Role of acidified sodium silicate in low temperature bitumen extraction from poor-processing oil sand ores

Process aids are generally required to improve bitumen recovery from poor-processing oil sand ores containing a relatively high amount of divalent metal ions and fine solids/clays. In this paper, the role of acidified sodium silicates as a dispersant/depressant of clay fines in bitumen extraction was evaluated using a laboratory hydrotransport extraction system (LHES) at low temperature (35 degrees C). Bitumen recovery experiments showed that adding acidified silicates during the bitumen extraction process resulted in a higher degree of bitumen liberation from sand grains, a faster bitumen flotation rate, and a better bitumen froth quality than adding caustic. Solution chemistry analysis demonstrated that acidified sodium silicate is a better process aid than caustic because it has three functions: to precipitate calcium and magnesium in the process water, which minimizes the synergistic effect of divalent cations in inducing a clay coating on the bitumen surface and clay gelation; to maintain an adequate pulp slurry pH for better bitumen-air bubble attachment; and to disperse/depress clay fines from flotation by its specific species.