A review on removal of mercury from flue gas utilizing existing air pollutant control devices (APCDs)

Mercury is a highly toxic heavy metal pollutant. It is of great significance to develop cost-effective mercury pollution control technologies of coal-fired flue gas. Among various mercury from flue gas removal methods, the application of existing air pollution control devices (APCDs) to remove mercury from flue gas is one of the most valuable methods because it doesn't need to install additional mercury removal equipment, reducing the cost of mercury removal. This review summarizes the recent progress of mercury from flue gas removal by APCDs (e.g., SCR denitration device, WFGD system and dust removal device). SCR denitration device can achieve partial removal of mercury in flue gas through combined with WFGD system, but easy inactivation and poor sulfur/water/heavy metals resistance of SCR catalyzers are still the main problems. WFGD systems can remove most of Hg²⁺ (80%-95%), but have low treatment ability for Hg⁰. Various oxidants can effectively oxidize Hg⁰ into Hg²⁺. However, traditional oxidants have high prices and secondary pollution due to the formation of by-products. Fabric filters (FFs), electrostatic precipitators (ESPs) and hybrid fabric filters (HFs) can all control the emission of mercury in the flue gas to a certain extent, especially can effectively remove most of Hg^P and part of Hg²⁺, but has low removal capacity for Hg⁰. Compared with ESP, FF has better capture efficiency for Hg²⁺ and Hg⁰, and a combination of ESP and FF, that is HF, can effectively improve the mercury removal capacity.