Current water management strategies require recycling and reuse of oil sand process affected water (OSPW) to as much as 80%. Continuous recycling and reuse of OSPW degrades water quality as the concentrations of total dissolved solids (TDS) and dissolved organic materials (DOM) accumulate. This results in a net increase in operating and maintenance costs and an impact on the extraction process and bitumen recovery. Remaining water containing fines and suspended clays adds to the mature fine tailings and associated problems for tailings pond treatment and management. Presence of residual bitumen and other organics is known to create difficulties in common practices for flocculation and dewatering of tailings. With the problems stated above, one may consider a pre-treatment approach rather than the common post-treatment remedies.
The ore grade profoundly affects the efficiency of bitumen recovery in the hot water extraction of bitumen, the principal step in the bitumen extraction process. Sodium hydroxide is commonly added to the conditioning step to improve bitumen recovery. As the sodium ions build in concentration, they disperse clays in the ore and create tailings that resist dewatering. This is especially true for low-grade and oxidized ores, which present the greatest challenges in bitumen recovery and produce the major portion of tailings due to high fines content. With current trends for increasing production from mining operations to almost double by 2020, industry has to adopt new technologies to manage tradeoffs between water and energy.
We present a new approach toward total water management by introducing environmentally friendly process aids that can improve bitumen recovery from low-grade oil sands ores. Lab-scale experimental data from a Denver flotation cell and hydrotransport loop were analyzed to evaluate the efficiency on the processability of high and low grade oil sands, water chemistry and tailings management. The results demonstrate that using new process aids during the conditioning stage improves bitumen recovery from low-grade oil sands and can accelerate tailings settling. This pretreatment approach can be incorporated into current oil sands mining processing facilities and delivers environmental and economical benefits. A critical evaluation for use of new process aids versus sodium hydroxide is given in detail.