Separation performance of desanding and deoiling hydrocyclones treating three-phase feeds: Effect of oil-particle aggregates

The study presents preliminary results on the separation of a three-phase (oil, particulate SiO2, water) feed by desanding and deoiling hydrocyclones. Optical microscopy confirms formation of oil particle aggregates (OPAs) of a range of morphologies. Presence of OPAs does not affect the efficiency of oil separation but lowers the efficiency of separation of solids. In both hydrocyclones, OPAs preferentially partition into the overflow stream so that oil and SiO2 can be viewed as the lead and the follower phases, respectively. A model is developed to calculate the fraction of the follower phase incorporated in aggregates. Applied to data from the desander, the model shows that similar to 30% to 40% of SiO2 is captured in oil/SiO2 aggregates and that the fraction does not depend on the split ratio. In contrast, during deoiling, the fraction of SiO2 locked up in oil/SiO2 aggregates does not exceed 10% and is lower at lower split ratios; these observations can be attributed to aggregate break-up in a higher shear flow in the deoiler.