Abstract
Oil sands fluid fine tailings deposits are challenging to reclaim due to their inherently high natural water content, low permeability, and low strength. Combinations of polymers and (or) coagulants are used by operators to improve the dewatering and strength properties of the tailings. However, considerably more work has been done to evaluate polymer performance with short-term dewatering metrics rather than with long-term metrics such as consolidation properties. This paper evaluates the potential of four novel polymers for use in fluid fine tailings treatment compared to a commercially available polymer and untreated tailings specimen. The performance of the polymers was assessed through initial screening with respect to short-term dewatering, evaluation of the consolidation and strength properties using large-strain consolidation tests, shear sensitivity in pipeline transport, and finally, large-strain consolidation modelling to appraise the relative potential performance under different strategies, such as terrestrial or aquatic reclamation options. One polymer exhibits remarkably fast dewatering at high void ratios, while another demonstrates dense and shear-resistant flocs. The paper discusses each polymer’s distinctive tailings fabrics and how their unique merits and limitations would benefit different reclamation eventualities. Finally, potential improvements of the polymers are suggested for future assessment.
Highlights
Surface mining of oil sands bitumen deposits produce tailings, which comprise water, sands, clays, residual hydrocarbons, and chemicals originating from the bitumen extraction process (RoyalSociety of Canada's report 2010)
The results indicate that, at a given solids content, the undrained shear strength achieved in both the AP-g-PAM and P(VBTMAC) treated FFT is significantly higher than that of the FLOPAM PT
This is stemming from the high polymer dosage requirements, which explains why the final height of the tailing-water interface is comparable to that of the other treated tailings, despite exhibiting the maximum overall settlement (Figure 8 b)
Summary
Surface mining of oil sands bitumen deposits produce tailings, which comprise water, sands, clays, residual hydrocarbons, and chemicals originating from the bitumen extraction process (RoyalSociety of Canada's report 2010). While the sand fraction that settles out is relatively nonproblematic, a significant proportion of the fines remains suspended in the water. These are referred to as fluid fine tailings (FFT). Some settling of solids occurs, but generally, after 3 to 5 years, a stable suspension > 200% gravimetric water content (
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