Influence of near-wall air position on the high-temperature corrosion and combustion in a 1000 MWth opposed wall-fired boiler

摘要

Low NOx burner together with air-staging system are commonly used in coal-fired power plants in China to reduce NOx emission. However, severe high-temperature corrosion on the water-cooled wall have occurred frequently, because this combustion system result in fuel-rich atmosphere in the main combustion zone and generates a large amount of CO and H2S, which is the main reason for the high-temperature corrosion in the furnace. Near-wall air (NWA) is an economical and effective way to reduce the concentration of CO and H2S. There are two common NWA arrangement, one position is on the side walls, the other is on the front and rear walls. This study numerically investigated the effects of NWA positions on the high-temperature corrosion and combustion of a 1000 MWth opposed wall-fired boiler for better solution of the high-temperature corrosion. The numerical models were validated by the measured data of CO concentration on the side walls. Then the effect of NWA position and NWA ratios (0-1%) on the reducing atmosphere, combustion, and NO generation were numerically studied. The results show that both NWA positions have no effect on the reducing atmosphere and combustion condition when the NWA ratio is lower than 0.5%, but it works when the ratio increase to more than 0.5%. Moreover, it is recommended to arrange NWA on the side walls with the NWA ratio at 1% for better controlling the high-temperature corrosion problems and maintaining good combustion conditions simultaneously, since the concentrations of CO and H2S near side walls were significantly decreased.