Magnetite and water addition control for a dense medium coal washing circuit

A coal washing circuit is studied for the purpose of better control of the density of medium used in dense medium cyclones to enhance separation efficiency. The process dynamics is mathematically modelled and a controller is designed following model predictive control method. The objective of the control is to adjust the medium density to follow an optimal density profile set by an upper level control/optimisation system. The main focus of this study is therefore on the modelling of the coal washing process and design of a lower level controller that manipulates the actuators directly. A pump-storage system introduced in our previous study is considered in the model to save energy consumption of the process. For the actuators, a screw conveyor is introduced to add magnetite to the corrected medium sump for density correction of the recovered medium. After the model and control system are presented, simulations are carried out to verify the effectiveness of the proposed system. In particular, the controller is applied to the system to track two different density profiles. Results of these simulations show that the controller designed is able to track a given density profile with minimal tracking errors.