Process intensification in centrifugal contactor separator: hydrodynamics, mass transfer, and bio-based applications
Centrifugal contactor separators (CCS) are process-intensified devices in which liquid-liquid mixing, reaction, and phase separation occur simultaneously within a single compact unit. The CCS has found applications in nuclear fuel processing, wastewater treatment, extraction of value-added compounds, and biodiesel production. The CCS consists of an annular region for liquid-liquid mixing and a rotor region for phase separation. Due to the complex hydrodynamics in the CCS, the liquid holdup in the annular region is often low, making residence time in this region a critical parameter governing mixing and reaction performance.
In her thesis, Savitha Sundaraiah focused on determining critical CCS performance indicators. Initial studies involved experimental investigations of the hydrodynamics in the CCS using residence time distribution measurements. The results demonstrated that rotor speed strongly controls liquid flow behavior, mixing characteristics, and phase interaction inside the reactor. Furthermore, the CCS was shown to generate very small droplets and large interfacial areas, thereby enhancing mass transfer between liquid phases. Sundaraiah developed a simple experimental methodology to determine droplet size distribution and interfacial area in the annular region, indicating that droplet breakup and interfacial area are mainly governed by rotor speed.
In addition, Sundaraiah studied biodiesel synthesis from sunflower oil and methanol using sodium methoxide as a catalyst in both batch reactors and the CCS. She systematically evaluated the influence of operating conditions, including temperature, rotor speed, and catalyst concentration. Kinetic models of different reaction orders were solved numerically, and a pseudo-first-order kinetic model was found to adequately describe biodiesel synthesis in the CCS. Overall, the CCS demonstrated high biodiesel yield within short processing times, highlighting its potential as an efficient process-intensified reactor.