Effects of alkaline earth oxides on precipitation behavior of metallic iron under CO atmosphere

Abstract

In gaseous reduction of iron ore fines, alkaline earth oxides have profound effects on the precipitation behavior of fresh metallic iron on the particle surface. In this work, in situ observation was performed to reveal the influence of alkaline earth oxides on the precipitation morphology and micro-structure variation of fresh metallic iron from microscopic level by simulation of the gas-solid reaction condition on the surface of ore particles. Experimental results indicate that doping MgO in the particle surface can inhibit the reduction of iron oxide and however doping CaO, SrO and BaO promote; all alkaline earth oxides tested in this study can change the precipitation morphology of fresh metallic iron; minimum doping mole fraction of one oxide to inhibit iron whiskers growth (N _AO) is related to its cation radius $\left( {r_{A^{2 + } } } \right)$ and its extranuclear electronic layers $\left( {n_{A^{2 + } } } \right)$, which can be expressed as $N_{AO} = 1.3 \times 10^{ - 5} r_{A^{2 + } }^2 \sqrt {n_{A^{2 + } } }$.