Dewatering of oil sands tailings with an electrokinetic geocomposite

The oil sands industry generates large quantities of mineral waste, such as fluid fine tailings (FFT), whose disposal is often challenging. The use of planar electrokinetic geocomposites (eGCPs) in FFT disposal areas could improve in-situ dewatering by allowing water to drain after it is expulsed during consolidation and by permitting the use of electro-osmosis (EO) to displace a significant portion of the remaining water. Four dewatering experiments involving mature fine tailings (MFT) are presented here: in three of them increasing normal stresses are applied on the MFT followed by EO; in the fourth test, EO is applied before the normal stress is increased. The results show that eGCPs adequately filter MFT; the particles did not clog or blind the filter. MFT were significantly dewatered under an applied normal stress followed by EO. EO was very efficient at extracting the more tightly bound water that remained after mechanical dewatering. In one configuration, a significant improvement of the shear strength from nearly 0 kPa to a mean value of 25 kPa was obtained, which is significantly higher than the 10 kPa required by Alberta regulations. The final solids content in that case was about 70%, starting from an initial solids content of 45%. The energy required for that test was 10.6 kW h per dry tonne.