A three-dimensional detailed numerical model of a field-scale rotary kiln incinerator

Abstract

A detailed three-dimensional numerical model of baseline (support burners only) operation in a rotary kiln incinerator is presented. The focus of this model is on gas-phase fluid mechanics, neglecting solid waste combustion and radiative heat transfer. The model is compared to experimental data, and although relatively crude, it demonstrates remarkably good qualitative and quantitative predictive capability. The model demonstrates that thermal buoyancy is the cause of observed vertical stratification near the exit of the modeled kiln. The model also suggests that the addition of turbulence mixing air actually increases the degree of stratification rather than augmenting mixing, as had been previously suggested. Elucidating the mechanism by which this occurs has resulted in a reinterpretation of the experimental data. The model also suggests that there is probably a zone of recirculation across the kiln exit plane. A parametric study using the model shows that the location and quantity of leak air into the kiln have a major influence on the flow inside the kiln. The study suggests that preheating turbulence air may have little effect on gas-phase mixing. Overall, this modeling study has demonstrated that a relatively simple numerical model of a rotary kiln incinerator can provide valuable insight into the more » process, especially when used in conjunction with experimental data. 21 refs., 17 figs., 3 tabs. « less