Effect of Slurry Solids Concentration and Ball Loading on Mill Residence Time Distribution

Abstract

The residence time distribution (RTD) of mineral slurry and slurry holdup volume in an industrial ball mill has been successfully studies using tracer tests. Six different conditions of solids concentration and three levels of ball loading were assessed. The effects of the slurry solids concentration and the ball loading on the mean residence time of slurry were clearly depicted in the results. Using the mass balance of salt tracer inside the mill, the slurry flow rate through the mill was estimated and the calculated values compared reasonably with the measured ones within the limits of experimental error. Further, based on the measured flow rates and residence times, it was possible to estimate the slurry holdup volume inside the mill. The correlation between slurry holdup volume with ball loading, slurry solids concentration and feed flow rate yielded plausible results. ANOVA statistical tests (F-test and t-test) were utilized to assess the adequacy of the correlation equation and the significance of the correlation coefficients.