Effects of polymer dosage on dewaterability, rheology, and spreadability of polymer-amended mature fine tailings

“…Few findings in the public literature are available discussing the behaviour of polymer amended oil sands MFT. Mizani et al (2013) reported that the low polymer dose showed more dewatering potential in thin lift (0.50 m). Mathews et al (2011) reported that in-line mixing at the field scale increased the solids content from 30 -35% to 45 -55% within 24 hours after tailings deposition in thin lifts (0.60 m).…”

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confidence: 98%

Microstructure and macroscopic behaviour of polymer amended oil sands mature fine tailings

Bajwa¹

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After several years following deposition, oil sands fine tailings settle to a solids content of 30 ~ 40% and are subsequently termed mature fine tailings (MFT).Once they have reached this state, MFT do not appreciably dewater, even after several decades. The particle size and dispersed structure of the fines (and possibly residual bitumen), negatively impacts the consolidation behavior of MFT.Several technologies currently being trialed to accelerate dewatering of MFT, such as in-line flocculation, centrifuge, and tank thickening, flocculate the tailings using a polymer. The addition of polymer results in substantial dewatering in the short term (24 hours) after in-line flocculation, and increases dewatering in tank thickening and centrifugation. This is well understood in industry. However, the polymer may also change longer term dewatering behaviour by potentially changing the consolidation characteristics and water-retention characteristics of the tailings.To assess the effect of polymer on all aspects of dewatering behaviour, column experiments simulating deposition of in-line flocculated tailings were undertaken for different times, different thicknesses, and under different environmental conditions. This allowed for the study to separate initial dewatering from selfweight consolidation, subsequent desiccation, and further consolidation of desiccated tailings when they are buried by fresh deposition. The behaviour was iv analyzed by tracking fabric changes using mercury intrusion porosimetry and scanning electron microscopy.Differences in dewatering behaviour following initial self-weight consolidation due to differences in polymer dose appeared to be minimal. Consolidation behaviour of previously desiccated tailings converged to the same properties by 80 kPa vertical effective stress. Optimizing for dose should therefore be done in terms of self-weight consolidation. It was observed that optimizing for yield stress may yield a higher optimal dose than for dewatering.

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“…Average solids content before and after freeze-thaw cycles (Johnson et al, 1993) . (Mizani et al, 2013). ... 89 Table 9.…”

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confidence: 99%

“…... 89 Table 9. Mineral composition of raw MFT (Mizani et al, 2013) xvi Figure 20. Saturation stages in the SWCC (Vanapalli et al, 1996).…”

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confidence: 99%

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Combined Evaporation and Freeze-Thaw Effects in Polymer Amended Mature Fine Tailings

Sardon¹

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Evaporation and freeze-thaw phenomena are known to contribute to dewatering and densification of fine tailings streams generated from oil sands bitumen extraction.This thesis reports on studies of 1-Dimensional freezing of polymer-amended mature fine tailings that have different stress histories with respect to degree of desiccation by evaporation and self-weight consolidation. Freezing is accomplished using an electric cooling plate specially mounted in an insulated column. Polymer-amended tailings are placed at a lift of one half-meter, which has been allowed to consolidate. Temperature is recorded using thermocouples, while the densification and dewatering is tracked by monitoring of water content, pore water pressure, and cryo-suctions. After one freezethaw cycle is applied, the samples are cored and then loaded to examine differences in consolidation behaviour post-freezing. Results with respect to dewatering indicate that desiccation and one freeze-thaw cycle enhanced the dewatering process and increased the average solids content of the tailings by 6% when compared to MFT that only underwent consolidation. Also, when comparing the self-weight consolidation and desiccation phases for the three Column Tests, it was found that desiccation increases the efficiency of the freezing process. Lastly, no significant differences in compressibility and permeability properties were found between tailings that underwent just self-weight consolidation and tailings that underwent self-weight consolidation and one freeze-thaw cycle.iii

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Effects of polymer dosage on dewaterability, rheology, and spreadability of polymer-amended mature fine tailings

Cited by 12 publications

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Shear behvaiour of oil sand fine tailings in simple shear and triaxial devices

Shear behvaiour of oil sand fine tailings in simple shear and triaxial devices

Microstructure and macroscopic behaviour of polymer amended oil sands mature fine tailings

Combined Evaporation and Freeze-Thaw Effects in Polymer Amended Mature Fine Tailings

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