Session: 11-08-02: Multiphase Flows and Applications II

Paper Number: 166908

Effect of Mixing Speed on Droplet Size of Pure and Surfactant Stabilized Oil-Water Emulsions 

The emulsion of two immiscible liquids like oil-in-water (O/W) and water-in-oil (W/O) is unstable in nature due to differences in polarity and density between the two unlike liquids. However, emulsions of these two liquids are also unstable due to the increase in Gibbs-free energy and high interfacial area forming between oil and water. Nevertheless, investigators call an emulsion “unstable” when it separates in a few seconds, unlike “stable” emulsions, which could remain stable for an indefinite period that may last for a few days or more.

Although the breakup of oil and water droplets in batch separators is due to the intensity of mixing given initially to the two liquids, speed effects on droplet size and distribution are not well understood. A significant amount of work in literature focused only on one type of emulsion and surface-active agent. Furthermore, there is currently no data concerning pure (stabilizer-free) emulsion to isolate the role of stabilizers like surfactants or solid particles on droplet size. Therefore, the aim of this work is to study the effects of mixing speed (between 1000 RPM and 2500 RPM) on mean droplet size and droplet distribution of both pure emulsions and emulsions stabilized by nonionic surfactants. Pure (oil-in-water (O/W)) emulsions were formed through only using mineral oil (Exxol D110 – specific gravity 0.805) and distilled water whereas surfactant-stabilized (O/W) emulsions contained 0.050% wt. of Tergitol 15-S-7 (hydrophilic) in the water phase. Similarly, surfactant-stabilized W/O emulsions contained Span^® 80 (hydrophobic) of 0.050% wt. in the oil phase. The droplets of all emulsions (pure O/W, T15S7-stablized O/W and SP80-stabilized W/O) were formed in a state-of-the-art portable dispersion characterization rig (P-DCR). After forming emulsions in the P-DCR facility, a sample of those emulsions were transferred to a trinocular microscope acquired from “Amscope.com” for size analysis. The microscope not only provides a live image of the droplets of the emulsion, but it also can record a video of the rapid motion of dispersed droplets in the continuous phase.

The size of oil droplets was studied at two volumetric water concentrations (WCs = 75% and 90%) whereas the size of water droplets was studied at 25% WC. According to data gathered from this work, we proved that water droplets in general have sizes that are bigger than the size of both stabilizer-free and surfactant-stabilized oil droplets. This trend was not only observed right away after emulsion formation but also after 2- and 4-hours following formation.

Presenting Author: Ram Mohan The University of Tulsa

Presenting Author Biography: Dr. Ram Mohan is a Professor of Mechanical Engineering at the University of Tulsa and a fellow of ASME. He has over 34 years of experience of which 28 years are in academia and 17 years in industry (11 years concurrently). He teaches and conducts research in the areas of Process Control Systems, Multiphase Flow Separation, Oil-water Dispersion Characterization, Instrumentation and Signal Processing, Manufacturing Processes and High-Pressure Fluid Applications. Dr. Mohan received his Ph.D. and M.S. Degrees in Mechanical Engineering from the University of Kentucky, and his B.Sc (Engg.) degree from the University of Kerala, India. He serves as the Director/Co-Director of Tulsa University Separation Technology Projects (TUSTP) since 1996 and has experience in successfully directing projects funded by US Department of Energy (DOE) – 13 years, National Science Foundation (NSF) – 9 years, Oklahoma Center for the Advancement of Science and Technology (OCAST) – 12 years and several international companies in the Petroleum Industry – for more than 25 years. Dr. Mohan has served as the site Director of the Industry/University Cooperative Research Center I/UCRC) on Multiphase Transport Phenomena sponsored by National Science Foundation (NSF). He has authored or co-authored more than 90 refereed publications in the areas of his research, more than 300 conference presentations, 10 patents/invention disclosures. Dr. Mohan has received several best paper awards and service awards from ASME, SME, AAUP and other organizations and has made several invited and keynote speeches to SPE, AIChE and several companies such as Chevron, Shell, StatoilHydro, BP, Calscan Energy, PEMEX, TOTAL, Schlumberger, Petrobras, ConocoPhillips, NATCO, Emerson Process Management, and ONGC.

Authors:

Khalid Alanazi University of Tabuk
Ram Mohan The University of Tulsa