Energy & Fuels, Vol.34, No.4, 4129-4138, 2020
Intrinsic Solid-State Reaction Characteristics of Coals and Chars in a Direct Carbon Fuel Cell: With Focus on Significance Assessment of Fuel-Borne Factors
In this study, we attempted to evaluate relative significance of the factors that have been proposed to affect the electrochemical reaction of coals in a direct carbon fuel cell (DCFC). In the present DCFC system, we used three raw coals (bituminous, intermediate bituminous, and sub-bituminous) and the corresponding chars that were adsorbed on a porous Ni plate. The plate was then rolled to make a cylindrical anode. The intrinsic properties (e.g., gas composition, surface area, oxygen-functional groups, and nature of mineral matter in their ashes) of fuels were characterized. The electric current and potential were measured at 600 degrees C for anodes fueled by an equal mass (1 g) of raw coal or char. It was found that the electrochemical performance of raw coal was not sensitive to the gases evolved by the coal unless a large amount of coal was used. A striking difference in potential-current curves was observed between chars; the electrochemical activity of sub-bituminous char was much higher than that of the other chars. This was caused mainly by the larger amount of catalytic (Ca and Fe) components exposed on the surface of the char. The surface area did not have a significant effect because of its non-wetting nature.