基于界面动力学理论的电场中液滴聚并机理研究

The high-effective coalescence of water droplets under electric field is a challenge of dehydration of crude oil in petroleum production process, and it is also a technical key to enhance the efficiency of oil-water separation. However, the classical theory of electrostatic coalescence which takes the continuous phase or the dispersed phase as studied object can hardly give reasonable scientific explanations to many special phenomena due to the chemical flooding. The fundamental reasons that impede the electrocoalescence of water droplets in high efficiency are the properties of oil/water interfacial film, such as viscoelasticity etc. Therefore, the most direct and effective method to solve the problems mentioned above is to study the electrocoalescence mechanism of water droplets from the aspect of interface dynamics. Based on the point, this subject is going to discuss the dynamics of oil/water interfacial film during the electrocoalescence process of water droplets, such as the motion, instability and coalescence. By combining theoretical analysis with experiments adopting high speed microscope photography technology and considering thermal movement and interactions of molecular as well as interfacial structure, the rules of dynamics of oil/water interfacial film responding to electric field are explored at the micro- and nanoscale, which deeply reveal the influence of the properties of oil/water interfacial film on the deformation, break-up and coalescence of water droplets under the electric field. The model combining electro-hydrodynamic with interfacial dynamic theory is established to interpret the mechanism of electrocoalescence of water droplets at the level of dynamics of interface. Finally, the scientific methods to promote the efficiency of oil-water separation under the electric field will be presented. The multiphase interfacial behaviors studied in this research belong to the category of micro- and nanoscale, therefore, the research results are important for the improvement of basic theories system of multiphase separation, which will provide theoretical basis for enhancing the efficiency of electrostatic dehydrator and designing of the new and efficient electrostatic coalescer.

提高电场作用下油中水滴的聚并效率是原油电脱水的难点与技术关键。以体相为研究对象的静电聚并理论，难以解释界面膜粘弹性所引起的聚并障碍等科学问题。因而，从界面动力学角度对水滴聚并机理进行研究是解决该问题的最直接方法。本课题拟针对油中水滴静电聚并过程中界面膜的运动、失稳及融合等界面动力学问题，采用理论分析与高速显微试验相结合的研究方法，综合考虑界面分子热运动、交联结构变化以及分子间作用力等因素，在微纳尺度上探索电场激励下油水界面膜的运动响应规律及失稳机理，揭示界面膜性质对水滴变形与破碎的影响机制，建立水滴聚并的电水动力学-界面动力学耦合模型，从界面动力学层面深入阐释静电聚并机理，得到提高静电聚并效率的科学方法。本课题属于多相界面行为的微纳尺度研究范畴，研究成果对完善多相分离基础理论体系具有重要作用，为提高电脱水器的分离效率和研发高效电脱设备提供科学依据。

根据任务书的研究内容，构建了微观实验系统和微液滴制备系统，对不同电场参数、物性参数下油中水滴的变形、破裂和聚并等微观行为进行了深入研究，基于经典力学和界面流变学理论，揭示了油中水滴变形、破裂和聚并的内在机制。主要研究成果如下：.（1）建立了电场作用下纯净液滴界面膜变形的理论模型，得到了纯净界面的运动模式相图，明确了液滴振动模式间的转变规律，揭示了界面膜性质对纯净界面瞬态响应过程的影响机制。.（2）基于纯净界面运动模型与界面流变学本构方程相耦合，实现了对粘弹性界面运动过程的理论描述，从界面动力学角度揭示了界面粘弹性对界面瞬态响应过程的影响机制。.（3）明确了液滴发生破裂行为的临界条件。研究了物性参数、电场参数对于液滴破裂形式的影响，得到了液滴破裂模式相图，揭示了影响液滴破裂特征的主要因素，提出了抑制液滴破裂的方法。.（4）基于弹塑性力学中的应力-应变关系，分析了液滴轴向拉伸的力学性能，利用弹性模量对液滴的破裂形式进行划分，利用应力-应变理论阐释了高强电场中液滴破裂的动力学机理。.（5）探究了物性参数、电场参数对于液滴不聚并的影响，得到了液滴聚并-不聚并的电场强度相图，阐明了界面膜性质、液滴放电对液滴不聚并的影响机理，提出了促进液滴聚并的方法。.（6）完成了液滴聚并过程界面动态响应规律的研究，得到了粘性控制模式下界面特征、聚并时间的演变规律，揭示了界面膜性质和电场参数对液滴界面演变的影响机理。.研究成果完善了静电聚并理论体系，为新型静电聚结设备的研发提供了有力的理论指导。项目研究期间，参加国内外学术会议6次，做会议报告9次；发表SCI论文25篇（二区14篇，三区8篇）、EI论文2篇；申请国家发明专利6项，已授权4项。