Study of particulate matter removal mechanism by using non-thermal plasma technology

Numbers of diesel engines in both stationary and mobile applications are increasing nowadays. Diesel engines emit lower Hydrocarbon (HC) and Carbon monoxide (CO) than gasoline engines. However, they can produce more nitrogen oxides (NOx) and have higher particulate matter (PM). On the other hand, emissions standards are getting stringent day by day due to considerable concerns about unregulated pollutants and particularly ultrafine particles deleterious effect on human health. Non-thermal plasma (NTP) treatment of exhaust gas is known as a promising technology for both NOx and PM reduction by introducing plasma inside the exhaust gas. Vehicle exhaust gases undergo chemical changes when exposed to plasma. In this study, the PM removal mechanism using NTP by applying high voltage pulses of up to 20 kVpp with a repetition rate of 10 kHz are investigated. It is found that, voltage increase not necessarily has a positive effect on PM removal in diesel engine emissions.

Modelagem e simulação da formação de hidrocarbonetos na combustão do gás natural

A exaustão de um veículo de motor a diesel é uma importante fonte de poluentes atmosféricos, pois forma uma matriz complexa composta de poluentes regulados e não regulados pelos órgãos governamentais. Dentre os poluentes regulados podemos citar óxidos de nitrogênio (NOx) e material particulado. Os poluentes não regulados são pouco estudados até hoje e dentre estes encontra-se a classe dos hidrocarbonetos policíclicos aromáticos e seus derivados nitrados (nitro-HPA). Estes são encontrados na exaustão do diesel na forma gasosa ou agregados ao material particulado. Hoje, o interesse em estudos destes compostos vem aumentando, devido às suas atividades carcinogênicas e mutagênicas às quais estão sujeitas as populações dos centros urbanos. O impacto causado pelos nitro-HPA emitidos por motores a ciclo diesel ao ambiente não está ainda completamente estabelecido. Este estudo consiste na modelagem e simulação do processo de combustão de hidrocarbonetos na faixa de C1 a C4 com o objetivo de descrever a formação de compostos aromáticos, principalmente HPA, e óxidos de nitrogênio a partir de modelos cinéticos de combustão propostos na literatura como referência e fazendo uso do software de simulação Kintecus. Este projeto tem como objetivo em longo prazo propor um modelo cinético para combustão do óleo Diesel. Foi iniciada a construção de um modelo cinético de combustão a partir de modelos de hidrocarbonetos simples de C1 a C4, com formação de aromáticos, HPA e óxidos de nitrogênio. Os modelos originais foram avaliados e modificados a fim de estudar como parâmetros do modelo afetam a concentração das espécies de interesse. Foi observado a tendência de formação de benzeno e fulveno em baixas temperaturas e a tendência de formação de antraceno, pireno, fenantreno a temperaturas mais altas. Foi avaliado que a conversão NO-NO2 ocorre em maiores proporções em reações iniciadas a baixas temperaturas, 600 K. Os resultados indicam que propano é o maior responsável por esta conversão. O modelo final obtido resultou da união dos modelos de combustão Hori e Marinov mais inclusão do GRI-Mech 3.0 e reações adicionais de NOx retiradas da base de dados NIST

替代燃料二甲醚的燃烧特性及其污染物甲醛的生成消耗机理研究

化石燃料的不可再生性决定了其不能长久为全球经济和科技的发展提供能源动力，从可持续发展和能源战略的角度考虑，能够替代石油及其衍生品的清洁替代燃料研究已经成为提高能源供应安全、改善环境污染问题、应对气候变化的重要措施，对替代燃料的研究和应用已经成为各方关注和开发的热点。 二甲醚(DME、CH3OCH3)是一种最简单的醚类，它不含C-C健，可以由天然气、煤、生物质燃料等大量制备，而且具有较高的辛烷值(55-60)，较低的碳氢化合物、CO排放，没有PM排放，因而被认为是一种非常有发展前景的发动机替代燃料，已经受到了广泛的关注。但是，在发动机燃用DME的实验研究表明，在其排气中有非常规污染物甲醛(HCHO)、乙醛(CH3CHO)，甲酸甲酯(HCOOCH3)等排放，这些有机污染物会对环境和人类健康产生严重的危害，在环保要求日益严格的趋势下，这就制约了二甲醚的规模化应用。因此，对二甲醚燃烧性能、氧化中间产物甲醛等的产生和排放机理、相关污染物抑制技术需要进行着重研究，这对二甲醚燃料规模化应用、相关二甲醚燃烧器设计、燃烧性能的优化以及污染物控制技术的研究等都有着重要的理论指导意义和参考价值。 为了充分理解二甲醚燃料的燃烧特性、非常规污染物甲醛的产生和消耗机理，本文以实验和二甲醚化学反应动力学机理为指导，对二甲醚预混燃烧的燃烧特性、相关污染物和甲醛产生和消耗的机理做了详细的研究；并针对二甲醚燃料的不同应用背景，对二甲醚燃料低温下的氧化和甲醛生成特性、DME与LPG掺混燃烧特性和甲醛生成消耗机理进行了深入的研究，具体工作有： 研究了二甲醚预混燃烧特性、火焰中甲醛等污染物的产生特性，建立了火焰中甲醛取样、测量的方法和实验平台。并对当量比和燃料流量对二甲醚预混燃烧的燃烧特性、甲醛生成特性影响进行了考察，实验结果表明二甲醚是一种优良的替代燃料，在二甲醚火焰中甲醛是其重要的中间产物，甲醛浓度分布与当量比和预混气流速密切相关。当量比一定时，随着预混气流速的增加，火焰中甲醛产生的范围变窄，且甲醛浓度峰值逐渐移向燃烧器出口，而甲醛产生的浓度峰值数值上相差不大，甲醛在形成峰值后被快速消耗，其浓度在0.1mm内下降到几乎为零；在二甲醚流量一定时，随着当量比的增加，火焰中产生了更多的甲醛，火焰中甲醛分布的范围也变宽，而且当量比越大，甲醛的消耗也变缓，在当量比为0.8时，甲醛浓度从峰值到被消耗距离变为2mm，远大于当量比0.6和0.7下0.1mm的消耗距离。 对二甲醚预混燃烧进行数值研究和化学动力反应机理分析后发现，在二甲醚燃烧中，二甲醚的氧化反应途径主要是通过脱氢生成CH3OCH2和在高温下的直接裂解反应而进行，其中脱氢反应是低温下二甲醚消耗的主要途径，而在高温反应阶段(T>1000K)，DME的直接裂解和燃料的脱氢反应共同起主导作用；非常规污染物甲醛通过DME脱氢产物CH3OCH2的裂解和外部氧化而生成，在高温时通过DME直接裂解后被氧化产生；甲醛的消耗反应则是通过与H、O、OH和CH3基的氧化反应而完成，其中与O、OH基的反应在燃烧中起主要作用。因此二甲醚燃烧中甲醛的抑制关键在燃烧中甲醛的消耗阶段，采取有效的技术措施，如优化燃烧器结构提高二甲醚燃烧室内的温度、在燃烧区保证充足的氧气供应等措施，加快甲醛的消耗速度以促进其被完全氧化，可以实现二甲醚燃烧中甲醛的零排放。 针对柴油发动机燃用DME燃料时，燃料在燃烧室停留时间过短，造成部分未燃二甲醚随尾气排放，对DME在低温下(<800K)的氧化特性和甲醛生成特性进行了实验研究。结果表明，二甲醚在200℃左右就开始发生氧化反应，在200~400℃温度范围内被氧化而生成大量中间产物甲醛，且在此温度范围内甲醛不易被氧化分解，而发动机尾气温度（一般在200~600℃之间）处于甲醛最易生成的范围，因此未燃二甲醚在尾气中发生低温氧化反应生成的甲醛，是发动机燃用DME而排放高浓度甲醛的重要来源。研究结论为柴油发动机燃用DME抑制非常规污染物甲醛的排放提供了新的参考。 DME作为替代燃料，部分替代及与其他石化系燃料掺混燃烧是目前的重要应用方向，对DME与LPG掺混燃烧特性和甲醛生成特性进行了实验研究，结果表明，在DME与LPG掺混燃烧中，固定当量比和燃料质量流量的条件下，两种燃料存在一个最佳掺混比，在此掺混比例下，混合燃料着火提前，燃料燃烧性能最佳；DME与LPG混合燃料中，二甲醚是燃烧中甲醛产生的主要来源，控制DME的完全氧化和燃烧是抑制DME与LPG掺混燃烧排放甲醛的主要途径，这为更好地应用DME与LPG混合燃料提供了参考。 能否清洁高效燃烧是决定替代燃料DME应用规模和途径中的关键任务，本文对DME燃烧特性、非常规污染物甲醛的生成排放特性、低温下DME的氧化特性、DME与LPG掺混燃烧特性的研究，从不用的应用方向和领域对DME清洁高效燃烧进行了探讨和研究，研究成果可以为清洁高效利用二甲醚、抑制甲醛排放，以及开发相关燃烧技术、燃烧器提供实验依据和理论指导。本文在DME燃烧特性和非常规污染物甲醛的产生与排放方面取得了具有创新性的研究结果。

An initial assessment of the literature on the measurement, control, transport, transformation and health effects of unregulated diesel engine emissions. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Characterisation of indoor air organic pollutants in Brisbane

The occurrence and levels of airborne polycyclic aromatic hydrocarbons and volatile organic compounds in selected non-industrial environments in Brisbane have been investigated as part of an integrated indoor air quality assessment program. The most abundant and most frequently encountered compounds include, nonanal, decanal, texanol, phenol, 2-ethyl-1-hexanol, ethanal, naphthalene, 2,6-tert-butyl-4-methyl-phenol (BHT), salicylaldehyde, toluene, hexanal, benzaldehyde, styrene, ethyl benzene, o-, m- and pxylenes, benzene, n-butanol, 1,2-propandiol, and n-butylacetate. Many of the 64 compounds usually included in the European Collaborative Action method of TVOC analysis were below detection limits in the samples analysed. In order to extract maximum amount of information from the data collected, multivariate data projection methods have been employed. The implications of the information extracted on source identification and exposure control are discussed.

Long-term exposure to gaseous air pollutants and cardio-respiratory mortality in Brisbane, Australia

Air pollution is ranked by the World Health Organisation as one of the top ten contributors to the global burden of disease and injury. Exposure to gaseous air pollutants, even at a low level, has been associated with cardiorespiratory diseases (Vedal, Brauer et al. 2003). Most recent epidemiological studies of air pollution have used time-series analyses to explore the relationship between daily mortality or morbidity and daily ambient air pollution concentrations based on the same day or previous days (Hajat, Armstrong et al. 2007). However, most of the previous studies have examined the association between air pollution and health outcomes using air pollution data from a single monitoring site or average values from a few monitoring sites to represent the whole population of the study area. In fact, for a metropolitan city, ambient air pollution levels may differ significantly among the different areas. There is increasing concern that the relationships between air pollution and mortality may vary with geographical area (Chen, Mengersen et al. 2007). Additionally, some studies have indicated that socio-economic status can act as a confounder when investigating the relation between geographical location and health (Scoggins, Kjellstrom et al. 2004). This study examined the spatial variation in the relationship between long-term exposure to gaseous air pollutants (including nitrogen dioxide (NO2), ozone (O3) and sulphur dioxide (SO2)), and cardiorespiratory mortality in Brisbane, Australia, during the period 1996 - 2004.

Application of chemometrics to analysis of soil pollutants

This overview focuses on the application of chemometrics techniques for the investigation of soils contaminated by polycyclic aromatic hydrocarbons (PAHs) and metals because these two important and very diverse groups of pollutants are ubiquitous in soils. The salient features of various studies carried out in the micro- and recreational environments of humans, are highlighted in the context of the various multivariate statistical techniques available across discipline boundaries that have been effectively used in soil studies. Particular attention is paid to techniques employed in the geosciences that may be effectively utilized for environmental soil studies; classical multivariate approaches that may be used in isolation or as complementary methods to these are also discussed. Chemometrics techniques widely applied in atmospheric studies for identifying sources of pollutants or for determining the importance of contaminant source contributions to a particular site, have seen little use in soil studies, but may be effectively employed in such investigations. Suitable programs are also available for suggesting mitigating measures in cases of soil contamination, and these are also considered. Specific techniques reviewed include pattern recognition techniques such as Principal Components Analysis (PCA), Fuzzy Clustering (FC) and Cluster Analysis (CA); geostatistical tools include variograms, Geographical Information Systems (GIS), contour mapping and kriging; source identification and contribution estimation methods reviewed include Positive Matrix Factorisation (PMF), and Principal Component Analysis on Absolute Principal Component Scores (PCA/APCS). Mitigating measures to limit or eliminate pollutant sources may be suggested through the use of ranking analysis and multi criteria decision making methods (MCDM). These methods are mainly represented in this review by studies employing the Preference Ranking Organisation Method for Enrichment Evaluation (PROMETHEE) and its associated graphic output, Geometrical Analysis for Interactive Aid (GAIA).

Variability of input parameters related to pollutants build-up in stormwater quality modelling

The variability of input parameters is the most important source of overall model uncertainty. Therefore, an in-depth understanding of the variability is essential for uncertainty analysis of stormwater quality model outputs. This paper presents the outcomes of a research study which investigated the variability of pollutants build-up characteristics on road surfaces in residential, commercial and industrial land uses. It was found that build-up characteristics vary highly even within the same land use. Additionally, industrial land use showed relatively higher variability of maximum build-up, build-up rate and particle size distribution, whilst the commercial land use displayed a relatively higher variability of pollutant-solid ratio. Among the various build-up parameters analysed, D50 (volume-median-diameter) displayed the relatively highest variability for all three land uses.

Composition and source identification of road deposited pollutants

Road deposited solids are a mix of pollutants originating from a range of anthropogenic sources common to urban land uses and soil inputs from surrounding areas. These particles accumulate potentially toxic pollutants thereby posing a threat to receiving waters. Reliable estimation of sources of particulate pollutants in build-up and quantification of particle composition is important for the development of best management practices for stormwater quality mitigation. The research study analysed build-up pollutants from sixteen different urban road surfaces and soil from four background locations. The road surfaces were selected from residential, industrial and commercial land uses from four suburbs in Gold Coast, Australia. Collected build-up samples were analysed for solids load, organic matter and mineralogy. The soil samples were analysed for mineralogy. Quantitative and qualitative analysis of mineralogical data, along with multivariate data analysis were employed to identify the relative source contributions to road deposited solids. The build-up load on road surfaces in different suburbs showed significant differences due to the nature of anthropogenic activities, road texture depth and antecedent dry period. Analysis revealed that build-up pollutants consists primarily of soil derived minerals (60%) and the remainder is composed of traffic generated pollutants and organic matter. Major mineral components detected were quartz and potential clay forming minerals such as albite, microline, chlorite and muscovite. An average of 40-50% of build-up pollutants by weight was made up of quartz. Comparison of the mineral component of build-up pollutants with background soil samples indicated that the minerals primarily originate from surrounding soils. About 2.2% of build-up pollutants were organic matter which originates largely from plant matter. Traffic related pollutants which are potentially toxic to the receiving water environment represented about 30% of the build-up pollutants at the study sites.

Photocatalytic disinfection of bacterial pollutants using suspended and immobilized TiO(2) powders

The photocatalytic disinfection of Enterobacter cloacae and Enterobacter coli using microwave (MW), convection hydrothermal (HT) and Degussa P25 titania was investigated in suspension and immobilized reactors. In suspension reactors, MW-treated TiO(2) was the most efficient catalyst (per unit weight of catalyst) for the disinfection of E. cloacae. However, HT-treated TiO(2) was approximately 10 times more efficient than MW or P25 titania for the disinfection of E. coli suspensions in surface water using the immobilized reactor. In immobilized experiments, using surface water a significant amount of photolysis was observed using the MW- and HT-treated films; however, disinfection on P25 films was primarily attributed to photocatalysis. Competitive action of inorganic ions and humic substances for hydroxyl radicals during photocatalytic experiments, as well as humic substances physically screening the cells from UV and hydroxyl radical attack resulted in low rates of disinfection. A decrease in colony size (from 1.5 to 0.3 mm) was noted during photocatalytic experiments. The smaller than average colonies were thought to occur during sublethal (•) OH and O(2) (•-) attack. Catalyst fouling was observed following experiments in surface water and the ability to regenerate the surface was demonstrated using photocatalytic degradation of oxalic acid as a model test system

Characterisation and source identification of selected pollutants in house dust

House dust is a heterogeneous matrix, which contains a number of biological materials and particulate matter gathered from several sources. It is the accumulation of a number of semi-volatile and non-volatile contaminants. The contaminants are trapped and preserved. Therefore, house dust can be viewed as an archive of both the indoor and outdoor air pollution. There is evidence to show that on average, people tend to stay indoors most of the time and this increases exposure to house dust. The aims of this investigation were to: " assess the levels of Polycyclic Aromatic Hydrocarbons (PAHs), elements and pesticides in the indoor environment of the Brisbane area; " identify and characterise the possible sources of elemental constituents (inorganic elements), PAHs and pesticides by means of Positive Matrix Factorisation (PMF); and " establish the correlations between the levels of indoor air pollutants (PAHs, elements and pesticides) with the external and internal characteristics or attributes of the buildings and indoor activities by means of multivariate data analysis techniques. The dust samples were collected during the period of 2005-2007 from homes located in different suburbs of Brisbane, Ipswich and Toowoomba, in South East Queensland, Australia. A vacuum cleaner fitted with a paper bag was used as a sampler for collecting the house dust. A survey questionnaire was filled by the house residents which contained information about the indoor and outdoor characteristics of their residences. House dust samples were analysed for three different pollutants: Pesticides, Elements and PAHs. The analyses were carried-out for samples of particle size less than 250 µm. The chemical analyses for both pesticides and PAHs were performed using a Gas Chromatography Mass Spectrometry (GC-MS), while elemental analysis was carried-out by using Inductively-Coupled Plasma-Mass Spectroscopy (ICP-MS). The data was subjected to multivariate data analysis techniques such as multi-criteria decision-making procedures, Preference Ranking Organisation Method for Enrichment Evaluations (PROMETHEE), coupled with Geometrical Analysis for Interactive Aid (GAIA) in order to rank the samples and to examine data display. This study showed that compared to the results from previous works, which were carried-out in Australia and overseas, the concentrations of pollutants in house dusts in Brisbane and the surrounding areas were relatively very high. The results of this work also showed significant correlations between some of the physical parameters (types of building material, floor level, distance from industrial areas and major road, and smoking) and the concentrations of pollutants. Types of building materials and the age of houses were found to be two of the primary factors that affect the concentrations of pesticides and elements in house dust. The concentrations of these two types of pollutant appear to be higher in old houses (timber houses) than in the brick ones. In contrast, the concentrations of PAHs were noticed to be higher in brick houses than in the timber ones. Other factors such as floor level, and distance from the main street and industrial area, also affected the concentrations of pollutants in the house dust samples. To apportion the sources and to understand mechanisms of pollutants, Positive Matrix Factorisation (PMF) receptor model was applied. The results showed that there were significant correlations between the degree of concentration of contaminants in house dust and the physical characteristics of houses, such as the age and the type of the house, the distance from the main road and industrial areas, and smoking. Sources of pollutants were identified. For PAHs, the sources were cooking activities, vehicle emissions, smoking, oil fumes, natural gas combustion and traces of diesel exhaust emissions; for pesticides the sources were application of pesticides for controlling termites in buildings and fences, treating indoor furniture and in gardens for controlling pests attacking horticultural and ornamental plants; for elements the sources were soil, cooking, smoking, paints, pesticides, combustion of motor fuels, residual fuel oil, motor vehicle emissions, wearing down of brake linings and industrial activities.