In the quest to mitigate carbon emissions, researchers are constantly seeking innovative solutions to capture and store CO2. A recent study published in the journal *Carbon Capture Science and Technology* sheds new light on the behavior of natural limestone-based CO2 sorbents, offering insights that could significantly impact the energy sector.
The research, led by Maximilian Krödel from the Laboratory of Energy Science and Engineering at ETH Zurich, delves into the morphological changes of Havelock limestone during repeated carbonation-calcination cycles. These cycles are crucial in calcium looping, a process that shows promise for capturing CO2 from power plants and industrial sources.
Krödel and his team examined the evolution of the limestone’s pore structure in three distinct ranges: 2–100 nm, 200–3000 nm, and greater than 3000 nm. Their findings reveal that during the first carbonation cycle, pores in the smallest range (2–100 nm) are fully filled with CaCO3 at a CaO conversion rate of over 60%, leading to a dramatic loss of approximately 90% of the sorbent’s total surface area. In contrast, larger pores in the other two ranges are only partially filled or remain largely unaffected.
The study’s results challenge the conventional understanding of the carbonation process. “Our findings suggest that the reaction is limited by diffusion as soon as the surface of CaO is fully covered with CaCO3 crystallites,” Krödel explains. This challenges the widely held belief that a CaCO3 product layer of critical thickness limits CO2 diffusion to CaO.
The implications of this research are profound for the energy sector. By tuning the pore diameter of CaO-based sorbents to be larger than 100 nm, the pore volume and surface area can be largely regenerated over multiple cycles. This could lead to the development of more efficient CO2 capture technologies, ultimately reducing the cost and environmental impact of carbon capture processes.
Krödel’s work not only provides a deeper understanding of the carbonation-calcination cycles but also offers a roadmap for designing more effective sorbents. As the world continues to grapple with the challenges of climate change, such advancements are crucial for achieving sustainable energy solutions.
The study, “Experimental and numerical investigation of the morphological changes of a natural limestone-based CO2 sorbent over repeated carbonation-calcination cycles,” was published in the journal *Carbon Capture Science and Technology*, offering a beacon of hope for the future of carbon capture technology.