Modeling of single coal particle combustion in O_2/N_2 and O_2/CO_2 atmospheres under fluidized bed condition

摘要

A one-dimensional transient single coal particle combustion model was proposed to investigate the characteristics of single coal particle combustion in both O_2/N_2 and O_2/CO_2 atmospheres under the fluidized bed combustion condition. The model accounted for the fuel devolatilization, moisture evaporation, heterogeneous reaction as well as homogeneous reactions integrated with the heat and mass transfer from the fluidized bed environment to the coal particle. This model was validated by comparing the model prediction with the experimental results in the literature, and a satisfactory agreement between modeling and experiments proved the reliability of the model. The modeling results demonstrated that the carbon conversion rate of a single coal particle (diameter 6 to 8 mm) under fluidized bed conditions (bed temperature 1088 K) in an O_2/CO_2 (30:70) atmosphere was promoted by the gasification reaction, which was considerably greater than that in the O_2/N_2 (30:70) atmosphere. In addition, the surface and center temperatures of the particle evolved similarly, no matter it is under the O_2/N_2 condition or the O_2/CO_2 condition. A further analysis indicated that similar trends of the temperature evolution under different atmospheres were caused by the fact that the strong heat transfer under the fluidized bed condition overwhelmingly dominated the temperature evolution rather than the heat release of the chemical reaction.