Bracket 7 Lower Pressure Frame 8 Upper Pressure Frame 12 Hydraulic Cylinder 41 Grinding Race Surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroaki Kanemoto Inventor Hiroaki Kane City 3-36 Takaracho, Kure City, Hiroshima Babkotuku Hitachi Co., Ltd. Kure Research Institute (72) Nobuyasu Makoto 36-36 Takaracho, Kure City, Hiroshima Prefecture Babkotsu Hitachi Stock Company Kure Institute

Claims (4)

[Claims] 1. A rotating crushing table, a crushing roller facing the crushing table, and a pressurizing means for applying a pressure to the crushing roller. In a state in which a pressure is applied to the crushing roller by the pressurizing means. In a roller mill for crushing an object to be crushed between the crushing table and the crushing roller, in a residual coal treatment area after the supply of the object to be crushed is stopped,
A method for controlling a pressing force of a roller mill, wherein the pressurizing means makes the pressure applied to the crushing roller higher than the pressure when the supply of the crushed object is stopped to operate the roller mill. 2. The pressure control method for a roller mill according to claim 1, wherein the pressure applied to the crushing roller in the residual coal treatment region is increased substantially in proportion to time. 3. The pressure control method for a roller mill according to claim 1, wherein the upper limit of the pressure applied to the crushing roller in the residual coal treatment area is 30% to 300% of the pressure applied to the roller mill. . 4. The pressing force control method for a roller mill according to claim 1, wherein the pressurizing means is a hydraulic cylinder.