Phase separation of water-in-oil nanoscale emulsion using non-Laplacian electrostatic field

Oil-water separation of crude oil containing emulsified water droplets is a complex and intensive process in the oil and gas industry. Small micro- and nano-metric droplet sizes render gravity-based separation impractical. Conventional electro-coalescers using immersed electrodes for oil-water separation must limit their applied electric field to avoid electrical shorting, making them ineffective for coalescing nanoscale droplets. Environmentally toxic demulsifying chemicals are thus used to further promote coalescence, but the process effluent reaches water bodies including the ocean and fresh water. In this talk, we demonstrate a significantly more effective electro-coalescence method based on corona discharge that drastically enhances the rate of phase separation of nanoscale emulsions and eliminates the use of toxic demulsifiers. By introducing a space charge emitter electrode with an air gap separating the electrode and the emulsion, we can avoid droplet-mediated electrical shorting and apply ~8 times stronger electric field, resulting in much faster phase separation of nanoscale water in oil emulsions for water cuts between 2% and 20%. We visualize the droplet chaining and coalescence events and demonstrate that the rate of oil-water separation via electrocoalesence scales with the square of the applied electric field. Last, we design a practical embodiment of a corona-demulsifier which enables rapid, continuous oil-water separation of nanoscale emulsions.