Effects of Iron Ores on the Combustion Behavior of Coke and NOx Emission during Sintering Process

抄録

Calcium ferrite could promote the CO–NO reduction reaction, and its formation is affected by iron ores during sintering process. In present study, effects of iron ore coating layers on coke combustion rate and NOx emission were investigated in a visualize combustion equipment, and an optimized ore blending structure was proposed by sinter pot test. Due to the melting of iron ore coating layers at high temperature, coke transformed from coated to naked. With increasing of the binary basicity of the iron ore coating layers, the formation of calcium ferrite increased, resulting in increasing of the melt fluidity. The lower the formation temperature of the melts, the sooner coke was exposed, and the peak combustion rate linearly increased with the melt fluidity of iron ore coating layers. Meanwhile, compared to the high-silicon ores, the maximum NOx emission concentration and conversion rate of N element were lower with the low-silicon ores. NOx emission concentration showed an inverted W-shape trend and had an 8-shape relation with coke combustion rate. Due to the difference of the capability of calcium ferrite formation in coating layers, the conversion rate of N element was linearly negative and positive correlated with the basicity of iron ore coating layers and mass of CO emission, respectively. In addition, with the proportions of the low-silicon limonite and hematite increased in sinter mixture, NOx emission gradually decreased. As a consequence, with exclusively using low-silicon lignite and hematite in sinter mixture, NOx emission decreased by about 20% and sinter indexes significantly improved.