New technologies for PGM smelting: An overview of the ConRoast process. Rodney Jones

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1 New technologies for PGM smelting: An overview of the ConRoast process Rodney Jones

2 Mintek

3 Mintek Government-owned minerals research organization (established in 1934) Based in Randburg, South Africa Substantial capabilities in all metallurgical disciplines Employs 780 people (270 researchers) Annual budget of R390m ($50m) State & corporate funding (30:70)

4 DC arc furnace Cylindrical steel shell Refractory lined Central graphite electrode Anode imbedded in hearth Metal layer in electrical contact with anode Energy supplied by open plasma arc Fairly uniform temperature distribution

5 DC arc furnace Cylindrical steel shell Refractory lined Central graphite electrode Anode imbedded in hearth Metal layer in electrical contact with anode Energy supplied by open plasma arc Fairly uniform temperature distribution

6 DC arc furnace Slag Metal Cylindrical steel shell Refractory lined Central graphite electrode Anode imbedded in hearth Metal layer in electrical contact with anode Energy supplied by open plasma arc Fairly uniform temperature distribution

7 DC arc furnace Slag Metal Cylindrical steel shell Refractory lined Central graphite electrode Anode imbedded in hearth Metal layer in electrical contact with anode Energy supplied by open plasma arc Fairly uniform temperature distribution

8 DC arc furnace Cylindrical steel shell Refractory lined Central graphite electrode Anode imbedded in hearth Metal layer in electrical contact with anode Energy supplied by open plasma arc Fairly uniform temperature distribution

9 DC arc furnace Graphite electrode Off-gas port Feedport Water-cooled shell Slag Tap-holes Metal Anode

10 DC arc furnaces for melting metals date back to 1878 Sir William Siemens used a DC arc furnace in 1878 with a vertical graphite cathode, with the arc transferred to the melt in contact with a water-cooled bottom anode

11 Inside the DC arc furnace

12 The ConRoast Process The ConRoast process is based on reductive smelting in a DC arc furnace in the effective absence of sulfur, where an iron-based alloy is used to collect the valuable metals This addresses the three big challenges in PGM smelting today: The sulfur problem The chromium problem The containment problem

13 The sulfur problem - SO 2 emissions in matte smelting Legislation on emissions of sulfur (as SO 2 ) and other minor elements will get increasingly tougher A more environmentally-friendly process is needed for the future

14 The chromium problem Two main PGM orebodies are Merensky (sulfide) and UG2 (chromitite) Traditional matte-smelting process imposes strict limits on the quantity of chromite that can be present in smelter feed This constraint restricts recovery of PGMs in the production of ore concentrates ConRoast tolerates high levels of chromite by ensuring that the chromium is dissolved in the slag (as CrO not Cr 2 O 3 )

15 Mine Opex Breakdown 72% of operating costs 11% of operating costs Crushing & Milling Concentrator 8% 5% 4% Smelter Base Metals Refinery Precious Metals Refinery

16 Distribution of operating costs for PGM processing Operating costs Mining 72% Recovery Concentrating 11% 85% Smelting 8% 95-98% Refining 9% 99%

17 The containment problem As increasing quantities of UG2 (chromitite) ore are processed, the number of furnace failures has increased Even water-cooled copper cooling systems battle to contain highly superheated and corrosive molten matte ConRoast benefits from having melting temperatures of slag and alloy close to each other

18 Opportunities Mining & Concentrating Could look very different if constraints were removed with respect to base metal, sulfur, and Cr 2 O 3 contents Smelter Lower technical risk on main furnace when smelting high-chromium feed materials Can smelt difficult materials Low-grade high-chromium concentrates Revert tailings Converter slag

19 Autocatalyst addition Autocatalysts can also be added to the furnace Accurate sampling and analysis is required

20 Processing up to t/m Clean process By-product slag Alloy ingots Large-scale smelting at Mintek

21 Tapping alloy

22 Alloy Mass of alloy is about 10% or less of the mass of feed material

23 Slag Discardable slag less than 1 g/t PGMs Slag meets US EPA TCLP and acid rain test criteria for safe disposal Slag is used as a by-product for purposes such as concrete aggregate, road fill or shot blasting

24 Clean gas emissions Gas discharged via a baghouse, SO 2 scrubber, and stack

25 1.5 MW furnace First alloy tapped for Braemore Platinum, 2 October tons smelted in ten months 840 tons of alloy produced in 10 months oz of PGMs produced in alloy form in first nine months

26 Kγ Recovery model for PGM smelting R Co Kγ RFe = 1 (1 Kγ ) R Fe Recovery, % PGMs Kγ = 184 Ni Kγ = 28 Co Kγ = 9 Cr Kγ = Kγ recovery equation for NiO, CoO, and CrO PGM behaviour can be modelled this way too (empirically) Fe recovery, %

27 Upgrade to 3 MW furnace at Mintek DC arc furnace was upgraded in August 2008

28 Upgrade from 1.5 MW to 3 MW furnace at Mintek 4.25m diameter versus 3m diameter

29 Upgrade to 3 MW furnace at Mintek

30 3 MW furnace First slag and alloy tapped on 4 and 21 October tons smelted in new furnace so far tons smelted in total tons of alloy produced > oz PGMs produced

31 Commercial partnership Established PGM producers were approached The South African Mineral and Petroleum Resources Development Act (MPRDA) of May 2004 opened up new opportunities for emerging mines and concentrators Atomaer funded a technology development programme in exchange for a period of exclusive use of the technology Independence Platinum was established Braemore Resources acquired Independence Platinum; listed on AIM (London) and JSE (Johannesburg)

32 Braemore Platinum Braemore Platinum (Pty) Ltd is now a wholly owned subsidiary of Jubilee Platinum Braemore have the exclusive licence to Mintek s ConRoast process for PGM production Braemore intends to have the first industrial ConRoast based toll smelter in operation by 2011

33 Mintek s s DC furnaces