DEFINING OVERLOAD CONDITIONS FOR 7.6-CM KNELSON CONCENTRATOR BY USE OF SYNTHETIC FEEDS

Synthetic feeds of fine and coarse (80% passing 100 and 600 mu m) sili ca and magnetite (to mimic gangue) with fine (8-75 mu m) tungsten (to mimic gold) were used to study the Knelson concentrator. The optimum f low rate of fluidization water was first determined for each gangue ty pe; this varied from 1.7 l/min for fine silica to 5.6 l/min for coarse magnetite. Overloading of the Knelson concentrator was then investiga ted at the optimum flow rate. With the fine silica gangue no overload occurred under any of the operating conditions studied. There was very little overload with the fine magnetite gangue, but the coarse silica gangue produced appreciable overload-though only after a significant bed of tungsten concentrate had been formed. With the fine magnetite g angue the onset of overloading occurred earlier than with coarse silic a. Finally, with coarse magnetite severe overloading occurred almost i mmediately. Overloading was modelled using a first-order kinetic rate constant for erosion of the concentrate bed and a critical mass of con centrate above which it takes place. The results clearly demonstrate t he importance of removing oversize to maximize recovery by the Knelson concentrator, particularly with a high-density gangue.