Use of a magnetic fluidized bed in studying Geldart Group B to A transition

This paper presents a study of the transition of fluidization behaviour fro m Geldart Group B to A, through imposing a magnetic field on a fluidized be d of 0.141 m internal diameter. Iron particles of 330, 800 and 1600 mum in diameter were used as bed solids. The magnitude of the interparticle attrac tive force was varied by adjusting the electrical current through a pair of Helmholtz coils. The minimum fluidization and minimum bubbling velocities were obtained for various field intensities, enabling determination of the boundary between Group B and A behaviour. The characteristic interparticle forces at the B/A boundary were determined by establishing the relationship between interparticle force and the electrical current through the field c oils. It was shown that the B/A transition occurred at the interparticle fo rce to fluid drag ratio of about 2.5 for the three types of particles used. Analysis shows that these values are comparable with those for fine powder s. (C) 2001 Elsevier Science Ltd. All rights reserved.