Bitumen extraction process
View Patent ↗A process for the extraction and recovery of bitumen from oil sands and a process for the treatment of tailings are disclosed. Bitumen is recovered in a process comprising contacting a polysilicate microgel with an ore sand oil to produce a froth comprising bitumen and a tailings stream comprising water, sand and clay fines. Preferably the tailings stream is dewatered and recovered water may be recycled to the extraction process. Polysilicate microgel may be carried through to a dewatering step and enhances flocculation in dewatering said tailings.
1. A process for extracting bitumen from an oil sands ore which comprises (a) providing an aqueous slurry of an oil sands ore and (b) contacting the slurry with a polysilicate microgel to extract bitumen from the ore to produce i) a froth comprising bitumen and ii) an un-flocculated aqueous tailings stream comprising sand and clay fines.
2. A process according to claim 1 further comprising (c) dewatering the aqueous tailings stream.
3. A process of claim 1 or 2 further comprising adding caustic in step (b) and prior to step (c).
4. A process of claim 2 further comprising adding a anionic polyacrylamide and one or both of (i) a multivalent metal compound and (ii) a low molecular weight cationic organic polymer after step (b) and before step (c) to flocculate the aqueous tailings stream.
5. A process of claim 1 wherein air is added during the contacting step (b).
6. A process according to claim 1 wherein the temperature in step (b) is 25 to 90° C.
7. A process according to claim 1 wherein the temperature in step (b) is 35 to 85° C.
8. A process according to claim 1 wherein the temperature in step (b) is 35 to 50° C.
9. A process according to claim 1 wherein the aqueous slurry is prepared by contacting an oil sands ore with water in an amount of 10% to 500%, based on the mass of the ore.
10. A process according to claim 9 wherein the aqueous slurry is prepared by contacting an oil sands ore with water in an amount of 50% to 200%, based on the mass of the ore.
11. A process according to claim 1 further comprising, after step (b) a step (d) permitting separation of the aqueous tailings stream into a middlings and a coarse tailings.
12. A process according to claim 11 further comprising removing the froth from the un-flocculated aqueous tailings and contacting the froth with solvent to extract bitumen from the froth and to produce a froth treatment tailings.
13. A process according to claim 12 wherein the solvent is selected from the group consisting of paraffinic C 5 to C 8 n-alkanes, and naphthenic solvents.
14. A process according to claim 11 further comprising contacting the middlings with air to produce a second froth, a second middlings and a fine tailings, and permitting separation of the second froth and the fine tailings.
15. A process according to claim 14 further comprising contacting the second middlings with air to produce a third froth and a second fine tailings.
16. A process according to claim 1 wherein the polysilicate microgel is a polyaluminosilicate microgel.
17. A process according to claim 2 wherein the oil sands ores comprise one or more of the following properties: (a) levels of clay fines of greater than 15%; (b) montmorillonite clay in an amount greater than 1 wt % of the total weight of the oil sands ore, (c) greater than 10 ppm of calcium, magnesium; and (d) ores less than 25 meters from the earth's surface that have been subject to oxidation; or a combination of two or more thereof in the oil sands ore.
18. A process of claim 1 wherein the aqueous tailings stream comprises 1) a middlings stream of unrecovered bitumen and clay fines; and 2) a coarse tailings stream comprising sand and clay fines.
19. A process according to claim 1 wherein step (c) comprises dewatering the middlings and coarse tailings separately further comprising, after step (b) and before step (c), step (d) permitting separation of the aqueous tailings stream into a middlings and a coarse tailings.
20. A process according to claim 19 further comprising removing the froth from the un-flocculated aqueous tailings and contacting the froth with solvent to extract bitumen from the froth and to produce a froth treatment tailings.
21. A process according to claim 20 wherein the solvent is selected from the group consisting of paraffinic C 5 to C 8 n-alkanes, and naphthenic solvents.
22. A process according to claim 21 further comprising contacting the second middlings with air to produce a third froth and a second fine tailings.
23. A process according to claim 22 further comprising contacting the second middlings with air to produce a third froth and a second fine tailings.