Characterization of mass transfer study in a Kuhni continuous extractor for rare earth processing using axial dispersion and backflow models

An experimental and modeling approach is presented to study the impact of operating parameters on mass transfer rate during reactive extraction in the Kuhni continuous extractor. Three mathematical models were implemented to calculate the column's concentration profile. For case studies, D2EHPA extractant diluted in kerosene as an organic solvent and the aqueous solution containing lanthanum and cerium ions were utilized as the reactive solutions to provoke chemical reactions forcing desirable physical changes. Increasing rotation speed from 75 to 195 rpm generated the highest mass transfer and interfacial area and smaller drop sizes at all phase flow rates and ion concentrations. The results showed that axial dispersion and backflow coefficients of the dispersed phase increment as the solvent flow rate and agitation speed increase. These coefficients decrease with the increment in the aqueous flow rate. The AARE values (11-15%) in two extraction and stripping stages showed that the axial dispersion model is the most accurate among the three assessed mass transfer models. The modeling presented in this paper can be used as an engineering tool to design high performance for rare earth processing.