Modeling Study of Selenium Migration Behavior in Wet Flue Gas Desulfurization Spray Towers

Wet flue gas desulfurization (WFGD) system is the core equipment for removing SO₂ from coal-fired power plants, and it also has an important synergistic effect on the removal of selenium. However, the removal efficiency of Se across WFGD systems is not as expected, and it varies greatly in different coal-fired units (12.5-96%). In this study, a mathematical model was established to quantitatively describe the selenium migration behavior in WFGD spray towers, including the conversion of gaseous selenium to particulate selenium and the capture of gaseous SeO₂ and particles by droplets. The calculation results show that the behavior of selenium in the spray tower can be divided into three stages: preparation, condensation, and removal. The condensation stage significantly affected the selenium distribution and its total removal efficiency. Furthermore, five factors which may affect the selenium behavior were investigated. Among them, the inlet particle size distribution and the droplet temperature had great impacts on the outlet selenium concentration, which may be the reason for the unstable selenium removal efficiencies. This study can help in understanding the migration process of selenium in WFGD spray towers and provide some guidance for the development of specific selenium control technologies.