Heap Bioleaching Technology For Nickel

Transcription

1 Lecture 14 Heap Bioleaching Technology For Nickel Keywords: Polymetallic Schist, Heap Bioleaching, Talvivaara Experience Heap bioleaching of a polymetallic nickel ore at Talvivaara, Finland. Talvivaara deposits located 350 Km south of the Arctic circle in Finland comprise of one of the largest nickel sulfide resources. The deposits are situated in the southern part of the early Proterozoic schist belt and the Ni-Cu-Co-Zn mineralizations are part of a high-grade, meta morphosed black schist, consisting of micas, quartz, graphite and sulfides. Sulfide minerals such as pyrite, pyrrhotite, sphalerite, pentlandite, chalcopyrite and violarite are present with an average composition of 0.23% Ni, 0.50% Zn, 0.13% Cu, 0.02% Co, 10.3% Fe and 8.4% S. Bioheap leaching was considered as the most economic option. In May 2005, a 17,000 tonnes on-site pilot heap was started with initial heap bioleaching in August In April 2008, ore mining started at open pit and in July 2008, heap bioleaching was started. Metal sulfides through bioleaching were produced in October The ore is crushed and screened in four stages into p80 < 8 mm. Materials less than 10 mm were agglomerated for heap bioleaching in the presence of sulfuric acid. After agglomeration, ore is stacked eight meters high on primary pad for about 18 months for bioleaching. The heaps were aerated and irrigated from the top. After this period, the leached ore was restacked on secondary heap to leach metals further through a secondary heap leach cycle. Indigenous microorganisms are used and viable conditions for bacterial growth created in the heaps.[85 86] 1

2 Heap bioleaching conditions are summarized below: Ore supply Particle size Temperature Duration 25 Mtpa P 80 8 mm C months for primary 3.5 years for secondary. Acid consumption Heap dimensions 15 Kg / tonne and 2 Kg / tonne for primary and secondary heaps. 8m high (dynamic) for primary. Secondary permanent pad (4 x 15m). Bioleaching tests with black schist samples were carried out with iron and sulfur oxidizing acidophilic bacteria which included both mesophiles and thermophiles. Water samples and bioleach solutions were found to contain many of the above microbes. The following organisms were detected in column tests at acidic ph. Acidithiobacillus ferrooxidans At. thiooxidans A.caldus Leptospirillum ferrooxidans Ferrimicrobium Sulfobacillus L.ferriphilum Ferroplasma Bacterial inoculum for the pilot heap was from near-by metal-rich ponds and the enrichment was grown on sulfur, ferrous ions as well as the ore. Enrichment culture contained At.ferrooxidans, 2

3 L. ferrooxidans and At. caldus. During some periods of leaching, moderate thermophiles like At.caldus and Sulfobacillus thermosulfidooxidans were observed to be dominant. Photographs illustrating heap bioleaching at Talvivaara are shown in fig A B C D Fig. 14.1: Photographs of Talvivaara heap bioleaching (A) General outline of heap bioleaching(b-c) Actual heaps (D) Irrigation (Photographs kind courtesy from Dr. Marja Riekkola-Vanhanen, Senior Biotechnology Adviser, Talvivaara Mining Company Plc, Espoo, Finland). (Permission from Talvivaara Mining Company Plc, Finland thankfully acknowledged) 3

4 Metals recovery flowsheet is illustrated in fig Fig. 14.2: Metals recovery flowsheet. (Kind courtesy from Dr. Marja Riekkola-Vanhanen, Senior Biotechnology Adviser, Talvivaara Mining Company Plc, Espoo, Finland). (Permission from Talvivaara Mining Company Plc, Finland thankfully acknowledged) 4

5 Demonstration leaching resulted in good recoveries. 80% nickel could be recovered within 400 days with 80% zinc in about 480 days. Copper and cobalt recoveries were lower for 500 days. Secondary leaching was continued till November Mineralogical data with respect to original heap material and the ore after secondary leaching are shown in table 14.1: Table 14.1: Heap leaching data for various minerals Mineral Before leaching After leaching Pentlandite 0.57 % 0.07 % Chalcopyrite 0.45 % 0.14 % Sphalerite 1.05 % 0.13 % Sulfur % Anticipated total recoveries from both primary and secondary heap bioleach systems are 85% Ni, 80% Zn and about 50% for Cu and Co. The leached metals are precipitated using hydrogen sulfide. 5

6 References (Lectures 13-14): 64. H.R. Watling, The bioleaching of nickel-copper sulfides, Hydrometallurgy, 91 (2008) K.A. Natarajan and I. Iwasaki, Role of galvanic interactions in the bioleaching of Duluth gabbro copper-nickel sulfides, Separation Science and Technology, 18 (1983) K. Bosecker, Leaching of lateritic nickel ores with heterotrophic microorganisms, in Biohydrometallurgy Int. Symp. Proc. CANMET, OTTAWA, Canada, (1986) p Q. Chen, Z.Fang, Bioleaching of Ni, Cu and Co from a low grade Ni-Cu sulfide ore. The Chinese Journal of Process Engineering 1, (2001) D.W. Dew, C. Van Buuren, K.McEwan, C. Bowker, Bioleaching of base metal sulphide concentrates: A comparison of mesophile and thermophile bacterial cultures. In: R.Amils, A.Ballester (Eds), Biohydrometallurgy and the Environment Toward the Mining of the 21 st Century (Madrid, Spain) Part A. Elsevier, Amsterdam, (1999) pp T. Heinzle, D. Miller, V. Nagel, Results of an integrated pilot plant operation using the BioNIC process to produce nickel. Proceedings Biomine 99 and Water Management in Metallurgical Operations. AMF, Glenside, S.A., (1999) pp C. Hunter, BioHeap TM leaching of a primary nickel-copper sulphide ore. Nickel/Cobalt- 8 Technical Proceedings (Perth). ALTA Metallurgical Services, Melbourne. (2002) 11p. 71. L.J Mason, N.M. Rice, The adaptation of Thiobacillus ferrooxidans for the treatment of nickel-iron sulphide concentrates. Minerals Engineering 15, (2002) R. Pogaku, B. Kodali, Optimization of bacterial oxidation process parameters for selective leaching of nickel by Thiobacillus ferrooxidans. International Journal of Chemical Reactor Engineering, Vol. 4. Article A1, (2006) 14pp. 73. J. Puhakka, O.H Tuovinen, Microbiological solubilisation of metals from complex ore material in aerated column reactors. Acta Biotechnologica 6, (1986a) J. Puhakka, O.H. Tuovinen, Biological leaching of sulfide minerals with the use of shake flasks, aerated columns, air-lift reactor and percolation techniques. Acta Biotechnologica 6, (1986b) 345-6,

7 75. M. Riekkola-Vanhanen, S., Heimala, Study of the bioleaching of a nickel containing black-schist ore. In: Amils, R, Ballester, A (Eds.), Biohydrometallurgy and the Environment toward the Mining of the 21 st Century (Madrid, Spain) Part A. Elsevier, Amsterdam, (1999) M. Riekkola-Vanhanen, Talvivaara black schist bioheapleaching demonstration plant. Advanced materials Research, (2007) L.R.G. Santos, A.F. Barbosa, A.D. Souza, V.A. Leao, Bioleaching of a complex nickeliron concentrate by mesophile bacteria. Minerals Engineering 19 (2006) Z.Wang, L.Zhao, The acidic oxidizing pressure leaching of Jinchuan pyrrhotite concentrates. In: Fu, C., He, H., Zhang, C. (Eds.), proceedings of the International Conference on Mining and Metallurgy of Complex Nickel Ores (Jinchang, China). International Academic Publishers, Jinchang, (1993), T. Williams, BIOHEAP TM bacterial leaching of the Sherlock Bay Nickel Mine primary nickel-sulphide ore in saline water. Nickel/Cobalt Conference (Perth). ALTA Metallurgical Services, Melbourne. (2006) 13p. 80. Y. Zhao, Z. Fang, Bioleaching of Ni-Cu sulfide with acidophilic thermophile Acidianus brierleyi. The Chinese Journal of Process Engineering 3, (2003) C.A. du Plessis, W. Slabbert, K.B Hallberg and D.B. Johnson, Ferredox: A Biohydrometallurgical processing concept for limonitic nickel laterites, Hydrometallurgy, 109 (2011), K. B. Hallberg, B.M. Grail, C.A. du Plessis and D.B. Johnson, Reductive dissolution of ferric iron minerals: A new approach for bioprocessing nickel laterites, Minerals Engineering, 24 (2011), K.Bosecker, Leaching of lateritic nickel ores with heterotrophic microorganisms. In: Sallely, J., McCready, R.G.L., Wichlacz P. (Eds.), Biohydrometallurgy International Symposium Proceedings. CANMET, Ottawa, (1986), G.S. Simate, S. Ndlovu, Bacterial leaching of nickel laterites using chemoautotrophic microorganisms: identifying influential factors using statistical design of experiments. International Journal of Mineral Processing 88 (2008),

8 85. Riekkola-Vanhanen M., Talvivaara Sotkamo Mine bioleaching of a polymetallic nickel ore in subarctic conditions. Nova Biotechnologica 10-1 (2010) pp Riekkola-Vanhanen M., Talvivaara mining company from a project to a mine. Paper presented at Biohydrometallurgy-12, Falmouth, Cornwall, UK (June 2012). 8