Tailings stream treatment processes
View Patent ↗A process for treating a tailings stream comprises (a) contacting (1) a gelling agent and (2) an activator with said tailings stream to produce a gel; (b) entrapping solids including sand and clay, and other solid particles with the gel; and (c) allowing the gel to strengthen and solidify to produce a trafficable deposit; wherein the tailings stream comprises water and solids, which solids comprise sand, clay and other solids particles, and wherein 5% by volume to 100% by volume of the solids have a particle size less than 0.05 mm, based on the total volume of the solids. The process may further comprises spreading the gel produced in step (a) or the trafficable deposit produced in step (c) over a surface. The present invention is particularly useful to treat tailings streams produced in processes to extract bitumen from oil sands ores.
1. A process for treating a tailings stream comprising (a) contacting (1) a gelling agent and (2) an activator with said tailings stream, wherein the tailings stream comprises water and solids, which solids comprise sand and clay, and wherein 5% by volume to 100% by volume of the solids have a particle size less than 0.05 mm, based on the total volume of the solids; (b) entrapping the solids within a gel; and (c) allowing the gel to strengthen and solidify to produce a trafficable deposit; wherein the gelling agent is selected from the group consisting of acrylamide, acrylate, urethane, phenoplast, aminoplast, vinyl ester-styrene, polyester-styrene, furfuryl alcohol-based furol polymer, epoxy, vulcanized oil, lignin, lignosulfonate, lignosulfite, montan wax, polyvinyl pyrrolidone, and combinations of two or more thereof.
2. A process according to claim 1 further comprising adding an accelerator in the contacting step (a).
3. A process according to claim 1 further comprising adding a reinforcing agent in the contacting step (a).
4. A process according to claim 3 further comprising spreading the gel produced in step (a) or the trafficable deposit produced in step (c) over a surface.
5. A process according to claim 4 wherein the surface is a sloped surface.
6. A process according to claim 1 further comprising depositing the gel produced in step (a) or the trafficable deposit produced in step (c) in a dewatering pit.
7. A process according to claim 1 wherein the tailings stream is produced in a process to extract bitumen from oil sands ores.
8. A process according to claim 1 wherein step (c) comprises a dewatering step.
9. A process according to claim 8 wherein dewatering occurs by air drying (evaporation), water run off, compression, syneresis, exudation, freeze/thaw, sublimation or combination thereof.
10. A process according to claim 9 wherein dewatering occurs by evaporation.
11. A process according to claim 9 wherein drying occurs by water run off.
12. A process according to claim 10 wherein the water run off is recovered and recycled.
13. A process according to claim 1 wherein the gelling agent is selected from the group consisting of acrylamides, acrylates, urethanes, and combinations of two or more thereof.
14. A process according to claim 1 wherein the gelling agent is an acrylamide and the activator is an inorganic peroxide.
15. A process according to claim 1 wherein the gelling agent is an acrylate and the activator is sodium thiosulfate or potassium persulfate in triethanolamine.
16. A process according to claim 2 wherein the accelerator is a multivalent metal compound or an oxidizer.
17. A process according to claim 16 wherein the accelerator is selected from the group consisting of calcium chloride, calcium sulfate, calcium hydroxide, aluminum sulfate, magnesium sulfate, and aluminum chloride, polyaluminum chloride, polyaluminum sulfate, and aluminum chlorohydrate.
18. A process according to claim 16 wherein the accelerator is sodium persulfate or potassium persulfate.
19. A process according to claim 2 wherein the accelerator is nitrilotrispropionamide (NTP), β-dimethylaminopropionamide (DAP), diethylaminopropionamide (REAPN), or dimethylaminopropionamide (DMAPN).
20. A process according to claim 3 wherein the reinforcing agent is selected from the group consisting of gravel, sand from mining operations, waste rock from mining operations; petroleum coke, coal particles; elemental crystalline sulfur; inorganic fibers; organic fibers, and combinations of two or more thereof.
21. A process according to claim 20 wherein the reinforcing agent is treated with a surface-active agent.
22. A process according to claim 20 wherein the reinforcing agent is organic fibers.
23. A process according to claim 1 wherein the gelling agent is added in an amount equal to 0.01 to 25,000 kg/tonne of solids in the tailings stream and the activator is added in an amount equal to 0.01 to 25% by weight, based on the weight of the gelling agent.
24. A process according to claim 23 wherein the gelling agent is added in an amount equal to 0.1 to 10 kg/tonne of solids in the tailings stream and the activator is added in an amount equal to 0.01 to 10% by weight, based on the weight of the gelling agent.
25. A process according to claim 2 further comprising adding a reinforcing agent in the contacting step (a), wherein the accelerator is added in an amount equal to 0.01 to 10% by weight, based on the weight of the gelling agent and the reinforcing agent is added in an amount equal to 0.01 to 700 kg/tonne of solids in the tailings stream.
26. A process according to claim 1 wherein the tailings stream further comprises polysilicate microgels, polyacrylamides, or combinations thereof.