Effects of H2SO4 and O2 on Hg0 Uptake Capacity and Reversibility of Sulfur-Impregnated Activated Carbon under Dynamic Conditions

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• 作者：Yuanyang Wei ; Danqing Yu ; Shitang Tong ; Charles Q. Jia
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：February 3, 2015
• 年：2015
• 卷：49
• 期：3
• 页码：1706-1712
• 全文大小：304K
• ISSN：1520-5851

文摘

Powder activated carbon (AC) injection is widely considered as the most viable technology for removing gaseous elemental mercury (Hg⁰) in flue gases of coal-fired power plants. However, sulfuric acid (H₂SO₄) can form on the external and internal surfaces of AC particles due to the presence of sulfur oxides, nitrogen oxides, oxygen, and moisture in flue gases. This work focuses on the effects of H₂SO₄ and O₂ on the Hg⁰ uptake capacity and reversibility of sulfur impregnated activated carbon (SIAC) under dynamic conditions. Experiments were conducted with 25 渭g-Hg⁰/m³ of nitrogen or air, using a semicontinuous flow fixed-bed reactor kept at 120 or 180 掳C. H₂SO₄ had a profound hindering effect on Hg⁰ uptake due to pore blockage. O₂ significantly enhanced Hg⁰ uptake and its reversibility, via the oxidation of Hg⁰ which facilitated chemisorption and the subsequent physisorption onto chemically adsorbed Hg. Absorption of Hg in H₂SO₄ was unlikely a significant contributor, when Hg⁰ concentrations were at levels of typical power plants (tens of ppb). The reversibility of and relative contributions of physisorption and chemisorption to Hg⁰ uptake would change with Hg⁰ concentrations in flue gases. These findings could be significant in developing a complete solution for Hg capture where the handling of spent sorbent materials and the possible secondary pollution need to be considered.