Canadian Journal of Chemical Engineering, Vol.93, No.8, 1392-1402, 2015
Observations on the yielding behaviour of oil sand slurries under vane and slump tests
Yield stress measurements were carried out on slurries prepared from five different ore samples of varying contents of bitumen and fines in the sand fraction. The rheological measurements were performed using the vane, slump, and relaxation methods, as well as by extrapolation of equilibrium flow curves to zero shear rate. In the case of the vane tests, it was found that the yield stress values agreed better with the results obtained from the other techniques when the yield stresses were calculated using a torque value at the point of departure from linearity on the initial section of experimental torque-time curves. It was found that the yield stress values of oil sand slurries increased with an increase in bitumen content in the ores. High-bitumen ores tended to yield within a volume of the slurry extending well beyond the geometry of the vane. In contrast, low-bitumen ores yielded much closer to the vane edges. As a result, the torque value at the point of departure from linearity on the torque-time curve was recommended for calculating the yield stress of high-bitumen ore slurries with the use of the vane technique. On the other hand, the maximum torque value on the torque-time curve can be used for determining the yield stress of low bitumen ores.