Understanding Shipboard Oil/Water Emulsions Using Macro- and Micro-scale Flows

Cari Dutcher | University of Minnesota, Twin Cities

WP18-1031

Objective

The separation of oil from bilgewater emulsions before they are released into the environment poses a unique challenge due to the inherent complexity and stability of these oil/water emulsions systems. Comprehensive scientific analysis of shipboard emulsions is needed to facilitate appropriate water treatment necessary for proper disposal. This project will enhance the “fundamental knowledge base” of the “generation, stabilization and worsening” of such shipboard emulsions, by studying the emulsions in the presence of complex, yet tunable, hydrodynamic fields with varied chemical conditions. Two complementary approaches will be used to systematically study bulk and single-droplet emulsion dynamics at the macro- and micro-scale, respectively. Many of the factors will be explored, including “zeta potential, shear/mixing, salinity, interfacial tension, water/oil/surfactant ratios, and morphological changes”. Ultimately, the results of this project will “assist the development of methodologies or technologies that can mitigate the formation and undesired consequences of shipboard emulsions”, through improved understanding of the factors that govern emulsions.

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Technical Approach

Integrating macro-scale (Task 1) and micro-scale (Task 2) approaches in parallel studies will provide new insights into the dynamics of complex emulsions, which will ultimately aid in developing more efficient processing techniques for their separation.

Task 1. On the macroscale, Taylor-Couette flow, or flow between concentric rotating cylinders, will be used to study mixing conditions on emulsion generation and stability. Unlike more traditional emulsification methods such as the use of a homogenizer, Taylor-Couette cells offer the ability to precisely control the hydrodynamic condition, including kinematic flow type, during emulsification. In this task, emulsions will be generated and studied with a custom-built Taylor-Couette cell with controlled radial fluid injection through the inner cylinder into a pre-established flow field. This task has two deliverables: 

(1) determination of the hydrodynamic (flow type) effects of pre-prepared bilgewater emulsion stability.
(2) determination of the hydrodynamic (flow type) effects on in-situ bilgewater emulsion formation.

Task 2. On the microscale, droplets generated in a microfluidic device will be used to simulate shipboard emulsions. The chemical composition of these droplets can be varied in-line, and they can also be subjected to flow fields that can be easily controlled in order to deform, perturb and manipulate them. In this task, the effect of surface-active additive concentrations on interfacial tension and viscosity will be measured precisely. Coalescence dynamics will also be probed to determine the parameters which profoundly impact the stability and separation of bilgewater emulsions. This task has three deliverables: 

(3) dynamic interfacial tension measurement of liquid-liqud interfaces in bilgewater emulsions.
(4) dispersed phase viscosity measurements in bilgewater emulsions.
(5) droplet collision and coalescence measurements.

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Benefits

Employing a two-pronged approach to studying emulsion formation and stability (both on the macro-scale and micro-scale) will enhance fundamental knowledge of the dynamic behavior of complex oil/water emulsions. This knowledge can then be applied to optimize the processes involved in the separation of oil from shipboard bilgewater emulsions, as well as recommendations for design of storage and processing equipment to avoid emulsion formation.

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Points of Contact

Principal Investigator

Cari Dutcher

University of Minnesota, Twin Cities

Phone: 612-624-0428

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