Demulsification characteristics of electrostatic–swirling coupling enhanced migration

Currently, achieving efficient demulsification of water-in-oil emulsions using physical methods is a great challenge in the field of oil–water separation. Herein, an electrostatic–swirling demulsifier, designed based on the principle of enhancing droplet migration through electrostatic–swirling coupling was combined with electrode insulation modification to regulate the droplet capture mode. Through multiphysics simulations and experimental tests, it was first clarified that the electric field force dominates the migration of water droplets to the side wall in the electrostatic–swirling coupling. The electric field force is 1.43-4.11 times of the centrifugal force. Secondly, the relationship between the migration trajectory of droplets, electric field, surface charge density, and continuous phase characteristics was articulated. The migration trajectory is affected by various factors. As the voltage (1 kV to 8 kV), surface charge density (1 × 10^-5C/m² to 5 × 10^-5C/m²) and continuous phase viscosity (11 cP to 6 cP) change, the migration time and angle of water droplets decrease significantly, from 52 ms and 210° to 14 ms and 50°, respectively. This shift causes the “collision site” to move far away from the continuous phase outlet, enabling the insulating modified film on the side wall to quickly capture and separate the water droplets. Further investigation into the macroscopic demulsification characteristics revealed that the separation efficiency of the dual-field coupling electrode insulation modification system increased from 11.84 % to 95.75 % after applying 5 kV voltage to the emulsions containing 600–2200 mg/L water. This study provides a new approach for compact and efficient demulsification of oil–water emulsions.