Effect of Water Content, Temperature and Average Droplet Size on the Settling Velocity of Water-in-Oil Emulsions

Abstract

-Water-in-oil (W/O) emulsions are complex mixtures generally found in crude oil production in reservoirs and processing equipment. Sedimentation studies of water-oil emulsions enable the analysis of the fluid dynamic behavior concerning separation of this system composed of two immiscible liquids. Gravitational settling was evaluated in this article for a model emulsion system consisting of water and a Brazilian crude oil diluted in a clear mineral oil as organic phase. The effects of water content and temperature were considered in the study of sedimentation velocity of water-oil emulsions. Water contents between 10% and 50 % and temperatures of 25, 40 and 60 °C were evaluated, and a Richardson-Zaki type correlation was obtained to calculate settling velocities as a function of the process variables investigated. Water contents and average droplet sizes were monitored at different levels in the settling equipment, thus enabling identification of the effect of these variables on the phenomena of sedimentation and coalescence of the emulsions studied. The results showed that the emulsion stability during sedimentation was governed by the emulsion water content, which yielded high settling velocities at low water contents, even when very small droplets were present. A quantitative analysis of the combined effects of drop size and droplet concentration supports the conclusion that a stronger effect is produced by the higher concentration of particles, compared with the relatively smaller effect of increasing the size of the droplets.

A Comprehensive Review on Emulsions and Emulsion Stability in Chemical and Energy Industries

“…Another approach to calculate/determine the droplet size distribution is through the combination of microscopic equipment, digital image processing software, and statistical tools . ZEISS particle analysis systems provide extensive information on the particle droplet analysis.…”

“…AxioVision is one of the light microscopes used for the analysis and measurement of shape, size, and orientation of the materials in the single phase or multiphase samples. Souza et al used the combined tools to investigate the effect of process conditions on the settling velocities of emulsions. Digital pictures were taken by a charged‐coupled device (CCD) from an optical microscope as shown in Figure .…”

“…The researchers took several pictures and scrutinized them in order to obtain d 32 diameter. The d 32 or Sauter diameter is the volumetric average diameter of a spherical droplet similar to the mean diameter of a particle system . Laser diffraction is another widely‐used technique to obtain the particle size distribution .…”

“…Furthermore, there are fairly high costs and errors with the common experimental procedures that are used to determine different fluid/emulsion systems and physical model properties. A number of researchers focused on the transport phenomena of emulsions in porous media to develop analytical models for better characterization of water/oil emulsions . Characterising fluids by surface tension (σ), density (ρ), viscosity (µ), a characteristic linear dimension (L), velocity (u), and influence of gravitational force (g) field may be expressed in the form of dimensionless numbers by employing Buckingham's Theorem.…”

Chemical Demulsification of Model Water-in-Oil Emulsions With Low Water Content by Means of Ionic Liquids

“…In fact, as the temperature increases the collision efficiency of the water droplets increases, favoring their coalescence (Azizi and Nikazar, 2015;Kim, 1999). In addition, at higher temperature, the continuous phase viscosity decreases, determining a higher sedimentation rate and therefore faster demulsification kinetics (according to Stokes' law) (Souza et al, 2015). In conclusion, at higher temperature, the effect of IL is completely hidden, all the samples show the same kinetic patterns and the use of the IL as demulsifier does not provide any significant improvement in the demulsification performances.…”