Abstract
The main objective of this work was the study of the fluidisation behaviour of a glass powder in order to allow its application by electrostatic pulverisation. The high density and the small diameter of the original product lead to bed channelling and slugging. To avoid these inconsistency problems, different fluidisation-aid techniques were experimented with: incorporation of easy-to-fluidise large spherical glass particles into the glass powder, the use of mechanical agitation and the addition of four different types of flow conditioners (or glidants). Four batches containing 1 w/w% of different fluidisation additives (two containing hydrophilic additives and two hydrophobic additives) were tested. Fluidisation additives were Aerosils®, which are nano-sized silica products. The quality of fluidisation was determined by monitoring the pressure drop through the bed during fluidisation experiments at decreasing air velocities.
Two sizes of spherical glass particles were used as easy-to-fluidise particles. Nevertheless, the fluidisation was not obtained by means of this technique. Using the stirring system, a better but still poor fluidisation was achieved, although its quality was improved by adding flow conditioners. An insignificant influence of the stirring speed on fluidisation was observed when using the fresh powder or batches containing hydrophilic fluidisation additives. Moreover, the influence of the proportion of additive was tested in six batches containing 0.1, 0.2, 0.3, 0.4, 0.5, and 1 w/w% of the agent, which led to the most satisfactory improvement in fluidisation behaviour of the glass powder.
