pellet
Patent Information
- Authority / Receiving Office
- AU · AU
- Patent Type
- Patents
- Current Assignee / Owner
- BINDING SOLUTIONS LTD
- Filing Date
- 2024-09-19
- Publication Date
- 2026-07-09
Smart Images
Figure 00000035_0000 
Figure 00000036_0000 
Figure 00000036_0001
Abstract
Description
Priority Cross-Reference The present invention claims priority to GB patent application 2314397.7 filed 5 20 September 2023, the entire contents of which is hereby incorporated by reference. Technical Field The invention relates to the production of pellets from a particulate material and to pellets so produced. Typically, the pellets are cured with carbon dioxide. 10 Background of the Invention The discussion of the background to the invention herein is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any aspect of the discussion was part of the 15 common general knowledge as at the priority date of the application. The production of pellets from particulate materials, such as particulate iron and other metal ores is generally known in the art. For instance, pellets of this nature are often used in a blast furnace for producing liquid iron, or in direct iron reduction (DRI) of iron 20 ore to generate sponge iron. The pellet is designed to be sufficiently strong to allow the pellet to be successfully transported and to be used within the blast furnace or an electric arc furnace. For example, when used in a blast furnace, the pellet must be able to retain its integrity through the blast furnace into the melting furnace, otherwise the performance of the blast furnace can be adversely affected. 25 Traditionally, pellets were formed using heat processes producing so-called, hot-bonded (indurated) briquettes. In induration techniques, initially, a “green” pellet is formed from the combination of particulate substrate (particulate material) and a binder, which is then shaped into a pellet (often using a pelletiser). As used herein, the term “green pellet” 30 takes its usual meaning in the art and refers to a pellet that does not yet have the required strength for its end use and requires further treatment or processing. The green pellets are hardened via a series of steps including drying, pre-heating, firing, and cooling of the green pellets. The primary purpose of the drying stage is the removal of moisture from the pellets, making them more stable and easier to handle. Removal of water in a 35 controlled manner prevents crack formation and maintains the structural integrity of the pellet. The temperature range of the drying stage is dependent on the chemical and physical properties of the green pellet; however, it is likely to be in the range of 100°C to 250°C for 5 to 10 minutes. The pre-heating stage usually takes place using a ramped 2024219865 19 Sep 2024 heating process from around 300°C to 350°C for 10 to 15 minutes, to up to around 1250°C to 1350°C. The pre-heating stage ensures that any metal hydrates or metal carbonates present decompose to their anhydrous forms. Decomposition of these types of compounds helps to improve the structural integrity of the resultant pellet by removing 5 water and / or gas which can react, causing overpressure and cracking of the pellet during firing. The firing stage will often take place at temperatures greater than 1350°C for roughly 10 to 20 minutes (for typical capacities such as 250 to 500 tons per hour (tph)) and will result in the sintering of the pellet, providing the strength needed to render it suitable for its end use. During the sintering process, the bonds within the pellet are 10 formed by recrystallisation and bridging, creating ceramic bonds and the formation of macro voids which allow for some expansion and stress relief. As used herein, the term “macro void” relates to voids within the pellet and have a size ranging from about 50 pm to about 1 mm in diameter. The void formation is particularly important where the briquette is a metal ore briquette, as reduction of the metal (for instance the hematite to 15 magnetite conversion in iron ore) causes volume changes and stresses on the briquette. As macro void formation does not occur without firing, alternative methods are needed to prevent disintegration of the pellet when placed under internal stress. As noted above, a common problem associated with pellets of this type is breakage of 20 the agglomerate. In an attempt to overcome this issue, particles are often bound together using a binder such as cement or clay in the hope of improving strength to enable further handling. However, a problem associated with using cement or clay is that it increases the amount of silica in the iron and slag produced at the end of the process. 25 Further, induration processes are uneconomical as they are complex, must be executed with care, and require the application of significant heat. For instance, the raw material preparation is critical. The components of the green pellet must be an appropriate size range, surface area, and moisture content in order to withstand the process as surface chemistry plays a significant role. Moreover, as the process involves multiple heating 30 stages, it requires a great deal of energy. As such, there is a need for a process of pellet production that is less energy intensive and more cost effective. Moreover, there is a need for a process where there is more flexibility in the physical state of the particulate material used, and which results in the 35 generation of pellets having comparable or even superior physical properties to those generated using an induration process, in particular in terms of strength, to enable processing and handling. The invention is intended to overcome or ameliorate at least some aspects of this problem. 2024219865 17 Oct 2025 Summary of Invention Accordingly, in a first aspect of the invention there is provided a process for producing a pellet, the process comprising: (i) providing particulate material selected from a carbonaceous material, metal, metal 5 ore, and mixtures thereof; an inorganic binder comprising a metal silicate, and an organic binder, wherein the organic binder comprises a natural polymer, a synthetic polymer, a glycerolipid, a cellulosic material, and combinations thereof, to form a mixture; (ii) compressing the mixture to form a pellet; and 10 (iii) curing the pellet by contacting the pellet with gaseous carbon dioxide. The process of the invention enables the rapid production of pellets which are of sufficient strength to be handled and transported without the need for the application of heat during pellet forming (although this may optionally form part of the process). They also have 15 good water resistance and have thermal properties suitable for the end use conditions of a blast or other furnace. For some formulations of pellet, the carbon dioxide enables the production of pellets of sufficient strength without the need to apply heat, where heat would previously have been essential to the hardening process. For other formulations of pellet, the carbon dioxide acts to accelerate the hardening of pellets which can be cold-20 formed over a greater period of time in the absence of the carbon dioxide strengthening catalyst. Therefore, the invention provides for the production of pellets in production locations where heat is not necessarily readily available, providing (in some cases) for simpler designs of the pellet manufacturing plants. Further, the generation of heat often results in production costs being incurred, and, dependent upon the source of energy 25 used to generate the heat, can result in damage to the environment by indirect carbon emissions from the energy generation. Therefore, unless care is taken to generate the heat responsibly, it’s use can be undesirable. It should be noted that, as used in this general description, the terms 30 “strength / strengthening" and “hard / hardening" are used roughly interchangeably to indicate the provision of, and ultimate robustness of, the pellet to, transport and handling. The terms “particulate material" and “particulate substrate" are also used interchangeably to refer to the pellet feedstock. 35 Additionally, the use of carbon dioxide provides for the sequestration of this material, which is well known as a major contributor to greenhouse gas emissions. It may be that the carbon dioxide is waste carbon dioxide, for instance as produced by heavy industry, 2024219865 17 Oct 2025 or acts as an offset where curing is also with heating and green energy resources could not be used. The use of carbon dioxide produced by heavy industry can be particularly 2024219865 19 Sep 2024 beneficial where the carbon dioxide is carbon dioxide produced by the iron or steel production industries, as these industries have traditionally produced large amounts of waste heat and carbon dioxide. For instance, a typical ironmaking operation including blast furnace and ancillary plant emits off-gas which is 5 to 50% carbon dioxide, which can equate to 2000 to 20,000 tonnes per day (tpd). However, gas flow rates will vary. For instance, a mid-range blast furnace can emit off-gas at 11,000 tpd (or 3860 litres per minute). Moreover, even small blast furnaces can produce 2000 tpd carbon dioxide (or 701 litres per minute). Therefore, whilst the impact is much lower than, for instance, a large power station, the impact of blast furnace operation is significant and can beneficially be decarbonised. Direct iron reduction (DRI) processes produce off-gas comprising around 30% carbon dioxide, even though some recapture is common in these systems; and electric arc furnaces emit off-gas comprising in the range 5 to 50% carbon dioxide. It is common practice to reuse the heat produced by industrial processes, including those described above, but typically carbon dioxide is either released into the atmosphere, or stored (physical storage or chemical storage). Such storage increases the cost of iron / steel production and wastes a potentially valuable chemical material, the carbon dioxide, by locking it away without further use (although the environmental benefits are clear). As such, finding ways to use the carbon dioxide produced, sequestering in a productive and beneficial way (as opposed to sequestering purely to remove the carbon dioxide from the atmosphere), can be hugely beneficial in reducing scope 1 and 3 emissions from industrial production sites (for instance iron and steel), or fossil fuel power stations. Moreover, the process of the invention uses carbon dioxide to produce a valuable product (i.e. the pellet feedstock, which in this case is often for iron and steel, but also possibly for the mining industry), sequestering the carbon dioxide as a carbonate. Further, as the pellets produced are often intended for use in iron or steel manufacture (for instance where they comprise metallic or metal ore substrates), the production of the pellets (potentially at the location of the iron or steel production site) using carbon dioxide resulting from the production of iron or steel (such as carbon dioxide found in off-gas arising from power or heat generation in internal combustion engines or induration plants at a mining site), creates a desirable circularity in the process which is environmentally and economically beneficial, reducing the overall carbon footprint of the production site. As noted above, the process of the invention provides for strong pellets which offer one or more of the benefits of being robust to transport, robust to handling, having good water resistance and having thermal properties suitable for the end use conditions of a blast or other furnace. Without being bound by theory, it is believed that the strength can be derived, without the need for heat, because the carbon dioxide reacts with the 4 2024219865 19 Sep 2024 inorganic binder (a metal silicate) to form a carbonate by anionic substitution. For instance, where the inorganic binder includes sodium silicate, the substitution reaction is believed to be: 5 Na2SiO3.nH2O + CO2 ^ Na2CO3 + SiO2 + nH2O (equation 1) This reaction, a separation of silica from sodium silicate using carbon dioxide, provides for a pellet with higher thermal stability than pellets of the same composition which are not cured by contact with carbon dioxide. Again, without being bound by theory, it is 10 believed that the silica has a greater affinity for the reactive functionalities in the particulate materials than for other silica groups. Resulting in a pellet containing bonds between the silica and the particulates, for instance the metal / metal oxides in the particulates, which would not be formed if the metal silicate were simply mixed with the particulate without further processing. In essence, reaction with the carbon dioxide to 15 form a metal carbonate as an alternative to a dehydrated metal silicate allows for the provision of discrete silica particles, which interact to form strong bonds with the particulate material in the pellet. Such that it is possible to utilise carbon dioxide as a catalyst to cure a binding system which contains a silicate component. 20 The reaction of the metal silicate with carbon dioxide to form the metal carbonate may be partial or complete. As the strength of the pellet is roughly proportional to the degree of reaction to form the free silica and carbonate, it is generally desirable that the reaction is complete, or nearly complete. For instance, that the reaction is at least 50% complete, often in the range 50% to 100% complete, often in the range 60% to 90%, or 70% to 25 80% complete. Hardening / strengthening of the pellet typically follows the gas penetration of the green pellet such that it will often be the outer surface of the pellet which initially hardens, with the core following after longer exposure to the carbon dioxide. It is for this reason that it can often be the case that a partial reaction is sufficient to provide a pellet with the strength required, as the hard exterior is sufficient to protect 30 the interior during handling. The particulate material will generally comprise a carbonaceous material, metal, metal ore, or mixtures thereof. In many cases, the particulate material will be selected from a metal ore, a metal, and combinations thereof, as the application of carbon dioxide to 35 green pellets comprising this particulate substrate provides particular benefits in terms of the improvements in observed strengths. The metal / metal ores may be further selected from metal residues, metal filings, metal fines, iron ore screenings, and collection 2024219865 19 Sep 2024 dusts from furnaces including blast furnaces, BOS, EAF and DRI. The collection dusts will typically comprise a combination of metal oxides, partial oxides, and metal fines. The particulate substrate is often sourced from the waste products of other industrial processes. The particulate substrate may comprise waste products from a single waste 5 stream (in which variation will be in particle size only) or waste products from a combination of waste streams (in which mixed waste of different compositions will be present). This is environmentally beneficial as the recycling and reuse of such materials reduces the amount of finite resources that may otherwise go to waste. 10 The carbonaceous material may be coke, graphite, carbon black, peat, or coal. Often the carbonaceous material will comprise graphite, coke, coal, or a combination thereof. It may be the case that the carbonaceous material comprises coke and / or coal. As used herein, the term "coal" is intended to include lignites, sub-bituminous coal, bituminous coal, steam coal and anthracite. Cokes have been found to be particularly problematic at 15 forming pellets and so the invention offers a particular benefit in the provision of stronger coke pellets. The metal may be, or the metal ore may contain; iron, zinc, nickel, copper, chromium, manganese, gold, platinum, silver, titanium, tin, lead, vanadium, cadmium, beryllium, 20 molybdenum, uranium, aluminium, or mixtures thereof; for instance, as elemental metal or in the form of, for example, oxides or silicates. Often, the particulate substrate comprises a metal, and more often the particulate substrate comprises iron. The use of iron is advantageous due to the ready availability of 25 iron and because it can be reused and recycled from the waste products of other processes to provide environmentally sustainable access to this material. Where the particulate substrate comprises a metal ore, often the ore will be an iron ore such as goethite, martite, limonite, siderite, taconite, hematite or magnetite. Often, where the particulate substrate is a metal ore, it will be an iron ore, such as hematite or magnetite. 30 The particulate substrate may be a powder or filings, the term “filings” being given its common meaning in the art. Often the particulate substrate has a particle diameter of 4 mm or less (broadest axis). Often the particle diameter will be in the range 30 pm to 4 mm, often 50 pm to 3 mm or 0.1 mm to 2 mm. Often, at least 10 wt% of the particulate 35 substrate is capable of passing through a 100 pm sieve prior to forming into a pellet. The presence of a range of particle sizes within the sample improves the packing of the materials within the pellet. 2024219865 19 Sep 2024 It may be the case that the particulate material be added in an amount of about 70 wt% to about 99.9 wt% of the mixture of step (i), often about 80 wt% to about 99 wt%, more often about 90 wt% to about 95 wt%. At these levels there is a balance between the need for other components and the desire to maximise the levels of the particulate substrate as it is the reactive feedstock that is the reason for pelletisation. It may be the case that the particulate material comprises a metal ore, a metal, and combinations thereof, added in an amount of about 70 wt% to about 99.9 wt%, often about 80 wt% to about 99 wt%, more often about 90 wt% to about 95 wt%. It may be the case that the particulate material comprises a carbonaceous material. It may be the case that the particulate material is added in an amount of about 70 wt% to about 99.9 wt%, often about 80 wt% to about 99 wt%, more often about 90 wt% to about 95 wt%. It may be the case that the particulate material has a moisture content of less than 25%, as above these levels, dilution of the particulate impacts the ability to form compact agglomerates. Often the moisture content will be in the range of about 1 wt% to about 25 wt%, often from about 3 wt% to about 20 wt%, more often from about 5 wt% to about 15 wt% of the mixture. The inorganic binder comprises one or more metal silicates. It may be the case that the metal silicate comprises a group I or group II metal silicate, or more than one group I and / or group II metal silicates. Whilst other metal silicates may be successfully used as the inorganic binder of the invention, it has been found that group I and group II metals are more reactive in the presence of carbon dioxide (promoting carbonate formation) than other metals. As a result, “free” silicates readily form where the metal silicate is a group I or group II silicate, promoting enhanced cross-linking of the silicate bonds and improving the thermal properties of the pellet. Some less labile metal silicates may require the application of pressure and heat to promote cross-linking. As such, the metal silicate will often be selected from sodium silicate, potassium silicate (e.g. K2SiO3), calcium silicate (e.g. CaSiO3, Ca2SiO4), magnesium silicate (e.g. MgSiO4), and combinations thereof. It may be the case that the metal silicate is selected from sodium silicate, potassium silicate, magnesium silicate, or combinations thereof. Where the metal silicate comprises calcium silicate, it may be present in its natural mineral state, such as wollastonite (i.e. CaSiOs) and larnite (i.e. CazSiO4). It will not generally be present as a calcined product (such as Portland cement). It may be the case that the metal silicate is selected from sodium silicate, magnesium silicate, or combinations thereof. Sodium silicate has been found to be particularly beneficial possibly due to its high ion lability. Sodium silicate is also readily available and inexpensive. It may be the case that the metal silicate comprises sodium silicate and magnesium silicate. It has been found that 7 2024219865 19 Sep 2024 this combination of alkali metal silicates provides pellets with high cold compression strength. Without being bound by theory, as sodium silicate is more reactive than magnesium silicate, the sodium silicate should react preferentially as per the substitution reaction outlined above in equation 1. This should then allow the magnesium silicate to co-react to form a Na-Mg complex, and result in a combined salt. It is believed that the magnesium silicate converts to an amorphous, more reactive phase from its usual more stable, crystalline phase during this process. Alternatively, it may be the case that the alkali metal silicate comprises magnesium silicate, potassium silicate, or a combination thereof. The metal silicate may be in liquid form, powder form, or a combination thereof. When the metal silicate is in liquid form, it will be present in greater amounts because there is a lower level of active in liquid metal silicates than in powder metal silicates. Where the metal silicate is in liquid form, it is often present in the range about 1 wt% to about 6 wt%, often about 1.5 wt% to about 5.5 wt%, often about 2 wt% to about 5 wt%, often about 3 wt% to about 4 wt% of the mixture of step (i). Where the metal silicate is in powder form, it is often present in the range about 0.5 wt% to about 3.5 wt%, often about 1 wt% to about 3 wt% of the mixture. It may be the case that there are two or more metal silicates present. In the event that there are two or more metal silicates present, it may be the case that at least one is in liquid form and at least one is in powder form. When two or more metal silicates are present, at least one in liquid form and at least one in powder form, it is often the case that the liquid and powder form are present in the ratio of from 5:1 to 1:1. Optionally, the ratio may be 3:1, optionally the ratio may be 3:2. As such, the metal silicate may be present in the mixture in the range about 0.5 wt% to about 6 wt%, often in the range about 1 wt% to about 5 wt%, often in the range about 1.5 wt% to about 4 wt% of the mixture of step (i). At these levels, there is sufficient metal silicate present to ensure that binding occurs, but that the binder is not used in excess, reducing the overall amount of particulate substrate available from the pellet. Optionally, it may be the case that step (i), the forming of the mixture, further comprises the addition of an organic binder. It has been found that the presence of an organic binder, in addition to the inorganic binder, enhances the speed of curing. It may be the case that the organic binder comprises a natural polymer (e.g. lignosulfonates), a synthetic polymer (e.g. polyacrylics, styrene-acrylate copolymers, polyvinyl alcohol, or a synthetic organic resin); a cellulosic material; a glycerolipid (e.g. mono-, di-, or tri-esters of glycerol); a polysaccharide; or combinations thereof. As used herein, the term “polyacrylics” takes its usual meaning in the art and refers to a class of synthetic polymers 8 2024219865 19 Sep 2024 derived from acrylic acid or its esters. Examples of polyacrylics 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 the copolymerization of styrene and acrylic acid or its derivatives. Examples of styrene-acrylate copolymers include, but are not limited to, 2-Ethylhexyl acrylate styrene (2-EHA), Ethyl acrylate styrene (EA), Methyl methacrylate styrene (MMA), and Butyl Acrylate Styrene (BA). Often, the styreneacrylate copolymer will comprise Ethyl acrylate styrene (EA). As used herein, the term “cellulosic material" takes its usual meaning in the art and refers to any material derived from or containing cellulose. Cellulosic materials include natural materials primarily composed of cellulose, but also synthetic derivatives of cellulose. As used herein, the term “glycerolipid" takes its usual meaning in the art and refers to a type of lipid molecule that consists of a glycerol backbone esterified with one or more fatty acids or acyl groups. It may be the case that the organic binder is selected from a natural polymer (e.g. lignosulfonates), a synthetic polymer (e.g. polyacrylics, styrene-acylate copolymers, a synthetic organic resin such as polyacrylamide resin or phenol-formaldehyde resin (including resole resin, which is a base catalysed phenol-formaldehyde resin with a formaldehyde to phenol ratio of greater than one, usually around 1.5, or Novolac resin, which has a formaldehyde to phenol molar ratio of less than one)) or polyvinyl alcohol); a cellulosic material, such as cellulosic fibres, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), or hydroxyethyl methyl cellulose (MHEC); a glycerolipid (e.g. glyceryl acetate, glyceryl diacetate, and glyceryl triacetate); and / or a polysaccharide, such as starch (for example, wheat, maize, barley and potato starch, and / or molasses) or gum (for example, gum Arabic, guar gum and / or xanthan gum). It may be the case that the organic binder is selected from polyacrylamide resin, polyvinyl alcohol, a phenol formaldehyde resin (such as novolac or resole resin), a polyacrylic (e.g. polyacrylic acid (PAA), poly(methyl methacrylate) (PMMA, polyacrylamide (PAM)), a styrene-acrylate copolymer (e.g. 2-Ethylhexyl Acrylate Styrene (2-EHA), Ethyl Acrylate Styrene (EA), Methyl Methacrylate Styrene (MMA), and Butyl Acrylate Styrene (BA)), glyceryl triacetate, glyceryl diacetate, cellulosic fibres, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxyethyl methyl cellulose (MHEC), wheat starch, maize starch, barley starch, potato starch, gum Arabic, guar gum, xanthan gum, and combinations thereof. It may be the case that the organic binder is selected from polyacrylamide resin, polyvinyl alcohol, a phenol formaldehyde resin, a polyacrylic, a styrene-acrylate copolymer, glyceryl diacetate, glyceryl triacetate, cellulosic fibres, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxyethyl methyl cellulose (MHEC), or combinations thereof. It may be the case that the organic binder is 9 2024219865 19 Sep 2024 selected from polyacrylamide resin, polyvinyl alcohol, a phenol formaldehyde resin, glyceryl triacetate, polyacrylamide, ethyl acrylate styrene, cellulosic fibres, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), or combinations thereof. It may be the case that the organic binder is selected from polyacrylamide resin, polyvinyl 5 alcohol, a phenol formaldehyde resin, cellulosic fibres, carboxymethyl cellulose (CMC), glyceryl triacetate, or combinations thereof. The organic binder may comprise a cellulosic material, polyacrylamide resin, polyvinyl alcohol, a phenol-formaldehyde resin, or a combination thereof. The organic binder may 10 comprise polyacrylamide resin, a cellulosic material, or a combination thereof. The organic binder may comprise a cellulosic material. Where the organic binder comprises a cellulosic material, it may be the case that the organic binder comprises carboxymethyl cellulose (CMC), cellulosic fibres, hydroxyethyl 15 methyl cellulose (MHEC), or a combination thereof. It may be the case that the organic binder comprises carboxymethyl cellulose (CMC) and / or hydroxyethyl methyl cellulose (MHEC). It may be the case that the organic binder comprises carboxymethyl cellulose (CMC). CMC is advantageous because it can be added in powder form which allows for control of the overall moisture content of the pellet. CMC also has a long shelf-life in 20 comparison to other plant derived binders. This is because other plant derived binders are often more susceptible to microbial attack and so break down more easily. Sometimes the organic binder may be hydroxyethyl methyl cellulose (MHEC), which has been found to have particularly good adhesive qualities and helps to enhance the strength of the pellet. However, as MHEC is highly water soluble, this may affect the shelf life of the final 25 pellet, reducing this in comparison to pellets containing CMC. Typically, the CMC has an active polymer content of about 40% to about 90% and a pH in the range of about 5 to about 9, or about 6 to about 8 when in solution. Further, the CMC will often be of number average molecular weight (Mn) in the range of from about 30 3,000 to about 70,000. Optionally, the CMC will be of number average molecular weight in the range of from about 10,000 to about 50,000. Without being bound by theory, it is believed that, with lower number average molecular weights of CMC, for instance in the range about 10,000 to about 50,000, it is possible to prepare a solution of high concentration, which in turn can improve the strength of the pellets. Any known 35 technique, such as size-exclusion chromatography (SEC), gel permeation chromatography (GPC), or light scattering, may be employed to determine the number average molecular weight (Mn). The specific measurement conditions, including 2024219865 23 Mar 2026 temperature, solvent, and calibration standards, will be selected based on the chosen technique and in accordance with appropriate industry standards. Polyvinyl alcohol (PVA) may be used as an organic binder instead of or in addition to other organic binders, such that the organic binder may comprise about 10 wt% to about 100 5 wt%, often about 20 wt% to about 90 wt% or about 50 wt% to about 75 wt% PVA. Where the organic binder comprises PVA, the organic binder is typically added in the range of about 0.01 wt% to about 2.0 wt% of the pellet, often about 0.05 wt% to 1.5 wt% of the pellet or about 1 wt% of the pellet. Without being bound by theory, the PVA is believed to provide good mixing of components 10 and high strength as the polymer network formed by PVA is strong. Further, the process of pelleting with PVA excludes air from the particulate material, which may reduce oxidation of the particulate substrate where this is metal. Metal oxidation is undesirable for the simple reason that it reduces the amount of the metal (e.g. metallic iron) available for processing by the end user. 15 PVA is typically commercially formed from polyvinyl acetate by replacing the acetic acid radical of an acetate with a hydroxyl radical by reacting the polyvinyl acetate with sodium hydroxide by saponification. Partially saponified means that some of the acetate groups have been replaced by hydroxyl groups and thereby forming at least a partially saponified polyvinyl alcohol residue. Typically, the PVA has a degree of saponification of at least 20 about 80%, typically at least about 85%, at least about 90%, at least about 95%, at least about 99% or about 100% saponification. Typically, it is utilised as a solution in water. The PVA may be modified to include, for example, a sodium hydroxide content. Typically, the PVA binding material has 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. Further, the PVA will often be 25 of number average molecular weight (Mn) in the range of from about 15,000 to about 150,000. Optionally, the PVA will often be of number average molecular weight in the range of from about 30,000 to about 120,000. Without being bound by theory, it is believed that, with lower number average molecular weights, for instance in the range about 15,000 to about 60,000, it is possible to prepare a solution of high concentration, 30 which in turn can improve the strength of the pellets. Where the organic binder comprises a polyacrylamide resin, it will often be an anionic polyacrylamide resin of medium-high number average molecular weight (Mn) and medium-high charge density. For instance, the number average molecular weight may be in the range 100,000 to 2,000,000, often in the range 500,000 to 1,500,000. The 35 charge density will typically be in the range 25 to 50%. Any known technique in the art 2024219865 19 Sep 2024 may be employed to measure the charge density of the polymer. Suitable methods include, but are not limited to, potentiometric titration, conductometric titration, electrophoretic mobility, light scattering, and nuclear magnetic resonance (NMR). The specific measurement conditions, such as temperature, solvent, and calibration 5 standards, will be selected based on the chosen technique and in accordance with appropriate industry standards. Where the organic binder comprises a polysaccharide, this may be starch or amylase starch. For instance, it may be pregelatinised potato starch. It may be added in the amount of about 0.8 wt% of the final pellet, often about 0.6 wt%. The use of a 10 polysaccharide as a component of the mixture may be desirable as polysaccharides often also function as thickening agents. The organic binder may be present in the mixture in the range about 0.2 wt% to about 5 wt% of the mixture, optionally in the range about 0.25 to about 0.45 wt%, optionally in the range about 0.3 to about 0.4 wt%. 15 It may be the case that the organic binder is of viscosity in the range about 1,000 MPa.s to about 16,000 MPa.s, often in the range about 2,000 MPa.s to about 10,000 MPa.s, or in the range about 3,000 MPa.s to about 7,000 MPa.s. The viscosity can be measured using standard techniques known in the art, such as capillary viscometers, rotational 20 viscometers, and oscillatory rheometers. The specific measurement conditions, including temperature, solvent, and calibration standards, will be selected based on the chosen technique and in accordance with appropriate industry standards. Typical measurement conditions include temperatures ranging from 20°C to 25°C, using solvents such as water or organic solvents, and calibration with standard viscosity reference materials. 25 The mixture of step (i) may further comprise a flux additive to promote fluidity of the mixture during subsequent processing. In instances where a flux additive is present, the flux additive may be selected from silica, dolomite, fluorite, calcium oxide, magnesium oxide, carbon, aluminium, dunnite, basalt, and combinations thereof. Where present, the 30 flux additive will often be present in the range about 0.5 wt% to about 2 wt%, often about 1 wt% to 1.5 wt% of the mixture. As noted above, it may be the case that the carbon dioxide used to cure the pellet is carbon dioxide generated from one or more industrial processes. This could be termed 35 “waste” carbon dioxide, or, when used, “recycled” carbon dioxide. As such, the process of the invention may further comprise the step of capturing carbon dioxide generated 2024219865 19 Sep 2024 from one or more industrial processes for use in curing the pellet. The step of curing the pellet comprises contacting the pellet (the green pellet) with gaseous carbon dioxide. The contacting will often be placing the pellets in a stream of gas. This may be achieved by passing a flow of carbon dioxide over a static bed of the pellets, or by transporting the pellets through a moving stream of gas. The gas stream may be almost entirely carbon dioxide (e.g. “pure” or “purified” carbon dioxide), or it may be carbon dioxide mixed with an inert carrier gas such as argon or nitrogen. As used herein the term “inert carrier” is intended to include any gas which will not react with the carbon dioxide, or the materials in the green pellet. Typically, however, the carbon dioxide will comprise in the range about 70 wt% to about 100 wt% of the gas stream, often about 80 to about 99 wt%, or about 90 to about 95 wt%, to maximise the contact between the reactive carbon dioxide gas and the pellets, thereby ensuring that hardening occurs as quickly as possible, and that the time taken for curing step (iii) is minimised. One advantage of utilising a gas stream is that the carbon dioxide supply is continually replenished, this would not occur where, for instance, the pellets were placed in a sealed chamber and allowed to react in a static atmosphere of carbon dioxide. It will often be the case that curing of the pellet by contacting the pellet with gaseous carbon dioxide occurs by introducing the pellets into a gas stream comprising carbon dioxide at a flow rate in the range about 1 to about 100 litres per minute, often about 2 to about 50 litres per minute, or about 2 to about 20 litres per minute. At these rates, there is sufficient carbon dioxide present to ensure good contact with the pellets, without undue unreacted carbon dioxide passing beyond the point of contact (such that it would need to be recirculated to avoid waste). Flow rates would be adapted within this range for the pellet load being cured, pellet volume, residence time, pressure used, and temperature, as would be understood by the skilled reader. The curing of the pellet may be at atmospheric pressure, although it will often be at slightly increased pressure, for instance in the range about 1 Bar to about 3 Bar (1 Bar = 0.1 MPa), often about 1.5 Bar to about 2.5 Bar or about 1.5 Bar to about 2 Bar. At these pressures carbon dioxide penetration of the pellets is enhanced relative to atmospheric pressure. Pressures would be adapted within this range for the pellet load being cured, pellet volume, residence time, carbon dioxide flow rate, and temperature, as would be understood by the skilled reader. The pellets will remain in the gas stream until the hardening reaction (i.e. silicate to carbonate to subsequently liberate silica) has progressed to the point where the pellets are sufficiently strong. This would depend upon the pellet load being cured, pellet 13 2024219865 19 Sep 2024 volume, pressure, carbon dioxide flow rate, and temperature, as would be understood by the skilled reader. Whilst the pellets can be cured at ambient temperature (cold-formed), for some 5 formulations this would require an extended curing time to provide the desired levels of strength. As such, it may be the case that the step of curing the pellet (step iii), additionally comprises the application of heat at a temperature in the range about 50°C to about 1000°C. Heating the pellets during contact with the gaseous carbon dioxide reduces the curing time. 10 The term “cold-formed" means, for example, without curing, sintering, or heating to above about 50°C or above about 40°C or about 30°C, such that the pellet would generally, if any heat were applied, be heated to less than 50°C. In other words, it may often be the case that if there is an application of heat during pellet formation, only low 15 levels of heat will be applied. Further, when the pellet is formed, although frictional heat may be generated by any pressing and / or extrusion processes used, and the binder may undergo exothermic reactions in situ, this will sometimes be the only heat present, and does not constitute heating as noted above as it is not the application of external heat. These inherent heating mechanisms would not be expected to generate enough heat to 20 impact the formation of the pellet. The advantage of cold-forming is significant in terms of reduction in energy expenditure relative to the induration manufacture techniques commonly used. There is also no need for high-temperature furnaces to produce the pellet, resulting in a simpler and more economically and environmentally beneficial manufacturing process. 25 However, similarly to the use of carbon dioxide from industrial processes as described above, those processes also produce excess heat, which could be utilised in heating the pellets during the curing step of the invention thereby mitigating the heat expenditure of the industrial process by engineering the system (for instance through the use of 30 heat exchangers) to reuse waste heat produced elsewhere. As such, it may be the case that the application of heat comprises application of heat generated from one or more industrial processes, for instance from the steel or iron making industries. As noted above, it may therefore be advantageous to heat the pellets during curing to a temperature in the range about 50°C to about 1000°C. It may be the case that the 35 pellets are heated during curing to a temperature in the range about 60°C or about 100°C to about 900°C, often about 150°C to about 800°C, often about 200°C to about 600°C, or often about 200°C to about 400°C. It may be the case that the pellets are heated during curing to a temperature in the range about 400°C to about 800°C, or 2024219865 19 Sep 2024 about 600°C to about 800°C. At these temperatures it is possible to cure pellets in a few minutes, for instance in about 30 seconds to about 30 minutes, often about 1 minute to about 15 minutes or about 2 minutes to about 10 minutes, such that pellet formation is very rapid compared to the longer curing times (hours, in some cases 5 days) that can be needed where heat is not used as part of the process. The process of the invention includes the step of compressing the substrate mixture to form the pellet. This may be via any of a range of compressive techniques, such as passing the substrate mixture through compressive wheels (such as on a roller press), 10 compressive screws, hammer mills, a hydraulic press, a mechanical press, or pressure plates. The pellet may be formed by extrusion, such that there is a step of forming the pellet comprising extruding the mixture. The extrusion process may take place at a temperature in the range of about 30°C to about 70°C, often in the range of about 35°C to about 55°C, the temperature increases arising from frictional heat generated during 15 the extrusion process. Further the process may take place at atmospheric pressure or under vacuum. As used herein, the term “under vacuum” takes its normal meaning in the art, in that the extrusion process may be conducted at pressure less than atmospheric pressure. One method that may be used is a roller pressing process (RPP), wherein the step of compressing the substrate mixture comprises passing the mixture through a roller 20 press configured to produce pellets. The rollers exert continuous pressure, forming the substrate mixture into pellets as they pass through the gap between the rollers. This method allows for continuous production and can handle a variety of materials, producing pellets with consistent size and density. Another method that may be used is a coldpressing technique (CTS), where the substrate mixture is placed in a mould or die and 25 subjected to high pressure using a hydraulic or mechanical press. The pressure compacts the material into a solid pellet without the use of heat ensuring the pellets are dense and cohesive. This method is advantageous due to its energy efficiency, as it eliminates the need for heating. When a RPP method is adopted, the hydraulic pressure applied in step (ii) may often be 30 in the range about 50 Bar to about 300 Bar, often in the range about 100 Bar to about 250 Bar, or about 150 Bar to about 200 Bar. When a CTS method is adopted, pressure is calculated under 6 tonnes force. The pressure under 6 tonnes force will vary depending on the size of the die used (i.e. the internal diameter of the die). For instance, for a 10 mm die, the pressure applied in step (ii) may 35 be in the range about 6000 Bar to about 8000 Bar, often about 6500 Bar to about 7500 Bar. For a 16 mm die, the pressure applied in step (ii) may be in the range about 2000 2024219865 17 Oct 2025 Bar to about 5000 Bar, often in the range about 2500 Bar to about 4000 Bar, often in the range 2750 Bar to 3500 Bar. For a 20 mm die, the pressure applied in step (ii) may be in the range about 800 Bar to about 3500 Bar, often in the range about 1000 Bar to about 3000 Bar, often in the range about 1500 Bar to about 2500 Bar. 5 It may be the case that, prior to step (iii) of the process according to the first aspect of the invention, the pellets are subjected to an inert atmosphere. As used herein, the term “inert atmosphere" takes its usual meaning in the art and relates to an environment that contains gases that are non-reactive under specific conditions, more specifically gases which will not react with the carbon dioxide, or the materials in the green pellet. 10 Incorporation of this additional step prior to step (iii) can prevent any unwanted side reactions, enhancing the quality of the resultant pellet. It may be the case that subjecting the pellets to an inert atmosphere occurs by introducing the pellets into an inert gas stream at a flow rate in the range about 1 litre to about 100 litres per minute, often about 2 litres to about 50 litres per minute, or about 2 litres to about 20 litres per minute. In 15 instances where the process comprises an additional step of subjecting the pellets to an inert atmosphere, the pellets may be heated to a temperature in the range about 50°C to about 1000°C, about 60°C, or often about 100°C to about 800°C, often about 150°C to about 700°C, or more often about 200°C to about 600°C, prior to contact with gaseous carbon dioxide. The gas used to provide the inert atmosphere may comprise nitrogen or 20 argon. It may be the case that the gas used to provide the inert atmosphere comprises nitrogen. It may be the case that the process may further comprise the additional step (iv) of cooling the resultant pellets under an inert atmosphere. It may be the case that the inert 25 atmosphere comprises nitrogen or argon. It will often be the case that the inert atmosphere comprises nitrogen. Cooling under an inert atmosphere is advantageous, as it prevents any unwanted reactions from occurring. Processing in an inert atmosphere is frequently employed in experimental conditions due to the ease of controlling the atmosphere in small-scale reactions. 30 In a second aspect of the invention there is provided a pellet obtainable by a process according to the first aspect of the invention, and in a third aspect of the invention, a pellet comprising a particulate material selected from a carbonaceous material, metal, metal ore, and mixtures thereof; silica; and a metal carbonate, and an organic binder, wherein the organic binder comprises a natural polymer, a synthetic polymer, a 35 glycerolipid, a cellulosic material, and combinations thereof. The pellets of the second and third aspects of the invention have been found to have a unique chemical structure, 2024219865 17 Oct 2025 as described above. The reaction of the metal silicate with carbon dioxide provides for a metal carbonate and silica, this being believed to form bonds with the particulates, for instance with the metal / metal oxides in metal-containing particulates that would not exist in the absence of the curing in carbon dioxide. 5 Often the silica will be present as discrete particles, the surface of which is generally bonded via hydrogen bonds between hydroxyl groups present in the particulate material and oxide groups in the silicate, forming a composite material. 10 The volume and dimensions of the pellets will be dependent upon the end use of the pellets. For instance, pellets for steelmaking will generally be larger than pellets for DRI as in steelmaking the pellets must have sufficient mass to submerge into the molten steel. Typically pellets have an average volume in the range about 2.5 to about 25 cm3, often in the range about 3 to about 15 cm3, or about 5 to about 10 cm3. The pellets will 15 generally be sized to minimise surface area, and will often be, for instance, roughly spherical, ovoid, cylindrical or cubic structures. Unless otherwise stated, each of the integers described may be used in combination with any other integer as would be understood by the person skilled in the art. Further, 20 although all aspects of the invention preferably "comprise" the features described in relation to that aspect, it is specifically envisaged that they may "consist" or "consist essentially" of those features outlined in the claims. In addition, all terms, unless specifically defined herein, are intended to be given their commonly understood meaning in the art. 25 Further, in the discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, is to be construed as an implied statement that each intermediate value of said parameter, lying between the smaller and greater of the alternatives, is itself also 30 disclosed as a possible value for the parameter. In addition, clearly excluded, all numerical values appearing in this application are to be understood as being modified by the term "about". The term "wt%" and analogous terms is intended to mean the percentage of the component by weight in the final pellet by 35 weight. If additives, impurities, and / or water are present in the particulate starting material in step (i), the term “wt%” includes said additives, impurities and / or water. 2024219865 19 Sep 2024 Brief Description of the Drawings In order that the invention may be more readily understood, it will be described further with reference to the figures and to the specific examples hereinafter. 5 Figure 1 is a schematic diagram of a laboratory test rig for the process of the invention (iron ore test rig from ITR equipment, Poland); Figure 2 is an exploded schematic diagram of the test rig of Figure 1, focusing on the furnace; 10 Figure 3 is an XRD / SEM to show carbonate formation as a function of relative % of carbonate / silicate in the pellet. The pellet on the left of the image was cured in carbon dioxide, and is crystalline, indicating carbonate formation. The pellet on the right of the image was cured in air, and there is no indication of carbonate formation; Figure 4 is an optical microscope image 1200 x 1200 pixels, 140 magnification showing 15 carbonate formation on the surface of the left pellet of Figure 3 after partial curing; Figure 5 is an optical microscope image 1200 x 1200 pixels, 140 magnification showing the surface of the left pellet of Figure 3 after curing is complete; Figure 6 is a magnified optical microscope image of the surface of the left pellet of figure 3 showing carbonate formation on the surface; 20 Figure 7 is a graphical representation of the outcomes of Test ID No. 1 to Test ID No. 8, highlighting how the curing atmosphere and duration influence pellet cold crushing strength (CCS). Specifically, Figure 7(a) is a graphical representation of Test ID No. 1 (i.e. cured under CO2) and Test ID No. 2 (i.e. cured under air) at 200°C; Figure7(b) is a graphical representation of Test ID No. 3 (i.e. cured under CO2) and Test ID No. 4 (i.e. 25 cured under air) at 400°C; Figure 7(c) is a graphical representation of Test ID No. 5 (i.e. cured under CO2) and Test ID No. 6 (i.e. cured under air) at 600°C; and Figure 7(d) is a graphical representation of Test ID No. 7 (i.e. cured under CO2) and Test ID No. 8 (i.e. cured under air) at 800°C; and Figure 8 is a graphical representation of the cold crushing strength (CCS) of pellets 30 containing different silicates / silicate combinations under different curing conditions. The bar chart (i) on the left-hand side shows the CCS of pellets comprising solid sodium silicate (black fill), a combination of liquid sodium silicate and magnesium silicate (diagonal stripes ascending from left to right), and a combination of liquid sodium silicate and calcium silicate (horizontal stripes) when cured under air in an oven for 120 35 minutes. The bar chart (ii) on the right-hand side shows the CCS of pellets comprising solid sodium silicate (black fill), a combination of liquid sodium silicate and magnesium silicate (diagonal stripes ascending from left to right), a combination of liquid sodium silicate and calcium silicate (horizontal stripes), magnesium silicate (vertical stripes), 2024219865 19 Sep 2024 and calcium silicate (diagonal stripes descending from left to right) when cured under CO2 in the ITR rig. Detailed Description Examples The examples described herein include the formation of green iron ore pellets, which were agglomerated at ambient temperature by either a roller-press or a cylindrical die press. As used herein, the term “ambient temperature” takes its usual meaning in the art and refers to the temperature of the air surrounding a component and is often within the range 15°C - 25°C). The green pellets were cured under controlled conditions, including under a stream of CO2 gas, and various physical properties were measured. Specifically, the cold crushing strength (CCS), thermal durability, water resistance and appearance under an optical microscope was measured. Methodology Formation of Green Pellets Formation of the green pellets involves thorough mixing of iron ore particles with binder materials to form a blend. The blend is pressed into agglomerates to form the green pellets. Two methods of agglomeration (both conducted at ambient temperature) used in the examples described herein are (i) cylindrical test specimens (CTS), formed by a cylindrical die-press, and (ii) roller-pressed pellets (RPP), formed by a roller-press. (i) CTS A measured mass of iron ore particles is mixed with a binder, or binders, using a Hobart N50-G mixer, on speed setting 2, for 3 minutes. A portion of the resulting blended material is placed into a stainless-steel cylindrical die, of height 90 mm and internal diameter 20 mm, so that the material fills the die without compaction. A Baileigh Industrial H-Frame 20 Ton Shop Press (equivalent to HSP-20A) is used to push a piston down into the dye and compact the material. The pressure is 1,873 Bar (i.e. 187.3 mPa) calculated under 6 tonnes force. Specifically, pressure is applied to the piston until a force equivalent to 6 Tonnes (metric Tons) is measured. Upon reaching this value, the pressure 19 2024219865 19 Sep 2024 is immediately released. The Baileigh press is then used to push the agglomerated pellet of material from the die. This process is repeated so that a number of pellets are formed from the blended batch of material. 5 (ii) RPP The iron ore and binder formulation were mixed for 3 minutes in a Wirtgen WLM30 paddle mixer (high shear 45 rotations per minute (rpm)). Once the mixing was completed, the material was removed from the mixer and samples were produced as follows. 10 Material was fed into a hutt roller press at 160 Bar gauge pressure to produce ovoid roller pressed pellets at a size of approximately 27x18x10 mm (4.86 cm3). Pellets were transferred to the CO2 curing stage within 1 hour of production. The gas stream comprised 100% carbon dioxide at a flow rate of approximately 5 litres per minute, at atmospheric pressure. 15 The test rig synthesis is readily scalable, for instance to recycle carbon dioxide produced as off-gas in industrial processes by a suitably engineered design. Curing of Pellets (i) Curing under an air atmosphere (comparative) 20 To simulate typical curing conditions under an air atmosphere, pellets are placed on a metal tray within a vented drying oven at a specified temperature for a specified duration with no forced gas flow. 25 (ii) Curing in the presence of gaseous carbon dioxide To cure pellets under carbon dioxide, a test rig is used. Schematic diagrams of the test rig are found in Figures 1 and 2. The general procedure is as follows: 30 500 g samples of green pellets 16 were placed in the reactor 2 (such as a retort), on a bed of ceramic beads 17 and the system power modules 14 activated via the master switch 4. Gas flow through the reactor was initiated by process start button 8. Heating of the sample to the desired temperature is carried out under a flow of N2, at a rate of 5 l / min at atmospheric pressure, entering via gas inlet 3 and exiting through outlet 18. 35 Once the desired temperature is attained, the gas input is switched from N2 to CO2, at 5 2024219865 19 Sep 2024 l / min and atmospheric pressure via gas inlet 3, exiting through gas outlet 18. The temperature was controlled by the heating system, comprising heating furnace 1, heater off button 5, heater on button 6, LED indicator 7 (to indicate whether the heating furnace 1 is on or off), temperature controller 9, temperature gauge 10 and heater transformer 5 15. The on / off buttons (6 & 7) are operated manually to maintain the sample at the desired temperature. The temperature was held at 200°C, 400°C, 600°C and 800°C for residence times of 2, 5 or 10 minutes. The process was monitored using thermocouple 10, CO2 signal LED 11, N2 signal LED 12 and gas flow meter 13. As shown in Figures 1 and 2. 10 After the prescribed CO2 exposure, the samples were cooled under an inert atmosphere of N2 to prevent any further reactions. Optical Microscopy 15 Images were captured on an Olympus DSX system in bright field configuration. The scale is indicated on the illustrations. Carbonate Formation Observations were made from the microscopy images, 3-5. 20 Water Resistance Samples were immersed in water for 1 and 5 hours at ambient temperature and tested for compressive strength after drying. 25 Cold Crush Strength (CCS) The CCS values described herein were determined using standard methodology according to ISO 4700:2015 using a Mecmesin Omnitest Materials Tester 10. Results are presented with units of either kilonewton (kN) or kilogram-force (kgf). As used herein, 1 kgf = 0.00980665 kN. 30 Thermal Properties The thermal properties of the pellets were determined using standard methodology according to ISO 4696-2:2015 using the test ITR rig shown in Figures 1 and 2 below. This ISO provides a method for evaluating the degree of size degradation of iron ores under 35 conditions resembling those of a low-temperature reduction zone in a blast furnace (i.e. in a reducing environment at 550 °C). 2024219865 19 Sep 2024 Example 1 - Sodium silicate and magnetite Using the RPP methodology above, 2.0 wt% sodium metasilicate was mixed with 10 kg 5 magnetite iron ore (Dv90 = 186 pm, >97 wt% Fe3O4,>68 wt% Fe) at a temperature of 15°C. The resulting substrate mixture was formed into an agglomerate and cured at room temperature (approximately 20°C). The resulting pellets contained 2 wt% sodium metasilicate. Test data showed a partial reaction of the sodium silicate to form sodium carbonate and 10 silica, as indicated by a strength increase of roughly 50 kgf after curing for one hour. The shell was noticeably white, indicating carbonate formation, as shown in Figures 3 to 5. It would be expected that smaller pellets, of a size more typically used in industrial processes, would cure more quickly under these conditions. Example 2 - Sodium silicate, iron ore and carboxymethyl cellulose 15 Using the RPP methodology above, 10 kg magnetite iron ore (D80 = 500 pm, >97 wt% Fe3O4) and 2.0 wt% sodium metasilicate were mixed at ambient temperature. 0.25 wt% carboxymethylcellulose was then added with mixing for a further 3 minutes. The resulting substrate mixture was formed into an agglomerate. The pellets contained 2 wt% silicate and 0.25 - 0.5 wt% carboxymethyl cellulose. Curing 20 was facilitated under the test conditions described in Example 3. Example 3 - Curing with and without carbon dioxide at a range of temperatures In Test ID No. 1 to Test ID No. 8, four different curing temperatures have been used: 200°C, 400°C, 600°C and 800°C. At each temperature, curing atmospheres of air and CO2 have been used. The air curing occurred in a drying oven, while the CO2 curing took 25 place in an ITR rig, as detailed above. Under each of these conditions, samples of pellets were cured for different durations: 2 mins, 5 mins and 10 mins. In Test ID No. 1, the green pellets were cured at approximately 200°C, at atmospheric pressure, in carbon dioxide as described above. 30 In Test ID No. 2, a comparative test, the green pellets were cured at approximately 200°C, at atmospheric pressure, in air (i.e. in the absence of added carbon dioxide). 2024219865 19 Sep 2024 Test ID No. 3 to Test ID No. 8 repeated Test ID No. 1 and Test ID No. 2 at different temperatures, as shown in Table 1 below. The results are shown in Table 2, each of Test ID No. 2, Test ID No. 4, Test ID No. 6 and Test ID No. 8 are comparative. 5 Table 1 - Conditions for Test ID No. 1 to Test ID No. 8 Test ID No. Carbon Dioxide? Temperature 1 Yes 200°C 2 No 200°C 3 Yes 400°C 4 No 400°C 5 Yes 600°C 6 No 600°C 7 Yes 800°C 8 No 800°C Table 2 - Influence of curing atmosphere and duration on pellet cold crushing strength (CCS). 10 Test ID No. 1 CCS (kgf) -200°C Test ID No. 2 CCS (kgf) -200°C Test ID No. 3 CCS (kgf) -400°C Test ID No. 4 CCS (kgf) -400°C Green Strength 26.5 2 minutes 148 6 135 14 5 minutes 136 6 134 72 10 minutes 148 7 171 85 Test ID No. 5 CCS (kgf) -600°C Test ID No. 6 CCS (kgf) -600°C Test ID No. 7 CCS (kgf) -800°C Test ID No. 8 CCS (kgf) -800°C Green Strength 26.5 2 minutes 173 9 279 125 5 minutes 212 126 260 100 10 minutes 212 145 255 108 As can be seen at all temperatures, curing in the presence of carbon dioxide significantly increased the hardness of the pellet relative to the green strength (Test ID No. 1, Test ID 2024219865 19 Sep 2024 No. 3, Test ID No. 5 and Test ID No. 7) and relative to the comparative tests where the pellets are not exposed to carbon dioxide (Test ID No. 2, Test ID No. 4, Test ID No. 6 and Test ID No. 8). 5 Further, these increases are seen in very short periods of time, just two minutes, with, in many cases, little improvement being observed with longer exposure times, such that exposing the pellets to carbon dioxide for just a few minutes is sufficient to provide pellets that can be handled and transported as needed. This implies that exposing pellets to CO2 for just a few minutes is sufficient to produce pellets strong enough to be handled and 10 transported as required by the industry. This is vitally important, as pellet manufacture often occurs at the iron ore mining site and pellets must therefore be able to withstand transportation to the ironmaking site, which can be a large distance away. Further, whilst curing at 200°C provides for pellets which are sufficiently strong to meet 15 the criteria for transport and handling, if greater strength were required, the data shows that this can be obtained by increasing the curing temperature, with the highest CCS values observed for curing at 800°C. Therefore, for pellet formulations with a greater resistance to curing, additional heat could be applied. 20 As this is early-stage data, minor variances are reported which do not follow the trend and are believed to be experimental variance. For instance, in Test ID No. 1 and Test ID No. 3 the 5-minute value is lower than the 2- and 10- minute values, or Test ID No. 2, Test ID No. 4 and Test ID No. 6 where the initial results are lower than the green strength; however, it is clear that the overall trend supports this methodology leading to 25 increased strength over time. The outcomes of Test ID No. 1 to Test ID No. 8, which highlight how the curing atmosphere and duration influences pellet strength (CCS), are shown in Figures 7(a) to 7(d). 30 Example 4 - Impact of curing in carbon dioxide on water resistance The impact of CO2 curing on the water resistance of pellets was investigated on the pellets of Test ID No. 5 (10-minute exposure to carbon dioxide) and Test ID No. 6 (10-minute 35 exposure to air). The pellets of Test ID No. 5 and Test ID No. 6 were then measured for water resistance by immersion for 1 hour. The results are in Table 3 below. 2024219865 19 Sep 2024 Table 3 - Water resistance test for Test ID No. 5 and Test ID No. 6 Test ID No. Duration of Immersion Result CCS kgf 5 0 hours 212 1hr 109 6 0 hours 145 1hr 58 5 As can be seen, despite immersion in water for 1 hour, the strength of the inventive pellet (Test ID No. 5) only drops by around 50%, remaining at a CCS value that would enable transport, storage, and handling without loss of integrity. The comparative test pellet (Test ID No. 6) however, drops by roughly 60%, a much larger drop in relative strength, and to a level where there is a risk of degradation during handling. 10 Example 5 - Impact of curing in carbon dioxide on the thermal properties of the pellets The thermal properties of the pellets of Test ID No. 5 and Test ID No. 6 were determined 15 in order to confirm that there is no loss of hot strength for the pellets cured in carbon dioxide. The pellets were subjected to reduction conditions as per the RDI ISO test and subsequently tested for CCS. The results are shown in Table 4 below. Table 4 - Thermal property test for Test ID No. 5 and Test ID No. 6 20 Test ID No. CCS pre-reduction (kgf) CCS post-reduction (kgf) 5 212 146 6 145 128 These results show that whilst the expected low-level degradation occurred during this test (20 - 30%), neither test showed a significant loss in pellet strength, indicating that curing in carbon dioxide has a minimal impact on the thermal properties of the pellets. 25 2024219865 19 Sep 2024 Example 6 - Analysis of Metal Silicates Under Varied Curing Conditions This study shows the effect of curing in a CO2 atmosphere in the ITR rig for 10 mins 5 compared to curing in an air atmosphere in a drying oven for 120 mins. Moreover, this study also shows the effect of CO2 curing on different types of silicate binders (and combinations). Pellets are formulated using CMC combined with the following metal silicates / metal silicate combinations: 10 • Sodium silicate (solid) • Calcium silicate (solid) • Magnesium silicate (solid) • Magnesium silicate (solid) with sodium silicate (liquid) • Calcium silicate (solid) with sodium silicate (liquid) 15 Details of pellet formulations are shown in Table 5. Pellets were formed by the CTS method detailed above and cured (i) at 150°C under air in a drying oven or (ii) at the same temperature under CO2 in the ITR rig. Details of curing conditions are shown in Table 5. 20 Cured pellets were tested for CCS, and the results are shown in Table 5 and Figure 8. As is evident from the data, the CCS of the pellets cured under CO2 for 10 mins at 150°C in the ITR rig is greater than that of comparative pellets cured for 120 mins at 150°C in the drying oven. Therefore, this example provides evidence for the increase in CCS brought 25 about by use of the process according to the first aspect of the invention, and also illustrates the speed at which this benefit is attained (10 mins versus 120 mins). Acceleration of the curing process is advantageous, as it not only increases pellet production efficiency, but also reduces operational costs. 30 As can be seen from the results, sodium silicate produces the best-performing pellets. Calcium silicate and magnesium silicate perform poorly on their own when cured in air. However, when using the process according to the invention, pellets formed with calcium silicate and with magnesium silicate as the metal silicate showed a clear improvement in CCS when produced according to the process of the first aspect of the invention. 35 Moreover, surprisingly magnesium silicate when combined with liquid sodium silicate produced strong pellets. 2024219865 19 Sep 2024 This study shows the effect of curing at 150°C in a CO2 atmosphere in the ITR rig for 10 minutes and curing at 150°C in an air atmosphere in a drying oven for 120 minutes on the structural integrity of pellets. The results are shown below in Table 6. 5 As can be seen from the results tabulated below, pellets produced according to the process according to the first aspect of the invention are cured in a significantly shorter time. Shorter curing times have key benefits, such as high energy savings and increased production efficiency. In addition, pellets produced according to the process according to the first aspect of the invention have a lower RDI%. A low RDI% is a key indicator of 10 high-quality pellets that can withstand the demanding conditions of iron-making processes, leading to improved efficiency and productivity. Pellets fabricated according to the process according to the first aspect of the invention are therefore less likely to break down and have better structural integrity. Moreover, lower degradation is advantageous as it means that less dust and fines will be generated during reduction, minimising 15 material loss and reducing the risk of operational issues related to dust accumulation. Table 6 - RDI% values for Test ID No. 17-20 Test ID No. 17 Test ID No. 18 Pellet Formulation CMC (0.5%) + sodium silicate (2%) CMC (0.5%) + sodium silicate (2%) Curing Method Oven ITR rig Curing Conditions air CO2 Curing Temperature / °C 150 150 Curing Duration / mins 120 10 RDI % 6.4 5.4 Test ID No. 19 Test ID No. 20 Pellet Formulation CMC (0.5%) + magnesium silicate (2%) + sodium silicate (2.5%) CMC (0.5%) + magnesium silicate (2%) + sodium silicate (2.5%) Curing Method Oven ITR rig Curing Conditions air CO2 Curing Temperature / °C 150 150 Curing Duration / mins 120 10 RDI % 61.9 19.3 20 2024219865 19 Sep 2024 Example 8 - Comparison Between CMC and Polysaccharide Binders This study investigates the difference between CMC and a polysaccharide when used as 5 binders in pellets cured under CO2 in a process according to the invention. A batch of pellets (ID No. 21) was created and cured according to test ID No. 12, but instead including a polysaccharide in place of CMC as the binder. The polysaccharide was present at 0.25 wt%. The polysaccharide used in this example was a starch from Cargill USA. 10 The CCS of each batch of pellets was tested, and the results are shown in Table 7. The CCS of the pellets formulated with polysaccharide as a binder are lower than that of the pellets formulated with CMC as a binder. Whilst the CCS of the pellets which comprise a polysaccharide binder are viable for iron 15 ore pellets, this example illustrates that when the binder is a cellulosic material such as CMC, the CCS is notably higher when formed using the process according to the invention. Table 7: Pellet formulations used in Example 5, with CCS results. Test ID No. CMC / wt% Polysaccharide / wt% Na silicate / wt% Curing Duration / mins Curing method Curing Atmos. CCS / kN 12 0.25 - 2.00 10 ITR rig CO2 4.67 13 - 0.25 2.00 10 ITR rig CO2 3.50 20 It would be appreciated that the process and apparatus of the invention are capable of being implemented in a variety of ways, only a few of which have been illustrated and described above. 25 Unless the context requires otherwise, where the terms “comprise”, “comprises”, “comprised” or “comprising” are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components, or group thereof.
Claims
1. A process for producing a pellet, the process comprising:10(i) providing particulate material selected from a carbonaceous material, metal, metal ore, and mixtures thereof; an inorganic binder comprising a metal silicate, and an organic binder, wherein the organic binder comprises a natural polymer, a synthetic polymer, a glycerolipid, a cellulosic material, and combinations thereof, to form a mixture;(ii) compressing the mixture to form a pellet; and(iii) curing the pellet by contacting the pellet with gaseous carbon dioxide.
2. A process according to claim 1, wherein the hydraulic pressure applied in step (ii) is applied using a roller pressing process (RPP) in the range 50 Bar to 300 Bar.15 3. A process according to claim 1 or claim 2, wherein the pressure applied in step (ii)is applied using a cold-pressing technique (CTS) using a 10 mm die, wherein the pressure applied is in the range 6000 Bar to 8000 Bar calculated under 6 tonnes force; or wherein the pressure applied in step (ii) is applied using a cold-pressing technique (CTS) using a 16 mm die, wherein the pressure applied is in the range20 2000 Bar to 5000 Bar calculated under 6 tonnes force; or wherein the pressureapplied in step (ii) is applied using a cold-pressing technique (CTS) using a 20 mm die, wherein the pressure applied is in the range 800 Bar to 3500 Bar calculated under 6 tonnes force.25 4. A process according to any preceding claim, wherein the carbon dioxide of step (iii)is carbon dioxide generated from one or more industrial processes.
5. A process according to any preceding claim, further comprising the additional step of capturing carbon dioxide generated from one or more industrial processes for use 30 in step (iii).
6. A process according to any proceeding claim, wherein step (iii) additionally comprises application of heat at a temperature in the range 50°C to 1000°C.35 7. A process according to claim 6, wherein the application of heat comprises applicationof heat generated from one or more industrial processes.2024219865 17 Oct 20258. A process according to any preceding claim, wherein curing the pellet in step (iii)takes place at atmospheric pressure.
9. A process according to any one of claims 1 to 8, wherein curing the pellet in step5 (iii) takes place at a pressure in the range 1 Bar to 3 Bar.
10. A process according to any preceding claim, wherein the particulate material isadded in an amount of about 70 wt% to about 99.9 wt% of the mixture of step (i).10 11. A process according to any preceding claim, wherein the particulate materialcomprises a metal ore, a metal, and combinations thereof, optionally wherein the particulate material comprises iron.
12. A process according to any one of claims 1 to 10, wherein the particulate material 15 comprises a carbonaceous material.
13. A process according to any preceding claim, wherein the particulate material has a moisture content of less than 25%.20 14. A process according to any preceding claim, wherein the metal silicate is present inthe mixture in the range 0.5 wt% to 5 wt% of the mixture.
15. A process according to any preceding claim, wherein the metal silicate comprises a group I or group II metal silicate, optionally wherein the metal silicate is25 selected from sodium silicate (Na2SiO3), calcium silicate (CaSiO3, Ca2SiO4),potassium silicate (K2SiO3), magnesium silicate (MgSiO4), and combinations thereof.
16. A process according to claim 15, wherein the metal silicate is selected from sodium 30 silicate, magnesium silicate, and combinations thereof; or wherein the metal silicateis selected from potassium silicate, magnesium silicate, and combinations thereof.
17. A process according to any preceding claim, wherein the organic binder is present in the mixture in the range 0.2 wt% to 5 wt% of the mixture.3518. A process according to any preceding claim, wherein the organic binder comprises a polyacrylamide resin, a phenol formaldehyde resin, a polyacrylic, a styreneacrylate polymer, cellulosic fibres, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxyethyl methyl cellulose (MHEC), glyceryl triacetate, glyceryl2024219865 17 Oct 2025diacetate, polyvinyl alcohol, and combinations thereof, preferably wherein the organic binder comprises a polyacrylamide resin, a phenol formaldehyde resin, cellulosic fibres, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxyethyl methyl cellulose (MHEC), polyvinyl alcohol, glyceryl triacetate, and 5 combinations thereof, more preferably wherein the organic binder comprises frompolyacrylamide resin, cellulosic fibres, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), and combinations thereof, most preferably wherein the organic binder comprises carboxymethyl cellulose (CMC), cellulosic fibres, hydroxyethyl methyl cellulose (MHEC), and combinations thereof.1019. A process according to claim 18, wherein the organic binder comprises carboxymethyl cellulose (CMC).
20. A process according to claim 18, wherein the organic binder comprises polyvinyl15 alcohol.
21. A process according to any preceding claim, wherein the organic binder is ofviscosity in the range 3,000 to 16,000MPa-s.20 22. A process according to any preceding claim, further comprising the addition of aflux additive to the mixture.
23. A process according to claim 22, wherein the flux additive is selected from silica, dolomite, fluorite, calcium oxide, magnesium oxide, carbon, aluminium, dunnite, 25 basalt, and combinations thereof; optionally wherein the flux additive is selectedfluorite, aluminium, dunnite, basalt and combinations thereof.
24. A process according to any preceding claim, wherein curing of the pellet by contacting the pellet with gaseous carbon dioxide occurs by introducing the pellets30 into a gas stream comprising carbon dioxide at a flow rate in the range 1 to 100litres per minute.
25. A pellet obtainable by a process according to any preceding claim.35 26. A pellet comprising a particulate material selected from a carbonaceous material,metal, metal ore, and mixtures thereof; silica; and a metal carbonate, and an organic binder, wherein the organic binder comprises a natural polymer, a synthetic polymer, a glycerolipid, a cellulosic material, and combinations thereof.2024219865 17 Oct 202527. A pellet according to claim 26, wherein the metal carbonate is formed by reaction with an inorganic binder comprising a metal silicate and gaseous carbon dioxide.