Comparing modeling approaches in simulating a continuous pilot-scale wet vertical stirred mill using PBM-DEM-CFD

Abstract

Vertical stirred mills have become increasingly popular in size reduction operations in the fine and ultrafine range, being normally used in industry in continuous operation. The present work describes the application of a mechanistic mill modeling approach based on the population balance (PBM) to describe the performance of a pilot-scale gravity-induced continuous stirred mill using 6 mm steel grinding media. At first, DEM and coupled DEM-CFD were compared in simulation of the mill, clearly demonstrating the significant effect of incorporating explicitly the fluid flow in describing the motion of the grinding media. The work then uses data from the stirred mill grinding calcite in multiple passes for model calibration and validation, besides breakage parameters from previous studies. It shows that the population balance-based mechanistic mill model predictions vary depending on the number of mixers-in-series used to predict product size, but that are capable of describing very well the milling operation considering the mill as three perfectly mixed grinding zones in series.