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As a direct-to-blister copper flash smelting slag contains important levels of copper (14%) and lead (2–4%) it is subjected to a process of high temperature reduction. To recover copper as well as lead the slag is subjected then to a process of decopperization by reducing the oxide metal compounds in an electric furnace. This study presents an alternative to the above process by recovering Pb and Cu from the slag by a hydrometallurgical route using citric acid solutions. The objective of this study was to determine process parameters at which the effectiveness of the lead leaching process is greatest with the minimum transfer of copper to the solution. This paper presents the results of laboratory tests on flash smelting slag leaching with citric acid solutions. Process parameters (time, temperature, citric acid concentration, l/s ratio) at which the Pb concentration decreases from the initial value (3.05%) to the value of 0.41–0.6% in the post-leaching sediment were determined. Analogous values for copper were 12.44% (before leaching) and 11.5–11.8% (after). The lead and copper content was determined by atomic absorption spectrometry (AAS). The hydrometallurgical method could successfully replace the existing treatment of slag in an electric furnace and converter.

The formation of accretion layers within the waste heat boiler is a serious operational concern as it can potentially increase boiler downtime and, hence, limit continuous production. In previous Computational Fluid Dynamics studies, the accretion formation was predicted for an industrial-scale waste heat boiler, using a dust stickiness sub-routine of the model. In this study, a dust sampling campaign was used to validate this stickiness sub-routine. Furthermore, various sticking and reaction mechanisms of flue dust were investigated and compared to thermodynamic predictions. While the results suggest that the sub-routine is valid, the comparison of thermodynamics and species in the samples showed that the chemical reactions of the flue dust did not reach the thermodynamic equilibrium. Graphical Abstract

Copper smelting by-products are key raw materials for the production of selenium, tellurium, molybdenum, and rhenium. Understanding the distribution of these elements during the smelting process is critical for optimizing their directional enrichment, extraction, and utilization. This study investigates the distribution behavior of selenium, tellurium, molybdenum, and rhenium in the double-flash copper smelting process, using a copper smelter employing the double-flash process as a case study. Concentrations of selenium, tellurium, molybdenum, and rhenium were determined by inductively coupled plasma-atomic emission spectrometry and inductively coupled plasma mass spectrometry. The distribution of selenium, tellurium, molybdenum, and rhenium in the copper smelting system was determined through establishing the system’s material balance and integrating elemental test results. The findings indicated that during double-flash copper smelting processing, 47.9% of selenium and 34.9% of tellurium entered the electrorefining process with the anode copper, while 52.1% of selenium and 65.1% of tellurium were retained in the slag, dust, and filtered flue gas. In the flash smelting stage alone, 80.8% of molybdenum was transferred to the slag, while 82.9% of rhenium was released with the flue gas, of which 7.0% was captured in the dust. Graphical Abstract

One of the most common copper concentrate smelting furnaces is Flash smelting furnace which smelts over the half of the world's copper concentrates. The copper concentrate, air or oxygen enriched air and auxiliary fuel oil are charged into this furnace. Due to pyrolysis of copper concentrate, and reaction the decomposed products with oxygen intake, a large amount of heat release that causes the melting of copper concentrate. Since the copper concentrate, contains various minerals, and each of their reactions with atmospheric oxygen in the furnace creates certain conditions; by varying the percentage of minerals in the concentrate charged into the furnace, many problems are raised. In order to fix the problems, and also recognizing the proper actions at the time of changing minerals; within 6 months, inlet concentrate were mineralogically and chemically analyzed and the effect of concentrate minerals on-air and fuel consumption as well as the dust production were studied and The most appropriate concentrate which creates the best conditions in the Khatoon Abad Flash Furnace is obtained.

A mathematical model has been presented to study the combustion of a single copper concentrate particle with high moisture content. By using the presented model, the effect of particle moisture content on particle temperature, sulfur oxidation, and combustion heat generation has been evaluated. The mineralogical composition of the commonly used concentrate at Khatoonabad flash smelting furnace has been used in this study. It was found that the particle moisture content is removed in the sub-second time range and thus the moisture has marginal impact on the variation of particle temperature and on the reaction rate when the gas temperature is assumed to be constant in the reaction shaft. When a concentrate with high moisture content is charged, the particle size enlargement due to the agglomeration of concentrate particles causes an abrupt fall in the particle reaction rate.

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 Abstract

This study explored the behavior of lead, copper, and iron during the leaching process of flash smelting slag from direct-to-blister copper flash smelting using l-ascorbic acid solutions. Flash smelting slag is generated in considerable quantities by various copper smelters worldwide. One drawback of the single-stage flash smelting technology for copper concentrates is the production of large quantities of metal-rich by-products. However, through appropriate management of postprocess waste, valuable components such as copper or lead can be recovered. In practice, the slag is typically subjected to decoppering processes involving electric and converter furnaces. The hydrometallurgical process proposed in this study is aimed at replacing high-temperature recovery methods. The primary objective of the experiments was to investigate the effects of variations in specific leaching parameters and the addition of auxiliary substances on the leaching efficiency of lead, copper, and iron. Four parameters were adjusted during the tests: concentration of l-ascorbic acid, liquid-to-solid phase ratio, temperature, and time. An oxidizing agent in the form of perhydrol and citric acid with an oxidant were used as additives. Optimal process conditions were determined to achieve maximum lead leaching efficiency while maintaining relatively low leaching of copper and iron. The experiments indicated that leaching in ascorbic acid solutions resulted in lead extraction efficiencies ranging from approximately 68% to more than 88%, depending on the conditions. Conversely, relatively low leaching efficiencies of iron (4–12%) and copper (0–29%) were observed.

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.

Antimony is one of the most deleterious impurity elements in copper smelting and has a strong tendency to vaporize in the smelting furnace resulting in an enrichment of antimony in smelter flue dusts. The vaporization and condensation behavior of antimony species was studied in dust-free conditions simulating the off-gas train of a Flash Smelting Furnace at temperatures below 1273 K (1000 °C). The influences of the oxygen partial pressure and the condensate formation temperature on the characteristics of the precipitated antimony species were determined. It was found that practically all the vaporized antimony species precipitated between 853 K and 546 K (580 °C and 273 °C) and that a higher oxygen partial pressure favored precipitation at higher temperatures. The formation of antimony sulfate, which thermodynamically is the most stable antimony species in the studied conditions at temperatures below approximately 723 K (450 °C), was found to be kinetically constrained and the vaporized antimony species precipitated as oxides or sulfides depending on the oxygen partial pressure and the precipitate formation temperature.

A sampling campaign was carried out at an industrial nickel flash smelter with the aim of evaluating the trace element distributions along the smelting line from raw materials to high-grade nickel matte and discard slag. The industrial technology was direct-to-nickel matte smelting without conventional Peirce–Smith converters, thus having two different nickel mattes as smelting products and feeds in the refinery: the sulfidic low-iron nickel matte from smelting furnace and the low-sulfur electric furnace matte from slag cleaning. Major and trace element concentrations were obtained from the solidified samples by electron probe microanalysis and laser ablation–inductively coupled plasma–mass spectrometry. Due to the industrial sampling environment, i.e., the slow cooling rate of the samples, not all the trace element concentrations were able to be measured at the lowest detection limits of the techniques used in some of the phases formed after cooling. However, the obtained results and element distribution coefficients were in good agreement with equilibrium values published in the literature.