How to improve the classification accuracy and classification efficiency of the vortex classifier?

First, the structure and working principle of the vortex classifier

1 structure of vortex classifier

The vortex classifier is mainly composed of a guide vane, a rotor, a rotating shaft, a feeding port, a spreading disc, an air inlet, a fine powder outlet and a coarse powder outlet, and its structure is shown in Fig. 1.

2 eddy current classifier works

The material enters the volute from the top feeding port 5, is scattered to the spreading plate 6, and is sprinkled around under the rotation of the spreading plate 6. Under the action of gravity, the material falls to form a toroidal cylinder, and the airflow enters through two symmetrical air inlets 7, and the annular zone formed by the wind guide vanes 1 entering the cage and the guide vanes 1 is orthogonal to the material. Under the action of the suction and the rotation of the fan, the powder particles are subjected to the centrifugal force generated by the tangential velocity of the airflow and the drag force generated by the radial velocity, and the grading is generated under the balance of the two forces, and the centrifugal force of the fine particles is less than The drag force is then entered into the interior of the rotor 2 and is collected as it is discharged from the fine powder outlet 3 of the classifier. The coarse particles are subjected to centrifugal force greater than the drag force, colliding with the wall of the cylinder and falling into the bottom coarse powder outlet 8 to be discharged.

Second, optimize the structural parameters of the classifier

(1) Try to select the rotor of the grid blade type. The number of grids of the vane rotor is larger than that of the cylindrical mesh rotor. The material collision probability is large, the powder dispersion is good, and the vane rotor can be continuously graded.

(2) The shape of the blade is preferably Z-shaped or streamlined, which is more conducive to increasing the speed of the classification zone and reducing the velocity gradient.

(3) It is possible to add narrow blades between the rotor blades to form staggered blades to make the flow field distribution more stable, and when the length ratio of the long and short blades is 0.77, the tangential and radial velocity distribution of the outer edge of the cage is uniform, between the blades. The inertia and anti-whirlpool are weakened.

(4) The number of blades can be increased. The radial velocity between the blades is increased, and the tangential velocity is reduced. The particles are only subjected to centrifugal force and drag force, and the collision between the particles and the rotor blades is reduced, but not excessively increased.

(5) Select L-shaped guide vanes to reduce small particle agglomeration and reduce back mixing.

(6) Select the spiral rib spreading disc to extend the popular flow path and make the spreading more uniform.

Third, optimize the operating parameters of the classifier

1 reasonable control of feeding speed

With the increase of feed rate, the concentration of powder particles in the classification chamber will increase, resulting in the material being difficult to disperse, the collision between particles, the agglomeration phenomenon will increase, the probability of fine powder mixing into the coarse powder will increase, thus affecting the classification accuracy of the classifier. And grading efficiency. However, too low a feed rate will affect the grading yield, so the feed rate needs to be controlled reasonably according to the production situation.

2 reasonable control of rotor speed

On the one hand, the rotor speed affects the flow field stability around the rotor, and on the other hand affects the flow field stability between the rotor blades. At low speed, the influence of rotor speed on the tangential velocity of the annular zone is not obvious. As the rotor speed increases, the strength of the centrifugal force field around the rotor increases. At this time, the coarse particles are thrown toward the cylinder wall under the action of large centrifugal force, thus achieving effective The classification is carried out to further reduce the classification particle size. When the air volume is constant, the rotor speed is too high, which will cause large turbulence in the flow field around the rotor blade, which will affect the stability of the tangential velocity of the ring zone.

3 processing air volume and rotor speed to match

The amount of air volume determines the ability of the airflow to carry material, and the proper air volume allows the powder to be effectively dispersed. At the same time, the increase of the air volume can cause the airflow to generate sufficient drag force in the classification area, thereby facilitating the rapid discharge of the fine powder. In addition, the air volume should match the rotation speed of the rotor. If the air volume is too large or too small, it may cause positive and negative swirling between the rotor blades. In actual production, in order to obtain an effective classification, classification is usually carried out in the case where the air volume and the rotation speed are high.

In the production process, it is necessary to adjust the working parameters of the grading system reasonably to match each other so that the system maintains a stable working state.

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