An investigation of the effect of the interparticle forces on the fluidization behaviour of fine powders linked with rheological studies

This paper reports on an extensive experimental campaign aimed at studying the influence of interparticle forces on the fluidization behaviour of fine group A powders by changing the size distribution of the fine sub-cuts (particles below 45 m) and with increasing temperature. The fluidization behaviour of an alumina powder was investigated at temperatures ranging from ambient up to 400 ◦C and by adding to the material previously deprived of fines two fine sub-cuts of nominal size 0–25 m and 25–45 m, respectively. Four samples were investigated, containing 22% and 30% wt of fines and having similar particle size distribution but shifted towards smaller and bigger fines sub cuts. Fluidization and rheological tests were performed in parallel. Results obtained from pressure drop profiles, bed expansion profiles and bed collapse test were linked to the rheological analysis of the failure properties of the materials. The static angle of internal friction , the effective angle of internal friction e, cohesion C, the angle of wall friction w and wall adhesion A, the dynamic angle of internal friction and dynamic cohesion C were determined to underpin the role of the interparticle forces on the ability of the powders to flow and to their fluidization quality when adding small or big fines to the material.