Simultaneous oxidation of NO,SO_2 and Hg^0 from flue gas by pulsed corona discharge

A process capable of simultaneously oxidizing NO, SO2, and Hg^0 was proposed, using a nigh-voltage and short-duration positive pulsed corona discharge. By focusing on NO, SO2, and Hg^0 oxidation efficiencies, the influences of pulse peak voltage, pulse frequency, initial concentration, electrode number, residence time and water vapor addition were investigated. The results indicate that NO, SO2 and Hg^0 oxidation efficiencies depend primarily on the radicals （OH, HO2, O） and the active species （O3, H2O2, etc.） produced by the pulsed corona discharge. The NO, SO2 and Hg^0 oxidation efficiencies could be improved as pulse peak voltage, pulse frequency, electrode number and residence time increased, but they were reduced with increasing initial concentrations. By adding water vapor, the SO2 oxidation efficiency was improved remarkably, while the NO oxidation efficiency decreased slightly. In our experiments, the simultaneous NO, SO2, and Hg^0 oxidation efficiencies reached to 40%, 98%, and 55% with the initial concentrations 479 mg/m^3, 1040 mg/m^3, and 15.0 μg/m^3, respectively.

Review of elemental mercury(Hg^(0))removal by CuO-based materials

Mercury emission has become a great environmental concern because of its high toxicity,bioaccumulation,and persistence.Adsorption is an effective method to remove Hg^(0)from coal-fired flue gas,with adsorbents playing a dominant role.Extensive investigations have been conducted on the use of CuO-based materials for Hg^(0)removal,and some fruitful results have been obtained.In this review,we summarize advances in the application of CuO-based materials for Hg^(0)capture.Firstly,the fundamentals of CuO,including its crystal information and synthesis methods,are introduced.Then,the Hg^(0)removal capability of some typical CuO-based adsorbents is discussed.Considering that coal-fired flue gas also contains a certain amount of NO,SO_(2),H_(2)O,NH_(3),and HCl,the impacts of these species on adsorbent Hg^(0)removal efficiency are summarized next.By generalizing the mechanisms dominating the Hg^(0)removal process,the rate-determining step and the key intermediates can be discovered.Apart from Hg^(0),some other air pollutants,such as CO,NOx,and volatile organic compounds(VOCs),account for a certain portion of flue gas.In view of their similar abatement mechanisms,simultaneous removal of Hg^(0)and other air pollutants has become a hot topic in the environmental field.Considering the Hg^(0)re-emission phenomena in wet flue gas desulfurization(WFGD),mercury capture performance under different conditions in this device is discussed.Finally,we conclude that new adsorbents suitable for long-term operation in coal-fired flue gas should be developed to realize the effective reduction of mercury emissions.

Supported catalysts for simultaneous removal of SO_(2),NO_(x),and Hg^(0)from industrial exhaust gases:A review

The simultaneous removal of SO_(2),NO_(x)and Hg^(0)from industrial exhaust flue gas has drawn worldwide attention in recent years.A particularly attractive technique is selective catalytic reduction,which effectively removes SO_(2),NO_(x)and Hg^(0)at low temperatures.This paper first reviews the simultaneous removal of SO_(2),NO_(x)and Hg^(0)by unsupported and supported catalysts.It then describes and compares the research progress of various carriers,eg.,carbon-based materials,metal oxides,silica,molecular sieves,metal-organic frameworks,and pillared interlayered clays,in the simultaneous removal of SO_(2),NO_(x)and Hg^(0).The effects of flue-gas components(such as O_(2),NH3,HCl,H2 O,SO_(2),NO and Hg^(0))on the removal of SO_(2),NOx,and Hg^(0)are discussed comprehensively and systematically.After summarizing the pollutantremoval mechanism,the review discusses future developments in the simultaneous removal of SO_(2),NOx and Hg^(0)by catalysts.

双金属Fe^0-Cu^0的合成及其催化过硫酸钠(PS)降解邻苯二甲酸二丁酯的研究

以铜金属有机骨架材料Cu3(BTC)2·12H2O(Cu-BTC)为前驱体,通过浸渍还原方法成功制备出粒径为20-30 nm的Fe^0-Cu^0双金属催化剂.为评估该双金属催化剂对过硫酸钠(PS)的催化活性,对邻苯二甲酸二丁酯(DBP)进行氧化降解研究.考察了Fe^0/Cu^0的摩尔比、PS浓度、催化剂用量及初始pH对DBP降解的影响.结果表明在Fe^0/Cu^0<1.0时,DBP的降解去除率随着双金属催化剂Fe^0/Cu^0摩尔比的增加而增大.DBP的降解率随着PS和Fe^0-Cu^0双金属催化剂浓度的增加而增大,并在PS和Fe^0-Cu^0浓度分别为1.62 mmol·L^-1和0.3 g·L^-1时达到最佳去除效果.除pH值为7.0外,DBP的降解率随着初始pH值的增加而下降.

Impact of H_(2)S on Hg^(0)capture performance over nitrogen-doped carbon microsphere sorbent:experimental and theoretical insights

A nitrogen-doped carbon microsphere sorbent with a hierarchical porous structure was synthesized via aggregation-hydrothermal carbonization.The Hg^(0)adsorption performance of the nitrogen-doped carbon microsphere sorbent was tested and compared with that of the coconut shell activated carbon prepared in the laboratory.The effect of H_(2)S on Hg^(0)adsorption was also investigated.The nitrogen-doped carbon microsphere sorbent exhibited superior mercury removal performance compared with that of coconut shell activated carbon.In the absence of H_(2)S at a low temperature(≤100℃),the Hg^(0)removal efficiency of the nitrogen-doped carbon microsphere sorbent exceeded 90%.This value is significantly higher than that of coconut shell activated carbon,which is approximately 45%.H_(2)S significantly enhanced the Hg^(0)removal performance of the nitrogen-doped carbon microsphere sorbent at higher temperatures(100–180℃).The hierarchical porous structure facilitated the diffusion and adsorption of H_(2)S and Hg^(0),while the nitrogen-containing active sites significantly improved the adsorption and dissociation capabilities of H_(2)S,contributing to the generation of more active sulfur species on the surface of the nitrogen-doped carbon microsphere sorbent.The formation of active sulfur species and HgS on the sorbent surface was further confirmed using X-ray photoelectron spectroscopy and Hg^(0)temperature-programmed desorption tests.Density functional theory was employed to elucidate the adsorption and transformation of Hg^(0)on the sorbent surface.H_(2)S adsorbed and dissociated on the sorbent surface,generating active sulfur species that reacted with gaseous Hg^(0)to form HgS.

Development of LnMnO_(3+σ) perovskite on low temperature Hg0 removal

LnMnO_(3+σ)(Ln=La,Pr,Nd,Sm,Eu,Gd or Dy)perovskites synthesized by sol-gel method were employed for gaseous elemental mercury(Hg^(0))removal from coal-fired flue gas.Characterization results revealed the structure of the perovskites presented a phase transition process from rhombohedral system to O-and O'-orthorhombic structure with the change of A-site rare earth elements.The perovskites showed satisfactory Hg^(0) removal capacity in a narrow temperature range of 100-150℃.NdMnO_(3+σ) with an O-O'orthorhombic structure presented the best Hg^(0) removal performance,which markedly depends on four factors:crystal structure,oxygen vacancy density,Mn^(4+)/Mn^(3+) ratio and surface element segregation.The Hg^(0) removal mechanism was illustrated based on the mercury temperature programmed desorption experiment and X-ray photoelectron spectroscopy characterization.Both chemisorption and catalytic oxidation played a role in the Hg^(0) removal process.Chemisorption dominated the Hg^(0) removal,due to the slow catalytic oxidation rate at low temperature.This work preliminarily established the relation between the structure of rare earth manganese perovskite and Hg^(0) removal performance.

海水改性分子筛吸附剂脱除燃煤烟气中Hg^0的实验研究

由于在吸附剂中引入卤族元素可以极大地促进其对燃煤烟气中Hg-0的脱除,考虑到海水中含有丰富的氯元素,因此采用海水改性来提高吸附剂脱除Hg-0的效率。在氧气体积分数为6%的氮氧（94%N2＋6%O2）基本气氛下进行了改性吸附剂脱除Hg-0的活性测试。研究表明：经海水改性后提高了吸附剂的脱汞效率且改性吸附剂对Hg-0主要以化学吸附的方式脱除;改性吸附剂的最高脱汞效率达到90%,相比于Na（13X）分子筛原样的脱汞效率提升了约40%,表明通过海水改性来提高吸附剂脱汞效率是可行的。