Research progress on elemental mercury (Hg⁰) removal in flue gas using non-thermal plasma technology

Elemental mercury (Hg⁰) removal is a crucial target for mercury pollution control in flue gas. This article focuses on Hg⁰ removal in flue gas using corona discharge (CD) and dielectric barrier discharge (DBD) technologies, and provides a mechanistic perspective on the development and influencing factors of non-thermal plasma (NTP) technology for Hg⁰ removal. The influence factors include reactor configurations, power supplies, energy density, residence time, oxidation methods, gas composition, and the synergy between NTP and catalysis/adsorption, etc. This study reveals that the use of a pulsating electrical power supply significantly increases electron densities in both CD and DBD systems, thereby ensuring high energy efficiency and economic viability. Cl₂ proves to be more effective than HCl as a chlorine source for Hg⁰ removal. NO significantly reduces Hg⁰ oxidation efficiency, while the effects of SO₂ and H₂O remain unclear. Energy density distribution is closely related to plasma devices, power supplies, and overall reactor configurations. Direct oxidation proves to be more effective than indirect oxidation for Hg⁰ removal. The combination of NTP with adsorption/catalysis technologies shows significantly better Hg⁰ removal efficiency compared to using NTP alone. This study can provide theoretical support for enhancing Hg⁰ removal mechanisms and optimizing process control parameters in industrial applications of NTP technology.