Influence of O₂/CO₂ Atmosphere on the Combustion Process and Product Characteristics of Coal and Refuse-Derived Fuel

Oxyfuel CO2 capture technology is one of the important pathways for the cement industry to achieve low-carbon production. It enables CO2 enrichment, significantly reducing the difficulty and cost of the CO2 capture. Currently, theoretical research on the impact of altered atmospheres on fuel combustion processes is insufficient. This study investigates the combustion characteristics of coal and refuse-derived fuel (RDF), constructs kinetic models for their combustion under different atmospheres based on thermal analysis kinetics theory, and explores the mechanisms by which the atmosphere affects combustion products. The results show that under the O2/CO2 atmosphere, the combustion time of coal and RDF increased by 37.32 and 5.69%, respectively, while the burnout temperatures rose by 31 and 17.6 °C. The decomposition rate of residues improved, and the volatilization rate of heavy metal ions decreased, favoring their solidification. The combustion of volatiles and decomposition of carbonates and sulfides were suppressed. The generation of CxHy, CO, and NO increased, while CO2 and SO2 emissions decreased. The release temperature of HCl decreased. The activation energy of fixed carbon combustion decreased, causing the release of NO and NO2 to shift to lower temperature zones. Therefore, oxyfuel CO2 capture technology is beneficial for heavy metal and sulfur solidification, chlorine removal, and alleviation of Cl enrichment in kilns, although it increases NO generation.