JPH04244275A - Classifying apparatus - Google Patents

Abstract

PURPOSE:To obtain a product having a small mean particle size and particle size distribution reduced in the mixing ratio of a fine powder component by preliminarily classifying the fine powder contained in a ground raw material to recover the same before grinding said raw material. CONSTITUTION:In the classifying apparatus 2 arranged to the upper part of a grinder 1, the drive shaft composed of the hollow shaft 3 supported at the center of a classifying chamber in a rotatable manner and a plurality of the classifying blades 12 integrally rotating around the drive shaft are provided and a fine powder discharge pipe 17 is connected to the hollow pipe 3. A plurality of the guide vanes 13 freely revolvable around vertical shafts 13a are arranged to the outer peripheries of the classifying blades 12 in a concentric circular state and a guide cone 14 having an inverted cone shape and having a plurality of slits 14b provided to the conical surface thereof is provided. Further, a plurality of dish-shaped dispersing plates 15 each composed of an almost horizontal disc having a perforated plate or metal net provided thereto on the outer peripheral side thereof and having a weir 15 formed to the outer periphery of the end edge thereof or having an outer periphery higher than the central part thereof are arranged so as to cover the classifying blades 12 and the guide vanes and a raw material scraper 15a is fixed to the hollow pipe 13 and a raw material charging supply pipe 16 is provided to the casing 2a of the classifying apparatus 2.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a classification device attached to a pulverizer for pulverizing chemicals used in the ceramics industry and filler industry, and is a classification device that separates classified raw materials into fine powder and coarse powder by air flow. It is related to.

0002

[Prior Art] The purpose of a classification device is to use airflow to sort powder and granules crushed by a crusher into powders of a desired particle size to produce products.The classification principle is gravity classification, inertia force It is broadly divided into classification and centrifugal force classification. Of these, centrifugal force classification, which is suitable for large-volume classification of powder, includes a free-vortex type in which the airflow is swirled by making the shape of the classification chamber spiral, and There are two types: forced vortex type, in which the airflow is forcibly swirled by rotating blades installed in the air, and type that uses both free vortex and forced vortex, which is a combination of these two types.

[0003] In addition, there are two types of classification devices: those installed separately from the crusher to guide the powder and granules crushed by the crusher, and those installed separately from the crusher to guide the powder and granules crushed by the crusher, and those installed attached to the crusher to guide the powder and granules in the crushing chamber. There is an attached type that classifies particles by introducing them into a classification chamber by air conveyance, but the latter type has a wide range of applications, such as the vertical crusher shown in Figure 6 and the centrifugal flow mill shown in Figure 7. It is often used as an accessory to crushing equipment.

[0004]Recently, along with the diversification of pulverized raw materials and the expansion of demand for ultrafine powder, requirements for the particle size distribution of products have become more sophisticated. There is an increasing demand for products that keep the amount of much finer particles passing through within a certain ratio. To illustrate this case, for example, when the raw material of curve X in the particle size distribution curve shown in FIG. For example, curve Y), when the actually obtained product after pulverization became curve Z, the average particle size was satisfied, but the 0.1 μm pass was 1.1%, which was 1%.
In some cases, the product was defective because the product exceeded the above limit.

[0005]

[Problems to be Solved by the Invention] As mentioned above, when a product is subjected to harsh pulverization conditions where the average particle size is fine to a certain extent and the proportion of fine powder mixed in is not very high, it is necessary to attach a regular classifier. These conditions cannot be achieved by using a grinder that directly grinds the raw material containing a large amount of fine powder, resulting in problems such as over-grinding.

[0006]

[Means for Solving the Problems] Therefore, in order to solve the above problems, in the classification device of the present invention, a hollow It has a drive shaft made of a tube and a plurality of circumferential classification blades that rotate integrally around the drive shaft.A fine powder discharge pipe is provided above the hollow tube, and air for classification is placed around the outer periphery of the classification blade. A plurality of guide vanes rotatable around a vertical axis are arranged concentrically with the hollow tube in order to give a turning to the hollow tube, and a guide vane with a substantially reverse shape is connected to the guide vane at the lower part of the guide vane. A classification device equipped with a guide cone having a truncated cone shape, wherein a horizontal disc-shaped dispersion plate covering the classification blades and guide vanes is fixed to the hollow tube, and a dispersion plate is provided vertically on the dispersion plate. At the same time, a plurality of scrapers extending radially in the circumferential direction are fixedly installed, and a supply pipe for the pulverized raw material is arranged in the casing of the classification device directly above the dispersion plate and the scraper, and the reverse truncated shape of the guide cone is installed. A plurality of slits are provided on the circumference of the conical surface to allow the rising air to pass through, and the dispersion plate has multiple stages, and the area larger than the outer diameter of the classification blade is formed with a perforated plate or wire mesh, and the upper perforated plate The pore diameter or the wire mesh (the size of the mesh) was made larger than that of the lower layer.

[0007]

[Operation] In the classification apparatus of the present invention, the raw material is supplied to the classification chamber via the supply pipe and falls onto the rotating multistage distribution plate. When the fine powder mixed in the fallen raw material moves outward on the dispersion plate, it falls through the through holes or wire mesh provided in the dispersion plate and moves to the lower dispersion plate. The air falls onto the guide vanes and classification blades placed below, rides on the airflow, and undergoes the classification action. Coarse particles that cannot pass through the holes or the wire mesh spiral outward on the dispersion plate due to centrifugal force and the scraping action of the scraper provided on the dispersion plate, and are distributed evenly around the circumference of the dispersion plate at the outer edge of the dispersion plate. It overflows and falls downward. At this time, most of the coarse particles of the raw material fall downward along the inner surface of the casing due to the action of gravity, but the fine powder contained in the falling raw material is caught in the upward airflow from the crusher located below the classification device. The liquid then rotates and passes through the guide vane to the classification vane. here,
The rotating classification blade receives the classification action, and the coarse powder in the fine powder is knocked off by the classification blade and cannot pass through the classification blade, but instead slides down the wall of the guide cone below in a spiral pattern and falls. , it falls along the inner surface of the outermost casing and heads toward the crusher. At this time, the fine powder contained in the coarse powder that spirally slides and falls along the wall of the guide cone crosses the slits provided several times around the circumference on the slope of the guide cone several times. The airflow that rises from the slit is accompanied again by the airflow and is again subjected to the classification action toward the classification blade. The fine powder below the classification point that has been classified by the classification blade passes through the classification blade, passes through the hollow tube, and is discharged outside the machine from the fine powder discharge pipe. In the crusher, the aforementioned coarse particles of New Feed and the coarse powder after classification are both subjected to the crushing action, and only the powder with a relatively fine particle size rides on the upward airflow and heads toward the guide vane, where it is transported upward. It is classified using a classification blade in the same way as described above.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be explained below based on the drawings. 1 to 5 show embodiments of the present invention, FIG. 1 is a longitudinal cross-sectional view of a classification device, FIG. 2 is a plan view taken from II-II in FIG. 1, and FIG. 3 is a plan view taken from III-III in FIG. 1. Plan view, Figure 4
5 is a perspective view showing another embodiment of the guide cone, and FIG. 5 is a longitudinal sectional view of a main part showing another embodiment of the dispersion plate. The solid arrows in the figure indicate the flow of raw materials, and the dotted arrows indicate the flow of airflow.

In the figure, the classification device 2 is a vertical crusher 1a.
A hollow tube 3 is installed directly above a crusher 1 such as a centrifugal fluid crusher 1b, and a hollow tube 3 is connected to a pair of upper and lower bearings 4 concentrically with the crusher 1.
, 5 and is rotatably disposed. The bearings 4 and 5 are mounted on a pedestal 6 erected at the upper center of the casing 2a of the classifier 2.
A chain wheel 7 is attached to the upper end of the hollow tube 3, and a variable speed electric motor 9 is connected via a roller chain 8.
It is rotationally driven by a chain wheel 10 attached to the output shaft of. On the other hand, the lower part of the hollow tube 3 hangs down into the classification chamber, and as shown in FIG. 12 is attached, and a plurality of guide vanes 13 are attached to the outer periphery of the classification vane 12 and can be rotated around a rotating shaft 13a fixed to the upper end flange of a guide cone 14 fixed to the casing 2a via a support 14a. The inclination of the airflow is set in such a direction that the airflow flowing in synchronization with the rotational direction of the classification blades 12 becomes a swirling flow. Note that the classification blade 12 is also inclined in the same direction as the guide vane 13 and has a spiral shape.

In the embodiment shown in FIG. 1, the conical surface of the guide cone 14 is provided with slits 14b extending downward along the slope at equal intervals around the circumference, and the airflow from below is guided through the slits 14b. Invades the inside of the cone 14. Further, as another example of the slits, as shown in FIG. 4, it is conceivable that the slits are arranged in a staggered manner in multiple stages horizontally on the conical surface. In either case, the fine part of the coarse powder that spirally slides down the conical slope of the guide cone 14 is carried by the upward air current entering the guide cone 14 from the slit 14b to the classification blade 12 again. The main role of the slit 14b is to collect the particles after they have been subjected to the classification action.

Further, directly above the classification vanes 12 and the fixed guide vanes 13, disc-shaped dispersion plates 15 of a size large enough to cover both are arranged in multiple stages. Each of the dispersion plates 15 has through holes 15c arranged in a staggered manner over the entire surface of the dispersion plate 15 in an area larger than the outer diameter of the classification blades 12 as shown in FIG. 2, or formed in a wire mesh. Ru. The size of the through holes or the mesh of the wire mesh is said to be larger towards the top. A cylindrical weir 15b is provided on the outer periphery of the edge of the dispersion plate 15, and a plurality of scrapers 15a extending in a radial direction perpendicular to the dispersion plate 15 are arranged on the dispersion plate 15 at equal intervals on the circumference. It is designed to be rotated together with the hollow tube 3. The reason for providing the weir 15b is to ensure that the raw material introduced from the raw material supply pipe 16 overflows equally from the circumference of the distribution plate 15. Weir 15b on the distribution plate 15
As shown in FIG. 5, instead of providing a dispersion plate, the dispersion plate may be formed not into a horizontal disk but into a dish shape in which the outer periphery is higher than the center. Casing 2 directly above distribution plate 15 and scraper 15a
A supply pipe 16 for the pulverized raw material is provided at one point a. In addition, a pedestal 3 and a chain foil 7 are placed above the upper end of the hollow tube 3.
An air and fine powder discharge pipe 17 is connected to the protective cover 7a, and is connected to a suction fan (not shown). Note that a truncated conical lid 3a is provided at the bottom of the hollow tube 3 to prevent short paths of airflow.

Next, the operation of the classification device 2 constructed as described above will be explained. When the raw material is introduced into the classification chamber through the supply pipe 16, the raw material that falls onto the dispersion plate 15 which is rotationally driven by the variable speed electric motor 9 is scraped by the scraper 15a.
The centrifugal force acting on the dispersion plate 15 causes the fine particles to be evenly distributed over almost the entire circumference, and while the fine particles pass through the holes 15b and the wire mesh, the coarse particles evenly overflow the dispersion plate 15 and are mostly dispersed as shown in FIG. The large lump falls downward as shown by arrow A. However, the fine powder contained in the raw material is accompanied by the airflow rising toward the guide vane 13 due to the suction force of a suction fan (not shown), and is classified toward the classification blade as shown by arrow B. As a result of classification, fine powder below the classification point passes through the inside of the hollow tube 3 and is discharged from the fine powder discharge pipe 17 (arrow D), but coarse powder above the classification point is rejected by the classification blade 12 as shown by arrow C. It slides down inside the guide cone 14 and heads toward the crusher 1. However, in the classification device of the present invention, since the guide cone 14 is provided with the slit 14b, a portion of the rising airflow from the crusher 1 is transferred from the slit 14b to the guide cone 14.
The fine powder contained in the coarse powder that enters the inside and slides down the conical slope in a spiral shape is stirred up and entrained, and then passes through the guide vane 13 again to the classification blade 12 where it is subjected to the classification action again, so that the fine powder is removed. Preventing it from going to the crusher 1. In this way, the large lump of raw material indicated by the arrow A mentioned above and the coarse powder falling down the slope of the guide cone 14 are pulverized by the pulverizer, and the pulverized powder passes through the guide vanes 13 and the guide cone 14. Riding on the passing air current, it heads toward the classification blade 12 and receives a classification action. The behavior after classification is as described above. Adjustment of the classification point is mainly done by controlling the rotation speed of the classification vane 12, and the inclination angle of the guide vane 13 is changed as a supplementary means, but this work is complicated as it has to be changed manually by interrupting operation. Therefore, it cannot be used frequently. In an actual machine where it is often desired to change the inclination angle of the guide vane 13 automatically during operation, a micromotor is used instead of the bearing 13b that supports the rotating shaft 13a of the guide vane 13 to remotely change the inclination angle of the guide vane 13. Change by operation.

As described above, in the classification device of the present invention, after the fine powder contained in the raw material is removed in advance in the form of preliminary classification by the classification device, the coarse powder after classification is once again passed through the slit of the guide cone. The fine powder contained in the coarse powder is collected by the updraft, and only the remaining granules and coarse powder are fed to the pulverizer, which is ideal for preventing over-grinding. As shown by curve Y, it is possible to obtain a product having a desired particle size structure with a relatively small average particle size, a narrow and sharp particle size distribution with little contamination of fine powder.

[0014]

[Effects of the Invention] In the classification device of the present invention, the fine powder contained in the raw material is dropped through the through holes provided in the dispersion plate or the wire mesh, and is reliably collected and used for pulverization before being pulverized, thereby preventing over-pulverization. As a result, sharp fine powder with uniform grains and narrow particle size distribution can be obtained as refined powder. Furthermore, as over-grinding is prevented, the crushing efficiency is improved.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a classification device showing an embodiment of the present invention.

FIG. 2 is a plan view taken along line II-II in FIG. 1;

FIG. 3 is a plan view taken along III-III in FIG. 1;

FIG. 4 is a perspective view showing another embodiment of the guide cone of the classification device of the present invention.

FIG. 5 is a longitudinal sectional view of a main part showing another embodiment of the dispersion plate of the classification device of the present invention.

FIG. 6 is a longitudinal cross-sectional view of a conventional vertical crusher.

FIG. 7 is a longitudinal cross-sectional view of a conventional centrifugal flow device.

FIG. 8 is a particle size distribution curve diagram showing an example after pulverization.

[Explanation of symbols]

1　Crusher 1a Vertical crusher 1b Centrifugal fluid milling device 2 Classification device 2a Casing 3 Hollow tube 4 Bearing 5 Bearing 6 Mount 7 Chain foil 8 Roller chain 9 Variable speed electric motor 10 Chain foil 11 Disk 12 Classifying blade 13 Guide vane 13a Rotation axis 13b Bearing or micro motor 14 Guide cone 14a Support 14b Slit 15 Dispersion plate 15a Scraper 15b Weir 15c Through hole 16 Supply pipe 17 Discharge pipe

Claims (1)

[Claims] [Claim 1] A drive shaft consisting of a hollow tube arranged in the upper part of the crusher and rotatably supported in the center of the classification chamber, and a plurality of circumferential classification blades rotating integrally around the drive shaft. A fine powder discharge pipe is provided above the hollow tube, and a plurality of guide vanes rotatable around a vertical axis are arranged on the outer periphery of the classification vane to give swirl to the classification air. The classification device is provided with a guide cone arranged concentrically with the hollow tube and connected to the guide vane and having a substantially inverted truncated cone shape at the bottom of the guide vane, the classification vane and the guide vane being connected to the guide cone. A horizontal disk-shaped dispersion plate covering the hollow tube is fixed to the hollow tube, and a plurality of circumferential scrapers extending vertically and radially on the dispersion plate are fixed, and the dispersion plate is fixed to the hollow tube. A supply pipe for the pulverized raw material is arranged in the casing of the classification device directly above the plate and the scraper, a plurality of slits are provided on the circumference of the inverted truncated conical surface of the guide cone for passing the upward air flow, and the dispersion plate is arranged in multiple stages. , and the area larger than the outer diameter of the classification blade is formed by a perforated plate or a wire mesh, and the hole diameter of the upper perforated plate or the wire mesh is made larger than that of the lower stage.