3D-DEM-CFD simulation of heat and mass transfer, gas combustion and calcination in an intermittent operating lime shaft kiln

The model has been applied to an industrial PFR-kiln of 18 m height. A realistic particle size distribution of the limestone with particles ranging from 50 to 90 mm has been set. Methane combustion provides the heat for calcination and is simulated by a two-step mechanism. Simulation results show a nearly uniform temperature distribution in the calcination zone but significant inner particle temperature gradients. The calcination degree depends on the particle location within the kiln and decreases towards the outer kiln walls. Measured and simulated temperatures are compared. Maximum temperature values as well as its characteristic oscillation induced by the periodic kiln operation could be reproduced by the simulation, especially keeping in mind the difficulties of thermocouple measurements under the harsh conditions in industrial reality.