Siltation of Ore Particles in Leaching Tanks: Causative Factors and Mitigation Measures

Abstract

Siltation involves the accumulation of sediment over a considerable period of time and this may occur in closed systems like leaching tanks. Most mining companies in Ghana experience siltation problems during leaching of gold ore. This paper examines the potential causes and possible mitigation measures of siltation. Particle size analysis, slurry settling rate tests and agitation efficiency analysis were used in identifying causative factors of siltation whiles deflocculation test and grind analysis were conducted to ascertain mitigation measures.  Results from the study indicated that, high settling velocity of particles, inefficient milling and classification, poor slurry agitation and particle flocculation were the major causative factors leading to siltation. Size analysis results revealed P₆₇ of 106 µm instead of P₈₀ of 106 µm, a situation which affects particle suspension by agitators leading to siltation. This study therefore suggests that increase in milling residence time and particle deflocculation are potential remediation measures for curbing siltation. Extended grinding of ball mill feed resulted in 94% passing 106 µm while settling velocity was reduced by 71% after deflocculant addition at 1000 ppm.

Keywords: Siltation, Deflloculation, Settling Velocity, Grinding