Study on high-temperature corrosion in a 600 MW opposed firing boiler

Low-nitrogen burners and air-staging system, which would generate a large amount of CO and H2S in the furnace, are frequently adopted in the coal-fired boilers in China. This is one of the main reasons for the high-temperature corrosion of the water-cooled wall, while the other is the high wall temperature. In this study, the influences of boiler load, burner tilt angle and near-wall air (NWA) nozzles numbers on the high-temperature corrosion of water-cooled wall in a 600 MW opposed firing boiler are numerically investigated. The results show that the H2S concentration does not decline monotonously with the decreasing boiler load. The H2S concentration declines from 443 to 396 ppm while the average wall temperature decreases by 146 K dramatically when the load descends from 100% BMCR to 50% BMCR. When the effect on both side walls are considered, it is confirmed that the high-temperature corrosion of the water-cooled wall would not be alleviated significantly by adjusting the burner tilt angle in this study. Compared with standard condition, the average temperature drops moderately and the maximum H2S concentration drops dramatically from 434 to 367 ppm in the main combustion zone near the left wall when the angle is set at 5 degrees. The reducing atmosphere could be significantly alleviated when NWA nozzles are put into operation. Moreover, a sharp drop of the average CO concentration from 7.8% to 2.1% occurs when only the lower two layers of NWA nozzles are operating.