WATER TREATMENT IN OIL SANDS: A NOVEL APPROACH TO CALCIUM CONTROL

摘要

The extraction of bitumen from surface-mined oil sands in Alberta, Canada is a water-based process that involves making an ore-water slurry and then recovering the bitumen product as a froth. Water from the tailings is recycled to the plant. Soluble ions in the recycle water, particularly divalent cations at high levels, can hurt the extraction process and contribute to heat-exchanger scaling. A tailings treatment known as the consolidated tailings (CT) process was developed that uses soluble calcium but results in elevated calcium concentrations in the release water. In order to apply the CT process to reclaim the tailings stream, an understanding of reactions controlling the calcium levels in the recycle water is required. To help control calcium levels a high-clay-content tailings stream was re-routed to commingle with the high-calcium release water from the consolidated tailings. The CEC of the clays, coupled with the residence time in the tailings pond, helps to control the calcium. The calcium content in the recycled water was successfully modelled through an understanding of the clay CEC and the water chemistry. This novel approach to calcium control at the Suncor Energy oil sands plant was critical to the implementation of the innovative CT process for the reclamation of fluid fine tailings.