An in-situ process to consolidate oil sands mine tailings

Abstract

The oil sands mining tailings inventory is growing and current treatment technologies are costly or unable to recover water effectively and handle the high solids content of the waste. Here we consider in-situ treatment of mature fine tailings (MFT) where additives are injected directly into the tailings to consolidate the solids so that the pond area can be reclaimed. This method eliminates the need for a dilution pre-step in the treatment of MFT. In a series of experiments, the impact of additives (iron(III) chloride and polyacrylamide), mixing speed, gas additives, and process scale on the de-watering performance of treated MFT was examined. It was found that the in-situ treatment method resulted in a better tailings product (higher final solids content) than an ex-situ method with ideal mixing conditions. The injected gases contributed to de-watering, chemically (by CO2 decreasing the pH of the tailings pore water) and physically (by convective mixing). After treatment, a layer of supernatant water continuously accumulates at the top of the tailings layer. The results demonstrate that injection of chemicals into the tailings layer leads to water rejection from the tailings layer leading to a layer with high solid content.