CFD modeling of oxy-coal combustion: prediction of burnout, volatile and NO precursors release

The devolatilisation step of coal is a vital stage in both air-coal and oxy-coal combustion and there is interest in whether methods of estimating the reaction parameters are similar for both cases. A network pyrolysis model, the FG-DVC (Functional Group-Depolymerisation Vaporisation Cross-linking) code was employed to evaluate the effect of temperature (1273-1773 K) and heating rate (10-10 K/s) on the devolatilisation parameters of two coals of different rank. The products distribution between char and volatiles, and volatiles and NH3/HCN release kinetics were also determined. In order to assess the accuracy of the FG-DVC predictions, the values for nitrogen distribution and devolatilisation kinetics obtained for a temperature of 1273 K and a heating rate of 10 K/s were included as inputs in a Computational Fluid Dynamics (CFD) model for oxy-coal combustion in an entrained flow reactor (EFR). CFD simulations with the programme default devolatilisation kinetics were performed. The oxygen content in oxy-firing conditions ranged between 21 and 35%, and air-firing conditions were also employed as a reference. The experimental coals burnouts and oxygen concentrations from the EFR experiments were employed to test the accuracy of the CFD model. The temperature profiles, burning rates, char burnout and NO