A Study of Ultra-Fast CO2 Desorption Kinetics for a Microwave-Enhanced Regeneration Process | AIChE

A Study of Ultra-Fast CO2 Desorption Kinetics for a Microwave-Enhanced Regeneration Process


Gray, M. L., U.S. Department of Energy, National Energy Technology Laboratory
Ji, T., National Energy Tech. Lab.
Soong, Y., National Energy Technology Laboratory

Regeneration of CO2-rich solvents plays a significant role in carbon capture technology. In a traditional aqueous amine-based post-combustion carbon capture process, thermal regeneration cycles are usually conducted using superheated steam. It takes several hours to swing an aqueous amine solution over a temperature range. Furthermore, a significant amount of make-up water is required for each steam regeneration step. This implies an inherently slow process and a huge energy penalty (as a large amount of solvent is water which also needs to be heated or cooled down), when the conventional temperature swing absorption process is used.

In this work, a microwave (MW)-enhanced regeneration process was able to provide ultra-fast CO2 desorption from an aqueous amine solution and a non-aqueous solution. Due to their polarization properties, amine-CO2 pairs in the solution are strong MW energy absorbers. With localized MW heating on amine-CO2 pair molecules, absorbed CO2 can immediately dissociate from amine groups even when the bulk temperature is as low as at 70 oC. Based on the kinetics of desorption, the activation energy of CO2 desorption under MW conditions was significantly reduced compared to traditional thermal regeneration. The mechanical study implied that hot-spots on the amine groups may trigger the desorption reaction and then alter reaction pathways. With this MW-enhanced regeneration process, ultra-fast desorption kinetics and possible low temperature regeneration are able to be achieved. As a consequence, the huge capital investment due to large equipment size, the large energy penalty required for solvent regeneration, and the significant thermal-degradation of amine in the traditional regeneration process may be avoided.