Breakage and reformation of flocs in oil sands tailings slurries

Abstract

Tailings management presents a key challenge in eff ectively exploiting oil sands resources, since ever y barrel of bitumen recovered generates two to three barrels of tailings waste. With the recent adoption of Canad ian Energy Resources Conservation Board Directive 74, however, this waste can no longer be discharged as-i s, but must be dewatered and rendered trafficable within f ive years of generation. Not only are process taili ngs targeted for remediation, but also the approximatel y 700 million m 3 of mature fine tailings that have been accumulated over decades of processing and lie in l arge containment ponds. Chemical strategies for dewatering tailings involve treatment with additives that bind the tailings pa rticles together into larger flocs, with floc size and shap e influencing settling rates and compaction. Mecha nical operations such as centrifugation or even pipeline transport, however, can break apart flocs, altering their sedimentation and packing behavior. In this resear ch, mature fine tailings were treated with a range of organic flocculants and coagulants to induce floc formation . Floc breakage and reformation were assessed rheo logically and by dynamic measurements of particle size distri butions.