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Graphical Abstract:

Graphical Abstract:

Graphical Abstract:

Abstract: 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 Abstract:

Abstract: The world of stainless steel production was 52 Mt in 2019, and the annual amount of slags including electric furnace, AOD converter, ladle, and casting tundish, was estimated at 15–17 Mt. Nowadays, only a minor fraction of slags from stainless steel production is utilized and a major part goes to landfilling. These slags contain high-value elements (Cr, Ni, Mo, Ti, V…) as oxides or in metallic form, some of them being environmentally problematic if dumped. Thus, any approach toward circular economy solutions for stainless steel slags would have great economic and environmental impacts. This contribution examines the slags from different process stages, and the available and new potential means to increase internal recycling and to modify slags composition and structure by optimizing their properties for reclaiming in high-value applications. Eventual methods are, e.g., fast controlled cooling and modifying additives. Means to recover valuable metals are discussed as well as potential product applications to utilize various slags with different chemical, physical, and mechanical properties. By integrating the treatments and steering of slags′ properties to the total process optimization system, the principles of circular economy could be achieved. Graphical Abstract:

The effectivity of present copper smelting technologies have their roots in industrial and laboratory-scale experience accumulated over the past decades. Since early ‘60s, the tools for improving the processing conditions and smelting vessel design included scale modelling and manual computing of homogeneous multicomponent equilibria. The scale models were isothermal, room temperature constructions where water or air was used as medium and dimensionless numbers ensured scale down and scale up similarities. Today, numerical modelling has opened new insight into the high temperature process modelling where chemical reactions and their heat sinks and sources can be included in the simulations. The utilisation of computational thermodynamics enables a rigorous management of the phase equilibria in industrial multi-components slag-matte-metal systems. This development will be visualised in the framework of various enabling techniques.

ABSTRACTThe effectivity of present copper smelting technologies have their roots in industrial and laboratory-scale experience accumulated over the past decades. Since early ‘60s, the tools for improving the processing conditions and smelting vessel design included scale modelling and manual computing of homogeneous multicomponent equilibria. The scale models were isothermal, room temperature constructions where water or air was used as medium and dimensionless numbers ensured scale down and scale up similarities. Today, numerical modelling has opened new insight into the high temperature process modelling where chemical reactions and their heat sinks and sources can be included in the simulations. The utilisation of computational thermodynamics enables a rigorous management of the phase equilibria in industrial multi-components slag-matte-metal systems. This development will be visualised in the framework of various enabling techniques.

ABSTRACTBehaviour of trace elements in the nickel matte smelting was studied at 1673 K (1400°C) by equilibration-quenching techniques followed by direct phase analyses using electron probe X-ray microanalysis and laser ablation-inductively coupled plasma-mass spectrometry. The matte-slag samples at silica saturation were equilibrated with SO2-CO-CO2-Ar mixtures of fixed pSO2, pS2and pO2in order to obtain a pre-determined oxidation degree for the sulphide matte, and thus to generate a targeted iron concentration of the nickel-copper–iron sulphide matte (Ni:Cu = 5, w/w), depending on the slag chemistry. The slag composition was varied from 0 to 2 wt-% K2O and 0–10 wt-% MgO in silica saturation. The studied trace elements were Co, Ge, Pb, Se and Sn, but also the matte-to-slag distributions of the slag forming fluxing components Mg (MgO) and Si (SiO2) were determined experimentally. Selenium was the only trace element studied which strongly enriched in the low-iron nickel mattes, and the deportment became larger when the sulphide matte depleted with iron. All the other trace elements behaved in the opposite way.

In this study, the equilibrium distributions of selected trace elements between molten iron-saturated copper alloy and selected iron silicate slags were measured, and the effects of silica fluxing on them. In addition to the copper and iron main components of the system, trace elements like antimony, gallium, germanium, gold, indium, and silver were added in experiments that spanned the temperature range of 1473–1573 K (1200–1300 °C). Experimental charges were quenched and prepared in polished mounts. In situ analyses of the resulting phases were made directly on the mounts without the need of phase separation prior to analysis. Electron probe X-ray microanalysis was used for concentrations at or above approximately 100 ppmw, and laser ablation-inductively coupled plasma-mass spectrometry for the lower concentrations in the slags. The very low slag concentrations of germanium, antimony, and indium obtained indicate that these elements can be removed from the slag by reduction, whereas gallium concentrations in the slag were high. Consequently, gallium removal from iron residues, such as zinc smelting jarosite, is difficult without volatilization. Based on the present observations, the industrial reduction processes for the treatment of smelting and refining slags as well as for the processing of iron residues, and extracting the reducible metal oxides and their metal values can be optimized. The target in fluxing should be to maintain the slag compositions with a silica concentration higher than about 28 wt%.

ABSTRACTCopper matte converting is the key step to ensure high primary copper recovery in the smelting chain. Its development and the fundamental research carried out over the past decades will be reviewed. The operational challenges and environmental concern of batch-wise Peirce-Smith Converting vessel have induced more than 50 years ago attempts to continuous converting process which have materialised in the last two decades in the flash converting technology, utilised currently in one smelter in USA and three smelters in China. Their annual copper production is in excess of 1.5 Mt, and selected fundamental studies behind this major technological invention will be examined.

Copper matte converting is the key step to ensure high primary copper recovery in the smelting chain. Its development and the fundamental research carried out over the past decades will be reviewed. The operational challenges and environmental concern of batch-wise Peirce-Smith Converting vessel have induced more than 50 years ago attempts to continuous converting process which have materialised in the last two decades in the flash converting technology, utilised currently in one smelter in USA and three smelters in China. Their annual copper production is in excess of 1.5 Mt, and selected fundamental studies behind this major technological invention will be examined.

Abstract: An experimental investigation was conducted to elucidate the main features of the processes taking place in the shaft of a continuous flash-converting furnace for solid copper mattes. The experiments were conducted in a large laboratory furnace. The test variables included the matte grade, oxygen content in the process gas, particle size of the feed material, and oxygen-to-matte ratio. The observed variables included the fractional completion of the oxidation reactions, fraction of sulfur remaining in the particles, copper-to-iron atomic ratio, particle-size distribution, morphology, and mineralogy of the reacted particles. The experiments showed substantial differences in the oxidation behavior of high-grade (72 pct Cu) and low-grade (58 pct Cu) matte particles. Low-grade matte particles reacted evenly throughout the furnace, increased in size, and experienced no substantial fragmentation during oxidation. High-grade matte particles tended to be oxidized unevenly and experienced severe fragmentation leading to generation of dust. The order of the effects of the test variables on the observed variables was found to be (1) the oxygen-to-matte ratio, (2) the particle size of the feed material, and (3) the oxygen content in the process gas. Microscopic examination revealed that the oxides of copper and iron were the main oxidation products, with little elemental copper present in the reacted particles. Potential implications of the experimental findings on the operation of an industrial flash-converting furnace are discussed.

Abstract: 1999 marked the 50th anniversary of the Outokumpu flash-smelting process. Originating during the post-World War II energy crisis, flash smelting is a high-intensity process developed to attain ever-increasing throughputs and intensities. Many innovations and continuous development ensued during the next 50 years before today’s state-of-the-art copper-making process chain and environmental benchmarking technology (e.g., Outokumpu flash smelting, Kennecott-Outokumpu flash converting, and flash technology) became possible. This article reviews how Outokumpu flash furnace design, especially cooling for higher heat loads, has improved over the years.

Abstract: This article describes the use of a general-purpose computational-fluid-dynamics code for improving and optimizing waste-heat boilers in the Outokumpu flash smelting process. The codes offer opportunities to study the transport phenomena for fluid and particulate flow and heat and mass transfer. The simulation includes gas- and dust-flow behaviors and gas cooling by convection and radiation. The results were used in the boiler modification for increased capacity and higher cooling efficiency. The modified boiler, with its unique design, has been in use at Outokumpu’s Harjavalta copper smelter since June 1995 with excellent performance.

The Outokumpu flash smelting process has been developed for the production of copper, nickel and lead from their sulphidic concentrates by Outokumpu Oy. To date, there are 38 flash smelting licences sold for copper, nickel and sulphur production world-wide. At present the use of complex concentrates in large amounts in the flash smelting process is not possible, due to the accumulation of impurities in the present plant practice where flue dust is circulated. If it were technically possible to smelt complex concentrates in the flash smelting furnace, it would make vast resources of relatively low-cost raw materials available to flash smelters. However, different practices for treating complex copper and nickel concentrates in the flash smelting furnace can be studied with combined laboratory studies and computer simulations.Computer simulation of flash smelting requires a substantial knowledge of the behavior of particles during their flight in the particle-gas suspension. The reactions taking place in the flash smelting furnace can be simulated in a laboratory scale furnace where the reactions can be quenched at different stages. Furthermore, the experiments can easily be adjusted to approach conditions of different zones in the reaction shaft of an industrial flash smelting furnace. During recent years, a single-particle laminar-flow furnace has been used to study flash-oxidation of three different copper concentrates in nitrogen-oxygen atmospheres with gas preheating temperatures of 500-1100°C. Extensive research work was focused on the removal of arsenic and antimony from complex copper concentrates. Later on, the experimental results will support the current work of the computer simulation on the Outokumpu flash smelting process.The computer simulation of the Outokumpu flash smelting process started in 1992, aiming at improving the energy efficiency of the process and investigating applicability of the process to complex raw materials. The work was started with laboratory flow-models and with gas flow and heat transfer in a full-scale flash smelting furnace and a waste-heat boiler. The final model will be built up step-by-step by adding two-phase flow, radiation heat transfer, and chemical reactions to the basic model.

The modern world continuously demands more raw materials for manufacturing all kinds of products. Nowadays, the lifetime of a single product can be very short, as is the case with electronic appliances. Waste electrical and electronic equipment (WEEE) is one of the fastest growing waste categories, and one of the most promising recycling routes for WEEE is to use it as a feed material in pyrometallurgical copper smelting. This article presents new experimental observations regarding the behavior of tellurium in secondary copper smelting process, and compares the results to primary smelting experiments. In secondary smelting conditions, most of tellurium distributed into the copper phase, and the distribution coefficient between copper and slag decreased with increasing oxygen partial pressure. In the primary smelting experiments, most of tellurium was vaporized into flue dusts, and the distribution coefficient between copper matte and slag increased with increasing oxygen pressure, i.e. increasing matte grade.