Dynamic wetting of dense Ni foil by molten carbonate

Wetting Kinetics of Lithium-Sodium Orthoborate on Nickel and Stainless Steel under CO2-Lean and Saturated Conditions

Contact angle measurements were conducted on lithium-sodium orthoborate, an alkali-metal borate-based high-temperature carbon capture sorbent, in contact with nickel and stainless steel under air, N2, and CO2 atmospheres at 600 °C in order to assess the compatibility of this innovative sorbent with packed-bed reactors, typically used in the commercial carbon capture industry. On nickel, the results reveal the melt to be wetting (contact angle θ ≤ 90°), albeit with a contact angle reaching an apparent equilibrium over the experimental time considered. It was found that θ was lower under N2 than under CO2, which was explained as a consequence of the oxide-ion activity difference between the CO2-lean and saturated melts. On stainless steel, however, the melt rapidly spreads, tending toward complete wetting of the metal sheet (θ = 0°) in all atmospheres. For the two metals investigated, the results indicate high to very high wettability, hence the adequacy of using lithium-sodium orthoborate in conventional gas-liquid contactors, further backing this sorbent as a potential alternative to existing sorbents for CO2 capture.

Wetting Kinetics of Molten Carbonate on Carbon

The wettability of molten carbonate on carbon determines the electrochemical performances of high-temperature direct carbon fuel cells (DCFCs). However, a universal method to measure the high-temperature wettability of molten carbonate is absent and the wetting kinetics is not well understood. Herein, we develop a dispensed drop (DD) method to measure the wetting kinetics of molten carbonate (Li₂CO₃-Na₂CO₃-K₂CO₃, 43.5:31.5:25.0, molar ratio) on the carbon substrate at 450-750 °C under controlled atmospheres (100%Ar, 100%CO₂, and 1%O₂-99%N₂). The measured contact angles under different conditions reveal that increasing the O^2- concentration in the gas-liquid-solid (GLS) interface decreases the contact angle. In addition, elevating the temperature, introducing O₂ in the gas atmosphere, or pretreating the carbon substrate can enhance the wetting kinetics of molten carbonates. The molten carbonate completely wets the carbon substrate in 150 min in Ar gas atmosphere and in 30 min in 1%O₂-99%N₂ gas atmosphere at 600 °C. Further, it takes only 30 min to completely wet the pretreated carbon substrate in Ar atmosphere at 600 °C. Overall, this paper offers the DD method to study the wettability of molten carbonate on the carbon substrate, which is helpful to understand the underlying wetting mechanism and engineer the electrode design for DCFCs.