Closing-to-wall air protection is an effective measure to prevent high-temperature slagging and corrosion of waterwalls of coal-fired boilers. The mechanism is to lower the wall temperature and mitigate the reducing atmosphere by introducing closing-to-wall air to the areas with high slagging and corrosion risks through the air nozzles on the waterwall. In this project

three layers of closing-to-wall air nozzles were installed on the front/rear wall of the opposed-firing boiler of a supercritical 600 MW unit. Subsequently

cold-state industrial test of the closing-to-wall air aerodynamic field and hot-state combustion operation tests were conducted. The results show that

the closing-to-wall airflow could reach the middle of the sidewall and achieve good coverage and purging on the corrosion-prone area in the furnace. At 600 MW

450 MW and 300 MW

after the closing-to-wall air system was put into operation

the average volume fraction of near-wall O_2 increased to over 3.0%

and that of near-wall H_2S reduced to lower than 200×10~(–6)

by more than 80%. The high-temperature slagging and corrosion of the waterwall could be effectively alleviated.