Turbulent dispersion coefficients in cyclone flow: An empirical approach

Among the various theories available to predict cyclone collection efficien cy, the finite diffusivity theory of Mothes and Loffler (1988) has been sho wn to give the best fit of the observed grade-efficiency curves. However, l ack of knowledge on the dependence of the particles' turbulent dispersion c oefficient with cyclone geometry, operating conditions and particle size ha s so far hindered the application of this theory for predictive purposes an d for improved cyclone design. In this work, this theory is applied for pre dictive purposes, through the use of an empirical relation for the particle s turbulent dispersion coefficient. The proposed relation is based on an an alogy with turbulent dispersion in packed beds, and correlates the particle radial Peclet and Reynolds numbers. Laboratory-scale reverse-flow cyclones of previously unpublished geometries were built to test the applicability of the proposed relation. The Mothes and Loffler ( 1988) theory, when coupl ed with the proposed estimates of turbulent dispersion coefficients, is a p owerful tool for predicting cyclone collection efficiency, short of using c omputational fluid dynamics tools.