Treatment of aqueous suspensions

Abstract

A process in which material comprising an aqueous liquid with dispersed particulate solids 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 material during transfer, by combining with the material an effective rigidifying amount of aqueous solution of a water-soluble polymer. The process is particularly suitable for the treatment of the tailings underflow resulting from a mineral processing operation and the co-disposal of fine and coarse tailings fractions. In addition, liquor released during the rigidification step is of high clarity.

1 . A process in which material comprising an aqueous liquid with dispersed particulate solids 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 material during transfer, by combining with the material an effective rigidifying amount of an aqueous solution of a water-soluble polymer.  
   
   
       2 . A process according to  claim 1  in which the water soluble polymer has an intrinsic viscosity of at least 3 dl/g and is formed from ethylenically unsaturated water-soluble monomer or blend of monomers.  
   
   
       3 . A process according to  claim 1  in which the water soluble polymer is anionic.  
   
   
       4 . A process according to  claim 3  in which the 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.  
   
   
       5 . A process according to  claim 1  in which the water soluble polymer is non-ionic.  
   
   
       6 . A process according to  claim 5  in which the polymer is formed from monomer(s) selected from the group consisting of (meth)acrylamide, hydroxy alkyl esters of (meth)acrylic acid and N-vinyl pyrrolidone.  
   
   
       7 . A process according to  claim 1  in which the water soluble polymer is cationic.  
   
   
       8 . A process according to  claim 7  in which the polymer is formed from monomer(s) selected from the group consisting of dimethyl amino ethyl(meth)acrylate-methyl chloride, (DMAEA.MeCl) quat, diallyl dimethyl ammonium chloride (DADMAC), trimethyl amino propyl(meth)acrylamide chloride (ATPAC) 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.  
   
   
       9 . A process according to  claim 1  in which the dispersed particulate solids are mineral.  
   
   
       10 . A process according to  claim 1  in which the process comprises the disposal of mineral slurry residues from a mineral processing operation.  
   
   
       11 . A process according to  claim 1 , in which the material is derived from the tailings from a mineral sands process.  
   
   
       12 . A process according to  claim 1  in which the dispersed particulate solids have particle sizes less than 100 microns, in which at least 80% of the particles have sizes less than 25 microns.  
   
   
       13 . A process according to  claim 1  in which the dispersed particulate solids has a bimodal distribution of particle sizes comprising a fine fraction and a coarse fraction, in which the fine fraction peak is substantially less than 25 microns and the coarse fraction peak is substantially greater than 75 microns.  
   
   
       14 . A process according to 1 in which the material has a solids content in the range 15% to 80% by weight by weight.  
   
   
       15 . A process according to  claim 1  comprising flocculating an aqueous suspension of solids in a vessel to form a supernatant layer comprising an aqueous liquor and an underflow layer comprising thickened solids forming the material, separating the supernatant layer from the underflow, wherein the underflow containing the particulate material flows from the vessel and, in which the material is then pumped to a deposition area where it is allowed to stand and rigidify, and wherein the effective rigidifying amount of the aqueous solution of the water-soluble polymer is mixed with the material after flocculating the suspension and before the material is allowed to stand.  
   
   
       16 . A process according to  claim 15  in which wet or dry coarse particles are added to the underflow from the vessel either before or during the addition of an effective rigidifying amount of the water soluble polymer.  
   
   
       17 . A process according to  claim 15  in which the material is transferred to a holding vessel prior to being pumped to the deposition area.  
   
   
       18 . A process according to  claim 1  in which the material is pumped to an outlet, where it is allowed to flow over the surface of previously rigidified material, wherein the material is allowed to stand and rigidify to form a stack.  
   
   
       19 . A process according to  claim 1  in which the effective rigidifying amount of the aqueous solution of the water-soluble polymer is mixed with the material prior to a pumping stage.  
   
   
       20 . A process according to  claim 1  in which the effective rigidifying amount of the aqueous solution of the water-soluble polymer is mixed with the material during or subsequent to a pumping stage.  
   
   
       21 . A process according to  claim 1  in which the effective rigidifying amount of the aqueous solution of the water-soluble polymer is mixed with the material as it exits the outlet.  
   
   
       22 . A process according to  claim 1  in which the material is dewatered during rigidification, releasing liquor.  
   
   
       23 . A process according to  claim 22  in which the liquor is recycled to a mineral processing operation.  
   
   
       24 . A process according to  claim 22  in which the clarity of the liquor is improved by the addition of an aqueous solution of water-soluble polymer.  
   
   
       25 . A process according to  claim 22  in which the liquor contains dissolved valuable materials and, in which the liquor is subjected to further processing to reclaim or re-use the valuable materials.  
   
   
       26 . A process in which material comprising an aqueous liquid with dispersed particulate solids is transferred as a fluid to a settling area, then allowed to dewater to release liquor, and in which dewatering is improved whilst retaining the fluidity of the material during transfer, by combining with the material an effective dewatering amount of aqueous solution of a water-soluble polymer.  
   
   
       27 . A process according to  claim 26  comprising flocculating an aqueous suspension of solids in a vessel to form a supernatant layer comprising an aqueous liquor and an underflow layer comprising thickened solids forming the material, separating the supernatant layer from the underflow, wherein the underflow containing the material flows from the vessel and in which the material is then pumped to a settling area where it is allowed to dewater, and wherein the effective dewatering amount of the aqueous solution of the water-soluble polymer is mixed with the material after flocculating the suspension and before the material is allowed to dewater.  
   
   
       28 . A process according to  claim 26  in which wet or dry coarse particles are added to the underflow from the vessel either before or during the addition of an effective dewatering amount of the water soluble polymer.  
   
   
       29 . A process according to  claim 26  in which the liquor is recycled to a mineral processing operation.  
   
   
       30 . A process according to  claim 26  in which the clarity of the liquor is improved by the addition of aqueous solution of water-soluble polymer.  
   
   
       31 . A process according to  claim 26  in which the liquor contains dissolved valuable materials and in which the liquor is subjected to further processing to reclaim the or reuse the valuable materials.