JP2535751B2 - How to crush powder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a wet grinding method,
The present invention relates to a technique for producing fine particles that efficiently finely pulverizes coal ore and various ores and provides a dry fine powder without a solid-liquid separation step by appropriately selecting a liquid medium.

[0002]

2. Description of the Related Art Conventionally, a wet pulverization method using water as a medium is generally used in fine pulverization to ultrafine pulverization. By using this method, even if the particles become fine, since the particles are dispersed in water, if there is a certain amount of water, agglomeration of particles, a crusher, since adhesion to the grinding medium does not occur, It is also possible to produce fairly fine particles (on the order of 10 μm).

However, in the wet pulverization method, a solid-liquid separation step is necessary after pulverization to obtain a dried product.
In particular, the finer the particle size of the granules, the more difficult the solid-liquid separation becomes, and the more troublesome not only the cost but also the operation becomes. In general, fine powder contains a large amount of water and has high viscosity and adhesiveness, so that any method requires dehydration to take special measures.

Further, the state in which the pulverizing effect is most enhanced in the wet pulverization using a liquid as a medium is that the liquid is present in a small amount rather than in a large amount, and the movement of the pulverizing medium is finally guaranteed. This is the case. In such a state, the viscosity of the slurry due to the crushed material and the liquid is high, and it has been confirmed that the viscosity most suitable for pulverization exists depending on the substance and the particle size. On the other hand, when a certain amount of liquid is present, the viscosity increases as the crushing progresses and the particle size of the crushed material becomes finer, and when the viscosity exceeds a certain value, the crushing effect decreases.

[0005]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawback of the prior art in the wet pulverization method, that is, the difficulty of solid-liquid separation of fine powder or ultrafine powder after pulverization having high viscosity and adhesiveness, and pulverization It is intended to provide a method of pulverizing a granular material which is effective and efficient.

[0006]

The present inventors have SUMMARY OF THE INVENTION In order to solve the drawbacks of the wet grinding method, the results of extensive studies on the relationship between the grinding results and Nakadachieki in grinding operations, media and liquids carbon dioxide was added to the liquid, by the action of liquids carbon dioxide in a supercritical state, not only greatly reduce the viscosity of medium liquid, found that it is possible to obtain a double effect that also lowers grinding limit, the The invention was completed.

According to the present invention, a crusher is provided with crushed material and balls .
And after inserting the liquid medium, liquid carbon dioxide gas
Add carbon dioxide by press-fitting with a high-pressure pump so that the pressure is close to
To perform crushing operation above the critical temperature and critical pressure
From the method of pulverizing powder and granular material in which liquid carbon dioxide acts in a supercritical state, and in the above method , the liquid medium and the liquid carbon dioxide have the same volume, and the addition rate of the liquid carbon dioxide to the pulverization container is 10% or less. There is provided a method for pulverizing a granular material, which is characterized in that

As the crusher, the crushing container has a pressure resistant structure.
Select a ball mill and insert the crushed material, balls and liquid medium in advance.
Then, afterwards, the liquid carbon dioxide gas will reach a critical pressure with a high-pressure pump.
Press into the vicinity. Since carbon dioxide has a critical temperature of 31 ° C. and a critical pressure of 72.8 atm , carbon dioxide is in a liquid state at room temperature under the critical pressure. That is, the operation of the crusher in the present invention is carried out at room temperature and at a pressure near the critical pressure of carbon dioxide.
Then, start with the state of crushed material + liquid (medium liquid + liquid carbon dioxide gas). Progresses grinding, the viscosity of the particle size of the crushed material is finely becomes medium liquid rises, simultaneously heat generation due to the motion of the grinding media and the temperature of the mill is increased, and, in the mill temperature
As the temperature rises, the pressure inside the mill also expands and rises. When the temperature inside the mill is 31 ° C. and the pressure exceeds 72.8 atm , the liquid carbon dioxide gas becomes supercritical. Therefore, the crushing operation is liquid coal
The temperature inside the mill is adjusted so that the acid gas can maintain the supercritical state.
And pressure should be kept constant. Although liquid carbon dioxide has a density close to that of liquid in the supercritical state, its viscosity is about 1/100 of that of liquid, and it acts as a substance that reduces the viscosity of the liquid medium, resulting in a reduction of the crushing limit particle size. Bring effect.

Further, when a substance having a low saturated vapor pressure such as acetone is used as the medium liquid, the medium liquid is vaporized when the pressure is released after pulverizing for a certain period of time, so that the solid-liquid separation step is not performed. Fine particles can be easily obtained.

Next, the present invention will be described in more detail by way of examples.

[0011]

Example: Coal and silica (particle size 149-210 μm, 1
00g) as a crushed sample, withstand pressure (120Kg / cm
² ) Ball mill with inner diameter of 155 mm and inner height of 2
00 mm, ball diameter 11.8 mm, volume filling rate 40
%, The rotation speed of the mill is 64.9 rpm), and the liquid medium capacity is 2
The grinding operation was performed for 2 hours at 50 cc.

Coal has an average particle size of 8. as a result of crushing operation using only the medium liquid using ion-exchanged water as the medium liquid.
2 μm, silica stone was 4.2 μm. Next, the average particle size of the result of pulverizing the medium liquid and liquid carbon dioxide gas in the same amount (volume) was 7.6 μm for coal and 3.
It was 8 μm. Further, an average particle size of coal was 6. when the medium liquid and the liquid carbon dioxide gas were added in equal amounts (volumes), and the liquid carbon dioxide gas was crushed at a temperature of 34 ° C. and a pressure of 80 atm in a supercritical state. It was 2 μm, and silica was 3.2 μm. On the other hand, the average particle size when only liquid carbon dioxide was used was 9.6 μm for coal and 6.0 μm for silica.

Further, the medium was crushed in the same manner as described above, using acetone instead of ion-exchanged water. Coal has an average particle size of 1 as a result of the crushing operation using only the liquid medium.
It was 0.8 μm and silica was 4.9 μm. Further, by adding an equal amount (volume) of liquid carbon dioxide to the liquid medium, the temperature was 34 ° C.,
The average particle size of the result of pulverization operation with liquid carbon dioxide gas in a supercritical state at a pressure of 80 atm is 8.8 μm for coal.
m and silica were 3.5 μm.

As described above, it can be seen that when the liquid carbon dioxide gas is added as compared with the case where only the liquid medium is used, a more excellent crushing effect can be obtained when the liquid carbon dioxide gas is allowed to act in the supercritical state.

Next, using acetone as the medium liquid, the crushing effect was investigated for the mill container by the addition ratio (%) of the medium liquid or the medium liquid + liquid carbon dioxide gas. The pulverization time was 2 hours, the liquid medium and the liquid carbon dioxide gas were equal in volume (volume), and the liquid medium + liquid carbon dioxide gas was pulverized at a temperature of 34 ° C. and a pressure of 80 atm with the liquid carbon dioxide gas in a supercritical state. The results are shown in Fig. 2, and it can be seen that the crushing result depends on the addition rate. With respect to the pulverized sample, when the addition rate is high, the pulverization result is poor, and when the addition rate is about 6.7%, the best pulverization result is shown. Since the critical value of acetone is 235 ° C. and the pressure is 47 atm, acetone is not in a supercritical state.

[0016]

According to the present invention, utilizing the characteristics of <br/> in a supercritical state of the liquid body carbon dioxide, by suppressing the increase in the viscosity of the medium liquid by the progress of grinding, milling limits of granule The grain size can be reduced. Further, by shortening the crushing time and using a substance having a low saturated vapor pressure such as acetone as the medium liquid, the conventional dehydration / drying process can be greatly simplified. Further, since the fine particles after the crushing operation are present in the supercritical liquid, it also has an advantage that extraction of a specific substance contained in the fine particles and the like simultaneously proceed.

[Brief description of drawings]

FIG. 1 is a diagram showing a particle size distribution of fine particles obtained by using coal (particle size 149 to 210 μm) as a crushed sample and adding a medium liquid or an equal amount (volume) of liquid carbon dioxide gas to the medium liquid to perform a crushing operation. Is.

FIG. 2 Coal and silica (particle size 149-210 μm)
As a crushed sample, acetone was used as a medium,
Liquid carbon dioxide acts at supercritical state at ℃ and pressure of 80 atm
FIG. 3 is a diagram showing an addition rate of a medium liquid or a medium liquid + liquid carbon dioxide gas (volume equivalent amount) to a pulverized sample, and an average particle size of fine particles obtained by pulverization by performing the pulverization operation.

Claims (3)

(57) [Claims] 1. After inserting a crushed material , a ball and a liquid medium into a crusher , the liquid carbon dioxide gas is brought to near the critical pressure of carbon dioxide gas.
Is added by pressurizing with a high-pressure pump,
And a method of pulverizing a granular material in which liquid carbon dioxide gas is caused to act in a supercritical state by performing a pulverizing operation at a pressure equal to or higher than a critical pressure . 2. The powder and granular material according to claim 1, wherein the medium liquid and the liquid carbon dioxide gas have the same volume, and the addition ratio of the medium liquid and the liquid carbon dioxide gas is 10% or less with respect to the ground sample. Grinding method. 3. The method for pulverizing a powder or granular material according to claim 1, wherein a substance having a low saturated vapor pressure is used as the liquid medium.