(569j) Model-Based Prediction of Drop-Drop Coalescence in an Electric Field

Electrocoalescence describes the phenomenon by which coalescence of an electrically conducting phase, dispersed in an insulating phase, is achieved by applying an electric field between a high voltage and a ground electrode. In separation technology, electro-coalescers help to enhance the performance of common sedimentation units. Since larger particles sink faster, coalescence of small droplets is desired so as to decrease the residence time, and thus, separator sizes. Although electro-coalescers are broadly applied in industry, i.e. for water-crude oil separation, the system behaviour is not yet fully understood. 

Coalescence enhancement of water droplets in oil emulsions is commonly contemplated for the separation of an aqueous phase dispersed in a dielectric oil phase with a considerably lower dielectric constant than that of the dispersed phase. The characteristics and geometry of the electrode system have a large impact on the performance of an electrostatic coalescer and are actually strictly linked to the type of the applied electric field and the emulsion used. Furthermore, addition of chemicals and heating has also been revealed to further enhance the electrocoalescence of water droplets. In this work, the coalescence of two water drops sinking in a dielectric oil phase at an applied high voltage, pulsed dc electric field, in particular with regards to the effects of pressure and temperature on coalescence performance is investigated. The developed model helps to recognise and prove approaches to electrocoalescence mechanisms, the dispersion flow direction with respect to the applied electric field, as well as the electric field configuration. A model development and experimental verification will be presented in detail.