The simultaneous centralized control of elemental mercury emission and deep desulfurization from the flue gas using magnetic Mn-Fe spinel as a co-benefit of the wet electrostatic precipitator

Recently, wet electrostatic precipitator (WESP) is proposed to install downstream of the wet flue gas desulfurization (FGD) to control the emission of ultrafine particulates and the gypsum rain. In this work, the simultaneous centralized control of elemental mercury emission and deep desulfurization from the flue gas using magnetic Mn-Fe spinel was developed as a co-benefit of the WESP. Mn-Fe spinel showed an excellent ability for the simultaneous capture of SO₂ and Hg⁰ at the temperature window of the WESP (i.e. 50-100°C). Its excellent magnetization ensured that it can be easily separated from the mixture with ultrafine particulates in the WESP for the centralized control of Hg pollution. However, Mn-Fe spinel after Hg⁰ capture had a serious biological toxicity due to the formation of water soluble HgSO₄. Therefore, Mn-Fe spinel after Hg⁰ capture was regenerated by the washing of a NaClO solution and the adsorbed Hg on Mn-Fe spinel was then collected as a high concentration of Hg^{2 +} for the safe disposition. Meanwhile, the centralized control of Hg⁰ emission by Mn-Fe spinel was cost-effective because Mn-Fe spinel after the regeneration can be used to capture Hg⁰ and SO₂ for the next cycle with no degradation of the adsorption ability.