JPH0819702A - Method for highly purifying diatomaceous earth - Google Patents

Abstract

PURPOSE:To purify diatomaceous earth easily and at a low cost by pulverizing diatomaceous earth under a constant condition and recovering particles with a size of a specified value or less are recovered after classification. CONSTITUTION:Natural diatomaceous earth is pulverized in a dry or wet condition. In the pulverization operation, raw earth is crushed to a particle size of 3-10mm using a jaw crusher, etc., as the need arises, and then pulverized to a particle size of 1.0-0.1mm using roll crusher, edge runner, etc., and further into fine particles using ball mill, colloid mill, etc. Finally, as required, ultrafine particles with a particle size of 1-20mum are obtained by the use of fluid pulverizer, micro ultrafine pulverizer, friction disk mill, etc. The pulverized diatomaceous earth is classified to recover particles with a particle size of 10mum or less. In the classification, the use of a gravity sedimentation method in a wet process and a centrifugal separation method in a dry process is recommended in view of operational efficiency.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for purifying diatomaceous earth.

[0002]

2. Description of the Related Art Diatomaceous earth is a silicic acid substance having a fine porous structure with a diameter of several μm, and has been widely used for a long time in fields such as filtration aids, heat insulating building materials, catalyst carriers, fillers, and dynamite. ing.

The diatomaceous earth naturally produced contains a small amount of crystalline SiO ₂ such as quartz and feldspar, and impurities such as pyrite, specifically about several percent to several tens percent. . If these impurities are contained, for example, when diatomaceous earth is used as a filler for silicone rubber, etc., the reinforcing effect on the silicone raw rubber will not be sufficient, and the effect of improving tensile strength will be poor. There is a risk of becoming. Further, depending on the type of impurities, some may chemically attack the silicone rubber molecules.

Thus, impurities in diatomaceous earth will reduce various characteristic values in the above-mentioned fields in which diatomaceous earth is used, so it is desirable to remove them as much as possible. However, conventionally, no method has been known for increasing the purity of diatomaceous earth easily and at low cost.

It is an object of the present invention to provide a novel method for improving the purity of diatomaceous earth easily and at low cost.

[0006]

In order to solve the above problems, in the present invention, diatomaceous earth is pulverized under a certain condition,
Classification is performed to collect particles having a particle size of 10 μm or less.

[0007]

In the present invention, the difference in the crushing strength between the diatom shell (amorphous SiO ₂ ) contained in the natural diatomaceous earth and the impurities such as quartz, feldspar, pyrite, etc. In addition, based on the findings of the present inventors that the diatom shells are finely pulverized as compared with the above impurities, and as a result, the diatom shells are concentrated in a fine particle size of 10 μm or less,
The diatomaceous earth can be highly purified by simple operations such as crushing and classification.

Hereinafter, the present invention will be described in more detail based on the embodiments. The diatomaceous earth used in the present invention may be any naturally occurring raw soil, and the raw soil is fired at a temperature of 800 to 1200 ° C. for about 1 to 3 hours. It is also possible to use a thing.

[0009] For high purification, first, such natural diatomaceous earth is ground. The pulverization method is not particularly limited as long as diatomaceous earth is pulverized under uniform conditions to sufficiently fine particles, and either wet or dry method may be used. The wet method requires less power for crushing, and the problem of deterioration of the working environment due to scattering of crushed fine particles does not occur easily, but the following classification operation, firing in a kiln Considering this, it is preferable to use the dry method in terms of cost.
If the wet process is used, the water content should be 20%.
It is desirable to set it to about 0 to 300% by weight.

The crushing operation is carried out by, for example, if necessary, for example,
The raw soil is roughly crushed to a suitable size of about 3 to 10 mm by using a jaw crusher, a gyrate crusher, etc., and then a particle size of 1.0 is obtained by using a roll crusher, an edge runner, an impact crusher, etc. Intermediate pulverization is performed up to about 0.1 mm, and further fine pulverization is performed using, for example, a stamp mill, a ball mill, a colloid mill, a fluid pulverizer, a centrifugal force pulverizer, and the like, and if necessary, a fluid pulverizer (jet Mill), a micro-ultrafine pulverizer (hammer mill), a friction disc mill (disc attrition mill), etc. to finally perform ultrafine pulverization to obtain particles having a particle size of about 1 to 20 μm.

In the dry method, atomization is carried out by collision and friction between particles under uniform conditions, and the crushed particle size is caused by the difference in strength between diatom shells and other impurities contained in natural diatomaceous earth. It is desirable to use a fluid crusher that is likely to cause a difference. On the other hand, in wet grinding, a ball mill (tube mill) or the like is preferably used.

The work energy required for such crushing depends on the type of crusher used and whether it is a wet type or a dry type. Therefore, it cannot be unconditionally specified, but if an excessively high energy is applied. However, even impurities such as quartz, feldspar, and pyrite, which are stronger than diatom shells, may be crushed to the same extent as diatom shells. It is not desirable because the purity of SiO ₂ cannot be increased. Therefore, the diatom shell (compressive strength in a dry state of about 50 kg / cm ² ) is usually 1 to 10 μm.
The amount of work is sufficient to pulverize to a particle size of about m, and may be appropriately set depending on the model of the pulverizer used and the like. For example, diatomaceous earth with a particle size of about 1 to 5 mm,
In order to finely pulverize to a desired final particle size using a fluid pulverizer, it is desirable to set the flow velocity of the air used to about Mach 2.5 to 3.0.

Next, the diatomaceous earth thus pulverized is subjected to a classification treatment to recover particles of 10 μm or less, more preferably 8.0 μm or less, and further preferably 6.0 μm or less. The classification operation is not particularly limited as long as it can separate and collect particles having a desired particle diameter as described above, and a sieving method, a gravity sedimentation method, a centrifugal sedimentation separation method, a cyclone method, an electrostatic separation method. Etc. can be used, but in terms of work efficiency, the gravity sedimentation method is used in the dry type,
In the wet method, it is desirable to use the centrifugal sedimentation method.

The particle size recovered in this manner is 10 μm or less.
The lower particles are diatom shells (amorphous SiO ₂Is less than 90% by weight
Naturally produced raw material or
Is much higher in purity than the fired product.
It

[0015]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. As test materials, white original soil (produced in Takasu-cho, Kitaakita-gun) and black original soil (produced in Takasu-cho, Kitaakita-gun) were thoroughly dried in advance and pulverized to 100 μm or less using a roll crusher and a crusher impactor. About 1000 ℃
After crushing the calcined product obtained by calcining for about 2 hours, and partly classifying using a gas stream classifier, collecting 50 μm or less,
Using a jet mill (Nippon Pneumatic Mfg. Co., Ltd., supersonic jet pulverizer PJM), the medium pulverized raw material was further finely pulverized.

Subsequently, the finely pulverized raw material was classified by a high-precision powder air stream classifier (Nippon Pneumatic Mfg. Co., Ltd., powder air stream classifier MDS) to obtain fractions of various particle sizes. . Fractions of various particle diameters thus obtained were respectively analyzed by an X-ray powder diffractometer (Rigaku Denki Co., Ltd., RAD-III).
During C), quartz, which is the main constituent of diatomaceous earth impurities,
The reflection intensities of feldspar and pyrite were calculated and their ratios to the values before classification were calculated. The obtained results are shown in FIG. FIG.
As is clear from the above, in any of quartz, feldspar, and pyrite, the classification is 6 μm or less and the reflection intensity ratio is 0.48
~ 0.89, the content ratio of impurities is reduced,
It can be seen that the purity is improved.

The total silicic acid (T-SiO 2) in each fraction is
Ratio of ₂₎ solubility in silicate _{(S-SiO 2) (S} -Si
₂ shows the results of O ₂ / T-SiO ₂ ) determined by the glass bead method and the available silicic acid quantification method. In the classified products of 6 μm or less, the content of soluble silicic acid is high, It was confirmed that the purity was improved.

[0018]

As described above, according to the present invention, the purity of diatomaceous earth can be increased by a simple operation of crushing and classifying diatomaceous earth, and a filter aid, a heat insulating building material, a catalyst carrier, and a filling agent. Product value can be increased in various applications such as agents.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the particle size of a classified product of diatomaceous earth and the XRD reflection intensity ratio of impurities.

Fig. 2 Particle size of diatomaceous earth classification product and total silicic acid (T-SiO2)
₂₎ it is a graph showing the relationship between the ratio of soluble silicate (S-SiO ₂₎ in.

Claims (5)

[Claims] 1. A method for highly purifying diatomaceous earth, which comprises pulverizing diatomaceous earth under constant conditions and classifying the particles to recover particles having a particle diameter of 10 μm or less. 2. The method for purifying diatomaceous earth according to claim 1, wherein the diatomaceous earth is pulverized in a state of being moistened with water and subjected to classification by centrifugal sedimentation separation. 3. The method for highly purifying diatomaceous earth according to claim 1, wherein the diatomite is pulverized under dry conditions and then classified. 4. The method according to claim 1, wherein the pulverization is carried out using a fluid pulverizer. 5. The method for highly purifying diatomaceous earth according to claim 1, wherein the diatomaceous earth is calcined prior to the pulverizing operation.