RELATED APPLICATIONS

[0001] The present application claims priority to U.S. provisional application No.: 63/343,715, filed on May 19, 2022, the contents of which are incorporated by reference in their entirety.

FIELD OF THE INVENTION

[0002] The present invention generally relates to filter aid compositions and processes for dewatering a slurry, optionally a mined ore slurry. More specifically, the invention relates to adding to contacting a slurry to be dewatered with a filter aid comprising one or more fatty alcohol polyglycol ethers and then dewatering the slurry to achieve increased filtration rate and decreased moisture content in the filter cake.

BACKGROUND OF THE INVENTION

[0003] Many industrial processes use dewatering and filtering steps, in which the water content of a bulk solid or slurry is reduced by filtering or other methods. Dewatering processes are necessary, for example, in the treatment of sludge (for example, in sludge ponds or sludge from municipal wastewater treatment process), slurries and in paper-based pulp as well as in other paper treatment processes.

[0004] Dewatering methods are also used in mining, for example, in dewatering of mine tailings, and metal ores. Specifically, the mining, processing, and purification of naturally occurring minerals often involve one or more processing or treatment operations in which fine mesh size particles of the mineral of interest are suspended or dispersed in a continuous medium, e.g., a continuous aqueous medium, and the mineral particles are then separated from the medium.

[0005] It is preferable to reduce the residual moisture content of the recovered mineral material (i.e., dewatering) to as low a value as is practicable. Generally, dewatering may be achieved by either mechanical means (e.g., filtration and centrifugation) or thermal drying. In general, mechanical means are more cost effective as compared to thermal drying. However, in spite of its economic advantages, mechanical dewatering often becomes inefficient with finer particle sizes.

[0006]

[0007] For example, in coal processing plants, mined coal is ground and washed to remove sulfur and gangue materials therefrom. In the fine coal circuit of such facilities, fine mesh size coal (e.g., 28 mesh size and smaller) is recovered and dewatered using various filtering and/or drying equipment. For example, vacuum filtering equipment is often used to dewater fine mesh size coal in such processing facilities. Such equipment is typically capable only of reducing the fine coal filter cake moisture content to a certain extent (e.g., 25-30 % residual moisture by weight). Centrifugal driers of various types may also be employed in the fine coal circuits of coal processing facilities to dewater coal in the size range up to and including 9.5 mm by 0.6 mm. Such driers are typically used in conjunction with dewatering screens located immediately upstream of said driers in the dewatering operation. The lowest moisture content that such driers are capable of accomplishing as a practical matter is dependent upon a variety of factors including the particle size of the coal being dewatered.

[0008] In a further example of mineral processing, minerals of value may be separated from the relatively worthless gangue by flotation in an aqueous medium. The resulting ore concentrates comprise a slurry or pulp of ore concentrates in water, often in undesirably great amounts of water. The slurry from the flotation process, having about 15-25% solids by weight, is introduced to a thickener where the solids settle and become concentrated at the bottom. Flocculants are occasionally added to the slurry to facilitate this settling process. The thickener overflow consisting of a large volume of high quality water may be returned to the mill water supply for further use. The thickened solids, typically 35% to 75% by weight, are then pumped to a filter where additional water is removed and a filter cake is built up on a filter media. The filter cake is discharged as the product while the filtrate is returned to the thickener. However, in the filtration of ore concentrated without the use of a filtration aid, the resulting filter cake is generally wet, plastic, sticky and difficult to handle.

[0009] Filter aids are a group of relatively inert materials that can be used in filtration pretreatment. Traditionally, anionic or nonionic surfactants have been used to reduce the surface tension of the water associated with the metal ore, or other material to be dewatered. The water is thus removed more readily leading to decreased filter cake moisture. Thus, surfactants, such as sulphosuccinate esters are currently used as filter aids in the mineral ore processing industry, however these materials often contribute significant cost to the overall process.

[0010] Polymers are also widely used as filtration aids. Commonly used polymeric filtration aids include polyacrylamide homopolymers and copolymers of acrylamide and acrylic acid, which are described, for example, in US 5,185,135. Such negatively charged polyacrylamide copolymers are known to cause flocculation (and are, indeed, exploited as flocculants) and this property is undesirable in a filter aid because water that is captured in flocs is not easily released. This effect of polymers is seen especially in disc filters. Thus, polyacrylamide polymers when used as flocculation agents in metal ore processing, lead to an increase in filter cake moisture levels, even in the presence of a surfactant filter aid. Furthermore, the presence of metal ore flocculants makes filtering with, for example, a filter disk system, difficult because the flocculation causes disc filter capacity to increase and the cake thickness to increase. This results in increased filtering resistance, which again results in filter cake with high moisture.

[0011] There are generally two objectives related to the addition of filter aids. One is to form a layer of second medium which protects the basic filter medium of the system. This is commonly referred to as "precoat". The second objective of filter aids is to improve the flow rate by decreasing cake compressibility and increasing cake permeability. This type of usage is termed as "admix" or "body feed".

[0012] Thus, currently in mineral ore processing, filter aids may be used to improve processing costs by increasing filter throughput, increasing life of the filter media (as it is protected by the filter aid precoat) and increasing dry solids of the filter cake (the second objective cited above). As overall industrialization increases, the need for higher throughput filtering processes increases.

[0013] There is especially a need to develop filtration aids suitable for all filter types for use in ore mining. As reserves of high grade iron ores become scarcer, it is expected that greatly increased tonnage of lower-grade iron ores will be recovered in the foreseeable future. These lower grade ores usually have to be ground to smaller particle size to liberate the valuable metal. Thus, smaller particles often block the filters which results in a loss of production and increased cost. Development of compositions, in particular dewatering aids, and methods to increase the efficiency of processing such low grade and mineral slurries are needed. [0014] The processing of lower grade ore sources involves the removal of unwanted minerals (such as silicates and carbonates) which are an intrinsic part of the ore rock itself (gangue). Development of compositions and methods to increase the efficiency of processing such low grade ores is highly desired in the industry. In particular dewatering aids, for use in improving the processing efficiency of mineral ores and mineral slurries are needed.

[0015] It is therefore an object of the invention to provide a filtration and dewatering aid that may be used in the mineral ore industry as well as other industries where dewatering is essential part of the process. Other industries that need new dewatering or filtration aids are sludge dewatering, in, for example, municipal wastewater treatment plants, pulp dewatering in, for example, the paper industry, tailings dewatering, oil sand dewatering, mineral dewatering.

[0016] It is an additional purpose of the present application to provide a process for using the inventive filtration aids for dewatering a slurry.

[0017] The present application discloses filter aid compositions and processes for dewatering a slurry in order to increase filtration rate, increase dry solids content in the cake, and/or decrease water content in the cake compared to dewatering the slurry in the absence of the inventive filter aids.

[0018] The inventive method satisfies a need for a cost effective and efficient dewatering agents for the mining industry.

SUMMARY OF THE INVENTION

[0019] The present disclosure provides a composition for dewatering a slurry, optionally an aqueous ore slurry. In some embodiments, the composition comprises one or more fatty alcohol polyglycol ethers, wherein the fatty alcohol polyglycol ethers have a number average molecular weight selected from 500-2200 g/mol, 550-1800 g/mol, and 600-1500 g/mol. In some embodiments, the one or more fatty alcohol polyglycol ethers are linear, branched, or a combination thereof. In some embodiments, the one or more fatty alcohol polyglycol ethers are formulated as a pourable solid, liquid, solution, slurry, or combination thereof.

[0020] In some embodiments, the one or more fatty alcohol polyglycol ethers: (a) are non-ionic surfactants, optionally having anionic and/or cationic substituents; (b) are prepared by ethoxylation of linear or branched fatty acids; (c) have a degree of ethoxylation ranging from 2 to 5; or (d) any combination of (a)-(c).

[0021] The present disclosure also provides a filter aid comprising a pourable liquid surfactant. In some embodiments, the pourable liquid surfactant comprises: (a) 80 to 99.9 % by weight of the one or more fatty alcohol polyglycol ethers of claims 1 or 2; and (b) 0.1 to 12% by weight of water.

[0022] In some embodiments, the pourable liquid surfactant has (a) a freezing temperature ranging from -15 to -1 °C; (b) a density ranging from 0.94 to 0.98 g/cm ³ (at 30 °C); (c) a dynamic viscosity ranging from 40 to 70 mPas (at 25 °C); and (d) a pH in the range of 5-7, when formulated as a 1% solution in water.

[0023] In some embodiments, the composition or filter aid, when added to a slurry to be dewatered at a dosage ranging from 1-200 grams of the composition or filter aid per ton of dry solid in the slurry (g/t) and the slurry is further dewatered to form a cake, results in increased filtration rate, increased dry solids content in the cake, and/or decreased water content in the cake compared to dewatering the slurry in the absence of the composition or filter aid.

[0024] The present disclosure also generally encompasses a method for dewatering a slurry, optionally an ore slurry. In some embodiments, the method may include: a) contacting a slurry to be dewatered with a filter aid comprising one or more fatty alcohol polyglycol ethers, wherein the one or more fatty alcohol polyglycol ethers have a number average molecular weight selected from 500-2200 g/mol, 550-1800 g/mol, and 600-1500 g/mol; and are linear, branched, or a combination thereof; b) dewatering the slurry by a method selected from disk filtration, pressure filtration, vacuum filtration, and gravity filtration through a filter to form a cake and a filtrate; c) recovering the cake, optionally for further processing; and d) recovering the filtrate, optionally for further processing;

[0025] wherein steps (a)-(d) are effected successively.

[0026] In some embodiments, the one or more fatty alcohol polyglycol ethers: (a) are non-ionic surfactants, optionally having anionic and/or cationic substituents; (b) are prepared by ethoxylation of linear or branched fatty acids; (c) have a degree of ethoxylation ranging from 2 to 5; (d) are formulated as a pourable solid, liquid, solution, slurry, or combination thereof; or (e) any combination of (a)-(d).

[0027] In some embodiments, the filter aid comprising one or more fatty alcohol polyglycol ethers is/are formulated as a pourable concentrate comprising 80 to 99.9 % by weight of the one or more fatty alcohol polyglycol ethers and 0.1 to 12% by weight of water.

[0028] In some embodiments, the pourable concentrate has (a) a freezing temperature ranging from -15 to -1 °C; (b) a density ranging from 0.94 to 0.98 g/cm ³ (at 30 °C); (c) a dynamic viscosity ranging from 40 to 70 mPas (at 25 °C); and (d) a pH in the range of 5-7, when formulated as a 1% solution in water.

[0029] In some embodiments, some or all of the filter aid is pre-mixed with the slurry to be dewatered. In other embodiments, some or all of the filter aid is precoated onto the filter.

[0030] In some embodiments, the slurry to be dewatered is chosen from a mined ore slurry, a metal ore slurry, an iron ore slurry, an oil sand slurry, a tailings slurry, a municipal wastewater sludge, a vegetal pulp, optionally, for paper manufacture, and a food and/or beverage pulp.

[0031] In some embodiments, the filter aid is added to the slurry to be dewatered at a dosage ranging from 1-200 grams of the filter aid per ton of dry solid in the slurry (g/t). In exemplary embodiments, the filter aid is added to the slurry to be dewatered at a dosage ranging from 40-80 g/t.

[0032] In exemplary embodiments, method results in increased filtration rate, increased dry solids content in the cake, and/or decreased water content in the cake compared to dewatering the slurry in the absence of the filter aid.

[0033] In some embodiments, the method may be effected at any time during a slurry dewatering process selected from a wet mineral ore dewatering processes, a sludge dewatering processes, a pulp dewatering processes, an oil sand dewatering processes, a tailings dewatering process, and a food and/or beverage sludge/pulp dewatering processes. [0034] The invention also provides a solid ore product comprising one or more compositions or filter aids disclosed herein, obtainable by a method disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention will be described in more detail with reference to appended drawings, described in detail below.

[0036] FIG 1 provide an exemplary picture of a Buchner funnel apparatus for evaluation of filter aid efficiency according to Example 1.

[0037] FIG 2 provides a graph of percent decrease in moisture content of filtered ore cakes achieved by various filtration aids compared to blank according to Example 1.

[0038] FIG 3 provides a graph of percent decrease in surface drying time of filtered ore cakes achieved by various filtration aids compared to blank according to Example 1.

DETAILED DESCRIPTION OF THE INVENTION

[0039] Before describing the invention, the following definitions are provided. Unless stated otherwise all terms are to be construed as they would be by a person skilled in the art.

DEFINITIONS

[0040] As used herein, the singular forms "a", "and", and "the" include plural referents unless the context clearly dictates otherwise. All technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs unless clearly indicated otherwise.

[0041] As used herein, the term "slurry" refers to any flowable suspension of particles or fibers in liquid, e.g.,. water. As used herein, the term "slurry" may refer to, for example a metal ore slurry, iron ore slurry, or a mineral ore slurry, for example, coal slurry, or an oil sand slurry. The term "slurry" may refer to a flowable sludge, for example a wastewater sludge, or a cellulose pulp. Such a pulp may be dewatered, for example in the paper manufacturing industry.

[0042] As used herein "dewatering" means the removal of water from solid, semi solid (for example pulp or gel) material, or soil or a slurry by any process suitable for industrial application.

[0043] As used herein "dewatering aid" generally refers to a substance added to a slurry (e.g., a mineral ore or tailings slurry) to enhance removal of water from solid, semi solid (for example pulp or gel), or soil material, within the bulk slurry by any process suitable for industrial application. Such processes include filtration, thickening, centrifugation, and sedimentation.

[0044] As used herein "filter aid" and "filtration aid" refer to a substance added to a slurry (e.g., a mineral ore or tailings slurry) to enhance removal of water from solid, semi solid (for example pulp or gel), or soil material, within the bulk slurry by any filtration process suitable for industrial application. Mining filter aids are generally surface active agents that help reduce the moisture content of mineral concentrates during filtration applications. These products tend to reduce the surface tension of water so that water is easily removed from mineral surfaces during filtration. Filter aids are widely used in all wet mineral processing applications where reducing moisture content of filtered cakes is desired. Application areas include both sulfide and non-sulfide minerals processing and as well as coal filtration. Filtration aids may act to flocculate particles into larger, more filterable agglomerates. Filter aids may also adsorb to or coat the surface of particles, thereby altering surface properties, such as hydrophilicity and smoothness, allowing for water to more easily flow across and be released from the surface of the coated particle during filtration.

[0045] Filtration aids, particularly the fatty alcohol polyglycol ether filtration aids of the present invention, are used to enhance filtration processes, wherein the enhancements generally sought include increase in filtration rate and minimization of liquid in the filter cake (i.e., lower residual moisture in retained solids).

[0046] Filter aid dosage requirements vary widely based on the application. Filter aids can be applied neat or in diluted form to various points of application in the solid-liquid separation process. Filter aids can be added to form a layer of second filter medium which protects the basic filter medium of the system. This is commonly referred to as "precoat". Filter aids can be added to improve the flow rate by decreasing cake compressibility and increasing cake permeability. This type of usage is termed as "admix" or "body feed", during which filter aids can be added to spray water applications onto filter cakes during filtration so that filter wash efficiency is improved, or added directly into the mineral or to concentrated slurries upstream of filtering processes and also prior to other dewatering processes, such as thickening and centrifugation.

[0047] As used herein, the term "flocculation" generally refers to the tendency for fibers to collect together in bunches in the presence of flow, and especially in the presence of filter aids; the same word also refers to the action of high-mass polymers in forming bridges between suspended colloidal particles, causing strong, relatively irreversible agglomeration.

[0048] The term "flocculant" may generally refer to a reagent that may bridge neutralized or facilitate coagulation of particles into larger agglomerates, typically resulting in more efficient settling. Flocculation process generally involves addition of a flocculant followed by mixing to facilitate collisions between particles, allowing for the destabilized particles to agglomerate into larger particles that can be removed by gravity through sedimentation or by other means, e.g., centrifugation, filtration.

[0049] As used herein, the terms "polymer" or "polymeric additives" and similar terms are used in their ordinary sense as understood by one skilled in the art, and thus may be used herein to refer to or describe a large molecule (or group of such molecules) that may comprise recurring units.

Polymers may be formed in various ways, including by polymerizing monomers and/or by chemically modifying one or more recurring units of a precursor polymer. Unless otherwise specified, a polymer may comprise a "homopolymer" that may comprise substantially identical recurring units that may be formed by, for example, polymerizing, a particular monomer. Unless otherwise specified, a polymer may also comprise a "copolymer" that may comprise two or more different recurring units that may be formed by, for example, copolymerizing, two or more different monomers, and/or by chemically modifying one or more recurring units of a precursor polymer. As used herein, the term "copolymer" generally encompasses any known form of polymer derived from more than one species of monomer, including, but not limited to branched copolymers, graft copolymers, and linear copolymers, such as block, alternating, periodic, statistical, random, and gradient copolymers. Unless otherwise specified, a polymer or copolymer may also comprise a "terpolymer" which generally refers to a polymer that comprises three or more different recurring units. Any one of the one or more polymers discussed herein may be used in any applicable process, for example, as a strengthening agent or promoter. [0050] As used herein, the term "anionic" generally refers to a chemical moiety that possesses a negative charge or that is positively charged at a pH within the normal operating range of a filtration processes.

[0051] As used herein, the term "cationic" generally refers to a chemical moiety that possesses a positive charge or that is positively charged at a pH within the normal operating range of a filtration processes.

[0052] As used herein, the term "nonionic" generally refers to a chemical moiety that possesses a neutral charge.

[0053] As used herein, the term "water-soluble" generally refers to polymer products that are fully miscible with water. When mixed with excess of water, the cationic emulsion polymer in the polymer product is preferably fully dissolved and the obtained polymer solution is preferably free from discrete polymer particles or granules.

[0054] As used herein, the term "aqueous solution" or "solution" generally refers to a mixture of water and a water-soluble solute or solutes which are completely dissolved. The solution may be homogenous. When mixed with excess of water, the cationic emulsion polymer in the polymer product is preferably fully dissolved and the obtained polymer solution is preferably free from discrete polymer particles or granules.

[0055] As used herein, the term "aqueous suspension", "aqueous slurry", or "slurry" generally refer to a heterogeneous mixture of a fluid that contains insoluble or sparingly soluble solid particles sufficiently large for sedimentation. Suspensions and slurries of the present invention may also comprise some amount of solid particles, often termed colloidal particles, which do not completely settle or take a long time to settle completely.

[0056] As used herein, the term "surfactant" generally refers to compounds that lower the surface tension (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, or dispersants.

[0057] The terms, "total solids" or "total solids content" are used interchangeably herein and generally refer the total amount or weight of dry solids contained in a mixture of solids and liquids, e.g., a filter cake.

[0058] As used herein, the term "ppm" refers to parts per million on the basis of milligrams of solute per liter of aqueous solution or slurry (e.g., mg/L).

[0059] As used herein, the terms "g/t" or "g/ton" denote grams of dry/neat mass (additive, solute, and/or particle) per ton of dry solids in a slurry.

[0060] As used herein, the phrases "% by wt." denotes pounds of dry mass of additive per dry mass of solids in the formulation, solution, or slurry, multiplied by 100%.

DESCRIPTION OF THE INVENTION

[0061] Filtration is a crucial step in mining processes. As global demand for ores continuously increases, mining companies tend to increase throughput with existing process and minimum CAPEX. The filtration unit is often a bottle neck for increasing capacity. Use of filter aids helps mining companies increase filter throughput and increase dry solids in the cake, which reduces cost of transportation and improves quality of ore for metal processing companies. [0062] Another trend in the mining industry followed by several tailings dam failures has been to start dewatering tailings to avoid risk of tailing dam failures and also to recover and reuse process water. Legislation for dewatering of tailings is already in place in several counties in south America and this trend is likely to spread in the future.

[0063] Although dewatering of tailings does not bring economic benefits, it is recognized that, if legislation becomes stricter, mines will have to start dewatering tailings in order to operate. This represents a commercial opportunity, as mines typically produce tailings several hundred times more than they produce valuable metals. Therefore, it is important to identify chemistries that can dewater mineral slurry quicker and to a higher solid content.

[0064] The various exemplary embodiments disclosed herein generally relate to methods for filtering and dewatering in industrial processes. Exemplary methods may generally comprise the use of one or more filter aids according to any embodiment of the invention to filter an aqueous suspension, slurry, or pulp. The present embodiments also generally relate to a product that may be produced by any of the methods described herein.

[0065] Fatty alcohol polyglycol ethers are nonionic surfactants, prepared by ethoxylation of fatty alcohols with ethylene oxide or propylene oxide using alkaline catalyst. They may be branched or linear in structure. The degree of ethoxylation can vary depending on the chain length of the fatty acid and the purpose for which it will be used.

[0066] Ethoxylation is a chemical reaction in which at least one ethylene oxide unit adds to a substrate. It is the most widely practiced alkoxylation, which involves the addition of epoxides to substrates.

[0067] In the usual application, alcohols and phenols are converted into R(OC2H4)nOH where n typically ranges from 1 to 10 or higher in number. Such compounds are called alcohol ethoxylates. Alcohol ethoxylates function as surfactants and are widely used in cosmetic and other commercial products.

[0068] Industrial ethoxylation is primarily performed upon fatty alcohols in order to generate fatty alcohol ethoxylates, also known as fatty alcohol polyglycol ethers, which are a common form of nonionic surfactant (e.g., octaethylene glycol monododecyl ether). Such alcohols may be obtained by the hydrogenation of fatty acids from seed oils, or by hydroformylation in the Shell higher olefin process.

[0069] The industrial ethoxylation reaction proceeds by blowing ethylene oxide through the alcohol at 180 °C and under 1-2 bar of pressure, with potassium hydroxide (KOH) serving as a catalyst. The process is highly exothermic (AH -92 kJ/mol of ethylene oxide reacted) and requires careful control to avoid a potentially disastrous thermal runaway.

[0070] ROH + n C ₂ H ₄ O - R(OC ₂ H ₄ ) _n OH

[0071] The starting materials are usually primary alcohols as they tend to react 10-30x faster than do secondary alcohols. Typically, 5-10 units of ethylene oxide are added to each alcohol, however ethoxylated alcohols can be more prone to ethoxylation than the starting alcohol, making the reaction difficult to control and leading to the formation of a product with varying repeat unit length (the value of n in the equation above). Better control can be afforded by the use of more sophisticated catalysts, which can be used to generate narrow-range ethoxylates. [0072] The resulting fatty alcohol polyglycol ethers are characterized by excellent wetting properties, low foam, and high effectiveness even at low temperatures. Ethoxylated alcohols are considered to be a high production volume (HPV) chemical by the US EPA.

[0073] The present disclosure generally encompasses a composition for dewatering a slurry or a filter aid comprising a pourable surfactant. This composition or filter aid may comprise one or more branched or linear fatty alcohol polyglycol ethers having a number average molecular weight ranging from 500-2200 g/mol.

[0074] The present disclosure also generally encompasses a method for dewatering a slurry, optionally an ore slurry. This method may comprise contacting a slurry to be dewatered with a filter aid comprising one or more fatty alcohol polyglycol ethers, wherein the one or more fatty alcohol polyglycol ethers have a number average molecular weight selected from 500-2200 g/mol, 550-1800 g/mol, and 600-1500 g/mol; and are linear, branched, or a combination thereof.

[0075] Surprisingly, the inventors have found that the filter aid comprising one or more fatty alcohol polyglycol ethers have excellent filtering capabilities, with reduced water throughput time and reduced filter cake moisture. The molecules can thus be used as effective filter aids in all conventional filtering systems, including, but not exclusively, in mining oil sand, paper and pulp applications, food and beverage pulp dewatering and in sludge dewatering in municipal/industrial wastewater treatment. Generally, the filter aids may be used with any conventional filters including rotary (disc and drum) and horizontal belt filters, magnetic filters or pressure filters.

[0076] It was also surprisingly found that the inventive filter aids comprising fatty alcohol polyglycol ethers outperformed a benchmark product comprising a surface active agent. An embodied filter aid applied as dosage ranging from 40-100 g/t of concentrate decreased surface dry time by 2.5-16.3%. This increase in filtration rate allows for capacity to be increased without replacing existing units. Dry solids in the filter cake increased by 1.5-2.1 %, compared to a benchmark product. This increase in dry solids means less energy is required for downstream processes, such as further filtration, drying, and pelletizing. An exemplary plant spends 5.3 Million Euro/year for filter aids (1900 MT/year). Desktop calculations indicated that a 1.6% increase in dryness of cake could save up to 4 Million Euro/year for a pelletizing unit with capacity of 10 million MT/year. Therefore, the inventive filtration aids have the potential to save significant amounts of money.

[0077] Traditionally, surfactants and polymers are used as filter aids in disc filters in iron ore processing. An advantage of the inventive fatty alcohol polyglycol ethers chemistry is that the molecular weights are much lower than found in typical polymeric filter aids, such as dry polyacrylamide. This reduces the negative flocculation effect. Simultaneously the fatty alcohol polyglycol ether groups have surface-active properties, which give the mineral hydrophobic properties and therefore help water release from the filter cake.

[0078] In particular, the results disclosed herein demonstrate that the compositions, filter aids, and methods for dewatering a slurry of the present disclosure may be used to achieve increased filtration rates and to produce filter cakes with increased dry solids content in the cake and/or decreased water content in the cake compared to dewatering slurry in the absence of the composition or filter aid.

[0079] The subject methods for dewatering a slurry, optionally an ore slurry, afford one or more of the following advantages: (i) Increase in filtrate throughput, allowing for filtration capacity to be increased with existing filtrations units, (ii) increased dry solids content in the cake and/or decreased water content in the cake, and (iii) lower solidification temperature, allowing for storage and application in freezing conditions without need of any additional chemicals (antifreeze).

[0080] The present disclosure provides a composition for dewatering a slurry, optionally an aqueous ore slurry. In some embodiments, the composition comprises one or more fatty alcohol polyglycol ethers, wherein the fatty alcohol polyglycol ethers have a number average molecular weight selected from 500-2200 g/mol, 550-1800 g/mol, and 600-1500 g/mol. In some embodiments, the one or more fatty alcohol polyglycol ethers are linear, branched, or a combination thereof. In some embodiments, the one or more fatty alcohol polyglycol ethers are formulated as a pourable solid, liquid, solution, slurry, or combination thereof.

[0081] In some embodiments, the one or more fatty alcohol polyglycol ethers: (a) are non-ionic surfactants, optionally having anionic and/or cationic substituents; (b) are prepared by ethoxylation of linear or branched fatty acids; (c) have a degree of ethoxylation ranging from 2 to 5;. or (d) any combination of (a)-(c).

[0082] The present disclosure also provides a filter aid comprising a pourable liquid surfactant. In some embodiments, the pourable liquid surfactant comprises: (a) 80 to 99.9 % by weight of the one or more fatty alcohol polyglycol ethers of claims 1 or 2; and (b) 0.1 to 12% by weight of water.

[0083] In some embodiments, the pourable liquid surfactant has (a) a freezing temperature ranging from -15 to -1 °C; (b) a density ranging from 0.94 to 0.98 g/cm ³ (at 30 °C); (c) a dynamic viscosity ranging from 40 to 70 mPas (at 25 °C); and (d) a pH in the range of 5-7, when formulated as a 1% solution in water.

[0084] In some embodiments, the composition or filter aid, when added to a slurry to be dewatered at a dosage ranging from 1-200 grams of the composition or filter aid per ton of dry solid in the slurry (g/t) and the slurry is further dewatered to form a cake, results in increased filtration rate, increased dry solids content in the cake, and/or decreased water content in the cake compared to dewatering the slurry in the absence of the composition or filter aid.

[0085] The present disclosure also generally encompasses a method for dewatering a slurry, optionally an ore slurry. In some embodiments, the method may include: a) contacting a slurry to be dewatered with a filter aid comprising one or more fatty alcohol polyglycol ethers, wherein the one or more fatty alcohol polyglycol ethers have a number average molecular weight selected from 500-2200 g/mol, 550-1800 g/mol, and 600-1500 g/mol; and are linear, branched, or a combination thereof; b) dewatering the slurry by a method selected from disk filtration, pressure filtration, vacuum filtration, and gravity filtration through a filter to form a cake and a filtrate; c) recovering the cake, optionally for further processing; and d) recovering the filtrate, optionally for further processing;

[0086] wherein steps (a)-(d) are effected successively.

[0087] In some embodiments, the one or more fatty alcohol polyglycol ethers: (a) are non-ionic surfactants, optionally having anionic and/or cationic substituents; (b) are prepared by ethoxylation of linear or branched fatty acids; (c) have a degree of ethoxylation ranging from 2 to 5; (d) are formulated as a pourable solid, liquid, solution, slurry, or combination thereof; or (e) any combination of (a)-(d). [0088] In some embodiments, the filter aid comprising one or more fatty alcohol polyglycol ethers is/are formulated as a pourable concentrate comprising 80 to 99.9 % by weight of the one or more fatty alcohol polyglycol ethers and 0.1 to 12% by weight of water.

[0089] In some embodiments, the pourable concentrate has (a) a freezing temperature ranging from -15 to -1 °C; (b) a density ranging from 0.94 to 0.98 g/cm ³ (at 30 °C); (c) a dynamic viscosity ranging from 40 to 70 mPas (at 25 °C); and (d) a pH in the range of 5-7, when formulated as a 1% solution in water.

[0090] In some embodiments, some or all of the filter aid is pre-mixed with the slurry to be dewatered. In other embodiments, some or all of the filter aid is precoated onto the filter.

[0091] In some embodiments, the slurry to be dewatered is chosen from a mined ore slurry, a metal ore slurry, an iron ore slurry, an oil sand slurry, a tailings slurry, a municipal wastewater sludge, a vegetal pulp, optionally, for paper manufacture, and a food and/or beverage pulp.

[0092] The specific dosage range may be adjusted according to the initial moisture content in the slurry to be filtered, the slurry particle size distribution and the particle specific surface area. A filter aid may be added in the form of a solid, suspension, slurry, solution or any convenient form, to the material to be filtered. In exemplary embodiments, the filter aids are added as pourable concentrates or neat liquids containing from 0 to 12% by weight of water. Depending on need, the filter aids may be diluted with an appropriate liquid prior to use.

[0093] In some embodiments, the filter aid is added to the slurry to be dewatered at a dosage ranging from 1-200 grams of the filter aid per ton of dry solid in the slurry (g/t). In exemplary embodiments, the filter aid is added to the slurry to be dewatered at a dosage ranging from 40-80 g/t.

[0094] In exemplary embodiments, method results in increased filtration rate, increased dry solids content in the cake, and/or decreased water content in the cake compared to dewatering the slurry in the absence of the filter aid.

[0095] In some embodiments, the method may be effected at any time during a slurry dewatering process selected from a wet mineral ore dewatering processes, a sludge dewatering processes, a pulp dewatering processes, an oil sand dewatering processes, a tailings dewatering process, and a food and/or beverage sludge/pulp dewatering processes.

[0096] The invention also provides a solid ore product comprising one or more compositions or filter aids disclosed herein, obtainable by a method disclosed herein.

[0097] The filter aids of the present invention may be used in most industrial dewatering and filtering applications such as filtering wet mineral ore before or after beneficiation processes, sludge dewatering, tailings dewatering, pulp dewatering, filtering, and oil sand dewatering. The filter aids of the present invention may be used in most food and beverage pulp dewatering processes.

[0098] Having described the invention in detail the invention is further described in the following examples.

EXAMPLES

[0099] The following examples are presented for illustrative purposes only and are not intended to be limiting. Example 1: Dewatering efficiency of fatty alcohol polyglycol ether filter aids

[0100] To determine the effectiveness of the inventive filter aids in comparison with a benchmark filter aid, dewatering tests were performed according to an industry standard Buchner funnel testing method. The Buchner funnel apparatus is shown in Figure 1.

[0101] Reference Experiment

[0102] An initial reference experiment was carried out without a filter aid to determine the total filtration time to be used for subsequent experiments. Mineral ore slurry samples were prepared by adding 2 kg of a mineral ore slurry (50% solids content) to a beaker while mixing at 300 rpm using an overhead mixer. The resulting slurry was mixed for 1 minute, after which the contents of the beaker were poured onto a Buchner funnel. Vacuum was adjusted to 0.78 bar, simulating industrial conditions. Vacuum was applied to the system until the surface of the mineral cake to become dry (surface drying time in seconds) and the vacuum was maintained for an additional 20 seconds. The surface drying time plus the 20 second extra drying time was recorded and used as the total filtration time to be used for subsequent experiments.

[0103] The total filtration time was kept constant for all experiments in order to ensure that changes in results were caused by the filter aid in use. This is also an accurate simulation of industrial conditions since an industrial disc filter has the same rotation speed regardless of whether a filter aid is used.

[0104] Filter Aid Comparison Experiments

[0105] Experiments were performed using fatty alcohol polyglycol ether filtration aids of the present invention (e.g., "Products 1-5"). Products 1-5 were prepared by industrial ethoxylation reactions by blowing ethylene oxide through the appropriate fatty alcohol at 180 °C and under 1-2 bar of pressure, with potassium hydroxide (KOH) serving as a catalyst. The resulting fatty alcohol polyglycol ether filtration aids, e.g., Products 1-5, are both linear and branched chains with varying degrees of ethoxylation and molecular weights. A commercially available non-ionic surfactant filtration aid (e.g., "Benchmark") was obtained and used as a basis for comparison. Properties of filtration aids are listed in Table 1.

[0106] Mineral ore slurry samples were prepared by adding 2 kg of the mineral ore slurry (50% solids content) to a beaker while mixing at 300 rpm using an overhead mixer. To the beaker was added filtration aid (Benchmark or Product 1-5) in undiluted form to achieve dosage levels ranging from 30-100 g/t, measured as grams filtration aid per ton of dry solids in the slurry. Blank experiments were performed in the absence of filtration aid. Filtration aid dosages are listed in Table 1.

[0107] After filtration aid addition, the resulting slurry was mixed for 1 minute, and then the contents of the beaker were poured onto a Buchner funnel. Vacuum was adjusted to 0.78 bar, simulating industrial conditions, and maintained for the total filtration time determined from the reference experiment.

[0108] Filtration performance was determined visually by measuring the time required for the surface of the mineral cake to become dry (surface drying time in seconds). This visual observation is a measure of relative dewatering rate.

[0109] Immediately after filtration was complete, the dry solids content and final moisture content of the resulting cake was determined. The whole filter cake containing moisture (roughly 1100 grams), was placed on a metal plate and weighed, after which the filter cake was placed in a 105°C oven overnight for at least 16 hours. After drying, the cake and plate were reweighted, from which the final moisture and dry solids content (percentage by weight) were calculated. Results are listed in Table 1. Graphical depictions of percent moisture reduction and percent surface drying time reduction are shown in FIG 2 and FIG 3, respectively.

[0110] Table 1. Filtration aid properties and dewatering test results for fatty alcohol polyglycol ethers vs benchmark

[0111] Results indicate that at lower dosage (~40 g/t), the fatty alcohol polyglycol ethers (e.g., Products 1, 2 and 4) surprisingly provided 2-fold to 3-fold improvement in moisture reduction compared to the benchmark filter aid. At this dosage, all fatty alcohol polyglycol ethers (e.g., products 1 to 5) outperformed benchmark for surface drying time reduction, with results ranging from 250-2000%.

[0112] At higher dosage (~80 g/t), the improvements are less pronounced; however, fatty alcohol polyglycol ether (Product 2) outperformed the benchmark for moisture reduction and provided similar surface drying time reduction. At this dosage, Products 1 and 4 outperformed benchmark for surface drying time reduction, with results ranging from 450-600%.

[0113] The results strongly suggest that filter aids comprising fatty alcohol polyglycol ethers with MW ranges from 500-2200 g/mol, linear or branched, and degree of ethoxylation between 2-5 will provide the best results for dewatering ore slurries in an industrial setting.

[0114] These results provide initial proof of concept that the inventive fatty alcohol polyglycol ether filtration aids provide surprising improvements over the benchmark, including decreased surface dry time, increased filtration rate, increased dry solids content of filter cake, and decreased moisture content of filter cake.

[0115] The novelty of the results shown in Table 1 is that fatty alcohol poly-glycol ether chemistry has excellent performance in the filtering application. Fatty alcohol polyglycol ethers are nonionic surfactants characterized by excellent wetting properties, low foam and high effectiveness even at low temperatures. Without being bound to theory, it can be rationalized that the reason for filtration rate improvement is based on the chemical and physical properties of the inventive dewatering aids, which act to (i) reduce surface tension of liquid component of the ore slurry and (ii) increasing the hydrophobicity of the surface of the ore particles, which is generally seen in good filterability. Other filter aids, including the Benchmark, work in this manner, but the inventive filtering aids outperform benchmark.

[0116] Increase in filtrate throughput is very beneficial considering filtration is often a bottleneck for capacity increase. The inventive fatty alcohol polyglycol ether filter aids allow for filtration capacity to be increased with existing filtrations units. An additional advantage of the inventive fatty alcohol polyglycol ether products is that these products have lower solidification temperature (freezing points for a 1% solution in water were approximately -5 °C) compared to the benchmark. This means that product can be stored and applied in freezing conditions without need of any additional chemicals (antifreeze).

[0117] Having fully described the invention and exemplary embodiments, the invention is further defined by the claims which follow.