This paper presents a dynamic simulator of the semi-autogenous grinding operation deduced from first principles coupled to an on-line parameter estimation scheme able to simulate industrial operations for control purposes. Model equations are based on conventional non-stationary population balance approach to develop the necessary dynamic model of the semi-autogenous mill operation. The model is able to predict the time-evolution of key operating variables such as product flow rate, level charge, power-draw and load position. as function of other important variables such as mill rotational speed and fresh feed characteristics. The set of ordinary differential equations was solved using MATLAB/SIMULINK as a graphic programming platform, a very helpful tool for understanding the grinding phenomenon. Using an on-line parameter estimator, the simulator was tested and validated at an 1800 t/h copper-ore mill showing the effectiveness of the system to track the dynamic behaviour of the variables. It is now being used for the study of advanced control schemes. (C) 2008 Elsevier Ltd. All rights reserved.The authors acknowledge with thanks the financial support provided by FONDEF under Project D0211077 and DICYT-USACH.11FONDEFfcubillo@usach.clFONDEF [D0211077]; DICYT-USACH1FONDEF22