View Points of Tata Steel on revision of Threshold value of Manganese Ore

Transcription

1 View Points of Tata Steel on revision of Threshold value of Manganese Ore Workshop on Threshold Value of Minerals for Eastern States Organised by Indian Bureau of Mines, Ministry of Mines, Government of India at Noamundi, Jharkhand Presenter: Rajeeb K Mohanty Principal Geologist (Ferro Alloys & Minerals) Date :

2 Disclaimer Statements in this presentation describing the company s performance may be forward looking statements within the meaning of applicable securities laws and regulations. Actual results may differ materially from those directly or indirectly expressed, inferred or implied. Important factors that could make a difference to the company s operations include, among others, economic conditions affecting demand/supply and price conditions in the domestic and overseas markets in which the Company operates, changes in or due to the environment, Government regulations, laws, statutes, judicial pronouncements and/or other incidental factors. 2

3 Outline of Presentation 1 Background 2 Geographical distribution of Manganese ore in India 3 Beneficiation studies 4 Distribution of different grades of subgrade Mn ore in Tata Steel leases 5 World scenario - Production status & lower limit of Mn% 6 Recommendations 3

4 Background 4

5 BACKGROUND Indian Bureau of Mines (IBM) have invited inputs from all stakeholders including concerned members of public for revision of the threshold value of minerals vide letter no C-284/3/CMG/2017, dated 24/03/2017. "Threshold Value of minerals" means limit prescribed by the Indian Bureau of Mines from time to time based on the beneficiability and or marketability of a mineral for a given region and a given time, below which a mineral obtained after mining can be discarded as waste. At present, the threshold value for Manganese ore notified by IBM in 2009 is 10% Mn, i.e % Mn is defined as subgrade. 5

6 Geographical distribution of Manganese ore in India 6

7 GENESIS OF MANGANESE ORE OCCURRENCE IN INDIA (AS PER IBM - MANGANESE ORE VISION 2020 AND BEYOND DOCUMENT) S. no. Type of Ore Deposit Characteristic features of ore Distribution in India 1 Syngenitic Gonditic Deposits Formed contemporaneously with the host rock. Mainly associated with Gondite rocks Mainly Siliceous Ore from Central India MP; Maharashtra Gujarat; Rajasthan 2 Syngenitic Reef Deposits These are Syngenetic manganese ore associated with intrusive rocks (Kodurite). Ores of hybrid origin associated with high grade metamorphosed Kodurite suit of rocks Andhra Pradesh & Telengana Koraput and Bolangir Districts of Odisha 3 Replacement Deposits Secondary in nature, These are Epigenitic class of ores, Lateritoid ores occurring in places on the outcrop of precambrian rocks formed by the surface replacement of the constituents of these rocks by percolating water. Iron Ore Series in Jamda Koira Valley of Singhbhum and Odisha Dharwar in Karnataka and Goa Mainly Ferrugenous Ore 4 Laterite deposits & Supergene enrichment These too belong to epigenetic class of ores associated with all the above type of deposits 7

8 MANGANESE OCCURRENCES IN INDIA MANGANESE RESOURCE DISTRIBUTION OF DIFFERENT ORE TYPES Total Resources 475 Mt Reserves/Resources of Manganese Ore as on (in,000 Tons) State Total Reserve (A) Total Resource (B) Total Resources (A&B) Ore Type Source: 2/production-and-distribution-of-manganese-in-india/19758 Goa Jharkhand Karnataka Ferrugenous West Bengal Odisha Andhra Pradesh Telengana Kodurite Gujarat MP MH Siliceous Rajasthan Total Ref : Mineral Year Book- 2015, IBM published in March

9 GENERAL METHODS OF BENEFICIATION OF DIFFERENT MANGANESE ORES Source: IBM Manganese Ore Vision

10 MINERALOGY AND CHEMISTRY OF MANGANESE ORES (JODA AREA, ODISHA) Type of minerals Manganese Minerals Iron Minerals Silicate Minerals Alumina Minerals Major Minerals Pyrolusite (MnO2), Psilomelane ((Ba,H 2 O) 2 Mn 5 O 10 ), Cryptomelane (K(Mn) 8 O 16 ) Hematite (Fe2O3), Goethite (FeO(OH)) Kaolinite (Al 2 Si 2 O 5 (OH) 4 ), Quartz (SiO2) Gibbsite (Al(OH) 3 ) Minor Minerals Lithiophorite ((Al,Li)MnO 2 (OH) 2 ), Rhodocrocite (MnCO 3 ), Nsutite (MnO 2 (OH) 2 ) Limonite (FeO(OH),H2O) Range of Chemical analysis Ore 25% to 54% Mn 5% to 30% Fe 1% to 25% SiO2 1% to 15% Al2O3 Subgrade 10% to 24.99% Mn 12% to 40% Fe 5% to 35% SiO2 5% to 15% Al2O3 10

11 Beneficiation studies 11

12 GENERIC BENEFICIATION STRATEGIES FOR EFFICIENT UTILIZATION OF LOW GRADE MANGANESE ORES If, Mn% <25 & Mn/Fe <1 in Mn Ore, For achieving metallurgical grade specification the economics may not be promising 12

13 PROBLEMS : MN ALLOY PRODUCTION USING LOW GRADE ORE a. Use of low grade ferruginous manganese ore with Mn <25, Mn/Fe<1 increase alloy production cost because : Increased power, coke and flux consumption Increase slag volume which results in lower process throughput b. High Mn ferroalloys is difficult to produce by such ore blends and steel producers always prefer high Mn ferroalloys 13

14 PROBLEMS FACED IN BENEFICIATION OF LOW GRADE FERRUGINOUS ORE (a) Complexity and variability in mineralogy (b) Technical difficulties during Separation of Mn & Fe a) Narrow density difference in Mn & Fe Minerals (Fe bearing minerals & Pyrolusite : 4.73) Concentration criteria for Gravity Methods ( Jigs, Spirals and Dense media Cyclone) Concentration criterion (>2.5) ( B A Wills, 2006, pp-225) CC = (D h - D f ) / (D l - D f ) = (5.25-1)/(4.73-1) = 1.13 b) Both are paramagnetic with narrow difference in magnetic characteristics Ref. : Non-Ferrous Metal Ores: Deposits, Minerals and Plants, 2002 (c) Economic unviability of hyrdo-metallurgical and pyro-metallugical routes mainly due to lower yield. Ore grade Mn :25 %, Theoretical product yield = 0.80*250 = 200 kg/ton ( Assumption : Mn Recovery :80%) 14

15 TATA STEEL HAD CARRIED OUT NUMBER OF BENEFICIATION STUDIES ON LOW GRADE MN ORES, TWO CASE STUDIES ARE PRESENTED Case Study -I : (RMIIMTG/ MFA/TR/15/4) Beneficiation of Low grade Manganese ore fines with dry Magnetic Separation. Case Study II : (R&D/ Report/57/10) Magnetic Separation process and a detailed Specification Report to process the Low Grade Mn Ore fines 15

16 Case Study - I : (RMIIMTG/ MFA/TR/15/4) Beneficiation of Low grade Manganese ore fines with dry Magnetic Separation (Head Grade: 18.79% Mn, 0.83 Mn/Fe) 16

17 Moisture loss 1. FEED CHARACTERISTICS Head Sample Head Sample Chemical Analysis Mn Fe (T) SiO 2 Al 2 O 3 Mn/Fe Temperature 17

18 2. MINERALOGICAL CHARACTERIZATION Size-wise mineralogical characterization 18

19 3. CONSTRAINTS OF DRY BENEFICIATION Nature of association - Ore being Ferruginous in nature & with the similarity of the Fe bearing minerals & Mn bearing minerals property, it would be difficult to separate the same with higher separation efficiency, resulting in higher Mn loss in rejects. Slime coating - Fe bearing mineral are disseminated in finer size and Mn - bearing minerals in coarser size. So from dry beneficiation, it is difficult to remove slime coating with dry process. Hence effecting the quality for metallurgical usage in terms of Mn to Fe ratio. Availability of technology - the suitable beneficiation technology is not available in the mineral industry to treat the ferruginous manganese ore with higher separation efficiency. Applicability - o The Odisha belt Iron ore group range of Manganese ore are ferruginous in nature. o Complex association of Fe bearing minerals, which are gangue minerals o With such complex association, dry process alone would be difficult. 19

20 4. GENERIC CONSTRAINTS IN BENEFICIATION Moisture - Gangue bearing minerals such are gibbsite & Kaolinite are hygroscopic in nature and has tendency to hold moisture hence affecting the separation efficiency and operation. Dust issue - The gangue bearing minerals like Kaolinite and gibbsite are friable in nature and tends to produce more fines hence problem of dust formation and also may seem difficulty of screening. Suffers Capacity - equipment on an average tends to have lower capacities than corresponding wet methods. 20

21 5. PROCESS FLOW TEST RESULTS Bamebari Dump fines Project: A Reject mm screen 3mm screen Wt(%) Legend -10 mm stockpile -10mm stockpile Mn Rec Mn to Fe mm stockpile mm stockpile -10mm 100 stockpile mm stockpile mm screen mm screen 3mm screen 3mm screen Double deck screen + 10 mm Top 3mm deck:10mm +3mm Bottom deck: 3mm +3mm +3mm +3mm + 3 mm mm mm 3 2Roll crusher Roll crusher Roll crusher crusher CSS: 3mm 3 Roll CSS: 3mm -3mm 4 2-3mm 4CSS: 3mm crusher 2 Roll crusher CSS: CSS: 3mm 3mm -3mm 4 2-3mm CSS: 3mm 3 RERMS 2-3mm RERMS 4 RERMS RERMS RERMS RERMS non-mag RERMS RERMS 2 non mag RERMS RERMS non-m Plant Flowsheet of Project: A Non-mag RERMS RERMS Product non-mag Non-mag non-mag P 4 RERMS 5 2mag Reject Non-mag Reject non-mag 4 5 Non-mag Product Product Reject 5 6 Product 6-10mm 8stockpile Reject Non-mag 8 7 Reject 7 7 Product -10mm sto RERMS 1: Two roll machine Mag cleaning configuration Mass Balance for Bamebari Dump Fines Sl No Stream Mn(%) Mn to Fe Mn Rec Yield 1 Feed (-10 mm stockpile) Product Reject Mn 21

22 6. CONCLUSIONS The head grade of Mn % ore was used for carrying out the beneficiation studies, which produced a concentrate of 29.53% Mn, with an yield of 31 % (by weight). The summary of test work is as under: Mass Balance for Bamebari Dump Fines Sl No Stream Mn(%) Mn to Fe Mn Rec Yield 1 Feed (-10 mm stockpile) Product Reject It can be concluded that the product cannot be used directly for production of alloy and needs to be blended with better grade ore for metallurgical use. Even if the material beneficiated with the combination of roasting and magnetic separation techniques, the quality may not improve substantially due to the friable nature of the iron bearing particles might generate ultrafine particles resulting the magnetic separation becomes more complex. Hence beneficiability of low grade 18.79% Mn is not feasible. 22

23 Case Study - II : (R&D/ Report/57/10) Magnetic Separation process and a detailed Specification Report to process the Low Grade Mn Ore fines (Head Grade: 26.7% Mn, 1.2 Mn/Fe) 23

24 1. ORE CHARACTERISATION (a) Chemical Analysis The variation in important constituents Mn : Fe : SiO2 : 8-12 (b) Major Mineral phases Mn Mineral : Pyrolusite, Psilomelane, Bixbite, etc Fe Minerals : Hematite, Goethite, etc Gangue : Quartz, Kaolinite, etc Counts Jodawest Bamibari Malda # # $ $ $ * * * * Hematite + Pyrolusite $ Quartz # Cryptomelane Position [ 2Theta] (a) XRD analysis (b) QEMSCAN Mineralogical analysis 24

25 2. BENEFICIATION STUDIES Particle Size :0-10mm (A) Coarse Magnetic Separation (Intensity : 1.1 T) Particle Size : <3mm (B) Crushing (<3mm) & Magnetic separation (C) Dry Screening (1mm), Crushing (<3mm) & Magnetic separation (D) Wet Screening Crushing (<3mm) & Magnetic separation 25

26 3. RESULTS Feed Grade 8-10 % Mn rise 6-8% Fe reduction Yield ~40% 26

27 4. CONCLUSIONS The head grade 26.7 Mn % content was used for carrying out the study. Coarse magnetic separation of 0-10mm was not successful. Crushing followed by magnetic separation can enhance Mn content by 8-10 units and can reduce Fe content by 6-8 units. Hence, this process is effective only for ores with Mn >25% & Mn/Fe >1. Dry and Wet removal of slimes and Magnetic separation can improve Mn : 11.8% and Mn/Fe : 1.4 but this imposes environmental as well as cost economic challenges due to additional cost of water and filtration. Sintering & briquetting is required to utilize these fines for use as feed in the furnace, which further increases the cost of the project. The end product based on beneficiation tests does not meet our required feed grade (Mn 45% and Mn/Fe 4.4) for producing Ferro manganese. 27

28 BENEFICIATION STUDIES FOR FERRUGINOUS MANGANESE ORE OF KARNATAKA (Source: IBM Manganese Ore Vision 2020) 28

29 BENEFICIATION TECHNIQUES FOR FERRUGINOUS ORE OF KARNATAKA- LOW GRADE ORE Source: IBM Manganese Ore Vision 2020 Summary: Feed Grade: 34.1% Mn, 17.7% Fe, 8.5% SiO2, 1.93 Mn/Fe Output Grade: 49.5% Mn, 9.1% Fe, 9.2% SiO2, 5.44 Mn/Fe (Yield 40%) Reject Grade: 24.4% Mn, 24.2% Fe, 7.8% SiO2, 1.01 Mn/Fe 29

30 Distribution of different grades of subgrade Mn ore in Tata Steel leases 30

31 DISTRIBUTION OF SUBGRADE Mn ORE (+10-25%Mn) WITHIN THE LEASEHOLD AREAS OF TATA STEEL - MANGANESE GROUP OF MINES Based on the present exploratory data & statistical analysis, the approximate distribution of subgrade ore from 10-25% Mn in terms of incremental 5% increase in Mn content is given as under. Grade Range Tonnage (%) Mn% Fe% Mn/Fe > > > Grand Total Mn% 31

32 STATUS OF SUB GRADE MATERIAL WITHIN THE EXISTING PITS Actual Material type Grade Range Tonnage (%) Mn% Fe% Mn/Fe Overburden 0 -> > Subgrade > > Cumulative Cumulative impact of Mn grade at each 5% increase in Threshold limit Grade Range Tonnage (%) Mn% Fe% Mn/Fe Remarks 0 -> Mn Threshold Limit 0 -> Mn Threshold Limit 0 -> Mn Threshold Limit 0 -> From the above distribution of Mn content with 5% incremental grade, it can be observed that there is very thin marginal increase of Mn content with due weightage to tonnage. The 20 to 25%Mn grade is the only class interval which is above 20% Mn (averaging to 21.81) and this is supportive of our proposal to revise the threshold value upward to 20% Mn. In the event of revision of existing threshold value to 20%, it will facilitate stacking of 20 to 25% Mn grade, which will have better value proposition for future improvement in beneficiation technology, as otherwise this class interval would get diluted. 32

33 World scenario - Production status & lower limit of Mn% 33

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35 WORLD SCENARIO: MAJOR PRODUCERS OF MANGANESE ORE WITH GRADE MANGANESE ORE: WORLD PRODUCTION, BY COUNTRY COUNTRY UNIT Mn Content (%) (In Thousand metric tons) AUSTRALIA Gross weight 6,474 6,963 7,172 7,448 7, Mn content 2,650 2,860 2,950 2,975 3,049 BRAZIL Gross weight 3,125 2,738 2,796 2,833 2, Mn content 1,223 1,139 1,164 1,180 1,040 CHINA Gross weight 13,000 14,000 14,500 15,000 15, Mn content 2,600 2,800 2,900 3,000 3,000 GABON Gross weight 3,201 4,070 3,637 4,297 4, Mn content 1,536 1,858 1,650 1,967 1,863 INDIA Gross weight 2,858 2,542 2,470 2,320 2, Mn content 1, SOUTH AFRICA Gross weight 7,172 8,652 8,943 10,988 12, Mn content 2,900 3,400 3,600 4,300 5,200 UKRAINE, CONCENTRATE Gross weight 1, ,234 1,525 1, Mn content Source: USGS Mineral Yearbook 2014 No open source information is available about the sub-grade and cut off grade/threshold value of Manganese ore in major producing countries. For lower grade manganese ore, it is mentioned in various articles, that they are beneficiated in respective Ore Beneficiation Plants in all the countries. But the minimum grade of ore beneficiated is not mentioned for any major producing country in the public domain. Only China has kept lower limit of Manganese ore at 20% Mn. All other countries have kept lower limit of Manganese ore for their use greater than 20%. No other country is maintaining threshold value of 10% Mn except India. 35

36 Recommendations 36

37 RECOMMENDATIONS The majority of Mn resources established in India under various categories is ferruginous in nature (75%) representing formation of Mn ore by secondary enrichment in Iron environment. There is similarity of the Fe bearing minerals & Mn bearing minerals property, hence it would be difficult to separate the same with higher separation efficiency, resulting in higher Mn loss in rejects. The beneficiation of test cases discussed, one with head grade of 18.79% Mn (0.83 Mn/Fe) and other with 26.7% Mn (1.2 Mn/Fe), has indicated that the improvement of grade is ~ 29.53% Mn & 1.43 Mn/Fe (31% yield) and 38.6% Mn & 2.5 Mn/Fe (40% yield) by weight respectively using the present applicable beneficiation techniques for ferruginous manganese ore. The product grade generated with this beneficiation process cannot be used directly for making Ferromanganese. Further test work is in progress to improve the grade and yield to make, beneficiability of low grade manganese ore economically feasible. The general proportion of occurrence of sub grade ore in Joda region with class interval of 10 to 15, 15 to 20 and 20 to 25% Mn is 44, 42 and 14% by volume respectively. The average grade in these class interval is 12.93, and 21.83%Mn. Summarising, based on the above data, we recommend that the existing threshold value of 10% Mn should be revised upward to 20%Mn for ferruginous manganese ore, since the test work has indicated that there is very marginal improvement in grade of Mn ore <20 % & Mn/Fe ratio on beneficiation, moreover it does not have direct marketability. 37

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