A new type of cylinder-electrode electrostatic coalescer with insulation was designed and developed. When the W/O emulsion flowed through the electrodes, under the applied electrical field, the tiny water droplets coalesced into bigger droplets and then settled out to separate. With the laboratory experiments, W/O emulsion separation characteristics was investigated. The relationship among the electrode diameter and length, electrical field intensity and water cut was investigated. Also the influence of these parameters was analyzed. It is shown that, without the electrodispersion happening, the coalescer separation efficiency of water-in-oil emulsion increases as the electric field intensity increases. Also the separation efficiency is influenced by the affecting time of electric field and the electrostatic force between the droplets in the water-in-oil emulsion. When the water content is low, the influence of electric field affecting time plays an important role and it’s proved that the longer the electric field affecting time, the higher the separation efficiency. Under the condition of high water content, the influence of electric field affecting time decreases. When the electrostatic force between the droplets in the water-in-oil emulsion increases, the separation efficiency also turns higher. The high-speed camera was used to observe and record the droplets’ size from the coalescer exit. It’s estimated that the droplets’ size increased dramatically. Accordingly, the new cylinder-electrode electrostatic coalescer showed high efficiency in the separation of diesel oil/water emulsion.

W/O emulsion,    , Coalescer,   ,  Cylinder electrodes,    ,  Separation efficiency