Sorption measurements for determining surface effects and structure of solid fuels

Abstract Novel experimental results on temperature dependent diffusion of CO 2 inside porous char particles are provided as well as corresponding data on adsorption of oxygen and carbon dioxide. For this purpose, different chars from a Colombian coal were generated either in a flat flame burner (FFB) under realistic conditions for pulverized coal combustion with heating rates in the order 10 4 –10 5  K/s or in a thermogravimetric analyser (TGA) at low heating rates and inert conditions (Ar). The chars produced are used for kinetic adsorption measurements with a suspension balance to determine temperature dependent diffusion coefficients for CO 2 up to 160 °C. Based on these data the resistance factor for Knudsen diffusion, which describes the influence of the inner particle morphology on gas diffusion, was determined. The results indicate that the diffusion coefficients of the chars converge to the same value with rising temperature, ending in a Knudsen diffusion dominated regime. Furthermore, adsorption measurements for O 2 and CO 2 were conducted up to temperatures of 150 °C and 450 °C, respectively, on coal chars for the first time. Based on the pure component results, multicomponent adsorption has been predicted based on the well-known multi component IAST model. The results indicate that individual species selectivity changes with temperature.