Induction and Coverage Times for Crude Oil Droplets Spreading on Air Bubbles

Mona Eftekhardadkhah,Gisle Øye

doi:10.1021/es403574g

Mona Eftekhardadkhah, Gisle Øye

Open Access

https://doi.org/10.1021/es403574g

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Abstract

The interactions between crude oil droplets and air bubbles were studied by the droplet-bubble micromanipulator technique. Eight crude oils were investigated, and some aspects of the involved mechanisms were discussed. The induction time was measured for air bubbles approaching crude oil droplets in different aqueous phases. Distinct differences were observed in the presence and absence of salts, which showed the importance of long-ranged electrostatic repulsive forces on thin-film stability. The results also suggested that adsorption of dissolved hydrocarbons at air bubble surfaces may increase the potential energy barrier in the thin liquid film. Furthermore, the time needed for crude oil droplets to spread over the air bubble surfaces (referred to as coverage time) was determined for the crude oils. The results showed that the spreading velocity decreased with increasing viscosity of the crude oil. The detailed understanding of this type of interaction is considered to be a precursor for improving the oil removal efficiency during the flotation process.

Highlights

Huge quantities of oily produced water are generated during production and processing of crude oil
Gas flotation is a complex set of various sub-processes, and optimal oil removal can only be achieved by understanding the controlling mechanisms for each sub-process
The important requirement for successful flotation is quick drainage and rupture of the thin aqueous film that is formed upon close approach between drops and bubbles.[5,6]. This will result in oil drops spreading over the gas bubbles, and the oil is removed by flotation

Summary

Introduction

Huge quantities of oily produced water are generated during production and processing of crude oil. The process is based on gravitational separation, where the density difference between the continuous and dispersed phases is increased by the addition of gas to the produced water. This will promote the formation of oil−gas agglomerates.[3,4]. In studies of the thin film between one single drop and one single bubble, the stability is expressed in terms of the induction time, i.e., the time from initial contact of the drop and bubble to rupture of the film.[7,8] Further, it seems accepted that the final rupture of the thin film is due to instabilities in the interfacial regions This often results in significant variations of the observed induction times.[7,9−15]

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