Flash Smelting Research Articles

Experimental Approach to Matte–Slag Reactions in the Flash Smelting Process

ABSTRACT Improving metal–slag separation in pyrometallurgical processes is increasingly important. Due to the harsh conditions, direct observations of the molten phases behavior in the settler of the Outotec Flash Smelting Furnace (FSF) are not possible and the ways to improve metal settling can only be studied by simulation and modeling. This study focuses on kinetics and mechanisms of the chemical reactions between matte droplets and slag, which were investigated in laboratory-scale heat-quench equipment at a typical smelting temperature of 1300°C as a function of time in both air and argon atmosphere. The reaction mechanism in the FSF settler was formulated and results in argon atmosphere also indicate that the oxidation of cuprous sulfide by ferric ions in the slag contributes strongly to the copper losses in the slag.

Molecular Dynamics Simulation on Microstructure and Physicochemical Properties of FexO-SiO2-CaO-MgO-“NiO” Slag in Nickel Matte Smelting under Modulating CaO Content

To improve the conditions of extracting iron from nickel smelting residues, the composition modulating from FexO-SiO2-CaO-MgO-“NiO” slag source for matte smelting using high MgO nickel sulfide concentrate was carried out. Based on the molecular dynamics simulation and experimental characterization, the effect of CaO content in nickel slags on the physicochemical properties, the microstructure evolution, and the feasibility of subsequent iron extraction were analyzed. The results showed that, for nickel smelting slag with 9 wt.% MgO, 13–15 wt.% CaO and Fe/SiO2 ratio of 1.2, the melting temperature of nickel slag was lower than 1200 °C, and the viscosity was lower than 0.22 Pa·s at 1350 °C. The electric conductivity was similar to that of the industrial slag, and the interfacial tension between slag and matte was relatively large, which ensured a good separating characteristic. It not only met the requirements for the slag performances in the existing flash smelting process but also improved conditions for the subsequent iron extraction. Additionally, it could be adapted to the current situation where an increasing MgO content exists in the nickel sulfide concentrate.

Izdvajanje kobalta iz primarnih i sekundarnih materijala - pregled

<b>Introduction/purpose:</b> Cobalt is a strategic metal for industrial application. Cobalt recovery from oxidic ores such as laterite and sulphidic ores, and from secondary materials during acidic treatment and precipitation is a highly used strategy ensuring different products such as cobalt hydroxide, cobalt oxide, and finally metallic cobalt. <b>Methods:</b> Familiarity with cobalt behavior in hydrometallurgical processes such as dissolution at atmospheric and high pressure, precipitation, neutralization, filtration and hydrogen reduction is most important for cobalt recovery from ores and secondary materials. Pyrometallurgical methods such as roasting and flash smelting are applied for the treatment of sulphidic ores combined with solvent extraction and electrolysis in order to obtain cathodic cobalt. <b>Results:</b> Powders of nickel-cobalt hydroxide were obtained from ores using sulphuric acid under high pressure in an autoclave and after precipitation with MgO. Solvent extraction was used to separate cobalt from nickel. The final step of cobalt recovery from a solution is using electrolysis. Cobalt and cobalt compounds such as cobalt carbonate and cobalt hydroxide can be obtained from secondary materials in hydrometallurgical operations. <b>Conclusion:</b> Hydrometallurgical and pyrometallurgical processes are mostly applied for cobalt recovery from primary ores (oxidic and sulphidic compounds) and from secondary materials (cemented tungsten carbide, polycrystalline diamond blanks, and waste cathodic materials from lithiumion batteries).

Experimental determination and thermodynamic optimization of the CuCl–ZnCl2, ZnCl2–FeCl3, CuCl–FeCl3, CuCl–CuCl2, FeCl2–FeCl3, FeCl2–CuCl2 and CuCl–PbCl2 phase equilibria

In copper flash smelting, flue dust causes corrosion problems in the heat recovery boiler of the gas train due to formation of dust accretions on the boiler walls. Within these, presence of heavy metal chlorides results in formation of molten salt deposits causing rapid corrosion. CuCl–ZnCl2, FeCl3–ZnCl2 and CuCl–FeCl3 systems were studied experimentally by equilibration-quenching, scanning electron microscopy and energy-dispersive X-ray spectroscopy in order to evaluate melting behaviour of these chlorides, typically present in the corrosive dust deposits. In addition, CuCl–PbCl2, CuCl–CuCl2, FeCl2–FeCl3 and CuCl2–FeCl2 phase diagrams were optimized incorporating and evaluating all available phase diagram and thermodynamic data on the systems. The modified quasi-chemical model was used to describe the thermodynamic properties of molten phases and compound energy formalism was used to model the terminal solid solutions. The calculated phase diagrams are presented and compared with experimental observations as well as with all available phase diagram data from existing literature.

Online monitoring and assessment of energy efficiency for copper smelting process

The copper flash smelting process is characterized by its involvement of wide energy sources and high energy consumption, so the energy conservation is usually a highly concerned topic for the flash smelting enterprises. However, due to the complexity of the system, it is quite difficult to perform a timely comprehensive analysis of the energy consumption of the whole production system. Aiming to realize an online assessment of the energy consumption of the system, great effort was first made in Jinguan Copper, Tongling Nonferrous Metals Group Co. Ltd. Methods were proposed to solve technical difficulties such as the acquisition and processing of data with different sampling frequencies, the online evaluation of the electricity consumption, and timely evaluation of product output in the periodic process. As a result, a software system was developed to make the online analysis of the energy consumption and efficiency from the three levels ranging from the system to the equipment. The analytical results at the system level was introduce. It’s found that electricity is the most consumed energy in the system, accounting for 77.3% of the total energy consumption. The smelting unit has the highest energy consumption, accounting for 52.8% of the total energy consumed in the whole enterprise.

Catalytic Role of Process Dust in SO2-to-SO3 Conversion in Flash Smelting Heat Recovery Boilers

The aim of this work is to examine the catalytic role of copper smelter, copper converter, and nickel smelter process dusts in SO2-to-SO3 conversion at 750°C. To clarify the role of specific oxides in greater detail, synthetic dusts containing varying concentrations of either CuO or Fe3O4 were also studied. All studied dusts catalyzed SO3 conversion. Among the industrial flue dusts, the highest concentration of SO3 formed in the presence of copper smelter dust. Comparing individual oxides, CuO had a greater impact on the SO3 formation. Such catalytic effects of smelter dusts may lead to SO3 concentrations in the process gas so high that sulfuric acid dew point corrosion may occur.

Leaching of lead and copper from flash smelting slag by citric acid

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.

Estimation of Spectral Emissivity and S/Cu Ratio From Emissions of Copper Concentrates at the Flash Smelting Process

The project focused on the investigation of new sensing techniques in the copper production industry, specifically in the flash smelting of copper concentrate process. In this paper, we report a direct relationship between the visible and near-infrared emission spectra in the combustion of copper concentrates by changing some operating conditions such as the sulfur-copper and the oxygen ratios provided to the reaction zone. Spectral processing techniques are applied to the measured spectra. The first one aims to separate both continuous radiations mainly associated to incandescent particles and heating walls with discontinuous emissions associated with some emitting atoms and molecules. This goal was carried out using airPLS baseline estimation algorithm. The second processing technique aims to find the continuous emission only associated with the combustion of copper concentrate particles, eliminating the background spectra associated with the smelter walls. This goal was carried out by directly measuring walls emission at operating temperature and in the absence of flame. The most relevant results show that the estimation of the total radiation associated with each measured spectra is an intrinsic parameter of the process that can provide useful information to the operator that supervises the industrial process. It allows estimate quantitatively the sulfur-copper ratio in order to online monitor the mineral characteristics of the copper concentrate that is entering the process. On the other hand, the approach of a first prototype of the emissivity model for the copper concentrate particles, which validated with measurements, becomes a promising tool that will allow increasing the development of optoelectronic applications around this industry process.

Behavior of Waste Printed Circuit Board (WPCB) Materials in the Copper Matte Smelting Process

The amount of waste electrical and electronic equipment (WEEE) in the world has grown rapidly during recent decades, and with the depletion of primary ores, there is urgent need for industries to study new sources for metals. Waste printed circuit boards (WPCB) are a part of WEEE, which have a higher concentration of copper and precious metals when compared to primary ore sources. PCB materials can be processed using pyrometallurgical routes, and some industrial processes, such as copper flash smelting, have utilized this type of waste in limited amounts for years. For the purpose of recycling these materials through smelting processes, this work studied the behavior of WPCB scrap when dropped on top of molten slag. A series of experiments was carried out during this research at a temperature of 1350 °C, in an inert atmosphere with different melting times. The time required for complete melting of the PCB pieces was 2–5 min, after which molten alloy droplets containing Cu, Pb, Sn, Ni, Au, and Ag formed and started descending toward the bottom of the crucible. The ceramic fraction of the PCB material mixed with slag and the polymer fraction was pyrolyzed during the high-temperature experiments. The results give an understanding of PCB melting behavior and their use as a part of the smelting furnace feed mixture. However, more research is needed to fully understand how the different elements affect the process as the amount of PCB in the feed increases. The physical behavior and distribution of PCB materials in fayalite slag during the smelting process are outlined, and the results of this work form a basis for future studies about the chemical reaction behavior and kinetics when PCB materials are introduced into the copper smelting process.

Parameters that affect the dissolution of Indonesian galena concentrate in fluorosilicic acid and hydrogen peroxide

Pyrometallurgical process still dominates the extraction of galena concentrates. The process used to extract the lead includes reduction smelting in a blast furnace, air flash smelting (Boliden process), oxygen flash smelting (Kivcet, Boliden Kaldo, Outokumpu), air-slag bath smelting (Isasmelt) and oxygen-slag bath smelting (QSL). However, those generate dust, SO 2 gas and volatile Pb liquid. As a result, such processes are ineffective to treat the complex sulfides and low-grade flotation con concentrates. Referring to the lack of high-grade lead ore the lead pyrometallurgical is a problem in the future. In addition, the environmental regulation becomes very strict lately. Those pushes the metallurgist to seek the alternative process that are environmentally friendly and able to treat the low-grade concentrates. Lead extraction through hydrometallurgical process is considered to be safer as the process do not produce dust, SO 2 gas and lead vapor.Researches for lead extraction through hydrometallurgical routes have been performed using various leaching agents such as acetic acid, ferric methanesulfonate, ferric chloride, ferric fluorosilicate and nitric acid with hydrogen peroxide and ferric ion as the oxidants. So far, no lead plant operates hydrometallurgically in an industrial scale. Fluorosilicic acid has a potential to be used as the leaching reagent for concentrating the lead because of high lead solubility in this solution and cheaper price of the reagent in compared to sulfamate and fluoroborate solutions. This research used galena concentrates from a mining area in Bogor, Indonesia, fluorosilicic acid and hydrogen peroxide as the oxidants. The highest Pb extraction percentage of 99.26% was achieved from the leaching experiment using 3.44 M of H 2 SiF 6 and 9.79 M of H 2 O 2 , at 97 o C and concentrate particle size distribution of -100+150 mesh after 135 minutes. The XRD analysis of the leaching residue with no oxidant showed the presence of galena, sphalerite and chalcopyrite, while the residue of the leaching with oxidant showed anglesite (PbSO 4 ), galena, sphalerite, sulphur and pyrite. Lead extractions were increased by the increase of temperature and concentration of fluorosilicic acid. The best solid percentage that gave the highest lead extraction percentage was 12%. Variations of rotation speeds at the range of 300-700 rpm did not significantly influence lead extraction percentage. However, the particle size distribution that resulted in the best extraction percentage of lead is 100+150#, at which the finer particle size of the concentrate give a lower extraction percentage of the lead due to PbSO 4 precipitation.

Flash Smelting Copper Concentrates Spectral Emission Measurements.

In this paper, we report on spectral features emitted by a reaction shaft occurring in flash smelting of copper concentrates containing sulfide copper minerals such as chalcopyrite (CuFeS2), bornite (Cu5FeS4) and pyrite (FeS2). Different combustion conditions are addressed, such as sulfur-copper ratio and oxygen excess. Temperature and spectral emissivity features are estimated for each case by using the two wavelength method and radiometric models. The most relevant results have shown an increasing intensity behavior for higher sulfur-copper ratios and oxygen contents, where emissivity is almost constant along the visible spectrum range for all cases, which validates the gray body assumption. CuO and FeO emission line features along the visible spectrum appear to be a sensing alternative for describing the combustion reactions.

Evolution of Size and Chemical Composition of Copper Concentrate Particles Oxidized Under Simulated Flash Smelting Conditions

An experimental study was conducted to elucidate the evolution of size and chemical composition of La Caridad copper concentrate particles during oxidation under simulated flash smelting conditions. Input variables tested included particle size and oxygen concentration in the process gas. The response variables included the size distributions, chemical composition, and morphology of the reacted particles at seven locations along a laboratory reactor. Particles with initial size 45 µm contained varying amounts of chalcopyrite and pyrite, and tended to either maintain or decrease their mean size upon oxidation. When size reduction was observed, dust was produced because of fragmentation, and the particles showed no evidence of collisions during flight. The main oxidation products detected in the particles consisted of matte, cuprospinel, and magnetite. A plot of the mean size divided by the mean size in the feed against the fraction of sulfur eliminated generalized the experimental data so far reported in the literature, and helped identify the reaction path followed by the particles.

Tolerating the Intolerable: Flash Smelting of Copper and the Construction of Technological Constraints.

Material and energy constraints have had a major influence in the history of technology. However, prior research has surprisingly little to say about what these constraints actually are, how they emerge, and which are the mechanisms through which they influence technological change. This article studies a case where energy constraints were supposedly the source of a radical innovation in copper smelting in post-Second World War Finland. It finds that the constraints were significantly more ambiguous and socially constructed than the technologists themselves acknowledged, and highlights the context dependence of constraints and how technologists may perceive them. Technological feasibility influences the perception of constraints, and the perception of constraints influences what is found to be technologically feasible. This relationship is moderated by political power wielded by technologists.

Effects of Matte Grade on the Distribution of Minor Elements (Pb, Zn, As, Sb, and Bi) in the Bottom Blown Copper Smelting Process

With increasing impurity contents in concentrates, the control of the minor elements is an important issue for the oxygen bottom blown copper smelting process (Shuikoushan process or SKS process). In this work, the distribution behaviors of the minor elements (such as Pb, Zn, As, Sb, and Bi) among the matte, slag, and gas phases as a function of matte grades was investigated by adjusting the ratios of oxygen/ore in the SKS process. With a matte grade around 70%, about 82% As and 70% Bi enters the gas phase, and about 70% Sb and 64% Zn reports to the slag phase, while 55% lead enters the matte phase. The tendency of changes in the distribution of the minor elements in the SKS process is different from that in the Isasmelt process and the Flash smelting process. It may be concluded from this study that the distributions of the minor elements could be optimized to reduce adverse effects in the SKS process by regulating the matte grade.

The Effect of Deposit Temperature on the Catalytic SO2-to-SO3 Conversion in a Copper Flash Smelting Heat Recovery Boiler

The aim of the work was to study the catalytic role of copper flash smelter deposit in the SO2-to-SO3 conversion. In addition, the effect of process gas temperature at 548 K to 1173 K (275 °C to 900 °C) on the amount of SO3 formed was addressed both in the absence and presence of genuine copper flash smelter deposit. The SO3 conversion rate changed as a function of process gas temperature, peaking at 1023 K (750 °C). A dramatic increase in the SO2-to-SO3 conversion was observed when process dust was present, clearly indicating that process dust catalyzes the SO2-to-SO3 conversion. Based on these results, the catalytic ability of the deposit may lead to sulfuric acid dew point corrosion.

Energy Criteria for Selecting a Sulfide Concentrate Melting Method in Copper Production

Comparative analysis is provided for contemporary pyrometallurgical copper smelting processes used most extensively in world practice (Flash Smelting Outokumpu, Top Submerged Lance Technology (TSL) – Isasmelt and Ausmelt, El Teniente Converter, Mitsubishi Continuous Smelting, smelting in a Vanyukov furnace, Flash Smelting + Flash Converting) with ageing methods (reverberatory and shaft melting). Results are provided for calculating the energy expended for these processes. The most energy economic and ecologically secure technologies for copper smelting are revealed.

Reaction Mechanism and Distribution Behavior of Arsenic in the Bottom Blown Copper Smelting Process

The control of arsenic, a toxic and carcinogenic element, is an important issue for all copper smelters. In this work, the reaction mechanism and distribution behavior of arsenic in the bottom blown copper smelting process (SKS process) were investigated and compared to the flash smelting process. There are obvious differences of arsenic distribution in the SKS process and flash process, resulting from the differences of oxygen potentials, volatilizations, smelting temperatures, reaction intensities, and mass transfer processes. Under stable production conditions, the distributions of arsenic among matte, slag, and gas phases are 6%, 12%, and 82%, respectively. Less arsenic is reported in the gas phase with the flash process than with the SKS process. The main arsenic species in gas phase are AsS (g), AsO (g), and As2 (g). Arsenic exists in the slag predominantly as As2O3 (l), and in matte as As (l). High matte grade is harmful to the elimination of arsenic to gas. The changing of Fe/SiO2 has slight effects on the distributions of arsenic. In order to enhance the removal of arsenic from the SKS smelting system to the gas phase, low oxygen concentration, low ratios of oxygen/ore, and low matte grade should be chosen. In the SKS smelting process, no dust is recycled, and almost all dust is collected and further treated to eliminate arsenic and recover valuable metals by other process streams.

Hydrometallurgical recovery of lead from direct-to-blister copper flash smelting slag

Furnace slag from direct-to-blister smelting of copper concentrates contains 12–15% of copper and 2.5–4% of lead. In this form it cannot be deemed as waste material, and thus it is subjected to a high-temperature process of slag decopperization; after this, converting process is performed on the Cu–Pb–Fe alloy being the product of decopperization process in electric furnace. An interesting alternative to the presently used processing of flash smelting slag would be its hydrometallurgical processing and selective recovery of Pb and Cu. This paper presents the results of laboratory tests on flash smelting slag leaching with acetic acid solutions and acetic acid with urea additive. The experiments performed allowed to optimize the process parameters to such an extent that Pb content in the post-leaching sediment is practically equal to the value obtained through the high-temperature process performed in electric furnace.

Mineral chemistry and phase equilibrium constraints on the origin of accretions formed during copper flash smelting

This paper delves into the constraints on the nature, origin and thermal evolution of the accretions formed in the uptake shaft of the flash smelting furnace operated by Atlantic Copper in Huelva, Spain, outlining recommended practices for preventing accretion buildup. The accretions were investigated using quantitative electron probe microanalysis, X-ray diffraction and digital imaging techniques, and the experimental data on mineral composition, crystal chemistry and textural relationships were interpreted in terms of thermodynamic phase equilibrium in the SiO2-Fe-O-S system. The results suggest that two distinct types of accretions were formed by the fractional crystallization of two coexisting immiscible melts, under changing conditions of oxygen partial pressure (pO2). The type I accretion of magnetite + delafossite ± cuprite ± tridymite ± metallic copper crystallized from a fractionating copper-rich melt at pO2 above about 10−5 atm, while the type II accretion of magnetite + fayalite + metallic copper + chalcocite derived from a melt with lower copper concentration when pO2 levels dropped below that critical level. Phase compositions and textures were consistent with a cooling history of both compositionally contrasting liquids from about 1,250 °C, the liquidus temperature of magnetite, to eutectic or near-eutectic temperatures of around 1,100 °C. The maintenance of appropriate temperatures — above the liquidus temperature of magnetite — and oxygen partial pressure levels may be critical for the prevention of accretion buildup.

Process innovations and sustainability in Finnish metallurgical industries

ABSTRACTSustainability is a central issue in metallurgical processes due to their energy intensiveness and environmental impacts. The role of metallurgical industry in Finland is significant accounting for 12% of the value of exports. Meanwhile it is also responsible for 7% of CO2 emissions. Sustainability has been in focus during the latest decennia. Foremost progresses in iron and steelmaking for energy saving and reduction of emissions are surveyed in this contribution. Ferroalloys smelting is a highly energy intensive process. Utilization of local low-grade chromite ore led to major technological advances including innovative agglomeration technique, closed smelting furnace with pre-heating and off-gas recovery contributing to high energy efficiency and low carbon footprint in ferrochrome production. In non-ferrous metallurgy developments in flash smelting for copper rose from a need of substantial reduction of energy consumption and SO2 emissions. The focus was then set on energy efficient technologies with low carbon footprint, sulphur fixation and fugitive emissions. Oxygen in smelting, continuous converting, direct to blister and direct nickel matte smelting are the main achievements. The impact of novel technologies to global sulphur emissions and local environmental issues in the smelters has been considerable.