Measurement of Floc Size and the Influence of Size Distribution on Geotechnical Properties of Oil Sands Fluid Fine Tailings

Abstract

Large volumes of fluid fine tailings (FFT) from oil sands mining operations pose difficult engineering challenges because they do not readily dewater and due to their fluid state, require containment. A common approach to reduce FFT volume by water removal is to treat the clay suspension with a coagulant and flocculant to form highly porous aggregates called flocs. This work investigated the effect of increased floc size on geotechnical properties of FFT. A method utilizing a flocculation system and images of flocs was developed to determine floc size distribution of a treated FFT sample. Floc size was measured with image analysis software using images obtained directly after flocculation. Treatment recipes, combining an optimal dose of coagulant and polymer, were designed to give clear release water and highly visible flocs suitable for measurement. Floc size distributions were then determined for each of the optimal treatments. Two of these treatments were further analyzed to assess compressibility, hydraulic conductivity, and vane shear strength. Both compressibility and vane shear strength showed to be sensitive to changes in floc size distribution while hydraulic conductivity did not appear to be largely impacted by floc size.