Primary Copper Production Research Articles

Beyond ‘Community Craft Specialisation’ in Prehistoric Mainland Southeast Asian Metallurgy: Copper Smelting Behaviours at Khao Sai On, Nil Kham Haeng, Non Pa Wai, Phromthin Tai, and Tha Kae in Central Thailand

Archaeology in Lopburi Province has been under long-term development since the 1970s and has led to the discovery of Khao Wang Prachan Valley (KWPV) as one of three currently known primary copper production (mining and smelting) sites in Southeast Asia. However, since the 1980s, archaeometallurgical research has focused mainly on the two sites of Non Pa Wai (NPW) and Nil Kham Haeng (NKH), dated from the Neolithic (ca. 1800 B.C.) to Early Iron Age (ca. 2300 B.C.), that are known to have large sequences of archaeological material linked to copper production. Although other sites with evidence of copper production are known in this restricted geographical area, their assemblages have not previously been subjected to archaeometric study. This article discusses the results of archaeometallurgical analyses of slags from Khao Sai On (KSO), Tha Kae (TK), and Phromthin Tai (PTT) with sequences dated during the Middle-Late Iron Age. Slag analysis reveals that different smelting behaviours were occurring at these sites. One heterogenous smelting behaviour at Khao Sai On was probably linked to a smaller community practicing metallurgy among other activities, while Phromthin Tai shows more homogeneous production linked to a larger settlement. Although these three sites are located within 26 km of each other, smelters were probably exploiting different local copper deposits around KWPV. The results seem to support a community based type of production where production behaviours are linked to local geology, technical competence, and intensity of exploitation.

Ricardo’s Law of Comparative Advantage in Bronze Age, Iron Age, and Early Historic Mainland Southeast Asian Metallurgy: Copper-base Metal Production, Exchange, and Consumption Behaviours at Khao Sai On, Nil Kham Haeng, Non Pa Wai, Phromthin Tai, Sab Champa, and Tha Kae in Central Thailand

Since its late 1970s to early 1980s discovery, the Khao Wong Prachan Valley (KWPV) of central Thailand has been assumed to have been a major supplier of copper in Bronze Age, Iron Age, and Early Historic Southeast Asia. KWPV was the first regional metal production system to be characterised by lead isotope (LI) analysis in the late 2000s, revealing a coherent signature easily distinguished from subsequent analyses of production systems at Phu Lon (northern Thailand) and the Vilabouly Complex (central Laos). Despite KWPV’s scale of production, its LI signature has scarcely been detected at Bronze Age metal consumption sites in nearby northeast Thailand and not at all in Iron Age assemblages. We study copper production and copper/bronze consumption behaviours of Iron Age and Early Historic sites in KWPV’s immediate vicinity: Khao Sai On, Phromthin Tai, Tha Kae, and Sab Champa. Khao Sai On and Phromthin Tai production signatures are highly consistent with those previously established, while the uranogenic tendency at Tha Kae explains outliers from Bronze Age Non Pa Wai and Nil Kham Haeng. Analysis of consumption assemblages reveals little to no consistency with local production signatures. This tendency was tested with LI Iron Age and Early Historic datasets for Ban Khu Muang, Ban Mai Chaimongkol, Ban Pong Manao, and Ban Pong Takhob. The pattern is clear: central Thai populations imported copper/bronze, potentially from the Vilabouly Complex or production loci with closely comparable signatures. We examine this counterintuitive behaviour inductively using Ricardo’s Law of Comparative Advantage combined with a technological appreciation of the relatively low productivity of central Thai primary copper production. This suggests central Thailand’s unattached copper producers freely exchanged copper for exotic goods (bronze, glass, semi-precious stone), with potentially poor terms of exchange, from their desire to participate in wider regional trends in conspicuous consumption.

Analysis of China's non-ferrous metals industry's path to peak carbon: A whole life cycle industry chain based on copper

Copper is an essential nonferrous metal, and the adjustment of its whole industry chain structure is conducive to realizing a carbon peak in the nonferrous metal industry. We have performed a life cycle assessment to calculate the carbon emissions of the copper industry. Based on the carbon emissions scenarios of shared socioeconomic pathways (SSPs), we have utilized material flow analysis and system dynamics to analyze the structural changes in the copper industry chain from 2022 to 2060 in China. The results show that (1) the flows and in-use stocks of all types of copper resources will increase significantly. The overall copper supply may meet demand around 2040–2045 due to secondary copper production potentially replacing primary copper production to a large extent, and trade supply is the primary pathway for meeting copper demand. (2) The total carbon emissions from the regeneration system are the smallest (4 %), followed by the production and trade subsystems, accounting for 48 %. The embodied carbon emissions from copper product trade in China have expanded annually. (3) Under the SSP scenario, the copper chain carbon emission peak will be achieved by approximately 2040. Based on a balanced copper supply and demand scenario, the recycled copper recovery efficiency must reach 84.6 %, and the energy structure (the proportion of non-fossil energy in electricity) must reach 63.8 % by 2030 to achieve the carbon peak target for the copper industry chain in China. The above conclusions indicate that actively promoting adjustments in the energy structure and resource recovery processes may help encourage the carbon peak of nonferrous metals in China by realizing the carbon peak of the copper industry.

Prediction, evaluation and optimization of China's copper resource supply system under carbon constraints

Copper is one of China's strategic mineral resources, and its supply security is of great strategic significance to China. In this study, a model of China's copper resource supply system under carbon constraints is constructed using the system dynamics method, and the future supply potential of the system is analyzed and evaluated. Based on the evaluation results, the differential evolution algorithm is used to optimize the supply system to obtain the optimal supply structure that meets the supply-demand balance and carbon emission constraints. Under the carbon constraint scenario, although the carbon emissions of China's copper supply system have declined, a series of problems have also been exposed: such as insufficient primary copper production, excessive dependence on external copper resources, and excessive scrapping of unstable copper-containing products, The supply of secondary copper is affected by the import policy. These factors not only hinder the carbon emission reduction of the copper industry, but also make China's future copper supply full of uncertainty. The optimized supply system significantly reduces carbon emissions (12,664,300 tons per year on average) while meeting the supply-demand balance conditions. The optimal supply structure under the carbon constraint is 26.7 %, 36.3 %, and 37.0 % of the supply shares of the production, recycling, and trading subsystems, respectively. The study results found that improving recycling efficiency can effectively reduce carbon emissions, and when the recycling rate reaches 80 %, China's copper resource supply system will achieve “carbon peak” in 2025, with a peak carbon emission of 41.182 million tons. According to the results, this study suggests that policymakers should strengthen the exploration of primary copper resources, support the development of the secondary recovery industry, and realize diversified import distribution.

Sector-level estimates for global future copper demand and the potential for resource efficiency

We evaluate the effectiveness of resource efficiency strategies for copper by quantifying the effect of technological and behavioral changes on primary copper demand. We assess multi-product sector-level estimates based on service needs under the Shared Socioeconomic Pathway 2 with Representative Concentration 2.6 W/m2 (SSP2-RCP2.6) in a baseline and eight different resource efficiency strategies. Our results show that final global copper demand will increase under the SSP2-RCP2.6 scenario from 24.3 Mt in 2015 to 44.4 Mt in 2050. Copper demand for vehicles and transportation infrastructure will quadruple. Improved scrap sorting and higher collection rates can decrease primary copper production (from copper ore) in 2050 by 2.3 and 2.2 Mt, respectively. The largest copper losses occur through hibernating stocks in the appliances sector. With ambitious material efficiency and demand-side sufficiency, it is possible to return to the primary copper production levels of 2020, despite growing service needs.

Diverse strategies for copper production in Chalcolithic Iberia

Our understanding of early copper metallurgy in the Iberian Peninsula is mostly based on analysis from well-studied regions in the Southeast and Southwest. This paper focuses on two recently recovered Chalcolithic metallurgical assemblages outside these traditional research foci: two slagged crucibles from Lugar Viejo III (Zaragoza) and two large slag cakes from Cueva del Cañaveralejo (Córdoba). Analysis of the compositions and microstructures of the artifacts using optical microscopy and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) suggests they are related to primary copper production, namely smelting in crucible-furnaces under relatively oxidizing conditions, as is standard for this period. The slag layers on crucibles from Lugar Viejo indicate the production of copper with minor amounts of arsenic, also typical for this period. Of special note is the use of organic temper in the crucibles from Lugar Viejo, a practice found at the nearby site of Moncín but rare at other sites in Iberia. However, the slags from Cueva del Cañaveralejo are atypical in their large size (approx. 125 g each), fayalitic composition, unusual efficiency as demonstrated by a low copper content, and lack of arsenic; furthermore, the high sulfur content raises the possibility of the use of sulfidic ores. Results from both sites are compared against published data from well-known sites such as Los Millares, Las Pilas, Almizaraque, and Bauma del Serrat del Pont. The new data from Lugar Viejo and Cueva del Cañaveralejo reinforce the interpretation of metallurgy in the Iberian Peninsula as a low-skilled, conservative technology but also indicate the need for more research into regional variations. (See Supplementary Data 1 for a summary in Spanish).

Examining the influence of copper recycling on prospective resource supply and carbon emission reduction

Copper is an economic and strategic metal consumed and produced in many nations. Previous studies of future copper demand and supply have revealed some deficiencies at the macro level. To minimize these gaps, we present here a comprehensive recycling scenario to examine the future copper sustainability for more than 50 countries by 2100. End-of-life metal recycling optimization can be a transparent, flexible and broadly applicable solution, coupled with circular economy strategies to reduce the supply of such metals and related environmental risks. Substantial recycling (estimated at 40 to 65 percent) would be more conducive to reducing primary demand in regions with large populations and rapid industrial growth. Although Latin America and Caribbean, Africa and Oceania can be identified as regions with low demand and recycling intentions by 2100, carbon emissions in Latin America will peak at 70 million tons by 2050 owing to concentrated primary copper production. In order to fully realize recycling targets, more efforts should be made to formulate policies and regulations for the copper industry, systematically scrap collection, and innovate effective technologies.

Environmental hotspot analysis of primary copper production in China and its future improvement potentials

The production of resources e.g., copper (Cu) has induced many environmental issues worldwide, due to the growing demand to satisfy the world growing population. China, as the largest Cu production country in the world, deserves a special attention. However, the Life Cycle Assessment (LCA)-based environmental profile of Cu produced in China remains unclear due to insufficient representativeness, inconsistency of methodologies applied, and absence of reliable upstream datasets. In the present study, this critical gap was filled using globally harmonized LCA methodologies and facility-level data, technologically representing 77% of China's total Cu production capacity, with consideration of environmental burden embedded in upstream raw materials. Environmental issues were prioritized using LCA weighting and normalization method, while key contributing factors were identified via Life Cycle Impact Assessment (LCIA). Weighted and normalized results showed that Global Warming Potential (GWP) was found to be the priority issue whose contribution to the overall environmental impact reached up to 47%. LCIA results demonstrated that the environmental impacts of China Cu production were primarily caused by production process of raw materials (51%–66%), followed by fuels used for transport by sea and land (11%–22%) and electricity consumption (5%–12%), depending on impact categories. Based on the study results and the importance of GWP, special attention was given to energy systems and direct GWP relevant emissions, by investigating smelting technologies. Five ways towards a more environmentally improved Cu industry associated with the challenges to be addressed were put forward in the outlook (e.g., the use of green electricity can effectively reduce CO2 emission by 14%–29%).

Measuring environmental impacts from primary and secondary copper production under the upgraded technologies in key Chinese enterprises

Copper is a strategic resource to support China's low carbon transition and economic development. China must meet its high copper demand with its limited copper reserve, indicating that it is essential to promote sustainable copper resource management by encouraging secondary copper supply. However, both primary and secondary copper production result in significant environmental impacts. Thus, it is urgent to evaluate such impacts so that appropriate mitigation pathways can be identified. This study conducts life cycle assessment (LCA) at the corporate level to measure the environmental impacts of both primary and secondary copper production. Results show that the total environmental impact from secondary copper production accounted for 7.7%–14.3% of that from primary copper production. Human carcinogenic toxicity is the most significant environmental impact for both primary and secondary copper production. Electricity is the dominant contributor to such environmental impacts. Factors that lead to such environmental impacts are also identified, suggesting that it is critical to increase secondary copper production. Finally, several policy recommendations are proposed to facilitate sustainable copper resource management in China.

Technological reconstruction of the late prehistoric primary copper production of the Vilabouly Complex (central Laos)

Technological reconstruction of the late prehistoric primary copper production of the Vilabouly Complex (central Laos)

Mine-to-smelter integration framework for regional development of porphyry copper deposits within the Chilean context

ABSTRACT Trends toward the widespread use of electric vehicles and renewable energy sources all point to continued growth in copper demand. This demand will be met mainly by new primary copper production, with recycling expected to contribute significantly to copper supply. Significant quantities of copper ore are presently mined from porphyry deposits in which typically, near-surface copper oxides are recovered hydrometallurgically by leaching, solvent extraction and electrowinning, whereas the deeper copper sulphides are only amenable to milling followed by pyrometallurgical processing and electrolytic refining. The Chilean copper porphyries together are the largest group of operating copper mines and are likely to remain so into the future. However, several of these deposits are forecast to show increasing levels of arsenic-bearing minerals, such as enargite. As mature copper mining districts exhaust the near-surface oxides and higher-grade sulphides, individual mines will need to adjust their operations accordingly. However, it is considered that due to such changes, re-engineering efforts might be more economically coordinated across several mines, to collectively handle the evolving ore feeds. The present paper adapts a discrete event simulation (DES) approach to support mine-to-smelter integration within porphyry copper districts. Sample computations are presented that are loosely based on the Chilean context.

Blowin’ in the wind: The beginning of primary metallurgy in the Early Bronze Age Aegean

AbstractOur understanding of Early Bronze Age copper smelting in the Southern Aegean has improved dramatically in the last two decades through a combination of fieldwork, laboratory analyses and experimental reconstructions. The current model which has emerged from these various studies centers on a perforated furnace stack that is used in conjunction with ceramic pot bellows. This study undertakes a critique of the current model and through a series of experimental reconstructions and the analysis of results suggests that the current model has conflated various strands of evidence and resulted in a confused model. It is argued here that primary copper production in the Early Bronze Age Southern Aegean was more likely a two‐stage process that did not rely on the simultaneous use of natural draught and bellows. Along with other examples of wind‐powered furnaces, the working of the Aegean perforated furnace is reconsidered and a new model proposed along with a consideration of the wider implications.

Hydrometallurgical Leaching of Copper Flash Furnace Electrostatic Precipitator Dust for the Separation of Copper from Bismuth and Arsenic

Flash furnace electrostatic precipitator dust (FF-ESP dust) is a recycle stream in some primary copper production facilities. This dust contains high amounts of copper. In some cases, the FF-ESP dust contains elevated levels of bismuth and arsenic, both of which cause problems during the electrorefining stages of copper production. Because of this, methods for separation of copper from bismuth and arsenic in FF-ESP dust are necessary. Hydrometallurgical leaching using a number of lixiviants, including sulfuric acid, sulfurous acid, sodium hydroxide, and water, were explored. Pourbaix diagrams of copper, bismuth, and arsenic were used to determine sets of conditions which would thermodynamically separate copper from bismuth and arsenic. The data indicate that water provides the best overall separation between copper and both bismuth and arsenic. Sodium hydroxide provided a separation between copper and arsenic. Sulfurous acid provided a separation between copper and bismuth. Sulfuric acid did not provide any separations between copper and bismuth or copper and arsenic.

Transient CFD Modeling of Matte Settling Behavior and Coalescence in an Industrial Copper Flash Smelting Furnace Settler

Copper losses into slag within the flash furnace settler is an economically important topic for the primary copper production. Since the settler is not easily accessible to experimental studies due to harsh reaction conditions, numerical simulations are a promising alternative to obtain more insights into the settling behavior of matte. This study aims to increase the process understanding by developing a CFD flash furnace settler model of an industrial flash furnace. Thereby, the CFD model accounts for bath level changes, polydispersity, and coalescence of matte. Coalescence is modeled by an own empirical model focusing on gravitational coalescence. Matte settling shows size-dependent sedimentation within the slag layer, as supported by an own sampling study. Lowering the slag viscosity by a third decreases the copper loss by approximately 37 pct, while slightly increasing it leads to comparable results. Finally, average copper losses of 0.98 wt pct are estimated, finding good agreement with industrial data.

Analyzing the environmental impact of copper-based mixed waste recycling-a LCA case study in China

Copper-based mixed wastes include copper-containing wastes from the chemical, metallurgy, copper processing, printing, electronic component manufacturing, and other industries. Copper-based mixed wastes have high humidity and a significantly lower copper content than general waste copper, pose serious environmental hazards, and are very difficult to recover. The recycling of copper-based mixed wastes has important economic and environmental significance. Chinese companies have started extracting copper and other metals from copper-based waste mixtures and have achieved a high economic efficiency. This paper assesses the environmental impacts of copper-based mixed waste recycling and suggests possible optimization measures for the production process with respect to environmental impacts. The life cycle assessment (LCA) method is adopted to evaluate the effects of different production processes and to compare the environmental impacts of copper recovery from copper-based mixed waste recycling to the environmental impacts of primary and secondary copper production. Sensitivity analysis is conducted to estimate and evaluate the effects of possible production process optimization measures on environmental impacts. The results show the following: 1) The environmental impact of the copper-based mixed waste recovery process is generally superior to that of primary copper production in China on average, while it is inferior to that of secondary copper production. For example, the fossil energy consumption in primary copper production accounts for 74.9% of the impact of this process. 2) Smelting is the production process with the greatest environmental impact throughout the life cycle of copper-based mixed waste, accounting for 64.5% of the normalized index of the total environmental impact; and electrolysis and zinc recovery reach 19.8% and 12.1% of the total normalized index, respectively. 3) The raw materials and emission components with the largest environmental impacts are the carbon emissions from coal use and carbon dioxide emissions during smelting, the use of electricity during electrolysis, and the use of heavy oil and lime as raw materials during refining; these five items account for 69.7% of the total environmental impact. Thus, efforts at process improvement should focus on the full life cycle of energy utilization in the smelting process and on energy and material depletion in the refining and electrolysis processes. Specific process improvements and simulation analyses are important directions for further research.

Spectral Characterization of Copper and Iron Sulfide Combustion: A Multivariate Data Analysis Approach for Mineral Identification on the Blend

The pyrometallurgical processes for primary copper production have only off-line and time-demanding analytical techniques to characterize the in and out streams of the smelting and converting steps. Since these processes are highly exothermic, relevant process information could potentially be obtained from the visible and near-infrared radiation emitted to the environment. In this work, we apply spectral sensing and multivariate data analysis methodologies to identify and classify copper and iron sulfide minerals present in the blend from spectra measured during their combustion in a laboratory drop-tube setup, in which chemical reactions that take place in flash smelting furnaces can be reproduced. Controlled combustion experiments were conducted with two industrial concentrates and with high-grade mineral species as well, with a focus on pyrite and chalcopyrite. Exploratory analysis by means of Principal Component Analysis (PCA) applied on the spectral data depicted high correlation features among species with similar elemental compositions. Classification algorithms were tested on the spectral data, and a classification accuracy of 95.3% with a support vector machine (SVM) algorithm with a Gaussian kernel was achieved. The results obtained by the described procedures are shown to be very promising as a first step in the development of a predictive and analytical tool in search of fitting the current need for real-time control of pyrometallurgical processes.

Environmental benefits of secondary copper from primary copper based on life cycle assessment in China

China is the largest producer and consumer of refined copper in the world. The large amount of copper consumption not only creates added pressure surrounding resource availability but also causes prominent environmental problems. Although copper can be recycled to alleviate resource pressure, there are significant differences between mining primary copper and recycling scrap copper in view of resources, energy consumption, and pollution emissions. These factors were analyzed to better understand the total environmental effects of refined copper from extracting primary ore and recycling scrap copper. The results of this analysis showed that the most serious environmental impacts of refined copper were human toxicity, abiotic depletion potential, and global warming potential. The environmental impacts were mainly caused by the mining and smelting of primary copper by pyrometallurgy. For secondary copper, refining and electrolysis were the main factors. Thus, these main processes, which cause major environmental impacts, should be promoted technologically. According to the results, the total environmental impact of secondary copper was only 1/8 that of the primary copper production process, which indicates that regeneration has better environmental benefits. Furthermore, the sensitive analysis showed that electricity was the most sensitive factor of both technologies. By optimizing the energy structure and increasing the proportion of regeneration, can also reduce the environmental impact. It was suggested that energy structure should be improved and secondary copper should be given more attention and be developed vigorously. Finally, ways to reduce the environmental impact of primary copper and secondary copper industries were recommended.

Simulation-based exergy, thermo-economic and environmental footprint analysis of primary copper production

The transition from a Linear to Circular Economy has become a societal challenge to be tackled. However, the increasing complexity of materials and products increases also the sophistication of the circular economy systems required to deal with them. These systems are very resource consuming, therefore, a rigorous evaluation of the impact of every “actor” in circular economy must be done at design and operation stages to ensure the sustainability of the metal-production value chain.A circular economy system implies, among others, low consumption of energy and material resources and low production of wastes or pollutant emissions. Its sustainability cannot therefore be evaluated just with one indicator. In this paper, we integrate indicators such as recovery rates, environmental impact indicators, as well as the quantities and qualities of the flows, losses and emissions, quantified through exergy. These must all be considered and evaluated simultaneously to perform a rigorous sustainability analysis.The challenges of achieving a circular processing system and society are illustrated using a unique copper flowsheet that covers the complete processing chain from ore to refined metal including among others minor elements refining, scrap recycling, residue processing, steam utilization, sulphur capture and power generation in 129 unit operations linked by 289 streams and all the compositional and thermochemical detail. Using a simulation-based approach, two scenarios have been studied and compared: (i) a representative primary copper flowsheet and (ii) excluding all waste treatment processes. This unique simulated flowsheet permits a complete evaluation of various scenarios of all copper related processing options (while any additional unit operations can also be added) and also rigorously permits an allocation of impacts of all flows, products, residues etc. as a function of the complete mineral composition.This approach to evaluating systems shows how to estimate the true losses from a system and will be a key approach to evaluate the true circularity of the circular economy system.

Selective reductive leaching of cobalt and lithium from industrially crushed waste Li-ion batteries in sulfuric acid system

Recycling of valuable metals from secondary resources such as waste Li-ion batteries (LIBs) has recently attracted significant attention due to the depletion of high-grade natural resources and increasing interest in the circular economy of metals. In this article, the sulfuric acid leaching of industrially produced waste LIBs scraps with 23.6% cobalt (Co), 3.6% lithium (Li) and 6.2% copper (Cu) was investigated. The industrially produced LIBs scraps were shown to provide higher Li and Co leaching extractions compared to dissolution of corresponding amount of pure LiCoO2. In addition, with the addition of ascorbic acid as reducing agent, copper extraction showed decrease, opposite to Co and Li. Based on this, we propose a new method for the selective leaching of battery metals Co and Li from the industrially crushed LIBs waste at high solid/liquid ratio (S/L) that leaves impurities like Cu in the solid residue. Using ascorbic acid (C6H8O6) as reductant, the optimum conditions for LIBs leaching were found to be T = 80 °C, t = 90 min, [H2SO4] = 2 M, [C6H8O6] = 0.11 M and S/L = 200 g/L. This resulted in leaching efficiencies of 95.7% for Li and 93.8% for Co, whereas in contrast, Cu extraction was only 0.7%. Consequently, the proposed leaching method produces a pregnant leach solution (PLS) with high Li (7.0 g/L) and Co (44.4 g/L) concentration as well as a leach residue rich in Cu (up to 12 wt%) that is suitable as a feed fraction for primary or secondary copper production.

Assessment of the Harmfulness of the Slags from Copper Smelting Processes, in an Aspect of their Management

AbstractThere are two methods to produce primary copper: hydrometallurgical and pyrometallurgical. Copper concentrates, from which copper matte is melted, constitute the charge at melting primary copper in the pyrometallurgical process. This process consists of a few stages, of which the basic ones are roasting and smelting. Smelting process may be bath and flash. Slag from copper production, on the end of process contain less 0,8%. It is treat as a waste or used other field, but only in a few friction. The slag amount for waste management or storage equaled 11 741 – 16 011 million tons in 2011. This is a serious ecological problem. The following slags were investigated: slag originated from the primary copper production process in the flash furnace of the Outtokumpuja Company in HM Głogów 2 (Sample S2): the same slag after the copper removal performed according the up to now technology (Sample S1): slag originated from the primary copper production process in the flash furnace of the Outtokumpuja Company in HM Głogów 2, after the copper removal performed according the new technology (Sample S3). In practice, all tested slags satisfy the allowance criteria of storing on the dumping grounds of wastes other than hazardous and neutral.