Method for extracting bitumen from an oil sand stream

1. A method for extracting bitumen from an oil sand stream, the method comprising the steps of:

(a) providing an oil sand stream;

(b) contacting the oil sand stream with a liquid, the liquid comprising a solvent comprising an aliphatic hydrocarbon having from 3 to 9 carbon atoms per molecule thereby obtaining a solvent-diluted oil sand slurry wherein at least about 90 percent by weight of asphaltenes in the oil sand stream remain dissolved;

(c) separating the solvent-diluted oil sand slurry, thereby obtaining a first solids-depleted stream and a first solids-enriched stream;

(d) filtering the first solids-enriched stream obtained in step (c), thereby obtaining bitumen-depleted sand and at least a first filtrate, and a second filtrate, and the second filtrate is at least partly reused in the contacting of step (b);

(e) increasing a S/B weight ratio of at least a part of the first filtrate by combining it with a stream having a higher S/B weight ratio thereby obtaining a combined stream wherein at least some asphaltenes are caused to precipitate from the combined stream; and

(f) separating the combined stream, thereby obtaining a second solids-depleted stream and a second solids-enriched stream wherein the second solids-depleted stream comprises less than two percent by weight of solids.

2. The method of claim 1 , wherein the solvent in step (b) comprises less than one percent by weight aromatics.

3. The method of claim 2 , wherein the aliphatic hydrocarbon has from 4 to 7 carbons per molecule.

4. The method of claim 1 wherein the solvent-diluted oil sand slurry obtained in step (b) has a solvent-to-bitumen (S/B) weight ratio of from 0.5 to 1.5.

5. The method of claim 4 wherein the solvent-diluted oil sand slurry obtained in step (b) has a solvent-to-bitumen (S/B) weight ratio of from 0.6 to 1.3.

6. The method of claim 5 wherein the solvent-diluted oil sand slurry obtained in step (b) has a solvent-to-bitumen (S/B) weight ratio of from 0.7 to 1.1.

7. The method of claim 1 wherein the solvent-diluted oil sand slurry obtained in step (b) comprises from 10 to 60 volume percent of solids.

8. The method of claim 7 wherein the solvent-diluted oil sand slurry obtained in step (b) comprises from 20 to 40 volume percent of solids.

9. The method of claim 1 wherein the first solids-enriched stream obtained in step (c) comprises from 30 to 70 volume percent of solids.

10. The method of claim 9 wherein the first solids-enriched stream obtained in step (c) comprises above 40 volume percent of solids.

11. The method of claim 1 wherein at least a part of the first solids-depleted stream is reused in the contacting of step (b).

12. The method of claim 1 wherein the first filtrate has a S/B weight ratio of from 0.5 to 1.5.

13. The method of claim 12 wherein the first filtrate has a S/B weight ratio of from 0.7 to 1.1.

14. The method of claim 1 wherein the first filtrate comprises at most 5.0 wt. % of solids, based on the bitumen content in the first filtrate.

15. The method of claim 1 wherein a part of the first filtrate is reused in the contacting of step (b).

16. The method of claim 1 , wherein the second filtrate has a S/B weight ratio of above 3.0.

17. The method of claim 1 wherein in step (e) at least a part of the first filtrate is combined with at least a part of the second filtrate.

18. The method of claim 1 wherein the combined stream in step (e) has an S/B weight ratio of at least 1.1.

19. The method of claim 1 wherein the second solids-enriched stream obtained in step (f) is reused in the filtering of step (d).

20. The method of claim 1 wherein the oil sand is an Athabasca oil sand.

21. The method of claim 1 wherein the solids-depleted stream comprises about 0.04 percent by weight ash.