Fluidization Characteristics of a Fine Magnetite Powder Fluidized Bed for Density-Based Dry Separation of Coal

Gas-solid fluidized bed separation technique is very beneficial for saving water resources and for the clean utilization of coal resource. The hydrodynamics of 0.15-0.06 mm fine Geldart B magnetite powder were experimentally and numerically studied to decrease the lower size limit. The results show that the static bed height should be controlled near 300 mm (e. g., 300-350 mm). The bubble size, amount, and frequency of the fine particle bed are smaller than those of the bed containing 0.3-0.15 mm large Geldart B particles, thus leading to a higher bed activity. The pressure drop and density of the fine particle bed are uniform and stable, which indicates a good fluidization quality. Furthermore, simulated results are consistent with experimental data, which indicates the correctness and effectiveness of the simulations. The superficial gas velocity should be adjusted to not more than 1.8U(mf) for the fine particle bed. Additionally, wide size range magnetite powder, which contains 94.23 wt% < 0.3 mm particles with a 0.3-0.06 mm particles content of 91.38 wt%, was used in an industrial scale modularized demonstration system for 50-6 mm coal density separation. The ash content of feed coal was reduced from 55.35% to 14.67% with a probable error, E, value of 0.06 g/cm(3).