Molten ionic oxides for CO₂ capture at medium to high temperatures

Abstract

Molten ionic oxides based on sodium borate and mixed alkali-metal borates show remarkably fast sorption kinetics and intrinsic regenerability as liquid absorbents for CO2 capture at medium to high temperatures

Sorbents for the Capture of CO2 and Other Acid Gases: A Review

“…Molten salts are a recently discovered class of liquid phase sorbent that operate at elevated temperatures. A number of advantages of certain salts for CO 2 capture, including high capacities, fast kinetics, and excellent stability, have been demonstrated with molten alkali metal borates. ,, These materials may be tuned for entirely liquid phase reactions or for the phase change precipitation of reaction products, introducing opportunities to handle captured SO x and NO x impurities . As high temperature liquid phase materials, these sorbents are uniquely positioned, although a number of uncertainties and challenges remain around their corrosive nature and their practical operation at scale. , …”

Net-Negative Emissions through Molten Sorbents and Bioenergy with Carbon Capture and Storage

“…The approach temperatures in the sorbent and steam heat exchangers were taken as 5 and 20 °C, respectively. Sorbent properties based on those of lithium−sodium borate (Li 0.5 Na 0.5 ) x B 1−x O 1.5−x (x = 0.75) were taken from literature, where the enthalpy of reaction 212 ± 13 kJ/mol, 22 has been reported and the specific heat capacity was assumed to be within 50% of that of the sodium borate Na x B 1−x O 1.5−x (x = 0.75). 29 The LP outlet pressure was optimized to minimize the levelized cost of electricity, with the same approach reported previously, 26 giving a pressure of 25 kPa for all cases with carbon capture.…”

“…In this work, we explore how a new class of molten salt-based sorbent materials could contribute to increasing the techno-economic feasibility of BECCS. Molten sorbents are liquids under high temperatures at which CO 2 is exposed to the sorbent and separated from the flue gas stream, typically 600–700 °C. , Significant opportunities exist despite the fact that molten sorbents are at a lower technology readiness level than other sorbents. Advantages of molten sorbents include high capacities, fast kinetics, excellent stability, combined capture of multiple acid gases, and low energy penalties. , The work presented here follows the principles presented in our previous analyses, which proposed a conceptual design for a large 800 MW e coal fired power plant.…”

“…Molten sorbents are liquids under high temperatures at which CO 2 is exposed to the sorbent and separated from the flue gas stream, typically 600−700 °C. 22,23 Significant opportunities exist despite the fact that molten sorbents are at a lower technology readiness level than other sorbents. Advantages of molten sorbents include high capacities, fast kinetics, excellent stability, combined capture of multiple acid gases, and low energy penalties.…”

Bench-Scale Demonstration of Molten Alkali Metal Borates for High-Temperature CO2 Capture

“…On the other hand, the lithium-sodium borate (Li 0.5 Na 0.5 ) x B 1−x O 1.5−x (x = 0.75) sorbent reacts to form entirely liquid products with CO 2 , forming a eutectic carbonate in the melt, a so-called "liquid-to-liquid" sorbent. 25,26 The two sorbents, Na unforeseen challenges and limitations at scale. In this work, we investigate how the molten alkali metal borates scale and in doing so demonstrate some promising advantages of these materials for the first time.…”