On the mechanisms and behavior of coal syngas transport and reaction within the anode of a solid oxide fuel cell

Gemmen, Randall; Trembly, Jason

doi:10.1016/j.jpowsour.2006.06.012

Cited by 78 publications

(51 citation statements)

References 21 publications

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“…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] further reported a multi-step heterogeneous elementary reaction mechanism for CH 4 reforming using Ni as catalyst.…”

Section: Dcfcmentioning

confidence: 99%

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

Shi

Wang

et al. 2013

Journal of Power Sources

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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]...

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Section: Dcfcmentioning

confidence: 99%

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

Shi

Wang

et al. 2013

Journal of Power Sources

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“…I agree with the authors that challenges exist with coking in SOFC anode compartments that process hydrocarbon fuels. But a certain amount of internal reforming with appropriate fuel steam content can typically be accomplished today without coking challenges [6,[17][18][19][20][21][22][23]. In addition, novel SOFC materials sets have been prominently shown to allow SOFC operation on hydrocarbon fuels without coking [24][25][26][27][28].…”

mentioning

confidence: 99%

“…The authors only consider carbon monoxide electrochemical oxidation, whereas it is known that water-gas shift reactions readily occur in the typical anode compartment of an SOFC [20,21,29].…”

mentioning

confidence: 99%

Support for the high efficiency, carbon separation and internal reforming capabilities of solid oxide fuel cell systems

Brouwer

2010

Journal of Power Sources

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“…Using kinetics models derived from testing data, a one-dimensional anode diffusion and permeation gas transport model, and electrochemical reaction boundary conditions at the anode-electrolyte interface, Lehnert et al (2000) calculated that manipulation of anode porosity and tortuosity could slow the reformation reaction by as much as 20%. Gemmen and Trembly (2006) used a similar approach to consider the effect of pressurization. Their model predicted an increase in methane and decrease in 2.4 hydrogen within an anode structure for operating pressures above 8 atm.…”

Section: Pressurization and Methane Reformingmentioning

confidence: 99%

“…Hydrogen compositions can range from about 30% to over 50% depending on subjection of the syngas to water-gas shift, CO 2 removal, hydrogen separation, and desulphurization processes (Gemmen andTrembly 2006, Pettniau et 2.6 al. 2005).…”

Section: Fuel Gas Compositionmentioning

confidence: 99%

Modeling of Pressurized Electrochemistry and Steam-Methane Reforming in Solid Oxide Fuel Cells and the Effects on Thermal and Electrical Stack Performance

Recknagle¹,

Khaleel²

2009

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Executive SummaryThis report summarizes work done to extend the electrochemical performance and methane reforming submodels to include the effects of pressurization and to demonstrate this new modeling capability by simulating large stacks operating on methane-rich fuel under pressurized and nonpressurized conditions. Pressurized operation boosts electrochemical performance, alters the kinetics of methane reforming, and affects the equilibrium composition of methane fuels. This work developed constitutive submodels that couple the electrochemistry, reforming, and pressurization to yield an increased capability of the modeling tool for prediction of solid oxide fuel cell (SOFC) stack performance.The electrochemistry model was advanced to characterize the increased SOFC performance due to diminished activation polarization. The activation polarization depends upon the exchange current density between the electrodes and electrolyte. The exchange current density is increased by elevated pressure resulting in decreased polarization loss. The Nernst potential is also increased with pressure, and, when augmented by the decreased polarization, provides increased cell voltage and stack power.The operating pressure has competing effects on reformation; it increases the methane conversion rate while also increasing the equilibrium methane concentration. The methane conversion rate expression developed by this work accounted for these effects. The rate expression used equilibrium gas compositions for temperatures ranging from 650° to 850°C and pressures of 1 to 10 atmospheres, and incorporated the steam-methane reaction equation. The gas compositions were used to calculate the equilibrium constant, and the reforming reaction equation established the form of the forward and backward terms. The combination of these elements resulted in an expression of the overall conversion rate that correctly accounts for the pressurization effect on the kinetics and the reverse reaction.The models accounting for the pressure effects on the electrochemistry and methane reforming were applied in stack simulations to examine how they can potentially change the distributions of fuel, air, current density, temperature, and reforming rates within large area stacks. An ordinary 20x20-cm cross-flow stack model geometry was used as a generic example of a "large" planar stack to demonstrate how the modeling tool can be applied to any proposed stack design for a similar analysis. We expect differences in the scalar distributions depending upon the size and configuration of the stack. We also expect the trends of pressurization effects on the reforming rates, temperatures, current density, gas concentrations, and pressure drops would be the same for any other planar stack under pressurized operation. Cases of operating pressures ranging from 1 to 10 atmospheres and 2 reformation rates differing by a factor of 10 were simulated. The predictions showed consistently increased electrical performance for both reforming rate cases with increased operating p...

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On the mechanisms and behavior of coal syngas transport and reaction within the anode of a solid oxide fuel cell

Cited by 78 publications

References 21 publications

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

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

Support for the high efficiency, carbon separation and internal reforming capabilities of solid oxide fuel cell systems

Modeling of Pressurized Electrochemistry and Steam-Methane Reforming in Solid Oxide Fuel Cells and the Effects on Thermal and Electrical Stack Performance

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