Comparison of devices used for continuous production of emulsions: Droplet diameter, energy efficiency and capacity

Abstract

Liquid-liquid emulsions are used in various sectors, including food, health care, personal care, home care and nutrition. There is an increasing need for developing equipment and devices for producing emulsions with desired drop size distribution (DSD) in a continuous mode of operation to fulfil market demands. In this work, we experimentally investigated droplet size distributions of emulsions made using selected cavitation-based emulsion producing devices operated in a continuous mode. Emulsion production devices considered in this work are wet mill, Soldo cavitator, Dynaflow cavitator and different scales of vortex based hydrodynamic cavitation devices. The continuous emulsion production experiments were performed for generating 5 % rapeseed oil-in-water emulsions using different devices. Performance of different emulsion production devices based on energy efficiency of emulsification $\left(\eta \right)$, energy consumption per kilogram of emulsion $\left(E\right)$, interfacial area created per unit energy consumption ${\left(A_{net}\right)}_P$, Sauter mean diameter $\left(d_{32}\right)$, other characteristic diameters $\left(D10,D50,D90\right)$, and drop size distribution (DSD) was compared. Among all the devices, vortex based hydrodynamic cavitation (HC) devices showed excellent performance in terms of lower $d_{32}$ and DSD with low $E$ and high $\eta$. The smallest scale of vortex-based HC device exhibited the highest efficiency (∼0.16 % at $E$ = 2.6 kJ/kg) over the entire range of $E$ compared to the other devices considered in this study. The presented data and analysis will be useful for selection of emulsion producing devices for desired emulsion characteristics and production capacity.