Effect of sinter basicity on the interactive reaction of composite burdens

With the deepening of the concept of interactive reaction and the development of several studies, metallurgists are no longer simply concerned with the metallurgical properties of a single charge. Instead, they comprehensively consider the interactive reaction of composite burdens. The interactive reaction is mainly affected by the chemical composition, microstructure, reduction temperature, and other factors of the ferrous burdens. In this study, taking a sinter with different basicities and a mixed ore of sinter and lump as the research object, the effect of sinter basicity on the smelting and dripping paraments of a composite burden and the interactive reaction between different burdens was investigated using melting–dripping equipment. The results show that the dripping temperature of a single sinter increases with sinter basicity. In the integrated burdens protocol, the proportion of lump ore increased, and the interaction between the burdens was enhanced, which is mainly manifested as a reduced softening start temperature and melting start temperature of the composite burden. The air permeability of the mixed charge was improved. A change of burden structure enhances the interaction between minerals with increasing sinter basicity, resulting in a change in the liquid phase composition, which reduces the melting point of the primary slag phase, and when the basicity of the sintered is too high, it will deteriorate the gas permeability of the material column. This result is not conducive to the intensive smelting of blast furnaces. At the same time, the sintered mineral phase changes throughout the reduction process were characterized using SEM-EDS and XRD, and the main phases in the slag phase are wustite and calcium silicate. The interactive reaction between the sinter and lump produces low melting point materials, which is verified by calculating the phase diagram of CaO–SiO₂–FeO. With increasing sinter basicity, the content of 2CaO·SiO₂ at different breakpoints decreased. This result shows that the high melting point phase formed during the reduction process of the sinter decreases, the liquid phase formation temperature of the composite burden decreases, and the interaction between the burdens increases. Therefore, appropriately increasing the sinter basicity and increasing the lump ore proportion benefits the enhanced smelting of a blast furnace. The theoretical and experimental results obtained in this research are of great importance for improving the production application of the proportion of lump in the furnace and developing efficient and low-carbon ironmaking.