Novel design of ferronickel smelting slag by utilizing red mud as a fluxing agent: Thermochemical computations and experimental confirmation

The effect of red mud on the melting behavior of ferronickel slag was investigated in a laboratory-scale horizontal tube furnace. Melting and softening of slag samples fluxed with different amounts of red mud were examined by an in-situ visualization technique in the temperature ranges from 1673 K to 1823 K. FactSage™ 7.0 was used to perform thermodynamic calculations of the multi-component system of ferronickel slag and red mud. The liquid phase area was extended to lower temperatures by adding red mud, and this implied that red mud was an excellent flux. The primary solid phase field was confirmed to be dependent on the red mud content from X-ray diffraction measurements. Microscopic observations using a scanning electron microscope (SEM-EDX) confirmed that the primary solid phase changed from olivine to spinel with the addition of red mud.