Combustion modeling and performance evaluation in a full-scale rotary kilnincinerator

This work summarizes the results of numerical investigations and in situ me asurements for turbulent combustion in a full-scale rotary kiln incinerator (RKI). The three-dimensional (3D) governing equations for mass, momentum, energy, and species, together with the kappa-epsilon turbulence model, are formulated and solved using a finite volume method. Volatile gases from sol id waste were simulated by gaseous CH4 distributed nonuniformly along the k iln bed. The combustion process was considered to be a two-step stoichiomet ric reaction for primary air mixed with CH4 gas in the combustion chamber. The mixing-controlled eddy-dissipation model (EDM) was employed to predict the conversion rates of CH4, O-2, CO2, and CO. The results of the predictio n show that reverse flows occur near the entrance of the first combustion c hamber (FCC) and the turning point at the entrance to the second combustion chamber (SCC). Temperature and species are nonuniform and are vertically s tratified. Meanwhile, additional mixing in the SCC enhances postflame oxida tion. A combustion efficiency of up to 99.96% can be achieved at similar to 150% excess air and 20-30% secondary air. Reasonable agreement is achieved between numerical predictions and in situ measurements.