| At present,mainstream flue gas desulfurization,denitrification and demercuration technology is mainly composed of series stage treatment arrangement.However,this technology is not suitable to be used to flue gas treatment from the median and small industrial boilers and furnaces,as a result of the shortages of high construction and operational costs and larger occupying area.Hence,to develop an efficient and economical method for simultaneous desulfurization and denitrification and demercuration is one of the hot topics in the field of air pollution control,has the important theory meaning.The oxidation method has been proven to be an effective method for simultaneous removal of sulfur dioxide（SO2）,nitric oxide（NO）and elemental mercury（Hg0）.Therefore,this subject intends to use the ultraviolet/Na Cl O2advanced oxidation process for simultaneous flue gas desulfurization,denitrification and demercuration experimental research.The main research contents are as follows:（1）Explore the performance of different advanced oxidation process in desulfurization,denitrification and demercuration under the same reagent cost conditions,mainly including UV-H2O2,UV-Na Cl O,UV-Na2S2O8 and UV-Na Cl O2.The research results show that UV-Na Cl O2 has the best performance.（2）The experiment found that NH4OH and Na Cl O2 produced a significant synergistic promotion effect.The addition of NH4OH can effectively absorb NO2 and promote the removal of NO to a certain extent,but the high concentration of NH4OH is not conducive to NO oxidation and NO2 absorption.The optimal concentration ratio of NH4OH and Na Cl O2 is 3.0%wt and 1.0-1.1%wt.The best removal efficiency of SO2and NO were 98.7%and 98.1%,respectively.（3）An ultraviolet-visible Spectrophotometer（UV-vis）was used to study the mechanism of the synergistic effect of NH4OH and Na Cl O2.The study found that the introduction of NH4OH would significantly increase the absorbance of Na Cl O2 at 260nm,and revealed that its key mechanism is the formation of OH--Cl O2-complexes.Therefore,the addition of NH4OH can maintain Cl O2-in the solution environment in its intrinsic state.（4）The synergistic effect of Na Cl O2 and NH4OH on mercury removal was studied,and the influence of factors such as p H,reaction temperature,flue gas velocity,coexisting gas and solution anions were further investigated.The addition of NH4OH was to help Na Cl O2 preserving and/or stabilizing Hg2+meanwhile inhibiting the photo-production of Cl O2.In the absence of UV,decreasing p H promoted the release of Hg2+from Na Cl O2-NH4OH;introducing NO,SO2,O2,Br-,Cl-and HCO3-suppressed Hg0 oxidation.In the presence of UV,rising temperature accelerated the release of Hg2+from Na Cl O2-NH4OH;while SO2,Br-and HCO3-facilitated Hg0oxidation.The experimental results show that the best removal efficiency of Hg0 is91.8%.（5）It is determined that the denitrification and mercury removal oxidation products are characterized by X-ray photoelectron spectroscopy（XPS）and electron spin resonance（ESR）.The nitrogen-containing products are mainly NH4NO3 and Na NO3,and the mercury-containing products are mainly Hg Cl2.The ESR characteristic spectrum confirmed that the main oxide species of the UV-Na Cl O2system were Cl O·,HO·,Cl O2 and Cl2O2.Finally,based on the characterization results and related literature,the reaction mechanism of UV-Na Cl O2 simultaneous desulfurization,denitration and demercuration was speculated.（6）Finally,this study carried out the macroscopic reaction kinetic calculation of denitrification and mercury removal:the calculation results show that the Ha value of the denitrification process with and without UV irradiation is 730-780 and 229-403,respectively;the Ha value of the demercuration process with and without UV irradiation is 69-305 and 23-133,respectively.It shows that the Na Cl O2-NH4OH and UV/Na Cl O2-NH4OH oxidation processes belonged to fast and/or instantaneous reaction.Thus,the gas-film mass transfer was the rate-determining step. |
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