THE CARLOS DÍAZ SYMPOSIUM ON PYROMETALLURGY Cu2007, Volume III

Transcription

1 THE COPPER-COBRE SERIES OF CONFERENCES: A PRIME FORUM FOR ACTIVE DISCUSSION OF COPPER SMELTING TECHNOLOGY PRACTICE AND INNOVATION Carlos Díaz 210 Radley Rd., Mississauga, ON, Canada, L5G 2R7 cmdiaz@sympatico.ca Phillip Mackey Xstrata Process Support Falconbridge, Ontario, Canada pmackey@xstrata.ca ABSTRACT Since its inception, in 1987, the Copper-Cobre series of conferences has established itself as the prime world forum for discussing advances in copper process metallurgy, in particular copper sulfide smelting, copper recovery by leaching and electrowinning and copper electrorefining. All copper producing countries have actively participated in the pyrometallurgy symposia held in the framework of these conferences. In 1999 and 2003, the close to 100 pyrometallurgy papers that were presented had to be accommodated in two volumes. In the present paper*, the authors firstly provide a brief historical sketch of the Copper-Cobre conferences and then focus on providing a retrospective look at the dramatic changes that have taken place in copper smelting in the last few decades, primarily as discussed in the Copper-Cobre and precursor conferences pyrometallurgy proceedings. Topics include: the development of autogenous, increasingly more intensive, environmentally sound and energy efficient smelting processes; significant improvements in Peirce-Smith converting practice and at the same time the commercialization of alternative continuous converting routes; the consequent expansion and modernization of smelters; the increasing compliance with strict government environmental regulations in most copper producing regions of the world; the realignment of the copper smelting industry throughout the world; and trends in copper smelting R&D. A look at the future closes these reflections on the contribution of the Copper-Cobre conferences to the advancement of copper smelting technology. * This is an abridged version of the paper of the same title to be published in the proceedings of Copper=Cobre The references, omitted from this version, are to be found in the complete version of the paper. Proceedings of Cu2007 Volume III The Carlos Díaz Symposium on Pyrometallurgy Toronto, Canada, August 25-30, 2007

2 INTRODUCTION In the early 1960s, when the present co-authors were initiating their professional careers, the primary copper industry was dramatically different from the present industry. In those years, the world saw the tail end of the so-called post-war industrial boom that kept copper demand healthy especially in North America, Japan and Europe. Copper prices were relatively stable with a tendency to slowly rise, while production costs stayed in check. In fact, the price of key industry consumables such as fossil fuel did not significantly change for decades. As well, the requirements for environmental control at copper-making operations were generally lax in many parts of the world. Perhaps in part resulting from this rather long, stable period for the industry, copper extractive metallurgy technologies had also remained fundamentally unchanged for decades. But change was in the air literally, and over the next 30 years the present co-authors would witness the greatest transformation of copper smelting practice that the industry had ever experienced since the substitution of the American copper-making route for the Welsh technology at the dawn of the 20 th century. Many, if not all, of the major advances in copper extractive metallurgy that have taken place in the last few decades would be eventually documented in the proceedings of the Copper-Cobre series of conferences. During this period, there was an unprecedented growth of world primary copper output. Mining, mineral processing and smelting technologies had to adapt to satisfy the rapidly increasing demand for the red metal. In 1970, world mine annual copper output was 6.4 million tonnes. Over the next 36 years, this would more than double to just over 15 million tonnes in In fact, the cumulative primary copper output in the period , 355 million tonnes, is about 3 times larger than the present authors estimated total copper output from the dawn of the age of metals (circa 4000 BC) up to Regardless of the impact of other important factors, the staggering growth of demand for copper would have sufficed to trigger deep changes in the extractive metallurgy of the metal. THE COPPER INDUSTRY IN THE 1960s In the 1960s, the dominant copper pyrometallurgical technology consisted largely of fuel-fired reverberatory smelting; calcine produced by roasting concentrate was fed to hot charge furnaces, while as-received filter cake concentrate was fed to cold charge furnaces. The furnace product, usually fairly low-grade copper matte, was treated in Peirce-Smith converters to generate blister copper, material which in turn was fire refined and cast into anodes. Multihearth roasters were used in most plants practicing hot charge reverb smelting. The first commercial application of fluid bed roasting of copper concentrate took place in the USA in 1961 at the Copperhill smelter. The same technology was later adopted at Morenci. Although the reverb furnace had been used for centuries in metals production, the first large reverberatory for smelting copper concentrate was commercialized in the USA at the dawn of the 20 th century. Over the years, the reverb increased in size and underwent structural and operational improvements. Dimensions of a typical 1960s furnace were 10.7 m wide by 35.1 m long (35 ft. by 115 ft), with a nominal capacity of about 700 to 900 tonnes of cold charge per day or about 1200 tonnes of hot charge. Reverb smelting was highly energy intensive, generated a low SO 2 containing off-gas unsuitable for producing sulfuric acid, and was a source of fugitive emissions. Most smelters produced mattes with grades in the 30-45% Cu range. Converter productivity was low due to the long cycles required to convert low-grade matte and the frequent tilting of vessels off-tuyeres to skim slag and charge new batches of reverb matte; converter tilting was in turn a major source of fugitive emissions. Except for a few smelters in Europe and Japan, sulfur dioxide abatement from smelter gases was uncommon. Only converter gases were of sufficient strength to be processed directly in sulfuric acid plants. For instance, in the early 1970s, in the USA, where there were 16 copper smelters, acid production accounted for less than about 20% of the sulfur input in smelter new metal-bearing feed. A higher capture of sulfur was just unfeasible from reverb smelters that generated a multiplicity of relatively weak off-gas streams. Notable exceptions to this smelting practice were Outokumpu s and Inco s flash smelting processes developed independently in the late 1940s. Although the Finnish technology was adopted by Furukawa in the 1950s, other Japanese smelters made a similar move only in the late 1960s and early 1970s. In the late 1960s, radical departures from conventional technology were also incubating at other locations. In Canada, Noranda was developing a continuous bath smelting process for the direct production of blister copper that would be conducted in a horizontal, cylindrical, tilting vessel equipped with tuyeres. In Australia, Howard Worner was testing a U-shaped, lance-equipped countercurrent furnace to simultaneously produce blister copper and a discard slag directly from concentrate. In Japan, Mitsubishi was piloting its three-furnace copper continuous smelting process, and had introduced a new lime-ferrite slag in the blister producing (converting) stage. Finally, following testing of concentrate smelting in converters with oxygen-enriched air at its Garfield Smelter, Kennecott had decided to use this

3 technology to expand production at the El Teniente Smelter in Chile. The failure of this attempt would ultimately lead to the development of the El Teniente Converter. In summary, when, in the early 1970s, the copper industry, especially in the Americas, was confronted with the need to modernize, there were already proven or promising alternative smelting technologies available. THE COPPER-COBRE SERIES OF CONFERENCES Over the years, the Metallurgical Society of CIM (Metsoc) and the Chilean Institute of Mining Engineers (CIME) have continuously disseminated information on primary copper operations through publications and annual meetings, as part of their activities. CIME, in 1973, and MetSoc, in 1984, held international symposia that were specifically devoted to the production of primary copper and that can be considered as precursors of the Copper-Cobre series of conferences (Table 1). The 1973 CIME copper conference, held as First Latin American Congress of Mining and Extractive Metallurgy, consisted of three symposia, one devoted to mining, the second to mineral processing, and the third to smelting. The papers presented in the latter, and published in a volume entitled The Future of Copper Pyrometallurgy, provided a forum for discussing the intense process innovation work that was taking place at the time in Australia, Canada, Chile and Japan, and advances in flash smelting. The essence of this event was captured in the following comments made by Herb Kellogg during the discussion of the papers: I just wonder how many of you realize how fortunate you are to be sitting at a meeting where you are discussing four new smelting processes for copper. I have been attending meetings on extractive metallurgy for more than thirty years and this is a very recent phenomenon. I think the state of affairs that we have now holds great interest and excitement. In the second half of the 1970s and the early 1980s, there was an active exchange of copper industry operators and researchers and academics between Canada and Chile. It was not surprising, then, to see a significant Chilean presence in the Copper 84 Symposium, held in Québec City in August 1984 as part of the 23 rd Annual Conference of Metallurgists. The conditions were ripe for a more formal collaboration between the Canadian and the Chilean sister societies when one of the present co-authors (PJM), at the time President of MetSoc, visited Chile in May 1983 on copper business accompanied by Professor N.J. Themelis of Columbia University. In discussions with representatives from the state owned copper producers Codelco and Enami, the University of Chile and CIME, there was agreement in principle to jointly organize an international copper conference. In subsequent discussions, the other present co-author (CMD), representing MetSoc, and Prof. Gustavo Lagos of the University of Chile developed the protocol for these conferences. The conferences would be devoted to discuss advances in the extractive metallurgy of copper, copper applications, and general industry issues. The first of the Copper-Cobre conferences was held in Viña del Mar, Chile, in November-December At the 1987 conference, a Joint Organizing Committee was formed and it was agreed to hold a Chilean- Canadian conference every four years, alternating between Canada and Chile. TMS also became a co-organizing society of the 1991 and 1999 Copper-Cobre conferences that were held in Ottawa and Phoenix respectively. The original partners, MetSoc and CIME, co-organized the other two conferences that have been held in Chile, Copper- Cobre 95 and Copper-Cobre At the latter conference, the MMIJ and the GDMB were accepted as co-organizers of future Copper-Cobre conferences. In subsequent discussions, TMS also came on board. Following Copper-Cobre 2007, future conferences will be held every three years. Table 1 briefly summarizes the key features of the copper smelting symposia that have been held to date as part of the Copper-Cobre conferences. Additional details are given in the complete paper.

4 Table 1 Key Features of the Copper Pyrometallurgy Symposia Held as Part of the Copper-Cobre and Precursor Conferences Date Venue Aug. 27-Sept. 1, Santiago, Chile Québec City, August 19-22, Québec, Canada Nov. 30-Dec. 3, Viña del Mar, Chile August 18-21, 1991 Nov , 1995 Oct , 1999 Nov. 30-Dec. 3, 2003 Ottawa, Ontario, Canada Santiago, Chile Phoenix, Arizona, USA Santiago, Chile No. of Papers No. of Countries No. of Smelters Main Topics Covered New bath smelting processes; Use of oxygen; Thermodynamics of continuous copper smelting; Environmental issues New processes; Use of oxygen; Smelter development; Ni-Cu converting; Scrap smelting Operating plant developments; R&D topics; Process Modeling and Control Vol. V Smelting Operations) - 52 papers. Vol. VI (Technology Development)-44 papers. Vol. IV - Book 1 (Smelter Operations)- 41 papers Vol. IV-Book 2 (Technology Development)- 37 papers Smelter modernization and expansions throughout the world (including SO 2 capture); Optimization; Slag copper losses and slag cleaning; General technology development; Scrap recycling-impurity control; Process modeling and control; Kinetics and transport phenomena. Smelter modernization and expansion at worldwide smelters; Quality management and productivity increase; General process improvements; New process development; Smelter fundamentals. Vol. V - Smelting operations and advances - New and expanded smelters worldwide; Plant updates; Bath smelting; Continuous converting; Other technology topics. Vol. VI - Technology Development: Process modeling; Fundamentals. Vol. IV - Book 1- Smelting operations worldwide; Smelter modernization and expansions; Novel technologies; Other technology topics. Vol. IV - Book 2 - Technology developments; Process modeling; Fundamentals. Notes: 1 Precursor conference held as part of the First Latin American Congress of Mining and Extractive Metallurgy; 2 Precursor conference held as part of the 1984 Conference of Metallurgists; 3 First of the present Copper-Cobre series of conferences; 4 Count does not include some of the smelters covered in the smelter survey.

5 THE ENVIRONMENTAL-ENERGY CHALLENGE (1970s AND 1980s) Social pressure to tackle the environmental problems created by the rapid expansion of industry in the post World War II years, and the dramatic increase of the cost of oil in the 1970s were the key factors that triggered a true revolution in copper smelting practice throughout the world in the 1970s and 1980s. Technology Innovation As earlier discussed, in the late 1960s, novel copper smelting technologies incorporating the use of oxygen enrichment were incubating in various locations; some of these would be commercialized in the 1970s. Inco pioneered the utilization of tonnage oxygen in copper smelting with the commercialization of its oxygen flash smelting technology at its Copper Cliff smelter in This was the first commercial autogenous copper smelting process. At Copper Cliff, all of the SO 2 from the highly concentrated Inco furnace off-gas stream was captured in a liquefaction plant. The first commercial Noranda reactor was commissioned at the Horne smelter on March 1 st, The Noranda process, originally conceived for the direct production of copper from concentrate, was the first to yield high-grade copper matte in one stage, thus initiating a trend that would be later followed by all other modern copper smelting processes. Successive increases of oxygen enrichment of the blast was a key factor to achieve steady expansion of the Noranda reactor smelting capacity from the original 720 to 2,400 tonnes of new metal-bearing feed per day by the end of the 1980s. In 1974, Kennecott decided to substitute Noranda reactors for reverbs at its Utah Garfield smelter to meet new environmental regulations. Commissioning of the new facilities in 1978 marked the first commercial use of tonnage oxygen in a US primary copper smelter. In 1974, Mitsubishi commercialized its three-stage continuous copper smelting technology at its Naoshima smelter. A new copper smelter, using the Mitsubishi process, commenced operations at the Canadian Kidd Creek copper-zinc-silver metallurgical complex in The capacity of the Kidd Creek smelter was doubled in about 10 years by the simple expedient of steadily increasing the oxygen intensity in the original smelting and converting furnaces. In the late 1960s, Kennecott, in partnership with the Chilean government, undertook a mine-millsmelter expansion program at El Teniente. At the smelter, the new production target would be achieved by concentrate smelting in converters using oxygen enrichment of the blast. The project included the installation of a 400 tonnes/day oxygen plant. This technology failed to achieve the increased production target, and the smelter became a production bottleneck. Following the nationalization of Chile s big copper operations in 1971, a focused research effort at El Teniente led to the development of two technologies, namely the roof-mounted/oxy-fuel burners fired reverb and the Teniente Converter. At El Teniente, with the commercialization of the oxy-fuel burner technology in 1975, furnace throughput more than doubled, and oil consumption per tonne of DSC was reduced by almost 60%. However, the El Teniente smelter would only reach the late 1960s expansion program target capacity with the commercialization of the Teniente Converter in January Four factors combined to speed up the implementation of the El Teniente technologies in other Chilean smelters: the need to increase smelting capacity, the urgency to reduce consumption of expensive imported oil, the relatively low capital cost of the El Teniente alternatives, and expediency in the transfer of technology. The oxy-fuel fired reverb technology was later adopted in other countries. The Vanyukov process was developed in the former USSR in the late 1960s and early 1970s and was commercialized at the Norilsk copper and nickel complex in Although the technology has been successfully practiced to date, it has never been used beyond the borders of the former USSR. Two new technologies, SIROSMELT and CONTOP, were discussed at the MetSoc of CIM Copper 84 conference. SIROSMELT, developed in the 1970s by John Floyd at CSIRO in Australia was the precursor of Ausmelt and ISASMELT, two top submerged lance technologies that have been gaining increasing acceptance in copper smelting in the last ten years. CONTOP, developed by KHD Humboldt Wedag in Germany, was temporarily applied in Asarco s El Paso smelter in Texas. Groundbreaking testing of continuous conversion of copper matte was conducted in Canada and Slovakia. In fact, in the 1940s, Inco extended the principles of its oxygen flash smelting process to the

6 successful converting of finely comminuted white metal to blister copper, and in 1960, Slovak researchers from the Technical University of Kosice used a top blowing bath converting approach. However, continuous conversion of copper matte made its commercial debut with the commissioning of the Mitsubishi process at the Naoshima smelter. In turn, flash conversion of solid white metal was the subject of a Kennecott patent filed in 1981, and granted in Kennecott in association with Outokumpu would later develop a commercial copper flash conversion process. In the late 1980s, continuing work at Inco led to the development of the oxygen top-blowing, nitrogen bottom stirring technology for converting finely comminuted nickel contaminated copper sulfide concentrate. Also, in the period , Noranda tested a novel continuous converting route consisting of spray converting molten, high-grade matte with a jet of oxygen-enriched air. While the results were promising, economic studies showed that the merits of retrofitting this technology in Noranda s existing copper smelters were insufficient to justify further process development. Process modeling and control also received much attention in the 1970s and 1980s, as reflected by the 9 papers on these subjects presented to the first of the Copper-Cobre conferences in It is of interest for this story to mention that a seminar on Reduction of Sulfur Dioxide Emissions from Non- Ferrous Smelters was held as part of Copper 87. This seminar attracted participants from Canada, Chile, China, European countries, Japan, as well as from other copper producing countries. The Environment Japan and Western Europe At the start of this period, Japan was well advanced in consolidating and revamping its own copper smelters. In fact, Furukawa became the first foreign copper producer that adopted the Finnish flash smelting technology. Furukawa s Ashio smelter commissioned its Outokumpu furnace in In the late 1960s and early 1970s, other Japanese smelters followed suit; Kosaka, Saganoseki, Toyo, Tamano and Hitachi commissioned Outokumpu flash furnaces in respectively 1967, 1970, 1971 and 1972 (Tamano and Hitachi). In the early 1980s, the Japanese smelters were capturing more than 99% of the sulfur input, and were thus complying with stringent environmental regulations. With the sole exception of the Rönnskar smelter in Sweden, by the mid 1970s, the Western European copper smelters had also adopted the Outokumpu flash smelting technology. Norddeutsche Affinerie commissioned its flash furnace in Shortly afterwards, secondary hoods were installed in the converters, and filters were built for cleaning secondary process off-gas streams and fugitive gases. Emission of <1% of smelter sulfur input was achieved. Huelva started-up its flash furnace in 1975; a second acid plant was built, and Huelva was fixing about 99% of smelter sulfur input. United States In the USA, the biggest primary copper producer at the start of this period, the combined impact of the tightening of the environmental regulations and the increase in the cost of energy would lead not only to major copper smelting technology changes but also to the closure of a number of smelters, and to a realignment of the industry. The 1970 Clean Air Act was Congress response to the states slow progress in controlling pollution, and in 1971, the EPA established 90% sulfur capture as the standard for copper smelters. Several states adopted the EPA s recommendation. Eleven smelters, accounting for 73% of the US primary copper smelting capacity, were affected by these measures. This marked the beginning of a long controversy between the copper producers and the EPA. Nevertheless, industry undertook a multimillion dollar clean-up program. In the 1970s the copper industry was also shaken by two successive huge increases in the price of oil and a consequent deep worldwide recession. While the price of copper fell sharply, the cost of production increased rapidly as a result of double-digit inflation. At the struggling smelters, it was obvious that the energy- and labor-intensive and environmentally unfriendly reverb had outlived its usefulness. In the 1980s, the modernization of the US copper smelters began in earnest. Asarco s Hayden and Kennecott s Chino substituted Inco oxygen flash smelting furnaces for reverbs in 1983 and 1984 respectively; an Outokumpu flash furnace was commissioned at Magma s San Manuel smelter in 1988; and two Contop cyclones were mounted on one reverb at Asarco s El Paso smelter. The Outokumpu technology had been

7 installed at the new Hidalgo plant in Smelters that could not justify the cost of modernization were closed; others that had been partially modernized, such as Anaconda with a new fluid bed roaster-electric furnace, were later closed due to poor economics. The number of smelters decreased from 15 in 1981 to 8 in However, the increased capacity of the modernized smelters somewhat compensated for the loss of production due to smelter closures. By the end of the 1980s, the American copper smelters sulfur capture had reached 90% of input in new copper-bearing feed. Canada Copper smelter modernizations in Canada led to significant environmental achievements. Inco had been processing 100% of its Copper Cliff copper circuit oxygen flash furnace off-gas in a sulfur dioxide liquefaction plant since At Noranda s Horne smelter, an acid plant was commissioned in 1989 to treat the Noranda reactor off-gas. At Noranda s Gaspé smelter, sulfuric acid was produced by fixing sulfur from the fluid bed roaster off-gas and part of converter gas since 1973; and, following the closure of the fluid bed roaster in 1982, from converter gas only (Gaspé was shut down in 2002). Kidd Creek had been fixing over 90% of the smelter sulfur since start-up in However, the most substantial changes would later occur at Inco s Copper Cliff smelter, where annual sulfur dioxide emissions had to be reduced from 685,000 to 265,000 tonnes by The smelter nickel circuit, with 24 operating Herreshoff roasters and 2 reverbs, was a source of large volumes of very weak gas that could not be treated in an acid plant. A drastic change of smelting technology was inescapable to meet the new emission limit. Chile During the early 1970s, all of the Chilean copper smelters were run by state-owned corporations. The three Codelco smelters - Chuquicamata, Potrerillos and Caletones accounted for almost 80% of the country s blister and anode copper production. As mentioned earlier, in the late 1970s and 1980s, most of these smelters adopted the El Teniente developed technologies, in particular the Teniente Converter. The sole exception to this trend was the installation of an Outokumpu flash furnace in Chuquicamata in The total or partial modernization of the Codelco and Enami smelters, that had already taken place, would facilitate compliance with the strict environmental regulations that were eventually imposed by the government in the 1990s. EXPANSION OF COPPER SMELTER OUTPUT (1990-To date) The foregoing shows that at the end of the 1980s, industry had a number of environmentally sound, energy efficient copper flash and bath smelting alternatives available. All of these processes use oxygen-enriched air or just tonnage oxygen as reacting gas; utilize the heat of reaction of the sulfide minerals of the feed to satisfy most, if not all, the heat requirements of the process; have high specific smelting rates; yield high grade matte, usually analyzing 60-70% Cu; and produce low-volume, strong offgas streams amenable to sulfur fixation in acid plants or sulfur dioxide liquefaction facilities. Not surprisingly, in the last two decades, copper smelting R&D endeavors have mainly focused on productivity increases, a trend that had already started in the 1980s. In addition, the processing of copper sulfide concentrates has increasingly become a highly competitive custom smelting industrial activity, and lowering processing costs is now essential to succeed. Other important advances in this period have been the commercialization of new continuous conversion technologies, the increasing compliance with strict government environmental regulations in most copper producing regions of the world, and the development of furnace refractory structure cooling techniques aiming at extending vessel campaign life. There has also been an intensification of computerized process control techniques. Productivity and Production Increases In the 1990s and early years of the current century, the accelerated economic growth of China and India, and other South-Eastern Asian countries, has caused a rapidly increasing demand for copper and other metals. Industry has responded by expanding existing smelters, building new smelters and, more importantly for this story, increasing process intensity. All of these developments have been discussed in the 1991, 1995, 1999 and 2003 Copper-Cobre conferences, as reflected by the numerous papers found in the respective proceedings on these as well as other copper smelting topics. In the present paper the

8 increase in process intensity is illustrated by briefly reviewing developments on flash smelting and top submerged lance (TSL) technologies. Flash Smelting Today, Outokumpu flash is the dominant copper smelting technology in the world. It was also the first in reaching an annual furnace throughput of over 1 million tonnes of dry concentrate, a remarkable achievement. The story of the capacity increase of the Toyo smelter furnace, by steadily increasing the oxygen enrichment of the reacting gas and successive modifications of the concentrate burner, provides a good example of the path to high levels of process intensity. Progress at Toyo, since the start-up of their program is summarized in Table 2. Besides substantial increases in furnace capacity and matte grade, burner design advances have led to improved concentrate combustion pattern, and in turn better furnace metallurgy and decreased dusting rate. In 2006, the Toyo flash furnace concentrate throughput had already reached 3,600 tonnes/day. All papers relating to capacity increase at the Toyo smelter emphasize the importance of strong, continuous cooperation between researchers and operators in achieving R&D program goals. Table 2 - Effect of oxygen enrichment on the Toyo flash furnace operation Oxygen enrichment of reacting gas, vol% Dry concentrate feed rate, tonnes/day 1,000 1,600 2,450 Matte grade, Cu % Dusting rate, weight % of DSC The increase in the intensity of oxygen utilization in flash smelting over the years can be better visualized by using the process intensity index introduced by Herbert Kellogg and one of the present authors (CMD) in For flash smelting, this index is defined as Nm 3 of O 2 consumed per hour per m 3 of reaction shaft. Studies show that the oxygen intensity of flash smelting has more than tripled over the years from a level of 55 (in the 1950 to 1970s) to 175 Nm 3 O 2 /h/m 3 reaction shaft (Toyo in 2006). Top Submerged Lance (TSL) Technology Ausmelt and ISASMELT are spin offs of the precursor TSL SIROSMELT technology. TSL is a very intensive and flexible technology. It can operate over a wide range of feed rates, temperatures and oxygen potentials. Advances in both Ausmelt and ISASMELT have been customarily discussed at the Copper-Cobre conferences. In 1981, John Floyd established Ausmelt to develop and commercialize the technology that he had invented and tested in CSIRO. In the 1980s, he demonstrated the versatility of the technology to successfully process a broad variety of materials -copper, nickel and tin concentrates among them - to desired products. The commercialization of the Ausmelt technology started in the 1990s. In a relatively short period of time, the Ausmelt technology has established itself as a commercially attractive route for smelting-converting copper concentrates. This has been an outstanding achievement. The ISASMELT technology was first developed for lead smelting. Mount Isa Mines commissioned lead ISASMELT furnaces in In 1987, a pilot plant was successfully built to investigate the applicability of the technology to copper smelting. Based on this work, the first two commercial ISASMELT copper furnaces were commissioned at Mount Isa and the Cyprus Miami copper smelter in 1992, operating at feed rates of 115 and 80 tonnes of dry concentrate per hour respectively. Following an upgrade of the facilities at Mount Isa in 1998, the sole remaining operating reverb was shut down, and all copper smelting was subsequently conducted in the ISASMELT furnace. In , annual new copper-bearing feed through one single ISASMELT furnace reached 1 million tonnes. Increasing the oxygen enrichment of the reacting gas was again a factor in increasing furnace capacity. Furnace campaign life is now well over two years. The technology has so far been adopted by Sterlite Industries (India), Yunnan Copper (China), Southern Copper (Perú), and Mopani Copper Mines (Zambia).

9 The ISASMELT furnaces of the Sterlite Industries Tuticorin smelter and of the Southern Perú s Ilo smelter have annual copper concentrate smelting capacities of 1.3 and 1.2 million tonnes respectively. Since the acquisition of Mount Isa in 1993, Xstrata Technology handles the commercialization of ISASMELT. How has ISASMELT made so much progress since commercialization of the technology in 1992? The present authors believe that the secret of this success is in the following quotation from one of the most recent papers on the technology: Improvements in process control, achieved over more than 13 years of operation at Mount Isa, have resulted in a highly advanced control system that ensures that refractory wear is minimized. This sort of development can only be achieved over many years in an operations environment. This is just another excellent example of the merits of developing technology in continuous, direct cooperation with operators. Other Technologies In the twenty-year period following the commercialization of the Mitsubishi process at the Naoshima smelter, the process was selected for only one new smelter, Kidd Creek in Canada. More recently, however, there has been renewed interest: the technology was adopted for the expansion of the Onsan smelter in Korea and the green field Gresik smelter in Indonesia. These smelters, with original design annual copper production capacity of 160,000 (Mitsubishi line only) and 200,000 tonnes respectively (later expanded), were spin-offs of a larger Mitsubishi line that replaced the original line plus an old reverb at Naoshima in The present annual copper production capacity at the Naoshima smelter, for example, is 270,000 tonnes. In Chile, the Teniente Converter is the dominant copper smelting technology. The six units in operation have a combined annual copper concentrate smelting capacity of about 3.5 million tonnes. All of these vessels operate autogenously with close to 100% dry concentrate injection. Teniente Converters are also currently in operation in smelters in Mexico, Zambia and Thailand. In early 2003, the Altonorte smelter commissioned a continuous bath smelting reactor, with inside shell dimensions 5.3 x 26.4 m, to replace its existing oxy-fuel fired reverb, the sole reverb still operating in Chile at the time. The new reactor, the biggest bath smelting vessel in the world, has a design dry concentrate processing capacity of 3,100 tonnes/day, most of which is injected through tuyeres. In the period January 2005-June 2006, the average daily reactor throughput was 2,780 tonnes of concentrate plus 630 tonnes of recycled material. The foregoing indicates that the Mitsubishi as well as the tuyere injection technologies are on the way to reaching an annual concentrate processing capacity of 1 million tonnes of concentrate per day in a single primary smelting unit. Realignment of Smelter Copper Production The realignment of the copper smelting industry, initiated in the 1970s-1980s, has continued in the 1990s and early years of the 21 st century. Main developments have been the expansion of smelters in Chile and Japan; the expansion of existing smelters and the commissioning of new smelters in China, India and other Asian countries, reflecting globalization of the industry; and the closure of still more smelters in the USA, where at present there are only three operating smelters, each practicing a different technology. It is also worth noting that during the latter part of the 20 th century in particular, the commissioning of new, large copper mines was essentially based on concentrate shipping to distant custom smelters; examples of this trend are Escondida, Los Pelambres and Collahuasi in Chile, and Antamina in Perú. A notable exception is Olympic Dam which started-up in 1988 in Australia, where remote location and concentrate quality issues required a captive smelter. Figure 1 presents variations in primary copper smelter output of selected countries in the period The data, that reflect the realignment of the industry as discussed in the previous paragraph,

10 show the following: Steady growth in copper smelter output in Chile from 1960; a decline in copper smelter output in the USA, starting in the late 1990s and a relatively constant copper smelter output in Canada; a steady increase in copper smelter output in Japan since 1960, reflecting the continuing expansion of the Japanese custom smelting industry; a similar trend in Europe as existing smelters were modernized and expanded; and finally, a sharp rise of custom smelting in China, starting at the dawn of the present century, as shown by the substantial increase in copper smelter output. This trend also continues. As known, China is now the most important market for the world mineral industry, with India not far behind. Continuous Conversion Figure 1 - Changes in Smelter Copper Output of Selected Countries in the Period The implementation of flash smelting-flash converting technology at the Kennecott Utah smelter in 1995 consolidated the age of continuous converting inaugurated by Mitsubishi in In addition, the feeding of a finely comminuted solid primary smelting matte to the Kennecott-Outokumpu (K-O) flash converter permitted for the first time the decoupling of smelting and converting, thus opening new opportunities in copper smelting. Two years later, in November 1997, the Horne smelter commissioned the Noranda continuous converter, a horizontal, cylindrical, tilting vessel equipped with tuyeres. Advances relating to the application of these processes have been discussed in papers presented at the 1995, 1999 and 2003 Copper-Cobre conferences. While the K-O converter and the Noranda converter are each being used at a single smelter, the Mitsubishi converter, an integral part of the Mitsubishi continuous smelting process, is being used in the Naoshima, Kidd Creek, Onsan and Gresik smelters. It was also adopted to process matte from a Noranda reactor at the former Port Kembla smelter in Australia. The key features of the three commercially proven copper continuous converting technologies are discussed in details in the complete paper. In recent years, Codelco has been developing its own copper continuous conversion process, also using a horizontal, cylindrical, tilting vessel equipped with tuyeres. In turn, Ausmelt has piloted a TSL copper continuous converting process (C3) and the ZTS Non-Ferrous Metals Group will soon commission the first commercial C3 process installation at its Houma smelter in Shangxi Province, China. 1 This chart is based, with acknowledgement, on information from a number of sources. Refer to complete paper in the Cu 2007 proceedings for details.

11 Reflecting on the factors that have contributed to the extension of the Utah smelter flash converting furnace campaign life under very aggressive conditions, the present authors want to single out advances on furnace design and techniques to protect furnace integrity in the age of high process intensity as one of the most important. The Peirce-Smith Converter Peirce-Smith converting has been the standard route to blister copper production from primary smelting matte for about a century, and it is still the dominant copper converting technology. In the last few decades, increasingly larger converters have been built and operated; mechanized tuyere punching has been adopted in most smelters; oxygen enrichment of the blast has become a widespread practice; better refractories have been introduced, thus extending converter campaign life; computerized converter models are being employed as an effective process control technique; and other operating practices have been improved, including application of the Air Liquide shrouded injector successfully used at Xstrata s Sudbury nickel smelter for more than 6 years. Unfortunately, in many copper smelters, the many merits of the Peirce-Smith converter are offset by work environment and environmental weaknesses. However, in a number of smelters, venting of tapholes, the use of vented tunnels for transferring melts, secondary and tertiary hooding of converters, and improved converting practices have dramatically reduced secondary emissions; and oxygen enrichment of the blast and the staggering of converters in stack have permitted feeding relatively steady, high strength converter gas streams to acid plants. Sumitomo s Toyo smelter, that operates Peirce-Smith converters, emits just 1 kg of SO 2 per tonne of blister copper produced. Based on their expertise in controlling fugitive emissions, Sumitomo decided to add one Peirce-Smith converter to Toyo as part of the most recent expansion of the smelter. This decision, they said, reduced the smelter expansion capital cost by utilizing existing facilities, and minimized operational risks. The operation of Peirce-Smith converters in other smelters has not been obstacle to achieve total compliance with stringent environmental regulations; Norddeutsche Affinerie and Boliden are two good examples of sound environmental copper smelter operation. The foregoing indicates that the Peirce-Smith converter is proving to be much more resilient than the reverberatory furnace, and it will still have a place in copper smelters in the foreseeable future. Slag Cleaning and Other Technology Topics The rapid substitution of high intensity flash and bath smelting processes for reverberatory smelting in the last few decades renewed the interest for separate slag cleaning routes. The subject of an Outokumpu paper presented at Copper 87 was the substitution of milling-flotation for electric furnace settling-reduction to recover copper from smelter slag at Harjavalta in A copper smelter survey, also published in 1987, reported that 29% of the smelters participating in the survey were using milling-flotation and 27% were using electric furnaces or electrodes immersed in the primary smelting furnace settler for recovering copper from slag. The number of papers on process modeling and control, and on the results of fundamental research that have been presented at recent Copper-Cobre conferences are a reflection on: (a) the importance that process control has acquired in the age of high process intensity ; and (b) of a continued interest in developing new knowledge relevant to process improvement. The Environment The progressive increase of sulfur fixation in copper smelters in selected countries and worldwide in the period is presented in Figure This chart has been built up using the best available data and estimates obtained, with acknowledgement, from a range of sources. Refer to complete paper in the Copper-Cobre 2007 proceedings for details.

12 Figure 2 - Increase of Sulfur Fixation in the Copper Smelting Industry of Selected Countries and Worldwide ( ). From a world average SO 2 fixation level of about 12% in 1960, when annual copper smelter output was about 4.3 million tonnes, the industry now operates at a world average of about 90% SO 2 fixation, with a copper smelter output three times higher. The leading role of Japan and Western Europe in reducing copper smelting SO 2 emissions is clearly evident in the graph. By the early 1990s, sulfur fixation in the USA was approaching 90%; in Chile, this would only occur ten years later. SO 2 fixation in China has been progressively increasing over the years, in part to satisfy an increasing demand for sulfuric acid. The fairly steep increase in world average SO 2 fixation since the early 1990s reflects the adoption of modern smelting technologies, especially in large producing countries such as Chile, USA and China, mainly in response to new, stringent local environmental regulations. The world average SO 2 fixation rate will rise even further in the near future as new, large Isasmelt plants are ramped up in Zambia and Peru during 2007, and new modern smelters are brought on line in China. With the adoption of modern flash or bath copper smelting technologies, with high oxygen enrichment, achieving almost full SO 2 fixation from primary smelting furnace off-gas has ceased to be the problem posed by the old reverb. In many smelters, converting primary smelting matte to blister, and inherent hot metal ladle transfers, has become the last frontier to be perfected for SO 2 fixation, including capture of fugitive emissions. As discussed earlier, a few smelters that operate Peirce Smith converters - Toyo and Norddeutsche Affinerie are prime examples - have already crossed this bridge, thus meeting the most stringent current worldwide environmental regulations. Which is the ultimate potential of Peirce Smith converting to respond to possible even more stringent environmental regulations in the future? This is an outstanding question. Older smelters, with more cramped converter aisles plants built in the first half or early second half of the 20 th century have had difficulty adapting the modern primary and secondary hoods required for good SO 2 capture from Peirce Smith converters. The high cost of overcoming this problem was an important factor leading to the closure of various smelters in the USA. There is no obvious solution to this problem in smelters with old converter aisles in Chile, the USA, China and elsewhere. Most smelters built in the last decades of the 20 th century have modern converter aisles better suited to allow a very high SO 2 capture, including collection and capture of fugitive gas essentially by mimicking a Toyo-style or Norddeutsche Affinerie-style approach. In greenfield plants, continuous converting technology might be adopted, for example, the 200,000 tpy Xiangguang Copper Co. smelter near Yangu in Shandong Province in China has adopted Outokumpu flash smelting and Kennecott-Outokumpu flash converting similar to that in Utah.

13 The World Copper Smelter Survey One of the key contributions to the Copper 2003-Cobre 2003 pyrometallurgy symposium was the paper presenting the results of the world copper smelter survey that was conducted as an initiative of the symposium organizing committee. Operating data of 52 smelters from all copper producing regions of the world were compiled. In 1988, 80% of smelter primary copper production corresponded to plants each with an annual capacity below 200,000 tonnes, whereas in 2003 this proportion had dropped to only 25%. The comparison also showed that increasing oxygen enrichment in furnace reacting gas and the grade of primary smelting matte, and decreasing energy consumption and sulfur emissions had been major trends in copper smelting in the 15 years period between the two surveys. The survey has become a most valuable source of information for industry and academia. THE FUTURE The discussion of recent advances in copper smelting presented in the preceding sections of this paper is in itself an announcement of future developments. Following are some additional thoughts on this matter. Increasing process intensity even further will remain an important goal for operators and researchers; close cooperation between them will reinforce the need for strong, on-site process engineering teams. Pursuing higher process intensity will require parallel efforts to further extend furnace campaign life and the integrity of tapping and skimming passages by developing improved refractory materials and building even more efficient furnace structure cooling systems. Perfecting computerized process on-line monitoring and controlling systems will also have high priority in the industry R&D agenda. This will in turn require developing tougher and more reliable sensors to measure on-line temperature and composition of reactor feed and of product molten and gaseous streams, and detect location of melt interfaces. With the imminent commercialization of TSL continuous conversion, four continuous copper smelting-converting options will be potentially available for building greenfield smelters: Outokumpu- Kennecott, Mitsubishi, ISASMELT and Ausmelt. Current developments indicate that the TSL technologies will increase their participation in world smelter primary copper output. The flash smelting-converting and TSL technologies share the merits of decoupled smelting-converting operations, elimination of molten transfers, and total containment of process off-gas. The future of smelting and converting tuyere-equipped, tilting vessels very much depend on controlling fugitive emissions and increasing processing capacity. The metallurgical community will follow with great interest Codelco s current endeavours to achieve these goals. In this regard, both the Noranda and the El Teniente technologies have the potential to offer still additional environmentally sound, continuous smelting-converting routes to the primary copper-making industry. The Peirce-Smith converter in its advanced, modern form has still many years to go. Further process and environmental enhancements accompanied by advanced process control will position batch converting as an increasingly competitive alternative to continuous converting. However, as earlier discussed, a number of current Peirce-Smith converter equipped plants may be approaching the limits to effectively capturing fugitive gas emissions, and may have no other option than adopting one of the new converting processes. The present strong demand for copper is likely to continue for some time, spurring further advances in copper smelting technology, and sustaining the trend towards larger copper smelters detected by the 2003 copper smelter survey. This trend has continued in recent years. For example, in 2006, the ten largest smelters accounted for about 30% of world smelter copper output. Larger plants have lower unit production costs, an essential factor for the successful operation of existing and new custom smelters. As earlier discussed, the adoption of modern processes has permitted the effective capture of a large proportion of sulphur input in plants throughout the world. There will be further migration of techniques from plants where fugitive emissions are largely under control to those that lag behind. In a number of smelters, controlling fugitive gases and dust emissions is still high priority. Water conservation is also an issue, especially for smelters in remote, drier locations such as, for example Chile,

14 Australia and China. Advances on slag treatment, minor element control and furnace integrity may open the door to new one-step copper-making processes for more conventional copper concentrates. Despite the technological elegance of such a concept, any new process would have to be competitive with the existing, high capacity two-step processes. With the advent of the oxygen-intensive modern copper smelter, process energy requirement is now drastically lower than that of the almost extinct fossil fuel fired reverberatory furnace. However, as energy prices continue rising and, in the not distant future, carbon emission taxes are applied, work will be required to harness waste heat from operations such as fire refining furnaces and acid plants. In this regard, it is important to mention current work in Chile aiming to develop continuous blister copper fire refining. Recycling of secondary materials through copper smelters currently done in some Japanese, Canadian and European plants will become a more extended practice. In this respect, bath smelting processes have the edge. Thus, the environment friendly, energy neutral copper smelting industry appears to be just around the corner. Finally, it should be noted that while in the 1960s and 1970s much of the R&D work in copper smelting was a Northern Hemisphere (Japan, Canada, Europe) endeavour, in later decades, substantial advances in copper smelting technology have originated in the Southern Hemisphere (Australia, Chile). With the expansion of copper smelting operations in China, India and South East Asia, it is reasonable to expect that future new developments will also emerge from these countries. The present authors hope that the outstanding challenges in copper smelting technology provide the young extractive metallurgists of today the opportunity to have professional careers as exciting and rewarding as they have had the privilege to enjoy. ACKNOWLEDGEMENTS The authors express their profound appreciation to the many colleagues and friends who have generously contributed to the success of the Copper-Cobre series of conferences, and in particular to the organizers of the Copper Pyrometallurgy symposia. One of the present authors (CMD) is deeply indebt with the organizers of the 2007 copper pyrometallurgy symposium for choosing the event to kindly recognize his lifetime dedication to the advancement and teaching of this technological discipline. The authors also wish to express their deep appreciation to many colleagues and friends in the industry who assisted them with various aspects during the preparation of this paper. Full acknowledgement for sources of data for the figures used in this paper is provided in the complete paper to be published in the Copper- Cobre 2007 proceedings. One of the present authors (PJM) wishes to thank Xstrata Process Support for permission to publish this paper. REFERENCES As noted above, the complete references for the paper are included in the full paper to be published in the Proceedings of Cu 2007

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