Investigation on the flocculation of oil sands mature fine tailings with alkoxysilanes

Mature fine tailings (MFT), a mineral matrix of residual hydrocarbons, water, and fine clays, are generated by the extraction of bitumen from oil sands. Finding ways to get MFT to dewater more quickly is critical to improving the reclamation of tailing ponds. Although many methods have been developed to treat MFT, most of them have been rejected for lack of technical or economic feasibility. The aim of this study was to investigate the performance of alkoxysilanes on dewatering and densifying MFT. The performance of five alkoxysilane types was evaluated by capillary suction time (CST), settling percentage, and solids content. Among them, bis(3-trimethoxysilylpropyl)amine (bis-amine) performed best, especially when combined with centrifugation. Bis-amine was then used in an experimental design to study the influence of alkoxysilane dosage and initial solids content on MFT dewatering and densification. The experimental design showed that certain operation conditions produced sediments with low CST (below 20 s), relatively high solids content (over 42 wt%), very low turbidity (about 6.0 NTU) and minimal concentration of solids in the supernatant (0.2 wt%), which facilitates the reuse of the recovered water from MFT flocculation in the oil sands extraction process. In addition to these promising findings, it is important to point out that no calcium was added, and that bis-amine has a lower molecular weight, and therefore is less shear-sensitive than the commercial high molecular weight polymers used to treat MFTs in commercial applications.