Effect of basicity on sintering behavior of saprolitic nickel laterite in air

• The vast majority of minerals are refractory in the sinter with natural basicity.
• Quaternary basicity should be adopted to evaluate the effect of CaO.
• An appropriate amount of addition CaO could facilitate the formation of melt phase.
• The optimal basicity for the sintering of saprolitic nickel laterite is 1.0.

Nickel pig iron (NPI) production has been experiencing robust development recently in China. For NPI production by smelting technology in either a blast furnace or an electric arc furnace, sintering is imperative to supply a qualified feedstock. In this research, the sintering behaviors of saprolitic nickel laterite with various quaternary basicities ((CaO + MgO)/(SiO2 + Al2O3) mass ratio) were investigated in terms of phase transformation, microstructure and fusion temperature. Experimental results show that the main minerals formed during sintering with natural basicity are refractory materials such as spinel ((Mg,Ni)(Fe,Al,Cr)2O4), forsterite ((Mg,Fe)2SiO4) and enstatite ((Mg,Fe)SiO3). With increasing basicity from natural basicity (0.50) to 2.0, all the three fusion characteristic temperatures decrease initially and then increase with a valley at the basicity of 1.0. It's revealed that the addition of an appropriate amount of CaO could lower the liquid temperature and increase the amount of melt, improving the sintering consolidation of saprolitic nickel laterite.

Mineralogical constituents of saprolitic nickel laterite sintering with natural basicity (0.5) are those refractory minerals with high melting point such as spinel, forsterite and enstatite, which are unfavorable to the formation of melt phase for consolidation. With the increasing basicity from natural basicity (0.50) to 2.0, the fusion characteristic temperatures (TD, TS, and TF) of the laterite ore decrease initially and then increase with a valley at the basicity of 1.0, at which TD, TS and TF are 1272 °C, 1299 °C and 1306 °C, respectively.Figure optionsDownload as PowerPoint slide