(121e) Optimization of Rotary Calcination Processes
Calcination is an energy intensive process whereby a particulate feed is thermally treated to bring about a desired chemical and/or physical transformation. This process is commonly carried out in a continuous rotary drum with heated walls. Developing better process understanding of calcination can significantly improve the quality of the end product as well as save energy and material costs. There is a lack of predictive models for material flow and heat transfer, however, particularly upon scale-up from the lab and pilot scale to the manufacturing scale. The two important indices for continuous calcination are: (1) the characteristic time of calcination in the cross-sectional direction and (2) the residence time of the particles in the calciner. While calcination performance is determined by the competition of both indices, desired performance can be obtained only when the residence time of the particles inside the calciner is longer than the time necessary for cross-sectional heat transfer. A combination of experiments and discrete element method (DEM) simulations are used to provide insight into the effects of operating conditions, geometry design, and material properties on residence time and heat transfer time. This presentation will discuss results of studies on these competing timescales and their implications for scale-up of continuous rotary calciners.