SO_2/Hg removal from flue gas by dry FGD

To study the mechanism of SO2 and Hg removal from flue gas, an experimental packed bed reactor was designed to simulate the dry FGD, where a mixture of lime and fly ash in ratio 1：3 w/w was used as the S02 and Hg sorbent, and steam at temperature of 100 ℃ was applied for activation of the sorbent, while the activation time set to 20 rain. The experimental factors including the SO2/Hg sorbent characteristics, 50% breakthrough time for SO2/Hg removal, sorbent packed bed depth and reaction temperature were investigated. The experimental results show that after steam activation, the BET specific surface area and specific pore volume increased from 37.8 to 45.5 m^2/g and from 0.42 to 0.51 cm^3/g, respectively. With activation of the sorbent by steam, the 50% breakthrough times of SO2 and Hg removal increased from 34 to 42 rain and from 23 to 45 rain, respectively. When the packed bed depth was increased from 5 to 25 ram. the 50% breakthrough times for Hg and S02 removal increased from 12 to 52 rain and from 6 to 47 rain, respectively. With the increase of the reaction temperature, the 50% breakthrough of SO2/Hg removal decreased accordingly. Steam activation can efficiently improve SO2/Hg removal simultaneously.

Highly efficient Hg2+ removal via a competitive strategy using a Co-based metal organic framework ZIF-67

The stronger coordination ability of mercury ions with organic ligands than the metal ions in metal organic framework(MOFs) provides an accessible way to separate mercury ions from solution using specific MOFs. In this study, a Co-based MOF(ZIF-67, Co(mIM)) was synthesized. It did not introduce specific functional groups, such as-SH and-NH, into its structure through complicated steps. It separate Hgfrom wastewater with a new strategy, which utilized the stronger coordination ability of Hgwith the nitrogen atom on the imidazole ring of the organic ligand than the Coions. Hgreplaced Conodes from ZIF-67 and formed a more stable precipitate with m IM. The experimental results showed that this new strategy was efficient. ZIF-67 exhibited Hgadsorption capacity of 1740 mg/g, much higher than the known MOFs sorbents. m IMs is the reaction center and ZIF-67 can improve its utilization. The sample color faded from purple to white due to the loss of cobalt ion. It is a great feature of ZIF-67 that allows users to judge whether the sorbent is deactivated intuitively. ZIF-67 can be sustainable recycled by adding organic ligands to the solution after treatment due to its simple synthesis method at room temperature. It’s a high-efficient and sustainable sorbent for Hgseparation from wastewater.

Pd/activated carbon sorbents for mid-temperature capture of mercury from coal-derived fuel gas

Higher concentrations of Hg can be emitted from coal pyrolysis or gasification than from coal combustion, especially elemental Hg. Highly efficient Hg removal technology from coal-derived fuel gas is thus of great importance. Based on the very excellent Hg removal ability of Pd and the high adsorption abilities of activated carbon（AC） for H2 S and Hg, a series of Pd/AC sorbents was prepared by using pore volume impregnation, and their performance in capturing Hg and H2 S from coal-derived fuel gas was investigated using a laboratory-scale fixed-bed reactor. The effects of loading amount, reaction temperature and reaction atmosphere on Hg removal from coal-derived fuel gas were studied. The sorbents were characterized by N2 adsorption, X-ray diffraction（XRD） and X-ray photoelectron spectroscopy（XPS）. The results indicated that the efficiency of Hg removal increased with the increasing of Pd loading amount, but the effective utilization rate of the active component Pd decreased significantly at the same time. High temperature had a negative influence on the Hg removal. The efficiency of Hg removal in the N2-H2S-H2-CO-Hg atmosphere（simulated coal gas） was higher than that in N2-H2S-Hg and N2-Hg atmospheres, which showed that H2 and CO, with their reducing capacity, could benefit promote the removal of Hg. The XPS results suggested that there were two different ways of capturing Hg over sorbents in N2-H2S-Hg and N2-Hg atmospheres.