Free surface flow in the mixing zone of an annular centrifugal contactor

Abstract

in Wiley InterScience (www.interscience.wiley.com).The annular centrifugal contactor has been developed as the central piece of equipment for advanced liquid-liquid extraction processes for use in recycling spent nuclear fuel. While a sufficient base of experience exists to support successful operation of current contactor technology, a more complete understanding of the fluid flow within the contactor would enable further advancements in design and operation of future units. In particular, an important characteristic of the flow that is not well understood and which significantly complicates computational modeling of the contactor is the complex free surface flow in the annular mixing zone. This study presents the results of time-dependent, multiphase computational fluid dynamics (CFD) modeling using the volume-of-fluid (VOF) interface tracking method to characterize the mixing zone in a model centrifugal contactor. Laser doppler velocimetry (LDV) measurements of the actual flow velocities within the contactor were also performed. The experimental results were compared with simulations using various turbulence modeling schemes. The CFD model predictions using a coarse grid large eddy simulation (LES) method are in good agreement with the experimental measurements and observations. 2007 American Institute of Chemical Engineers AIChE J, 54: 74-85, 2008

Experimental study of the hydraulic operation of an annular centrifugal contactor with various mixing vane geometries

“…The LDV setup was described previously in , 12 and consisted of a two-component measuring system. Because of the contactor's annular geometry, only backscatter measurements were possible, and, therefore, a transceiver was used rather than an off-axis or forward scatter receiver.…”

CFD Simulation of Annular Centrifugal Extractors

“…(13) Wardle et al [141] have presented a comparison of experimental measurements and computational modeling of the free surface flow in the mixing zone of an annular centrifugal contactor. It was found that CFD modeling using the LES turbulence simulation method even for a relatively coarse computational grid was able to qualitatively and quantitatively predict the actual dynamics of the flow in the contactor mixing zone.…”

“…Wardle and coworkers were the first to attempt to apply free-surface capturing CFD methods to simulate gas-liquid free surface flow in the centrifugal contactor mixing zone at relevant conditions [27,141]. Using volume of fluid (VOF) methods [142] and the commercial code Fluent, the freesurface flow in a lab-scale centrifugal contactor having a 50.8 mm rotor was explored [141].…”

“…Using volume of fluid (VOF) methods [142] and the commercial code Fluent, the freesurface flow in a lab-scale centrifugal contactor having a 50.8 mm rotor was explored [141]. Conditions were chosen for a low-moderate flow rate at a typical rotation rate for this size device (377 rad/s).…”

“…It was seen that fewer vanes resulted in greater liquid volume, liquid height, and fluidrotor contact due to reduced "pumping" by the housing vanes with the ranking in order being 4V > 8V > CV. A case with the addition of a gap between the vane and the outer wall and one with a narrower annular gap were also tested for the 8V case (additional images and analysis for these cases is reported in Wardle et al [141]). It was found that the volume holdup (and consequently the residence time) could be increased by 54% by adding a vane-wall gap equal to half the annular gap.…”