Claims:We Claim:

1. A process for recovery of ultra-fine particles from iron ore beneficiation plant tailing to improve the concentrate weight recovery and grade, comprising

providing iron ore beneficiation plant(BP) tailing comprising of 43 to 55% Fe, 11 to 13% alumina, and 11 to 14% silica, having particles size 70 to 80% below 10 micron;

subjecting said BP tailing to magnetic separation using high gradient magnetic separator (HGMS) involving fine matrix of 0.150 mm under magnetic field intensity such as to recover the maximum iron bearing minerals from BP tailing including said ultrafine particles of below 10 micron size.

2. A process as claimed in claim 1 comprising subjecting said BP tailing to two-stage magnetic separation using high gradient magnetic separator (HGMS).

3. A process as claimed in anyone of claims 1 or 2 comprising subjecting the said BP tailings through two stage high gradient magnetic separator (HGMS) following in first stage (rougher) HGMS maintaining the magnetic field intensity 7000 to 8000 Gauss preferably 8000 Gauss and recovering said first stage magnetic concentrate as product while the rougher tailing fed to scavenger HGMS maintaining magnetic field intensity in the range of 8000 to 9000 Gauss preferably 9000 Gauss, said scavenger HGMS tailing resulting final tailing.

4. A process as claimed in anyone of claims 1 to 3 wherein in both stage, the slurry solid percentage was maintained 25 to 30%.

5. A process as claimed in anyone of claims 1 to 4 wherein the second stage HGMS magnetic concentrate was re-circulated to first stage HGMS to further improve the grade.

6. A process as claimed in anyone of claims 1 to 5 wherein the recovery and grade of product obtained following said two stage HGMS comprises maximum weight recovery varying from 32 to 42% with 59.4 to 63.6% Fe for input feed Fe 43 to 47.5%.

7. A process as claimed in anyone of claims 1 to 6 wherein the size of the iron bearing minerals in two-stage HGMS final tailing obtained comprised 85% below 3 mm, Hematite content is 26.0%, goethite and limonite is 28.0% and quartz and kaolinite 39% by area.

8. A process as claimed in anyone of claims 1 to 7 wherein said fine matrix used is preferably 0.150mm matrix size which is made from steel wool to capture the maximum iron bearing minerals.

9. A process as claimed in anyone of claims 1 to 8 wherein Fe content in final tailing of the process is 35.0 to 36.0%.

10. A process as claimed in anyone of claims 1 to 9 wherein particles of size <4 µm size of iron bearing minerals >85.0% are rejected as tailing.

Dated this the 24th day of May, 2018
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)
IN/PA-199
, Description:FIELD OF THE INVENTION

The present invention relates to a process for recovery of iron bearing minerals from beneficiation plant(BP) tailing. More particularly, the present invention is directed to a process for recovery of ultra-fine particles from beneficiation plant tailing to improve the concentrate weight recovery and grade.After processing the low to medium grade (55 to 60%Fe) iron ore at beneficiation plant, 18 to 25% of the material is discarded as tailing. The discarded tailing consists of 44 to 55% Fe, 11 to 13% alumina, and 11 to 14% silica. In existing slime recovery plant (SRP) through cyclone, spiral and SLON magnetic separator the recovery of BP tailing is 6 to 10%. To further improve the recovery of BP tailing the two-stage magnetic separation process has been developed according to present invention using high gradient magnetic separator (HGMS) with fine matrix (0.150mm) with the magnetic field intensity of 600 and 700 amps (8000 to 9000 Gauss). The second stage magnetic concentrate was re-circulated to first stage HGMS (Rougher stage). The overall recovery obtained from the developed process is varying from 32 to 42% weight recovery with 59.4 to 63.6% Fe for input feed Fe 43 to 47.5%. Slurry solid percentage 25 to 30% was maintained during the two-stage HGMS trials.

BACKGROUND OF THE INVENTION
Applicant’s existing ore beneficiation plant (OBP) at Bellary, Karnataka, caters to the partial requirement of beneficiated iron ore feed of required quality for pellet and sinter making units. The Bellary-Hospet sector of iron ore mines is endowed with huge reserves of iron ore. The iron ore of this region is although rich in iron content but suffers from two major disadvantages; i) high alumina content in the iron ore, and ii) fragileness of the ore (low tumbler index) which generates huge quantity of fines and slimes during mining and beneficiation. Said OBP of the applicants, operates 20 MTPA capacity beneficiation plant to process medium and low grade iron ore fines containing 58 - 61% Fe and 55 - 60% Fe respectively. During beneficiation, around 18 - 25% of the processed material is rejected as tailing. The discarded tailing contains 43 - 50% Fe, 11 - 13% alumina, and 11 - 14% silica. The tailing sample consists of ultra fines (<10 µm) in the range of 70 - 80%. In order to recover the additional iron bearing minerals from the rejected beneficiation plant tailing, 1600 TPD capacity slime recovery plant(SRP) is in operation.In SRP through cyclone, spiral and SLON magnetic separator the recovery of BP tailing is 6 to 10%.

In present slime recovery circuit, 40% of the material was discarded in de-sliming cyclone. Because of more quantity of rejection at that stage decreases the overall concentrate weight recovery of slime recovery plant.The gravity separation process is not effective for ultra fine particles. They are capable to handle minimum size up to 25 µm size. Beneficiation plant tailing sample consists of 70 to 80% 10 µm size particles. In SLON magnetic separator the minimum matrix size available for separation is 1mm. These matrices are not effective to capture the ultra fine particles.

US provisional patent No. 61/279,945 dated 28thOct. 2009,which is incorporated herein by reference in its entirety provides devices, systems, methods and processes to treat iron containing treatment slurries in such a fashion as to separate magnetically susceptible particles from non magnetic particles. A unique magnetic separation device is described that is useful for separating a slurry including magnetic particles and non magnetic partilces.The magnetic separation device consists of a permanant magnet attached to a frame. This patent is all about the magnetic separation device and separation process of the mentioned device.

US patent No. 4,192,738, dated 11March’1980 by Colombo et.al. describes the process for scavenging iron from tailings producced by the flotation beneficiation of iron ore. This process includes the step of scavanging the flotation tailings using wet high intensity magnetic separation (WHIMS). There is also disclosed a process for increasing the recovery of iron ore in a flotation beneficiation process. This iron ore recovery process includes the steps of feeding the magnetic concentrate produced by the scavanging process to a flotation system and then carrying out an additional flotataion step.This is not relevant to our process. They processed flotation tailing in magnetic separation.

Luzheng Chen et.al. (International journal of mineral processing and extractive metallurgy review, Vol 34, No. 5, 2013, p.p. 1-6) reported In pulsating high gradient magnetic separator (HGMS) the matrix plays a key role and it provides the carrier for the magnetic particles to be captured and transported to the non magnetic filed as magnetic product. HGMS of ultrafine hematite with the finest 1mm rod matrix has been investigated on a pilot pulsating HGMS separator. The results of this investigation indicate that this matrix achieves a significantly improved performance for the ultrfine hematites, compared to the coarser 2mm rod matrix.

Steel Authority of India Limited (Aquaforest TIFF junction evaluation),discusses about the system for the beneficiation of slime produced through iron ore processing and a process for such beneficiation. This patent is related to processing of iron ore washing plant rejects. The washing plant rejects (Classifier overflow) was processed through a cluster of hydrocyclones for desliming and some part hydrocyclone concentrate is treated through slow speed spiral classifier (SSSC) thereafter and rest is treated through medium intensity magnetic separator (MIMS). In MIMS, only very high quality larger hematite iron ore minerals are captured and an innovative self-vibrating launder is employed to recover the valuable iron particles from MIM’s reject. From this process recovered 63% Fe grade concentrate, <5.0% Silica with washing plant rejects Fe 49%. In this invention, the SSSC product contains 8% of less than 400 mesh and MIMS magnetic concentrate contains 9% of this fraction, and overall <400 mesh fraction in the final product concentrate goes up to 12%. Here, hydro-cyclone and MIMS were used for coarser materials in nature.

The present invention thus provides a process to overcome the limitation of existing ore beneficiation by enabling recovery of the maximum iron bearing minerals from BP tailing involving two-stage magnetic separation process whereby iron ore particles below 10 micron size can be substantially recovered and used in pellet base feed mix with significant economic advantage.
In Metso technical specification of High gradient magnetic separators,continuous operation, (the metso magnetic separator catalog) described about the salient features of the equipment. Here, Metso make magnetic separator was used for developing the process for separation of BP tailing which consists of ultra fine partilces (10 micron >70%).

OBJECTS OF THE INVENTION

The basic object of the present invention is directed to provide a process for recovery of ultra-fine particles from iron ore beneficiation plant tailing to improve the concentrate weight recovery and grade.

A further object of the present invention is directed to provide a process for recovery of ultra-fine particles from iron ore beneficiation plant tailing wherein maximum iron bearing minerals from BP tailing involving two-stage magnetic separation process whereby iron ore particles below 10 micron size can be substantially recovered usinghigh gradient magnetic separator (HGMS) with fine matrix (0.150mm).

A still further object of the present invention is directed to provide a process for recovery of ultra-fine particles from iron ore beneficiation plant tailing wherein selective magnetic field strength is applied to each stage of said two-stage magnetic separation process to significantly improve the recovery of iron bearing ultra fine particles from BP tailing.

A still further object of the present invention is directed to provide a process for recovery of ultra-fine particles from iron ore beneficiation plant tailing wherein the second stage magnetic concentrate is re-circulated to first stage HGMS (Rougher stage)to further improve the grade.

A still further object of the present invention is directed to provide a process for recovery of ultra-fine particles from iron ore beneficiation plant tailing whereinoverall recovery would be in the range varying from 32 to 42% weight recovery with 59.4 to 63.6% Fe, for input feed Fe 43 to 47.5%.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a process for recovery of ultra-fine particles from iron ore beneficiation plant tailing to improve the concentrate weight recovery and grade, comprising

providing iron ore beneficiation plant(BP) tailing comprising of 43 to 55% Fe, 11 to 13% alumina, and 11 to 14% silica, having particles size 70 to 80% below 10 micron;

subjecting said BP tailing to magnetic separation using high gradient magnetic separator (HGMS) involving fine matrix of 0.150mm under magnetic field intensity such as to recover the maximum iron bearing minerals from BP tailing including said ultrafine particles of below 10 micron size.

A further aspect of the present invention is directed to a process comprising subjecting said BP tailing to two-stage magnetic separation using high gradient magnetic separator (HGMS).

A still further aspect of the present invention is directed to a process comprising subjecting the said BP tailings through two stage high gradient magnetic separator (HGMS) following in first stage (rougher) HGMS maintaining the magnetic field intensity in the range of 7000 to 8000 Gauss preferably 8000 Gauss and recovering said first stage magnetic concentrate as product while the rougher tailing fed to scavenger HGMS maintaining magnetic field intensity in the range of 8000 to 9000 Gauss preferably 9000 Gauss, said scavenger HGMS tailing resulting final tailing.

A still further aspect of the present invention is directed to a process wherein in both stage, the slurry solid percentage was maintained 25 to 30%.

Another aspect of the present invention is directed to said process wherein the second stage HGMS magnetic concentrate was re-circulated to first stage HGMS to further improve the grade.

Yet another aspect of the present invention is directed to said process wherein the recovery and grade of product obtained following said two stage HGMS comprises maximum weight recovery varying from 32 to 42% with 59.4 to 63.6% Fe for input feed Fe 43 to 47.5%.

A further aspect of the present invention is directed to a process wherein the size of the iron bearing minerals in two-stage HGMS final tailing obtained comprised 85% below 3 mm, Hematite content is 26.0%, goethite and limonite is 28.0% and quartz and kaolinite 39% by area.

A still further aspect of the present invention is directed to aprocess wherein said fine matrix used is preferably 0.0150mm matrix size which is made from steel wool to capture the maximum iron bearing minerals.

A still further aspect of the present invention is directed to aprocess wherein Fe content in final tailing of the process is 35.0 to 36.0%.

A still further aspect of the present invention is directed to aprocess wherein particles of size <4 µm size of iron bearing minerals >85.0% are rejected as tailing.

The above and other objects and advantages of the present invention are described hereunder in greater details with reference to following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: shows graphically the particle size analysis of iron ore beneficiation plant(BP) tailing.
Figure 2: shows the process flow diagram for existing Slime recovery plant for processing BP tailing.
Figure 3: shows the two-stage HGMS process flow sheet to treat BP tailing according to present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWINGS

The present invention relates to a process for recovery of ultra-fine particles from iron ore beneficiation plant tailing to improve the concentrate weight recovery and grade.The process according to present invention improve the recovery of iron ore fines from BP tailing through two-stage magnetic separation using high gradient magnetic separator (HGMS) with fine matrix (0.150mm) with the magnetic field intensity of 600 and 700 amps (8000 to 9000 Gauss). The second stage magnetic concentrate was re-circulated to first stage HGMS (Rougher stage). The overall recovery obtained from the developed process is varying from 32 to 42% weight recovery with 59.4 to 63.6% Fe for input feed Fe 43 to 47.5%. Slurry solid percentage 25 to 30% was maintained during the two-stage HGMS trials.

The BP tailing consists of 43 to 50% Fe with 70 to 80% ultra fines of -10 µm size. Hematite content is 57.0%, goethite and limonite is 12 to 14% and quartz and kaolinite is 29% by area.To recover the ultra-fines of iron bearing minerals through any gravity separation process is not possible. Size analysis and chemical analysis of beneficiation plant tailing are shown in Figure 1 and Table 1 respectively. The process flow diagram with results of slime recovery plant is shown in Figure 2 and Table 2 respectively.
Table 1: Chemical analysis of beneficiation plant tailing

Fe,% SiO2,% Al2O3,%
43.0- 47.5 11.30-13.25 11.49-13.74
Table 2: Slime recovery plant feed and product analysis

Description Wt,% Fe,% SiO2,% Al2O3,%
Feed 100 47.50 11.30 11.49
Total concentrate 24.20 61.63 5.14 3.64
Tailing 75.80 42.87 13.42 14.06

To recover the maximum iron bearing minerals from BP tailing the two-stage magnetic separation process have been developed by using fine matrix (0.150mm) to capture the maximum iron bearing minerals. Two-stage magnetic studies have been carried out using HGMS. The flow diagram of the process flow is shown in Figure 3. The BP tailing is treated in first stage (rougher) HGMS by maintaining the magnetic field intensity 8000 Gauss. The first stage magnetic concentrate was considered as final product. The rougher tailing was fed to scavenger HGMS. The scavenger HGMS tailing was considered as final tailing. In second stage (scavenger) HGMS the magnetic field intensity 9000 Gauss was maintained. In both stage, the slurry solid percentage was maintained 25 to 30%. The second stage HGMS magnetic concentrate was re-circulated to first stage HGMS to further improve the grade. The 0.150 mm matrix size was used for recovering ultra fine iron bearing minerals. The recovery and grade of product of developed 2 stage HGMS process is shown in Table 3. The size of the iron bearing minerals in two-stage HGMS final tailing is 85% below 3 microns. Hematite content is 26.0%, goethite and limonite is 28.0% and quartz and kaolinite is 39% by area.
Table 3:Feed, Recovery and Product grade of two-stage HGMS process developed

Description Wt,% Fe,% SiO2,% Al2O3,%
Feed 100 43.0 - 47.5 11.30 - 13.25 11.49 - 13.74
Total concentrate 32.0 - 42.0 59.4 - 63.6 4.30 - 5.16 2.39 - 4.84
Tailing 58.0 - 68.0 35.3 - 35.9 16.53 - 17.11 17.92 - 18.29

In high gradient magnetic separation it is possible to capture the ultra fine particles to the maximum extent. Because of this with the help of two stages magnetic separation achieved maximum recovery and grade compared to existing circuit. The matrix plays a key role in determining the performance of a high-gradient magnetic separator; it provides the carrier for the magnetic particles to be captured and transported to the nonmagnetic field as magnetic product.

Thus theprocess for recovery of ultra-fine particles from iron ore beneficiation plant tailing to improve the concentrate weight recovery and grade according to present invention is having the following novel features:
1. Beneficiation circuit is designed to process ultra-fine particles of 70 to 80% of -10 µm size using magnetic separation process.
2. The finer matrix is used to recover the iron bearing minerals.
3. To recover maximum iron bearing minerals two-stage magnetic separation process was selected using HGMS.
4. To further improve the grade of second stage magnetic separator product, the magnetic concentrate was re-circulated to first stage.
5. Particles of size of < 4 µm size ofiron bearing minerals are recovered in developed 2 stage magnetic separation process.
6. Through newly developed flow sheet, better concentrate grade and higher recovery were obtained.
7. A suitably optimized beneficiation circuit for BP-2 tailing has been developed.
8. The rejection of tails with lower Fe, i.e., 35 to 36%.
9. The rejection of tails consists of iron bearing minerals < 4.0 µm >85.0%.

It is thus possible by way of the present invention to provide a process for further recovery of iron bearing minerals from discarded beneficiation plant(BP) tailing containing 18 to 20% of processed material that consists of 43 to 55% Fe, 11 to 13% alumina and 11 to 14% silica, wherein the particles below 10 micron size of the BP-2 tailing is 70 to 80% and to recover the maximum iron bearing minerals from BP tailing,two-stage magnetic separation process is employed using high gradient magnetic separator (HGMS) with fine matrix (0.150mm) with the magnetic field intensity of 600 and 700 amps (8000 to 9000 Gauss). The second stage magnetic concentrate is re-circulated to first stage HGMS (Rougher stage) to further improve the grade of second stage magnetic separator product. The overall recovery obtained from the developed process is varying from 32 to 42% weight recovery with 59.4 to 63.6% Fe for input feed Fe 43 to 47.5%. The recovered material can be used in pellet base mix.