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

The mineral contentof biomass plays an important role in the gasificationrate of biomass-derived char. The understanding and quantificationof mineral-related phenomena are thus of importance when consideringgasification reactor design. In the present work, the potassium-inducedcatalytic phenomena during gasification of biomass-derived char havebeen studied. Char samples with similar structure and different intrinsicpotassium content were gasified in a steam atmosphere at a temperaturerange of 700-800 & DEG;C. It was found that for all the samples,irrespective of the temperature and the initial potassium content,there is a critical K/C ratio (5 x 10(-3)), whereafterthe catalytic phenomena prevail. The instantaneous conversion rateof the char is positively correlated with the potassium content andthe progressively increasing conversion. The application of the modifiedrandom pore model was able to capture the later stages of conversionby the introduction of two additional parameters (c and p). It was found that these constants are notjust fitting parameters but that there is an underlying physical significancewith c being directly related to the intrinsic potassiumcontent while being temperature independent and with p being temperature dependent.