LES of swirl-stabilised pulverised coal combustion in IFRF furnace No. 1

Swirl-stabilised turbulent flow and pulverised coal combustion in the semi-industrial (2.5 MW) IFRF furnace No. 1 are for the first time simulated by means of large eddy simulation and compared to results from the experimental campaign and RANS predictions by Weber et al. (1992). The large eddy simulation uses the Euler-Lagrange framework for two-phase flows and relatively simple sub-models for the particle heat-up, devolatilisation, char combustion and radiation governing the pulverised coal combustion process are employed. The simulations yield improved predictions of the velocity statistics in the quarl region and result in a favourable agreement of the mean species profiles along the burner centreline compared with the measurements, while some temperature underprediction can be observed. Furthermore, the transient Euler-Lagrange approach allows for a cross-comparison of the velocity and scalar statistics between the two phases and the comparison of the mean axial velocity and temperature shows the two phases to be near thermal and kinetic equilibrium along the burner axis. Individual particle time histories, which are crucial for the coal combustion sub-processes and overall flame stabilisation, are analysed. It is found that there is a lack of oxygen in the inner quarl region leading to a decreased volatile burning rate, which could however, be related to the simplified EBU turbulence-chemistry interaction model.