Hydrodynamic study on magnetized fluidized beds with Geldart-B magnetizable particles

Abstract

When Geldart-B magnetizable particles are fluidized under the simultaneous influence of the gravitational field and the magnetic field, there appear several flow regimes with different hydrodynamic behaviors. The present study focused on the hydrodynamics in the magnetized fluidized bed (MFB) flow regime. The applied magnetic field was axial, uniform, and steady; with Geldart-B iron particles as bed material experiments were conducted in both 2D and 3D beds. According to the gas–solid flow hydrodynamics, the MFB flow regime could be further divided into two distinguishable sub-regimes: magnetized-bubbling regime and channel-bubbling regime. In the channel-bubbling sub-regime, fluidization quality deteriorated due to the channel formation. In the magnetized-bubbling sub-regime, bubble sizes decreased while bubble frequency increased with increasing magnetic field intensities; fluidization quality was gradually improved. Meanwhile, bubbles were severely suppressed in the lateral direction, causing the change in bubble shape from nearly round to elliptic. Several reasons for both bubble size reduction and bubble shape change were analyzed. In addition, a new operational phase diagram was drawn to provide a panoramic view of the fluidization behaviors of Geldart-B magnetizable particles under the action of uniform magnetic fields.