Experimental Liquidus Studies of the Pb-Fe-Si-O System in Equilibrium with Metallic Pb
- PDF / 4,799,290 Bytes
- 22 Pages / 593.972 x 792 pts Page_size
- 58 Downloads / 217 Views
THE chemical compositions of slags in typical lead smelting operations can be represented by the Pb-Zn-Fe-Cu-Si-Ca-Al-Mg-O system. Accurate data on slag-solid-metal phase equilibria, activities of lead species in the slag, and partitioning of elements between gas, slag, metal, and solid phases are essential to support the further optimization and development of complex lead smelting, refining, and recycling processes. The present experimental studies of gas-slag-metalsolid oxide phase equilibria in the Pb-Fe-Si-O low-order system are an important part of an integrated thermodynamic modeling and experimental research program for the above multicomponent system. Particular focus in this study has been given to resolving discrepancies between the previously reported data and providing new data for conditions not previously investigated in all slag systems containing iron oxide in equilibrium with metallic lead. The earlier studies of the lead-containing slag systems[1–11] were focused on equilibria in air, with limited investigations[12] at most reducing conditions (equilibria with metallic iron), which have low PbO concentrations
M. SHEVCHENKO and E. JAK are with the Pyrometallurgy Innovation Centre (PYROSEARCH), The University of Queensland, Brisbane, QLD 4072, Australia. Contact e-mail: m.shevchenko@ uq.edu.au Manuscript submitted May 11, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
in the slag ( 1873 K (1600 C)] over the cristobalite liquidus field. Other predicted primary phase fields were fayalite (Fe2SiO4), wustite (FeO1+x), melanotekite (PbOÆ FeO1.5ÆSiO2), melilite (range of solid solutions between 2PbOÆFeOÆ2SiO2 and 2PbOÆFe2O3ÆSiO2), 5PbOÆFeO1.5Æ SiO2, lead silicates (alamosite PbSiO3, lead orthosilicate Pb2SiO4, and 4-lead silicate Pb4SiO6), lead ferrites (1:1 lead ferrite PbOÆFeO1.5, plumboferrite PbOÆ4FeO1.5, magnetoplumbite PbOÆ10FeO1.5), and lead oxide (massicot, PbO). However, the exact extents of these phase fields are unknown. The current study focuses on the equilibria of the slag-(solid oxide)-(liquid Pb) phases over wide range of temperatures [923 K to 1773 K (670 C to 1500 C)] and compositions.
II.
EXPERIMENTAL TECHNIQUE AND PROCEDURE
A. Experimental Procedure and Sample Examination The experimental procedure and apparatus have been described in detail in previous publications by PYROSEARCH.[11,27,28] Initial mixtures were made by mixing high-purity powders of Fe2O3 (99.945 wt pct purity), PbO (99.9 wt pct purity), SiO2 (99.9 wt pct purity), supplied by Alfa Aesar, MA; and ‘‘FeO’’ (99.9 wt pct purity), supplied by Sigma Aldrich, MO. The reagent ‘‘FeO’’ was assumed to be FeO1.05, because there is no stable phase of the exact FeO composition. Pb powder (99.95 wt pct purity; supplied by Sigma Aldrich, MO) was added 20 to 30 wt pct in excess of the mass of the oxide mixture to ensure metallic lead was present at the final equilibrium. Fe powder (99.998 wt pct purity, supplied by Alfa Aesar, MA) was used for selected experiments in equilibrium with metallic iron and for preparation of the fayal
Data Loading...
