Influence of secondary air on combustion process and pollutant emissions in a sludge fluidized bed incinerator

Numerical simulations of a 120 t/d sludge fluidized bed incinerator were performed using Computational Particle Fluid Dynamics (CPFD) method. The effects of secondary air on temperature distribution, gas distribution and pollutant emissions were investigated. The results show that the secondary air with a tangential arrangement significantly enhance flow field disturbance in the furnace compared with the original opposed arrangement. This can increase temperature and temperature distribution uniformity in the dilute phase region. The tangential arrangement facilitates vortex formation within the furnace, thereby accelerating gas-solid mixing and enhancing O2 concentration uniformity in radial sections. Compared with the opposed arrangement, the tangential arrangement can promote the oxidation of CO and SO2 while enabling effective reductive removal of NO. The computational results demonstrate that under the tangential arrangement, CO emissions at the furnace outlet decrease by 96.44%, with simultaneous reductions of 6.80% for NO and 53.42% for SO2, indicating significant improvements in comprehensive pollutant emissions control.