MODELING OF OXYGEN-CHEMISORPTION KINETICS ON COAL CHAR

It has been demonstrated that the char active surface area (ASA) is a relevant parameter for evaluating the reactivity of low- and high-temperature coal chars. The kinetics of oxygen chemisorption by coal chars is important (1) for evaluating the autoignition potential of pyrolysis chars during temporary storage or transport and (2) to investigate the mechanisms involved in oxygen chemisorption, as heterogeneous combustion is influenced by the chemisorption of oxygen on char surface. Rates of oxygen uptake by char at a range of chemisorption temperatures were monitored using a thermogravimetric balance. Oxygen chemisorption rate data on low-temperature (500°C) coal char at various temperatures have been tested with three kinetic models and one diffusion model. Furthermore, chemisorption data from a low-temperature (500°C) char have been compared with data from a high-temperature (950°C) char. Chemisorption between 100° and 215°C was investigated. Possible controlling mechanisms suggested by each model are presented. © 1990.