Treatment of oil sands tailings with lime at elevated pH levels

A method for dewatering oil sands tailings comprising:

• providing an oil sands tailings stream including clay, bicarbonates, and 10-55% solids by weight;
• increasing the pH of the tailings stream by combining the tailings stream with lime to produce a lime-tailings mixture having (i) a pH of at least 12.0, (ii) substantially no bicarbonates, and (iii) soluble calcium cations to chemically modify the clay via pozzolanic reactions, the lime having a concentration of at least 3,000 ppm;
• and
• dewatering the lime-tailings mixture to produce a first stream having 10% or less solids by weight and a second stream having 50% or more solids by weight.

A method for treating oil sands tailings, the method comprising:

• providing an oil sands tailings stream having clay, bicarbonates, and 10-55% solids by weight;
• adding lime having a concentration of at least 3,000 ppm to the tailings stream to produce a lime-tailings mixture having (i) a pH of at least about 12.0, (ii) substantially zero bicarbonates, and (iii) soluble calcium cations to chemically modify the clay via pozzolanic reactions;
• and
• dewatering the lime-tailings mixture to produce a first stream having 10% or less solids by weight and a second stream having 50% or more solids by weight.