Performance Evaluation of Ultrasonic Atomization Process for Ethanol Separation and Recovery

Ultrasonic atomization, a process of generating fine droplets through irradiation of high-frequency ultrasound to a gas–liquid interface from the liquid underneath, is applied to separating ethanol from its aqueous solution. Towards its practical use, the process of collecting in two cooling stages the ethanolenriched mist—generated via an ultrasonic atomizer (ultrasonic transducer operated at 2.4 MHz) with continuous feed of ethanol–water solution—using two cooling units in a series has been developed. The effects of operating conditions, especially cooling temperatures and gas flowrate, on ethanolenrichment and condensation characteristics are examined. It is found that the highly-enriched ethanol recovery could be attained in the 2nd stage by optimizing the 1stand 2nd-stage cooling temperatures (as moderate as 5°C and up to −10°C, respectively). Regarding the carrier-gas flowrate, ethanol-rich mist consisting of small-size droplets tends to be carried selectively in favor of lower gas flowrate. Nevertheless, the desired recovery of enriched ethanol—i.e., a highest possible value of the recovered quantity of ethanol as well as the recovery concentration itself—is expected to be obtained in the 2nd stage by raising the carrier-gas flowrate under the present operating conditions. While the proposed two-stage cooling process tends to collect rather an appreciable quantity of less-enriched ethanol solution in the 1st stage, it is the 2nd stage that assures the desired quality of enriched-ethanol recovery.