Liquid‐Liquid Centrifugal Extractors: Types and Recent Applications – a Review

Abstract

In light of the elevating pressures toward adopting intensifying technologies, centrifugal extractors are increasingly drawing attention as a promising alternative to traditional extraction equipment. Recently, many fields have applied them in research and that resulted in a considerable amount of information that may be hard to follow. To keep interested researchers updated, this work presents the state‐of‐the‐art status of those devices. That is, the different types of centrifugal extractors are first surveyed with emphasis on those available on the market nowadays. Then, their recent applications are covered with exclusion of two fields: oil‐water separations and nuclear industry, as the purpose is to accent centrifugal extractors' potential and compatibility with the widest possible range of applications beyond traditional ones. A further section addresses the hydrodynamics of annular centrifugal contactors that form a major subfamily of centrifugal extractors. Those annular variants have received special focus throughout this work, since not only are they the most encountered devices in literature but also still to date under development with latest versions being 3D‐printed.

Effects of the Structure, Operation, and Physical Parameters on the Actual Phase Ratio and Interface Radius in the Separation Zone of an Annular Centrifugal Contactor

“…However, μ o /μ a and γ/γ* have little effect on R o/a and r i . The N can reach more than 5000 rpm when the ρ a − ρ o is greater than 0.2200 g/cm 3 . The closer the R o/a is to 0.45, the better the hydrodynamic properties of the extracted system are in the ACC.…”

“…■ GREEK LETTERS μ viscosity, mPa•s μ o viscosity of the organic phase, mPa•s μ a viscosity of the aqueous phase, mPa•s σ surface tension, mN/m γ interfacial tension, mN/m γ* constant interfacial tension, mN/m ρ density, g/cm 3 ρ a density of the aqueous phase, g/cm 3 ρ o density of the organic phase, g/cm 3…”

“…It is difficult to directly measure r a and r o . They can be obtained as follows 43 (2) (3) where Q o and Q a are the flow rates of the light and heavy phases over the light phase and heavy phase weirs, respectively, given in milliliters pe minute; K o and K a are the actual organic phase and aqueous phase circular weir coefficients in the centrifugal field, respectively; f is 0.95 (assumed fraction of the circumference available for flow); and ω is the angular velocity, given in radians per minute. Some of these parameters in eqs 2 and 3 for calculating r o and r a are empirical values, resulting in the calculation results being inconsistent with the actual operation of the ACC.…”

“…A typical structure of the working module is shown in Figure , which plays a key role in the extraction and separation performance. The ACC has many advantages such as small hold-up volume, low residence time, good phase separation performance, and high mass transfer efficiency. − ACC have been widely used in many fields including chemical industries, − wastewater treatment, − biological engineering, and high-level liquid waste partitioning. ,− Also, ACC hold great promise for rapid demulsification and fast deoxygenation. , …”

Hydrodynamics Study on Annular Centrifugal Contactors: CINC V 02 as an Example

“…Among multiple variants of CEs on the market, annular centrifugal contactors (ACCs) appear to be the most implemented in the recent literature [9]. On the one hand, they comply with the aforesaid trends as being inherently intensifying devices that merge mixing/reaction and separation in one envelope of much-reduced volume compared to typical equipment.…”