2012 Progress 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 , Louisiana State University - Baton Rouge
Current Institution: Michigan State University
EPA Project Officer: Lasat, Mitch
Project Period: May 16, 2012 through March 31, 2015 (Extended to March 31, 2016)
Project Period Covered by this Report: May 16, 2012 through May 31,2013
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 is 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 are to: (1) create hydrophilic, regenerable coatings to mitigate membrane fouling, (2) develop tools for predictive and diagnostic modeling of hydrocyclone flow for performance optimization, (3) design superoleophilic membranes to continuously whicker oil, and (4) design and build a pilot scale crossflow filtration hydrocyclone for concept validation.
 
An outreach component of the project aims 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 is to demonstrate that communities have a stake in research projects aimed at addressing the significant human health and environmental risks posed by oil spills.

Progress Summary:

Task 1: Design of hydrophilic, regenerable membrane coatings for efficient oil-water separation
 
We are developing hydrophilic coatings to reduce membrane fouling by oil during filtration of oil-water mixtures. In initial efforts, we grew polymer brushes by polymerization of potassium 3-sulfopropyl methacrylate from initiators on Au-coated surfaces. This yields polymer brushes that are extremely hydrophilic. Although oil can wet these brushes, upon introduction of water the oil beads up on these films (Fig. 1), which should reduce fouling. Unfortunately, when we attempted to grow the films on nylon membranes, the brush density was not sufficient to achieve a similar effect.
 
 
To overcome this challenge, we are depositing polyelectrolyte multilayer films on porous membranes. Although not as hydrophilic as poly(sulfopropyl methacrylate) brushes, these coatings also bead oil in the presence of water. More importantly, deposition of polyelectrolyte multilayers on membranes is a simple process that coats even the interior of membrane pores under appropriate conditions. We are also varying the surface charge of the polyelectrolyte coatings to repel oil droplets coated with charged surfactants. Preliminary results suggested that oil rejection depends on the droplet charge, but this has been difficult to reproduce. Nonetheless, we suspect that negatively charged surfaces will resist fouling by negatively charged oil droplets. Tailoring coatings based on the surfactant in an emulsion is a new paradigm in fouling-resistant membranes.
 
Task 2: Computational modeling of liquid-liquid separation crossflow filtration hydrocyclone (LL-CFFH)
 
Numerical simulations used to study the hydrodynamic features of the system are based on the Reynolds Stress Model to close the Reynolds Average Navier-Stokes equation. The simulations were performed using ANSYS-FLUENT 13.0. The flow fields in the LL-CFFH were studied for four different Reynolds numbers: ReDin = 5687, 8530, 11373, and 14217 based on the inlet hydraulic diameter, Din.
 
 
Figure 2. Effect of the Reynolds number on total grade efficiency for LL-CFFH with an aspect ratio 4. The density of dispersed phase particle is 730 kg/m3
 
 
The effect of the Reynolds number and geometric aspect ratio on hydrodynamics and separation efficiency were investigated. In Fig. 2 the effect of the Reynolds number on the grade efficiency is shown. The separation efficacy, for this geometry, is significantly improved for large particles as the Re number increases, but it becomes worse for small particles. Additional results not shown for brevity indicate that the separation efficiency is significantly influenced by the presence of the porous media as well as the flow field. In addition, cylindrical hydrocyclones with an aspect ratio greater than 4.0 exhibit lower grade efficiency due to a weaker swirl.
 
To test the effect of the no slip condition on the LL-CFFH performance, we constructed a filtration system where a mechanically rotated membrane is fed by an initially non-swirling suspension of negatively buoyant (0.46 g/mL) hollow glass microspheres. The pore size of the membrane was 0.14 µm while the size of microspheres was in the 5 µm to 27 µm range. The filtration performance of this rotary crossflow membrane filtration system was evaluated by comparing fouling result in experiments with and without rotation. Less fouling was observed when membrane was rotating (Fig. 3). By tracking the microsphere size distribution in the feed as a function of time, we showed that larger particles were preferentially excluded from the cake when the membrane was rotating. Results of computational fluid dynamics (CFD) simulations (not shown) were in good agreement with experimental data. These results indicate that the rotation-induced centrifugal force may be used to mitigate membrane fouling.
 
Figure 3. Concentration of hollow glass beads in the feed tank as a function of time during cross-flow filtration with and without rotating the membrane.
 
 
Task 3: Design of superoleophilic membranes to continuously whicker oil
 
We prepared superhydrophobic coatings to wicker oil, but thus far they are not effective under the pressures required for filtration.
 
Task 4: Design of the prototype hydrocyclone system
 
We have assembled two hydrocyclones one for pretreatment of feed waters containing components with the specific gravity of larger than 1 and one for oil-water separation.
 
Task 4.1: Design and testing of solid-liquid separation hydrocyclone (SL-H)
 
The SL H was built in several configurations to identify the geometry with optimal separation properties (Fig. 5). Intended as a pretreatment device, SL-H would be challenged with complex feeds that contain not only oil but also suspended components with specific gravity higher than 1. Accordingly, SL-H was subjected to preliminary testing with several types of feed water including simpler ones (oil-in-water emulsions, sand suspensions) but also oil-sand-water suspensions that more closely represented likely field conditions. Based on results with fine sand (Fig. 6), we identified the optimal geometry of this pretreatment unit.
 
 
Figure 5: Three of several SL-H geometries tested (left) and a photo of the SL-H assembly (right)
 
In experiments with and oil-sand-water suspensions (1 g of sand and 1 g of oil per liter of water), we observe that in the presence of oil, the efficiency of sand separation deteriorates, while in the presence of sand, the separation of oil improves (Table 1). These observations could be explained if one assumes that the finest sand particles stick to oil droplets to form aggregates thereby stabilizing the oil emulsion and increasing the effective oil droplet size. Under these conditions, we can indeed expect that smaller particles of sand attached to oil will go to the overflow.
 
Figure 6: Effect of flow ratio and hydrocyclone geometry on the separation efficiency. Mo is the mass of sand in the overflow, Mi is the mass of sand in the feed, Qu is the volume flow rate of the underflow, and Qi is the inlet volume flow. G4, G8, and G9 are various geometries tested (see Fig. 5, left).
 
Table 1. Separation efficiency of sand-oil-water mixture. Co is the concentration of sand in the overflow, Ci is the concentration of oil or sand in the feed, Cu is the concentration of oil in the underflow.
 
 
Task 4.2: Design and testing of liquid-liquid separation hydrocyclone (LL-H) and liquid-liquid crossflow filtration hydrocyclone (LL-CFFH)
 
The LL-CFFH (Fig. 7) was very recently manufactured for us by ChemIndustrial Systems, Inc. (CSI), Cedarburg, WI (http://www.chemindustrial.com). Michael Lloyd and Rick Paul of CSI visited MSU January 7, 2013, and presented their manufacturing capabilities including hydrocyclones (http://www.hydroclone.com/). During a reciprocate visit by Vlad Tarabara on May 16, 2013, we agreed on the parameters of the de-oiling hydrocyclones that CSI would manufacture for the project team.
 
 
Figure 7: Solid-liquid hydrocyclone (SL-H) used as a pretreatment process for LL-CFFH
 
The overall cost was $2,210. The hydrocyclone has already been made and was received by the MSU team on June 28, 2013.
 
The LL-CFFH was designed to be used either as a conventional deoiling hydrocyclone (with one of the consensus optimal geometries) or as a crossflow filtration hydrocyclone. Figure 7 illustrates the LL-CFFH with the lower (parallel) section replaced with cylindrical ceramic membrane rendering the HC to be a cross-flow filtration hydrocyclone. Currently, we are working on connecting this LL-CFFH to the pump and the data acquisition system. No research data has been acquired with this unit, but we expect that it will be ready within one month.
 
Extension effort
 
A kick-off meeting was held during the Gulf of Mexico Oil Spill and Ecosystem Science Conference in New Orleans, Louisiana on January 21, 2013. This event was attended by investigators and support staff from both Michigan and Louisiana. It was brought up at the meeting that the resulting oil-water separation equipment and technologies developed from the project might prove extremely valuable not only for spill response but also for oil field related operations. Thus, it was suggested that once a project prototype was developed to the point of successful operation that the device be presented and demonstrated to select industry leadership for evaluation. Further, it was agreed that formal presentation to the general public should also be done after the working prototype was fully developed and proven.
 
Prior and subsequent to the kick-off meeting initial outreach was achieved using mass-media and personal contact methods. Newspaper and blog articles were published describing the project and expected outcomes. Personal contacts were made by the outreach team to local governmental organizations and to citizens participating in Extension sponsored programs. A domain name, oilwaterproject.com, was registered and will be used as a clearinghouse site for documenting the project and for receiving public feedback. The principal outreach investigator, Alan Matherne, visited the MSU campus and Kalamazoo area in March to begin gathering information for developing outreach materials.
 

Future Activities:

Task 1
We are performing oil-water filtration experiment with membranes coated by polyelectrolyte multilayers to examine the fouling reduction these films offer. To create superhydrophilic films, we may include silica or zeolite nanoparticles to increase surface roughness.
 
Task 2
Simulations will continue with the goal to:
  • Identify geometric parameters that maximize the performance of LLH and LLCFFH. Parameters to vary will include the wall taper angle for a conical hydrocyclone, the various lengths of each sections, the inlet velocity (or Reynolds number), the pressure drop, the applied back pressure on the underflow;
  • Validate the computational results with the performance of the LLCFFH in the laboratory;
  • Identify a geometry that will maintain a strong swirl over the porous region. This may require several inlets and outlets as the swirl dies rapidly in the presence of a porous wall. The swirl is needed to mitigate fouling of the porous media.
Task 3
We will prepare superhydrophobic polypropylene films to examine wickering of oil, although we are not sure whether such film can remain superhydrophobic in the presence of surfactants or under high pressure.
 
Task 4
We will complete the assembly of the LL HC and will test it with model oil-water emulsion and samples of produced water. Further, we plan to work with ChemIndustrial to explore the potential of miniclones (http://www.hydroclone.com/products/miniclone.htm). These devices seem to be very promising because of the possibility of arraying them and because these devices afford the highest acceleration of all hydrocyclone models. The former may help to overcome perhaps the most serious drawback of CFFHs –low product flux, while the latter should allow separation of very smaller oil droplets. We contemplate submitting an SBIR proposal (with CSI as the lead and the MSU team as a sub-constructor) on miniclones for oil-water separation.
 
Outreach
The website will be further developed and made available to the public. A comprehensive PowerPoint presentation will be developed outlining the project, progress made thus far, and proposed outcomes. Louisiana Sea Grant will assist in producing a companion video to go along with the website and PowerPoint. Community organizations in oil-spill affected Louisiana and Michigan areas will be identified and invitations extended to the leaders to have the outreach team deliver presentations to the organizations. Survey instruments will be developed and used to obtain feedback from the community organizations contacted.

Journal Articles:

No journal articles submitted with this report: View all 43 publications for this project

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

Progress and Final Reports:

Original Abstract
  • 2013 Progress Report
  • 2014
  • Final Report