Coke Formation and Degradation in SOFC Operation with a Model Reformate from Liquid Hydrocarbons

Timmermann, H.; Sawady, W.; Campbell, Dennis; Weber, André; Reimert, R.; Ivers‐Tiffée, Ellen

doi:10.1149/1.2838909

Cited by 44 publications

(24 citation statements)

References 7 publications

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“…Additionally, heating the fuel directly to operating temperature of the stack without prereforming of the fuel at lower temperatures increases the probability of hydrocarbon cracking and carbon formation in the heat exchangers or pipelines [16]. Without pre-reforming, some higher hydrocarbons can coke the nickel substrate at the anode electrode resulting in performance degradation and ultimately destruction of the cell [17,18]. Due to the above-mentioned issues, prereforming of hydrocarbon fuels is usually necessary.…”

Section: Fuel Systemmentioning

confidence: 99%

Experimental Analysis on Performance and Durability of SOFC Demonstration Unit

et al. 2010

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A technical description and experimental analysis of a SOFC demonstration unit is presented. The unit contains most of the primary BoP‐components of a complete SOFC system, except of air and fuel recirculation equipment or fuel system compressor. Natural gas is used as the fuel and electricity is supplied to the electric grid. A 5 kW power class planar SOFC stack from Research Centre Jülich is assembled to the demo unit and a long‐term experiment is conducted to assess the characteristic performance and durability of different components of the unit (e.g. the SOFC stack, the fuel pre‐reformer and air heat exchangers). The evolution of absolute voltage drop of the stack over time is found to be of the same magnitude when compared to short stack experiments. Thus, other system components are not observed to cause an increase in the characteristic voltage drop of the stack. Two BoP‐components, the afterburner and the power conversion unit failed to operate as designed. The performance of other BoP‐components i.e. fuel pre‐reformer and heat exchangers were satisfactory during the test run, and no significant performance loss could be measured.

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Section: Fuel Systemmentioning

confidence: 99%

Experimental Analysis on Performance and Durability of SOFC Demonstration Unit

et al. 2010

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“…11 Many researchers have investigated the impact of different fuels with carbon contents, both experimentally and numerically, and demonstrated their degrading effect on the cell performance and the cell microstructure. 3,[11][12][13][14][15][16][17][18][19] Based on 3,7,18,[20][21][22] operating z E-mail: vanja.subotic@tugraz.at temperature defines the structure of the carbon formed. High operating temperatures (higher than 600…”

mentioning

confidence: 99%

Strategy for Carbon Gasification from Porous Ni-YSZ Anodes of Industrial-Sized ASC-SOFCs and Effects of Carbon Growth

Subotić

Schluckner

Stöckl

et al. 2016

J. Electrochem. Soc.

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Auxiliary power units (APUs) running on carbon-containing fuels provide solutions for high-efficient power supply and emission reduction. In order to ensure safe operation, unwanted degradation caused by carbon depositions should be avoided or controlled. Early detection allows trigerring of counteractions and avoids rapid deterioration of the cell performance as well as mechanical degradation of the cell microstructure and it is presented here. This study also shows that carbon does not only block the active catalyst sites and porous gas channels thus deteriorating the cell performance, but massive carbon depositions lead to destruction of the lattice YSZ-structure. In order to prolong the lifetime of the investigated cells, carbon-dioxide is tested as a possible agent for gasification of deposited carbon. Supplying with CO 2 gasifies carbon to carbon-monoxide, but experimental investigations show further degradation of the cell performance and a reduced methane conversion rate. A method, which represents a combination of CO 2 fed to the anode and an overvoltage applied to the cell, enabled complete performance regeneration in a cell-protecting manner. Solid oxide fuel cells are high-efficient devices, which convert the chemical energy of gaseous fuels directly into electrical energy without additional conversion steps. The heat losses occurring during the operation at temperatures between 600-1000• C can be used as a high-quality heat energy. SOFCs offer a great fuel flexibility and compared to other fuel cell types they can internally reform hydrocarbons. Internal conversion of carbon-containing fuels over nickel as the most widely used catalyst tends to promote carbonaceous deposits on the anode surface as well as inside the anode, causing deactivation of the fuel cells.1-3 The usage of other alternative materials such as Cu-, Gdand Sm-stabilized ceria-based materials or conducting oxides is possible to suppress carbon depositions, but Ni still offers a considerably better conductivity and electrocatalytic performance. 4-7Carbon deposition.-To date many researchers have investigated SOFC anode degradation. Khan et al.8 made a short review of Ni-YSZ degradation mechanisms, classifying these into four types: nickel coarsening, coking, redox instability and sulfur poisoning. A detailed analysis of challenges for nickel steam-reforming catalyst for industrial application can further be found in study from Sehestad.9 However, regarding operation of Ni-YSZ based SOFCs, if the cell is operated under expected conditions, which exclude sulfur in the fuel and the presence of oxygen on the anode side, redox instability and sulfur poisoning can be excluded as possible degradation phenomena. Nickel coarsening is a process where metal powder begins to sinter and small particles grow in size. It reduces the cell conductivity and worsens the cell performance. The sintering of nickel is also known to prone carbon formation, which requires prevention of this mechanism in order to reduce carbon build. 9 Coking can lead to an i...

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“…(2) is not directly influenced by the exact value of R ext (as long as it is high compared to the other membrane resistances), it is because we will consider situations where the membrane transport of hydrogen (or, oxygen) is not negligible compared to the flow rates into the anode and cathode compartments, that there is an indirect influence of R ext via the relation i = E oc /R ext and the mass balances, Eqs. (11) and (12) to be discussed below, on p H 2 ,A and p H 2 ,C and thus on E oc . These effects are self-consistently considered in our model.…”

Section: Fuel Cell Operationmentioning

confidence: 98%

“…(9)b; H 2 ,mem is set to zero in Eqs. (11) and (12), while on the left-hand side of Eq. (11)c a term 2 O 2 ,mem is added.…”

Section: Modifications For Butane As Fuel And/or Oxygen Ion Conductinmentioning

confidence: 99%

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Thermodynamic analysis of direct internal reforming of methane and butane in proton and oxygen conducting fuel cells

Biesheuvel

Geerlings

2008

Journal of Power Sources

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Coke Formation and Degradation in SOFC Operation with a Model Reformate from Liquid Hydrocarbons

Cited by 44 publications

References 7 publications

Experimental Analysis on Performance and Durability of SOFC Demonstration Unit

Experimental Analysis on Performance and Durability of SOFC Demonstration Unit

Strategy for Carbon Gasification from Porous Ni-YSZ Anodes of Industrial-Sized ASC-SOFCs and Effects of Carbon Growth

Thermodynamic analysis of direct internal reforming of methane and butane in proton and oxygen conducting fuel cells

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