Orientador: Clóvis Augusto Ribeiro / Coorientador: Mary Rosa Rodrigues de Marchi / Banca: Carolina Lourencetti / Banca: Eny Maria Vieira / Resumo: A fuligem proveniente das queimadas de cana-de-açúcar exerce um importante papel na translocação dos HPAs, gerados em processos de combustão incompleta, através dos diversos compartimentos ambientais. Quando trazido até áreas urbanas, o material particulado fino gerado na queima pode provocar problemas respiratórios e carregar consigo os HPAs, dentre os quais há alguns com alto potencial carcinogênico. Tendo em vista o pequeno número de estudos relacionados a HPAs na matriz de fuligem de cana e a utilização de extrações com solventes em praticamente todos esses, o objetivo deste trabalho foi a verificação do comportamento térmico dos HPAs prioritários da US-EPA, adsorvidos em fuligem de cana, frente a um programa de aquecimento controlado, no intuito de obter informações para a implementação e otimização de um sistema de dessorção térmica para extração dessas substâncias. Foram aplicadas as técnicas de termogravimetria (TG), análise térmica diferencial (DTA) e calorímetria exploratória diferencial (DSC) a amostras de: padrões de 16 HPAs isolados; fuligem de cana fortificada com cada um destes padrões; fuligem fortificada com todos os 16 padrões simultaneamente (amostra composta); material de referência certificado SRM 1649a da NIST e finalmente, uma amostra de material particulado atmosférico obtida na cidade de Araraquara, São Paulo. Foram obtidas as temperaturas de fusão e sublimação dos padrões isolados, além das faixas de temperatura que acompanham suas perdas de massa, que variaram de 70 a 380 ºC. No estudo da adsorção na matriz, foi observado que esta contribui para um padrão de perda de massa mais homogêneo e difuso, sugerindo uma possível interação, entretanto sem modificar o intervalo de vaporização/sublimação dos HPAs... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The soot originated from the sugar cane burning plays an important role in the translocation of PAHs, generated in incomplete combustion processes, through multiple environmental compartments. When brought to urban areas, fine particulate matter generated in the burning can cause respiratory problems and carry PAHs, among which are some with high carcinogenic potential. Given the small number of studies related to PAHs in the sugar cane soot matrix and the use of solvent extraction in almost all of these, the aim of this paper was to check the thermal behavior of de US-EPA priority PAHs, adsorbed on sugar cane soot and subjected to a controlled heating program, in order to get information for the implementation and optimization of a thermal desorption system for the extraction of these substances. Thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) techniques were applied to samples of: 16 US-EPA PAH standards, individually; sugar cane soot fortified with each of these standards; soot spiked with all 16 standards simultaneously (composite sample); NIST Standard Reference Material 1649a (urban dust); and finally, an airborne particulate matter sample, obtained in the city of Araraquara, Sao Paulo, Brazil. Melting and vaporization/sublimation temperatures of the isolated standards were obtained, together with the temperature ranges that accompany their mass loss, which varied from 70 to 380 ºC. In the study of matrix adsorption, it was observed that it contributes to a more homogeneous and diffuse mass loss, suggesting a possible interaction with the PAHs, however without modifying the range of vaporization/sublimation of adsorbed PAHs. The comparison of the composite sample with SRM 1649a and airborne particulate matter brought certain... (Complete abstract click electronic access below) / Mestre

A emissão de poluentes em megacidades e áreas industriais pode ter fortes impactos no clima e na saúde. Nos últimos anos tem sido crescente a preocupação com emissões atmosféricas contendo partículas nanométricas, cuja presença, juntamente com compostos orgânicos voláteis, óxidos de nitrogênio e outros, pode resultar na formação de uma série de substâncias gasosas poluentes e na formação de aerossóis. Medições mais precisas da concentração e distribuição de tamanho de fuligem são importantes, não só do ponto de vista ambiental, mas também para a saúde humana. O objetivo deste trabalho foi determinar a distribuição de tamanho de partículas na chaminé de uma refinaria em Cubatão. Para isso foi utilizada uma abordagem baseada nos métodos de inversão, tradicionalmente usados para calcular parâmetros de aerossóis atmosféricos, ao contexto dos aerossóis de tochas industriais. Os resultados se mostraram consistentes com a literatura científica, sendo possível determinar alguns parâmetros da distribuição do tamanho de partículas provenientes da chama de uma tocha industrial utilizando um sistema lidar de três comprimentos de onda com um nível de discrepância aceitável. Um estudo do expoente de Angström foi realizado com o objetivo de validar o algoritmo de inversão desenvolvido neste trabalho. Os resultados deste estudo mostraram que os dados experimentais corroboram com as curvas teóricas e, portanto, o algoritmo pode ser utilizado como ferramenta para a medição de emissões atmosféricas provenientes de tochas industriais. O desenvolvimento deste projeto representará um passo importante, não somente do ponto de vista tecnológico, mas principalmente como recurso para tratar de problemas de emissões que futuramente poderão surgir, dentre as medidas voltadas ao controle de mudanças climáticas. / The emission of pollutants in megacities and industrial areas can have strong impacts on climate and health. In recent years there has been a growing concern about air emissions containing nanometric particles whose presence, together with volatile organic compounds, nitrogen oxides, and others, can result in the formation of a series of gaseous pollutants and aerosol. More accurate measurements of the concentration and size distribution of soot are important not only from an environmental point of view, but also to human health. The objective of this study was to determine the particle size distribution in the chimney of a refinery in Cubatao. For this it used an approach based on inversion methods traditionally used to calculate parameters of atmospheric aerosols, the context of aerosols of industrial torches. The results were consistent with the scientific literature, it is possible to determine some parameters of size distribution of particles from an industrial torch flame using a system handling three wavelengths with an acceptable level of mismatch. A study by the Angstrom exponent was carried out in order to validate the inversion algorithm developed in this work. The results of this study showed that corroborate experimental data with the theoretical curves and thus the algorithm can be used as a tool for measuring atmospheric emissions from industrial torches. The development of this project will be an important step, not only from a technological point of view, but rather as a resource to address emission problems that may arise in the future, among the measures aimed at controlling climate change.

The size of a soot particle has an effect on smoke detector alarm activation. It is the purpose of this paper to identify changes to soot particle size and examine if those size changes effect smoke detector alarm times in the ceiling jet. Changes in particle size has been attributed to delays in detector activation, however, little evidence exists to support that particle size changes occur in the ceiling jet where detector activation occurs. This paper presents the results from laser scattering experiments and calculations conducted to support and validate the experimental findings. The laser scattering from various aerosols was collected, over time, to examine changes in particle size due to agglomeration in the smoke aging process. The laser scattering measurements were made at two linear polarizations, vertical (VV) and horizontal (HH), and scattering angles ranging from 20 to 155 degrees. A laser with a wavelength of 632.8 nm was used as a light source. The aerosol laser scattering results were then compared to the results from the Mie scattering theory. The Mie scattering theory was adjusted using a lognormal distribution to generate theoretical light scattering curves expected from a polydisperse aerosol typical of smoke. The collected data was examined using a combination of the Mie theory with various particle sizing techniques, including dissymmetry ratio and polarization ratio, to look for changes in laser scattering indicating changes in particle size.

Sérios problemas ambientais têm origem em processos de combustão incompletos. Entre os produtos indesejados está a fuligem, considerada como um dos principais fatores da mudança climática observada nos último anos. Desta forma, ferramentas para diagnóstico da emissão de material particulado se fazem necessárias. Com o advento do laser, o desenvolvimento de técnicas óticas não intrusivas teve início. Dentre elas, destaca-se a técnica denominada incandescência induzida por laser (laser induced incandescence – LII), a qual pode gerar resultados resolvidos no espaço para a fração volumétrica de fuligem. Neste contexto, este trabalho apresenta um estudo experimental sobre a produção de fuligem em duas situações: na primeira, foram estudadas chamas laminares pré-misturadas de etileno e ar aplicando-se a técnica LII. Os resultados foram calibrados a partir da fração volumétrica de fuligem média empregando a técnica de extinção de luz, obtendo-se, então, resultados quantitativos espacialmente resolvidos da fração volumétrica de fuligem. A utilização de diferentes gases no escoamento anular também foi avaliada. A segunda situação abordada envolve o estudo de chamas laminares não pré-misturadas utilizando o gás natural como combustível. O impacto da diluição de inertes em diferentes proporções sobre a fração volumétrica de fuligem em diversas alturas da chama foi estudado por meio da técnica LII. Os resultados obtidos foram comparados à outros resultados presentes na literatura e servirão como validação de futuros modelos de formação de fuligem. / Serious environmental problems are assigned to incomplete combustion processes. Among the unwanted products, soot can be related as an important factor of climate changes observed in the last years. Thus, particulate material emissions diagnostic tools are necessary. Due the laser advent, the development of non-intrusive optical techniques was possible. One of the most importante technique is the laser induced incandescence, LII, which can generate spatially and temporally resolved results of soot volume fraction. In this context, an experimental study regarding the soot production was developed in two different situations: in the first one, premixed laminar flames of ethylene and air were investigated by applying the LII technique. The results were calibrated through the average of soot volume fraction results obtained by the light extinction technique. Therefore, it was possible to obtain quantitative results of spatially resolved soot volume fraction. Different gases employment at the annular flow were also evaluated. The second situation studied involves the analysis of natural gas laminar non-premixed flames. The impact of different inert gas dilution ratio on the soot volume fraction at different heights of the flame was evaluated by the LII technique. The results were compared to other authors and will serve as validation for future soot formation models.

Les suies et leur caractérisation constituent des sujets de recherche très actuels dans divers domaines tels que le diagnostic de la combustion, la combustion numérique, l’optique atmosphérique, l'environnement et les applications de santé. Notre étude se concentre sur les propriétés radiatives des agrégats de suie issus de flammes de combustion ; notre objectif est de déterminer l’effet de la présence de suies sur le transfert de chaleur par rayonnement pour la simulation d'applications industrielles à haute température impliquant la combustion de gaz. Les études actuelles de modélisation du transfert de chaleur par rayonnement à travers les mélanges gazeux chargés de suies ne considèrent que l'absorption comme phénomène d'interaction rayonnement-matière. Des corrélations généralisées sont utilisées pour déterminer les propriétés radiatives des suies, soit sur la base de morphologies générées numériquement, soit plus simplement à partir de la taille moyenne des suies, de leur dimension fractale et de leur fraction volumique. Cependant, lorsque la taille de l'objet atteint l'ordre de grandeur des longueurs d'onde du rayonnement incident, l'interaction matière-rayonnement est susceptible d’être plus complexe du fait du phénomène de diffusion au niveau de l’agrégation qui ne peut plus être ignoré.Dans notre travail, nous établissons une méthodologie complète assortie d’une chaîne de calcul allant de la définition d'une morphologie de suie réaliste jusqu'au calcul du transfert de chaleur par rayonnement. À cette fin, des observations de suies émises par des flammes propane / air, méthane / air et méthane / oxygène sont effectuées par Microscopie Electronique à Balayage (MEB). La tomographie MEB est appliquée pour la première fois sur une suie issue d’une flamme propane / air, en combinaison avec la Microscopie Electronique en Transmission (MET) pour les observations. Des techniques d'analyse fractale 2D et 3D sont utilisées pour étudier les propriétés fractales d’agrégats de suie virtuels (générés numériquement) et de l'objet obtenu par la tomographie. Les propriétés radiatives des suies sont ensuite calculées en utilisant notre propre code d’Approximation Dipolaire Discrète (ADD – Discrete Dipole Approximation, ou DDA, en anglais). Une attention particulière est accordée à la modélisation ADD des suies en raison de l’indice optique complexe élevé de leur matériau constitutif, et aux méthodes numériques d’intégration directionnelle car les moyennes directionnelles des propriétés radiatives sont nécessaires pour les simulations ultérieures de transfert radiatif. La morphologie et les propriétés radiatives de l’agrégat de suie réaliste (tomographié) sont comparées à celles d'agrégats de suie numériques représentatifs, générés par un algorithme d’agrégation amas-amas limitée par la diffusion (Diffusion Limited Cluster-Cluster Aggregation, ou DLCCA, en anglais). Les compatibilités et les écarts entre les propriétés radiatives sont examinés, et les différences entre agrégats numériques représentatifs d’une part et agrégat réaliste d’autre part en termes de propriétés radiatives sont soulignées. Enfin, l'effet de la présence et de la morphologie des suies sur le transfert de chaleur par rayonnement est étudié par la résolution de l'équation du transfert radiatif en utilisant la méthode des ordonnées discrètes (Discrete Ordinates Method, ou DOM, en anglais) dans un mélange gazeux chargé de suies et dans une configuration académique 1D de plaques parallèles isothermes. / Soot and its characterization are of interest to researchers from various domains such as combustion diagnostics, numerical combustion, atmospheric optics, environmental and health applications. In this study, the main interest is on the radiative properties of soot aggregates issued directly from combustion flames in order to determine the effect of the presence of soot on the radiative heat transfer in the simulation of high temperature industrial applications involving gas combustion. Current studies modeling the radiative heat transfer through sooty gaseous media consider only the absorption as the main phenomenon of material-radiation interaction. Generalized correlations are used to determine the radiative properties of soot: these radiative properties are either computed over numerically generated aggregate morphologies or simply as a function of the soot average size, the fractal dimension and the volume fraction. However, the material-radiation interaction is susceptible to be more complex and morphology dependent at the aggregate level because of multiple scattering when the size of the object reaches the order of magnitude of the incident radiation wavelengths.In our work, we investigate the possibility to establish a computational methodology and workflow, starting from the definition of a realistic soot morphology up to the computation of the radiative heat transfer. To that end, observations of soot issued from propane/air, methane/air and methane/oxygen flames are performed using Scanning Electron Microscopy (SEM). SEM tomography is applied for the first time on soot issued from a propane/air flame, combined with Transmission Electron Microscopy (TEM) observations. 2D and 3D fractal analysis techniques are used to investigate the fractal properties of virtual (numerically generated) soot clusters and also of the tomography reconstructed objects. The radiative properties of soot are then computed using our in-house developed DDA (Discrete Dipole Approximation) code. Special attention is paid to the DDA modeling of soot because of the high complex extinction index of the material, and to the directional integration numerical methods because direction-averaged radiative properties are required for the subsequent radiative heat transfer simulations. The morphology and the radiative properties of the realistic morphology are compared to the ones of representative soot aggregates numerically generated by a DLCCA (Diffusion Limited Cluster-Cluster Aggregation) algorithm. The similarities and discrepancies on the radiative properties are investigated, and the differences between representative virtual aggregates on the one hand and the tomography reconstructed object on the other hand in terms of radiative properties are highlighted. Finally the effect of the presence and of the morphology of soot on the radiative heat transfer within a sooty gaseous mixture in a 1D isothermal parallel plate configuration is investigated by the resolution of the radiative transfer equation using DOM (Discrete Ordinates Method).

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Includes bibliographical references. / by Mark C. Zaretsky. / M.S.

To investigate the interaction between nanoparticles and electromagnetic waves, a numerical simulation model based on FEM was built in this thesis. Numerical simulation is an important auxiliary research method besides experiments. The optical properties of nanoparticles consist of scattering, absorption, and extinction, and in the case of nanoparticle suspension, the transmission is also involved. This thesis addressed two typical applications based on the established model, one was regarding the nanofluids for solar energy harvesting, and the other was regarding the optical properties of atmospheric soot. In the case of the nanofluids solar energy harvesting, the established model provided a convenient and rapid screening of potential nanoparticles and nanofluids candidates for solar energy harvesting. A core-shell structure nanoparticle, using Cu as the core material in a diameter of 90 nm coated with 5 nm thickness graphene, exhibited a better photothermal property under the solar radiation. In the second case regarding atmospheric soot, the established model provided an efficient method for understandings on the optical properties and warming effects of realistic soot particles. It was found that the sizes and material characteristics of soot, would greatly affect their scattering and absorption of light. Moreover, two submodels were introduced and integrated, which can better predict behaviors of real atmospheric soot involving their core-shell structures (moisture or organic condensates) and their fractal agglomerate structures. In conclusion, the established model helps to understand the interaction between nanoparticles and electromagnetic waves, which shows great potentials of wide applications.

Measurements of soot emission properties are of interest in both fundamental research and combustion-based industries. Laser-induced incandescence of soot particles is a novel technique that allows unobtrusive measurements of both soot volume fraction and particulate size with significant advantages. An apparatus utilizing this technique has been customized and used to provide measurements of soot concentration and particle sizing of a laminar, diffusion methane/air flame at pressures of 10, 20 and 40 atm at 6~mm above the burner. Soot volume fraction measurements correlate well with literature findings at all pressures. Despite similar trends, particle size values are found to be consistently larger than values reported in literature. Discussion on the errors of laser-induced incandescence as well as recommendations for improving the apparatus and results are herein.

Laminar axisymmetric syngas-air, syngas-methane mixture-air and biogas-air diffusion fames were studied over the pressure range of 5 to 20 atm to investigate the effect of pressure and dilution on soot formation. Spectral soot emission (SSE) optical diagnostic technique was used to measure the soot volume fraction and soot temperature in these flames. The fuel matrix consisted of three syngas fuels, two syngas-methane mixtures and two biogas fuels. In general, soot formation in syngas-methane mixtures and biogas diffusion flames showed strong pressure dependence at lower pressures but this dependence got weaker at elevated pressures. No soot was detected by SSE diagnostic technique in syngas-air flames at all pressures. The suppressive effect of carbon dioxide on soot formation prevailed at all pressures in syngas-methane mixtures and biogas flames.

Measurements of soot emission properties are of interest in both fundamental research and combustion-based industries. Laser-induced incandescence of soot particles is a novel technique that allows unobtrusive measurements of both soot volume fraction and particulate size with significant advantages. An apparatus utilizing this technique has been customized and used to provide measurements of soot concentration and particle sizing of a laminar, diffusion methane/air flame at pressures of 10, 20 and 40 atm at 6~mm above the burner. Soot volume fraction measurements correlate well with literature findings at all pressures. Despite similar trends, particle size values are found to be consistently larger than values reported in literature. Discussion on the errors of laser-induced incandescence as well as recommendations for improving the apparatus and results are herein.