Sodium Free Processing of Oil Sands Ores: Toward Total Water Management in Mining Operations

摘要

Current water management strategies require recycling and reuse of oil sand process water (OSPW) as much as 80%. Continuous recycling and reuse of OSPW results in a degradation of the quality of water namely increases of total dissolved solids (TDS) and dissolved organic materials (DOM). This results in a net increase in operating and maintenance costs and an impact on extraction process and bitumen recovery. Remaining water containing fines and suspended clays adds to the mature fine tailings and associated problems for tailing ponds 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 problems stated above, one may consider a pre-treatment approach in place of the common post-treatment remedies. The ore grade profoundly affects the efficiency of bitumen recovery in the hot water extraction of bitumen which is a principal step in the current commercial technology for bitumen extraction in mining operations. Sodium hydroxide is often added to the conditioning step of the process and is needed to obtain higher bitumen recovery from most oil sand feeds. Use of NaOH, however, results in accumulation of sodium ions in recycled water, causing higher clay dispersion and producing tailings with poor geotechnical properties that turn into mature fine tailings. 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. 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 novel process aids for sodium-free processing of various oil sands ores. Lab experimental data were analyzed to evaluate the efficiency on the processability of low grade oil sands, water chemistry and tailing management. Our results demonstrate that the use of new process aids during the conditioning process leads to an improvement in bitumen recovery from low grade oil sands and can accelerate tailings settling resulting in better water management. The process aids were also used in combination of polymer flocculants to treat process tailings, resulting in better tailings dewatering and consolidation. This approach offers a potential chemical solution for total water management that can be incorporated into current ore processing facilities and delivers some operational and economic benefits.