Huang Xin, He Limin, Luo Xiaoming, Xu Ke, Lü Yuling, Yang Donghai
College of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao 266580, China.
Surface Engineering Pilot Test Center, China National Petroleum Corporation, Daqing 163000, China.
Langmuir. 2020 Dec 1;36(47):14255-14267. doi: 10.1021/acs.langmuir.0c02371. Epub 2020 Nov 18.
Electrocoalescence technology is an important method for the demulsification of crude oil emulsion, but its development is restricted by the short circuit caused by droplet chain formation. To reveal the formation mechanism of droplet chains, the electrocoalescence behaviors of two droplets and droplet clusters under pulsed direct current (DC) electric fields are experimentally studied. The two droplets usually successively undergo complete coalescence, partial coalescence, and noncoalescence as the electric field strength increases. The critical electric field strengths for complete coalescence under pulsed DC electric fields with different frequencies are obtained. The effects of the electric field waveform and frequency on the noncoalescence characteristics of two droplets and the stability of droplet chains are explored. The droplet chains under a high-frequency electric field are more stable and longer than those under a low-frequency electric field due to the reduction of the movement distance and the generation of daughter droplets from tip streaming. The reversal of the composition of electric forces due to charge transfer is the fundamental mechanism of noncoalescence of two droplets and chain formation in the emulsion under a pulsed DC electric field.
电聚结技术是原油乳液破乳的一种重要方法，但其发展受到液滴链形成导致的短路限制。为揭示液滴链的形成机制，对脉冲直流电场作用下两个液滴及液滴簇的电聚结行为进行了实验研究。随着电场强度增加，两个液滴通常依次经历完全聚结、部分聚结和不聚结。获得了不同频率脉冲直流电场下完全聚结的临界电场强度。探讨了电场波形和频率对两个液滴不聚结特性及液滴链稳定性的影响。由于运动距离减小和尖端流产生子液滴，高频电场下的液滴链比低频电场下更稳定、更长。电荷转移导致电力组成的反转是脉冲直流电场下乳液中两个液滴不聚结及链形成的基本机制。
