COMPARISON OF DIFFERENT DIAGNOSTIC TECHNIQUES FOR THE ASSESSMENT OF COAL PYROLYSIS RATE

Simulation of fluidized bed combustion by commercial tools such as Barracuda or other CFD codes requires suitable kinetic models. Notably in fluidized bed reactors pyrolysis takes place with high heating rate in the temperature range of 800-900 °C and with coarse particle sizes (up to 10 mm). Therefore, intrinsic kinetics must be combined with modeling of heat and mass transfer. Intrinsic kinetics can be obtained by conventional TGA analysis at low heating rate (2-20 K/min) and with small particle size (in the order of 100 ?m). Recently a fluidized bed reactor purposely designed for operation with small particle size in combination with FTIR gas analysis has been used in Aachen to measure pyrolysis kinetics with high particle heating rate compatible with fluidized bed conditions [1]. Another innovative method to assess the rates of pyrolysis under fluidized bed conditions has been proposed by Solimene [2] in Naples and relies on the measurement of time resolved pressure. In the present work these different methodologies have been used for a German bituminous coal "Auguste Victoria" to obtain pyrolysis behavior over a broad range of operating conditions. Results show that for the two fluidized bed test rigs, using larger particle sizes, transport limitations become important. As expected, for this regime the reactions rates become lower the larger the particle size.