Team

Abstract

A method for producing pellets, the method comprising the steps of: providing a granular substrate selected from metal ores, metal ore-containing waste, fine metal powder, iron slag, iron filings, mineral waste, carbonaceous materials, electric arc furnace waste, or combinations thereof; mixing the granular substrate with a binder formulation comprising at least one binder material to form a substrate mixture; applying pressure to the substrate mixture to induce the formation of a hydrogel; and forming aggregates wherein water is present to promote hydrogel formation. Along with a pellet obtained by the method of the present invention.

Description

[0001] The present invention relates to a method for producing pellets from a particulate substrate and a binder, particularly wherein the method induces hydrogel formation, and to pellets obtained using these methods.

[0002] Although abundant in the Earth's core, the amount of usable carbon, as well as various metals and metallic ores, is finite. Environmental costs, particularly in terms of pollution, exist associated with the mining of metallic ores and metals (e.g., iron) and smelting activities. Therefore, maximizing waste recycling is desirable, which in turn reduces the amount of waste that must be processed and stored, for example, in the case of iron scrap, typically through long-term storage in heaps or pools.

[0003] The production of pellets from carbonaceous materials, particulate metals, and metal ores is commonly known in the art. Typically, the particles are bound together using a binder to form pellets. During the pelletizing process, the binder is usually added as a powder. However, powders can be difficult to process into pellets that are stable and sufficiently robust to be transported not only to the location of use but also to large processing plants at their destination. Powdered binders can also explode or easily escape into the atmosphere. This is because the loss of material can be economically unfavorable, poses a risk of direct personal injury, and may produce inhalation hazards with short-term toxic effects or leading to long-term illness.

[0004] Furthermore, pelletizing processes using powders often produce inconsistent results, and this can be problematic when production is scaled up due to difficulties in effectively dispersing the powder in industrial-scale mixers. Interference may also exist between binder components as a result of temperature and pressure effects. The use of powders can also affect solubility differences in unpredictable ways. This means that extensive testing is required before industrial-scale use, making the transition from formulation to industrial pelletizing more difficult and expensive.

[0005] Therefore, it is desirable to develop a process for pelletizing pellets in which the pellets have improved ease of manufacture without loss of strength and stability. This invention aims to overcome or improve at least some aspects of this problem.

[0006] Accordingly, in a first aspect of the invention, a method for producing pellets is provided, the method comprising the steps of: providing a particulate substrate selected from metal ores, metal ore-containing waste, fine metal powder, iron slag, iron filings, mineral waste, carbonaceous materials, electric arc furnace waste, or combinations thereof; mixing the particulate substrate with a binder formulation comprising at least one binder material to form a substrate mixture; applying pressure to the substrate mixture to induce the formation of a hydrogel; and forming aggregates; wherein water is typically present to promote hydrogel formation.

[0007] Mechanically induced gelation to form hydrogels allows binder formulations to be more effectively dispersed within the granular substrate in the final pellet product. Unbound by theory, it is argued that hydrogel formation not only binds the substrate particles together, improving the strength of the final pellet, but also acts as a processing aid, as the binder formulation is more dispersible in hydrogel form and can therefore possess a lubricating effect. Overall, this improves pellet processing, resulting in more consistent outcomes. Furthermore, binder materials capable of forming hydrogels are more easily dispersed in industrial-scale mixers than powdered binders. Moreover, the incorporation of hydrogel-forming binder materials allows for the easy dispersion of additional powdered binders, thus addressing problems associated with using only powdered binders. Correspondingly, this leads to improved efficiency by reducing machine load and overheating. Moreover, it has been noted that less binder formulation is required to achieve strength comparable to known binder formulations, as gelation enhances the bonding properties and allows any existing binder material that does not directly form part of the hydrogel to strengthen polymer bonds. Furthermore, the final pellets produced in the process of this invention have been unexpectedly found to be more robust, with higher strength and stiffness, which reduces the need for post-production heating (e.g., drying or curing processes) to stabilize the pellets for storage, transportation, and use. This has significant environmental benefits, as less energy is required to produce pellets of sufficient strength from granular material. Additionally, process efficiency is improved, as pelletizing can be completed rapidly without the need for heating equipment or delays that could be caused by additional heating stages. Moreover, the pellets obtained by the method according to the first aspect of the invention also generally exhibit high thermal stability, meaning that the pellets are reduced to carbon at a controlled rate and do not disintegrate in the furnace.

[0008] In addition to the benefits derived from hydrogel formation during pelleting, applying pressure to the substrate mixture containing the binder formulation and the particulate substrate provides accelerated gel formation compared to "standing" at ambient temperature. Therefore, the process of agglomerate formation and subsequent pelleting is rapid and readily achievable. The term agglomerate is used in its usual sense in the art, referring to particulate material formed by an aggregate of particles physically or chemically linked together.

[0009] Typically, at least one binder material in an adhesive formulation is hydrogel-forming. If there is only one binder material, such that the adhesive formulation contains or consists of a single binder material, then that binder material will generally be hydrogel-forming. If more than one binder material is present, one or more of them can be hydrogel-forming, and there may be accompanying binder materials that do not form hydrogels. It is believed that hydrogel-forming binder materials form a hydrogel around a particulate substrate, thereby providing the benefits described above.

[0010] As used herein, the term "hydrogel" refers to a material that is neither a free-flowing liquid nor a solid, but a gel composed of a gel-forming material, such as a hydrophilic polymer that is insoluble in water. In other words, a hydrogel can be a semi-solid substance. Typically, hydrogels are formed by a gel-forming material, such as a hydrophilic polymer that forms an interconnected, cross-linked network that can trap, absorb, and / or otherwise retain water, thereby producing a gel. Some hydrogels can be diluted with another liquid, such as water, which disrupts the interconnected network, resulting in a solution, although generally the hydrogels of this invention will be cross-linked hydrogels that do not dissolve upon dilution.

[0011] Typically, water is present to enable hydrogel formation. This can be moisture naturally present in the particulate substrate or water specifically added to enable hydrogel formation. The amount of water in the hydrogel is typically in the range of about 1% to about 5% by weight, or about 2% to about 4% by weight, or about 2.5% to about 3.5% by weight, or about 3% by weight. At higher levels, excessive dilution of the system with water has been found, making gel formation less efficient because water lowers the viscosity of the system, providing less mechanical force for binding and less densification of the resulting pellets. Not bound by theory, it is thought that not all the water mixed with the binder formulation is present in the final hydrogel. This is because a small amount plays a role in ensuring the dissolution or mixing of other components.

[0012] It is well known that hydrogels typically require some time to form, which can be referred to as "resting" and is usually 1 to 2 hours. This can be undesirable as it delays the production process. The key to this invention is the application of pressure to the substrate mixture. It has been unexpectedly found that the application of this pressure induces rapid gel formation, causing the hydrogel to form almost instantly, typically within seconds (e.g., 0-60 seconds, typically 1-20 seconds or 2-5 seconds). This has the advantage that agglomerates form very quickly, and subsequent processing (e.g., pelletizing and / or curing) can proceed without delay. It is important to note that pressure is applied to the substrate mixture prior to agglomerate formation. Therefore, the hydrogel has already formed before any subsequent granulation or pelletizing step. It is possible that the pelletizing method also applies pressure to the agglomerates or granulated agglomerates to hold the agglomerates together, but if the pressure is applied during pelletizing, it is subsequent to and different from the pressure applied to induce hydrogel formation.

[0013] As described above, the binder formulation contains at least one binder material, which will typically form a hydrogel. However, it is possible that the binder formulation contains two or more binder materials, one or more of which may form a hydrogel, but non-hydrogel-forming binder materials may also be present. Therefore, the method of the present invention may include the step of mixing a first binder material and a second binder material with a particulate substrate to form a substrate mixture. In this example, the first and second (and optionally additional) binder materials are added during the step of mixing the particulate substrate with the binder formulation (in this case, containing two or more binder materials) to form the substrate mixture. Alternatively, a first hydrogel-forming binder material may be mixed with the particulate substrate to form a substrate mixture, and a second binder material may subsequently be mixed with the hydrogel. In this example, the first binder material may be hydrogel-forming, and the second may be non-hydrogel-forming. Of course, there may be more than one binder material mixed with the particulate substrate, and more than one binder material mixed with the formed hydrogel. Both methods have been found to provide robust pellets obtainable through rapid production techniques.

[0014] The method of the present invention includes the step of applying pressure to a substrate mixture to induce hydrogel formation, thereby inducing / accelerating gel formation. This can be achieved by any of a range of compression techniques, such as passing the substrate mixture through compression rollers (e.g., on a roller press) or pressure plates.

[0015] One method frequently used to apply pressure to a substrate mixture to induce hydrogel formation is a roller press, as it can be easily incorporated into a pelletizing production line (whether single-machine or multi-machine). Roller presses can be equipped with smooth wheels (also known as smooth rollers) to provide compression, such that the step of applying pressure to the substrate mixture involves passing the substrate mixture through the smooth wheels of the roller press. Smooth wheels can have a smooth surface or can be characterized by a variety of surface patterns. As used herein, the terms "wheel" and "roller" should be considered synonymous and can be used interchangeably. Smooth surfaces are often used for materials requiring minimal friction and easy compression, thus ensuring consistent production of pellets with uniform density. Alternatively, roller presses can have textured surfaces. Textured surfaces can include multiple indentations whose shape, size, and distribution can vary. For example, textured surfaces can include grooves, or straight, spiral, or grid-like patterns. Textured surfaces can help increase friction and enhance material grip and compression, which is particularly useful for harder or more fibrous materials. When the surface of the wheel is textured, the texture often has a depth in the range of 0.1 mm to 0.5 mm, typically in the range of 0.2 mm to 0.4 mm.

[0016] The agglomerates produced after the step of applying pressure to the base mixture can be solid blocks or in the form of flat strips of material, which can benefit from granulation prior to pelletizing. Therefore, an optional step in the process is to pass the agglomerates through a granulator (configured with a screen size suitable for the material and the desired end use) prior to pelletizing. Screen sizes can range from about 1.75 mm to about 10 mm, typically from about 2 mm to about 5 mm, or from 2.25 mm to 3.5 mm. Smaller particulates have been found to provide slightly improved pellet strength, but higher strength is observed due to the presence of gel regardless of particulate size. It has also been found that providing particulates of different sizes can be beneficial, as the resulting stacking effect can enhance the strength of the produced pellets.

[0017] Aggregates can be cold-formed. The term "cold-formed" means, for example, without curing, sintering, or heating to above about 60°C, or above about 40°C, or about 30°C. In other words, it is generally likely that if heat is applied during aggregate formation, only a low level of heat will be applied. Furthermore, when aggregates are pelletized, although frictional heat can be generated by any pressing and / or extrusion process used, and the binder material can undergo an exothermic reaction in situ, this will sometimes be the only heat applied and does not constitute heating as noted above, because it is not an application of external heat. These inherent heating mechanisms are not expected to generate sufficient heat to affect pellet formation.

[0018] The situation may involve a method according to a first aspect of the invention comprising passing a base mixture through the smooth rollers of a first roller press (i.e., to mechanically induce gelation and form agglomerates), wherein the first roller press is operatively connected in series with a granulator and / or a second roller press configured to produce pellets from the agglomerates. For example, in this method, the base mixture may pass through the smooth compression rollers of the first roller press that induces gelation. The resulting gel-containing agglomerates (i.e., agglomerates produced by the smooth compression rollers of the first roller press) may then be passed directly through the rollers of the second roller press configured to produce pellets, or indirectly via the granulator through the rollers of the second roller press configured to produce pellets (i.e., the agglomerates pass through the granulator and the subsequently granulated agglomerates pass through the rollers of the second roller press configured to produce pellets). The rollers of the second roller press may include a series of uniformly spaced recesses along their length, which allows pellet formation. The application of pressure not only reduces the gelation time to almost nothing—essentially, this happens in just a few seconds when the material is compressed through the smooth compression rollers of a roller press or using similar techniques—but also provides a high-quality gel, resulting in high-quality pellets at a low cost because fewer binder formulations are required compared to pellets manufactured using non-gelation techniques.

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

[0020] Typically, this method will include an additional step of forming pellets from the agglomerates, as pelletizing provides agglomerates in a form that is easy to transport and handle, while also facilitating easy selection of the desired amount of material. Pellets can be formed using a second roller press comprising rollers having a series of uniformly spaced recesses along their length as described above. Alternatively, pellets can be formed by extruding the agglomerates or granules formed from the agglomerates. Therefore, the method may include an additional step of forming pellets, which involves extruding the agglomerates. The extrusion process can be carried out in about 30 minutes. 0 C to approximately 70 0 Within the range of C, typically around 35 0 C to approximately 55 0 The process is carried out at temperatures within the range of C. Furthermore, the process can be performed at atmospheric pressure or under a vacuum. As used herein, the term "under a vacuum" takes its usual meaning in the art, meaning that the extrusion process can be performed at pressures less than atmospheric pressure.

[0021] Pelletizing can be cold-formed (i.e., it does not require post-production heating or curing). As noted above, the term "cold-formed" means, for example, without curing, sintering, or heating to above about 60°C, above about 40°C, or about 30°C. In other words, it is often the case that if heat is applied during pellet formation, only a low level of heat will be applied. Alternatively, it may be the case that after pellet formation, the method includes an additional step of applying a low level of heat, such as heating in the range of about 100°C to about 250°C. Low-level heating allows for faster pellet formation and can be in the range of about 100°C to about 250°C, or typically about 150°C to 200°C. When low-level heating is applied, it can be applied for a period of time ranging from about 1 minute to about 24 hours. The application of heat generally promotes the drying and curing of the pellets, ensuring they are ready for transport and use when needed. Those skilled in the art will understand and appreciate that factors such as ambient temperature, the nature of the components in the formulation, and the desired properties of the pellets to be produced (e.g., low water content) will influence whether external heat is recommended, the level of heat applied, and the duration of application. Therefore, those skilled in the art will consider factors such as whether to use an optional heating step utilizing low levels of heat in the process, and the duration and level of heat applied in the process, for example, providing an environment of about 30°C to 50°C (based on ambient temperature or heating) for 6 to 24 or 9 to 18 hours may assist pellet formation. Alternatively, heating for a shorter period in the range of 125°C to 175°C, such as 1 minute to 3 hours, or 15 minutes to 100 minutes, may be desirable. Thus, the agglomerates and subsequently the pellets can be cold-formed or formed by applying low levels of heat such that they are formed at temperatures in the range of about 10°C to about 250°C, or about 15°C to about 200°C, or about 20°C to about 150°C.

[0022] The advantages of cold-forming pellets or using only low-level heat forming of pellets are significant in terms of reduced energy consumption compared to conventionally used hardening manufacturing techniques. High-temperature furnaces are also unnecessary for pellet production, resulting in a simpler and more economically and environmentally beneficial manufacturing process.

[0023] Traditionally, pellets are formed using thermal processes to produce so-called thermally bonded (hardened) lumps. In hardening techniques, initially, a combination of a granular substrate and a binder formulation forms “green” pellets, which are then shaped into pellets (typically using a pelletizing machine). As used herein, the term “green pellet” takes its common meaning in the art and refers to pellets that do not yet possess the strength required for their end use and require further processing or treatment. Green pellets are hardened through a series of steps including drying, preheating, firing, and cooling. The primary purpose of the drying stage is to remove moisture from the pellets, making them more stable and easier to handle. Controlled removal of water prevents crack formation and maintains the structural integrity of the pellets. The temperature range of the drying stage depends on the chemical and physical properties of the green pellets; however, it is likely to last 5 to 10 minutes in the range of 100°C to 250°C. The preheating stage typically occurs using a ramp heating process from about 300°C to 350°C for 10 to 15 minutes to up to about 1250°C to 1350°C. The preheating stage ensures that any metal hydrates or metal carbonates present decompose into their anhydrous forms. The decomposition of these types of compounds, by removing water and / or gases, helps improve the structural integrity of the resulting pellets, which may react, leading to overpressure and cracking of the pellets during firing. The firing stage typically occurs at temperatures above 1350°C for approximately 10 to 20 minutes (for typical capacities such as 250 tph to 500 tph) and results in the sintering of the pellets, providing the strength required to make them suitable for their end use. During the sintering process, bonds within the pellets form through recrystallization and bridging, resulting in ceramic bonding and the formation of macropores, which allow for some expansion and stress release. As used herein, the term "macropores" refers to voids within the pellets and has a size ranging from about 50 µm to about 1 mm in diameter. In the case of metallic ore agglomerates, void formation is particularly important because metal reduction (e.g., the conversion of hematite to magnetite in iron ore) leads to volume changes and stress on the agglomerates. Since large voids do not form without firing, alternative methods are needed to prevent the agglomerates from disintegrating when placed under internal stress. The gelling technique described in this paper provides such an alternative by offering rapidly induced improved chemical bond strength.

[0024] Furthermore, hardening processes are uneconomical compared to the processes of this invention because they are complex, must be carefully executed, and require significant heat application. For example, raw material preparation is critical. The components of the green pellets must have appropriate size ranges, surface areas, and moisture content to withstand the process, as surface chemistry plays a significant role. Moreover, it requires a large amount of energy because the process involves multiple heating stages. Therefore, a less energy-intensive and more cost-effective pellet production process is needed. Furthermore, a process is needed where there is greater flexibility in the physical state of the particulate materials used, and which results in the formation of pellets with physical properties comparable to or even superior to those produced using hardening processes. The methods of this invention, through their use of hydrogel binder formulations, contribute to providing a solution to this problem.

[0025] As noted above, water is generally required for hydrogel formation, and this will typically be present to facilitate it. While water may be added to the particulate substrate before or during the mixing process, or to a combination of the particulate substrate and the binder formulation, it is generally the case that the particulate substrate contains moisture, and the water used for hydrogel formation originates from that moisture. The method of the present invention is simplified when moisture is present within the particles, as the step of adding water to the mixture is unnecessary. Typically, the particulate substrate will contain water in the range of about 0.5 wt% to about 10 wt%, typically about 1 wt% to 6 wt%, and typically 1.5 wt% to 4 wt%, as hydrogel formation is optimal at these levels.

[0026] Typically, particulate substrates are selected from metal ores, metal-bearing waste, fine metal powder, iron slag, iron filings, mineral waste, carbonaceous materials, electric arc furnace waste, or combinations thereof. Particulate substrates often originate from waste products of other industrial processes. Particulate substrates can comprise waste products from a single waste stream (where variation will only occur in particle size) or waste products from a combination of waste streams (where mixed wastes of different compositions will exist). This is environmentally beneficial because the recycling and reuse of such materials reduces the amount of finite resources that might otherwise become waste, introducing the desired circularity into these industrial processes.

[0027] Unbound by theory, it is believed that regardless of whether the particulate substrate contains a single waste type or a combination of different waste types, the use of gel binder formulations facilitates the distribution of waste in the pseudomatrix before agglomeration.

[0028] The carbonaceous material can be coke, graphite, carbon black, peat, or coal. Typically, the carbonaceous material will comprise coke and / or coal. As used herein, the term "coal" is intended to include lignite, sub-bituminous coal, bituminous coal, thermal coal, and anthracite. Coke has been found to be particularly problematic in terms of pellet formation, and therefore the present invention offers particular benefit in providing more robust coke pellets.

[0029] Mineral waste may include mill scrap, mill sludge, fine powder from ore, and / or metal-containing waste.

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

[0031] Typically, granular substrates contain metals, and more commonly, they contain iron. The use of iron is advantageous due to its availability and because it can be reused and recycled from waste products of other processes to provide an environmentally sustainable source of the material. When the granular substrate contains metallic ore, the ore will typically be iron ore, such as goethite, limonite, siderite, ferruginous ore, hematite, or magnetite. Typically, when the granular substrate is a metallic ore, it will be iron ore, such as hematite or magnetite, due to the availability of these materials and the need for efficient utilization of both the raw material and any iron-containing waste.

[0032] The particulate substrate can be powder or debris (filaments), with the term "debris" given its common meaning in the art. Typically, the particulate substrate has a particle size of 4 mm or less (widest axis). Typically, the particle size will range from 0.1 mm to 4 mm. Typically, at least 10% by weight of the particulate substrate is capable of passing through a 100 µm sieve before being formed into pellets. The ability to pelletize small particulate materials is excellent for the "recycling" of waste that would be extremely difficult to handle and reuse without pelletizing. Furthermore, for raw materials, such as ores, it ensures that a much higher percentage of material is available at the point of final use, with less waste resulting from the loss of small particles, which have been sheared off from the surface of larger agglomerates, for example, during transport and handling. The presence of a range of particle sizes within the sample improves the accumulation of material within the agglomerates during pellet formation, for example, via extrusion or via a roller press comprising rollers having a series of uniformly spaced recesses along their length. As noted above, the term agglomerate is used in its usual sense in the art, that is, particulate material formed by an aggregate of particles that are physically or chemically linked together.

[0033] Typically, the particulate matrix is ​​added in an amount of about 70% to about 99.9% by weight of the pellets, typically about 80% to about 99% by weight, and more typically about 90% to about 95% by weight. This maximizes the matrix content in the pellets while allowing sufficient binder formulation to ensure the stabilization of the particles. Typically, the ratio of binder formulation to particulate matrix is ​​about 1.5% to about 3.6% by weight of binder formulation to about 98.5% to about 96.4% by weight of particulate matrix, typically about 2.5% to about 3% by weight of binder formulation to about 97.5% to about 97% by weight of particulate matrix.

[0034] The binder formulation comprises at least one binder material, which may be selected from natural polymers, synthetic polymers (e.g., synthetic organic resins), cellulose materials, glycerides, polysaccharides, inorganic binders, or combinations thereof. As used herein, the term "cellulose material" takes its usual meaning in the art and refers to any material derived from or containing cellulose. Cellulose materials include natural materials composed primarily of cellulose and synthetic derivatives of cellulose. As used herein, the term "glyceride" takes its usual meaning in the art and refers to a lipid molecule consisting of a glycerol backbone esterified with one or more fatty acids or acyl groups.

[0035] The adhesive formulation may contain at least one adhesive material selected from synthetic polymers, cellulose materials, glycerides, inorganic adhesive materials, or combinations thereof.

[0036] Examples of natural polymers include, but are not limited to, lignin sulfonates. Examples of synthetic polymers include, but are not limited to, polyvinyl alcohol, polyacrylic acids, styrene-acrylate copolymers, and synthetic organic resins, such as, for example, polyacrylamide resins or phenolic resins. As used herein, phenolic resins include resole resins or novolac resins, where resole resins are base-catalyzed phenolic resins having a formaldehyde to phenol ratio greater than 1, typically about 1.5, and novolac resins have a formaldehyde to phenol molar ratio less than 1. As used herein, the term "polyacrylic acid" takes its usual meaning in the art and refers to a class of synthetic polymers derived from acrylic acid or its esters. Examples of polyacrylic acids include, but are not limited to, polyacrylic acid (PAA), poly(methyl methacrylate) (PMMA), and polyacrylamide (PAM). As used herein, the term "styrene-acrylate copolymer" takes its usual meaning in the art and relates to synthetic polymers formed by copolymerization of styrene and acrylic acid or its derivatives. Examples of styrene-acrylate copolymers include, but are not limited to, styrene-2-ethylhexyl acrylate (2-EHA), styrene-ethyl acrylate (EA), styrene-methyl methacrylate (MMA), and styrene-butyl acrylate (BA). Typically, styrene-acrylate copolymers will contain styrene-ethyl acrylate (EA). Examples of glycerides include monoesters, diesters, or triesters of glycerol, such as glyceryl acetate, glyceryl diacetate, and glyceryl triacetate. Examples of cellulosic materials include, but are not limited to, cellulose fibers, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxyethyl methyl cellulose (MHEC), or combinations thereof. Examples of synthetic triglycerides include, but are not limited to, glyceryl 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 binders include, but are not limited to, silicates (e.g., Group I or Group II metal silicates, such as sodium silicate (Na₂SiO₃), potassium silicate (K₂SiO₃), calcium silicate (CaSiO₃), magnesium silicate (MgSiO₄), aluminum silicate, or combinations thereof) or refractory materials, including, but 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, zirconium oxide, or combinations thereof). As used herein, the term "refractory material" refers to a material resistant to thermal stress, high pressure, or chemical corrosion.

[0037] These materials provide a combination of hydrogel-forming and non-hydrogel-forming binders, offering compositional flexibility while providing the improved pellet strength and processability of the present invention. These binders have the advantage that they can be used at low concentrations and therefore will not significantly affect the metallurgical or physical properties of the substrate mixture. Typically, the binder formulation will contain at least one binder selected from cellulose materials, synthetic polymers, glycerides, one or more silicates (esters), or combinations thereof.

[0038] The adhesive formulation may contain at least one adhesive material selected from cellulose fibers, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxyethyl methyl cellulose (MHEC), polyacrylamide resin, polyvinyl alcohol, phenolic resin, polyacrylic acid, styrene-acrylate copolymer, glycerol ester, one or more silicates (esters) or combinations thereof.

[0039] Typically, the adhesive formulation contains at least one adhesive material selected from cellulose fibers, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyacrylamide resin, polyvinyl alcohol, one or more silicates (esters), polyacrylamide, ethyl acrylate styrene (EA), triacetin, diacetin, phenolic resin, or combinations thereof.

[0040] Typically, the adhesive formulation contains at least one adhesive material selected from cellulose fibers, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol, polyacrylamide resin, one or more silicates (esters), polyacrylamide, phenolic resin, triacetin, or combinations thereof.

[0041] The adhesive formulation may contain at least one adhesive material selected from polyacrylamide resin, polyvinyl alcohol, phenolic resin, carboxymethyl cellulose (CMC), triacetin, sodium silicate, magnesium silicate, or combinations thereof.

[0042] The adhesive formulation may contain at least one adhesive material selected from polyacrylamide resin, polyvinyl alcohol, phenolic resin, carboxymethyl cellulose (CMC), sodium silicate, magnesium silicate, or combinations thereof.

[0043] Binder formulations (such as those used in this context as component-based binders) are typically added in powder form, although gel or other pre-dissolved forms (e.g., bound in a liquid suspension) are envisioned. In examples where the binder formulation is added as a powder, water will be present to promote in-situ gelation of the binder formulation. Providing the binder formulation as a powder, compared to liquid addition, allows for good control over the total water content of the pellets. Applying pressure to the substrate mixture improves the cold strength of the pellets, 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, for example, takes the form of a film. One example where the binder formulation forms a film might be when the amount of water in the mixture is limited, resulting in less solubility of the binder formulation in water, preventing hydrogel formation.

[0044] The synthetic polymers can be polyacrylamide resins, polyvinyl alcohol, and / or phenolic resins, such as methyl phenolic resins or phenolic varnish resins; the cellulose materials can be cellulose fibers, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), and / or hydroxyethyl methyl cellulose (MHEC); and / or polysaccharides can be starches, such as wheat, corn, barley, and potato starches, gum arabic, guar gum, and / or xanthan gum. These materials have been found to provide good gel formation and pellet reinforcement relative to pellet strength in the absence of gel formation.

[0045] When the binder material contains cellulose, it is typically carboxymethyl cellulose (CMC), cellulose fibers, hydroxyethyl methyl cellulose (MHEC), or a combination thereof. CMC is advantageous because it can be added in powder form, allowing control over the total moisture content of the pellets. CMC also has a longer shelf life compared to other plant-derived binders. This is because other plant-derived binders are generally more susceptible to microbial attack and therefore more prone to decomposition. Sometimes the binder material can be hydroxyethyl methyl cellulose (MHEC), which has been found to have particularly good binding qualities and helps enhance pellet strength. However, because MHEC is highly water-soluble, this can affect the final pellet's shelf life, reducing it compared to pellets containing CMC.

[0046] Typically, the binder material comprises at least one of CMC, polysaccharides, PVA, and / or polyacrylamide resin as the binder material for forming the hydrogel. More than one of CMC, polysaccharides, PVA, and polyacrylamide resin may be present in combination with each other or in combination with other binder materials. Typically, silicates (esters) (e.g., Group I or Group II silicates, such as sodium silicate), glycerides, cellulose fibers, and / or phenolic resins will be present. Silicates (esters), glycerides, cellulose fibers, and phenolic resins typically do not form hydrogels. The binder formulation may therefore comprise a combination of: a) one or more of CMC, polysaccharides, PVA, and polyacrylamide resins and b) one or more of silicates (esters) (e.g., Group I or Group II silicates), glycerides, cellulose fibers, and phenolic resins. The binder formulation may comprise a combination of: a) one or more of CMC, PVA, and polyacrylamide resins and b) one or more of silicates (esters) and phenolic resins. It is possible that the adhesive formulation consists essentially of the components listed in a) and b) above.

[0047] Typically, CMC can be used as a binder in place of other binders, or in addition to other binders, such that the binder formulation may contain about 10% to about 100% by weight, typically about 20% to about 90% by weight, or about 50% to about 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 about 3% by weight of the pellets, typically about 0.1% to about 2.5% by weight of the pellets, typically about 0.15% to about 1% by weight of the pellets, or typically about 0.2% to about 0.8% by weight. At these levels, the binder formulation provides good reinforcement to the pellets.

[0048] Typically, CMC has an active polymer content of about 40% to about 90% and a pH in solution ranging from about 5 to about 9, or from about 6 to about 8. Furthermore, CMC typically has a molecular weight ranging from about 3,000 to about 70,000. Optionally, CMC will have a molecular weight ranging from about 10,000 to about 50,000. Without being bound by theory, it is believed that by utilizing the lower molecular weight of CMC, for example, in the range of about 10,000 to about 50,000, high-concentration binder solutions can be prepared, which in turn can improve the strength of the pellets.

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

[0050] Unbound by theory, it is believed that PVA provides good mixing of components and high strength because the polymer network formed by PVA is strong. Furthermore, the process of pelletizing PVA removes air from the particulate material, which can reduce oxidation when the particulate substrate 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 formed from polyvinyl acetate, which is reacted with sodium hydroxide via saponification, replacing the acetate groups of the acetate ester with hydroxyl groups. Partial saponification means that some acetate groups have been replaced by hydroxyl groups, thereby forming at least partially saponified polyvinyl alcohol residues. Typically, PVA has a saponification degree 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%. It is typically used as a solution in water. PVA can be modified to include, for example, a sodium hydroxide content. Typically, PVA binders have an active polymer content of about 12% to about 13% and a pH in the range of about 4 to about 7 when in solution. Furthermore, PVA typically has a molecular weight in the range of about 15,000 to about 150,000. Optionally, PVA typically has a molecular weight in the range of about 30,000 to about 120,000. Unbound by theory, it is believed that high-concentration binder solutions can be prepared using lower molecular weights, for example, in the range of about 15,000 to about 60,000, which in turn can improve the strength of the pellets.

[0052] When the adhesive material contains polyacrylamide resin, it is typically an anionic polyacrylamide resin with a molecular weight of 100,000 Da to 10,000,000 Da and a charge percentage of 25-50%. When the adhesive material contains polyacrylamide resin, it can be added in the range of about 0.05% to 0.7% by weight, typically about 0.1% to about 0.3% by weight, and typically about 0.2% to about 0.4% by weight.

[0053] When the binder material contains polysaccharides, this can be starch or amylase starch. For example, it can be pregelatinized potato starch. It can be added in an amount of about 0.8% by weight of the final pellet, typically about 0.6% by weight. Using polysaccharides as a component of binder formulations may be desirable because polysaccharides often also act as thickeners.

[0054] The inorganic binder may comprise one or more silicates (e.g., silicates in the form of their sodium salts), or refractory materials, including but not limited to oxides, carbides, or nitrides of silicon, aluminum, magnesium, calcium, and zirconium, or combinations thereof. For example, refractory materials may comprise alumina, refractory clay, bauxite, chromite, dolomite, magnesite, silicon carbide, zirconium oxide, or combinations thereof.

[0055] Typically, inorganic binders comprise one or more silicates. Inorganic binders may contain two to four different silicates, such as combinations of Group I and Group II silicates. One or more silicates are typically selected from sodium silicate (Na₂SiO₃), magnesium silicate (MgSiO₄), calcium silicate (CaSiO₃), aluminum silicate, and combinations thereof. One or more silicates may be in liquid, powder, or a combination thereof. It is possible that the inorganic binder is in powder form because silicates are more concentrated in powder form. It is also possible that the binder comprises an inorganic binder in combination with synthetic polymers and / or cellulose materials.

[0056] Typically, inorganic binders (alone or in combination with one or more other binders) are present in the pellets in the range of about 0.5% to about 2.5% by weight, usually in the range of about 1% to about 2% by weight or about 1.25% to about 1.75% by weight.

[0057] When silicates are present, and one or more silicates are in liquid form, they will generally be present in larger quantities because the levels of active ingredients in liquid silicates are lower than those in powdered silicates. In the case where one or more silicates are in liquid form, they are typically present in the pellets in the range of about 0.5 wt% to about 6 wt%, typically about 1 wt% to about 5 wt%, typically 1.25 wt% to 3 wt%, and typically 1.5 wt% to 2 wt%.

[0058] When one or more silicates are in powder form, they are typically present in the pellets in the range of about 0.5% to about 3.5% by weight, or typically in the range of about 1% to about 3% by weight or 1.5% to about 2.5% by weight.

[0059] Typically, the total binder formulation will be added in an amount from about 0.05 wt% to about 7.0 wt% of the pellets. It is typically in the range of about 0.3 wt% to about 6 wt%, typically in the range of about 0.4 wt% to about 5 wt%, and typically in the range of about 0.8 wt% to about 4 wt%. It has been found that when less than about 0.05 wt% of the binder formulation is present, the structural integrity of the aggregates is low. In the case where one or more binder materials are hydrogel-forming, they will typically be present in the range of about 0.05 wt% to about 1.5 wt% of the pellets (alone, or in combination with one or more non-hydrogel-forming binder materials). It is typically in the range of about 0.07 wt% to about 1.0 wt%, or about 0.1 wt% to about 0.9 wt%.

[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 (typically in the form of graphite), lubricants, surfactants (e.g., sodium dodecyl sulfate), stearates (e.g., calcium stearate or sodium stearate), stabilizing fibers, or combinations thereof. Processing aids can make the entire process more efficient, which in turn saves 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 mixture.

[0062] In a second aspect of the invention, pellets obtained by the method of the first aspect of the invention are provided, comprising a particulate substrate selected from metal ores, metal-containing waste, fine metal powder, iron slag, iron filings, mineral waste, carbonaceous materials, electric arc furnace waste, or combinations thereof; and a binder formulation. Typically, after agglomeration, the pellets can be formed at a temperature ranging from about 10°C to about 60°C. Alternatively, the method of the first aspect of the invention may include an additional step of applying a low level of heat, for example, at a temperature ranging from about 100°C to about 250°C. Low-level heating allows for faster pellet formation and can be applied at a temperature ranging from about 100°C to about 250°C, or typically from about 150°C to 200°C. When low-level heating is applied, it can be applied for a period ranging from about 1 minute to about 24 hours.

[0063] Typically, the pellets according to the second aspect of the invention have a diameter of 2.5 cm. 3 Up to 15 cm 3 Within a range, usually within 3 cm 3 Up to 12 cm 3 or 7 cm 3 Up to 11 cm 3The average volume within the range. Pellets will typically be sized to minimize surface area and will generally be, for example, roughly spherical, oval, cylindrical, or cubic in shape.

[0064] Unless otherwise stated, each integral described may be used in combination with any other integral understood by those skilled in the art. Furthermore, while all aspects of the invention generally "comprise" the features described with respect to that aspect, it is specifically contemplated that they may "compose" or "substantially constitute" those features. Additionally, all terms, unless specifically defined herein, are intended to be given their meaning as commonly understood in the art.

[0065] Furthermore, in the discussion of this invention, unless otherwise stated, the disclosure of alternative values ​​for the upper or lower limit of the permissible range of a parameter should be interpreted as an implicit statement that each intermediate value of the parameter between the smaller and larger alternative choices is itself disclosed as a possible value of the parameter.

[0066] Furthermore, unless explicitly excluded, all numerical values ​​appearing in this application should be understood to be modified by the term "about". The term "weight %" and similar terms are intended to refer to the percentage of a component by weight in the final pellet by weight. If additives, impurities, and / or water are present in the particulate starting material in step (i), the term "weight %" includes said additives, impurities, and / or water.

[0067] To make the invention easier to understand, it will be further described with reference to the accompanying drawings and specific embodiments herein.

[0068] Figure 1 (a) and Figure 1 (b) illustrates two alternative configurations of the roller press wheel. Figure 1 (a) is a schematic diagram of a single smooth wheel having a smooth surface suitable for applying pressure to a substrate mixture; and Figure 1 (a) is a schematic diagram of a single concave wheel, for example, which would typically be used for pellet formation;

[0069] Figure 2 This diagram illustrates the relative positioning of two smooth rollers in use, which forces the base mixture between the rollers, resulting in the application of pressure and gel formation.

[0070] Figure 3 (a) to Figure 3 (c) graphically depicts the results from Examples 1 to 3. Figure 3(a) illustrates how the mechanically induced gelling process (i.e., MC 2 and MC 3) according to the first aspect of the invention affects the cold crush strength of pellets having binder combination 1 compared to a method without mechanically induced gelling (i.e., MC 1). The y-axis corresponds to the cold crush strength (kgf), and the x-axis corresponds to the mixing conditions MC 1, MC 2, and MC 3 (i.e., the set of bars grouped from left to right). Bars including descending diagonal lines from left to right represent ore 1 (i.e., fine magnetite), bars including ascending diagonal lines from left to right represent ore 2 (i.e., coarse magnetite), and blocky gray bars represent ore 3 (i.e., hematite). Figure 3 (b) illustrates how the mechanically induced gelling process (i.e., MC 2 and MC 3) according to the first aspect of the invention affects the cold crush strength of pellets with binder combination 2 compared to a method without mechanically induced gelling (i.e., MC 1). The y-axis corresponds to the cold crush strength (kgf), and the x-axis corresponds to the mixing conditions MC 1, MC 2, and MC 3 (i.e., the set of bars grouped from left to right). Bars including descending diagonal lines from left to right represent ore 1 (i.e., fine magnetite), bars including ascending diagonal lines from left to right represent ore 2 (i.e., coarse magnetite), and blocky gray bars represent ore 3 (i.e., hematite). Figure 3 (c) illustrates how the mechanically induced gelling process (i.e., MC 2 and MC 3) according to the first aspect of the invention affects the cold crush strength of pellets having binder combination 3 compared to a method without mechanically induced gelling (i.e., MC 1). The y-axis corresponds to the cold crush strength (kgf), and the x-axis corresponds to the mixing conditions MC 1, MC 2, and MC 3 (i.e., the set of bars grouped from left to right). The bars including descending diagonal lines from left to right represent ore 1 (i.e., fine magnetite), and the blocky gray bars represent ore 3 (i.e., hematite).

[0071] Figure 4 The results from Examples 9 and 10 are graphically depicted. The y-axis corresponds to the cold crush resistance (kgf), and the x-axis corresponds to the applied load in kN. Dashed lines represent a 3.15 mm sieve size, and solid lines represent a 2.00 mm sieve size;

[0072] Figure 5 The results from Example 11 are graphically depicted. The y-axis corresponds to the cold crush resistance (kgf). Dotted bars represent ore 5 under mixing condition 1, bars with vertical lines represent ore 5 under mixing condition 2, bars with horizontal lines represent ore 5 under mixing condition 2, bars with descending diagonal lines from left to right represent ore 6 under mixing condition 1, bars with ascending diagonal lines from left to right represent ore 6 under mixing condition 2, and blocky gray bars represent ore 6 under mixing condition 2.

[0073] Figure 6The results from Example 13 are graphically depicted. The y-axis corresponds to the cold crush resistance (kgf), and the bars correspond to test IDs 1 through 4. Dotted bars represent test ID 1 under mixing condition 1, bars with horizontal lines represent test ID 2 under mixing condition 1, bars with diagonal lines descending from left to right represent test ID 3 under mixing condition 3, and blocky gray bars represent test ID 4 under mixing condition 3; and

[0074] Figure 7 (a) through (c) graphically depict the results from Example 14. Figure 7 (a) shows the results from ore 8. The y-axis corresponds to RDI% < 2.8 mm, and the x-axis corresponds to the various mixing conditions (i.e., MC 1 and MC 3). Specifically, the blocky gray bars correspond to RDI% < 2.8 mm under mixing condition 1, and the bars with sloping lines descending from left to right and the bars with horizontal lines both correspond to the results of RDI% < 2.8 mm under mixing condition 3. Figure 7 (b) shows the results from ore 9. The y-axis corresponds to RDI% < 2.8 mm, and the x-axis corresponds to various mixing conditions (i.e., MC 1 and MC 3). Specifically, the blocky gray bars correspond to RDI% < 2.8 mm under mixing condition 1, and the bars with sloping lines descending from left to right correspond to RDI% < 2.8 mm under mixing condition 3. Figure 7 (c) shows the results from ore 10. The y-axis corresponds to RDI% < 2.8 mm, and the x-axis corresponds to various mixing conditions (i.e., MC 1 and MC 3). Specifically, the blocky gray bars correspond to RDI% < 2.8 mm under mixing condition 1, and the bars with sloping lines descending from left to right correspond to RDI% < 2.8 mm under mixing condition 3.

[0075] Example

[0076] The examples described below illustrate how the use of mechanically induced gelation (MIG) in the production of iron ore pellets can improve the cold crushing strength (CCS) and reduction disintegration index (RDI) of the resulting pellets.

[0077] Ore type

[0078] Eight different iron ores were used in the described embodiments. These are as follows:

[0079] Ore 1: High-purity fine magnetite ore with an iron content of 71.2% as iron oxide, a particle size distribution (PSD) of <300 µm, and a Dv90 of 166 µm.

[0080] Ore 2: High-purity crude magnetite ore with an iron content of 68.0% as iron oxide, a PSD of <4 mm accepted as is, and a Dv90 of 1432 µm.

[0081] Ore 3: Hematite ore with an iron content of 65.0% as iron oxide, a PSD of <250 µm accepted as is, and a Dv90 of approximately 50 µm.

[0082] Ore 4: Hematite ore with an iron content of 67.1% and a nominal Dv90 of 150 µm.

[0083] Ore 5: Magnetite ore with 68% iron content and a nominal Dv90 of 323 µm.

[0084] Ore 6: Magnetite ore with 68% iron content and a nominal Dv90 of 150 µm. It is the same material as Ore 5, but has a different, slightly finer grain size distribution.

[0085] Ore 7: Hematite ore containing pseudomorphous hematite and goethite contents, with an iron content of 67.6% and a Dv90 of 102µm.

[0086] Ore 8: Mineralogically characterized as primarily hematite with variations in magnetite and goethite contents. Ore 8 is a relatively coarse material with an iron content of 64.5% and a Dv90 of 565 µm.

[0087] Ore 9: Goethite ore containing iron hydroxyl oxide with a Dv90 of 538 µm.

[0088] Ore 10: Pseudo-hematite ore with an iron content of 67.5% and a Dv90 of 97 µm.

[0089] Experimental Procedure

[0090] Initially, the ore is dried to allow for control over its moisture content when used. The iron ore (5 kg or 10 kg) and binder formulation are mixed in an Eirich EL10 mixer according to the test methodology for mixing condition 2 or mixing condition 3 described below. Homogenization occurs for one minute before adding 3% w / w water. Water is added over a one-minute period while the mixer is running, and then the mixture is allowed to stand for another 2 minutes at 300 rpm. Once the four-minute mixing is complete, the material is removed from the mixer.

[0091] The control sample was then fed through a Sahut Conreur roller press with concave rollers at a force of 42.2 kN and a pelletizing wheel speed of 5 rpm to produce a sample with dimensions of approximately 27 × 18 × 10 mm (4.86 cm). 3 (The ball). A schematic diagram of an example of a concave wheel is shown in... Figure 1 In (b), the pellet was then kept at 40°C for 24 hours.

[0092] The embodiments of the present invention are also fed into a Sahut Conreur roller press. The roller size is 30 mm × 100 mm. Using as... Figure 1 and 2 The smooth roller shown is used to mechanically induce a gelation process by producing a material belt, which is then fed through a Sahut Conreur granulator with a 2 mm screen aperture to reduce the size of the produced belt. The material is then fed through a concave roller (such as...). Figure 1 (as illustrated in (b)) to produce a material with approximately 27 × 18 × 10 mm (4.86 cm). 3 The pellets were then prepared to the desired size. The pellets were then kept at 40°C for 24 hours.

[0093] Cold Crush Strength (CCS)

[0094] Cold compressive strength (CCS) was tested according to ISO 4700 (from 30 pellets per batch) using MecmesinOmnitest 10.

[0095] Reduction Powdering Index Test

[0096] The thermal properties of the pellets were tested by determining their Reduction Pulverization Index (RDI) according to standard ISO 4696-2:2015. In this test, the pellets were subjected to a reducing environment at 550°C, followed by a tumble test to measure the amount of pulverization after reduction. These conditions are similar to those in the low-temperature reduction zone of a blast furnace in an integrated steelmaking process.

[0097] Mixed conditions

[0098] (i) Mixed Condition 1 (MC 1)

[0099] In MC 1 (i.e., control), the sample was run without any mechanically induced gelation.

[0100] The drying and mixing of the ore and binder formulation were carried out as described above, followed by feeding through a roller press under a force of 42.2 kN and a pelletizing wheel speed of 5 rpm to produce a product with dimensions of approximately 27 × 18 × 10 mm (4.86 cm). 3 (The ball)

[0101] (ii) Mixed Condition 2 (MC 2)

[0102] MC 2 relates to mechanically induced gelation with a bonding material.

[0103] For these samples, as detailed above (see 'Experimental Procedure'), binder material 1 was mixed with the ore. Initially, this material was fed through a smooth wheel at a force of 42.2 kN and a wheel speed of 7.5 rpm to mechanically induce gelation and form a belt. The belt was then granulated to 2 mm. Binder material 2 was then incorporated, and the mixture was again fed through a concave wheel at 300 rpm for 3 minutes using an Eirich EL10 mixer. The final material was then fed through a concave wheel at a force of 42.2 kN and a pelletizing wheel speed of 5 rpm to produce a size approximately 27 × 18 × 10 mm (4.86 cm²). 3 (The ball)

[0104] (iii) Mixed Condition 3 (MC 3)

[0105] MC 3 involves mechanically induced gelation with two bonding materials.

[0106] For these samples, binder materials 1 and 2 were mixed with the ore. Initially, the material was fed through a smooth wheel at an applied force of 69.4 kN and a wheel speed of 7.5 rpm to mechanically induce gelation and form a belt. The belt was then granulated to 2 mm. The material was then fed through a concave wheel at an applied force of 42.2 kN and a pelletizing wheel speed of 5 rpm to produce a product with dimensions approximately 27 × 18 × 10 mm (4.86 cm²). 3 (The ball)

[0107] The effects of carboxymethyl cellulose (CMC) and silicates

[0108] In Examples 1 to 3 outlined below, adhesive combination 1 is used. Adhesive combination 1 comprises a binder material 1 of carboxymethyl cellulose (CMC) added at 0.5% w / w and a binder material 2 of sodium silicate added at 2% w / w.

[0109] Example 1

[0110] Example 1 uses ore 1. The moisture content of the material fed into the roller press is between 2.5% w / w and 2.8% w / w.

[0111] Table 1: CCS results of pellets produced in Example 1

[0112]

[0113] The results showed an increase in CCS between the control and the two tests involving mechanically induced gelation. The largest increase was observed when a combination of two binders was used under mixing condition 3.

[0114] Example 2

[0115] Example 2 uses ore 3. The moisture content of the material fed to the roller press is in the range of 2.8% w / w to 3.0% w / w.

[0116] Table 2: CCS results of pellets produced in Example 2

[0117]

[0118] The results showed an increase in CCS between the control and the two tests involving mechanically induced gelation. The largest increase was observed when a combination of two binders was used under mixing condition 3.

[0119] Example 3

[0120] Example 3 uses ore 2. The moisture content of the material fed to the roller press is in the range of 2.5% w / w to 2.8% w / w.

[0121] Table 3: CCS results of pellets produced in Example 3

[0122]

[0123] The results showed an increase of 90 kgf in CCS between mixing conditions 1 and 3.

[0124] Effects of polyacrylamide and sodium silicate

[0125] In Examples 4 to 6, adhesive combination 2 is used. Adhesive combination 2 comprises adhesive material 1, which is polyacrylamide, added at 0.5% w / w, and adhesive material 2, which is sodium silicate, added at 2% w / w.

[0126] Example 4

[0127] Example 4 uses ore 1. The moisture content of the material fed to the roller press is in the range of 2.8% w / w to 3.0% w / w.

[0128] Table 4: CCS results of pellets produced in Example 4

[0129]

[0130] The results showed an increase in CCS between the control and the two tests involving mechanically induced gelation. The largest increase was observed when a mechanical process was applied to a single binder material under mixing condition 2.

[0131] Example 5

[0132] Example 5 uses ore 3. The moisture content of the material fed to the roller press is in the range of 2.2% w / w to 2.9% w / w.

[0133] Table 5: CCS results of pellets produced in Example 5

[0134]

[0135] The results showed an increase in CCS between the control and the two tests involving mechanically induced gelation. The largest increase was observed when a combination of two binders was used under mixing condition 3.

[0136] Example 6

[0137] Example 6 uses ore 2. The moisture content of the material fed to the roller press is in the range of 2.2% w / w to 2.8% w / w.

[0138] Table 6: CCS results of pellets produced in Example 6

[0139]

[0140] The results showed an increase of 38 kgf in CCS between mixing conditions 1 and mixing conditions 2.

[0141] Effects of PVA and phenolic compounds

[0142] In Example 7, adhesive combination 3 is used. Adhesive combination 3 comprises adhesive material 1, which is polyvinyl alcohol, added at 0.5% w / w, and adhesive material 2, which is phenolic resin, added at 0.5% w / w.

[0143] Example 7

[0144] Example 7 uses ore 1. The moisture content of the material fed to the roller press is in the range of 2.8% w / w to 3.0% w / w.

[0145] Table 7: CCS results of pellets produced in Example 7

[0146]

[0147] The results showed an increase in CCS between the control and the two tests involving mechanically induced gelation. The largest increase was observed when a mechanical process was applied to a single binder material under mixing condition 2.

[0148] Effect of changing the amount of CMC and sodium silicate

[0149] Example 8

[0150] In Example 8, four batches of pellets were produced, each using 5 kg of ore 1. These batches were produced according to the experimental procedure and mixing conditions 3. The levels of binder materials used are shown in Table 8 below. Binder combination 1 was used, wherein binder 1 was CMC and binder 2 was sodium silicate. The moisture content of the material fed to the roller press was between 2.4% w / w and 3.0% w / w. The addition rates of the two binders varied as shown in Table 8 below.

[0151] Table 8: CCS results of pellets produced in Example 8

[0152]

[0153] When compared to Example 1 – Mixing Condition 3, reducing the level of the binder formulation resulted in a lower CCS value. However, all remained higher than in Example 1 – Mixing Condition 1, demonstrating that mechanically induced gelation has a positive effect on the physical properties of the pellets.

[0154] Effects of changing the mechanical settings of the roller press

[0155] The applied force on the roller press was varied (from 13.9 kN to 69.4 kN) in combination with one of two granulator screen sizes (2.00 mm and 3.15 mm). Examples 9 and 10 investigated the effects of these variations.

[0156] Example 9

[0157] Pellet production was carried out using 5 kg batches of ore 1. Binder combination 1 was used. Binder 1 was CMC and binder 2 was sodium silicate. Binder 1 and binder 2 were mixed with the ore as in the experimental procedure. The mixture was then initially fed through a smooth roller at a force of 13.9 kN to 69.4 kN and a roller speed of 4.5 rpm to mechanically induce gelation and form a belt, which was then granulated to 3.15 mm. The granules were then fed through a roller press at a force of 42.2 kN and a pelletizing roller speed of 5 rpm to produce pellets with a size of approximately 27 × 18 × 10 mm (4.86 cm²). 3The pellets are then kept at 40°C for at least 24 hours.

[0158] Table 9: CCS results of pellets produced in Example 9 – Effect of pelletizer screen aperture and pressure.

[0159]

[0160] Example 10

[0161] Pellet production was carried out using 5 kg batches of ore 1. Binder combination 1 was used. Binder 1 was CMC and binder 2 was sodium silicate. Binder 1 and binder 2 were mixed with the ore as in the experimental procedure. The feed was then initially passed through a smooth roller at a force of 13.9 kN to 69.4 kN and a roller speed of 4.5 rpm to mechanically induce gelation and form a belt, which was then granulated to 2.00 mm. The feed was then passed through a roller press at a force of 42.2 kN and a pelletizing roller speed of 5 rpm to produce pellets with dimensions approximately 27 × 18 × 10 mm (4.86 cm²). 3 The pellets are then kept at 40°C for at least 24 hours.

[0162] Table 10: CCS results of pellets produced in Example 10 – Effect of pelletizer screen aperture and pressure.

[0163]

[0164] Results from Examples 9 and 10 show that mechanically induced gelation is effective for applied forces ranging from at least 13.9 kN to 42.2 kN. Smaller pelletizer screen sizes have a better effect on pellet CCS, but for both 2.00 mm and 3.15 mm screens, the results are positive.

[0165] Reproducibility studies

[0166] Example 11

[0167] The reproducibility of the results was studied. Batches (5 kg each) were produced from ores 5 and 6. For each ore, a control test was run using mixing condition 1, and two runs were performed using mixing condition 2. In all cases, binder combination 1 was used, while the following mechanical settings were kept constant: hydraulic pressure 45.3 kN, wheel speed 5 rpm, and pelletizer screen aperture 2 mm. The pellets were then held at 150°C for 2 hours. The CCS of the pellets was tested. The results are shown in Table 11 and... Figure 5 The standard deviation of CCS from each batch of test pellets is included.

[0168] The average strength of pellets formed by mechanically induced gelation using the method according to the first aspect of the invention (i.e., mixing condition 2) is greater than the average strength of control pellets (i.e., mixing condition 1 without mechanically induced gelation). This is true for both ores and for repeated tests for each ores. Good consistency exists between the results for ores 5 and 6, indicating that minor differences in particle size distribution have no substantial impact.

[0169] This embodiment clearly demonstrates the repeatability of the beneficial effects of mechanically induced gelation, and the particular effectiveness of the method according to the first aspect of the invention.

[0170] Table 11 – CCS results of pellets produced in Example 11

[0171]

[0172] Polysaccharides were used as binders.

[0173] Example 12

[0174] Batch of pellets were formulated using binder combination 4, which contains polysaccharides as part of the binder combination.

[0175] Specifically, adhesive combination 4 includes:

[0176] Binder 1: 0.5% by weight of polysaccharide containing approximately 25% distillers' grains

[0177] Binder 2: 2% by weight of granular solid sodium silicate.

[0178] Ore 4 (hematite) and ore 6 (magnetite) were used, and pellets were manufactured using 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.

[0179] Table 12: CCS results of pellets produced in Example 12

[0180]

[0181] When polysaccharides are used as one of the binding materials, the pellets produced by the method according to the first aspect of the invention have high strength and are advantageous compared to the pellets produced from ore 3 using mixing conditions 3 in Example 1.

[0182] The influence of ores containing pseudo-hematite and goethite

[0183] Example 13

[0184] Batch of pellets were manufactured from ore 7, which, as noted above, contains pseudomorphous hematite and goethite. Binder combination 1 was used, and two batches (Test ID 1 and Test ID 2) were created using mixing condition 1, and two batches (Test ID 2 and Test ID 4) were created using mixing condition 3. Heating was performed at 150°C for 2 hours. The cold crush strength (CCS) of the resulting pellets was tested, and the results are shown in Table 13. Figure 6 middle.

[0185] Table 13: CCS results of pellets produced in Example 13

[0186]

[0187] Ores of this nature are typically particularly difficult to agglomerate due to their mineralogical properties. Therefore, while the CCS values ​​produced by this ore are lower than those observed for other ores produced using binder combination 1, this is to be expected. That said, although the value may be smaller compared to other ores, the results still show a significant increase in strength in the pellets produced using mixing conditions 3 compared to those produced using mixing conditions 1. This highlights the improvement in strength achieved through the use of the method according to the first aspect of the invention (i.e., involving mechanically induced cementation), even when using problematic ores.

[0188] Effect of MIG on Reduction Diffusion Index (RDI)

[0189] Example 14

[0190] Pellets were formed from ores 8, 9, and 10. The method according to the first aspect of the invention (i.e., mixing condition 3) was used, with a granulation screen size of 2 mm, and the corresponding wheel speed and pressure are shown in Table 14. The pellets were then held at 40°C for 24 hours. A control test was conducted using mixing condition 1.

[0191] Binder combination 1 (as above) was used for ores 8 and 10, and binder combination 5 was used for ores 9.

[0192] Adhesive combination 5 includes:

[0193] Binder 1: 10% aqueous liquid PVOH. Addition rate: 4%.

[0194] Binder 2: A phenolic resin. Addition rate: 0.5%.

[0195] The RDI of the pellets was tested and the results are presented in Table 14 and 15. Figure 7 In (a)–(c).

[0196] Table 14: CCS and RDI results for pellets produced in Example 14

[0197]

[0198] * Conversion factor ((bar × 100) × 28.3) / 10,000

[0199] As is evident from the results, an improvement in RDI occurs when the method according to the first aspect of the invention is used. This is particularly significant in the case of ore 8. The results indicate that the use of mechanically induced gelation according to the method of the invention provides pellets with greater resistance to disintegration during the early stages of reduction.

[0200] It should be understood that the methods and pellets of the present invention can be implemented in various ways, of which only some have been described and illustrated above.

Claims

1. A method for producing pellets, the method comprising the following steps: a. Provide a granular substrate selected from metal ores, metal ore-containing waste, fine metal powder, iron slag, iron filings, mineral waste, carbonaceous materials, electric arc furnace waste, or combinations thereof; b. Mixing the granular substrate with an adhesive formulation comprising at least one adhesive material to form a substrate mixture; c. Applying pressure to the substrate mixture to induce hydrogel formation; and d. Formation of aggregates Water is present to promote hydrogel formation.

2. The method according to claim 1, wherein at least one adhesive material is an adhesive having hydrogel-forming properties.

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

4. The method according to any of the preceding claims, wherein the first adhesive material and the second adhesive material are mixed with the particulate substrate to form the substrate mixture.

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

6. The method according to any of the preceding claims, wherein applying pressure to the substrate mixture to induce hydrogel formation includes passing the substrate mixture through a compression wheel.

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

8. The method according to any of the preceding claims, comprising the step of forming pellets from the aggregates.

9. The method of claim 8, wherein the step of forming the agglomerates comprises passing the agglomerates through a roller comprising a series of uniformly spaced recesses along its length.

10. The method according to claim 8 or claim 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 of the preceding claims, comprising granulating the agglomerates prior to pelletizing.

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

13. The method according to any of the preceding claims, wherein the particulate substrate comprises water in the range of about 0.5% by weight to about 10% by weight.

14. The method of claim 13, wherein the particulate substrate comprises water in the range of about 1% to about 6% by weight.

15. The method according to any of the preceding claims, wherein the particulate substrate comprises a metal.

16. The method according to any of the preceding claims, wherein the particulate substrate comprises iron.

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

18. The method according to any of the preceding claims, wherein the adhesive material is selected from natural polymers, synthetic polymers, cellulose materials, glycerides, polysaccharides, inorganic adhesive materials, or combinations thereof.

19. The method according to claim 18, wherein the bonding material is selected from cellulose fibers, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxyethyl methyl cellulose (MHEC), polyacrylamide resin, polyvinyl alcohol, phenolic resin, glycerol ester, polyacrylic acid, styrene-acrylate copolymer, one or more silicates (esters) or combinations thereof.

20. The method according to claim 18 or claim 19, wherein the bonding material is selected from cellulose fibers, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyacrylamide resin, polyvinyl alcohol, one or more silicates (esters), polyacrylamide, ethyl acrylate styrene (EA), triacetin, diacetin, phenolic resin, or combinations thereof.

21. The method according to any one of claims 18 to 20, wherein the bonding material is selected from cellulose fibers, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol, polyacrylamide resin, one or more silicates (esters), polyacrylamide, phenolic resin, triacetin, or combinations thereof.

22. The method according to any one of claims 18 to 21, wherein the adhesive material is selected from polyacrylamide resin, polyvinyl alcohol, phenolic resin, carboxymethyl cellulose (CMC), triacetin, sodium silicate, magnesium silicate, or combinations thereof.

23. The method according to any one of claims 18 to 22, wherein the adhesive material is selected from polyacrylamide resin, polyvinyl alcohol, phenolic resin, carboxymethyl cellulose (CMC), sodium silicate, magnesium silicate, or combinations thereof.

24. The method according to any one of claims 18 to 23, wherein the adhesive material comprises a combination of: a) one or more of carboxymethyl cellulose, cellulose fibers, PVA and polyacrylamide; and b) one or more of silicates (esters) and phenolic resins.

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

26. The method according to any of the preceding claims further comprises the step of adding a separate processing aid to the substrate mixture.

27. A pellet obtained by the method according to any of the preceding claims, comprising a particulate substrate selected from metal ore, metal ore-containing waste, fine metal powder, iron slag, iron filings, mineral waste, carbonaceous materials, electric arc furnace waste, or combinations thereof, and a binder formulation.

28. The pellets of claim 27, wherein the pellets are heated to a temperature in the range of 10°C to 250°C.

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