A study of dynamic interfacial mechanisms for demulsification of water-in-oil emulsions.

摘要

Demulsification (emulsion breaking) is necessary in many practical applications such as the petroleum industry, coating, painting, and waste water treatment in environmental technology. Chemical demulsification is the most widely applied method of treating water-in-oil and oil-in-water emulsions and involves the use of chemical additives to accelerate the emulsion breaking process.; The stability of emulsions is largely affected by the nature of the interface/film and surfactant adsorption mechanisms. A modified surfactant adsorption model is described for ionic surfactant adsorption on the surface. Hydrodynamic and thermodynamic factors on the emulsion stability were briefly described.; A new technique has been developed to measure the static/dynamic film tension and film rheological properties (such as Gibbs film elasticity, film dilational modulus) of the emulsion and foam films. The measuring technology can be useful in studying the stabilization/destabilization mechanisms for the emulsion and foam films.; To understand the demulsification process, the film tension measurement was used. Using samples of actual crude oil emulsions and brine, the data presented for several commercial-type demulsifiers show a strong connection between good performance (fast coalescence) and dynamic film rheological properties. Measurements of dynamic interfacial tension and activities with a conventional drop-volume apparatus support the water/oil/water film results. Measurements of static interfacial tension fail to correlate with the performance data. The data provide useful insight into physico-chemical mechanisms needed to obtain rapid coalescence, and could help guide the development of higher performance demulsifiers. To understand the role of demulsifier (emulsion breaker) destabilization mechanisms, the effect of the single components of demulsifiers and their blends, the separation efficiency of water-in-crude oil emulsions in relationship to the oil emulsion film and oil/water interfacial rheology (such as dynamic film/interfacial tension and film/interfacial elasticity and the demulsifier film and interface diffusivity) were studied. The measurements were consistently made on systems with known oil, water and demulsifier chemistry. These measurements were then correlated with field performance data.; For the extensive work, particle-particle interactions inside the film were studied in emulsion stabilization/destabilization mechanisms.