Numerical Simulation of Pellet Drying Process in Updraught Drying of Chain Grate Based on CFD-DEM

The quality of the iron ore pellet and the yield of its drying process are directly affected by the drying condition. Such conditions are complex to be predicted or measured due to the heat and mass transfer process of the pellet in chain grate. However, it is difficult to measure the temperature and drying rate of the pellets directly due to the high temperature and the sealing of chain grate. In this paper, a model is established based on the computational fluid dynamics—discrete element method to describe the heat and mass transfer in updraught drying (UDD) in chain grate. The distribution of temperature field and the change of pellets drying rate in UDD are calculated and analyzed. The results indicate that the temperature gradient of pellet bed increases and the water content gradient decreases in movement direction and height direction of pellet bed. The temperature increasing rate and drying rate of the pellet bed show a trend from increasing to decreasing, and this is consistent with previous research. During this period, the temperature of pellet reaches a maximum value of 316 K and the drying rate of pellet reaches a maximum value of 0.42 kg/(m3 s). In addition, the temperature and the drying rate change little in the direction of width of pellet layer, which proves the rationality of simplifying UDD into a two-dimensional model. The proposed model can be used to predict the properties of the pellet drying process and optimize the process parameters.