Measuring segregation in fluidized bed with magnetizable and nonmagnetizable particles based on magnetic permeability

Abstract

Co-fluidization of two types of particles is frequently encountered in the chemical and energy industry. The segregation behavior between them is of great importance. The accurate determination of segregation index (S) for any gas velocity (Ug) from the experimental perspective is the first and critical step towards the deep understanding of such segregation. As for the fluidized bed with magnetizable and nonmagnetizable particles, a new method resting on the quick measurement of magnetic permeability in the corresponding settled bed was established to ease the measurement of S. The S-Ug relationship measured via this method almost coincided with that determined traditionally, demonstrating its rationality and good feasibility. This new method avoided the sampling of particles from the settled bed and subsequent separation of the two types of particles, thus eliminating many problems concerned in these two steps and being more efficient. The only caveat was that the relationship between S and magnetic flux density in the settled bed had to be calibrated first. Additionally, the obtainment of the settled bed that could represent the given Ug was found to be critical to the accurate measurement of S. The key lay in acquiring the stable and representative fluidization state, which was recommended to obtain via decreasing the gas flow from high values to the target Ug with a rate smaller than 1.23 × 10−4 m/s2. The slow decrease of Ug could leave the particles sufficient time to migrate to their stable equilibrium positions, which was usually hindered by the internal friction among themselves.