Hannu Johto

Distribution equilibria and slag chemistry of DON smelting

Equilibrium fluxing chemistry and metal value distributions of nickel matte smelting in the one-step direct nickel matte technology have been determined experimentally at 1350–1450°C in MgO-bearing iron silicate slags at silica saturation. The aim was to approach the detailed smelting chemistry at typical concentrations 2.5–10 wt-% iron in MgO-bearing iron silicate slags at silica saturation by quenching and X-ray microanalysis. The results obtained under controlled P(O2) and P(S2) as well as constant P(SO2) = 0.1 atm show that copper and nickel solubilities in the slag as well as matte-to-slag distributions favour matte when the slag is modified by magnesia. At the same time, along with increasing magnesia content of the slag, its iron activity is affected by the dissolution of MgO in the slag, and iron concentration of the formed nickel matte is lowered considerably, and its sulphur concentration increased at constant oxygen and sulphur pressures of the gas phase.

Solubility study of the copper-lead system

Abstract In this study isothermal equilibration experiments were done at 866–1 166 K for the copper–lead (Cu-Pb) binary system. The experiments, conducted in a quartz ampoule, enabled the solubility limits at each end of the phase diagram to be obtained. In addition to the experiments, a literature survey and compilation of the experimental data of the solid solubilities was done. Critically evaluated and selected literature data and our own experimental values were used to optimise the fcc phase interaction parameters. According to the experiments the lead solubility in solid copper at the copper-rich end is smaller than previously reported. The liquidus curve at the lead-rich end was validated with our own experimental results, which agree well with previous experimental data. The thermodynamic assessment of the Cu-Pb system, in the area of fcc_A1 solid solutions, has been improved.

Fundamental Process Equilibria of Base and Trace Elements in the DON Smelting of Various Nickel Concentrates

The converter-less nickel matte smelting technology (DON) adopted more than 20 years ago in Boliden Harjavalta smelter has been since that applied successfully to the processing of large number of nickel sulphide concentrates of various Ni-to-Cu ratios and MgO contents. The operational point of the technology is far from the conventional primary nickel smelting in the smelting-converting route. Therefore, a careful scouting of distribution equilibria of the base and trace elements in the smelting conditions of DON process has been conducted, in order to obtain quantitative information about the equilibria and thermodynamic properties of the nickel mattes at low iron concentrations, less than 10 wt% [Fe] in matte. The series of investigations has included novel experimental and analytical techniques for increasing the reliability and sensitivity of the phase equilibria as well as the element distribution observations carried out in typical high-grade nickel matte smelting conditions.

Trace Metal Distributions in Nickel Slag Cleaning

To capture efficiently the valuable trace metals from nickel slag using electric furnace, it is important to study their distributions between the slag and metallic phases in the furnace. It is impossible to calculate accurately these distributions without experimental measurements. Therefore, in this work, selected trace metal distributions and phase equilibria between K2O containing iron-silicate slags and a metallic Ni-Fe-Cu alloy in nickel slag cleaning furnace conditions were studied. The experimental method developed and applied during the work, involved a modified quenching technique that included equilibration of the samples in semi-sealed quartz ampoules in an inert atmosphere and metallic Fe saturation. The use of the semi-sealed quartz ampoule prevents the escape of volatile elements from the sample during equilibration. Chemical compositions of the phases and the trace elements were analysed by EPMA. From the measured compositions, the trace metal distribution coefficients between the molten Ni-Fe-Cu alloy and slag were calculated.

Review of Boliden Harjavalta Nickel Smelter

Boliden Harjavalta has operated a flash smelter for nickel sulphide concentrates in Finland since late 1959. The original nickel flash smelting process was modified in 1995 to a novel nickel matte smelting (DON) with semi-low iron where the batchwise operated converting became obsolete. Since that, the process has been applied to multiple chemically variable nickel sulphide concentrates with high environmental performance. In this paper, the status of the current smelter operations is described together with the recent modernizations of the nickel flash smelting furnace and the slag cleaning furnaces.

Phase Diagram of System As2S3-Cu2S-PbS at 773-1173 K

Abstract The phase equilibrium of the system As2S3–Cu2S–PbS and its pseudo binaries with low arsenic contents were studied using isothermal equilibrium and quenching experiments at temperatures between 773 and 1173 K. Based on the experimental results, the phase diagrams of these systems have been estimated. Both estimated pseudo binary phase diagrams indicate higher arsenic sulphide solubility into liquid than previously reported in the literature. The liquidus isotherms of the system As2S3–Cu2S–PbS indicate narrow fully molten area widening with increasing temperature between diginite and galena primary phase fields. On a étudié l’équilibre de phase du système As2S3–Cu2S–PbS et ses pseudos binaires avec de faibles teneurs en arsenic en utilisant des expériences d’équilibre isotherme et de trempe à des températures entre 773 K et 1173 K. On a estimé les diagrammes de phase de ces systèmes en se basant sur les résultats expérimentaux. Les deux diagrammes de phase, pseudos binaires, estimés indiquent une solubilité plus élevée du sulfure d’arsenic dans le liquide que ce qui avait été rapporté auparavant dans la littérature. Les isothermes du liquidus du système As2S3–Cu2S–PbS indiquent une région étroite complètement fondue qui s’élargit avec une augmentation de la température entre les champs de phase primaire de la diginite et de la galène.

Phase diagram of the system Cu2S–PbS–ZnS at 873–1273 K

Abstract An equilibration quenching technique was used in this work to study experimentally the phase relations in the Cu2S–PbS–ZnS system at the temperature range 873–1273 K. The phase diagrams and optimised thermodynamic data set have been created for the systems PbS–ZnS and Cu2S–PbS–ZnS with the experimental results of this work and selected data reported in the literature by the CALPHAD (CALculation of PHAse Diagrams) method over the temperature range of 773–1473 K. The obtained thermodynamic dataset allows calculation of the thermodynamic properties and phase equilibria in the PbS–ZnS and Cu2S–PbS–ZnS systems and shows good agreement with experimental results. Dans ce travail, on a utilisé une technique de trempe d’équilibration pour étudier expérimentalement les relations de phases du système Cu2S–PbS–ZnS dans la gamme de température de 873 à 1273 K. Utilisant la méthode CALPHAD (CALculation of PHAse Diagrams), on a créé les diagrammes de phases et l’ensemble de données thermodynamiques optimisées des systèmes PbS–ZnS et Cu2S–PbS–ZnS, dans la gamme de température de 773 à 1473 K, au moyen des résultats expérimentaux de ce travail et de données choisies rapportées dans la littérature. L’ensemble de données thermodynamiques obtenues permet le calcul des propriétés thermodynamiques et des équilibres de phases des systèmes PbS–ZnS et Cu2S–PbS–ZnS, qui sont en bon accord avec les données expérimentales.