Flotation columns have been widely used in mineral processing all over
the world. They have been systematically incorporated in a lot of mil
ls, specially as a final cleaning stage. However, they differ in many
aspects from conventional flotation cells. Different physical dimensio
ns of collection and froth zones, different ways of generating and dis
tributing the air bubbles in the system and the new use of wash water
on the top of the froth, pose different control problems and opportuni
ties. New operational variables, with different variability and relati
onships among them, demand new efforts in better process variable meas
urements, models development and control strategies of flotation colum
ns. Most of the actual installations still use conventional instrument
ation and conventional distributed PI control. Improvements in operati
on and control of flotation columns can be achieved by a better knowle
dge of its dynamics. In the literature some phenomenological model dev
elopments have been reported, but a rather large number of model param
eters have to be estimated from experimental data. In this work an exp
erimental study of the dynamic behaviour of two flotation columns at d
ifferent scales is presented. A 5x10 cm rectangular section and 1.35 m
high laboratory scale column and a 10 cm diameter and 8.5 m high pilo
t scale column were used to obtain dynamic relationships for the air-w
ater system. Field instrumentation was installed and calibrated, and d
ata signals communicated to a PC computer through a serial A/D/A inter
face. Changes in gas, wash water and feed flowrates, and tailing valve
opening were specially designed and carried out to obtain experimenta
l responses of pulp level, gas holdup and bias, at different operating
conditions. Main nonlinearities and interactions were show to be very
useful to explain common control problems.