Application of Cavitation Based Micro-Bubbles to Recover Neutrally Buoyant Oil Droplets

Small neutrally buoyant oil droplets are difficult to remove from water under any condition, but this difficulty is compounded in oil spills in open water. While floating oil can be collected using several existing methods, there are currently few practical methods for recovering neutrally buoyant oil dispersed in the water column. In this work, a large number of cavitation generated microbubbles, small enough to attach to oil droplets and large enough to help the droplets rise to the surface in a timely manner were effectively used for oil recovery.

Bubble generators using special nozzle designs induced cavitation in submerged water jets creating cavitation, bubble shearing and break up, and generated masses of poly-dispersed bubbles, ranging in size from a few microns to 300 microns. The generators used vortex cavitation initiated in swirl chambers. The bubble sizes and numbers produced were measured by means of image analysis of high speed videos. The effects of the various operating conditions on the bubble size distributions were investigated. The recovery of three types of crude oils from water under various salinities and bubble concentrations was measured.