MODELLING OF CEMENT GRINDING CIRCUITS FOR PREDICTIVE CONTROL

A first principles model of a cement grinding circuit is developed for the purpose of multi-variable model predictive control (MPC). The model is based on a series of mixed flow reactors with an ideal screen to model flow between the two chambers in the ball mill. The separator is modelled by efficiency curves. Breakage of the particles is modelled as a first order process in terms of functions for the specific rate of breakage and the fragment distribution from breakage. These breakage functions are empirically based. A stationary solution for the model is found and dynamic simulations of step changes in the manipulated variables are shown.