Pyrometallurgy Innovation Centre (PYROSEARCH)

  • Nickel laterite Part 2 - thermodynamic analysis of phase transformations occuring during reduction roasting

    Rhamdhani, M. A.; Hayes, P. C.; Jak, E. (2010). Thermodynamic and phase transformation analyses of nickel laterite ores processed in industry have been carried out. The nickel in the laterite ores is principally associated with Fe rich goethite and serpentine particles. The thermodynamic analysis suggests that the nickel recovery from the Fe rich matrix is limited by equilibrium. The nickel recovery from the single phase serpentine/ olivine appears to be higher for particles with Mg/Fe molar ratio <8. The nickel partitioning to the alloy phase is sensitive to the change of temperature and oxygen partial pressure both in the case of reduction roasting of Fe rich goethite and serpentine. It has also been shown in the current study that the optimum conditions for high nickel recovery from the Fe rich goethite and serpentine are different.

  • Nickel laterite Part 1 – microstructure and phase characterisations during reduction roasting and leaching

    Rhamdhani, M. A.; Hayes, P. C.; Jak, E. (2010). Detailed microstructure and phase characterisations of processed nickel laterite ore feed, reduced ore and leached ore have been carried out using scanning electron microscope, synchrotron X-ray powder diffraction and electron probe X-ray microanalysis as a part of study aimed to increase Ni recovery from the laterite ores. The majority of the nickel in the ore feed were found to be associated with fine grained goethite (Fe rich matrix of limonite composite) and serpentine particles. These phases were transformed to magnetite and olivine respectively upon reduction roasting. Nanosize metallic particles were also observed on the free surface of limonite composite particles following reduction roasting. Upon leaching, >90% of the nickel in the Fe rich matrix was leached out, while <50% was removed from the olivine and its composites. The characterisation results from this study were used to assist the analysis of thermodynamic and phase changes during reduction roasting and leaching described in Part 2 of the paper.

  • Fundamental Studies in Ironmaking Slags to Lower Operating Temperatures and to Recover Titania From Slag

    Zhao, B. J.; Jak, E.; Hayes, P. C. (2010). The eutectic temperature between iron and carbon is 1150 degrees C. This is the lowest temperature in which Fe-C solution can be tapped from a blast furnace. Current operating temperatures of iron blast furnace are much higher than 1150 degrees C and limited by melting temperature of the slag. There is room to lower the operating temperature of the iron blast furnace. As a result, coke consumption and CO, gas emissions can be reduced and campaign length of the furnace can be increased. A key factor in achieving the low operating temperature of the blast furnace is to use an optimum slag composition that can be tapped at low temperature. Phase equilibria studies have been undertaken in the system "TiO2"-CaO-MgO-Al2O3-SiO2 at carbon saturation. Extensive experimental data are presented in the form of pseudo-ternary "TiO2"-(CaO+MgO)-(Al2O3+SiO2) at fixed MgO/CaO and Al2O3/SiO2 ratios. Melting temperatures of complex slag are described as functions of basicity weight ratio (CaO+MgO)/(SiO2+Al2O3) and TiOx concentration. The phase diagrams determined in this study explain the behaviour of titanium-containing slag such as Panzhihua ironmaking slag. These diagrams will be used for selection of optimum slag composition with low liquidus temperature for both Ti-free and Ti-containing slag. The possibility of lowering ironmaking temperature by adding titania has been discussed based on the experimental data determined in this study. A large amount of iron blast furnace slag containing 20-25 wt% "TiO2" are produced in Panzhihua Iron & Steel. "TiO2" has to be concentrated before it can be efficiently extracted from the slag. It was found in this study that titanium is present in the blast furnace slag mainly in two minerals, perovskite CaTiO3 and pseudobrookite (Mg2+, Al3+, Ti3+, Ti4+)(3)O-5. Electron probe X-ray microanalysis (EPMA) has been used to determine phase assemblage of the slag quenched from high temperature and the compositions of the phases. It was found that "TiO2" is 58 wt% in perovskite and 80-90 wt% in pseudobrookite. The particle size of the pseudobrookite is much larger than that of the perovskite. It was found that the composition of the current Panzhihua ironmaking slag is located in the perovskite primary phase field. The maximum "TiO2" concentration in the recovered materials is only 58 wt% if the crystal phase is perovskite. With the information provided in this study it may be possible to recover "TiO2" from the Panzhihua slag in the form of pseudobrookite so that recovered materials contains 80-90 wt% "TiO2" and can be used directly for production Of pure TiO2.

  • Phase equilibria of fayalite-based slags for the slag cleaning process in copper production

    Henao Zapata, Hector M.; Pizarro, C.; Font, J.; Moyano, A.; Hayes, P. C.; Jak, E. (2010).

  • Viscosity and electrical conductivity of copper slag at controlled oxygen potential

    Zhao, B.; Jak, E.; Hayes, P. C.; Font, J.; Moyano, A. (2010).