Experimental Measurements of Drop Size Distributions in 30？mm Diameter Annular Centrifugal Contactor with 30% TBP-Nitric Acid Biphasic System

For design and development of liquid-liquid extraction systems, it is essential to have an accurate estimation of hydrodynamic and mass transfer characteristics of the employed contactor. In the present study, experimental evaluations consisted primarily of determining the maximum solution throughput that could be processed without cross-phase contamination at a given rotor speed, O/A flow ratio, and organic-aqueous solution pair in a 30？mm bowl diameter centrifugal contactor. In addition, analysis included experimental drop size determinations as well as holdup determination. The experimental drop size distributions are expected to be helpful for modeling work. 1. Introduction Centrifugal contactors represent an efficient class of solvent extractors as compared to conventional system of columns and mixer-settlers. Based on the construction, these can be classified as differential and discreet (staged) contactors. For details, user is referred to Laddha and Degaleesan [1]. For staged variants, essentially design of mixing as well as settling zones differ; for example, original (SRL) Savannah River Lab design was having a paddle mixer and a centrifugal settler, whereas contemporary (ANL) Argonne National Lab design is based on annular mixing zone coupled with a centrifugal settler. Advantages of centrifugal contactors include low floor area as well as low head space requirement, lower inventory, elimination of interstage pumping, higher mass transfer efficiencies, and a better settling due to high “ ” separation. Design philosophy was explained by Leonard et al. [2], and contemporary research work was reviewed by Vedantam and Joshi [3]. In this work, hydrodynamics in a biphasic system were studied with 30？mm bowl diameter centrifugal extractor, designed and developed indigenously. The salient dimensions of this extractor are listed in Table 1. Table 1: Dimensions of the annular centrifugal extractor used in the study. 2. Importance of Drop Size Distribution Determination in Centrifugal Extractors A better understanding of the drop breakage and coalescence phenomena inside solvent extractor is required for robust design. The rate of mass transfer in liquid-liquid dispersions created in solvent extractors solely depends on the interfacial area, mass transfer coefficient, and the degree of mixing of the two phases. The interfacial area is related to holdup by the following relation: where is the Sauter mean diameter and the volume fraction of the dispersed phase. It is commonly observed that is proportional to the mean drop diameter ( ). Therefore, most of