Study on mineralogical crystallization of granulation of gas quenching blast furnace slag

Abstract

The process of granulation in blast furnace slag (BFS) by gas quench­ing can effectively recover the waste heat of BFS and improve the value-added nature of the BFS byproduct. With decreasing temperature, BFS crystallizes into melilite, anorthite, spinel, etc. Mineral crystallization, however, is not conducive to the production of amorphous BFS beads. This study uses thermodynamic simulation and remelting experiments to study the influences of basicity, acidity, and the MgO and Al2O3 content of the BFS on the crystallization. By controlling the composition of the BFS, mineral crystallization in the process of granulation in BFS, by gas quenching, could be prevented. The results show that increasing the basicity of the BFS causes the mineral crystallization temperature to increase rapidly. The mineral phase then crystallizes at a higher temperature, which is not conducive to the formation of an amorphous phase. Increasing the acidity of the BFS can greatly decrease the crystallization temperature, e.g., when the acidity increases to 1.3, amorphous BFS beads can be obtained at the gas quenching tem­perature (1623 K). Although increasing the MgO and Al2O3 contents in the BFS had little effect on the crystallization temperature and yield, the preparation of amorphous BFS beads by gas quenching could be realized by adjusting the acid­ity of the BFS.