ELECTROWET COALESCER TO ENLARGE DROPS IN EMULSION
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ELECTROWET COALESCER TO
ENLARGE DROPS IN EMULSION
ASHISH GADHAVE, ASHISH BANDEKAR, JIANYU ZHOU
DR. GEORGE G. CHASE
DEPARTMENT OF CHEMICAL AND BIO‐MOLECULAR
ENGINEERING
14 TH FEBRUARY 2018
1
Introduction
• Recent work at the University of Akron has produced a
novel Electrowet Coalescer (EWC) device to improve
separation of immiscible liquid emulsions.
• Students formed an entrepreneurial team to look into
commercial applications.
• The team participated in NSF I‐Corps training session.
• The work presented here is part of this effort
2
NSF I‐Corps
• National Science Foundation‐Innovation Corps.
• Prepares Scientists and engineers to extend their focus
beyond the university labs.
• Accelerates the economic and societal benefits of research
projects that are ready to move towards commercialization.
• Offers entrepreneurial training.
• Customer discovery to determine if EWC device should be
developed for industries.
• Comments and suggestions on the EWC device are welcome.
Ashish Gadhave.
Chemical & Biomolecular Engineering Dept.
University of Akron 3
Email: adg80@zips.uakron.edu
Relation To Produced Water
• Produced water (PW) treatment operations may have by‐
product streams that are concentrated in petroleum liquids
• Operations to increase the petroleum concentration (or
reduce water content) of these streams can benefit the oil
production industry:
Source of petroleum with less water requires less energy
to process.
Make PW operations contribute to the company’s profit
instead of being a necessary expense.
Possible reduction in disposal costs.
4
Proof of Concept
We conducted proof of concept experiments using diesel fuel.
In future work we are interested in testing the process on crude oil.
Results
• The EWC significantly enhanced barrier filter performance by
increasing drop size with small increase in power consumption.
• This shows the technology can be economically applied.
5
Separation Of Water Drops From Oil
Many methods are available to remove water from oils
• Thermal and chemical methods tend to be very expensive but
highly efficient
• Physical methods (gravity, centrifuge, etc.) are less expensive
but performance diminishes for small drop sizes
Removal of very small drops
• To improve the effectiveness of physical methods to remove
very small drops, coalescing devices are commonly applied
• Coalescing filters upstream of the physical method are
commonly used
6
Two Types of Ideal Filters
BARRIER FILTERS COALESCER
1‐step 2‐step
operation, operation
coalescence
Enlarged
and separation
drops
More efficient
removal by a
downstream
M= Accumulated physical
water separator
+
7
Motivation to remove water from diesel fuel • All fuels contain some water in suspension, coming from different sources.
Objective
• Filtration of water‐ULSD emulsion using fiber mats had efficiency of 98%
or slightly higher *#.
• The drops of size more than 100 μm can be efficiently removed using
physical separations such as barrier filters, gravity settlers, hydrocylones,
etc.
• However separation efficiency reduces for drops of size < 100μm.
• The LONG TERM GOAL of this work is to develop an electrowet‐coalescer
device (EWC) to enlarge drops prior to separation.
• Sarfarz U. Patel, George G. chase. Separation of water droplets from water‐in‐diesel dispersion using super hydrophobic
polypropylene fibrous membranes. Separation and Purification Technology; Vol 126: 62‐68
9
# John A.Boxall, Carolyn A.Koh, E.Dendy Sloan, Amadeu K.Sum and David T. WU. Droplet Size Scaling of water‐in‐oil emulsion
under turbulent flow. Langmuir,2012,28(1) : 104‐110.
What is Electrowetting?
• The electrowetting effect is the change in solid‐electrolyte contact
angle due to an applied potential difference between the solid and the
electrolyte.
Basic Electrowetting
• In electrowetting, an electrode is first coated with a dielectric followed by
coating with a hydrophobic layer.
10•Without the presence of external electrical stresses, the ions are randomly
distributed in the droplet. (A)
•With the external electrical potential across the droplet, the ions tend to
migrate towards the oppositely charged electrodes. (B)
No Potential applied Electrical potential applied
A B
•The electric double layer formed between the insulator/liquid interface
causes the contact angle modulation.
•In electrowetting, the additional electrical force alters the shape of the
droplet and thus change in the contact angle.
11Coalescence
• Coalescence is a process in which two or more droplets
merge to form one united droplet.
• When the applied potential is increased quickly, the
droplet moves from one place to another.
• Different mechanisms and phenomena lead to
coalescence. Electric fields can be used to promote
coalescence by increasing the attractive force between
the droplets.
12Drops coalescing • For coalescence of water drops suspended in diesel; the drops should stay in contact with each other till the thin film existing between the drops gradually ruptures. • Introduction of electric field increases the attractive force between the droplets causing a faster rupture of the thin diesel film. • Coalescence of drops in a dispersion is also enhanced by difference in speed between drops in a dispersion and EW is a tool for achieving it. 11
Hypotheses
• In the designed system, under electrowetting conditions, the drops
will move slower and grow larger than in non‐electrowetting
conditions.
• Electric fields in electrowetting system attract drops to the
electrowetting surface and thus better coalescence.
• The applied electric potential difference will be much smaller.
• The EWC device can be self‐cleaning.
14PRIOR WORK (BY CO‐AUTHORS)
15Electrowet Coalescer
• A Thin-Slit-Radial Flow EWC was designed and fabricated*.
Schematic of Thin‐Slit‐Radial Flow EWC 16
*A. Bandekar, G. Chase. Coalescence of water drops in water‐ULSD dispersion via electrowetting. 2016Drop Size Distribution
1400
Only EWC
1200
Upstream
1000
Drop count per volume
Downstream after 20 mins
800 Downstream after 40 mins
Downstream after 60 mins
600
400
200
0
0 20 40 60 80 100 120 140 160 180 200
Drop Diameter (microns)
Figure. Drop size distribution of water drops in inlet and outlet of EWC
when applied potential was 350 V and flow was continuous 17
A. Bandekar, G. Chase. Coalescence of water drops in water‐ULSD dispersion via electrowetting. 2016EWC + Barrier Filter
1400
1200
Drop count per volume
1000 Upstream
Electrowet‐coalescer Exit
800
Downstream
600
400
200
0
0 20 40 60 80 100 120 140 160 180 200
Drop size (μm)
Figure. Performance of thin-slit radial flow EWC.
18Power Analysis
Filter Media Power: ∆P . Q
EWC + Filter Media: VI + ∆P . Q
Efficiency (%) 19
* Goutham Viswanadam, George Chase. Water-diesel secondary dispersion separation using superhydrophobic
tubes of nanofilters. Dissertation. 2013.
# Sarfaraj Patel, George Chase. Separation of emulsified water from ULSD. Dissertation. 2013.Current Work
• Modified Design.
• Lower Voltage.
• Work in progress. Cannot disclose details.
4 cm
2 mm
Upstream sample Downstream sample after
60 min 20Advantage of EWC
Conventional separation
Techniques
Low Efficiency, Low Energy cost
OR
High Efficiency, High Energy cost
Electrowet Coalescer
High Efficiency, Low Energy CostConclusion
The work* proved the EWC concept using a thin‐slit‐radial flow
EWC
• Drops were enlarged in continuous flow
• The drop size increased from ~33 micron to ~110 micron.
• The enlarged drops were easily separated out by using
normal filtration techniques.
• EWC device helps to increase the separation efficiency at
minimum energy cost.
22
*A. Bandekar, G. Chase. Coalescence of water drops in water‐ULSD dispersion via electrowetting. 2016Future work
• More compact size
• Reduced applied voltage
• Improve scaling of EWC to different volumetric flow rates
• Collaborate with industry/commercialize
23Acknowledgement
• Produced Water Seminar for partial financial support
• Thank you for opportunity to present the research
results
• Coalescence Filtration Nanofibers Consortium (CFNC).
24Thank you.
Questions?
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