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1 This article was downloaded by: [Politechnika Wroclawska] On: 22 June 2012, At: 06:20 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Separation Science and Technology Publication details, including instructions for authors and subscription information: Hydrometallurgy in Kghm Polska Miedz SA Circumstances, Needs and Perspectives of Application Tomasz Chmielewski a a Wroclaw University of Technology, Faculty of Chemistry, Division of Chemical Metallurgy, Wroclaw, Poland Available online: 13 Apr 2012 To cite this article: Tomasz Chmielewski (2012): Hydrometallurgy in Kghm Polska Miedz SA Circumstances, Needs and Perspectives of Application, Separation Science and Technology, 47:9, To link to this article: PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

2 Separation Science and Technology, 47: , 2012 Copyright # Taylor & Francis Group, LLC ISSN: print= online DOI: / Hydrometallurgy in Kghm Polska Miedz SA Circumstances, Needs and Perspectives of Application Tomasz Chmielewski Wroclaw University of Technology, Faculty of Chemistry, Division of Chemical Metallurgy, Wroclaw, Poland Systematically shrinking copper resources and remarkably declining copper ores grade leads to the growing role of hydrometallurgical processes in manufacturing copper and accompanying metals. Technical, economical, and ecological aspects of application of hydrometallurgy were discussed with regard to dominating smelting methods. Specific conditions of in the Polish copper industry were evaluated and important aspects of necessary application of hydrometallurgy at KGHM for more effective processing of copper ores and concentrates were indicated. The hydrometallurgical unit operations compulsory in unique conditions of Polish copper industry: high content of carbonates, decreasing content of Cu, and increasing content of Pb, As, and organic carbon were analyzed. Hydrometallurgy was recognized as the only real chance for more rational utilization of metal resources from the Polish copper deposits. The advantageous chemical and mineralogical composition of Polish copper ores and concentrates and easy access to sulphuric acid additionally substantiate the need for comprehensive research work. Keywords copper metallurgy; leaching technologies; polish copper ores INTRODUCTION The standard treatment of copper flotation sulphide concentrates by smelting, converting, and electrorefining has dominated the world copper industry. Research and development for hydrometallurgical alternatives to traditional pyrometallurgical processes has remarkably intensified in the recent years. A wide range of chemical and biological processes for copper recovery from concentrates have emerged (1 11). These processes are all successful in leaching of copper from polymineral and chalcopyrite concentrates, purifying the leach solutions (PLS) using modern separation processes, mainly solvent extraction, and recovering a high value, high purity copper metal product. Received 15 October 2011; accepted 21 February Presented as plenary lecture during Separation Science Theory and Practice 2011 Conference, Kudowa Zdrój, Poland, June 5-9, 2011 Address correspondence to Tomasz Chmielewski, Wroclaw University of Technology, Faculty of Chemistry, Division of Chemical Metallurgy, Wybrzeze, Wyspianskiego 27, , Wroclaw, Poland. tomasz.chmielewski@pwr.wroc.pl Hydrometallurgical processes can be divided into predominantly sulphate, mixed sulphate=chloride, and chloride types (11). Within the sulphate grouping, processes can be sub-grouped as either atmospheric or superatmospheric in pressure, and chemical or biological in the leaching process. There are fewer chloride processes but advances in chemistry, equipment, and process development have vaulted the chloride systems back into the competition. Significant or dominating role of hydrometallurgical unit operations in the production of numerous non-ferrous (Al, Cu, Ni, Co, Zn) and precious metals (Ag, Au, PGE) is an evidence of the essential position and important meaning of chemical methods of metals manufacturing in modern extractive metallurgy. Hydrometallurgical operations are also widely applied for the production of copper and about 4.5 mln tones of Cu are nowadays recovered in the world from ores, by-products, and concentrates, which includes around 25% of total copper production (12). In the 1960s and 1970s numerous novel and alternative to smelting technologies of copper productions have been comprehensively investigated and attempted for industrial application (3). Several reasons were the base of such approach. Principally, then existing flotation=smelting methods appeared to be not effective enough. Moreover, a very important aspect for technological alterations in copper production was a high emission of gaseous and liquid effluents, not acceptable by environmental and social regulations. It was acknowledged that hydrometallurgy can be the only accepted way to enhance the degree of metals recovery and to reduce environment pollution. There are many reasons for pursuing alternatives to conventional processing, some of which are: the capital cost of smelter and refinery complexes is very high, hydrometallurgy is less capital intensive, regardless of the production capacity. Smelter economics are more scale sensitive than hydrometallurgical alternatives, smelters are limited in ability to treat concentrates that contain high levels of harmful impurities (As, Sb, Pb), 1264

3 HYDROMETALLURGY 1265 gold is frequently associated with copper concentrates. In some cases, high recovery of gold by flotation is accompanied by high levels of pyrite flotation, resulting in a low-grade copper concentrate for treatment, it may make sense to the overall economics of a mining operation to account for production of a lower grade concentrate with higher overall recovery of copper from the mine; followed by treatment of the lower grade copper concentrate at the mine site to make copper metal; along with the use of by-product weak acid from the copper recovery process as a reagent to leach and recover copper at the mine site. The overall economics achieved by this approach may give the advantage to an alternative to smelting. copper concentrates may frequently contain significant levels of base and precious metals (Pb, Ni, Co, Zn, V, Mo, Ag, Au). Copper smelters are fairly efficient in the recovery of gold, silver, and PGMs. Non-ferrous metals are recovered either with low degree or not at all, some copper heap leach - SX=EW process plants are running out of ore feed. These plants have fully functional SX=EW plants available for further copper recovery as electrowon cathode. In this case, it may make sense to adopt a copper concentrate hydrometallurgy process as the front end of the process plant and further utilize existing capital, hydrometallurgical plants may be more suited to application of modular incremental project development if required. Initially, hydrometallurgy was applied for low grade copper sulphide and oxide ores, which could not be processed by smelting (1,3,5,6). Primary ores have been beneficiated by flotation and concentrates were smelted and refined and the copper was produced by electrolysis. Recently, hydrometallurgy is a method of processing of flotation concentrates, in particular at low capacity or high complexity of the feed (Fig. 1) (1,7 11). Copper hydrometallurgy has been extensively studied as an alternative route to chalcopyrite concentrate treatment, since this mineral is most abundant among copper-bearing sulphides. The challenge of process development for chalcopyrite leaching in sulphate media is generally to leach chalcopyrite quickly and completely with high yield of elemental sulphur. A high sulphur yield leads to reduced costs for oxygen or air for mineral leaching and reduced neutralization=acid disposal costs. However, to overcome the slow and incomplete leaching of chalcopyrite at lower temperature, two problems must be solved: formation of passive films on the chalcopyrite surface and, potential FIG. 1. Alternatives for copper production from primary and secondary ores. (SX- solvent extraction, EW electrowinnig). (Color figure available online) blocking and wetting of chalcopyrite by liquid elemental sulphur. Historically, numerous hydrometallurgical treatment processes have been developed to treat copper concentrates, but none have achieved sustained commercial production (3,5,10). Reasons for failure range from low copper recovery in the primary leach step to poor quality copper product that requires electrorefining. Such a problem does not exist in the case of Polish copper deposits, where chalcopyrite is a minor sulphide contrary to chalcocite and bornite, dominating and easiest to leach (36,48,52,55,59). Based on existing facilities and announced project developments, annual mine production capacity in the period of is expected to grow at an average rate of around 4.4% per year to reach 24.2 million tons in 2014 an increase of around 4.7 million tons (24%) from that in Of the total increase, the copper-in-concentrate capacity is expected to increase by 3.8 million tons (4.7%=year) to reach 19 million tons and solvent extraction electrowinning (SX-EW) production by 850,000 t (3.7%=yr) to reach 5.2 million tons. Most of the new mine projects and expansions are located in Brazil, Chile, Congo, Mongolia, Peru, the United States, and Zambia, which together account for around 3.4 million tons (72%) of the projected mine capacity increase during this period (Table 1). Annual smelter capacity is projected to grow by an average of 2.6%=year to reach 20.7 million tons in 2014, an increase of 2.5 million tons (14%) from that in Asia will be the leading contributor to growth (2.3 million tons), with expansions and new projects expected mostly in China, but also in India and Iran. Africa is the second leading contributor owing to developments in Zambia. North American smelting capacity will fall by 10% due to closures of plants in Canada. There also is a real risk factor in developing new, hydrometallurgical technology. Many of the new processes have

4 1266 T. CHMIELEWSKI TABLE 1 Projected World copper production capacities (in thousand tons) until 2014 (12) ( 000 t Cu) Accumulated growth % Avg annual growth SX-EW 4,330 4,513 4,576 4,784 5,041 5, % 3.7% Concentrates 15,131 15,428 15,733 16,334 17,557 18, % 4.7% Total Mines 19,461 19,941 20,309 21,118 22,598 24, % 4.4% Total Smelters 18,166 18,341 18,751 19,411 20,066 20, % 2.6% Electrolytic Refineries 18,507 18,641 19,222 20,282 21,292 21, % 3.4% Total Refineries 23,606 23,905 24,602 25,830 27,097 27, % 3.3% Year on year growth (tonnage) 2009= = = = =14 Accumulated growth SX-EW Concentrates ,223 1,426 3,852 Total Mines ,480 1,563 4,700 Total Smelters ,510 Electrolytic Refineries ,060 1, ,365 Total Refineries ,228 1, ,208 unique and complex chemistry, processing conditions and parameters, or equipment. These processes have not had adequate commercial demonstration to mitigate the risk. The cost of licensing new technology, while also assuming the risk of being first to commercially practice, can mitigate against new technology selection. Against this backdrop, significant progress has been made recently in advancing the use of hydrometallurgy for copper ore and concentrate treatment. Currently, at least five separate sulphate-based commercial plants have started or are under construction for copper recovery. These include the Mt. Gordon Copper (13 15), Phelps Dodge Total Pressure Oxidation (16,17), Alliance Copper BIOCOP (18), the Oxiana Sepon Copper (19) and InMet Las Cruces Copper (20). The Activox (21), CESL (22,23), Dynatec (24), and Xtrata Albion (25) processes have been known for some time and are well represented in the literature. This article will focus on more recent sulphate process development, which is specific for Polish sedimentary copper ores and concentrates, which contain carbonate gangue. Mt. Gordon Copper Western Metals Limited (Australia) commenced in 1998 a hydrometallurgical operation at the Mount Gordon Ferric Leach facility. The plant ramped up to design production levels very rapidly. The Mt. Gordon Copper was developed to leach chalcocite (Cu 2 S) ores from the historic gunpowder deposit in Northern Queensland, Australia. The process used low-temperature pressure oxidation to directly leach copper from the ore followed by SX=EW of copper from the resulting pregnant leach solution. The plant operation achieved an annualized copper production of 50,000 metric tons Cu as LME - grade cathode in In the Mt. Gordon process, chalcocite first leaches to form a covellite reaction product (CuS) and then the covellite product leaches to form soluble copper (Cu 2þ ) and elemental sulphur (S o ). Fe(III) ion is regenerated by gaseous oxygen in the autoclave, simultaneously with leaching. Other copper minerals will also leach with oxygen in the presence of a Fe(III)=Fe(II) solution. In addition to the reactions involving the copper minerals, pyrite in the ore will also oxidize to a limited extent (2-3%). This minor oxidation is beneficial in regenerating soluble iron(ii) to iron(iii) and in forming sulphuric acid for the leach system. The leached copper sulphate is forwarded for SX-EW of copper cathode. Crushed and milled ore is delivered in the form of a thickened slurry to the plant, where it is dewatered to 14 18% moisture content. Filtration before leaching is important to maintain the overall leach circuit water balance and to avoid excessive dilution of the leach liquor. Improvements were made and the plant returned to design capacity within 18 months of startup. In late 2003, Western Metals sold the project to Aditya Birla Group of India who intended to convert the plant to a concentrator and ship the concentrates to their Dahej Smelter in western India. By mid-2003, the Mount Gordon plant was producing at the rate of over 45,000 tonnes per year of LME Grade A copper cathode from ore that contained over 9 percent copper and high pyrite. The plant incorporated a number of innovative processing techniques, including

5 HYDROMETALLURGY 1267 low-temperature pressure autoclaves followed by stirred open tanks to oxidize and leach the chalcocite. The raffinate, at 65 C, contained 10 g=l Fe(III) ions, 35 g=l Fe(II), 79 g=l sulfuric acid, and 10 g=l copper sulfate and initiated leaching of the ore. The leach slurry was subsequently pumped into two five-compartment stainless steel autoclaves operating in parallel at about 90 C and about 8 atm of total pressure. The autoclaves were supplied with approximately 80 tonnes per day of oxygen to convert Fe(II) sulfate to Fe(III) sulfate, which then leached the copper from the chalcocite. Retention time in the autoclaves was about one hour. Leach slurry from the autoclaves reported to atmospheric leach tanks, which were used to complete the leaching process and also to cool the slurry. Approximately 90% of the copper was recovered from the ore. The pregnant leach solution (PLS) contained about 30 g=l copper and 35 g=l total iron. Filter cake (leach residue) was re-slurried and neutralized with lime and pumped to the conventional tailings impoundment. PLS was then pumped to the solvent extraction circuit arranged as two extraction and two stripping stages. Electrolyte was pumped to two electrowinning (EW). Total Pressure Oxidation The total pressure oxidation process (TPO) uses high temperature and pressure oxidation conditions to oxidize all sulphide minerals to sulphates and sulphuric acid. Conveniently, total pressure oxidation also results in iron precipitation as hematite, controlling the concentration of iron. Phelps Dodge pioneered a large-scale application of total pressure oxidation at its Bagdad copper leaching plant in Arizona. At this facility, approximately 16,000 t=y of Cu can be recovered from concentrates that previously were sent to a smelter. Under total oxidation conditions, 140 t of acid are produced per day for application to Bagdad s stockpile leach operation. In this way an acid credit is derived. A single autoclave is used to leach the concentrates which then proceed to flashing (to return the slurry to atmospheric pressure), slurry cooling, CCD washing, and then copper SX=EW. The autoclave stream is merged with the stockpile leach solution stream to provide a combined PLS feed to the SX=EW facility. The acid from the autoclave process is then recycled in the SX raffinate back to the stockpile leach. The washed autoclave residue is neutralized with lime in four stages. If significant precious metals were present (not the case with Bagdad concentrate), the neutralized residue could be cyanide leached. Total pressure oxidation is very suitable for application where the acid from pressure leaching can be used beneficially. The process has been commercially demonstrated at a large scale and could easily be scaled up to larger size if required. Total pressure oxidation for copper concentrate treatment should now be regarded as proven technology. Freeport-McMoRan Copper & Gold Inc. developed pressure leaching process for copper sulphide concentrate and the process was implemented in commercial scale in 2008 in Morenci plant for production about 80,000 tons of copper. This process was fully presented during the Coper-Cobre 2007 Conference in Toronto and well described in literature (7 9,26,27). Sepon Copper In 2005, Oxiana Ltd of Australia commenced operation of their Sepon Copper Project located in Laos. The Sepon Project is designed to produce 60,000 tons of LME Grade A cathode copper per year from mainly chalcocite ore containing about 5% copper, low pyrite, and carbonate minerals. The process plant utilizes ferric-sulfate atmospheric leaching, flotation of pyrite and elemental sulphur, and acid pressure autoclave technology to leach the copper prior to SX-EW to produce cathode (19). The Sepon Copper was elaborated and developed for the recovery of copper from the inaccessible Sepon copper deposit in Laos. The mineralogy of Sepon is complex. Copper is present mainly as chalcocite with pyrite and a large component of clay mineralization. The flowsheet involves atmospheric acid ferric sulphate leaching of copper followed by residue washing and pyrite=elemental sulphur flotation. The key development in this flowsheet is the autoclave treatment of the flotation pyrite=sulphur concentrate. The autoclave oxidation of pyrite=sulphur will provide virtually all acid and ferric sulphate required for the copper leaching process. It produces a basic ferric sulphate product which can then be re-leached to produce a strong ferric sulphate solution for application to atmospheric leaching of copper. The process can be considered a hybrid of a copper leach and pyrite oxidation process. The autoclave will be fed with 230 tonnes per day of oxygen and will be operating at 220 C. It will oxidize pyrite and leach any remaining copper minerals. The autoclave discharge slurry will be followed by several leach tanks. This slurry containing both Fe(III) sulfate and copper sulfate will be pumped to the atmospheric leach tanks. Copper recovery is expected to be about 90 percent for the operation. Leach tailings will be neutralized with lime and pumped to a conventional tailings impoundment. The Sepon process offers the possibility of scavenging any remaining copper minerals in the pyrite float concentrate (that were not leached in the atmospheric leach). These minerals would leach under the total oxidation conditions employed, thus increasing overall copper recovery. Las Cruces Copper Project, Spain The Las Cruces Project is located near Seville in Southern Spain. Project feasibility studies have been completed

6 1268 T. CHMIELEWSKI and indicate that the project will produce 66,000 tons per year of LME Grade A cathode copper using acid ferric sulfate atmospheric leaching to extract copper from chalcocite ore that contains about 7 percent copper (28). The thickener underflow will be heated to 90 C and pumped to a series of atmospheric leach tanks equipped with oxygen sparges. Leach residence time will be about 7 hours and the tanks will operate at various slurry densities, depending upon the ore grade fed to the plant. It is estimated that about 91% of the copper will be leached in the tanks. Leach tank discharge slurry will contain the PLS which will assay about 40 g=l copper, 25 g=l sulfuric acid, and 50 g=l iron. The atmospheric leach tanks will leach the copper minerals without the use of a pressure autoclave, oxidizing the copper minerals and some of the pyrite and also converting ferrous sulfate to ferric sulfate, sufficient to leach the copper. Leach residues will be thickened and filtered with the PLS reporting to an SX-EW circuit. The SX-EW circuits will be similar to the Sepon plant flowsheet. Raffinate from the SX circuit will be recycled to the leaching circuit. The plant will incorporate a raffinate bleed treatment circuit in which raffinate bleed will be preneutralized, passed through a secondary extraction circuit, further neutralized, and then discharged. Site cash costs are estimated to be about US$0.40 per pound of cathode copper produced, similar to the Sepon Project costs. BIOCOP The BIOCOP process was developed by the BHP Billiton biotechnologies group based in Johannesburg, South Africa. The process uses thermophile bacteria to oxidize and leach copper from sulphide concentrates. The bacteria oxidize sulphide minerals to metal sulphates and sulphuric acid at temperatures of C. The BIOCOP flowsheet has a number of interesting features. Oxygen is used for bioleaching. This necessitates the presence of an oxygen plant. Previously, bioleach plants for gold and base metal applications were operated with air blowers. Arsenic may be removed in a separate step to produce a residue for disposal. Copper may be recovered by SX=EW. Excess acid may be used in heap leaching if appropriate. The Alliance Copper joint venture group (BHP Billiton and Codelco) has commercialized the process in Chile. A 20,000-mtpy Cu plant has been built near Chuquicamata with the long-term goal of treating arsenical concentrates from the Mansa Mina deposit. The plant is integrated with a heap leach circuit to allow for an acid credit back to the bioleach plant. In the bioleach process, partial acid neutralization is practiced in the two-stage bioleach using limestone addition to the bioleach slurry. This neutralization incurs an operating cost that is not present in total oxidation and effectively reduces the available acid credit from the bioleach process. Nevertheless, for specific applications, the bioleach approach may be favored relative to pressure leaching. Clearly, the successful startup of the Alliance Copper project in Chile has validated the technology at a significant scale. The Mount Gordon Project led the way for the largescale commercial development of the acid ferric-leaching technology of copper ores. The Sepon Project has taken the next step in the commercialization of this technology. The Las Cruces Project, with a slightly different twist, will advance the technology even further. Chalcocite ores are easier to leach than chalcopyrite ores. However, the knowledge that is being gained from these three operations will greatly benefit and advance copper hydrometallurgical technology and will aide in the advancement of chalcopyrite treatment processes. Hydrometallurgical treatment of copper concentrates using chemical and biological leaching is making inroads to the field traditionally dominated by smelting and refining. The field has tended to advance thus far by necessity or unique opportunity. The Mt. Gordon and Sepon processes were developed to recover copper from ores that were not easily amenable to conventional flotation. The total pressure oxidation process was commercialized by Phelps Dodge where the acid from the total oxidation autoclave can be beneficially used in the stockpile leach process at Bagdad. The BIOCOP process has been applied to a unique opportunity at the Chuquicamata complex in Chile. Copper concentrates containing high arsenic concentrations (not easily treated through a smelter) will be treated through the commercial bioleach plant with byproduct weak acid solutions used for associated heap leaching operations. Chloride processes remain particularly attractive due to rapid copper leaching, high solution strength, very low sulphur to sulphate oxidation, and low temperature=atmospheric pressure operation. Among them Intec Copper (29,30) and HydroCopper (31 35) are the most advanced and ready for commercialization. Unfortunately, no part of the chloride method has been applied in commercial scale for processing of copper concentrates. It is predicted that further niche applications of hydrometallurgy for concentrate treatment will continue into the future. However, the industry is still waiting for a technology that can compete on an operating cost=capital cost and metal recovery basis with the conventional smelting= refining process. Depending on local conditions and drivers, any or all of the processes listed could meet this requirement.

7 HYDROMETALLURGY 1269 SPECIFIC CONDITIONS OF COPPER PRODUCTION AT KGHM Polish LGOM copper deposits (Legnica - Glogow Copper Basin, SW Poland) exhibit a unique, sedimentary, and complex nature (36,37). These results are in the presence of three lithological ore fractions: dolomitic, sandstone, and shale (Table 3). From these three ore fractions shale reveals two exceptional and contradictory properties. It exhibits the highest concentrations of copper and accompanying metals (Ag, Ni, Co, Zn, Pb, V, Mo...) but simultaneously is the most troublesome in terms of flotation upgradeability (Tomaszewski, 1995). In the shale fraction a fine dissemination of metal sulfides in the carbonate matter and in black shale-clay rocks that form the majority of the gangue is observed. Such a fine dissemination of copper sulfides in the carbonate-organic matrix considerably reduces the susceptibility of the ore to both effective sulphides liberation and to froth flotation (39,42 45). A relative increase of concentration of shale-clay and carbonate fractions in flotation feeds, which are known as mostly hard-to-treat in flotation circuits, is currently observed. According to the latest data (38,39) the content of the shale fraction in the Lubin deposit is about 15% and occasionally can even reach 25%. Complex and unique mineralogical structure as well as chemical composition of Polish copper ores mined from sedimentary deposits is the principal reason for copper, silver, and other metals losses to flotation tailings (38,39). The presence of shale creates additional technical, economical, and ecological issues. A selective liberation of fine metals-bearing particles disseminated in the carbonate host matrix would be the only way to enhance metals recovery. However, it appears to be ineffective by physical methods in the existing milling circuits. Consequently, the hydrophilic gangue-sulphide intergrowths seriously reduce both flotation selectivity and the metal grade in the concentrate TABLE 2 Sulphate-based copper hydrometallurgical processes for sulphide ores and concentrates at different status development (1,10,13,16,18 21,23 25) Status Temp. C Pressure atm Regrind d 80, mm Special conditions Activox Pilot plant Oxygen overpressure. Very fine ground chalcopyrite Albion Porocess Pilot plant Atmospheric leaching of very finely ground chalcopyrite AA-UBS Pilot plant Reground chalcopyrite pressure leaching with addition of surfactant Bactech= Mintek bioleach Pilot plant Low temp. bacterial leaching. Very fine grinding to overcome chalcopyrite passivation. BIOCOP Commercial High temp. bioleach using termophile bacteria. CESL Copper Demo plant Chloride assisted pressure sulphate leaching of chalcopyrite. Dynatec Pilot plant Pressure leaching of chalcopyrite using low grade coal as additive. Mt. Gordon Commercial Pressure leaching of chalcocite=pyrite ore in Fe(III) solution. Platsol Pilot plant Total pressure oxidation in the presence of g=l NaCl. Precious metals leached in one step. Sepon Copper Total Pressure Oxidation Las Cruces Commercial 80 Cu 1 at FeS 2 50 Atmospheric leach for copper from Cu 2 S. Pressure leaching of FeS 2 to make H 2 SO 4 and Fe 3þ for copper leaching Commercial Extreme conditions of T and p designed to rapidly destroy chalcopyrite and other sulphides Commercial Atmospheric leach for copper from sulphide ore.

8 1270 T. CHMIELEWSKI TABLE 3 Composition of lithological ore layers and content of copper, silver, and organic carbon in feed of the KGHM copper concentrators in nineties (38) and in 2004 (39) Rudna Polkowice Sieroszowice Lubin Ore component 90 s s s 2004 Carbonate ore % Shale ore, % Sandstone ore, % Cu content, % Ag content, g=mg C org content, % (40). Therefore, it can be concluded that the existing beneficiation technologies currently applied for processing of Polish copper ores have already reached the limit of their technological efficiency (41,42). The quality of Polish copper ores, which exhibit a decreasing copper content and a growing amount of shale fraction as well as impurities (Pb, As), have been deteriorating for years. It essentially affects the decreasing copper content in flotation concentrates and lowers recovery of metal (43) and is the main reason for the high costs of copper production. Analysis of flotation indices in all KGHM concentrators reveals the descending trend for both the recovery and the concentrate grade. It is particularly apparent at the Lubin Concentrator (ZWR Lubin), where copper recovery is currently below 86% and the metal content in concentrate is slightly above 14% (Figs. 2 and 3). Similar unfavorable trend is also observed for silver, but even when the content of other accompanying metals is relatively high (Pb, Zn, Ni, Co, Mo, V), some of them are either recovered only partially or not at all. Currently used technologies at ZWR Lubin have already reached the limit of their efficiency and they are the major reason of increasing metals losses and increasing production costs. The high content of shale fraction in Polish copper ores, has accordingly been considered as a main reason of existing technical problems of ores beneficiation. Shale layer, contrary to carbonate and sandstone fractions, is unique in terms of lithology, mineralogy, geochemistry, and high technological requirements. According to Tomaszewski (44), the black shale presented in the LGOM deposit is the carrier of about 25% of the copper reserves and about 30 40% of copper accompanying metals. Kijewski and Jarosz (45) assess that bituminous shale includes 5 8% of the ore resource in the deposit. The shale series, called the copper-bearing shale, forms in the deposit layers of thickness from to 1.7 m. It is a heterogeneous material, mainly consisting of bituminous shale, whose basic components are clay minerals, FIG. 2. Decrease of copper recovery at Lubin Concentator between 1991 and 2008 (KGHM data). (Color figure available online) FIG. 3. Decrease of copper grade in flotation concentrate at Lubin Concentator within (KGHM data). (Color figure available online)

9 HYDROMETALLURGY 1271 TABLE 4 Metals content in Lubin flotation concentrate (KGHM data: August=September, 2009) Cu Ag Pb Ni Co Zn As Mo V C org 15,42% 875 ppm 2.67% 470 ppm ppm ppm ppm 290 ppm 650 ppm 8.1% Concentrator TABLE 5 Mineralogical composition of flotation feeds at KGHM concentrators ( ) (41) Bornite% Chalcocite, digenite% Chalcopyrite% Pyrite, Marcasite% Covellite% Sphalerite% Tennantite% Galena% Lubin Polkowice Rudna carbonate minerals (dolomite and calcite), organic substance (mainly of sapropel origin), and detritic material (37). Dark or black color of the shale is considerably related to the presence of carbonaceous organic matter. As a result of the method of exploitation of the copper deposit, which is currently used, the shale ore is processed in the copper concentrators as a blend with the sandstone and carbonate lithological layers. Table 3 exhibits an average lithological composition of the copper ore, which was used as a feed in the processing plants in the 1990s and in This clearly emphasizes that the shale fraction content in the flotation feed of the KGHM Polish Copper processing plants has almost doubled. The application of modern hydro- or biometallurgy, well known and approved in the world for copper recovering, becomes an urgent necessity in the Polish copper industry to reverse unfavorable trends in flotation results, particularly at the Lubin Concentrator (46). The application of atmospheric leaching, one of the processing options, has to be considered as a complimentary process for processing of shale flotation by-product or flotation concentrate at ZWR Lubin, which are difficult to beneficiate using existing techniques. This approach, presented by the author within the research program of BIOSHALE (43) primarily involved the separation of the most troublesome ore fraction (shale containing middlings) from the flotation circuit and introduction of hydrometallurgical methods for their alternative, effective processing. Sedimantary copper ores from all three LGOM deposits (Lubin, Pokowice, and Rudna) exhibit specific polymetallic and polymineral composition (Tables 4 and 5). Bornite and chalcocite are generally dominating copper-bearing sulphides, with chalcopyrite and covellite as a minor component. This is very advantageous for hydrometallurgical treatment, since chalcocite and bornite are the easiest leachable in contrast to chalcopyrite being the most refractory in leaching. Additionally, Polish copper ores contain pyrite and marcasite, the minerals which are well known as electrochemical activators in sulphides leaching (47 52). Sulphide minerals in Lubin flotation products form a vast number of intergrowths, creating intermineral galvanic cells (53), which remarkably elevate the leaching rate. Moreover, the content of the accompanying metals (Zn, Co, Ni, V, Mo) is also very high, in particular in both the Lubin ore and concentrate (Table 4 and 5). Zinc, cobalt, molybdenum, and vanadium are still underestimated components and are not recovered by the current technologies. Unfortunately, the ores and concentrates from LGOM moreover contain rather undesirable components such as lead, arsenic, and organic carbon. They create severe technical and ecological problems and are the reason of limiting application of flotation concentrates as a feed for flash smelter. The application of an alternative or complimentary hydrometallurgical technology is able to solve, or at least to reduce, these problems remarkably. CONCEPTS OF HYDROMETALLURGY CONSIDERED AND INVESTIGATED FOR KGHM CONDITIONS The following concepts of application of hydrometallurgy have been investigated for processing of flotation middlings or concentrates from the Lubin mine: Wroclaw University of Technology concept (a): Atmospheric leaching of the concentrate followed by pressure precipitation of Fe and precipitation of Cu powder by pressurized hydrogen, combined with regeneration of Fe(II) to Fe(III) under oxygen pressure (1970s) (54), Wroclaw University of Technology concept (b): Atmospheric leaching of the concentrate followed by pressure precipitation of Fe and diaphragm electrolysis of Cu with simultaneous anodic oxidation of Fe(II) to Fe(III) (1970s) (56),

10 1272 T. CHMIELEWSKI Ammonia Arbiter process (Anaconda Co.): Ammonia leaching of flotation concentrates, Solvent Extraction þelectrowinnig. Institute of Ono-ferrous Metals (IMN, Gliwice (1970s)), ing of shale middlings from Lubin Concentrator (tailings from cleaning flotation at Lubin Concentrator), Bioshale project ( ), EC resources (55,56), HYDRO project: Wroclaw University of Technology. Non-oxidative, atmospheric, or pressure leaching in oxygenated H 2 SO 4 solutions and in the presence of Fe(III) ( ), (National Center for Research and Development) under the IniTech Enterprise. The idea of application of hydrometallurgy at KGHM was considered (57,58) and extensively investigated within the period of in the BIOSHALE international research project financed by the European Commission in the frame of VI FP. The project was performed by 16 European universities and leading research institutions, including Wroclaw University of Technology (WUT) and KGHM Cuprum, Wroclaw (57,58). The idea of application of hydro- or biometallurgy for Lubin shale middlings was elaborated by several laboratories from WUT (43,44,59 62) in cooperation with international institutions and was based on the separation of shale enriched material (middlings) for separate hydrometallurgical processing (Fig. 4). The results collected during the three year long project exhibited susceptibility of shale middling for non-oxidative, atmospheric, and pressure leaching and indicated the need for a further research program in order to improve the metals recovery at Lubin Concentrator. This approach can still be considered as one of the process alternatives for Lubin middlings. Another, currently examined approach, comprises application of atmospheric or pressure leaching in order to elevate copper and other metals recovery from the Lubin FIG. 4. General BIOSHALE concept of separate processing of black shale ore fraction from Polish copper deposits. (Color figure available online) flotation concentrate. The idea has been extensively investigated by the Division of Chemical Metallurgy at the Wroclaw University of Technology within the HYDRO research project financed by the National Center for Research and Development (NCBiR) in the framework of the IniTech Enterprise. The process consists of numerous unit operations: feed preparation (grinding, nonoxidative leaching and separation of gypsum, separation of magnesium), atmospheric or pressure leaching, metals separation from solution after leaching (solvent extraction and ion exchange), processing of solid residue for Ag and Pb recovering, removal and stabilization of toxic components (As), and waste treatment. To increase the efficiency of metals recovery from the Lubin ores, the feed to leaching can be both the currently produced commercial flotation concentrate as well as a low grade concentrate of higher metals recovery. According to the technical analysis presented by KGHM (Table 6) (45) a reduction of concentrate grade by about 50% may result in the increase of copper recovery by more than 5% (above 30 Mln US$ a year). Another important supplementary advantage of the idea of HYDRO project is the elevation of the recovery of silver, lead, and nickel, and the recovery of zinc, cobalt, molybdenum, and vanadium, which are totally lost in current technologies for Lubin concentrate. Moreover, application of the Lubin concentrate as a feed for hydrometallurgy can remarkably reduce the organic carbon, arsenic, and lead content in the feed for flash smelting at the Glogow Smelter. The level of concentration of these deleterious components cannot be currently accepted. Analysis of specific conditions of Polish copper industry and mineralogy of exploited copper ores leads to the selection of sulphuric acid as a leaching agent. Sulphuric acid is easily and not expensively accessible from the local KGHM smelters. Its unstable demand and selling frequently creates serious problems and is a source of additional costs. Hydrometallurgy offers a rational and cost-effective utilization of an excess of acid, taking into account specific lithological and mineralogical composition of Polish copper ores and concentrates, with a dominating content of carbonate matter. Sulphuric acid is necessary in applying for a chemical non-oxidative leaching to liberate metal sulphides from carbonate matter as well as for either atmospheric or pressure leaching in acidified iron(iii) solutions. Non-Oxidative Leaching Non-oxidative acid leaching of copper concentrate, or by-products of beneficiation of Polish copper ores, has to be initially used to decompose acid-consuming carbonate matter and to liberate metal-bearing minerals from the carbonate intergrowths. This non-oxidative leaching consists of selective (without breaking sulfides) chemical calcium and magnesium carbonates decomposition by means of

11 HYDROMETALLURGY 1273 TABLE 6 Producton capacity and copper content in flotation tailings assuming a reduced cocentrate grade by 50% for Lubin, Polkowice and Rudna concnetrators (45) Base data for 2008 Calculated parameters Concentrator Ore, % Concentrate % Tailings % Recovery Cu% Concentrate Mg=year Concentrate% Recovery Cu% Tailings % Concentrate Mg=year Lubin Polkowice Rudna sulfuric acid, according to the reactions: CaCO 3 þ H 2 SO 4 þ H 2 O ¼ CaSO 4 2H 2 O #þco 2 " ð1þ MgCO 3 þ H 2 SO 4 ¼ MgSO 4 þ CO 2 "þh 2 O Calcium sulfate dihydrate (gypsum) precipitates as a dominating solid reaction product, whereas water-soluble magnesium sulfate and gaseous carbon dioxide are other reaction products. Since the particles of middlings are fine, leaching of the carbonate gangue with H 2 SO 4 is very rapid and can be performed at ambient temperatures in standard simple construction reactors equipped with mechanical stirring. The amount of H 2 SO 4 applied in the non-oxidative leaching directly corresponds to the content of carbonates and must be precisely controlled in order to maintain the final ph of the pulp at a level enabling its direct transfer either to the flotation circuit without any need for ph correction or to the oxidative leaching and bioleaching. Therefore, for further flotation, the amount of sulfuric acid introduced to the leaching operation should always be kept below the analytically determined maximum amount of acid required for the total carbonates decomposition. Kinetics of non-oxidative acid leaching of the middlings from the Lubin Concentrator was already investigated for different degrees of carbonates decomposition varying from 20 to 100% (44,62 64). The key parameter determining the amount of sulfuric acid required for carbonates leaching is the maximum demand for acid ðz max H 2 SO 4 Þ, which is the mass of pure H 2 SO 4 necessary for a total decomposition of carbonates present in 1 kg of the dry solid feed. The z max H 2 SO 4 parameter should be determined analytically by laboratory tests. Sulfuric acid is introduced to the reactor containing shale slurry at a rate that assures its total utilization. The maximum demand for sulfuric acid for the Lubin middlings and Lubin concentrate was 490 and 220 g H 2 SO 4 =kg of dry material, respectively. The process control of non-oxidative leaching is based on ph measurement of leached middlings suspension after introduction of desired amount of sulfuric acid. On the basis of kinetic results for the Lubin middlings, it was ð2þ found that the process is very rapid and after about 5 minutes almost the entire amount of acid is used up. The observed further ph changes (up to about minutes) correspond to the saturation of the slurry with CO 2. Non-oxidative leaching is not only very fast but also selective. It does not cause chemical decomposition of metal sulfides under non-oxidative conditions created by the carbon dioxide. Atmospheric Leaching Atmospheric leaching of sulphidic copper ores, byproducts, and concentrates is a principal unit operation in which copper and other metal values are leached out by means of oxidation of sulphidic sulphur to its elemental or sulphate form. Dissolution of metals being in the sulphidic form (Cu, Zn, Ni, Co, Mo, V), requires the presence of oxidation agent: gaseous oxygen or=and iron(iii). Copper, which is present in the feed predominantly as chalcocite (Cu 2 S) and bornite (Cu 5 FeS 4 ), can be leached very rapidly by oxygenated H 2 SO 4 solution and the leaching rate increases remarkably in the presence of iron(iii). Atmospheric leaching is usually performed at temperatures below 100 C and at various concentration of iron(iii), usually in the range of g=l. The following chemical reactions describe the leaching of copper sulphides, which are present in Polish copper ores and concentrates. Cu 2 S þ 2Fe 2 ðso 4 Þ 3! 2CuSO 4 þ 4FeSO 4 þ S o CuS þ Fe 2 ðso 4 Þ 3! CuSO 4 þ 2FeSO 4 þ S o Cu 5 FeS 4 þ 6Fe 2 ðso 4 Þ 3! 5CuSO 4 þ 13FeSO 4 þ 4S o CuFeS 2 þ 2Fe 2 ðso 4 Þ 3! CuSO 4 þ 5FeSO 4 þ 2S o To maintain the effective leaching conditions iron(ii) sulphate has to be continuously regenerated to iron(iii) sulphate by gaseous oxygen introduced to the leaching slurry in the following reaction: 4FeSO 4 þ O 2 þ 2H 2 SO 4! 2Fe 2 ðso 4 Þ 3 þ 2H 2 O ð3þ ð4þ ð5þ ð6þ ð7þ

12 1274 T. CHMIELEWSKI According to leaching and regeneration reactions taking place during atmospheric leaching, one can evaluate that the need for oxygen and acid depends remarkably on the mineralogical composition of the leached feed and has to be determined in laboratory examinations. The effect of sulphuric acid, temperatures, solid=liquid ratio, particle size distribution, stirring rate, and at the oxygen flow rate are the key parameters of the atmospheric leaching and have to be investigated for each leaching feed. Particle size analyses for Lubin middlings and concentrates indicated that they are rather too coarse in terms of the leaching rate. Parameter d 80 exceeded 100 mm even after non-oxidative leaching with H 2 SO 4 (carbonates decomposition, R w ¼ 30 90%). Additional microscopic SEM observations lead to the conclusion that most coarse particles are formed by shale material, which cannot be chemically decomposed during treatment with acid, even in the presence of oxygen. Therefore, separation of particle fraction above mm and its additional regrinding seem to be very desirable to facilitate further leaching. Pressure Leaching Pressure leaching has an extensive application, particularly in the processing of zinc, nickel, and copper sulphides and in the pretreatment of refractory gold ores, in which gold is finely dispersed in sulphidic lattice. Especially, the pressure hydrometallurgy is widely used in nickel recovery from laterite ores. Currently, the tests are being performed to apply pressure leaching for processing of byproducts and flotation concentrates of the specific properties and composition, making difficulties in their treatment by pyrometallurgy. Pressure leaching exhibits numerous advantages creating an intensive investigation on an industrial scale. The main advantages of application of the pressure leaching processes are: high rate of leaching reaction, elimination of SO 2, other gases and dust emission, high selectivity of pressure leaching, possibility of arsenic utilization or stabilization (as a low solubility scorodite), total recovery of noble metals, no restriction of the scale production. The pressure leaching of sulphidic feed (copper middlings or concentrates) is performed in H 2 SO 4 solutions, at elevated temperatures and in the presence of pressurized oxygen. Sulphuric acid is produced at KGHM smelters as a by-product during the processing of copper sulphide concentrate by pyrometallurgy and was selected as the most suitable, cheap, and easy-accessible leaching agent. Initial leaching temperature, sulphuric acid concentration, oxygen partial pressure, solid=liquid ratio, particle size distribution, and stirring rate are the key parameters influencing the pressure leaching of copper sulphide middlings or concentrates. Pressure leaching has to be performed in pressure reactors (autoclaves) in the temperature range from 100 to 180 C using oxygen as an oxidizing agent. The pressure leaching of the Polish copper concentrates has always to be preceded with non-oxidative acidic treatment of the feed in order to totally decompose the acid-consuming components, predominantly carbonates. The following chemical reactions can be attributed to the copper pressure leaching under mild conditions (temperatures below 150 C), when elemental sulphur is a dominating product of oxidation of sulphidic sulphur: Cu 2 S þ O 2 þ 2H 2 SO 4! 2CuSO 4 þ S o þ 2H 2 O; Cu 5 FeS 4 þ 6H 2 SO 4 þ 3O 2!5CuSO 4 þ FeSO 4 þ 4S o þ 6H 2 O; CuFeS 2 þ 2H 2 SO 4 þ O 2! CuSO 4 þ FeSO 4 þ 2S o þ 2H 2 O: ð10þ In pressure leaching processes conducted at temperatures above 150 C soluble sulphate is dominating in leaching products, according to the reactions: 2Cu 2 S þ 5O 2 þ 2H 2 SO 4! 4CuSO 4 þ 2H 2 O ð8þ ð9þ ð11þ 4Cu 5 FeS 4 þ 4H 2 SO 4 þ 37O 2! 20CuSO 4 þ 2Fe 2 O 3 þ 4H 2 O ð12þ 4CuFeS 2 þ 4H 2 O þ 17O 2! 4CuSO 4 þ 2Fe 2 O 3 þ 4H 2 SO 4 ð13þ It is well seen from reactions 8 13, that the selection of pressure leaching temperature conditions determines consumption of oxygen and acid. Under mild conditions elemental sulphur remains in the solid residue, whereas pressure leaching at temperatures above 150 C leads to conversion of sulphidic sulphur to soluble sulphate and requires additional treatment for its removal. Atmospheric or pressure leaching of the Lubin concentrate will remarkably elevate the recovery of copper and other metals. Such valuable metals as zinc, cobalt, vanadium, and molybdenum are not recovered by present technologies. Moreover, application of hydrometallurgy for the Lubin concentrates is a chance for rational utilization of the excess of sulphuric acid produced in KGHM smelters. CONCLUSIONS Hydrometallurgical treatment of copper concentrates using chemical or biological leaching is making inroads to the field traditionally dominated by smelting and