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Suncor speeds tailings-pond reclamation

By OGJ editors
HOUSTON, Oct. 23
-- Suncor Energy Inc. is seeking approvals for a process it says can shrink the environmental footprint of oil sands mining operations.

The process, called tailings reduction operations (TRO), accelerates the settling of fine clay, sand, water, and residual bitumen in ponds after oil sands extraction.

TRO addresses mature fine tailings, which are clay particles less than 44 µm in diameter that can stay in suspension for centuries without processing, making planting and surface reclamation impossible.

Since the 1990s, Suncor has added coarse sand and gypsum to mature fine tailings to accelerate the release of water. But the process is still slow, requiring a growing number of long-lived tailing ponds.

The expansive surface disturbance, chance that large numbers of ponds will last for many years after operations cease, and effects on water supply and quality are important environmental concerns for oil sands mining.

With TRO, Suncor says mature fine tailings settle out of suspension in about a month. The speed allows the company to reuse water and ponds and to more promptly begin reclamation of the ponds themselves.

The technology involves dredging mature fine tailings from a pond bottom, mixing the suspension with a polymer flocculent, and spreading the sludge-like mixture over a “beach” with a shallow grade.

The flocculent adheres to and combines clay particles, making them fall out of suspension. The separated water flows into a pond from the bottom of the graded beach, and mechanical spreading and disking accelerate drying of the fines.

Suncor says the separated fines have been used as construction material. In addition to reducing the number of tailing ponds needed to support mining and extraction, TRO can reduce the time to reclamation for a tailing pond from 40 years at present to 7-10 years, a company official says.

Suncor has applied to Alberta’s Energy Resources Conservation Board, Alberta Environment, and its board of directors for approval to use the technology.

It hopes to begin accelerating its use of TRO in 2010, the same year in which it will complete its first reclamation of a tailings pond.


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