Treatment of aqueous suspensions
View Patent ↗A process in which a suspension comprising dispersed particulate material in an aqueous medium is transferred as a fluid to a deposition area, then allowed to stand and rigidify, and in which rigidification is improved whilst retaining the fluidity of the suspension during transfer, by combining with the suspension during transfer a rigidifying amount of a treatment system which comprises i) a water-soluble synthetic polymer and ii) a water-soluble natural or seminatural polymer. Improved rigidification can be achieved, including dose efficiency especially in regard to the amount of synthetic polymer required. In addition improvements in the clarity of liquor released from the suspension can be achieved.
1. A process in which a mineral suspension comprising dispersed particulate material in an aqueous medium is transferred as an underflow from a thickener to a deposition area, then allowed to stand and rigidify, and in which rigidification releases aqueous liquor and is improved whilst retaining the fluidity of the suspension during transfer, by combining with the suspension during transfer a rigidifying amount of a treatment system which comprises
i) a water-soluble synthetic polymer and
ii) a water-soluble natural or seminatural polymer wherein the water soluble synthetic polymer is either anionic or non-ionic, has an intrinsic viscosity of at least 3 dl/g, and is formed from an ethylenically unsaturated water-soluble monomer or blend of monomers, wherein the synthetic polymer is formed from monomer(s) selected from the group consisting of (meth)acrylic acid, allyl sulphonic acid and 2-acrylamido-2-methyl propane sulphonic acid as the free acids or salts thereof, optionally in combination with non-ionic co-monomers, selected from the group consisting of (meth)acrylamide, hydroxy alkyl esters of (meth)acrylic acid and N-vinyl pyrrolidone, and wherein the synthetic polymer and natural or seminatural polymer are each combined with the suspension at a dose of 10 grams to 10,000 grams per tonne of material solids.
2. A process according to claim 1 in which the natural or seminatural polymer is based on cellulose.
3. A process according to claim 1 in which the suspension of particulate material is a waste material from a mineral processing operation.
4. A process according to claim 1 in which the suspension of particulate material is derived from mineral processing operations and is selected from the group consisting of red mud from a Bayer alumina process, tailings from the extraction of base metals, tailings from the extraction of precious metals, tailings from the extraction of iron, tailings from the extraction of nickel, coal tailings, mineral and oil sands and coal fines.
5. A process according to claim 1 in which the particulate material is hydrophilic in nature.
6. A process according to claim 1 in which the suspension of particulate material is transferred along a conduit and through an outlet to the deposition area.
7. A process according to claim 1 in which the suspension of particulate material that has been transferred to the deposition area releases aqueous liquor upon standing.
8. A process according to claim 1 in which the suspension of particulate material upon reaching the deposition area flows over the surface of previously rigidified material, wherein the material is allowed to stand and rigidify to form a stack.
9. A process according to claim 1 in which the suspension of particulate material is transferred by pumping it through a conduit and the polymer is added subsequently to the pumping stage.
10. A process according to claim 1 in which the suspension of particulate material is transferred by pumping it through a conduit and polymer is added during or prior to the pumping stage.
11. A process according to claim 1 in which the suspension of particulate material is transferred through a conduit having an outlet wherein the polymer is added to the suspension as it exits the outlet.
12. A process according to claim 1 in which the suspension of particulate mineral material is transferred through a conduit having an outlet wherein the polymer is added to the suspension before it exits the outlet.
13. A process according to claim 1 in which the synthetic polymer and natural or seminatural polymer are added in aqueous solution.
14. A process according to claim 1 in which the synthetic polymer and natural or seminatural polymer are added in the form of particles.