Hydrodynamic performance evaluation of a novel eductor liquid–liquid extractor using CFD modeling

Abstract

The hydrodynamic aspect of a novel eductor type contacting device for liquid–liquid extraction (LLE) system has been evaluated by computational fluid dynamics (CFD) modeling. CFD results were validated by droplet rise velocity and dispersed phase holdup in water/toluene system; errors were 20.7% and 15.4%, respectively. The results of CFD simulation have shown that the existence of venturi above the nozzle-jet improves the mixing due to extension of mixing region. Educator mixing performance was investigated by the effects of the parameters: jet velocity, the throat to nozzle area ratio (At/An), the column to nozzle diameter ratio (Dc/Dn), the projection ratio (Ltn/Dt), and two phases flow ratio (Qc/Qj) on the dispersed phase holdup, the suction ratio (Rs), the mixing efficiency (ηm) and the mixing energy efficiency (ηe). A new efficiency named “overall efficiency” was defined as ηo=ηm·ηe to determine the optimum operation and design condition of the eductor. The values of important parameters were determined as a) the jet velocity less than 2m/s; b) At/An around 100; c) the ratio of Dc/Dn<50; d) 1<Ltn/Dt<2 and the value of Qc/Qj although being flexible, but smaller values are preferred for achievement of higher mixing efficiency.