Geldart A⁻ particles: Hydrodynamics of Geldart A magnetite powder with modulation by ultrafine coal particles in Gas-solid Fluidized Bed Coal Beneficiator (GFBCB)

The Gas-solid Fluidized Bed Coal Beneficiator (GFBCB) is an important technology used in the dry coal beneficiation process, which requires lower bed density and very uniform density distribution. Geldart A⁻ particles, Geldart A magnetite particles “modulated” by a small fraction of Geldart C ultrafine coal particles, is proposed. Fundamental studies are carried out to provide a comprehensive understanding of its hydrodynamics, including the minimum fluidization velocity, bed expansion, and spatial bed density distribution. By adding the ultrafine coal particles, the minimum fluidization velocity (U_mf) is lowered, with a modified U_mf correlation proposed, the bed expansion drastically increased (by up to 30%), with more gas being retained in the bed for improved flowability, and the corresponding bed density decreased to 1600–2000 kg/m³, with more uniform distribution, all contributing to a more desirable separation environment for coal beneficiation.