Steam Gasification of Unreacted Biomass-Derived Char : Potassium-Induced Phenomena and Their Effects on the Intrinsic Reactivity

In the present work, the effects of minerals, especially the potassium-induced catalytic phenomena, and temperature during the gasification of unreacted biomass char gasification, collected from an industrial gasifier, have been studied. Char samples with similar structure and different intrinsic potassium content were gasified in steam atmosphere at a temperature range of 700-800 °C. It was found that for all the samples, irrespective of temperature and initial potassium content there is a common critical potassium surface coverage (expressed as K/C ratio), whereafter the catalytic phenomena prevail. Different kinetic models were applied to describe the conversion rates and the corresponding kinetic parameters have been determined. The modified random pore model captured the later stages of conversion by introducing the two additional parameters (c and p). A closer evaluation of the values obtained revealed that the c constant is directly related to the intrinsic potassium content and is temperature independent at the investigated temperature range. On the other hand, a clear correlation of the potassium content and the p parameter with an underlying temperature dependence is also observed