TECHNICAL FIELD
The present disclosure relates to the field of processing of ore fines. Particularly, the present disclosure relates to a method for preparing bentonite in a slurry form for agglomeration of ore fines to obtain ore pellets. The disclosure also relates to a method for agglomeration of ore fines by adding the bentonite slurry.
BACKGROUND OF THE DISCLOSURE
Metal industry processes metal ores to prepare agglomerates such as indurated (heat-hardened) agglomerates or cold bonded agglomerates for smelting operations. For example, manganese ores, chromite ore, iron ores are ground to a desired particle size and agglomerated to produce agglomerates in the form of heat hardened sinter, pellets, or cold bonded briquettes, pellets, extrusion products, etc. These agglomerates are charged into a furnace for smelting. During the production of agglomerates, powder bentonite is used as a binder. The powder bentonite is produced in a grinding plant where raw lump bentonite is subjected to drying and grinding for producing powder bentonite with a preferred size of 80% passing 45 microns.
Bentonite is the most-used binder in agglomeration processes of ferrous and non-ferrous fines because of its advantageous properties over other inorganic and organic binders and their combinations. Bentonite absorbs water to form a semi-solid gel with a strong hydrostatic pressure difference. Initially, it allows only water molecules to pass through and after becoming saturated it repels the water molecule. Powder bentonite is mixed with ore fines, other additives and water to prepare wet ore pellets (also referred to as “green” pellets) which are subsequently dried and fired to provide dry ore pellets. The bentonite binder composed of silicate materials exhibits enough binding properties that tightly bind the ore fines and additives particles in green pellet form with more similarity in the size distribution of all green pellets. Bentonite, being a clay type binder, has a good swelling property. It has a property of absorbing water and subsequent expansion. Sodium bentonite has good swelling properties due to the presence of sodium cation that allows water penetration. Bentonite has strong hygroscopicity and expandability and can absorb water as much as eight to 15 times its dry mass. Because of the water absorption capacity of bentonite, it is very useful in controlling the green balling/briquetting operation (formation of wet pellets) during the agglomeration of fines and powders. Moreover, Bentonite also controls the drying rate during subsequent treatment of such agglomerates. This property of bentonite provides said agglomerates enough shock

strength during drying and as a result, unfired agglomerate burst less and do not suffer from excess or uncontrolled fines generation during drying and preheating operation.
Although Bentonite provides several advantages as a binder in agglomeration processes, it has certain limitations. One of the main limitations is that the efficiency of binding exhibited by bentonite depends on the extent of absorption of water and bentonite absorbs water slowly.
The binding mechanism of bentonite involves: (1) bentonite, in powdered form, is mixed with fines/powders of different raw materials. For example, bentonite is mixed with ground iron ore for preparing iron ore pellets; (2) water is added to the mixture of ground ore and bentonite; (3) bentonite absorbs moisture and swells; (4) due to shearing action of different mixing equipment, plates or layers of swelled bentonite move over grains of fines to be agglomerated and forms a film; and (5) the bentonite films over particles of ore fines hold the particles together to provide strength thereby providing wet/green agglomerates. Additionally, when the green agglomerate is subjected to drying, these films get dried, and strength is achieved by the dried agglomerate.
In the above-mentioned mechanism, the step of absorption of water by bentonite is kinetically un-favorable. Therefore, bentonite takes more time to get fully hydrated. If the bentonite does not absorb enough water, it does not swell to its maximum value and hence its plates or layers will not undergo maximum shearing to cover grains of materials to be agglomerated. For improving the kinetics of water absorption, swelling, as well as reducing the cost of processing of bentonite, very limited work has been reported.
U.S. Patent No. 3,258,327 discloses a binder mixture comprising 1 to 5% bentonite with the remaining mixture comprising kaolinite clay, partially degraded illite clay and chlorite clay. This clay mixture is mixed with grounded iron ore in an amount of 0.25 to 5 % by weight based on the weight of the iron ore. The document is directed to decreasing the amount of bentonite added while maintaining the ratio of CaO+MgO to SiO2 in the range of 1 -1.5% by adding other clays. This document is completely silent on the kinetics of water absorption, the kinetics of bentonite swelling after the absorption of water, maximum utilization of swelling property of bentonite, increasing the binding efficiency of bentonite, or improving the spread of bentonite over matrix material.

PCT Publication No. WO2009109024A1 discloses preparation of iron ore pellets by mixing finely ground iron ore and a binder mixture. The binder mixture comprises 30 - 80 % by weight of bentonite and 10 - 30 % by weight of molasses. The publication further discloses addition of an organic binder selected from an anionic polyacrylamide, synthetic polymers derived from natural cellulosic polysaccharides or from modified starches, from alkaline metal carbonates and bicarbonates, from soluble alkaline metals hydroxides or mixtures thereof. This document is completely silent on the kinetics of water absorption and swelling of bentonite, maximum utilization of swelling property of bentonite, increasing the binding efficiency of bentonite, or improving the spread of bentonite over matrix material.
U.S. Patent No. 3,779,782 discloses combining and mixing wet bentonite in a stockpile with soda ash, the moisture in the wet bentonite bringing about reaction to form an improved binder after a suitable aging period. The document is directed to the processing of lump bentonite for producing sodium activated bentonite. Sodium activation is known to improve the swelling behavior of bentonite; however, the art is silent on the kinetics of water absorption, the kinetics of bentonite swelling by water absorption, maximum utilization or percentage of realization of swelling property of bentonite, increasing the binding efficiency of bentonite or improving the spread of bentonite over matrix material.
CN102816926A discloses a binder comprising 90-100 parts of bentonite, 3-5 parts of alkali, and 1-3 parts of cellulose ethers or cellulose sodium. This document is also directed to the production of sodium activated bentonite comprising organic binders and is silent on the kinetics of water absorption by bentonite, its swelling and the related aspects.
A few studies have explored the surface modification of bentonite. US5,292,908 discloses surface modification of bentonite to make it dispersible in water or organic liquids for adjusting rheology. US5,491,248 discloses bentonite prepared by adsorption of alkyl-substituted silane compound onto bentonite particles. These documents are directed to surface modification of bentonite but are silent on its function as a binder in agglomeration processes such as pelletization, sintering, briquetting, extrusion, etc. of iron ore, chromite fines, manganese fines, and other ferrous and non-ferrous fines and waste by-products.
US5,426,079 is directed to a method of improving water-swellable clay properties by re-drying. The method disclosed herein comprises drying and grinding lump bentonite to obtain powder

bentonite, adding water to powder bentonite, and again drying and grinding this wet or moistened bentonite to powder form.
CN103397178A discloses a method of producing a bentonite containing slurry comprising carboxy-methyl cellulose and powder bentonite. Here, a composite binder comprising bentonite powder and CMC is prepared by mixing and grinding. The composite binder, bentonite and water are mixed to produce bentonite slurry which is used in pellet making. The disadvantage of this method is that it requires addition of carboxy methyl cellulose (CMC) into the bentonite-based slurry which is costly and the additional step of mixing and grinding CMC and bentonite to produce composite binder further increases the cost. The method is applicable solely to powdered bentonite.
RU2628947C1 describes a method where bentonite-based pulp is fed through pneumatic nozzles to prepare sinter charge material. The document teaches addition of a polymer, sodium carbonate, sodium chloride, or calcium oxide to bentonite-based pulp as a bentonite activator. The method is applicable solely to powdered bentonite.
CN109136546A is directed to beneficiation of bentonite. The method comprises sodiumization of bentonite and addition of glucose and CMC to the bentonite. Further, bentonite processed in this manner is dried and ground to provide powder bentonite which is used in pellet making.
CN103525384B discloses a process of making bentonite slurry for application in horizontal drilling process. This process is not applicable to ore pelletization. Further, the method is only applicable to ground powdered bentonite.
CN1843910A discloses a method for preparing a bentonite-based grout. A suspension of bentonite is prepared, sodiumized, and the suspension is processed to form grout. The process is not applicable to ore pelletization.
SU1664833A1 describes a method to produce bentonite suspension for application in the food industry and wine-making industry. The methods described here are not applicable to ore pelletization.

There is a need in the art for a method of processing bentonite for making ore pellets where the swelling property of bentonite is exploited to increase the binding efficiency of bentonite to obtain improved ore pellets. The present disclosure attempts to address this need.
STATEMENT OF THE DISCLOSURE
The present disclosure relates to a method for preparing a bentonite slurry, comprising soaking
bentonite in water for about 2 hours or more and stirring the water to obtain a bentonite slurry.
The present disclosure also related to a method for preparing ore pellets, comprising: a) preparing an ore composition comprising ore fines, a carbonaceous agent, and a fluxing agent; b) preparing the bentonite slurry as described herein; c) mixing the ore composition, the bentonite slurry, and water to obtain a pellet mix; and d) pelletizing the pellet mix to obtain ore pellets.
The methods for preparing ore pellets described herein increase a green compressive strength (GCS) of wet unfired pellets by about 5-20%; decreases bursting of wet unfired pellets upon thermal shock test by about 3-10%; and/or increases strength of wet unfired pellets upon thermal shock test by about 10-25% compared to those obtained from using powder bentonite.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1 shows an exemplary schematic of the structure of bentonite prior to addition of water
and its behaviour upon addition of water followed by application of shearing forces.
Figure 2 shows a conventional method of processing lump bentonite to prepare powder bentonite and a method of making ore pellets by adding powder bentonite.
Figure 3 shows a schematic of the present disclosure’s method of processing lump or powder bentonite to prepare a bentonite slurry and a method of making ore pellets by adding the bentonite slurry.
Figure 4 shows an exemplary preparation of slurry bentonite according to the methods of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE
With respect to the use of any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results. Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising” or “containing” or “has” or “having” wherever used, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
Reference throughout this specification to “some embodiments”, “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment may be included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases “in some embodiments”, “in one embodiment” or “in an embodiment” in various places throughout this specification may not necessarily all refer to the same embodiment. It is appreciated that certain features of the disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.
The term “about” as used herein encompasses variations of +/-10% and more preferably +/-5%, as such variations are appropriate for practicing the present invention.
For smelting of ores in a furnace, ores are prepared in the form of pellets. To prepare ore pellets, ores are ground to a desired size to provide ore fines which are mixed with a binder and other additives such as carbonaceous materials and fluxing agents and the mixture is pelletized. The ore pellets are charged in a furnace for smelting. Bentonite is the most used binder for preparing ore pellets.
Raw bentonite is available in a lump form. However, lump bentonite cannot be used directly for pellet making as it does not form a uniform pellet mixture. Therefore, lump bentonite is

dried and ground to form powder bentonite of desired particle size which is then used for pellet making. Thus, in the conventional method of pellet making, bentonite is added in a powder form to ore fines to prepare ore pellets. The present disclosure provides a method for preparing a slurry bentonite and employs the slurry bentonite for pellet preparation.
There have been prior studies where bentonite is prepared in a slurry form; however, in these studies, surfactants or agents that modify the surface structure/properties of bentonite are also added to the slurry. Prior studies employ surfactants or surface-modifying agents to prepare slurry bentonite because bentonite forms lumps when water is added to it. That is, a homogenous or uniform slurry of bentonite is not immediately obtained by addition of water to bentonite. Addition of surfactants or surface-modifying agents facilitates formation of a uniform/homogenous slurry of bentonite by reducing surface tension and thereby breaking bentonite lumps formed by addition of water. One such agent used in prior studies to prepare slurry bentonite is carboxy methyl cellulose (CMC). CMC is very costly and needs pre¬processing such as grinding to a desired size, etc. Thus, prior methods for preparing bentonite slurry are costly due to addition of other agents and involve pre-processing steps. Further, bentonite slurries containing surfactants, surface-modifying agents, or other additives may not be suitable for preparing ore pellets as these additional agents could have undesirable effects on pellet properties or in the downstream processing furnaces.
The present disclosure provides a method for preparing a bentonite slurry, where lump or powder bentonite is soaked in enough water for a sufficient amount of time allowing swelling of bentonite. By allowing soaking of bentonite in enough water for sufficient duration, addition of surfactants or surface modifying agents is not required in the present invention. Bentonite soaked in enough water for sufficient time swells. The swelled bentonite settles at the bottom of the water which upon stirring the water forms a homogenous solution or a slurry. Further advantage of the present method is that lump as well as powder bentonite can be used to prepare the slurry. As discussed above, raw bentonite is present in lump forms and needs to be dried and ground to a powder form for its use in pellet making. In the present method, raw lump bentonite can be used directly without drying and grinding to prepare a slurry. Thus, the present method reduces pre-processing of bentonite and the costs associated with it.
A method for preparing a bentonite slurry according to the present disclosure comprises soaking bentonite in water for about 2 hours or more and stirring the water to obtain a bentonite

slurry. Bentonite used for preparing the slurry can be in lump form or powder form. In some embodiments, the lump bentonite has a size of about minus 15 mm and more preferably about minus 5 mm. In some embodiments, the lump bentonite has a size of about minus 15 mm to about minus 5 mm, including values and ranges thereof.
In some embodiments, bentonite is soaked in water at a concentration of about 25% by weight or lower. For example, in some embodiments, about 25%, 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% by weight, including values and ranges thereof, of bentonite is soaked in water for about 2 hours or more.
In some embodiments, about 12.5%, 11.5%, 10.5%, 9.5%, 8.5%, 7.5%, 6.5%, 5.5%, 4.5%, 3.5%, 2.5%, or 1.5% by weight of bentonite is soaked in water for about 2 hours or more. In an exemplary embodiment, about 12.5% by weight of bentonite is soaked in water for about 2 hours or more.
In some embodiments, desired amount of bentonite is soaked in water for about 1-2 hours, 1.5-2.5 hours, or 2-3 hours. Preferably, bentonite is soaked in water for about 2 hours.
After soaking of bentonite in water for desired duration, water is stirred at a rate of about 10-60 rpm for about 2-5 minutes to obtain the bentonite slurry. In some embodiments, water is stirred at a rate of about 10-50, 10-40, 10-30, 10-25, 10-20, 20-60, 20-50, 20-40, 20-30, 25-60, 25-50, 25-45, 30-60, or 30-50 rpm for about 2, 3, 4, or 5 minutes to obtain the slurry bentonite.
The bentonite slurry prepared in the manner described above is employed for preparing ore pellets. The slurry comprises fully hydrated and swelled bentonite which acts as a binder for agglomeration of ground ore (ore fines) to prepare ore pellets.
In the conventional method of preparing ore pellets, ore fines are agglomerated using bentonite as a binder, wherein bentonite is used in a powder form. To produce this powdered bentonite, raw lump bentonite is dried and ground in grinding plants dedicated solely to grinding bentonite. The powdered bentonite is produced which has a preferred size of 80% passing 45 microns. Coarser particles above this passing size are not preferred due to poor binding property compared to finer bentonite. The powdered bentonite is mixed with ore fines and other

additives to be agglomerated in a mixer. Water is also added to the same mixer. Upon addition of water, ore fines, additives, and powdered bentonite form a wet mixture which is transported to agglomerating/pelletizing units such as disc, drums, briquetting press, extrusion, etc. However, during this wet mix formation, very little time is given to bentonite to swell completely before application of shear forces by the mixing equipment. The less time for absorbing water results in less swelling of bentonite and hence less shearing of bentonite layers or plates to form a film effectively over particles of ore fines to be agglomerated. It is impractical to increase the time for water absorption before shearing in a real plant operation as bentonite can take as much as 24 hours to completely swell when present in a mixture with ore fines. In the laboratory, a swelling test was conducted by leaving bentonite in water for 24 hr-ASTM-D5890. When the agglomerate body produced by such bentonite was tested for mechanical strength and thermal shock resistance, said agglomerate body was expected to be of lower strength because of the inefficient coating of grains by bentonite. Thus, allowing longer times for bentonite to swell in a mixture of ore fines, additives, and bentonite may not provide desired results.
The present disclosure provides a method where a bentonite slurry is employed to prepare ore pellets. The method for preparing ore pellets according to the present disclosure comprises: a) preparing an ore composition comprising ore fines, a carbonaceous agent, and a fluxing agent; b) preparing a bentonite slurry by soaking bentonite in water for about 2 hours or more and stirring the water to obtain the bentonite slurry; c) mixing the ore composition, the bentonite slurry, and water to obtain a pellet mix; and d) pelletizing the pellet mix to obtain ore pellets.
In the present method for preparing ore pellets, an ore composition is prepared by mixing ore fines, a carbonaceous agent, and a fluxing agent. Unlike prior art methods, bentonite in powder form is not added to the ore composition. Instead, a bentonite slurry is prepared as described herein and the bentonite slurry is mixed with the ore composition. Specifically, the ore composition is added to a mixing equipment (mixer). The bentonite slurry is added to said mixing equipment. Water is added to said mixing equipment (i.e., in addition to the water present in the bentonite slurry, extra water is added to the mixing equipment) to obtain a pellet mix with a desired moisture level. The pellet mix comprising the ore composition, the bentonite slurry and water is mixed in said mixing equipment for a period of 1-4 minutes.

In the conventional method, when powder bentonite is added to fines and water is added, powder bentonite needs time for absorbing water and swelling followed by shearing of bentonite layers onto ore fines which are being agglomerated. However, since time required for swelling of bentonite is more, providing this time is not practical in an industrial plant setting due to productivity concerns. When bentonite is added in the form of a pre-swelled slurry as described herein, it does not need further time in the mixing equipment for absorbing water and swelling. The pre-swelled bentonite immediately starts coating the surfaces of fines and dust which are being agglomerated. Since bentonite is swelled significantly more in the pre-swelling step, its layers or plates also get sheared more due to the action of the mixing equipment. The more the shearing of bentonite plates, the more is the surface area of ore fines being covered by bentonite and hence better binding. Thus, the use of slurry bentonite improves the efficiency of binding without compromising time in the mixing equipment. Further, if the slurry is produced by soaking lump bentonite, it eliminates pre-processing steps of drying and grinding bentonite lumps and eliminates the cost associated with it (almost 20% of the powder bentonite cost is attributable to the drying and grinding of lump bentonite).
The mechanism of binding of bentonite, how it changes with the changes in processing conditions, and advantages of the methods of the present disclosure over conventional methods using powder bentonite are discussed below.
Bentonite is a natural smectite clay that forms a colloidal structure in water-borne or solvent-based systems. Each particle of bentonite is composed of thousands of sub-microscopic platelets. These are stacked with a layer of water or organic molecules in between - similar to a sandwich. Figure 1(a) shows a schematic of the bentonite platelets stacked over one another. It shows bentonite platelets stacked or layered over one another with exchangeable cations in between two layers. Figure 1(b) shows the addition of water to the bentonite molecules. In this figure, water molecules are trying to enter the space between two layers of bentonite wherein exchangeable cations are present. Figure 1(c) shows swelled bentonite due to absorption of water with bentonite platelets being relatively far from each other as compared to those in Fig. 1(a) and 1(b). This figure also shows exchangeable cations and absorbed water molecules in between bentonite platelets. Once the swelled bentonite is subjected to any shearing force (such as during mixing of bentonite with ore fines to be agglomerated), platelets of swelled bentonite slide over each other and spread to relatively much larger distance (such as in Fig. 1(d)). These platelets provide the bonding strength to the unfired wet agglomerates (these are sometimes

referred to as “green” agglomerates, e.g., green pellets) such as green pellets, granules, extrusion products, briquettes, etc. Once these agglomerates are dried, these platelets further provide bonding strength due to drying of the film. Moreover, during drying, bentonite controls the rate of drying so that the green agglomerates do not burst to generate excess fines. During the firing of these agglomerates, bentonite further provides strength due to the formation of silicate melt/bonds. This is the mechanism of binding of bentonite; however, during the large-scale operation for making bentonite-based agglomerates, favourable conditions are not met for bentonite to function properly as discussed below with the help of Figure 2.
Figure 2 shows the conventional method of bentonite processing where ferrous and non-ferrous fines are agglomerated using powder bentonite. Fig. 2(a) shows the processing of lump bentonite. The lump bentonite is dried to reduce the moisture level (generally below 12%) to make it suitable for grinding. The dried bentonite is then ground to produce powder bentonite. The size of the powder bentonite is generally 80% passing 45 microns so that it works as a better binder compared to any coarser size bentonite. However, due to inefficiencies in the grinding process, powder bentonites are sometimes coarser also such as 60 or even less % passing 45 microns. Figure 2(b) shows the application of powdered bentonite in the agglomeration process. It shows that powder bentonite, fines (which need to be agglomerated), and water are added into mixer equipment simultaneously for mixing. Due to the simultaneous addition of water along with bentonite and fines, water is absorbed by both fines and bentonite. This causes a lower availability of water for bentonite to cause its swelling. Further, the industrial units or plants (where bentonite is used as a binder for agglomeration of fines) are generally very high-capacity plants such as 60-600 TPH which means that the whole mass of water, fines, and bentonite resides inside the mixing equipment for a very short duration such as a few minutes or seconds only. In such a short time, bentonite is not able to absorb enough water for swelling as water absorption by bentonite is a slow process. Since the water absorption is not complete (in the mixing step of Fig. 2(b)), therefore, swelling of bentonite is also not adequate. Figure 1(b) and 1(c) show that water absorption and swelling of bentonite is a necessary step so that platelets of bentonite can undergo effective shearing (as shown in Fig. 1(d)) to cover the grains or particles of fines/powders which need to be agglomerated. Since the swelling of bentonite in the mixture is not adequate (due to less time available for swelling) in the process of Figure 2(b), therefore its platelets do not get sheared to cover more surface area of particles (during the mixing step of Figure 2(b)) which are under agglomeration. Hence, the strength provided by such bentonite to said agglomerates is inferior to what it can provide

if the properties of bentonite such as its swelling and shearing of platelets are exploited or utilized to its maximum. This results in lower strength of wet agglomerates, dry agglomerates, and most importantly, lower shock strength when subjected to thermal drying operation.
Figure 3 shows the method of the present disclosure for processing of bentonite and how it is employed in the agglomeration of fines. Figure 3(a) shows that lump bentonite is dried, the dried bentonite (with a desired level of moisture) is subjected to grinding. The ground bentonite with a preferable size of 80% passing 45 microns is added to a water reservoir at a concentration of 12.5% by weight or low. The bentonite is allowed to soak in the water for a minimum of 2 hours during which it absorbs moisture and subsequently swells. This swelled bentonite is mechanically stirred in the water to form a bentonite slurry. Fig. 3(b) shows one more route of processing bentonite wherein even grinding of lump bentonite is not required for it to be used as a binder in the agglomeration of fines. In Fig. 3(b), instead of powder bentonite (such as in Fig 3(a)), lump bentonite is added directly to the water tank or reservoir at a concentration of 12.5% or lower by weight of the mixture of water and bentonite. It is then allowed to soak in the water for a minimum of 2 hours during which it absorbs moisture. During moisture absorption, lump bentonite swells enough so that when mechanically stirred it gets dissolved in water to form a slurry. Hence both the processing routes (shown in Fig. 3(a) and 3(b)) enable the production of bentonite slurry with that shown in 3(b) being even more cost-effective due to elimination of drying and grinding steps and associated cost. Bentonite slurries formed by methods shown in Fig. 3(a) and/or 3(b) are employed in the agglomeration of fines.
Figure 3(c) shows the addition of slurry bentonite in the agglomeration process. It shows that bentonite in the form of a slurry prepared as described herein, ferrous or non-ferrous ore fines (which need to be agglomerated), and water are added into mixer equipment simultaneously for mixing. During this process, any supplementary water, if required, is added to the mixer, otherwise, the majority of the water comes with bentonite slurry itself. Since the bentonite in the bentonite slurry is already swelled sufficiently due to absorbing enough water, bentonite in this method of ore pelletization is not deficient in water. As noted earlier, the industrial units or plants where bentonite is employed as a binder for agglomeration of fines, are generally very high-capacity plants such as 60-600 TPH which means that the mixture of water, ore fines, other additives and bentonite resides inside the mixing equipment for a very short duration such as a few minutes or seconds only. In such a short time, powder bentonite is not able to absorb enough water for swelling, however, slurry bentonite already contains pre-wet and pre-swelled

bentonite by providing sufficient time for water absorption prior to its addition to the mixing equipment (as shown in Fig. 3a and 3b). The water absorption by bentonite is a slow process, therefore, this step becomes inefficient when powder bentonite is mixed with ore fines and water for a short duration as done in the conventional method. However, as shown in Fig 3c, the addition of pre-swelled bentonite overcomes this drawback associated with the use of powder bentonite as a binder in the agglomeration of fines. Pre-absorption of water by bentonite (as shown in Fig. 3a and 3b) results in pre-swelling of bentonite. Figure 1(b) and 1(c) show that water absorption and swelling of bentonite is important so that platelets of bentonite can undergo shearing (as shown in Fig. 1(d)) to cover the grains or particles of ore fines/ore powders that need to be agglomerated. Since pre-swelled bentonite is added in the method of the present disclosure shown in Figure 3, its platelets get sheared effectively to cover more surface area of particles (during the mixing step of Figure 3(b)) under agglomeration. Hence, the strength of ore pellets/agglomerates prepared by employing the slurry bentonite is significantly more than those produced using by mixing powder bentonite with ore fines. The addition of slurry bentonite in the method of pelletizing ores results in better strength of wet agglomerates, dried agglomerates, and most importantly, significantly better shock strength when subjected to thermal drying operation. In the method depicted in Figure 3, the steps in bentonite binding mechanism shown in Fig. 1(b) and 1(c) occur prior to mixing of bentonite with ore fines. This effectively increases the time of mixing available for the step shown in Fig. 1(d) where, due to the shearing action of mixing devices/equipment, bentonite is sheared to cover grains/particles of ore fines/powder thereby binding these ore fines.
The method for preparing ore pellets by adding bentonite slurry as described herein can be employed to make pellets of ferrous as well as non-ferrous ores. For example, in some embodiments, the method for preparing ore pellets by adding bentonite slurry comprises mixing bentonite slurry with ore fines such as iron ore fines, chromite ore fines, or manganese ore fines.
Accordingly, in some embodiments, provided herein is a method for preparing ore pellets, said method comprising: a) preparing an ore composition comprising a carbonaceous agent, a fluxing agent, and ore fines selected from iron ore fines, chromite ore fines, or manganese ore fines; b) preparing a bentonite slurry as described herein; c) mixing the ore composition, the bentonite slurry, and water to obtain a pellet mix; and d) pelletizing the pellet mix to obtain ore pellets. In some embodiment, the step of mixing of the ore composition, the bentonite slurry,

and water to obtain the pellet mix comprises a) adding the ore composition to a mixer; b) adding the bentonite slurry to said mixer; c) adding water to said mixer to obtain the pellet mix; and d) mixing the pellet mix in said mixer for a period of 1-4 minutes.
In some embodiments, the ore fines are powder fines or crushed fines. In some embodiments, the crushed ore fines have a size less than 10 mm.
In some embodiments, provided herein is a method for preparing iron ore pellets, said method comprising: a) preparing an iron ore composition comprising a carbonaceous agent, a fluxing agent, and iron ore fines selected from hematite fines, goethite fines, and/or magnetite fines; b) preparing a bentonite slurry as described herein; c) mixing the ore composition, the bentonite slurry, and water to obtain a pellet mix; and d) pelletizing the pellet mix to obtain ore pellets.
In some embodiments, the carbonaceous agent is selected from the group consisting of coke, coal, a carbonaceous material such as soot, and a combination thereof.
In some embodiments, the fluxing agent is selected from the group consisting of pyroxenite flux, olivine flux, lime, dolomite, and a combination thereof.
The present methods for preparing ore pellets by adding a bentonite slurry provide many advantages. For example, in some embodiments, the method increases a green compressive strength (GCS) of wet unfired pellets by about 5-20%, 5-18%, 5-15%, 5-12%, or 5-10%, including values and ranges thereof, compared to those obtained from using powder bentonite. In some embodiments, the method increases the green compressive strength of wet unfired pellets by about 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%, including values and ranges thereof, compared to those obtained from using powder bentonite.
In some embodiments, the method for preparing ore pellets by adding a bentonite slurry as described herein decreases bursting of wet unfired pellets upon thermal shock test by about 3-10%, including values and ranges therebetween, compared to those obtained from using powder bentonite. In some embodiments, bursting of wet unfired pellets upon thermal shock test is decreased by about 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, including values and ranges thereof, compared to those obtained from using powder bentonite. In an exemplary

embodiment, the thermal shock test comprises heating wet unfired pellets (“green” pellets) to 500°C at a rate of ~67 °C/min. The number of burst pellets, crack containing pellets and un-cracked pellets are counted at the end of the thermal shock test.
In some embodiments, the method for preparing ore pellets by adding a bentonite slurry as described herein increases strength of wet unfired pellets upon thermal shock test by about 10-25%, 10-20%, or 10-15%, including values and ranges thereof, compared to those obtained from using powder bentonite. In some embodiments, the strength of wet unfired pellets upon thermal shock test is increased by about 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or 25% including values and ranges thereof, compared to those obtained from using powder bentonite.
In some embodiments, the addition of bentonite slurry to the ore composition controls excess densification of ore pellets and provides pellets with improved drying behavior compared to those obtained from using powder bentonite.
It is to be understood that the foregoing descriptive matter is illustrative of the disclosure and not a limitation. While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. Those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. Similarly, additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based upon description provided herein.
Descriptions of well-known/conventional methods/steps and techniques are omitted so as to not unnecessarily obscure the embodiments herein. Further, the disclosure herein provides for examples illustrating the above-described embodiments, and in order to illustrate the embodiments of the present disclosure certain aspects have been employed. The examples used herein for such illustration are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the following examples should not be construed as limiting the scope of the embodiments herein.

EXAMPLES
Example 1: Preparation of a bentonite slurry and iron ore pellets by employing the bentonite slurry (prepared from lump bentonite)
Iron ore fines (Fe Source), pyroxenite flux (MgO and SiO2 source), limestone (CaO source), carbon bearing wastes, and anthracite coal were ground together. This co-grinding of raw materials produced a ground ore concentrate (GOC) containing the required amount of total iron, CaO, MgO, and carbon fuel. This ground ore concentrate was used to study the effect of powder bentonite vis-à-vis slurry bentonite in pellet making.

To prepare pellets by adding powder bentonite, 25 g of powder bentonite (i.e. 0.5% of dry mix) and 5 kg of GOC was taken and loaded into a high-intensity mixer. The pan of the high-intensity mixer was operated at 35 rpm for 5 minutes for dry mixing. Once the dry mixing was completed, the rotor blades of the high-intensity mixer were operated and simultaneous addition of 400 g water (i.e. 8%) was done. The high-intensity mixer was operated for 5 minutes for wet mixing. After that wet mix was taken out and green pellets were prepared using a lab-scale disc pelletizer. For a comparison purpose, 10-12.5 mm size pellets were produced as these are the pellets which get tested for green ball quality parameters in industrial pellet plants.
For making pellets by adding slurry bentonite, 25 g of lump bentonite (with a size of minus 5 mm for the purpose of getting the representative sample, however, for large-scale operation bigger particles can be taken) was taken. It was soaked in 300 g water (6% of dry mix) for 2 hours and after absorption of water and swelling of bentonite, the mixture was stirred to produce a slurry comprising swelled bentonite. Figure 4 shows the preparation of a bentonite slurry. It can be seen from this figure how bentonite absorbed water with time and settled down. The settled bentonite when stirred produced slurry that was employed for the pellet making.

For making pellets, 5 kg of GOC was taken and loaded into a high-intensity mixer. The pan of the high-intensity mixer was operated at 35 rpm for 5 minutes during which slurry was added to it. Once the addition of slurry was completed and 5 min of mixing was completed, the rotor blades of the high-intensity mixer were operated and simultaneously, 100 g water (2%) was added. The high-intensity mixer was operated for 5 minutes for wet mixing. After that wet mix was taken out and green pellets were prepared using a lab-scale disc pelletizer. For a comparison purpose, 10-12.5 mm size pellets were produced.
The green or moist pellets produced by employing powder bentonite and slurry bentonite were tested for green ball quality parameters such as green pellet compressive strength (GCS), drop no (by dropping 30 pellets, one pellet at a time from 45 cm until breakage), dried pellet compressive strength wherein pellets are dried at 105 °C for 3 hours. The green pellets were also subjected to the thermal shock test designed with heating patterns similar to an industrial pellet plant. The peak shock temperature given to pellet was 500 °C wherein pellets were heated to reach 500 °C at a heating rate of ~67 °C/min. The number of burst pellets, crack containing pellets and un-cracked pellets were counted and reported. These values are provided in Table 2.

From Table 2, it can be seen that green ball qualities obtained by employing slurry bentonite (prepared from lump bentonite) were better compared to those obtained using powder bentonite. For almost the same moisture content of green balls, GCS improved by ~13% for pellets prepared using slurry bentonite compared to those using powder bentonite. The drop

number was almost the same for slurry bentonite and powder bentonite-based pellets. DCS also improved slightly. The major improvement was observed in the thermal shock properties of pellets where bursting of pellets decreased from 5.56% to 0%. This improvement is expected to result in a decrease in return fines generation during pellet production at an industrial iron ore pelletizing plant. The pellets which were getting burst are reported as cracked and un-cracked pellets. Even though the crack pellets look increased, it is due to the decrease in the burst pellet and not otherwise. Moreover, the length of cracks in cracked pellets was much smaller in the case of pellets prepared using slurry bentonite. The strength of pellets measured after the thermal shock was also found to improve significantly from 2.1 kg/p to 2.47 kg/p. This improvement is expected to result in improvement in pellet bed permeability and hence better firing of pellets.
Example 2: Preparation of iron ore pellets by employing low-grade iron ore and bentonite slurry (prepared from powder bentonite)
Iron ore fines (Fe Source), olivine flux (MgO and SiO2 source), limestone (CaO source), carbon bearing wastes, and anthracite coal were ground together in the commercial pellet plant. This co-grinding of raw material produced a ground ore concentrate (GOC) which was used in the commercial pellet making plant. This ground ore concentrate was used for the pellet making to compare the effect of powder bentonite vis-à-vis slurry bentonite. Moreover, since the bentonite platelets are expected to spread more once the bentonite is pre-swelled by making bentonite slurry, therefore, slurry bentonite prepared from powdered bentonite was also tested for its effect on green ball qualities of pellet prepared using low-grade ores.
Low-grade ore pellets have the tendency to burst more as compared to high-grade ore pellets. In this study, it was tested whether slurry bentonite can counter the bursting of pellets produced using low-grade ores. For this purpose, iron ore slime with high alumina, LOI (loss on ignition) as compared to ground ore concentrate was used.


For making pellets using powder bentonite, 25 g of powder bentonite (i.e. 0.5% of dry mix) and 5 kg of iron-bearing materials (GOC and Iron ore slime) were loaded into a high-intensity mixer. The pan of the high-intensity mixer was operated at 35 rpm for 5 minutes for dry mixing. Once the dry mixing was completed, the rotor blades of the high-intensity mixer were operated and simultaneous addition of 400 g water (i.e. 8%) was done. The high-intensity mixer was operated for 5 minutes for wet mixing. After that wet mix was taken out and green pellets were prepared using a lab-scale disc pelletizer. 10-12.5 mm size pellets were produced. A set of 5 base case pellets were prepared wherein iron ore slime was varied from 0 to 40%.
For making pellets using slurry bentonite, 25 g of the same powder bentonite was taken. It was soaked in 300 g water (6% of dry mix) for 2 hours and after absorption of water and swelling of bentonite, the mixture was stirred to produce a slurry comprising swelled bentonite. 5 kg of iron-bearing material (GOC and iron ore slime combination) was taken and loaded into a high-intensity mixer. The pan of the high-intensity mixer was operated at 35 rpm for 5 minutes during which bentonite slurry prepared from powder bentonite was added to it. Once the addition of slurry was completed and 5 min of mixing was also completed, the rotor blades of the high-intensity mixer were operated and simultaneously, 100 g water addition (2%) was done. The high-intensity mixer was operated for 5 minutes for wet mixing. After that wet mix was taken out and green pellets were prepared using a lab-scale disc pelletizer. 5 sets of 10-12.5 mm size pellets were prepared by varying iron ore slime and compared with respective powder-based pellets.
The effect of slurry bentonite vis-à-vis powder bentonite on green ball qualities was tested for each set of pellets. The green or moist pellets produced by employing both powder and slurry bentonite were tested for green ball quality parameters in the manner similar to Example 1. The composition of these pellets in terms of the percentage of ground ore concentrates and iron ore slime (IOS) is shown in Tables 4 and 5. Tables 4 and 5 also provide green ball quality parameters namely, moisture, GCS, DCS, Drop no, Burst pellet % (after the thermal shock), crack pellet % (after the thermal shock), uncracked pellet percentage (after the thermal shock), and strength of pellets after thermal shock.


It is to be noted that low-grade ores due to their finer size, high goethite content, and high clay content tend to burst more compared to standard high-grade ores. However, due to high goethite and clay minerals, their other green ball qualities can be superior as compared to high-grade ore. From Table 4 and Table 5, it is evident that the green ball quality either remained

the same or improved when pellets were prepared with slurry bentonite instead of powder bentonite. Moreover, the thermal shock properties, in terms of crack pellets and burst pellet percentage, improved significantly when bentonite was used in the form of slurry instead of powder. Interestingly, slurry bentonite also resulted in control over excess densification of pellets. Excess densification of pellets prepared with higher iron ore slime results in higher DCS and hence bursting/cracking of pellets. During the mixing of slurry bentonite with iron ore, finer particles tend to get agglomerated to form bigger particles and hence do not go into the cavities/voids to make the pellet excessively dense. This is reflected in lower DCS when slurry bentonite is used for higher iron ore slime usage at 20% and above. Below 20% iron ore slime usage, DCS is in the range of respective base pellets.
These Examples confirm that bentonite in the form of slurry is beneficial in the agglomeration of fines. It not only decreases the cost of production, such as by avoiding the cost of drying and grinding of raw lump bentonite as required for conventional processing, but also has the potential to decrease fines generation during the firing of the agglomerates. Moreover, slurry bentonite also improved thermal shock properties of iron ore pellets prepared with ore composition comprising low-grade ores such as high alumina, high goethite, high gangue, and finer particle size material. Slurry bentonite is expected to show similar effects on the agglomeration of other ferrous and non-ferrous fines.

We Claim:
1. A method for preparing a bentonite slurry, comprising soaking bentonite in water for about 2 hours or more and stirring the water to obtain a bentonite slurry.
2. The method as claimed in claim 1, wherein the bentonite is lump bentonite or powder bentonite.
3. The method as claimed in claim 2, wherein the lump bentonite has a size of about minus 15 mm and more preferably about minus 5 mm.
4. The method as claimed in any one of claims 1-3, wherein the bentonite is added to water at a concentration of about 25% by weight or lower.
5. The method as claimed in claim 4, wherein the bentonite is added to water at a concentration of about 12.5% by weight or lower.
6. The method as claimed in any one of claims 1-5, wherein the water is stirred at a rate of 10-60 rpm for 2-5 minutes to obtain the bentonite slurry.
7. A method for preparing ore pellets, comprising:
a. preparing an ore composition comprising ore fines, a carbonaceous agent, and a
fluxing agent;
b. preparing the bentonite slurry as claimed in any one of claims 1-6;
c. mixing the ore composition, the bentonite slurry, and water to obtain a pellet mix;
and
d. pelletizing the pellet mix to obtain ore pellets.
8. The method as claimed in claim 7, wherein said mixing of the ore composition, the
bentonite slurry, and water to obtain the pellet mix comprises:
a. adding the ore composition to a mixer;
b. adding the bentonite slurry to said mixer;
c. adding water to said mixer to obtain the pellet mix; and
d. mixing the pellet mix in said mixer for a period of 1-4 minutes.
9. The method as claimed in claim 7 or 8, wherein the ore fines are iron ore fines, chromite ore fines, or manganese ore fines.
10. The method as claimed in any one of claims 7-9, wherein the ore fines are powder fines or crushed fines.
11. The method as claimed in claim 10, wherein the crushed fines have a size less than 10 mm.

12. The method as claimed in claim 10, wherein the iron ore fines are hematite fines, goethite fines, or magnetite fines.
13. The method as claimed in any one of claims 7-12, wherein the carbonaceous agent is selected from the group consisting of coke, coal, a carbonaceous material, and a combination thereof.
14. The method as claimed in any one of claims 7-13, wherein the fluxing agent is selected from the group consisting of pyroxenite flux, olivine flux, lime, dolomite, and a combination thereof.
15. The method as claimed in any one of claims 7-14, wherein the method increases a green compressive strength (GCS) of wet unfired pellets by about 5-20% compared to those obtained from using powder bentonite.
16. The method as claimed in any one of claims 7-15, wherein the method decreases bursting of wet unfired pellets upon thermal shock test by about 3-10% compared to those obtained from using powder bentonite.
17. The method as claimed in any one of claims 7-16, wherein the method increases strength of wet unfired pellets upon thermal shock test by about 10-25% compared to those obtained from using powder bentonite.