Comprehensive understanding of SO3 effects on synergies among air pollution control devices in ultra-low emission power plants burning high-sulfur coal

Abstract

Abstract The environmental issue of SO3 pollution caused by coal-fired power plants attracts increasing attention. This work focused on the synergies between air pollution control devices in a 660 MW power plant burning high-sulfur coal. Parameters such as gas temperature and flow rate were varied within wide ranges under actual conditions. Both continuously tested SO3 concentration and on-line operational data were combined to establish a correlation between device performance and operational parameter. Results indicated that the gas temperature acted as a bridge of synergies between the electrostatic precipitator (ESP) and wet electrostatic precipitator (WESP). The SO3 removal efficiency across the ESP increased from 60.3% to 91.1% with the gas temperature decreasing from 136.7 to 114.8 °C, leading to the increase in corona current and the decrease in spark-over frequency of WESP. Moreover, additional electric field stages are also effective to enhance the corona current and reduce spark-over frequency. Furthermore, deviations between the design and operational data within 0–100% loading provided a correction to appropriately choose the gas velocity. With the proposed countermeasures, the SO3 emission can achieve a favorable level less than 5 mg/m3. The research findings provide a valuable technical pathway to eliminate the SO3 emission from power plants burning high-sulfur coal.