| A shortage of sensors preventing the measuring of certain control variables, or the poor reliability of the ones available are factors which limit the use of the modern automatic command in the process of column flotation. This work has allowed for progress in the field, by studying the use of techniques based on knowledge of the column flotation process in order to measure the interface's position, the bias and the air holdup.;As the meaning of the interface's position, we proposed the use of neural models to detect the inflection point in a conductivity profile. These models give sturdiness to the sensors because they can even generalize the shape of a defective conductivity profile's shape in order to link it up to the bias value. The methods and instruments developed have been experimentally validated under conditions similar to the ones we find in the industry. The results are very much satisfactory because the relative error's average obtained is of only 3.6% for the level's measure and of 10.5% for the bias measure.;In order to measure the amount of air in the collect area, we have developed a sensor and a new method which simultaneously calculates the amount of air and the liquid's conductivity inside the column. Both have been validated in stationary and transitory state, in a pilot column, and have obtained excellent results (7.5%, relative error's average, on 500 tests and in relation to the measure under pressure in a two-phase system).;Other contributions to this work are: (a) an experimental system in laboratory, instrumented and equipped with a control and supervision interface that was an inspiration for other setups (McGill University in Montreal and Canmet in Ottawa), (b) the conception of an electronic system which facilitates the operation in real time of the different sensors developed (improvements from 30s to 1s for the complete measure of the conductivity profile), (c) the use of an odd number of internal electrodes in the conductivity sensor allowing an electric flow between neighboring electrodes only. |
