Kullan talteenotto malmeista – uutta ja ikivanhaa Jaakko Leppinen Rikastustekniikan seminaari, Oulu 23-24.8.2016 World gold production in 2012 Europe Finland 10,800 Sweden 6,000 Spain 3,600 Serbia 0,900 Greece 0,800 Romania 0,600 Poland 0,500 Slovakia 0,300 Denmark 0,100 •2 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Gold production routes Hydrometallurgical processing of gold ores and concentrates is currently dominated by cyanide leaching and around 60% of all gold is produced Artisanal mining using cyanide. Amalgamization Hydro metallurgy Smelting •3 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Artisanal gold mining • 10 to 15 million artisanal miners producing around 380-450 tonnes Au/a in more than 70 countries • About 100 million people – workers and their families - depend on artisanal mining compared to about 7 million people worldwide in industrial mining • These gold mining operations are particularly dangerous, as they often use the mercury amalgamation process to extract gold from ores. • • •4 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Gold production in the past Gold washing Wash table Manual grinding Smelting •5 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Gold production today •6 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Developments in gold ore processing • Gold collected from stream beds (8000 BC) Gravity separation techniques • Washing of alluvial gold (before 3500 BC) • Mining of gold (3500 BC) • Smelting (3000 BC) High-temperature techniques • Cupellation to separate other metals from gold-silver alloys (2000 BC) • Parting to separate silver from gold (600 BC) Amalgamization • Amalgamization (100 BC) • Leaching with aqua regia (700 AC) Leaching • Leaching with chloride (1850 AC) Cyanidation • Cyanidation (1890) • Flotation process 1905 Flotation • Refractory ore treatment with pressure oxidation (1985) Hydrometallurgical • Refractory ore treatment with bio-oxidation (1986) treatment of refractory ores • Use of alternative lixiviants for gold leaching (2000-) Alternative gold lixiviants • Sensor based ore sorting for gold ores (2000-) Sensor based ore sorting •7 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Mineralogical considerations for gold ore types FREE-MILLING GOLD ORE REFRACTORY GOLD ORE LOCKED PARTICLE IN SILICATE LIBERATED GOLD INVISIBLE GOLD IN SULFIDE COMPOSITE GRAIN FINE INCLUSIONS IN SULFIDE LOCKED PARTICLE IN SULFIDE Leaching? Leaching? Flotation? Flotation? Fine grinding? Fine grinding? Gravity separation? Gravity separation? Decompostion of gold bearing minerals? •8 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Process options for gold processing Heap Leaching Gold Flotation Agitated Cyanide Crushing Grinding Leaching Gold Free Milling Au Gravity Ore concentrate Gold concentrate to Crushing Grinding Flotation smelter or leaching Refractory Agitated Cyanide Crushing Grinding Flotation Pre-oxidation Gold Au Ore Leaching •9 •© Outotec – All rights reserved •Rikastustekniikan seminaari 2016 Mineral Processing Plant Gravity concentrate Gravity separation CRUSHING TAILINGS TREATMENT ORE Paste T thickening a Classification GRINDING i THICKENING l Crushing Grinding Flotation Thickening Filtration FILTRATION i n Concentrate FLOTATION g Sorting Tailing Thickening Filtration Concentrate •10 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Mineral Processing Plant Gravity concentrate Gravity separation ORE Paste T thickening a Classification i Crushing Grinding Flotation Thickening Filtration l i n Concentrate g Sorting Tailing Thickening Filtration Concentrate •11 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Size range applicability of gravity separation equipment •12 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Shaking table •13 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Main Applications of Flotation in Gold Processing 1. Flotation of free gold and gold-bearing sulfide minerals to produce a gold- rich concentrate. The concentrate can be treated by: o Cyanidation o Regrinding and cyanidation o Intensive cyanidation, o Oxidative pretreatment and cyanidation o Direct smelting 2. Flotation of carbonaceous material, carbonates, or other material that would otherwise interfere with processing •14 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Cyanidation process for gold Gold ore Crushing Comminution Grinding Leaching Cyanide leaching S L Sorption in activated carbon Zinc cementation Merrill-Crowe Recovery Elution from activated carbon Electrowinning Smelting Gold •15 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Carbon-in-pulp (CIP) process ORE FROM GRINDING CYANIDE LEACHING CARBON ADSOPTION slurry ACTIVATED CARBON LOADED CARBON ELECTROWINNING ELUTION TAILING REGENERATION BARREN CARBON •16 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Cyanidation process routes for gold Gold ore Crushing Comminution Heap leaching Grinding Leaching Cyanide leaching Heap leaching Solid-liquid separation Zinc cementation Carbon in Column Carbon in Pulp Carbon in Leach Recovery (Merrill-Crowe) CIC CIP CIL Gold is Gold adsorbed on Gold adsorbed on Gold adsorbed on precipitated from activated carbon activated carbon activated carbon in cyanide solution from cyanide from cyanide slurry cyanide using zinc powder solution (CIC) solution with solution with solids. Adsorption solids. Adsoprtion take place in a takes place separate stage simultaneously (CIP) with leaching (CIL) •17 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Cyanidation process for gold Gold ore 1-10 g/t Tailings 0.1-1 g/t Cyanide leaching Solution 1-5 mg/l Sorption in activated carbon Carbon 5-10 kg/t Elution from activated carbon 100-1000 Au in ore mg/l Electrowinning Au in solution Dore bars Smelting 70-80% Au in carbon Refining 99.99% Gold bullion Gold •18 Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Cyanidation process Some milestones: 1867 First patent on cyanide leaching 1889 First cyanidation plant : Crown Mine in New Zealand First commecial scale plant 1890 First cyanidation plant in South Africa: Robinson Deep 1891 First cyanidation plant in USA: Mercur, Utah 1894 Johnson patents charcoal adsorption from cyanide solutions Zinc cementation for gold 1904 Merrill introduces zinc dust for gold precipitation recovery from solution 1906 Crowe applies vacuum deareation to zinc precipitation Carbon in pulp CIP 1949 First CIP plant at San Andreas in Honduras 1951 CIP process patented by McQuiston and Chapman New elution methods from 1952 USBM develops carbon elution process (Zadra) activated carbon 1970 First cyanide heap leach operation in Carlin, Nevada Heap leaching of gold 1973 AARL elution process 1985 First pressure oxidation plant at Homestake McLaughlin (USA) Pre-treatment methods 1986 Start-up of cencentrate biological oxidation plant in Fairview, for refractory gold South Africa •19 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Treatment of gold concentrates in copper smelters Electro Copper refining cathodes Anode slime Anode Gold slime Palladium treatment Platinum •20 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Treatment of gold concentrates in copper smelters Electro Copper refining cathodes Anode slime Anode Gold slime Palladium treatment Platinum •21 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved •22 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Hand sorting in 1556 •23 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Sorting of vein-type gold ore Laser image Sorting image Photo •24 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Preconcentration of material – Sensor Based Ore sorting • Suitable particle size 10-250 mm •1 • Depending on ore characteristics •2 10 to 70 % of material can be rejected • Capacities capable of meeting the •3 needs of many concentrators (upto 500 tph per unit) • Today - mature technology • Good understanding of mineralogy •4 and ore geology is required •1 • Feeding of unsorted material • The most common sensors: •2 • NIR sensor optical and X-ray transmission •3 • Color sensor (XRT) •4 ..\..\..\TOMRA\CommodasUltrasort_QUARZITE.mov • Separation chamber •25 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved •26 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Refractory gold ore INVISIBLE GOLD IN SULFIDE FINE INCLUSIONS IN SULFIDE •27 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Process options for refractory gold ores GOLD ORE CONCENTRATION PRESSURE CHEMICAL FINE GRINDING BIO OXIDATION ROASTING OXIDATION OXIDATION CYANIDATION GOLD •28 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Occurence of gold in recractory ores, examples Mineral composition in concentrates Ccp Sp Gn Bou Apy Py Total % % % % % % % Conc A 0.17 < 0.1 < 0.1 0.02 9.05 65.28 74.53 Conc B 2.47 1.58 0.54 0.31 15.60 63.48 83.98 Ccp = chalcopyrite (CuFeS2) Sp = sphalerite (ZnS) Gn = galena (PbS) Bou = bournonite (PbCuSbS3) Distribution of gold between minerals Apy = arsenopyrite (FeAsS) Py = pyrite (FeS2) •29 •Rikastustekniikan seminaari 2016 •© Outotec – All rights reserved Chemical reactions in pressure oxidation Autoclave 2FeS2 + O2 + 2H2O 2FeSO4 + 2H2SO4 Decomposition of sulfide minerals through 4FeSO4 + O2 + 2H2SO4