Numerical simulation of a gas-flotation oil–water hydrocyclone separator

Efficient oil–water separation of produced fluids from high water-cut oilfields requires significant improvement in hydrocyclone separation performance. In this work, computational fluid dynamics simulations were applied to analyze the influence of integrating gas flotation with hydrocyclone separation. To describe the internal flow behavior and the distribution of oil droplets in gas-assisted operation, the Mixture multiphase model together with the Realizable <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>k</mml:mi> </mml:math> - <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>ε</mml:mi> </mml:math> turbulence model was utilized. Based on a conventional liquid-liquid hydrocyclone, a porous medium region was incorporated into the large cone section to represent microporous walls for microbubble injection, thereby achieving the coupling of flotation and hydrocyclone separation. The results show that gas injection enhanced the separation efficiency from 83.56 % to 95.96 %. Moreover, microbubble size exhibited a pronounced influence on separation performance: smaller bubbles facilitated better oil-water separation. The optimal performance was obtained with an air bubble diameter of 5 μm, where the separation efficiency reached 97.73 %.