Evaluation of the separation performance of an air dense medium gas-solid fluidized bed for coal cleaning: Effect of the binary dense media

Abstract

The binary dense media plays a significant role in the air dense medium gas–solid fluidized bed for coal separation. Magnetite powder with a narrow size fraction of −0.20 + 0.15 mm and −0.35 + 0.25 mm quartz sand were mixed in proportion to form a binary dense media. The separation performance of −13 + 6 mm coal was evaluated through the combination of various indicators of the yield and ash content of products, combustible material recovery, relative segregation degree, and probable error. Results suggested that the optimal separation performance was achieved by an adjustment of the appropriate operational gas velocities of the bed and use of the binary dense media with a suitable composition as the separating medium. The proportion of the quartz sand mixed in the binary dense media should be adjusted as 10% or 20% and the fluidization number could be varied from 1.6 to 1.8. The satisfactory ash content and yield of clean coal were 10.12% and 68.29%, respectively, with a combustible material recovery of 92.09%. The largest relative segregation degree was 0.95, and the minimum probable error was 0.085 g/cm3 with a standard deviation of 0.024 g/cm3. These findings indicated efficient coal cleaning.