Research progress on variation patterns, influencing mechanisms and control of maximum temperatures in sintering exhaust gases

The maximum temperature of sintering exhaust gas reflects the advancement of the combustion zone within the material bed and the intensity of gas-solid heat transfer. It serves as an external quantitative indicator of terminal thermal stability, correlating with but not equating to the precise location of the sintering endpoint. Based on industrial monitoring data and mechanistic studies, the temperature distribution of sintering exhaust gas along the machine length exhibits a spatial pattern of initially low temperatures, followed by a rise and subsequent decline. The wet material zone at the machine head exhibits lower temperatures due to evaporation heat absorption and heat exchange limitations. Temperatures gradually increase as drying and preheating are completed and the combustion zone descends, reaching a maximum when the combustion zone advances to the bottom of the material bed and approaches the burn-through point. Temperatures then gradually decrease in the rear section of the machine tail and are relatively sensitive to operating condition disturbances. The peak sintering exhaust gas temperature is influenced by the coupled effects of fuel, process parameters, and raw materials. Finer fuel particle size and increased mixture moisture content reduce peak temperature. Higher carbon content, ignition intensity, and bed thickness elevate peak temperature. Alkalinity and its regulation methods alter thermal intensity in high-temperature zones by affecting liquid phase formation and thermal equilibrium. Excessively low temperatures may lead to insufficient liquid phase formation, restricted development of the sintered phase, and reduced strength. Conversely, excessively high temperatures or prolonged exposure to high temperatures may induce over-sintering and promote the formation of thin-walled, large-pore structures, adversely affecting sinter quality. Future research should focus on the synergistic objectives of "quality-energy consumption-emissions", combining mechanistic and data-driven approaches to investigate the online characterization and regulation of the maximum sintering exhaust gas temperature, thereby supporting the development of low-carbon sintering processes.