Experimental and numerical analysis for the derivation of a dynamic solid bed model in rotary drums considering mixing and segregation processes

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In a process simulation for rotary kilns always transient start-up procedures appear. During the process segregation effects and different motion behaviors arise inside the bed, which are caused by the change of the filling degree and the material properties. The heat penetration into the bed is transient due to the incomplete mixing, whereby a temperature difference between the core and the surface is emerged. Furthermore the transient behavior occurs by the change in mass flow, the type of fuel, the flame control and the energy input.In this project, the existing experiences, experiments and tools of the two research institutes will be used to model the segregation and mixing behavior of mono and poly-disperse solid beds in the cross section of a rotary kiln. This model will represent the transient heat transfer into the bed and the temperature distribution in the bed in dependence of the particle size, the material properties and the operational parameters. The dynamic model (unit operation module) will then be converted into a corresponding flow sheet simulation.Starting point of the work are several experiments and phenomenological models derived therefrom, which were developed for steady state situations by one of the two research groups cooperating on this topic. The transfer of this knowledge to particulate flow systems, reflecting in a time resolved manner the effect of transient inner and outer boundary conditions, will be carried out by the second partner, using of particle based Discrete Element (DEM) simulations, which allow a rigorous description of the underlying physical processes. These simulations will be verified with already available steady state experiments and new, transient investigations conducted within the planned project. The results obtained will be introduced into the unit operation module under development and will be used to complement and modify the already known relations and equations.