Coal is the second largest energy resource used for electricity production in the world and is expected remain unchanged through 2030. The main problem of using coal in conventional combustion power plants is serious environmental pollution due to CO₂ emissions. In this context, electrochemical conversion of solid carbon to generate electricity is one of the most efficient technologies using liquid electrolyte at high temperature which is environmentally friendly.

Raw coal as a fuel has some advantages and disadvantages in terms of mineral impurities inhabited in the coal which affect the DCFC performance. Kaolin is a common mineral found in coal fuels which has an advantage over other impurities. It was demonstrated that clay impurities in the coal such as kaolin and montmorillonite react catalytically to enhance graphite oxidation in a half-cell set up DCFC and improve the cell performance [1]. Although other impurities such as alumina, anatase and pyrite have limited impacts on the electrochemical oxidation of graphite, quartz was presented a decline in the current density of electro-oxidation of graphite. Thermal investigation of different coal impurities into ternary eutectic carbonate mixture has been done to show the impacts of these impurities on the melting process and kinetics of the melting process [2]. However it isn’t obvious yet what the impacts of these impurities have on the electrochemical performance of the cell and which disruption or modification will happen with addition of them on eutectic carbonate mixtures.

In this work different ratios of kaolinite mineral were purposely added to the ternary eutectic carbonate electrolyte to investigate the thermal properties of the mixture and its melting behaviour. Particularly, DTA data were analysed in terms of changing melting temperature of the mixture and the determination of activation energy using different heating rates to asses these effects.

The effect of kaolinite on the half-cell performance of a DCFC was also examined by adding kaolinite with different ratios into the eutectic carbonate electrolyte. The OCP, current density and polarization performance have been measured for the half-cell set up and results compared for different ratios of kaolinite and pure eutectic.

Reference:

1-Tulloch, J.; Allen, J.; Wibberley, L.; Donne, S. et al. Influence of selected coal contaminants on graphitic carbon electro-oxidation for application to the direct carbon fuel cell. J. Power Sources 2014, 260,140−14910.1016/j.jpowsour.2014.03.026

2-M.J. Glenn, J.A. Allen, S.W. Donne Thermal investigation of a doped alkali-metal carbonate ternary eutectic for direct carbon fuel cell applications Energy Fuels, 29 (8) (2015), pp. 5423-5433