Ultra-low temperature sono-assisted CO₂ stripping/ carbon-rich solvent regeneration using different ultrasonic frequencies

ABSTRACT

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.

KEYWORDS:

• CO₂ stripping
• acoustic cavitation
• acoustic streaming
• low-temperature operation
• solvent regeneration
• sonication

Acknowledgements

The authors acknowledge the financial support of the Mission Innovation – Innovation Challenge (IC#3) CCUS Project F. No. DST/TM/EWO/MI/CCUS Project/25 (G1) Government of India, Ministry of Science & Technology, Technology Bhavan, New Delhi.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Krishna Kumar Nagarajan

Krishna Kumar Nagarajan completed B. Tech Chemical engineering from Adhiyamaan College of Engineering and M. Tech in Chemical Engineering from Anna University in 2020, Chennai. Currently, he is pursuing his Ph. D from Anna University, Chennai, India. His research focuses on the application of ultrasonics in the regeneration of CO2 rich solvents. His primary research interests revolve around solvent regeneration at low temperatures and the influence of frequency on the regeneration process.

Ambedkar Balraj

Dr. Ambedkar Balraj is an Associate Professor in the Department of Chemical Engineering, Sri Sivasubramaniya Nadar (SSN) College of Engineering, India, with expertise in the field of carbon capture and process intensification. He has a total of 13 years of teaching/research experience at various institutions and research and development in India and abroad. He obtained his B.Tech. in Chemical Engineering in 2001 from VIT Vellore, M. Tech in 2005 from NIT Trichy and his doctoral dissertation was from the IIT Madras, India. He has published over 27 reputed journal publications, 1 book, 1 book chapter, 4 patents filed, and INR 2.56 crores of funded research projects to his credit. He was instrumental in developing Carbon Capture Research Lab at SSN College of Engineering, Chennai, India.

Ramamurthy Nagarajan

Dr. Ramamurthy Nagarajan is Alumni Community Chair Professor in the Department of Chemical Engineering at IIT Madras. He obtained his B.Tech. in Chemical Engineering in 1981 from IIT Madras, and a Ph.D. from Yale University in 1986. Then he served as a Research Faculty in the West Virginia University until 1988, and from 1988 till 2003, he was a Senior Technical Staff Member with IBM Storage Systems’ Development Lab in San Jose. He is a Professor at IIT Madras since 2004. He was the Institute’s first-ever Dean of Alumni & International Relations. During his decade-long tenure he was instrumental in increasing the fund-raising from alumni and corporates by 150 times upto $15 million USD, and enabling 20 joint Doctorate programs with top Universities around the world. He also served as the Department Head from 2018 to 2021. His teaching and research endeavors are focused on cleanroom processes, nano-technology, ultrasonic process-intensification, and recently, nanoemulsions for medicinal applications.

Ravichandar Babarao

Dr. Ravichandar Babarao, (Senior Lecturer) leads the Molecular Modelling Team in Applied Chemistry and Environmental Science department, School of Science, RMIT University, Melbourne, Australia. He also holds a visiting scientist position at CSIRO, Manufacturing, Clayton. He received his PhD from National University of Singapore in 2010 before joining Oak Ridge National Laboratory (ORNL) as a Postdoctoral Research Associate in Chemical Science Division. Then in 2012, he moved to CSIRO as a postdoctoral research fellow and then promoted to Research Scientist in 2014 before moving to RMIT in 2016. In recognition of his outstanding contribution to energy and environmental sustainability, he was awarded the 2015 Prosper.net Scopus Young Scientist Award in the Energy category among Asia –Pacific region. He was also awarded the prestigious Alexander von Humboldt Fellowship to spend time in research institutes in Germany for 6-18 months. In addition, he was awarded the 2016 RACI Rennie Memorial Medal and a Victoria Fellowship from the Victorian government for his excellence in research in Chemical and Physical Science. He was awarded the 2019 Peter Schwedtfeger Award from the Australian Association of von Humboldt Fellows. He was one among the fifteen researchers to be named in the 2020 Class of Influential Researchers from Industrial Engineering and Chemistry Research. His current area of research is to use state of the art computational techniques for accelerating the discovery of novel robust porous materials, in particular metal–organic frameworks or porous coordination polymers for sustainable energy and environmental applications.