Mineral-char interactions during char combustion of a high-volatile coal

We report on recent investigations of the role of inorganic mineral matter on the evolution of char structure during carbon burnout. Char samples collected in a carefully controlled, laminar flame-supported entrained flow reactor have been characterized using a number of microscopy tools. Observations of the inorganic structure of chars produced at a variety of combustion conditions are coupled with in situ particlesizing pyrometry measurements of the char particle population with an eye toward identifying the mechanism of mineral interaction and its effects on carbon burnout kinetics during pulverized coal char combustion. No evidence of a macroscopic ash film which has been hypothesized to retard char oxidation kinetics, was found on the chars. High-resolution electron microscopy, however, shows a surprising amount of inorganic mineral in solid solution within the carbonaceous matrix. This intimate mixing of organic and inorganic constituents may affect reactivity by both blocking oxygen access to active carbon sites and influencing the microscopic carbon structure that evolves during combustion.