氮氧化物(NO_x)产生机理及控制技术现状

随着我国工业化进程的高速发展,煤炭燃烧释放出来的氮氧化物也越来越多,而氮氧化物则是环境污染的主要空气污染物之一,氮氧化物(NOX)的排放问题正越来越受到人们的关注。文章阐述了氮氧化物(NOx)的产生机理及主要控制技术手段。     

我国氮氧化物治理技术的现状和研究进展

对中国的氮氧化物气体处理方法进行了综述。内容包括氮氧化物的生成和主要控制方法，中国氮氧化物废气的治理技术现状和氮氧化物处理技术的最新研究进展。     

国内火电厂氮氧化物排放现状及控制技术探讨

氮氧化物是＂十二五＂期间国家污染物总量控制对象之一。本文在概述国内火电厂氮氧化物排放现状及控制法规的基础上,详细论述了目前火电行业烟气中氮氧化物的主要控制技术及其应用现状、优缺点,并简要总结了我国火电行业氮氧化物控制存在的问题,最后对国内火电行业氮氧化物的污染控制提出了建议。     

氮氧化物治理现状及发展趋势

随着氮氧化物对环境及人类活动影响的日趋严重,如何减少氮氧化物废气的产生及排放量成为人们越来越关注的主要问题之一。本文综述了氮氧化物治理技术现状及应用前景,阐述了烟气脱硝技术的新进展,其中光催化氧化法和微生物法等经济、有效、无二次污染的新技术将成为未来研究氮氧化物治理的主要趋势。     

国内水泥行业氮氧化物治理及氨排放浅议

水泥制造过程中产生的氮氧化物对大气环境造成严重污染,目前主要的末端治理手段为SNCR脱硝技术。文中针对水泥窑SNCR脱硝技术应用作了简要分析,对氮氧化物排放和氨排放的相关性作了探讨,指出氮氧化物治理应在现有技术条件下,平衡氮氧化物排放和氨排放,并继续加大清洁生产技术和新型氮氧化物治理技术的研究。     

含NO_x尾气生物处理技术的研究进展

氮氧化物(NOx)是主要的大气污染物之一,其治理一直是大气污染控制的难题。生物法处理NOx是一种较新的氮氧化物废气污染控制技术。文章系统地介绍了生物法处理氮氧化物的基本原理,详细论述了当前国内外生物法处理NOx的研究和应用现状,分析讨论了生物法处理氮氧化物存在的问题和发展趋势。     

烟气脱硝技术研究进展与现状

随着氮氧化物对人类活动及环境影响的日趋严重,如何减少烟气中氮氧化物的产生及排放量成为人们越来越关注的主要问题之一。综述了氮氧化物治理的烟气脱硝技术,重点对主要的干法烟气脱硝技术和湿法烟气脱硝技术的研究进展和现状就行了阐述,对未来的研究方向和研究前景进行了展望。     

机动车尾气中氮氧化物的分析检测技术

机动车尾气当中的氮氧化物会对生态环境和人类带来影响,对其进行有效分析,可以确认有害气体的排出是否超标。基于此,本文主要介绍了几种常见的机动车尾气氮氧化物分析检测技术工作原理,并构建了一套机动车尾气氮氧化物评价体系,这几种方法均可以对机动车尾气氮氧化物浓度的变化情况进行及时反应,但各有优点,需要通过使用一些辅助设备才能更好地提升氮氧化物的分析效果。     

焦炉DN-SGT脱硝技术(源头控硝)

<正>氮氧化物是大气污染的主要成分之一,目前国内大部分焦化企业的氮氧化物排放量都在600~2000mg/m~3,特别是5.5米捣固型焦炉,氮氧化物排放量严重超标(≥1000mg/m~3)。目前控制焦炉烟气中氮氧化物排放的主要方法是进行烟气脱硝,但投入大,能耗高、二次污染严重、运行费用高。即便如此,国内目前还没有一家正式运行的脱硝装置。宁芳青教授领导的团队,另辟捷径,提出了一种全新的"DN-SGT脱硝技术"方法,即从源头上控制焦炉氮氧化物产生量。     

水泥工业的氮氧化物及其处理

近些年来在环境保护的压力下,水泥工业氮氧化物的减排也变得越来越重要。文章综述了水泥工业氮氧化物的来源和排放现状,介绍了目前氮氧化物的主要处理技术:低氮燃烧器、催化选择还原法、非催化选择还原法和还原气氛法,并分析了以上技术的优点和存在的问题。     

Emission of nitrous oxide from soils used for agriculture

Nitrous oxide is emitted into the atmosphere as a result of biomass burning, and biological processes in soils. Biomass burning is not only an instantaneous source of nitrous oxide, but it results in a longer term enhancement of the biogenic production of this gas. Measurements of nitrous oxide emissions from soils before and after a controlled burn showed that significantly more nitrous oxide was exhaled after the burn. The current belief is that 90% of the emissions come from soils. Nitrous oxide is formed in soils during the microbiological processes nitrification and denitrification. Because nitrous oxide is a gas it can escape from soil during these transformations. Nitrous oxide production is controlled by temperature, pH, water holding capacity of the soil, irrigation practices, fertilizer rate, tillage practice, soil type, oxygen concentration, availability of carbon, vegetation, land use practices and use of chemicals. Nitrous oxide emissions from agricultural soils are increased by the addition of fertilizer nitrogen and by the growth of legumes to fix atmospheric nitrogen. A recent analysis suggests that emissions of nitrous oxide from fertilized soils are not related to the type of fertilizer nitrogen applied and emissions can be calculated from the amount of nitrogen applied. Legumes also contribute to nitrous oxide emission in a number of ways, viz. atmospheric nitrogen fixed by legumes can be nitrified and denitrified in the same way as fertilizer nitrogen, thus providing a source of nitrous oxide, and symbiotically living Rhizobia in root nodules are able to denitrify and produce nitrous oxide. Conversion of tropical forests to crop production and pasture has a significant effect on the emission of nitrous oxide. Emissions of nitrous oxide increased by about a factor of two when a forest in central Brazil was clear cut, and pasture soils in the same area produced three times as much nitrous oxide as adjacent forest soils. Studies on temperate and tropical rice fields show that less than 0.1% of the applied nitrogen is emitted as nitrous oxide if the soils are flooded for a number of days before fertilizer application. However, if mineral nitrogen is present in the soil before flooding it will serve as a source of nitrous oxide during wetting and drying cycles before permanent flooding. Thus dry seeded rice can be a source of considerable nitrous oxide. There are also indirect contributions to nitrous oxide emission through volatilization of ammonia and emission of nitric oxides into the atmosphere, and their redistribution over the landscape through wet and dry deposition. In general nitrous oxide emissions can be decreased by management practices which optimize the crop's natural ability to compete with processes whereby plant available nitrogen is lost from the soil-plant system. If these options were implemented they would also result in increased productivity and reduced inputs. This revised version was published online in August 2006 with corrections to the Cover Date.     

An Engineering Approach for Estimating the Formation of Nitric Oxide from Fuel‐Nitrogen

Explicit approximate equations for estimating the conversion factor of fuel‐nitrogen into nitric oxide are presented. They depend on the fuel‐nitrogen mole fraction, the initial nitric oxide mole fraction, and the kinetics‐equilibrium mole fraction of nitric oxide. This last parameter expresses a limiting value of fuel‐nitrogen conversion; it includes the complex nitrogen chemistry and depends thus on combustion conditions. Experimental results demonstrate that the kinetics‐equilibrium mole fraction for fuel‐lean and high‐temperature conditions can be well estimated by the chemical‐equilibrium mole fraction, but for lower temperatures the kinetics‐equilibrium mole fraction has to be described by other correlations.     

The catalytic oxidation of ammonia: influence of water and sulfur on selectivity to nitrogen over promoted copper oxide/alumina catalysts

The CuO/Al₂O₃ system is active for ammonia oxidation to nitrogen and water. The principal by-products are nitrous oxide and nitric oxide. Nitrous oxide levels increase with the addition of various metal oxides to the basic copper oxide/alumina system. Addition of sulfur dioxide to the reaction stream sharply reduces the level of ammonia conversion, but has a beneficial effect on selectivity to nitrogen. Added water vapour has a lesser effect on activity but is equally beneficial in terms of selectivity to nitrogen. The CuO/Al₂O₃ is also active for the selective catalytic reduction of nitric oxide by ammonia, but this reaction is not effected by sulfur dioxide addition. A mechanism for ammonia oxidation to nitrogen is proposed wherein part of the ammonia fed to the catalyst is converted into nitric oxide. A pool of monoatomic surface nitrogen species of varying oxidation states is established. N₂ or N₂O are formed depending upon the average oxidation state of this pool. An abundance of labile lattice oxygen species on the catalyst surface leads to overoxidation and to N₂O formation. On the other hand, reduced lability of surface lattice oxygen species favours a lower average oxidation state for the monoatomic surface nitrogen pool and leads to N₂ formation.     

采用碱液回收外排尾气中的氧化氮生产硝酸钠的工艺研究

采用碱液(纯碱或烧碱)对水吸收后外排尾气中的氧化氮回收工艺进行了研究,大幅度降低了外排尾气中氧化氮的排放量,有效地控制了氧化氮对环境造成的影响,并得到产品硝酸钠,取得了良好的社会效益与经济效益.     

水泥窑协同处置高氮危废对氮氧化物排放的影响

结合窑系统运行情况,研究了水泥窑协同处置高氮固危废对氮氧化物排放的影响。结果表明：废有机溶剂(DMAC)为稳定高氮物料,单独入窑对NO_x排放和CO无明显影响;废有机溶剂(DMAC)与碱性铝灰以及酸性蒸馏残渣混合后,稳定有机氮被分解转化为不稳定氮化物,入窑后氮氧化物显著增加,最高达到197.2 mg/m³。铝灰因含丰富的氮化铝,入窑有利于氮氧化物排放,相较于未处置固危废期间最多降低了25.7 mg/m³。水泥窑氮氧化物含量的高低主要受入窑物料氮化物稳定性及其均化发酵程度的影响,为降低氮氧化物的波动,每坑浆渣调配完成后至少均化发酵1周再使用。     

Studies on Thermal Decomposition of Energetic Nitrourea Salts

Thermal decomposition of nitrourea salts (K, Na, Ag, Ba) was studied in hydrogen atmosphere, helium atmosphere and vacuum by gas chromatography and mass spectrometry. The evolution of dinitrogen oxide, water, hydrazine, nitrogen dioxide and the formation of cyanate salts during thermodecomposition of nitrourea salts in helium and hydrogen were confirmed. In vacuum the evolved gaseous products changed to dinitrogen oxide, water, nitrogen monoxide, nitrogen gas indicating that interreaction between evolved gaseous products occurred. The same solid products – cyanate salts – are formed showing vacuum having no effects upon the decomposition mechanism.     

Kinetics of the selective catalytic reduction of nitric oxide with ammonia on a platinum catalyst

The selective catalytic reduction of nitric oxide with ammonia on an alumina-supported platinum catalyst has been studied by the method of differential reactor analysis. In the temperature region of 400–600 K and concentrations of 0–1000 ppm of ammonia and nitric oxide and 0–1% oxygen three reactions are important: oxidation of ammonia by oxygen to nitrogen, reduction of nitric oxide by ammonia to nitrogen and reduction of nitric oxide by ammonia and oxygen to nitrous oxide. The differential reactor data were fitted to several Langmuir—Hinshelwood models using a non-linear least squares fitting computer program. The fitted models were tested by simulation of integral reactor data. The best fits were obtained from a dual site Langmuir—Hinshelwood model involving associative adsorption of ammonia and nitric oxide on the same sites and associative adsorption of oxygen on different sites.     

硝基氯苯装置氮氧化物废气的处理

介绍了硝基氯苯装置氮氧化物废气的危害、来源及治理现状,并介绍了循环吸收法处理氮氧化物尾气的工艺原理和流程.     

CO气相偶联制草酸二乙酯工艺流程模拟

采用流程模拟软件PRO/II,对一氧化碳与亚硝酸乙酯合成草酸二乙酯工艺过程进行模拟。建立了工业过程设计详细流程,提供了模拟使用的主要物性参数、动力学模型及流程数据及其来源。流程模拟计算结果与实际生产数据吻合证明了模拟的可靠性。模拟考察了一氧化氮再生反应设计转化率对主要过程参数,如循环比、放空气中一氧化氮含量及乙醇补充量的影响。结果表明提高再生过程一氧化氮设计转化率,可以降低循环比,提高偶联过程CO的转化率,但亚硝酸乙酯利用率下降,乙醇补充量需相应提高。再生反应器较为适宜设计条件为:一氧化氮再生转化率为(92±2)%,压力为101.3～150kPa及温度为(308±2)K。     

Reaction of nitric oxide and nitric oxide + carbon monoxide with amorphous Fe-Co-B alloy powders

The activity of amorphous Fe---Co---B alloy powder was investigated for the decomposition and the reduction of nitrogen monoxide. The transient response technique and a fixed bed reactor were applied to study the interactions of the Fe---Co---B alloy with two gas mixtures: NO + Ar at 353 and 573 K and NO + CO + Ar at 333–573 K. Moessbauer spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to study the state of the initial sample and the samples utilized in both gas mixtures. It is shown that the amorphous Fe---Co---B alloy powder has an activity for the direct decomposition of nitric oxide to nitrous oxide and nitrogen at a high gas space velocity (26 000 h⁻¹). Oxygen from the decomposed nitric oxide poisons the surface for the formation of nitrogen. In the presence of carbon monoxide (a NO + CO + Ar gas mixture) nitric oxide is reduced to nitrous oxide at 333–353 K and fully reduced to nitrogen at 373–573 K. The quantities of the carbon dioxide formed are not equal to the values expected from the stoichiometry of the NO + CO reaction. Probably, the interaction of carbon monoxide with the adsorbed oxygen (left on the surface by the decomposed nitric oxide) enhances the rate of nitric oxide decomposition to nitrous oxide and nitrogen. The rate limiting steps for both reactions of nitric oxide decomposition, as indicated by the transient response data, change with increasing temperature. The data from the Moessbauer spectroscopy and the X-ray photoelectron spectroscopy (XPS) studies have shown that the amorphous Fe---Co---B alloy powder undergoes phase changes under the conditions of both, the NO + Ar and the NO + CO + Ar gas mixtures. Boron migrates to the surface of globules and serves the accumulation of oxygen by the formation of B₂O₃ (or B(OH)₃).