Comparison of hydrodynamics in a gas-solids fluidized bed with binary particle systems for dry coal beneficiation

Abstract Fluidization behaviour of two binary particle systems, magnetite225-sand225 (M225-S225) particles with the same mean diameter (dp) and magnetite225-sand304 (M225-S304) particles with the same aerodynamic diameter (da) were observed in a two-dimensional fluidized bed. The number, size and rise velocity of gas bubbles in the binary fluidized bed were characterized by image analysis. A decreasing minimum fluidization velocity (Umf) with increasing sand volume fraction was found in the M225-S225 system while a nearly constant Umf was found in the M225-S304 system. Increasing trends of both bubble size and bubble rise velocity along the bed height were detected and a linear correlation between the bubble size and rise velocity was found for binary systems. The higher the fraction for one type of particles in the binary system is, the closer to the corresponding single-component system the hydrodynamic phenomena and bubble properties will be in both binary systems.