Performance prediction of floatex density separator in processing iron ore fines – a relative velocity approach

Effective use of a Floatex density separator (FDS), a continuous teetered bed separator, in beneficiating iron ore fines in terms of alumina and silica removal has been investigated. Particle behaviour in an FDS is described using steady state force balance on the particle. A relative velocity approach coupled with the mass balance has been adopted for theoretical performance predictions of multispecies particulate systems having density and size variations. Prediction of suspension density has been identified as most crucial due to the strong dependence of FDS performance on it. It was established that a threshold bed pressure exists below which the unit acts merely as a size classifier. Above this threshold pressure the bed develops significantly, formation of a proper fluidised suspension takes place and concentration effect dominates. Higher teeter water rates enhance hydraulic transport but reduce the yield to the underflow. Predicted separation performance has been validated for fines from one Indian iron ore. The effect of superficial teeter water velocity and bed pressure on process performance has been studied from a theoretical as well as an experimental stand point. Apart from the process variables, liberation characteristics of the ore have significant effect on the performance of the unit. It is established that the FDS has great potential to remove substantial alumina and silica even in single stage operation. This is very significant in an Indian context where high alumina in iron ore fines poses a major problem in downstream operations.