Thermodynamic analysis and reaction behaviors of alkali metal elements during iron ore sintering

Abstract

Reaction thermodynamics and behaviors of alkali metal compounds were studied by FactSage7.1 and sinter pot trials. Main transformation behavior of alkali metal compounds was divided into three parts: part of alkali metal chloride was gasified and emitted into the flue gas, and most of alkali metal chloride turned into sulfate, which was remained in the finished sinter, through reacting with sulfur oxide; KAlSi3O8 and NaAlSi3O8 were transformed into KAlSi2O6, NaAlSi2O6 and alkali metal oxides by reacting with calcium oxide. Moreover, newly formed alkali metal oxides turned into sulfate and silicate, entering finished sinter finally. Only a small amount of KAlSi3O8 and NaAlSi3O8 were reduced into gaseous alkali metals in ambient strong reduction atmosphere and removed into the flue gas. 21.67% of potassium and 14.56% of sodium entered flue gas. In finished sinter, alkali metal elements existed in the form of alkali metal sulfate, silicate and aluminosilicate. The influences on alkali metal elements distribution, basicity (mass ratio of CaO to SiO2 in sinter), sulfur content, chloride content and coal ratio of raw materials indicated that increasing basicity level, rising coal ratio and adding CaCl2 promoted the removal of alkali metal elements into the flue gas. However, with sulfur content increasing in raw materials, alkali metal elements distribution ratio in the finished sinter rose.