Optimized separation

Selected examples of the influence of cyclone underflow density to a closed circuit grinding system

Summary: To achieve an optimum performance out of a closed circuit grinding system, the correct density regime of the hydrocyclones is of utmost importance and has to be adjusted to each systems´ requirement. One of the most important relationships for the optimization of the hydrocyclone recovery is the knowledge that the viscosity of the slurry increases with decreasing circulating load. In other words the cut point of the cyclone gets coarser with lower circulating loads. To achieve a better quality (or steeper recovery) the underflow density can be optimized enabling the operator to achieve the lowest possible amount of misplaced particles and thus best product quality. This optimization is the basis for the success and quality of all downstream processes and the economical success of operations.

1. Minimizing ultrafines in the hydrocyclone underflow

The guideline to operate hydrocyclones at their lowest possible overflow density and their highest possible underflow density in closed circuit grinding is of common knowledge. The underlying principle is minimizing ultrafines recycled back to the mill.


To describe the recovery curve of a hydrocyclone, two separate curves have to be evaluated. There is a recovery curve for the solids and one for the liquid. The two main figures to evaluate a recovery curve are the D50 and the shape of the curve. This paper will not describe the calculation...

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