Design Attributes and Scale Up Testing of Annular Centrifugal Contactors Page: 3 of 11
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Development of the annular centrifugal contactor (ACC) by researchers and engineers
at the U.S. government laboratories began in the early 1960s. The basic design is credited to
Webster, who worked at the Savannah River Laboratory (12). Bernstein et al., at Argonne
National Laboratory, added the annular mixing zone (3). Another Argonne researcher, Ralph
Leonard, led the development of many practical contactor concepts and improved upon the
design and utility (4,). Research and process development with contactors continues at the
national laboratories and has progressed into commercial applications (6).
Commercialization of annular centrifugal contactor technology began eleven years ago
with the technology transfer of a patent from the Department of Energy's Idaho National
Engineering and Environmental Laboratory (7). Since that time, a number of design
enhancements have been made and patented that led to a device better suited to a variety of
liquid-liquid processes. Multiple sizes were designed to provide total throughput ranging from
0.25 to 700 liters per minute (_9). Interchangeable heavy phase weir rings were incorporated
into the rotor to allow separation of a wide range of density pairs. A low mixing sleeve was
added to aid in direct separation of viscous and difficult liquids (10). Clean in place (CIP)
capability was achieved by adding a hollow central shaft with spray nozzles to the rotor (11).
The resulting annular centrifugal contactor is a low rpm, 100-600g centrifuge powered
by a direct drive, variable speed motor. A variable frequency drive is used to control speed,
start-up, shut down and also conveniently display other electrical status information. Properly
optimized, this centrifuge can efficiently separate two immiscible liquids of differing densities
throughout a 100% change in feed ratio and flow rate without adjustment.
Laboratory testing of highly radioactive feeds using mini-contactors of similar design has
been conducted on numerous flowsheets related to nuclear fuel cycle studies. Recent work at
such locations as: Argonne National Laboratory, Idaho National Laboratory, Savannah River
Laboratory, in France, and in China has successfully demonstrated high separation and
decontamination factors for many elements using a variety of organic extractant solvents (12-
16). Vandegrift et al also reported the results of nuclear fuel cycle multi-flowsheet testing at
the 2004 Waste Management Conference (17).
Difficulties related to maintaining consistent flow and stage efficiency are observed due
to the small inlets, outlets and orifices inherent in mini-contactors having 1 or 2 cm. diameter
rotors. Such limitations make it difficult to predict how many stages will be required to meet
the separation goals in both pilot and full scale processing applications. Therefore, testing with
larger units has been suggested to support process facility designs. Leonard et al summarized
some hydraulic performance problems while using 2 cm contactors and indicated that most are
resolved in units of 4 cm diameter or greater (18,19). He also reported on the hydraulic
performance of a 5 cm contactor and found no indication of the typical mini-contactor types of
efficiency losses due to such phenomena as slug flow or phase inversion (20). However,
single stage efficiencies were not directly measured on the 5 cm unit during this study. Testing
at the INL will be conducted using 5-25 cm rotor contactors to further address these issues and
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Meikrantz, David H. & Law, Jack D. Design Attributes and Scale Up Testing of Annular Centrifugal Contactors, article, April 1, 2005; [Idaho Falls, Idaho]. (digital.library.unt.edu/ark:/67531/metadc886659/m1/3/: accessed November 14, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.