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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Avaliação das diversas fontes e tipos de biomassa do estado de Alagoas: estudo de suas características físico-químicas e seu potencial energético / Evaluation of various types of sources and biomass the state of Alagoas: study of its chemical and physical characteristics of its potential energy

Souza, José Edmundo Accioly de 26 September 2011 (has links)
In this study the use of available agro-industrial and forest residues, in Alagoas, were evaluated for use in ceramic furnaces to energy generation. At first, a survey of various types of biomass in Brazil and in Alagoas was made, followed by a investigation of the main permanent and temporary crops that could generate agro-industrial residues. Later, studies of the forms of use of agro-industrial residues as well as a quantitative assessment and energy that can be generated from the agro-industrial residues from major crops of Alagoas were conducted. The main agro-industrial residues next to the bigger five ceramics, located in adjacent municipalities of Alagoas were characterized in terms of physical-chemical parameters, comparing energy demands with their possible use in furnaces. The process of manufacturing of briquettes was also subject to a case study involving such a process on laboratory scale. The economic evaluation of the use of agro-industrial residues considering the preparation, transportation and energy consumption in furnaces and one simulation, considering various scenarios for the use of agro-industrial residues, with reference to a ceramic Arapiraca were made. In addition, the case of utilization of eucalyptus wood for energy generation was assessed using economic and financial study, simulating the culture of this crop in a rural settlement. The various aspects investigated here showed that the agro-industrial residues from the processing of agricultural production in the State of Alagoas could be used in ceramic and can completely replace the fuel currently used in furnaces, for one ceramic located in the Arapiraca region, where these kind of residues are available. In the case of ceramics located in regions where the availability of agro-industrial residues is limited, an alternative of renewable fuel, would be the culture of energy forests with native or exotic species, such as the eucalyptus. / Nesse estudo foi avaliada a utilização de resíduos agroindustriais e florestais do Estado de Alagoas, para utilização em fornos cerâmicos para geração de energia. Inicialmente, foi realizado um levantamento dos diversos tipos de biomassa existentes no Brasil e em Alagoas, seguido de um levantamento das principais culturas agrícolas permanentes e temporárias que poderiam gerar resíduos agroindustriais. Após, foram efetuados estudos das formas de utilização dos resíduos agroindustriais assim como uma avaliação quantitativa e da energia que pode ser gerada, a partir dos resíduos agroindustriais provenientes das principais culturas agrícolas de Alagoas. Os principais resíduos agroindustriais dos municípios limítrofes as cinco principais cerâmicas de Alagoas foram caracterizados, do ponto de vista físico-químico, comparando-se demandas energéticas com a possível utilização desses em fornos ou fornalhas. O processo de fabricação de briquetes também foi alvo de um estudo de caso envolvendo tal processo em escala laboratorial. A avaliação econômica do aproveitamento dos resíduos agroindustriais considerando a preparação, o transporte e o consumo energético em fornalhas e fornos cerâmicos foi alvo de investigação e uma simulação, considerando vários cenários para o aproveitamento de resíduos agroindustriais, tomando como referência uma cerâmica em Arapiraca. Complementarmente, a hipótese de utilização da lenha de eucalipto para a geração de energia foi avaliada através de estudo econômico e financeiro, simulando o plantio dessa cultura em um assentamento rural. Os vários aspectos aqui investigados apontaram que os resíduos agroindustriais provenientes do beneficiamento da produção agrícola do Estado de Alagoas poderiam ser usados nos fornos cerâmicos sem processamento ou adensados e poderiam substituir totalmente os combustíveis atualmente utilizados nos fornos ou fornalhas, de cerâmicas localizadas na região de Arapiraca, privilegiada nesses tipos de resíduos, pela alta produção agrícola. No caso de cerâmicas, localizadas em regiões onde exista pouca disponibilidade de resíduos agroindustriais, uma alternativa em termos de combustível renovável, seria o plantio de florestas energéticas com espécies nativas ou exóticas como, por exemplo, o eucalipto.
42

Termovalorização da biomassa de aguapé (Eichhornia crassipes) através de pirólise em reator forno rotativo / Thermovalorisation of water hyacinth (Eicchornia crassipes) biomass through pyrolysis in rotary kiln reactor

Carregosa, Ingred Suellen Carvalho 27 July 2016 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Lignocellulosic biomass use for obtaining biofuels has been showing itself with much more evidence during these past years through cellulosic ethanol and biooils, biogases and biochars. Aquatic plants of lignocellulosic basis, Eichhornia crassipes species, commonly known by water hyacinth, represent a major environmental problem due to their invasive nature and their high proliferation rate. In this work we evaluated the possibility of use this biomass source from pyrolysis in a rotary kilns reactor in three different temperatures. The results evidence that the major yield of the liquid fraction (bio-oil + acid extract) was obtained at 500 ºC (42.11%). For 400 ºC and 600 ºC, the biochar and biogas had major production, 37.78% and 42.36%, respectively. Bio-oils characterization by GC/MS produced in microscale allowed an investigation upon the scale-up phenomenon under the bio-oils composition. The results show that, in qualitative terms, the chemical composition of bio-oils was not changed, however, at semiquantitative aspect, show they are produced in distinguish relative percentages. The mainly chemical classes identified in biooils were: acids, alcohols, phenols and sugar derivatives. Bio-oils showed in average, 68% of calorific power of the fuels derived from petroleum, glimpsing enforcement on the energetic area. In the produced biochars, with yields between 37% and 26%, the increase on pyrolysis temperature has provided an increase upon carbon concentration, and a decreasing upon the hydrogen and oxygen concentrations, reflecting in high aromaticity of the materials. These materials ware tested in some aspects about the soils management, nutritional function and water retention. In view of this, the water hyacinth pyrolysis has associated sustainability concepts and green chemistry, putting concepts of renewable energetic sources together and glimpsing an environmental problems inhibition, to offer an alternative to the 2nd generation of bio-fuels production. / O uso de biomassas lignocelulósicas para a obtenção de biocombustíveis apresenta-se com muito mais evidência nos últimos anos através do etanol celulósico e de bio-óleos, biogás e biocarvão. As plantas aquáticas de base lignocelulósica da espécie Eichhornia crassipes, popularmente conhecida por aguapé, representam um grande problema ambiental devido ao seu caráter invasor e sua alta taxa de proliferação. Neste trabalho avaliou-se a possibilidade de aproveitamento dessa fonte de biomassa a partir do processo de pirólise em um reator cilindro rotativo em três diferentes temperaturas. Os resultados demonstraram que o maior rendimento da fração líquida (bio-óleo + extrato ácido) foi obtido a 500 ºC (42,11%). Para as temperaturas de 400 e 600 ºC, o biocarvão e o biogás tiveram maior produção, 37,78% e 42,36%, respectivamente. A caracterização por CG/EM dos bio-óleos produzidos em microescala permitiram investigar o efeito de scale-up sob a composição dos bio-óleos. Os resultados mostraram que em termos qualitativos, a composição química dos bio-óleos não foi alterada, no entanto, no aspecto semiquantitativo mostraram que são produzidos em percentuais relativos distintos. As principais classes químicas identificadas nos bio-óleos foram: ácidos, álcoois, fenóis e derivados de açúcares. Os bio-óleos apresentaram em média 68% do poder calorífico do combustível derivado de petróleo, vislumbrando uma aplicação na área energética. Nos biocarvões produzidos, com rendimento variando de 37% a 26%, o aumento da temperatura de pirólise proporcionou um aumento na concentração de C, e uma diminuição nas concentrações de H e O, refletindo em maior aromaticidade dos materiais. Estes materiais foram testados sob alguns aspectos quanto ao manejo de solos, função nutricional e retenção de água. À vista disto, a pirólise de aguapé relacionou conceitos de sustentabilidade e química verde, unindo o conceito de fontes de energias renováveis com a inibição de problemas de cunho ambientais, ao oferecer uma biomassa alternativa para a produção de biocombustíveis de 2ª geração.
43

Experimental study and modeling of hydrodynamic and heating characteristics of flighted rotary kilns / Etude et modélisation de fours tournants équipés de releveurs

Bongo Njeng, Alex Stéphane 04 November 2015 (has links)
Ce travail porte sur l'étude de fours tournants équipés de releveurs. Ce sont des contacteurs gaz/solide largement répandus dans de nombreux secteurs industriels mettant en oeuvre des solides divisés. Cependant en raison d'une faible connaissance du fonctionnement de ces équipements notamment en matière d'écoulement ou de transfert thermique, leur utilisation repose encore beaucoup sur le savoir faire des opérateurs acquis avec le temps. Ainsi ce travail vise à fournir aux ingénieurs des outils de connaissance et d'extrapolation pour les accompagner dans les phases de dimensionnement, mais aussi d'optimisation de procédés existants, en particulier pour des fours tournants en chauffage indirect et équipés de releveurs. La première partie de cette étude porte sur l'influence des conditions opératoires sur l'hydrodynamique des solides divisés de forme et taille différentes. Pour ce faire, des procédures expérimentales pour la mesure de distribution des temps de séjours des particules solides ont été mises en oeuvres. Deux pilotes de four tournant ont été utilisés. Ces derniers ont un ratio longueur sur diamètre équivalent mais un ratio de taille de 2. L'hydrodynamique des fours a été caractérisée quantitativement à partir des résultats expérimentaux en terme de temps de séjour des solides, taux de remplissage du four ainsi que de la dispersion axiale des particules. Ces derniers ont été modélisés par analyse dimensionnelle dans un souci de généralité en prenant en compte la présence d'éléments internes (releveurs, grille) ou diaphragmes en sortie, mais aussi des paramètres opératoires tels que la vitesse de rotation du tube, son inclinaison ou le débit des particules solides. La seconde partie de cette étude s'intéresse aux processus de transfert thermique dans les fours tournants en chauffage indirect et équipés de releveurs. Cette étude repose sur la mesure des profils de température à la paroi, dans la phase gazeuse et le lit de particules solides. L'analyse de ces profils de température se focalise sur la détermination des coefficients de transfert de chaleur entre la paroi et le lit de solides d'une part, et entre la paroi et le gaz d'autre part. Une méthode d'analyse globale de système mince et un bilan global intégrant la puissance fournie pour la chauffe sont utilisés pour la détermination de ces coefficients de transfert. Les résultats obtenus permettent d'une part de mettre en évidence l'effet des releveurs ainsi que l'influence des paramètres opératoires sur ces coefficients de transfert de chaleur et d'autre part d'établir par analyse dimensionnelle des modèles pour ces derniers. Enfin, ce travail se termine par la mise en place d'un modèle dynamique simplifié de four tournant en chauffage indirect permettant la détermination des profils de température le long du four et pouvant être facilement adapté à divers procédés. / The present work addresses a fundamental study on flighted rotary kilns. They are gas-solid reactors, used in a variety of industries to process heterogeneous media. However, operating these kilns mainly relies on the know-how of operators due to insufficient fundamental understanding. The aim of this work is to provide engineers with relevant tools and models to assist in the design stage and the performance improvement of existing operating process units, in particular indirectly heated rotary kilns, inclined and equipped with lifters. In the first part, we studied the effects of operating parameters on the flow of materials of differing properties and shape. For this purpose, residence time distribution measurements were performed through experimental stimulus response tests. Two pilot-scale rotary kilns with similar length-to-diameter ratios, but a dimension ratio of about two were used in this study. We focused on the effects of lifter shape and configurations. The effects of the rotational speed, the kiln slope, the mass flow rate and the exit dam height were also analyzed. The flow of solids was quantitatively characterized primarily by the experimental mean residence time, hold-up, and axial dispersion coefficient. Using a dimensional analysis, models were established to predict the mean residence time, the filling degree and the axial dispersion coefficient, providing basic information on the kiln design, solid particle properties and operating conditions. In the second part, we studied the heat transfer mechanisms occurring in the flighted rotary kiln by measuring temperature profiles at the wall, the freeboard gas and the bulk of solids. Analysis of the temperature profiles focused on two main issues: assessment of the heat transfer coefficient between wall and gas, and assessment of the heat transfer coefficient between wall and solid particles. The lumped system analysis and a heat balance using the power supplied for the heating were applied to determine the experimental heat transfer coefficients. The effects of operating conditions and lifting flights were analyzed. Both heat transfer coefficients were then correlated through dimensional considerations. Lastly a global dynamic model mainly based on the models developed in this study can be used to determine wall, gas and bulk solids axial temperature profiles in an indirectly heated flighted rotary kiln. This global model needs to be completed with specific models related to a reaction so as to be used as a framework for the simulation of specific industrial rotary kilns.
44

Charcoal Kiln Detection from LiDAR-derived Digital Elevation Models Combining Morphometric Classification and Image Processing Techniques

Zutautas, Vaidutis January 2017 (has links)
This paper describes a unique method for the semi-automatic detection of historic charcoal production sites in LiDAR-derived digital elevation models. Intensified iron production in the early 17th century has remarkably influenced ways of how the land in Sweden was managed. Today, the abundance of charcoal kilns embedded in the landscape survives as cultural heritage monuments that testify about the scale forest management for charcoal production has contributed to the uprising iron manufacturing industry. An arbitrary selected study area (54 km2) south west of Gävle city served as an ideal testing ground, which is known to consist of already registered as well as unsurveyed charcoal kiln sites. The proposed approach encompasses combined morphometric classification methods being subjected to analytical image processing, where an image that represents refined terrain morphology was segmented and further followed by Hough Circle transfer function applied in seeking to detect circular shapes that represent charcoal kilns. Sites that have been identified manually and using the proposed method were only verified within an additionally established smaller validation area (6 km2). The resulting outcome accuracy was measured by calculating harmonic mean of precision and recall (F1-Score). Along with indication of previously undiscovered site locations, the proposed method showed relatively high score in recognising already registered sites after post-processing filtering. In spite of required continual fine-tuning, the described method can considerably facilitate mapping and overall management of cultural resources.
45

Tang sancai

Jiang, Qichen January 2009 (has links)
This thesis studies Tang sancai, a multi-coloured lead-glaze ceramic decorated ware which emerged in the Tang dynasty (AD 618 - AD 907), attaining mass production in the middle of the Tang era and declining towards its end. It examines the functions of sancai in its different aspects, namely as burial objects, as containers for ritual offerings and as architectural material. I argue that Tang sancai ware as burial objects were employed exclusively by the Tang imperial and elite families. The approach to my argument is made, in a first stage, through the observation of the physical locations of tombs that contained Tang sancai wares to demonstrate that these tombs belonged to the Tang imperial and elite family members. In a further step, I bring up two Tang decrees which laid down regulations for burials, to indicate that there was a strict hierarchical system for the allocation and utilization of burial land. These two Tang texts enable us to establish that the tombs located around the area of the imperial tombs belonged to the Tang officials and elite, and therefore not to ordinary people. In addition, the study I undertake of the structure of the tombs, with layout and organization mirroring palatial environments, reinforces my argument to that end. Lastly, I look at the cost of production of Tang sancai showing that it was higher than that of unglazed ceramics and that, consequently, sancai wares were, from an economical point of view, inaccessible to the common people. This thesis also reflects on the agency of Tang sancai, considering its aesthetic qualities and its suitability in the functions for which it served, as a force in engaging the viewers. The lasting debate on whether Tang sancai utensil-shaped wares were used for everyday eating and drinking is dealt with in this thesis by carefully examining the locations of the shards that were excavated at the sites of imperial palaces. My research enables to point out that this data is not sufficient to ascertain that this type of Tang sancai was used as daily wares. On the contrary, on the grounds that these locations were the places where ritual performances took place, I argue that sancai utensil wares were used as presentation containers for ritual performances. In the absence of records in Tang texts which could have informed about the relationship between Tang sancai and religious practice, I borrow an evidence from Japan, in the form of the hand-brush writing on a couple of Nara sancai dishes, which were copies of Tang sancai made in Japan during the time of Tang, mentioning that these vessels were specifically for use for ritual ceremonies. Furthermore, on the basis of analyses made on lead-glazed ware, some scholars assert that such ware is poisonous and could not have been used to contain food or drink, as much as no evidence exists to show that ancient Chinese had used lead-glazed wares for that purpose. This leads to the clarification that Tang sancai utensil-shaped wares were not produced for everyday use, their purpose having actually been to serve as vessels for offerings in rituals. I further observe that this connection between sancai and ritual-themed objects, initiated by the Tang, has in fact pervaded through the succeeding dynasties affirming its role in religious ceremonials. Finally, this thesis also looks at Tang sancai as an architectural material to show that it was skillfully used in decorating buildings, not only as tiles and tile-ends, but also as large-sized roof ornaments. The research reveals, in the process, the possible dates when sancai architectural material started to be used popularly during the Tang era.

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