Study On Oil-Water Interface Characteristics And Drop Interaction Forces

Oil-water interface is widely existed in the traditional onshore crude oil exploitation and production,oil gathering and transportation,station and field processing,as well as the rising offshore oil development and other processes.The existence of natural or artificial surfactant decreases the surface free energy,and the oil-water two-phase is easy to be mixed and dispersed stably.As a result,it's extremely difficult to achieve oil-water separation with different water content,mine gathering and transportation and sewage treatment under the effect of surfactants.At present,most of the studies on the emulsified oil-water interface are mainly focused on the demulsification efficiency,but the understanding of the microscopic mechanism of oil-water interface is insufficient.The existence of a large number of surfactants increases the risk of corrosion in the pipeline and storage tank,which also increases the difficulty for subsequent refinery processing and sewage treatment.As a result,the energy consumption is increased,which is not conducive for energy conservation and emission reduction.In order to analyze the above problems,the key is to carry out the research on the microcosmic mechanism of oil-water interface,including the research on dynamics and coalescence behavior between dispersed droplets and the regulation methods of dynamic behavior of surfactants absorbed on oil-water interface.In this paper,the dynamic microcosmic mechanism of deformable oil-water interface is studied.Based on the mechanical behavior between dispersed droplets and interface properties under the influence of surfactant,the dynamic interaction law of droplets under controllable collision rate is studied.Firstly,the drop probe technique is is used to directly measure the interaction force of drop/drop and drop/surface under the influence of surfactant by coupling with Atomic Force Micriscopy(AFM).Furthermore,the mechanical behavior of droplets immersed in solutions with the presence of macromolecular polymers and aggregates is studied by AFM in combination with liquid-phase displacement technology for displacing liquid-phase environment.The drop interaction forces under controllable collision rate is predicted and analysed,considering the influence of oil-water interface deformation on drop collision rate and the surface force,including the van der Waals force based on Lifshitz theory,the electrostatic double-layer force based on Poisson Boltzmann theory.The influence of surfactant and polymer aggregates in the complex phase environment on drop interaction is expounded from a microscopic perspective.The interfacial collective diffusion coefficient,equilibrium interfacial concentration and convection diffusion behavior of absorbed surfactant are quantitatively described.The dynamic distribution of surfactant at the interface and the influence on the force during the drop interaction are simulated by coupling the effect of fluid flow inside droplet.Meanwhile,the regulation of underwater oleophobicity of polyelectrolyte covered surface is achieved.The adhesion force between oil droplet and oleophobic surface underwater is measured by AFM,which is an important way to characterize the degree of underwater oil repellency on solid surface.