Abstract：The particle characteristics, fuel characteristics and fuel-nitrogen conversion characteristics of Datong coal in the O₂-CO₂ environment were studied using the high temperature preheating technology of circulating fluidized bed. The results show that Datong coal can be preheated to 850 ℃ steadily by circulating fluidized bed, and the required heat to preheat is all provided by partial combustion of pulverized coal. After preheating, the particle size of semi-coke decreases, the specific surface area and the pore volume increase by 10 and 2 times, respectively, and the pore structure becomes developed. 72.10 %of carbon and 54.99 % of nitrogen are converted to the gas respectively during the process of preheating of Datong coal by circulating fluidized bed in O₂-CO₂ environment. The concentrations of CO, H₂, CH₄ and CO₂ in gas are 11.5 %, 9.7 %, 2.11 % and 79.6 %, respectively, and the gas heating value reaches 2 848.7 k J·m^-3. N-Q and N-X in coal are converted to N-6 and N-5, and the mass fraction of N-6 increase from 17.28 % to32.11 %.

Keywords: Datong coal; circulating fluidized bed; O₂-CO₂; preheating