A Critical Review on CO<sub>2</sub> Stripping/Carbon-Rich Solvent Regeneration: Process Intensification by Combined Sonication and Nanoparticles
Ambedkar Balraj, Mangaleswari Santhosh Kumar, Shree Vidhya Ramamoorthy, Sudharsan Sukumar
Abstract
As of 2024, the CO 2 level in the midtroposphere is measured at 427 ppm. CO 2 is a highly heat-trapping gas and is emitted through coal, oil, and natural gas combustion. An increase in the CO 2 concentration in the atmosphere is a major driver of climate change. One effective method for capturing CO 2 is solvent-based absorption, typically using an aqueous monoethanolamine (MEA) solution. MEA solutions face challenges primarily due to the substantial energy consumption associated with operating at high temperatures around 120 °C. These elevated temperatures lead to many issues in the process, posing significant barriers to industrial deployment. To address these issues, researchers have explored alternative regeneration methods. This review will evaluate alternative solvent regeneration methods for CO 2 capture, focusing on energy efficiency and cost reduction. Key techniques include sonication and nanoparticle-enhanced regeneration, which aim to lower energy demands and intensify the regeneration process. Sonication (20 kHz–1.7 MHz) induces CO 2 stripping through bubble formation and bubble breaking effects, along with heat dissipation. Nanoparticles (SiO 2, TiO 2, ZnO, ZrO 2, Al 2 O 3, Fe 2 O 3, Fe 3 O 4, CuO, and Ni) enhance absorption through Brownian motion, the grazing effect, bubble breaking, and hydrodynamic assistance, which results in higher mass transfer. In desorption, the heat transfer is enhanced due to the hydrodynamic effect and thermal properties of the nanoparticles. Utilizing these synergistic effects in CO 2 stripping can significantly intensify this process. Further, the scope for future work in large-scale implementation of this technique has been discussed.