Experimental characterization of a laboratory centrifugal separator

A 7.5 cm (3'') Knelson centrifugal separator was used to recover free gold from a high grade stock sample. Feed rate, density, size distribution and fluidizing water pressure were systematically tested. Operated at the suggested water pressure (33 kPa), gold recovery at low to intermediate feed rate (0.3-0.6 kg/min) was 89 or 95% of what was found recoverable by amalgamation. Gangue density was the most significant input variable, as gold recovery dropped to 66% at high flow rate (2.1 kg/min) with a gangue of 4.0 g/cm(3), compared to 87-88% at the original density, 3.2 g/cm(3), and low flow rate (0.4 kg/min). Recovery decreased slightly with decreasing fluidizing water pressure, and increased slightly as gangue size increased, at the low gangue density. Recoveries were high for most size classes, with slight decreases for the -37 and 105-300 mu m classes. These are attributed to fines recovery and particle shape problems, respectively. The implications of the study are discussed both for plant and lab operation.