Experimental Verification of Solid-like and Fluid-like States in the Homogeneous Fluidization Regime of Geldart A Particles

The mechanisms underlying homogeneous fluidization of Geldart A particles have been debated for decades. Some ascribed the stability to interparticle forces, while others insisted a purely hydrodynamic explanation. Valverde et al. (2001) fluidized 8.53-mu m (i.e., Geldart C) particles by the addition of fumed silica nanoparticles and found that even during homogeneous fluidization both solid-like and fluid-like behavior can be distinguished. However, it is still unclear whether both states exist for true Geldart A particles. In this paper, the particulate fluidization characteristics of three typical Geldart A powders were studied by camera recording, electrical capacitance tomography, and pressure fluctuation. For the first time, the existence of both a solid-like state dominated by interparticle forces and a fluid-like state dominated by fluid dynamics during homogeneous expansion of Geldart A particles was experimentally verified. Furthermore, the ability and performance of the used measurement techniques to identify different flow regimes were compared.