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.

In this work, slow pyrolysis of sawdust of Eucalyptus pilularis biomass and ternary molten carbonate eutectic [Li2CO3, 43.5%; Na2CO3, 31.5%; and K2CO3, 25% (mole percentage)] in thermogravimetric analysis at three different temperatures, 600, 750, and 900 °C, was studied. These salts affect the slow pyrolysis process, including changes in the volatile release mechanism and the morphology of remnant char material. The initial results show that, in the presence of molten carbonate, biomass particles make bubble-shaped larger particles, which result in less volatile emissions and more char residue. It is suggested that the ternary eutectic has a chemical diluent and catalytic role, particularly in the case of higher salt doping. Results from scanning electron microscopy images give strong evidence that molten carbonates capture volatiles inside swelling carbon particles, which causes the generation of various sizes of pores as well as char-making reactions, and at a higher temperature, the bubble-shaped particles will rupture. Swelling of this nature has previously only been observed clearly in coal precursors; however, this is the first observation in a biomass-based system. Also, at a temperature above 750 °C, decomposition of molten carbonate generates CO2 and carbon/carbonate gasification produces CO as well as a more “activated” biochar.

A systematic assessment of the electrochemical activity of two different parent coal types, pyrolysed at temperatures between 500 and 900°C higher heating temperature (HHT), is presented in this work.Analysis shows that certain coal chars are catalytically activated in molten carbonate media at 600°C, however activity does not appear to follow trends established for ashless carbon sources. It is seen here that it is not possible to predict activity based solely on electrical resistance, surface functionalization, or the BET surface area of pyrolysed coals. Instead, it is suggested that coal ash type, abundance and distribution plays a pivotal role in activating the coal char to allow fast electrochemical oxidation through a catalytically enhanced pathway. Activation from ash influence is discussed to result from wetting of the molten carbonate media with the carbon surface (change in polarity of electrode surface), through ash mediated oxide adsorption and transfer to carbon particles, or possibly through another catalytic pathway not yet able to be predicted from current results.

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