MIXING IN FLOTATION COLUMNS .3. INTERNAL CIRCULATION

A mixed zones-in-series model, allowing for backflow between adjacent zones, has been used to describe the flow structure established in the collection zone of a flotation column. Experimental residence time di stribution data were used to quantify the backflow parameter (lambda), using the tracer breakthrough time; this parameter was shown to depen d essentially only on the superficial liquid velocity and the column d iameter (d(C)) and the following correlation was obtained: lambda = 0. 347 exp(0.303d(C)) u(L)-(0.530+0.0348d(C)). The circulation velocity o f the additional circulatory flow induced by the gas stream was also d etermined; the experimental results were well corroborated by predicti ons using theoretical axial velocity models.