Ultra-low temperature sono-assisted CO<inf>2</inf> stripping/ carbon-rich solvent regeneration using different ultrasonic frequencies

Carbon dioxide emission from anthropogenic sources plays a major role in global warming and climate change. Conventional amine-based carbon capture is matured technology that has limitations on high-temperature use imposed by solvent degradation and solvent loss during CO2 stripping/regenerating solvent. The present experimental investigation involves the application of tank-type (bath-type) sonication for CO2 stripping from aqueous carbon-rich 30 wt% MEA solvent in a low temperature-controlled environment, using ultrasonic frequencies of 25 kHz (cavitation-dominant), 360 kHz (streaming-dominant), and 58/132 kHz dual-mode (combined phenomena). The results are analyzed to understand the effects of carbon loading, CO2 stripping efficiency, stripping rate, temperature profile, and energy demand. The stripping rate is higher in the low-temperature range of 6°C to 12°C for all the frequencies due to the sonication effect. In the mid setpoint range of 15°C to 30°C, the CO2 stripping rate is lower due to the combination of sonication and temperature effect, and when the temperatures increase from 40°C to 45°C, the stripping rate increases gradually due to additional temperature effect. A high cyclic capacity of 1.12 mol CO2/kg. was observed for 360 kHz frequency at 12°C. The lowest energy of 3.94 kJ/mol CO2 was achieved for 360 kHz at a setpoint of 12°C. Factors such as sonication frequency, CO2 loading (mol CO2/mol soln.), temperature, and nominal power of ultrasonics play an important role in determining the sensible energy required for CO2 stripping. Specifically, CO2 stripping at the low temperature set point of 6°C and 12°C is found to be promising in all frequencies, indicating that CO2 stripping is primarily promoted by sonication, rather than by temperature.