Binder composition for iron ore agglomeration

Abstract

The invention relates to a binder composition for manufacturing iron ore pellets, comprising: a) at least two organic binders LO in solid particulate form, the organic binders being at least: - a water-soluble anionic polymer P1 having a weight average molecular weight of 500 to 200,000 Dalton, and, - a water-soluble anionic polymer P2 having a weight average molecular weight of more than 500,000 Dalton; and; b) at least one inorganic binder LI in solid particulate form, wherein the solid particles of the binder LO have a number median particle size of more than 500 microns, the number median particle size of the particles of the binder LI being less than one third of the number median particle size of the solid particles of the binder LO.

Description

Technical Field

[0001] This invention relates to a binder composition for manufacturing iron ore pellets. More specifically, the binder composition contains at least two organic binders and at least one inorganic binder. These binders possess specific properties. Existing technology

[0002] Iron ore should be charged into the blast furnace in the form of large pellets. If the ore is in granular form and these particles are too small to be directly charged into the blast furnace, they must be processed into pellets. Due to the increasing use of low-grade ores, it is necessary to grind the ore into finer particles. Pelletizing (or pelletizing) is the only satisfactory method for producing furnace charge from these fine particles.

[0003] Pelletizing is achieved by adding a binder to fine-grained ore and stirring it in the presence of a small amount of water (typically moisture in the ore) to form a wet mixture, which is then shoveled into a pelletizing drum or disc pelletizer, for example. Green pellets (or raw pellets, referred to as raw pellets before they are sintered by firing) are then fired in a furnace at a series of temperatures, from an inlet temperature typically between 200 and 400 degrees Celsius to a final high temperature (e.g., 1,200 degrees Celsius).

[0004] Key pellet characteristics include initial strength or wet strength, dry strength (after drying green pellets in a furnace at 105°C), and the pellets' tendency to become brittle (or burst or flak) at the firing temperatures exposed to the furnace. Flaking tendency can be defined by determining the minimum temperature at which flaking occurs, or by observing the percentage of fines formed during a specific firing cycle. Careful selection of the moisture content of the mixture and the porosity of the pellets is essential. A high "drop number" of green pellets is desirable. For cost reasons, the amount of binder should be as low as possible, and its flowability should allow for uniform and easy addition of the binder in such small quantities to ensure homogeneity.

[0005] Traditionally, binders have been clay (usually bentonite), cement (usually Portland cement), or lime. However, several proposals have been made to use organic polymers as binders. Therefore, natural polymers, particularly cellulose polymers, have been considered, but they are not entirely satisfactory. In fact, precisely controlling their addition to particulate materials can be quite difficult. Synthetic polymers (typically water-soluble linear anionic polymers with molecular weights of 1 million to 20 million, existing in powder form) have also been proposed for many years, but their use has also presented challenges.

[0006] For example, WO 2017 / 037207 discloses an adhesive composition comprising a water-soluble polymer with a molecular weight of 1,000 to 20,000 Da, a copolymer with a molecular weight greater than 300,000 Da, and an inorganic pelletizing agent. In the same field, US5002607 describes an adhesive composition comprising a water-soluble polymer with a molecular weight less than 50,000 Da, an adhesive polymer with a molecular weight greater than 1 million Da, and an inorganic pelletizing agent.

[0007] The polymer particles are typically relatively large, usually exceeding 700 μm. The results obtained with these large particle sizes are not entirely satisfactory. In fact, the resulting pellets tend to be contaminated by dust adhering to their surface, which is subsequently blown out during the metallurgical use of the pellets. This problem is believed to be due to the pellet surface being stickier than ideal. Whatever the reason, a disadvantage of pellets is that when air blows across the pellet bed, metallic ore dust is carried into the air and out of the furnace. This can cause contamination problems and undesirable wear on furnace fans and other components, as well as related equipment.

[0008] Patents EP 0225171 and EP 288150 specify particular synthetic polymers with a dry particle size of 20 to 300 μm. This size is preferably less than 100 μm, and by weight, this proportion is at least 50%.

[0009] Using smaller particles often provides better granulation performance (including reduced dust issues), but it introduces some handling challenges. These particles are typically milled gel particles. However, handling very small, broken gel particles also presents problems. On one hand, there is a risk of the fine polymer powder being blown away during the mixing process; on the other hand, the flow properties of the particles are not entirely satisfactory; and finally, accurately metering the particles into the granular material can be difficult. Summary of the Invention

[0010] The applicant has unexpectedly discovered a binder composition for manufacturing iron ore pellets, comprising at least two organic binders and at least one inorganic binder, which possess specific properties that allow for maintaining satisfactory granulation performance, minimizing dust problems, improving processability, and permitting the use of large polymer particles. Furthermore, within the scope of this invention, the pellets can have a more uniform shape compared to binders based on other polymers.

[0011] More specifically, the present invention relates to a binder composition for manufacturing iron ore pellets, comprising:

[0012] a) An organic adhesive LO in at least two solid particulate forms, wherein at least one is:

[0013] - A water-soluble anionic polymer P1 with a weight-average molecular weight of 500 to 200,000 Daltons, and

[0014] - A water-soluble anionic or amphoteric polymer P2 with a weight-average molecular weight greater than 500,000 Daltons; and

[0015] b) At least one inorganic adhesive LI in the form of solid particles,

[0016] The solid particles of the adhesive LO have a median particle size greater than 500 micrometers.

[0017] The number median particle size of adhesive LI is less than one-third of the number median particle size of solid particles of adhesive LO.

[0018] Therefore, the adhesive composition comprises a mixture of anionic water-soluble polymer P1, anionic or amphoteric water-soluble polymer P2, and inorganic binder LI.

[0019] Another aspect of the invention relates to iron ore pellets containing 50 to 5000 ppm of the binder composition of the invention.

[0020] The term "polymer" refers to a homopolymer and a copolymer of at least two different monomers.

[0021] As used herein, the term "water-soluble polymer" should be understood to mean a polymer that, when dissolved in 20 g / L water at 25°C... -1 When the concentration of the solution is dissolved in deionized water and stirred for 4 hours, an aqueous solution without insoluble particles is obtained.

[0022] The numerical range includes a lower limit and an upper limit. Therefore, the numerical ranges of "0.1 to 1.0" and "from 0.1 to 1" include the values ​​0.1 and 1.0, respectively.

[0023] According to the present invention, the weight-average molecular weights of water-soluble polymers P1 and P2 are determined by measuring their intrinsic viscosity. Intrinsic viscosity can be measured by methods known to those skilled in the art, and in particular can be calculated graphically from reduced viscosity values ​​at different concentrations, wherein the graphical method involves plotting the reduced viscosity value (on the vertical axis) as a function of concentration (on the horizontal axis) and calculating by extrapolating the curve to zero concentration. The intrinsic viscosity value is read on the vertical axis or using the least squares method. The weight-average molecular weight can then be determined using the Mark-Houwink equation:

[0024] [η]=KM α

[0025] [η] represents the intrinsic viscosity of the polymer as determined by solution viscosity measurement.

[0026] K represents an empirical constant.

[0027] M represents the molecular weight of the polymer.

[0028] α represents the Mark-Houwink coefficient.

[0029] α and K depend on the specific polymer-solvent system. Tables known to those skilled in the art provide α and K values ​​based on the polymer-solvent system.

[0030] The water-soluble polymer P1 has a weight-average molecular weight of 500 to 200,000 Daltons, more preferably 1,000 to 50,000 Daltons, and even more preferably 1,000 to 10,000 Daltons.

[0031] The weight-average molecular weight of water-soluble polymer P2 is greater than 500,000 Daltons, more preferably greater than 1 million Daltons. The weight-average molecular weight of water-soluble polymer P2 is typically less than 40 million Daltons, preferably less than 30 million Daltons.

[0032] The water-soluble polymer P1 is anionic, therefore it contains anionic monomers, and optionally contains nonionic monomers.

[0033] Advantageously, polymer P1 contains 50 to 100 mol%, more preferably 70 to 100 mol%, and even more preferably 90 to 100 mol% of anionic monomer.

[0034] The nonionic monomers of the water-soluble polymer P1 are preferably selected from acrylamide, methacrylamide, N-alkylacrylamide, N-alkylmethylacrylamide, N,N-dialkylacrylamide, N,N-dialkylmethylacrylamide, alkoxylated acrylates, alkoxylated methacrylates, N-vinylpyridine, N-vinylpyrrolidone, hydroxyalkyl acrylates, hydroxyalkyl methacrylates, and mixtures thereof. Among these nonionic monomers, the alkyl groups are advantageously C1-C5, more advantageously C1-C3. They are preferably straight-chain alkyl groups.

[0035] The anionic monomers of the water-soluble polymer P1 are preferably selected from monomers having carboxylic acid functional groups and their salts, including acrylic acid, methacrylic acid, itaconic acid, and maleic acid; monomers having sulfonic acid functional groups and their salts, including acrylamide-tert-butylsulfonic acid (ATBS), allyl sulfonic acid, methyl allyl sulfonic acid and their salts; and monomers having phosphonic acid functional groups and their salts.

[0036] Salts can be alkali metal salts or alkaline earth metal salts. The term "alkali" should be understood as alkali metal, preferably lithium, sodium, or potassium. The term "alkaline earth" should be understood as alkaline earth metal, preferably calcium or magnesium.

[0037] Preferably, polymer P1 is a polymer of at least one anionic monomer, said anionic monomer containing at least one carboxylate functional group -C(=O)-O. - X + X is an alkali metal and at least one carboxylate functional group -C(=O)-O - X' + , where X' is an alkaline earth metal.

[0038] Therefore, this does not rule out the presence of anionic monomers containing carboxylic acid functional groups (unneutralized) in polymer P1. In other words, it is possible for both anionic monomers with carboxylic acid functional groups and the same monomers with carboxylate functional groups to coexist.

[0039] Advantageously, when the anionic monomer of polymer P1 exists in both its carboxylic acid form and its carboxylate form, the proportion of the carboxylate form relative to the total of the carboxylate and carboxylic acid forms is 10 to 100 mol%, more preferably 20 to 100 mol%.

[0040] Advantageously, 40 to 60 mol% of the carboxylate functional groups of polymer P1 are neutralized by alkali metal salts, and 40 to 60 mol% of the carboxylate functional groups are neutralized by alkaline earth metal salts.

[0041] Even more preferably, at least one anionic monomer containing a carboxylate functional group of polymer P1 is an acrylate.

[0042] Polymer P1 is advantageously at least a polymer of a mixture of an alkali metal salt (preferably sodium) and an alkaline earth metal salt (preferably calcium) of acrylic acid CH2=CH-C(=O)OH.

[0043] According to a preferred embodiment, the carboxylate functional groups of polymer P1 are neutralized by sodium and calcium.

[0044] Advantageously, polymer P1 contains at least sodium acrylate and calcium acrylate.

[0045] Polymer P1 can be linear or structured by at least one structural agent, which can be advantageously selected from polyene unsaturated monomers (having at least two unsaturated functional groups), such as vinyl, allyl, acrylic, and epoxy functional groups, and may include, for example, sodium allyl sulfonate, sodium methyl allyl sulfonate, sodium methyl allyl disulfonate, methylene bisacrylamide, diallylamine, triallylamine, triallyl ammonium chloride, tetraallyl ammonium chloride, or structured by macromolecular initiators, such as polyperoxides, polyazo compounds, and polytransfer agents, such as polymer captan polymers or hydroxyalkyl acrylates and ethylene oxide.

[0046] Polymer P1 can also be structured using controlled radical polymerization (CRP, or more specifically, RAFT, or Reversible Addition Fragmentation Chain Transfer).

[0047] The solid polymer particles P1 are in powder form. These particle forms are obtained using techniques known to those skilled in the art.

[0048] The powder form of polymer P1 can be obtained by polymerizing in an aqueous solution and then drying by drum drying, spray drying, radiation drying (e.g., microwave drying) or fluidized bed drying.

[0049] Preferably, polymer P1 is in powder form, obtained by polymerization in an aqueous solution followed by drum drying.

[0050] Polymerization to obtain the polymer P1 according to the invention is generally carried out via a free radical pathway. This includes free radical polymerization using UV, azo, redox, or thermal initiators, as well as CRP or more specifically RAFT-type polymerization techniques.

[0051] During the polymerization of polymer P1, several additives (azo compounds, redox pairs, transfer agents, terminators, etc.) known to those skilled in the art can be advantageously added. Some of these may contain sulfur, such as sodium bisulfite, sodium metabisulfite, or sodium persulfate.

[0052] The polymerization reaction of polymer P1 can be initiated in the presence of an oxidation / reduction pair. A preferred sulfur-containing oxidant is sodium persulfate.

[0053] Preferably, polymer P1 contains up to 2% by weight of sulfur, more preferably up to 1% by weight of sulfur, said sulfur being derived from sodium bisulfite, and / or sodium metabisulfite, and / or sodium persulfate.

[0054] "A and / or B" means A, or B, or A and B.

[0055] The water-soluble polymer P2 is an anionic or amphoteric polymer, and therefore contains anionic monomers, optional cationic monomers, and optional nonionic monomers.

[0056] The nonionic monomers of the water-soluble polymer P2 are preferably selected from acrylamide, methacrylamide, N-alkylacrylamide, N-alkylmethylacrylamide, N,N-dialkylacrylamide, N,N-dialkylmethylacrylamide, alkoxylated acrylates, alkoxylated methacrylates, N-vinylpyridine, N-vinylpyrrolidone, hydroxyalkyl acrylates, hydroxyalkyl methacrylates, and mixtures thereof. Among these nonionic monomers, the alkyl group is advantageously C1-C5, more advantageously C1-C3. They are preferably straight-chain alkyl groups. Acrylamide is the most preferred nonionic monomer.

[0057] The anionic monomer of the water-soluble polymer P2 is preferably selected from monomers having a carboxylic acid functional group and their salts, including acrylic acid, methacrylic acid, itaconic acid, and maleic acid; monomers having a sulfonic acid functional group and their salts, including acrylamide-tert-butylsulfonic acid (ATBS), allyl sulfonic acid, methyl allyl sulfonic acid and their salts; and monomers having a phosphonic acid functional group and their salts. Preferred anionic monomers are acrylic acid and its salts.

[0058] The salt can be an alkali metal salt or an alkaline earth metal salt. Advantageously, the alkali metal is sodium.

[0059] The cationic monomer of the water-soluble polymer P2 is preferably selected from quaternized or salted dimethylaminoethyl acrylate (ADAME), quaternized or salted dimethylaminoethyl methacrylate (MADAME), diallyl dimethyl ammonium chloride (DADMAC), acrylamide propyltrimethylammonium chloride (APTAC), and methacryloylaminopropyltrimethylammonium chloride (MAPTAC).

[0060] Advantageously, the cationic monomer of polymer P2 has a halogen as a counterion, preferably a chloride ion. The preferred cationic monomer is dimethylaminoethyl acrylate (ADAME) quaternized with methyl chloride.

[0061] Preferably, polymer P2 is a copolymer of acrylamide and sodium acrylate.

[0062] Polymer P2 can be linear or structured by at least one structural agent, which can be advantageously selected from polyene unsaturated monomers (having at least two unsaturated functional groups), such as vinyl, allyl, acrylic, and epoxy functional groups, and may include, for example, sodium allyl sulfonate, sodium methyl allyl sulfonate, sodium methyl allyl disulfonate, methylene bisacrylamide, diallylamine, triallylamine, triallyl ammonium chloride, tetraallyl ammonium chloride, or structured by macromolecular initiators, such as polyperoxides, polyazo compounds, and multitransfer agents, such as polymeric thiols or hydroxyalkyl acrylates and ethylene oxide.

[0063] Polymer P2 can also be structured using CRP polymerization technology or, more specifically, RAFT-type technology.

[0064] Advantageously, the polymer P2 has a star-shaped structure, having a central portion (core) and polymer-based arms extending radially from said central portion.

[0065] The water-soluble polymer P2 is advantageously a copolymer of at least one nonionic monomer (advantageously acrylamide) and at least one anionic monomer (advantageously acrylic acid and / or its salt).

[0066] The polymer microgel advantageously contains 0 to 100 mol% of a cationic monomer, preferably 0 to 80 mol%, more preferably 0 to 60 mol%, and even more preferably 0 to 50 mol%. Specifically, polymer P2 preferably contains 5 to less than 100 mol% (excluding 100%), more preferably 10 to 80 mol%, and even more preferably 20 to 60 mol% of sodium acrylate; and greater than 0 to 95 mol% (excluding 0%), more preferably 20 to 90 mol%, and even more preferably 40 to 80 mol% of acrylamide.

[0067] The solid particles of polymer P2 are in the form of powder or microspheres. These particle forms are obtained using techniques known to those skilled in the art.

[0068] The polymer P2 in powder form can be obtained by gel polymerization, aqueous solution polymerization followed by drum drying, spray drying, radiation drying (e.g., microwave drying), or fluidized bed drying.

[0069] The powder form of water-soluble polymer P2 can also be obtained by water-in-oil emulsion polymerization (reverse emulsion), followed by distillation / concentration steps and spray drying of the resulting liquid.

[0070] P2 polymer microspheres are advantageously obtained by reverse suspension polymerization.

[0071] Preferably, polymer P2 is in the form of powder obtained by gel polymerization or microbeads obtained by reverse suspension polymerization.

[0072] The polymer P2 of this invention is obtained by polymerization via a free radical pathway. This includes free radical polymerization using UV, azo, redox, or thermal initiators, as well as CRP or more specifically, type-specific polymerization techniques.

[0073] The adhesive composition of the present invention further comprises an inorganic binder L1. This L1 binder is advantageously non-polymeric. It is preferably selected from sodium carbonate, sodium bicarbonate, sodium phosphate, sodium silicate, urea, calcium oxide, bentonite, and mixtures thereof.

[0074] Preferably, the adhesive composition comprises P1+P2+LI and includes:

[0075] -2 to 40% by weight of polymer P1,

[0076] -20 to 60% by weight of polymer P2, and

[0077] -30 to 70% by weight of adhesive LI,

[0078] The sum of the weight percentages of P1, P2, and LI equals 100%.

[0079] More preferably, the adhesive composition comprises:

[0080] -5 to 30% by weight of polymer P1,

[0081] -25 to 55% by weight of polymer P2, and

[0082] -35 to 65% by weight of adhesive LI,

[0083] The sum of the weight percentages of P1, P2, and LI equals 100%.

[0084] Even more preferably, the adhesive composition contains:

[0085] -8 to 25% by weight of polymer P1,

[0086] -35 to 50% by weight of polymer P2, and

[0087] -40 to 60% by weight of adhesive LI,

[0088] The sum of the weight percentages of P1, P2, and LI equals 100%.

[0089] According to the present invention, adhesives LO (P1 and P2) and adhesive LI are in the form of solid particles, such that the number median particle size (D) of the solid particles of adhesive LO is such that... 50The particle size is greater than 500 micrometers, and the number median particle size of adhesive LI is less than one-third of the number median particle size of solid particles of adhesive LO.

[0090] Number median particle size (D) 50 ) is defined as the maximum size of a particle (the diameter for spherical particles) such that half the particles in the particle group (half the number of particles) have a size lower than this value.

[0091] For spherical particles, particle size refers to the average diameter measured using a laser diffraction particle analyzer according to conventional techniques known to those skilled in the art. An example of a device used for measuring particle size is the Malvern Instruments Mastersizer.

[0092] Advantageously, the median particle size of the organic binder LO is 500 to 5000 micrometers, more preferably 500 to 2000 micrometers.

[0093] The adhesive composition according to the invention is generally formed by simply mixing its components (each component is in powder form).

[0094] Finally, a last aspect of the invention relates to an iron ore pellet containing a binder composition of 50 to 5000 ppm by weight of the iron ore pellet.

[0095] Particle preparation typically involves adding a binder composition to fine-grained ore and stirring it in the presence of a small amount of water (preferably moisture in the ore) to form a wet mixture, which is then pelletized, for example, in a pelletizing drum or disc pelletizer.

[0096] The present invention is illustrated by the following embodiments, but its scope is not limited. Example

[0097] Synthesis of P1 polymer

[0098] Polymer P1 was obtained by a method known to those skilled in the art for polymerizing acrylic acid in aqueous solution. The monomer was introduced into a heated reactor by casting, simultaneously with the initiator and transfer agent solutions. The initiator solution consisted of ammonium persulfate and sodium bisulfite as a reducing agent. The proportion of sulfur in all components involved in the process was strictly less than 2% (by weight) of the total formulation. Polymer P1 was neutralized with soda ash to obtain sodium counterions, or with soda ash and calcium oxide (in a 50 / 50 weight ratio) to obtain sodium and calcium counterions with different properties. This neutralization was performed on the polymer prior to the end of polymerization. At the end of polymerization, the polymer solution was drum-dried to obtain polymer P1 in powder form.

[0099] Therefore, four tests were conducted, and four P1 polymers were synthesized, namely P1-A (according to the present invention), P1-B (according to the present invention), P1-C (comparative example), and P1-D (comparative example).

[0100] Synthesis of P2 polymer

[0101] Polymer P2 was obtained from acrylamide and sodium acrylate via gel polymerization as known to those skilled in the art. At the end of polymerization, the polymer gel was granulated, dried, ground, and sieved to obtain polymer P2 in powder form.

[0102] Therefore, four tests were conducted, and four P2 polymers were synthesized: P2-A (according to the present invention), P2-B (according to the present invention), P2-C (comparative example), and P2-D (comparative example).

[0103] Pellet production

[0104] In the following examples, green iron ore pellets comprising the amounts of various compounds shown in Table 1 were prepared. The green pellets were prepared by concentrating iron ore concentrate in the presence of a binder composition. The binder amounts (by weight percentage) shown in Table 1 are based on the total weight of the iron ore concentrate. The iron ore concentrate used in the examples in Table 1 was Brazilian hematite concentrate.

[0105] The inorganic binder LI used is sodium carbonate, obtained from two different sources: LI-1 (according to the present invention) and LI-2 (comparative example).

[0106] As shown in Table 2, various comparative adhesive compositions of the present invention (CEX 1 to CEX 12) and (C1 to C5) were prepared. They all consist of an inorganic adhesive L1 and two organic adhesives, the organic adhesives being previously synthesized polymers P1 and P2. In each case, the adhesive composition was prepared by mixing the three components using a mixture to homogenize them.

[0107] The manufacturing process of green ore pellets is generally known to those skilled in the art. We produced different green ore pellets to test different binder compositions.

[0108] First, mix the binder composition into the dry mineral concentrate and homogenize it with the required amount of water (moisture content of 8 to 9% by weight). Use a KitchenAid mixer to mix the mineral concentrate and binder composition.

[0109] Next, a small portion of the previously obtained mineral concentrate and binder composition is placed in a rotating pelleting tray (approximately 40 cm in diameter), and atomized water is added to initiate pellet growth, thereby forming pellet precursors (or seeds). This results in pellet seeds with a size of 2.5 to 4 mm.

[0110] Then, by placing 55 grams of pellet seeds into a rotating pelleting pan and adding some of the remaining mixture (mineral concentrate + binder composition) during the 5 to 6 minute growth period, finished green pellets with a size of 9.5 to 12.5 mm are obtained. Atomized water can be added if necessary.

[0111] The moisture content, number of pellets, wet compressive strength, and dry compressive strength of the green pellets obtained under each condition were measured, and the results are summarized in Table 3.

[0112] Number of wet balls (NWD)

[0113] The wet drop ball number (NWD) is determined as follows: Wet green pellets with a particle size of 11.2 to 12.5 mm are repeatedly dropped from a height of 46 cm onto a horizontally placed steel plate until the pellets break. Visible cracks form on the surface of the pellets. The number of drops required for the pellet to reach its breakage / fracture point is determined. This measurement is performed on 20 pellets. The average of these 20 measurements is called the wet drop ball number (NWD).

[0114] Wet compressive strength (WCS)

[0115] Twenty wet green pellets with a particle size of 11.2 to 12.5 mm were stored in a sealed container. The pellets were then individually removed and placed in a standard Andilog measuring apparatus. The maximum force applied upon pellet fracture was determined. The average of these 20 measurements is termed the "wet compressive strength" (WCS).

[0116] Dry compressive strength (DCS)

[0117] Twenty green pellets with a particle size of 11.2 to 12.5 mm were dried in an oven at 105°C for at least two hours. After drying, each dried pellet was individually placed into a standard Andilog measuring device. The maximum force applied when the pellet broke was determined. The average of these 20 measurements is called the "dry compressive strength" (DCS).

[0118] Table 1: Organic and Inorganic Adhesives

[0119]

[0120] Table 2: Amounts of binder and minerals required to obtain green pellets

[0121]

[0122] Table 3: Physical properties of green pellets

[0123] test Surface appearance of pellets NWD WCS(kg) DCS (kg) C1 Smooth and glossy 4.5 1:35 6.3 C2 Smooth and glossy 4.9 1.3 4.9 C3 Smooth and glossy 6.5 1.3 5.1 C4 Smooth and glossy 6 1.3 4.2 C5 Smooth and glossy 6 1.3 4.7 CEX1 Slightly grainy - matte 2.9 1.4 6.2 CEX2 It has a very grainy texture (like orange peel). 4.2 1 2.9 CEX3 It has a very grainy texture (like orange peel). 4 1.2 2.7 CEX4 Smooth and very wet-sticky 3.5 1 1.8 CEX5 It has a very grainy texture (like orange peel) and is porous. 3.8 1 1.7 CEX6 Smooth and too wet - very sticky 3.1 0.85 1.65 CEX7 Smooth and very wet-sticky 3.2 0.9 1.85 CEX8 It has a very grainy texture (like orange peel) and is porous. 4 1 1.95 CEX9 It has a very grainy texture (like orange peel) and is porous. 4.2 1 2 CEX10 It has a very grainy texture (like orange peel) and is porous. 1 0.3 0.85 CEX11 Slightly grainy (orange peel-like) – matte 3,2 1,3 3,0 CEX12 It has a very grainy texture (like orange peel). 3,5 1 2,5

[0124] Table 3 shows that, compared with the green pellets of CEX 1 to CEX 12 in the comparative tests, the green pellets of Examples C1 to C5 using the adhesive composition of the present invention have a smoother surface.

[0125] Improving the surface condition of pellets is crucial for industrial manufacturers because granular and / or rough surfaces can lead to increased abrasion and tumble index, resulting in reduced marketable pellet sizes and increased dust content in the furnace and during processing.

[0126] Compared to tests of comparative adhesive compositions CEX 1 to CEX 12, the adhesive compositions C1 to C5 of the present invention exhibit improved dry compressive strength. This parameter is crucial for industrial manufacturers because it allows for the determination of pellet behavior in the furnace: higher dry compressive strength will prevent pellet breakage in the bed and will result in pellets with greater hardness.

[0127] In contrast, composition C3 improves NWD and DCS compared to binder composition C5. Therefore, the counterionic selection of polymer P1 affects the physical properties of the pellets.

[0128] Based on tests of comparative adhesive compositions CEX 2, CEX 3, and CEX 4, it was observed that the molecular weight selection of polymers P1 and P2 is very important for obtaining smooth pellet surfaces and good physical properties.

[0129] Testing of the comparative binder composition CEX 5 showed that the ratio between the particle size of the organic binder and the particle size of the inorganic binder is crucial. If this ratio is outside the required range, the resulting pellets are too brittle and therefore fragile.

[0130] Testing of the comparative binder composition CEX 6 showed that the amount of each binder in the green pellets is also an important criterion. If these amounts are outside the required range, the pellets will be very sticky (which leads to reduced productivity) and not strong enough for industrial manufacturers.

[0131] Tests on comparative adhesive compositions CEX 7, CEX 8, and CEX 9 showed that the presence of at least two organic binders (i.e., polymer P1 and polymer P2) is essential. Without either of these two polymers, the surface of the pellets is rough and the physical properties are unsatisfactory.

[0132] Tests on the comparative binder composition CEX 10 showed that the presence of the organic binder LO is extremely important. Without the organic binder (with only the inorganic binder LI present), the pellet surface is not smooth and does not have satisfactory mechanical properties.

[0133] Finally, the comparative binder compositions CEX 11 and CEX 12 show that when the median particle size D of polymer P1 or polymer P2 is... 50 Below 500 μm, the surface of the pellets is not smooth and does not have satisfactory mechanical properties.

Claims

1. A binder composition for manufacturing iron ore pellets, said binder composition comprising: a) An organic adhesive LO in at least two solid particulate forms, wherein at least one is: - A water-soluble anionic polymer P1 with a weight-average molecular weight of 500 to 200,000 Daltons, and - A water-soluble anionic or amphoteric polymer P2 with a weight-average molecular weight greater than 500,000 Daltons; and b) At least one inorganic adhesive LI in the form of solid particles, The solid particles of the adhesive LO have a median particle size greater than 500 micrometers. The number median particle size of adhesive LI is less than one-third of the number median particle size of solid particles of adhesive LO.

2. The adhesive composition according to claim 1, characterized in that, The polymer P1 is a polymer of at least one anionic monomer, the anionic monomer comprising (1) at least one carboxylate functional group -C(=O)-O. - X + X is an alkali metal, and (2) at least one carboxylate functional group -C(=O)-O - X' + , where X' is an alkaline earth metal.

3. The adhesive composition according to claim 2, characterized in that, The polymer P1 is at least a mixture of an alkali metal salt and an alkaline earth metal salt of acrylic acid CH2=CH-C(=O)OH.

4. The adhesive composition according to claim 2 or 3, characterized in that, The alkali metal is sodium, and the alkaline earth metal is calcium.

5. The adhesive composition according to any one of claims 1-3, characterized in that, The polymer P1 contains up to 2% by weight of sulfur, which is derived from sodium bisulfite and / or sodium metabisulfite and / or sodium persulfate.

6. The adhesive composition according to any one of claims 1-3, characterized in that, Polymer P2 is a copolymer of acrylamide and sodium acrylate.

7. The adhesive composition according to any one of claims 1-3, characterized in that, Polymer P2 is a copolymer containing 5 mol% to less than 100 mol% sodium acrylate and greater than 0 mol% to 95 mol% acrylamide.

8. The adhesive composition according to any one of claims 1-3, characterized in that, The inorganic binder LI is selected from sodium carbonate, sodium bicarbonate, sodium phosphate, sodium silicate, calcium oxide, bentonite, and mixtures thereof.

9. The adhesive composition according to any one of claims 1-3, characterized in that, It consists of P1+P2+LI, and contains: -2 to 40% by weight of polymer P1, -20 to 60% by weight of polymer P2, -30% to 70% by weight of adhesive LI, The total weight percentage of P1+P2+LI is 100%.

10. An iron ore pellet, wherein, based on the weight of the iron ore pellet, it contains 50 to 5000 ppm of a binder composition according to any one of claims 1 to 9.

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