CFD simulation of the influence of viscosity on the performance of a two-stage centrifugal separator

Two-stage centrifugal separators are the most novel generation of gravity separators that are increasingly used in the beneficiation of coal and minerals. The flow pattern and behavior in these separators is very complex. In this research, computational fluid dynamics (CFD) and discrete phase model (DPM) were used to investigate the influence of medium viscosity on the flow field and on the performance of a two-stage centrifugal separator. Volume of fluid (VOF) and Reynolds stress model (RSM) were used to tack the liquid-liquid interface and turbulence modeling, respectively. With increase in the medium viscosity, the performance of the separator was decreased as a consequence of decreasing the tangential velocity, and the air volume fractions inside the separator. Moreover, a high viscosity increases the drag force and consequently the medium recovery into the float stream. Such an effect consequently increased the separation density of the separator. When the medium viscosity was changed from 1×10-3 to 3.09×10-3 Pa.s, the medium recovery of the first and the second stages of the separator were increased about 56% and 23.7 %, respectively. Ecart probable (Ep) values for the first and second stages were also increased 98% and 131%, and the air volume fractions were decreased about 38.73% and 29.35%, respectively.