Prediction of conductive heating time scales of particles in a rotary drum
AUTHOR(S)
A. Cuitiño, B. J.Glasser, F.J. Muzzio, H. N. Emady, K. V. Anderson, W. G. Borghard
PUBLISHER
Elsevier
SOURCE
Chemical Engineering Science
YEAR
ABSTRACT
Modeling conductive heat transfer from rotary drum walls to a particle bed via discrete element method simulations, three time scales were determined: 1) the characteristic heating time of the bed, τ; 2) the particle thermal time constant, τp; and 3) the contact time between a particle and the wall, τc. Results fall onto a monotonic curve of τ/τc vs. ϕ (τp/τc), with three heating regimes. At low ϕ, conduction dominates, and the system heats quickly as a solid body. At high ϕ, granular convection dominates, and the bed heats slowly at a nearly uniform temperature. At intermediate ϕ, the system heats as a cool core with warmer outer layers. The results of this work have important implications for improving the design and operation of rotary drums (e.g., energy-intensive calcination processes). By calculating τp and τc from material and operating parameters, the characteristic heating time, τ, can be predicted a priori.
KEYWORDS
Calcination, catalyst manufacture, Conduction, heat transfer, particle technology