Characterization of impregnated particles via powder rheology

This work presents a specific application of a new powder rheometer prototype, for the characterization of liquid-impregnated particles which are used in chemical engineering for gas treatment on fixed beds. This new type of rheological characterization can provide useful information about the surface state of the particles and could contribute to the optimization of the impregnation process. The rheometer, consisting of a stress-imposed rheometer coupled with a vibrating cell, generates a Brownian-like motion at a macroscopic scale which makes the sample behave as a non-Newtonian condensed fluid, and allows rheological property measurements of powders which are very sensitive to changes on their surface. Their rheological behavior and its relationship with the impregnation ratio have been analyzed for several samples having different impregnation ratios, thanks to a free volume structural model taking into account the shear rate, the frictional stress, the granular pressure, the vibration frequency, the vibration energy, the free volume distribution and the mass of the samples. The resulting interpretation suggests a stepped kinetic of impregnation: first the liquid adsorbs on the surface of the silica matrix, then it fills progressively the pores, and finally it coats the outer surface of the particles.