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

Abstract

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.

Thermal Conductivity of Molten Carbonates with Dispersed Solid Oxide from Differential Scanning Calorimetry

“…In Figure 1, the TGA weight loss detected before the first heating cycle was due to evaporation of moisture (<200 °C) and melting (~495 °C) of LNC (eutectic Li and Na carbonates) in the LNC-MO mixture [33]. No significant weight loss was observed, demonstrating a high thermal and chemical stability of the sample during the analysis [34]. The steady baseline of the DSC cooling curves (Figure 2) before the exothermic peaks also confirms the chemical stability and retention of the homogeneity of the sample [33,35].…”

“…The endothermic peak is intense and well defined in the third heating cycle, but not even initiated in the first heating cycle. This illustrates that the repeated solid and liquid phase transition had established a better thermal contact after a few thermal cycles [33,34]. The heating curve recorded between 650 and 690 °C (Al melting behavior) in the third cycle (after establishing a better thermal contact) was used to determine the thermal resistance of the sample.…”

Performance Analysis of a Hybrid System Consisting of a Molten Carbonate Direct Carbon Fuel Cell and an Absorption Refrigerator

“…Although the research and development of MCDCFCs have made great progress in aspects such as electrolyte development [14,15], prototype design [16,17] and lifetime extension [18,19], the energy conversion efficiency of MCDCFCs is still low [20]. Alternatively, the MCDCFC performance can be also equivalently improved by building cogeneration systems [21][22][23][24][25], since a large proportion of the chemical energy stored in fuels is released as waste heat.…”

Electrolyte Melt Compositions for Low Temperature Molten Carbonate Thermocells

“…In Figure 6 the decomposition process is monitored by measuring the change in electrolyte weight on heating to 900 ºC under N 2 atmosphere. The weight loss observed before 200 ºC is due to the removal of moisture 12 and the sudden drop around 300 ºC is attributed to the implemented isothermal condition followed by the different heating rates used in the measurement algorithm (Table 3). The electrolyte mixtures solid to liquid phase transition shows the respective change in TGA curve around 400 ºC for the ternary carbonate mixtures (LNKC, LNKC-CC, LNKC-LF).…”

“…As mentioned in the DSC discussion the high interface thermal resistance between the solid sample and alumina pan in high heating rate can shift the corresponding liquid weight change in TGA to high/low temperatures. 12 The lattice energy and cation polarization power of the salt have strong effects on their thermal 18 stability. 34 As shown in Table 1, the larger lattice energy of the CaCO 3 prompts the early decomposition in LNKC-CC.…”