Gravitational classifiers

In mineral processing plant , Two basic types of gravitational classifiers employed today are the spiral classifiers and the rake classifier. They both introduce the feed submerged into a pool area and subject the solids to an upflow current. The overflow is obtained from a peripheral weir that provides the vertical velocity. A solid whose terminal settling velocity is high enough will settle against this current and report to the base of the pool. At this point, a rake or screw conveys the solids out of the pool and up the beach to drain the “sands” product before discharging it over the end of the slope. Figure 1 is a schematic of a spiral classifier. The rake classifier has a series of rakes (actually blades) that operate in a reciprocating fashion to move the sands up the beach.

A third type is termed a “hydroseparator.” The feed again enters submerged through a circular centralized feedwell, and the peripheral overflow weir causes an upward velocity. The underflow is raked toward the central outlet and is pumped out. The unit looks much like a conventional gravitational thickener or clarifier except that the unit is shallower and the bottom slope is usually steeper. The speed of a rake mechanism is normally two or more times that of a thickener, because of the more granular nature of the solids and the higher solids rate per unit area.

The main advantage of the rake and spiral classifiers is their higher percent solids of the sands product, because the product is drained. The hydroseparator has the advantage of higher capacity from a single unit as it uses a much larger pool area. The hydrocyclone is a widely used classifier that employs centrifugal force.
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sinonine technology team