Mitigating the Adverse Effects of Ultrafines in Pressure Filtration of Oil Sands Tailings

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The ultimate goal of oil sands tailings management is to achieve >70 wt% solids in the tailings stream so that it is ready for reclamation. Research in the past several decades indicates that a combination of chemical amendment (e.g., polymer flocculants + coagulants) and mechanical treatment is necessary to achieve this ultimate goal. Of the mechanical treatment techniques, pressure filtration holds the most promise. Several case studies reported in the Tailings & Mine Wastes 2019 Conference in Vancouver, BC, show that typical mine tailings could be dewatered to >= 85 wt% solids using commercial filter press. However, when the same technology was used in oil sands tailings, the pressure filtration cake only reached about 60 wt% solids. The applicants' past research identified an ultrafine fraction, which was centrifuged from mature fine tailings and contained a mix of ultrafine sub-micron clays and bitumen-in-water emulsion droplets, as the main reason for the poor pressure filtration of the mature fine tailings. In the proposed project, we would continue the research to identify the roles of the constituent materials in the ultrafine fraction (clay types, size, bitumen coating and free bitumen) and develop mitigation technologies to eliminate their detrimental effects in filter press operation. The main focus is not to attempt to separate/remove the ultrafine fraction, but to selectively aggregate the ultrafine fraction to form high strength coagula, flocs and/or geo-polymers. The research is expected to make rapid dewatering of the oil sands tailings to >70 wt% solids by filter press technically and economically feasible.