Flocculation and dewatering of oil sands tailings with hyperbranched functional polyolefins

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The oil sands reserves in Alberta are a major Canadian natural resource. They are the third largest source of crude oil in the world, only surpassed by those of Saudi Arabia and Venezuela. Unfortunately, Canadians pay a high environmental price to use this valuable natural resource. The extraction process adopted by the oil sands industry produces about 1.5 barrels of fluid fine tailings for every barrel of bitumen processed. Tailings are a mixture of water, sand, clays, and residual bitumen. The tailings are transferred to ponds where the sand settles fast, but the fine clays remain suspended for a long time before significant settling takes place. After many years, a stable suspension containing about 30 wt% of fine clays, called mature fine tailings, is formed. Mature fine tailings have the consistency of yogurt. It is not possible to walk or drive on top of these ponds. Consequently, the area they occupy becomes a wasteland that cannot be recovered. It has been estimated that the accumulated volume of mature fine tailings will exceed one billion cubic meters by 2020. The continuing collection of tailings has created a severe environmental problem in Alberta because the current treatment technologies cannot significantly reduce the volumes of legacy and fresh tailings.