Session: 10-07-01: Fluid Mechanics and Rheology of Nonlinear Materials and Complex Fluids

Paper Number: 111435

111435 - Effect of Water Cut and Temperature on the Stability of Emulsifier-Free Oil-Water Dispersion in Batch Separators at Various Stirrer Speeds 

 

Brief Abstract (Research Summary)

The stability of an emulsifier-free oil-water dispersion in a 200 ml batch (gravity-based) separator with a 54mm diameter was described using experimental data. The objective of the study was to investigate the impact of various water cuts (WC = 25%, 50%, 75%, and 90%) and temperatures (T = 25°C, 60°C and 80°C) on the starting times of water and oil separation, full emulsion’s separation time, and volumes of emulsion at various stirrer speeds (600-2500 rpm). The two immiscible phases were EXXSOL^TM D110 (mineral oil) and distilled water, with density and viscosity ratios of 0.805 and 0.330, respectively. For the fluid systems studied in this work, the emulsion formed with WCs ≥ 75% was significantly influenced by stirrer speed and did not separate for several hours at speeds ≥ 1000 rpm. Emulsions of WCs ≤ 50%, on the other hand, were stirrer speed independent and separated fully immediately after formation. According to the experimental results, increasing the temperature delayed the starting time of water sedimentation and was unsuccessful overall in the separation process. For WCs ≥ 75%, emulsions displayed a shear-thinning behavior with viscosities reaching more than 2300 Cps at lower shear rates and water-like viscosities at higher shear rates.

 The motivation for this work 

An emulsion is a liquid-liquid dispersion of two immiscible phases, with one phase dispersed in the other as smaller droplets. The process of forming this dispersion is known as homogenization. This type of dispersion is encountered in many industrial applications (e.g., cosmetic, pharmaceutical, energy, petroleum, Petrochemical, and food). Therefore, the development of advanced separation techniques for the recovery of expensive solvents is of great importance for these fields. In  batch separators, for example, oil creams at the top of the separator and water sediments at the bottom according to the fluid properties (e.g., density, viscosity, and surface tension difference between dispersed and continuous phase) and dispersed phase volume fraction.  These, however, should not be the only parameters that determine the performance of such equipment. For example, performance at certain dispersed phase and fluid properties can change due to agitation speed, temperature, and higher WCs. Therefore, to obtain reliable and optimum performance of a gravity-based separator, exposure to other operational conditions (such as stirrer speed effect, elevated temperatures, and various ranges of WCs) is a necessity.

Contribution of the Work

Since the design of a batch separator requires expensive pilot-experimental data, literature in the past was mainly focused on mechanistic modeling and laboratory-small-scale data. To our best knowledge, there is no single mechanistic or empirical modeling until this time that describes how the droplet-droplet coalescence time, droplet-interface coalescence time, thin film, and droplet size growth are affected by stirrer speeds during emulsion formation. Currently available mechanistic models are only based on simple physical knowledge of droplet deformation through unvalidated assumptions. In addition, these mechanistic models were only validated for a small range of experimental data (mostly W/O emulsions and mixing speeds < 1000rpm) and mentioned no effects of agitation speed on droplet size during emulsion formation. 

Because existing mechanistic and empirical models for gravity-based separators did not account for the effect of stirrer (agitation) speed during the emulsification of blank (emulsifier-free) liquid-liquid dispersion in their model development, and due to the complexity of solving the problem mathematically, this work aims to expand knowledge of this subject by experimentally investigating the effect of water cut at stirrer speeds ranging from 600-2500 rpm. Additionally, this research aims to evaluate the effect of temperature on the stability of emulsifier-free emulsions. 

Data Collection Procedure

In this study, emulsions were formed using a portable state-of-the-art dispersion characterization rig (P-DCR).  This facility is outfitted with a high-resolution camera and measurement instrument for capturing and scanning the live evolution of emulsion separation profiles as settling time proceeds. As soon as emulsions are formed, recording starts and the live evolution of emulsion interfaces is observed live in this facility.

 

Presenting Author: K. Alanazi The University of Tulsa

Presenting Author Biography: Khalid Alanazi is a graduate of the Erosion/Corrosion Research Center (E/CRC) at the University of Tulsa (TU) and a Ph.D. candidate with the Tulsa University Separation Technology Projects (TUSTP) team. His current research interests include solid particle erosion (SPE) of engineering materials, two-phase flow, non-ionic surfactant stabilized oil-water dispersion, and emulsifier-free oil-water dispersion. He received his M.Sc. degree in mechanical engineering from TU in 2020 and his B.Sc. degree from the University of Tabuk (UT) in 2015. During his time at the E/CRC, he worked on a number of projects involving SPE in gas and liquid-dominated flows. Prior to joining TU, Alanazi was a teaching assistant at UT from 2016 to 2017, where he taught several courses in material engineering, material mechanics, and fluid mechanics.

Authors:

K. Alanazi The University of Tulsa
R. Mohan The University of Tulsa
s.s. Kolla Oklahoma State University
O. Shoham The University of Tulsa