An evaluation of the efficacy of various coal combustion models for predicting char burnout

Abstract

Coal combustion is comprised of several subprocesses including devolatilization and heterogeneous reactions of the coal char with O2, CO2, H2O and potentially several other species. Much effort has been put forth to develop models for these processes which vary widely in both complexity and computational cost. This work investigates the efficacy of models for devolatilization and char reactions at either end of the complexity and cost spectrums for a range of particle sizes and furnace temperatures and across coal types. The overlap of simulated devolatilization and char consumption is also examined. In the gas phase, a detailed kinetics model based on a reduced version of the GRI 3.0 mechanism is used. The Char Conversion Kinetics and an nth-order Langmuir-Hinshelwood models are considered for char oxidation. The Chemical Percolation and Devolatilization and a two-step model are considered for devolatilization. Results indicate that high-fidelity models perform better at representing particle temperature and mass data across a wide range of O2 concentrations as well as coal types. A significant overlap in devolatilization and char consumption is observed for both char chemistry and devolatilization models.