CONTROLLING THE RHEOLOGY OF A METAL ORE RESIDUE

Abstract

A method can prepare an aqueous mineral suspension from an aqueous metal ore residue into which there is introduced a polymer (P) having a molecular weight Mw measured by GPC of from 100,000 to 3.106 g/mol and prepared by free radical polymerization of at least one anionic monomer (m). The suspension produced may have a Brookfield viscosity greater than 2,000 mPa.Math.s and/or a flow threshold of greater than 40 Pa.

Claims

1. A method for preparing: the method comprising: adding, in an aqueous metal ore residue, a first component comprising a polymer (P) with a molecular mass Mw, measured by GPC, in a range of from 100,000 to 3.Math.10.sup.6 g/mol and prepared by a method comprising radical polymerization at a temperature greater than 50° C., the polymer (P) comprising: a polymer (P1) prepared in direct emulsion from reagents comprising (a) an anionic monomer comprising a polymerizable olefinic unsaturation and a carboxylic acid group; and (b) an ester of acrylic acid and/or methacrylic acid, in the presence of a radical-generating compound comprising ammonium persulfate and/or, an alkaline metal persulfate and optionally further an —Fe.sup.II, Fe.sup.III, Cu.sup.I, and/or Cu.sup.II ion; and/or a polymer (P2) prepared in reverse emulsion from reagents comprising (a) an anionic monomer comprising a polymerizable olefinic unsaturation and a carboxylic acid group, optionally as a salt; and (c) acrylamide, an acrylamide derivative, and/or a salt of an acrylamide derivative, in the presence of a radical-generating compound comprising ammonium persulfate and/or an alkaline metal persulfate and optionally further an comprising Fe.sup.II, Fe.sup.III, Cu.sup.I, and/or Cu.sup.II ion, wherein the aqueous mineral suspension produced has (i) a dry solids content greater than 40 wt. % of the suspension and (ii-a) a Brookfield viscosity, measured at 100 rpm and at 25° C., greater than 2,000 mPa.Math.s; (ii-b) a flow threshold measured at a temperature of 25° C. using a rheometer with imposed shearing, equipped with a bladed spindle, for a particular torsional loading, greater than 40 Pa, and/or (ii-c) a Brookfield viscosity, measured at 100 rpm and at 25° C., greater than 2,000 mPa.Math.s and a flow threshold, measured at a temperature of 25° C. using a rheometer with imposed shearing, equipped with a bladed spindle, for a particular torsional loading, greater than 40 Pa.

2. The method of claim 1, wherein the suspension has: a viscosity greater than 2,500 mPa.Math.s, a viscosity of less than 10,000 mPa.Math.s

3. The method of claim 1, wherein the suspension has: a flow threshold greater than 80 Pa; or a flow threshold of less than 700 Pa.

4. The method of claim 1, wherein the suspension has a dry solids content greater than 50 wt. %.

5. The method of claim 1, wherein the suspension comprises from 0.01 to 2 wt. % of the polymer (P) (dry/dry relative to the ore residue).

6. The method of claim 1, comprising: adding two different polymers (P) or further adding compound comprising a natural thickening polymer derivative, synthetic thickening polymer derivative, mineral thickening polymer derivative, organic thickening polymer derivative, a mineral thickener and/or a polysaccharide.

7. The method of claim 1, wherein the metal ore comprises lithium, strontium, lanthanide, actinide, uranium, rare earth, titanium, zirconium, vanadium, niobium, chromium, molybdenum, tungsten, manganese, iron, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, tin, and/or lead ore, or wherein the metal ore comprises a metal oxide, a metal sulfide, or a metal carbonate; or wherein the metal ore residue comprises a residual amount of metal of less than 2,000 g per tonne (dry/dry) relative to the amount of metal ore residue.

8. The method of claim 1, wherein the polymer (P) is added: before pumping the aqueous metal ore residue; or during pumping the aqueous metal ore residue; or after pumping the aqueous metal ore residue; or after concentrating the aqueous metal ore residue; or before conveying the aqueous metal ore residue; or before storing the aqueous metal ore residue; or during storing the aqueous metal ore residue.

9. The method of claim 1, wherein the polymerization is carried out at a temperature in a range of from 50 to 98° C.; or wherein the polymer (P1) is prepared in water, alone or in combination with an organic solvent; or wherein the polymer (P2) is prepared without solvent or in an organic solvent; or wherein the polymer (P) has a molecular mass Mw, measured by GPC, in a range of from 200,000 g/mol to 2.5.Math.10.sup.6 g/mol; or wherein the polymer (P2) is completely or partially neutralized.

10. The method of claim 1, wherein the anionic monomer comprises a polymerizable olefinic unsaturation and has one or two carboxylic acid groups.

11. The method of claim 1, wherein the polymerization further comprises polymerizing another monomer comprising: (d) 2 acrylamido-2-methylpropane sulfonic acid, 2-sulphoethyl methacrylate, sodium methallyl sulfonate, and/or styrene sulfonate, optionally as a salt, or (e) a compound of formula (I):
R.sup.1—(CH.sub.2CH.sub.2O).sub.m—(PO).sub.n—R.sup.2  (I) wherein m and n are independently 0 or an integer or decimal less than 150, and m or n is different from 0, PO is independently CH(CH.sub.3)CH.sub.2O or CH.sub.2CH(CH.sub.3)O, R.sup.1 is a group comprising a polymerizable olefinic unsaturation, R.sup.2 is a hydrocarbon group comprising 6 to 40 carbon atoms; or (f) a monomer comprising polyalkylene glycol acrylate, polyalkylene glycol methacrylate, allyl polyalkylene glycol, methallyl polyalkylene glycol , and/or 3 methyl-3-buten-1-ylpolyalkylene glycol; or (g) a cross-linking monomer or a monomer comprising a first and a second olefinic unsaturation.

12. An aqueous mineral suspension, comprising: an aqueous metal ore residue; and a polymer (P) with a molecular mass Mw, measured by GPC, ranging from 100,000 to 3.Math.10.sup.6 g/mol and prepared by a method comprising radical polymerization at a temperature greater than 50° C., and the polymer (P) comprising: polymer (P1) prepared in direct emulsion from reagents comprising an anionic monomer comprising a polymerizable olefinic unsaturation and a carboxylic acid group; and (b) ester of acrylic acid and/or methacrylic acid, in the presence of a radical-generating compound comprising ammonium persulfate and/or alkaline metal persulfate and optionally further an Fe.sup.II, Fe.sup.III, Cu.sup.I, and/or Cu.sup.II ion; a polymer (P2) prepared in reverse emulsion from comprising (a) an anionic monomer comprising a polymerizable olefinic unsaturation and a carboxylic acid group, optionally as a salt; and (c) acrylamide, an acrylamide derivative, and/or a salt of an acrylamide derivative; in the presence of a radical-generating compound comprising ammonium persulfate and/or alkaline metal persulfate and optionally further an Fe.sup.II, Fe.sup.III, Cu.sup.I, and/or Cu.sup.II ion, wherein the aqueous mineral suspension, has (i) a dry solids content greater than 40 wt. % of the suspension and: (ii-a) a Brookfield viscosity, measured at 100 rpm and at 25° C., greater than 2,000 mPa.Math.s; (ii-b) a flow threshold measured at a temperature of 25° C. using a rheometer with imposed shearing, equipped with a bladed spindle, for a particular torsional loading, greater than 40 Pa; and (ii-c) a Brookfield viscosity, measured at 100 rpm and at 25° C., greater than 2,000 mPa.Math.s and a flow threshold, measured at a temperature of 25° C. using a rheometer with imposed shearing, equipped with a bladed spindle, for a particular torsional loading, greater than 40 Pa.

13. The method of claim 1, wherein the suspension has a viscosity in a range of from 2,500 mPa.Math.s to 10,000 mPa.Math.s.

14. The method of claim 13, wherein the suspension has a viscosity in a range of greater than 3,000 mPa.Math.s.

15. The method of claim 13, wherein the suspension has a viscosity in a range of greater than 4,000 mPa.Math.s.

16. The method of claim 13, wherein the suspension has a viscosity in a range of at less than 8,000 mPa.Math.s.

17. The method of claim 13, wherein the suspension has a viscosity in a range of at less than 7,000 mPa.Math.s.

18. The method of claim 1, further comprising: adding a second component comprising an alginate, guar gum, xanthan gum, cellulose derivative, starch, bentonite, laponite, and/or clay.

Description

[0146] The particular, advantageous or preferred characteristics of the method according to the invention define suspensions according to the invention which are also particular, advantageous or preferred.

[0147] The following examples illustrate the various aspects of the invention.

[0148] The polymers used in the method according to the invention are prepared.

[0149] Polymer (P1A) is prepared by placing 420 g of deionised water and 2.15 g of sodium dodecyl sulphate into a one-litre glass reactor with mechanical stirring and oil bath heating.

[0150] In a 600 mL beaker with a dosing pump and magnetic stirring, a pre-emulsion is prepared comprising: [0151] 205 g of deionised water, [0152] 1.85 g of sodium dodecyl sulphate, [0153] 164 g of ethyl acrylate, [0154] 132 g of methacrylic acid, [0155] 6 g of divinyl benzene, [0156] 4.8 g ethylene glycol dimethacrylate.

[0157] 0.26 g of ammonium persulphate dissolved in 5 mL of deionised water is weighed into a 10 mL beaker, as initiator 1.

[0158] 0.2 g of ammonium persulphate diluted in 20 g of water is weighed into a 20 mL test tube fitted with a dosing pump, as initiator 2.

[0159] The reactor is heated to 85° C. and initiator 1 is injected. Then, over 2.5 hours, the pre-emulsion is injected into the reactor which is kept at 85° C. Initiator 2 is injected in parallel into the reactor during the polymerisation step and concomitantly with the addition of the pre-emulsion

[0160] Heating is continued for 1 hour at 85° C. Then, the reaction medium is treated while warm for 30 minutes with a solution of 0.3 g of persulphate in 10 g of water.

[0161] Lastly, the pumps are rinsed with water.

[0162] The medium is heated again for 60 min at 80° C.

[0163] A polymer dispersion (P1A) is obtained with a molecular mass Mw, measured by GPC, of 2.10.sup.6 g/mol at 30% by weight of solids content and a pH of 2.8.

[0164] Polymer (P1B) is prepared by placing 420 g of deionised water and 4.1 g of sodium dodecyl sulphate into a one-litre glass reactor with mechanical stirring and oil bath heating.

[0165] In a 600 mL beaker with a dosing pump and magnetic stirring, a pre-emulsion is prepared comprising: [0166] 170 g of deionised water, [0167] 2 g of sodium dodecyl sulphate, [0168] 159 g of ethyl acrylate, [0169] 107 g of methacrylic acid, [0170] 19 g of 2-tetradecyl octadecanol methacrylate oxyethylated 25 times.

[0171] 0.9 g of ammonium persulphate dissolved in 5 mL of deionised water is weighed into a 10 mL beaker, as initiator 1.

[0172] 0.09 g of sodium metabisulphite in 5 g of water is weighed into a 20 mL test tube fitted with a dosing pump, as initiator 2.

[0173] The reactor is heated to 75° C. and initiator 1 and initiator 2 are injected. Then, over 2 hours, the pre-emulsion is injected into the reactor which is kept at 75° C.

[0174] Heating is continued for 1 hour at 85° C. Then, the reaction medium is treated while warm for 30 minutes with a solution of 0.3 g of persulphate in 10 g of water.

[0175] Lastly, the pumps are rinsed with water.

[0176] The medium is heated again for 60 min at 80° C.

[0177] A polymer dispersion (P1B) is obtained with a molecular mass Mw, measured by GPC, of 500,000 g/mol at 30% by weight of solids content and a pH of 3.0.

[0178] The raw material used for this series of tests is an aqueous metal ore residue from a Chilean copper mine located in the north of the country. This is waste resulting from the separation of the ore containing the useable metal from the rock extracted from the mine. This aqueous copper ore residue is in the form of a water-based suspension.

[0179] The samples used for these tests were collected at the outlet of a conventional thickener used to concentrate the aqueous metal ore residue before it is deposited in a storage pond. The first sample is taken just after a peristaltic pump, the second sample after a centrifugal pump.

[0180] Various measurements were taken beforehand on the aqueous residue in the absence of the polymer according to the invention: [0181] particle size distribution using a Mastersizer 2000 laser granulometer (Malvern), [0182] solid content using a Mettler-Toledo dry balance, [0183] Brookfield viscosity at 100 rpm using a Brookfield DV3T viscometer with a suitable spindle, [0184] flow limit value using a Brookfield DV3T viscosity meter with a bladed spindle.

[0185] The particle size distribution by volume shows the presence of multiple particle populations with different sizes: [0186] point (A) at the peristaltic pump outlet located after a conventional thickener in the copper ore residue processing facility: D(0.1)=1.2 μm, D(0.5)=22.1 μm, D(0.9)=139 μm, [0187] point (B) at the centrifugal pump outlet located after a conventional thickener in the copper ore residue processing facility: D(0.1)=1.1 μm, D(0.5)=22.3 μm, D(0.9)=147 μm.

[0188] The other characteristics of the polymer-free copper ore residue are shown in Table 1.

TABLE-US-00001 TABLE 1 Point (A) Point (B) % Solids content 62.8 60.4 pH 8.3 8.3 Conductivity in μS/cm 1,630 1,729 Brookfield viscosity at 100 rpm, in mPa .Math. s 925 560 Flow limit in Pa 25 13

[0189] Thickening tests are then performed on aqueous residue samples from points (A) and (B).

[0190] A sample of suspension of aqueous copper ore residue is transferred into a 500 mL beaker and then mechanically stirred with a Raynerie mixer. Stirring varies from 800 to 1,000 rpm.

[0191] Then polymers (P1A) or (P1B) according to the invention are added and left to stir for 5 to 10 min.

[0192] Stirring is then stopped to measure the Brookfield viscosity at 100 rpm and the flow limit value.

[0193] The test is repeated, adding different amounts of polymer of 0.05%, 0.1%, and 0.15% by dry/dry weight, relative to the suspension. The results are shown in Table 2.

TABLE-US-00002 TABLE 2 Point (A) Point (B) Dosing in % dry/dry - Polymer (P1A) (P1B) (P1A) (P1B) Brookfield viscosity at 100 rpm, in mPa .Math. s 0.05 1,256 1,090 600 650 0.1 1,460 1,470 880 830 0.15 2,050 1,970 1,100 1,250 Flow limit in Pa 0.05 27 39 23 19 0.1 42 53 37 35 0.15 85 70 54 48

[0194] Another series of tests is conducted on other samples of aqueous copper ore residue with solids contents of 50% and 61%. A similar protocol is implemented with polymer (P1A) and (P1B) at doses of 0.05% and of 0.1% by dry/dry weight.

[0195] The flow limits are measured immediately after adding polymers (P1A) or (P1B) (T0), then after one hour (T1), after two hours (T2), and finally after 24 hours (T24). The results are shown in Table 3.

TABLE-US-00003 TABLE 3 T0 T1 T2 T24 Polymer (P1A) (P1B) (P1A) (P1B) (P1A) (P1B) (P1A) (P1B) Flow limit in Pa at 61% solids content Point (A) - 14 22 22 26 23 43  96 136 0.05% Point (B) - 48 26 69 28 74 35 144 101 0.05% Point (A) - 51 42 51 54 66 82 156 142 0.01% Point (B) - 47 48 50 50 52 62 136 140 0.01% Flow limit in Pa at 50% solids content Point (A) -  9  9 22 16 30 38 126 116 0.1% Point (B) - 20 16 55 44 60 90 244 136 0.1%

[0196] In the absence of polymer, it was found that the aqueous suspensions of copper ore residue have low viscosities that disrupt their storage in ponds and can present uncontrolled flow hazards.

[0197] The addition of polymers (P1A) or (P1B) according to the invention makes it possible to significantly increase these viscosities as well as to control the flow threshold of these suspensions.

[0198] With the polymers according to the invention, it is therefore possible to thicken aqueous copper ore residues, in particular at a thickener outlet, while controlling their rheology.

[0199] These residues can then be stored more efficiently and safely in ponds, in particular by stacking up successive layers of thickened residue. Stacking residue up in successive layers with an appropriate slope makes it possible to increase the useful life of the storage ponds which usually have limited surface areas.