Pressure Filtration of Oil Sands Mature Fine Tailings

Abstract

Dewatering of the oil sands mature fine tailings (MFT) is studied through pressure filtration following treatment by dual polymer flocculants. Polymer pairs consisting of anionic polyacrylamide (A3335) and cationic polyDADMAC (Alcomer 7115), and A3335 and non-ionic polyethylene oxide (PEO) are tested. The effect of the residual bitumen in MFT on dewaterability and filtration is also assessed. Ideal clay systems of kaolinite are compared against kaolinite slurries homogenized with bitumen at the same concentration that exists in the MFT. The dual polymer treatment of MFT is found to be more efficient than the single polymer treatment in terms of shorter capillary suction times (CST), higher filter cake solids content, higher net water release (NWR), faster water release rate, and lower specific resistance to filtration (SRF). Additionally, it is found that the addition of bitumen to pure kaolinite decreases filterability performance, but the kaolinite/bitumen mixture had comparable filterability to dual polymer flocculated MFT if treated with the same dosage of the dual polymers. The porosity of the filter cakes are assessed with micro computed tomography (micro-CT). It is found that the porosity correlates well with solids content data and that pore connectivity increases with dual polymer treatment.