DESC:Technical Field of the Invention

The present disclosure generally relates to the field of Mineral processing and Metallurgy. More particularly, the present disclosure relates to a process particularly for the beneficiation and recovery of enriched iron values of 50-58 %Fe from lean and low grade iron ore fines of 28- 36%Fe [-10 mm size] or from the fines of iron ore mine waste of several mines from different places by using dry medium intensity magnetic separation technique. An overall enrichment of Fe content by 20-26 units by dry magnetic separation technique is the unique disclosure. This disclosure is also applicable on the ores containing martite mineral predominant iron ores in any region.

Background of the Invention

Andhra Pradesh (AP) has been reported to possess iron ore mines in the districts like Prakasam, Kadapa, Kurnool, Anantapur, Krishna. Unfortunately, the iron ores from these regions are lean in grade and needs further upgradation to use them as feed for iron and steel industry. Unless such lean ores are subjected to a state-of-the-art beneficiation, such materials are of no use for iron and steel industry.

In view of the gradual depletion of high-grade iron ores in the country in general and in the south India in particular, there is a need to upgrade the iron quality to meet the required standards of blast furnace or DRI plants either as lumps, sinter feed or as pellet. This necessity assumes more significance in view of the NSP [National steel policy] 2017, which emphasizes the production of 300 million tons/annum steel production by 2030 from the current level of 100 Million tons/annum steel production.

In India, major supply of quality iron ores are reported from Odisha, Jharkhand, Chhattisgarh, Madhya Pradesh, Karnataka and Goa. Although there are few scattered known iron ore deposits in Tamil Nadu, Andhra Pradesh and Maharashtra, these states did not find place as the iron ore mineral occurring states of India, primarily due to the low Fe content in the iron ores of these regions.

Prior art in iron ore fines processing: The iron ore washing plants in general carryout primary and secondary crushing of the high and medium grade ores and subject the crushed ore to high pressure water washing cum scrubbing and screening to collect +10 mm size fractions as the lump ore or calibrated ore and utilize it either in blast furnace or in DRI units based on the Fe %, SiO2% and Al2O3% for making iron either as pig iron or sponge iron. The P %, S % in these lumps should be less than 0.05%. The blast furnaces need -40mm+10 mm size while the DRI plants operate on -20mm +5 mm size iron ores.

The -10 mm size fraction generated in such operations, is known/referred as fines, needs beneficiation to utilize the beneficiated material as sinters if no further size reduction is carried out on such -10 mm size fines. Alternately, such fines can be ground/reduced to < 50 um size by grinding followed by treating on WHIMS/Flotation machines/flocculation technique, or their combination to prepare pellet grade material [ assaying > 63% Fe].

The typical processing unit operations involved in Iron ore beneficiation on typical size fractions mentioned are provided in the figure 1 (Typical iron ore processing by size) below which is self-explanatory. The fines treatment is always a wet process since the lump size preparations needs multi-stage crushing of run of mine ore followed by wet vibratory screening with intensive water spraying. The unit operations that are generally adopted to recover iron values from fines are generally heavy media, jigs, spirals, shaking tables, hydro cyclones and wet low, medium and high intensity magnetic separators or their combinations.

The treatment of -10mm or -6 mm fractions by dry medium intensity magnetic separators in commercial application has not been reported so far in the prior art.

Heifen Zhang et al [2015] as disclosed in their publication appeared in Separation Science and Technology, attempted applicability of dry high intensity magnetic separation on low grade hematite ore assaying 29.14%Fe and could upgrade the Fe content to 36.22% with 75.97% recovery i.e an up gradation of around 7 units on particles of < 10 mm size [magnetic induction at drum surface reported as 9000 gauss].

The same authors also indicated in the same publication that the studies carried out on a limonite ore assaying 24.53%Fe, Fe could be upgraded to 32.6% Fe [8 units upgradation] with 77.62% recovery using dry high intensity magnetic separator having fixed magnetic induction on 0.9 Tesla [9000 gauss] on the surface of the drum. In either case the maximum units up gradation is less than 10 units and the Fe grade could be raised only to less than 37% Fe which cannot be utilized in iron industry.

No commercial plant reported so far is using dry medium intensity magnetic separator as an unit operation to upgrade the Fe content in the -10mm size fines.

In the present invention, the iron ore minerals source is from Chaballi mine in YSR Kadapa district of Andhra Pradesh which contains Fe between 30% and 44%Fe. The iron minerals present in this ore are hematite, martite, goethite and limonite with predominant occurrence of hematite having physical characters similar to martite in addition to presence of martite in the ore.

The ore from the Chaballi mine, Kadapa district is being low in Fe content < 45%Fe, currently being subjected to beneficiation by Jigging technique [using -20+8mm. or -18+5mm sized ore] to upgrade the Fe content to 50%Fe to 56% Fe from a feed varying between 36% and 44% Fe by M/S Benita Industries Pvt Ltd. However, while preparing the feed to the jigging plant at -20+8 mm or -18+5 mm size, nearly 50-60 wt,% of the material of below -10 mm or -5 mm size material are produced and stock piled as fines having Fe content varying between 28-38% which cannot be used by iron & steel industries unless beneficiated to the sinter quality grade[>50%Fe] at least.

The present disclosure is pertaining to the judicious utilization of such low grade iron ore fines [100% passing -10 mm size] by adopting the novel technique of dry magnetic separation at medium intensity to upgrade the Fe content to > 50% with overall yield varying between 20 to 40 wt,%, at an intensity of around 6000-7000 gauss, depending on the Fe content in the feed, which is either to unknown to iron ore treating commercial plants across the globe. The process disclosure can be completely dry [the patent main disclosure] or combination of dry and wet to minimize the loss of iron values. The dry magnets used are Rare Earth Drum of ERIZ [model 15-12-1(15” dia x 12 “wide] and Rare Earth Roll [model 6-5-1] [6” dia x 5” wide]. The schematic of the disclosures is given Figs.2 &3 and elucidated.

Therefore, there is no commercial plant reported so far that is using dry medium intensity magnetic separator as a unit operation to upgrade the Fe content in the -10mm size fines.

Brief Summary of the Invention

The following presents a simplified summary of the disclosure in order to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure and it does not identify key/critical elements of the invention or delineate the scope of the invention. Its sole purpose is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

Exemplary embodiments of the present disclosure are directed towards development of a suitable process routes for beneficiation and recovery of iron values from low grade iron ore fines of -10 mm size. The Fe minerals enrichment and recovery can be obtained from the -10 mm or below sized particles containing 26-38% Fe.

This invention is about the application of dry magnetic separation technique on – 10 mm +0.5 mm size materials at a magnetic intensity of 6000- 7000 Gauss and more precisely @~ 6500 gauss. This process also facilitates additional production of 30- 45 % Fe bearing material as by product from such ore fines also by dry medium intensity magnetic separation which can be utilized in the cement industry as a source of iron. This is however an optional step to minimize wastage.

The Chaballi iron ore is being subjected to stage crushing and screening into -18 mm+ 5 mm and -5 mm size and the +5 mm fraction which is between 40-50wt,% of the ore, is being subjected to jigging by M/S Benita industries Pvt Ltd to upgrade the Fe content to > 46-56%Fe as lumps and being marketed to various end user industries in Tamilnadu, Karnataka and A.P regions in India.

The cut size varies between 10 mm and 5 mm, hence the material of - 8 mm size was considered in this case as the feed size for the purpose of exemplary description of the process. Otherwise, this process disclosure can be applied on -10 mm size and below size fines.

The -8 mm size material which is reported to contain 28%Fe to 38%Fe in general is being supplied to local cement industries currently as a source of iron in cement manufacturing units.

The feed size considered to this disclosure is d80 of ~8-4 mm size [say - 5 mm] with Fe varying between 28% and 42%. The Al2O3 content 5-10%, LOI 4-8% and SiO2 25-32% are the likely variation.

This size material [say -8 mm size chosen in this case] is washed in screw classifier/scrubber that can give mild scrubbing action facilitating loosening of clay and adhering slimes. The scrubbed/washed fines by screw classifier/scrubber facilitates removal of ~20-35wt,% of the material below - 0.5 mm or - 0.3 mm size containing 12-28 % Fe with predominant clay and silica. The scrubbing is not an essential step and can be avoided by resorting to efficient washing on high frequency vibratory screen with water sprays or by screw classification or by combination of both. The objective is removing the adhering clay bearing slimes from the + 0.3 mm size [or any coarse size chosen like 0.5 mm or above] material thus can be achieved by attrition scrubbing, drum scrubbing, vibratory wet screening, screw classification, cross flow separation and hydro cyclone or their combinations. For the purpose of this novel disclosure one such combination is used to remove adhering fines. The cut off size can be between 0.05mm to 2 mm. If the feed is < 10 mm size the cut off size can be chosen as per the material/mass distribution in the finer fractions of -0.5 mm present in the iron ore fines.

The typical particle size distribution and assay of the iron ore fines after wet screening is provided in Table-1 which by and large represents the Chaballi mine. However, the sample selected, and the disclosures mentioned are on the ~30% Fe bearing material selected and on a composite sample collected from various dumps [-8mm size] stacked near Benita iron ore mining area. The minerals present in these fines are hematite, goethite, limonite, quartz, feldspar, clay with magnetite and Martinized magnetite. The typical dry screen and wet screen analysis after mild scrubbing are provided in Table-1.
Table-1

The scrubbed/washed and deslimed feed is collected into two fractions as coarse and fines. The coarse can be between - 8 mm + 0.5 mm and the fines fraction can be -0.5 mm fraction for example purpose.

This cut off size can be varied between 0.1 to 1.2 mm, instead of 0.5 mm, but in this disclosure 0.5 mm size is considered for convenience and to produce more material with enriched Fe content by dry process. A screen of 1.5 mm size is practically viable to screen efficiently and economically by wet vibratory screening.

The Fe content in the slimes fraction varies between 28-14% Fe while the Fe content in the +0.5 mm size fraction varies between 28-44%Fe which however hinges on the feed assay variation between 28 and 38 %Fe.

It is an object of the present invention to effectively utilize the low/lean iron ore bearing material of - 8 mm size containing Fe minerals like hematite, martite, goethite and limonite in association with gangue minerals clay, and quartz + feldspar as major gangue, as a material suitable for commercial applications employing the process flow-sheets developed involving various stages and steps of scrubbing/washing, desliming, classification, magnetic operations and their combinations thereof.

It is an object of the present invention to disclose and provide a commercially viable flow-process to enrich the quality of iron to meet the commercial specifications by a combination of, scrubbing/washing, screening, drying, dry medium intensity magnetic separation technique [6000-7000 Gauss] which obviates the drawbacks of the hitherto known prior art as detailed above and also by wet medium/high intensity magnetic separation techniques [8,000-14,000 gauss] applicable to wet size scrubbed fines.

The -8 mm sized material is to be scrubbed in drum scrubber followed by vibratory screening of the drum scrubber overflow [coarse fraction] to segregate the particles into + 0.5 mm and - 0.5 mm sized fractions. A commercial drum scrubber can also be utilized for scrubbing the fines followed by either screw classifier or wet vibratory screen to separate the clay bearing fines/slimes of 0.5 mm and below. Also, only screw classifier can be used to dislodge the fines. The Screw Classifier Overflow (SCOF) contains particles measuring below ~ 500 microns (0.5mm). This cut off size can be decided at much finer sizes depending on the quantity, and quality of the -8 mm size ore fines.

The typical assay of the SCOF varies in the range of ~ 14-26 % Fe, whereas, the SCUF assay varies in the range of 30-44 %Fe depending on the feed quality, which varies between 28-38%Fe in the fines expected from the low-grade iron ores of these two states in A.P.

Brief Description of the Drawings

Other objects and advantages of the present invention will become apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments, in conjunction with the accompanying drawings, wherein like reference numerals have been used to designate like elements, and wherein the present invention is illustrated schematically in Figures 2, and 3 of the drawings accompanying this specification with tentative schematic of Fe values assay and recovery from the - 8 mm size material.

Figure 1 illustrates a prior art depicting the typical iron ore processed by size.

Figures 2a and 2b illustrates a flowchart depicting the typical schematic of processing -8 mm size iron ore fines by unique dry medium intensity magnetic separation technique according to the exemplary embodiment of the present invention.

Figure 3 illustrates a flowchart depicting the typical schematic of processing -10 mm size iron ore fines by unique dry and wet medium intensity magnetic separation technique according to the exemplary embodiment of the present invention.

Detailed Description of the invention

It is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

The use of “including”, “comprising” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. Further, the use of terms “first”, “second”, and “third”, and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another.

Referring to the drawings, Figures 2a and 2b illustrates a flowchart (200) depicting the typical schematic of processing -8 mm size iron ore fines (10) by unique dry medium intensity magnetic separation technique according to the exemplary embodiment of the present invention. The suggested route in the present invention for the iron concentrates recovery and enrichment is by treating the deslimed + 0.5 mm sized fraction [this size can be varied between 0.1 to 1.5 mm and for convenience the cut size being mentioned as 0.5 mm in this case] by using dry medium intensity magnetic separation technique application at ~ 6500 gauss.

The schematic novel routes for recovery of iron values by desliming with screw classifier/ wet vibratory screen (14) to reject the - 0.5 mm size fraction. Further classifying the deslimed + 0.5 mm fraction material either after drying by known methods of drying or by natural sun drying (16) to < 5-6% moisture, into +1.5 mm and -1.5mm+0.5mm size fractions. The figure 2a reflects the details without resorting to further classification of -8mm+0.5 mm size. This cut off size can be ~ 1 mm to 2 mm as well, or any lower size applicable/feasible commercially for dry screening.

The -8 mm+0.5mm size fraction after drying (16) is directly processed on dry magnetic drum magnets at 6000-70000 gauss (18) to reject material with, ~ 20% Fe as 1st non-magnetic-1 fraction (22). The magnetic fraction-1 (20) is further treated on medium intensity drum magnet at 6500 (18) intensity to obtain enriched magnetic product-2 (28) with > 50% Fe [50%-56%Fe bearing product can be obtained.

This product [-8mm+0.5 mm] is suitable to be used as sinter feed. The non-magnetic product-1 (22) and non-magnetic product-2 (26) obtained is subjected to further size reduction to < 2 mm size, in our case roll crusher (24) is utilised for size reduction to < 2 mm size. This -2 mm sized material is treated on dry drum magnet at 6500 gauss (18) to reject non-magnetic product -3 (30) with < 20% Fe[14-20%Fe] and the magnetic product-3 (32) is further treated on dry medium intensity drum magnet at 6500 gauss (18) to obtain Fe enriched magnetic product-4 of < 2 mm as the 2nd sinter quality product of >50% Fe. The grade can be increased by sacrificing yield i.e at reduced weight recovery. The resulting non-magnetic product-4 (36) on -2 mm material can be used as feed to cement industry.

Thus, by treating -8mm+0.5 mm size dried iron ore fines (10), sinter quality product of 50-56%Fe is obtained at 20-40wt% overall yield.

Figure 2b is a minor modification of figure 2a, where the -8mm+0.5 mm (10) dry material is screed into two fractions as -8mm+1.5mm and -1.5mm + 0.5 mm and treating the -8mm+1.5 mm size fraction as well as the -1.5 mm+0.5 mm size fractions separately on dry medium intensity drum magnet/roll magnet having field intensity of ~ 6500 gauss. Although drum magnets were used, as illustrated in this disclosure, dry roll magnets can also be used which may necessitate frequent belts replacement adding to maintenance cost. The roll magnets facilitate utility of magnetic intensity of 8000-12000 gauss which may be considered when higher yield is needed at lower grade.

This uniqueness of iron content up gradation by dry magnets at ~ 6500 gauss (18) on - 8mm+0.5 mm is primarily due to the uniqueness of the iron minerals present in such fines (10). The iron mineral present having martite like physical characters, such upgradation by dry magnetic separation was observed feasible. However, this technique can be adopted on any iron ore fines having containing iron ore minerals formed under partial reduced conditions on hematite ores or partial oxidized conditions on magnetite ores or on martite bearing ores.

The other alternate route through which the iron can be enriched commercially from such fines is schematically given in Figure 3. This alternate process indicates apart from recovering the enriched iron bearing concentrates of > 50% Fe [50-56%Fe] by dry magnetic separation, also indicates the possibility of obtaining > 50% Fe bearing iron concentrate from the insitu fines of the iron ores of <10 mm by wet high intensity magnetic separation. The recovery of iron values from the scrubbed and screened (12) wet fines can also be enriched to > 45-52% Fe by spiral concentration (17) after desliming. If it is required to obtain 50-60% Fe grade production, the spiral concentrate can be routed through WHIMS [wet high intensity magnetic separation] to produce > 50-60% Fe. This is an additional step to reduce the waste and to recover the iron values present in the < 1 mm size fines obtained after scrubbing/screening of <10 mm size iron fines.

The iron content in the deslimed iron ore fines can be enriched and recovered by treating them on spirals (17) alone, or on wet high intensity magnetic separator between 9000-15000 gauss intensity, or by a combination of spiral and WHIMS as described in Figure. 3.

Figure 3 illustrates a flowchart (300) depicting the typical schematic of processing -10 mm size iron ore fines by unique dry and wet medium intensity magnetic separation technique according to the exemplary embodiment of the present invention. As shown in Fig. 3, the cut off size is considered as 1.5mm/1.2 mm. The Screw classifier overflow and/or vibratory wet screen underflow (12) is subjected to hydro cyclone (13) to remove < 50 um fraction as cyclone overflow can be rejected through thickener to the tailings pond. This cut off size mentioned is tentative and can be selected between 20 micron to 100 micron or even higher size as per the %Fe permissibility into the tailings pond. The underflow of hydro cyclone (13) to be treated on wet high intensity magnetic separator (17) [WHIMS] at > 9000 gauss to collect magnetic concentrate with > 46-60% Fe either in single stage or after cleaning the 1st stage magnetic product (20) once again on WHIMS (15). The non-magnetic fraction (22) to be discarded to the tailings pond. The middling’s obtained from WHIMS operation (17) can be utilised as source of finer size iron product with >32%Fe to the cement industry as well.

Prior to treating the cyclone (13) underflow in spiral/ WHIMS/or (17) their combination, it is prudent to pass the slurry through LIMS [Low intensity magnetic separator] of < 2000 gauss to ensure removal of magnetite particles which otherwise likely to choke the WHIMS. This is, however, is an optional step. Alternately, the deslimed hydro cyclone underflow can be treated on spirals in one or 2 stages or in combination of spiral concentrate to be subjected to wet high intensity magnetic separation [WHIMS] at 9000-15000 gauss magnetic intensity.

The dry drum magnetic separation (18) applicability on -8 mm size iron ore on low grade iron ores (10) as described in Fig. 2a & 2b to prepare >52%Fe to 56%Fe [ 20-26 units upgradation] is a novel route which has not been reported in the iron ore processing techniques either applied commercially or reported in the prior art.

In accordance with a non-limiting exemplary embodiment of the present disclosure, a process for beneficiation of iron ore fines/mine waste fines by combination of various steps like scrubbing, washing, desliming, classification, spiral, medium/high intensity magnetic separation, has been disclosed which comprises:
i) Scrubbing/washing of the low-grade iron ore fines or mine waste fines to facilitate liberation and removal of sticky clay minerals from the surfaces of coarse material.
ii) Desliming the scrubbed material with low iron content < 14-18%Fe in a screw classifier to obtain products termed as overflow (SCOF) predominant with clay and underflow (SCUF) with depleted slimes. It is suggested that a commercial hydro cyclone, fine screens like Derik screens or floatex density separator [cross flow separator] units can also be used for this purpose. Recovering the iron values from both the SCOF and SCUF fractions following the steps as described in the Figures 2 & 3. The cut off size may vary between 0.5 to 0.1 mm based on the Fe content. However, the recommended cut of size may be 0.2 mm to 0.5 mm by screw classifier with or without scrubbing in attrition or drum scrubber.
iii) Subjecting the SCOF from (ii) to hydro cyclone to obtain the slimes (ultra-fines) measuring 0- 0.05 mm in size (the cut size also be between 20 to 100 µm) with set of hydro cyclones while collecting the rest as slime free hydro cyclone underflow. The ultra-fines are recovered by 1 or 2 stages of cloning to ensure the removal of -0.03 mm (-30 µm or the size selected) sized material for effective removal of fine clay and silica values. The slime particle size for recovery chosen (i.e 0.03 mm) is tentative and can vary between 0.1 mm to 0.02 mm (20-100 µm).
iv) The slimes measuring -30 µm in size (from ‘iii’ step) are collected in a thickener as feed for clay content upgradation or for final rejection into tailings pond. This fraction of - 0.03mm size ultra-fines contain >12-22% Al2O3 and can be utilised as a source of clay by further treatment to reduce the unwanted constituents like iron, silica as per the end user specification and is not a part of this disclosure.
v) The cyclone underflow material are to be subjected to wet high intensity magnetic separation [8000-15000 gauss] to enrich the iron to > 48-60% Fe and the non - magnetic fraction to be rejected. The number of stages of WHIMS treatment hinges on the quality of product needed and on the Fe content of HC UF. Fine size wet magnetic concentrate of > 50-60%Fe can be obtained from this fraction as wet magnetic product of < 0.8 mm size. In case after scrubbing the ore, the material is wet screened to +1.5 and -1.5-mm fractions, the -1.5 mm fraction is to be subjected to hydro cyclone to reject the slimes up to 0.1 mm size. The cyclone underflow is further treated on either on spirals or on wet high intensity magnetic concentrators or a combination of both produces > 50%Fe bearing wet concentrate as an additional sinter quality wet product.
vi) For treating the SCUF, it is prudent to select 1.2 mm screen since the 100% passing - 1.2 mm fraction will have d80 of 700 microns which is an ideal size for spiral/WHIMS operation. Coarser size [if selected beyond 1.5 mm] may cause operating difficulties on WHIMS at 8000-15000 gauss intensity.
Subjecting the dried and cooled -8mm +1.2 mm size material to ambient temperature [< 50 0C] on medium intensity drum magnetic separator [6000-7000 gauss] to collect magnetic-1 and non-magnetic-1 products. The magnetic-1 product is treated on drum magnet again at @ 6500 gauss intensity to produce magnetic-2 and non-magnetic -2 products. The 2nd magnetic product obtained is the enriched Fe of >53%. The overall yield at this stage varies between 15-20 wt% .
The non-magnetic product-2 to be roll crushed or subjected to any size reduction unit to reduce size to < 2 mm to facilitate liberation and this < 2 mm material either alone or by combining with the -1.5mm + 0.5 mm fraction to be subjected to 2 stage drum magnetic separator at 6500 gauss to obtain a magnetic-4 product of < 2 mm size having 50-55% Fe. Thus, sinter quality products of -8mm+1.5 mm, and -2mm sizes having >50%Fe can be produced at an overall yield of 25-35wt% of the feed tonnage.
The insitu dry fraction of -1.5 mm + 0.5 mm can also be treated exclusively on dry medium intensity magnetic separator in 2 stages as shown in fig.2a.
vii) The 1st stage dry non-magnetic product having 16-22% Fe and the 3rd stage dry non-magnetic product having 15-22%Fe, can be mixed together and retreated on dry magnet at ~ 6500 gauss [5000-7000 gauss] to improve the grade to > 32% Fe which can be a source of iron to cement plants feed or any other utility by routing it through roll crushing to <2 mm size.

According to a non-limiting exemplary embodiment of the present disclosure, the main advantages of the present invention are:
1. Effective enrichment of Fe values by 20-26 units by following the steps of washing, desliming, classifying, and subjecting the classified wet fine fractions to WHIMS & dry coarse fraction on dry medium intensity magnetic separators like drums or rolls or combination of both after drying the washed ore.
2. Possibility of effectively recovering the valuable Fe values having > 50% Fe [@ > 20-35 wt,% of the throughput] from the low grade -6 mm or -10 mm washed ore fines of Chaballi mine, Kadapa district.
3. Possibility of recovering coarse sized dry magnetic concentrate with > 50-56% Fe by DMIMS [dry medium intensity magnetic separator ~6,500 Gauss] on the +1.5 mm and -1.5 +0.5 mm sized iron fines.
4. The quality of Fe can be upgraded to > 50-56% Fe from a feed quality of 28-38% Fe in the -6mm or -10 mm size fines.
5. Improvement of quality of Fe content by 12-18 units by application of dry magnetic separation [6000-7000Gauss] on -8mm +1.5 mm size material and on -2 mm size material to obtain > 50% Fe is the uniqueness of this disclosure to augment the eventual grade to > 46-56%Fe.

Although the present disclosure has been described in terms of certain preferred embodiments and illustrations thereof, other embodiments and modifications to preferred embodiments may be possible that are within the principles and spirit of the invention. The above descriptions and figures are therefore to be regarded as illustrative and not restrictive.

Thus, the scope of the present disclosure is defined by the appended claims and includes both combinations and sub combinations of the various features described herein above as well as variations and modifications thereof, which would occur to persons skilled in the art upon reading the foregoing description.
,CLAIMS:1. A process (200) for beneficiation and recovery of saleable Fe values from low grade iron ore with dry medium intensity magnetic separator technique, comprises:
subjecting, low-grade iron to a washing technique, a desliming technique, a screening technique followed by a dry (200) and a wet (300) magnetic separation techniques;
adopting, dry magnetic separation technique (200) at medium intensity to upgrade the Fe content to > 53% with yield varying between 20 to 50 wt,%, depending on the Fe content in the feed;
wherein the process involves:
scrubbing and/or washing, - 8 mm size material in screw classifier (14)/ scrubber (12) to facilitate liberation and removal of sticky clay minerals from the surfaces of coarse material;
desliming, the said scrubbed material (12) with low iron content < 14-18%Fe in a screw classifier (14) to obtain products termed as overflow (SCOF) predominant with clay and underflow (SCUF) with depleted slimes;
subjecting, the received SCUF to dry and/or wet magnetic separation techniques to upgrade the Fe content to > 53%;
Characterized in that:
the said dry magnetic separation (200) process involves:
a) drying (16) and/or screening (17), the SCUF on 1 or 2 mm screen to obtain slime free coarse to reduce the surface moisture to < 6 %;
b) subjecting, the dried and cooled -8mm +1.2mm size material is treated to ambient temperature [< 50 0C] on medium intensity drum magnetic separator (18) [6000-7000 gauss] to collect magnetic product as, 2nd product with > 48%Fe-58%Fe and non-magnetic product;
c) treating, the magnetic-1 product (20) on drum magnetic separator (18) again at 6500 gauss intensities to produce magnetic-2 (28) and non-magnetic-2 (26) products;
d) after drum magnetic separation (18), the non- magnetic material (22) resulting of +1.5 mm sized material is further crushed to < 1.5mm size by roll crusher or any commercial size reduction machine (24);
e) subjecting, the roll crushed (24) non-magnetic material (22) to 2nd stage drum magnetic separation (18) on medium intensity magnetic separator to obtain product with 46-56%Fe as 3rd Fe concentrate in the size range -1.5-0 mm at 6500 gauss to obtain a magnetic-4 product (34) of < 2 mm size having 50-55% Fe;
f) mixing together and retreating, 1st stage dry non-magnetic product (22) having 16-22% Fe and the 3rd stage dry non-magnetic product (30) having 15-22%Fe, on drum magnet (18) at ~ 6500 gauss [5000-7000 gauss] to improve the grade to > 32% Fe which can be a source of iron to cement plants feed or any other utility; and
g) finally, the sinter quality products of -8mm+1.5 mm, and -2mm sizes having >50%Fe can be produced at an overall yield of 25-35wt% of the feed tonnage.

2. The process (200) as claimed in claim 1, wherein involves combination of wet and dry magnetic separation technique (referring Fig.3), the process includes:
the combination of wet and dry magnetic separation process is more or less the same till the removal of the clay bearing fines;
wherein the combinational process involves:
after scrubbing the ore, the material is wet screened (15) to +1.5 and -1.5-mm fractions, the -1.5 mm fraction is to be subjected to hydro cyclone (13) to reject the slimes up to 0.1 mm size.
treating, cyclone underflow (13) on either on spirals or on wet high intensity magnetic concentrators (17) or a combination of both to produce > 50%Fe bearing wet concentrate as an additional sinter quality wet product;
after wet screened (15), the dried and cooled -8mm +1.2 mm size material is subjected to ambient temperature [< 50 0C] on medium intensity drum magnetic separator [6000-7000 gauss] (18) to collect magnetic-1 and non-magnetic-1 products;
treating, the magnetic-1 product (20) on drum magnetic separator (18) again at 6500 gauss intensities to produce magnetic-2 (28) and non-magnetic-2 (26) products;
after drum magnetic separation (18), the non- magnetic material (22) resulting of +1.5 mm sized material is further crushed to < 1.5mm size by roll crusher or any commercial size reduction machine (24);
subjecting, the roll crushed (24) non-magnetic material (22) to 2nd stage drum magnetic separation (18) on medium intensity magnetic separator to obtain product with 46-56%Fe as 3rd Fe concentrate in the size range -1.5-0 mm at 6500 gauss to obtain a magnetic-4 product (34) of < 2 mm size having 50-55% Fe;
mixing together and retreating, 1st stage dry non-magnetic product (22) having 16-22% Fe and the 3rd stage dry non-magnetic product (30) having 15-22%Fe, on drum magnet (18) at ~ 6500 gauss [5000-7000 gauss] to improve the grade to > 32% Fe which can be a source of iron to cement plants feed or any other utility; and
finally, the sinter quality products of -8mm+1.5 mm, and -2mm sizes having >50% Fe can be produced at an overall yield of 25-35wt% of the feed tonnage.

3. The process (200 & 300) as claimed in claim 1, wherein the deslimed (hydro cyclone overflow) fine particles (- 0.030 mm) obtained are the clay and silica rich and can be rejected. This cut off size hinges on the permissible rejection of iron grade into the final tailings.

4. The process (300) as claimed in claim 1, wherein the hydro cyclone (13) underflow, or screen oversize can be a source of fine iron concentrate of > 45-58% Fe by treating on WHIMS (17).

5. The process (200 & 300) as claimed in claim 1, wherein the coarse -8.0 mm + 1.2 mm sized fraction is processed either by dry magnetic separation equipment with magnetic intensity varying between 6000 - 7000 Gauss (18) in a single stage or in combination of stages.

6. The process (200 & 300) as claimed in claim 1, wherein the 1st stage dry magnetic separator (20) non- magnetic fraction (22) is further subjected to drum medium intensity magnetic separation (18) after passing it through roll crusher (24) to reduce the size < 2 mm /-1.5 mm or < 1 mm, to obtain a 2nd iron concentrate of -1.5 mm size with > 45-57%Fe.

7. The process (200 & 300) as claimed in claim 1, wherein the number of cleaning stages required depends on the feed quality and on the product quality.

8. The process (200 & 300) as claimed in claim 1, wherein the production of enriched magnetic concentrates can be entirely by dry process by removing the < 0.2 mm or 0.3 mm size material from the fines after scrubbing and screening (12 & 14).

9. The process (200 & 300) as claimed in claim 1, wherein the process selected to scrub (12) and remove the fines can be carried out by the known arts in the field and the cut of size of rejection can be as per the % Fe rejection chosen in the final tailings.

10. The process (200 & 300) as claimed in claim 1, wherein the cut off size of screens selected for dry separation (18) on the dry magnets is only tentative and can be any size that is commercially feasible to separate into + and – fractions on dried iron ore fines.