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

[Display omitted] • New method based on magnetic permeability was established to measure segregation. • Sampling of particles from settled bed and subsequent separation could be avoided. • S - U g curves determined as per new/traditional methods coincided with each other. • Key to measuring S for a U g lay in getting corresponding stable fluidization state. • Stable fluidization state can be obtained via reducing gas flow slowly to given U g. 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 (U g) 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 - U g 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 U g 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 U g with a rate smaller than 1.23 × 10−4 m/s2. The slow decrease of U g could leave the particles sufficient time to migrate to their stable equilibrium positions, which was usually hindered by the internal friction among themselves. [ABSTRACT FROM AUTHOR]