Effect of grinding aids on the time-flow characteristics of the ground product from a batch ball mill

To explore the probable mechanism for enhancement of breakage rate of parti cles brought about by additives during fine grinding in media mills, the fl ow characteristics of the ground product were estimated using the Jenike fl ow factor tester for blank, additive and additive delayed samples, ground t o various grinding intervals up to 30 min duration. It was found from shear tests results that the presence of calcium stearate as an additive in the mill material charge during fine grinding of calcite in a batch ball mill h ad increased its bulk density and major consolidation pressure, while reduc ing the compressibility, internal friction factor, effective angle of frict ion, unconfined yield strength, shearing cohesion, extrapolated tensile str ength and flowability index. All these changes were more significant during the finer stages of grinding and, from the point of bulk solids flow, they are all flow favourable variations. The flow parameters were characterised by relating them to major consolidation pressure with appropriate equation s and it was found that for the blank sample most of the parameters can be fitted with long-hand type equations, while for the parameters of the addit ive sample exponential equations were found to be the best fit. (C) 1999 El sevier Science S.A. All rights reserved.