Study On The Performance And Mechanism Of Mercury Removal Of Activated Carbon Composite Adsorbent In Simulated Flue Gas

Mercury is one of the trace metals emitted during coal combustion.it is the only metallic element that maintains a liquidstate under standard conditions.Mercury has adverse effects on the environment and on the physiological health of humans,because of its bioaccumulation and biomagnification properties.The mercury emitted during coal combustion occurs mainly in the states of elemental(Hg0),the oxidized state(Hg2+),and the particle-associated(Hgp)state.Hg2+ and Hgp can be easily removed by an electrostatic precipitator and a wet scrubber.However,these devices cannot effectively capture Hg0 and thus Hg0 was the main mercury state emitted to the atmosphere.Therefore,removal of mercury from flue gases has become a hot issue in recent years.In the present study,two kinds of adsorbents prepared from resin and fly ash/bamboo were employed to remove mercury from flue gases.The mercuy removal properties and mechanisms of prepared adsorbents were investigated and the results were as follows:(1)Fly-ash-modified bamboo-shell carbon blacks were prepared,and the properties and mercury removal abilities of the prepared carbon blacks were evaluated.The fly ash acted as a support for the carbon structure during the carbon black preparation,and demonstrated the ability to fix a portion of the carbon contained in volatile compounds during carbonization,resulting in a higher carbon yield of the carbon black containing fly ash;it had a higher BET surface area and a higher mercury removal ability than carbon black without fly ash.Strong pore structure,in the range of 1000-10000 nm,appeared after the addition of fly ash,which became stronger with higher fly-ash content.Additionally,the mercury compounds generated through the catalytic effect of fly ash(around 200°C)had lower thermal stabilities than those generated on carbon(280°C),according to the TPDD experiments,indicating that the addition of fly ash was favorable for the recycling of the mercury compounds and the regeneration of used carbon black.(2)The mothed of traditional activated carbon was optimised.Using cation exchange resin and Fe(NO3)3 solution for cation exchange,after crushing,compression,heat treatment,carbonization and activation,Activated carbon of Fe2O3 uniform dispersion was prepared.The effects of Fe,thermal treatment,carbonization temperature and activation on the properties of Fe dopped activated carbons were investigated by TG,BET,SEM and XPS analyses.It was found that the presence of Fe could effectively fix the volatile compounds during thermal treatment,resulting in the increase of yield and BET surface of Fe dopped activated carbon.The Fe dopped activated carbon prepared at the activation temperature of 800? showed the highest mecury removal ability during removal of mercury from simulated flue gases at the temperatures of 80,150 and 180?,respecvtely.The mercury removal rates of the above activated carbon were 75%,29.26% and 44.87% at the treatment temperature of 80,150 and 180?,respectively.