Multivariable predictive control of a pilot flotation column

The aim of this work is the control of hydrodynamic variables of a pilot flotation column working with a three-phase system (air-water-ore) in an industrial environment. Since hydrodynamic variables are closely related to metallurgical and economical performances of the unit, the implementation of such a control strategy is crucial to optimize its operation. The hydrodynamic variables here considered are the gas hold-up in the collection zone and the fraction of wash-water underneath the interface. They are controlled by manipulating gas flow rate and wash-water flow rate respectively. Hydrodynamic variables are controlled through a constrained model predictive control (MPC) strategy. This choice is dictated by the interdependency of these controlled variables and the capability of predictive controllers to handle process constraints. Identification tests lead to a representative model of the system under nominal operating conditions but indicate variations of process behavior with changing operating regimes. Results show good control performances, confirming the potential use of MPC to control hydrodynamic variables for real-time optimization of full-scale flotation columns.