燃烧过程颗粒物的形成及我国燃烧源分析

燃料燃烧会排放一次颗粒物和二次颗粒物,一次颗粒物中亚微米粒子主要是由于无机矿物质经蒸发-成核-凝结-凝并的途径形成的;超微米颗粒的产生不同于亚微米颗粒的形成,是由于破碎机理.二次颗粒物是由气态前驱体在大气中转化而成的.我国燃烧源主要是煤燃烧、燃油机动车和农村生活燃料等.深入认识颗粒物的形成及燃烧源的特征对有效控制颗粒物的排放是很有帮助的.     

民用散煤燃烧排放颗粒物微观特征

为深入了解民用散煤燃烧排放颗粒物对大气环境的影响,利用自行设计的采样装置采集民用散煤燃烧颗粒物并采用扫描电镜-能谱(SEM-EDX)分析颗粒物的形貌和元素组成。结果表明,民用散煤燃烧排放的颗粒物主要有焦油球,飞灰,片状或块状碳质颗粒,矿质颗粒,烟尘集合体,其他颗粒。从形貌上看,民用散煤燃烧排放颗粒物以球形和类球形颗粒为主,占颗粒总数的49.2%,烟尘集合体很少,占颗粒总数的3.6%。从元素组成来看,民用散煤燃烧排放颗粒物主要是炭质颗粒,占排放颗粒总数的77.2%,S元素在颗粒中较为常见,但大多数含量较低。从粒径分布来看,民用散煤燃烧排放颗粒物主要是微小颗粒物,绝大多数(81.0%)颗粒分布在1μm粒径范围内。民用散煤燃烧是大气污染物的重要来源之一,应制定相应的管控措施。     

柴油车尾气碳烟颗粒物催化燃烧催化剂的最新研究进展

柴油车尾气排放的碳烟颗粒已经引起了严重的环境污染问题,必须加以净化处理.柴油车碳烟颗粒的低温燃烧离不开高活性的催化剂.针对柴油车排放的碳烟颗粒物后处理方法中的催化氧化技术,总结了近年来几种主要类型的碳烟燃烧催化剂(贵金属催化剂、碱金属催化剂、单组分过渡金属氧化物催化剂、多组分混合氧化物催化剂和固定结构复合氧化物催化剂)的最新研究进展,并对该研究方向存在的主要问题和应用前景进行了探讨.     

柴油机排放颗粒物净化技术研究进展

柴油机被认为是城市大气微粒的主要污染源.柴油机颗粒物组成复杂并且颗粒粒径甚小,大都属于亚微米级粒子和纳米级粒子.因而柴油机颗粒物对人类健康和大气环境的影响受到世人的广泛关注.本文主要对柴油机排放颗粒物的生成机理、化学组成及危害、物理性质、检测方法和净化技术等方面进行综述与探讨.     

100 MW锅炉NaOH颗粒生成的数值模拟

煤粉燃烧过程中矿物质的气化、成核、凝结等过程是炉膛中亚微米颗粒形成的主要途径。本文运用CFD软件针对某100 MW锅炉内NaOH颗粒形成进行了数值研究,计算得到了炉内的温度分布、氧浓度分布和亚微米颗粒数量浓度和质量浓度分布。结果显示,亚微米颗粒的生成数量与温度具有强烈的相关性,温度较高的区域亚微米颗粒数量浓度较大,温度较低的区域则较小;而在炉膛的高温区内,NaOH颗粒的质量浓度并不是最高,而是最低,同时随着炉膛高度的增加,NaOH颗粒的质量浓度逐渐增加。计算结果为今后数值研究燃煤过程中亚微米颗粒的形成与演化奠定基础,为研究温度等燃烧条件对亚微米颗粒形成的影响、抑制其排放等方面提供了一种有效研究手段。     

大气超细颗粒物观测和扩散模拟研究进展

总结了近年来不同地区对不同环境下大气超细颗粒物的观测和扩散模拟研究进展。大量的观测研究结果表明,大气超细颗粒物的时空分布、组成特征、形成和成长的特性因观测地区的不同而存在很大差异,受气象因素和局部污染源的影响很大;其来源主要包括固定、移动燃烧源的直接排放和大气中颗粒成核现象,前一种来源一般是局部的,而后一种来源则是区域性的。目前,大多数关于大气超细颗粒物扩散的模拟研究都是针对其质量浓度的,对其数浓度扩散的模拟研究主要集中在小范围(机动车排放烟云的研究方面),在城市区域范围上的研究和应用还很少。最后,探讨和展望了大气超细颗粒物今后的主要研究方向和研究中面临的挑战。     

柴油机排放颗粒物净化技术研究进展

柴油机被认为是城市大气微粒的主要污染源。柴油机颗粒物组成复杂并且颗粒粒径甚小,大都属于亚微米级粒子和纳米级粒子。因而柴油机颗粒物对人类健康和大气环境的影响受到世人的广泛关注。本文主要对柴油机排放颗粒物的生成机理、化学组成及危害、物理性质、检测方法和净化技术等方面进行综述与探讨。     

大气雾霾污染的原因与防治对策分析

通过对雾霾污染的研究分析,指出雾霾污染的2个原因:一是由于污染物排放,使大气环境中细微颗粒物增多。目前城市大气环境中细微颗粒物主要来源于汽车尾气的排放,其次是工业燃煤的污染排放,也有区域之间细微颗粒物飘移的影响。二是气象条件,主要是水平方向静风伴随着垂直方向上出现逆温。在大气环境中细微颗粒物增多和静风逆温天气条件的共同作用下,形成雾霾污染。大力推广应用LNG汽车,使用清洁燃料,是改善城市区域环境空气质量的重要途径;城区内的电力、供热生产燃气化,也是改善环境空气质量的有效举措。治理雾霾污染不仅需要政府的努力,也需要全社会的共同参与,加强环境污染管理和监管执法是治理雾霾污染的重要保障。     

"二重源解析"技术及其系统实现

化学质量平衡是被广泛用于空气质量管理的受体模型之一.由于混合源(城市扬尘)和单一源因颗粒物源谱的严重共线性,采用美国环境保护署推荐使用的EPA-CMB8.2,无法定量解析出各排放源初始态和扬尘态颗粒物的贡献值和分担率.针对这一问题,完善和规范了"二重源解析"技术原理,开发了具有"二重源解析"功能的NKCMB3.0.对鞍山市样品污染物来源解析的试验结果表明,"二重源解析"技术在对混合源和单一源同时进行源解析时是有效的.     

蜂窝煤燃烧烟气中多环芳烃的定量研究及粒径分布特征

通过对蜂窝煤燃烧排放的烟气中多环芳烃的定量分析,研究了17种多环芳烃在烟气颗粒相和气相中的分配以及在不同粒径颗粒物上的分布特征。结果表明：在室温下燃煤排放的多环芳烃总量以在气相中存在为主,但总体毒性则主要存在于颗粒相中;多环芳烃主要分布在亚微米级颗粒上,分子量越大的多环芳烃越趋于富集在细颗粒上,因而对健康的危害就越大。     

Updating the conceptual model for fine particle mass emissions from combustion systems

Atmospheric transformations determine the contribution of emissions from combustion systems to fine particulate matter (PM) mass. For example, combustion systems emit vapors that condense onto existing particles or form new particles as the emissions are cooled and diluted. Upon entering the atmosphere, emissions are exposed to atmospheric oxidants and sunlight, which causes them to evolve chemically and physically, generating secondary PM. This review discusses these transformations, focusing on organic PM. Organic PM emissions are semi-volatile at atmospheric conditions and thus their partitioning varies continuously with changing temperature and concentration. Because organics contribute a large portion of the PM mass emitted by most combustion sources, these emissions cannot be represented using a traditional, static emission factor. Instead, knowledge of the volatility distribution of emissions is required to explicitly account for changes in gas-particle partitioning. This requires updating how PM emissions from combustion systems are measured and simulated from combustion systems. Secondary PM production often greatly exceeds the direct or primary PM emissions; therefore, secondary PM must be included in any assessment of the contribution of combustion systems to ambient PM concentrations. Low-volatility organic vapors emitted by combustion systems appear to be very important secondary PM precursors that are poorly accounted for in inventories and models. The review concludes by discussing the implications that the dynamic nature of these PM emissions have on source testing for emission inventory development and regulatory purposes. This discussion highlights important linkages between primary and secondary PM, which could lead to simplified certification test procedures while capturing the emission components that contribute most to atmospheric PM mass.     

杭州市空气颗粒物污染特征及变化规律研究

根据2006—2010年杭州市空气颗粒物的监测数据及2002、2006、2008年空气颗粒物来源解析结果,对杭州市空气颗粒物浓度、化学组分与污染来源等特征的变化规律进行分析,以期为空气颗粒物污染控制提供决策依据。结果表明,近年来杭州市PM10浓度有所下降,但一类功能区PM10仍超出《环境空气质量标准》(GB 3095—1996)的要求(≤0.04mg/m3),杭州市空气颗粒物污染以细颗粒物为主,空气颗粒物的二次转化、机动车尾气尘等产生的二次粒子污染相对严重;煤烟尘对杭州市PM10的贡献率下降明显,城市扬尘、二次粒子和机动车尾气尘对PM10的贡献率有所增加,是杭州市PM10的主要来源。     

Contribution of residential wood combustion to PM10 levels in Portugal

Wood is commonly used in residential combustion for heating purposes; however, it can be a major source of air pollutants, namely fine particles, volatile organic compounds and carbon monoxide. Since 2004, the PM10 daily limit value has been surpassed in Portugal, and the European Commission has stated that plans and programs must be designed in order to reduce these levels. In Portugal, 18% of PM10 emissions are due to residential wood combustion, which may deeply impact the PM10 levels in the atmosphere. The main aim of this study is to investigate the impact of residential wood combustion on the air quality in Portugal. The air quality modelling system MM5/CHIMERE was applied over Portugal for a winter month, for the following three scenarios: the reference scenario, considering the actual emissions of PM10; scenario 1, where residential wood combustion emissions are not considered; and scenario 2, which takes into account a complete conversion from traditional fireplaces to certified appliances (with a 90% reduction in PM emissions). The residential wood combustion contribution to PM10 air quality concentration values during January 2007 ranges from 0 to 14 μg m^?3, with a mean contribution of 10 μg m^?3 in the Lisboa area and 6 μg m^?3 in the Porto region. Concerning the legislated values, the area where the daily average limit value (50 μg m^?3) is exceeded decreases by 46% in the simulation when residential combustion is not considered. The modelling results for scenario 2 are not significantly different from those for scenario 1. In summary, the regulation of the residential wood combustion sector is as an effective way to reduce the PM10 levels in the atmosphere as regards air quality plans and programs.     

Directions for combustion engine aerosol measurement in the 21st century

The Coordinating Research Council convened two Real-Time PM Measurement Workshops in December 2008 and March 2009 to take an intensive look at the current status and future directions of combustion aerosol measurement. The purpose was to examine the implications of parallel rapid developments over the past decade in ambient aerosol science, engine aftertreatment technology, and aerosol measurement methodology, which provide benefits and challenges to the stakeholders in air quality management. The workshops were organized into sessions targeting key issues in ambient and source combustion particulate matter (PM). These include (1) metrics to characterize and quantify PM, (2) the need to reconcile ambient and source measurements, (3) the role of atmospheric transformations on modeling emissions and exposures, (4) the impact of sampling conditions on PM measurement, and (5) the potential benefits of novel PM instrumentation. This paper distills the material presented by subject experts and the insights derived from the in-depth discussions that formed the core of each session. The paper's objectives are to identify areas of consensus that allow wider practical application of the past decade's advances in combustion aerosol measurement to improve emissions and air quality modeling, develop emissions reduction strategies, and to recommend directions for progress on issues in which uncertainties remain.     

Analysis and discussion on formation and control of primary particulate matter generated from coal-fired power plants

Particulate matter (PM) has been becoming the principal urban pollutant in many major cities in China, and even all over the world. It is reported that the coal combustion process is one of the main sources of PM in the atmosphere. Therefore, an investigation of formation and emission of fine primary PM in coal combustion was conducted. First, the sources and classification of coal-fired primary PM were discussed; then their formation pathways during the coal combustion process were analyzed in detail. Accordingly, the emission control methods for fine particles generated from coal-fired power plants were put forward, and were classified as precombustion control, in-combustion control, and postcombustion control. Precombustion control refers to the processes for improving the coal quality before combustion, such as coal type selection and coal preparation. In-combustion control means to take measures for adjusting the combustion conditions and injection of additives during the combustion process to abate the formation of PM. Postcombustion control is the way that the fine PM are aggregated into larger ones by some agglomeration approaches and subsequently are removed by dust removal devices, or some high-performance modifications of conventional particle emission control devices (PECDs) can be taken for capturing fine particles. Finally, some general management suggestions are given for reducing fine PM emission in coal-fired power plants.

ImplicationsThe analysis and discussions of coal properties and its combustion process are critical to recognizing the formation and emission of the fine primary PM in combustion. The measures of precombustion, in-combustion, and postcombustion control based on the analysis and discussions are favorable for abating the PM emission. Practically, some measures of implementation do need the support of national policies, even needing to sacrifice economy to gain environmental profit, but this is the very time to execute these, and high-performance PECDs, especially novel devices, should be used for removing fine PM in flue gas.     

Apportionment of ambient primary and secondary fine particulate matter at the Pittsburgh National Energy Laboratory particulate matter characterization site using positive matrix factorization and a potential source contributions function analysis

Fine particulate matter (PM2.5) concentrations associated with 202 24-hr samples collected at the National Energy Technology Laboratory (NETL) particulate matter (PM) characterization site in south Pittsburgh from October 1999 through September 2001 were used to apportion PM2.5 into primary and secondary contributions using Positive Matrix Factorization (PMF2). Input included the concentrations of PM2.5 mass determined with a Federal Reference Method (FRM) sampler, semi-volatile PM2.5 organic material, elemental carbon (EC), and trace element components of PM2.5. A total of 11 factors were identified. The results of potential source contributions function (PSCF) analysis using PMF2 factors and HYSPLIT-calculated back-trajectories were used to identify those factors associated with specific meteorological transport conditions. The 11 factors were identified as being associated with emissions from various specific regions and facilities including crustal material, gasoline combustion, diesel combustion, and three nearby sources high in trace metals. Three sources associated with transport from coal-fired power plants to the southeast, a combination of point sources to the northwest, and a steel mill and associated sources to the west were identified. In addition, two secondary-material-dominated sources were identified, one was associated with secondary products of local emissions and one was dominated by secondary ammonium sulfate transported to the NETL site from the west and southwest. Of these 11 factors, the four largest contributors to PM2.5 were the secondary transported material (dominated by ammonium sulfate) (47%), local secondary material (19%), diesel combustion emissions (10%), and gasoline combustion emissions (8%). The other seven factors accounted for the remaining 16% of the PM2.5 mass. The findings are consistent with the major source of PM2.5 in the Pittsburgh area being dominated by ammonium sulfate from distant transport and so decoupled from local activity emitting organic pollutants in the metropolitan area. In contrast, the major local secondary sources are dominated by organic material.     

Impact of the composition of combustion generated fine particles on epithelial cell toxicity: influences of metals on metabolism

Inhaled airborne particulate matter (PM) represents a potentially significant health hazard to humans. Exposure to PM strongly correlates with pulmonary inflammation and incidences of severe respiratory distress, including increased hospital admissions for breathing disorders, asthma, emphysema, and chronic bronchitis. PM generated from the combustion of fuel oils and coals contain a number of water-soluble transition metals including Fe, V, and Zn.

We have evaluated the impact of PM types with varying composition collected from the combustion of oils and coals on the health and metabolism of lung cell cultures. Three colorimetric assays (sulforhodamine B (SRB), Janus green, and MTT) have been adapted to quantify the impact of PM on rat lung alveolar type II epithelial cells (RLE-6TN cells). The PM toxicity metrics evaluated were inhibition of cell proliferation (SRB and Janus green) and inhibition of cellular metabolism (MTT). Cell proliferation is inhibited in a consistent dose-dependent manner by PM concentrations from 25 to 250 μg/ml. At a level of 100 μg/ml, oil-derived PM diminishes cell metabolism by as much as 40% relative to controls; the degree of inhibition is strongly dependent on PM particle size and metal content. Conversely, coal-derived PM at the same dosage diminishes cell metabolism by no more than 20% relative to controls. All three assays provide highly repeatable results and consistent toxicity rankings of the PMs evaluated. Overall, metabolic inhibition as measured by the MTT assay was deemed the most appropriate metric for PM toxicity, primarily due to its applicability with in vivo-like confluent cell monolayers.     

柴油车排气后处理装置PDPF的试验研究

介绍了一种用于柴油车排气后处理的PDPF的结构和工作原理。通过对比试验考察了PDPF的性能,包括ETC试验、全负荷烟度试验、自由加速烟度试验以及总功率检测。带PDPF与不带PDPF相比,PDPF对ETC排气中PM的降低效率达57.5%;对全负荷的滤纸式烟度和不透光烟度影响不大;使自由加速烟度有所下降;对发动机的动力性和经济性几乎没有影响。可靠性试验研究显示出PDPF的良好应用前景。