Opperating Micro–tubular SOFCs with Hydrogen Chloride and Hydrogen Sulfide Containing Fuels and Synthetic Wood Gas
G. Buchinger, P. Hinterreiter, T. Raab, S. Griesser, W. Sitte, D. Meissner, R. Claassen, D. Claassen - Opperating Micro–tubular SOFCs with Hydrogen Chloride and Hydrogen Sulfide Containing Fuels and Synthetic Wood Gas - Journal of Fuel Cell Science and Technology, Vol. 3, No. 1, 2006, pp. 280-283
Solid oxide fuel cells are known to be able to handle a large variety of different fuels.
Because of the greenhouse effect the use of carbon dioxide neutral gases or liquids are of
special interest. In this context wood-gas has a big potential to be an alternative fuel for
solid oxide fuel cells (SOFCs). The gas is generated by a fluidized bed steam gasifier and
consists of various components such as 25 Vol % carbon monoxide, 20 Vol % carbon
dioxide, 10 Vol % methane, 2.5 Vol % ethylene, 0.5 Vol % propylene, 2 Vol % nitrogen,
and the rest hydrogen (values in dry state). The water concentration of the original
pyrolysis gas is about 35 Vol %. Besides these main ingredients there are of course many
impurities like dust, tars, ammonia, hydrogen sulphide, and hydrogen chloride present in
the product gas. Especially the last two ones may lead to degeneration of the fuel cell
anode and must therefore be almost totally removed before feeding the gas into the cell.
In order to reduce energy losses, hot gas cleaning systems are favored. This, however,
limits the possibility to reduce the impurity concentrations to very low levels. Therefore
the aim of this work is to define the maximum acceptable output concentrations for the
hydrogen chloride adsorber also in combination with hydrogen sulphide, since for a
micro-tubular SOFC there are as yet hardly any data available. In order to determine the
influence of the hydrogen chloride on the performance of the fuel cell, different concentrations
of this impurity were fed to the cell. Here, also the flow rate was changed while
the electrochemical output was determined. In addition it was analyzed if there were any
effects when changing from pure hydrogen to the HCl containing fuel. This was investigated
at 1123 K and 1173 K, which are the preferred working temperatures for our cells.
Cooling down as well as heating up procedures were tested with cells between 1173 K
and 573 K. In a second series of experiments, combinations of hydrogen chloride and
hydrogen sulphide of variable concentrations were tested. As before, changing between
pure hydrogen and the acid containing fuel at above given temperatures was analyzed by
determining the cell performance. In parallel to the above experiments, synthetic wood
gas was used for operating the microtubular fuel cell while monitoring the electrochemical
output with time.