Analyses of multi-size particle mixing behavior in an ore pre-reduction rotary kiln by discrete element method

The particle distribution in pre-reduction rotary kiln directly affects the reduction process of iron ore, and in-depth understanding of the mixing behavior is helpful to improve the product quality and productivity. The present work focused on the mixed dynamics of multi-component and multi-size systems in rotary kiln using discrete element method (DEM). We first confirmed that the final particle distribution and mixing degree are independent of the initial particle distribution, and then further discussed the influence of the key operating parameters such as rotating speed, average size ratio and filling degree on mixing behavior. The size segregation pattern of three components shows that the large particles segregated to the outer region, while the small particles were concentrated in the core region, forming an annular distribution with different particle sizes. Furthermore, the results also indicate that the rotational speed and fill degree show strong influence on the mixing time and have little influence on the mixing quality. Conversely, the average size ratio significantly affects on the mixing quality. The particle segregation is suppressed and the coal and iron ore particles are well mixed together for the whole bed when the average size of coal particles is smaller than that of iron ore particle. The findings of this work provide a reference for controlling and optimizing the particle mixing process in prereduction rotary kiln. (authors)