3.4.4 Dewatering
The third stage in concentrating copper consists of dewatering, that is, separating the ore dust from the water. It is a two-step process.
The first step is called "thickening." It is done in a large round tank that looks like a swimming pool.
The copper ore froth is poured into the tank and dispersed by a current generated by a rake that rotates slowly at the bottom of the tank.
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The ore sinks slowly to the bottom of the tank and forms a thick sediment which is recovered and removed by a pipe.
The second step is filtration. It removes most of the water remaining in the ore. The sediment is pressed against a filter or the water drawn from the sediment through a filter.
Systems that draw the water from the sediment all work more or less the same way, that is, like a large vacuum cleaner with a sieve at the end of the suction pipe.
The holes in the sieve are so small that only the water can go through. The ore dust, which is too large, accumulates at the surface of the filter where it forms a slurry that is recovered later.
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