A steady state model of a rotary kiln incinerator

A simple steady state model for a rotary kiln incinerator operating under excess-air mode is developed and the resulting governing equations are solved numerically. The focus is to examine the effects of some usually ignored factors, including the thermal radiation between all enclosed surfaces in a kiln, the solid/gas reaction and the existence of surface flame, on the kiln behaviour, but to fit all experimental data exactly. The results demonstrate that, since the length/diameter ratio is small for a rotary kiln incinerator, the thermal radiation heat transfer is the most significant process determinant, and the usually adopted 'unity view factor' assumption might introduce serious errors. The effects of other factors, such as heat convection/conduction contributions, the enclosed surface emissivity, and the feed particle size, are only secondary. The thermal radiation exchanges between gas and exposed surfaces are also discussed.