DEM-BASED SIMULATION FRAMEWORK AS A TOOL TOPREDICT GRINDING IN AG/SAG MILLS

摘要

With the growing need to comminute Brazilian Itabirite iron ores to fine sizes for pellet production, the importance of grinding has risen in recent years. Given the benefits of SAG and AG mills in comparison to competing technologies, a number of projects are considering their incorporation in the new plants. Questions still exist, however, on the level of confidence that can be met in their design, considering how unusual these iron ores are in comparison to the ones normally ground in these machines. Empirical and phenomenological models of SAG and AG have been widely used in the design of these mills. However, in spite of their success, these models fail to describe the details of both the grinding environment and of the breakage mechanisms that act inside the machine. Recognising these and other challenges, a new mechanistic model framework has been proposed which overcomes the limitations of currently used models, by coupling the population balance model, the discrete element model (DEM) to functions that describe internal classification at the mill grate. The paper describes the model framework, demonstrating how it can address appropriately effects such as mill speed, mill filling and size distribution, on the response of a pilot-scale SAG mill. It is envisaged that the model, in the future, will become a useful tool to predict the behaviour of ores in these mills under different operating conditions, prior to running pilot plant tests.