Abstract

The drying behavior of suspension droplets is important in many industrial applications for the material processing, ceramic, chemical or food industry involving spray dryers. This fact is particularly significant for high load and temperature conditions close to those found in the mentioned industrial applications (Masters, 1991). In this work, the drying behavior of acoustically levitated multiphase droplets has been experimentally investigated. The experiments have been performed using ceramic suspensions like those used in the manufacture of porcelain tiles. The initial composition has a mean particle size and relative density of 3.25 m (standard size) and 2.7 respectively. An acoustic tube levitator modified to allow experiments at high temperature conditions has been used (Mondragon et al., 2009). The flow rate, temperature and relative humidity of this air stream can be controlled by an air conditioning system. A CMOS camera and a back-light illumination system are used to measure the droplet cross-sectional area and vertical position of the droplet during the drying process (Yarin et al., 1999, 2002; Kastner et al., 2001; Brenn, 2005). The effect of the flocculation state (flocculated-deflocculated), solid mass load (0.65 < YS < 0.70), particle size distribution of the porcelain composition (1.95 m < dP50 < 3.25 m), ambient air temperature (70ºC < T < 100ºC) and initial droplet volume (0.4 l < V0 < 0.7 l) on the mean porosity of the grain and its mechanical strength has been studied. The experimental results obtained indicate that the most important parameters to be considered for the porosity are the particle size of the composition and the initial solid mass load. The most important parameters to be considered for the mechanical strength are the initial droplet volume, the particle size of the composition and the initial solid mass load. High initial solid mass load and standard particle size distribution are the optimal conditions to obtain low porosity and high mechanical strength.