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Spiral Classifier || Operation and Technique (2nd)
Apr 02, 2018

4) Number of classifier blades

Reasonably determine the number of classifier blades. Increasing the number of blades helps to increase the area or the aspect ratio. It is easier to meet high operational requirements and improve the vitality of the equipment, but at the same time, it also tends to make all devices more complicated. Therefore, in addition to meet special requirements and restrictions of the pulp, a smaller number of blades should be used. In summary, most classifiers use single spiral blades.


With the same flow rate, as the number of blades increases, the inter-blade area decreases, its radial speed increases, and the tangential speed of the surface decreases. This is due to the side wall effect of the blades, which will help the particles are only subjected to inward air drag and centrifugal forces, reducing the collision of the particles with the blades and facilitating the classifying of the particles. Therefore, the increasing of blades quantity helps to improve the classifier performance. In practice, due to the influence of the blade thickness, and the limit of mechanical processing, the blades should not be too many.


5) The pitch of the classifier

The pitch is generally 0.5-0.6 times the diameter of the screw. Generally, it uses equal pitch but can also use unequal pitch, such as the short pitch of the overflow end, the long pitch of the return sand end, which will not only increase the amount of returning sand back, but also ensure smooth agitation at the end of the overflow to facilitate the improvement of overflow quality and throughput.


6) Width of classifier tank

The width of the spiral classifier tank is greatly related to the discharge speed of the overflow product. The wider tank, faster speed of overflow discharge and the possibility of the coarse particles discharged with the overflow become greater. On the other hand, the wider tank, the greater the settlement area of the ore and the easier to settle. Therefore, the width of the groove on the classification effect is not significant, but it is closely related to the processing capability of the classifier. The width is larger and the processing capacity is also greater. On the contrary, the processing capacity is small. Therefore, the width of the classifier tank body should be compatible with the processing capacity of ball mill. When purchasing, the attention should be paid to the width of the classifier and the processing capacity of ball mill so as to choose the right classifier and ball mill.

The width of the classifier tank depends on the screw diameter of the return sand (i.e., the specification of classifier) and is 100--200 mm larger than the screw diameter.


7) Spiral diameter of classifier

The diameter of the spiral represents the specifications of the spiral classifier, which restricts the width of the tank body, thereby affecting the size of the tank classifying area, affecting the overflow production capacity and the ability to return sand back. Therefore, the spiral diameter of the classifier must be calculated to match the capacity of the ball mill and meet the requirements for classifying particle size at the same time. Selecting the diameter of the appropriate screw makes the classification performed in the best production state.


8) Guide vane tilt angle

Under the same conditions, with the increase of the guide vane tilt angle, the classification accuracy index shows a decreasing trend. It has been proved that the classifying efficiency of the guide vane should be highest between 85° and 90°.

Under the same conditions, with the increase of the guide vane angle, the classification accuracy index has decreased, the average particle size has increased, and the output has also increased. The optimal inclination angle of the guide vane is between 85° and 90°.


9) Blade wear

The wear of the classifier blades is a normal production phenomenon. After the blades are worn out, the grinding fineness become coarse in relative to the decreasing of returning sand amount. In addition, if the blade wears badly, it will affect the life of the classifier, so check the blade wear timely during work and replace the worn blades.