Sonothickening: Continuous in-line concentration/clarification of fine particle suspensions by power ultrasound

A novel technique has been developed for the concentration of fine particle suspensions based on the transient response of particles smaller than 10 m u m to ultrasound. Sonically induced particle velocities have been measured and magnitudes of the sonic forces acting on a particle in a suspension ca lculated over a range of particle sizes, sound frequencies, sound intensiti es and suspension concentrations. Particle velocities of up to about 12 ms( -1) were obtained at the sonic transducer tip when the particle size is app roximately 1 mu m. The solid phase of the suspension acquired a higher velo city than the continuous Liquid phase, facilitating velocity difference as the mechanism of concentration. An in line concentrator for suspensions was designed, utilizing this relative velocity and the trajectory deviation of the particles in the acoustic field. Using the novel concentrator it has b een demonstrated that the concentration of suspensions could be increased b y up to 50% in a single pass through the radiation field. Power intensities between 40 and 60 W cm(-2) achieved the highest increases of suspension co ncentration. Operating and design variables such as feed velocity, feed con centration, particle size, ultrasonic intensity and frequency were investig ated experimentally.