Boivin, A., Dufour, R., Peloquin, G. and St-Laurent, M.

The objective of most thickeners is to produce mud at the highest possible solids fraction in order to improve the separation efficiency. Extracting this dense mud from a thickener can be challenging and operation at high underflow rate is often causing channelling where liquor is short circuiting to the underflow. A new paste removal system that allows extraction of very thick mud at high flow rates was designed and tested in our laboratory. It consists of a device that mechanically extracts the mud out of the thickener and brings it to the underflow pump. Consistent operation with red mud at up to 54% solids was obtained in our laboratory. These results led to the development of a 3-m diameter flat-bottom pilot thickener fitted with the new paste removal system. The system is described and typical results are presented.