Effect of rheology and solids concentration on hydrocyclones performance: A study involving the design variables of an optimized hydrocyclone

Abstract

Despite several advances in the field of separations in hydrocyclones, achieving high separation efficiency in these devices when operating with concentrated non-Newtonian suspensions is still a challenge, and any improvement in this aspect can be a significant contribution. Thus, the objective of this study was to evaluate the behavior of a hydrocyclone operating with concentrated pseudoplastic suspensions. The device used in this study was the Maximum Overall Efficiency Hydrocyclone (MOEH), which is the result of a geometric optimization study developed by our research group whose objective was to obtain a hydrocyclone geometry that led to high separation efficiencies. The polymer carboxymethyl cellulose (CMC) was used as a rheological modulator at different concentrations. Changing the concentration of CMC in the suspension from 0.2 wt% to 1.0 wt%, it was observed reductions of 27% and 23% for the Euler number and overall efficiency of the MOEH hydrocyclone, respectively. When operating with dilute pseudoplastic suspensions (CCMC < 0.6 wt%), the drop in the separation performance could be mitigated with appropriate increments in the dimensions of the underflow diameter and reductions in the vortex finder length. Above a concentration of 0.8 wt% CMC the hydrocyclone operated as a stream splitter, with reduced efficiency of less than 2%, and the modifications in the design variables were not sufficient to reverse the detrimental effect of the increased slurry viscosity. The results obtained in this study show the relevant effect of non-Newtonian fluids in the functioning of hydrocyclones and the importance of the correct choice of geometric configurations and operating conditions to reduce the impact of the rheology in the separation performance.