Modeling of the Regenerative Heat Flow of the Wall in Direct Fired Rotary Kilns

Abstract

An analytical one-dimensional model was developed to predict the effect of the different kiln variables on the regenerative heat transfer by the wall in a rotary kiln. The basis of this model is introducing a lumped capacity layer with infinite conductivity in radial direction. The thickness of this layer is determined from the heat penetration in a semi-infinite body. The parameters considered are kiln diameter, rotational speed, filling degree, material properties of the wall, and gas-to-wall and wall-to-solid heat transfer. From the model, it can be concluded that in technical rotary kilns, the regenerative heat transfer by the wall is much smaller than the direct heat flow from the gas. Nevertheless, under the slumping condition and in laboratory kilns, the effect of the wall can be up to 40%.