Stirred media mill performance and grinding wear prediction

Important results from the project

Grinding in stirred media mills are attrition driven, but it is unknown if the efficiency is limited by charge pressure, charge shear stresses or viscous flow. The goal for the project is to create possibilities for a future optimization tool for minimizing energy consumption and wear in industrial milling circuits. The main objective of the project is to build a physics-based numerical model that can virtually reproduce the grinding process. For the preliminary study, this objective was obtained by combining different numerical methods to recreate the physical behavior in the mill.

Expected long term effects

Experimental testing has been carried out to investigate how grinding efficiency is coupled to energy consumption for various load cases. Measurements of energy consumption, power, energy loss through cooling, particle size and rheology have been obtained. Results from the simulation of the stirred media mill show that the model can capture the interaction between pulp-structure-grinding beads. Flow patterns on both fluid and grinding beads and its influence of different density and viscosity can be shown. This opens possibilities for future optimizations tools in grinding.

Approach and implementation

Advanced measurements in combination with numerical modelling and validation have been carried out. A fundamental part is the experimental study and analysis of grinding in a stirred media mill to obtain calibration data for numerical models is significant. Also, formation of a physically based model of the stirred media mill for simulations is included. Simulation of the grinding process for various load cases for prediction of load intensity have been done. Model validation against pulp- and cooling water flows, energy and wear patterns experimental data are in agreement.