Analysis of Direct Carbon Fuel Cell Based Coal Fired Power Cycles With CO2 Capture

Abstract

This work presents an analysis of the application of direct carbon fuel cells (DCFC) to large scale, coal fueled power cycles. DCFCs are a type of high temperature fuel cell featuring the possibility of being fed directly with coal or other heavy fuels, with high tolerance to impurities and contaminants (e.g., sulfur) contained in the fuel. Different DCFC technologies of this type are developed in laboratories, research centers or new startup companies, although at kW-scale, showing promising results for their possible future application to stationary power generation. This work investigates the potential application of two DCFC categories, both using a "molten anode medium" which can be (i) a mixture of molten carbonates or (ii) a molten metal (liquid tin) flowing at the anode of a fuel cell belonging to the solid oxide electrolyte family. Both technologies can be considered particularly interesting for the possible future application to large scale, coal fueled power cycles with CO2 capture, since they both have the advantage of oxidizing coal without mixing the oxidized products with nitrogen; thus releasing a high CO2 concentration exhaust gas. After a description of the operating principles of the two DCFCs, it is presented a lumped-volume thermodynamic model which reproduces the DCFC behavior in terms of energy and material balances, calibrated over available literature data. We consider then two plant layouts, using a hundred-MW scale coal feeding, where the DCFC generates electricity and heat recovered by a bottoming steam cycle, while the exhaust gases are sent to a CO2 compression train, after purification in appropriate cleaning processes. Detailed results are presented in terms of energy and material balances of the proposed cycles, showing how the complete system may surpass 65% lower heating value electrical efficiency with nearly complete (95%-\-) CO2 capture, making the system very attractive, although evidencing a number of technologically critical issues.(1) DCFC types belonging to the second category are developed for instance by Contained Energy LLC. with a MCFC-based technology using molten carbonates at the electrolyte and as a molten anode medium.

CO2 capture in integrated steelworks by commercial-ready technologies and SEWGS process

“…Mass and energy balances of the overall plants have been estimated using the proprietary code GS, which was developed by the GECoS group of Politecnico di Milano to assess the perfor-mance of gas/steam cycles as well as a variety of other plant options including IGCC, membranes, fuel cells and sorbent-based systems (Campanari, 2000;Campanari et al, 2012;Chiesa and Consonni, 2000;Consonni, 1992;Gazzani et al, 2013c;Macchi et al, 1995;Romano, 2013). The code is conceived for the predic-tion of gas turbine performance at the design point and includes the onedimensional design of the turbine, functional to calculate the expansion through a stage-by-stage approach, estimating the cooling flows and the evolution of the cooled expansion (Chiesa and Macchi, 2004).…”

HDCFC Performance as a Function of Anode Atmosphere (N2-CO2)

“…The most developed SOFCtype DCFCs include the fluidized bed-SOFC developed by Gur at Stanford University 7,11 and the molten tin anode SOFC (LTA-SOFC) developed by Tao at CellTech Power. 14,15 The most promising MCFCtype DCFC is under development at the Laurence Livermore National Laboratory (LLNL). 6,16 MCFCs show the advantage of maintaining a higher degree of contact between the solid fuel and the molten electrolyte in the anode chamber.…”

A SnO2-samarium doped ceria additional anode layer in a direct carbon fuel cell

“…The relatively high theoretical electrode potential of Sn/SnO 2 (~0.96 V at 700 C), which is close to the theoretical electromotive force of the carbon complete oxidation reaction (1.02 V at 700 C), brings a high efficiency of the cell [33,34]. Besides, the high solubility of sulfur in molten Sn makes Sn a promising anode material for DCFCs fed with coal, and the formed SnS could be removed easily from the top of the molten anode due to the difference in density [35,41]. However, the application of metallic Sn in the anode of a DCFC posed new questions.…”