Alkali removal with mineral sorbents – Part I: Sorption capacity and reaction kinetics

Aluminosilicate sorbents show the potential to reduce alkali-related problems during solid fuel conversion such as deposit build-up and corrosion damages. The alkali capacity, the reaction kinetics and the surface area development of the sorbents under operating conditions are essential parameters for the mathematical description of the alkali sorption. In this work, three sorbents, kaolin, bauxite and bentonite, are characterized in this regard by thermogravimetric analysis. The sorption behavior of kaolin surpasses the other sorbents due to the highest loading capacity and the temperature-stability of the porous structure. However, the suitability as sorbent in solid fuel conversion processes is given for all materials. A mathematical sorption model is applied to the experimental data in order to derive kinetic parameters of the sodium and potassium sorption under syngas and flue gas atmosphere. Thus, this work provides the necessary dataset for the design and optimization of the sorbent use in industrial processes. [Display omitted] •Characterization and modelling of the alkali capture behavior of mineral sorbents.•Determination of the maximum alkali loading, reaction rates and surface area.•Sorption behavior of kaolin shows good suitability for industrial application.•Derivation of kinetic parameters provides database for modelling the alkali sorption.