High-silica calcium-enhancing synergistic SiO₂ interval regulation gradient alkalinity reduction sintering production process

On the premise of relatively stable blast furnace burden structure, domestic steel enterprises generally have surplus sintering capacity. Reducing sinter basicity can release sintering capacity and cut ironmaking costs, yet low-basicity sintering changes the bonding phase system, resulting in lower sinter yield, tumbler strength and utilization coefficient, as well as deteriorated low-temperature reduction degradation performance. Current control strategies lack systematic mechanism research and precise component standards. To solve this problem, a complete low-basicity sintering process was developed and verified. A series of laboratory sintering tests are conducted to clarify the effects of SiO₂, CaO and other components on sinter quality. Three conventional basicity reduction routes were compared, and single calcium reduction caused the least performance degradation. According to calcium ferrite generation characteristics of nine typical iron ore fines from micro-sintering tests, an optimized silicon-calcium co-enhancement route was proposed by adding more high-silicon ore and lime. Sinter indexes show a U-shaped trend with increasing SiO₂, and the optimal performance is achieved at SiO₂ of 5.2%-5.3% and 5.7%-5.9%. Gradient basicity reduction industrial trials were carried out on a sintering line of a steel plant in Anhui with combined silicon enrichment, calcium el- evation and MgO control, steadily reducing sinter basicity from 1.90-2.07 to below 1.82. Industrial data prove that the sinter utilization coefficient is improved and low-temperature reduction degradation index is optimized, realizing synchronous promotion of production efficiency and metallurgical performance. Key component control intervals are defined and a standardized gradient basicity reduction scheme is formed, providing theoretical and practical support for industrial low-basicity sintering. Further research can be carried out on mineral phase stabilization mechanism of ultra-low basicity sinter and its long-term adaptability with blast furnace.