Abstract:The viscosities of molten Fe_nO-MgO-SiO₂ and Fe_nO-MgO-CaO-SiO₂ semi-synthetic slags for nickel flash smelting were mearured in the temperature range of 1200-1450℃ by use of a rotational viscometer. The mass ratio of Fe to SiO₂ was fixed at 1.2, calcium oxide and magnesium oxide contents varied in the range of 2%-8% and 9%-12%(mass fraction), respectively. The results show that silicate anions become smaller by increasing CaO content, which results in the viscosity decrease of slag. In the case of addition of MgO the viscosity behaviour is complicated. When MgO content is less than 11%, the viscosity increases with the increase of MgO at all temperatures tested . However, when the MgO content is more than 11%, the viscosity decreases slightly for Fe_nO-MgO-CaO-SiO₂ system. At higher MgO contents, low-viscosity slags can be obtained by adding CaO. As for a given composition, the viscosity decreased with increasing temperature .The higher the temperature, the more MgO can be added before saturation. The effect of Fe₃O₄ on the viscosity is quite significant. The viscosity of slag increases to 300mPa·s at 1300℃ when Fe₃O₄ content varied from 2.84% to 9.53%. The viscosity values are expressed as the functions of temperature and composition. A comparison between Fe_nO-MgO-SiO₂ and Fe_nO-MgO-CaO-SiO₂ systems are also given.

Key words: nickel flash smelting; high-magnesium slag; viscosity