Coalescence and Break-Up Behaviors of Nanodroplets under AC Electric Field

Abstract

Water must be separated from water-in-oil (W/O) emulsion because of the corrosion it brings to the relative equipment in the process of transportation and storage. It is an effective method to apply external electric field to achieve high performance of separating small, dispersed water droplets from W/O emulsion; however, the coalescing micromechanism of such small salty droplets under AC electric field is unclear. In this paper, molecular dynamics simulation was adopted to investigate the coalescence and separation process of two NaCl-aqueous droplets under AC electric field and discuss the effect of AC electric field frequency, as well as the time required for contacting, the critical electric field strength, the dynamic coalescence process and the stability of the final merged droplet. The results show that the critical electric field strength of the droplet coalescence increases with the increase of frequency, while the time required for droplet contacting becomes shorter. The shrinkage function curve was applied to characterize the droplet coalescence effect and it was found that the droplets coalescence and form a nearly spherical droplet under the AC electric field with a frequency of 1.25 GHz and strength of 0.5 V/nm. When the electric field frequency is 10 GHZ, the merged droplet presents a periodic fluctuation with the same period as the AC electric field, which mainly depends on the periodic movement of cations and anions under the AC electric field. The results can provide theoretical basis for the practical application of electrostatic demulsification technology in the petroleum or chemical industry from the microscopic perspective.

Study on the Performance of an Electric-Field-Enhanced Oil–Water Separator in Treating Heavy Oil with High Water Cut

“…When the droplets passed through the rectangular channel of the VIEC module, they were subjected to electric field force. According to the studies of Song et al on the numerical simulation of droplets, the electric field force on the droplets can be expressed, using the Maxwell stress tensor [25], as follows:…”

Directionality and additivity effects of molecular acidity and aromaticity for substituted benzoic acids under external electric fields

“…Essential in many chemical and physical phenomena and processes, the impact of external fields has attracted noticeable attention lately in the literature 1–16 because it can influence the molecular structure, 17–22 chemical reactivity, 23–28 and other electronic properties. 29–34 In a previous study, we investigated the impact of uniform external electric fields on molecular acidity and aromaticity propensities for the benzoic acid molecule.…”