| The emission of mercury in china has attracted worldwide attention.Elemental mercury emissions from coal-fired power plant were the main source of air mercury pollution.The technologies used to remove elemental mercury in coal-fired power plant can be mainly divided into two groups:powder activated carbon(PAC)injection,and co-benefit of selective catalytic reduction unit with wet fuel gas desulfurization(SCR+WFGD).However,The application of those technologies is limited due to the low chlorine content in feed-coal,and introduced mercury into byproducts.In this study,Magnetic Fe-Ti-Mn spinel and pyrrhotite were developed as a recyclable sorbent to centralized control elemental mercury from the flue gas as a co-benefit of electrostatic precipitators combined with fabric filter(ESP+FF)and wet electrostatic precipitators(WESP).Moreover,Fe-containing sphalerite was developed to store high concentration of elemental mercury.The major conclusions are summarized as follows:(1)Fe-Ti-Mn spinel was sprayed between ESP and FF to adsorb elemental mercury in the fuel gas.its capacity for elemental mercury capture at 150 ? in the presence of 400 ppm of SO2 and 10%of H2O was approximately 0.8 mg g-1.Due to the excellent magnetization,Fe-Ti-Mn could be easily separated from the fly ash mixture in FF using magnetic separation.Meanwhile,after the thermal treatment at 450 ?,the adsorbed HgO on Fe-Ti-Mn spinel could desorb as a high concentration of gaseous elemental mercury to reclaim elemental mercury and regenerate the sorbent.Moreover,the deactivation of elemental mercury capture caused by the sulfation of Fe-Ti-Mn spinel could be suppressed after water washing.(2)Pyrrhotite was sprayed into fuel gas before WESP to adsorb elemental mercury.The rate of pyrrhotite for gaseous elemental mercury capture at 60 ? was 0.28 ?g g-1 min-1,which was not suppressed by SO2.After the magnetic separation from the mixture collected by the WESP,the spent pyrrhotite could be thermally regenerated for the recycle.The experiment of 5 cycles of Hg0 capture and regeneration demonstrated that the degradation of the adsorption efficiency and the magnetization was not clearly observed.Meanwhile,the ultratrace concentration of gaseous elemental mercury in the flue gas was concentrated as a very high concentration of mercury vapor in the regeneration process,which facilitated the centralized control of mercury pollution.(3)Fe-containing sphalerite,synthesized by hydrothermal method,could be used to store high concentrations of elemental mercury released by the sorbents regeneration process.Its capacity for elemental mercury capture was much greater than 8.65 mg g-1 and the reaction rate of 4.82 ?g g-1 min-1 at room temperatures.The formed Hg species on Fe-containing sphalerite was HgS,so it was thermally stable at room temperatures,poor leachable and low toxicity to microorganism.Fe-containing sphalerite could be developed as a treatment for the accidental breakage of the devices containing liquid mercury.Study showed 0.3 g leaked liquid mercury could be well stabilized by 8 g Fe-containing sphalerite.In conclusion,the application of Fe-Ti-Mn spinel,pyrrhotite and Fe-containing sphalerite could remove elemental mercury from flue gas effectively and economically,and realized the resource utilization of mercury,which showed a broad application prospects. |
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