Froth Treatment in Athabasca Oil Sands Bitumen Recovery Process: A Review

Bitumen froth treatment is an integrated process step in the Athabasca oil sands bitumen recovery operations. Its objective is to separate mineral solids and water from the bitumen froth. The bitumen froth is diluted with naphthenic or paraffinic solvents to lower its viscosity to facilitate the separation; therefore, bitumen froth treatment is the removal of inorganics (mineral particles and water droplets) from a bitumen organic solvent solution. The micrometer sized mineral particles (mainly clays) and water-in-oil emulsion droplets are the most difficult to remove from the bitumen froth. Research has been carried out that has led to an understanding of the formation, stabilization and properties of the water-in-oil emulsions in the bitumen organic solvent solution. It is known that the water-in-oil emulsions are formed by water entrained into the bitumen froth during the water-based extraction process and stabilized by natural surfactants in bitumen (especially asphaltene) and fine mineral particles. In fact, the fine mineral particles are the main detriments in stabilizing the water-in-oil emulsions, for the emulsified water droplets were found to be easy to destabilize and remove in the absence of fine mineral particles. Effective removal of the fine mineral particles and water droplets requires both (1) that the fine mineral particles form larger aggregates and (2) that the water-in-oil emulsions can be destabilized. Different demulsifiers have been studied in froth treatment, but the focus was more on the "surfactant-stabilized" water-in-oil emulsions. Therefore, this approach can only partly contribute to item (2). No efforts were made to aggregate the fine mineral particles. Therefore, it was proposed that a possible approach for the effective bitumen froth treatment would be to develop and use process aids that can both aggregate the fine mineral particles and destabilize the water-in-oil emulsions. Several other potential directions to improve bitumen froth treatment have also been pointed out based on the literature review.