Final Report: Affinity-Based Hydrocyclone Filter for Oil-Water Separation and Oil Spill Cleanup

EPA Grant Number: R835183
Title: Affinity-Based Hydrocyclone Filter for Oil-Water Separation and Oil Spill Cleanup
Investigators: Tarabara, Volodymyr , Bruening, Merlin , Bénard, André
Institution: Michigan State University
EPA Project Officer: Lasat, Mitch
Project Period: May 16, 2012 through March 31, 2015 (Extended to March 31, 2016)
Project Amount: $500,000
RFA: Environmental Impact and Mitigation of Oil Spills (2011) RFA Text |  Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Ecosystems

Objective:

The goal of this research project, as set in the proposal, was to develop a hybrid hydrocyclone-membrane technology that separates oil-water mixtures into a water stream that meets standards for discharge into the environment and an oil stream sufficiently dewatered for energy use. The four specific research objectives of the project were: (1) to create hydrophilic, regenerable coatings to mitigate membrane fouling; (2) to develop tools for predictive and diagnostic modeling of hydrocyclone flow for performance optimization; (3) to design superoleophilic membranes to continuously whicker oil; and (4) to design and build a pilot scale crossflow filtration hydrocyclone for concept validation.

An outreach component of the project aimed at engaging and connecting communities in Louisiana and Michigan that were affected by recent oil spills (BP’s Gulf of Mexico spill and Enbridge’s Kalamazoo River spill). The objective of the outreach effort was to demonstrate that communities have a stake in research projects aimed at addressing the significant human health and environmental risks posed by oil spills.

Summary/Accomplishments (Outputs/Outcomes):

Hydrocyclones and membranes are among the most important technologies currently used for separating oil-water dispersions and emulsions. In this project, we studied three types of swirling flow devices that can separation oil-water mixtures while combining high throughput and improved oil performance: a) solid-liquid separation hydrocyclones as a pre-treatment process for liquid-liquid separation, b) rotating tubular membranes for liquid-liquid separations, and c) liquid-liquid separation hydrocyclones (regular and filtering). Liquid-liquid separations were the main focus of the project. Specifically, we explored hydrocyclones with swirl chambers of redesigned shape, rotating membranes for treating emulsions with finely dispersed oil, and crossflow filtration hydrocyclones – hybrid devices that combine hydrocyclonic and membrane separations in one unit process. The project combined computational fluid dynamics (CFD) simulation and experimental studies at the laboratory scale. The work was structured as a sequence of separate four research Tasks accompanied by an outreach effort lead by the team from the Louisiana State University and with participation of project personnel from the MSU team.

Task 1: Design of hydrophilic, regenerable membrane coatings for efficient oil-water separation

In Task 1 we designed two types of hydrophilic membrane coatings — polyelectrolyte multilayer films and zwitterionic brushes — for oil-water microfiltration. Polyelectrolyte multilayer films were oleophobic, with oil contact angles above 100° in water, and rejected nearly 100% of the oil in filtration of oil water-mixtures. Unfortunately, severe fouling occurred within minutes of beginning filtration. Polyelectrolyte brushes showed much higher resistance to fouling by oil. Polyanionic brushes completely rejected oil droplets stabilized by sodium dodecyl sulfate; moreover, the permeate flux was constant with time, suggesting that the electrostatic repulsion of negatively charged droplets prevented membrane fouling. Brush polymerization time was an important variable that affected oil rejection. The polyanionic brushes, however, collapsed in the presence of a cationic surfactant pointing to the importance of the role that the surfactant plays during fouling by oil-in-water emulsions, particularly with polyelectrolyte brushes.

To address this challenge, we explored whether zwitterionic (poly(sulfobetaine methacrylate)) brushes can resist fouling by oil emulsions stabilized with both cationic and anionic surfactants. The brushes showed complex swelling behavior that depended on brush thickness and surfactant type. We conclude that while superhydrophilic polyzwitterionic brushes resist fouling, free ions may screen zwitterion charges and alter brush hydration; such changes in brush swelling should be taken into account when selecting the porous membranes for the modification by the antifouling brushes.

Task 2: Computational modeling of liquid-liquid separation crossflow filtration hydrocyclone (LL-CFFH)

Task 2 was dedicated to the computational design of swirling flow devices for effective oil-water separation. We performed a range of computational fluid dynamics (CFD) simulations to calculate velocity and pressure profiles within such devices with the ultimate goal of optimizing their design and performance.

First, an axially rotating tubular ceramic membrane operated in a crossflow regime was studied numerically considering oil-water dispersion as a model feed. The increased shear stress on the membrane surface due to the angular and the crossflow velocities decreased the accumulation of droplets on the membrane while increasing the separation efficiency. The droplet cutoff size was observed to decrease with an increase in the Reynolds and Swirl numbers while the separation efficiency strongly depended on the Swirl and Stokes numbers but only weekly on the Reynolds number. We conclude that by increasing the Swirl number of the flow, it may be possible to remove very fine droplets by centrifugal force only and avoid membrane fouling.

Second, we examined the internal flow structures within liquid-liquid separation hydrocyclones with parabolic and hyperbolic wall profiles of the swirl chamber to explore how these two geometries affect the reverse flow vortex core, short circuit flows, and the separation efficiency. Internal flow structures for different geometric conditions have motivated the redesign of the hydrocyclone geometry so as to support a longer and stable reverse flow vortex core and for greater separation efficiency. We showed that both the parabolic and hyperbolic designs provide improved separation efficiency over that with a standard conical chamber; the hyperbolic swirl chamber, however, showed a greater potential for the reduction of effective length of the hydrocyclone while maintaining the same separation efficiency.

Third, we studied key hydrodynamic aspects and the separation performance of the crossflow filtration hydrocyclone - a device that combines desirable attributes of a crossflow filter and a vortex separator into one unit to separate oil from water. The velocity and pressure fields within the CFFH were estimated by numerically solving the Navier-Stokes equations using a Large Eddy Simulation (LES) approach while the Lagrangian approach was employed to track the trajectories of dispersed droplets. We showed that a) at higher Reynolds number the flow core was unstable core with numerous recirculation zones observed in the flow field while b) at lower Reynolds numbers and for lower permeabilities of the porous filter, an improved separation efficiency could be achieved. Increasing permeate flowrate while maintaining high oil rejection will likely be the key for the acceptance of the technology by the industry.

Task 3: Design of superoleophilic membranes to continuously whicker oil

This task has not proven fruitful and is no longer a focus of the work.

Task 4: Design of the prototype hydrocyclone system an concept validation studies

In Task 4 we have assembled and studied rotating flow systems of three types:

  1. A rotating microfiltration membrane;
  2. A solid-liquid separation hydrocyclone (SL-H) for separating dispersed phases heavier than water;
  3. A liquid-liquid separation hydrocyclone – both conventional (LL-H) and filtering (denoted as crossflow filtration hydrocyclone (LL-CFFH)) - for separating oil- water dispersions.

The separation devices were evaluated in laboratory-scale experimental studies. The proof-of-concept study of a rotating a tubular membrane showed the rotation-induced centripetal force preferentially moved larger negatively buoyant particles away from the membrane. The benefit of the rotating membrane system is in the higher centripetal force near the lumen wall than can be achieved by simply introducing a rotating flow into the membrane channel. However, for the rotational speed tested (1725 rpm), the rotation had minimal effect on particles with diameters <8 μm. We concluded that while a similar effect with oil droplets in water would require higher feed flow rates or lower permeate fluxes, but a rotating membrane may help avoid a pretreatment step to remove large oil droplets.

Second, we evaluated efficiency of solid-liquid separations by hydrocyclone as a pretreatment step for liquid-liquid separation. In doing so we employed a reconfigurable 22 mm hydrocyclone that was custom manufactured for our team by ChemIndustrial Systems, Inc. We used feeds that contained water, oil and sand (1000mg(sand)/L and 1000mg(oil)/L) to investigate the impact of agglomeration on the separation efficiency. We identified the optimal geometry of the hydrocyclone and found that the separation efficiency of oil does not show a statistically significant dependence on the presence of sand in the feed. The separation efficiency of sand, however, decreased in the presence of oil in the feed. The trend was attributed to the removal of oil-associated small particle of sand through the overflow.

Third, we designed and built a liquid-liquid crossflow filtration hydrocyclone (LL-CFFH) and evaluated its performance using conventional liquid-liquid separation hydrocyclone (LL-H) as a comparative basis. Both LL-H and LL-CFFH were also custom-manufactured for the project by CSI. Most separation experiments were performed with 1000 mg//L aqueous emulsions of mineral oil (860 g/L specific gravity). The separation efficiency was in the 37% to 52% range for the optimal split ratio of ~ 9%. The results showed that the substitution of the hydrocyclone’s tailpipe with a membrane did not detrimentally affect the hydrocyclones performance. The fact that the LL-CFFH with the largest pore size membrane showed the highest indicated that practically important larger permeate flow rates can be achieved at the same time with acceptable quality of treated water. Membrane fouling tests were also performed to determine the effect of the hydrocyclone on the membrane performance. To distinguish effects of flow rotation and crossflow shear, results of LL-CFFH tests were compared with baseline data obtained from crossflow filtration tests with a stationary membrane. We showed that reduction of fouling observed in the LL-CFFH process is a synergistic benefit of combining the membrane and the hydrocyclone in a single LL-CFFH unit. The hybrid device produced a high quality de-oiled stream (membrane permeate) in addition to relative de-oiled underflow stream.

Outreach and extension

The outreach effort centered on organizing annual events with two overarching goals: 1) Engage communities in Louisiana and Michigan that were affected by recent oil spills (BP’s Gulf of Mexico spill and Enbridge’s Kalamazoo River spill) and 2) Connect researcher and practitioners involved in mitigating the two spills.

The first joint presentation was made at the 2014 No-Spills Conference in Traverse City, Michigan where the research and outreach plans were presented by Prof. Tarabara. Later in the year, Prof. Benard provided a project overview and a research update to the Louisiana Sea Grant Marine Extension Program faculty at their quarterly meeting in Baton Rouge, Louisiana. The 2015 and 2016 annual events took place at MSU (in 2015) and LSU campuses (in 2016) in the formal of panel discussions and were broadcast as webinars. The title of each of the two events was "Oil spills in Michigan and Louisiana: What can scientists, engineers and affected communities in Michigan and Louisiana learn from each other and teach policy makers?"

The outreach effort culminated in the event organized, in February 2017, as a conference workshop “Research needs in the area of physical methods of oil spill remediation: Lessons learned in remediating oil spills in the Gulf of Mexico and Michigan” at the Gulf of Mexico Oil Spill and Ecosystem Science (GoMOSES) conference in New Orleans, LA.

Multiple experts from Michigan and Louisiana participated in the panels and the GoMOSES workshop. The presentations and ensuing discussions helped identify differences and similarities in the impacts of the two oil spills in our two States and management strategies that were used to mitigate the impacts.

Conclusions:

We showed that reduction of fouling observed in the LL-CFFH process is a synergistic benefit of combining the membrane and the hydrocyclone in a single LL-CFFH unit. The hybrid device produced a high quality de-oiled stream (membrane permeate) in addition to relative de-oiled underflow stream. The outreach effort centered on organizing annual events with two overarching goals: 1) engage communities in Louisiana and Michigan that were affected by recent oil spills (BP’s Gulf of Mexico spill and Enbridge’s Kalamazoo River spill); and 2) connect researcher and practitioners involved in mitigating the two spills.


Journal Articles on this Report : 5 Displayed | Download in RIS Format

Other project views: All 43 publications 5 publications in selected types All 5 journal articles
Type Citation Project Document Sources
Journal Article Ji P, Motin A, Shan W, Benard A, Bruening ML, Tarabara VV. Dynamic crossflow filtration with a rotating tubular membrane: using centripetal force to decrease fouling by buoyant particles. Chemical Engineering Research and Design 2016;106:101-114. R835183 (2013)
R835183 (Final)
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  • Journal Article Motin A, Tarabara VV, Benard A. Numerical investigation of the performance and hydrodynamics of a rotating tubular membrane used for liquid–liquid separation. Journal of Membrane Science 2015;473:245-255. R835183 (2013)
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  • Journal Article Motin M, Tarabara VV, Petty CA, Benard A. Hydrodynamics within flooded hydrocyclones during excursion in the feed rate: understanding of turndown ratio. Separation and Purification Technology 2017;185:41-53. R835183 (Final)
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  • Journal Article Yang Z, Tarabara VV, Bruening ML. Adsorption of anionic or cationic surfactants in polyanionic brushes and its effect on brush swelling and fouling resistance during emulsion filtration. Langmuir 2015;31(43):11790-11799. R835183 (Final)
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  • Journal Article Yang Z, Zhang S, Tarabara VV, Bruening ML. Aqueous swelling of zwitterionic poly(sulfobetaine methacrylate) brushes in the presence of ionic surfactants. Macromolecules 2018;51(3):1161-1171. R835183 (Final)
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  • Supplemental Keywords:

    water pollution, cleanup, separations, energy recovery, oil spill, produced water, crossflow filtration, deoiling hydrocyclone, computational fluid dynamics, multiphase flow, membrane, microfiltration, liquid-liquid separation, affinity separation, polyelectrolyte multilayers, superhydrophilic and superhydrophobic films

    Relevant Websites:

    Michigan State University U.S. EPA Science to Achieve Results Project   Exit

    Progress and Final Reports:

    Original Abstract
  • 2012 Progress Report
  • 2013 Progress Report
  • 2014