Viscosities of Li₂CO₃-Na₂CO₃ and Li₂CO₃-K₂CO₃ Binary Melts

Abstract

Viscosities of Li₂CO₃-Na₂CO₃ and Li₂CO₃-K₂CO₃ binary melts, which are assumed as the electrolytes of molten carbonate fuel cell, have been measured in entire composition range. A gas injection system was introduced and the torsion wire replaced with thick one to obtain the reliable viscosity of carbonate melts. lsothermal viscosities showed downward convex curves in entire composition range for both melts. Highest viscosity was found for Li₂CO₃ and minimum values were found at 70∼80mol% of Na₃CO₃ and K₂CO₃ for higher temperatures. The activation energies for both melts decreased monotonously with increasing Na₂CO₃ and K₂CO₃, Therefore, it is considered that these melts are simple mixture and the decrease of viscosity is due to volume expansion by mixing. The viscosity at the working temperature of molten carbonate fuel cell, about 923K, is 7∼9mPa·s.