Description:FIELD OF INVENTION
The present invention relates to method for beneficiation of low-grade hematite and maghemite mixed iron ore to recover iron-bearing minerals with higher Fe. The hematite and maghemite associated iron ore is semi-hard in nature, and it consists of lower Fe, high silica and alumina. Maghemite (?-Fe2O3) associated with hematite in an iron ore is a mineral formed from magnetite oxidation at low temperatures, an intermediate metastable term of the magnetite to hematite oxidation and could be mixed with both. It has magnetic susceptibility similar to magnetite. For mixed maghemite and hematite 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 blast furnace iron making and pellet making process. Hematite and magnetite associated iron ore is processed by applying screening process to separate -40+10, -10+5mm and -5mm, grinding of -5 mm followed by MIMS and two stage wet high intensity magnetic separation to get the concentrate suitable for blast furnace iron making and pellet making process. The different process stages with the optimised beneficiation technique for hematite and maghemite associated iron ore are directed to favour value addition in the optimised beneficiation technique. The process of hematite and mixed maghemite low grade iron ore beneficiation would enable a better concentrate grade and higher recovery through screening, grinding to required liberation size, medium intensity magnetite separation, followed by two stage wet high intensity magnetic separation process.
BACKGROUND OF THE INVENTION
The gradual depletion of high grade iron ore vis-à-vis price escalation and demand to meet increased plant capacity has forced steelmakers and mine owners to develop beneficiation processes to make use of low-grade iron ores. Beneficiation of low grade iron ores fines and their usage is the right approach and only alternative for steelmakers to control the cost and is a step towards resource conservation and sustainable growth. In order to produce an acceptable quality of concentrate for use, preliminary beneficiation studies are essential. The choice of beneficiation treatment depends on association of iron ore minerals, the nature of the gangue minerals present and its association with the iron minerals.
For the optimum size required for the beneficiation process to remove the alumina and silica, detailed size-wise analysis and characterization studies have been carried out to determine the association of minerals and liberation size. The hematite and maghemite associated iron ore needs to be screened based on Fe content and further grinding of low grade Fe material to the required size to achieve a better quality product with less silica& alumina and higher Fe.
Low grade iron ore with high silica and alumina cannot be utilized 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. The removal of silica and alumina and up-gradation of iron content through the beneficiation process are essential before utilising low-grade, high siliceous iron ore in metallurgical plants. 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 presence of the type of iron ore minerals, nature of the gangue minerals 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.
The patent titled“Beneficiation process for low-grade fine-grain dip-dyed maghemite”, Application No: CN114669395A, The invention relates to a beneficiation process for low-grade fine-grain disseminated maghemite, which comprises the following steps: (1) coarse crushing: crushing low-grade fine-grain disseminated maghemite ore until the crushing granularity is 25-50mm; (2) primary waste throwing, specifically, iron ore with the particle size being 25-50 mm is subjected to waste throwing in advance, ore I is obtained, and the waste ore throwing rate is 15-25%; (3) carrying out intermediate crushing on ore I; (4) secondary waste throwing: carrying out secondary waste throwing on the ore I with the crushing particle size of 15-25mm to obtain ore II, and enabling the waste ore throwing rate to be 2-8%; (5) crushing the ore II to below-2mm to obtain fine ore; (6) ore grinding: grinding the fine ore to obtain ore pulp I; (7) roughing by a medium field intensity magnetic separator: roughing the ore pulp I to obtain iron rough concentrate I; (8) regrinding the iron rough concentrate to obtain ore pulp II; (9) de-sliming: carrying out magnetic de-sliming on the ore pulp II to obtain iron rough concentrate II; and (10) low-intensity magnetic concentration of the iron rough concentrate: performing low-intensity magnetic concentration on the iron rough concentrate II twice to obtain iron concentrate. The method is simple in process, high in adaptability and low in ore grinding cost.
The patent titled “Separate grinding-magnetic levitation combined separation process for maghemite” Application No: CN115921093A: The invention relates to a separate grinding-magnetic levitation combined separation process of maghemite, which is characterized in that raw ore is divided into normal ore with the grade of 25% -30% and extremely poor ore with the grade of 20% -25%, and then the two kinds of ore are fed into the process treatment of the invention, and the process comprises the following steps: 1) Separately grinding: normal ore is fed into a main process for primary ore grinding and grading, weak magnetic and strong magnetic tailing throwing and secondary ore grinding and grading treatment; feeding extremely poor ores into a closed-circuit semi-autogenous grinding, coarse grain weak-magnetism strong-magnetism tailing discarding and two-stage continuous ore grinding and grading; 2) Selecting: the separately ground products are combined and fed into a two-stage weak magnetic strong magnetic tailing discarding process, a continuous weak magnetic process and a reverse flotation process, and the final concentrate grade is obtained to be over 67.5 percent. The invention has the advantages that: 1) The method is suitable for the property change of raw ores, normal ores and extremely poor ores are ground respectively, the coordination of ore blending can be realized, and the production is stable; 2) The gravity separation is cancelled, the reverse flotation is reserved, the ore grinding magnetic separation is enhanced, the combined separation of the ground products is realized, the flow is simplified, the separation effect is improved, and the production cost is reduced.
The patent titled “Beneficiation process of maghemite” Application No: CN108580029A: The invention relates to a beneficiation process of maghemite. Raw ores are the maghemite. The iron grade is 41%-43%. The content of ferruginous clay is over 30%. The beneficiation process of the maghemite is characterized in that crushed products with the grain size being 12-0 mm are processed according to the following technological flow comprising that (1) pre-grading and closed-loop ore grinding are conducted during ore grinding, (2) weak intensity magnetic separation-medium intensity magnetic separation-high intensity magnetic separation-elutriation magnetic separation are conducted during magnetic separation, and (3) spiral chute roughing separation, concentration and scavenging are conducted during gravity separation; and the comprehensive concentrates composed of magnetic separation concentrates and gravity separation concentrates are obtained, wherein the grade of the comprehensive concentrates is 62% or over, and the recovery rate is 62.00-63.00%. The beneficiation process of the maghemite has the advantages that the crushed products are graded in advance, only one-stage closed loop ore grinding is adopted, and therefore investment and energy consumption are reduced; (2)magnetic separation concentrates are directly obtained from the products of the one-stage ore grinding through an elutriation magnetic separator; and (3) tailing discarding is conducted on coarse and fine classification overflow of cyclone to remove the ferruginous clay before gravity separation, so that the influence of the ferruginous clay on the quality of the gravity separation concentrates is lowered.
The patent titled “Anshan type maghemite segmented grinding and gravity-magnetism technological process” Application No: CN115430517A: The invention discloses a raw ore segmented grinding and gravity-magnetism technological process, and belongs to the technical field of ore dressing. Raw ore is coarsely crushed and then subjected to operation of the semi-autogenous grinding-screening system, products pass through the weak magnetic machine, the strong magnetic machine and the primary grinding and grading system, and obtained tailings are screened and then thrown away; the concentrate is subjected to primary ore grinding classification system and secondary magnetic separation, the obtained concentrate is subjected to coarse-fine classification to obtain coarse-grain settled sand and fine-grain overflow, and the obtained tailings are discarded; the coarse grain settled sand is subjected to coarse snail separation and fine snail separation, gravity concentrate and fine snail tailings are obtained, the coarse snail tailings and the fine snail tailings are mixed, subjected to secondary grinding classification system operation, mixed with fine grain overflow and subjected to third-time magnetic separation and fourth-time magnetic separation, and magnetic concentrate, third-time magnetic separation tailings and fourth-time magnetic separation tailings are obtained; and tailings are discarded, magnetic separation concentrate and gravity separation concentrate are mixed, and concentrate with the grade being 65% or above is obtained. According to the method, flotation operation is omitted, use of chemicals is reduced, the cost is reduced, the process only comprises heavy and magnetic processes, the process is relatively simple, and operation and control are convenient.

The patent titled “Beneficiation process for low-grade fine-grain dip-dyed maghemite”, Application No: CN114669395A: The invention relates to a beneficiation process for low-grade fine-grain disseminated maghemite, which comprises the following steps: (1) coarse crushing: crushing low-grade fine-grain disseminated maghemite ore until the crushing granularity is 25-50mm; (2) primary waste throwing, specifically, iron ore with the particle size being 25-50 mm is subjected to waste throwing in advance, ore I is obtained, and the waste ore throwing rate is 15-25%; (3) carrying out intermediate crushing on ore I; (4) secondary waste throwing: carrying out secondary waste throwing on the ore I with the crushing particle size of 15-25mm to obtain ore II, and enabling the waste ore throwing rate to be 2-8%; (5) crushing the ore II to below-2mm to obtain fine ore; (6) ore grinding: grinding the fine ore to obtain ore pulp I; (7) roughing by a medium field intensity magnetic separator: roughing the ore pulp I to obtain iron rough concentrate I; (8) regrinding the iron rough concentrate to obtain ore pulp II; (9) de-sliming: carrying out magnetic de-sliming on the ore pulp II to obtain iron rough concentrate II; and (10) low-intensity magnetic concentration of the iron rough concentrate: performing low-intensity magnetic concentration on the iron rough concentrate II twice to obtain iron concentrate. The method is simple in process, high in adaptability and low in ore grinding cost.
The patent titled “Separate grinding-magnetic levitation combined separation process for maghemite” Application No: CN115921093A: The invention relates to a separate grinding-magnetic levitation combined separation process of maghemite, which is characterized in that raw ore is divided into normal ore with the grade of 25% -30% and extremely poor ore with the grade of 20% -25%, and then the two kinds of ore are fed into the process treatment of the invention, and the process comprises the following steps: 1) Separately grinding: normal ore is fed into a main process for primary ore grinding and grading, weak magnetic and strong magnetic tailing throwing and secondary ore grinding and grading treatment; feeding extremely poor ores into a closed-circuit semi-autogenous grinding, coarse grain weak-magnetism strong-magnetism tailing discarding and two-stage continuous ore grinding and grading; 2) Selecting: the separately ground products are combined and fed into a two-stage weak magnetic strong magnetic tailing discarding process, a continuous weak magnetic process and a reverse flotation process, and the final concentrate grade is obtained to be over 67.5 percent. The invention has the advantages that: 1) The method is suitable for the property change of raw ores, normal ores and extremely poor ores are ground respectively, the coordination of ore blending can be realized, and the production is stable; 2) The gravity separation is cancelled, the reverse flotation is reserved, the ore grinding magnetic separation is enhanced, the combined separation of the ground products is realized, the flow is simplified, the separation effect is improved, and the production cost is reduced.
The patent titled “Beneficiation process of maghemite”Application No: CN108580029A:The invention relates to a beneficiation process of maghemite. Raw ores are the maghemite. The iron grade is 41%-43%. The content of ferruginous clay is over 30%. The beneficiation process of the maghemite is characterized in that crushed products with the grain size being 12-0 mm are processed according to the following technological flow comprising that (1) pre-grading and closed-loop ore grinding are conducted during ore grinding, (2) weak intensity magnetic separation-medium intensity magnetic separation-high intensity magnetic separation-elutriation magnetic separation are conducted during magnetic separation, and (3) spiral chute roughing separation, concentration and scavenging are conducted during gravity separation; and the comprehensive concentrates composed of magnetic separation concentrates and gravity separation concentrates are obtained, wherein the grade of the comprehensive concentrates is 62% or over, and the recovery rate is 62.00-63.00%. The beneficiation process of the maghemite has the advantages that the crushed products are graded in advance, only one-stage closed loop ore grinding is adopted, and therefore investment and energy consumption are reduced; (2)magnetic separation concentrates are directly obtained from the products of the one-stage ore grinding through an elutriation magnetic separator; and (3) tailing discarding is conducted on coarse andfine classification overflow of cyclone to remove the ferruginous clay before gravity separation, so that the influence of the ferruginous clay on the quality of the gravity separation concentrates is lowered.
The patent titled “Anshan type maghemite segmented grinding and gravity-magnetism technological process” Application No: CN115430517A: The invention discloses a raw ore segmented grinding and gravity-magnetism technological process, and belongs to the technical field of ore dressing. Raw ore is coarsely crushed and then subjected to operation of the semi-autogenous grinding-screening system, products pass through the weak magnetic machine, the strong magnetic machine and the primary grinding and grading system, and obtained tailings are screened and then thrown away; the concentrate is subjected to primary ore grinding classification system and secondary magnetic separation, the obtained concentrate is subjected to coarse-fine classification to obtain coarse-grain settled sand and fine-grain overflow, and the obtained tailings are discarded; the coarse grain settled sand is subjected to coarse snail separation and fine snail separation, gravity concentrate and fine snail tailings are obtained, the coarse snail tailings and the fine snail tailings are mixed, subjected to secondary grinding classification system operation, mixed with fine grain overflow and subjected to third-time magnetic separation and fourth-time magnetic separation, and magnetic concentrate, third-time magnetic separation tailings and fourth-time magnetic separation tailings are obtained; and tailings are discarded, magnetic separation concentrate and gravity separation concentrate are mixed, and concentrate with the grade being 65% or above is obtained. According to the method, flotation operation is omitted, use of chemicals is reduced, the cost is reduced, the process only comprises heavy and magnetic processes, the process is relatively simple, and operation and control are convenient.

The patent titled “High-yield two-product mixed maghemite beneficiation process”Application No: CN108889441A: The invention relates to a high-yield two-product mixed maghemite beneficiation process. The high-yield two-product mixed maghemite beneficiation process comprises three-section breakage including coarse breaking, medium breaking and fine breaking on mixed maghemite, and is characterized by further comprising the following steps: sieving operation, a one-section closed circuit grinding operation implemented by a one-section ball-milling-cyclone, primary beneficiation operation, coarse and fine classification operation, reselection operation, secondary magnetic separation operation and centrifuging operation; a primary magnetic separation operation sieve treats overflow products of one-section closed circuit grinding operation, sieving operation and undersizes, the coarse and fine classification operation treats bulk concentrate obtained by primary beneficiation, the reselection operation treats coarse grain products of the coarse and fine classification operation, the secondary beneficiation operation treats coarse particle products of the coarse and fine classification operation, and the centrifuging operation treats bulk concentrates of secondary weak magnetic separation. The high-yield two-product mixed maghemite beneficiation process has the advantages that iron ore concentrates I with grade being 62% for pelletizing raw materials and iron ore concentrates II with grade being 58% for sintered raw materials can be selected out.

Traversing the prior arts, it was observed that very few works has been done in the field of development of specific, precise and economically viable beneficiation process for hematite and maghemite associated iron ore is required to utilise in blast furnace and pellet making process.

Hence, in the present work, based on size-wise analysis and liberation size, the material was processed through a screening, grinding to optimum liberation size, medium intensity magnetic separation followed by two stage wet high intensity magnetic separation on a ground sample.
OBJECTIVE OF THE INVENTION
The main objective of this invention is to develop a defined, precise beneficiation process for hematite and maghemite associated iron ore to attain maximum concentrate weight recovery and grade.
Another objective of the present advancement is to process low-grade hematite and maghemite associated iron ore with high silica and alumina, by adopting a screening, grinding, MIMS and two stage magnetic separation using WHIMS
Yet another objective of the present advancement is to develop a process for the recovery of iron-bearing minerals from low-grade hematite and maghemite associated iron ore with high silica and alumina, wherein separation of high Fe product can be separated by screening process.
A still further objective of the present invention is to provide a process for the recovery of iron-bearing minerals from low-grade hematite and maghemite associated iron ore with high silica and alumina, wherein separation can be achieved by grinding of the material at optimum liberation size before processing in medium intensity magnetic process (MIMS).
Another objective of the present invention is to provide a process for the recovery of iron-bearing minerals from low-grade hematite and maghemite associated iron ore with high silica and alumina, wherein separation of high Fe product can be separated by medium intensity magnetic separation process (MIMS) before feeding to wet high intensity magnetic separation process (WHIMS).
Yet another objective of the present invention is to provide a process for the recovery of iron-bearing minerals from low-grade hematite and maghemite associated iron ore with high silica and alumina, wherein selective magnetic field strength is applied to stage-wise magnetic separation using WHIMS to significantly improve the recovery of iron-bearing particles.
A still further objective of the present invention is to provide a process for the recovery of iron-bearing minerals from low-grade hematite and maghemite associated iron ore with high silica and alumina, wherein the rougher WHIMS magnetic product is further processed in cleaner WHIMS to improve the concentrate Fe grade.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to a method for beneficiation of low-grade hematite and maghemite mixed iron ore to recover iron bearing minerals therein comprising the following steps:
(i) providing the low grade hematite and maghemite associated iron ore feed including Fe content varying from 52.0 to 55.0%,
SiO2 – 14.00 to 17.30%
Al2O3 – 4.00 to 5.55% and
LOI – 2.29 to 3.40%;
(ii) screening of said low grade iron ore feed using double deck screen to separate -40+10 mm, -10+5 mm and -5 mm and thereby separate the -40+10 mm and -10+5 mm as beneficiated final products based on enhanced Fe content;
(iii) subjecting the -5 mm size to grinding such as to pass at least 80% passing below 0.150 mm;
(iv) processing of thus ground material of step (ii) above through medium intensity magnetic separation (MIMS) process to generate the magnetic concentrate with enhanced Fe;
(v) processing of MIMS non magnetic through magnetic separation process using Rougher WHIMS by subjecting to magnetic field intensity based recovery of the iron-bearing minerals as non mag concentrate;
(vi) further enriching the non magnetic concentrate of step (v) above through the Rougher WHIMS magnetic concentrate Fe grade, to carry out magnetic separation process using cleaner WHIMS, to thus generate beneficiated and recovered Fe containing enriched said (a) -40+10mm, (b) -10+5mm, (c ) MIMS magnetic concentrate and (d) cleaner WHIMS magnetic concentrate together as final beneficiated concentrate.

A further aspect of the present invention is directed to the process, wherein the 85.80 to 89.20% particles in the received feed are below 5mm.

A still further aspect of the present invention is directed to the process, wherein the mineralogical phases present in the feed sample used are as follows: Maghemite: 12.0 to 16.0%, Hematite: 56.0 to 58.0%, Goethite: 1.5 to 3.5%, Quartzite: 14.0 to 18.0%, Kaolinite: 7.5 to 9.5% and others : 1.75 to 2.25%.

A still further aspect of the present invention is directed to the process, wherein the liberation size of the iron bearing particles are as follows: -1mm:50 to 55%, -0.500mm: 60 to 66%, -0.150mm:78 to 85% and -0.075mm:87 to 89%.

Another aspect of the present invention is directed to the process comprising subjecting the said low-grade hematite and maghemite associated iron ore sample to screening, grinding, MIMS with fixed magnetic field intensity, and two stage WHIMS by stage wise varying magnetic field intensities.

Yet another aspect of the present invention is directed to the process wherein stage wise magnetic field intensity parameters maintained at MIMS, rougher and cleaner WHIMS are as follows:
Medium intensity magnetic separator (MIMS):
Feed density: 1.25 to 1.35g/cc and preferably 1.30g/cc
Fixed magnetic field intensity: 7000 Gauss
Rougher wet high intensity magnetic separator (WHIMS):
Feed density: 1.20 to 1.30 g/cc, preferably 1.25 g/cc
Magnetic field intensity: 6000 to 9000 gauss, preferably about 8000 gauss.
Cleaner wet high intensity magnetic separator (WHIMS):
Feed density: 1.20 to 1.28 g/cc, preferably 1.22 g/cc
Magnetic field intensity: 4000 to 6000 gauss, preferably about 5000 gauss.

A still further aspect of the present invention is directed to the process wherein the recovery and grade of final concentrate obtained by following said screening, grinding, MIMS and two stage WHIMS comprises maximum weight recovery varying from 62.90 to 69.80% with 61.78 to 64.80% Fe, 4.52 to 6.10% SiO2, and 2.11 to 2.48% Al2O3 and related overall tailing loss is 30.20 to 37.10% with 30.30 to 39.33% Fe, 39.98 to 43.19% SiO2, and 7.35 to 11.89 Al2O3.

Another aspect of the present invention is directed to the process wherein the silica content in the final concentrate obtained by following said screening, grinding, MIMS followed by two stage magnetic separation comprises 4.52 to 6.10% SiO2 with an input feed of SiO2 14.0 to 17.30%.

A still further aspect of the present invention is directed to the process wherein the Fe content in the final tailing of the process is 30.30 to 39.33%, SiO2 is 39.98 to 43.19% and alumina is 7.35 to 11.89%.

Another aspect of the present invention is directed to the process wherein Fe recovery in final concentrate is varying from 72.70 to 84.00%, SiO2 reduction in concentrate is varying from 60.58 to 71.60%.

The advancement is described here under in greater detail in relation to the following non-limiting exemplary illustrations as per the accompanying figures wherein:
Figure 1. Optical micrographs of mixed maghemite and hematite iron ore.
Figure 2. Developed beneficiation process for low grade hematite and maghemite associated iron ore.
DETAILED DESCRIPTION OF THE INVENTION
To recover maximum iron-bearing minerals from low-grade, high silica and high alumina iron ore, it was processed through a stage-wise beneficiation process involving:
• Screening of received iron ore fines using double deck screen to separate -40+10mm, -10+5mm and -5mm. -40+10mm and -10+5 mm is considered as final product based on the Fe content.
• Grinding of -5mm size to 80% passing below 0.150 mm.
• Processing of ground material i.e. -0.150mm through medium intensity magnetic separation (MIMS) process to get the magnetic concentrate with higher Fe.
• Processing of MIMS non magnetic through magnetic separation process using Rougher WHIMS by applying various magnetic field intensity to recover the iron-bearing minerals as concentrate.
• To further increase the magnetic separation Rougher WHIMS magnetic concentrate Fe grade, the magnetic concentrate was further processed through magnetic separation process using cleaner WHIMS to upgrade the Fe%.
• The -40+10mm, -10+5mm, MIMS mag concentrate and cleaner WHIMS magnetic concentrate together considered as final concentrate.
• The rougher and cleaner WHIMS nom magnetic product was considered as final tailing.
The overall concentrate weight recovery obtained from the screening, grinding, magnetic separation using MIMS and two stage magnetic separation process using WHIMS is 62.90 to 69.80%, with 61.78 to 64.80% Fe, 4.52 to 6.10% SiO2, and 2.11 to 2.48% Al2O3.
The overall final tailing loss through screening, grinding, MIMS and two stage WHIMS is 30.20 to 37.10% by weight loss, with 30.30 to 39.33% Fe, 39.98 to 43.19% SiO2, and7.39 to 11.89% Al2O3. The overall Fe recovery is varying from 72.70 to 84.00%, and the silica reduction is varying from 60.58 to 71.60%.
The parameters maintained at MIMS, rougher and cleaner WHIMS as follows:
Medium intensity magnetic separator (MIMS):
Feed density: 1.25 to 1.35g/cc and preferably 1.30g/cc
Fixed magnetic field intensity: 7000 Gauss
Rougher wet high intensity magnetic separator (WHIMS):
Feed density: 1.20 to 1.30 g/cc, preferably 1.25 g/cc
Magnetic field intensity: 6000 to 9000 gauss, preferably about 8000 gauss.
Cleaner wet high intensity magnetic separator (WHIMS):
Feed density: 1.20 to 1.28 g/cc, preferably 1.22 g/cc
Magnetic field intensity: 4000 to 6000 gauss, preferably about 5000 gauss.
EXAMPLES
The low-grade, hematite and maghemite associated iron ore fines is received for development of beneficiation process to recover iron bearing minerals with higher Fe by removing silica and alumina. The size of the received hematite and maghemite associated iron ore sample was less than 40 mm. The chemical analysis of the hematite and maghemite associated iron ore fines is shown in Table 1. The feed sample consists of Fe 52.0 to 55.0%, SiO2 14.0 to 17.30%, Al2O34.00 to 5.55%, and LOI 2.29 to 3.40%.

Table 1: Chemical analysis
Fe,% SiO2,% Al2O3,% LOI,%
52.0 to 55.0 14.00 to 17.30 4.00 to 5.55 2.29 to 3.40

Detailed characterization studies have been carried out on a hematite and maghemite associated iron ore feed sample using an optical microscope. The size-wise analysis of the received sample is shown in Table 2. From size-wise analysis it was found that 85.80 to 89.20% particles are below 5 mm size.

Table 2:Size-wise analysis of received sample
Size, mm Wt.,% Fe(T), % SiO2, % Al2O3, %
-40+10 1.10 to 2.00 60.8 to 62.5 6.20 to 7.50 2.05 to 2.68
-10+5 9.70 to 12.20 61.4 to 63.2 5.00 to 6.85 1.95 to 2.32
-5+0.150 64.00 to 73.25 53.40 to 55.10 14.20 to 17.50 3.85 to 4.44
-0.15 17.85 to 18.88 42.87 to 46.80 20.10 to 23.25 7.80 to 9.21

The phase analysis of the sample is shown in Table 3, and the liberation analysis is shown in Table 4. The micrographs of the low-grade, hematite and maghemite associated iron ore samples are shown in Figure 1. The low-grade, hematite and maghemite associated iron ore consists of 56.0 to 58.0% hematite and 12.0 to 16.0% maghemite are the major iron-bearing mineral and 14 to 18% quartzite and 7.5 to 9.5% kaolinite are the major gangue-bearing mineral. The other minor iron-bearing minerals is goethite. At 0.150mm size the 78 to 85% of the iron bearing particles are liberated from silica.
Table 3: Phase analysis
Mineral Phases %
Hematite 56.0 to 58.0
Maghemite 12.0 to 16.0
Goethite/Limonite 1.50 to 3.50
Quartzite 14.0 to 18.0
Kaolinite 7.50 to 9.50
Others 1.75 to 2.25

Table 4: Liberation analysis
Size %
-1 mm 50 to 55
-0.500 mm 60 to 66
-0.150mm 78 to 85
-0.075 mm 87 to 89

The grind ability and bond work index of low-grade, hematite and maghemite associated iron ore are 1.20 to 1.42 and 9.40 to 11.00 kWh/t.

The ground material was subjected to screening process using double deck screen of 10 and 5 mm size. In screening process, separated -40+10 mm, -10+5mm and -5 mm. -40+10mm and -10+5mm is considered as final product due to higher Fe content. The -5mm material was ground to 80% passing -0.150mm based on liberation studies. The ground material was subjected to medium intensity magnetic separator (MIMS) with fixed magnetic field intensity of 7000 Gauss. The feed density was varied from 1.25 to 1.35g/cc and preferably 1.30g/cc. The MIMS magnetic concentrate was considered as final product. In MIMS achieved 37.60 to 39.60% concentrate weight recovery with 63.70 to 65.80% Fe, 3.89 to 4.66% SiO2 and 1.50 to 1.98% Al2O3. The MIMS non magnetic was subjected to rougher WHIMS for further recovering of iron minerals and MIMS non magnetic consist of 40.09 to 41.42% Fe, 26.28 to 28.07% SiO2 and 6.33 to 7.47% Al2O3 with 46.20 to 51.6% by weight. In rougher WHIMS, magnetic field intensity was maintained from 6000 to 9000 gauss, preferably about 8000 gauss, and slurry density was maintained at 1.20 to 1.30 g/cc, preferably 1.25 g/cc at other constant parameters like rod matrix 1.5mm, ring speed 3 rpm, and pulsation 250 rpm. The rougher WHIMS magnetic concentrate was further processed in cleaner WHIMS for Fe up gradation. In cleaner WHIMS, magnetic field intensity was maintained from 4000 to 6000 gauss, preferably about 5000 gauss, and slurry density was maintained at 1.20 to 1.28 g/cc, preferably 1.22 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 14.50 to 16.00% with 60.80 to 61.50% Fe, 5.80 to 7.50 SiO2, and 2.98 to 4.20% Al2O3. The rougher WHIMS and cleaner WHIMS non magnetic was considered as final tailing. The overall concentrate weight recovery was obtained from developed flow sheet is 62.90 to 69.80% with 61.78 to 64.80% Fe, 4.52 to 6.10% SiO2, and 2.11 to 2.48% Al2O3.The overall tailing loss is 30.20 to 37.10% with30.30 to 39.33% Fe, 39.98 to 43.19% SiO2, and 7.35 to 11.89 Al2O3.The Fe recovery is 72.70 to 84.00% and silica reduction is 60.58 to 71.60%.
The developed flow sheet for processing of low-grade hematite and maghemite associated iron ore is shown in Figure 2. The test results are shown in Table 5.
Table 5: Test results of low grade hematite and maghemite associated iron ore

ADVANTAGES OF THE INVENTION:
Primary advantages of the beneficiation process are as follows:
The defined, precise beneficiation method for hematite and maghemite associated iron ore attains maximum concentrate weight recovery and grade.
The method processes low-grade hematite and maghemite associated iron ore with high silica and alumina, by adopting a screening, grinding, MIMS and two stage magnetic separation using WHIMS
The method provides a process for the recovery of iron-bearing minerals from low-grade hematite and maghemite associated iron ore with high silica and alumina, wherein separation of high Fe product can be done by screening process.
The method provides a process for the recovery of iron-bearing minerals from low-grade hematite and maghemite associated iron ore with high silica and alumina, wherein separation of high Fe product can be done by medium intensity magnetic separation process (MIMS) before feeding to wet high intensity magnetic separation process (WHIMS).
The method provides a process for the recovery of iron-bearing minerals from low-grade hematite and maghemite associated iron ore with high silica and alumina, wherein the rougher WHIMS magnetic product is further processed in cleaner WHIMS to improve the concentrate Fe grade. , Claims:WE CLAIM:
1. A method for beneficiation of low-grade hematite and maghemite mixed iron ore to recover iron bearing minerals therein comprising the following steps:
(i) providing the low grade hematite and maghemite associated iron ore feed including Fe content varying from 52.0 to 55.0%,
SiO2 – 14.00 to 17.30%
Al2O3 – 4.00 to 5.55% and
LOI – 2.29 to 3.40%;
(ii) screening of said low grade iron ore feed using double deck screen to separate -40+10 mm, -10+5 mm and -5 mm and thereby separate the -40+10 mm and -10+5 mm as beneficiated final products based on enhanced Fe content;
(iii) subjecting the -5 mm size to grinding such as to pass at least 80% passing below 0.150 mm;
(iv) processing of thus ground material of step (ii) above through medium intensity magnetic separation (MIMS) process to generate the magnetic concentrate with enhanced Fe;
(v) processing of MIMS non magnetic through magnetic separation process using Rougher WHIMS by subjecting to magnetic field intensity based recovery of the iron-bearing minerals as non mag concentrate;
(vi) further enriching the non magnetic concentrate of step (v) above through the Rougher WHIMS magnetic concentrate Fe grade, to carry out magnetic separation process using cleaner WHIMS, to thus generate beneficiated and recovered Fe containing enriched said (a) -40+10mm, (b) -10+5mm, (c ) MIMS magnetic concentrate and (d) cleaner WHIMS magnetic concentrate together as final beneficiated concentrate.

2. The process as claimed in claim 1, wherein the 85.80 to 89.20% particles in the received feed are below 5mm.

3.The process as claimed in anyone of claims 1 or 2, wherein the mineralogical phases present in the feed sample used are as follows: Maghemite: 12.0 to 16.0%, Hematite: 56.0 to 58.0%, Goethite: 1.5 to 3.5%, Quartzite: 14.0 to 18.0%, Kaolinite: 7.5 to 9.5% and others : 1.75 to 2.25%.

4. The process as claimed in anyone of claims 1 to 3, wherein the liberation size of the iron bearing particles are as follows: -1mm:50 to 55%, -0.500mm: 60 to 66%, -0.150mm:78 to 85% and -0.075mm:87 to 89%.

5. The process as claimed in anyone of claims 1 to 4 comprising subjecting the said low-grade hematite and maghemite associated iron ore sample to screening, grinding, MIMS with fixed magnetic field intensity, and two stage WHIMS by stage wise varying magnetic field intensities.

6. The process as claimed in anyone of claims 1 to 5, wherein stage wise magnetic field intensity parameters maintained at MIMS, rougher and cleaner WHIMS are as follows:
Medium intensity magnetic separator (MIMS):
Feed density: 1.25 to 1.35g/cc and preferably 1.30g/cc
Fixed magnetic field intensity: 7000 Gauss
Rougher wet high intensity magnetic separator (WHIMS):
Feed density: 1.20 to 1.30 g/cc, preferably 1.25 g/cc
Magnetic field intensity: 6000 to 9000 gauss, preferably about 8000 gauss.
Cleaner wet high intensity magnetic separator (WHIMS):
Feed density: 1.20 to 1.28 g/cc, preferably 1.22 g/cc
Magnetic field intensity: 4000 to 6000 gauss, preferably about 5000 gauss.

7. The process as claimed in anyone of claims 1 to 6 wherein the recovery and grade of final concentrate obtained by following said screening, grinding, MIMS and two stage WHIMS comprises maximum weight recovery varying from 62.90 to 69.80% with 61.78 to 64.80% Fe, 4.52 to 6.10% SiO2, and 2.11 to 2.48% Al2O3 and related overall tailing loss is 30.20 to 37.10% with 30.30 to 39.33% Fe, 39.98 to 43.19% SiO2, and 7.35 to 11.89 Al2O3.

8. The process as claimed in anyone of claims 1 to 7 wherein the silica content in the final concentrate obtained by following said screening, grinding, MIMS followed by two stage magnetic separation comprises 4.52 to 6.10% SiO2 with an input feed of SiO2 14.0 to 17.30%.

9. The process as claimed in any of claims 1 to 9, wherein the Fe content in the final tailing of the process is 30.30 to 39.33%, SiO2 is 39.98 to 43.19% and alumina is 7.35 to 11.89%.

10. The process claimed in anyone of claims 1 to 9 wherein Fe recovery in final concentrate is varying from 72.70 to 84.00%, SiO2 reduction in concentrate is varying from 60.58 to 71.60%.

Dated this the 15th day of July, 2023
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

IN/PA-199