Vortex air classifier double-layer rotating cage suitable for superfine powder separation

Abstract

The utility model discloses a vortex air classifier double-layer rotating cage suitable for superfine powder separation, and belongs to the technical field of powder preparation. A double-layer rotating cage structure is designed on the basis of centrifugal separation and sedimentation velocity difference of coarse and fine particles. The specific implementation method is as follows: the outer layer of the rotating cage consists of rotating cage blades which are uniformly distributed in the circumferential direction and is vertically fixed between an upper wheel carrier and a lower wheel carrier, and coarse and fine particles are subjected to centrifugal separation at the rotating cage blades to finish primary grading; the rotating cage inner layer is composed of a drainage cone and a triangular connecting support, the triangular connecting support and the lower wheel carrier are connected and fixed through threads, and the outer edges of the three arc-shaped faces of the drainage cone are attached to the inner edge of the upper wheel carrier. The taper angle of the drainage cone ranges from 5 degrees to 15 degrees, and the axial length of the drainage cone ranges from 1 / 8 to 1 time of the axial length of the rotating cage blade. And coarse and fine particles at the tail end of the drainage cone are separated for the second time due to settling velocity difference. The longer the drainage cone is, the smaller the particle size of the obtained fine powder product is and the narrower the particle size distribution is.

Description

A double-layer rotary drum vortex air classifier suitable for ultrafine powder sorting Technical Field

[0001] This utility model relates to a double-layer rotating cage for ultrafine powder sorting in an eddy air classifier, belonging to the field of powder preparation technology. Background Technology

[0002] Ultrafine powders, due to their unique physical and chemical properties, are widely used in pharmaceuticals, 3D printing, and fine chemicals. Since the particle size and distribution of ultrafine powders directly affect product performance and quality, achieving finer powders with narrower particle sizes has become a necessity for industry development. Vortex air classifiers are commonly used pneumatic classification equipment for the mechanical preparation of ultrafine powders. They offer advantages such as high classification efficiency, adjustable particle size, and large output. They classify materials by utilizing the different forces experienced by coarse and fine particles in an airflow field, obtaining fine particles that meet particle size requirements. A common method for obtaining small-sized fine powder products using vortex air classifiers is to increase the rotor speed. As the rotor speed increases, the centrifugal force on the particles in the classification force field also increases. Larger particles are thrown towards the cylinder wall and have difficulty entering the interior, thus collecting finer particles and reducing the classified particle size. However, increasing the rotor speed increases equipment energy consumption and load. Furthermore, since the maximum rotational speed of the rotating drum is limited by factors such as motor power, torque, cooling performance, control precision, material strength, and mechanical balance, it is a practical method to improve the rotating drum structure to change the movement trajectory of coarse and fine particles, reduce the classification particle size, and obtain powder with a narrow and fine particle size distribution. Summary of the Invention

[0003] This invention proposes a double-layer rotating drum for vortex air classifiers suitable for ultrafine powder separation. By utilizing the inner layer (guide cone) of the rotating drum to change the movement trajectory of fine powder passing through the outer layer (blade channel) of the rotating drum, ultrafine powder can be separated from fine powder, thereby reducing the classification particle size and obtaining ultrafine powder.

[0004] A double-layer rotating drum for vortex air classifiers suitable for ultrafine powder sorting is characterized in that: the outer layer of the rotating drum is composed of rotating drum blades (2), which are evenly distributed circumferentially and vertically fixed between the upper wheel frame (3) and the lower wheel frame (1) to form an airflow channel; the inner layer of the rotating drum is composed of a guide cone (4), which is connected and fixed to the triangular connecting bracket (5) by threads. The triangular connecting bracket is connected and fixed to the lower wheel frame by threads. The outer edge of the three arc-shaped surfaces of the guide cone fits against the inner edge of the upper wheel frame to ensure the sealing between the inner and outer layers of the rotating drum. The cone angle of the guide cone is in the range of 5 to 15°, and the axial length of the guide cone is between 1 / 8 and 1 times the axial length of the rotating drum blades. The fineness of the fine powder product can be adjusted by adjusting the length of the guide cone. As the guide cone grows longer, the particle size of the fine powder product becomes smaller and the distribution becomes narrower.

[0005] The working principle of the vortex air classifier is mainly based on the flow guiding structure to create a strong vortex field after the airflow enters the classifier. Simultaneously, the rotating drum, a moving component, rotates. Particle size classification is achieved through the dynamic balance between the centrifugal force on the particles and the drag force of the airflow. Fine particles flow with the airflow through the channels between the drum blades, enter the center of the drum, and are discharged from the fine powder outlet. Coarse particles are thrown against the cavity wall by centrifugal force and settle, collected by the conical collection bucket, and discharged from the coarse powder outlet. To analyze the working mechanism of the double-layer rotating drum, under a constant cone angle (12°), gas-phase and gas-solid two-phase numerical simulations were performed on double-layer rotating drums with different guide cone lengths. These simulations were compared with those of a rotating drum with only radial blades. The gas-phase simulation revealed that the airflow in the double-layer rotating drum is obstructed by the inner guide cone. The airflow enters the center of the drum after forming a certain angle at the bottom of the guide cone, and the angle between the streamline and the horizontal line gradually increases with the increase of the guide cone length. The increased angle hinders the radial movement of the airflow towards the center, thus more effectively preventing larger particles from entering the fine powder region. Only finer particles can enter the fine powder outlet with the airflow. Gas-solid two-phase numerical simulations show that coarse and fine powders first undergo centrifugal classification at the outer edge of the rotating drum. The drum blade channels act as a screen, allowing finer particles to pass through the channels between the blades under centrifugal separation, completing the first classification. Because the double-layer rotating drum adds a guide cone as the inner layer, the fine powder entering the drum after centrifugal classification undergoes secondary sorting. Ultrafine powder moves upward with the airflow to the center of the drum and is collected as fine powder, while coarser particles are blocked by the guide cone and settle under gravity, completing the second classification. The longer the guide cone, the finer the particle size of the fine powder product.

[0006] The beneficial effects of this utility model are as follows: the outer and inner layers of the double-layer rotating cage achieve two-stage separation of coarse and fine particles. The rotating cage blade channel, i.e., the outer layer of the rotating cage, performs centrifugal classification of coarse and fine particles, while the guide cone, i.e., the inner layer of the rotating cage, uses the principle of gravity sedimentation to achieve secondary separation of finer powders. The outer layer of the rotating cage completes the forced separation of coarse particles, while the inner layer of the rotating cage implements the precise capture of ultrafine particles. The secondary control of particle size distribution is achieved through flow field optimization. The motion trajectory of coarse and fine particles is shown in Figure 2.

[0007] This invention is suitable for dry classification of various powders. Attached Figure Description

[0008] Figure 1 shows the structure of the double-layer rotating cage;

[0009] Figure 2 is a schematic diagram of the particle trajectory in a double-layer rotating cage.

[0010] In the diagram: 1. Lower wheel frame; 2. Rotary drum blades; 3. Upper wheel frame; 4. Drain cone; 5. Triangular support. Detailed Implementation

[0011] This utility model patent proposes a double-layer rotating drum for vortex air classifier suitable for ultrafine powder sorting, as shown in Figure 1. The outer layer of the rotating drum consists of rotating drum blades (2), which are evenly distributed circumferentially and vertically fixed between the upper wheel frame (3) and the lower wheel frame (1) to form an airflow channel; the inner layer of the rotating drum consists of a guide cone (4), which is threadedly connected and fixed to a triangular connecting bracket (5). The triangular connecting bracket is threadedly connected and fixed to the lower wheel frame. The outer edge of the three arc-shaped surfaces of the guide cone fits against the inner edge of the upper wheel frame to ensure the sealing between the inner and outer layers of the rotating drum. The cone angle of the guide cone ranges from 5 to 15°, and the axial length of the guide cone ranges from 1 / 8 to 1 times the axial length of the rotating drum blades. The particle size of the desired ultrafine powder can be controlled by adjusting the length of the guide cone.

[0012] In this invention, with the operating parameters and other structural parameters remaining unchanged, a comparative classification experiment was conducted using a radial straight-blade rotary cage and a double-layer rotary cage designed in this invention. Experimental results show that, compared to the radial straight-blade rotary cage, the double-layer rotary cage designed in this invention reduces the classified particle size by up to 62.5% and improves the classification accuracy by up to 51.3%; the average particle size of the obtained fine powder product is reduced by 43.2%, and the particle size distribution index is reduced by 8%. This indicates that the double-layer rotary cage in this invention, by changing the particle motion characteristics, reduces the classified particle size and improves the classification accuracy, thus obtaining ultrafine powders with a narrow and fine particle size distribution.

[0013] The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made to this utility model without departing from the principle of this utility model, and these improvements and modifications also fall within the protection scope of the utility model claims.

[0014] The three embodiments of this utility model patent employ a double-layer rotating cage with three different axial lengths (1 / 2, 3 / 4, and 1 times the axial length of the rotating cage blades), and use calcium carbonate as the raw material for material classification. The particle size distribution is shown in Table 1.

[0015] Table 1. Differential particle size distribution of calcium carbonate raw material

[0016]

[0017] For simplicity, the commonly used radial straight-blade rotary cage is designated as Cage A, and the double-layer rotary cages with axial lengths of 1 / 2, 3 / 4, and 1 times the flow cone are designated as Cage B0.5, Cage B0.75, and Cage B1, respectively. Compared to Cage A, the three types of double-layer rotary cages reduce the particle size of the classified particles by 24.3%, 50.2%, and 62.5%, respectively, and improve the classification accuracy by 38.7%, 44.1%, and 51.3%, respectively. Under the conditions of an air velocity of 9 m / s, a rotary drum rotation speed of 1200 rpm, and a feeding speed of 12 kg / h, the average particle size of the fine powder product obtained by rotary drum A is 10.5 μm, while the average particle sizes of the fine powder products obtained by rotary drums B0.5, B0.75, and B1 are 9.1 μm, 7.3 μm, and 5.9 μm, respectively. The particle size distribution index of the fine powder product obtained by rotary drum A is 1.13, while the particle size distribution indices of the fine powder products obtained by rotary drums B0.5, B0.75, and B1 are 1.15, 1.17, and 1.23, respectively (Note: the larger the particle size distribution index, the narrower the particle distribution). This indicates that the double-layer rotary drum designed in this invention can reduce the particle size of the vortex air classifier and improve the classification accuracy, which is beneficial for obtaining high-quality fine powder with a narrow particle size distribution. Furthermore, the longer the guide cone, the finer the product and the narrower its distribution.

Claims

1. A double-layer rotary drum for an eddy air classifier suitable for ultrafine powder sorting, characterized in that: The outer layer of the rotating cage consists of rotating cage blades (2), which are evenly distributed circumferentially and vertically fixed between the upper wheel frame (3) and the lower wheel frame (1) to form an airflow channel; the inner layer of the rotating cage consists of a guide cone (4), which is connected and fixed to the triangular connecting bracket (5) by threads; the triangular connecting bracket is connected and fixed to the lower wheel frame by threads; the outer edge of the three arc-shaped surfaces of the guide cone fits against the inner edge of the upper wheel frame to ensure the sealing between the inner and outer layers of the rotating cage; the cone angle of the guide cone is in the range of 5 to 15°, and the axial length of the guide cone is between 1 / 8 and 1 times the axial length of the rotating cage blades; the fineness of the fine powder product can be adjusted by adjusting the length of the guide cone, and the particle size of the fine powder product becomes smaller and the distribution becomes narrower as the guide cone grows longer.

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