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

Abstract

The annular centrifugal contactor (ACC) is highly efficient solvent extraction equipment and has been successfully used in many industrial fields. The phase distribution of two phases in the separation zone of the rotor is an important factor affecting the hydraulic performance of the ACC. It can be characterized by the actual phase ratio (Ro/a) and interface radius (ri). So far, there have been few systematic research studies on the effects of the structure, operation, and physical parameters on them. This work systematically investigated the effects of the structure [the radius of the heavy phase weir (ra*) and radius of the light phase weir (ro*)], operation [rotor speed (N), flow ratio (Fo/a), and total flow (Q)], and physical parameters [density difference (ρa – ρo), viscosity ratio (μo/μa), and interfacial tension (γ/γ*, γ* is the constant interfacial tension)] on the hold-up volume, Ro/a, and ri in the 20 mm ACC using a liquid fast separating method. The results show that Ro/a and ri increased with the increase of N, Fo/a, and ra* and decreased with the increase of ro*, Q, and ρa – ρo. However, μo/μa and γ/γ* have little effect on Ro/a and ri. The N can reach more than 5000 rpm when the ρa – ρo is greater than 0.2200 g/cm3. The closer the Ro/a is to 0.45, the better the hydrodynamic properties of the extracted system are in the ACC. A new model associated with these parameters was established to calculate ri. The results show that the ρa – ρo of the extraction system is the main factor affecting the ri with a degree of influence of 0.5654, followed by the combination of different-size phase weirs with a degree of influence of 0.4052. Moreover, the ri values obtained by the model are in good agreement with those obtained by experiments. The experimental results will provide relevant references for the improvement and optimization of the ACC.