Switching cyclones to increase product particle size range for ore milling circuits

A commonly used continuous grinding mill circuit model is expanded to a hybrid model which contains both continuous and discrete dynamics. The discrete dynamics in the grinding mill circuit are as a result of switching individual cyclones in a cluster of cyclones. With the additional discrete dynamics an investigation was conducted to establish whether the switching of cyclones can be used as an additional manipulated variable. A nonlinear model predictive controller was implemented using the hybrid grinding mill model. Through simulations it is shown that the switching of cyclones can be used to extend the range of control for the product particle size. When applying a substantial disturbance it was found that certain setpoints could not be reached by the NMPC controller, however by switching in an additional cyclone the particle size setpoint could be reached. Simulation results are given to show that the discrete switching of hydrocyclones can be considered as a manipulated variable for hybrid model based controllers to achieve additional controller benefits.