Investigating Slime Coating in Coal Flotation Using the Rheological Properties at Low CaCl2 Concentrations

Slime coating is known to have one of the detrimental effects of clay in coal flotation. In this study, the viscosity measurements of coal-clay-mixture suspensions and corresponding batch flotations were performed with increasing CaCl2 concentrations (ranged in 1-20 mM). It was found that at 4-6 mM concentration a significant transfer from Newtonian to non-Newtonian behavior occurred; meanwhile, the clay recovery increased dramatically. In this process, clay recovery through true flotation with entrainment excluded gradually increased. Cryo-SEM analysis, furthermore, confirmed that more coating clay appeared in higher CaCl2 concentrations. Thus, the rheology measurement could be used as a method for determining whether the slime coating occurred in flotation pulp with low salinity.