Experimental characterization and elementary reaction modeling of solid oxide electrolyte direct carbon fuel cell

Abstract

A detailed mechanistic model for solid oxide electrolyte direct carbon fuel cell (SO-DCFC) is developed while considering the thermo-chemical and electrochemical elementary reactions in both the carbon bed and the SOFC, as well as the meso-scale transport processes within the carbon bed and the SOFC electrode porous structures. The model is validated using data from a fixed bed carbon gasification experiment and the SO-DCFC performance testing experiments carried out using different carrier gases and * Corresponding author. Tel.: +86-10-62789955; Fax: +86-10-62770209.Email: shyx@tsinghua.edu.cn.2 at various temperatures. The analyses of the experimental and modeling results indicate the strong influence of the carrier gas on the cell performance. The coupling between carbon gasification and electrochemical oxidation on the SO-DCFC performance that results in an unusual transition zone in the cell polarization curve was predicted by the model, and analyzed in detail at the elementary reaction level. We conclude that the carbon bed physical properties such as the bed height, char conversion ratio and fuel utilization, as well as the temperature significantly limit the performance of the SO- DCFC.Key words: solid oxide electrolyte; direct carbon fuel cell; elementary reaction; modeling; heterogeneous chemistry This work is focuses on the solid oxide electrolyte direct carbon fuel cells (SO-DCFC) which are capable of conversing chemical energy in the solid carbon fuel into electricity.These offer a number of advantages over the traditional carbon conversion technologies 3 as well as alternative DCFCs such as: the abundance of the fuel source, high theoretical efficiency, high CO 2 emission reduction potential, relatively higher reaction activity ascribed to its high operating temperatures, and avoidance of liquid electrolyte consumption, leakage and corrosion [3]. Due to these advantages, some researchers have investigated DFFCs for application in large-scale power plants [4,5] considering their potential merits for high efficiency and emission reduction.SO-DCFC performance improvement relies on optimal electrochemical reactions, carbon gasification and mass transport processes. Since experimental studies on SO-DCFC are rather complex, expensive, and time-consuming, comprehensive mathematical models are essential for the technology development. A validated mechanistic model would offer means to gain insight into the complex physical phenomena governing fthe uel cell performance that is not readily accessible experimentally, and it can also be useful tool for cell design and operating condition optimization.Modeling and experimental studies of SO-DCFCs have been reported recently by several researchers [6][7][8][9]. Numerous SOFC models considering the intricate interdependency among ionic and electronic conduction, gas transport phenomena, and electrochemical processes have been reported in the literatures for pure hydrogen, syngas or methane [10][11][12][13][14][15][16][17][18][19][20]. Hecht et al. [21]...

Effect of structural properties of carbon-based fuels on efficiency of direct carbon fuel cells

“…On the other hand, it suffers from low power density, which must be increased to make it commercially viable. In a DC-SOFC [9,10], carbon can be electrochemically oxidized directly to CO 2 according to Eq. 1:…”

Utilisation of coal for energy production in fuel cells

“…In the case depicted in Figure 1, the electrochemical oxidation of carbon particles mainly occurs according to reaction (1) [27,28]. The current and power generated from DC-SOFC (1) could be directly addressed to direct carbon oxidation according to reaction (1), making it easily possible to determine the activity of solid particles in the anode reaction of the direct electrochemical oxidation of fuel.…”

Progress and Challenges in the Direct Carbon Fuel Cell Technology

“…49carbon fuel cells have been operated on a wide range of fuels including coal, liquid hydrocarbon fuels, biomass and organic waste. Some of these fuels have been used directly within the fuel cell with very little pre-treatment whilst others have been heavily processed and purified to produce a fuel that is almost pure carbon [34]. Dudek et al [35] have reported an investigation of various types of carbon blacks and have tried to correlate their electrochemical reactivity in a molten carbonate electrolyte based DCFC with micro-and nanostructures of carbons, which shows in Fig.…”