Amenability to beneficiation of a low grade Manganese ore fines from Sandur Region, Karnataka, India
R V Vinayak Kumar, M. R. Patil, B. P. Ravi
Dept. of Mineral Processing, VSKU PG Centre, Nandihalli 583119.
*Corresponding Author E-mail: vinayak.rvminpro@gmail.com
Abstract:
A low grade ferruginous Mn ore assaying 21.77%Mn and 28.53%Fe mines of Sandur region was subjected to amenability to beneficiation process comprising of -wet screening over 10,6,3,1mm-split jigging of screen over sizes in a mineral jig,-crushing of jig tails to -1mm–magnetizing reduction roasting of crushed jig tails and natural minus 1 mm powder 600oC for 0.5 hour with 10% coal reductant followed by water quenching and wet low intensity magnetic separation to remove ferruginous impurities yielded a composite concentrate assaying 32.36% Mn, 21.53% Fe,1.5 Mn/Fe ratio with 68.7% Mn distribution at 46.2 wt.% yield meets the specifications of metallurgical industry after suitably agglomerating the concentrate. The sample is amenable to processing
KEY WORDS: Sandur region.
INTRODUCTION:
Manganese ore is a useful and essential constituent of steel. Since no quality steel can be produced without a small amount of manganese, manganese is aptly called ‘Achilles heel’ of the steel industry. Sandur schist belt comprises: basic igneous rock (meta basalts and pillow lava), ferruginous and manganiferous fillite/shale, younger intrusive banded ferruginous quartzite, iron, manganese ore and laterite. The manganese ore bodies are found to be associated with the phyllites and their altered products. The ore bodies are considered to be syngenetic and the later stage have undergone reconstitution by low grade metamorphism and also the supergene agencies have acted upon them to form superficial deposits at or near the surface. The systematic mining of manganese ore in this belt started as early as 1905 and has been mined from different open-cast mines. Manganese ore occurs at and around Deogiri forming part of the Kumarswamy range and extends further to Ramanadurga range of hills separated by the rivulet Narihalla. The schist belt consists of basic igneous rocks in the form of flows and pillows, phyllited, banded ferruginous quartzites, vein quartz, manganiferous greywackes and thin beds of carbonates.The different blocks identified in this belt are Deogiri, Swamihalli, Subbarayanahalli, Sunderbench, Ramgad, Seshagiri and Donikolla. A number of manganese ore deposits of varying dimensions occur all along the western margin of the Sandur schist belt over a length of 40 km with widths ranging from 0.2 to 1.5 km, which occurs between the Lower Yeshwanth Nagar and Upper Donimalai Formations. The resources is about 10.99 million ton (as on 1.4.2006) and Manganese ore deposits mainly confined to western part of the schist belt and concentrated at Deogiri, Subbrayanahalli mines areas. Recent review of literature indicated that beneficiation studies on utilization of ferruginous manganese ores from Sandur are scanty except the works of Hiremath et.al.(2013) and Gopalkrishna et.al.(2015,2016 and 2017). The authors used slightly higher grade of Mn as compared to low grade ferruginous manganese ore fines that are dumped in SK (Sillukolla) mines area. The amenability of low grade ferruginous manganese ore fines from SK mines, Swamihalli forest will not only pave way for their utilization and conservation of good grade manganese ore fines but also reduces forest land used for dumping low grade ferruginous manganese ore that can be reclaimed and afforested. Amenability of ferruginous Mn samples from Swamimalai forest area (SK mines area) with an aim of improving Mn grade>30% Mn/Fe ratio preferably>1.5 to beneficiation methods like washing and jigging and as well as magnetizing roast followed by magnetic separation are being attempted.
EXPERIMENTAL:
The low grade/waste dump manganese ore fines (-10 mm) samples were collected from SK mines, Sandur, Karnataka for beneficiation study. The sample was then subjected to standard sampling – feed preparation, characterization, physical and chemical beneficiation amenability tests as per the standard practice enumerated.
RESULTS AND DISCUSSION:
Characterization studies:
The representative samples from SK mines comprised of mostly black coloured fines with chips predominating over powdery material. Some brownish yellow coloured soft friable chips and coated powder grains were noticed. The sample used to soil the fingers. Pyrolusite, psilomelane, manganite and braunite are reported to be the manganese ore minerals while quartz, hematite, limonite, goethite and clay are associated gangue minerals based on microscopic studies The sample analyzed 21.77% Mn, 28.53% Fe, 0.76 Mn/Fe ratio The characterization study indicated clearly that the sample was low grade ferruginous manganese fines that needs beneficiation for use in local metallurgical purpose after agglomeration.
Amenability of sample to size analysis:
A representative sample was subjected to wet size analysis and fractions were analysed. The results are given in Table 1.
Table-1; Sieve Analysis of SK Mines Sample.
|
Size in mm |
Wt% Retained |
Assay% |
Distn% |
Cum Wt% Retained |
Assay% |
Mn/Fe ratio |
Distn. Mn % |
|||
|
Mn |
Fe |
Mn |
Fe |
Mn |
Fe |
|||||
|
-20+10 |
12.16 |
27.24 |
25.38 |
15.22 |
10.82 |
12.16 |
27.40 |
25.10 |
1.09 |
30.57 |
|
-10+6 |
12.01 |
27.82 |
26.14 |
15.35 |
11.01 |
24.17 |
||||
|
-6+3 |
20.87 |
26.46 |
26.00 |
25.37 |
19.02 |
45.05 |
28.19 |
24.97 |
1.13 |
25.37 |
|
-3+2 |
10.96 |
25.21 |
26.87 |
12.69 |
10.32 |
56.01 |
26.91 |
26.53 |
1.01 |
13.96 |
|
-2+1 |
1.05 |
26.24 |
26.23 |
1.27 |
0.97 |
57.06 |
||||
|
-1+0.5 |
13.06 |
23.37 |
27.85 |
14.02 |
12.75 |
70.12 |
18.60 |
29.56 |
0.63 |
30.10 |
|
-0.5+0.25 |
8.11 |
19.01 |
27.64 |
7.08 |
7.86 |
78.23 |
||||
|
-0.25+0.15 |
4.05 |
15.05 |
30.62 |
2.80 |
4.35 |
82.28 |
||||
|
-0.15+0.075 |
9.16 |
7.62 |
35.47 |
3.21 |
11.39 |
91.44 |
||||
|
-0.075+0.045 |
4.80 |
7.50 |
38.65 |
1.66 |
6.51 |
96.25 |
||||
|
-0.45 |
3.75 |
7.80 |
38.02 |
1.34 |
5.00 |
100.00 |
||||
|
Head Cal |
100.00 |
21.77 |
28.53 |
- |
- |
|
21.77 |
28.53 |
0.76 |
100.0 |
The results clearly indicate that washing and wet screening has improved the Mn/Fe ratios significantly at size more than 1mm. with yield of 57.06 wt.%. Similar results were obtained by Gopalkrishna et.al. (2015, 2016 and 2017) perhaps owing removal of Mn bearing ferruginous clayey slimes. The washed coarse sandy products were black in colour and slimes were dull yellowish black coloured powder. The previous works Hiremath et.al. (2013), Gopalkrishna et.al.(2015,2016 and 2017) and IBM (2011) indicated the jigging of washed chips/ lumps and magnetizing reduction roast followed by magnetic separation of low Mn/Fe ratio sample for ferruginous manganese ores of Sandur region. Hence jigging tests was performed on crushed and natural-10+6 mm-6+3mm and -3+1mm sample fractions separately. The -1mm natural–crushed sample with low Mn/Fe ratio was subjected to reduction roast followed by WLIMS.
Amenability to jigging:
Effect of flow rate; The tests were conducted by using a mineral jig (hartz jig). Feed sample prepared by coning and quartering method and variation of water flow rate using in the experiments to remove the gangue minerals from ore mineral and upgrade. The results pertaining to varying water flow rate is given in Table 2. The results indicate that increase in water flow rate from 3 to 6 lpm decreased the Mn/Fe ratio and increased the wt% yield of concentrate. Optimum results were obtained at 4.5 minutes, 6 lpm water flow rate producing concentrate assaying 32.92% Mn, 22.38% Fe, ~1.5Mn/Fe ratio just meeting the stipulated specification at maximum yield of 51.42% ( overall wt.% yield of 12.4 for the chips size).
Table-2: Effect of water flow rate Conditions: Feed size:-10+3 mm, Time: 4.5 minutes, Aperture 1 mm, Stoke 30mm, 250 RPM
|
Water Flow Rate |
6 lpm |
4 lpm |
3 lpm |
||||||
|
Products |
Wt% |
Mn% |
Fe% |
Wt% |
Mn% |
Fe% |
Wt% |
Mn% |
Fe% |
|
Concentrate |
51.42 |
32.92 |
22.38 |
48.54 |
32.13 |
22.34 |
40.05 |
33.92 |
21.06 |
|
Middling |
24.36 |
27.17 |
26.82 |
24.89 |
26.93 |
26.37 |
29.30 |
28.86 |
25.43 |
|
Tailing 1 |
18.87 |
21.57 |
30.33 |
19.76 |
21.88 |
30.28 |
25.26 |
22.43 |
29.82 |
|
Hutch |
5.36 |
15.70 |
35.24 |
6.81 |
13.99 |
35.92 |
5.38 |
14.68 |
35.75 |
|
Head Cal |
100.00 |
28.46 |
25.65 |
100.00 |
27.57 |
25.83 |
100.00 |
28.50 |
25.34 |
Effect of split jigging:
Jigging tests were carried out for 4.5 minutes, 1 mm aperture, 30mm Stroke, 250 rpm and at 6 lpm water flow rate. The results are given in table 3. The results indicate that the composite sample of split jigging yielded a composite concentrate assaying 33.21% Mn, 22.55% Fe,~1.5 Mn/Fe ratio just meeting the specification at overall wt.% yield of 25 with38.2% Mn overall distribution with respect to ROM feed. The jig rejects and -1 mm sample constituting final rejects assayed 21.27% Mn, 28.82% Fe, 0.74Mn/Fe ratio at75 wt% yield with 61.8 % Mn distribution.
Amenability of reduction roasting:
The jig rejects and-1 mm sample constituting final rejects assayed 21.27% Mn, 28.82% Fe, 0.74Mn/Fe ratio at75 wt.% yield with 61.8 % Mn distribution. The samples were stage crushed to -1mm and subjected to magnetizing roasting at 600oC for 0.5 hour with 10% coal reductant followed by water quenching and wet low intensity magnetic separation to remove ferruginous impurities. The above process yielded a concentrate assaying 31.33% Mn, 20.34% Fe,~1.5 Mn/Fe ratio at 21.22 overall wt% yield with overall Mn recovery of . The composite process results are shown in Table 3. The results indicate that the sample is amenable to reduction roasting followed by WLIMS. A combination of wet screening, split jigging of -20+1 mm fraction, followed by stage crushing of jig rejects and -1mm fraction, drying, reduction roasting at 600oC for 0.5 hour followed by water quenching and wet low intensity magnetic separation yielded a composite concentrate assaying 32.36% Mn, 21.53% Fe, 1.5Mn/Fe ratio with 68.7% Mn distribution at 46.2 wt% yield meets the specifications of metallurgical industry after suitably agglomerating the concentrate. The results are similar to findings previous works.
CONCLUSIONS:
The low grade ferruginous Mn ore assaying 21.77%Mn and 28.53%Fe mines of Sandur region is amenable to process of jigging, reduction roasting of crushed jig tails and ore fines followed by WLIMS yielding concentrate with>30% Mn, Mn/Fe >1.5 with 68% Mn recovery, which can be used in metallurgical industry after suitable agglomeration. The ore is amenable to beneficiation.
Table-3: Split size Jigging Conditions; Time: 4.5 minutes, Water flow rate: 6 lpm Aperture 1 mm, Stoke 30mm, 250 RPM
|
Size range |
Products |
Wt% (OA Wt%) |
Assay% |
Mn/Feratio |
|
|
Mn% |
Fe% |
||||
|
-20+6mm |
Concentrate |
45.03 |
33.05 |
23.38 |
1.41 |
|
Middling |
28.45 |
26.78 |
27.41 |
|
|
|
Tailing |
24.03 |
22.50 |
28.45 |
|
|
|
Hutch |
2.49 |
15.96 |
29.86 |
|
|
|
Head Cal |
100.00 |
27.40 |
25.91 |
1.09 |
|
|
-6+3mm |
Concentrate |
46.40 |
33.51 |
21.36 |
1.57 |
|
Middling |
27.20 |
26.53 |
26.64 |
|
|
|
Tailing |
22.93 |
21.22 |
29.52 |
|
|
|
Hutch |
3.47 |
16.10 |
30.00 |
|
|
|
Head Cal |
100.00 |
28.19 |
24.97 |
1.13 |
|
|
-3+1mm |
Concentrate |
40.00 |
32.00 |
23.00 |
1.39 |
|
Middling |
27.14 |
27.87 |
27.47 |
|
|
|
Tailing |
21.43 |
21.01 |
29.86 |
|
|
|
Hutch |
11.43 |
17.87 |
30.45 |
|
|
|
Head Cal |
100.00 |
26.91 |
26.53 |
1.06 |
|
|
Com-20+1mm |
Concentrate Cal |
43.81 (25.00) |
33.21 |
22.55 |
1.5 |
|
Middling Call |
27.60 |
27.06 |
27.18 |
|
|
|
Tailing Cal |
22.80 |
21.60 |
29.25 |
|
|
|
Hutch Cal |
5.80 |
17.24 |
30.28 |
|
|
|
Head Cal |
100.00 |
27.50 |
25.80 |
1.06 |
|
|
|
Jig rejects[M+T+H] Cal |
56.19 (45.12) |
23.04 |
28.33 |
0.81 |
|
Com -1mm |
-1mm rejects |
(29.88) |
18.60 |
29.56 |
0.63 |
|
Overall rejects |
75.00 |
21.27 |
28.82 |
0.74 |
|
Table-4; Wet screening, split jigging, crushing to -1mm, reduction roast followed by WLIMS
|
Products |
Wt% |
Assay % |
Mn/Feratio |
% Mn Distn |
|
|
Mn |
Fe |
||||
|
-20+1mm Jig concentrate |
25.00 |
33.21 |
22.55 |
1.5 |
38.2 |
|
-1mm Redn Roast Non mag Concentrate |
21.22 |
31.33 |
20.34 |
1.5 |
30.5 |
|
-1mm Redn. Roast Mag tails |
53.78 |
12.67 |
34.54 |
0.36 |
31.3 |
|
Head Cal |
100.00 |
21.77 |
28.53 |
0.76 |
100.0 |
|
Final Comp Mn Concentrate Cal |
46.22 |
32.36 |
21.53 |
1.50 |
68.7 |
REFERENCES:
1. M S. Hiremath, Vinayak Kumar and C Rudrappa, (2013,’Beneficiation Studies On Manganese Ores Of Deogiri Area, Sandur Schitst Belt, Karnataka Craton’ Ind Min 37 (1), 161-169.
2. S J Gopalkrishna, BP Ravi and UM Reddy (2016),’ Improving Mn/Fe ratios of ferruginous manganese ores from Sandur’, IJIR,2 (9),pp1657-58.
3. S J Gopalkrishna, BP Ravi and UM Reddy (2017), ‘Jigging studies of ferruginous manganese ore’. Proc MPT 2017 NML Chennai,pp 382-89.
4. IBM (2015), Monograph and vision 2020 of Manganese
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Received on 16.07.2018 Modified on 29.09.2018 Accepted on 05.1.2018 ©A&V Publications All right reserved Research J. Science and Tech. 2018; 10(4):291-294. DOI: 10.5958/2349-2988.2018.00041.4 |
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