Coal-fired Flue Gas NO_x And Mercury Removal Mechanism On Biomass Activated Carbon

In this paper, the coal-fired flue gas NO_Xand Hg removal mechanism bybiomass activated carbon was studied. The homemade biomass activatedcarbon and modified activated carbon were used to evaluate flue gas NO_XandHg removal performance in the fixed bed adsorbent evaluation system underdifferent conditions.In this paper，biomass activated carbon of different materials were madeunder different activator concentrations and activation temperatures in thehomemade biomass preparation system. Different concentration of halogenscompound were used to modify the commercial activated carbon. In the fixedbed system, the flue gas NO_Xand Hg removal efficiency of activated carbonsamples were evaluated. The influences of the reaction temperature, inletconcentration, adsorbent and conditions on the removal efficiency werestudied.The experimental results showed that, the adsorption capacity of biomassactivated carbon didn’t increase when the concentration of ZnCl2increased.The overall trends firstly increased and then decreased, and each type of straw biomass activated carbon is corresponding to an optimalconcentration. The best activation concentration of green soy bean straw andcorn straw was30%, and the best activation concentration of rice straw was40%.The mercury adsorption capacity of biomass carbon did not increasewhen the activation temperature increased. The overall trends firstlyincreased and then decreased. When the temperature reached its best value,mercury removal performance of biomass activated carbon decreased withhigher temperature softly.The adsorption efficiency of Hg by original unmodified activated carbondropped when the temperature increased. The adsorption efficiency ofchloride modified activated carbon arised with the temperature increased, butwhen the temperature was higher than120℃, the physical adsorption wasweakened by desorption, and the overall efficiency of activated carbondropped.The increasing of the NO concentration inhibited the adsorption of NO ofactivated carbon. The adsorption efficiency of NO of activated carbondropped with the temperature increased.Without the existence of NO, the mercury adsorption efficiency ofbiomass activated carbon was59.48%. When NO existed, the mercuryadsorption capacity of biomass activated carbon increased significantly. Activated carbon surface had certain oxygen-containing functional groups, theoxygen functional groups could react with NO. When O₂existed, it wouldaccelerate the formation of NO₂, thus the activated carbon acted as catalyst,NO₂could react with Hg, thus improving the Hg⁰adsorption efficiency.