Use of Supercritical CO2 and N2 as Dissolved Gases for the Atomization of Ethanol and Water

Supercritical dissolved gas atomization (SDGA) is an atomization process in which a gas at temperatures and pressures above the critical point is used as the atomizing medium. The concept of SDGA has been applied mainly using CO2 as atomizing gas in various processes developed for the production of fine particles of pharmaceuticals, polymers, and chemical products and for the atomization of fuels. In this work, SDGA, using ethanol and water as the liquids to be atomized, has been experimentally studied. The spray characteristics, in terms of droplet size and distribution, have been investigated using a laser diffraction analyzer. Ethanol has been chosen due to the large miscibility with CO2 and for its wide use as a solvent in particle formation processes. The use of N-2 as an atomizing gas has been also studied. Very narrow droplet size distributions were produced down to 2.5 mu m. The properties of the liquid to be atomized (water or ethanol) showed a negligible effect on droplet size. The main parameter that influences droplet size is the gas to liquid mass ratio. Nitrogen has a better potentiality as an atomizing gas with respect to carbon dioxide.