JP4485950B2 - Dry pulverization apparatus and dry pulverization method - Google Patents

Description

  The present invention relates to a dry pulverization apparatus suitable for use in producing abrasives, abrasives, filler materials, and the like, and a dry pulverization method using the apparatus.

  Ceramic powders such as alumina and silicon carbide used as abrasives, abrasives, fillers, etc. are generally produced by pulverizing raw material powders having a large average particle diameter. The pulverization method is roughly divided into a batch pulverization method and a continuous pulverization method, and the continuous pulverization method is further roughly divided into an open circuit pulverization method and a closed circuit pulverization method. Closed circuit grinding is widely adopted. The pulverization method includes a dry pulverization method and a wet pulverization method. When a dry product is required, a dry pulverization method that does not require a drying step is often employed.

  The dry closed circuit pulverizer is disclosed in, for example, “Chemical Engineering Handbook”, Maruzen, October 25, 1978, p. 1265. The outline will be described below with reference to FIG.

  As shown in FIG. 4, the conventional dry closed circuit pulverization apparatus includes a pulverization unit 120 for dry pulverization of an object to be pulverized 110, and a pulverized product 121 obtained by the pulverization unit 120. A classification means 130 for classifying the powder 131 into a relatively large coarse powder 132 and a circulation means 140 for circulating the coarse powder 132 obtained by the classification means 130 to the pulverizing means 120 are schematically configured.

  In this apparatus, the fine powder 131 obtained by the classification means 130 is collected, and the coarse powder 132 is repeatedly pulverized until the average particle diameter is within a predetermined range. The collected fine powder is used as it is, or further classified as needed, and used for various applications.

  However, in the conventional dry pulverizer, a product having a desired average particle size may not be obtained efficiently.

  The average particle diameter of the alumina powder suitably used as an abrasive or an abrasive is 45 to 90 μm, for example. However, in the above-mentioned conventional apparatus, when the fine powder obtained by the classification means is further classified to obtain alumina powder having such an average particle diameter, if a pulverizer is used as the pulverization means, the desired particle size in the fine powder is obtained. Since many particles having a larger particle size are mixed, the useful particle size range in the fine powder is narrow and inefficient.

  In order to expand the useful particle size range in the fine powder, a fine pulverizer may be used as a pulverizing means. In this case, the amount of fine powder contained in the fine powder increases, so the classification efficiency of the fine powder is poor. It was inefficient.

  This invention is made | formed in view of this situation, and it aims at providing the dry-type grinding | pulverization apparatus and dry-type grinding | pulverization method which can obtain the product of a desired average particle diameter efficiently.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have reached the present invention.
The present invention provides the dry pulverization apparatus and dry pulverization method described below.
(1) a pulverizing means for dry pulverizing the material to be crushed;
A first classifying means for classifying the pulverized product obtained by the pulverizing means into a fine powder having a relatively small average particle diameter and a coarse powder having a relatively large average particle diameter;
A second classification means for classifying the coarse powder obtained by the first classification means into a fine powder having a relatively small average particle size and a coarse powder having a relatively large average particle diameter;
Circulating means for circulating the coarse powder obtained by the second classifying means to the pulverizing means ;
In the second classification means, classification means for classifying the obtained fine powder into a fine powder having a relatively small average diameter and a fine powder having a relatively large average diameter;
A dry pulverizing apparatus comprising: a circulating means for circulating the fine powder obtained by the classifying means to the pulverizing means .
(2) Third classification means for classifying the fine powder obtained by the second classification means into a fine powder having a relatively small average particle diameter and a coarse powder having a relatively large average particle diameter;
A circulating means for circulating the coarse powder obtained by the third classifying means to the pulverizing means ;
In the third classification means, classification means for further classifying the obtained fine powder into fine powder having a relatively small average diameter and fine powder having a relatively large diameter;
The dry pulverization apparatus according to (1), further comprising a circulation means for circulating the fine powder obtained by the classification means to the pulverization means .
(3) The dry pulverizing apparatus according to (1) or (2), wherein the pulverizing means is a ball mill.
(4) The dry pulverization apparatus according to any one of (1) to (3), wherein the first classifying means is an airflow classifier.
(5) The dry pulverization apparatus according to any one of (1) to (4), wherein the second classification means is a sieve.
(6) The dry pulverizing apparatus according to (2) above, wherein the third classifying means is a sieve.
(7) It further has a recovery means for recovering each fine powder obtained by the first classification means and the second classification means,
The dry pulverizing apparatus according to (1) above, wherein the collecting means for collecting the fine powder obtained by the second classifying means is provided with iron removing means.
(8) It further has a recovery means for recovering each fine powder obtained by the first classification means and the third classification means,
The dry pulverization apparatus according to (2), wherein the recovery means for recovering the fine powder obtained by the third classification means is provided with an iron removal means.
(9) The dry pulverizer according to (7) or (8) above, wherein the fine particles obtained by the first classifying means have an average particle diameter of 5 to 25 μm.
(10) The dry process as described in (7) above, wherein the fine powder obtained by the second classification means has an average particle diameter of 45 to 90 μm and a bulk specific gravity of 1.7 to 2.3. Crushing equipment.
(11) The dry powder according to (8) above, wherein the fine particles obtained by the third classification means have an average particle diameter of 45 to 90 μm and a bulk specific gravity of 1.7 to 2.3. Crushing equipment.
(12) The dry pulverization apparatus according to any one of (1) to (11) , wherein the object to be pulverized is alumina.
(13) a pulverization step for dry pulverizing the object to be crushed;
A first classification step of classifying the pulverized product obtained by the pulverization step into a fine powder having a relatively small average particle size and a coarse powder having a relatively large average particle size;
A second classification step of classifying the coarse powder obtained by the first classification step into a fine powder having a relatively small average particle size and a coarse powder having a relatively large average particle size;
A circulation step of circulating the coarse powder obtained by the second classification step to the pulverization step ;
In the second classification step, the fine powder obtained is further classified into a fine powder having a relatively small average diameter and a fine powder having a relatively large average diameter; and
A dry pulverization method comprising: a circulation step of circulating the fine powder obtained by the classification means to the pulverization step .
(14) The method further includes a recovery step of recovering the fine powders obtained by the first classification step and the second classification step,
The dry pulverization method according to (13) above, wherein the recovery step of recovering the fine powder obtained by the second classification step includes an iron removal step.
(15) a third classification step of classifying the fine powder obtained by the second classification step into a fine powder having a relatively small average particle size and a coarse powder having a relatively large average particle size;
A circulation step of circulating the coarse powder obtained by the third classification step to the pulverization step ;
In the third classification step, a classification step of classifying the obtained fine powder into a fine powder having a relatively small average particle diameter and a fine powder having a relatively large average particle size;
The dry pulverization method according to (13) , further comprising a circulation step of circulating the fine powder obtained by the classification step to the pulverization step .
(16) The method further includes a recovery step of recovering the fine powders obtained by the first classification step and the third classification step,
The dry pulverization method according to (15) above, wherein the recovery step of recovering the fine powder obtained by the third classification step includes an iron removal step.

  As described above, the dry pulverization apparatus of the present invention comprises a pulverization means for dry pulverization of an object to be pulverized, and a pulverized product obtained by the pulverization means. A first classification means for classifying into powder, and a second for classifying the coarse powder obtained by the first classification means into a fine powder having a relatively small average particle diameter and a coarse powder having a relatively large average particle diameter. Classifying means for further classifying the fine powder obtained by the second classifying means into a fine powder having a relatively small average diameter and a fine powder having a relatively large average diameter as the second classifying means. And a circulating means for circulating the coarse powder and fine powder obtained by the second classifying means to the pulverizing means.

  The dry pulverization apparatus of the present invention further includes a recovery means for recovering the fine powders obtained by the first classifying means and the second classifying means, respectively, and the fine grind obtained by the second classifying means. The recovery means for recovering the powder is preferably provided with iron removal means.

  In the dry pulverization apparatus of the present invention, the fine powder obtained by the second classification means is further classified into a fine powder having a relatively small average particle diameter and a coarse powder having a relatively large average particle diameter. And a third classifying means for classifying the fine powder obtained by the third classifying means into a fine powder having a relatively small average diameter and a fine powder having a relatively large average diameter, if necessary. And a circulation means for circulating the coarse powder and fine powder obtained by the third classification means to the pulverization means.

  In this case, it further has a collection means for collecting the fine powder obtained by the first classification means and the third classification means, respectively, and collects the fine powder obtained by the third classification means. The recovery means is preferably provided with iron removal means.

  In the dry pulverizing apparatus of the present invention, a ball mill is suitable as the pulverizing means. An airflow classifier is suitable as the first classifying means, and a sieve is suitable as the second classifying means and the third classifying means.

  Moreover, it is preferable that the average particle diameter of the fine powder obtained by the said 1st classification means is 5-25 micrometers, and the average particle diameter of the fine powder obtained by the said 2nd classification means or the said 3rd classification means is It is preferably 45 to 90 μm, and the bulk specific gravity is preferably 1.7 to 2.3. Further, as the material to be crushed, ceramics such as alumina and silicon carbide are preferable, and alumina is particularly preferable.

  The dry pulverization method of the present invention includes a pulverization step for dry pulverizing a material to be pulverized, and classifying the pulverized material obtained by the pulverization step into a fine powder having a relatively small average particle size and a coarse powder having a relatively large average particle size. A first classification step, and a second classification step of classifying the coarse powder obtained by the first classification step into a fine powder having a relatively small average particle diameter and a coarse powder having a relatively large average particle diameter; Furthermore, if necessary, providing the second classification step with a classification step of classifying the fine powder obtained by the second classification step into a fine powder having a relatively small average diameter and a fine powder having a relatively large average diameter; A circulation step of circulating the coarse powder and fine powder obtained in the second classification step to the pulverization step.

  The dry pulverization method of the present invention further includes a recovery step of recovering the fine powders obtained in the first classification step and the second classification step, respectively, and the fine pulverization obtained in the second classification step. It is preferable that the iron removal process is included in the collection | recovery process which collect | recovers powder | flour.

  Moreover, instead of having the collection | recovery process which collect | recovers the fine powder obtained by the said 2nd classification process, the fine powder obtained by the said 2nd classification process is further a fine powder with a relatively small average particle diameter. A third classification step for classifying the powder into a relatively large coarse powder; and a fine powder obtained by the third classification step, if necessary, a fine powder having a relatively small average diameter and a fine powder having a relatively large average diameter; It is good also as a structure which further provides the classification process classified into 3 in a 3rd classification process, and the circulation process which circulates the coarse powder and fine powder obtained by the said 3rd classification process to the said grinding | pulverization process.

  In this case, it has the collection process which collects each fine powder obtained by the 1st classification process and the 3rd classification process, and the collection which collects the fine powder obtained by the 3rd classification process It is preferable that the process includes an iron removal process.

FIG. 1 is a diagram illustrating a dry pulverization apparatus and a dry pulverization method according to a first embodiment of the present invention. FIG. 2 is a schematic diagram of an apparatus used to measure bulk specific gravity herein. FIG. 3 is a diagram showing a dry pulverization apparatus and a dry pulverization method according to the second embodiment of the present invention. FIG. 4 is a diagram showing a conventional dry pulverization apparatus and dry pulverization method.

[First Embodiment]
Next, based on FIG. 1, a dry pulverization apparatus according to a first embodiment of the present invention and a dry pulverization method using the apparatus will be described.

  As shown in FIG. 1, the dry pulverization apparatus of this embodiment includes a pulverization unit 20 for dry pulverization of an object to be pulverized 10 and a pulverized product 21 obtained by the pulverization unit 20 with a fine particle having a relatively small average particle diameter. The first classification means 30 for classifying the powder 31 and the relatively large coarse powder 32, and the coarse powder 32 obtained by the first classification means 30, and the fine powder 51 having a relatively small average particle diameter, The second classification means 50 for classifying into a relatively large coarse powder 52, and the fine powder 51 obtained by the second classification means 50 as necessary further relative to the fine powder having a relatively small average diameter. Classifying means for classifying into large fine powder is provided in the second classifying means 50 (not shown), and the coarse powder 52 and fine powder (not shown) obtained by the second classifying means 50 are supplied to the pulverizing means 20. And a circulation means 70 for circulation.

  Further, in the dry pulverization apparatus of the present embodiment, the fine powder product collecting means 40 for collecting the fine powder 31 obtained by the first classification means 30 as a “fine powder product” and the second classification means 50 are obtained. Coarse powder product collecting means 60 for collecting the fine powder 51 as a “coarse powder product” is further provided. The coarse powder product collecting means 60 is preferably provided with iron removing means (not shown) for removing iron from the fine powder 51.

  In addition, "fine powder product" and "coarse powder product" respectively indicate a product having a relatively small average particle size and a relatively large product (also referred to as a product) obtained in the present embodiment. Shall.

  In the dry pulverization method of this embodiment using this apparatus, a pulverization step of dry pulverizing the object to be pulverized 10 and a pulverized product 21 obtained by the pulverization step are compared with fine powder 31 having a relatively small average particle diameter. First coarsely classified coarse powder 32 and coarse powder 32 obtained by the first classified step, fine powder 51 having a relatively small average particle diameter and coarse powder relatively large A second classification step of classifying the fine powder 51 into a fine powder 51 obtained by the second classification step, if necessary, and further classifying the fine powder 51 having a relatively small average diameter and a fine powder having a relatively large average diameter. The step is provided in the second classification step, and the circulation step for circulating the coarse powder 52 and the fine powder obtained in the second classification step to the pulverization step. Moreover, it has the collection process which collect | recovers each fine powder 31 and 51 obtained by the 1st classification process and the 2nd classification process, and the collection process which collects the fine powder 51 obtained by the 2nd classification process Preferably includes an iron removal step.

  In the present embodiment, the material of the material to be crushed 10 is not particularly limited, and examples thereof include ceramics such as alumina and silicon carbide. The form is preferably powder.

  Alumina powder has advantages such as being able to impart high wear resistance and high transparency to a resin composition containing this as a filler material, and is used in various applications. Specific examples of the raw material suitable for use in obtaining such an alumina powder include fused alumina.

  The physical properties of the fine powder product obtained by the first classifying means 30 and the coarse powder product obtained by the second classifying means 50 are not particularly limited, and are appropriately designed according to the use.

  However, the average particle size of the fine powder product obtained by the first classifying means 30 is preferably in the range of 5 to 25 μm, and more preferably in the range of 10 to 20 μm.

  If the average particle diameter of the fine powder product is less than 5 μm, the amount of fine powder contained in the coarse powder 32 increases, and the classification efficiency of the second classification step of reclassifying the coarse powder 32 may be reduced, which is not preferable. If the average particle size of the fine powder product is more than 25 μm, the useful particle size range of the fine powder product becomes narrow and the recovered amount of the coarse powder product decreases, which is not preferable.

  On the other hand, the average particle diameter of the coarse powder product obtained by the second classification means 50 is preferably in the range of 45 to 90 μm, and more preferably in the range of 55 to 75 μm. The bulk specific gravity of the product is preferably in the range of 1.7 to 2.3, more preferably in the range of 1.8 to 2.1.

  When the average particle diameter of the coarse powder product is less than 45 μm, the dispersibility when blended in the resin composition as a filler material is deteriorated, and there is a possibility that the properties such as non-uniformity of the resin composition are deteriorated. When the average particle diameter of the coarse powder product exceeds 90 μm, when blended in the resin composition as a filler material, particles having a diameter larger than the thickness of the resin layer may be included, thereby reducing the surface smoothness of the resin layer. There is a risk of degrading characteristics such as. In addition, when the bulk specific gravity of the coarse powder product is less than 1.7, the filling property when blended in the resin composition as a filler material is deteriorated, and when the bulk specific gravity exceeds 2.3, the residence time in the pulverizing means 20 is reduced. It is necessary to lengthen the length, resulting in overgrinding and inefficient productivity.

  In the present specification, the “average particle size” is measured in accordance with the laser diffraction method and the method of “JIS R 6002: 1998 3. Type of test method a) screening test method”. The “specific gravity” is measured according to “JIS R 6126-1970”. That is, in this specification, “average particle diameter” and “bulk specific gravity” are measured as follows.

1. Measurement of average particle diameter (JIS R 6002; screening test method):
1.1 Apparatus and standard sample 1.1.1 Test machine A low-tap test machine with an impulse number of 156 times / min and a rotation number of 290 times / min is used.
1.1.2 Screen A test screen screen having an inner frame size of 200 mm in inner diameter and 45 mm in depth is used.
1.1.3 Standard Sample The standard sample used to correct the sieving result is obtained by sieving the brown alumina abrasive material into the standard particle size distribution of each particle size and giving a reference value for the particle size distribution.
1.2 Operation The screening test operation is as follows.
a) Take a 100 g sample.
b) A test screen specified in JIS Z 8801 (for example, “JIS Z 8801 test screen”, diameter 200 mm × height 45 mm, manufactured by Iida Seisakusho Co., Ltd.) with a small opening of the sieve. Stack on a tray in order.
c) Place the sample in the first stage sieve and shake with a tester for 5 minutes.
d) Measure the sample weight on each sieve and pan to 0.1 g. At this time, if the total mass of the sample becomes 99.0 g or less, a retest is performed.
1.3 Calculation Calculate the mass percentage of the screened sample.
1.4 Correction with standard sample The calculated value is corrected with the standard sample to obtain the measured value.

2. Measurement of bulk specific gravity (JIS R 6126):
2.1 Collect approximately 120 ml of sample and dry.
2.2 Test Method 2.2.1 Apparatus A test apparatus including a funnel 141, a stopper 142, a cylinder 143, and a support base 144 having the dimensions (unit: mm) shown in FIG. The material of each member is as follows.
Funnel 141: Stainless steel Stopper 142: Brass Cylinder 143: Brass (Brass is attached to the brass seamless pipe)
(Dimensions and shapes other than those specified above and in the figures may be appropriate.)
2.2.2 Operation (1) Accurately measure the volume of the cylinder 143 to 0.1 ml with tap water.
(2) The outlet of the funnel 141 is closed with the stopper 142, about 120 ml of the sample is placed in the funnel, and then the cylinder 143 is placed directly under the funnel 141.
(3) Pull out the stopper 142 and drop the entire amount of the sample into the cylinder 143. The sample swelled from the upper surface of the cylinder 143 is removed so as to be lightly scooped while bringing the metal plate into close contact with the upper edge of the cylinder 143 at an angle of 30 to 45 degrees. Next, the weight of the sample in the cylinder is accurately measured to 0.1 g.
(4) Repeat operations (2) and (3) three times for the same sample. When the difference between the maximum and minimum weights of 3 times is 1.0 g or more, the operations of (2) and (3) are further repeated to take 3 numbers with a range of less than 1.0 g.
2.2.3 Calculation The bulk specific gravity is calculated by the following formula.

  Bulk specific gravity = ((W ₁ + W ₂ + W ₃ ) / 3) / V [g / ml]

Here, W ₁ , W ₂ , W ₃ : Weight of each time the sample entered the cylinder (g)
V: Cylinder volume (ml)

  The pulverizing means 20 is not particularly limited as long as it can pulverize the material to be pulverized 10, and can be appropriately selected according to the physical properties of the desired product.

  For example, when obtaining a fine powder product having an average particle diameter of 5 to 25 μm and a coarse powder product having an average particle diameter of 45 to 90 μm and a bulk specific gravity of 1.7 to 2.3, A generally defined grinder is preferably used. Among these, a ball mill is preferable. By using a ball mill, a fine powder product and a coarse powder product having the above-described physical properties can be obtained efficiently. Moreover, it is inexpensive among pulverizers and is advantageous in terms of equipment cost.

  The first classifying means 30 is not particularly limited as long as it can classify the pulverized product 21 obtained by the pulverizing means 20, and examples thereof include an airflow classifier and a sieve. Especially, since it is excellent in the classification efficiency (recovery efficiency of a fine powder product) of the fine powder 31, an airflow classifier is preferable.

  The second classifying means 50 is not particularly limited as long as the coarse powder 32 obtained by the first classifying means 30 can be classified, and examples thereof include an airflow classifier and a sieve. Especially, since it is excellent in the classification efficiency (recovery efficiency of a coarse powder product) of the fine powder 51, a sieve is preferable.

  Examples of the iron removing means for removing iron from the fine powder 51 (coarse powder product) include a magnetic separator. By providing such iron removal means, iron content mixed in the powder in the pulverization step, classification step, etc. can be removed, and a high-quality coarse powder product with few impurities can be obtained.

  Moreover, you may provide the same iron removal means also in the fine powder collection | recovery means 40 which collect | recovers the fine powder 31 (fine powder product) as needed.

  In the dry pulverization apparatus of this embodiment and the dry pulverization method using the apparatus, the fine powder 31 obtained by the first classifying means 30 is recovered as a “fine powder product”, and the coarse powder 32 is secondly reused. A configuration is adopted in which the fine powder 51 and the coarse powder 52 are classified by the classification means 50 and the obtained fine powder 51 is recovered as a “coarse powder product”.

  As described above, in the present embodiment, since the product is collected in two stages by dividing into two types of products having different average particle diameters, “fine powder product”, “coarse powder” “Products” may be used, and a wide useful particle size range of each collected product can be secured, which is efficient. Moreover, since only the coarse powder 32 remaining after the fine powder 31 containing fine powder is classified by the second classification means 50, the coarse powder 32 can be classified in a state where the influence of the fine powder is small. Therefore, the classification efficiency of the second classification process is not reduced due to the presence of the fine powder.

  Therefore, according to this embodiment, a product having a desired average particle diameter (for example, a fine powder product having an average particle diameter of 5 to 25 μm, and an average particle diameter of 45 to 90 μm and a bulk specific gravity of 1.7 to 2). .3 coarse powder product) can be obtained very efficiently.

  In addition, according to this embodiment, since the ball mill etc. are employ | adopted as the grinding | pulverization means 20, when bulk specific gravity is 42 to 58% of true specific gravity (for example, alumina (true specific gravity 3.98), bulk specific gravity 1. 7-2.3) and high coarse powder products can also be obtained efficiently.

  If the raw material alumina such as electrofused alumina is dry-pulverized according to the present embodiment, an alumina powder having physical properties suitable as an abrasive, an abrasive, a filler material, and the like can be obtained efficiently. In particular, the alumina coarse powder product obtained according to the present embodiment has good compatibility with the resin, and when used as a filler material, it can provide a resin composition having a high filling rate and high transparency.

[Second Embodiment]
Next, based on FIG. 3, a dry pulverization apparatus according to a second embodiment of the present invention and a dry pulverization method using the apparatus will be described. The same constituent elements as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The difference between the dry pulverization apparatus of the present embodiment and the first embodiment is that the fine powder 51 obtained by the second classifying means 50 is not recovered, and this is further refined into a fine powder 81 having a relatively small average particle diameter. 3rd classifying means 80 for classifying into relatively large coarse powder 82, and if necessary, fine powder 81 obtained by third classifying means 80 is further relative to fine powder having a relatively small average diameter. The third classifying means 80 is provided with a classifying means for classifying the powder into a large fine powder (not shown), and the coarse powder and the fine powder (not shown) obtained by the third classifying means 80 are pulverized. And a circulation means 100 for circulating the water.

  In this embodiment, instead of the coarse powder product collecting means for collecting the fine powder 51 obtained by the second classification means 50 as a coarse powder product, the fine powder 81 obtained by the third classification means 80 is used. Coarse powder product collecting means 90 for collecting the coarse powder product is provided. This coarse powder product collecting means 90 is preferably provided with iron removing means (not shown) for removing iron from the fine powder 81 as in the first embodiment.

  The third classifying means 80 is not particularly limited as long as it can classify the fine powder 51 obtained by the second classifying means 50, and examples thereof include an airflow classifier and a sieve. Especially, since it is excellent in the classification efficiency (recovery efficiency of a coarse powder product) of the fine powder 81, a sieve is preferable.

  Further, the dry pulverization method of the present embodiment is different from the first embodiment in that the fine powder 51 obtained by the second classification step is relatively larger than the fine powder 81 having a relatively small average particle diameter. The fine powder 81 obtained by the third classification step for classifying into the coarse powder 82 and, if necessary, the third classification step is further classified into a fine powder having a relatively small average diameter and a fine powder having a relatively large average diameter. The classification step to be provided in the third classification step, and the circulation step of circulating the coarse powder 82 and the fine powder obtained in the third classification step to the pulverization step.

  According to this embodiment, the fine powder 51 obtained by the second classification means 50 is further classified into a fine powder 81 and a coarse powder 82, and the fine powder 81 is recovered as a coarse powder product. Therefore, in addition to the effect of the first embodiment, a coarse powder product having a more stable particle size distribution can be obtained, and the useful particle size range of the coarse powder product can be broadened.

  Next, examples according to the present invention will be described.

Example 1
Dry closed circuit pulverization was performed using the same dry pulverization apparatus as in the first embodiment.
As a material to be pulverized, a coarsely pulverized product of electrofused alumina (particle size of 2 mm or less) was used. Vibrating ball mill with an internal volume of 0.5 m ³ as grinding means (grinding medium: alumina balls, filling rate 70%), forced vortex type airflow classifier (MS-4 type manufactured by Hosokawa Micron) as the first classification means, second As a classifying means, a circular vibrating sieve was adopted. In addition, liners (alumina and rubber) were applied to the powder-contacted parts such as equipment and wind pipes in the dry apparatus. Thereby, the amount of metal impurities in the product can be reduced.

First, the vortex flow rate of the vibration type ball mill was set to 800 kg / h. In the first classifying means, a coarse powder product having a rotation speed of 450 rpm, an air volume of 120 m ³ and an average particle diameter of 16 μm was obtained. In the second classifying means, a 125 μm sieve mesh was attached and the coarse powder was removed, and a coarse powder product having an average particle diameter of 61 μm and a bulk specific gravity of 1.87 was obtained. The yield of the coarse powder product was 72%. Thus, according to the present Example, the product of the desired average particle diameter was able to be obtained efficiently.

(Example 2)
Dry closed circuit pulverization was performed using the same dry pulverization apparatus as in the second embodiment.
As a material to be pulverized, a coarsely pulverized product of electrofused alumina (particle size of 2 mm or less) was used. An air-swept type rolling ball mill having an internal volume of 1.0 m3 as grinding means (grinding medium: alumina balls, filling rate: 45%), and a forced vortex type airflow classifier (MS-1 type manufactured by Hosokawa Micron) as the first classification means In-plane sieves were used as the second classifying means and the third classifying means.

  First, the passing flow rate of the rolling ball mill was set to 250 kg / h. In the first classifying means, a fine powder product having a rotation speed of 1100 rpm, an air volume of 15 m 3 and an average particle diameter of 11 μm was obtained. In the second classification means, a 250 μm sieve mesh is attached to remove coarse powder, and in the third classification means, a 106 μm sieve mesh is attached to remove coarse powder, and a 45 μm sieve mesh is attached to remove fine powder and the size is adjusted. As a result, a coarse powder product having an average particle diameter of 58 μm and a bulk specific gravity of 1.93 was obtained. The yield of the coarse powder product obtained by the third classification means was 69%. Thus, according to the present Example, the product of the desired average particle diameter was able to be obtained efficiently.

  Moreover, the iron content in the product could be reduced from 240 ppm to 10 ppm or less by subjecting the coarse powder product obtained by the third classifying means to iron removal using a drum type magnetic separator.

(Example 3)
Dry closed circuit pulverization was performed using the same dry pulverization apparatus as in the first embodiment.
An electromelting mullite coarsely pulverized product (particle size of 1 mm or less) was used as the material to be pulverized. An air-swept type rolling ball mill with an internal volume of 1.0 m3 was used as the pulverizing means, a forced vortex type airflow type classifier (MS-1 type manufactured by Hosokawa Micron) was used as the first classifying means, and a circular vibrating sieve was used as the second classifying means. .

  First, the passing flow rate of the rolling ball mill was set to 250 kg / h. In the first classifying means, a fine powder product having a rotation speed of 750 rpm, an air volume of 15 m 3 and an average particle diameter of 20 μm was obtained. In the second classifying means, a coarse powder product having an average particle diameter of 74 μm and a bulk specific gravity of 1.83 is obtained by attaching a 150 μm sieve mesh to remove coarse powder, attaching a 53 μm sieve mesh to remove fine powder, and sizing. was gotten. The yield of the coarse powder product obtained by the second classifying means was 74%. Thus, according to the present Example, the product of the desired average particle diameter was able to be obtained efficiently.

(Comparative example)
Dry closed circuit pulverization was performed using the dry pulverization apparatus shown in FIG.
As a material to be pulverized, a coarsely pulverized product of electrofused alumina (particle size of 2 mm or less) was used. A vibrating ball mill having an internal volume of 0.5 m ³ (grinding medium: alumina balls, filling rate 70%) was used as the grinding means, and a circular vibrating sieve was used as the classification means. Furthermore, a classifying means was provided in order to commercialize the obtained fine powder, and a forced vortex type airflow classifier (MS-1 type manufactured by Hosokawa Micron) was adopted.

First, the passing flow rate of the vibration type ball mill was set to 800 kg / h. In the classifying means, a 125 μm sieve mesh was attached and the coarse powder was removed, and a fine powder having an average particle diameter of 45 μm was obtained. Further, in the forced vortex type airflow classifier, a product having an average particle diameter of 63 μm and a bulk specific gravity of 1.95 was obtained with a rotational speed of 900 rpm, an air volume of 15 m ³ and fine powder removed. The yield of this product was 48%.

Industrial Applicability According to the present invention, it is possible to provide a dry pulverization apparatus and a dry pulverization method capable of efficiently obtaining a product having a desired average particle diameter.

Claims (16)

Pulverizing means for dry pulverizing the object to be crushed;
A first classifying means for classifying the pulverized product obtained by the pulverizing means into a fine powder having a relatively small average particle diameter and a coarse powder having a relatively large average particle diameter;
A second classification means for classifying the coarse powder obtained by the first classification means into a fine powder having a relatively small average particle size and a coarse powder having a relatively large average particle diameter;
Circulating means for circulating the coarse powder obtained by the second classifying means to the pulverizing means ;
In the second classification means, classification means for classifying the obtained fine powder into a fine powder having a relatively small average diameter and a fine powder having a relatively large average diameter;
A dry pulverizing apparatus comprising: a circulating means for circulating the fine powder obtained by the classifying means to the pulverizing means . A third classification means for classifying the fine powder obtained by the second classification means into a fine powder having a relatively small average particle diameter and a coarse powder having a relatively large average particle diameter;
A circulating means for circulating the coarse powder obtained by the third classifying means to the pulverizing means ;
In the third classification means, classification means for further classifying the obtained fine powder into fine powder having a relatively small average diameter and fine powder having a relatively large diameter;
The dry pulverization apparatus according to claim 1, further comprising a circulation means for circulating the fine powder obtained by the classification means to the pulverization means .   The dry pulverizing apparatus according to claim 1 or 2, wherein the pulverizing means is a ball mill.   The dry pulverizing apparatus according to any one of claims 1 to 3, wherein the first classifying means is an airflow classifier.   The dry pulverization apparatus according to any one of claims 1 to 4, wherein the second classification means is a sieve.   The dry pulverizing apparatus according to claim 2, wherein the third classifying means is a sieve. And further having a recovery means for recovering each fine powder obtained by the first classification means and the second classification means,
The dry pulverization apparatus according to claim 1, wherein the recovery means for recovering the fine powder obtained by the second classification means is provided with an iron removal means. And further having a recovery means for recovering each fine powder obtained by the first classification means and the third classification means,
The dry pulverization apparatus according to claim 2, wherein the recovery means for recovering the fine powder obtained by the third classification means is provided with iron removal means. The dry pulverization apparatus according to claim 7 or 8 , wherein an average particle diameter of the fine powder obtained by the first classification means is 5 to 25 µm. The dry pulverizer according to claim 7 , wherein the fine powder obtained by the second classifying means has an average particle diameter of 45 to 90 µm and a bulk specific gravity of 1.7 to 2.3. 9. The dry pulverization apparatus according to claim 8 , wherein the fine powder obtained by the third classifying means has an average particle size of 45 to 90 μm and a bulk specific gravity of 1.7 to 2.3. The dry pulverization apparatus according to any one of claims 1 to 11 , wherein the object to be pulverized is alumina. A pulverization process for dry pulverizing the object to be crushed;
A first classification step of classifying the pulverized product obtained by the pulverization step into a fine powder having a relatively small average particle size and a coarse powder having a relatively large average particle size;
A second classification step of classifying the coarse powder obtained by the first classification step into a fine powder having a relatively small average particle size and a coarse powder having a relatively large average particle size;
A circulation step of circulating the coarse powder obtained by the second classification step to the pulverization step ;
In the second classification step, the fine powder obtained is further classified into a fine powder having a relatively small average diameter and a fine powder having a relatively large average diameter; and
A dry pulverization method comprising: a circulation step of circulating the fine powder obtained by the classification means to the pulverization step . While further having a recovery step of recovering each fine powder obtained by the first classification step and the second classification step,
14. The dry pulverization method according to claim 13 , wherein the recovery step of recovering the fine powder obtained by the second classification step includes an iron removal step. A third classification step of classifying the fine powder obtained by the second classification step into a fine powder having a relatively small average particle size and a coarse powder having a relatively large average particle size;
A circulation step of circulating the coarse powder obtained by the third classification step to the pulverization step ;
In the third classification step, a classification step of classifying the obtained fine powder into a fine powder having a relatively small average particle diameter and a fine powder having a relatively large average particle size;
The dry pulverization method according to claim 13 , further comprising a circulation step of circulating the fine powder obtained by the classification step to the pulverization step . And further having a recovery step of recovering the fine powders obtained by the first classification step and the third classification step,
The dry pulverization method according to claim 15 , wherein the recovery step of recovering the fine powder obtained by the third classification step includes an iron removal step.

Images