The Influence of Alkali Metals on the Sintering Mineralization Process of Iron Ore.

To investigate the influence of alkali metal compounds in different forms on the sintering mineralization process of iron ore, the basic sintering characteristics of iron ore with alkali metal contents ranging from 0 to 4% were measured using the micro-sintering method, and the influence mechanism was analyzed using thermodynamic analysis and first-principles calculations. The results showed that (1) the addition of KCl/NaCl increased the lowest assimilation temperature (LAT) and the index of liquid-phase fluidity (ILF), while that of K2CO3/Na2CO3 decreased the LAT but increased the ILF of iron ore. (2) The pores formed by the volatilization of KCl/NaCl suppressed the diffusion of Fe3+ and Ca2+, which inhibited the formation of silico-ferrite of calcium and aluminum (SFCA). The addition of K2CO3/Na2CO3 promoted the formation of a silicate liquid phase with better fluidity, intervening in the solid-phase reaction between iron ore and CaO. (3) The alkali metal compounds in different forms concentrated in silicate but showed lower levels of distribution in iron-bearing minerals in the form of a solid solution. Furthermore, the formation of an alkali metal-bearing solid solution decreased the microhardness of minerals. This decrease in microhardness and in the content of the SFCA bonding phase directly contributed to the decrease in the compressive strength of the sinter.