EP3801811A2

EP3801811A2 - Method for controlling the sedimentation of a mining derivative

Info

Publication number: EP3801811A2
Application number: EP19737157.8A
Authority: EP
Inventors: Mehdi Bouzid; Benoît MAGNY; Jacques Mongoin
Original assignee: Coatex SAS
Current assignee: Coatex SAS
Priority date: 2018-06-08
Filing date: 2019-06-05
Publication date: 2021-04-14
Also published as: MX2020012448A; ZA202007711B; WO2019234315A2; CN112272583B; CL2020003159A1; PE20210079A1; CN112272583A; FR3082124B1; BR112020023480A2; CA3102186A1; AU2019282374A1; CO2020014705A2; US20210170309A1; MA52769A; FR3082124A1; AU2019282374B2; WO2019234315A3

Abstract

The invention relates to a method for controlling the sedimentation of an aqueous mineral suspension of a mining derivative by means of the gravimetric concentration of the aqueous suspension in the presence of a flocculating agent and a polymer (P) which has a GPC-measured molecular mass Mw of between 2000 and 20000 g/mol and is prepared using at least one free radical polymerisation reaction of at least one anionic monomer (M). The invention also relates to the resulting suspension, which has a Brookfield viscosity of less than 1 800 mPa.s or a yield point of less than 80 Pa.

Description

CONTROLLING THE SEDIMENTATION OF A MINING DERIVATIVE

DESCRIPTION

The invention relates to a method for controlling the sedimentation of an aqueous mineral suspension of a mining derivative by gravimetric concentration of the aqueous suspension in the presence of a flocculation agent and a polymer (P) of molecular weight Mw measured by GPC ranging from 2,000 to 20,000 g / mol prepared by at least one radical polymerization reaction of at least one anionic monomer (M).

The invention also relates to the suspension produced whose Brookfield viscosity is less than 1800 mPa.s or the flow threshold is less than 80 Pa.

The method according to the invention is implemented during a mining process for mining at least one mining deposit. These mining processes generally make it possible to obtain at least one metal to be valorized from a metallic ore. The metallic ore also includes a residue of this metallic ore. Mining processes are usually carried out using water as a carrier for the treatment or transport of solids. The mining derivative is therefore usually an aqueous mining derivative.

According to the invention, the fraction of the metal ore to be upgraded is a metal or several metals or a derivative of a metal or a derivative of several metals.

According to the invention, the aqueous metal ore residue thus results from at least one step of separating the metal to be upgraded or a derivative of the metal to be valorized from a metal ore, in particular from a metal ore produced by mineral extraction. During the implementation of the method according to the invention, an essential step consists in adding at least one polymer (P) in an aqueous mining derivative. This step therefore concerns the treatment of a mining derivative. It can also concern the treatment of the metallic ore which is to be valorized. This step is therefore generally implemented in a mining process comprising different stages of treatment of the metal ore, metal or metal derivative for recovery or treatment of the metal ore residue.

Typically, the mining processes comprise several stages of treatment of the metallic ore, several stages of treatment of the metal to be valorized or treatment of the metal derivative to be valorized as well as several stages of treatment of the metal ore residue. In a conventional manner, a mining process comprises one or more of the following steps:

crushing metal ore,

- grinding of metallic ore, especially dry grinding or wet grinding, generally in water,

separation, in particular by flotation, of the metal to be valorised or of a derivative of the metal to be valorised and the metal ore residue, in particular the residue in aqueous form,

purification or enrichment of the metal to be valorized or of a derivative of the metal to be valorised, in particular by flotation,

concentration of the residue of metal ore or of the metal to be valorised or of a derivative of the metal to be valorised, for example by filtration, by sedimentation, by gravity, by use of a thickener, by flocculation,

partial separation of the aqueous residue of metallic ore and a portion of the water,

- transporting the metallic ore, the aqueous metal ore residue or the metal to be valorized or a derivative of the metal to be valorized,

storing the metal ore, the aqueous metal ore residue or the metal to be upgraded or a metal derivative to be upgraded.

If necessary, it is important to have effective methods that improve sedimentation or that do not lead to a decrease in sedimentation rate.

Methods are known for preparing an aqueous mineral suspension from an aqueous mining derivative, in particular such methods used during the treatment, transport or storage of such a derivative.

EP 2686275 discloses a method for controlling the rheology of an aqueous dispersion which comprises adding a natural polymer and then adding a synthetic polymer to the aqueous system.

EP 1976613 relates to the concentration of an aqueous suspension of solid particles by adding a flocculant organic polymer and an agent selected from the group consisting of radical agents, oxidizing agents, enzymes and radiation.

An article by Aixing Fan et al. (A study of dual polymer flocculation, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 162, 2000, 141-148) describes improving the flocculation of alumina particles with two different polymers. EP 2771289 also relates to the concentration of an aqueous suspension of solid particles by introduction of a flocculant organic polymer and the addition of an agent system comprising an oxidizing agent and a control agent.

The document WO 2014-019993 describes a method for concentrating an aqueous suspension of solid particles by adding a flocculant organic polymer and an active agent chosen from radical agents, oxidizing agents and reducing agents.

In order to make them manipulable, the known suspensions generally have a reduced concentration of solids. In fact, the addition of water can make it possible to lower the viscosity or the yield point of these suspensions.

However, the addition of water leads to problems of water consumption, energy consumption or even problems of organization and storage of aqueous waste metal ore. Generally, sedimentation is disturbed when water is added to an aqueous suspension of a mining derivative.

It is therefore important to have methods for controlling the sedimentation of an aqueous mineral suspension from an aqueous mining derivative having a high concentration of dry matter.

It is also important to have such methods which make it possible to prepare stable suspensions, especially at high concentrations of dry matter. Likewise, it is important to have such methods that make it possible to prepare stable suspensions whose particle size of the dry matter particles is relatively coarse or poorly homogeneous.

Compatibility with the various constituents of the aqueous mineral suspensions prepared from an aqueous mining derivative is also an important property to be investigated, in particular the compatibility with a flocculating agent that can be used to treat the aqueous mining derivative, especially the compatibility with a polyacrylamide or with a polyacrylamide derivative.

Likewise, the control of the viscosity of aqueous mineral suspensions prepared from a mining derivative is important, in particular for their pumping, to facilitate their agitation or for their transport.

Moreover, it is important to have methods that make it possible to control the threshold of flow of aqueous residue of metallic ore. In particular, it is important to provide a minimum flow threshold for an aqueous metal ore residue that eliminates or limits the risk of sedimentation of the solid portion of the residue in the absence of shear or in the presence of low shear. The reduction of water consumption during the treatment of aqueous mining derivatives must also be sought. The recovery or recycling of water during the various stages of the mining processes are also to be favored.

Both the amount of separated or recycled water and the quality of the separated or recycled water must be sought.

Also, it is important to be able to control the behavior of aqueous mineral suspensions prepared from an aqueous mining derivative in order to avoid problems within processing, storage or transport facilities. Indeed, these facilities can be damaged, blocked or clogged in the event of drift or lack of control of the viscosity, the flow threshold or sedimentation of an aqueous mineral suspension prepared from an aqueous mining derivative.

There is therefore a need for improved methods for controlling the sedimentation of an aqueous mineral suspension from an aqueous mining derivative.

The method according to the invention makes it possible to provide a solution to all or part of the problems of the methods for controlling the sedimentation of an aqueous mineral suspension from an aqueous mining derivative of the state of the art.

Thus, the invention provides a method for controlling the sedimentation of an aqueous mineral suspension comprising at least one flocculation agent and whose solids content is greater than 10% by weight of the suspension, chosen from:

an aqueous residue of metallic ore,

an aqueous suspension of metal ore and

an aqueous suspension of a metal to be valorized or a metal derivative to be valorized and derived from a metallic ore,

comprising the gravimetric concentration of the aqueous suspension in the presence of at least one polymer (P) of molecular weight Mw measured by GPC ranging from 2,000 to 20,000 g / mol and prepared by at least one radical polymerization reaction, at a concentration of at a temperature above 50 ° C, at least one anionic monomer (M) comprising at least one polymerizable olefinic unsaturation and at least one carboxylic acid function or a salt thereof, in the presence of at least one radical generating compound selected from hydrogen peroxide, benzoyl peroxide, acetyl peroxide, lauryl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ammonium persulfate, an alkali metal persulfate, preferably sodium persulfate or potassium persulfate, an azo compound, such as 2,2'-azobis (2- (4,5-dihydroimidazolyl) propane, 2,2'-azobis (2-methylpropionamidine) dihydrochloride, diazo-valero-nitrile, acid 4,4'-azobis (4-cyanovaleric), AZDN or 2,2'-azo-bis-isobutyronitrile and combinations thereof or combinations thereof with an ion selected from Fe ¹¹ , Fe ^m , Cu ¹ , Cu ¹¹ and their mixtures.

The method according to the invention makes it possible to control the sedimentation of an aqueous mineral suspension whose solids concentration is greater than 10% by weight of the suspension, the rheology of the suspension prepared for a solids concentration is greater than 10 % by weight or greater than 15% by weight of the suspension.

Preferably, the suspension prepared according to the method according to the invention has a solids concentration of less than 20% by weight or less than 30% by weight or even less than 35% by weight or even less than 40% by weight. or 50% by weight.

Also preferably, the suspension prepared according to the method according to the invention has a dry matter concentration ranging from 10 to 50% by weight or from 10 to 40% by weight or from 10 to 35% by weight or from 10 to 30% by weight. % by weight or 10 to 20% by weight or alternatively from 15 to 50% by weight or from 15 to 40% by weight or from 15 to 35% by weight or from 15 to 30% by weight or from 15 to 20% by weight % by weight, or alternatively from 20 to 50% by weight or from 20 to 40% by weight or from 20 to 35% by weight or from 20 to 30% by weight.

The method according to the invention comprises the gravimetric concentration of the aqueous suspension. Preferably, this gravimetric concentration of the aqueous suspension comprises the separation of a supernatant phase and a sediment bed.

According to the invention, these two phases constituting these two fractions of the aqueous suspension differ essentially by their difference in concentration of dry matter.

Such a difference leads to different properties for the supernatant phase and for the sediment bed.

In a preferred manner according to the invention, the gravimetric concentration of the aqueous suspension comprises the separation of a supernatant phase whose solids content is less than 5% by weight. In a preferred manner according to the invention, the gravimetric concentration of the aqueous suspension comprises the separation of a bed of sediment with a dry matter concentration greater than 40% by weight.

More preferably according to the invention, the gravimetric concentration of the aqueous suspension comprises the separation of a supernatant phase having a dry matter concentration of less than 5% by weight and a sediment bed whose concentration of material dry is greater than 40% by weight. According to the invention, the supernatant phase and the sediment bed have different rheological properties. In particular according to the invention, the sediment bed has particular rheological properties.

Thus, in addition to sedimentation, the method according to the invention makes it possible to control other essential properties of the aqueous suspension prepared. This method thus makes it possible to control both the Brookfield viscosity and the flow threshold of the prepared suspension, in particular the sediment bed.

In a preferred manner according to the invention, the concentration by gravimetry of the aqueous suspension comprises the separation of a supernatant phase and a bed of sediment which has:

a Brookfield viscosity, measured at 100 rpm and at 25 ° C., of less than 1800 mPa.s or

a flow threshold measured at a temperature of 25 ° C. by means of an imposed stress rheometer, equipped with a finned wheel, for a particular torsional torque, less than 80 Pa, or

a Brookfield viscosity, measured at 100 rpm and at 25 ° C., of less than 1800 mPa.s and a flow threshold measured at a temperature of 25 ° C. by means of an imposed stress rheometer equipped with a finned mobile, for a particular torque, less than 80 Pa.

According to the invention, the flow threshold, which characterizes the flow resistance, is measured on a sample of an aqueous mineral suspension, in particular an aqueous metal ore residue. The flow threshold is the stress that must be applied to a suspension in order to cause its flow. If the stress is insufficient, the suspension elastically deforms while if the stress is sufficient, the suspension can flow in the manner of a liquid.

According to the invention, the flow threshold expressed in Pascal (Pa) is measured at a temperature of 25 ° C. by means of an imposed constraint Brookfield DV3T rheometer equipped with a suitable finned wheel. Without destroying the underlying structure, the finned mobile is immersed in the material to the first immersion mark. After a waiting time of 5 min, the measurement is carried out without pre-shearing at the speed of 0.5 rpm. This relatively low speed is preferred in order to minimize the inertial effects of the finned mobile. The variation of the torsion torque measured by the apparatus to maintain a rotational speed of 0.5 rpm is monitored as a function of time. The value of the limit The flow rate or threshold of flow of the aqueous residue is indicated by the apparatus when this variation becomes zero.

According to the invention, the flow threshold is measured at a temperature of 25 ° C by means of an imposed stress rheometer equipped with a finned wheel for a particular torsion torque.

In a preferred manner according to the invention, the sediment bed has a yield point less than 70 Pa or less than 60 Pa, more preferably less than 50 Pa or less than 40 Pa, much more preferably less than 30 Pa or less than 30 Pa. 20 Pa.

Also preferably according to the invention, the sediment bed has a yield point greater than 10 Pa, preferably greater than 12 Pa, much more preferably greater than 15 Pa.

Also preferably according to the invention, the sediment bed has a yield point greater than 10 Pa, more preferably greater than 12 Pa, much more preferably greater than 15 Pa and less than 70 Pa or less than 60 Pa, more preferably less than 50 Pa or less than 40 Pa, much more preferably less than 30 Pa or less than 20 Pa.

According to the invention the Brookfield viscosity is measured at 100 rpm and at 25 ° C, for example by means of a Brookfield DV3T rheometer. According to the invention, the Brookfield viscosity of the suspension prepared is generally less than 1800 mPa.s. Preferably, the method according to the invention makes it possible to prepare a suspension which has a viscosity of less than 1500 mPa.s or less than 1200 mPa.s. More preferably, the viscosity is less than 1000 mPa.s or less than 900 mPa.s. More preferably, the viscosity is less than 800 mPa.s or less than 700 mPa.s, or even less than 500 mPa.s. According to the invention, the amount of polymer (P) used can vary quite widely. In a preferred manner according to the invention, the suspension prepared comprises from 0.01 to 2% by weight or from 0.01 to 1.8% or else from 0.01 to 1.5% of polymer (P) (dry on dry relative to the ore residue). More preferably, the suspension prepared comprises from 0.01 to 1.2% or from 0.01 to 1% or from 0.02 to 0.8%, or from 0.03 to 0.5% or else from 0, 04 to 0.25% or 0.04 to 0.15% by weight of polymer (P) (dry on dry relative to the ore residue).

The method according to the invention can implement one or more polymers (P). Preferably, the suspension prepared then comprises one, two or three different polymers (P). The method according to the invention may also comprise the addition addition of at least one compound selected from a lignosulfonate derivative, a silicate, an unmodified polysaccharide and a modified polysaccharide.

The method according to the invention comprises the addition to an aqueous residue of metal ore of at least one polymer (P). Preferably, the metal ore is not an aluminum ore. Also preferably according to the invention, the metal ore is selected from lithium ore, strontium, lanthanides, actinides, uranium, rare earths, titanium, zirconium, vanadium, niobium, chromium, molybdenum, tungsten, manganese, iron, cobalt , rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, tin, lead. More preferably according to the invention, the metal ore is selected from uranium ore, molybdenum, manganese, iron, cobalt, nickel, copper, silver, gold. More preferably, it is a copper ore. It can also be a derivative of several metals to be valued including copper, zinc and cobalt.

According to the invention, the metallic ore comprises at least one metal or at least one metal derivative for recovery obtained by separating all or part of the residue from the metal ore. In a preferred manner according to the invention, the metallic ore comprises a metal oxide, a metal sulphide or a metal carbonate.

According to the invention, the metal ore residue may comprise some residual amount of metal. In particular, the metal ore residue may comprise a residual amount of metal less than 2,000 g per tonne (dry / dry) based on the amount of metal ore residue. This amount of metal within the metal ore residue can generally range from 10 to 2,000 g per tonne (dry / dry) or from 10 to 1,000 g per tonne (dry / dry), based on the amount of residue of metallic ore.

During the implementation of the method according to the invention, the polymer (P) may be added during one or more steps of the mining process comprising the gravimetric concentration of the aqueous suspension.

In a preferred manner according to the invention, the gravimetric concentration of the suspension is carried out by means of at least one device chosen from a conventional thickener, a high-density thickener and a high-performance thickener.

Also preferably according to the invention, the addition of the polymer (P) is carried out before the gravimetric concentration of the suspension or during the gravimetric concentration of the suspension.

More preferably according to the invention, the addition of the polymer (P) is carried out at the same time as the addition of the flocculating agent, thus carried out simultaneously with the addition flocculating agent. Also more preferably according to the invention, the addition of the polymer (P) is carried out during the gravimetric concentration of the suspension and simultaneously with the addition of the flocculating agent.

Also more preferably according to the invention, the addition of the polymer (P) is carried out at the same place as the addition of the flocculating agent, thus carried out parallel to the addition of the flocculating agent. Also more preferably according to the invention, the addition of the polymer (P) is carried out during the gravimetric concentration of the suspension and in parallel with the addition of the flocculating agent.

The method according to the invention implements at least one particular polymer (P). It is prepared by a polymerization reaction in the presence of at least one radical-generating compound chosen from hydrogen peroxide, benzoyl peroxide, acetyl peroxide, lauryl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ammonium persulfate, a persulfate of alkali metal, preferably sodium persulfate or potassium persulfate, an azo compound, such as 2,2'-azobis (2- (4,5-dihydroimidazolyl) propane, 2,2'-azobis (2-methylpropionamidine) dihydrochloride) , diazo-valero-nitrile, 4,4'-azobis (4-cyanovaleric), AZDN or 2,2'-azo-bis-isobutyronitrile, and combinations or combinations thereof with an ion selected from Fe ¹¹ , Fe ^m , Cu ¹ , Cu ¹¹ and mixtures thereof Preferably, this polymerization reaction does not use benzoyl peroxide.

In addition to this radical-generating compound, the polymerization reaction can also be carried out in the presence of at least one compound comprising phosphorus at the oxidation state I, preferably a compound chosen from hypophosphorous acid (H ₃ PO ₂ ) and a derivative of hypophosphorous acid (H ₃ PO ₂ ), preferably a compound comprising at least one hypophosphite ion (H ₂ PO ₂ ), more preferably a compound chosen from sodium hypophosphite (H ₂ PO ₂ Na), potassium hypophosphite (H ₂ PO ₂ K), calcium hypophosphite ([H ₂ PO ₂ ] ₂ Ca) and mixtures thereof.

Similarly, the polymerization reaction may be carried out in the presence of at least one compound comprising phosphorus at oxidation level III, preferably a compound chosen from phosphorous acid and a phosphorous acid derivative, more preferably a compound comprising at least one phosphite ion, especially a compound selected from sodium phosphite, calcium phosphite, potassium phosphite, ammonium phosphite and combinations thereof.

The polymerization reaction can also be carried out also in the presence of at least one compound comprising a bisulfite ion, preferably a chosen compound among ammonium bisulfite, an alkali metal bisulfite, especially sodium bisulfite, potassium bisulfite, calcium bisulfite, magnesium bisulfite and combinations thereof. The polymerization reaction may also be carried out in the presence of from 0.05 to 5% by weight, relative to the total amount of monomers, of at least one compound chosen from a xanthate derivative, a mercaptan compound and a formula (I):

XOOC

in which :

where X is independently H, Na or K and

R is independently a C 1 -C 6 -alkyl group, preferably a methyl group, in particular a compound of formula (I) which is disodium trithiocarbonate diisopropionate (DPTTC).

According to the invention, the polymerization reaction is carried out at a temperature above 50 ° C. Preferably, the polymerization reaction is carried out at a temperature ranging from 50 to 98 ° C or from 50 to 95 ° C or from 50 to 85 ° C.

A higher temperature, especially greater than 100 ° C, can be implemented by adjusting the pressure of the reaction medium to prevent evaporation.

Preferably, the polymerization reaction is carried out in water.

It can also be used in a solvent, alone or in a mixture with water, in particular an alcoholic solvent, in particular isopropyl alcohol. More preferably, it is carried out in water.

Advantageously, the polymer (P) used according to the invention has a molecular weight Mw measured by GPC ranging from 2200 to 10 000 g / mol. Preferably, the polymer (P) used according to the invention has a molecular weight Mw ranging from 2,400 to 9,500 g / mol or from 2,400 to 8,000 g / mol, more preferably from 2,400 to 6,500 g / mol. g / mol. The polymer (P) used according to the invention is therefore not a flocculation agent.

According to the invention, the molecular weight Mw is determined by Steric Exclusion Chromatography (CES) or in English "Gel Permeation Chromatography" (GPC). This technique uses a Waters liquid chromatography apparatus equipped with a detector. This detector is a Waters refractometric concentration detector. This liquid chromatography apparatus is equipped with a column steric exclusion in order to separate the different molecular weights of the copolymers studied. The liquid elution phase is an aqueous phase adjusted to pH 9.00 using 1 N sodium hydroxide containing 0.05 M NaHCO ₃ , 0.1 M NaNO ₃ , 0.02 M triethanolamine and 0.03% of NaN ₃ .

In a first step, the copolymer solution is diluted to 0.9% dry in the solubilization solvent of the CES, which corresponds to the liquid phase of elution of the CES, to which 0.04% of dimethylformamide which is added is added. the role of flow marker or internal standard. Then, it is filtered at 0.2 μm. 100 μl are then injected into the chromatography apparatus (eluent: an aqueous phase adjusted to pH 9.00 with 1N sodium hydroxide containing 0.05 M NaHCO ₃ , 0.1 M NaNO ₃ , 0.02 M of trietanolamine and 0.03% NaN ₃ ).

The liquid chromatography apparatus contains an isocratic pump (Waters 515) with a flow rate of 0.8 mL / min. The chromatography apparatus also comprises an oven which itself comprises in series the following column system: a precolumn of the Guard Column Ultrahydrogel Waters type, 6 cm long and 40 mm inside diameter, and a linear column of the Ultrahydrogel Waters type. 30 cm long and 7.8 mm inside diameter. The detection system consists of a type RI Waters 410 refractometric detector. The oven is heated to a temperature of 60 ° C and the refractometer is heated to a temperature of 45 ° C.

The chromatography apparatus is calibrated by means of standards of powdered sodium polyacrylate of various molecular weights certified by the supplier: Polymer Standards Service or American Polymers Standards Corporation (molecular weight ranging from 900 to 2.25 × 10 ⁶ g / mol and polymolecularity index ranging from 1.4 to 1.8).

The polymer (P) used according to the invention may be totally or partially neutralized, in particular at the end of the polymerization reaction.

According to the invention, the neutralization of the polymer is carried out by neutralizing or salifying all or part of the carboxylic acid functions present within the polymer.

Preferably, the neutralization is carried out by means of a base, for example by means of an alkali metal derivative or an alkaline earth metal derivative.

The preferred bases are chosen from CaO, ZnO, MgO, NaOH, KOH, NH ₄ OH, Ca (OH) ₂ , Mg (OH) ₂ , monoisopropyl amine, triethanolamine, triisopropylamine, 2-amino-2-methyl-1-propanol. (AMP), triethylamine, diethylamine, monoethylamine. In a particularly preferred manner, the neutralization is carried out using MgO, NaOH, KOH, Ca (OH) ₂ , Mg (OH) ₂ , alone or in combination. According to the invention, the polymerization reaction uses at least one anionic monomer (M) which comprises at least one polymerizable olefinic unsaturation and at least one carboxylic acid function or a salt thereof. Preferably, the anionic monomer (M) comprising at least one polymerizable olefinic unsaturation comprises one or two carboxylic acid functions, in particular a single carboxylic acid function. More preferentially, it is chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and their mixtures, more preferably acrylic acid.

Preferably, the polymerization reaction uses 100% by weight of anionic monomer (M) or from 70% to 99.5% by weight of anionic monomer (M) and from 0.5% to 30% by weight. at least one other monomer.

Advantageously, the polymerization reaction can therefore also employ at least one other monomer chosen from:

another anionic monomer, preferably a monomer selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride and mixtures thereof,

2-acrylamido-2-methylpropanesulphonic acid, 2-acrylamido-2-methylpropanesulphonic acid salt, 2- (methacryloyloxy) ethanesulfonic acid, 2- (methacryloyloxy) ethanesulfonic acid salt, sodium methallyl sulfonate styrene sulphonate and combinations or mixtures thereof

a nonionic monomer comprising at least one polymerizable olefinic unsaturation, preferably at least one polymerizable ethylenic unsaturation and in particular a polymerizable vinyl functional group, more preferably a nonionic monomer chosen from styrene, vinylcaprolactam, esters of an acid comprising at least one monocarboxylic acid function, in particular an ester of an acid selected from acrylic acid, methacrylic acid, and mixtures thereof, for example hydroxyethylacrylate, hydroxypropylacrylate, hydroxyethylmethacrylate, hydroxypropylmethacrylate, alkyl acrylate, in particular C 1 -C 10 alkyl acrylate, preferentially Ci-C ₄ -alkyl acrylate, more preferably methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, isobutyl acrylate, n-butyl acrylate, alkyl methacrylate, in particular methacrylate Ci-C _l0 alkyl, preferably methacrylate Ci-C ₄ -alkyl, pl we preferentially methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, aryl acrylate, preferably phenylacrylate, benzyl acrylate, phenoxyethyl acrylate, aryl methacrylate, preferably phenyl methacrylate, benzyl methacrylate, phenoxyethyl methacrylate and

a monomer of formula

in which :

R ¹ and R ² , which are identical or different, independently represent H or CH ₃ ,

L ¹ independently represents a group chosen from C (O), CH ₂ , CH ₂ -CH ₂ and O-CH ₂ -CH -CH ₂ -CH ₂ ,

L ² independently represents a group chosen from (CH ₂ -CH ₂ O) _x , (CH ₂ CH (CH ₃ ) O) _y , (CH (CH ₃ ) CH ₂ 0) _z and their combinations and

x, y and z, identical or different, independently represent an integer or decimal number between 0 and 150 and the sum x + y + z is between

10 and 150.

In a particularly preferred manner, the monomer of formula (P) is such that:

- R ¹ represents CH ₃ ,

- R ² represents H,

L ¹ represents a group C (O),

L ² independently represents a combination of groups chosen from (CH ₂ -CH ₂ O) _x , (CH ₂ CH (CH ₃ ) O) _y , (CH (CH ₃ ) CH ₂ 0) _z and

10 and 150.

Preferably, the polymer (P) used according to the invention is a non-sulfonated polymer.

During the preparation of the polymer (P) implemented according to the invention, a separation step can also be implemented. According to the invention, the separation can be carried out after the total or partial neutralization of the polymer (P). It can also be implemented before neutralization of the polymer (P). The aqueous solution of the polymer (P), totally or partially neutralized, can be treated according to static or dynamic fractionation methods known per se. One or more polar solvents are thus used, in particular belonging to the group consisting of methanol, ethanol, n-propanol, isopropanol, butanols, acetone and tetrahydrofuran, thus producing a separation in two phases. During separation, the least dense phase comprises the major fraction of the polar solvent and the fraction of low molecular weight polymers, the densest aqueous phase contains the fraction of polymers of higher molecular weight. The temperature at which the selection process of the polymer fraction is carried out can influence the partition coefficient. It is generally between 10 and 80 ° C, preferably between 20 and 60 ° C. When separating, it is important to control the ratio of the amounts of dilution water and polar solvents.

When carrying out a dynamic separation method, for example by centrifugation, the ratios of the extracted fractions generally depend on the centrifugation conditions.

Selection of the polymer fraction can also be improved by treating again the denser aqueous phase with a new amount of polar solvent, which may be different. It can also be a mixture of polar solvents. Finally, the liquid phase obtained after treatment can be subjected to distillation to remove the solvent (s) used for the treatment.

In a particularly unexpected manner, the method according to the invention makes it possible to control the properties of the aqueous mineral suspension, in particular to control its sedimentation, despite the presence of at least one flocculation agent in this suspension. The method according to the invention is effective in the presence of many types of flocculating agent. In a preferred manner according to the invention, the flocculation agent is chosen from a polyacrylamide, a polyacrylamide derivative.

The sedimentation control method according to the invention makes it possible to prepare a suspension of aqueous metal ore residue comprising at least one polymer (P) which has particularly advantageous properties, especially particularly advantageous rheological properties.

Thus, the invention also provides an aqueous mineral suspension comprising at least one flocculation agent and whose solids content is greater than 10% by weight of the suspension, chosen from:

an aqueous residue of metal ore, an aqueous suspension of metal ore and

comprising at least one polymer (P) of molecular weight Mw measured by GPC ranging from 2,000 to 20,000 g / mol and prepared by at least one radical polymerization reaction, at a temperature above 50 ° C, of at least one anionic monomer (M) comprising at least one polymerizable olefinic unsaturation and at least one carboxylic acid function or a salt thereof, in the presence of at least one radical-generating compound chosen from hydrogen peroxide, benzoyl peroxide and acetyl peroxide , lauryl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ammonium persulfate, an alkali metal persulfate, preferably sodium persulfate or potassium persulfate, an azo compound, such as 2,2'-azobis (2- (4, 5-dihydroimidazolyl) propane, 2,2 ^{dihydrochloride,} azobis (2-methylpropionamidine), diazo-valero-nitrile, 4,4'-azobis (4- cyanovaleric acid), AIBN or 2,2'-azo-bis -isobutyronitrile and their combinations or associations respec with an ion selected from Fe ¹¹ , Fe ⁱⁿ , Cu ¹ , Cu ¹¹ and mixtures thereof.

Preferably, the aqueous inorganic suspension according to the invention is obtained by gravimetric concentration of the aqueous suspension in the presence of at least one polymer (P) according to the invention.

Also preferably, the aqueous mineral suspension according to the invention is obtained during the implementation of the method according to the invention.

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.

EXAMPLES

The following examples illustrate the various aspects of the invention.

A polymer is prepared during the method according to the invention.

The polymer (PI) is prepared by introducing into a one-liter glass reactor equipped with mechanical stirring and oil-bath heating 212 g of water and 0.08 g of sodium sulfate. iron heptahydrate.

In a 500 ml beaker equipped with a dosing pump, 303 g of acrylic acid at 100% by weight and 15 g of water are weighed. In a 100 ml test tube equipped with a dosing pump, 25.6 g of sodium hypophosphite monohydrate dissolved with 30 g of water are weighed.

In a 100 ml test tube equipped with a dosing pump, 21 g of hydrogen peroxide 130 V and 35 g of water are weighed.

The reactor is heated to 95 ° C. and the monomer, the hypophosphite solution and the hydrogen peroxide solution are added in parallel in 120 min while maintaining the temperature of the reaction medium at 95 ° C.

Finally, the pumps are rinsed with water.

The medium is again heated for 60 min at 95 ° C.

The solution is then neutralized with sodium hydroxide 50% by weight in water to pH 8 and then diluted to a solids content of 42% by weight. The polymer (P1) of molecular weight Mw measured by GPC of 4500 g / mol is obtained.

The raw material used for this series of tests is an aqueous metal ore residue from a Chilean copper mine in the north of the country. It is a waste resulting from the separation of the rock extracted from the ore mine including the metal to be valorized.

This aqueous residue of copper ore is in the form of a suspension in water. Various prior measures have been carried out on the aqueous residue in the absence of polymer according to the invention:

particle size distribution by means of a Mastersizer 2000 (Malvern) laser granulometer: D (80) of 243.1 μm and

solid rate using a Mettler-Toledo dry scale: 63.5%.

A test is then carried out to evaluate the effectiveness of the polymer on the sedimentation of an aqueous residue suspension of copper ore during the concentration of this residue by sedimentation. This sedimentation is carried out on a suspension having a solids content of 30% by weight. This suspension having a solid content of 30% by weight is prepared by diluting the aqueous residue suspension having a solids content of 63.5% by weight.

A sample of 30% by weight aqueous copper ore slurry is transferred to a 500 ml beaker and then mechanically stirred with a Raynerie mixer. Stirring is performed at 500 rpm.

Then, a polymer (P1) according to the invention is added at a dose of 0.05% by dry weight / sec relative to the dry residue and is left stirring for 15 min. The suspension thus dispersed is then incorporated into a graduated 2-liter test tube equipped with mechanical stirring at 0.8 rpm.

A fixed dose of an acrylamide flocculating agent is incorporated in a dose equivalent to 12 g / T dry / sec of residue.

An experiment using the polymer (P1) and a comparative test in the absence of a polymer in the suspension are carried out.

After preparation of a slurry sample, settling occurs gradually over time by the phenomenon of flocculation of the solid particles included in the aqueous copper ore residue. These particles agglomerate to form agglomerates of heavier particles. These agglomerates sediment then more quickly. The supernatant aqueous phase is found on the surface and the sediment at the bottom of the test tube. At 25 ° C and using a Brookfield DV3T viscometer using a suitable finned module, flow threshold measurements were made on samples of aqueous suspension of copper ore residue at 30% by weight of extract. dry.

A threshold of flow (Pa) of the suspension having undergone a very low shear rate (approximately 1 to 10 s ¹ ) (UN-YS) is carried out. It corresponds to the flow threshold of the aqueous residue suspension of copper ore at the bottom of a thickener.

A flow threshold (Pa) of the high shear suspension (about 100 to 1000 s ¹ ) (FS-YS) is also performed.

It corresponds to the flow threshold at the outlet of a thickener of the aqueous residue suspension of the copper ore.

The sedimentation rate is also measured using the graduation of the specimen and a stopwatch. The measurement is made by observing the separation of the supernatant water phase and sediment. It is done in cm per minute then converted to meter per hour (m / h).

The results are shown in Table 1.

Table 1

In addition, a test is carried out in a semi-industrial installation. The decanter is cylindrical in shape with a transparent wall. Its volume is 30 L, it is stirred by means of a low power motor feeding a stirring of 1 rpm. The suspension of aqueous copper ore residue implemented has a solids content of 69%. dry weight

The preparation of the suspension is similar to the previous preparation, the solids content is 30% by dry weight / sec. The dose of polymer remains the same. It is 0.05% by dry weight / sec. The polymer (P1) is introduced into the top of the thickener in parallel with the feed well. The feedwell is the zone through which the feed of aqueous residue of ore is made and the introduction of flocculant.

The material used for the concentration of the aqueous residue in the presence of a polymer according to the invention is a plexiglass pilot thickener provided with a low intensity stirrer producing a stirring of 1 rpm. A flow threshold measurement (Pa) of the medium shear suspension (about 10 to 100 s ¹ ) (MS-YS) is performed. It corresponds to the flow threshold at the bottom of a thickener at the level of the transport pump to the aqueous residue storage units of copper ore.

A flow threshold measurement (Pa) of the suspension having undergone a very high shear rate (approximately 1000 to 10,000 s ¹ ) (HFS-YS) is also carried out. It corresponds to the flow threshold in the pipe located after the transport pump at the outlet of a thickener and which leads to the aqueous tailings storage units of copper ore. The results are shown in Table 2.

The sedimentation rate is also measured using the graduation of the specimen and a stopwatch. The measurement is made by observing the separation of the supernatant water phase and sediment. It is done in cm per minute then converted to meter per hour (m / h). It is between 7 and 8 m / h.

Table 2

It is found that with the use of a polymer according to the invention, the increase in the solid content of the aqueous suspension of copper ore residue at the outlet of a thickener does not lead to a drift in the viscosity of the suspension. This suspension with increased concentration can be further agitated in a conventional installation and is more easily handled, thus avoiding the risk of blocking stirring devices.

In addition, its improved solids content allows a reduction in water consumption relative to the amount of copper ore residue treated.

These tests also show that the presence of the polymer (P1) according to the invention makes it possible to considerably improve the flow threshold values of the aqueous suspension of copper ore residue without disturbing the sedimentation rate within the device. concentration.

The control of the rheology at the outlet of a thickener makes it easier to unload and transport this aqueous suspension to storage basins.

Claims

A method for controlling the sedimentation of an aqueous mineral suspension comprising at least one flocculation agent and whose solids content is greater than 10% by weight of the suspension, chosen from:

an aqueous residue of metallic ore,

an aqueous suspension of metallic ore and

comprising the gravimetric concentration of the aqueous suspension in the presence of at least one prepared polymer (P) with a molecular weight Mw measured by GPC of from 2,000 to 20,000 g / mol and by at least one radical polymerization reaction, at a concentration of at a temperature above 50 ° C, at least one anionic monomer (M) comprising at least one polymerizable olefinic unsaturation and at least one carboxylic acid function or a salt thereof, in the presence of at least one radical-generating compound selected from hydrogen peroxide, benzoyl peroxide, acetyl peroxide, lauryl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ammonium persulfate, an alkali metal persulfate, preferably sodium persulfate or potassium persulfate, an azo compound, such as 2,2'-azobis (2- (4,5-dihydroimidazolyl) propane, 2,2'-azobis (2-methylpropionamidine) dihydrochloride, diazo-valero-nitrile, 4,4'-azobis- (4-cyanovaleric acid) ), AZDN or 2,2'-azo -bis-isobutyronitrile and combinations thereof or combinations thereof with an ion selected from Fe ¹¹ , Fe ^m , Cu ¹ , Cu ¹¹ and mixtures thereof.

2. Method according to claim 1 for which the suspension has a concentration of dry matter:

greater than 10% by weight or more than 15% by weight or

- less than 20% by weight or less than 30% by weight or even less than 35% by weight or even less than 40% by weight or 50% by weight or ranging from 10 to 50% by weight or from 10 to 40% by weight or 10 to 35% by weight or 10 to 30% by weight or 10 to 20% by weight or alternatively 15 to 50% by weight or 15 to 40% by weight or 15 to 15% by weight 35% by weight or 15 to 30% by weight or 15 to 20% by weight, or alternatively from 20 to 50% by weight or from 20 to 40% by weight or from 20 to 35% by weight or from 20 to 30% by weight.

3. Method according to one of claims 1 or 2 wherein the gravimetric concentration of the aqueous suspension comprises the separation of a supernatant phase and a bed of sediment.

4. Method according to one of claims 1 to 3 for which the gravimetric concentration of the aqueous suspension comprises the separation of a supernatant phase and a bed of sediment having:

a Brookfield viscosity, measured at 100 rpm and at 25 ° C, of less than 1800 mPa.s or

5. Method according to one of claims 1 to 4 for which the gravimetric concentration of the aqueous suspension comprises the separation of a supernatant phase and a bed of sediment having:

a yield point less than 70 Pa or less than 60 Pa, preferably less than 50 Pa or less than 40 Pa, more preferably less than 30 Pa or less than 20 Pa, or

a flow threshold greater than 10 Pa, preferably greater than 12 Pa, more preferably greater than 15 Pa, or

a yield threshold greater than 10 Pa, preferably greater than 12 Pa, more preferably greater than 15 Pa and less than 70 Pa or less than 60 Pa, preferably less than 50 Pa or less than 40 Pa, more preferably lower; at 30 Pa or less than 20 Pa or

a viscosity of less than 1500 mPa.s, preferably less than 1200 mPa.s, more preferably less than 1000 mPa.s or less than 900 mPa.s, much more preferably less than 800 mPa.s or less than 700 mPa.s, or even less than 500 mPa.s.

6. Method according to one of claims 1 to 5 for which the gravimetric concentration of the aqueous suspension comprises the separation of a supernatant phase whose solids content is less than 5% by weight and a bed of sediment. whose dry matter concentration is greater than 40% by weight.

7. Method according to one of claims 1 to 6 for which the suspension comprises from 0.01 to 2% by weight of polymer (P) (dry on dry relative to the ore residue), preferably from 0.01 to 1.8% or from 0.01 to 1.5%, more preferably from 0.01 to 1.2% or from 0.01 to 1%, more preferably from 0.02 to 0.8% or from 0 to , 03 to 0.5%, even more preferably 0.04 to 0.25% or 0.04 to 0.15%.

8. Method according to one of claims 1 to 7 comprising the addition of one, two or three different polymers (P) or the additional addition of at least one compound selected from a lignosulfonate derivative, a silicate, an unmodified polysaccharide and a modified polysaccharide.

9. Method according to one of claims 1 to 8 for which:

^■ the metal ore is selected from lithium ore, strontium, lanthanides, actinides, uranium, rare earth metals, titanium, zirconium, vanadium, niobium, chromium, molybdenum, tungsten, manganese, iron, cobalt, rhodium, iridium, nickel, palladium , platinum, copper, silver, gold, zinc, cadmium, tin, lead or

The metal ore comprises a metal oxide, a metal sulfide or a metal carbonate; or

• the metal ore residue contains a residual amount of metal less than 2,000 g per tonne (dry / dry) based on the amount of metal ore residue; preferably, a quantity of metal ranging from 10 to 2,000 g per tonne (dry / dry) or from 10 to 1,000 g per tonne (dry / dry), based on the amount of metal ore residue.

10. Method according to one of claims 1 to 9 for which:

The gravimetric concentration of the suspension is carried out by means of at least one device chosen from a conventional thickener, a high-density thickener, a high-performance thickener, or for which: The addition of the polymer (P) is carried out:

before the gravimetric concentration of the suspension or

during the gravimetric concentration of the suspension or

simultaneously with the addition of the flocculating agent or

- parallel to the addition of the flocculating agent or

during the gravimetric concentration of the suspension and simultaneously with the addition of the flocculating agent or

during the gravimetric concentration of the suspension and in parallel with the addition of the flocculating agent.

11. Method according to one of claims 1 to 10 for which:

the polymerization reaction is also carried out in the presence of at least one compound comprising phosphorus at the oxidation state I, preferably a compound chosen from hypophosphorous acid (H3PO2) and a hypophosphorous acid derivative ( H ₃ PO ₂ ), preferably a compound comprising at least one hypophosphite ion (H ₂ PO ₂ ), more preferably a compound selected from sodium hypophosphite (H ₂ PO ₂ Na), potassium hypophosphite (H ₂ PO ₂ K) calcium hypophosphite ([H ₂ PO ₂ ] ₂ Ca) and mixtures thereof or

the polymerization reaction is also carried out in the presence of at least one compound comprising a bisulfite ion, preferably a compound chosen from ammonium bisulfite, an alkali metal bisulfite, in particular sodium bisulfite, potassium bisulfite, bisulphite, calcium, magnesium bisulphite and their combinations or

the polymerization reaction is carried out in the presence of at least one compound comprising phosphorus with the degree of oxidation P1, preferably a compound chosen from phosphorous acid and a phosphorous acid derivative, more preferably a compound comprising at least one phosphite ion, in particular a compound chosen from sodium phosphite, calcium phosphite, potassium phosphite, ammonium phosphite and their combinations or

the polymerization reaction is also carried out in the presence of 0.05 to 5% by weight, relative to the total amount of monomers, of at least one compound selected from a xanthate derivative, a mercaptan compound and a compound of formula

(I): XOOC

in which :

where X is independently H, Na or K and

R represents independently a C ₁ -C ₅ -alkyl group, preferably a methyl group, in particular a compound of formula (I) which is disodium trithiocarbonate diisopropionate (DPTTC) or

the polymerization reaction is carried out at a temperature ranging from 50 to 98 ° C, preferably from 50 to 95 ° C or from 50 to 85 ° C or

the polymerization reaction is carried out in water, in a solvent, alone or in a mixture with water, in particular an alcoholic solvent, in particular isopropyl alcohol, preferably in water or

the polymer (P) has a molecular weight Mw measured by GPC ranging from 2200 to 10,000 g / mol, preferably from 2,400 to 9,500 g / mol or from 2,400 to 8,000 g / mol, more preferably from 2 to 400 to 6,500 g / mol; or

the polymer (P) is totally or partially neutralized, in particular at the end of the polymerization reaction or

the polymerization reaction uses:

o 100% by weight of anionic monomer (M) or

from 70% to 99.5% by weight of anionic monomer (M) and from 0.5% to 30% by weight of at least one other monomer.

12. Method according to one of claims 1 to 10 wherein the anionic monomer (M) comprising at least one polymerizable olefinic unsaturation comprises one or two carboxylic acid functions, preferably comprises a single carboxylic acid function, preferably is selected from acid acrylic, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and mixtures thereof, more preferably acrylic acid.

13. Method according to one of claims 1 to 11 for which the polymerization reaction also implements at least one other monomer chosen from: another anionic monomer, preferably a monomer selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride and mixtures thereof,

a nonionic monomer comprising at least one polymerizable olefinic unsaturation, preferably at least one polymerizable ethylenic unsaturation and in particular a polymerizable vinyl function, more preferably a nonionic monomer selected from styrene, vinylcaprolactam, the esters of an acid comprising at least one function monocarboxylic acid, in particular an ester of an acid selected from acrylic acid, methacrylic acid, and mixtures thereof, for example hydroxyethylacrylate, hydroxypropylacrylate, hydroxyethylmethacrylate, hydroxypropylmethacrylate, alkyl acrylate, in particular C ₁ -C 10 alkyl acrylate, preferentially Ci-C ₄ -alkyl acrylate, more preferably methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, isobutyl acrylate, n-butyl acrylate, alkyl methacrylate, in particular methacrylate Ci-C _l0 alkyl, preferably methacrylate Ci-C ₄ alkyl, p preferred are methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, aryl acrylate, preferably phenyl acrylate, benzyl acrylate, phenoxyethyl acrylate, aryl methacrylate; preferably phenylmethacrylate, benzylmethacrylate, phenoxyethylmethacrylate and

a monomer of formula

in which :

L ¹ independently represents a group chosen from C (O), CH ₂ ,

CH ₂ -CH ₂ and O-CH ₂ -CH ₂ -CH -CH ₂ , L ² independently represents a group chosen from (CH ₂ -CH ₂ O) _x , (CH ₂ CH (CH ₃ ) O) _y , (CH (CH ₃ ) CH ₂ 0) _z and their combinations and

- x, y and z, identical or different, independently represent an integer or decimal number between 0 and 150 and the sum x + y + z is between 10 and 150.

14. Method according to one of claims 1 to 13 wherein the flocculating agent is selected from a polyacrylamide, a polyacrylamide derivative.

15. An aqueous mineral suspension comprising at least one flocculation agent and whose solids content is greater than 10% by weight of the suspension, chosen from:

an aqueous residue of metallic ore,

an aqueous suspension of metal ore and

comprising at least one polymer (P) of molecular weight Mw measured by GPC ranging from 2,000 to 20,000 g / mol and prepared by at least one radical polymerization reaction, at a temperature above 50 ° C, of at least one anionic monomer (M) comprising at least one polymerizable olefinic unsaturation and at least one carboxylic acid function or a salt thereof, in the presence of at least one radical-generating compound chosen from hydrogen peroxide, benzoyl peroxide and acetyl peroxide , lauryl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ammonium persulfate, an alkali metal persulfate, preferably sodium persulfate or potassium persulfate, an azo compound, such as 2,2'-azobis (2- (4, 5-dihydroimidazolyl) propane, 2,2'-azobis (2-methylpropionamidine) dihydrochloride, diazo-valero-nitrile, 4,4'-azobis (4-cyanovaleric), AZDN or 2,2'-azo-bis -isobutyronitrile and combinations or associations thereof with an ion selected from Fe ¹¹ , Fe ¹¹¹ , Cu ¹ , Cu ¹¹ and mixtures thereof.

An aqueous mineral suspension according to claim 15:

obtained by gravimetric concentration of the aqueous suspension in the presence of at least one polymer (P) or

obtained according to the method according to one of claims 1 to 14.