Fredrik Engström

Development of a model for copper converting

Abstract Building on previous work reported in the literature, a dynamic model of the operation of the Peirce-Smith Converter has been developed to describe the distribution of the major elements present. The fundamental principle of the model was a thermodynamic calculation. The situation of non-equilibrium conditions was considered by dividing the converter into different zones linked by predefined flow parameters. The model was verified against actual converter plant data, with the simulated results for the major elements being in good agreement with the plant data. The agreement between plant and calculated data for Pb, and Zn was not as good and more work is required regarding this aspect. En se basant sur des travaux antérieurs rapportés dans la littérature, on a développé un modèle dynamique de l’opération du Convertisseur de Peirce-Smith afin de caractériser la distribution des principaux éléments chimiques présents. Le principe fondamental de ce modèle repose sur un calcul thermodynamique. On a considéré la situation des conditions hors d’équilibre en divisant le convertisseur en différentes zones reliées par des paramètres d’écoulement prédéfinis. On a confronté le modèle à des données issues du convertisseur d’une usine existante, les résultats simulés montrant un bon accord avec les données de l’usine en ce qui concerne les éléments majoritaires. La concordance des données de l’usine et des valeurs calculées pour le plomb et le zinc n’était pas aussi bonne et, donc, une investigation plus poussée concernant cet aspect du modèle s’avère nécessaire.

Characterisation of buildup in an electric furnace for smelting copper concentrate

The results from a characterisation of buildup in an electric smelting furnace for treating copperrich feed material at the Boliden Ronnskar smelter in Sweden are presented. The aim of the work was to obtain better knowledge about the mechanisms behind the formation of the buildup. Samples from the buildup were taken during the rebuilding of the furnace. The samples were characterised using chemical and mineralogical techniques. The buildup consists mainly of different phases such as spinel, matte, olivine and metalloids and has a complex and varying mineralogy, which indicates that the buildup is not formed under equilibrium conditions.

Thermodynamic process modelling of black copper addition to a Peirce-Smith converter: effect on the distribution of antimony and bismuth

Abstract The effect of adding black copper, originating from treating waste electrical and electronic equipment (WEEE), to a Peirce-Smith converter has been investigated by using a thermodynamic process model. The model was formulated, by the authors, in an earlier publication and expanded, in the present work, to include the minor elements antimony and bismuth. The results show that the model describes the distribution of Bi well, whereas the distribution of Sb is not described as well and should only be used for trends. Addition of black copper lowers the removal of Bi and Sb compared to a converter cycle without addition. To maintain a good removal of Bi and Sb, black copper should be added as early as possible during a converter cycle.

Laboratory Treatments of EAF Slag for its Use in Construction

Laboratory treatments of a plant EAF slag sample 71686 were conducted using stabilizers containing P2O5 and air granulation. The results show that it is necessary to add the stabilizers to increase contents of P2O5 from 0.39% to 0.7% for the slag stabilization. By a fast air cooling, most of the granules from the granulation are spherical, with a low internal porosity and dense structure. Content of Fe2O3 in the granules increased from 7.92% to 18.4% and FeO decreased from 14.3% to 7.8%, due to an oxidation during the slag granulation. Contents of metal elements, As, Cd, Cr, Mo, Pb, Ni and Zn, in the leachates from the treated slag samples were lower than the limit values for leaching from inert wastes pursuant to Directive 1999/31/EC. The slag samples after the treatments may then be regarded as environmentally friendly to use in construction.

Plant Treatments of EAF Slag for its Use as Construction Materials

At the steel plant of Höganäs Sweden AB, different steel grades were produced using an Electric Arc Furnaces (EAF). The slag tapped by the EAF often disintegrated during cooling. Slag fines from the disintegration are difficult to handle and to use as materials in construction. The plant tests of EAF slag treatments using stabilizer MCP-F of high P2O5 content were thus conducted, with 1st and 2nd campaign adding 10 and 20 kg MCP-F/ton slag, respectively. The MCP-F addition in slag pots and other test operations were carried out smoothly, without impacting the EAF steel production. Rates P2O5 recovery in the EAF slag were lower in some test heats. Studies may thus be carried out in future to increase the P2O5 recovery from MCP-F, hence, achieving a higher efficiency of stabilization treatments for the slag from the EAF plant.

The need for fundamental measurements for a sustainable extraction of metals

Abstract The increased need for efficient material processing and efficient utilisation of more complex raw materials and the need for recycling or reusing byproduct and waste streams, are all increased challenges in material processing. To cope with these challenges, there is a need for new basic physical and thermodynamic data. The present paper gives four examples, as well as preliminary data, of areas where increased knowledge of fundamental parameters will increase the possibility for a sustainable extraction of metals. The examples include measurement of solubility of pure individual slag minerals, determination of distribution of leachable elements between different mineralogical phases in slag, influence of alumina on liquidus temperature of a copper slag and thermal diffusivity measurements in magnetite based iron ore pellets, all important in different ways to increase the sustainability of the respective materials involved.

Large-Scale WEEE Recycling Integrated in an Ore-Based Cu-Extraction System

At Boliden’s Rönnskär smelter, WEEE is smelted in a Kaldo process and the black copper, together or without the slag, is charged to the PS converter. This process route has proven to be a viable way to obtain a high WEEE smelting capacity in an originally ore-based process system. Experience shows that the slag in the PS converter is usually not fully liquid, and the amount of solids present in the slag increases due to introduction of slag and black copper from WEEE smelting. The effect of increased content of Al2O3 and Cr in the slag on the liquidus temperature has been calculated using FactSage both for the converter slag and for the slag in the electric smelting furnace. The potential of changed slag chemistry is discussed. The consequences of the applied praxis on the removal of Antimony in the converter have been modeled using SimuSage.

Understanding the bottom buildup in an electric copper smelting furnace by thermodynamic calculations

ABSTRACT Thermodynamic calculations were used to investigate the liquidus temperature of the slag and the possible influence on the buildup formation in an electric copper smelting furnace. The impact of parameters such as Fe/SiO2 ratio, partial pressure of oxygen and the content of the oxides ZnO, Al2O3 and Cr2O3 in the slag were investigated with respect to the liquidus temperature of the slag. Results show that the chromium content in the slag has the greatest impact on the liquidus temperature and on the formation of solid particles. The characterisation of the buildup done earlier showed that spinel phases were among the dominating phases. This is supported by the thermodynamic calculations in the present paper, where the chromite solid solution was found to be the primary precipitation phase.

Air Quenching of Steel Slag to Enhance its Hydraulic Activity for Recycling the Slag as Materials in Cement and Concrete Applications

A steel slag has been treated by air granulation, in order to enhance cementitious properties of the slag. Two samples with sizes ranged 1.68-2.38mm and 212-297μm and coded as Slag A and Slag B, respectively, were chosen from the granulated slag for investigations. A sample of the original steel slag was also studied. XRD analyses indicated the formations of α-C2S, β-C2S, C2F, C2MS2, f-MgO and α-C2S, C2F, f-MgO in Slag A and Slag B, respectively. The phases in the two slag samples were quite different from the phases found in steel slag. The SEM results show a reduction of C2S sizes from 10-20μm for the steel slag to nano-scales by air quenching for Slag B. This treatment of air quenching has increased the cumulative heat of hydration to 105.35J/g measured for Slag B, almost two times greater than that of the steel slag. The study results demonstrate a high potential for utilizations of the steel slag in cement and concrete applications after the slag treatment by air quenching. The treatment may thus lead to an environmental friendly and cost-effective recycling for the steel slag. This can also contribute to the sustainable developments in the steel and cement/concrete industries.

Dissolution behavior of fluorine from AOD slag after treatments for volume stabilization

AOD slag samples from steel works of Outokumpu Stainless Company were used to study F-dissolution relating to treatments for volume stabilization. Results from the slag tests and sample characterizations indicate that the slag re-melting with or without reduction and granulation with either water or gas have rather small effects on F leaching, as well as formation of different C2S polymorphs. The chemical composition and cooling condition are the two important parameters to control F leaching from slag samples. These two parameters should be combined together in an optimum way by the steel industry to treat slags for F-immobilization.