Catalytic Oxidation of Hg0 in Wet FGD by Air–contributions to the Development of the Chemical Model of the Process
Due to expected more stringent emission standards there is a lot of scientific and development effort focused on the development of the mercury removal technologies,mainly directed in two alternatives; the enhancement of homogenous oxidation of Hg0 to soluble Hg2+in flue gases by the addition of chlorides or bromides into the boiler or the adsorption of Hg2+and Hg0 on the impregnated activated carbon (AC).Third option gaining more attention lately is the possibility to modify the wet FGD to oxidize dissolved Hg0 and retain it in the wet FGD.In previous experiments the parametric study was performed to quantify the influence of different parameters on the removal efficiency of Hg0 from the gaseous phase.In this work we have critically reviewed and summarized the results developing the following relationship which can describe the removal efficiency: Hg0 removed (％)=(-14.1+0,5828*E)*(e^(-0.14*SO3 2-)) Where E is redox potential of Pt/calomel pair and SO3 2-is the concentration of sulphite ions in mmolL-1.0≥Hg0 removal efficiency≤100.The chemical system includes the species like SO2 3-at concentration (mgL-1): 17-2322 (0.26-36.3 mmolL-1),chloride at concentration (gL-1): 0 or 5,SO4 2-at concentration (gL-1): 8-10,S2O6 2-at concentration (mgL-1:) 0 or 250-500,Fe2+addition (mgh-1L-1): 0 or 0.45-1.65,Mn2+at concentration (mgL-1): 0 or 1-25,temperature 22±2 oC and gaseous phase flow rate (Lh-1L-1): 40±7.The oxidation rate of Hg0 in ngh-1L-1 by some chemical oxidants that may appear in the oxidation reaction(s) of SO3 2-by air to SO4 2-is given in the experiments where oxygen was excluded.Among chemicals tested Fe3+and Na2S2O8 are not effective,better is H2O2 and even more the combination of H2O2 and Fe2+/Fe3+.The addition of S2-ions causes rapid and complete depletion of the Hg2+from the solution.Carbonate ions seem to complex Hg2+ions stabilizing the concentration of Hg2+in the solution in the range of pH values between 2.5 and 5.6.The findings of this work can contribute to the development of the realistic chemical model of the Hg0 removal process in wet FGD by catalytic air oxidation.The chemical equilibrium and kinetics have to be considered and specific chemical composition of the solution in wet FGD (depending on coal composition and the technological solutions from the boiler to the last emission control process) must be taken into account in developing such a model
Andrej Stergar(ｓ)ek Milena Horvat Sergio Ribeira Guevara Peter Frkal Jo(s)t Stergar(s)ek
“Jo(z)ef StefanInstitute,Ljubljana,Slovenia Nuclear Institute,Bariloche,Argentina Notranjski regijski park,Cerknica,Slovenia
国际会议
The 8th International Symposium on Gas Cleaning at High Temperatures(第八届国际高温气体净化技术研讨会 GCHT-8)
太原
英文
49-62
2010-08-23（万方平台首次上网日期，不代表论文的发表时间）