The Effects of Rotary Kiln Operating Conditions and Design on Burden Heating Rates as Determined by a Mathematical Model of Rotary Kiln Heat Transfer

A mathematical model of heat transfer in a directly-fired rotary kiln is developed and used to examine the effects of operating and design parameters on burden temperature. The model includes a mean beam length radiation model and axial zoning. Conductive and convective heat transfer are also included. Radiation between immediately adjacent zones is permitted. Calculation of heat transfer rates is facilitated by the use of an electric circuit analogue. An iterative solution procedure is adopted to solve the energy balance equations.

At the conditions examined, the model predicts that coflowlng gas and solid streams result in higher average burden temperatures than do counterflowing streams. The moisture level of the feed is predicted to be a key operating parameter. The effects of kiln length, burden residence time, firing rate, and flame length are also examined.