The investigation of the coal ignition temperature and ignition characteristics in an oxygen-enriched FBR

Abstract Oxygen-enriched circulating fluidized bed (CFB) technology is considered as one of the low carbon emission power generation technologies. By recycling the flue gas into the furnace, the CO 2 concentration in the exhaust gas can reach over 90%. The coal ignition temperature and ignition characteristics are important factors for boiler design and for choosing the feeding temperature during the transition from air-firing to oxy-firing. The ignition and combustion processes of five types of coal under four different atmospheres (air, O 2 27%, O 2 40%, O 2 53%) were measured in a laboratory scale fluidized bed reactor (FBR) with an under-bed preheat system. Using thermocouples and a gas analyzer, the changes in bed temperature and the concentrations of different components, such as O 2 , CO 2 and CO, in flue gas were directly measured to determine the coal ignition temperature, T i F . It was found that T i F decreases with increasing O 2 concentration. At lower bed temperatures, two-stage ignition processes were observed in certain ranges of initial bed temperature and oxygen concentration. The influence of initial bed temperature on volatile release and the SO 2 emission in the ignition processes were also discussed.