Flash Smelting Research Articles

Comparison of environmental performance of modern copper smelting technologies

The fight against climate change has emphasized the importance of understanding the environmental performance of metal production technologies. This is especially true for copper whose consumption will increase significantly due to electrification and, therefore, understanding the associated footprint becomes essential. This study uses simulation-based life cycle assessment (LCA) together with a commercial flowsheet simulation program to compare several copper smelting technologies against each other when producing metallic blister copper from sulfide copper ore. The lowest LCA values for three concentrate compositions and three capacities were obtained for Flash Smelting technology with Peirce-Smith converting (FSF-PSC). The unit CO2 emissions decreased with increasing capacity. The reduction obtained when the capacity was doubled was 1–9%, depending on the technology. The main source of CO2 emissions was electricity generation, including the use for oxygen production. For instance, for FSF-PSC it accounted for 91% of the climate change when global data source was used for electricity, translating into an 80% reduction if non-fossil electricity was introduced. A reduction of up to 85% in climate change can be achieved by changing from the highest emission producing technology, the Side Blowing Furnace – Top Blowing Converter (SBF-TBC), to the lowest (FSF-PSC) and by using non-fossil electricity.

The changing dynamics of the gas-dust flow in the flash smelter at Nadezhda metallurgical plant due to addition of a shield. Part 1. Model calculations

A poorer quality of the raw materials that go in the flash smelter operated by Nadezhda Metallurgical Plant, as well as the use of man-made deposits and fine ore concentrates with high concentrations of particles smaller than 10 μm, leads to a higher amount of entrained dust. Dust entrained by the gas flow leads to the formation of accretion in the slag end, uptake shaft and waste heat boiler. A higher dust entrainment is associated with higher loads on the gas duct, higher material turnover, decreased performance and recovery of non-ferrous metals. Fitting the furnace crown with a shield avoiding any major changes to the furnace design or the smelting process helps change the dynamics of the gas flow and lower dust entrainment. This paper defines the optimum location and dimensions of such shield. Depending on the particle size and the density of the gas-dust flow, with the shield installed, the estimated reduction in the amount of dust getting in the dust treatment system may reach 20%. 

Reaction Sequences in Flash Smelting and Converting Furnaces: An In-depth View

Flash smelting and flash converting are mature technologies in copper and nickel sulfide smelting. The sensitivity of operation concerning the furnace design is evident. It is obvious that when two unit operations are carried out in separate spaces in the same furnace, skills related to maintenance of suspension oxidation of fine minerals, fluxing, fluid as well as heat flows and the overall energy balance are required. Despite these fundamental features, the flow-sheet wide understanding of linking the suspension oxidation of sulfides with the subsequent smelting processes in the furnace as well as the chemistry of its off-gas train is largely absent in the scientific literature. This review gives a detailed outlook on the microscale phenomena in flash smelting and flash converting furnaces accumulated during the last decades. It connects their vital features and chemistries with the reaction tendencies and heat fluxes in the different parts and reaction zones of the furnace as well as in the off-gas train from the smelter to the acid plant.Graphic

On the Kinetic Behavior of Recycling Precious Metals (Au, Ag, Pt, and Pd) Through Copper Smelting Process

The recycling and recovery of precious metals from secondary materials, such as waste-printed circuit boards, are an important area of circular economy research due to the limited existing resources and increasing amount of e-waste produced by the rapid development of technology. In this study, the kinetic behavior of precious metals Au, Ag, Pt, and Pd between copper matte and iron-silicate slag was investigated at a typical flash smelting temperature of 1300 °C in both air and argon atmospheres. SEM–EDS, EPMA, and LA-ICP-MS-advanced analysis methods were used for sample characterization. The results indicate that precious metals favor the matte phase over slag, and the deportment to matte occurred swiftly within a short time after the system had reached the experimental temperature. With increasing contact times, the precious metals were distributed increasingly into the sulfide matte. The distribution coefficients, based on experimentally measured element concentrations, followed the order of palladium > platinum > gold > silver in both air and argon, and the matte acted as an efficient collector of these precious metals. The obtained results can be applied to industrial copper matte smelting processes, and they also help in upgrading CFD models to simulate the flash smelting process more precisely.Graphical

Study of the micromorphology and health risks of arsenic in copper smelting slag tailings for safe resource utilization

Slag tailings are produced by “cooling-grinding-ball milling-flotation” and other processes of slag, while slag is produced by the flash smelting of the original ore. The utilization and environmental hazards of arsenic in slag tailings have become a focus of attention. This study on slag tailings reveals the presence of arsenic in copper smelting tailings from the mineralogy and leaching perspectives, and the noncarcinogenic and carcinogenic risks of arsenic to the human body were assessed by using the USEPA health risk model. The surface particles of the slag tailings were unevenly dispersed, and the mineral crystals were relatively complete. A small amount of secondary minerals had grown on the mineral surface. Most of the fine particles adhered to the surface of the main mineral to form inclusions. The mineral composition of the slag tailings was dominated by maghemite (Fe3O4) and fayalite (Fe2SiO4), and the arsenic-bearing minerals were unevenly distributed, where As (Ⅴ) fine particles were embedded in maghemite, amorphous phase and fayalite. There was a large amount of residual arsenic in the slag tailing particles, and the leaching content of arsenic in the toxicity leaching procedure was always lower than the limit of 5 mg/L. The health risk to the exposed population was evaluated by the USEPA health risk model. Since the exposed population in the industrial land is mainly adults, it is determined that the tailings will not cause harm to children's health. In this evaluation, the exposure duration (length of service of the workers) of 30 years, exposure frequency of 314 d/y and body weight of 60 kg (average weight of the workers) were taken as the parameters of three exposure pathways: hand-oral ingestion, respiratory system inhalation and skin contact. Therefore, longer activity time of the workers in the tailing workshop corresponds to a higher HI (hazard index). Although the arsenic in the slag tailings had a certain degree of bioavailability, it was not sufficient to adversely affect human health.

Thermodynamic Analysis of Copper Smelting, Considering the Impact of Minor Elements Behavior on Slag Application Options and Cu Recovery

Valorization of slag from metallurgical processes becomes ever more important as a measure to reduce the environmental impact of metal production operations. To this end, the slag composition has to be changed so that the expected technical and environmental requirements of potential end-users can be met. This paper provides a thermodynamic analysis of the copper flash smelting process which was done based on calculation with the FactSage thermodynamic software package. The purpose was to understand the effect of operational parameters on slag chemistry and elemental partitioning in the process. The results of the thermodynamic analysis are used to understand the content changes of impurities considered as harmful to the environment in the slag. Laws and standards regulating the influence of pollutants were analyzed to understand the impact of content changes on application of slag in different markets. A further important aspect is to increase Cu recovery to the matte as recovering more copper is the major economic driver. The study confirms that an increase in the matte grade and temperature lead to higher partitioning of Pb, Zn, and As to the slag. With increasing matte grade, the volatilization of these elements decreases, and with higher operating temperature solubility of Cu and S in slag will increase. The increase of the Fe/SiO2 ratio maximizes the distribution coefficient (wt.% in matte/wt.% in slag ratio) of Pb and reduces the distribution coefficient of As to the slag. Using the current evaluation, the sensitivity of slag quality and metal recovery on operating parameters and slag marketability is estimated. By example of two fictitious smelters it is shown how conditions in existing smelters can be modified to improve the slag marketability and Cu recovery. It is demonstrated that a suitable compromise between slag quality for improved saleability, metal recovery, and optimal operation of the metallurgical process needs to be identified and implemented.

Formation mechanism of arsenic-containing dust in the flue gas cleaning process of flash copper pyrometallurgy: A quantitative identification of arsenic speciation

The proper disposal of arsenic-containing smelting dust has been an important challenge in the copper pyrometallurgy industry which is mostly limited by the variability of arsenic content and species in different types of dusts. The eight types of flash smelting dusts produced along the gas line have been extensively characterized and comparatively studied. Arsenic content gradually increases along the flash smelting (FS) and flash converting (FC) parts of the gas line, and a negative correlation with the pH and copper content has been observed. PM10 accounts for 81.65% and 95.02% of the flash copper furnance (FSF) dust pocket dust and FSF electrostatic precipitator (ESP) dust, respectively. The size distribution variation inply the As enrichment in finer particles. The valence state of arsenic tends to migrate to reach higher valence states along both the FSF and FCF gas line, and the formation mechanism of different types of arsenic particles differs. The As(III)-O mainly remains in the WHB convection part dust and most of them are oxidized to arsenate compounds. More than 80% of the arsenic species was present in the ESP as As(V) and As(III)-arsenite. Fragmentation of concentrate particles and rapid condensation by gas phases lateral flushing of the pipe may produce arsenic particles in the waste heat boiler (WHB), while those remaining in the dust pocket and the ESP may result from adsorption, condensation, and chemical reactions. Temperature is the main factor that affects the deposition site of As2O3 particles. Alkali metal oxide particles influence As content and speciation in dusts by promoting the arsenate formation.

Arsenic and SO2 hotspot in South-Eastern Europe: An overview of the air quality after the implementation of the flash smelting technology for copper production.

This extensive study considered the air pollution data after the flash smelting technology for copper production had become fully operational. The assessment of the air quality after the implementation was significantly important, since the modernisation was necessary for reducing the environmental contamination in one of the most polluted regions in South-Eastern Europe. The concentrations of SO2, PM10 and toxic elements (As, Pb, Cd, Ni) in PM10 samples were monitored at different sites, with respect to the copper smelter, in the period 2016-2019. The air quality evaluation was performed concerning the corresponding limit and target values defined by the Serbian and European legislation, as well as the World Health Organization Air Quality Guidelines (WHO AQG). The measured SO2 concentrations indicated frequent exceedances of the defined daily and annual limit values, at both national and European level. Although exceedances were not as pronounced as in the period before the implementation of the new technology, the episodes of extreme air pollution with SO2 persisted on the daily basis. The maximum daily SO2 concentration of 2125μgm-3 was more than 100 times higher compared to the WHO AQG, but lower compared to the period before the implementation of the flash smelting technology. The air quality considering PM10 and especially As levels in PM10 samples was notably poorer after the modernisation. The annual target value for As, defined by the European and Serbian Regulation, was exceeded at all the measuring sites, with maximum exceedance of more than 90 times at the suburban site during 2019. The frequent exceedances of the corresponding annual limit and target values were also denoted for Pb and Cd in PM10 samples. The analysed data emphasised that the Bor area could still be characterised as an environmental hotspot in Serbia and beyond.

Behavior of copper and lead during mineralurgical and hydrometallurgical processing of flash smelting slag

There are only a few smelters processing copper concentrates directly into blister copper. Despite the many advantages of this process, a serious challenge of this technology is the need to process the resulting flash smelting slag. It contains 12–15% copper and 2.5–4% lead. In this form, it cannot be considered as waste material and, therefore, a high-temperature reduction process is carried out. This decopperization process is energy- and time-consuming. The use of mineralurgical and hydrometallurgical processes, selective enrichment of the appropriate slag fractions in copper and lead, followed by its hydrometallurgical processing and recovery of Cu and Pb could be an interesting supplement to the methods used so far. The article presents results of research on the possibility of separation of useful components from copper slag using the original method of sieve analysis, gravitational enrichment and magnetic separation. Preliminary results of tests were made on a laboratory scale. Then, selective leaching of copper and lead from flash smelting slag was carried out, obtaining very promising results.

Special Issue on “Process Modeling in Pyrometallurgical Engineering”

This Special Issue on “Process Modeling in Pyrometallurgical Engineering” consists of 39 articles, including two review papers, and covers a wide range of topics related to process development and analysis based on modeling in ironmaking, steelmaking, flash smelting, casting, rolling operations, etc [...]

Pyrometallurgical Removal of Arsenic from Electrostatic Precipitators Dusts of Copper Smelting

This work describes the experimental results of pyrometallurgical removing of arsenic from the dust collected in the electrostatic copper precipitators within the gas cleaning system of a Copper Flash Smelting Furnace. The generation of dust in the copper smelting worldwide ranges from 2 - 15 wt% per ton of a copper concentrate. In Chile, copper smelters produce approximately 110 kt/y of dust with a concentration of arsenic between 1 and 15 wt%. The dust is a complex of metals oxides and sulfurs with copper concentrations greater than 10 wt% and relatively high silver concentrations. Since its high arsenic concentration, it is difficult to recover valuable metals through hydrometallurgical processes or by direct recirculation of the dust in a smelting furnace. Thus, the development of pyrometallurgical processes aimed at reducing the concentration of arsenic in the dust (<0.5 wt%) is the main objective of this study, giving particular attention to the production of a suitable material to be recirculated in operations of copper smelting. The work provides a detailed characterization of the dust including the Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN), Scanning Electron Microscope-Energy Dispersive X-ray Analysis (SEM/EDS), X-Ray Diffraction (XRD), the elemental chemical analysis using Atomic Adsorption (AAS), and X-Ray Fluorescence (X-RF). By considering that arsenic volatilization requires a process of sulfidation-decomposition-oxidation, this work seeks to explore the roasting of mixtures of copper concentrate/dust, sulfur/dust, and pyrrhotite/dust. By the elemental chemical analysis of the mixture after and before the roasting process, the degree of arsenic volatilization was determined. The results indicated the effects of parameters such as roasting temperature, gas flow, gas composition, and the ratio of mixtures (concentrate/dust, sulfur/dust, or pyrrhotite/dust) on the volatilization of arsenic. According to the findings, the concentration of arsenic in the roasted Flash Smelting dust can be reduced to a relatively low level (<0.5 wt%), which allows its recirculation into an smelting process.

Prospects for the use of steam-piston engines to increase the economic attractiveness of environmentally friendly processes for the processing of copper-molybdenum concentrates of promising deposits in Kazakhstan

The use of old metallurgical processes is accompanied by releasing process gas into the atmosphere because its subsequent processing is not possible. New technological processes using oxygen flash smelter make it possible to obtain a sufficient concentration of sulfur oxide in process gases for sulfuric acid commercial production. A necessary element of the new type of power plants is heat recovery boilers that generate steam that can be used to generate electricity, which will increase the economic efficiency of oxygen flash smelter plants. The article shows that it is practically impossible to use steam turbines to generate electricity from this steam, and the use of steam-piston engines is proposed.

Strategies for arsenic pollution control from copper pyrometallurgy based on the study of arsenic sources, emission pathways and speciation characterization in copper flash smelting systems.

Arsenic in copper flash smelting (FS) systems not only affects the quality of products but also poses significant technological and environmental problems. Based on the assessment of arsenic mass partitioning in the FS system, arsenic elimination in off-gassing and tailings is 22%, and most of the arsenic output (69%) is recycled in the FS system. Circulating arsenic, especially arsenic in recycled dust and slag concentrate, is the key reason for high-arsenic-content feed. Dust-type recycled materials (RMs) contribute much more arsenic to the feed than slag-type RMs. Flash smelting furnace electrostatic precipitator (FSF ESP) dust contributes makese the largest contribution to arsenic among the dust-type RMs of mixed dust, especially trivalent arsenic, followed by FSF and flash converting furnace waste heat boiler (FCF WHB) dust, which contributes pentavalent arsenic. FCF WHB dust exhibits a relatively low arsenic content, consisting mainly of As(V)-O. Slag-type recycled materials contribute As(V)-O to the total feed, and As(III) originates from copper concentrates. Considering the arsenic contribution and environmental risk, reducing the recovery of FSF ESP dust can greatly decrease the arsenic grade of FSF feed and volatile As2O3. As one of the main arsenic sources in feed, FSF slag concentrate should be carefully disposed of if separated from feed materials because of its high arsenic-related environmental risk. In contrast, WHB dust and FCF slag are more suitable as RM due to their high copper content and low arsenic risk.

Efficient and safe disposition of arsenic by incorporation in smelting slag through copper flash smelting process

During copper (Cu) production, the concomitant arsenic (As) is generally dispersed into various As-bearing byproducts which need to be disposed separately. This work presents an integrated disposition method for the hazardous As by returning the As-bearing byproducts to the copper flash smelting process and solidifying As into smelting slag. After recovering the remnant Cu in smelting slag, the tailings slag become the only output of As in Cu production system. The statistics show that under this operation mode the As brought in and out of the copper production system can keep balance. Investigations reveal that the As species in copper slag include Cu-As intermetallics, Cu-As sulfides and the As incorporated in fayalite phase and glassy silicates matrix. The tailings slag produced from slag flotation process exhibits a leaching toxicity lower than the USEPA and SEPA regulatory thresholds. This work indicates the copper flash smelting process is promising for the efficient and safe disposition of As via recirculation processing of As-bearing byproducts.

Copper Flash Smelting Process Balance Modeling

Process control in flash smelting is based on mass and energy balance from which the operational parameters (oxygen coefficient, oxygen enrichment, and flux demand) are obtained to achieve matte and slag with defined compositions and at defined temperatures. Mineral compositions of copper concentrates, and their blends, have been used in order to optimize the heat process balance. The classical balance methodology has been improved by using equations for molecular ratios and distribution coefficients that have been calculated using FactSage™. This paper describes the development of balance equations and compares their theoretical (equilibrium) results with industrial data logs of the smelting process.

Flash Smelting Furnace Renewal and Productivity Improvement in the Saganoseki Smelter and Refinery

Flash Smelting Furnace Renewal and Productivity Improvement in the Saganoseki Smelter and Refinery

A novel direct reduction-flash smelting separation process of treating high phosphorous iron ore fines

Phosphorus (P) is one of the most deleterious elements in iron ore, it is easy to form iron phosphides that make steel brittle during reduction processes. A new process (direct reduction and flash smelting separation (FSS)) of treating high phosphorus iron ore (HPIO) is introduced in this paper. By limiting the smelting separation between slag and iron to the level of about 1 s, the reduction and migration process of P element was restrained, and the content of P element in the metallic iron obtained after separation was limited to about 0.3 wt%. The effects of flash smelting temperature and ore particle size on the flash smelting process were studied. The migration process of phosphorus was analyzed, and a mathematical model of this smelting process was established to facilitate the visualized understanding and regulation of this process.

Characterization of Copper Smelting Flue Dusts from a Bottom-Blowing Bath Smelting Furnace and a Flash Smelting Furnace

The smelting technology and flue dust treatment have an influence on the physical and chemical characteristics of flue dusts collected in copper smelting. We characterized flue dusts from a Bottom-Blowing Bath Smelting (BBS) process and from a Flash Smelting (FS) process by determining their comprehensive physical, chemical, and mineralogical characteristics. Annual flue dust generation data showed that the rate of the BBS process (2 to 3 pct) was clearly lower than that of FS process (5 to 6 pct). The results revealed that copper smelting flue dusts from the FS exhibited a larger entrainment of solids and a smaller particle size than the BBS. The crystallographic and chemical compositions of the samples indicated that the FS flue dusts have a higher degree of crystallinity than those of the BBS. Fe3O4, CuSO4 and PbSO4, Fe3O4, CuFe5O8 were the predominant crystalline phases in the FS and BBS flue dusts, respectively. In the FS and BBS flue dusts, amorphous multicomponent Cu-Zn-FeOx and Cu-Zn-S phases were formed, respectively. Mineralogical examinations and a stepwise chemical extraction confirmed that the majority of arsenic existed in amorphous form and mostly as pentavalent As5+ arsenate or As2O5 except that in BBS-ESPD.

Integrated Battery Scrap Recycling and Nickel Slag Cleaning with Methane Reduction

Innovative recycling routes are needed to fulfill the increasing demand for battery raw materials to ensure sufficiency in the future. The integration of battery scrap recycling and nickel slag cleaning by reduction with methane was experimentally researched for the first time in this study. Industrial nickel slag from the direct Outotec nickel flash smelting (DON) process was mixed with both synthetic and industrial battery scrap. The end products of the slag-scrap mixtures after reduction at 1400 °C in a CH4 (5 vol %)-N2 atmosphere were an Ni–Co–Cu–Fe metal alloy and FeOx–SiO2 slag. It was noted that a higher initial amount of cobalt in the feed mixture increased the recovery of cobalt to the metal alloy. Increasing the reduction time decreased the fraction of sulfur in the metal alloy and magnetite in the slag. After reduction, manganese was deported in the slag and most of the zinc volatilized. This study confirmed the possibility of replacing coke with methane as a non-fossil reductant in nickel slag cleaning on a laboratory scale, and the recovery of battery metals cobalt and nickel in the slag cleaning process with good yields.

Computational Approaches for Studying Slag–Matte Interactions in the Flash Smelting Furnace (FSF) Settler

Computational methods have become reliable tools in many disciplines for research and industrial design. There are, however, an ever-increasing number of details waiting to be included in the models and software, including, e.g., chemical reactions and many physical phenomena, such as particle and droplet behavior and their interactions. The dominant method for copper production, flash smelting, has been extensively investigated, but the settler part of the furnace containing molten high temperature melts termed slag and matte, still lacks a computational modeling tool. In this paper, two commercial modeling software programs have been used for simulating slag–matte interactions in the settler, the target being first to develop a robust computational fluid dynamics (CFD) model and, second, to apply a new approach for molten droplet behavior in a continuum. The latter is based on CFD coupled with the discrete element method (DEM), which was originally developed for modeling solid particle–particle interactions and movement, and is applied here for individual droplets for the first time. The results suggest distinct settling flow phenomena and the significance of droplet coalescence for settling velocity and efficiency. The computing capacity requirement for both approaches is the main limiting factor preventing full-scale geometry modeling with detailed droplet interactions.