pellet

Abstract

This invention provides a pelletizing process that improves the ease of pellet production without compromising strength and stability. [Solution] A method for producing pellets, comprising the steps of: providing a particulate substrate selected from metal ore, metal ore-containing waste, metal powder, iron residue, iron scrap, inorganic waste, carbonaceous material, arc furnace waste, or a combination thereof; mixing the particulate substrate with a binder formulation containing at least one binding material to form a substrate mixture; applying pressure to the substrate mixture to induce the formation of a hydrogel; and forming aggregates, wherein the presence of water promotes hydrogel formation; and pellets obtained by the method of the present invention.

Description

[Technical Field]

[0001] The present invention relates to a method for producing pellets from a particulate substrate and a binder, and to pellets obtained using the method, and more particularly to a method in which hydrogel formation is induced. [Background technology]

[0002] Although carbon, various metals, and metal ores are abundant in the Earth's core, their usable quantities are limited. Mining and smelting of metal ores and metals, such as iron, incur environmental costs, particularly from a pollution perspective. Therefore, maximizing the recycling of waste materials is desirable, thereby reducing the amount of waste that requires handling and storage. For example, in the case of iron waste, storage is typically carried out through long-term storage in piles or reservoirs.

[0003] The production of pellets from carbonaceous materials, particulate metals, and metal ores is generally known in the art. In many cases, pellets are formed by binding particles together with a binder. In the pelletizing process, the binder is generally added as a powder. However, it can be difficult to process the powder into pellets that are stable and strong enough not only for transport to the point of use but also for transport within large processing plants at the destination. Powder binders are also explosive and can easily dissipate into the atmosphere. This can result in economic losses due to material loss, as well as the risk of direct personal injury and inhalation that may cause short-term toxicity or long-term illness.

[0004] Furthermore, pelletization processes using powders often result in variability, and efficient powder dispersion in industrial-scale mixers is difficult, which can pose problems when scaling up production. Additionally, interference between binder components can occur due to the effects of temperature and pressure. The use of powders can also unpredictably affect solubilization differences. This means that considerable testing is required before industrial-scale use, making the transition from composition design to industrial pelletization more difficult and costly. [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, it is desirable to develop a pelletizing process that improves the ease of pellet production without compromising strength and stability. The present invention aims to overcome or alleviate at least some aspects of this problem. [Means for solving the problem]

[0006] Accordingly, in a first aspect of the present invention, a method for producing pellets is provided, the method comprising the steps of: providing a particulate substrate selected from metal ore, metal ore-containing waste, metal powder, iron residue, iron scrap, inorganic waste, carbonaceous material, arc furnace waste, or a combination thereof; mixing the particulate substrate with a binder formulation comprising at least one binding material to form a substrate mixture; applying pressure to the substrate mixture to induce the formation of a hydrogel; and forming aggregates, the method comprising the steps of, in general, the presence of water which facilitates the formation of the hydrogel.

[0007] By mechanically inducing gelation to form a hydrogel, the binder formulation can be more efficiently dispersed throughout the particulate substrate in the final pellet product. While not strictly theoretical, hydrogel formation is thought to not only improve the strength of the final pellet by binding the substrate particles together, but also act as a processing aid. This is because the binder formulation becomes more easily dispersed in hydrogel form and therefore can exhibit a lubricating effect. Overall, this improves pellet processing and reduces variability in results. Furthermore, binders capable of forming hydrogels disperse more easily than powder binders in industrial-scale mixers. Additionally, incorporating binders capable of forming hydrogels makes it easier to disperse additional powder binders, thereby addressing problems associated with using powder binders alone. Consequently, mechanical load and overheating are reduced, and efficiency is improved. Furthermore, gelation improves bonding properties, and existing binder materials that do not directly form part of the hydrogel can strengthen polymer bonds, resulting in a reduction in the amount of binder formulation required to achieve strength equivalent to known binder formulations. Moreover, the final pellets produced in the process of the present invention have been found to be surprisingly stronger and possess higher strength and rigidity, thereby reducing the need for post-production heating (e.g., drying or curing processes) to stabilize the pellets for storage, transport, and use. This has significant environmental advantages in that it reduces the energy required to produce pellets of sufficient strength from particulate material. Furthermore, process efficiency is improved in that pelletization can be completed rapidly without the need for heating equipment and without the delays that may occur due to additional heating steps. In addition, the pellets that can be obtained by the method according to the first aspect of the present invention generally exhibit high thermal stability. This means that the pellets carbonize at a controlled rate and do not collapse in the furnace.

[0008] In addition to the advantages obtained by hydrogel formation during pellet manufacturing, applying pressure to the substrate mixture containing the binder formulation and particulate substrate accelerates gel formation compared to "standing" at ambient temperature. Therefore, the process of forming aggregates and subsequent pelletization can be carried out quickly and easily. The term aggregate has its usual meaning in the art, namely, a particulate material formed from aggregates of physically or chemically bound particles.

[0009] In general, at least one binding material in a binder formulation is hydrogel-forming. If only one binding material is present, and therefore the binder formulation contains or consists of a single binding material, that binding material is hydrogel-forming overall. If multiple binding materials are present, one or more may be hydrogel-forming, and non-hydrogel-forming binding materials may be included. The above advantages are thought to be provided by the hydrogel-forming binding material forming a hydrogel around the particulate substrate.

[0010] As used herein, the term "hydrogel" means a material that is neither a readily flowing liquid nor a solid, and is composed of gel-forming materials such as hydrophilic polymers that are insoluble in water. In other words, a hydrogel can be a semi-solid substance. Typically, hydrogels are formed through gel-forming materials such as hydrophilic polymers that form an interconnected crosslinking network capable of trapping, absorbing, and / or retaining water to form a gel. Some hydrogels can be diluted with another liquid, such as water, which breaks the interconnected network and turns them into a solution, but the hydrogels of the present invention are typically crosslinked hydrogels that do not dissolve when diluted.

[0011] Typically, the presence of water enables hydrogel formation. This may be naturally occurring moisture in the particulate substrate, or it may be water added specifically to facilitate hydrogel formation. The amount of water in the hydrogel generally ranges from approximately 1% to 5% by weight, or approximately 2% to 4% by weight, or approximately 2.5% to 3.5% by weight, or approximately 3% by weight. At higher levels, it has been found that excessive dilution of the system by water reduces the gel-forming effect. This is because the decrease in viscosity of the system due to water reduces the mechanical forces for bonding, thereby suppressing the densification of the resulting pellets. While not strictly theoretical, it is thought that not all of the water mixed with the binder formulation is present in the final hydrogel, as a small amount acts to ensure the dissolution or mixing of other components.

[0012] Hydrogels are generally known to require a certain amount of time to form. This is sometimes referred to as "setting," and is often 1-2 hours. This can be undesirable as it delays the manufacturing process. The essence of this invention is to apply pressure to the substrate mixture. Surprisingly, it has been found that the application of this pressure induces rapid gel formation, thereby causing the hydrogel to form almost immediately, generally within a few seconds (e.g., 0-60 seconds, often 1-20 seconds, or 2-5 seconds). This has the advantage that aggregates are formed very quickly, allowing subsequent processing (e.g., pelletizing and / or curing) to proceed without delay. It is important to note that the pressure is applied to the substrate mixture before aggregate formation. Therefore, the hydrogel is formed before the subsequent granulation or pelletizing step. In pelletizing methods, pressure may also be applied to aggregates or granulated aggregates to hold the pellets together, but if pressure is applied during pelletizing, this pressure is after and different from the pressure applied to induce hydrogel formation.

[0013] As described above, the binder formulation contains at least one binding material, which is often hydrogel-forming. However, the binder formulation may contain two or more binding materials, one or more of which may be hydrogel-forming, but non-hydrogel-forming binding materials may also be present. Therefore, the method of the present invention may include the step of mixing a first binding material and a second binding material with a particulate substrate to form a substrate mixture. In this example, the first and second (and optionally further) binding materials are added during the step of mixing the particulate substrate with the binder formulation (in this case, containing two or more binding materials) to form a substrate mixture. Alternatively, the first hydrogel-forming binding material may be mixed with the particulate substrate to form a substrate mixture, and then the second binding material may be mixed with the hydrogel. In this example, the first binding material may be hydrogel-forming, and the second binding material may be non-hydrogel-forming. Naturally, there may be two or more binders mixed with the particulate substrate, and there may also be two or more binders mixed with the formed hydrogel. In either case, it was found that high-strength pellets obtained by rapid manufacturing techniques were provided.

[0014] The method of the present invention comprises the step of applying pressure to a substrate mixture, thereby inducing the formation of a hydrogel, thereby inducing / facilitating gel formation. This can be done by any various compression techniques, such as passing the substrate mixture through a compression wheel or pressure plate (such as on a roller press).

[0015] One method often used to apply pressure to a substrate mixture to induce hydrogel formation is a roller press. This is because it can be easily integrated into a pelletizing production line (whether it is a single machine or multiple machines). A blank wheel (also called a blank roller) can be fitted to the roller press to provide compression. Thus, the step of applying pressure to the substrate mixture includes passing the substrate mixture through the blank wheel of the roller press. The blank wheel may have a smooth surface or various surface patterns. As used herein, the terms “wheel” and “roller” are synonymous and can be used interchangeably. A smooth surface is often used for materials that require minimal friction and are easily compressible, thereby ensuring the consistent production of pellets with uniform density. Alternatively, the roller press may have a textured surface. A textured surface may include multiple depressions that may differ in shape, size, and distribution. For example, a textured surface may include grooves or linear, spiral, or grid patterns. Textured surfaces help increase friction and improve the grip and compressibility of the material, which is particularly useful for harder or more fibrous materials. When the surface of a wheel is textured, the texture often has a depth ranging from 0.1 mm to 0.5 mm, often in the range of 0.2 mm to 0.4 mm.

[0016] The aggregates formed following the step of applying pressure to the base material mixture may be solid lumps, or in some cases, in the form of flat ribbon-like material, which may be advantageous to granulate before pelletization. Therefore, an optional step in the process may be to pass the aggregates through a granulator (with a screen size suitable for the material and the desired end use) before pelletization. The screen size may range from approximately 1.75 mm to approximately 10 mm, and in many cases, from approximately 2 mm to approximately 5 mm, or 2.25 mm to 3.5 mm. Smaller granules may slightly improve pellet strength, but it has been found that regardless of granule size, the presence of gel results in higher strength. It has also been found that providing granules of different sizes may be beneficial, as the resulting packing effect can improve the strength of the resulting pellets.

[0017] Aggregates can be formed by cold working. The term "cold working" means, for example, that no hardening, sintering, or heating to above approximately 60°C, 40°C, or 30°C is performed. In other words, if heating occurs during aggregate formation, it is usually only at a low level. Furthermore, frictional heat may be generated by the pressurizing and / or extrusion steps used when pelletizing the aggregates, and the binder material may undergo an exothermic reaction in situ, but this is in some cases the only heat applied and not external heat, so it does not constitute the heating described above. These inherent heating mechanisms are not expected to generate enough heat to affect pellet formation.

[0018] A method according to a first aspect of the present invention may include passing a substrate mixture through a blank wheel of a first roller press (i.e., mechanically inducing gelation to form aggregates), wherein the first roller press is operationally connected in series with a granulator and / or a second roller press configured to produce pellets from the aggregates. For example, in this method, the substrate mixture can be passed through a blank compression wheel of a first roller press to induce gelation. The resulting gel-containing aggregates (i.e., aggregates produced by passing through a blank compression wheel of a first roller press) can then be passed either directly or indirectly through a granulator to the rollers of a second roller press configured to produce pellets (i.e., the aggregates are passed through a granulator, and the subsequently granulated aggregates are passed through the rollers of a second roller press configured to produce pellets). The rollers of the second roller press may have a series of equally spaced recesses along their length, thereby enabling pellet formation. By applying pressure, the gelation time is shortened to almost zero. In short, this gelation occurs in just a few seconds as the material passes through the blank compression wheel of a roller press or is compressed using a similar technique. Moreover, it provides a gel of excellent quality, and as a result, the pellets produced are of high quality yet require less binder formulation compared to pellets produced using non-gelling techniques, resulting in lower costs.

[0019] In the step of applying pressure to a substrate mixture to induce the formation of a hydrogel, the applied load is often in the range of 11kN to 75kN, 25kN to 70kN, or 39kN to 56kN. Within these force ranges, the gel is formed rapidly (almost immediately upon application of the load) without using unnecessary energy that would increase costs and diminish the environmental advantages of the present invention. Instead of the applied load, the step of applying pressure to the substrate can be measured in bar units. For completeness, the pressure value measured in bar units can be converted to the applied load (kN) using the following conversion factor: ((bar × 100) × 28.3) / 10,000.

[0020] Typically, this method includes an additional step of forming pellets from the aggregates. This is because pelletization makes the aggregates easier to transport and handle, and also facilitates the selection of the desired amount of material. The pellets can be formed using a second roller press equipped with rollers containing a series of equally spaced recesses along its length, as described above. Alternatively, the pellets can be formed by extruding the aggregates or granules formed from the aggregates. Therefore, this method may include an additional step of forming pellets, which includes extruding the aggregates. This extrusion process can be carried out at temperatures in the range of about 30°C to about 70°C, often in the range of about 35°C to about 55°C. Furthermore, this step can be carried out under atmospheric pressure or vacuum. As used herein, the term “under vacuum” has the usual meaning in the art and means that the extrusion process can be carried out at a pressure below atmospheric pressure.

[0021] The pellets can be cold-formed (i.e., no heating or hardening is required after manufacturing). As mentioned above, the term "cold-formed" means, for example, that no hardening, sintering, or heating to above approximately 60°C, 40°C, or 30°C is performed. In other words, if heat is applied during pellet formation, it is usually only at a low level. Alternatively, after pellet formation, the method may further include an additional step of applying low levels of heat, such as heating in the range of approximately 100°C to 250°C. Low-level heating allows for faster pellet formation. This low-level heating may be in the range of approximately 100°C to 250°C, or often in the range of approximately 150°C to 200°C. If low-level heating is performed, it can be done for a period ranging from approximately 1 minute to approximately 24 hours. Heating generally accelerates the drying and hardening of the pellets, thereby ensuring they are ready for transport and use when needed. Those skilled in the art will understand and recognize that factors such as ambient temperature, the properties of the components in the mixture, and the desired characteristics of the pellets produced (e.g., low moisture content) influence whether external heating is necessary, and if so, the level and duration of the heat applied. Therefore, those skilled in the art will consider such factors when deciding whether to use a low-level heating step in the process, and when determining the duration and level of heating in the process. For example, pellet formation can be supported by providing an environment of approximately 30°C to 50°C (either based on ambient temperature or by heating) for 6 to 24 hours or 9 to 18 hours. Alternatively, heating in the range of 125°C to 175°C for a shorter period, such as 1 minute to 3 hours or 15 minutes to 100 minutes, may be preferable. Therefore, aggregates and subsequent pellets can be formed by cold formation or by applying low levels of heating, and thus aggregates and subsequent pellets can be formed at temperatures in the range of approximately 10°C to 250°C, or approximately 15°C to 200°C, or approximately 20°C to 150°C.

[0022] The advantage of forming pellets by cold forming or forming pellets using only low-level heat is significant in terms of reduced energy consumption compared to commonly used firing production techniques. In addition, since a high-temperature furnace is not required for producing pellets, the production process is simpler, more economical and environmentally beneficial.

[0023] Traditionally, pellets have been formed using thermal processes that produce so-called high-temperature bonded (calcined) briquettes. In calcination techniques, a “green” pellet is first formed from a combination of particulate substrate and binder formulation, and then this is molded into pellets (often using a pelletizer). As used herein, the term “green pellet” has the usual meaning in the art and refers to a pellet that does not yet possess the strength required for its end use and requires further processing or modification. Green pellets are cured through a series of steps including drying, preheating, heat treatment, and cooling. The main purpose of the drying stage is to remove moisture from the pellet to make it more stable and easier to handle. By removing water in a controlled manner, crack formation is prevented and the structural integrity of the pellet is maintained. The temperature range for the drying stage depends on the chemical and physical properties of the green pellet, but is generally in the range of 100°C to 250°C for 5 to 10 minutes. The preheating stage is typically carried out using a gradient heating process from approximately 300°C to 350°C to approximately 1250°C to 1350°C for 10 to 15 minutes. The preheating stage ensures that any present metal hydrates or metal carbonates decompose into their anhydrous forms. The decomposition of these types of compounds contributes to improving the structural integrity of the resulting pellets by removing water and / or gases that could react during heat treatment, potentially causing overpressure and cracking of the pellets. The heat treatment stage is often carried out at temperatures above 1350°C for approximately 10 to 20 minutes (for typical processing capacities such as 250–500 tph), which sinters the pellets and provides the strength necessary to make them suitable for their final application. During the sintering process, bonds within the pellets are formed by recrystallization and crosslinking, resulting in the formation of ceramic bonds and macrovoids, which allow for some degree of expansion and stress relaxation. As used herein, the term "macrovoid" refers to voids within the pellets, having a size ranging from approximately 50 μm to approximately 1 mm in diameter. Void formation is particularly important when the briquette is a metal ore briquette, because the reduction of the metal (for example, the conversion of hematite to magnetite in iron ore) causes volume changes and stress in the briquette.Since macrovoid formation does not occur without heat treatment, an alternative method is required to prevent the collapse of pellets when placed under internal stress. The gelation technique described herein provides such an alternative method by providing rapidly induced improved chemical bonding strength.

[0024] Furthermore, compared to the process of the present invention, the calcination process is complex, must be carried out carefully, requires the application of a significant amount of heat, and is therefore not economical. For example, raw material adjustment is critically important. Since surface chemistry plays an important role, the components of the green pellets must have an appropriate size range, surface area, and moisture content to withstand the process. Furthermore, the process includes multiple heating stages and therefore requires a large amount of energy. Accordingly, there is a need for a pellet manufacturing process that is less energy intensive and more cost effective. Furthermore, there is a need for a process that has greater flexibility in terms of the physical state of the particulate material used and results in the production of pellets having physical properties that are equivalent to or even better than those produced using a calcination process. The method of the present invention contributes to providing a solution to this problem through the use of a hydrogel binder formulation.

[0025] As mentioned above, hydrogel formation generally and typically requires the presence of water, which promotes hydrogel formation. Water may be added to the particulate base material, or may be added to the combination of the particulate base material and the binder formulation before or during the mixing process, but the particulate base material contains moisture, and the water for hydrogel formation is often derived from this moisture. When moisture is present within the particles, the step of adding water to the mixture is unnecessary, thus simplifying the method of the present invention. The particulate base material often contains water in an amount ranging from about 0.5% by weight to about 10% by weight, often from about 1% by weight to 6% by weight, and often from 1.5% by weight to 4% by weight, because hydrogel formation is optimal at these levels.

[0026] Typically, particulate substrates are selected from metal ore, metal ore-containing waste, metal powder, iron residue, iron scrap, inorganic waste, carbonaceous materials, arc furnace waste, or combinations thereof. Particulate substrates often originate from waste products of other industrial processes. Particulate substrates may contain waste products from a single waste stream (in which case the variation is only in particle size) or waste products from a combination of multiple waste streams (in which case there will be mixed waste with different compositions). This is environmentally beneficial because the recycling and reuse of such materials reduces the amount of finite resources that would otherwise be discarded, and introduces desirable circularity to these industrial processes.

[0027] While not strictly theoretical, it is believed that the use of gel binder formulations helps distribute waste into the pseudomatrix before aggregates form, regardless of whether the particulate substrate contains a single type of waste or a combination of different waste types.

[0028] The carbonaceous material may be coke, graphite, carbon black, peat, or coal. The carbonaceous material often includes coke and / or coal. As used herein, the term "coal" is intended to encompass lignite, subbituminous, bituminous, general coal, and anthracite. Coke has proven particularly problematic in pellet formation. Therefore, the present invention offers a particular advantage in that it provides higher-strength coke pellets.

[0029] Inorganic waste may include mill scale, mill sludge, ore-derived fine powder, and / or metal-containing waste.

[0030] The metals may be iron, zinc, nickel, copper, chromium, manganese, gold, platinum, silver, titanium, tin, lead, vanadium, cadmium, beryllium, molybdenum, uranium, aluminum, or mixtures thereof, or inorganic waste metal ore may contain these, and these may exist, for example, as elemental metals, or for example, in the form of oxides or silicates.

[0031] In many cases, particulate substrates contain metals, and more often, iron. The use of iron is advantageous because it is readily available and can be reused and recycled from waste products of other processes, providing an environmentally sustainable access to this material. When particulate substrates contain metallic ore, the ore is often iron ore such as goetite, limonite, siderite, taconite, hematite, or magnetite. Often, when particulate substrates are metallic ore, the metallic ore is iron ore such as hematite or magnetite because these materials are readily available and there is a need to efficiently utilize both the raw materials and iron ore-containing waste.

[0032] The particulate substrate may be powder or scrap, and the term "scrap" is used in the usual sense in the art. Often, the particulate substrate has a particle diameter (maximum axis) of 4 mm or less. Often, the particle diameter is in the range of 0.1 mm to 4 mm. Often, at least 10% by weight of the particulate substrate can pass through a 100 μm sieve before being formed into pellets. The ability to pelletize fine particulate matter is advantageous in terms of "recycling" waste materials that would be extremely difficult to handle and reuse if not pelletized. Furthermore, in the case of unused materials such as ore, for example, waste due to the loss of small particles detaching from the surface of larger aggregates during transport and handling is reduced, ensuring that a much higher percentage of the material is available at the time of final use. The presence of various particle sizes in the sample improves the filling of the material within the aggregates when pelletizing, for example, by extrusion molding or by roller pressing with rollers containing a series of equally spaced recesses along its length. As stated above, the term aggregate has its usual meaning in the art, namely, particulate materials formed from aggregates of physically or chemically bound particles.

[0033] Typically, particulate substrate is added in amounts of approximately 70% to 99.9% by weight of the pellet, often approximately 80% to 99% by weight, and more often approximately 90% to 95% by weight. This maximizes the substrate content in the pellet while allowing for a sufficient amount of binder formulation to ensure particle stabilization. Typically, the ratio of binder formulation to particulate substrate is approximately 1.5% to 3.6% by weight for the binder formulation to approximately 98.5% to 96.4% by weight for the particulate substrate, and often approximately 2.5% to 3% by weight for the binder formulation to approximately 97.5% to 97% by weight for the particulate substrate.

[0034] The binder formulation comprises at least one binding material, which can be selected from natural polymers, synthetic polymers (such as synthetic organic resins), cellulose materials, glycerolipids, polysaccharides, inorganic binding materials, or combinations thereof. As used herein, the term "cellulose material" has the usual meaning in the art and means any material derived from or containing cellulose. Examples of cellulose materials include natural materials mainly composed of cellulose and synthetic derivatives of cellulose. As used herein, the term "glycerolipid" has the usual meaning in the art and means a type of lipid molecule consisting of a glycerol skeleton esterified with one or more fatty acids or acyl groups.

[0035] The binder formulation may include at least one binder selected from synthetic polymers, cellulose materials, glycerolipids, inorganic binders, or combinations thereof.

[0036] Examples of natural polymers include, but are not limited to, lignosulfonates. Examples of synthetic polymers include, but are not limited to, polyvinyl alcohol, polyacrylic materials, styrene-acrylate copolymers, and synthetic organic resins, such as polyacrylamide resins or phenol-formaldehyde resins. As used herein, phenol-formaldehyde resins include resol resins, i.e., base-catalyzed phenol-formaldehyde resins in which the ratio of formaldehyde to phenol is greater than 1, and usually about 1.5, or novolac resins in which the molar ratio of formaldehyde to phenol is less than 1. As used herein, the term "polyacrylic material" has the usual meaning in the art and refers to a class of synthetic polymers derived from acrylic acid or its esters. Examples of polyacrylic materials include, but are not limited to, polyacrylic acid (PAA), poly(methyl methacrylate) (PMMA), and polyacrylamide (PAM). As used herein, the term "styrene-acrylate copolymer" has the common meaning in the art and refers to a synthetic polymer formed by copolymerization of styrene with acrylic acid or its derivatives. Examples of styrene-acrylate copolymers, but are not limited to, 2-ethylhexyl acrylate styrene (2-EHA), ethyl acrylate styrene (EA), methyl methacrylate styrene (MMA), and butyl acrylate styrene (BA). In many cases, styrene-acrylate copolymers include ethyl acrylate styrene (EA). Examples of glycerolipids include mono-, di-, or tri-esters of glycerol, such as glyceryl acetate, glyceryl diacetate, and glyceryl triacetate. Examples of cellulose materials, but are not limited to, cellulose fibers, carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), hydroxyethylmethylcellulose (MHEC), or combinations thereof.Examples of synthetic triglycerides include, but are not limited to, glycerol triacetate. Examples of polysaccharides include, but are not limited to, wheat, corn, barley, and potato starch, or gums (e.g., gum arabic, guar gum, or xanthan gum). Examples of inorganic bonding materials include, but are not limited to, silicates (e.g., silicates of Group I or Group II metals, e.g., sodium silicate (Na2SiO3), potassium silicate (K2SiO3), calcium silicate (CaSiO3), magnesium silicate (MgSiO4), alumina silicate, or combinations thereof) or refractory materials, and examples of refractory materials include, but are not limited to, oxides, carbides, or nitrides of silicon, aluminum, magnesium, calcium, and zirconium (e.g., alumina, refractory clay, bauxite, chromite, dolomite, magnesite, silicon carbide, zirconia, or combinations thereof). As used herein, the term "fire-resistant material" refers to a material that is resistant to thermal stress, high pressure, or corrosion by chemical reagents.

[0037] These materials provide a combination of hydrogel-forming and non-hydrogel-forming binders, thereby offering improved pellet strength and processability, as well as compositional flexibility, in accordance with the present invention. These binders can be used at low concentrations, thus having the advantage of not significantly affecting the metallurgical or physical properties of the substrate mixture. The binder formulation often includes at least one binder selected from cellulose materials, synthetic polymers, glycerolipids, one or more silicates, or combinations thereof.

[0038] The binder formulation may include at least one binding material selected from cellulose fibers, carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), hydroxyethylmethylcellulose (MHEC), polyacrylamide resin, polyvinyl alcohol, phenol-formaldehyde resin, polyacrylic substances, styrene-acrylate copolymer, glycerolipids, one or more silicates, or combinations thereof.

[0039] The binder formulation often contains at least one binding material selected from cellulose fibers, carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), polyacrylamide resin, polyvinyl alcohol, one or more silicates, polyacrylamide, ethyl acrylate styrene (EA), glyceryl triacetate, glyceryl diacetate, phenol-formaldehyde resin, or combinations thereof.

[0040] The binder formulation often contains at least one binding material selected from cellulose fibers, carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), polyvinyl alcohol, polyacrylamide resin, one or more silicates, polyacrylamide, phenol-formaldehyde resin, glyceryl triacetate, or combinations thereof.

[0041] The binder formulation may include at least one binding material selected from polyacrylamide resin, polyvinyl alcohol, phenol-formaldehyde resin, carboxymethylcellulose (CMC), glyceryl triacetate, sodium silicate, magnesium silicate, or a combination thereof.

[0042] The binder formulation may include at least one binding material selected from polyacrylamide resin, polyvinyl alcohol, phenol-formaldehyde resin, carboxymethylcellulose (CMC), sodium silicate, magnesium silicate, or a combination thereof.

[0043] Binder formulations (used in this context to include the binding material as a component) are generally added in powder form, but gel form or other pre-solubilized forms (e.g., bound to a liquid suspension) are also conceivable. In cases where the binder formulation is added as a powder, the presence of water promotes the in-situ gelation of the binder formulation. Providing the binder formulation as a powder allows for better control of the overall moisture content of the pellet compared to adding a liquid. Applying pressure to the substrate mixture improves the cold strength of the pellet, reducing or eliminating the need for prolonged heating or drying processes and the energy input required for such processes. Such advantages may not exist if the binder formulation does not form a hydrogel but instead takes the form of, for example, a film. One example of a situation in which the binder formulation forms a film is when the amount of water in the mixture is limited, resulting in suppressed dissolution of the binder formulation in water and preventing hydrogel formation.

[0044] The synthetic polymer may be polyacrylamide resin, polyvinyl alcohol, and / or phenol-formaldehyde resin, such as resol resin or novolac resin; the cellulose material may be cellulose fiber, carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), and / or hydroxyethylmethylcellulose (MHEC); and / or the polysaccharide may be starch, such as wheat, corn, barley, and potato starch, gum arabic, guar gum, and / or xanthan gum. These materials have been found to provide good gel formation and pellet strengthening compared to pellet strength without gel formation.

[0045] When the binder contains cellulose material, the cellulose material is often carboxymethylcellulose (CMC), cellulose fiber, hydroxyethyl methylcellulose (MHEC), or a combination thereof. CMC is advantageous because it can be added in powder form, thereby allowing control of the overall moisture content of the pellet. CMC also has a longer shelf life compared to other plant-derived binders. This is because other plant-derived binders are more susceptible to microbial attack and decompose more easily. Sometimes the binder is hydroxyethyl methylcellulose (MHEC). Hydroxyethyl methylcellulose (MHEC) has been found to have particularly good adhesion and contribute to improved pellet strength. However, MHEC exhibits high water solubility, which can affect the shelf life of the final pellet, resulting in a shorter shelf life compared to pellets containing CMC.

[0046] In general, the binder material includes at least one of CMC, polysaccharides, PVA, and / or polyacrylamide resin as a hydrogel-forming binder material. Two or more of CMC, polysaccharides, PVA, and polyacrylamide resin may be present in combination with each other or in combination with other binder materials. Often, silicates (e.g., silicates of Group I or Group II elements such as sodium silicate), glycerolipids, cellulose fibers, and / or phenol-formaldehyde resins are present. Silicates, glycerolipids, cellulose fibers, and phenol-formaldehyde resins generally do not form hydrogels. Therefore, the binder formulation may include a) one or more of CMC, polysaccharides, PVA, and polyacrylamide resins, and b) one or more of silicates (e.g., silicates of Group I or Group II elements), glycerolipids, cellulose fibers, and phenol-formaldehyde resins. The binder formulation may include a combination of a) one or more of CMC, PVA, and polyacrylamide resins, and b) one or more of silicates and phenol-formaldehyde resins. The binder formulation may essentially consist of the components listed in a) and b) above.

[0047] In many cases, CMC can be used as a binder, either in place of or in addition to other binders, and the binder formulation may contain about 10% to 100% by weight, often about 20% to 90% by weight, or about 50% to 75% by weight of CMC. When the binder formulation contains CMC as a binder, the binder formulation is typically added in the range of about 0.01% to 3% by weight of the pellet, often about 0.1% to 2.5% by weight of the pellet, often about 0.15% to 1% by weight of the pellet, and often about 0.2% to 0.8% by weight of the pellet. At these levels, the binder formulation provides good reinforcement of the pellet.

[0048] Typically, CMCs have an active polymer content of approximately 40% to 90% and a pH in the dissolved state ranging from approximately 5 to 9, or 6 to 8. Furthermore, CMCs often have a molecular weight in the range of approximately 3,000 to 70,000. Optionally, CMCs may have a molecular weight in the range of approximately 10,000 to 50,000. While not strictly theoretical, it is thought that lower molecular weights of CMCs, for example in the range of approximately 10,000 to 50,000, allow for the preparation of high-concentration binder solutions, thereby improving the strength of the pellets.

[0049] As a binder, PVA can be used either in place of other binders or in addition to other binders. PVA may be used as a binder together with synthetic organic resins. Binder formulations can contain approximately 10% to 100% by weight of PVA, often approximately 20% to 90% by weight, or approximately 50% to 75% by weight. When the binder formulation contains PVA as a binder, the binder formulation is typically added in the range of approximately 0.01% to 2.0% by weight of the pellet, often approximately 0.05% to 1.5% by weight, or approximately 0.07% to 1% by weight of the pellet.

[0050] While not strictly theoretical, PVA is considered to offer good mixing of components and high strength because the polymer network formed by PVA is robust. Furthermore, the pelletizing process using PVA removes air from the particulate material, thereby reducing oxidation of the particulate substrate if it is metallic. Metal oxidation is undesirable for the simple reason that it reduces the amount of metal (e.g., metallic iron) available for processing by the end user.

[0051] PVA is typically commercially produced from polyvinyl acetate by saponification, which involves reacting polyvinyl acetate with sodium hydroxide to replace the acetate groups with hydroxyl groups. Partial saponification means that some of the acetate groups are replaced with hydroxyl groups, thereby forming at least partially saponified polyvinyl alcohol residues. Typically, PVA has a degree of saponification of at least about 80%, typically at least about 5%, at least about 90%, at least about 95%, at least about 99%, or about 100%. PVA is typically used as an aqueous solution. PVA may be modified to include, for example, sodium hydroxide content. Typically, PVA binding materials have an active polymer content of about 12% to about 13% and have a pH in the range of about 4 to about 7 in the dissolved state. Furthermore, PVA often has a molecular weight in the range of about 15,000 to about 150,000. Optionally, PVA often has a molecular weight in the range of about 30,000 to about 120,000. While not strictly theoretical, it is believed that when the molecular weight is lower, for example in the range of approximately 15,000 to 60,000, it is possible to prepare a high-concentration binding material solution, thereby improving the strength of the pellets.

[0052] When the binder material includes polyacrylamide resin, the polyacrylamide resin is often an anionic polyacrylamide resin having a molecular weight of 100,000 to 10,000,000 Da and a charge ratio of 25 to 50%. When the binder material includes polyacrylamide resin, the polyacrylamide resin can be added in an amount of approximately 0.05% to 0.7% by weight, often approximately 0.1% to 0.3% by weight, and often approximately 0.2% to 0.4% by weight.

[0053] If the binder contains polysaccharides, these may be starch or amylase starch. For example, this may be pregelatinized potato starch. This can be added in an amount of about 0.8% by weight, often about 0.6% by weight, of the final pellet. Using polysaccharides as a component of the binder formulation may be desirable because polysaccharides often function as thickeners.

[0054] The inorganic bonding material may include one or more silicates (e.g., silicates in the form of sodium salts) or refractory materials, which are not limited to but include oxides, carbides, or nitrides of silicon, aluminum, magnesium, calcium, and zirconium, as well as combinations thereof. For example, refractory materials include alumina, refractory clay, bauxite, chromite, dolomite, magnesite, silicon carbide, zirconia, or combinations thereof.

[0055] In many cases, the inorganic binder contains one or more silicates. The inorganic binder may contain two to four different silicates, for example, a combination of silicates of Group I elements and silicates of Group II elements. The one or more silicates are often selected from sodium silicate (Na2SiO3), magnesium silicate (MgSiO4), calcium silicate (CaSiO3), aluminum silicate, and combinations thereof. The one or more silicates may be in liquid form, powder form, or a combination thereof. Because the powder form of silicates is more concentrated, the inorganic binder may be in powder form. The binder may contain the inorganic binder in combination with synthetic polymers and / or cellulose materials.

[0056] In most cases, inorganic binders (either alone or in combination with one or more other binders) are present in pellets in amounts ranging from approximately 0.5% to 2.5% by weight, often from approximately 1% to 2% by weight, or from approximately 1.25% to 1.75% by weight.

[0057] When silicates are present, and one or more are in liquid form, they are often present in larger quantities. This is because liquid silicates have lower levels of active ingredients compared to powdered silicates. When one or more silicates are in liquid form, they are often present in pellets in the range of approximately 0.5% to 6% by weight, often approximately 1% to 5% by weight, often 1.25% to 3% by weight, and often 1.5% to 2% by weight.

[0058] When one or more silicates are in powder form, the silicates are often present in the pellet in amounts ranging from approximately 0.5% to 3.5% by weight, often from approximately 1% to 3% by weight, or from 1.5% to 2.5% by weight.

[0059] In most cases, the entire binder formulation is added in an amount of approximately 0.05% to 7.0% by weight of the pellet. Often, it is in the range of approximately 0.3% to 6% by weight, often in the range of approximately 0.4% to 5% by weight, and often in the range of approximately 0.8% to 4% by weight. When the amount of binder formulation present is less than approximately 0.05% by weight, the structural integrity of the aggregate has been found to be poor. If one or more binding materials are hydrogel-forming, these binding materials (either alone or in combination with one or more non-hydrogel-forming binding materials) are often present in the range of approximately 0.05% to 1.5% by weight of the pellet, often in the range of approximately 0.07% to 1.0% by weight, or approximately 0.1% to 0.9% by weight.

[0060] As described above, hydrogels can act as processing aids. However, the method of the present invention may optionally further include the step of adding a separate processing aid to the substrate mixture. Processing aids include, but are not limited to, dilute solutions of cationic, anionic, or nonionic polymers, typically acrylic flocculants, carbon (often in the form of graphite), lubricants, surfactants (such as sodium lauryl sulfate), stearates (such as calcium stearate or sodium stearate), stabilizing fibers, or combinations thereof. Processing aids can make the entire process more efficient, thereby reducing both cost and energy.

[0061] The method of the present invention may further include the step of adding one or more additional additives to the base material mixture.

[0062] In a second aspect of the present invention, pellets obtained by the method of the first aspect of the present invention are provided, comprising a particulate substrate selected from metal ore, metal ore-containing waste, metal powder, iron residue, iron scrap, inorganic waste, carbonaceous material, arc furnace waste, or a combination thereof, and a binder formulation. Generally, after agglomeration, the pellets can be formed at a temperature in the range of about 10°C to about 60°C. Alternatively, the method of the first aspect of the present invention may include an additional step of applying a lower level of heat, such as in the range of about 100°C to about 250°C. The lower level of heating allows for faster pellet formation. This lower level of heating may be in the range of about 100°C to about 250°C, or often in the range of about 150°C to 200°C. When low-level heating is performed, this heating can be carried out over a period of time ranging from about 1 minute to about 24 hours.

[0063] Typically, a pellet according to a second aspect of the present invention is 2.5 cm 3 ~15cm 3 , in most cases 3cm 3 ~12cm 3 , or 7cm 3 ~11cm 3They have an average volume within a certain range. Pellets are generally sized to minimize surface area and are often, for example, nearly spherical, oval, cylindrical, or cubic in shape.

[0064] Unless otherwise specified, each integer given may be used in combination with any other integer as understood by those skilled in the art. Furthermore, while all aspects of the present invention often "include" the features described in relation to that aspect, it is also particularly assumed that they may "consist of" or "essentially consist of" those features. Furthermore, unless otherwise specifically defined herein, all terms shall have the meanings commonly understood in the art.

[0065] Furthermore, in the description of the present invention, unless otherwise specified, if an alternative value is disclosed for the upper or lower limit of the tolerance range of a parameter, it shall be implicitly understood that each intermediate value between the smaller alternative value and the larger alternative value of the parameter is also disclosed as a possible value for that parameter.

[0066] Furthermore, unless explicitly excluded, all numerical values ​​stated in this application should be understood to be modified by the term “approximately.” The term “weight %” and similar terms shall mean the weight percentage of the components in the final pellet. If additives, impurities, and / or water are present in the particulate starting material in step (i), the term “weight %” shall include such additives, impurities, and / or water.

[0067] To make the present invention easier to understand, it will be further described below with reference to the drawings and specific examples. [Brief explanation of the drawing]

[0068] [Figure 1]Figures (a) and (b) show two alternative structural configurations of a roller press wheel. (a) is a schematic diagram of a single blank wheel with a smooth surface suitable for applying pressure to a substrate mixture, and (b) is a schematic diagram of a single concave wheel typically used for pellet formation. [Figure 2] This diagram shows the relative positions of the two roller press blank wheels during use. Pressure is applied when the substrate mixture is pressed between the wheels, forming a gel. [Figure 3]Figures (a) to (c) are graphs showing the results of Examples 1 to 3. Figure (a) shows how the mechanically induced gelation process according to the first aspect of the present invention (i.e., MC2 and MC3) affects the cold crush strength of pellets using binder combination 1 compared to the method without mechanically induced gelation (i.e., MC1). The y-axis corresponds to the cold crush strength (kgf), and the x-axis corresponds to the mixing conditions MC1, MC2, and MC3 (i.e., a collection of bar graphs grouped from left to right). Bar graphs with diagonal lines sloping downward from left to right represent ore 1 (i.e., fine-grained magnetite), bar graphs with diagonal lines sloping upward from left to right represent ore 2 (i.e., coarse-grained magnetite), and uniform gray bar graphs represent ore 3 (i.e., hematite). (b) shows how the mechanically induced gelation process according to the first aspect of the present invention (i.e., MC2 and MC3) affects the cold crush strength of pellets using binder combination 2 compared to the method without mechanically induced gelation (i.e., MC1). The y-axis corresponds to cold crush strength (kgf), and the x-axis corresponds to the mixing conditions MC1, MC2, and MC3 (i.e., a collection of bar graphs grouped from left to right). Bar graphs with diagonal lines sloping downward from left to right represent ore 1 (i.e., fine-grained magnetite), bar graphs with diagonal lines sloping upward from left to right represent ore 2 (i.e., coarse-grained magnetite), and uniform gray bar graphs represent ore 3 (i.e., hematite). (c) shows how the mechanically induced gelation process according to the first aspect of the present invention (i.e., MC2 and MC3) affects the cold crush strength of pellets using binder combination 3 compared to the method without mechanically induced gelation (i.e., MC1). The y-axis corresponds to the cold crush strength (kgf), and the x-axis corresponds to the mixing conditions MC1, MC2, and MC3 (i.e., a collection of bar graphs grouped from left to right). Bar graphs with diagonal lines sloping downward from left to right represent ore 1 (i.e., fine-grained magnetite), and uniform gray bar graphs represent ore 3 (i.e., hematite). [Figure 4] This figure shows the results of Examples 9 and 10 in graph form. The y-axis corresponds to the cold crushing strength (kgf), and the x-axis corresponds to the applied load in units of kN. The dashed line represents a mesh size of 3.15 mm, and the solid line represents a mesh size of 2.00 mm. [Figure 5] This figure shows the results of Example 11 in graph form. The y-axis corresponds to the cold crushing strength (kgf). The dotted bar graph represents ore 5 under mixing condition 1, the vertical bar graph represents ore 5 under mixing condition 2, the horizontal bar graph represents ore 5 under mixing condition 2, the diagonal bar graph sloping downwards from left to right represents ore 6 under mixing condition 1, the diagonal bar graph sloping upwards from left to right represents ore 6 under mixing condition 2, and the uniform gray bar graph represents ore 6 under mixing condition 2. [Figure 6] This figure shows the results of Example 13 in graph form. The y-axis corresponds to the cold crush strength (kgf), and each bar graph corresponds to test IDs 1 to 4. The dotted bar graph represents test ID 1 under mixing condition 1, the horizontal bar graph represents test ID 2 under mixing condition 1, the diagonal bar graph sloping downwards from left to right represents test ID 3 under mixing condition 3, and the uniform gray bar graph represents test ID 4 under mixing condition 3. [Figure 7]Figures (a) to (c) are graphs showing the results of Example 14. Figure (a) shows the results for ore 8. The y-axis corresponds to RDI% < 2.8 mm, and the x-axis corresponds to various mixing conditions (i.e., MC1 and MC3). Specifically, the uniform gray bar graph corresponds to RDI% < 2.8 mm under mixing condition 1, and both the diagonal bar graph and the horizontal bar graph that descend from left to right correspond to RDI% < 2.8 mm under mixing condition 3. Figure (b) shows the results for ore 9. The y-axis corresponds to RDI% < 2.8 mm, and the x-axis corresponds to various mixing conditions (i.e., MC1 and MC3). Specifically, the uniform gray bar graph corresponds to RDI% < 2.8 mm under mixing condition 1, and the diagonal bar graph that descends from left to right corresponds to RDI% < 2.8 mm under mixing condition 3. Figure (c) shows the results for ore 10. The y-axis corresponds to RDI% < 2.8 mm, and the x-axis corresponds to various mixing conditions (i.e., MC1 and MC3). Specifically, the uniform gray bar graph corresponds to RDI% < 2.8 mm under mixing condition 1, and the diagonal bar graph sloping downwards from left to right corresponds to RDI% < 2.8 mm under mixing condition 3. [Examples]

[0069] The following examples demonstrate how the use of mechanically induced gelation (MIG) in the production of iron ore pellets improves the cold crush strength (CCS) and reduction decay index (RDI) of the resulting pellets.

[0070] Types of ore The embodiments described used eight different iron ores, which are as follows: Ore 1: High-purity fine-grained magnetite ore, iron content as iron oxide 71.2%, particle size distribution (PSD) <300 μm, Dv90 166 μm.

[0071] Ore 2: High-purity coarse-grained magnetite ore, iron content as iron oxide 68.0%, PSD < 4 mm, Dv90 1432 μm in received state.

[0072] Ore 3: Hematite ore, iron content as iron oxide 65.0%, PSD < 250 μm in received state, Dv90 approximately 50 μm.

[0073] Ore 4: Hematite ore, iron content 67.1%, nominal Dv90 150μm.

[0074] Ore 5: Magnetite ore, iron content 68%, nominal Dv90 323μm.

[0075] Ore 6: Magnetite ore, iron content 68%, nominal Dv90 150μm. It is the same material as Ore 5, but with a different particle size distribution, being slightly finer.

[0076] Ore 7: Hematite ore containing martite and goetite, iron content 67.6%, Dv90 102μm.

[0077] Ore 8: A diverse mineralogical composition mainly containing hematite, magnetite, and goetite. Ore 8 is a relatively coarse-grained material with an iron content of 64.5% and a Dv90 of 565 μm.

[0078] Ore 9: Goethite ore containing iron oxyhydroxide, Dv90, 538 μm.

[0079] Ore 10: Matite ore, iron content 67.5%, Dv90 97μm.

[0080] Experimental Procedure First, the ore was dried to allow control of its moisture content during use. Iron ore (5 kg or 10 kg) and the binder mixture were mixed in an Eirich EL10 mixer according to the test method for mixing condition 2 or mixing condition 3 described below. Homogenization was performed for 1 minute before adding 3% w / w water. Water was added over 1 minute while the mixer was running, and then the mixture was mixed for a further 2 minutes at a speed of 300 rpm. After 4 minutes of mixing, the material was removed from the mixer.

[0081] Next, the control sample was passed through a Sahut Conreur roller press equipped with a concave wheel at an applied force of 42.2 kN and a pellet wheel speed of 5 rpm, resulting in a pellet size of approximately 27 × 18 × 10 mm (4.86 cm). 3 Pellets of the following size were produced. A schematic diagram of an example of a concave wheel is shown in Figure 1(b). The pellets were then held at 40°C for 24 hours.

[0082] The embodiment of the present invention was also fed into a Sahut Conreur roller press. The wheel dimensions were 30 mm × 100 mm. The mechanical gelation process was induced by producing ribbons of the material using the blank wheels shown in Figures 1 and 2, and then these ribbons were passed through a Sahut Conreur granulator with a mesh size of 2 mm to reduce the size of the produced ribbons. Next, this material was fed into a concave wheel (shown in Figure 1(b)) to produce ribbons of approximately 27 × 18 × 10 mm (4.86 cm²). 3 Pellets of the following dimensions were produced. The pellets were then held at 40°C for 24 hours.

[0083] Cold crush strength (CCS) Cold compressive strength (CCS) was tested using Mecmesin Omnitest 10 in accordance with ISO 4700 (using 30 pellets from each batch).

[0084] Reduction decay index test The thermal properties of the pellets were tested by determining the reduction decay index (RDI) in accordance with the standard ISO 4696-2:2015. In this test, the pellets were subjected to a reducing atmosphere at 550°C, followed by a tumble test to measure the amount of decay after reduction. These conditions are similar to those of the low-temperature reducing zone in blast furnaces used in integrated steelmaking processes.

[0085] Mixing conditions (i) Mixing condition 1 (MC1) In MC1 (i.e., the control), the sample was processed without mechanically induced gelation.

[0086] After drying and mixing the ore with the binder composition as described above, the mixture was passed through a roller press at an applied force of 42.2 kN and a pellet wheel speed of 5 rpm to produce pellets with a size of approximately 27×18×10 mm (4.86 cm 3 ).

[0087] (ii) Mixing Condition 2 (MC2) In MC2, mechanically induced gelation was performed using one binding material.

[0088] For these samples, binding material 1 was mixed with the ore as detailed above (see "Experimental Procedure"). First, this material was passed through a blank wheel at an applied force of 42.2 kN and a wheel speed of 7.5 rpm to mechanically induce gelation and form a ribbon. Next, this ribbon was granulated to 2 mm. Then, after binding material 2 was mixed in again using an Eirich EL10 mixer at 300 rpm for 3 minutes, this final material was passed through a concave wheel at an applied force of 42.2 kN and a pellet wheel speed of 5 rpm to produce pellets with a size of approximately 27×18×10 mm (4.86 cm 3 )).

[0089] (iii) Mixing Condition 3 (MC3) In MC3, mechanically induced gelation was performed using two binding materials.

[0090] For these samples, binding material 1 and binding material 2 were mixed with the ore. First, this material was passed through a blank wheel at an applied force of 69.4 kN and a wheel speed of 7.5 rpm to mechanically induce gelation and form a ribbon. Next, this ribbon was granulated to 2 mm. Then, this material was passed through a concave wheel at an applied force of 42.2 kN and a pellet wheel speed of 5 rpm to produce pellets with a size of approximately 27×18×10 mm (4.86 cm 3 )).

[0091] Effects of carboxymethylcellulose (CMC) and silicates Examples 1 to 3, outlined below, use binder combination 1. Binder combination 1 includes binder material 1, which is carboxymethylcellulose (CMC) added at 0.5% w / w, and binder material 2, which is sodium silicate added at 2% w / w.

[0092] Example 1 In Example 1, ore 1 was used. The moisture content of the material passed through the roller press was in the range of 2.5% to 2.8% w / w.

[0093] [Table 1]

[0094] These results show an increase in CCS between the control and two tests that performed mechanically induced gelation. The largest increase was observed when using a combination of the two binders under mixing condition 3.

[0095] Example 2 In Example 2, ore 3 was used. The moisture content of the material passed through the roller press was in the range of 2.8% to 3.0% w / w.

[0096] [Table 2]

[0097] These results show an increase in CCS between the control and two tests that performed mechanically induced gelation. The largest increase was observed when using a combination of the two binders under mixing condition 3.

[0098] Example 3 In Example 3, ore 2 was used. The moisture content of the material passed through the roller press was in the range of 2.5% to 2.8% w / w.

[0099] [Table 3]

[0100] These results indicate that CCS increases by 90 kgf between mixing condition 1 and mixing condition 3.

[0101] Effects of polyacrylamide and sodium silicate Examples 4 to 6 use binder combination 2. Binder combination 2 includes binder material 1, which is polyacrylamide added at 0.5% w / w, and binder material 2, which is sodium silicate added at 2% w / w.

[0102] Example 4 In Example 4, ore 1 was used. The moisture content of the material passed through the roller press was in the range of 2.8% to 3.0% w / w.

[0103] [Table 4]

[0104] These results show an increase in CCS between the control and two tests performing mechanically induced gelation. The largest increase is observed when a mechanical process is used on a single binder material under mixing condition 2.

[0105] Example 5 In Example 5, ore 3 was used. The moisture content of the material passed through the roller press was in the range of 2.2% to 2.9% w / w.

[0106] [Table 5]

[0107] These results show an increase in CCS between the control and two tests that performed mechanically induced gelation. The largest increase was observed when using a combination of the two binders under mixing condition 3.

[0108] Example 6 In Example 6, ore 2 was used. The moisture content of the material passed through the roller press was in the range of 2.2% to 2.8% w / w.

[0109] [Table 6]

[0110] These results indicate that CCS increases by 38 kgf between mixing condition 1 and mixing condition 2.

[0111] Effects of PVA and phenol formaldehyde In Example 7, binder combination 3 is used. Binder combination 3 includes binder material 1, which is polyvinyl alcohol added at a concentration of 0.5% w / w, and binder material 2, which is phenol formaldehyde added at a concentration of 0.5% w / w.

[0112] Example 7 In Example 7, ore 1 was used. The moisture content of the material passed through the roller press was in the range of 2.8% to 3.0% w / w.

[0113] [Table 7]

[0114] These results show an increase in CCS between the control and two tests performing mechanically induced gelation. The largest increase is observed when a mechanical process is used on a single binder material under mixing condition 2.

[0115] Effects of changes in the amounts of CMC and sodium silicate Example 8 In Example 8, four batches of pellets were produced, each using 5 kg of ore 1. Each batch was produced according to the experimental procedure and mixing conditions 3. The levels of the binders used were as shown in Table 8 below. Binder combination 1 was used, where binder 1 was CMC and binder 2 was sodium silicate. The moisture content of the material passed through the roller press was 2.4% to 3.0% w / w. The addition rates of the two binders were varied as shown in Table 8 below.

[0116] [Table 8]

[0117] Reducing the level of the binder formulation resulted in lower CCS values ​​compared to Example 1 - Mixing Condition 3. However, all values ​​remained higher than those of Example 1 - Mixing Condition 1, indicating that mechanically induced gelation has a positive effect on the physical properties of the pellets.

[0118] The impact of changing the mechanical settings of a roller press. The applied force of the roller press was varied (from 13.9 to 69.4 kN) and this was combined with one of two granulator screen sizes (2.00 mm and 3.15 mm). Examples 9 and 10 investigate the effects of these changes.

[0119] Example 9 Pelletization was carried out using a 5kg batch of ore 1. Binder combination 1 was used. Binding material 1 was CMC, and binding material 2 was sodium silicate. Binding materials 1 and 2 were mixed with the ore according to the experimental procedure. This mixture was then passed through a blank wheel with an applied force of 13.9–69.4kN and a wheel speed of 4.5rpm to mechanically induce gelation and form ribbons, which were then granulated to 3.15mm. These granules were then passed through a roller press with an applied force of 42.2kN and a pellet wheel speed of 5rpm to form pellets approximately 27×18×10mm (4.86cm²). 3Pellets of the following size were produced. The pellets were then held at 40°C for a minimum of 24 hours.

[0120] [Table 9]

[0121] Example 10 Pelletization was carried out using a 5kg batch of ore 1. Binder combination 1 was used. Binding material 1 was CMC, and binding material 2 was sodium silicate. Binding materials 1 and 2 were mixed with the ore according to the experimental procedure. This mixture was then passed through a blank wheel with an applied force of 13.9–69.4kN and a wheel speed of 4.5rpm to mechanically induce gelation and form ribbons, which were then granulated to 2.00mm. These were then passed through a roller press with an applied force of 42.2kN and a pellet wheel speed of 5rpm to form pellets approximately 27×18×10mm (4.86cm²). 3 Pellets of the following size were produced. The pellets were then held at 40°C for a minimum of 24 hours.

[0122] [Table 10]

[0123] The results from Examples 9 and 10 demonstrate that mechanically induced gelation works with applied forces in the range of at least 13.9–42.2 kN. Smaller granulator screen sizes have a better effect on pellet CCS, but good results are obtained with both 2.00 mm and 3.15 mm screens.

[0124] Reproducibility testing Example 11 A test was conducted to verify the reproducibility of the results. Pellet batches (5 kg) were produced from ore 5 and ore 6. For each ore, a control test was performed using mixing condition 1, and two tests were conducted using mixing condition 2. In both cases, binder combination 1 was used, and the following mechanical settings were kept constant: hydraulic pressure 45.3 kN, wheel speed 5 rpm, and granulator screen opening 2 mm. The pellets were then held at 150°C for 2 hours. The pellets were tested for CCS. The results are shown in Table 11 and Figure 5. These results include the standard deviation of CCS within the test pellets obtained from each batch.

[0125] The average strength of pellets formed using mechanically induced gelation according to the process of the first aspect of the present invention (i.e., mixing condition 2) was greater than the average strength of control pellets (i.e., mixing condition 1 without mechanically induced gelation). This applies to both ores and to repeated tests of each ore. There is good consistency between the results for ore 5 and ore 6, indicating that slight differences in particle size distribution have no substantial effect.

[0126] This embodiment clearly demonstrates that the beneficial effects of mechanically induced gelation are reproducible, and that the process according to the first aspect of the present invention is particularly effective.

[0127] [Table 11]

[0128] Use of polysaccharides as binders Example 12 A batch of pellets was prepared using binder combination 4. Binder combination 4 includes polysaccharides as part of the binder combination.

[0129] Specifically, binder combination 4 includes the following: • Binding material 1: 0.5% by weight of polysaccharides containing approximately 25% distillation residue. • Binding material 2: 2% by weight of granular solid sodium silicate.

[0130] Pellets were prepared using ore 4 (hematite) and ore 6 (magnetite) under mixing condition 3. The pellets were then held at 150°C for 2 hours, and the cold crush strength (CCS) of the resulting pellets was tested. The results are shown in Table 12.

[0131] [Table 12]

[0132] When a polysaccharide is used as one of the binding materials, the strength of the pellets produced by the process according to the first aspect of the present invention is high and is better than that of the pellets produced from ore 3 using mixing condition 3 in Example 1.

[0133] Influence of ores containing martite and goetite Example 13 Pellet batches were prepared from ore 7. Ore 7 contains martite and goethite as described above. Using binder combination 1, two batches were prepared using mixing condition 1 (test ID 1 and test ID 2), and two batches were prepared using mixing condition 3 (test ID 2 and test ID 4). Heating was carried out at 150°C for 2 hours. The cold crush strength (CCS) of the obtained pellets was tested, and the results are shown in Table 13 and Figure 6.

[0134] [Table 13]

[0135] In many cases, ores with this property are particularly difficult to aggregate due to their mineralogical characteristics. Therefore, the CCS value obtained from this ore was lower than the values ​​observed for other ores produced using binder combination 1, which was expected. However, although the value may be lower compared to other ores, the results still show a significant increase in strength of pellets produced under mixing condition 3 compared to pellets produced under mixing condition 1. This clearly demonstrates that even when using problematic ores, an improvement in strength can be obtained by using the process according to the first aspect of the present invention (i.e., mechanically induced gelation).

[0136] The effect of MIG on the reduction decomposition index (RDI) Example 14 Pellets were formed from ore 8, ore 9, and ore 10. A process according to the first aspect of the present invention (i.e., mixing condition 3) was used, with a granulation mesh size of 2 mm, and the respective wheel speeds and pressures are shown in Table 14. The pellets were then held at 40°C for 24 hours. A control test was performed using mixing condition 1.

[0137] Binder combination 1 (as described above) was used on ore 8 and ore 10, and binder combination 5 was used on ore 9.

[0138] Binder combination 5 includes the following: Binder 1: Aqueous liquid PVOH with a concentration of 10%. Addition rate: 4%. Binder 2: Phenol-formaldehyde. Addition rate: 0.5%.

[0139] The RDI of the pellets was tested, and the results are shown in Table 14 and Figures 7(a) to (c).

[0140] [Table 14]

[0141] As is evident from these results, RDI is improved when using the process according to the first aspect of the present invention. This is particularly pronounced in the case of ore 8. These results indicate that by using mechanically induced gelation by the process of the present invention, pellets with greater resistance to disintegration in the initial stages of reduction are provided.

[0142] The methods and pellets of the present invention can be implemented in various forms, and it will be understood that those exemplified and described above are only a part of them.

Claims

1. A method for manufacturing pellets, wherein the method is a. A step of providing a particulate substrate selected from metal ore, metal ore-containing waste, metal powder, iron residue, iron scrap, inorganic waste, carbonaceous material, arc furnace waste, or a combination thereof; b. The step of mixing the particulate substrate with a binder formulation containing at least one binding material to form a substrate mixture; c. A step of applying pressure to the substrate mixture to induce the formation of a hydrogel; and d. Step of forming aggregates Includes, A method in which hydrogel formation is promoted by the presence of water.

2. The method according to claim 1, wherein at least one binding material is hydrogel-forming.

3. The method according to claim 1 or 2, wherein the binder formulation comprises two or more binding materials.

4. The method according to any one of claims 1 to 3, comprising mixing a first binder and a second binder with the particulate substrate to form the substrate mixture.

5. The method according to any one of claims 1 to 3, wherein a first binder material is mixed with the particulate substrate to form the substrate mixture, and a second binder material is mixed with the hydrogel.

6. The method according to any one of claims 1 to 5, wherein applying pressure to the substrate mixture thereby inducing the formation of a hydrogel includes passing the substrate mixture through a compression wheel.

7. The method according to any one of claims 1 to 6, wherein the applied force is in the range of 11 kN to 75 kN.

8. The method according to any one of claims 1 to 7, comprising the step of forming pellets from the aggregate.

9. The method according to claim 8, wherein the step of forming the pellets includes passing the aggregate through a roller having a series of recesses that are equally spaced along its length.

10. The method according to claim 8 or 9, wherein, after the step of forming the pellets, the method includes the step of heating the pellets to a temperature in the range of 10°C to 250°C.

11. The method according to any one of claims 1 to 10, comprising granulating the aggregate before pelletizing.

12. The method according to claim 11, wherein the granulation is performed using a screen size in the range of about 1.75 mm to about 10 mm.

13. The method according to any one of claims 1 to 12, wherein the particulate substrate contains water in an amount ranging from about 0.5% by weight to about 10% by weight.

14. The method according to claim 13, wherein the particulate substrate contains water in an amount ranging from about 1% by weight to about 6% by weight.

15. The method according to any one of claims 1 to 14, wherein the particulate substrate contains a metal.

16. The method according to any one of claims 1 to 15, wherein the particulate substrate contains iron.

17. The method according to any one of claims 1 to 16, wherein the particulate substrate is provided in an amount of about 70% to about 99.9% by weight of the pellets.

18. The method according to any one of claims 1 to 17, wherein the binding material is selected from natural polymers, synthetic polymers, cellulose materials, glycerolipids, polysaccharides, inorganic binding materials, or combinations thereof.

19. The method according to claim 18, wherein the binding material is selected from cellulose fibers, carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), hydroxyethylmethylcellulose (MHEC), polyacrylamide resin, polyvinyl alcohol, phenol-formaldehyde resin, glycerolipid, polyacrylic substance, styrene-acrylate copolymer, one or more silicates, or a combination thereof.

20. The method according to claim 18 or 19, wherein the binding material is selected from cellulose fibers, carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), polyacrylamide resin, polyvinyl alcohol, one or more silicates, polyacrylamide, ethyl acrylate styrene (EA), glyceryl triacetate, glyceryl diacetate, phenol-formaldehyde resin, or a combination thereof.

21. The method according to any one of claims 18 to 20, wherein the material is selected from cellulose fibers, carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), polyvinyl alcohol, polyacrylamide resin, one or more silicates, polyacrylamide, phenol-formaldehyde resin, glyceryl triacetate, or a combination thereof.

22. The method according to any one of claims 18 to 21, wherein the binding material is selected from polyacrylamide resin, polyvinyl alcohol, phenol-formaldehyde resin, carboxymethylcellulose (CMC), glyceryl triacetate, sodium silicate, magnesium silicate, or a combination thereof.

23. The method according to any one of claims 18 to 22, wherein the binding material is selected from polyacrylamide resin, polyvinyl alcohol, phenol-formaldehyde resin, carboxymethylcellulose (CMC), sodium silicate, magnesium silicate, or a combination thereof.

24. The method according to any one of claims 18 to 23, wherein the binding material comprises a combination of a) one or more of carboxymethylcellulose, cellulose fibers, PVA, and polyacrylamide, and b) one or more of silicates and phenol formaldehyde.

25. The method according to any one of claims 1 to 24, wherein the binder compound is added in an amount of about 0.05% to about 6.0% by weight of the pellets.

26. The method according to any one of claims 1 to 25, further comprising the step of adding a separate processing aid to the base material mixture.

27. A pellet obtained by the method according to any one of claims 1 to 26, wherein the pellet comprises a particulate base material selected from metal ore, metal ore-containing waste, metal powder, iron residue, iron scrap, inorganic waste, carbonaceous material, arc furnace waste, or a combination thereof, and a binder compound.

28. The pellet according to claim 27, wherein the pellet is heated to a temperature in the range of 10°C to 250°C.

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