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One of the technologies now undergoing trials at the operational scale in the oil sands industry to promote dewatering of fine tailings is in-line polymer mixing followed by air drying. Examples of these technologies include Shell’s atmospheric fines drying (AFD) and Suncor’s tailings reduction operations (TRO). Fine tailings (mature fine tailings or cyclone overflow tailings) are mixed with polymer to promote clay particle aggregation. The polymer is injected and mixed within a few metres of discharge points. The proper concentration of polymer and the optimum mixing intensity influence both dewatering processes (initial water release, desiccation, and consolidation) and the spreadability of the tailings over the disposal area. This optimisation significantly affects the initial water release by increasing floc formation, and of course minimises operational costs by keeping the polymer dose as low as possible. In this study, the optimum polymer dosage was determined to be 725 g/ton. Using higher dosage significantly affects the dewaterability due to consolidation. Scanning electron microscopy also showed the presence of free flocculants at higher polymer dosages. It is believed that the presence of free ionic flocculent may increase the negative charges which subsequently diminish the dewaterability potential. Also, in the practical polymer dose range of 600 to 1200 g/ton, the rheological properties of the tailings were measured using different rheometry techniques, slump tests and analytical calculation using flume test. The compatibility of yield stresses obtained in the laboratory with the field measurement of yield stresses confirms that mixing conditions used in the laboratory were representative of field mixing conditions.
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