Description:FIELD OF THE INVENTION

The present invention relates to the recovery of iron minerals from high siliceous low grade iron ore comprising of stage wise beneficiation process for beneficiation of low-grade, high-siliceous iron ore to recover iron-bearing minerals with higher Fe. High siliceous iron ore is hard in nature, and it consists of lower Fe and high silica with alumina. For high siliceous iron ore, it is more important to develop an effective beneficiation process to recover the iron-bearing minerals with high Fe to further utilise in the pellet-making process. The highly siliceous iron ore is processed by applying stage-wise gravity separation followed by magnetic separation after grinding and de-sliming the material to the required size based on silica liberation for iron up-gradation and removal of alumina as well as silica for pellet making. The different process stages with the optimised beneficiation technique for high siliceous iron ore are directed to favour value addition in the optimised beneficiation technique. The process of high siliceous low grade iron ore beneficiation of the present invention enables a better concentrate grade and higher recovery subjecting the high siliceous low grade iron ore to crushing followed by grinding in a closed circuit with a de-sliming cyclone to remove the ultrafine particles as overflow and further processing the underflow of said desliming cyclone through select three stage gravity separation followed by magnetic separation on said ground sample at select silica liberation size.

BACKGROUND ART

Low-grade iron ore cannot be directly utilised in the steel industry because it requires higher flux addition, generates a higher slag rate in BF, reduces the production rate, and consumes a higher fuel rate. Before utilising low-grade, high siliceous iron ore in metallurgical plants, the removal of silica and alumina and up-gradation of iron content through the beneficiation process are essential. A process adopted to upgrade ore by removing the silica and alumina is called the beneficiation process. Each iron ore has its own unique mineralogical characteristics and requires a specific beneficiation process to get the best product out of it. The selection of the beneficiation process depends on the nature of the gangue present and its association with the iron-bearing minerals. Several techniques are used in the beneficiation process to enhance the quality of the beneficiated product.

With the fast depletion of high-grade iron ore and to meet the iron ore requirements of steel plants, low-grade, high-siliceous iron ore, lower Fe, has been the focus of interest. High-siliceous iron ore occurs as hard rocks or in the form of weathered soft rocks. Till date, not much research work has been carried out on high siliceous iron ore as a feed material for iron and steel making with suitable processes for its beneficiation. Thus, in spite of the need for huge quantities of iron ore for the steel industry, at present no proven beneficiation methodology is available to beneficiate the highly siliceous iron ore.
On this reference is invited to the patent titled “BENEFICIATION PROCESS OF HIGH SILICEOUS LOW GRADE IRON ORE EXHIBITING COMPLEX LIBERATION CHARACTERISTICS”, Application No: INKO000292012, that relates to the beneficiation process of high siliceous low grade iron ore. A process of froth flotation to recover Fe values from high siliceous low- grade iron ore through beneficiation, comprising crushing of banded hematite jasper ore to -10mm size for pre-concentration in Jig unit and grinding the jig concentrate to -0.1mm size for flotation. The maintained test conditions are: the percent solids in the slurry is 20-30% solids, pH modifier is NaOH solution and pH of slurry is 8.5-10, the stirrer speed is maintained at 800 - 1000 revolutions per minute, dispersant used is Sodium Hexametaphosphate and optimum dosing of dispersant is 2-3 kg/ton of flotation feed, the collector used is Ether monoamines (Sokem 503C) and optimum dosing of collector is 1-1.5 kg/ton of flotation feed, frother used is Methyl Isobutyl Carbinol, MIBC and optimum dosing of frother is 0.1 kg/ton of flotation feed. The Fe content in the concentrate was found in the range of 61-62%.
The paper titled “Simultaneous use of direct and reverse flotation in the production of iron ore concentrate plant” Mining, REM, Int. Eng. J. 71 (2), Apr-Jun 2018, reveals that first, the sample consist of 44% Fe and 34.9% Silica was de-slimed at 38 µm and with the under¬flow a cut was performed in the 74 µm cyclone in order to separate the coarse particles from the fine. With the coarse particles, i.e. with the underflow, there a reverse flota¬tion was carried on obtaining a concentrate with 67.7% of Fe and 0.9% of SiO2. In the fine particle overflow, direct flotation was done, generating a low-quality concentrate with 40.9% of Fe and 39.7% of SiO2. The mass recovery in direct flotation was 88% and in the reverse flotation was 61.1%. The concentrate generated from two flotation had a mass recovery of 67.4% with a content of Fe of 53.4% and 21.6% SiO2.

Again the paper titled “Characterisation and Processing of Some Iron Ores of India”, Journal of The Institution of Engineers (India):Series D, volume 94, pages113–120 (2013) reveals that The soft friable siliceous blackish gray coloured iron ore fines from Chitradurga, Karnataka assayed 59.60 % Fe, 9.06 % SiO2, 1.06 % FeO, 1.09 % Al2O3, 0.05 % P, 0.03 % S, 4.02 % LOI and contained hematite [50 %], quartz [8 %], clay [2 %], goethite [35 %], martite [5 %], magnetite, apatite, chlorite, pyrite[Tr]. The produced concentrate assaying [62 % Fe, 6.02 % SiO2, 0.85 % FeO, 0.82 % Al2O3, 0.03 % P, 0.03 % S, 2.20 % LOI with 85 % Fe recovery at 80 wt% yield indicating the easy amenability of sample to gravity/WHIMS. The process comprised of stage grinding to -0.1 mm, de-sliming to remove 10 µm slimes, gravity–WHIMS.

At present there is thus a need in the art to develop a specific, precise, and economically viable beneficiation technique for processing of highly siliceous, hard iron ore based on exploring select stages that can be put in practice by also applying select ground sample size required for the beneficiation process to remove the silica, together with detailed characterization studies to be carried out to determine the association of minerals and liberation size.

Not only the highly siliceous iron ore needs to be ground to the required size to achieve a better quality product with less silica and higher Fe but there is also a need in the art to explore for select stages to aid beneficiation process for appropriate Fe recovery and silica rejection.

OBJECTS OF THE INVENTION
The basic objective of the present invention is to provide for a defined, precise process for recovery as beneficiation process for low-grade high siliceous iron ore to attain maximum concentrate weight recovery and grade.
A further objective of the present invention is to provide for a process for low-grade, highly siliceous iron ore that would adopt crushing, closed circuit grinding with de-sliming cyclone in circuit, followed by processing the de-sliming cyclone overflow and preferably underflow through three stage gravity separation followed by a two-stage magnetic separation process using wet high intensity magnetic separation (WHIMS).
A still further objective of the present invention is to provide a process for the recovery of iron-bearing minerals from low-grade, high-siliceous iron ore wherein select feed density is applied for de-sliming cyclone and spiral concentrate (rougher, cleaner, and scavenger) and selective magnetic field strength is applied to stage-wise magnetic separation using WHIMS to significantly improve the recovery of iron-bearing particles.
A further objective of the present invention is to provide a process for recovery of iron-bearing minerals from low-grade, high-siliceous iron ore wherein the cleaner spiral and scavenger spiral tailing samples are combined and re-circulated to a rougher spiral concentrator to further improve the concentrate weight recovery and reduce the tailing loss with lesser Fe.
Yet further objective of the present invention is to provide a process for the recovery of iron-bearing minerals from low-grade, high siliceous iron ore wherein the rougher WHIMS magnetic product is further processed in cleaner WHIMS to improve the concentrate Fe grade.
A still further objective of the present invention is to provide a process for recovery of iron-bearing minerals from low-grade, high siliceous iron ore wherein the de-sliming cyclone overflow is further processed in WHIMS to recover the iron-bearing minerals and increase the overall concentrate weight recovery.

SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a process for recovery of iron minerals from high siliceous low grade iron ore comprising of stage wise beneficiation process including the steps of:
subjecting the high siliceous low grade iron ore containing 45 to 55% Fe, 20 to 26% SiO2, 3.00 to 6.0% Al2O3 and 3.00 to 5.50% LOI to crushing to less than 1 mm;
grinding below 1 mm-sized crushed product to achieve about 83.7 – 85.2% passing preferably about 80% passing of less than 45 µm size in a closed circuit grinding with de-sliming cyclone to remove the ultrafine particles of size -10 µm as overflow;
processing of de-sliming cyclone underflow in a three-stage spiral concentrator as gravity separators including rougher, cleaner, and scavenger stages followed by two stage magnetic separation using wet high intensity magnetic separation (WHIMS) to recover the iron-bearing minerals as concentrate.
Preferably a process is provided wherein the cleaner spiral concentrator tailing and scavenger spiral concentrator concentrate were further treated (recirculated) through a rougher spiral concentrator to recover the Fe-bearing minerals, increase the concentrate weight recovery as well as the Fe grade, and reduce the tailing loss with a lower Fe content; and
processing of de-sliming cyclone overflow (O/F) is done in separate WHIMS to recover the iron bearing minerals to increase the concentrate weight recovery whereby Fe recovery is 73.01 to 76.43% and silica reduction is 71.34 to 74.08% and SiO2 rejection varies from 82.24 to 86.05%.
More preferably said process is provided wherein providing low-grade high siliceous iron ore fines, closed circuit grinding with de-sliming cyclone for gravity separation of said fines of de-sliming cyclone underflow at select feed density maintained at 1.07 to 1.10 gm/cc, preferably 1.08 gm/cc, with feed pressure maintained from 1.50 to 2.0 bar, preferably 2.0 bar, followed by said wet high intensity magnetic separation (WHIMS) post crushing and grinding the fines to select size, enables appropriate silica liberation and iron up-gradation in said fines with regard to maximum concentrate weight recovery and grade together with removal of alumina as well as silica from said fines thereby making it suitable for pellet making.

According to another preferred aspect of the process of the present invention wherein said stages of said beneficiations process are as per the following:
(i) Crushing BHQ (banded hematite quartzite) said low grade iron ore preferably containing 45.28 to 51.30% Fe; 20.50 to 26.50% SiO2; 3.48 to 3.80% Al2O3; and preferably 3.75 to 4.02% LOI to crushing from 10 mm to less than 1 mm after screening the material to remove fines before feeding at select feed density to the crusher;
(ii) Grinding the crushed material to below 1 mm-sized crushed product to achieve 83.7 – 85.2% passing of less than -45 µm size by adopting closed circuit grinding with a de-sliming cyclone and feeding in said cyclone at said select feed density that removes the ultrafine particles of size -10 µm as overflow (O/F) and provides for de-sliming cyclone underflow (U/F);
(iii) Performing gravity separation of the de-sliming cyclone underflow (U/F) based ground product in a three-stage spiral concentrators as gravity separators including rougher, cleaner, and scavenger concentrator including re-circulating cleaner spiral concentrator tailing and scavenger spiral concentrator concentrate through said rougher spiral concentrator to recover the Fe-bearing minerals with increased concentrate weight recovery as well as the Fe grade by reducing tailing loss having lower Fe content and attained as final concentrate at the outlet of cleaner spiral concentrator;
(iv) performing two stage wet high intensity magnetic separation (WHIMS) on scavenger spiral concentrator tailings by applying various select magnetic field intensity to recover the iron-bearing minerals as rougher WHIMS magnetic product that is further magnetically processed to obtain cleaner WHIMS magnetic product leading to final concentrate at the outlet of cleaner spiral concentrator; followed by
(v) processing de-sliming cyclone overflow (O/F) in separate wet high intensity magnetic separation (WHIMS) included in said closed circuit to recover iron bearing minerals to increase the concentrate weight recovery of the final concentrate when circulated at the outlet of cleaner spiral concentrator, with the tailings therefrom combined with the final tailings obtained at the outlet of rougher wet high intensity magnetic separation (WHIMS) unit.
Preferably in said process said feed low grade iron ore mineralogical phases include: Magnetite: 12.4 to 15.6%, Hematite: 42.1 to 47.1%, Goethite: 8.6 to 11.5%, Quartzite: 21.5 to 26.7% as the major gangue-bearing mineral, Kaolinite: 34.5 to 5.7% and others : 1.7 to 2.7%.
More preferably in said process the liberation size of the hematite particles at -45 µm is 78 to 82% is effective when adopting closed circuit grinding with a cyclone to remove the ultrafine particles of -10 µm as overflow
Size, mm %
-150 µm 62 to 67
-75 µm 70 to 75
-45 µm 78 to 82
-38 µm 84 to 88
-25 µm 90 to 93

According to yet another preferred aspect of the present invention there is provided said process wherein the liberation of iron bearing minerals at different size fractions in the feed sample is as follows: -45 µm : 83.7 – 85.2%, and -10 µm : 48.9 – 50.2% when collected by closed circuit cyclone as overflow.
Preferably said process comprises subjecting the said low-grade high siliceous iron ore sample to crushing and grinding, de-sliming, three-stage spiral (rougher, cleaner, and scavenger) followed by two stage WHIMS, recirculation of cleaner and scavenger spiral products and single stage WHIMS for treating de-sliming cyclone O/F by maintaining various magnetic field intensities and parameters maintained at various stages of the de-sliming cyclone, spiral concentrator and WHIMS, are as follows:
De-sliming Cyclone:
Feed density: 1.07 to 1.10 gm/cc, preferably 1.08 gm/cc.
Feed pressure: 1.50 to 2.0 bar, preferably 2.0 bar.
Rougher Spiral:
Feed density: 1.22 to 1.27 gm/cc, preferably about 1.25 gm/cc
Cleaner Spiral:
Feed density: Feed density: 1.22 to 1.27 gm/cc, preferably about 1.25 gm/cc
Scavenger Spiral:
Feed density: Feed density: 1.14 to 1.18 gm/cc, preferably about 1.15 gm/cc
Rougher WHIMS
Feed slurry density : 1.18 to 1.22 g/cc, preferably 1.20 g/cc
Magnetic field intensity: 4000 to 6000 gauss, preferably about 5000 gauss
Cleaner WHIMS
Feed slurry density: 1.18 to 1.22 g/cc, preferably 1.20 g/cc
Magnetic field intensity: 3000 to 5000 gauss, preferably about 4000 gauss
De-sliming cyclone WHIMS
Feed slurry density: 1.11 to 1.15 g/cc, preferably 1.13 g/cc
Magnetic field intensity: 4000 to 6000 gauss, preferably about 5000 gauss
Other parameters like rod matrix 1.5mm, ring speed, 3 rpm and pulsation 250 rpm were kept constant in rougher, cleaner and de-sliming cyclone WHIMS.
According to another preferred aspect of the process of the present invention the recovery and grade of final concentrate obtained by following said crushing, grinding, de-sliming, three stage spiral concentration followed by two stage WHIMS including recirculation of cleaner spiral tailing and scavenger spiral concentrate to rougher spiral, and processing of de-sliming cyclone O/F in single stage WHIMS enables the following:
maximum concentrate weight recovery varying from 53.82 to 61.67% with 61.42 to 63.27% Fe for input feed Fe 45.28 to 51.30%;
recovery of the final product increased from 44.66–52.56 to 53.82 to 61.97% after recirculation of cleaner spiral tailing and scavenger spiral concentrate product with overall tailing loss being 38.0 to 46.18% by weight loss, with 26.47 to 31.80% Fe, 44.33 to 49.38% SiO2, 5.09 to 5.97% Al2O3, and 5.87 to 6.94% LOI;
silica content in the final concentrate obtained by following said crushing, grinding, de-sliming three stage spiral concentration including recirculation of cleaner spiral tailing and scavenger spiral concentrate followed by two stage magnetic separation and processing of de-sliming cyclone O/F through single stage WHIMS comprises 5.87 to 6.87% SiO2 with an input feed of SiO2 20.50 to 26.50%;
Fe content in the final tailing of the process is 26.47 to 31.80 percent and SiO2 is 44.33 to 49.38%.
It was thus surprisingly found by way of the present invention that by involving select liberation size for silica by crushing and grinding the low grade iron ore by following closed circuit grinding with de-sliming cyclone to get and overflow and underflow and further by processing the underflow material of the cyclone based on stage-wise gravity separation and magnetic separation on the crushed and ground sample at the optimum liberation size, recovery of maximum iron-bearing minerals from low-grade, high siliceous iron ore with maximum silica rejection could be attained based on processing through following preferred stage-wise beneficiation process involving:
• Crushing of a BHQ iron ore from 10 mm to less than 1 mm after screening the material to remove fines before feeding it to the crusher.
• Grinding of below 1 mm-sized crushed product to achieve 80% passing less than 45 µm size by adopting closed circuit grinding with a cyclone to remove the ultrafine particles, i.e., -10 µm as overflow.
• Processing of de-sliming cyclone underflow in a three-stage spiral concentrator as gravity separators (rougher, cleaner, and scavenger) followed by two stage magnetic separation using WHIMS by applying various magnetic field intensity to recover the iron-bearing minerals as concentrate.
• Further cleaner spiral concentrator tailing and scavenger spiral concentrator concentrate were further treated (recirculated) through a rougher spiral concentrator to recover the Fe-bearing minerals, increase the concentrate weight recovery as well as the Fe grade, and reduce the tailing loss with a lower Fe content.
• Further processing of de-sliming cyclone overflow (O/F) in separate WHIMS to recover the iron bearing minerals to increase the concentrate weight recovery
The overall concentrate weight recovery obtained from the de-sliming, 3-stage spiral concentrator followed by a two-stage magnetic separation process, re-circulation of cleaner spiral tailing and scavenger spiral concentrate, and processing of de-sliming cyclone overflow in WHIMS is 53.82 to 61.97%, with 61.42 to 63.27% Fe, 5.87 to 6.87% SiO2, 1.95 to 2.70% Al2O3, and 1.80–2.44% LOI.
The overall final tailing loss through de-sliming, three-stage spiral concentrator, followed by two stage magnetic separation, re-circulation of cleaner spiral tailing and scavenger spiral concentrate, and further processing of de-sliming cyclone overflow in WHIMS is 38.0 to 46.18% by weight loss, with 26.47 to 31.80% Fe, 44.33 to 49.38% SiO2, 5.09 to 5.97% Al2O3, and 5.87 to 6.94% LOI. The overall Fe recovery is varying from 73.01 to 76.43%, and the silica reduction is varying from 71.34 to 74.08%.
BRIEF DESCRIPTION OF FIGURES
Fig 1: illustrates optical micrographs of low grade high siliceous iron ore;
Fig 2: illustrates process flow chart for the beneficiation process flow sheet for low-grade high-siliceous iron ore.

DETAILED DESCRPTION OF THE INVENTION

As discussed hereinbefore, the present invention provides for the recovery of iron minerals from high siliceous low grade iron ore comprising of stage wise beneficiation process for beneficiation of low-grade, high-siliceous iron ore to recover iron-bearing minerals with higher Fe. High siliceous iron ore is hard in nature, and it consists of lower Fe and high silica with alumina that needs to pass through the process of beneficiation to recover high iron bearing material by rejecting silica, that could be made possible by way of the process of the present invention.

The low-grade, high-siliceous iron ore from the Sandur-Hospet region is received for development of the beneficiation process to recover iron bearing minerals with higher Fe by removing silica. The size of the collected high siliceous iron ore sample was less than 10 mm. The chemical analysis of the high siliceous iron ore sample is shown in Table 1. The feed sample consists of Fe 45.28 to 51.30%, SiO2 20.50 to 26.50%, Al2O3 3.48 to 3.80%, and LOI 3.75 to 4.02%.

Table 1: Chemical analysis

Fe,% SiO2,% Al2O3,% LOI,%
45.28 to 51.30 20.50 to 26.50 3.48 to 3.80 3.75 to 4.02

Detailed characterization studies have been carried out on a high siliceous iron ore feed sample using an optical microscope. The phase analysis of the sample is shown in Table 2, and the liberation analysis is shown in Table 3. The micrographs of the low-grade, highly siliceous iron ore samples are shown in Figure 1. The low-grade, high siliceous iron ore consists of 42.1 to 47.1% hematite as the major iron-bearing mineral and 21.5 to 26.7% quartzite as the major gangue-bearing mineral. The other minor iron-bearing minerals are magnetite/ martite, and goethite, and kaolinite is the only minor gangue-bearing mineral. The magnetite and goethite/limonite constitute 12.4 to 15.6% and 8.6 to 11.5%, respectively.

Table 2: Phase analysis

Mineral Phases %
Hematite 42.1 to 47.1
Magnetite 12.4 to 15.6
Goethite/Limonite 8.6 to 11.5
Quartzite 21.5 to 26.7
Kaolinite 4.5 to 5.7
Others 1.7 to 2.7

Table 3: Liberation analysis

Size, mm %
-150 µm 62 to 67
-75 µm 70 to 75
-45 µm 78 to 82
-38 µm 84 to 88
-25 µm 90 to 93

The low-grade, high-siliceous iron ore sample of 10 mm in size was crushed using a laboratory jaw to obtain a crusher discharge of 100% below 1 mm in size. The crushed material was subjected to a grinding process using a laboratory ball mill. In ground product, the particle size is maintained at 45 µm 83.7 to 85.2%), and at this size the liberation percentage is 78 to 82%. The particle size analysis of the ground sample is shown in Table 4. The grindability and bond work index of low-grade, high siliceous iron ore are 1.30 to 1.52 and 10.10 to 12.50 kWh/t.

Table 4: Size analysis of ground sample

Size, µm %
-200 100.0
-150 98.5 – 99.6
-125 97.0 – 98.0
-75 93.2 – 94.8
-63 90.2 – 91.76
-45 83.7 – 85.2
-32 74.79 – 75.2
-25 68.1 – 69.5
-10 48.9 – 50.2
-2 20.4 – 22.2

The ground material was subjected to a de-sliming cyclone of 5" size with a 30 mm vortex finder and 20 mm spigot. The feed density maintained in the de-sliming cyclone was 1.07 to 1.10 gm/cc, preferably 1.08 gm/cc. The feed pressure was maintained from 1.50 to 2.0 bar, preferably 2.0 bar. The de-sliming cyclone underflow was fed to the rougher spiral concentrator. In a rougher spiral, feed density was maintained from 1.22 to 1.27 gm/cc, preferably about 1.25 gm/cc. The rougher spiral concentrate was further processed in a cleaner spiral to get a product with a higher iron content. In a cleaner spiral, feed density was maintained at 1.18 to 1.21 gm/cc, preferably about 1.20 gm/cc. In a cleaner spiral concentrator, concentrate weight recovery varies from 25.92 to 29.50% with 62.90 to 64.50% Fe, 4.89 to 5.89% SiO2, 1.20 to 2.05% Al2O3 and 1.50 to 2.30% LOI.

The rougher spiral tailing was further processed in a scavenger spiral. In the scavenger spiral, feed density was maintained at 1.14 to 1.18 gm/cc, preferably about 1.15 gm/cc. The cleaner spiral tailing and scavenger spiral concentrate were recirculated to the rough spiral to get maximum concentrate weight recovery with Fe grade.
The scavenger spiral tailing was fed to rougher WHIMS. In rougher WHIMS, magnetic field intensity was maintained from 4000 to 6000 gauss, preferably about 5000 gauss, and slurry density was maintained at 1.18 to 1.22 g/cc, preferably 1.20 g/cc at other constant parameters like rod matrix 1.5mm, ring speed 3 rpm, and pulsation 250 rpm. The rougher WHIMS mag was processed in cleaner WHIMS to further improve the concentrate Fe grade. In cleaner WHIMS, magnetic field intensity was maintained from 3000 to 5000 gauss, preferably about 4000 gauss, and slurry density was maintained at 1.18 to 1.22 g/cc, preferably 1.20 g/cc at other constant parameters like rod matrix 1.5mm, ring speed 3 rpm, and pulsation 250 rpm. In cleaner WHIMS, concentrate weight recovery was 11.01 to 17.05% with 61.20 to 62.80% Fe, 6.20 to 6.75% SiO2, 2.40 to 3.01% Al2O3 and 1.95 to 2.60% LOI.
The de-sliming cyclone overflow was processed in separate WHIMS (cyclone WHIMS) to recover the iron-bearing minerals and increase the overall concentrate weight recovery. In cyclone WHIMS, magnetic field intensity was maintained from 4000 to 6000 gauss, preferably about 5000 gauss, and slurry density was maintained at 1.11 to 1.15 g/cc, preferably 1.13 g/cc at other constant parameters like rod matrix 1.5mm, ring speed 3 rpm, and pulsation 250 rpm. In cyclone WHIMS achieved concentrate weight recovery of 15.42 to 16.90% with 59.89 to 61.65% Fe, 7.20 to 8.02% SiO2, 2.80 to 3.25% Al2O3 and 2.15 to 2.50% LOI. The cleaner spiral concentrate, cleaner HGMS mag and de-sliming cyclone WHIMS mas was considered as final concentrate. The rougher & cleaner WHIMS non mag and de-sliming cyclone WHIMS non mag was considered as final tailing.
The overall concentrate weight recovery was obtained from developed flow sheet is 53.82 to 61.97% with 61.42 to 63.27% Fe, 5.87 to 6.87% SiO2, 1.95 to 2.70% Al2O3 and 1.80 to 2.44% LOI. The overall tailing loss is 38.0 to 46.18% by weight loss, with 26.47 to 31.80% Fe, 44.33 to 49.38% SiO2, 5.09 to 5.97% Al2O3, and 5.87 to 6.94% LOI. The Fe recovery is 73.01 to 76.43% and silica reduction is 71.34 to 74.08% and SiO2 rejection is varying from 82.24 to 86.05%
The developed flow sheet for processing low-grade high siliceous iron ore is shown in Figure 2. The test results are shown in Table 5.
Table 5: Beneficiation process test results of low-grade high-siliceous iron ore

Thus according to an embodiment of the present invention a beneficiation process low-grade high siliceous iron ore is provided to get maximum concentrate weight recovery and Fe grade comprises the following steps:
Subjecting the 10 mm low-grade high siliceous iron ore feed sample to a crusher to get the product size of 1mm, grinding the crushed ore to achieve 83.7 – 85.2% passing -45 µm and subjecting the ground product through a de-sliming cyclone The de-sliming cyclone U/F was processed through a three-stage spiral (rougher, cleaner, and scavenger). The scavenger spiral tailing was further processed through WHIMS, consisting of rougher and cleaner WHIMS, by applying the selective magnetic field intensity to recover the iron bearing minerals from the feed sample. Further, to increase the concentrate recovery and grade, the cleaner spiral tailing and scavenger spiral concentrate products were recirculated to the rougher spiral. To further improve the overall concentrate weight recovery, the de-sliming cyclone O/F was processed through a separate single-stage WHIMS. , Claims:We Claim:

1. A process for recovery of iron minerals from high siliceous low grade iron ore comprising of stage wise beneficiation process including the steps of:
subjecting the high siliceous low grade iron ore containing 45 to 55% Fe, 20 to 26% SiO2, 3.00 to 6.0% Al2O3 and 3.00 to 5.50% LOI to crushing to less than 1 mm;
grinding below 1 mm-sized crushed product to achieve about 83.7 – 85.2% passing preferably about 80% passing of less than 45 µm size in a closed circuit grinding with de-sliming cyclone to remove the ultrafine particles of size -10 µm as overflow;
processing of de-sliming cyclone underflow in a three-stage spiral concentrator as gravity separators including rougher, cleaner, and scavenger stages followed by two stage magnetic separation using wet high intensity magnetic separation (WHIMS) to recover the iron-bearing minerals as concentrate.
2. The process as claimed in claim 1 wherein the cleaner spiral concentrator tailing and scavenger spiral concentrator concentrate were further treated (recirculated) through a rougher spiral concentrator to recover the Fe-bearing minerals, increase the concentrate weight recovery as well as the Fe grade, and reduce the tailing loss with a lower Fe content; and
processing of de-sliming cyclone overflow (O/F) is done in separate WHIMS to recover the iron bearing minerals to increase the concentrate weight recovery whereby Fe recovery is 73.01 to 76.43% and silica reduction is 71.34 to 74.08% and SiO2 rejection varies from 82.24 to 86.05%.
3. The process as claimed in claims 1 or 2 wherein providing low-grade high siliceous iron ore fines, closed circuit grinding with de-sliming cyclone for gravity separation of said fines of de-sliming cyclone underflow at select feed density maintained at 1.07 to 1.10 gm/cc, preferably 1.08 gm/cc, with feed pressure maintained from 1.50 to 2.0 bar, preferably 2.0 bar, followed by said wet high intensity magnetic separation (WHIMS) post crushing and grinding the fines to select size enables appropriate silica liberation and iron up-gradation in said fines with regard to maximum concentrate weight recovery and grade together with removal of alumina as well as silica from said fines thereby making it suitable for pellet making.

4. The process as claimed in claims 1-3 wherein said stages of said beneficiations process are as per the following:
(i) Crushing BHQ (banded hematite quartzite) said low grade iron ore preferably containing 45.28 to 51.30% Fe; 20.50 to 26.50% SiO2; 3.48 to 3.80% Al2O3; and preferably 3.75 to 4.02% LOI to crushing from 10 mm to less than 1 mm after screening the material to remove fines before feeding at select feed density to the crusher;

(ii) Grinding the crushed material to below 1 mm-sized crushed product to achieve 83.7 – 85.2% passing of less than -45 µm size by adopting closed circuit grinding with a de-sliming cyclone and feeding in said cyclone at said select feed density that removes the ultrafine particles of size -10 µm as overflow (O/F) and provides for de-sliming cyclone underflow (U/F);
(iii) Performing gravity separation of the de-sliming cyclone underflow (U/F) based ground product in a three-stage spiral concentrators as gravity separators including rougher, cleaner, and scavenger concentrator including re-circulating cleaner spiral concentrator tailing and scavenger spiral concentrator concentrate through said rougher spiral concentrator to recover the Fe-bearing minerals with increased concentrate weight recovery as well as the Fe grade by reducing tailing loss having lower Fe content and attained as final concentrate at the outlet of cleaner spiral concentrator;
(iv) performing two stage wet high intensity magnetic separation (WHIMS) on scavenger spiral concentrator tailings by applying various select magnetic field intensity to recover the iron-bearing minerals as rougher WHIMS magnetic product that is further magnetically processed to obtain cleaner WHIMS magnetic product leading to final concentrate at the outlet of cleaner spiral concentrator; followed by
(v) processing de-sliming cyclone overflow (O/F) in separate wet high intensity magnetic separation (WHIMS) included in said closed circuit to recover iron bearing minerals to increase the concentrate weight recovery of the final concentrate when circulated at the outlet of cleaner spiral concentrator, with the tailings therefrom combined with the final tailings obtained at the outlet of rougher wet high intensity magnetic separation (WHIMS) unit.
5. The process as claimed in claims 1-4 wherein said feed low grade iron ore mineralogical phases include: Magnetite: 12.4 to 15.6%, Hematite: 42.1 to 47.1%, Goethite: 8.6 to 11.5%, Quartzite: 21.5 to 26.7% as the major gangue-bearing mineral, Kaolinite: 34.5 to 5.7% and others : 1.7 to 2.7%.
6. The process as claimed in claims 1-5 wherein the liberation size of the hematite particles at -45 µm is 78 to 82% that is effective when adopting closed circuit grinding with a cyclone to remove the ultrafine particles of -10 µm as overflow
Size, mm %
-150 µm 62 to 67
-75 µm 70 to 75
-45 µm 78 to 82
-38 µm 84 to 88
-25 µm 90 to 93

7. The process as claimed in claims 1-6 wherein the liberation of iron bearing minerals at different size fractions in the feed sample is as follows: -45 µm : 83.7 – 85.2%, and -10 µm : 48.9 – 50.2% when collected by closed circuit cyclone as overflow.

8. The process as claimed in claims 1-7 wherein said process comprising subjecting the said low-grade high siliceous iron ore sample to crushing and grinding, de-sliming, three-stage spiral (rougher, cleaner, and scavenger) followed by two stage WHIMS, recirculation of cleaner and scavenger spiral products and single stage WHIMS for treating de-sliming cyclone O/F by maintaining various magnetic field intensities and parameters maintained at various stages of the de-sliming cyclone, spiral concentrator and WHIMS, are as follows:
De-sliming Cyclone:
Feed density: 1.07 to 1.10 gm/cc, preferably 1.08 gm/cc.
Feed pressure: 1.50 to 2.0 bar, preferably 2.0 bar.
Rougher Spiral:
Feed density: 1.22 to 1.27 gm/cc, preferably about 1.25 gm/cc
Cleaner Spiral:
Feed density: Feed density: 1.22 to 1.27 gm/cc, preferably about 1.25 gm/cc
Scavenger Spiral:
Feed density: Feed density: 1.14 to 1.18 gm/cc, preferably about 1.15 gm/cc
Rougher WHIMS
Feed slurry density: 1.18 to 1.22 g/cc, preferably 1.20 g/cc
Magnetic field intensity: 4000 to 6000 gauss, preferably about 5000 gauss
Cleaner WHIMS
Feed slurry density: 1.18 to 1.22 g/cc, preferably 1.20 g/cc
Magnetic field intensity: 3000 to 5000 gauss, preferably about 4000 gauss
De-sliming cyclone WHIMS
Feed slurry density: 1.11 to 1.15 g/cc, preferably 1.13 g/cc
Magnetic field intensity: 4000 to 6000 gauss, preferably about 5000 gauss
Other parameters like rod matrix 1.5mm, ring speed, 3 rpm and pulsation 250 rpm were kept constant in rougher, cleaner and de-sliming cyclone WHIMS.
9. The process as claimed in claims 1-8 wherein A process as claimed in anyone of claims 1 to 6 wherein the recovery and grade of final concentrate obtained by following said crushing, grinding, de-sliming, three stage spiral concentration followed by two stage WHIMS including recirculation of cleaner spiral tailing and scavenger spiral concentrate to rougher spiral, and processing of de-sliming cyclone O/F in single stage WHIMS enables the following:
maximum concentrate weight recovery varying from 53.82 to 61.67% with 61.42 to 63.27% Fe for input feed Fe 45.28 to 51.30%;
recovery of the final product increased from 44.66–52.56 to 53.82 to 61.97% after recirculation of cleaner spiral tailing and scavenger spiral concentrate product with overall tailing loss being 38.0 to 46.18% by weight loss, with 26.47 to 31.80% Fe, 44.33 to 49.38% SiO2, 5.09 to 5.97% Al2O3, and 5.87 to 6.94% LOI;
silica content in the final concentrate obtained by following said crushing, grinding, de-sliming three stage spiral concentration including recirculation of cleaner spiral tailing and scavenger spiral concentrate followed by two stage magnetic separation and processing of de-sliming cyclone O/F through single stage WHIMS comprises 5.87 to 6.87% SiO2 with an input feed of SiO2 20.50 to 26.50%;
Fe content in the final tailing of the process is 26.47 to 31.80 percent and SiO2 is 44.33 to 49.38%.

Dated this the 1st day of June, 2023 Anjan Sen
Of Anjan Sen and Associates
(Applicants Agent)
IN/PA-199