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

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. Itʹs 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.