(391c) CFD Simulation of Bubble Enhanced Hydrocyclone for Air-Water System Encountered in De-Oiling

De-oiling hydrocyclone has been used for years for its high capacity and separation efficiency. Recently, the applications are reported of air bubble enhanced hydrocyclone in removal of emulsified oil from water. This method, integrating hydrocyclone with flotation, is also worthy of consideration in biomass separations, such as algae harvest, especially oriented to bio-diesel collection. With the help of micro bubbles, the  separation efficiency of oil increased about 15% at the reportedly optimal air-liquid ratio for this purpose. In this work, a 3D CFD model was built to investigate the flow patterns of water and air bubbles in a 35mm bubble enhanced hydrocylone. The simulated velocity distribution was compared with experimental data and it showed a good agreement. It was found that the air fraction at underflow increased and the bubble removal became lower when the air-liquid ratio increased from 0.025% to 0.3%.  This result implied that more bubbles attached with oil could be in the underflow of the hydrocyclone, which provided one possible reason for the existence of the optimal air-liquid ratio.

Further more, this paper discussed the higher air-liquid ratio, i.e., the higher concentration of bubbles, which might increase bubble aggregation to form larger bubbles. Larger bubbles facilitate their removal because of higher rising velocities. To predict the process more accurately, CFD simulation including a population balance model is recommended.