Ultrasonic zeppelin-shape transducer for algae oil extraction

Abstract

Energy consumption worldwide is increasing each year. Alternative energy sources supplement these energy demands. Algae are one of such alternative energy sources. As oil needs to be extracted from the ground, algae are needed to be prepared for bio-fuel production. There are a few methods that are used for algae to crack open: chemical and mechanical. Among mechanical methods, the one that is suitable for that purpose is ultrasonication. The current paper presents an ultrasonic cylinder-shape transducer designed for that purpose. Commercial piezo-mechanical systems for algae processing are mostly ordinary longitudinal transducers. The efficiency of such systems is based on irradiation surface, which is normally about 1000 mm(2). In our system, we propose a different approach to increase the vibration area that produces a cavitation field needed to crack the cell wall of algae. Normally, the active end of transducers is immersed into a reservoir filled with algae-liquid mixture. We propose to create a vibrating reservoir as a part of transducer, thus enlarging the area of acoustic irradiation. Excitation is produced by two full-wave longitudinal transducers orientated opposite to each other and connected to a specifically designed resonant chamber. Experiments have been carried out using two colonial algae species, namely Scenedesmus acutus Meyen and single-cell Monoraphidium griffithii. Comparative experiments have been performed using the standard commercial ultrasonic system for algae processing and the proposed system. The key parameters obtained from the experiments include power consumption and destruction rate.