Claims:

WE CLAIM:
1. A method for enhancing cold compressive strength of chromite ore pellets, comprising steps of:
preparing slurry by mixing chromite ore fines and coke fines, followed by filtering the slurry;
adding binder and blast furnace slag to the filtered slurry to obtain a mixture;
pelletizing the mixture to obtain pellets; and
heating the pellets in a vertical shaft furnace under an oxidizing atmosphere at temperature ranging from about 1100°C to 1300°C to obtain the chromite ore pellets having enhanced cold compressive strength.
2. The method as claimed in claim 1, wherein the mixing of the chromite ore fines and the coke fines is carried out by ball milling in presence of a solvent comprising water; and wherein the solvent is in an amount ranging from about 8m3/hour to 11m3/hour, to obtain the slurry density ranging from about 1.7 kg/m3 to 2.3kg/m3.
3. The method as claimed in claim 1, wherein the step of preparing slurry further comprises mixing chromite ore fines, blast furnace slag and coke fines by balling milling in presence of a solvent comprising water, wherein the solvent is in an amount ranging from about 8m3/hour to 11m3/hour, to obtain the slurry density ranging from about 1.7 kg/m3 to 2.3kg/m3.
4. The method as claimed in claim 1, wherein the slurry is subjected to filtration to maintain moisture content of the filtered slurry to about 10% to 15%.
5. The method as claimed in claim 1, wherein the pelletizing is carried out in pelletizing disc by addition of solvent comprising water from about 1% to 5% by weight of the filtered slurry.
6. The method as claimed in claim 1, wherein the binder is selected from a group comprising bentonite, bitumen, animal glue and plant glue, or any combination thereof.
7. The method as claimed in claim 1, wherein the chromite ore fines is having a particle size ranging from about 1mm to 10mm
8. The method as claimed in claim 1, wherein the coke fines is in an amount ranging from about 1% to 10% by weight of the ore.
9. The method as claimed in claim 1, wherein the blast furnace slag is having particle size ranging from about 1mm to 10mm and is in an amount ranging from about 1% to 4% by weight of the filtered slurry.
10. The method as claimed in claim 1, wherein the binder is in an amount ranging from about 1% to 2% by weight of the filtered slurry.
11. The method as claimed in claim 1, wherein the blast furnace slag comprises ferrous oxide in an amount ranging from about 0.2% to 2%, calcium oxide in an amount ranging from about 32% to 38%, silicon dioxide in an amount ranging from about 32% to 38%, aluminum oxide in an amount ranging from about 16% to 22% and magnesium oxide in an amount ranging from about 6% to 11%.
12. The method as claimed in claim 1, wherein the cold compressive strength of the chromite ore pellets is enhanced by about 60% to 70%.
13. A chromite ore pellet having cold compressive strength ranging from about 110kg/p to 145 kg/p.
14. The chromite ore pellet as claimed in claim 13, wherein the chromite ore pellet is devoid of dust particle.
15. The chromite ore pellet as claimed in claim 13, wherein the chromite ore pellet is having a size ranging from about 6nm to 25nm. , Description:TECHNICAL FIELD
The present disclosure relates to a method for improving/enhancing the cold compressive strength of chromite ore pellet. The disclosure also relates a chromite ore pellet with improved/enhanced cold compressive strength.

BACKGROUND OF THE DISCLOSURE
Various methods are available in the art for agglomeration such as, pelletizing, briquetting and sintering. The different processes of pelletizing available are characterized by the type of induration process like straight grate and grate kiln etc.

During pelletizing, it is observed that there is a particular disadvantage associated with shaft furnace such as, irregular heating of the material between the peripheral outer zones and the central zones of the furnace, resulting in a non-uniform quality of the final product.

Multiple methods were identified and developed to eradicate the non-uniformity in the quality of final product and improve the efficiency of induration like straight grate technology or grate kiln technology in pelletizing, but improvement was not evident/observed in ferro chrome pelletizing. Also, the cost of the technology and the plant was unfavourably high, pushing up the cost of production of ore pellets with enhanced properties.

The present disclosure aims at addressing the issue that was faced in developing chromite ore pellets with enhanced properties, also the solution proposed in the disclosure is cost effective/economical.

SUMMARY OF THE DISCLOSURE
The present disclosure relates to a method for enhancing the cold compressive strength of chromite ore pellets.

In an embodiment, the method for enhancing the cold compressive strength of chromite ore pellets comprises steps of:
preparing slurry by mixing chromite ore fines and coke fines, followed by filtering the slurry;
adding binder and blast furnace slag to the filtered slurry to obtain a mixture;
pelletizing the mixture to obtain pellets; and
heating the pellets in a vertical shaft furnace under an oxidizing atmosphere at temperature ranging from about 1100°C to 1300°C to obtain the chromite ore pellets having enhanced cold compressive strength.

In an embodiment, the method of the present disclosure enhances the cold compressive strength of the chromite ore pellets in the range of about 60% to 70%.

The present disclosure further relates to chromite ore pellets having enhanced cold compressive strength.

DETAILED DESCRIPTION
The present disclosure relates to a method for enhancing the cold compressive strength of chromite ore pellets.

In an embodiment, the present disclosure relates to a method for enhancing the cold compressive strength of the chromite ore sintered pellets.

In an embodiment, the method of the present disclosure apart from enhancing the cold compressive strength of the chromite ore pellets, ensures minimum generation of fines/dust from the chromite ore pellets during subsequent handling of the said chromite ore pellets.

In an embodiment, the method for enhancing the cold compressive strength of chromite ore pellets comprises steps of:
preparing raw material mixture comprising chromite ore fines, coke fines;
pelletizing the mixture to obtain pellets; and
heating the pellets to obtain the chromite ore pellets with enhanced cold compressive strength.

In an embodiment, the raw material prepared in the method for enhancing the cold compressive strength of the chromite ore pellet is in a form of a slurry, to which binder and blast furnace slag is added.

In an embodiment, the method for enhancing the cold compressive strength of chromite ore pellets comprises steps of:
preparing slurry by mixing chromite ore fines with coke fines, followed by filtering the slurry;
adding binder and blast furnace slag to the filtered slurry to obtain a mixture;
pelletizing the mixture to obtain pellets; and
heating the pellets in a furnace to obtain the chromite ore pellets with enhanced cold compressive strength.

In an embodiment, the mixing of the chromite ore fines and coke fines is carried out by ball milling in presence of a solvent including but is not limiting to water to obtain a slurry having density ranging from about 1.7kg/m3 to 2.3kg/m3, wherein the solvent is in an amount ranging from about 8m3/hour to 11m3/hour, depending on rate of chromite ore fines feed during milling.

In another embodiment, the step of preparing slurry further comprises mixing chromite ore fines, blast furnace slag and coke fines by balling milling in presence of a solvent comprising water, wherein the solvent is in an amount ranging from about 8m3/hour to 11m3/hour, to obtain the slurry density ranging from about 1.7 kg/m3 to 2.3kg/m3. The concentration of the solvent is dependent on rate of chromite ore fines feed during milling.

In an embodiment, the chromite ore fines are having particle size ranging from about 1mm to 10mm.

In another embodiment, the chromite ore fines are having particle size of about 1mm, about 2mm, about 3mm, about 4mm, about 5mm, about 6mm, about 7mm, about 8mm, about 9mm or about 10mm.

In an embodiment, the chromite ore fines are in an amount ranging from about 90 to 95%.

In an embodiment, the coke fines are in an amount ranging from about 1% to 10% by weight of the chromite ore fines.

In another embodiment, the coke fines are in an amount ranging from about 1% to 4% by weight of the chromite ore fines.

In another embodiment, the coke fines are in an amount of about 1% by weight of the chromite ore fines, about 2% by weight of the chromite ore fines, about 3% by weight of the chromite ore fines, about 4% by weight of the chromite ore fines, about 5% by weight of the chromite ore fines, about 6% by weight of the chromite ore fines, about 7% by weight of the chromite ore fines, about 8% by weight of the chromite ore fines, about 9% by weight of the chromite ore fines or about 10% by weight of the chromite ore fines.

In an embodiment, the slurry is subjected to filtration to maintain the moisture content of the slurry in the range of about 10% to 15%, wherein the filtered slurry is in the form of a cake.

In an embodiment, the slurry is subjected to filtration to maintain the moisture content of the slurry to about 10%, about 11%, about 12%, about 13%, about 14% or about 15%.

In an embodiment, the filtered slurry comprises chromic acid in an amount ranging from about 47% to 50%, iron in an amount ranging from about 12% to 14% and silica in an amount ranging from about 3% to 6%.

In another embodiment, the filtered slurry comprises chromic acid in an amount of about 47%, about 48%, about 49% or about 50%, iron in an amount of about 12%, about 13% or about 14% and silica in an amount of about 3%, about 4%, about 5% or about 6%.

In an embodiment, the binder is selected from a group comprising bentonite, bitumen, animal glue, plant glue and any other organic binder, or any combination thereof.

In an embodiment, the blast furnace slag prior adding to the filtered slurry is ground to a particle size of about 1mm to 10mm and the ground blast furnace slag is disturbed in the filtered slurry in a homogenous manner.

In another embodiment, the blast furnace slag is having a particle size of about 1mm, about 2mm, about 3mm, about 4mm, about 5mm, about 6mm, about 7mm, about 8mm, about 9mm or about 10mm.

In an embodiment, the blast furnace slag is in an amount ranging from about 1% to 4% by weight of the filtered slurry.

In another embodiment, the blast furnace is in an amount of about 1% by weight of the filtered slurry, about 1.5% by weight of the filtered slurry, about 2% by weight of the filtered slurry, about 2.5% by weight of the filtered slurry, about 3% by weight of the filtered slurry, about 3.5% by weight of the filtered slurry or about 4% by weight of the filtered slurry.

In an embodiment, the blast furnace slag comprises ferrous oxide in an amount ranging from about 0.2% to 2%, calcium oxide in an amount ranging from about 32% to 38%, silicon dioxide in an amount ranging from about 32% to 38%, aluminium oxide in an amount ranging from about 16% to 22% and magnesium oxide in an amount ranging from about 6% to 11%.

In another embodiment, the blast furnace slag comprises ferrous oxide in an amount of about 0.2%, about 0.4%, about 0.6%, about 0.8%, about 1.0%, about 1.2%, about 1.4%, about 1.6%, about 1.8% or 2%, calcium oxide in an amount of about 32%, about 33%, about 34%, about 35%, about 36%, about 37% or about 38%, silicon dioxide in an amount of about 32%, about 33%, about 34%, about 35%, about 36%, about 37% or about 38%, aluminium oxide in an amount of about 16%, about 17%, about 18%, about 19%, about 20%, about 21% or about 22% and magnesium oxide in an amount of about 6%, about 7%, about 8%, about 9%, about 10% or about 11%.

In an embodiment, the calcium oxide in an amount 32% to 38% present in the blast furnace slag aids in adjusting the basicity of the pellets.

In an embodiment, the binder is in an amount ranging from about 1% to 2% by weight of the filtered slurry.

In another embodiment, the binder is in an amount of about 1% by weight of the filtered slurry, about 1.2% by weight of the filtered slurry, about 1.4% by weight of the filtered slurry, about 1.6% by weight of the filtered slurry, about 1.8% by weight of the filtered slurry or 2% by weight of the filtered slurry.

In an embodiment, the pelletizing is carried out in a pelletizing disc in presence of solvent including but is not limiting to water to obtain pellets of appropriate size.

In an embodiment, the pellets are heated in a vertical shaft furnace under an oxidizing atmosphere by supplying atmospheric air at a temperature ranging from about 1100°C to 1300°C.

In another embodiment, the pellets are heated in a vertical shaft furnace under an oxidizing atmosphere by supplying atmospheric air at a temperature of about 1100°C, about 1150°C, about 1200°C, about 1250°C or about 1300°C.

In an embodiment, the method of the present disclosure enhances the cold compressive strength of the chromite ore pellets by about 60% to 70%.

In another embodiment, the method of the present disclosure enhances the cold compressive strength of the chromite ore pellets by about 60%, about 61%, about 62%, about 63%, about 64%, about 65%, about 66%, about 67%, about 68%, about 69% or about 70%.

In an embodiment, the chromite ore pellets obtained by the method of the present disclosure apart from having enhanced cold compressive strength, generates negligible dust during firing/heating of the said chromite ore pellets during subsequent handling.

In an embodiment, the method of the present disclosure enhances the cold compressive strength of the chromite ore pellets when compared to methods which do not employ blast furnace slag.

The present disclosure further relates to chromite ore pellets.

In an embodiment, chromite ore pellets are having enhanced cold compressive strength ranging from about 110kg/p to 145kg/p.

In another embodiment, the chromite ore pellets are having enhanced cold compressive strength of about 110kg/p, about 115kg/p, about 120kg/p, about 125kg/p, about 130kg/p, about 135kg/p, about 140kg/p or about 145kg/p.

In an embodiment, the said chromite ore pellets are obtained by the method of the present disclosure.

In an embodiment, the chromite ore pellets are devoid of dust particles.

In another embodiment, the chromite ore pellets generate negligible dust during firing or heating during subsequent handling of the said chromite ore pellets.

In an embodiment, the chromite ore pellets are having size ranging from about 6nm to 25 nm

In another embodiment, the chromite ore pellets are having size ranging from about 10 nm to 20 nm

In another embodiment, the chromite ore pellets are having size of about 6nm, about 7nm, about 8nm, about 9nm, about 10nm, about 11nm, about 12nm, about 13nm, about 14nm, about 15nm, about 16nm, about 17nm, about 18nm, about 19nm or about 20nm.

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based upon the description provided. The embodiments provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments. The examples provided herein are intended merely to facilitate an understanding of ways in which the embodiments provided may be practiced and to further enable those of skill in the art to practice the embodiments provided. Accordingly, the following examples should not be construed as limiting the scope of the embodiments.

EXAMPLES
EXAMPLE 1: Enhancing cold compressive strength of chromite ore pellets.
About one ton of chromite ore fines are mixed with about 40 kg of coke fines, the mixture is ball milled with water to obtain slurry. The slurry is filtered to obtain filtered slurry in the form of a cake, having moisture content of about 10%. About 10kg bentonite is added to the filtered slurry, followed by adding about 10 kg to 35 kg of blast furnace slag to obtain a mixture.

The mixture is subjected to pelletizing in a pelletizing disc. The pellets formed are heated in a furnace at a temperature of about 1200°C to obtain chromite ore pellets with enhanced cold compressive strength.

EXAMPLE 2: Enhancing cold compressive strength (CCS) of chromite ore pellets by using blast furnace slag (BF slag) in an amount of about 1%, about 2% and about 3.5%, respectively.

About one tone of chromite ore fines are mixed with about 10kg of coke fines, the mixture is ball milled with water to obtain slurry. The slurry is filtered to obtain filtered slurry in the form of a cake, having moisture content of about 10%. About 1.15% of bentonite is added to the filtered slurry and the said filtered slurry is divided into 4 parts (Mix-A, Mix-B, Mix-C and Mix-D). About 0%, about 1%, about 2% and about 3.5% of blast furnace slag is added to each part, respectively.

Each mix is subjected to pelletizing in pelletizing disc. The pellets obtained from each mix are subjected to heating in a furnace at a temperature (induration temperature) ranging from about 1250°C to 1300°C to obtain chromite ore pellets. Table 1 below illustrates the cold compressive strength of the chromite ore pellets obtained from each of the mixes. From the table, it is evident that the chromite ore pellets obtained by mixes (Mix-B, Mix-C and Mix-D) having blast furnace slag at an amount of about 1%, about 2% and about 3.5% has enhanced cold compressive strength (CCS) of about 115kg/p, 128kg/p and 145kg/p, respectively when compared to the chromite ore pellets obtained by mix (Mix-A) not having blast furnace slag.

Parameters Unit Mix-A Mix-B Mix-C Mix-D
BF slag % 0 1 2 3.5
Bentonite % 1.15
Induration Temp. °C 1250-1300
CCS kg/p 85 115 128 145

Table 2

Additional embodiments and features of the present disclosure is apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein. The foregoing description of the specific embodiments fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, 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. With respect to the use of substantially 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. Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application. 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. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.