Ultrasonic

The use of ultrasonic (US) force field to aid both air- and liquid-based separation processes has gained an increasing recognition in recent years. The advantages expected from using US for separation processes include higher liquid removal rate, higher dry matter content in product, lower processing temperature, maintenance of product integrity, more selective product, and higher product recovery. In general, the passing of ultrasonic waves using suitable high intensity through air or liquid is accomplished by primary phenomena such as cavitation, radiation pressure, and secondary phenomena of a physicochemical nature such as dispersion, coagulation, and change in liquid properties. Only some US industrial separation applications, which are worth mentioning, are powder screens, cell separators, CERTUS-, Sofi-, Fractor-, Fuji- and Scamsonic-screening filters and Outotec Larox CC capillary action filter. The main reasons hindering large scale industrial breakthrough in US assisted separation techniques are nondevelopment of transducer technology, high energy consumption, problems to scale up the technology and control of erosion caused by cavitation at high ultrasonic intensities. The main focus of this paper is to present basic separation phenomena and some interesting separation applications connected to ultrasound.