Bitumen recovery from model systems using a warm slurry extraction process: effects of oilsands components and process water chemistry

Natural oilsands is a complex mixture of sand, clay, bitumen and connate water that can vary markedly from one sample to another. Also, oilsands processability is known to depend on composition and process water chemistry. Because these variables are hard to control, the effect of an individual oilsands component on bitumen recovery is difficult to determine. Here, we carry out a series of systematic screening experiments with model oilsands (MOS) to determine the effects of system components and water chemistry on bitumen recovery using a warm slurry extraction process. Atmospheric topped, blended or deasphalted bitumen were used at a constant level of 10-wt% in the preparation of the model systems. The solids components tested included: different size fractions of silica sand, and several commercial clay minerals, including illite, montmorillonite and kaolinite. Clay concentrations were varied up to 5-wt% of the total solids. Anions and cations at concentrations comparable to those in process water from a commercial oilsands extraction plant were also evaluated. Bitumen recovery results from these screening tests were compared with those for a base case, or standard, MOS mix comprising 10-wt% atmospheric topped bitumen, 21-wt% silica fines and 5-wt% deionized water at pH 8; coarse silica sand provided the balance to 100-wt% of solids, or 64-wt% of the MOS. Recovery results for the different screening test variables were classified into three categories: (1) Bitumen recoveries comparable to those for the standard MOS, i.e. size of coarse solids, bitumen type, sodium, chloride and sulfate ions. (2) Decreased bitumen recovery, reversible by addition of more NaOH, i.e. size/amount of fine solids and illite. (3) Bitumen recovery that could not be reversed, i.e. synthetic hydrophobic coarse solids, montmorillonite, kaolin, calcium and magnesium ions. (C) 2004 Elsevier Ltd. All rights reserved.