Demulsifier Performance in Bitumen Froth Treatment: Impact of Mixing and Froth Quality on Dewatering Rate

In the context of global energy transitions, optimizing the processing and refining methods is paramount. Specifically, in oil sand processing, ores of varying quality result in bitumen froths with higher than desired water or solid content, leading to challenges in processing and froth treatment. The underlying causes of these difficulties are not well-defined. This study investigates the impact of bitumen froth quality on water removal in naphthenic froth treatment using three distinct bitumen froths with varying bitumen, water, and solid contents. Experiments were conducted in the confined impeller stirred tank (CIST), a laboratory-scale mixing vessel designed to evaluate the effect of local mixing on competing rate processes. The design of the five impeller CIST ensures active circulation throughout the 1 L tank volume, providing more intense mixing and homogeneous turbulence distribution compared to the more typical single-impeller, 10 L, bench-scale mixing tank. A demulsifier was added to enhance water separation, with its dosage adjusted based on froth quality. The results show that froth quality significantly influences the water removal efficiency. Average-quality froths subjected to optimal mixing conditions (high mixing energy and low demulsifier injection concentration) achieved the highest water removal and the fastest initial settling rates, with most water settling within 10 min. In contrast, poor-quality froths required an induction time before effective dewatering, with high-solid and high-water froths exhibiting induction times of 20 and 25 min, respectively. Notably, high-water froths were more challenging to process than high-solid froths. These findings provide some of the first successful scale-down data elucidating the effects of poor froth quality on dewatering dynamics and performance, providing quantitative documentation of known industrial processing challenges and a bench-scale test, which can be used to further investigate processing strategies for poor-quality froth.