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

Electro-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 electrospray 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 were specifically investigated on the size of the beads. Among the parameters studied, voltage had a pronounced effect on the size of the 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 by increasing the voltage in the range of 0-10 kV. However, within the middle part of this range, an unstable transition occurred from the dripping mode to the jet mode where the size distribution was wide. 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.