Breaking of Emulsions with Chemical Additives: Using Surrogate Fluids to Develop a Novel Theoretical Framework and Its Application to Water-in-Crude Oil Emulsions

Abstract

We investigate the role of adding a water-soluble surfactant (Tween 20) that acts as a demulsifier on the stability of water-in-dodecane emulsions stabilized with Span 80. Performing bottle test experiments, we monitor the emulsion separation process. Initially, water droplets sediment fast (∼10 min) until they become closely packed and form the so-called dense packed layer (DPL). The presence of the DPL, a long-lived metastable highwater-fraction (70−90%) emulsion separating bulk oil and water layers, slows down significantly the kinetics (∼10 5 min) of water separation. Once the DPL is formed, the ratio of the volume of separated water to the total water amount is called as water separation efficiency. We assume that the emulsion stability is reached when the coverage of the emulsifier surfactant exceeds 80% and use the ideal solution approximation. From that, we rationalize the water separation efficiency and the minimum demulsifier concentration required to maximize it, in terms of the mean droplet size, the surfactant concentrations, the total water volume fraction, and the adsorption strength of the water-soluble surfactant. Model predictions and experimental findings are in excellent agreement. We further test the validity and robustness of our theoretical model, by applying it successfully to data found in the literature on water-in-crude oil emulsion systems. Ultimately, our results prove that the efficiency of a demulsifier agent to break a W/O emulsion strongly correlates to its adsorption strength at the W/O interface, providing a novel contribution to the selection guidelines of chemical demulsifiers.

Contactless Interfacial Thin‐Film Breaking Caused Splash‐Like Demulsification of Floating Micron Emulsions via Ionic Wind

“…The dense packed layer (DPL) stabilized by a surfactant is chosen as the emulsion to be treated, which is considered to be long‐lived metastable emulsions. [ 34 ] The emulsion layer is dyed with oil red dye to make the result clearer. The overall process contains three steps, demulsification, transportation, and collection.…”

Evolution of the Distribution Function of Drops in an Oil Emulsion

“…Although the processes of coalescence and fragmentation are characterized by an abrupt change in the properties of particles (sizes), in principle, for a sufficiently long period of time, the change in the average properties can be assumed to be quasicontinuous with an infinitely small jump. In particular, it can be assumed that the average size of drops and bubbles changes continuously with time and obeys the equation for the change in the average mass of particles over time The solution of this equation presents great difficulties associated with setting the form of the function , although some particular analytical solutions to equation ( 4), depending on the nature of the function setting, can be found in [3][4][5].…”

“…To prepare such oils for processing at a refinery, special equipment and chemicals are needed. Therefore, the possibility of rapid separation of water-oil emulsions is the main issue in the preparation of oil [2][3][4][5].…”