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Investigation on alternative disposal methods for froth treatment tailings—part 2, Recovery of asphaltenes


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In collaboration with Total E&P Canada (TEPCA), CanmetENERGY conducted an extensive research program to investigate possible alternatives for TSRU tailings disposal. We have reported on alternative methods for TSRU tailings disposal without recovery of asphaltenes in an earlier publication.[1] Because the asphaltenes are high-molecular-weight hydrocarbons and may have potential for use as fuel or paving material, in this work, we investigate possible approaches for recovery of the asphaltenes from TSRU tailings. Two methods were tested, solvent extraction and aggregation. In the first method aromatic solvent is mixed with TSRU tailings to dissolve the asphaltenes followed by centrifugation to remove mineral solids and water. The experimental results demonstrated that more than 90% of the asphaltenes in the tailings can be recovered from the tailings. The recovered asphaltenes contained only a small fraction of mineral solids and may be useable as coker feed. In the second method, TSRU tailings are agitated at elevated temperature (80°C) at which the asphaltene particles form large aggregates and separate from the tailings, giving an asphaltene-rich phase and almost asphaltene-free tailings. The recovered asphaltene aggregates still contain significant amounts of mineral solids and water, and would require further treatment. Several coking tests were conducted using the recovered asphaltenes and the asphaltene aggregates. The results demonstrated that about 40 wt% of the recovered asphaltenes can be converted to lighter oil fractions under the coking conditions used in this work.