[Objective] To address the issues of low reheated steam temperature and local overheating of platen superheaters(PSH) during low-load operation of a 660 MW ultra-supercritical tangentially fired once-reheat boiler

this study proposed a wall-mounted flue gas recirculation(FGR) arrangement in the burner region. The aim was to synergistically raise reheated steam temperature and suppress PSH overheating while maintaining combustion stability. [Methods] Numerical simulation was performed at 40% rated load to optimize the proposed layout. First

the baseline case and corner-mounted and wall-mounted concentrated FGR arrangements were compared. Subsequently

the feasibility of wall-mounted grouped injection was investigated. [Results] The results indicated that: corner-mounted FGR significantly increased the ignition distance of pulverized coal jets

which adversely affected low-load combustion stability. Both fire-side and rear-side concentrated FGR increased the heat absorption of the high-temperature reheater

but neither could simultaneously mitigate PSH local overheating. Fire-side grouped FGR substantially enhanced heat absorption of the reheater but still carried a risk of PSH overheating

whereas rear-side grouped FGR reduced the overheating risk but yielded only limited reheater improvement. A combined grouped arrangement

in which flue gas was injected through the two lower layers on the fire-side wall together with the upper layer on the rear-side wall

increased the heat absorption of the reheater by 18.9%

effectively mitigated local overheating of the PSH

and maintained stable combustion. [Conclusion] These findings provide design and optimization references for safe

flexible

and efficient boiler operation across wide load ranges in nextgeneration coal-fired power plants.