Two-dimensional coal combustion modeling of CFB

Abstract

In this study, a dynamic 2D model for a CFB combustor has been developed which integrates and simultaneously predicts the hydrodynamics, heat transfer and combustion aspects. Hydrodynamic model used in this study has been developed in our previous studies. Simulation model calculates the axial and radial distribution of voidage, velocity, particle size distribution, pressure drop, gas emissions and temperature at each time interval for gas and solid phase both for dense bed and for riser. The model has been validated against the data from a pilot-scale 50 kW CFB combustor and an industrial-scale 160 MW CFB combustor. A sensitivity analysis is carried out using the model to examine the effect of different operational parameters and coal properties on bed temperature and the overall CO, NO x and SO 2 emissions from the combustor. As a result of parametric study, it is observed that by increasing bed operational velocity or excess air ratio, bed temperature decreases and CO emission increases. Bed operational velocity has a more significant effect on CO emission than to bed temperature. Another effect of increasing excess air is the decrease of SO 2 and NO x emissions. However, NO x emission increases with the operational bed velocity while SO 2 emission decreases.