JP2002028529A - Grinding method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the grinding efficiency in a wet grinding method by which particles are ground so that the pulverized material is dispersed in a liquid medium. SOLUTION: The particles of a large grain diameter are selectively ground by circulating slurry composed of the carrier medium and the pulverized material between a stirring tank equipped with a classification function and a grinding machine and thus the grinding efficiency is increased. The classification process in the stirring tank is performed by using a difference in the precipitation speed of the pulverized material in the liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for pulverizing powders such as pigments and magnetic powders into fine powders. More specifically, the present invention relates to pulverization capable of improving the efficiency of pulverization and narrowing the particle size distribution. Involved in the method.

[0002]

2. Description of the Related Art In order to obtain fine powders such as pigments and magnetic materials, if the material is obtained in a lump, it is first coarsely pulverized to obtain a coarse powder of the material, and finely pulverized by various methods. Moreover, if it is a granular or powdery material, it is subjected to the fine pulverizing step as it is.

[0003] As a method of fine pulverization, there are a method of beating and crushing with a stamp mill or the like and a method of grinding. In the latter method, the material to be pulverized is put into a container together with a medium such as a steel ball or glass beads and stirred, and the effect of the impact and shear by the medium, that is, the grinding effect is used. Examples of the crushing device include a ball mill, an attritor, a sand mill, and a pin mill.

As a method of operating the above-mentioned apparatus, in addition to a batch type in which the material is charged into the apparatus and stirring is performed for a certain period of time, a separate stirring tank is provided for improving the pulverization efficiency, and the material and the dispersion medium are mixed. In addition to supplying the material to the pulverizer main body and circulating the pulverized material between the pulverizer and the stirring tank, a circulation type is widely used, and is a mainstream.

[0005]

According to the conventional method of operating a pulverizer, it is essentially impossible to selectively pulverize particles having a large particle size in either a batch type or a circulation type. In other words, not only the particles having a large particle size that should be crushed are crushed, but also the particles having a small particle size that do not need to be crushed are further crushed. The result will be wider.

Accordingly, a technical object of the present invention is to provide a pulverizing method capable of improving the pulverizing efficiency and suppressing the spread of the particle size distribution by preferentially pulverizing particles having a large particle size, and a pulverizing apparatus used for the method. To provide.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has been made as a result of studying a method of preferentially supplying large-diameter particles to a pulverizer in a circulation type pulverizer. It is. That is, the present invention relates to a pulverizer that includes a pulverizer and a stirring tank and circulates a slurry composed of a liquid dispersion medium and a material powder between the pulverizer and the stirring tank to perform wet pulverization. This is a crushing device characterized by having a classification function of:

Further, according to the present invention, in the above-mentioned pulverizing apparatus, the stirring tank is provided with a stirring mechanism for preventing the material powder from forcibly moving in the tank in the vertical direction. This is a pulverizing apparatus characterized in that the pulverization is carried out based on the difference in sedimentation speed of the powder.

Further, the present invention provides the use of the above crushing device,
A pulverization method characterized in that the material powder having a large particle diameter classified in the stirring tank is preferentially supplied to the pulverizer.

[0010]

In the stirring tank used in the conventional crusher,
The material powder is designed to be uniformly dispersed in the medium, and the turbulence is generated by stirring the center of the tank and providing an appropriate baffle plate on the inner wall of the layer. On the other hand, in the stirring tank of the present invention, a paddle that rotates at low speed near the inner wall of the tank is provided, and diffusion and mixing occur only in the horizontal direction without forcibly moving the material in the vertical direction of the tank. It has become.

[0011] The settling velocity of a particle in a fluid is determined by gravity and the viscous drag between the particle surface and the fluid. Since the viscous resistance is proportional to the contact area between the particles and the fluid, if the particles have the same shape, the specific surface area increases as the particle diameter decreases, and the viscous resistance per unit weight increases.
As for gravity, if the particles are made of the same material, the weight increases as the particle size increases.

Therefore, for extremely small particles, the gravitational force becomes negligible compared to the viscous drag, and the sedimentation velocity becomes extremely small. However, in the other particle diameter range, the sedimentation velocity increases as the particle diameter increases. I do. In the stirring tank in the pulverizer of the present invention, the powder is classified by utilizing this effect.

[0013] By supplying the slurry in which the material powder is dispersed in the medium to the pulverizer from the lower part of the tank, it is possible to selectively supply the particles having a large particle diameter to the pulverizer and pulverize them. . Conversely, particles having a small particle diameter stay in the tank for a longer time, and thus are less liable to be excessively pulverized. As a result, the efficiency of pulverization is improved, and the particle size distribution of the powder is narrowed.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram for explaining a pulverizing apparatus of the present invention. This crushing apparatus has a stirring tank 101, a crusher 102, and a pump 103 for supplying a material from the stirring tank 101 to the crusher 102 as main components.

The stirring tank 101 is provided with a paddle 104 that rotates along the inner wall of the stirring tank, and is rotated at a low speed by a motor 105. Due to the low speed rotation of the paddle, the slurry composed of the material powder and the dispersion medium is stirred without being forced to move in the vertical direction. The slurry was pumped through a discharge port provided at the bottom of the stirring tank.
3 to the pulverizer 102.

The supply speed of the slurry to the crusher is adjusted by the speed of the pump 103 and the opening and closing of the valve 106. The slurry supplied to the pulverizer stays in the pulverizer for a certain period of time, is returned to the stirring tank, and circulates between the stirring tank and the pulverizer until a required particle size is reached. In the stirring tank, small particles having a small particle diameter tend to stay at the upper side as described above, so a discharge port is provided at the upper side to appropriately take out the slurry,
It is also possible to operate continuously by a method of replenishing the material and the dispersion medium by the amount taken out.

FIG. 2 is a schematic diagram for explaining a conventional pulverizer. The stirring tank 201 of this pulverizing apparatus is provided with stirring blades 202 and baffle plates 203, and the slurry inside is stirred not only horizontally but also vertically by the action of the baffle plates. For this reason, unlike the stirring tank used in the present invention, the particle size distribution of the material powder is not formed in the vertical direction.

In each of the pulverizer of the present invention and the conventional pulverizer, 1000 kg of an alloy powder containing Fe as a main component was added.
1400 kg of toluene was charged as a dispersion medium, and the time required until the average particle size of the alloy powder became 50 μm or less was determined. The results are shown in Table 1.

[0020]

[Table 1]

As is apparent from the results, the pulverizer according to the present invention requires less than half the time required for pulverization. When the particle size distributions of the two were compared, it was found that the powder using the pulverizer of the present invention tended to be narrower.

[0022]

As described above, according to the present invention, a pulverizing method and a pulverizing apparatus capable of selectively pulverizing particles having a large particle diameter can be obtained. The time required for pulverization can be greatly reduced. In addition, since particles having a small particle diameter are less crushed excessively, the particle size distribution can be narrowed.

[Brief description of the drawings]

FIG. 1 is a schematic view of a crusher of the present invention.

FIG. 2 is a schematic view of a conventional pulverizer.

[Explanation of symbols]

 101, 201 Stirring tank 102 Crusher 103 Pump 104 Paddle 105 Motor 106 Valve 202 Stirring blade 203 Baffle plate

Claims (3)

[Claims] 1. A pulverizing apparatus including a pulverizer and a stirring tank, wherein a slurry comprising a liquid dispersion medium and a material powder is circulated between the pulverizer and the stirring tank to perform wet pulverization. A crushing device having a classification function. 2. The crushing apparatus according to claim 1, wherein the stirring tank includes a stirring mechanism that does not cause forced movement of the material powder in the tank in the vertical direction, and classifies the material powder by A pulverizing apparatus characterized in that the pulverization is performed based on a difference in sedimentation speed of the powder. 3. A crusher according to claim 1 or 2, wherein the material powder having a large particle size classified in the stirring tank is preferentially supplied to the crusher. And crushing method.