Figure 1 – Pilot flotation rig The cell was operated in batch mode (i.e. with no feed or tailing discharge). Water and silica were added directly to the tank prior to testing. The static pulp height was 0.57 m. Agitation was provided by a 6-blade Tailing Technology rotor (0.205 m diameter) driven by an 11-kW motor through a V-belt assembly, with a variable-speed drive to control the impeller speed. Impeller speed was measured with a digital tachometer. The rotor was positioned 0.10 m above the tank bottom. Air was supplied by a blower, controlled using a manual valve, and flowrate measured by a digital mass-flow sensor. Frother (Methyl isobutyl carbinol - MIBC) was added to the pulp at 100 ppm to stabilize bubble size. A full factorial experimental program was conducted to quantify the influence of baffling and superficial gas velocity (Jg). The cell was operated in two baffle configurations: a conventional rotor-stator assembly, or a stator-free mode with four flat baffles mounted close to the walls. Four levels of Jg were tested for each baffling mode, resulting in 8 experiments, with an additional 2 repeats to estimate experimental error. Table 1 summarizes the tested factors and levels. Table 1 – Experimental design Factor Levels Baffling Stator, Baffles Jg (cm/s) 0.0, 0.5, 1.0, 1.5 Particle settling at the tank bottom was monitored using a camera positioned beneath the cell. To trace suspension behaviour, 1 kg of +106-150 µm silica was added into the cell. The cell was operated at low percent solids, with the tracer being the only solid material. The critical impeller speed for just suspension (Njs) was measured by incrementally increasing the impeller speed until no particles remained settled for more than one second (Zwietering, 1958). The system was then set at the observed Njs. Power draw was measured using a power meter that recorded the electrical energy consumption of the flotation mechanism. To isolate the
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