Effect of operating variables upon liquid backmixing in a laboratory flotation bank

Abstract

Previous work has indicated the presence of backmixing in flotation banks, but the influence of operating variables upon the degree of backmixing has not been investigated. In this paper the operating variables considered are the bank flowrate, cell volume, aeration rate and frother concentration. A tracer technique in a small “open flow”, 4-cell flotation bank was used. The experimental results show that backmixing is a function of cell agitation, and the influence of operating variables is analyzed by considering their effect upon cell agitation. For unaerated cells backmixing flowrates: (1) decreased exponentially with increasing bank flowrate; (2) increased initially but then decreased with decreasing cell liquid volume; and (3) at higher cell volumes, were greater between cells in the middle of the bank than between cells at the end of the bank. For aerated cells backmixing flowrates: (1) changed only gradually with aeration rate, with responses differing between cells; and (2) were substantially reduced by addition of frother. By allowing for the cell volume change accompanying aeration, aeration is shown to reduce agitation and backmixing flowrates. Addition of frother amplifies these effects.