Density Distribution Stability and Bubbling Behaviors in a Density-Based Air Dense Medium Fluidized Bed: An Experimental Study

The air dense medium fluidized bed separation provides an alternative approach for the coal cleaning and the pre-discharging of gangue from the coarse iron particles. Density distribution of the bed plays significant role in the density-based separation. Effects of the initial static bed height, particle size of the dense medium, and fluidization number on the density distribution of the fluidized bed were experimentally investigated. The overall bed density along the radial direction showed a relatively low distribution of 1.72-1.82 g/cm³ in the middle region and a relatively high distribution of 1.80-1.88 g/cm³ in the circular region of the bed. The overall bed density along the axial direction presented a relatively high distribution of 1.75-1.84 g/cm³ in the middle position and a relatively low distribution in the top and bottom positions of the bed. The bubbling behaviors within a two-dimensional fluidized bed were studied using a high speed dynamic camera and the digital image processing method. The results indicate that the bubbling behaviors were more intense at the top and bottom positions of the bed. Increasing the particle size of dense medium facilitated reducing the number of air bubbles and widening the diameter distribution of the air bubbles within the bed. The fundamental researches in this work further provide the basis for the popularization and application of this dry beneficiation technology in industry.