JPH0587306B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for pre-pulverizing cement clinker using a vertical roller mill for pre-pulverizing cement clinker and ores such as cement raw materials.

BACKGROUND ART A vertical roller mill basically has a plurality of rollers arranged at intervals in the circumferential direction on a table that rotates around a vertical axis, and the material to be crushed, which is supplied to the center of the table, is It has a structure in which it is crushed and crushed by being caught between the roller and the roller.

In a certain prior art, a vertical roller mill is disposed upstream of a tube mill or the like and is used for coarse grinding, and the powder pre-pulverized by the vertical roller mill is supplied to the tube mill. (a) Vertical roller mills are better than tube mills for coarse grinding, and (b) the size of the balls, which are the grinding media of tube mills, can be reduced by reducing the particle size fed to tube mills. This improves the grinding efficiency of the tube mill itself.
Due to these reasons (a) and (b), it is possible to improve the crushing efficiency of the entire system.

Problems to be Solved by the Invention In such prior art, it is desired to reduce the particle size pre-pulverized by the vertical roller mill to maximize the pulverization efficiency.

An object of the present invention is to provide a method for pre-pulverizing cement clinker using a vertical roller mill, which enables pre-pulverizing to improve the grinding efficiency as much as possible.

Means for Solving the Problems The present invention arranges a plurality of rollers at intervals in the circumferential direction on a table that rotates around a vertical axis, and the material to be crushed that is supplied to the center of the table is In a method of pre-pulverizing cement clinker using a vertical roller mill, the table and rollers are inserted between the table and the rollers to crush and crush the material, and substantially all of the thus-pulverized material is taken out from below the table. This is a method for pre-pulverizing cement clinker using a vertical roller mill, characterized in that the pressing force with the rollers is selected such that the average surface pressure based on the projected area of the rollers is 8 to 20 kg/cm ² .

In a preferred embodiment, the surface pressure is between 10 and 20
Kg/ ^cm2 .

Effect According to the present invention, the pressing force between the table and the roller is selected such that the average surface pressure based on the projected area of the roller is 8 to 20 kg/cm ² . If the average surface pressure is less than 8 kg/cm ² , the particle size of the product obtained by pulverization by the vertical roller mill for pre-pulverization becomes too large. Furthermore, if this surface pressure exceeds 20 kg/cm ² , the strength of the structure for supporting the table and rollers must be unnecessarily increased, but the particle size after crushing becomes noticeably smaller. That's not the case. Therefore, the above-mentioned surface pressure is 8 to 20 kg/cm ²
By selecting this, it is possible to improve the pulverization efficiency as much as possible.

In conventional vertical roller mills that are used alone without a tube mill installed at the rear stage, multiple rollers are arranged on a table installed in a housing to crush and crush the material to be crushed, and air is introduced from the outer periphery of the table to crush the material. The structure is such that the powder is blown up, classified by a classifier placed above the table and rollers in the housing, fine powder is taken out, and coarse powder is returned to the table to be crushed and circulated. . In such vertical roller mills, the pressing force between the table and the rollers has generally been selected so that the average surface pressure based on the projected area of the rollers is approximately less than 8 kg/cm ² . The grinding efficiency of a single vertical roller mill is improved by this method.

According to the present invention, if the surface pressure is selected to be less than 8 kg/cm ² as in the prior art, the material to be crushed fed to the center of the table is compressed by the pressure between the table and the rollers. In order to grind particles to the required particle size in one grinding step, the actual grinding area must be made considerably smaller. For this purpose, it is necessary to reduce the layer thickness of the material to be crushed on the table. In this case, in order to obtain the required amount of material to be crushed per unit time, the structure must be enlarged, which is economically disadvantageous. In the present invention, such a problem can be solved by selecting the surface pressure in the range of 8 kg/cm ² or more as described above.

Embodiment FIG. 1 is a simplified cross-sectional view of a vertical roller mill for pre-pulverization to which the present invention is related. This vertical roller mill 1 for pre-pulverization has a housing 2 that is generally shaped like a right cylinder. Inside housing 2,
A table 3 having a vertical axis is arranged. This table 3 is rotationally driven by a motor 5 via a reducer 4 provided below.

A plurality of rollers 6 are arranged on the table 3 at intervals in the circumferential direction on a crushing orbital diameter Dφ.
The roller 6 has a rotation axis extending in the radial direction of the table 3 and is pivotally supported by the arm 7. Arm 7
is attached to a support 9 provided in a fixed position by a support shaft 8 having a horizontal axis. The roller 6 and the arm 7 can be retracted around the support shaft 8 as shown by the imaginary line 10 to perform maintenance and inspection.

The arm 7 is connected via a pin 13 to a piston rod 12 of a hydraulic cylinder 11 constituting a pressurizing device, and the cylinder 11 is connected by a clevis pin 14 to a bracket 16 mounted at a fixed position. By reducing the piston rod 12 of the cylinder 11, the roller 6 can be pressed against the table 3.

An inlet chute 17 is provided within the housing 2 and aligned with the axis of the table 3. Cement clinker and materials to be crushed, such as ores such as cement raw materials, are fed into this inlet chute 17 as shown by arrow 18 . From the lower part of the chute 17, the material to be crushed falls and is supplied to the center of the table 3.
The object to be crushed supplied to the center of the table 3 is caught between the table 3 and the roller 6 arranged on the crushing orbit diameter Dφ, and is crushed and crushed in the crushing orbit C section. Substantially the entire amount of the crushed material moves radially outward of the table 3 and falls onto an endless annular pedestal 19 provided below the table 3. The crushed material on the pedestal 19 is moved in the circumferential direction by a scraper 20 fixed to the table 3, and is taken out from the discharge hole 21 of the pedestal 19 via the outlet chute 22. This exit chute 2
The crushed material from 2 is sent to tube mill 2 in the latter stage.
3 and further ground to a smaller particle size by multiple grinding media.

2 is a side view of the roller 6, and FIG. 3 is a front view of the roller 6. The axis of rotation of roller 6 is indicated by reference numeral 24. When the projected area of this roller 6 on a plane 25 parallel to the rotational axis 24 is S, the average surface pressure of the pressing force of the roller 6 against the table 3 in terms of this projected area S is 8 to 8 according to the present invention. Selected as 20Kg/cm ² . The projected area S is approximately S=a·b, where a is the width of the roller 6 on the projection plane 25 parallel to the rotational axis 24 of the roller 6, and b is the diameter.

FIG. 4 is a graph showing the experimental results of one embodiment of the present invention. In the configuration shown in FIG. 1, the material to be crushed that is charged from the inlet chute 17 is cement clinker, and the work index Wi representing the crushability is 15.0 to 16.1 kW・h/ton.
The table 3 and roller 6 are made of high chrome cast iron, and the roller 6 has a width a = 340 mm and a diameter d.
=900mmφ, motor 5 that drives table 3
The table 3 is rotated at 40 to 45 rpm under the condition that the power consumption is kept constant at 3kW·h/uon. At this time, the 50% pass particle size of the pulverized material discharged from the outlet chute 22 is as shown in FIG.

From the results of this experiment, it can be seen that when the average surface pressure based on the projected area of the roller 6 is in the range of 8 to 13 kg/cm ² , the 50% pass particle diameter of the pulverized material is small and almost constant. Furthermore, if the average surface pressure of the roller is further increased, the results will be almost similar.
confirmed. By reducing the particle size of the pulverized material discharged from the pre-pulverizing vertical roller mill, the pulverizing efficiency in the tube mill 23 at the subsequent stage can be improved.

The average surface pressure based on the projected area of roller 6 is 8Kg/cm ²
If it is less than 50%, the 50% pass particle size of the resulting product will sharply increase, and the pulverization efficiency of the entire system when the vertical roller mill for pre-pulverization is combined with the tube mill 23 will decrease.

If the average surface pressure is selected to be higher than necessary for crushing efficiency, for example, a value exceeding 20 kg/cm ² , the strength of the arm 7 supporting the roller 6, the support 9, the table 3, the reducer 4, etc. will be reduced needlessly. In addition, the pressing force by the cylinder 11 must be increased, but on the other hand, the 50% pass particle size of the product obtained by crushing is noticeably reduced as shown in Figure 4. There isn't. Therefore, according to the invention, the surface pressure is selected in the range of 8 to 20 kg/cm ² .

Also preferably, the average surface pressure is 10 to 20 Kg/cm ²
This prevents the 50% pass particle size of the pulverized product from becoming too large even if there is some error in the average surface pressure.

In a vertical roller mill for pre-pulverization, it is important to carry out pulverization as quickly and efficiently as possible with a small number of opportunities for pulverization. For this purpose, when force is applied to the raw material particles, a crushing pressure that resists the crushing strength of the particles and reliably leads to crushing is an essential condition. If this is not the case, even if the particles are deformed by the applied force, they will not reach the crushing limit and will return to their original state again.
The energy for deformation is only released as heat, making it impossible to obtain the required pulverized particle size.

According to the experimental results shown in FIG. 4, the particle size of the pulverized material changes markedly to the 50% pass particle size when the average surface pressure of the roller reaches about 8 kg/cm ² . This means that the effective average surface pressure of the roller, which corresponds to the particle crushing limit mentioned above, is approximately 8 kg/
Suggests that more than ^cm2 is required. Therefore, when pre-pulverizing cement clinker as a material to be crushed using a vertical roller mill, the rotation speed of the table and the centrifugal acceleration at the crushing orbital diameter are approximately 1.2 to 1.2, as is well known to those skilled in the art. 1.5g
So that the average surface pressure of the pressing force between the table and the rollers based on the projected area of the rollers is 8 to 20 kg/
cm ² and under other conditions, for example, in one embodiment of the present invention, the clinker work index Wi can be increased to 15.0 as described above.
~16.1kW・h/ton, table 3 and roller 6
The material of is made of high chrome cast iron, and the width of roller 6 is a=
340mm, diameter d = 900mmφ, and the power consumption of the motor 5 that drives the table 3 was selected to be 3kW・h/ton, but even if these values and materials were selected,
It is also possible to practice the invention, and the invention is capable of other modifications.

Effects As described above, according to the present invention, a cement clinker pulverizing method using a vertical roller mill is realized, which can improve the pulverizing efficiency as much as possible when combined with a subsequent tube mill or the like. Ru.

[Brief explanation of drawings]

FIG. 1 is a simplified sectional view of a vertical roller mill for pre-pulverization to which the present invention is related, FIG. 2 is a side view of the roller 6, FIG. 3 is a front view of the roller 6, and FIG. It is a graph showing the experimental results of the inventor of the present invention. 1... Vertical roller mill for pre-grinding, 2... Housing, 3... Table, 6... Roller, 7... Arm, 9
...Strut, 11...Cylinder, 24...Rotation axis, 25
...projection surface.

Claims (1)

[Claims] 1. On a table rotating around a vertical axis,
A plurality of rollers are arranged at intervals in the circumferential direction, and the material to be crushed that is supplied to the center of the table is crushed and crushed by being caught between the table and the rollers, and the crushed material is essentially crushed. In a method of pre-pulverizing cement clinker using a vertical roller mill whose entire amount is taken out from below the table, the pressing force between the table and the rollers is an average surface pressure of 8 to 20 kg/cm ² based on the projected area of the rollers. A method for pre-pulverizing cement clinker using a vertical roller mill. 2. The method of pre-pulverizing cement clinker using a vertical roller mill according to claim 1, wherein the surface pressure is 10 to 20 kg/cm ² .