Abstract
Flotation is one of the most efficient techniques applied for phosphate upgrading. Desliming of flotation feed is a critical pre-request step for successful phosphate/gangue separation by flotation. Generally, the target of the desliming step is to minimize the feed fines to avoid their negative effects during flotation. However, such slimes normally contain phosphates which are considered as losses. An effective desliming should pay attention to minimizing the losses of phosphate bearing minerals in the removed slimes and, as a second target, to keep high phosphate recovery in the flotation feed. In this paper optimization of the desliming stage to achieve both targets at-a-time was studied using different techniques at different operating conditions. The applied slimes removal techniques included screening and hydrocycloning. It was found that desliming using hydrocyclone, at its optimum operating conditions, is better than desliming using screens. This is because the deslimed product contained small amount of phosphate slimes leading to efficient separation by flotation with an overall selectivity index B=0.739 defined by formula epsilon(1,c) = (100-epsilon(2,t))((1-B))/100((-B)) where epsilon(1,c) = P2O5 recovery in flotation concentrate, %; epsilon(2,t) = MgO recovery in both slimes and flotation tail, %.