The advantages and disadvantages of spiral classifier in China

The advantages of the spiral classifier are: stable and reliable performance, easy-to-operate, can be connected with the ball mill without pump. The biggest spiral classifier specification made in China is φ3.0 m, can reach artesian connection with φ3.6m x4.0 m ball mill. The big volume of the spiral classifier has buffer action and plays the role of transporting material, while the return concentration can be as high as 65% to 80%, thus good for the grinding operation. The disadvantage of the spiral classifier are: heavy body, large footprint, big maintenance workload, and difficult to achieve automatic control; affected by the density and shape, the material cannot be precisely classified according to particle size, resulting in low classification efficiency, typically only 20% to 40%; overflow particle size depends mainly on the concentration adjustment, usually the most detailed up to -0 074 mm.

Spiral classifier is composed by chute, hollow shaft, helical blade, spiral lifting device, thrust bearings, gears, feed port, discharging port and overflow weir. Classification chute is tilted placed with inclination for 12o-18. 5o, the bottom of the chute is semi-circular. The slurry is fed from feeding port and completes classification at the bottom of the grading slots. Fine-grained materials drain away from discharging port trough overflow weir with flow. Coarse products subside at the classification band, and then transported to grit discharging port by the spiral. Spiral is installed in the hollow spindle, both ends of which are supported by bearings; the upper end of the shaft is with the gear, the lower end of the shaft is placed within the lifting mechanism, if necessary, adjust the height of the spiral in the grading tank. Giving slurry continuously, then the overflow and grit will be continuously and respectively discharged. Spiral classifier and grinding bodies make a closed circuit, the grit are sent into the mill for re-grinding through the chute, the grit back to the mill is called return sand. 

(1) High weir spiral classifier. Usually used in the first-section grinding compatible with mill. 

(2) Submerged spiral classifier. Usually used in the second-section grinding and form a unit with mill. 

(3) Low weir spiral classifier. Generally used for washing or dehydration, is rarely used at present. 

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