Sodium transformation simulation with a 2-D CFD model during circulating fluidized bed combustion

Investigation of the release behaviors of alkali and alkaline earth metals is necessary to understand the mechanisms of ash-related problems such as fouling, slagging, and corrosion when burning fuel with high alkali contents. Using a 2-D circulating fluidized bed (CFB) combustion model combined with a sodium migration model, sodium transformation was predicted in a 30 kW CFB combustor. Simulation results from the 2-D model are in agreement with those from the 3-D model and experiments. Calculations and analysis of sodium transformation with different parameters, including furnace temperature, excess air, and secondary air ratio, were performed. The results show that a higher furnace temperature leads to a higher number of deposited sodium and ash particles on the probe surface. Increasing the amount of excess air or decreasing the secondary air ratio may reduce the amounts of deposited sodium and ash particles.