Breakup Characteristics of Water-in-Oil Emulsion Droplets Influenced by a Rigid Interfacial Film in the Presence of a Polymer Surfactant

The emulsified feedstock technique derived from micro-explosion has been applied to improve the feedstock atomization of heavy oil during the catalytic cracking process. The strength of an interfacial film, which is vital for the stability of emulsion, can be enhanced by some polymer surfactants. In this study, n-hexadecane was chosen as the model oil. The effect of oil–water interfacial film properties on the high-temperature breakup of emulsified droplets was investigated, especially the interfacial film strength of water-in-oil (W/O) emulsion in the presence of a commonly used non-ionic surfactant and/or polymer surfactant (Arlacel-P135). The mean diameter of dispersed water and interfacial tension and interfacial film strength of emulsions were measured. Afterward, two breakup modes of emulsified droplets were revealed by the single droplet heating test, which are "micro-explosion" and "breakup after bubble expansion". The emulsified droplet stabilized by Arlacel-P135 is more prone to "breakup after bubble expansion" for the rigid oil–water interfacial film hindering the coalescence of dispersed water. The stability and oil–water interfacial strength of emulsions stabilized by mixed surfactants consisting of Span80, Tween80, and Arlacel-P135 were enhanced with the increase in Arlacel-P135 dosage. Moreover, the addition of Arlacel-P135 (0.2–0.5 wt %) significantly reduced the average breakup delay time (τ) of W/O droplets, since the bubble nucleation was favored by the interfacial film structure formed by polymer surfactant.