Study on Structure and Reducibility of Iron Ore Sinter Containing Basic Oxygen Furnace Slag

Abstract

Basic Oxygen Furnace (BOF) slag is a byproduct of the steelmaking process. The amount of slag produced in steel production lines is substantial, not only in Vietnam but also worldwide. Reusing this large amount of slag is an essential requirement, and this study assesses a solution for reusing BOF slag by incorporating it into the sintering process. Experiments were conducted using iron ore, coal, and slag as raw materials for the sintering process using a suction fan apparatus. The sintered product was analyzed for its microstructure, reduction degree, and softening properties. The results indicate that the reducibility of the sinter containing the slag is equivalent to that without slag. The yield of sintered ore decreases by approximately 1% compared to when the slag from steelmaking is used as a flux. The results show that the yield of sintered products meeting standards (size and strength) has values ranging from 59.5 to 71.9%. Besides, the highest reduction degree was achieved with a 24% slag at a basicity of 1.6 and a temperature of 1100 °C. In contrast, the reduction degree of the sintered ore was lower at 1000 °C. The initial softening temperature was determined to be 1200 °C. The microstructure of the sintered ore revealed the formation of a liquid bonding phase. It can be concluded that the main bonding phase is calcium ferrite. The liquid phase showed an even distribution of calcium, silicon, oxygen, and iron elements.