DISPERSION PERFORMANCE OF DRY POWDER BY R ING NOZZLE JET

When particle diameter falls below a few microns, particles tend to ag glomerate and hence to degrade the performance of air classifiers. The dispersion of agglomerated particles is a key technology to improve c lassification accuracy. The dispersion effect of a ring nozzle jet on dry powder was examined. Fine alumina and toner were used as the sampl e powders. The performance can be expressed by a dispersability index, based on the size distributions of the powder before and after disper sion. Both powder concentration and air velocity at the nozzle throat were found to affect the dispersion performance, the dispersing bounda ry being determinable from these values. Dispersing boundary curves fo r fine alumina (D50 = 1.0 mum) and toner (D50 = 6.4 mum) were obtained by experiments. Classification performance, classification sharpness and division indices, for fine alumina and toner powders were improved by mounting the disperser immediately in front of the classifier.