Study Parameters Affecting Size Distribution of Beads Produced from Electro-Spray of High Viscous Liquids

Elecro-Hydrodynamics (EHD) spray is an important process in many engineering operations such as ink-jet printing, spray drying and atomization (liquid jet in air), dispersion and emulsification (liquid jet in liquid). In this work the method of electro-spray was employed to form droplets from a high viscous sodium-alginate solution using constant DC voltage. The droplets were cured in calcium chloride solution to produce solid beads. The main objective was to extend the knowledge of EHD spray to high viscous and non-Newtonian liquids (1000-5000 mPa.s). However, the effects of electric field strength, nozzle diameter, flow rate and concentration of liquid on size of the beads were specifcally investigated. Among the parameters studied, voltage had a pronounced effect on the size of beads as compared to the flow rate, the nozzle diameter and the concentration of alginate liquid. The size of beads was reduced to a minimum value with increasing the voltage in the range of 0-10 kV. However, within this range, an unstable transition was also occurred from dripping mode to jet mode. Increasing the height of fall of the droplets improved the sphericity of the beads, because of the increase of flight time for the droplets to relax before gelation.

Keywords:

electro-spray , non-Newtonian and viscid liquids , constant DC voltage , alginate beads