The IsaMill A Great Australian Mining Innovation Past, Present, Future N. W. Johnson Principal Consultant Mineralis Consultants Pty Ltd 1 CONTENTS 1. PAST Historical setting for McArthur River deposit* – 1955 to 1980 Development Program that commenced in 1989 *IsaMill technology developed for the McArthur River deposit 2. PRESENT IsaMill – Contributions to the present metallurgical landscape 3. FUTURE IsaMill – Possible directions for the future Relevant Companies: MIM Holdings Limited (Mount Isa Mines Limited) (McArthur River Mining Pty Ltd) Xstrata, Glencore 2 Location of McArthur River Mine (HYC Deposit) Geological location – Carpentaria Inlier (from brochure of McArthur River Mining Pty. Ltd.) 3 McArthur River stratiform Zn-Pb deposit in Carpentaria Inlier Background to the deposit 1. Discovered by geologists of Mount Isa Mines Limited in 1955. 2. Large stratiform Zn-Pb-Ag deposit by world standards: Open pit 227Mt 9.2% Zn, 4.1% Pb, 41 ppm Ag 3. Exposed only to low level metamorphism, hence minimal grain size increase. Mean grain size No. 2 O/B (µm): PbS <3, (Zn,Fe)S 36, FeS2 43, NSG 9 4. Contains a portion of its pyrite in the “carbonaceous pyrite” form (naturally hydrophobic), a property it shares with other stratiform Zn-Pb-Ag deposits in the Carpentaria Inlier (e.g. Mt. Isa, George Fisher, Century Zinc, Dugald River) Development thwarted up to 1980 by: 1. Lack of infrastructure in the isolated region i.e. increased capital costs 2. High capital costs for additional reasons, including O/B being underneath a major river (diversion needed if open pit) 3. Fine grained nature of the mineralisation (a metallurgical problem) 4 Background – McArthur River zinc/lead/silver deposit • Mid 1960’s “Light on the hill” in difficulty - UQ lecturers in U/G courses • 1966 - permanent accommodation at the site and access for larger metallurgical samples • Mount Isa pilot plant trials on McArthur River ore (1961/66/67/68) • Circuit development also sought in Australian and overseas laboratories • By late 1970s to 1980, a complete large pilot plant (50 tonnes/day) existed at the McArthur River lease in the N.T. and a major run in 1977/78 (18 months)* • Impetus to create company Hydrometallurgy Research Lab (Albion, Brisbane) *K. Miller, 1980. The McArthur River, N.T., zinc-lead prospect of M.I.M. Holdings, in Woodcock JT (ed.), Mining and Metallurgical Practices in Australasia, The Sir Maurice Mawby Memorial Volume, AusIMM, 182-183. 5 Reason for a new McArthur River Development Program commencing August 1989 (after limited activity for a decade) • Northern Territory Government indicated a strong desire for development of the deposit • Otherwise, the leases may be stripped from MIM Holdings 6 Concept for Development Phase commencing 1989 supplied by Brisbane Office of MIM Holdings (Given persistent low metal prices, greenfield projects required mid-teens %Zn in feed to be economic then.) • Metallurgical development to be done by Mineral Processing Research Section at Mount Isa • Open pit 227Mt 9.2% Zn, 4.1% Pb, 41 ppm Ag reclassified to U/G mine 104Mt 14.1% Zn, 6.4% Pb, 63 ppm Ag • Modest output U/G mine (no river diversion needed as no open cut) • Selective mining of the highest head grade ore-bodies near the bottom of the sequence (2 O/B, part of 3 O/B and 4 O/B) • Emphasis on Zn, not Pb; Imperial Smelting Furnace (ISF) for concentrate treatment and production of Zn within the project scope • Less ambitious and potentially much lower capital cost as capital for river diversion avoided, plus lower throughput; elevated zinc assay in feed. 7 The initial metallurgical approaches for the Development Phase commencing in 1989 for McArthur River ore 1. “Coarse” feed to rougher (P80 of 45 µm) to minimize initial grinding of high tonnage stream: - recovery in rougher step(s) of sphalerite/galena bearing composites mainly - rejection of liberated non sulphide gangue (NGS) and liberated pyrite to final tailing 2. Regrinding of rougher concentrate(s) to a size to be determined which provided sufficient liberation for preparation of a commercial concentrate. 3. Production of the following product(s) - Zn/Pb bulk concentrate* - Zn/Pb bulk concentrate* + zinc concentrate - other possible product combinations *for Imperial Smelting Furnace (ISF) technology 8 The McArthur River ore texture (discovered 1955) 9 Comparison of some major fine grained Pb/Zn Deposits – Rougher feed liberation level at stated sizing Reference: Johnson and Brown, 1990. An Assessment of McArthur River No. 2 Orebody, Research and Development Division of Mount Isa Mines Limited and Met Engineers of Canada, June. 10 Steps in the Development Phase (Laboratory Work) 1. 1989-90: Initial stage, regrinding to 15 µm (ball mill, inert media). Evaluation of concentrate quality (marketing study) – must regrind to 7µm. 2. Mid-1990: Purchase of laboratory batch bead mill (i.e. a stirred mill with inert media) with much increased capability. 3. 1990-91: Second stage of laboratory work with regrind to 7 µm. Allowed preparation of a commercial Zn/Pb bulk concentrate. 11 Development Phase Output: Circuit for McArthur River ore Typical results: Pb Zn Ag Silica Conc. 13% 40% 130ppm 4% Grade Conc. 64% 84% 63% - Recovery 12 Steps in the Development Phase (Pilot Plant Scale Testing of circuit followed by Plant Scale Testing of IsaMill in Existing Concentrators) 1. 1992: Pilot Plant Testing of proposed circuit, including regrinding to 7µm: - 100 litre Netzsch high speed horizontal stirred mill - 400 litre Metprotech vertical stirred mill Decision by the company to proceed with project. Selected Netzsch technology for regrinding; pilot plant operation revealed extensive changes were needed. 2. 1992-93: Development of IsaMill technology by extensive modification/enlargement of Netzsch bead mill to give a mill of 3000 litres (6 times > largest Netzsch mill). New application: “coarse” product sizing, high tph and low value product. 3. 1993-94: Staged testing of modifications/enlargement in 2 Mount Isa plants. 4. 1995: Start-up of McArthur River operation with 4 x 3000 litre IsaMills. 13 McArthur River operation commenced in 1995 with four IsaMills (3000 litres) for regrinding – a key aspect of metallurgical solution (Note: end of mill nearest camera is the discharge end) 14 Operating Principle (Note: 6 times larger than previous Netzsch horizontal stirred mills, patented product separator, different media/lining materials) GRINDING MECHANISM & MEDIA RETENTION Shaft rotating at high speeds generating disc tip Multiple stages of grinding speeds ~ 20 m/s Impeller pumps liquid back into chamber to retain media Displacement Body Grinding Disks Product exit Grinding Shaft Chamber PATENTED PRODUCT SEPARATOR Recirculating grinding patterns of media Rotor occur between disks due to variation in Media centrifuged to outside of grinding velocity profile across disks chamber by high centrifugal force generated inside mill CLASSIFICATION ZONE 15 Used with permission of Glencore Technology IsaMillTM Technology Growth (y axis - Cum. Installed Power, x axis - Years) 150 GREEN - M1000 & M500 140 Penasquito II (Goldcorp) BLUE - M 3000 Xstrata Cu-Antapaccay Leinster Nickel (BHPBilliton) RED - M 10,000 Climax Xstrata Cu-EHM 130 Penasquito I (Goldcorp) Red Dog Lonmin EP-C Thompson Creek Anglo Platinum BRPM Cosmos Dominicana Gold Somincor 120 Anglo Platinum PPRust North UFG Boynton Eldorado Gold 110 Anglo Platinum PPRust North Somincor Anglo Platinum Waterval Retrofit UFG 100 Anglo Platinum Waterval Retrofit 90 Anglo Platinum Amandelbult UG2 #1 Anglo Platinum Amandelbult Merensky Plant 80 Anglo Platinum Amandebult UG2 #2 Anglo Platinum Amandebult UG2 #2 70 McArthur River 60 Oceana Gold Prominent Hill Caribou Anglo Platinum Waterval UG2 50 Phu Kham Anglo Platinum PPL-A/B 40 Anglo Platinum PPL-C Cumulative Installed Power (MW) Installed Cumulative Centerra Gold Kumtor Lonmin EP-C 30 Phelps Dodge Morenci Anglo Platinum WLTRP KCGM Fimiston 20 McArthur River Expansion KCGM Gidgi George Fisher 10 McArthur River M10,000 Development TM Mt Isa Pb Circuit IsaMill Commercialisation 0 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 Used with permission of Glencore Technology 16 THE PRESENT 17 Developments in applications – IsaMill Initial Application – Very fine grinding Later Additional Applications 1. Normal regrinding 2. MIG – Mainstream Inert Grinding (10000 litre mill development) 3. Last stage of primary grinding (feeds up to 300 micron – 80% passing size) Note: Examples of 1 and 3 exist now at McArthur River site, in addition to very fine regrinding (see later slide). 18 Developments in volume of grinding chamber - IsaMill M10,000 M3,000 M500 M100 Used with permission of Glencore Technology 19 McArthur River operation – original and expanded circuits Note: Circuit expansions allowed some increase in cleaner stages. * Chadwick, 2013. Giant breaking strides, International Mining, February 2013, 68-83. * 2.5Mt/yr feed, 5.5Mt/yr after further expansion 20 McArthur River site – two examples of wider applications (Primary grinding section and normal regrinding, beyond original very fine regrinding) Duty At Commencement After Expansion* (1995) (2013) 1. Last stage of - 2 x M10000 primary grinding (150 to 45 µm*, P80) 2. Normal regrinding - 2 x M10000 3. Very fine regrinding 4 x M3000 6 x M3000 * Chadwick, 2013. Giant breaking strides, International Mining, February 2013, 68-83. 21 MIG - Mainstream Inert Grinding (Anglo Platinum, South Africa) (Step increase of 4% to 6% in recovery of platinum group elements) Used with permission