Thermal Investigation of a Doped Alkali-Metal Carbonate Ternary Eutectic for Direct Carbon Fuel Cell Applications

The carbonate eutectic mixture of Li 2 CO 3, K 2 CO 3, and Na 2 CO 3 is commonly used as an electrolyte within the direct carbon fuel cell. Here, seven different minerals common to the ash content of Australian bituminous coals (anatase TiO 2, SiO 2, CaCO 3, CaSO 4, Fe 2 O 3, FeS, and kaolin) were used to modify the ternary carbonate eutectic to explore the thermodynamics of the carbonate melting process. Thermal effects were examined using differential thermal analysis, where it has been shown that dissolution of the contaminant leads to liquid-phase disruption, the extent of which varies with dopant type. Furthermore, modeling of the melting process carried out using different heating rates allowed determination of the activation energy for melting in the presence of the various contaminants, where it was shown that the contaminants can dramatically affect the activation energy and, subsequently, the kinetics of the melting process.