The high temperature processing of nickel laterite ore is currently dominated by the Rotary Kiln-
Electric Furnace (RKEF) technology. The ratio of SiO2/MgO (S/M) in the ore is one of the critical
parameters that determines the success of the RKEF process. Incompatible S/M ratios in the ore
can cause aggressive chemical interaction between the slag and MgO refractory. The slag-refractory
interaction at conditions relevant to nickel laterite ore smelting was investigated in the present study.
Synthetic mixtures representing the slag compositions of nickel laterite ore smelting were prepared
by mixing MgO, SiO2, Al2O3, CaO, Fe2O3, and Fe and heating the mixtures in steel containers at
1300°C under an argon atmosphere for 3 hrs. Pure MgO crucible were used as containment material
in the melting process of the mixtures to represent the MgO refractory. The kinetics of the slagrefractory
reaction were investigated using samples with selected initial S/M ratios of 2.0 and
3.0 (wt/wt) (with constant CaO = 3 wt per cent, Al2O3 = 5 wt per cent, FeO = 10 wt per cent) by
performing melting at 1500°C in MgO crucibles for 5, 30, and 120 mins under an argon atmosphere.
The effect of the S/M ratio in slag on the slag-refractory interaction was also investigated by
performing melting of mixtures with different initial S/M ratios of 1.75, 2.0, 2.5, and 3.0 (wt/wt) in MgO
crucibles at 1500°C for 120 mins under an argon atmosphere. After the melting process, each
sample was quenched in water, mounted in resin, ground, polished, and coated. The interaction
between the slags and MgO refractory was then evaluated by analysing the polished samples using
a scanning electron microscope equipped with an energy dispersive spectroscopy (SEM-EDS).
Thermodynamic simulations using FactSage™ 8.0 thermochemical software were performed based
on the experimental slag compositions, refractory, and conditions to support the evaluation process.
The results show that a higher S/M ratio in slag leads to a higher tendency for the refractory
component to dissolve into the slag. A higher S/M ratio in slag also leads to an increasing extent of
solid-state diffusion of iron oxide into the remaining refractory grains. The dissolution of MgO into
the slag is rapid; the MgO concentration in the final slag increased by 2.4 wt per cent and
5.7 wt per cent at initial S/M ratios of 2.0 and 3.0 wt/wt, respectively, within 5 and 30 mins of the
melting process.