Evaluation of the Optimum Mesh of Grind for Nchanga Underground Copper and Open-Pit Cobalt ores in the laboratory

Abstract

The Nchanga concentrator of the Konkola Copper Mine Plc treats ore from both the underground and open pit mines. Differential flotation is employed in the treatment of the underground copper ore while bulk flotation is done on the open-pit cobalt ore. However, the underground copper circuit was characterised by low metal recoveries whilst the open pit circuit had problems with maintaining stable optimum metal recoveries. In an effort to improve recoveries on both circuits, testworks were conducted on feed material to the Nchanga concentrator. The feed material included underground copper and open pit cobalt ores. In this work, sampling using an appropriate sampling technique was done from the belt conveyors feeding ten 2.44m dia x 2.74 Head Wrightson overflow copper discharge ball mills and from the belt conveyors feeding one 2.74m dia. x 3.70m Head wrightson overflow cobalt rod mill. For both ores, parameters considered for the evaluation included the variation of grindability at various time intervals of 2 minutes for 20 minutes and the effect of grindability quality on flotation recoveries. Results from the testworks conducted have shown that the optimum mesh of grind for the underground copper ore is 55.59% passing 75µm (16.37% + 150µm) yielding metal recoveries of 85.12% TCu and 97.09% AICu. The optimum mesh of grind for the open-pit ore is 53.37% passing 75µm (13.41% + 150µm) yielding metal recoveries of 90.41% TCo and 93.64% AICo. This paper discusses laboratory testworks and the results that were obtained.
Key words Differential flotation, bulk flotation, recovery, grade.

(Af. J. of Science and Technology: 2002 3(1): 85-92)