Effect of Shear Energy Input on the Rheology of Flocculant-Dosed Kaolinite Suspensions

• Author / Creator

  Neelakantan, Ravi

• Thickened tailings technology is implemented in some oil sands operations in order to recycle warm process water, thereby reducing net water draw, and to reduce the size of tailings impoundment areas. The rheology of thickened tailings is complex and time-dependent, and the underlying mechanism of rheological degradation (J.M. Treinen and R. Cooke, HYDROTRANSPORT 18, BHR Group, Cranfield, UK, 487-499, 2010) is not well understood. In the present study, the time evolution of the particle size distribution (PSD) and vane yield stress of a kaolinite dispersion mixed with polymer flocculants is examined as a function of shear energy input. Size distributions are obtained using the Focused Beam Reflectance Measurement technique. The shear energy input was quantified with the use of a large-volume, customized concentric cylinder shearing apparatus which allowed for the testing of about 300cm3 of flocculated tailings per experiment. It was found that decreases in vane yield stress and aggregate size were correlated with energy input when acrylamide polymers were used as flocculants. In particular, very large aggregates appeared to break down to produce a significant population in the 10-100µm size range as shear energy input was increased, which was seen in other studies, e.g. Vaezi et al. (J. Colloid Int. Sci, 355, 96-105, 2011), who observed both size and structure (porosity) changes. A decrease in apparent volume is the main mechanism for rheological degradation of acrylamide flocculated thickened tailings. Lowering the slurry pH before flocculation from 8.5 to 7.0 resulted in a much greater equilibrium yield stress; however initial rates of yield stress decay and floc degradation were unaffected. Dual polymer flocculation with Magnafloc® LT27AG and HyChem HyperFloc CD650 resulted in increased rates of decay in both rheology and size distribution. Data obtained for non-conventional polymers (e.g. PEO) demonstrate the potential for elastic polymer structures to flocculate in high shear environments and the importance of other factors (aggregate shape, zeta potential) which require further investigation.

• Subjects / Keywords

  • Rheology

• Graduation date

  Spring 2016

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3VD6P93S

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.