Numerical study on the spatial distribution of energy release during char combustion

The energy distribution coefficient (Xc), the fraction of the total heat of reaction released at the char surface during combustion of char particles, was studied using the improved moving flame front (MFF) model. The energy distribution coefficient (Xc), considering homogeneous oxidation of CO in the boundary layer of the particle and reduction of CO2 at the surface, was derived explicitly. Under conditions in practical pulverized coal flames, the energy distribution coefficient (Xc) and the effective energy distribution coefficient (Xe), based on the heat-release calculated using the traditional single film model with CO as the only reaction product (SF-CO), were calculated and compared with the value commonly used in the SF-CO model. The results obtained show that the smaller the particle diameter, the greater the energy distribution coefficient. For the same particle diameter, the higher the particle temperature, the lower the energy distribution coefficient. Under the conditions of the calculation, the average value of the energy distribution coefficient Xc is approximately 0.7, and the average value of the effective SF-CO energy distribution coefficient is greater than 0.5, significantly larger than the value of 0.3 obtained by the traditional single film model.