The advances in the study of control alternatives for flotation columns are
reviewed. An integral solution to the control problem has to deal with
problems associated with instrumentation, process modelling, control
strategies and control algorithms. The term hierarchical control is used
here to mean the intelligent integration of available knowledge, control
algorithms and logic rules of decision. The selection of information,
algorithms and rules is based on the experimental and theoretical
knowledge of the column flotation process. The software support was designed and implemented in object oriented
computer programs. This technique allowed the implementation of a
combination of control techniques, algorithmics and heuristics, in the
form of a control strategy. This strategy has shown to fit well with
processes exhibiting complex dynamic characteristics. The hierarchical control was implemented in a pilot column and
included the following general aspects: co-ordination of distributed
conventional control loops, use of sets of control parameters for the froth
depth control loop according to the froth depth state, verification and
diagnosis of sensors, on-line predictive estimation of gas hold-up,
diagnosis of common operating problems and the use of predictive
control to account for feed flowrate changes.