Extractive Metallurgy of Copper part 15 doc

Costs of Copper Production 397 23.7 Production of Copper from Scrap Chapter 20 showed that copper scrap varies in grade from 99.5+% Cu (manufacturing wastes) to 5% Cu (recycled mixed-metal scrap). The high-grade manufacturing wastes require only reclamation, melting, casting and marketing which costs of the order of $O.lOkg of copper. Low-grade scrap, on the other hand, requires reclamation, sorting, smelting, refining and marketing, which costs about $0.5 per kg of copper, Table 23.2. Intermediate grade scrap treatment lies between these two extremes. For scrap recovery to be profitable, the difference between refined copper sales price and scrap purchase price must exceed these treatment charges. If it doesn’t, scrap is held off the market. 23.8 Leach/Solvent ExtractionlElectrowinning Costs The investment and operating costs of heap leachholvent extractiodelectro- winning plants are listed in Tables 23.12 and 23.13. The costs are shown to be considerably lower than those for conventional concentration/smelting/refining complexes. This accounts for the rapid adoption of leaching in the 1990’s, especially in Chile. Table 23.12. Heap leachlsolvent extractiodelectrowinning investment costs. Fixed investment costs for a heap leachlsolvent extractiodelectrowinning plant. The plant produces copper cathode plates ready for shipment from 0.75% Cu ‘oxide’ ore. Stainless steel cathodes and polymer concrete cells are used. Mine investment cost is not included. Component %US. per annual tonne of copper Heap leach system including leach pad, crusher, agglomerating 1600 drum, on-off heap building and removal equipment, piping, pumps, solution collection ponds etc. Solvent extraction plant including mixer-settlers, pumps, piping, storage tanks and initial extractant and diluent 400 Electrowinning plant including electrical equipment, polymer concrete cells, rolled Pb-Sn-Ca anodes, stainless steel cathodes, cranes, cathode stripping, washing and handling equipment Utilities and infrastructure 500 Engineering services, contingency, escalation etc. 300 Total (Dufresne, 2000) 3500 700 398 Extractive Metallurgy of Copper Table 23.13. Direct operating costs of a heap IeacWsolvent extractiodelectrowinning system. The plant produces copper cathode plates ready for shipment from 0.75% Cu ‘oxide’ ore. Stainless steel cathodes and polymer concrete cells are used. Ore cost is not included. Item $/ke of copper Heap leach operation including crushing, acid curing, 0.10 agglomeration, on-off heap constructionhemoval, solution delivery and collection Sulfuric acid 0.05 Solvent extraction plant operation, including maintenance 0.03 Reagent make-up: extractant, diluent, guar and CoS04.7H20 0.04 0.15 to loadout platform Local overhead (accounting, clerical, environmental, human 0.03 resources, laboratory, management, property taxes, safety) Total 0.40 Electrowinning tankhouse operation, delivering cathode plates Unfortunately, chalcopyrite ore (the world’s largest source of copper) cannot be processed by heap IeacWsolvent extraction/electrowinning, Chapter 17. Chalco- pyrite ores must be treated by conventional concentratiodsmelting/ refininghefining, irrespective of cost. The small investment requirement of IeacWsolvent extractiodelectrowinning plants is due to the small equipment and infrastructure requirements of these processes. Specifically, leaching and solvent extraction require much less equipment than concentrating, smelting, converting and anode making. An interesting aspect of pyrometallurgical and hydrometallurgical copper extraction is sulfuric acid production and use. Hydrometallurgical copper extraction requires sulfuric acid (Chapter 17) - pyrometallurgical copper processing produces it (Chapter 14). Companies with both processes benefit significantly from this synergistic effect, especially if the operations are close together. 23.9 Profitability The key to a profitable mine-to-market copper operation is, of course, a large, high Cu-grade orebody. Such an orebody maximizes copper production per tonne of ore mined, moved and processed. Optimal use of an orebody requires that each part of the orebody be processed by Costs of Copper Production 399 its most efficient method, e.g. leaching or concentratingismelting. Separation of the orebody into milling ore, leaching ore, leaching ‘waste’ and unleachable waste is crucial for profitable utilization of the resource. Mechanization, automation and computer control optimize resource utilization and profitability throughout the mine-to-market sequence. In-pit crushing and conveyor ore transport, computer controlled semi-autogenous milliball mill grinding and flotation; oxygen-enriched continuous smeltingiconverting; and mechanized stainless steel cathode/polymer concrete cell electrorefining and electrowinning have all contributed to lower costs, enhanced resource utilization and improved profitability. 23.10 Summary The total direct plus indirect cost of producing electrorefined copper from ore by conventional mininglconcentratiordsrneltingirefining is in the range of $1.5 to $2.2 per kg of copper. The total direct plus indirect cost of producing electrowon copper cathodes from ‘oxide’ and chalcocite ores (including mining) is in the range of $0.7 to $1.5 per kg of copper. Copper extraction is distinctly profitable when the selling price of copper is 42.5 per kg. It is unprofitable for some operations when the selling price falls below $1.5 per kg. At the former price, the industry tends to expand. At the latter, it begins to contract. References Bauman, H.C. (1964) Fundamentals of Cost Engineering in the Chemical Industiy. Reinhold Book Corporation, New York, NY, Chapter 1. Chemical Engineering (2001) (McGraw-Hill Publishing Company, New York, NY), data ohtaincd from July issues, 1983-2001. Dufresne, M. W. (2000) The Collahuasi copper project, Chile. CIMBuNetin, 93,25 30. EMJ (1998) Bajo de la Alumbrera, Argentina’s first mining mega-project. E&M.I, 199(5), pp. 46WW-54WW. Perry, R.H. and Chilton, C.H. (1973) Chemical Engineer’s Handbook, Fifth Edition, McGraw-Hill Book Company, New York, NY, 25-12 to 25-47. Peters, M.S. and Timmerhaus, K.D. (1968) Plant Design and Economics for Chemical Engineers, Second Edition, McGraw-Hill Book Company, New York, NY. Appendix A Stoichiometric Data for Copper Extraction Compound MW, kg/kg mol % Metal %O or S CuFeS2 CuSFeSl CUO cuzo CuSi03:2H20 cus cuzs cuso4 CuS0a:CuO 101.96 16.04 30.07 28.01 44.01 100.09 56.08 151.99 221.12 344.67 213.57 183.51 501.82 79.55 143.09 175.66 95.61 159.15 159.60 239.15 354.72 52.9 74.9 79.9 42.9 27.3 56.0% CaO 71.5 68.4 57.5 55.3 59.5 34.6 Cu 30.4 Fe 63.3 Cu 11.1 Fe 79.9 88.8 36.2 66.5 79.9 39.8 53.1 53.7 47.1 25.1 20.1 57.1 72.7 44.0% COz 28.5 31.6 5.4 c 0.9 H 36.2 0 7.0 C 0.6 H 37.1 0 16.6 C1 1.4H 22.5 0 35.0 25.6 20.1 11.2 2.3 H 27.3 0 34.2 SiOz 33.5 20.1 40.1 0 20.1 s 33.5 0 13.4 S 1.1 H 36.1 0 9.0 S 40 1 402 Extractive Metallurgv of Copper Compound MW, kg/kg mol % Metal Yo0 or S CuS04:3Cu(OH)2 452.29 56.2 1.2 H 223.15 71.85 159.69 23 1.54 87.91 92.40 119.97 151.90 399.87 18.02 84.3 1 40.30 74.69 90.75 240.25 154.75 223.20 239.30 303.30 60.08 64.06 80.06 81.38 97.44 161.44 57.0 71.7 69.9 72.4 63.5 60.4 46.6 36.8 27.9 11.2 47.8% MgO 60.3 78.6 64.7 73.3 37.9 92.8 86.6 68.3 46.7 50.0 40.0 80.3 67.1 40.5 35.4 0 7.1 S 28.6 0 14.4 S 22.3 30.1 27.6 36.5 39.6 53.4 42.1 0 21.1 s 48.0 0 24.1 S 88.8 39.7 21.4 35.3 26.7 41.4 0 20.7 S 7.2 13.4 21.1 0 10.6 S 53.3 50.0 60.0 19.7 32.9 39.6 0 19.9 S 52.2% C02 APPENDIX B Lesser-Used Smelting Processes The years following publication of the third edition of this book saw several matte smelting technologies fall into disfavor or fail to gain widespread adoption. This appendix provides a thumbnail sketch of these lesser-used smelting proc- esses. B.l Reverberatory Furnace Reverberatory smelting furnaces have been used for over a century. They domi- nated Cu smelting through the 1960's. Figure B.l illustrates the 'reverb'. It is heated by hydrocarbon fuel combustion. Concentrate (moist, dry or roasted*) and flux are fed through feedholes along the Fig. B.l. Reverberatory furnace for producing molten Cu-Fe-S matte from sulfide con- centrates and 'roasted' calcines*. (Boldt and Queneau, 1967, courtesy Inco Ltd.) *Roasted concentrate (calcine) is concentrate which has been oxidized (i) to remove sulfur as SO2 and (ii) to oxidize iron to iron oxide (Biswas and Davenport, 1994). The results of the roasting are (i) eMicient SO2 capture from the roaster offgas and (ii) production of high %Cu matte during rever- beratory and electric furnace smelting. Flash (and other) oxidation smelting processes have largely eliminated roasting from the smelter flowsheet. 403 404 Extractive Metallurgy of Copper Table B.l. Physical and operating details of reverberatory furnaces at Onahama, Japan, 2001. The furnaces smelt 33% Cu concentrate to molten 43% Cu matte. Smelter Onahama Smelting & Number of furnaces 2 Refining, Japan Hearth size, w x I x h, m slag layer thickness, m matte layer thickness, m active slag tapholes active matte tapholes Burner details number of burners endwall or roof combustion 'air' temperature OC volume% 02 in combustion 'air' fuel consumption kg per tonne of new concentrate oxygen consumption kg per tonne of new concentrate Feed details type of charge % moisture in charge Feed, tonnedday (dry basis) new concentrate silica flux recycle reverberatory furnace dust converter dust molten converter slag reverts other Production, tonnedday matte, tonnedday slag, tonnesiday mass% Si02/mass% Fe Cu recovery, reverberatory slag Cu recovery, converter slag offgas, thousand Nm3/hour vol% SO2, leaving furnace dust production, tonnedday a) 9.73 x 33.55 ~3.69 b) 11.1 x 33.27~ 4.00 0.6-0.9 0.4-0.6 1 4 6 endwall (a) 300; (b) 30 200 coal 2 1-27 110 moist concentrate 8 1060 (33% CU) 30 60 6 910 50 1030 (43% Cu)) 1010 (0.65% Cu) 0.9 I none recycle to reverb 180 1 60 (all recycled) 1120/1280 matte/slag temperatures, "C Appendix 405 sides of the roof. They form 'banks' along the sides of the furnace. Concentrate and flux at the edge of the banks react with hot combustion gas and air in the furnace, generating molten matte, molten slag and offgas, Chapter 4. The smelting is continuous. Matte and slag are tapped intermittently through separate tapholes. The matte is sent to converting, The slag is discarded. The length of a reverb is 3 to 4 times its width, which gives the slag and matte considerable time to separate. They are discarded without slag recovery treatment. Molten converter slag is treated for Cu recovery. Because hydrocarbon combustion gas contains little 02, the reverb is primarily a melting furnace. It does not oxidize concentrates well. As a result, it produces low-grade mattes, 40 to 50% Cu. Also, the smelting reactions are slow because the concentrate is not intimately mixed with air and combustion gas as in flash and other recent smelting furnaces. This results in poor use of the energy generated by concentrate oxidation and a large requirement for hydrocarbon fuel. Its slags are dilute in Cu (-0.6%). Burning of this hydrocarbon fuel generates a large quantity of offgas, especially if air is used for the combustion. This and the reverb's slow rate of concentrate oxidation give offgas with only about 1% SOz. This offgas is difficult to treat in a sulfuric acid plant, and simply releasing it to the environment is unacceptable in most parts of the world. The result of this is that only about IO of the 30 reverberatory furnaces operating worldwide in 1994 are still operating in 2002. An interesting use of the reverberatory furnace is for smelting automobile shredding residue, Fig. 20.3, mixed in the concentrate feed (Kikumoto et al., 2000). The residue's organic component acts as fuel to supplement that provided by oxy-fuel burners. The furnace's offgas (-1% SO2) is treated for SO2 capture in a gypsum (CaS04:2H20) plant. SO2 capture is efficient. Although the reverberatory smelting furnace is gradually disappearing, hearth furnaces are still used widely for melting intermediate grade copper scrap. Oxy- fuel burners are used to improve furnace efficiency and reduce offgas volume (McCullough et al., 1996; Beene, et al., 1999). B.2 Electric Furnace Electric furnace Cu matte smelting flourished in the 1970's (Biswas and Davenport, 1980, 1994). Most, however, closed due to their high electricity cost. The best-known Cu electric hrnace smelters are those in: 406 Extractive Metallurgy of Copper Dzhezkasgan, Kazakstan Ronnskar, Sweden (Isaksson and Lehner, 2000) Mufulira, Zambia (Zambia, 2002). The Dzhezkasgan smelter treats siliceous concentrates, the others treat normal Cu concentrate feed. Like the reverberatory furnace, the electric furnace (Fig. B.2) is mainly a melting unit. Energy is provided by passing electric current between self-baking carbon electrodes suspended in the furnace's molten slag layer. Resistance of the slag to current flow heats the slag and melts roof-charged concentrate (dry or roasted) and flux. Smelting is continuous. Matte and slag are tapped intermittently through separate tapholes in the furnace sidewalls. The matte (50-60% Cu) is tapped and sent to converting. The slag (0.5 to 1% Cu) is discarded. Molten converter slag is treated for Cu recovery. Although its use as a Cu smelting unit is diminished, the electric furnace is still used extensively for recovering Cu from molten slags. This use is discussed in Chapter 11. The electric furnace is also used for smelting dried and roasted Cu-Ni concentrates. Its advantage for this application is its reducing environment, which encourages Co and Ni to report to matte rather than slag (Aune and Strom, 1983, Voermann et al., 1998). Off gas 7r C Fig. B.2. concentrates and 'roasted' calcines. (Boldt and Queneau, 1967, courtesy Inco Ltd.) Electric furnace for producing molten Cu-Fe-S matte from dry sulfide [...]... Mitsubishi 157 Noranda 166 Converting of copper matte 13I , 155 (see also Peirce-Smith convcrting) blister copper product 140 Cu-Cu2Ssystem 135 continuous 155 flash 162 Mitsubishi 157 Noranda 166 converters for Ausmelt 127 flash 162, 162 Hoboken 150 Mitsubishi 157 , 158 Noranda 166, 166 Peirce-Smith 8, 137, 132, 133, 135 Copper anode 249,253,271 black 355 blister 249 casting 253,374 (see also Casting copper) ... (1992) The use of the f Vanyukov process for the smelting of various charges, in Extractive Metallurgy o Gold and Base Metals, Australasian Institute of Mines and Metallurgy, Parkville, Vic., 477 482 Bystrov, V.P., Komkov, A.A., and Smirnov, L.A (1995) Optimizing the Vanyukov process and furnace for treatment of complex copper charges, in Copper 95-Cobre 95, Vol IV-Pyrometallurgy o Copper, ed Chen,... of the copper electrorefinery (Section 16.5.1) where: (a) its Cu is electrowon from solution (b) its impurities are removed 413 4 14 Extractive Metallurgy o Copper f The past decade has seen an increase in the use of pressure leaching for decopperizing anode slimes (Hoffmann, 2000) Pressure leaching improves reaction kinetics and overall Cu recovery Autoclave temperatures of 125-1 50°C and oxygen partial... (see also Scrap, recovery of copper from) automobile 348 cable and wire 346 electronic 350 Copper recovery from slag 176 settling 176 flotation 181 Costs of copper extraction 385 accuracy, estimated level of 386 Cost index (mining equipment) 386 Covered electrorefining cells save energy 264 Crushing of copper ore 31 for leaching 299,296,297 for flotation 3 1 flowsheet 32 of grinding mill oversize 35... (1993) Mineralogical changes occurring during the decopperizing and deleading of Kidd Creek copper refinery anode slimes In Paul E Queneau International Symposium on Extractive Metallurgy o Copper, Nickel and f Cobalt, Vol I, Fundamental Aspects, ed Reddy, R.G and Weizenbach, R.N., TMS, Warrendale, PA, 377 401 Cooper, W.C (1990) The treatment of copper refinery anode slimes JUM, 42 ( ) 45 49 8, Davenport,... refining agents 277 control of 277 impurity behavior 269 silver 270 industrial data 274 inspection, short circuit 279 leveling agents 277 control of 277 location 18 map of world's refineries 24 passivation of anodes 282 periodic reversal of current 282 production, world 21 reagent control 277 scrap, anode 272,266 percent of anode feed 274 recycle of 272 scrap, electrorefining of 359 flowsheets 14,356... levels of As and Pb in concentrate and recycle converter slag The reducing atmosphere of the shaft furnace encourages volatilization of As and Pb rather than oxidation This permits As and Pb to concentrate in the shaft furnace offgas from which they are collected and sent elsewhere for recovery The charge to the shaft furnaces consists of briquetted concentrate (fine particles would be blown out of the... direct-to -copper smelting 192-195 electrorefining 270,271 electrowinning 335 fire refining 260 scrap smelting 356,357 smelting 69 direct-to -copper 192-195 flash 86 lsasmelt 125 Mitsubishi 21 1 Noranda 107 Teniente 115 blister copper, removal from 260 concentrations in: anodes, electrorefining 271 cathode copper, electrorefining 27 1 ASTM specification 368 cathode copper, electrowinning 333,335 tough pitch copper, ... Capper B.4 Shaft Furnace When the first edition of Extractive Metallurgy o Copper was published in 1976, f about ten copper producers were operating shaft (blast) furnaces to smelt lump sulfide agglomerates In 2001, the only shaft furnaces still in use are those at the Legnica and Glogow smelters in Poland (Czernecki et al., 1998) These furnaces survive because of: (a) their unusual concentrates: low in... Robinson, T (1999) Electrolytic copper f refining - 1999 world tankhouse operating data In Copper 99-Cobre 99 Proceedings o the Fourth International Conference, Vol III Refining and Electrowinning o Copper, ed f Dutrizac, J.E., Ji, J and Ramachandran, V., TMS, Warrendale, PA, 3 76 Hoffman, J.E (2000) Process and engineering considerations in the pressure leaching of copper refinery slimes In EPD Congress . over 95%. 4 10 Extractive Metallurgy of Capper B.4 Shaft Furnace When the first edition of Extractive Metallurgy of Copper was published in 1976, about ten copper producers were. kg of copper. The total direct plus indirect cost of producing electrowon copper cathodes from ‘oxide’ and chalcocite ores (including mining) is in the range of $0.7 to $1.5 per kg of copper. . M.L. (1992) The use of the Vanyukov process for the smelting of various charges, in Extractive Metallurgy of Gold and Base Metals, Australasian Institute of Mines and Metallurgy, Parkville,