Optimisation of the grinding circuit at Arafertil, Brazil

Arafertil's regrinding circuit is responsible for the recovery of apatite w ith a low degree of liberation, representing approximately 11% of the overa ll apatite concentrate production. Low grinding capacity prevented an ideal size distribution of product for maximum recovery in the subsequent flotat ian stage, as shown in a liberation study. This work was aimed at attaining the required increase in regrinding capaci ty, using process simulation by computer mathematical modelling, with the o bjective of implementing an optimised grinding and classification circuit. The ball mill and hydrocyclones models were calibrated, and their equations were defined, from industrial data acquired in the old concentrator config uration and results from laboratory grinding tests with power consumption m easurements. The model was validated by means of comparison between the results predicte d by simulation and those achieved in the plant after refurbishment. The ap atite flotation recovery increased from 31.5% to 48.0%, in agreement with t he previous apatite liberation study. (C) 1999 Elsevier Science Ltd. All ri ghts reserved.