Mining and processing of Athabasca oil sands in Alberta, Canada, is a great success story of government–industry collaboration, fulfilling increased domestic and worldwide demands for oil. However, economic and environmental incentives still exist in the oil sands industry to enhance oil recovery and reduce energy consumption and water use, while minimizing green-house gas emissions and tailings ponds. The current industrial bitumen extraction processes, after surface mining, are exclusively water-based and operate at elevated temperatures, typically between 45 and 50 °C. Robust low-temperature processes, with reduced in-take of feedwater, that are less sensitive to ore characteristics are in a strong demand from both environmental and economical point of views. In response to this demand, we propose a robust aqueous–nonaqueous hybrid bitumen extraction process, in which diluent such as kerosene and naphtha is added to the oil sands prior to oil sands slurry preparation to decrease bitumen viscosity and enhance bitumen liberation. With the proposed hybrid bitumen extraction process, the oil sand processing temperature can be reduced to ambient temperature. To prove this concept, bitumen recovery tests were carried out on four Athabasca oil sand ores of good to poor processability, using a Denver flotation cell operated at ambient temperature. Adding kerosene or naphtha to oil sands at 4–11 wt % of the bitumen content was found to significantly enhance flotation recovery of bitumen and bitumen froth quality, especially for poor processing ores. It was found that kerosene addition not only increased bitumen liberation kinetics determined using our novel in situ bitumen liberation visualization flow cell (BLVFC) but also improved bitumen aeration measured by induction time apparatus.

A novel visualization cell was designed to study the kinetics of bitumen liberation from oil sands. This novel visualization cell allows for direct observation of bitumen recession from sand grains in real time under various experimental conditions, thereby providing a better understanding of bitumen liberation and the critical role of process conditions in bitumen extraction from oil sands ores. Although direct recession of bitumen from sand grains is found to be the primary mechanism of bitumen liberation, the presence of entrained air in oil sands ores greatly enhances bitumen liberation via bitumen spreading over air bubbles. Imaging analysis of the recorded real-time bitumen liberation process allowed for quantitative analysis of bitumen liberation kinetics. A rapid bitumen recession and, consequently, high bitumen recovery were observed for a good processing ore, in contrast to a slower bitumen liberation and lower bitumen recovery for a high-fines ore, which was considered to be a poor processing ore. The weathering (aging) of good processing ore was found to significantly reduce bitumen liberation kinetics, leading to a lower bitumen recovery, even though the bitumen content and solids composition of the ore remained the same. These findings confirmed the critical role of bitumen liberation in bitumen extraction. Increasing the process water temperature was found to increase significantly bitumen liberation kinetics and led to a higher degree of bitumen liberation. While high pH facilitated bitumen liberation, the presence of excessive salts (16 000 ppm sodium) was found to be detrimental to bitumen liberation, in particular at high pH. The bitumen liberation study using this novel visualization cell was extremely valuable for identifying and understanding critical operating parameters that control bitumen liberation and, hence, ore processability, providing a scientific basis for designing breakthrough technology to improve processability of oil sands ores and reducing the environmental impact of oil sands development.