Elemental mercury removal from flue gas using heat and Co2+/Fe2+ coactivated oxone oxidation system

Abstract

Oxidation removal process of elemental mercury (Hg0) from flue gas using heat and Co2+/Fe2+ coactivated Oxone oxidation system in a spraying reactor was developed. The effects of several influencing factors and main flue gas compositions on Hg0 removal, and the active species, products, mechanism and mass transfer-reaction kinetic law of Hg0 removal process were investigated. The results show that heat and Co2+/Fe2+ have a significant synergistic effect for activating Oxone to produce free radicals and promote Hg0 removal. Hg0 removal can be improved via increasing Oxone concentration, Co2+/Fe2+ concentration, activation temperature or O2 concentration, and is inhibited with increasing solution pH, Hg0 inlet concentration or NO concentration. Changing SO2 concentration have double impacts on Hg0 removal. SO4− and OH produced from coactivation of heat and Co2+/Fe2+ are the key oxidants, which play a leading role in Hg0 removal. Oxone plays a complementary role in Hg0 removal. Hg0 removal processes using heat/Co2+ and heat/Fe2+ coactivated Oxone systems belong to fast reactions under optimized experimental conditions, and meets a total 2.8-order reaction (i.e. 1.0-order for Hg0, 1.1-order for Oxone and 0.7-order for Co2+) in Co2+/Oxone activation system, and a total 3.0-order reaction (i.e. 1.0-order for Hg0, 1.4-order for Oxone and 0.6-order for Fe2+) in Fe2+/Oxone activation system. Finally, the key mass transfer and kinetic parameters of Hg0 removal processes were also determined.