Silicon nitride granulating device

Abstract

The application belongs to the technical field of silicon nitride production, and particularly relates to a silicon nitride granulating device, which comprises a granulating tower and a spraying mechanism, further comprises a material feeding plate and a stirrer, the material feeding plate is arranged on the inner side wall of the granulating tower and is spirally arranged around the axis of the granulating tower, and the material feeding plate is located below the spraying mechanism, the stirrer is arranged in the spirally arranged material feeding plate along the axis of the granulating tower, and the material beads can be formed into a shape by rolling downward along the spiral of the material feeding plate under the action of air rotation during the process of hot air drying, the formed powder particles are more compact, have higher strength, are more regular in shape, have better surface smoothness, and are closer to a spherical shape, which is more conducive to the production of silicon nitride microspheres with a small diameter, especially micron-level silicon nitride microspheres.

Description

Technical Field

[0001] This invention belongs to the field of silicon nitride production technology, specifically relating to a silicon nitride granulation device. Background Technology

[0002] Silicon nitride is an important structural ceramic material, characterized by high hardness and wear resistance, exhibiting excellent properties and thus widely used in components requiring high strength and performance. Currently, silicon nitride granulation methods include dry pressing granulation, cold isostatic pressing granulation, and spray granulation. Dry pressing granulation involves shaping powder through a mold, followed by crushing and spheroidizing. Cold isostatic pressing granulation is similar, also involving shaping powder under pressure, followed by crushing and spheroidizing. The difference lies in the placement of the ceramic powder in a specific mold before being placed in a cold isostatic pressing device. Both dry pressing and cold isostatic pressing are pressure granulation methods. Their advantage is the high bulk density of the resulting granules, which is beneficial for improving the density of the green body; however, their disadvantages include difficulty in controlling the shape of the crushed granules due to the crushing process, making it difficult to achieve ideal spherical shapes, and the presence of noise and dust issues. Spray granulation involves directly spraying a mixed slurry into hot air within a granulation tower. The sprayed droplets contact the hot air, causing the water-soluble solvent in the droplets to evaporate rapidly. The solute shrinks to form microspheres, which then fall automatically to the bottom of the granulation tower under gravity, resulting in rapid drying and the formation of nearly spherical powder particles. Compared to the previous two methods, spray granulation produces powders with better shape consistency, making it more suitable for granulating micro-diameter, especially micron-sized, silicon nitride microspheres. However, due to the inherent characteristics of the spray granulation process, although the resulting particles are nearly spherical, defects such as hollowness and surface pits can easily occur during the water evaporation and shrinkage process. This can lead to problems such as insufficient strength and irregular particle shape in the silicon nitride microspheres. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a silicon nitride granulation device that produces more compact, stronger, more regular particle shape and better surface smoothness after molding.

[0004] The present invention includes a granulation tower and a spraying mechanism, and further includes a feeding plate and a stirrer. The feeding plate is disposed on the inner side wall of the granulation tower and spirally arranged around the axis of the granulation tower, and the feeding plate is located below the spraying mechanism. The stirrer passes through the spirally arranged feeding plate along the axis of the granulation tower.

[0005] Furthermore, the feeding plate is spirally arranged around the axis of the granulation tower at least once.

[0006] Furthermore, the width of the feeding plate is greater than or equal to one-third of the inner radius of the granulation tower and less than or equal to two-thirds of the inner radius of the granulation tower.

[0007] Furthermore, it also includes an air supply pipe for introducing hot air into the granulation tower, one end of which is connected to the air inlet of the granulation tower, and the end of the air supply pipe connected to the air inlet is tangent to the inner wall of the granulation tower.

[0008] Furthermore, the air inlet is located above the end of the delivery plate near the spray mechanism.

[0009] Furthermore, the spraying mechanism is a rotary sprayer, which is located in the middle of the upper part of the granulation tower, and the air inlet is located below the rotary sprayer.

[0010] Furthermore, the agitator is rotatably connected to the bottom of the granulation tower, and a rotating mechanism is provided on the outer side of the bottom of the granulation tower, which drives the agitator to rotate.

[0011] Furthermore, a material collection hopper is integrally provided at the bottom of the granulation tower, and the material collection hopper is arranged in a ring around the rotating mechanism.

[0012] Furthermore, the agitator includes a rotating shaft and blades disposed on the rotating shaft, the blades being inclined along the spiral direction of the feeding plate on the rotating shaft.

[0013] Furthermore, the blades are located between the upper and lower ends of the feeding plate in the axial direction of the rotating shaft.

[0014] The beneficial effects of this invention are as follows: the slurry is atomized and sprayed into the granulation tower by a spraying mechanism. In the granulation tower, the moisture in the atomized droplets gradually evaporates under the action of hot air. Under the continuous stirring action of the agitator, an air vortex is generated in the granulation tower. The droplets fall onto the feeding plate under the action of this air vortex and roll downwards along the spiral direction of the feeding plate to form a shape. In this invention, the air vortex generated by the rotation of the agitator can, on the one hand, ensure that the droplets can fall onto the feeding plate and roll along the spiral direction of the feeding plate, and on the other hand, increase the friction between the surface of the droplets and the feeding plate and the inner wall of the granulation tower, so that the surface of the droplets is subjected to greater extrusion force during the rolling process, and gradually compacts and forms a regular shape through friction with the feeding plate.

[0015] Compared to the spray drying granulation method where the pellets fall directly, the pellets of this invention can be formed by spiraling downwards along the feeding plate under the action of air swirl during the hot air drying process. The formed powder particles are more compact, stronger, more regular in shape, have better surface smoothness, and the particle shape is closer to that of a sphere, which is more conducive to the production of silicon nitride microspheres with small diameters, especially micrometer-sized ones. Attached Figure Description

[0016] Appendix Figure 1 This is a schematic diagram of the structure of the present invention.

[0017] Appendix Figure 2 This is a schematic diagram of the longitudinal section structure of the present invention.

[0018] Appendix Figure 3 This is a schematic diagram of the structure of the present invention after removing the top cover and spray mechanism.

[0019] Appendix Figure 4 This is a perspective structural diagram of the present invention.

[0020] In the diagram, 1-granulation tower; 11-air inlet; 12-collecting hopper; 2-spraying mechanism; 3-feeding plate; 4-mixer; 41-paddle; 5-air supply pipe; 6-rotating mechanism. Detailed Implementation

[0021] As attached Figure 1-4 As shown, the present invention includes a granulation tower 1 and a spraying mechanism 2, which is used to spray atomized slurry into the granulation tower 1. The present invention also includes a feeding plate 3 and a stirrer 4. The feeding plate 3 is disposed on the inner wall of the granulation tower 1 and is spirally arranged around the axis of the granulation tower 1, with the feeding plate 3 located below the spraying mechanism 2. The stirrer 4 is inserted into the spirally arranged feeding plate 3 along the axis of the granulation tower 1. The rotation direction of the stirrer 4 is the same as the spiral direction of the feeding plate 3 from its upper end to its lower end; that is, when the feeding plate 3 spirals downwards counterclockwise, the stirrer 4 rotates counterclockwise, and when the feeding plate 3 spirals downwards clockwise, the stirrer 4 rotates clockwise.

[0022] In use, the slurry is atomized and sprayed into the granulation tower 1 by the spraying mechanism 2. In the granulation tower 1, the moisture in the atomized droplets gradually evaporates under the action of hot air. Under the continuous stirring action of the agitator 4, an air vortex is generated in the granulation tower 1. The droplets move towards the inner wall of the granulation tower 1 under the action of this air vortex and fall onto the feeding plate 3, and roll downwards along the spiral direction of the feeding plate 3 to form a shape. In this invention, the air vortex generated by the rotation of the agitator 4 ensures that the droplets can fall onto the feeding plate 3 and roll along the spiral direction of the feeding plate 3. On the other hand, the force generated by the air vortex increases the friction between the droplet surface and the feeding plate 3 and the inner wall of the granulation tower 1, so that the surface of the droplet is subjected to greater extrusion pressure during the rolling process, and gradually compacts and forms a regular shape through friction with the feeding plate 3.

[0023] Compared to spray drying granulation where the pellets fall directly, the pellets of this invention are formed by spiraling downwards along the feeding plate 3 under the action of air swirl during the hot air drying process. The formed powder particles are more compact, stronger, more regular in shape, have better surface smoothness, and are closer to spherical in shape, which is more conducive to the production of small diameter, especially micron-sized silicon nitride microspheres. The spiral feeding plate 3 can increase the rolling path of the pellets in the limited space of the granulation tower 1 without hindering the circumferential flow of air inside the granulation tower 1.

[0024] In this invention, the feeding plate 3 is spirally arranged around the axis of the granulation tower 1 at least one turn. The number of spiral turns of the feeding plate 3 around the axis of the granulation tower 1 can be non-integer, such as one and a half turns, or integer, such as two turns. This ensures that, when projected along the axial direction of the granulation tower 1, the feeding plates 3 have overlapping or just overlapping portions. Viewed from a top or bottom angle of the granulation tower 1, the feeding plates 3 form a ring shape. This allows the droplets, when sprayed from the spray mechanism 2, to fall onto the feeding plates 3 under the action of air swirl, ensuring that the droplets roll and form along the feeding plates 3.

[0025] The width of the feeding plate 3 along the radial direction of the granulation tower 1 is greater than or equal to one-third of the inner radius of the granulation tower 1 and less than or equal to two-thirds of the inner radius of the granulation tower 1. This ensures that the middle of the spiral feeding plate 3 has space for the agitator 4 to rotate, while the feeding plate 3 itself has the width for the feeding beads to roll.

[0026] The present invention also includes an air supply pipe 5 for introducing hot air into the granulation tower 1. One end of the air supply pipe 5 is connected to the air inlet 11 of the granulation tower 1, and the end of the air supply pipe 5 connected to the air inlet 11 is tangential to the inner wall of the granulation tower 1. The direction of the hot air entering the granulation tower 1 along the air supply pipe 5 is the same as the rotation direction of the agitator 4. The hot air can enter the granulation tower 1 tangentially through the air inlet 11. Combined with the rotation of the agitator 4, it is more conducive to the hot air rotating and generating a swirling flow inside the granulation tower 1. Preferably, the air inlet 11 is located above the end of the feeding plate 3 near the spraying mechanism 2. The spraying mechanism 2 is a rotary sprayer and is located in the middle of the upper end of the granulation tower 1, specifically installed on the top cover of the upper end of the granulation tower 1. The rotary sprayer can spray in a ring shape into the granulation tower 1, which is conducive to the material droplets falling on the feeding plate 3. In order to reduce the interference of hot air intake on the spray, it is preferable that the air inlet 11 is located below the rotary sprayer.

[0027] The agitator 4 is rotatably connected to the bottom of the granulation tower 1, and is positioned upwards from the bottom of the granulation tower 1. A rotating mechanism 6, specifically a motor, is located on the outer side of the bottom of the granulation tower 1. Since the spray mechanism 2 is located in the middle of the upper end of the granulation tower 1, the agitator 4 is rotatably connected to the bottom of the granulation tower 1, and the rotating mechanism 6 is located at the bottom of the spray mechanism 2 to avoid interference between the agitator 4 and the spray mechanism 2.

[0028] The bottom of the granulation tower 1 is integrally provided with a collection hopper 12. After being rolled and formed on the feeding plate 3, the silicon nitride microspheres fall into the collection hopper 12 for collection and use in subsequent processes. Preferably, the collection hopper 12 is arranged in a ring around the rotating mechanism 6, which not only meets the material collection requirements but also provides sufficient space for the installation of the rotating mechanism 6.

[0029] The stirrer 4 includes a rotating shaft and impellers 41 mounted on the rotating shaft. The impellers 41 are inclined along the spiral direction of the feed plate 3 on the rotating shaft to facilitate the generation of an air vortex that matches the spiral direction of the feed plate 3 during rotation. In this invention, one or more sets of impellers 41 can be arranged on the rotating shaft according to actual size and requirements. Preferably, all impellers 41 on the rotating shaft are located between the upper and lower ends of the feed plate 3 in the axial direction of the rotating shaft to ensure that the air vortex generated when the impellers 41 rotate can act on the feed plate 3 area.

Claims

1. A silicon nitride granulation apparatus, characterized in that, The granulation tower (1) and spray mechanism (2) are included, as well as a feeding plate (3) and a stirrer (4). The feeding plate (3) is arranged on the inner side wall of the granulation tower (1) and spirally arranged around the axis of the granulation tower (1). The feeding plate (3) is located below the spray mechanism (2). The stirrer (4) is inserted into the spirally arranged feeding plate (3) along the axis of the granulation tower (1). The rotation direction of the stirrer (4) is the same as the spiral direction from the upper end to the lower end of the feeding plate (3). The stirrer (4) includes a rotating shaft and a blade (41) arranged on the rotating shaft. The blade (41) is inclined on the rotating shaft along the spiral direction of the feeding plate (3). It also includes an air supply pipe (5) for introducing hot air into the granulation tower (1), one end of which is connected to the air inlet (11) of the granulation tower (1), the air inlet (11) being located above the end of the feeding plate (3) near the spray mechanism (2), and the end of the air supply pipe (5) connected to the air inlet (11) being tangent to the inner wall of the granulation tower (1).

2. The silicon nitride granulation apparatus as described in claim 1, characterized in that, The feeding plate (3) is spirally arranged around the axis of the granulation tower (1) at least once.

3. The silicon nitride granulation apparatus as described in claim 1 or 2, characterized in that, The width of the feeding plate (3) is greater than or equal to one-third of the internal radius of the granulation tower (1) and less than or equal to two-thirds of the internal radius of the granulation tower (1).

4. The silicon nitride granulation apparatus as described in claim 1, characterized in that, The spraying mechanism (2) is a rotary sprayer and is located at the upper middle part of the granulation tower (1). The air inlet (11) is located below the rotary sprayer.

5. The silicon nitride granulation apparatus as described in claim 4, characterized in that, The stirrer (4) is rotatably connected to the bottom of the granulation tower (1), and a rotating mechanism (6) is provided on the outer side of the bottom of the granulation tower (1). The rotating mechanism (6) drives the stirrer (4) to rotate.

6. The silicon nitride granulation apparatus as described in claim 5, characterized in that, The bottom of the granulation tower (1) is integrally provided with a material collection hopper (12), which is arranged in a ring around the rotating mechanism (6).

7. The silicon nitride granulation apparatus as described in claim 1, characterized in that, The blade (41) is located between the upper and lower ends of the feed plate (3) in the axial direction of the rotating shaft.

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