Maintaining Permeability for Continuous Mature Fine Tailings Dewatering

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Oil sands tailings dewater extremely slowly once they form the so-called "mature fine tailings" (MFT). Theaccumulated MFT volume is over 800 million cubic meters and counting. Over the last few decades theindustry has developed a number of dewatering techniques (composite tailings, thickened tailings, in-linethickening/thin lift, centrifugation, filtration) to speed up the solid-liquid separation of the oil sands tailings.However, the performance of treatment is generally unsatisfactory, and the tailings could not be dewateredbeyond ~55 wt% solids by mechanical means, making the target of >=75 wt% solids (required for reclamation)seem un-achievable.Our recent results show that the difficulty of dewatering the oil sands tailings could be attributed to theresidual bitumen in MFT rather than the small size of the fine solids in the tailings. Our results show that anaqueous slurry of 35 wt% fine kaolinite (d50 = 4 µm) could easily filter to ~70 wt% solids using 50 g/tpolyacrylamide (PAM) under 6 bar pressure. However, after blending in 3 wt% of the residual bitumen, thekaolinite slurry could only be filtered to ~60 wt% solids at >1,500 g/t PAM, behaving like MFT.Based on these results, we ask the question: are the typically used PAM flocculants the best in dealing withthe residual bitumen? In the proposed project, we will answer this question and identify appropriate binders toalleviate the detrimental effect of the residual bitumen. The research techniques will include: 1) jar tests toevaluate the interaction of potential bitumen binders with residual bitumen isolated from MFT; 2) isothermaltitration calorimetric (ITC) study to investigate the binding strength between residual bitumen and bitumenbinders, and between fine solids and bitumen binders; 3) filter press tests of the MFT after treatment by thebitumen binders to observe the dewatering effect and the achieved cake % solids content; 4) micro computedtomography and cryogenic scanning electron microscopy to study the pore structures of the filter cake after thetreatment, and to investigate the reasons for the poor and improved dewatering performances.