Structural evolution and reactivity of coal chars during combustion in oxyfuel atmosphere

The coal chars were characterized by laboratory scale fixed bed, thermogravimetric analysis, ultimate analysis, N2 isothermal adsorption/desorption method and Brunauer-Emmett-Teller method. The specific surface area of two coal chars obtained by Brunauer-Emmett-Teller method could be estimated with the help of random pore model. It showed that random pore model had good ability to depict coal char combustion in oxyfuel, and the higher temperature increased the combustion rate of coal char. Specific surface area followed a similar trend to the micropore, indicating that the specific surface area was mainly determined by the micropore, which increased at the initial stage because of a large number of micropore expansion and generation of new pores. Total pore volume showed a maximum at a carbon conversion range of 0.2-0.4. The activation energy (AE) of Jiaozuo anthracite chars varied between 72 and 85 kJ/mol during combustion, and the values of the AE range between 46 and 77 kJ/mol for YBC. At the carbon conversion of >40%, the AE of two coal chars displayed a linear relationship, which was probably attributed to the pore structure variations of coal chars during combustion in oxyfuel. Copyright (C) 2016 Curtin University of Technology and John Wiley & Sons, Ltd.