氮氧化物污染控制——控制氮氧化物的生成

本文概述氮氧化物污染控制的方法,即通过控制氮氧化物的生成——改进燃烧技术,减少氮氧化物的生成,来控制氮氧化物对大气环境的污染。改进燃烧技术,正在成为广泛应用的氮氧化物污染控制技术。这种方法的主要优点是可经济有效地控制氮氧化物的排放量。实践表明,氮氧化物的排放量可降低60％以上。只要能满足氮氧化物的排放标准,通常优先应用改进燃烧技术减少氮氧化物的生成。此外,本文还扼要地介绍了氮氧化物生成的化学热力学和动力学的研究结果,这些结果是控制氮氧化物生成的理论基础。     

应用全球大气输送模型进行数值模拟的研究进展(英文)

TOMCAT模型作为多尺度大气输送模型(CTM)的一种,已经在全球范围内得到了广泛应用。大气输送模型是全球温室气体循环研究中一种有效工具,这对于理解全球生态系统的化学循环规律,预测未来气候变化及其对生物多样性的影响具有重要意义。在该模型中,对闪电产生氮氧化物和大气对流过程进行数值模拟是两个重要的因素。为了提高数值模拟的精确性,本文总结了对闪电产生的氮氧化物和大气对流过程进行数值模拟的研究进展,并对将来的研发方向进行了深入探讨。     

X-4105柴油机排气台架净化试验

以柴油机为动力的各种工程机械的排气中含有一氧化碳(CO),碳氢化合物(HC),氮氧化物(NOx)等有害成分,因柴油机本身机型的不同和工作状况的不同,其排出成分会有很大     

基于类比法推算青岛市排污权初始交易价格范围

从环境质量现状、集中供暖、社会经济发展水平、污染负荷4个角度,基于类比分析和数理统计分析方法推算青岛市化学需氧量、氨氮、二氧化硫及氮氧化物等主要污染物的排污权初始交易价格范围.研究结果表明,二氧化硫在3300~5800元/t、氮氧化物在3300~5800元/t、化学需氧量在4100~6000元/t,氨氮5200~6800元/t.本研究可为青岛市排污权试点工作的顺利开展提供技术参考.     

水泥窑炉NOx形成机理及处理技术

1前言 NOx在水泥窑炉污染气体中占有重要地位，其危害性主要表现在环境酸化、人体健康损害和光化学烟雾及温室效应等方面。NOx（氮氧化物）包括一氧化氮NOx二氧化氮NO：和一氧化二氮NxO（笑气）等．氮氧化物不仅是光化学烟雾的主要成分，也是形成酸雨的重要物质，对农业、林业、全球气候、自然环境及人类身体健康都具有极大的危害。     

能源相关的氮氧化物排放现状与控制研究

近年来我国大气污染治理和环保要求日益提高,氮氧化物的排放控制已成为亟待解决的环境问题之一。本文从氮氧化物的排放管理及控制技术介绍国内外能源相关的氮氧化物排放现状及其控制研究进展。最后,结合我国实际情况对氮氧化物排放控制研究前景进行展望。     

试论燃气燃烧过程氮氧化物的控制

探讨了燃气燃烧形成氮氧化物的机理，对其影响进行了分析。介绍了有关国家民用燃气氮氧化物的排放标准，讨论了柢氮氧化物燃烧技术的发展趋势。     

旋流燃烧煤粉锅炉NOx生成的数值模拟

焦炭燃烧选取扩散-动力模型,煤热解反应采用双挥发竞争模型,气相湍流选取RNGk—ε模型,燃烧湍流选用PDF模型,采用CFD软件对1台装有32只双调风旋流燃烧器两侧墙对冲布置的1025t／h燃煤锅炉炉内氮氧化物生成进行数值计算,研究了炉内温度场、氧浓度场以及氮氧化物浓度场的分布特性。发现三者在炉膛内均呈对称分布,燃烧区域内的温度和氮氧化物浓度较高而氧浓度较低,燃烧区域上方温度和氮氧化物浓度逐渐降低而氧浓度升高。研究了温度和空气系数对氮氧化物生成的影响,随着温度的升高,氮氧化物生成量呈升高趋势,而随着空气系数的增大,氮氧化物生成量呈降低趋势,     

火电厂脱硝技术与应用以及脱硫脱硝一体化发展趋势

造成大气污染、酸雨的产生以及光化学烟雾的主要原因就是氮氧化物,而且在火电厂的燃煤过程中主要排放这些氮氧化物,所以当前我国火电厂在运行过程中首先要解决的一个重要问题就是对燃烧中的氮氧化物的排放量进行最大程度的降低。因此本文就是对火电厂脱硝技术与应用以及脱硫脱硝一体化的发展趋势进行了具体的研究。     

低氮氧化物燃烧系统在家用燃气热水器中的应用

国内家用燃气热水器行业中燃烧技术已日趋成熟,但在低氮氧化物燃烧领域的研究和开发工作开展的相对较少,技术水平相比国外同行业有着较大的差距。近年来,随着国内环境污染问题日益严峻,如何在现有技术基础上对燃烧技术进行提升和改进,开发出更加节能环保的产品已得非常紧迫。结合一款低氮氧化物燃烧系统的开发,对低氮氧化物燃烧技术进行了简单介绍,重点介绍了一种浓淡火焰型燃烧技术在低氮氧化物燃烧系统开发中的设计和应用情况。     

Fire smoke toxicity: The effect of nitrogen oxides

Measurements of the toxic potency of fire effluents are required for fire-safety engineering and fire-hazard assessments. Toxic potency values may be generated using chemical analysis data and/or by animal protocols. The current ISO methods of calculating toxic potency values from chemical analysis data assume that the nitrogen oxides present in inhaled fire effluents are nitrogen dioxide, a highly irritant acid gas. Observations from real scale fire tests and bench scale tests which simulate the different fire stages show that, in some situations and particularly in proximity of the fire, the nitrogen oxides will be predominately nitric oxide but this can gradually change to nitrogen dioxide as the effluent moves away from the fire. Nitric oxide has a very different toxic potency and effect when compared to nitrogen dioxide. This paper considers the formation of nitric oxide and nitrogen dioxide in fire effluents, their potential toxic effects and the consequential need to reconsider the methods of calculating toxic potency values.     

ANN-GA approach for predictive modelling and optimization of NOx emissions in a cement precalcining kiln

China’s cement production is increasing, but the sustainable development of the cement industry is hindered by pollutants, especially nitrogen oxide, with serious health impacts. This study reports the use of an artificial neural network and a genetic algorithm to control the operation parameters of a new dry-process cement kiln technology to predict and optimise the nitrogen oxide emissions. Comparing the predicted value and actual value, the error of the model is less than 2%. The GA is used to search the optimal operation parameters to achieve the lowest concentration of nitrogen oxide emission, which is 165.9 mg/m³ under optimal conditions. The results of sensitivity analysis show that the furnace temperature, raw material quantity and third air temperature have the greatest influence on the nitrogen oxide emission. This model prediction and optimisation can provide a reference for enterprises in controlling operation parameters to reduce nitrogen oxide emission.     

Nitrous oxide emissions from the oxidation tank of a pilot activated sludge plant

This study discusses the results of the continuous monitoring of nitrous oxide emissions from the oxidation tank of a pilot conventional wastewater treatment plant. Nitrous oxide emissions from biological processes for nitrogen removal in wastewater treatment plants have drawn great attention over the last years, due to the high greenhouse effect. However, even if several studies have been carried out to quantify nitrous oxide emission rates from different types of treatment, quite wide ranges have been reported. Only grab samples or continuous measurements over limited periods were considered in previous studies, which can account for the wide variability of the obtained results. Through continuous monitoring over several months, our work tries to fill this gap of knowledge and get a deeper insight into nitrous oxide daily and weekly emission dynamics. Moreover, the influence of some operating conditions (sludge age, dissolved oxygen concentration in the oxidation tank, nitrogen load) was studied to determine good practices for wastewater treatment plant operation aiming at the reduction of nitrous oxide emissions. The dissolved oxygen set-point is shown to play a major role in nitrous oxide emissions. Low sludge ages and high nitrogen loads are responsible for higher emissions as well. An interesting pattern has been observed, with quite negligible emissions during most of the day and a peak with a bell-like shape in the morning in the hours of maximum nitrogen load in the plant, correlated to the ammonia and nitrite peaks in the tank.     

低温下逆流充氧强化去除地表原水中的氨氮和锰

利用中试滤柱系统,在低温条件下采用滤柱底部逆流充氧措施强化铁锰复合氧化膜滤料去除地表原水中的氨氮和锰,考察了充氧强度、运行参数(氨氮、锰浓度和滤速)等因素的影响,并对充氧前后氧化膜的微观特征(形态、组成、晶体结构)进行了分析。结果表明,在水温为8℃的条件下,当进水氨氮和锰浓度分别为2.0、3.0 mg/L时,逆流充氧后,完全去除锰所需的滤层厚度由80cm减少至60 cm,出水氨氮浓度由0.7 mg/L降至0,且随着充氧强度的增加,去除效率逐渐升高;当充氧强度为0.6 mL/(cm²·min)、滤速为7.0 m/h时,对氨氮和锰的去除效果最佳。此外,微观表征分析结果表明,逆流充氧使滤料表面形态在水力作用下发生了改变,但并未改变铁锰复合氧化膜的成分和晶体结构。因此,逆流充氧可显著提高低温条件下铁锰复合氧化膜滤料对地表原水中氨氮和锰的去除效率。     

Penetration of nitrogen oxides and particles from outdoor into indoor air and removal of the pollutants through filtration of incoming air

We studied the effect of ventilation and air filtration systems on indoor air quality in a children's day-care center in Finland. Ambient air nitrogen oxides (NO, NO2) and particles (TSP, PM10) were simultaneously measured outdoors and indoors with automatic nitrogen oxide analyzers and dust monitoring. Without filtration nitrogen oxides and particulate matter generated by nearby motor traffic penetrated readily indoors. With chemical filtration 50-70% of nitrogen oxides could be removed. Mechanical ventilation and filtration also reduced indoor particle levels. During holidays and weekends when there was no opening of doors and windows and no particle-generating activity indoors, the indoor particle level was reduced to less than 10% of the outdoor level. At times when outdoor particle concentrations were high during weekdays, the indoor level was about 25% of the outdoor level. Thus, the possible adverse health effects of nitrogen oxides and particles indoors could be countered by efficient filtration. We also showed that inclusion of heat recovery equipment can make new ventilation installations economical.     

工业锅炉氮氧化物的形成及降低措施

着重讨论了燃料燃烧过程中氮氧化物的产生及其对环境的危害，从保持一定的高温环境、供应充足而适量的氧气等方面提出了应采取的有效措施，以降低氮氧化物的产生和排放，减少环境污染。     

氧化石墨烯复合膜在含油废水处理中的研究进展

氧化石墨烯（GO）膜在水处理方面有较好效果,但纯氧化石墨烯膜稳定性差,抗污性差,通量低,对于油水分离不能达到最优的分离效果。通过引入功能材料进行物理和化学方法改性后,氧化石墨烯修饰的复合膜和氧化石墨烯基复合膜,水通量、防污性能和油水分离效率得到有效提高。本文介绍了国内外具有代表性的氧化石墨烯复合膜在含油废水处理方面的研究,并简要探讨了复合膜去除含油废水的机理,此外对氧化石墨烯复合膜材料的发展前景进行总结和展望。     

NOx monitoring of a simultaneous nitrifying-denitrifying (SND) activated sludge plant at different oxidation reduction potentials

Simultaneous nitrification-denitrification (SND) allows biological nitrogen removal in a single reactor without separation of the two processes in time or space but requires adapted control strategies (anoxic/aerobic conditions). In this study, the formation of gaseous nitric oxide (NO(G)) and nitrogen dioxide (NO(2G)) was monitored for SND in relation to the oxidation-reduction potential (ORP) and nitrogen removal in a lab batch reactor and a pilot membrane bio-reactor (MBR). In addition hospital wastewater (COD/N(tot)>6:1) was treated on site for 1 year. The highest total nitrogen removal rates of max 90% were reached at 220-240mV ORP (given as E(h)) with corresponding maximal NO(G) emissions rates of 0.9microgg(-1)VSSh(-1). The maximal emission rates of NO(2G) (0.2microgg(-1)VSSh(-1)) were reached at the same ORP level and the NO(2G) emissions correlated to the nitrite accumulation in the activated sludge up to 5mgl(-1)NO(2L)-N. It was shown that this correlation was due to biological production and not due to pH-dependent chemical conversion. Therefore, NO(2G) can be used as additional control loop for ORP-controlled SND systems to avoid the inhibition of denitrification and high nitrite concentrations in the plant effluent.     

Genetic potential for N2O emissions from the sediment of a free water surface constructed wetland

Removal of nitrogen is a key aspect in the functioning of constructed wetlands. However, incomplete denitrification may result in the net emission of the greenhouse gas nitrous oxide (N₂O) resulting in an undesired effect of a system supposed to provide an ecosystem service. In this work we evaluated the genetic potential for N₂O emissions in relation to the presence or absence of Phragmites and Typha in a free water surface constructed wetland (FWS-CW), since vegetation, through the increase in organic matter due to litter degradation, may significantly affect the denitrification capacity in planted areas. Quantitative real-time PCR analyses of genes in the denitrification pathway indicating capacity to produce or reduce N₂O were conducted at periods of different water discharge. Genetic potential for N₂O emissions was estimated from the relative abundances of all denitrification genes and nitrous oxide reductase encoding genes (nosZ). nosZ abundance was invariably lower than the other denitrifying genes (down to 100 fold), and differences increased significantly during periods of high nitrate loads in the CW suggesting a higher genetic potential for N₂O emissions. This situation coincided with lower nitrogen removal efficiencies in the treatment cell. The presence and the type of vegetation, mainly due to changes in the sediment carbon and nitrogen content, correlated negatively to the ratio between nitrate and nitrite reducers and positively to the ratio between nitrite and nitrous oxide reducers. These results suggest that the potential for nitrous oxide emissions is higher in vegetated sediments.     

Modeling of the production of secondary gaseous products in confined atmospheres

Confined environments are indoor spaces in which the air is not renewed or very poorly renewed by fresh outdoor air (spacecraft, submarines, etc.). In these environments, indoor air quality (IAQ) is expected to be highly influenced by homogeneous and heterogeneous chemistry. This paper presents a representative example of the contribution of these two phenomena to the production of secondary gaseous pollutants indoors by analyzing the chemical degradation of isoprene. An indoor air quality model was developed in the Matlab environment to compute the concentrations of both organic and nonorganic gaseous species involved in this mechanism. Two kinds of initial conditions (concentrations of nitrogen oxides, ozone and isoprene) were considered for the simulations. The results show strong interactions between homogeneous and heterogeneous reactions. Especially, the integrated reaction rate (IRR) of the heterogeneous hydrolysis of nitrogen dioxide emerges very high. Demonstration of strong interactions between inorganic and organic chemistries is also made, the conversion between NO and NO₂ being of central importance in the degradation cycle of isoprene. The type and amount of secondary products obtained are assessed. The results emphasize the strong influence of ozone and nitric oxide concentration levels indoors.