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Eom, Seongyong,Ahn, Seongyool,Kang, Kijoong,Choi, Gyungmin Elsevier 2017 Journal of Power Sources Vol.372 No.-
<P><B>Abstract</B></P> <P>In this study, a numerical model of activation and ohmic polarization is modified, taking into account the correlation function between surface properties and inner resistance. To investigate the correlation function, the surface properties of coal are changed by acid treatment, and the correlations between the inner resistance measured by half-cell tests and the surface characteristics are analyzed. A comparison between the model and experimental results demonstrates that the absolute average deviations for each fuel are less than 10%. The numerical results show that the sensitivities of the coal surface properties affecting polarization losses change depending on the operating temperature. The surface oxygen concentrations affect the activation polarization and the sensitivity decreased with increasing temperature. The surface ash of coal is an additional index to be considered along with ohmic polarization and it has the greatest effect on the surface properties at 973 K.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Activation and ohmic polarization were modified by experimental results. </LI> <LI> The charge transfer was calculated by the surface oxygen groups. </LI> <LI> The electrolyte resistance takes into account Si concentration. </LI> <LI> The absolute average deviations were less than 10%. </LI> </UL> </P>
Eom, Seongyong,Cho, Jaemin,Ahn, Seongyool,Sung, Yonmo,Choi, Gyungmin,Kim, Duckjool American Chemical Society 2016 ENERGY AND FUELS Vol.30 No.4
<P>A direct carbon fuel cell (DCFC) system directly converts the chemical energy of solid carbonaceous fuel into electrical energy. The electrochemical reaction of this system has an influence on the properties of solid fuel, such as crystal structure, element composition, and surface properties. In addition, when using raw coals as DCFC fuel, the volatile gases released from coal at a high temperature affect cell performance. The purpose of this study is to investigate the effect of fuel characteristics on the resistance of the inner DCFC system by electrochemical impedance spectroscopy (EIS) and equivalent circuits. Two kinds of solid carbon, graphite and sub-bituminous coal, were prepared to compare electrochemical characteristics by EIS measurement. The equivalent circuits were applied to the constant phase element (CPE) in a Randle circuit to explain the correlation between the fuel characteristic and electrochemical reaction resistance.</P>
Eom, Seongyong,Ahn, Seongyool,Kang, Kijoong,Choi, Gyungmin Elsevier 2017 ENERGY Vol.140 No.1
<P><B>Abstract</B></P> <P>Herein, we investigate the relationship between fuel surface properties and inner resistances of direct carbon fuel cells (DCFCs) by subjecting raw coal to a liquid-phase chemical treatment and correlating its surface property changes (e.g., degree of oxidation, surface area, and ash composition) with those of electrochemical resistances. Fuel surface characteristics are analyzed by thermogravimetry, gas adsorption, and X-ray photoelectron spectroscopy, with correlations established using the Pearson correlation analysis. The obtained results show that the surface Si content is strongly correlated with electrolyte resistance due to influencing the concentration of carbonate ions. Moreover, charge transfer resistance is strongly negatively correlated with the surface oxygen content, since oxygenated functional groups (e.g., carbonyl and quinone moieties) enhance the oxidation of solid carbon by increasing its reactivity and wettability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effects of surface properties on resistances are investigated in carbon fuel cell. </LI> <LI> The performance and resistance of raw coal and treated coals are compared. </LI> <LI> Si content on the fuel surface has a correlation with the electrolyte resistance. </LI> <LI> The charge transfer resistance is affected by surface oxygen groups. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
성연모,최철용,Cheoreon Moon,Seongyong Eom,이종재,김병두,최경민,김덕줄 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.8
The flow, combustion and emission characteristics of nontraditional ring-fired-type furnaces were investigated numerically to evaluatethe effects of incorporating additional inner water walls on the heat transfer, carbon burnout and emissions of nitrogen oxides. Both tangentiallyand ring-fired-type furnaces were considered and the ring-fired-type furnaces were divided into four inner-water-wall cases:without, normal type, radiant expended type and both radiant and convective expended type. The presence of the inner water wall led toan improvement of approximately 50% in the heat flux. In particular, the reduction in nitrogen oxide emissions was approximately 30%,whereas the carbon burnout was kept constant.