Control of a flotation column using fuzzy logic inference

This paper describes a fuzzy controller that was developed for the control, in real time, of three main variables of the column flotation process. Column flotation is a solid-solid separation process based on the physical and chemical properties of mineral particle surfaces. It is applied to the concentration of low grade ores and to ores that require very fine grinding to achieve mineral liberation. The economic exploitation of the process, guaranteeing the desired final product characteristics from a feed of varying composition, requires a stable operation, which is accomplished through the automatic control of some key process variables. The difficulties encountered in the development of process controllers for this process are related to the lack of reliable measuring devices for the process variables involved, with the non-existence of mathematical dynamical models that can be used in a controller synthesis and with its non-linear and time-varying behaviour. The process and the problems related with its control are briefly explained and the main reasons for fuzzy logic control application are discussed. The real time control system and the fuzzy controller structure and parameters are presented. A general overview of the pilot plant where the experimental work was performed is presented. Finally, results of the experimental work, carried out with the two-phase system (air and water), are summarised and the conclusions are drawn. (C) 2002 Elsevier Science B.V. All rights reserved.