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.