Rotary calcination is widely used in catalyst manufacturing and many other industrial processes. In this article, the influence of operational variables and material properties on the mean residence time (MRT), hold up, and axial dispersion was investigated in a pilot plant rotary calciner. Residence time distributions (RTD) of spherical, cylindrical, and quadrilobe catalyst particles were measured and contrasted. The Saeman's model was successfully applied to predict the experimental bed depth and the MRT as particles flowed through the calciner. It was observed that increasing the feed rate did not significantly affect the MRT. Results for the different particles indicated that cylinders and quadrulobes exhibited less axial dispersion than spheres due to the decreased flowability. A reliable method was developed to provide a reasonable RTD prediction in rotary calcination systems. (c) 2013 American Institute of Chemical Engineers AIChE J, 59: 4068-4076, 2013