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Investigation on alternative disposal methods for froth treatment tailings—part 1, disposal without asphaltene recovery


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In paraffinic froth treatment, tailings from the tailings solvent recovery unit (TSRU) contain a significant fraction of asphaltenes. In current commercial practice, the TSRU tailings are disposed of in a tailings pond where the large asphaltene particles and coarse tailings settle and the fines form mature fine tailings (MFT). With increasing public concern about the environmental impact of tailings ponds and stricter government regulations on tailings disposal, the oil sand industry has increased efforts to find alternatives that eliminate or reduce the use of tailings ponds. In collaboration with Total E&P Canada (TEPCA), CanmetENERGY conducted an extensive research program to explore alternatives for TSRU tailings disposal. TSRU tailings were produced from TEPCA's froth treatment pilot tests conducted at the CanmetENERGY froth treatment facility. Various processes were investigated, including flocculation and thickening, filtration, and centrifugation. A large number of bench-scale flocculation-thickening and filtration tests were conducted, followed by numerous pilot-scale flocculation-thickening tests and centrifugation tests. The experimental results demonstrate that TSRU tailings can be flocculated and thickened to produce paste-like sediment, and the hot water can be recovered and recycled. The thickened TSRU tailings have good water drainage and deposition of the sediment on a beach would result in further dewatering. Centrifugation of the TSRU tailings or filtration of the thickener underflow can produce a cake that appears to be very dry and suitable for disposal without pond containment.