CN104607393B - Turbo air classifier inclined flow guiding device - Google Patents

Abstract

A kind of turbo air classifier inclined flow guiding device, belongs to powder preparation field.The present invention changes Flow Field Distribution by the mounted angle of change turbo air classifier wind blade.Specific implementation method is:Prismatic blade is circumferentially uniformly fixed on upper lower fixed frame, wind blade bottom center line is in 10 °~20 ° angles with position tangent to periphery；Using blade bottom center line as rotary shaft, blade is rotated to 2 °~5 ° angles counterclockwise, so that air-flow when flowing through wind blade by a downward power, change air-flow annulus flow trace, the upward axial velocity of air-flow is reduced, particles collision and reunion probability is reduced, reaches raising effectiveness of classification, the purpose for reducing Cut size makes that more fine powder can be obtained and have stronger classifying capability in turbo air classifier rotating cage rotating speed range ability.

Description

Vortex air classifier inclined flow guide device

technical field

The invention relates to a flow guiding device used for dry material sorting by a vortex air classifier, which belongs to the field of powder preparation.

Background technique

In the design and development process of dry pneumatic classification, how to obtain fine particles with high precision and high efficiency is particularly important in today's increasingly tense global energy. Classifying the particles obtained after crushing raw materials to obtain fine powders with narrow particle size is one of the necessary steps in the preparation of functional materials.

The use of vortex air classifiers for material classification to obtain fine particles that meet the size requirements is the main means of dry powder preparation at present. The annular area between the inner edge of the air guide vane and the outer edge of the rotating cage is the main separation area for coarse and fine particles in the classification process. The air flow enters the volute of the classifier tangentially from two parallel and symmetrical air inlets, and enters the annular area through the guide device along the spiral volute, flows through the tumbler cage, and flows out from the upper air outlet in the center of the tumbler cage. Theoretically, the airflow is distributed in a planar vortex in the annular area, but due to the suction effect of the centrifugal fan, the airflow generates an upward axial velocity. On the one hand, its existence will cause the change of the velocity direction and affect the stability of the flow field; On the other hand, due to the upward axial velocity, the particles will be difficult to settle, so that the material curtain in the annular area is extremely narrow, the particle concentration increases, and the probability of particle collision and agglomeration increases, which is not conducive to the dispersion and classification of materials, and the classification accuracy is reduced. . Therefore, upward axial velocity is detrimental to classification.

In order to reduce the upward axial velocity of the airflow in the classification area, to obtain a stable flow field while appropriately increasing the sedimentation velocity of the particles, and to improve the classification performance of the vortex air classifier, the most effective method is to optimize the structure of the vortex air classifier. The air guide vane on the air guide device has an extremely important guiding effect on the airflow entering the classification annular area, and its structural characteristics directly affect the distribution of the flow field in the annular area. Therefore, the shape and installation angle of the air guide vane determine the classification of the vortex air classifier. One of the important factors of performance.

Contents of the invention

The present invention proposes an axially inclined flow guide device for a vortex air classifier, which reduces the upward axial velocity of the airflow in the annular classification area by changing the installation angle of the wind guide vanes on the flow guide device, so as to improve the stability of the flow field. Improve grading accuracy.

A flow guiding device for a vortex air classifier, characterized in that: the shape of the air guiding vanes (4) is straight, and the blades are evenly distributed in the circumferential direction during installation, and are fixed on the upper fixing frame (7) and the lower fixing frame (8) ); the centerline (11) of the bottom surface of the wind guide vane and the tangent line (10) of the circumference (9) where the centerline (11) of the bottom surface of the wind guide vane ( 11) is the axis of rotation, and the blade is rotated counterclockwise from the vertical initial position by 2° to 5°, so that the air flow is subjected to a downward force when flowing through the wind guide blade (4).

As shown in Fig. 2, the guide vane (4) adopts the installation method shown in Fig. 3 when installing. First, evenly distribute the blades in the circumferential direction, and fix them between the upper fixing frame (7) and the lower fixing frame (8) of the flow guide device, and make the centerline (11) of the bottom surface of the blade and the tangent line (10) of the circumference (9) of the blade form a 10°～20°(α) included angle, see Figure 3(a); then take the centerline (11) of the bottom surface of the blade as the rotation axis, and rotate the blade counterclockwise by 2°～5°(θ), see Figure 3 (b), that is, the model of the axially inclined deflector is obtained.

The suction effect of the centrifugal fan produces an upward lift force F _L on the airflow. After the wind guide vane is axially inclined, it exerts a force F _P perpendicular to the direction of the blade on the airflow (as shown in Figure 4). At this time, the axial direction of the airflow is affected by The total force F can be expressed by formula (1)

F＝F _L –F _P sinθ (1)

Among them, θ is the axial inclination angle of the wind guide vane.

When F is a positive value, it means that there is an upward axial acceleration in the classification area; on the contrary, when F is a negative value, there is a downward axial acceleration. Only when F is equal to or close to 0, the airflow can move smoothly in two dimensions. Therefore, the key to solving this problem is to determine the value of θ. According to the simulation results, the optimal inclination angle range is 2°～5°, which has been verified by material experiments.

The invention is suitable for dry classification of various powders.

Description of drawings

Figure 1 is a schematic diagram of the structure model of the vortex air classifier

In the figure: 1-air inlet; 2-volute; 3-air outlet; 4-wind guide vane; 5-annular zone; 6-cage

Fig. 2 is the schematic diagram of the guide device in the present invention

In the figure: 4-wind guide vane; 7-upper fixed frame; 8-lower fixed frame

Fig. 3 is a schematic diagram of the installation angle of the wind guide vane in the present invention

Among the figure: 9-the position circumference of the wind guide vane; 10-9 at the center point (O point) of the bottom surface of the wind guide vane; 11-the center line of the bottom surface of the wind guide vane; the angle between α-10 and 11; Axial inclination angle of wind blade

Fig. 4 is a schematic diagram of force analysis when gas flows through the diversion device in the present invention

In the figure: 4-wind guide vane; 7-upper fixed frame; 8-lower fixed frame

Detailed ways

The invention changes the flow track of the air flow in the annular area by installing the air guide blades between the upper and lower fixing frames of the flow guide device with an axial inclination at a reasonable angle, which can effectively reduce the upward axial velocity of the air flow inside the vortex air classifier and improve the flow rate. Field stability, improve the space utilization rate of the grading area, reduce the probability of particle collision, improve the grading accuracy, and reduce the grading particle size. When installing the air guide vanes, the axial inclination angle of the vanes should not be too large, otherwise a large downward axial velocity will be generated, which will accelerate the sedimentation of the particles, which is not conducive to the complete separation of the particles in the classification area. The blade axial inclination angle θ is 2°～5°.

In the present invention, other classification conditions remain unchanged, the α angle is fixed at 15°, and the axial installation inclination angle of the wind guide vane in the vortex air classifier is changed to conduct a comparative test. The blade axial inclination angle θ is 2°～5°, the maximum classification particle size can be reduced by 19.77%, and the maximum classification accuracy can be increased by 17.39%. Increasing the rotating speed of the rotating cage is a common method to reduce the particle size of the classification to obtain fine particles. Since the adjustable range of the rotating speed of the rotating cage of the vortex air classifier is certain, the ability to reduce the classification particle size by increasing the rotating speed of the rotating cage is also limited. The invention can make the classifier obtain finer powder within the range of rotating speed of the rotating cage, has stronger classifying ability, and can reduce energy consumption at the same time. In addition, due to the optimization of the flow guide device, the stability of the flow field is improved, the classification accuracy is improved, and a relatively ideal classification effect is achieved.

An embodiment of the present invention: the material to be classified is calcium carbonate, and its particle size consists of:

The particle size distribution of table 1 calcium carbonate raw material

The material classification experiment is carried out with a vortex air classifier with an inclined deflector, where the α angle is 15° and theta is 2.5°. Compared with the deflector with vertical blades with a θ of 0°, the particle size below 20 μm The percentage of fine particles increased by 8.2%, indicating that the reduced upward axial velocity is beneficial to reduce particle agglomeration to obtain fine particles.

Claims (1)

1. a kind of guiding device of turbo air classifier, it is characterised in that：The shape of wind blade (4) uses straight piece type, peace Blade is circumferentially uniformly distributed when dress, is fixed between upper holder (7) and lower fixed frame (8)；Wind blade bottom center line (11) it is in 10 °~20 ° angles with the tangent line of wind blade bottom center line (11) position circumference (9) (10), then with leaf Piece bottom center line (11) is rotary shaft, blade is rotated 2 °~5 ° angles counterclockwise from vertical initial position so that air-flow exists By a downward power when flowing through wind blade (4).