Description:TECHNICAL FIELD
Present disclosure relates in general to a field of material science and metallurgy. Particularly, but not exclusively, the present disclosure relates to goethitic low grade iron ore. Further, embodiments of the disclosure disclose an energy efficient grinding process for grinding the goethitic low grade iron ore.
BACKGROUND OF THE DISCLOSURE
Goethite is an ore primarily consisting of iron oxyhydroxide with ferric iron. Goethite is usually considered as a low-grade iron ore because of its composition. Generally, there are large reserves of high-grade hematite ore available world-wide . However, steady consumption of these high-grade hematite iron ores is a concern as these reserves are being depleted. In view of this growing concern, certain manufacturers or industries are forced to develop beneficiation strategies to utilize low grade iron ore specially goethitic ores. Since there are huge requirements for iron ore around the world, it equally demands usage of thousands of units of electricity in manufacturing or processing the iron ore. Current mining practice adopts a cut-off grade of 58% Fe content. As a result of which, tons of low grade in-situ deposits are locked in operating mines. Besides these in-situ deposits, huge stockpiles of low-grade ore has been created in all operating mines in course of removal of overburden and selective mining during mine development. However, this low-grade ore cannot be utilised due to low industrial value and marketability.
Moreover, based on the estimated demand and projected requirement of steel plants, existing reserves of high-grade hematite (>63% Fe) may not last beyond 25-30 years. Accordingly, it becomes imperative to utilize low-grade reserves to cater for increased demand of steel making. On the other hand, installation, and erection of new mining infrastructure is also expected to contain deposits of increasingly inferior grades due to non-availability in the ore mines. In addition to this, stringent environmental regulations involved in opening of new mines adds to this problem and other problems such as handling and disposal of tailings (slimes) and utilizing of iron ore at 45% Fe as a cut-off fixed by statutory authorities.
Further, low grade iron ore specially, goethitic has complex liberation characteristics. Liberation of such ores need fine to ultrafine grinding before beneficiation. Grinding in ultrafine size consumes high amount energy which makes entire ore processing option costly. Conventional, processes include continuous grinding processes in a ball mill or similar mill which consumes high number of energy units leading to an expensive and inefficient process. Further, some of the citations disclose such grinding processes which are listed below.
US3730445A describes a method of improving the grindability or grinding characteristics of aluminus clays or alumina-silica ores containing iron species by thermally treating the clays or ores at relatively high temperature in an air or oxidative atmosphere and subsequently grinding ore to a predetermined particle size.
CN102240588B describes a dry-grinding and dry-separation method of magnetite, which comprises feeding the crude ore of magnetite into a crusher for coarse crushing, and then feeding the crushed magnetite into a vibrating sieve for sieving. Controlling the sieve meshes within a range of 35-75 mm; feeding the oversize product to the crusher for intermediate crushing and then feeding the crushed oversize product into a high-pressure roller mill along with the undersize product for fine crushing.
WO2006018771A1 describes a method of assisting the liberation of a first mineral from a particulate low-grade ore containing said first mineral in a layered grain structure with at least a second mineral. The method includes increasing the aspect ratio of grains of the low-grade ore containing the first mineral by exposing the low grade ore to microwave energy.
US20090188998A1 describes an improved grinding process using ISA mill for the comminution of a particulate feed material or a particulate feed stream. This publication is particularly useful for size reduction of particulate material in the mining or mineral industries and especially for the size reduction of an ore, a concentrate or a carbonaceous material, such as coal.
CN1559689A describes a method that improves efficiency of the continuous ball mill and cuts down the consumption of energy. The method includes adjusting the rotating speed of ball mill, wherein the rotational speed makes cylindrical shells which is between 20~60%. Further, the inner feed inlet and outlet of the grinding machine increases the grate plate for blocking and adjusts the filling rate between 60~85%. Therefore, the ball mill turns round under such running parameter consuming less energy.
WO2008147793A2 describes a method of improving grinding of a bauxite containing slurry during the grinding stage of an alumina extraction process. The method includes adding an effective amount of one or more non-ionic surfactants, polyglycols, polyglycol ethers, anionic surfactants, anionic polymers, or a combination thereof to said bauxite containing slurry during the grinding stage of an alumina extraction process.
However, all the conventional processes described above, deals with energy consuming techniques for processing the low grade iron ore.
The present disclosure is directed to overcome one or more limitations stated above or any other limitation associated with the prior arts.

SUMMARY OF THE DISCLOSURE
One or more shortcomings of the prior art are overcome by method as claimed and additional advantages are provided through the method as described in the present disclosure.

Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

In one non-limiting embodiment of the present disclosure, a method for grinding metallurgical goethitic low grade iron ore is disclosed. The method comprises subjecting, the goethitic low grade iron ore to, a primary crushing, in a primary crusher. Followed by, a secondary crushing, in a secondary crusher to form granules of goethitic low grade iron ore of size 8mm or less. Further, the method includes grinding, the granules of goethitic low grade iron ore in a high-pressure grinding roll, wherein, the griding process results in reduction of the granules of goethitic low grade iron ore to a size of 2mm or less. The method further includes grinding, the granules of goethitic low grade iron ore having size of 2mm or less in a ball mill such that the grinding results in the granules of goethitic low grade iron ore to be powdered to a size of 75 micron or less.
In an embodiment, the method comprises of sieving and scrubbing the goethitic low grade iron ore after passing through the primary crusher and the secondary crusher.

In an embodiment, the primary crusher is a gyratory crusher, and the secondary crusher is a cone type crusher.

In an embodiment, the granules of goethitic low grade iron ore is sieved in a sieving screen after passing through the secondary crusher to separate to the granule size of 8mm or less.
In an embodiment, the granules of goethitic low grade iron ore are sieved though the sieving screen after gridingin the high-pressure grinding roll (HPGR) to match the granule size of 2 mm or less.

In an embodiment, the goethitic low grade iron ore comprises composition of 50 wt% of Iron (Fe) and 9 wt% of Aluminium oxide (Al2O3) with a moisture content ranging from 8 wt% to 10 wt% after scrubbing.

In an embodiment, the energy required for grinding of the goethitic low grade iron ore of size 8mm or less ranges from about 1.2Kwh/ton to 1.5Kwh/ton.

In an embodiment, the energy required for grinding of the goethitic low grade iron ore of size 2mm or less ranges from about 7 Kwh/ton to 7.5Kwh/ton.

In an embodiment, the high-pressure grinding roll (HPGR) grinds the goethitic low grade iron ore into a centre product granule and an edge product granule.

In an embodiment, the centre product granule and the edge product granule are mixed before screening.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
The novel features and characteristics of the disclosure are set forth in the appended description. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

Figure.1 is a flowchart describing a method for grinding goethitic low grade iron ore, according to an exemplary embodiment of the present disclosure.

Figure. 2 illustrates a graphical representation of particle size distribution (PSD) of goethitic low grade iron ore in a high-pressure grinding process (HPGR), according to an exemplary embodiment of the present disclosure

Figure. 3 illustrates a graph of XRD characterization of the goethitic low grade iron ore, according to an exemplary embodiment of the present disclosure.

Figure. 4 illustrates liberation analysis at different sizes of goethitic low grade iron ore, according to an exemplary embodiment of the present disclosure.

Figure 5 illustrates SEM imaging of the particle distribution of the goethitic low grade iron ore, according to an exemplary embodiment of the present disclosure.

Figure 6 illustrates particle size distribution (PSD) in the HPGR process and screen product, according to an exemplary embodiment of the present disclosure

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION
The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the description of the disclosure. It should also be realized by those skilled in the art that such equivalent methods do not depart from the scope of the disclosure. The novel features which are believed to be characteristic of the disclosure, as to method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a method that comprises a list of acts does not include only those acts but may include other acts not expressly listed or inherent to such method. In other words, one or more acts in a method proceeded by “comprises… a” does not, without more constraints, preclude the existence of other acts or additional acts in the method.
Embodiments of the present disclosure discloses a method for grinding metallurgical goethitic low grade iron ore. Low grade iron ore specially, goethitic low grade iron ore has complex liberation characteristics. Liberation of such ores needs grinding process to be carried out to ultrafine size as a prerequisite before beneficiation. Liberation analysis usually includes identification of minerals in polished sections of ore cores, particulates or lump materials, and quantifying them into a wide range of mineral characteristics, such as mineral abundance, grain size and liberation. Conventional grinding process comprises use of ball mill-ball mill combination. This grinding leads to a result of obtaining ultrafine size or powder but, consumes high amount energy which makes entire ore processing option/operation costly. Moreover, based on the estimated demand and projected requirement of steel plants, existing reserves of high-grade hematite (>63% Fe) may not last beyond 25-30 years. Accordingly, it becomes imperative to utilize low-grade reserves to cater for increased demand of steel making. On the other hand, installation and erection of new mining infrastructure to obtain high grade iron ore is also expensive as the expected ore may contain deposits of increasingly inferior grades due to non-availability of high-grade ore in the ore mines. In addition to this, stringent environmental regulations involved in opening of new mines adds to this problem and other problems such as handling and disposal of tailings (slimes).
According to various embodiment of the disclosure, a method for grinding metallurgical goethitic low grade iron ore is disclosed. The method includes a first step of primary crushing of the goethitic low grade iron ore in a primary crusher such as gyratory crusher. The primary crushing is followed by secondary crushing to form granules of the goethitic low grade iron ore of size 8mm or less. The secondary crushing is carried out in a cone type crusher. The granules of the goethitic low grade iron ore of size 8mm or less are then grounded in a high-pressure grinding roll (HPGR), wherein, the griding process results in reduction of the granules of goethitic low grade iron ore to a size of 2mm or less. Further, screening is carried out to separate ore size in the range of 2 mm or less. Followed by a further screening to remove the oversize (+2mm size) material. Oversize material is again recirculated to HPGR feed for further grinding. Finally, the granules of the goethitic low grade iron ore having size of 2mm or less is subjected to ball milling, wherein the grinding in ball milling results in the granules of goethitic low grade iron ore to be powdered to a size of 75 micron or less. This is used as feed for beneficiation process such as flotation, selective flocculation, magnetic separation and spiral.
Now referring to Figure 1, which illustrates a flowchart for a method for grinding metallurgical goethitic low grade iron ore. The present disclosure proposes an energy efficient method for grinding metallurgical goethitic low grade iron ore. The method is now described with reference to the flowchart blocks described in figure 1. The order in which the method is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the scope of the subject. The method is particularly applicable for goethitic low grade ores, and it may also be extended to other type of ores.

The method for grinding metallurgical goethitic low grade iron ore according to the present disclosure consists of a primary and a secondary crushing. At block 100, the goethitic low grade iron ore of varying sizes are introduced into a primary crusher. The primary crusher may be at least one of a gyratory crusher, wherein the goethitic low grade iron ore is crushed in the primary crusher for a pre-determined time period.

At block 101, the crushed goethitic low grade iron ore is then immediately introduced into a secondary crusher. The secondary crusher may be at least one of a cone type crusher, wherein the goethitic low grade iron ore is crushed in the secondary crusher for another pre-determined time period. Once the goethitic low grade iron ore undergoes the primary crushing and the secondary crushing, screening is carried out in order to determine the initial size of granules so obtained. In an embodiment, the acceptable size of the goethitic low grade iron ore after subjecting to primary and secondary grinding may be in the range of 8 mm or less. In case the granules are not within the acceptable size, the granules are subjected to the primary crushing and the secondary crushing until the acceptable size is achieved.

Further, the granules that are in the acceptable size range of 8mm or less are then subjected to grinding in a High-pressure grinding roll [HPGR] as shown in block 102. The granules are subjected to grinding within the HPGR to a size of 2 mm or less. Similarly, as disclosed above, the grinded granules in the HPGR are again subjected to screening process in order to determine if the granules are in the acceptable size range of 2mm or less. In case the granules are not within the acceptable size, the granules are subjected to grinding in the HPGR until the acceptable size is achieved.

The granules grinded in the HPGR are then subjected to a further grinding step as shown in block 103. The method includes a ball mill which receives the granules of size 2mm or less and then are subjected to grinding until an acceptable size or powder in the size of 75 micron or less is achieved. In an embodiment, the granules which are not within the acceptable size, are subjected to continuous grinding in the ball mill until the acceptable size or powder form is achieved.

Referring to figure 2, which illustrates a graph showing the particle size distribution of goethitic low grade iron ore after subjecting to the primary and secondary crushing. As shown in the graph, about 60 % proportion of the goethitic low grade iron ore is finer than 5 mm, and about 90 % proportion of the goethitic low grade iron ore is finer than 8 mm, whereas 100 % proportion of the goethitic low grade iron ore passes through 15 mm sieve after the primary and the secondary crushing. Due to the primary and secondary crushing of the goethitic low grade iron ore, the lumps and large ores are broken down into particle sizes that will be readily processed in the HPGR. Moreover, this allows the HPGR to work efficiently in obtaining the goethitic low grade iron ore product within acceptable size limits at a faster rate.

In an embodiment, it is apparent that the size of the goethitic low grade iron ore be less than 1 mm in order to obtain required liberation characteristics. Therefore, it is important to grind the iron ore to a size less than 1mm. Further, liberation analysis usually includes identification of minerals in polished sections of ore cores, particulates or lump materials, and quantifying them into a wide range of mineral characteristics, such as mineral abundance, grain size and liberation.

Referring to figure 3, which illustrates XRD characterization pattern of goethitic low grade iron ore sample. The X-ray diffraction (XRD) analysis of the grounded goethitic low grade iron ore shows that the ore contains 36.6% hematite, 53.1% goethite, 8.3% gibbsite indicating that sample is a goethite dominated ore.
Figure 4 liberation analysis of the goethitic low grade iron ore sample using a stereo-zoom microscope. It can be visualized from the figure that, the sample show a poor liberation characteristics, in a size range of above 1 mm, and more than 50% grains remain as interlocked grains. However, the liberation of iron minerals improves gradually when size is in the range of 100-micron. From the graph it becomes apparently clear that most of the locked iron bearing phases shall be liberated below 75 microns. This shows that feed material needs to be ground below 75 microns through energy efficient grinding process to achieve desired liberation characteristics.
Referring to figure 6, illustrates particle size distribution of the product in the HPGR. The HPGR during operation produces a mixture of centre and edge products. The construction of the HPGR is such that, during the course of grinding, the goethitic low grade iron ore is disintegrated into a centre product and an edge product. The centre product is much more finely grinded in comparison with the edge product, which undergoes a coarse grind. Therefore, once the goethitic low grade iron ore is grinded in the HPGR screening is carried out to determine size of the goethitic low grade iron ore. Usually, both the centre product and the edge product are mixed and then screened. During screening, if an oversize fraction (+2mm) of the goethitic low grade iron ore is obtained, then such goethitic low grade iron ore are recirculated to HPGR feed. If the Screened undersize material (-2mm size), then the goethitic low grade iron ore is subjected to ball mill to further grind the goethitic low grade iron ore to below 75 micron size.
Embodiments of the present disclosure discloses that, energy consumed by the primary crushing, the secondary crushing, the HPGR and the ball milling in order to grind the goethitic low grade iron ore may be as follows:
? Grinding of the goethitic low grade iron ore of size 8 mm to a size of 2 mm using HPGR was 1.2 KWH/ton to 1.5 KWH/ton.
? Further, grinding the goethitic low grade iron ore of size 2 mm to a size of 75 micron size using ball mill was 7.0KWH/ton to 7.5 KWH/ton.

Therefore, the overall consumption of energy to obtain the goethitic low grade iron ore of size 75 micron or less was 9 KWH/ton.

Experiment and Test study:

Table 1 shows characterization study based on seven locked cycle tests of crushing/grinding the goethitic low grade iron ore (i.e. A1 until A7) in the HPGR. Based on the testing, the cycles are carried out with 2.0 mm wet screening in the HPGR (with rolls of 0.9 m diameter and 0.25 m width) with feed material to verify the locked cycle condition at equilibrium. Test A1 has been carried out in combination with 1.0 mm screen. Tests A1 to A3 are carried out in similar, but at pre-determined HPGR operating parameters such as 3.5 N/mm2 specific pressure, 18.5 RPM roll speed, and 8.0% moisture content. Tests A4 and A5 are used to test at higher and lower (5.0 and 2.5 N/mm2) pressures respectively. Test A6 has been conducted at lower roll speed (9.5 RPM) whilst test A7 has been conducted at higher moisture content (10.0%). The effect of varying the HPGR operating parameters on product particle size distribution (PSD), specific throughput (SPT), and specific energy (SPE) has been shown in Table 1. Test A2 shows the optimized results of HPGR which produced center product size P80 of 2.4 mm with high specific throughput of 275 ts/hm3 with lowest specific energy of 1.5 KWH/ton. Bond work index of the crushed sample was found to be 11.2 KWH/ton which was reduced by 7.4% against bond work index value of feed. This is due to crack generation in HPGR product which is evident from Figure 5 showing SEM analysis of HPGR product. Size distribution of HPGR product (Centre and edge) with screen oversize fraction (+2mm) and undersize fraction (-2mm) is presented in Figure 6. Screen oversize fraction (+2mm) is recirculated to HPGR feed. Screen undersize material (-2mm size) is subjected to ball mill (with length of 0.92 m and diameter of 0.73 m) to further ground the ore to below 75micron size.
Ball mill has been operated at optimized pulp density of 65% solid by weight and mill speed of 50 rpm with charge filling of 30% by volume. Energy consumed by ball mill for grinding the material from 2 mm top size to 75 mm size was 7.5 KWH/ton. Thus, combination of HPGR followed by ball mill consumes 9 KWH/ton of energy in grinding the ore from 8 mm to 75micron size.
Based on the above operations and the tabulated results, the grinding process is energy efficient i.e., 38% reduction in grinding energy as compared to conventional grinding process which comprises ball mill- ball mill combination and consumes around 14.5 KWH/ton of energy (as shown in Table 2).

Table 1

Table 2
Stage HPGR-Ball mill Ball mill Units Method
HPGR from 8mm to 2mm 1.5 kWh/t Direct power
Ball mill from 2mm to 0.075mm 7.5 kWh/t Direct power
Ball mill from 8mm to 2mm 2.0 kWh/t Direct power
Ball mill from 2mm to 0.1mm 12.5 kWh/t Direct power
Overall 9.0 14.5 kWh/t

From the above table 2 which shows tabulated results of energy consumption by utilizing HPGR and Ball mill grinding in comparison with ball mill – ball mill combination. The resultant shows that the energy consumption of HPGR and ball mill combination utilizes less energy.
In one embodiment, grinding the goethitic low grade iron ore by following primary crushing, secondary crushing, HPGR and ball milling to obtain the goethitic low grade iron ore in sizes of 75 micron or less by consumes less energy in comparison with conventional techniques and methods.
Equivalents:

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.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

As an example, the application may include but not limiting to automotive industry.

Claims:We claim:

1. A method for grinding metallurgical goethitic low grade iron ore, the method comprising:
subjecting, the goethitic low grade iron ore to:
a primary crushing (100), in a primary crusher; and
a secondary crushing (101), in a secondary crusher to form granules of goethitic low grade iron ore of size 8mm or less;
grinding, the granules of goethitic low grade iron ore in a high-pressure grinding roll (HPGR) (102), wherein, the griding process results in reduction of the granules of goethitic low grade iron ore to a size of 2mm or less; and
grinding, the granules of goethitic low grade iron ore having size of 2mm or less in a ball mill (103); wherein the grinding process in the ball mill (103) results in the granules of goethitic low grade iron ore to be powdered to a size of 75 micron or less.

2. The method as claimed in claim 1 comprises sieving and scrubbing the goethitic low grade iron ore after passing through the primary crusher and the secondary crusher.

3. The method as claimed in claim 1, wherein the primary crusher is a gyratory crusher, and the secondary crusher is a cone type crusher.

4. The method as claimed in claim 1, wherein the granules of goethitic low grade iron ore is sieved in a sieving screen after passing through the secondary crusher to separate to the granule size of 8mm or less.

5. The method as claimed in claim 1, wherein the granules of goethitic low grade iron ore are sieved though the sieving screen after grinding in the high-pressure grinding roll (HPGR) to match the granule size of 2 mm or less.

6. The method as claimed in claim 1, wherein the goethitic low grade iron ore comprises composition of 50 wt% of Iron (Fe) and 9 wt% of Aluminium oxide (Al2O3) with a moisture content ranging from 8 wt% to 10 wt% after scrubbing.

7. The method as claimed in claim 1, wherein energy required for grinding of the goethitic low grade iron ore of size 8mm or less ranges from about 1.2Kwh/ton to 1.5Kwh/ton.

8. The method as claimed in claim 1, wherein energy required for grinding of the goethitic low grade iron ore of size 2mm or less ranges from about 7 Kwh/ton to 7.5Kwh/ton.

9. The method as claimed in claim 1, wherein the high-pressure grinding roll (HPGR) grinds the goethitic low grade iron ore into a centre product granule and an edge product granule.

10. The method as claimed in claim 9, wherein the centre product granule and the edge product granule are mixed before screening.