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Working Together for Tailings Excellence
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The
2001 Thickened Tailings Field Trial (Paste Technology) is a great
government-industry collaborative success story. This tailings management
improvement initiative was undertaken to advance the oil sands industry
commitment to, and focus on, tailings management excellence.
Traditionally, the fine solids and water that are left over after
the bitumen has been separated from the oil sands, have been discharged
into large settling 'ponds' where the fines slowly settle, thereby
releasing water that is suitable for recycling back to plant processes.
The primary drawbacks associated with this approach are the high costs
of construction and maintenance of the high-specification, above-grade
containment structures, the large areas required for construction
of stable tailings 'ponds', and the loss of heat from the warm process
water as it is exposed to ambient climatic conditions.
Thickened tailings technology involves rapid settling and sedimentation
of suspended fines within a process vessel through the addition of
chemicals that aid in 'flocculating' the fines solids and producing
water that is suitable for reuse back to the Extraction process with
little loss of process water temperature. This means less make-up
heating is required resulting in lower imported energy costs and reduced
greenhouse gas emissions. Additionally, the accelerated settling rate
of the fines produces a concentrated stream of fine solids which can
be deposited with less land disturbance and offer the potential for
accelerated land reclamation.
The 2001 Trial demonstrated the opportunity to very substantially
reduce, or even eliminate, the size of the tailings 'ponds' resulting
in more efficient water use, reduced costs of containment construction,
immediate recycle of the warm process water back to the bitumen Extraction
process and overall less land disturbance. The trial also provided
valuable insights respecting oil sands specific process control development
needs and identified sensitivities that will be addressed in developing
commercial tailings thickening processes.
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