Development of the next-generation of dewatering technologies for mature fine tailings (MFTs) from oil sands processing

Abstract

The oil sands industry is currently facing a challenge by regulators to develop dewatering technologies that can halt any further growth in the massive size of existing tailings ponds and also reclaim the contents of those ponds. The most recent technology involves in-tank and/or in-line addition of flocculants followed by a dewatering step (e.g. centrifugation, thin-lift dewatering). This work has focused on three different dewatering technologies. Firstly, a high-throughput method was developed to investigate the effects of ionic composition adjustment on MFTs dewatering through a centrifugation process. As a result, it was found that samples with different concentrations and valency of cations had different settling kinetic and higher concentrations and valency of cations caused faster settling. Also, changes in the ionic composition of samples suggest that there is a strong interaction (ion exchanging) between MFTs and added solution. Secondly, the effects of different factors (e.g. freezing time and temperature) on freeze-thaw dewatering of MFTs were studied using a temperature monitoring setup. It was found that partial freezing causes less dewatering compared to complete freezing after thawing. Finally, a lab-scale unit of low-speed rotary filtration was built and it was implemented to dewater polymer amended MFTs. By using this unit, effects of different factors were investigated on the dewatering efficiency of the rotary filtration unit through a DOE study. The DOE results showed that the flocculation conditions have a big impact on performance of the rotary filtration and for some of the DOE conditions, cakes were formed with more than 47 wt% which couldn’t be reached by just gravity settling of polymer amended MFTs. Also, freeze-thaw of the cakes after rotary filtration could increase the solids content.