PROCESS WATER CHEMISTRY IN BITUMEN EXTRACTION FROM OIL SANDS

1 . A method of monitoring and maintaining process water chemistry in a bitumen extraction process including a primary extraction stage including at least one primary separation vessel, and a secondary extraction stage comprising at least one separator, comprising the steps of:

(a) adding a caustic sodium salt to a mixture of oil sands, solvent and water to create a slurry comprising process water having a pH of about 9.0 to about 9.5, and a molar ratio of sodium to calcium ions between about 100:1 to about 200:1;

(b) maintaining the process water pH and sodium to calcium ratio in the ranges described in step (a) through the primary extraction stage, the secondary extraction stage and before recycling for reuse, by measuring the process water chemistry and adding chemicals as needed.

2 . The method of claim 1 comprising the step of adding an acidifying agent or a calcium salt, or both, after the secondary extraction stage to maintain the process water pH and sodium to calcium ratio in the desired ranges.

3 . The method of claim 2 comprising the further step of recycling the process water to the primary extraction stage.

4 . The method of claim 1 wherein the molar ratio of sodium to calcium is maintained between about 125:1 to about 150:1.

5 . The method of claim 4 wherein the secondary extraction stage comprises an agitation step and a separation step, whereby diluted bitumen is recovered associated with fine solids from the separation step.

6 . A system for extracting bitumen from oil sands, comprising a primary extraction stage including at least one primary separation vessel; a secondary extraction stage comprising at least one separator; at least one caustic sodium salt addition point in the primary extraction stage; and at least one calcium or polyvalent cation addition point in the secondary extraction stage.