Modelling Tar Conversion on SOFC Anodes
Herrmann, T., Dillig, M., Karl, J.
Tars are inevitable components of producer gas from gasification of biomass. Because of their condensing nature they are often regarded as the Achilles heel of biomass gasification. Studies have shown that tarladen producer gas can be utilized in solid oxide fuel cells (SOFC) without degradation problems. The nickel based anode acts as a catalyst for the steam reforming of hydrocarbons. Hence the integration of a biomass driven gasifier and a SOFC does not require extensive gas cleaning and additionally the heating value of the tars is not lost. However, there are constraints for the use of producer gas in SOFCs. Besides obvious poisons like sulfur species, fuel utilization and solid carbon formation must be considered carefully. Chemical equilibrium predicts almost complete conversion of common tars at SOFC operating temperatures of around 850 °C. However, because of short residence times and limited active surface area it was shown that equilibrium is not reached for all species (e.g. naphthalene). In order to predict the amount of converted tars and thus the amount of tolerable tars for SOFC operation, kinetic rates have to be evaluated. Our scientific approach to derive the rates is based on simple voltage measurements and equilibrium calculations. The perceptible voltage increase from a specific amount of tar is related to the maximal possible voltage increase -calculated from equilibrium conditions. By discretizing the cell and assuming first order reactions, kinetic constants have been evaluated.
modelling, tar, conversion, fuel cell
Biomass Conversion Technologies for Heating, Cooling and Electricity
Gasification for power, CHP and polygeneration
25th European Biomass Conference and Exhibition
429 - 434
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