DESC:FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

1 TITLE OF THE INVENTION :
A METHOD FOR CONDITIONING OF ROASTED IRON ORE TAILING FOR IMPROVED IRON UPGRADATION AND RECOVERY.



2 APPLICANT (S)

Name : JSW STEEL LIMITED;

Nationality : An Indian Company.

Address : JSW CENTRE,BANDRA KURLA COMPLEX,BANDRA(EAST), MUMBAI-400051, STATE OF MAHARASHTRA, INDIA.




3 PREAMBLE TO THE DESCRIPTION

COMPLETE

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION:

The present invention relates to the field of mineral processing especially beneficiation of ultra-fines. More particularly, the present invention is directed to provide a method for conditioning of roasted ultra-fine iron ore / tailings to obtain improved iron upgradation and recovery. The invention discloses a method for improving the Fe grade of final concentrate after beneficiation of iron ore through high temperature acidic pre-treatment for ultra-fine iron ore/tailings. The method comprises the steps of heating the ultra-fine iron ore/tailings in an acidic solution followed by high intensity stirring to prepare slurry for low intensity magnetic separation.

BACKGROUND OF THE INVENTION:

Across the world, steel industry is facing the challenge of handling ultra-fine tailings after beneficiation of iron ore. The dumping of the tailings as a waste material requires vast area and possess environmental threats. Beneficiation of lean iron ores using conventional techniques generates tailing material rich in gangue minerals Si and Al with fine size particles. This decreases the efficiency of unit processes such as magnetic separation and/ or froth floatation after reduction roasting; preventing an economically feasible method to recover the ultra-fine iron content. In the current study, a novel approach is employed to treat the roasted tailings material and recover the iron content.

Prior arts:
Acid pre-treatment and floatation for upgradation of iron ore is discussed in GB582450A:“Concentration of non-sulphide iron ores”. The iron ore pulp is de-slimed and conditioned at higher solid%. The addition of acid is proposed for surface treatment of the collector in a hydrocarbon solvent.

The patent CN101418359A “Method for extracting iron and high grade ferronickel alloy from laterite nickel mine” reveals a method for upgradation of laterite ore using reduction roasting, wet grinding and low intensity magnetic separation for iron with nickel in tailings and selective dissolution of iron in tailings using acid treatment. The obtained nickel is of grade 30%. The mentioned iron ore is comprised of 47.8% Fe, 0.91% Ni and 17.9% Mg.

In CN101545038A: “Method for producing iron ore concentrate by using poor tin sulphide ore tailings”, the inventor reveals a method to obtain iron rich concentrate from tailing of tin ore mines using a combination of smelting, magnetic separation and floatation, oxidising roasting and acid treatment. The mentioned tailings comprising 30.96% Fe, 15.55% S, 3.05 As and <1% of Cu and Sn, was upgraded to Fe grade 56 to 60% with a yield of 42% and Fe recovery of 79%

US4697744A: “Process for production of iron oxide fine powder” discloses a stepwise method to obtain high purity iron oxide fine powder thorough de-sliming of 10 micron particles, acid treatment (optional) and refining by gravity concentration and/or floatation. The processed raw material was in the size range of -250 micron and +10 microns and desirable results were obtained only for high grade hematite ores.

The premise of the present disclosure has been attempted to treat iron ore slurry for various applications however, the applicants herein use minimum number of treatment steps to upgrade the waste iron ore tailings and recover iron oxide suitable for downstream agglomeration units.

OBJECTIVE OF THE INVENTION:

The basic objective of the invention is to provide a method for conditioning of ultra-fine iron ore / tailings including a slurry conditioning method for ultra-fine iron ores to enhance the quality of the concentrate after beneficiation, to obtain improved iron upgradation and recovery.

A further object of the present invention is directed to provide a method for conditioning of ultra-fine iron ore / tailings including the steps of heating the ultra-fine iron ore/tailings in an acidic solution followed by high intensity stirring to prepare slurry for low intensity magnetic separation, to achieve improved Fe grade in the concentrate and recovery.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a method for conditioning of ultra-fine iron ore / tailings to obtain improved iron upgradation and recovery involving the steps of:
reduction roasting of the aforementioned tailing material in CO environment;
subjecting the dry roasted material to grinding;
preparing an aqueous solution of a acid of selected concentration and subjecting
said roasted tailing material and said aqueous solution of acid to mixing, comprising
a primary mixing step wherein the acidic mixture of roasted tailings is stirred at elevated temperature to obtain a slurry, and
a secondary mixing step wherein the acidic slurry is diluted and the mixture is mechanically stirred at room temperature; followed by
carrying out low intensity magnetic separation of the conditioned slurry to achieve improved iron grade and recovery.
A further aspect of the present invention is directed to said method wherein said roasting step provides a roasted product with 30-40% magnetite and 20-30% hematite and with no wustite.
A still further aspect of the present invention is directed to said method wherein the said grinding step results in a product of size fraction such as 75% being less than 10 micron size.
A still further aspect of the present invention is directed to said method wherein the aqueous solution comprises hydrochloric acid and water having a pH of less than 4 and preferably less than 2.
A further aspect of the present invention is directed to said method wherein the mixture of roasted tailing material in the aqueous acidic solution is such that it contains 10% of solids.
Another aspect of the present invention is directed to saidmethod wherein the primary mixing of slurry with acid solution is carried out at temperatures higher than 85oC for 10-20 minutes.
Yet another aspect of the present invention is directed to said method wherein the mixed material after primary mixing is diluted to 5 % of solids concentration.
A further aspect of the present invention is directed to said method wherein the secondary mixing is carried out for the diluted material at room temperature using a mechanical stirrer operated at 2000 rpm for 5-20 minutes.
A still further aspect of the present invention is directed to said method wherein the magnetic separation is carried out using a Davis tube apparatus operated at magnetic intensity of 1200-1300 Gauss, and at a oscillation frequency of 40Hz and amplitude of 100mm, with a slurry feed rate of 2 to5 lpm.

A further aspect of the present invention is directed to said method which is adapted to achieve iron value in the range of 55 to 60% in magnetic concentrate and a recovery of 40 to 60%.
The above and other aspects and advantages of the present invention are described hereunder in details with reference to following accompanying drawing and examples.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

Figure 1: shows Process flow diagram indicating the steps involved in the method of present invention including the inputs and outputs at each stage.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWING AND EXAMPLES

The present invention is directed to a system and method to upgrade waste iron ore tailing by means of roasting and acid treatment of mentioned roasted material followed by magnetic separation.
As shown in accompanying non limiting figure 1, illustrating the procedure of the present disclosure, roasted iron ore tailings with Fe grade of 42.7% is mixed with aqueous solution of HCl such that the pH of solution is < 2. The mixture of 10% solids undergoes a primary mixing step wherein the mixture is maintained at elevated temperature of 80-90oC for 10-20 minutes. The secondary mixing stage comprises dilution and mechanical stirring at ambient temperature for 5-20 minutes. The conditioned slurry obtained from these steps is enriched using low-intensity magnetic separation carried out using a Davis Tube Magnetic Separator. The apparatus is such configured that it operates at 1200 to 1300 Gauss with a controlled frequency of oscillation. The magnetic concentrate thus obtained has upgraded iron content ranging from 50 to 60%. The method in the present disclosure is able to recover 50 to 60% iron from the waste generated from beneficiation plant.
The following examples highlight the cases where positive impact of acidic pre-treatment is observed in the upgradation and recovery of iron. The typical process conditions of the underlining operations are mentioned in the detailed descriptions of the experiments. However those skilled in the art will understand the impact of variation in process parameters (such as magnetic intensity, oscillation frequency etc.) that will generate similar or better upgradation with same pre-treatment technique.

Examples
The accompanying embodiments together with the description below forms part of the specification and serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention. Table 1 shows the experimental details involved in the slurry conditioning, involving sample weight, liquid solid ratio, hot plate temperature, stirring time, slurry conditioning time and speed, acid concentration, input Fe%, magnetic concentrate Fe%, magnetic concentrate weight recovery and Fe recovery.

Example 1:
Roasted iron ore tailings of chemical analysis as shown in table 2, is taken in a beaker along with 100 ml water and 0 ml HCL (Hydro Chloric Acid). The mixture /slurry is then manually stirred for 10 minutes with slurry temperature maintained at 85°C. The slurry is then stirred at 2000 rpm for 10 minutes in the secondary mixing step. Magnetic separation of the conditioned slurry is carried out in a Davis tube magnetic separator configured to operate at 1250 Gauss and oscillation frequency of 40Hz. The magnetic concentrate thus obtained has a grade of Fe(T) 50% and weight recovery of 32% (refer Table 1). This becomes a base case for the present disclosure indicating the desirable impact of acidic pre-treatment.

Example 2:
Roasted iron ore tailings of chemical analysis as shown in table 2, is taken in a beaker along with 100 ml water and 2 ml HCL (Hydro Chloric Acid) having a concentration of 36%. The mixture / slurry is then manually stirred for 10 minutes with slurry temperature maintained at 85°C.The slurry is then stirred at 2000 rpm for 10 minutes in the secondary mixing step. Magnetic separation of the conditioned slurry is carried out in a Davis tube magnetic separator configured to operate at 1250 Gauss and oscillation frequency of 40Hz. The magnetic concentrate thus obtained has a grade ofFe(T)55% and weight recovery of 46% (refer Table 1).

Example 3:
Roasted iron ore tailings of chemical analysis as shown in table 2, is taken in a beaker along with 100 ml water and 5 ml HCL (Hydro Chloric Acid) having a concentration of 36%. The mixture / slurry is then manually stirred for 10 minutes with slurry temperature maintained at 85°C. The slurry is then stirred at 2000 rpm for 10 minutes in the secondary mixing step. Magnetic separation of the conditioned slurry is carried out in a Davis tube magnetic separator configured to operate at 1250 Gauss and oscillation frequency of 40Hz. The magnetic concentrate thus obtained has a grade ofFe(T)59% and weight recovery of 32% (refer Table 1).

Example 4:
Roasted iron ore tailings of chemical analysis as shown in table 2, is taken in a beaker along with 100 ml water and 1 ml HCL (Hydro Chloric Acid) having a concentration of 36%. The mixture / slurry is then manually stirred for 10 minutes with slurry temperature maintained at 85°C. The slurry is then stirred at 2000 rpm for 10 minutes in the secondary mixing step. Magnetic separation of the conditioned slurry is carried out in a Davis tube magnetic separator configured to operate at 1250 Gauss and oscillation frequency of 40Hz. The magnetic concentrate thus obtained has a grade of Fe(T) 57.5% and weight recovery of 42% (refer Table 1).
Experimental details:
Four sets of experimental trials were conducted by way of this invention as given in following Table 1. Chemical analysis and particle size analysis of roasted ultra-fine iron ore tailings are given in following Table 2 & 3 respectively.

Table 1. Details of the experiments and results
Experiment 1 Experiment 2 Experiment 3 Experiment 4
Weight(gram) 10 10 10 10
Liquid solid ratio 10 10 10 10
Temperature( oC) 32 85 85 85
Hot plate stirring Time (min) 10 10 10 10
Slurry conditioning time (min) 10 10 10 10
Slurry conditioning speed (rpm) 2000 2000 2000 2000
Acid addition(ml of HCl/10 gram of solids) 0 1 2 5
Input Fe% 42.7 42.7 42.7 42.7
Magnetic Field strength(Gauss) 1250 1250 1250 1250
Magnetic concentrate Fe% 50 57.5 55 59
Magnetic concentrate weight recovery 32 42 46 32
Fe recovery 37.4 56.5 59.25 44.2

Table 2 Chemical analysis of roasted ultra-fine iron ore tailings

Compound Fe2O3 Fe3O4 SiO2 Al2O3 LOI Others
% 25.76 34.02 21.45 12.22 3 2.8

Table 3 Particle size analysis of roasted ultra-fine iron ore tailings
Particle size(micron) 150 125 75 63 45 32 25 10 2
% 100 100 100 100 99 97 94 78 43

It is thus possible by way of the present invention to provide a method for conditioning of ultra-fine iron ore / tailingsto obtain improved iron upgradation and recovery through high temperature acidic pre-treatment for roasted ultra-fine iron ore/tailings, comprising the steps of heating the ultrafine iron ore/tailingsin the size range 10µm > 65% in an acidic solution followed by high intensity stirring to prepare slurry for low intensity magnetic separation.
,CLAIMS:We Claim:

1. A method for conditioning of ultra-fine iron ore / tailings to obtain improved iron upgradation and recovery involving the steps of:
reduction roasting of the aforementioned tailing material in CO environment;
subjecting the dry roasted material to grinding;
preparing an aqueous solution of a acid of selected concentration and subjecting
said roasted tailing material and said aqueous solution of acid to mixing, comprising
a primary mixing step wherein the acidic mixture of roasted tailings is stirred at elevated temperature to obtain a slurry, and
a secondary mixing step wherein the acidic slurry is diluted and the mixture is mechanically stirred at room temperature; followed by
carrying out low intensity magnetic separation of the conditioned slurry to achieve improved iron grade and recovery.
2. The method as claimed in claim 1 wherein said roasting step provides a roasted product with 30-40% magnetite and 20-30% hematite and with no wustite.
3. The method as claimed in claim 1 wherein the said grinding step results in a product of size fraction such as 75% being less than 10 micron size.
4. The method as claimed in claim 1 wherein the aqueous solution comprises hydrochloric acid and water having a pH of less than 4 and preferably less than 2.
5. The method as claimed in claim 1 wherein the mixture of roasted tailing material in the aqueous acidic solution is such that it contains 10% of solids.
6. The method as claimed in claim 1 wherein the primary mixing of slurry with acid solution is carried out at temperatures higher than 85oC for 10-20 minutes.
7. The method as claimed in claim 1 wherein the mixed material after primary mixing is diluted to5 % of solids concentration.
8. The method as claimed in claim 1 wherein the secondary mixing is carried out for the diluted material at room temperature using a mechanical stirrer operated at 2000 rpm for 5-20 minutes.
9. The method as claimed in claim 1 wherein the magnetic separation is carried out using a Davis tube apparatus operated at magnetic intensity of 1200-1300 Gauss, and at a oscillation frequency of 40Hz and amplitude of 100mm, with a slurry feed rate of 2 to 5 lpm.
10. The method as claimed in anyone of claims 1 to 9 adapted to achieve iron value in the range of 55 to 60% in magnetic concentrate and a recover of 40 to 60%.
Dated this the 3rd day of March, 2025
Anjan Sen
Of Anjan Sen & Associates
(Applicants’ Agent)
IN/PA-199