MnO_x改性活性炭用于模拟烟气中Hg^0的脱除

Removal of Hg^0 from simulated flue gas by MnO_x modified activated carbon

采用浸渍法制备了MnOx改性活性炭(MnOx/AC),用于模拟煤燃烧烟气中的元素态汞的脱除。实验研究了吸附剂的Mn负载量、吸附温度和烟气组分对所制备的改性活性炭的脱汞性能的影响,以及SO2对活性炭脱汞的抑制作用机理。研究结果表明,当模拟烟气中含有5%(体积) O2,Mn负载量为14%(质量),吸附温度为150℃时,改性活性炭的平均脱汞效率为97.0%(3 h)。模拟烟气中少量的O2和微量的HCl、NO均对汞的脱除起促进作用,而微量的SO2则对汞的脱除有抑制作用。通过吸附后的MnOx改性活性炭的TG/DTG、XPS和Hg-TPD分析,推测SO2对改性活性炭脱汞的抑制作用是由于其消耗MnOx中的晶格氧,形成的硫酸盐占据了14Mn/AC表面上的活性位点所致。模拟烟气中微量的NO可以有效降低SO2对脱汞的抑制作用。

The MnOx modified activated carbon(MnOx/AC) was prepared by impregnation method to simulate the removal of elemental mercury in coal combustion flue gas. The effects of Mn loading on sorbent, sorption temperature and flue gas composition on removal performance of elemental mercury in simulated flue gas were investigated. Mechanism of SO2 inhibition on mercury removal was revealed. The average Hg0 removal efficiency on MnOx/AC is 97.0% at 150℃ in 3 hours when Mn loading is 14%(mass) with 5%(vol) O2 in simulated flue gas. A small amount of O2 and trace amounts of HCl and NO promoted the removal of mercury in gas phase, while trace amount of SO2 inhibited it. TG/DTG, XPS and Hg-TPD analyses of spent MnOx modified activated carbon indicated that the inhibition of SO2 on Hg0 removal of modified activated carbon is due to the consumption of lattice oxygen in MnOx by formation of sulfate that occupies active sites on the surface of 14 Mn/AC. This inhibition of SO2 on removal of elemental mercury could be effectively reduced by adding trace amount of NO.