Session: 10-05-01: Multiphase Flows

Paper Number: 95920

95920 - Separating Oil-Water Mixtures Using Bump Arrays 

Separating particles with large fluxes, high precision, and small equipment footprints remains an important industrial separations challenge.  Microfluidic bump arrays, also called microfluidic deterministic lateral displacement devices, have been used to separate a wide variety of biological and non-biological particles ranging from polystyrene spheres to biconcave red blood cells, rod-shaped bacteria, decidedly non-spherical parasites, coiled up chromosomes, and cancer cells.  Dijkshoorn, et al., have even shown that hexadecane droplets in water may be separated using this family of techniques.  Nearly all separations using the bump arrays reported in a vast literature have been performed at very small Reynolds numbers under laminar flow conditions based on the conventional wisdom that laminar flow conditions are essential for separation.  The key to particle separation in these arrays is the interaction between the pin array and the fluid.  Stagnation streamlines create flow channels.  Particles small enough to remain within the flow channels (i.e., smaller than a cutoff diameter) as the particles approach pins simply pass from entrance to exit.  Particles too large to remain within a flow channel as they approach pins (i.e., larger than the cutoff diameter) “bump” (often without direct pin contact) into a neighboring channel.  With enough pins and “bumps” larger particles may be directed toward one side of the flow where they may be collected separately.  Low flowrates may suffice for microfluidic medical applications where smaller blood volumes are preferential, for example.  Yet, many if not most full-scale industrial applications require much larger flowrates (e.g., tens to thousands of gallons per minute), because low flowrates lead to untenably large equipment.  We have shown that mesofluidic bump arrays can separate particles from entering flows in the turbulent regime.  In this paper we focus on separation of oil-water mixtures. 

The ability to efficiently separate two-phase industrial (oil/water) mixtures is key for future use of valuable resources. Reclaiming over 1 trillion gallons annually of petroleum production water is critical for water recovery and reuse in the drought-ridden western US states.  Failure to reclaim this petroleum production water within the next 10 years is projected to put 30% of the US food production at risk due to lack of irrigation water from failing aquifers. Proving this technology is key to reuse of petroleum production water for crop production or to replace water from currently failing aquifers in rich agricultural lands (from the Dakotas down to Texas and west to California). 

We conducted experiments applying mesofluidic separation for flowing two-phase (oil/water) mixtures.  Experiments were conducted using oils of differing viscosities with water as the carrier fluid; separation was achieved over a range of oil-water concentrations.  We describe the results of these experiments in this paper. 

Presenting Author: Judith Bamberger FEDSM2020 Chair and Senior Research Engineer, Pacific Northwest National Laboratory

Presenting Author Biography: Dr. Bamberger is a Senior Research Engineering at Pacific Northwest National Laboratory specializing in slurry mixing and transport.

Authors:

Judith Bamberger FEDSM2020 Chair and Senior Research Engineer, Pacific Northwest National Laboratory
Leonard Pease Pacific Northwest National Laboratory
Carolyn Burns Pacific Northwest National Laboratory
Michael Minette Pacific Northwest National Laboratory