Sonic Energy Improves Industrial Separation and Mixing Processes
Date: Nov 11, 2013 Source: DOE Success Story (
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Challenge
Advanced membrane separation technologies offered improvements over conventional processes,
but were not being adopted in industrial operations because of the tendency of ultrafiltration
membranes to foul while in service. Considering biotechnology as a case in point, while
membrane filtration with micro-sized pores was the separation technology of choice, the protein
solutions tended to foul the membranes during filtration. However, none of the techniques
commonly used to improve ultrafilter performance, such as high cross-flow velocity, could beused with proteins.
In addition to many applications in biotechnology, enhanced membrane filtration technology
has broad potential for other industrial separations processes with fouling problems, such as
pharmaceuticals, cosmetics, food, chemicals, ceramics, electronic materials, bioreactors (cell
culturing and microbial production), nanomaterials, and municipal water and waste treatment—as
well as energetics studies.
The economical conversion of many commodity production lines to environmentally-friendly
processes was limited by downstream operations to separate product from biocatalyst, rather than
by the complex technology associated with the directed evolution of enzymes. New technology
was needed to improve the performance of membrane separations and enable biotechnology and
other industrial applications to become more economical.
Innovating Solutions
With DOE EERE SBIR support in 1999 and 2000—and follow-on DOE and other Federal
agency SBIR support for specific applications—Resodyn worked to address the membrane-fouling
problem by coupling filtration technology with a mechanically-driven, low-frequency acoustic
resonator. This new approach—which was distinct from both conventional impeller agitation and
ultrasonic mixing—involved acoustic pulses from the resonator impinging on the membrane,
creating micro-turbulence near the face of the membrane to assist in keeping the flux of permeate
from falling due to the buildup of a resistive gel layer.
Phase I demonstrated the enhancement of permeate flux through a 10,000 molecular weight cut-
off membrane from solutions with 1 to 5 percent protein (such as pepsin). Enhancements were
most pronounced for conditions with no cross-flow velocity. These are precisely the conditions in
which a free enzyme bioreactor would need to function because of the detrimental effect of cross-flow shear on proteins. In Phase II, Resodyn worked to optimize the design of the membrane
bioreactor for use in specific industrial processes and to further demonstrate that enzymes
proposed for use in these processes are not degraded in the sonic environment.
A pilot-scale modulator bioreactor was fabricated and mobilized for continuous testing of the new enzymatic-based process. Resodyn's acoustic mixing technology works by inducing low-frequency resonant sonic energy in a fluid, resulting in an increased rate of energy dissipation per unit mass of the fluid andallowing rapid and efficient dispersion of solids, gases, and immiscible liquids.
The technology is essentially a vessel with no moving parts inside and runs at approximately 60 Hertz. A patented drive system on the outside of the vessel serves as the resonant mechanical driver that radiates an acoustic energy field that mixes the vessel contents.
