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The main components of the spiral classifier are a semicircular water tank, a spiral device composed of a shaft and blades, the upper and lower bearing parts of the spiral shaft, the transmission device of the spiral shaft, and the lifting mechanism. Its specifications are expressed by the spiral diameter.
Spiral classifiers can be divided into single spiral and double spiral classifiers according to the number of spiral shafts, and can be divided into high weir type, low weir type, and sinking type according to the height of the overflow weir.
The overflow weir of the high weir spiral classifier is higher than the bearing center at the lower end of the spiral shaft but lower than the upper edge of the overflow end spiral. It has a certain sedimentation area suitable for coarse particle classification and can obtain an overflow particle size greater than 100 mesh.
The overflow weir of the low weir spiral classifier is lower than the center of the overflow end bearing, so the sedimentation area is small and the overflow production capacity is low. It is usually not used for classification operations but is used to wash ore sand for desludging.
The entire spiral at the overflow end of the submerged spiral classifier is immersed below the liquid surface in the sedimentation zone. Its sedimentation zone has a large area and depth, which is suitable for fine particle classification and can obtain an overflow particle size of less than 100 mesh.
Working Principle
The finely ground slurry is fed into the water tank from the feed port located in the middle of the sedimentation zone. The lower end of the inclined water tank is the slurry classification sedimentation zone. The spiral rotates at a low speed to stir the slurry, so that the light and fine particles are suspended on the surface and flow to the overflow weir to overflow and enter the next process. The coarse and heavy particles settle to the bottom of the tank and are transported to the discharge port by the spiral as returned sand. Usually, the spiral classifier and the mill form a closed circuit to return the coarse sand to the mill for re-grinding.
The advantages of the spiral classifier are its simple structure, stable and reliable operation, easy operation, and ease of forming a closed circuit operation with a mill with a diameter of less than 3.2 meters.
