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