Air Quality Monitoring Network Design to Control Nitrogen Dioxide and Ozone,Applied in Granada,Spain

This paper describes a method to design air quality monitoring networks for nitrogen dioxide and ozone and its application in Granada, a city located in Andalusia, southern Spain. The city has a population of 236,988 inhabitants, and traffic is its main source of air pollution. Sampling campaigns with passive diffusion samplers at 88 sites were carried out to obtain information on the pollution distribution in Granada. The average concentrations found for NO₂ and O₃ were 36.5 μg/m³ and 51.6 μg/m³, respectively. Maximum values of up to 57.1 μg/m³ NO₂ were found in Granada city center and O₃ reached 77.2 μg/m³ downwind from the emission source. After spatial interpolation of the obtained values with Geographical Information Systems, a selection of the best locations for the monitoring stations was made, in line with the macro- and microscale siting requirements of the European Directive 2008/50/EC on ambient air quality and cleaner air for Europe. Another sampling campaign with diffusive samplers was carried out in 2007 to determine if the locations of the air quality assessment stations were still representative for their zone. A correction was made in the control network following results of this verification campaign.     

Effect of Ultrasonic Irradiation on the Treatment of Poly-Aromatic Substances (PAHs) from a Petrochemical Industry Wastewater

The effects of sonication time, nitrogen, N₂(g), increasing temperature, dissolved oxygen (DO) and titanium dioxide (TiO₂) concentrations on the sonodegradation of polyaromatic hydrocarbons (PAHs) in petrochemical wastewaters were investigated. Sonication alone without N₂(g), DO and TiO₂ provided 80% maximum PAH yields at 2 5°C after 150 min. This PAH yield increased to 89–95% at 60 °C after 150 min sonication. The contribution of DO, N₂(g) and TiO₂ on the PAH removal was not significant compared to the control. In the presence of HCO₃ ^?, the degradation of hydrophobic PAH dibenz[a,h]anthracene (DahA)was suppressed in the acceleration step of the sonication. Maximum acute toxicity removal was reached by 30 min N₂(g) sparging, 4 mg/L DO and by 0.1 mg/L TiO₂ after 150 min sonication.     

Biological Nitrogen Removal Using the Supernatant of Ozonized Sludge as Extra Carbon Source

A sludge ozonation process with lab-scale anaerobic/oxic (A/O) system was used to investigate the utilization of the ozonized sludge (OS) supernatant as extra carbon source for denitrification. The optimal ozone dose for the sludge ozonation was 0.2 gO₃/gSS. The concentrations of SCOD, BOD, NH₃-N and TN in the supernatant increased respectively at this ozone dose. In the meantime, the sludge was significantly reduced. The OS supernatant had negative effect on nitrification because of low pH and alkalinity. After alkalinity adjustment, the A/O with the OS supernatant as the extra carbon source achieved a nitrogen removal rate of 78%, which was very close to the control experiment using glucose (79%).     

The High‐Pressure Characterization of Energetic Materials: 1,4‐Dimethyl‐5‐Aminotetrazolium 5‐Nitrotetrazolate

In‐situ high‐pressure room temperature synchrotron X‐ray diffraction and infrared microspectroscopy were used to examine the structural and vibrational properties and the equation of state of 1,4‐dimethyl‐5‐aminotetrazolium 5‐nitrotetrazolate (DMATNT). The X‐ray measurements show a smoothly varying pressure‐volume relationship to 20 GPa. However, the anisotropic ratios of the unit cell parameters reveal a discontinuity near 3.3 GPa, which can be attributed to an irreversible isostructural phase transition. A significant increase in the Infrared spectral intensity near this pressure coupled with Dayvdov splitting of the NO₂ bending and scissoring modes suggest the transition results in a skewing of the NO₂ groups and increasing asymmetry of the hydrogen bonding sublattice.     

肟交换法制备乙醛肟工艺的研究

肟交换法是一种制备乙醛肟的新兴工艺,但反应过程存在乙醛肟易被空气氧化等问题,且反应液中存在多组共沸物,分离提纯得到高纯度的乙醛肟较为困难。以丁酮肟为原料,通过向反应器内充入0.2 MPa的氮气,有效避免了乙醛肟氧化与原料乙醛、丁酮肟的挥发,乙醛肟反应选择性达96.12%。开发了产物的提纯工艺,通过Aspen Plus模拟,初步确定减压精馏分离反应液的基本流程,考察了压力、塔板数、回流比、进料位置等操作参数对分离过程的影响。在此基础上,依据模拟确定的操作参数进行实验,确定最优分离提纯工艺,得到纯度为95.33%的乙醛肟产品,收率可达94.31%。本研究可为肟交换法制备乙醛肟的工业化提供一定的指导。     

Improvement of surge current performances of ZnO varistor ceramics via C3N4-doping

ZnO-Bi₂O₃ based varistor ceramics doped with C₃N₄ were fabricated via solid state method. Experimental results show that C₃N₄ additive acts as an inhibitor in ZnO grain growth, and the average grain size decreases from 10.2–7.1 μm. The varistor breakdown voltage gradient increases from 222.3–282.3 V/mm, and the nonlinear coefficient increases from 51.9–58.2 with the increase of C₃N₄ content from 0 to 3.0 wt%. The C₃N₄-added samples exhibited smaller residual voltage ratio and better surge current withstanding capability. It is proposed that the C₃N₄-doping leads to substitution of nitrogen for oxygen in the grain boundary region, forming acceptor type defects. The acceptor type defects act as electron traps, increasing the barrier height from 1.31 to 1.50 eV and the depletion layer width from 54.9–61.8 nm, which increases the nonlinearity, and the surge current performances of the C₃N₄ doped ZnO varistor ceramics are improved.     

NO emission of oxygen-enriched CH4/O2/N2 premixed flames under electric field

This work investigates the electric field effect on nitrogen oxide (NO) pollutant formation and emission composition of premixed flames in order to provide better insight on the mechanism of controlling the combustion process by electro-physical means. The present study aims to investigate experimentally the effect of radial DC electric field on premixed laminar methane flame. The electric field effect on flame shape, emission composition and NO emission index of flame is investigated experimentally under the action of direct-current electric field under varying equivalence ratio and level of oxygen enrichment. The results show that ionic wind effects cause the distortion in flame shape. The ionic wind effects diminish with increasing flow rate and level of oxygen enrichment. Minimal effects on NO are measured for flames under the influence of electric field and vanished as the level of oxygen enrichment is increased. This was well supported by the temperature profile measurement in the post flame gas showing no field-induced modification also. It seemed that the action of an electric field on a flame with a geometry that remains practically undeformed produces very minimal effect on pollutant emission.     

Numerical Study of NOx Abatement Using Ozone Injection Integrated with Wet Absorption

Nitrogen oxides emitted from power plants and the chemical industry are poisonous to humans and animals, contribute to ozone depletion, and cause acid rain. More than 90% of nitrogen oxides (NO_x) consist of nitric oxide (NO), which is insoluble in water. Among the various available techniques of NO_x abatement, ozone injection is a promising method in which NO is oxidized to higher-order nitrogen oxides (NO₃, N₂O₃, N₂O₄, and N₂O₅), which can easily be absorbed in a wet scrubber. In this article, the ozone injection process integrated with an absorber column is numerically modeled and simulated at various operating conditions. The predicted results of NO_x oxidation with ozone injection and absorption in water agree with the published experimental results. The ozone injection process is modeled using a plug flow reactor, while the wet absorption is based on a rigorous rate-based RateFrac model. Detailed kinetic mechanisms of O₃-NO_x oxidation and absorption of nitrogen oxides in water are incorporated in the model to simultaneously predict the performance efficiency of the ozone reactor and absorber column. Thermodynamic properties of the components are estimated using an Electrolyte NRTL model. The influence of performance parameters (such as feed gas flow rate, inlet gas temperature, reactor configurations, ozone concentration, and NO/NO₂ molar ratio) on the oxidation efficiency of NO_x in the reactor and absorber column is investigated to predict the optimal operating conditions.     

The Synthesis and Energetic Properties of 5,7‐Dinitrobenzo‐1,2,3,4‐tetrazine‐1,3‐dioxide (DNBTDO)

Energetic tetrazine‐1,3‐dioxide, 5,7‐dinitrobenzo‐1,2,3,4‐tetrazine‐1,3‐dioxide ( DNBTDO ), was synthesized in 45 % yield. DNBTDO was characterized as an energetic material in terms of performance (V_det 8411 m s⁻¹; p_{C J} 3.3×10¹⁰ Pa at a density of 1.868 g cm⁻³), mechanical sensitivity (impact and friction as a function of grain size), and thermal stability (T_dec 204 °C). DNBTDO exhibits a sensitivity slightly higher than that of RDX , and a performance slightly lower (96 % of RDX ).     

3D22(Ⅱ)型氮氢气压缩机活塞环的改造

介绍了 3D2 2 (Ⅱ )型压缩机Ⅱ段活塞环由铸铁活塞环改为填充MC尼龙活塞环后活塞体结构尺寸变化的计算和改造后的效果。据此对该机Ⅰ、Ⅲ段也实施了改造