Arch-firing furnaces often struggle to balance sufficiently low NOx emissions and efficient burnout. A staged arch-firing configuration integrating deep air staging, coal reburning, and flue gas recirculation can address this challenge. Previous coal reburning studies were largely focused on high-volatile coals, without investigations reported for arch-firing furnaces designed to burn low-volatile coals such as anthracite. In order to confirm the usability of anthracite reburning in a 600 MW staged arch-firing furnace and meanwhile evaluate impacts of some key reburning factors on the low-NOx combustion characteristics, numerical simulations of the in-furnace airflow, pulverized-coal combustion, and NO production were carried out by varying the reburning residence time (τ = 0.8, 0.9, 1.0, and 1.1 s) and reburning jet temperature (T = 224, 376, and 526 °C), respectively. The observed low-temperature and extremely low-NO conditions in the reburning area confirmed the NO-reduction effectiveness of the anthracite reburning. As τ increased, all of the main flame penetration, combustion intensity in the lower chamber, and reburning function first strengthened and then weakened. Among the four τ cases, τ = 0.9 s achieved the lowest NOx emissions while τ = 1.1 s gave the best burnout. With τ fixing at 0.9 s, increasing T also led to a non-monotonic change in the reburning function, with the best low-NOx combustion performance (i.e., NOx emissions of 477 mg/m3 at 6% oxygen and a fly-ash carbon of 4.7%) appearing at T = 376 °C. Compared with (i) its predecessor furnace without reburning and (ii) the baseline staged arch-firing furnace prior to this study, here the optimized configuration achieved NOx reductions of 47.3% and 12.2%, respectively, and simultaneously elevated burnout. The gained results in this study have a good application prospect for arch-firing furnaces seeking a sufficiently low-NOx and high-burnout trade-off.
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