Electrohydrodynamic Atomization of Non-newtonian Liquids With High Solid Content: a Case Study for the Production of Powder.

Abstract

Electrohydrodynamic atomization (EHDA) is now a well-known technique among the researchers as a potential technique for industries. The technique uses electric fields to produce mono-dispersed charged droplets and ensures controlled production. The current work investigated the intrinsic aspects of Electrohydrodynamic atomization of non-Newtonian liquids with high solid content made from infant milk formula (IMF) powder. The aim was to determine the characteristics of sprays of IMF solutions with high solid content, compare them with characteristics of EHDA atomization of Newtonian liquids, and investigate the possibilities of out-scaling. In this context, the rheology and physical characteristics of IMF solutions at different solid content were determined. Then, a study of electrospray characteristics for each IMF solution was conducted in the dripping regime and in the jetting regime using a grounded nozzle and charged counter electrode. The visualization of the spray was done using a high-speed camera with backlight illumination. The results indicated that, in the dripping regime, an electric field influences formation of modes for solid content less than 40% w/w, which can be correlated to conventional electrospray modes. In the jetting regime, when the simple jet mode was operated at whipping break up produced small droplets compared to varicose break up. In regards to out-scaling the atomization of 55% w/w IMF solution, a thermal jacket system and a single nozzle with four orifices at 300 μm internal diameter each was manufactured. With this nozzle configuration, a throughput of ~3 L h-1 was achieved and droplets with broad size distribution (13 μm ≤ d ≤ 1900 μm) obtained. This was attributed to the whipping break up mechanism of the IMF electrospray jets. Further studies which should include carrying out tests in an evaporator with an aim of determining the properties of the product were recommended.