Kinetic study of pulverized coal devolatilization for boiler CFD modeling

Devolatilization is the first step of thermochemical conversion for pulverized coal-fired boilers. An accurate kinetic modeling is relevant for CFD simulation and optimal boilers operation. In this study, two typical pulverized coals are characterized in a drop tube furnace between 800 °C and 1400 °C and under inert atmosphere in order to measure the solid fuel mass loss as a function of time and heating conditions. The experimental data are used to determine reliable parameters of the Kobayashi scheme currently used in Code_Saturne open source CFD software. The kinetic parameters are derived from a simple devolatilization model coupled to an efficient optimization routine based on genetic algorithm (global optimization) and simplex method (local optimization). A close agreement is found between the simulation results and the experimental results. A simplified and predictive kinetic scheme based on the elemental composition of the coal is also tested and the agreement with the experimental results is clearly less satisfactory. Hence experimental characterization seems to be the most reliable way to assess kinetic parameters of coal devolatilization.