CO2 gasification of woody biomass chars: The influence of K and Si on char reactivity

Although the influence of metallic and alkaline elements on biomass char reactivity is well known, a quantitative assessment of this catalytic effect is hard to obtain because of the chemical and textural complexity of biomass. The effect of K and Si on the CO2 gasification reactivity of a biomass char was studied using thermogravimetric analysis. A beech sample was pyrolyzed at 800 degrees C and then impregnated with known amounts of silicon or potassium allowing to obtain a wide range of K/Si ratios. The reactivity of the impregnated samples was studied under a CO2 (20% vol.) atmosphere. The results show that at low conversion ratios, the char reactivity depends on its textural properties, with strong diffusional limitations. When conversion reaches 60%, the presence of a catalyst (K) and an inhibitor (Si) becomes the major parameter influencing reactivity. From these experiments, a general trend was obtained between K/Si ratio and reactivity as a function of conversion. (C) 2016 Academie des sciences. Published by Elsevier Masson SAS.