Investigation of Ultraviolet Light-Enhanced H2O2 Oxidation of NOx Emissions

Injecting aqueous solutions of hydrogen peroxide (H2O2) into hot flue gases can convert nitric oxide (NO) to higher oxidation states (NO2, HNO2, and HNO3), which can then be removed in a wet scrubber. The optimum temperature for such conversion is 500°C (930°F), at which H2O2 is thermally “activated” (split into free radicals). At lower temperatures ultraviolet (UV) light can be used to activate the peroxide molecules. In this pilot plant study at Kennedy Space Center, experiments were done with none, one, or two UV lamps on, with and without SO2 present in the flue gases, at various temperatures, and with various injection rates of peroxide. Temperatures ranged from 117 to 350°C (243 to 660°F), and the molar ratios (peroxide to NOx) ranged from 0.68 to 5.02. Conversions of NO varied from below 10 to above 70%, with the highest conversions occurring with higher temperatures, higher dosages of hydrogen peroxide, and with both UV lamps turned on. Conversions of NOx ?(NO+NO2) varied from below 5 to above 40%. The presence of SO2 did not inhibit NO or NOx conversion.     

NO_x排放控制技术的发展与比较

针对大气污染日益严重,NOx排放控制已成为亟待解决的问题。本文全面系统地介绍了国内外NOx排放控制技术的研究现状,通过分析NOx排控技术的优劣,提出了合理应用建议。     

Injection Nozzle for Ultraviolet Light-Enhanced H2O2 Oxidation of Air Pollutants in Flue Gas

Injecting aqueous solutions of hydrogen peroxide (H2O2) into hot flue gases can split the peroxide into OH and HO2 radicals. These reactive radicals readily oxidize air pollutants such as CO, VOCs, NO, mercury, and others. H2O2 is thermally “activated” (split into free radicals) rapidly at temperatures of 500°C and above. At lower temperatures, such as found in boiler exhaust flue gases, ultraviolet (UV) light can be used to activate the peroxide molecules. However, placing the UV lamps directly in the flue gases can lead to operating and maintenance problems, and “dilutes” the UV energy due to absorption by other gases. A “UV nozzle” has been developed that produces H2O2 radicals and delivers them into a flowing stream of boiler flue gases. Using a previously constructed pilot scale system at NASA's Kennedy Space Center, experiments were run to prove the concept of the nozzle, measuring the oxidation of NO as an indicator of radical formation and delivery. Data were taken at three temperatures, with none, one, or two UV lamps on, and with various injection rates of peroxide. Flue gas temperatures ranged from 85 to 304°C (186 to 580°F), and the molar ratios (inlet peroxide to inlet NOx) ranged from about 1.5 to over 15. Conversions of NO varied from 0% (at the lowest temperature tested) to above 50% (at highest temperature). Although increasing temperature had a marked effect on conversion, the activation of hydrogen peroxide by UV light was demonstrated in the temperature range of final flue gas exhaust gases (290–350°F). These results indicate that radicals can be created from hydrogen peroxide at reasonable temperatures using UV light, and that the radicals can be delivered into a flue gas stream where they can oxidize pollutants.     

Application of Multivariate Statistical Models to Prediction of NOx Emissions from Complex Industrial Heater Systems

Industrial fired heaters are a major source of nitrogen oxides (NOx). On-line analyzers, kinetic models with computational fluid dynamics, and empirical predictive models have been developed to monitor NOx emissions and analyze excessive NOx emissions. However, previous approaches have been applied only to single heater systems, not to large-scale multiheater systems. This paper proposes a hierarchical monitoring and diagnosis procedure to monitor NOx emissions from large-scale multiheater systems and to identify the root causes of excessive NOx emissions as well as heater malfunctions. The procedure provides a functional three-layer hierarchy: (1) prediction of NOx concentrations; (2) estimation of the influence of individual heaters on the predicted NOx; and (3) identification of the root causes by examining the detailed contributions of process variables to variations of the heater identified in step 2 as being the principal source of NOx. An integrated multiblock partial least-squares (PLS) model, created by combining standard PLS and multiblock PLS, is employed to predict the NOx emissions and estimate the influences of the heaters on the emissions. The validity of the proposed method is demonstrated through its application in two case studies.     

H_3PW_6Mo_6O_(40)·nH_2O催化过氧化氢清洁氧化环己酮合成己二酸

以自制H3PW6Mo6O40.nH2O为催化剂,在无有机溶剂、相转移催化剂的情况下,用过氧化氢氧化环己酮合成己二酸。探讨了催化剂用量、过氧化氢用量、反应时间、反应温度对反应的影响。确定了最佳反应条件为n(环己酮)∶(n磷钼钨杂多酸)∶(n过氧化氢)=100∶0.15∶400,在90℃反应5h,己二酸的分离收率达75.8%。     

降低热媒炉NO_x排放量的数值分析及验证

对某热媒炉NOx排放量超标的问题进行研究。采用CFD手段,对其进行结构优化设计;采用空气分级燃烧技术,预测NOx排放,得到了不同工况下的炉内温度及O2、CO和NOx等浓度分布。数值预测和试验结果都表明:在采用空气分级燃烧技术的情况下,增大二次空气量可以有效地减少NOx的生成排放,很好控制燃烧产物对大气的污染;在数值模拟中观察到随着二次空气量的增加,炉膛最高温度和平均温度降低,火焰或向一侧偏斜。该研究为空气分级低NOx燃烧系统改造效果的预报和应用提供重要参考依据。     

[Nd(PW11O39)(H2O)3](H2bpy)2·4H2O的水热合成及晶体结构

采用水热法合成稀土无机有机杂化化合物[Nd(PW11O39)(H2O)3 ](H2bpy)2·4H2O.采用NdCl3·6H2O,(NH4)3PW12O40·3H2O, 4,4'-联吡啶(bpy),和去离子水(摩尔比为4∶1∶4∶3900, pH=6)在130℃下进行水热反应3天,得到标题化合物的紫红色块状晶体,并进行了红外光谱分析,元素分析.用单晶X射线衍射法测得晶体结构,属三斜晶系,空间群为P-1,晶胞参数为a=1.18824(9) nm,b =1.35707(10)nm,c=1.77691(13)nm,α=71.551(2)°,β=82.478(2)°,γ=80.568(2)°.该晶体由无机的共价链∞1[Nd(PW11O39)(H2O)3]4- 和有机的二质子化的4,4'-联吡啶(H2bpy)2 及结晶水分子堆积而成的, 是一个新的稀土磷钨酸盐无机有机杂化化合物.     

Evaluation of UV LEDs Performance in Photochemical Oxidation of Phenol in the Presence of H2O2

A novel application of ultraviolet (UV) light emitting diodes (LEDs) as a light source for the degradation of organic contaminant has been investigated. Photocleaving of hydrogen peroxide (H2O2) via UV LEDs photolysis resulted in the generation of hydroxyl radicals. It was found that phenol removal was insignificant in the absence of hydrogen peroxide, therefore oxidation of phenol was attributed to the formed radicals. Two criteria were selected to provide detailed information on the performance of UV LEDs in phenol oxidation: (1) the reaction quantum efficiency and (2) the energy consumption. Statistical tools such as the response surface methodology and the ANOVA were applied to estimate the influence of various process parameters such as the wavelength (255, 269, and 276 nm) and H2O2 to phenol molar ratio (5, 50, and 100) on phenol degradation reaction quantum efficiency. The decay of phenol (initial concentration of 1.06 mM) was the most pronounced at 255 nm and H2O2 to phenol molar ratio of 50. Finally, the “figure-of-merit” was used to estimate the specific energy consumption of the UV LED-based process.     

过氧化氢氧化亚铁滴定法测定铬

过硫酸铵－硝酸银氧化铝亚铁滴定法测定铬量的方法[1-5]应用颇为广泛,但用于只能碱熔分解的试样时较为繁琐费时．作者提出用过氧化氢在碱性介质中氧化铬,用亚铁滴定法测定铬量的方法．过量的过氧化氢在碱性条件下极易煮沸分解,在氧化完全后加人适量的高锰酸钾再酸化,能有效地消除硫酸和磷酸中不可避免的还原性物质的影响．用氯化控还原高锰酸钾后以亚铁滴定六价铬（w）．方法适于碳素铬铁、铬铁矿等样品中铬的快速测定．分析结果令人满意．1实验部分1．l主要试剂过氧化氢（川．15g／mL）;高锰酸钾溶液：309几;氯化按溶液：15他几;硫…     

Pilot-Scale Evaluation of Denitrification Drainage Bioreactors: Reactor Geometry and Performance

Denitrification drainage bioreactors are emerging as an innovative practice to address water quality concerns stemming from nitrate leaching from drained agricultural lands. Although installation of these systems has begun in farms in the midwestern United States, the understanding of their design and in-field performance remains deficient. This study utilized a set of pilot-scale drainage bioreactors to evaluate the impact of bioreactor geometry on reactor hydraulic properties and to determine nitrate removal under steady-state conditions and during a simulated storm event. Bioreactors with different cross-sectional geometries but similar depths and total volumes were evaluated. The percent reduction of the influent nitrate mass was linearly correlated to the theoretical hydraulic retention time (HRT) with 30 to 70% NO3--N removals observed within the 4 to 8?h of retention time suggested for field installations. Tracer tests revealed that in situ HRTs were at least 1.5 times larger than theoretical HRTs.     

Phase Equilibrium of Ternary Systems LaX 3 C 18 H 16 N 3O 2Cl H 2O

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Hazard Control of NOxin Hot Stove

Hazard control of NOxis very important for the long life of hot stove shell and environmental protection.NOxconcentrations during different operation periods of hot stove were calculated according to thermodynamical and dynamical analyses.The results were verified by the previously measured data.Then,the influence of hot stove operation parameters on NOxconcentration and the mechanism of liquid water formation in hot stove were studied.The results indicated that in gas period,the dome temperature should be controlled below 1 420 ℃in order to decrease NOxemission.In the case of banking operation,NOxconcentration was about 40-60times higher than that in gas period.Hence,reasonable measures should be taken to reduce banking operation,especially in the situation of large excess air ratio.Since NOxformed during the whole operation process,the most effective way of preventing liquid water and HNO3generation is to control the pipe and shell temperature,which should be higher than the condensation temperature of water vapour.The condensation temperature should be considered as the design temperature of pipe and shell for hot stove.     

Conversion of pentahalogenated phenols by microperoxidase-8/H2O2 to benzoquinone-type products

This study reports the microperoxidase-8 (MP8)/H2O2-catalyzed dehalogenation of pentafluorophenol and pentachlorophenol, compounds whose toxic effects and persistence in the environment are well documented. The primary products of this dehalogenation reaction appear to be the corresponding tetrahalo-p-benzoquinones. Under the conditions used, the fluorinated phenol and its intermediate products are more susceptible to degradation than the corresponding chlorinated analogue and its products. The main degradation products of tetrachloro-p-benzoquinone and tetrafluoro-p-benzoquinone were identified as trichlorohydroxy-p-benzoquinone and trifluorohydroxy-p-benzoquinone, respectively. This secondary conversion of tetrafluoro-p-benzoquinone and tetrachloro-p-benzoquinone was not mediated by MP8, but was driven by H2O2. Evidence is presented for a mechanism where H2O2 molecules and not hydroxide anions are the reactive nucleophilic species attacking the tetrahalo-p-benzoquinones. In addition to the formation of the trihalohydroxy-p-benzoquinones, the formation of adducts of the tetrahalo-p-benzoquinone products with ethanol, present in the incubation medium, was observed. The adduct from the reaction of tetrachloro-p-benzoquinone with ethanol was isolated and identified as trichloroethoxyquinone. Thus, the present paper describes a system in which the formation of tetrahalo-p-benzoquinone-type products by an oxidative heme-based catalyst could be unequivocally demonstrated.     

Hydrothermal stability of MOx-Ce0.75Zr0.25O2 catalysts for NOx reduction by ammonia

Various acidic components（MOx：phosphate,sulfate,tungstate and niobate） were loaded on Ce0.75 Zr0.25 O2 powders by an impregnation method.The as-prepared catalysts were hydrothermally treated at 760 oC for 48 h in air containing 10 vol.% H2 O to obtain the aged catalysts.The catalysts were characterized by X-ray diffraction,Fourier transform infrared spectroscopy,H2 programmed-reduction,NH3 adsorption and deNOx activity measurements.The results showed that,among the catalysts investigated,the phosphated Ce0.75 Zr0.25 O2 catalyst showed the highest hydrothermal stability.The remained high acidity of the phosphated catalyst with moderate redox property helped to maintain the excellent NH3-SCR activity of hydrothermally aged catalyst.Cerium tungstate led to the poor redox property of the tungstated catalyst although the acidity of catalyst was still high.The decomposition of sulfates at temperatures higher than 600 °C restrained the usage of sulfated catalysts in high temperature conditions.The overall dehydration of niobate to niobium oxides led to the low acidity of hydrothermally aged Nb2 O5-Ce0.75 Zr0.25 O2 catalyst.     

CO,O2,H2O预覆盖对钯吸氢速率的影响

为了考察杂质气体对钯吸氢速率的影响，测定了钯粉末暴露在CO，O2，H2O中后25℃下的吸氢速率。与洁净钯吸氢速率相比，CO预覆盖引起钯吸氢速率降低最为显著，H2O次之；少量O2预覆盖却能引起钯吸氢速率显著增加。引起吸氢速率变化的微观机制主要是受氢原子在氢化物层的扩散或钯表面解离氢分子的化学吸附；O2预覆盖可使Pd表面形成多孔结构而增加了氢分子的解离位，从而增加吸氢速率；CO预覆盖后却占领了钯表面的氢分子解离位而减小了吸氢速率。250℃下的O2预处理是CO毒化钯活化的有效方法。     

Probing cellular protein targets of H2O2 with fluorescein-conjugated iodoacetamide and antibodies to fluorescein

Fatty acid ethyl ester synthase-III metabolizes both ethanol and carcinogens. Structure-function studies of the enzyme have not been performed in relation to site specific mutagenesis. In this study, three residues (Gly 32, Cys 39 and His 72) have been mutated to observe their role in enzyme activity. Gly to Gln, Cys to Trp and His to Ser mutations did not affect fatty acid ethyl ester synthase activity, but His to Ser mutant had less than 9% of control glutathione S-transferase activity. The apparent loss of transferase activity reflected a 28 fold weaker binding constant for glutathione. Thus, this study indicates that Gly and Cys may not be important for synthase or transferase activities however, histidine may play a role in glutathione binding, but it is not an essential catalytic residue of glutathione S-transferase or for fatty acid ethyl ester synthase activity.