Abstract
Large-scale deployment of direct air capture (DAC) technologies has become critical for mitigating climate change. Towards this end, energy-efficient regeneration of the sorbents used in the process of carbon capture from air is very important to significantly reduce the high operational cost of DAC. Guanidine compounds can be used with environmentally friendly aqueous amino acids (e.g., potassium sarcosinate) for fast and effective CO2 capture from air, and have a strong potential for low-energy CO2 release and sorbent regeneration. In this process, the amino acid absorbs the CO2 from the air, and the guanidine compounds react with the CO2-rich amino acid solution and crystallize as an insoluble carbonate salt. Separation and thermal regeneration of the precipitated guanidine carbonate salt leads to an overall low-temperature and low-energy direct air capture process. Effective CO2 release from the solid guanidine compound can be achieved by mild heating at 120 °C. In this study, to overcome the relatively inefficient traditional conductive heating of the crystalline solid (i.e., Methylglyoxal-bis(iminoguanidine) carbonate, MGBIG carbonate), we evaluated the feasibility of microwave heating of MGBIG carbonate in terms of power requirement, radiation time, and solids mass for efficient CO2 desorption. The energy consumption needed by a microwave oven and a conventional oven to regenerate the same mass of the sorbent was directly measured to compare the total energy required per unit mass of regenerated sample and provide an understanding of the potential benefits of microwave regeneration. We found that microwave heating effectively regenerates MGBIG carbonate, which may be facilitated by the water molecules that are co-crystallized with carbonate in the guanidine crystals. Microwave heating at 2.54 GHz with 1250 W is up to 17 times faster than conventional conductive heating at 160 °C, resulting in 40 % electrical energy reduction. These results indicate that microwave regeneration may be an energy-efficient method for fast regeneration of solid sorbents used for direct air capture.
| Original language | English |
|---|---|
| Article number | 123053 |
| Journal | Separation and Purification Technology |
| Volume | 309 |
| DOIs | |
| State | Published - Mar 15 2023 |
Funding
This work was supported by the U.S. Department of Energy, Office of Technology Transitions, through a Technology Commercialization Fund supported by the Office of Fossil Energy and Carbon Management. The research was conducted at ORNL, which is managed by UT Battelle LLC for DOE under contract DE-AC05-00OR22725. Part of the materials characterization (SEM, XRD) were performed at the Center for Nanophase Materials Sciences, which is sponsored at ORNL by DOE’s Scientific User Facilities Division. Notice of Copyright: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( https://energy.gov/downloads/doe-public-access-plan ).