MX2015003298A - Process for filtration enhancement of aqueous dispersions. - Google Patents

Abstract

A method for enhancing filtration performance in separating solids from liquids in an aqueous dispersion comprising a solids phase and a liquid phase in a two step process having a physical separation step and a filtration step comprising adding at least one filtration aid promoter and at least one synthetic polymer to the aqueous dispersion during and/or before the physical separation step resulting in concentrate and filtering the concentrate. The method may be applied in mining operations for dewatering mining slurry. Also, a composition applied in such method comprising at least one filtration aid promoter and at least one synthetic polymer. The filtration aid promoter comprises natural polymers, semi-natural polymers, coagulants and combinations thereof.

Description

PROCESS TO IMPROVE THE FILTRATION OF DISPERSIONS AQUEOUS BACKGROUND OF THE INVENTION Field of the invention The invention relates to compositions and methods that improve the filtration of aqueous dispersions. For example, in the desiccation of aqueous mineral suspensions by the addition of an auxiliary filtration promoter and synthetic polymer to the aqueous dispersion before filtration. In particular, the method improves filtration when the auxiliary filtration promoter and the synthetic polymer are added before and / or during the phase of separation of solids from the liquid phase in an aqueous suspension, but before the filtration of the concentrated aqueous phase . The compositions and methods have a particular application with respect to mining slurries.

The related technology Conventional metallurgical processing techniques involve the separation of valuable minerals from the low-value bargain in an aqueous medium. Minerals go through numerous processing operations to extract valuable components. The operations of Processing, such as grinding, milling, sieving, cycloning and flotation are used to enrich the most desirable components to form a mineral concentrate. The valuable minerals that are concentrated include precious metals (gold, silver, platinum), base metals (copper, nickel, zinc, lead, molybdenum), iron and carbon. Once the aqueous mineral suspension is concentrated, it is commonly subjected to a mechanical drying process to remove the liquid water from the mineral slurry concentrate. Excess moisture content in the dried mineral suspension can have deleterious effects on downstream process operations, which may include pelleting, autoclaving, calcination, or smelting, or greatly increasing transportation costs.

Wet processing is used because this type of process improves efficiency, increases recovery, reduces costs and minimizes air pollution. Mineral enrichment techniques, such as flotation processes, produce a mineral concentrate that contains an excessive amount of water. Water should be removed as much as possible, in order to reduce the energy costs associated with downstream operations and decrease transportation costs. In general, the drying is done with gravity thickeners, clarifiers, hydrocyclones, vacuum filtration and / or pressure filtration.

For example, the ore slurry can be dried in a two-stage method comprising the solid-liquid separation, such as in a gravity thickener, clarifier and / or hydrocyclone, which produces a liquid phase, the supernatant and a concentrate or subflow. . The concentrate or subflow comprises the valuable minerals that require additional drying which occurs in a second stage in which the concentrate or subflow is filtered, such as through vacuum filtration and / or pressure filtration.

Gravity thickeners, clarifiers and hydrocyclones are normally used to dry mineral concentrates with the help of coagulants and flocculants. As long as it is beneficial for sedimentation, these agents further hamper mechanical downstream drying.

All parts and percentages set forth herein are based on weight by weight, unless Specify otherwise, Mw is the weighted average molecular weight determined by SEC-MALLS analysis. MALLS is understood and refers to multi-angular laser light scattering. SEC-MALLS will be understood and referred to a size exclusion chromatography technique using MALLS to determine Mw.

BRIEF DESCRIPTION OF THE INVENTION The invention relates to compositions comprising auxiliary filtration promoters and synthetic polymer. These compositions are applied in methods for separating solids from liquids in aqueous dispersions comprising a filtration step. The filter aid and the synthetic polymer are added to the aqueous dispersion before and / or during the physical separation between a solid phase and a liquid phase., allowing solids to settle from dispersion. Then the solid phase can be filtered. Auxiliary filtration promoters include at least one of the natural polymers, semi-natural polymers or coagulants. Combinations thereof can be used.

Normally, the composition is applied in the drying processes in mining operations. Said drying processes generally comprise two stages, the The first stage involves the solid-liquid separation and the second separated stage involves the filtration of the concentrate or subflow of the solid-liquid separation stage. The solid-liquid separation is normally carried out with gravity thickeners, clarifiers, hydrocyclones and the like. The filtration is generally carried out by vacuum filtration, pressure filtration and the like. The auxiliary filtration promoter and the synthetic polymer are added to ore slurry before the solid-liquid separation step, during the solid-liquid separation step or during and before the solid-liquid separation step. The solid-liquid separation stage produces concentrate or subflow that requires additional drying through a separate filtration step.

Without being bound by any theory, the inventors believe that the application of the auxiliary filtration promoter and the synthetic polymer before and / or during the physical separation step affects the rheology of the resulting concentrate (or subflow) which improves the filtration process in the subsequent filtration stage. For example, the combination of the auxiliary filtration promoter and the synthetic polymer, when applied before and / or during the solid-liquid separation stage in mining operations the production of filtration cakes resulting from the separate filtration step increases.

DETAILED DESCRIPTION OF THE INVENTION Among the natural polymers that can be used for the auxiliary filtration promoter are polysaccharides, such as potato starch, xanthan gums, guar gums, dextran, cellulose derivatives and glycosaminoglycans. Commonly, the polydispersity index ("PDI") of the polysaccharide is from about 1.0 to about 10.0, more usually from about 1.1 to about 9.0, and most typically from about 1.2 to about 8.0. The ordinary experts in these techniques, after reading this description, will appreciate that all the intervals and values are contemplated within these expressly indicated intervals.

Preferably, the natural polymer comprises, dextran, which is generally available from various suppliers. Dextran having an Mw of from about 5,000 to about 40,000,000, preferably from about 50,000 to about 25,000,000 and more preferably from about 200,000 to about 10,000,000. The experts in these techniques, after reading this description, will appreciate that all the intervals and values within these expressly indicated ranges are contemplated. Natural polymers sold under the trade names of ZALTA® VM 1120 and Zalta VM 1122, both available from Ashland Inc., Wilmington, Delaware, USA, may be used. ("Ashland").

Semi-natural polymers include lignosulfonates, such as calcium lignosulfonate and chemically modified polysaccharides. Modified polysaccharides normally useful in the process include modified starches, such as cationic starch; modified guar gum, such as cationic guar gum; and modified celluloses such as anionic carboxymethyl cellulose and hydroxyethyl cellulose. Combinations of semi-natural polymers can be used.

The coagulant is usually selected from an inorganic coagulant, organic coagulant and combinations thereof. Inorganic coagulants include aluminum sulfate, aluminum chloride, polyaluminium chloride, aluminum chlorohydrate, ferric chloride, ferric sulfate, ferrous sulfate and sodium aluminate. Organic coagulants include polymers formed from dimethylammonium chloride diallyl monomers, ethylene imine and the comonomers of epichlorohydrin and di ethylamine. The inorganic coagulants also include cationically modified tannins and melamine-formaldehyde. Such coagulants include CHARGEPAC® 60, CHARGEPAC © 7 and AMERSEP® 5320, all available from Ashland.

Synthetic polymers include anionic, cationic, nonionic and amphoteric polymers, soluble in water. For the purpose of this description, the synthetic polymer will include copolymers and terpolymers, as well as homopolymers. Normally, the synthetic polymer has an Mw (MW) of about 40,000 to about 25,000,000, and those skilled in these techniques, upon reading this description, will appreciate that all ranges and values within these expressly stated ranges are contemplated. The synthetic polymer can be linear, branched or crosslinked. In general, the synthetic polymer functions as a flocculant.

Nonionic polymers include polymers formed from one or more water-soluble ethylenically unsaturated nonionic monomers, for example, acrylamide, methacrylamide, hydroxyethyl acrylate and N-vinylpyrrolidone, preferably acrylamide. The nonionic polymers also include alkoxyethylated multifunctional alcohols.

The cationic polymers are formed from one or more cationic ethylenically unsaturated monomers optionally with one or more of the nonionic monomers mentioned above. The cationic polymer can also be amphoteric always such that they are not more predominantly cationic groups than anionic groups. The cationic monomers include alkyldialkylamino (meth) acrylates, alkyl dialkylamino (meth) acrylamides and diallyl dimethyl ammonium chloride, including acid addition salts and quaternary ammonium salts thereof. Common cationic monomers include the quaternary ammonium salts of methyl chloride of ethyl dimethylamino acrylate and dimethyl aminoethyl methacrylate. Of particular interest are the copolymer of acrylamide with the quaternary ammonium salts of methyl chloride of dimethylamino ethyl acrylate (ADAME); the acrylamide copolymer and acrylamidopropyl trimethyl ammonium chloride (APTAC); and the copolymer of acrylamide and acryloxymethyl trimethyl ammonium chloride (AETAC); and the epichlorohydrin and dimethylamine copolymer.

The synthetic anionic polymers are formed from one or more ethylenically unsaturated anionic monomers or a mixture of one or more anionic monomers with one or more of the nonionic monomers mentioned above. Anionic monomers include acrylic acid, methacrylic acid, maleic acid, crotonic acid, itaconic acid, vinyl sulphonic acid, allylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamide, mixtures thereof, and salts thereof. same.

Of particular interest are the copolymers and / or terpolymers of monomers selected from the group consisting of acrylamide, AMPS, acrylic acid and (meth) acrylic acid. For example, the anionic polymer may be selected from the group consisting of copolymers derived from 2-acrylamido-2-methylpropanesulfonic acid, copolymers of acrylic acid and acrylamide, acrylic acid homopolymers, acrylamide homopolymers, and combinations thereof. Normally the acrylate copolymer of Sodium and acrylamide and the copolymer of acrylic acid and acrylamide are used as anionic polymer.

Also of particular interest are copolymers of AMPS and acrylamide in which the molar percent of AMPS is from about 10 mole percent to about 25 mole percent, and terpolymers of AMPS, acrylamide, and acrylic acid, wherein the mole percent AMPS is from about 10 mole percent to about 30 mole percent, the mole percent acrylamide is from about 40 mole percent to about 60 mole percent, and the. The molar percentage of acrylic acid is from about 20 mole percent to about 40 mole percent. Otherwise, homopolymers of acrylic acid or copolymers of acrylic acid and acrylamide are of particular interest.

The auxiliary filtration promoter and the synthetic polymer are applied in the methods for separating solids from a liquid dispersion. This process comprises the steps of adding the auxiliary filtration promoter and synthetic polymer to an aqueous dispersion of solids in liquids before and / or during the physical separation of the solids from the liquid, producing a Concentrate that comprises the solids, recover the concentrate and then filter the concentrate. Improved filtration is achieved with this method. Physical separation can occur by allowing the solids to settle from the liquid by the force of gravity, optionally with flocculation and / or agglomeration of the solid particles.

The method can be applied in mining operations. A method for desiccation of mining slurries, in particular, improved filtration performance, in a two-stage process having a solid-liquid separation stage and a filtration step, comprising the addition of at least one auxiliary filtration promoter, and at least one synthetic polymer to the mining slurry during or before, or during and before, the solid-liquid separation stage and then filtering the concentrate or sub-flow of the solid-liquid separation stage. Typically, mining slurries are aqueous dispersions comprising minerals, such as those selected from the group consisting of gold, phosphate, silver, platinum, copper, nickel, zinc, lead, molybdenum, iron, carbon and the like. Typically, the solid-liquid separation step is carried out in a medium for separating liquids from solids, such as a thickener by gravity, clarifier or hydrocyclone, and the auxiliary filtration promoter and the synthetic polymer may be added to the aqueous dispersion while the dispersion is in such media and / or before the dispersion enters said media. The filtration step is generally carried out in means for filtering liquid solids, such as a filter press or vacuum filter.

EXAMPLES Preparation of aqueous dispersions for filtration Unless otherwise indicated, aqueous dispersion samples were prepared by adding 1,000 mL of an aqueous dispersion to a graduated cylinder, where it was treated by the addition of the specified components of the auxiliary filtration promoter (ie, coagulant, natural polymer). and / or semi-natural polymer) as set forth in Table I, and tampering with the auxiliary filtration promoter in the dispersion three times with a plunger having punched holes.

Next, the synthetic polymer was added to the aqueous dispersion using the same mixing technique and the number of tamping. The Synthetic Polymer A used in the examples is an anionic copolymer available under the trade name FLOPAM® AN 113 from SNF Floerger, Andrezieu, France. The suppliers and / or trade names for the synthetic polymer and the component (s) of the auxiliary filtration promoter are set forth in Table IA.

The aqueous dispersion was sedimented and left in solution in the graduated cylinder for 72 hours. The supernatant was poured out of the graduated cylinder until only concentrated solids remained, that is, the concentrate remained in the specimen. The resulting suspensions were transferred quantitatively into beakers of suitable size for filtration.

Pressure filtration Unless otherwise indicated, filtration of concentrated slurries was performed at 30 psig with a FANN Press Filter © (FANN Instrument Company, Houston, Texas, USA), and low ash filter paper, hardened , FANN with a retention interval of particle size of 2-5 um. Before transferring to the filter press, the samples were first mixed by hand for 15 seconds. After transferring the sample, the filter press was sealed and pressurized air was applied to the filter press. The volume of fluid extracted from the sample Concentrate was measured as a function of time after application of the pressurized air.

Examples 1-16 and Comparative Examples A and B These examples show the use of natural polymers of Table I with a synthetic polymer (Synthetic Polymer A) to improve the filtration of an aqueous dispersion containing gold concentrate. Comparative Examples A and B use only Synthetic Polymer A as the polymer treatment. For Examples 6, 15 and 16, an additional 30 grams per ton of Natural Polymer A was added before filtration.

In all examples, except for Examples 4 and 5, the natural polymers of variable molecular weight were first added followed by the addition of Synthetic Polymer A. The amount of solids in the aqueous dispersion was 47.1 grams per liter before settling . The flocculant dose (Synthetic Polymer A) remained constant at 53.1 grams per ton, while the ratio of natural polymer to synthetic polymer ranged from 0 to 100%. The natural polymers used and the ratio of natural polymer to Synthetic Polymer A are set forth in Table II. The times to filter 10 and 20 ml were measured. The filtration rates were then calculated and compared with the corresponding comparative example to provide a percentage measure of the increase in the filtration rate (10% mLs and 20% mLs (sic)). These values and the. average of 10% mLs and 20% mLs, are shown in Table II.

The data in Table II demonstrate that the filtration rate of the aqueous dispersion containing gold concentrate increased when natural polymers were used together with the Synthetic Polymer A.

Examples 4 and 5 indicate that the order of addition (Synthetic Polymer A dosed before Polymer Natural A) does not adversely affect the filtration rate of the aqueous dispersion. Examples 6, 15 and 16 show that the additional Natural Polymer A does not positively or negatively impact the filtration rate.

Provide Promedon gave . . . . . . . . . . . . ~ ' . . i. . . . . . 1 . . . . . . . ,. . . . *. . . . l l i i l il Examples 17-74 and Comparative Examples C, D, E and F These examples show the use of natural polymers of Table I with a synthetic polymer (Synthetic Polymer A) to improve the filtration of an aqueous dispersion containing phosphate mineral. Comparative Examples C, D, E and F use only Synthetic Polymer A as the polymer treatment. The amount of solids in the aqueous dispersion ranges from 215.9 to 285.3 grams per liter before settling. The dose of flocculant (Synthetic Polymer A) in the examples ranges from 39.4 to 52.1 grams per ton, while the ratio of natural polymer to synthetic polymer varied from 0 to 200%. The natural polymers used and the ratio of natural polymer to Synthetic Polymer A are set forth in Table III. The times for filtering 15 and 30 mL were measured. The filtration rates were then calculated and compared with the corresponding comparative example to provide a percentage measure of the. increase in the filtration rate (% 15 mLs and% 30 mLs (sic)). These values and the average of% 15 mLs and% 30 mLs are shown in Table III.

The data in Table III show that the filtration rate of mineral dispersions containing mineral of phosphate increased when the natural polymers of variable molecular weight were added to the aqueous dispersion before Synthetic Polymer A and allowed to settle. The data indicate that natural polymers with a wide range of molecular weights are efficient filtering auxiliary promoters over a wide range of product proportions. ; i ' -, < . 3 - . 3 - '' i · . < .

! '· ; Examples 75-94 and Comparative Examples S and H These examples show the use of natural and / or semi-natural polymers of Table I with a synthetic polymer (Synthetic Polymer A) to improve the filtration of an aqueous dispersion containing gold concentrate. Comparative Examples G and H use only Synthetic Polymer A as the polymer treatment. Examples 92-94 use natural and semi-natural polymers, which were applied before Synthetic Polymer A. The amount of solids in the aqueous dispersion was 200.6 or 209.1 grams per liter before settling. The dose of flocculant (Synthetic Polymer A) in the examples was 112.2 or 143.5 grams per ton, while the proportion of natural polymer or polymer was inatural to the synthetic polymer varied from 0 to 100%. The natural and semi-natural polymers used and the proportion of natural and semi-natural polymers for the Synthetic Polymer A are set forth in Table IV. The times to filter 30 and 60 mL were measured. The filtration rates were then calculated and purchased with the corresponding comparative example to provide a percentage measure of the increase in the filtration rate (30% mLs and 60% mLs). These values and the average of% 30 mLS and% 60 mLs are shown in Table IV. l li . l l . l l l l l. í l l i ·. i l! l i i • i l l l i i . i l l l i i l l i l i i! l i i i i l i i. i l i l i l i • . i l i i. i l l i l i i i i i i i l l i l i i i l l i l ' i i The contents of Table IV demonstrate that the filtration rate of aqueous dispersions containing gold concentrate increased when natural polymers of variable molecular weight were added to the aqueous dispersion before Synthetic Polymer A and allowed to settle. Semi-natural polymers were also effective filtration enhancers when used alone or in combination with Natural Polymer B.

Examples 95-106 and Comparative Example I These examples show the use of natural polymers were inattriated with coagulants of Table I with synthetic polymer (Synthetic Polymer A) to improve the filtration of an aqueous dispersion containing gold concentrate. Comparative Example I only used Synthetic Polymer A as the polymer treatment. Examples 95-100 and 104-109 used natural or semi-natural polymers in combination with a coagulant, which was applied before Synthetic Polymer A. In Examples 108 and 109, Natural Polymer B and the coagulant were mixed together before dosing . The amount of solids in the aqueous dispersion was 208.1 grams per liter before settling. The dose of flocculant (Synthetic Polymer A) in the examples was 144.1 grams per ton, while the ratio of natural or semi-natural polymers with coagulant to the synthetic polymer ranged from 0 to 100%. The natural or semi-natural polymers with coagulant used and the proportion of such natural or semi-natural polymers with coagulant to the Synthetic Polymer A are set forth in Table V. The times for filtering 30 and 60 m.L. The filtration rates were then calculated and compared with the corresponding comparative example to provide a percentage measure of the increase in the filtration rate. { % 30 mLs and% 60 mLs). These values and the average of% 30 mLs and% 60 mLs are shown in the Table V.

The data in Table V shows that the filtration rate of aqueous dispersions containing gold concentrate increases when Polymer is added Natural B or Seminatural B Polymer, in combination with coagulants, to the aqueous dispersion before the Polymer Synthetic A, and left to settle. The combinations of Natural Polymer B and Coagulant A or B, were effective filtering orators mixed or dosed separately. - ' . j,

Claims (20)

1. A method for improving filtration performance for the separation of liquid solids in an aqueous dispersion, comprising a solids phase and a liquid phase in a two-stage process having a physical separation step and a filtration step that it comprises adding at least one auxiliary filtration promoter, and at least one synthetic polymer to the aqueous dispersion during or before, or during and before, the physical separation step resulting in a concentrate and filtering the concentrate.

2. The method of Claim 1 wherein the auxiliary filtering promoter comprises at least one of the following: a natural polymer, a semi-natural polymer or a coagulant.

3. The method of Claim 2, wherein the natural polymer comprises a polysaccharide.

4. The method of Claim 3, wherein the polysaccharide is selected from the group consisting of potato starch, xanthan gum, guar, dextran, cellulose derivative and glycosaminoglycan.

5. The method of Claim 2, wherein the coagulant is an inorganic coagulant selected from the group consisting of aluminum sulfate, aluminum chloride, aluminum polychloride, aluminum chlorohydrate, ferric chloride, ferric sulfate, ferrous sulfate, and sodium aluminum.

6. The method of Claim 2, wherein the coagulant is an organic coagulant selected from the group consisting of polymers comprising diallyl dimethyl ammonium chloride, ethylene imine and comonomers of epichlorohydrin and dimethyla, cationically modified tannins and melamine formaldehyde.

7. The method of Claim 2, wherein the seminatural polymer is selected from the group consisting of lignosulfonate, chemically modified polysaccharide and combinations thereof.

8. The method of Claim 1, wherein the synthetic polymer is a nonionic polymer comprising monomers selected from the group consisting of acrylamide, methacrylamide, hydroxyethyl acrylate and N-vinylpyrrolidone.

9. The method of Claim 1, wherein the synthetic polymer is an anionic polymer comprising monomers selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, crotonic acid, itaconic acid, vinyl sulfonic acid, allyl sulfonic acid, acid 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, combinations thereof and salts thereof.

10. The method of Claim 1, wherein the synthetic polymer is a cationic polymer comprising monomers selected from the group consisting of dialkylamino alkyl (meth) acrylate, acid addition salts of (meth) acrylate dialkylaminoalkyl, quaternary ammonium salts of meth) dialkylamino alkyl acrylate, dialkylaminoalkyl (meth) acrylamide, acid addition salts of dialkylamino alkyl (meth) acrylamide, quaternary ammonium salts of dialkylamino alkyl (meth) acrylamide, diallyl dimethyl ammonium chloride, acid addition salts of diallyl dimethyl ammonium, and quaternary ammonium salts of diallyl dimethyl ammonium chloride.

11. The method of Claim 1, wherein the synthetic polymer comprises an amphoteric polymer.

12. The method of claim 1, wherein the aqueous dispersion comprises a mineral selected from the group consisting of gold, phosphate, silver, platinum, copper, nickel, zinc, lead, molybdenum, iron and carbon.

13. A composition for improving the filtration of mining slurries comprising at least one auxiliary filtration promoter and at least one synthetic polymer.

14. The composition of Claim 13, wherein the auxiliary filtration promoter comprises at least one of the following: a natural polymer, a semi-natural polymer or a coagulant.

15. The composition of Claim 14, wherein the natural polymer comprises polysaccharide.

16. The composition of Claim 15, wherein the polysaccharide is selected from the group consisting of potato starch, xanthan gum, guar, dextran, cellulose derivative and glycosaminoglycan

17. The composition of Claim 14, wherein the seminatural polymer is selected from the group consisting of in lignosulfonate, chemically modified polysaccharide and combinations thereof.

18. The composition of Claim 14, wherein the coagulant is selected from the group consisting of a) an inorganic coagulant selected from the group consisting of aluminum sulfate, aluminum chloride, aluminum polychloride, aluminum chlorohydrate, ferric chloride, ferric sulfate, ferrous sulfate and sodium aluminate; b) an organic coagulant selected from the group consisting of polymers comprising diallyl dimethyl ammonium chloride, ethylene imine and comonomers of epichlorohydrin and dimethylamine, cationically modified tannins and melamine formaldehyde; Y c) combinations thereof.

19. The composition of Claim 13, wherein the synthetic polymer is selected from the group consisting of a) anionic polymer comprising monomers selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, crotonic acid, itaconic acid, vinylsulfonic acid, allylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, combinations thereof and salts thereof; b) cationic polymer comprising monomers selected from the group consisting of (meth) acrylate dialkylamino alkyl, acid addition salts of dialkylamino alkyl (meth) acrylate, quaternary ammonium salts of (meth) acrylate dialkylamino alkyl dialkylamino alkyl (meth) acrylamide , acid addition salts of dialkylamino alkyl (meth) acrylamide, quaternary ammonium salts of dialkylamino alkyl (meth) acrylamide, diallyl dimethyl ammonium chloride, acid addition salts of diallyl dimethyl ammonium chloride and quaternary ammonium salts of diallyl chloride dimethyl ammonium; Y c) nonionic polymer comprising monomers selected from the group consisting of acrylamide, methacrylamide, hydroxyethyl acrylate and N-vinylpyrrolidone.

20. The composition of Claim 13, wherein the synthetic polymer comprises amphoteric polymer.