Agitation effect on particle dispersion and separation in an agitated reflux classifier

•The differences between agitation effect and traditional factors were compared.•Statistical methods were used to study factor differences.•The mechanism of agitation on particle dispersion and separation was studied.•Agitation effect can improve the Sb grade at a lower cost of Sb recovery loss. This study aims to understand the agitation effect on particle dispersion and separation and provide guidance in the optimized use of the agitation effect in an agitated reflux classifier (ARC) to promote the separation performance. Two statistical models were developed to analyze differences in various factors of Sb grade and recovery of concentrate. Results indicated that the agitation effect is an excellent auxiliary factor that can replace some functions of other traditional factors to improve the Sb grade at a low cost of Sb recovery loss. Sieve analysis results of the pretreated products showed that on basis of 16 L/h fluidization rate, adding agitation of 350 rpm can increase the concentrate grade of −0.045 + 0.023 mm particles from 2.65 % to 3.85 %, while the recovery is only reduced by 18.05 % which is much lower than the recovery loss obtained by increasing the fluidization rate. And compared with feed concentration, the agitation effect was more advantageous when dealing with coarse particles of-0.15 + 0.045 mm. In the range of 0 to 350 rpm, agitation effect could improve concentrate grade with little negative effect on the recovery of coarse particles. Fluidized bed analysis was utilized to explain these phenomena. Results showed that the agitation effect could well adjust the density distribution of the fluidized bed in the ARC. It lifted particles to a high area, reduced the density of the suspension in conical section of the ARC, improved particle dispersion, and reduced mechanical entrainments. Meanwhile, particles lifted by mechanical agitation increased the bed density of the vertical section and enhanced the ability of the fluidized bed to separate particles according to their density.