Bitumen-air aggregates flow to froth layer: II. Effect of ore grade and operating conditions on aggregate composition and bitumen recovery

Size, rise velocity, shape, and composition of bitumen-air aggregates floating to the froth layer during the processing of 11.1% bitumen Estuarine ore, and 7.2% bitumen Marine ore under various operating conditions (caustic dosage and feed density) were determined. The flux of the bitumen-air aggregates inside a Primary Separation Vessel (PSV) processing 2 tonnes/hour of the ore was in-situ monitored and video recorded. The mass of bitumen contained in the aggregates floating to the froth layer under different operating conditions was calculated on the basis of the measured rise velocities and dimensions of the aggregates. It was found that the type of ore processed was the parameter having the largest effect on size and composition of the bitumen-air aggregates floating to the froth layer inside the PSV during a 50°C warm slurry extraction process. In the case of the Estuarine ore the average mass of bitumen contained in an average aggregate was ca. 9∗10−4 g, and the average aggregate size was ca. 1.0 mm. During processing of the low grade (Marine) ore the aggregates were smaller (within 0.33–0.69 mm) and they carried much less (from 0.17–1.37∗10−4 g) bitumen, depending on other operating conditions (caustic dosage and feed density). A good correlation between size of the bitumen-air aggregates and bitumen recovery in the primary separation vessel was found. Thus, size of the aggregates can be used as an indication of better flotation recovery.