(52c) Modeling of Heat Transfer in Rotary Calciners

Rotary calciners are commonly used in industry to achieve high-temperature chemical reactions or a phase change for granular systems. Many industries use rotary calciners for applications such as sintering limestone to make cement, or calcining petroleum coke in refining.  Though operational cost of the calciner is high, the design of calcination units is often conservative because many fundamental physics about the calcination process are widely unknown.  If a fundamental physical understanding of both solids flow and heat transfer within the calciner were attained, rotary calciners could be optimized for higher output and/or reduced operational cost. The objective of this presentation is to provide a fundamental understanding of heat transfer within the rotary calciner.  Discrete element method (DEM) modeling is used with a heat transfer code to study the heat transfer regimes within a rotary calciner heated at the walls.  Additionally, an analytical model is proposed for one heat transfer regime.  The analytical model describes the temperature profile within the granular bed of a rotary calciner.  The model assumes that the calciner operates within the rolling mixing regime, has no flights or baffles, and heat transfer from radiation and gas convection are small.  The analytical model provides a simple “back of the envelope” solution to the conduction heat transfer problem within the rotary calciner to take the place of time-consuming DEM simulations.