Charge dynamics of autogenous mills
A mill is autogenous when the grinding media is part of the feed (i.e. lumps of the material to be comminuted are used). Some advantages with this setup are a large size reduction, a final product that will be free of contamination (no influence of foreign matter from grinding media) and only liner wear costs.
The feed to a mill varies over time and the performance of an autogenous mill will to a large extent be dependent on the feed material properties, due to the use of the ore itself as grinding media. How an autogenous mill is affected by changes in feed material, mill speed or degree of filling is to be investigated in the project.
The aim of this project is to use inner and potential outer sensors to follow how the charge in an autogenous or pebble mill acts during operation. The sensor information will be used to link the dynamics to variation in feed material and mill operating procedures.
By understanding the fundamental relations and by the aid of sensor information, the goal is to keep a constant production from the mill and generate a stable grinding fineness.
The project is financed by LKAB.
In order to better understand the mill behaviour, pilot scale tests will be performed at LKAB, Malmberget. Results from the tests will also be used to validate a 3D mill model based on DEM (discrete element method).
Results and conclusions
Process analysis by simulations gives an insight of what happens inside the mill. The picture shows a 3D segment of a simulated pilot scale mill (1.5 m diameter and 0.1 m length), where the media is coloured by speed (red is faster and blue is slower).