Made available in DSpace on 2016-06-02T19:56:36Z (GMT). No. of bitstreams: 1 2673.pdf: 2958103 bytes, checksum: 0992644491515e2973ed1ac0c87e233c (MD5) Previous issue date: 2009-09-16 / The removal of ultrafine particles is becoming an increasingly important operation due to the occupational problems caused to the environment and to the human health, such as inhalation of particulate matter, as well as by its applications in industrial processes. Among the equipments commonly employed for the removal of particulates from aerosols, the electrostatic precipitator (ESP) is the one capable to remove particles in a large size range with high efficiencies and can be used in the recovery of products of high aggregated value. The aim of this work was to evaluate the influence of operational parameters in the collection efficiency of a plate-wire electrostatic precipitator operating in the removal of nano-sized particles. The experimental system simulated a contamination by polydispersed nanoparticles ranging from 6 to 245 nm in an extra pure air stream. The efficiency for nano-sized particles was obtained by counting of particles before and after the electrostatic precipitator, using an electrical mobility analyzer. This procedure was performed varying the potential is applied to the discharge electrodes. The results shows the ESP presented a high efficiency of removal for nanoparticles of aerosol, where efficiencies larger than 99% were obtained for all velocities studieds (1 to 10 cm/s, with intervals of 1 in 1 cm/s) for electric field from 4 to 5.5 kV/cm. The efficiency increased with the decrease of the diameter particles up to approximately 20 nm, probably due to the higher electrical mobility of smaller particles. For diameters below 20 nm there was a drop in collection efficiency, which may have been caused by the low particles charging. The classical Deutsch-Anderson model didn t adjustment to the experimental data, the theoretical efficiency overestimated the experimental efficiency. / A remoção de nanopartículas de aerossóis é importante devido aos efeitos adversos que estas podem causar ao meio ambiente e a saúde humana e também pelas aplicações em processos industriais. Dentre os equipamentos capazes de operar na remoção de material particulado, tem-se o precipitador eletrostático, que, além de controlar a poluição removendo as partículas de meios gasosos em ampla faixa granulométrica, pode ser utilizado na recuperação de produtos de alto valor agregado. No presente trabalho, avaliou-se o desempenho de um precipitador eletrostático do tipo placa-fio de simples estágio operando na remoção de nanopartículas de um aerossol. O sistema experimental simulava uma contaminação de partículas nanométricas polidispersas de NaCl, produzidas na faixa de 6 a 245 nm. O desempenho do precipitador foi avaliado através da análise da eficiência de remoção das nanopartículas, pela contagem das mesmas antes e após a passagem pelo equipamento, utilizando a técnica de mobilidade elétrica. Tal procedimento foi realizado variando-se o potencial aplicado aos eletrodos de descarga. Os resultados mostraram que o precipitador eletrostático é um equipamento com capacidade para remover partículas nanométricas de um aerossol com elevados valores de eficiência. Foi possível obter eficiência acima de 99% para todas as velocidades estudadas, de 1 a 10 cm/s, com intervalados de 1 em 1 cm/s para campo elétrico de 4 a 5,5 kV/cm. A eficiência do precipitador eletrostático tende a aumentar com o decréscimo do diâmetro das partículas até aproximadamente 20 nm, provavelmente devido à maior mobilidade elétrica das partículas menores. Para diâmetros abaixo de 20 nm houve uma queda na eficiência de coleta, que pode ter sido causada pelo baixo carregamento das partículas. O modelo clássico de Deutsch-Anderson não se ajustou bem aos dados experimentais, a eficiência teórica superestimou a eficiência experimental.

O presente trabalho reúne elementos para projeto de precipitadores eletrostáticos, com dados levantados de cinzas volantes provenientes da combustão de gases em caldeiras de carvão mineral. Os objetivos desta pesquisa são construir um dispositivo padronizado para medição da resistividade ôhmica de materiais, levantar dados de resistividade ôhmica das cinza volantes de carvão mineral utilizado no Brasil e, com estes dados, listar recomendações sobre cuidados no dimensionamento de precipitadores (cálculo da área de captação), quando este equipamento é posicionado após uma caldeira que queima o carvão mineral nacional. A metodologia utilizada foi baseada em norma americana ASME, em que o pó (material a ser testado) é colocado sobre eletrodos de descarga e de coleta, uma alta tensão elétrica é aplicada até atingir a tensão de ruptura elétrica e neste instante é medida a resistividade. A construção do experimento e procedimento de execução foram seguidos conforme esta norma. O material de teste foi coletado de precipitadores eletrostáticos existentes na região Sul do Brasil, onde o carvão mineral tem seu uso freqüente. Os resultados apresentaram baixos valores para resistividade da cinza volante nacional, se comparados com resultados de carvões de outros países. Sua variação em função da temperatura segue a tendência de cinza volantes de outros países, ou seja, aumento da resistividade ôhmica com o aumento da temperatura. Foram realizados também experimentos com material retirado de precipitadores eletrostáticos acoplados a caldeiras de biomassa, que forneceram valores de resistividade ainda menores do que os do carvão mineral nacional. O material de teste, composição química e processo de coleta foram totalmente caracterizados, disponibilizados e uma análise completa pôde ser realizada, fato inédito no Brasil. Esses resultados permitiram listar recomendações visando o projeto de precipitadores eletrostáticos acoplados a caldeiras que queimam carvão mineral nacional. / This report is a collection of elements to be used in the design of Electrostatic Precipitators, with experimental data of fly ashes from combustion gases of Mineral Coal Fired Boilers. The aims of this research are to construct a standard device to measure the ohmic resistivity of materials, to get data of ohmic resistivity of fly ashes from mineral coals used in Brazil and with this data, to list recommendations about the key points to size electrostatic precipitators (calculation of specific collection area), when this equipment is arranged after one boiler that burns Brazilian mineral coals. The method used was based on the ASME Standard, in which the fly ash (material to be tested) is put between the discharge and the collecting electrodes, a high electrical tension is applied until the electrical break down tension to be reached; at this moment, the resistivity is measured. The construction of this device and the experimental procedure were conducted according to this standard. The tested materials were collected from existing Electrostatic Precipitator of South of Brazil, where the mineral coal is commonly used. The results indicated low values of ohmic resistivity of the Brazilian fly ashes, if compared to results of coals from other countries. Its variation with the temperature has the same behavior of fly ashes from other countries, i.e., the ohmic resistivity increases when the temperature increases. It was also executed tests with particulate materials from electrostatic precipitator of biomass boiler whose ohmic resistivity is lower than the Brazilian mineral coal. The tested material, chemical composition, and collecting process were totally described, available and a full analysis can be executed; these data are inedita in Brazil. These results allow to list the recommendations to design Electrostatic Precipitators for Brazil Mineral Coal Fired Boilers.

The presented diploma thesis deals with the design of an electrostatic precipitator for a domestic automatic wood fuel boiler. The individual chapters describe the products of the combustion process, the principles of charging dust particles, describe existing patents related to electrostatic precipitators, commercial electrostatic precipitators and the last part of the work calculates a mathematical model, according to which previously designed and evaluated separator variants were designed and evaluated. Based on the results, the optimal variant of the electrostatic precipitator designed for a domestic boiler is then selected.

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<p>Pollution problems have drawn worldwide awareness and become significantly important now. Particulate matter (PM) emission is one of the key pollution issues. Particulate matter has a significant impact on the environment and human health, especially particle sizes that range below 10μm. Researches continuously work an improvement of fine particulate matter collections emitted from all kinds of sources, such as automobiles, industrial combustion, etc. Governments in many countries are planning to regulate the PM emission from the existing PM_10 (particle diameter<10μm) to new limits PM_2.5 (particle diameter<2.5μm) within the next few years. For this reason, present PM control system needs to be improved.</p><p>The objective of this work is to develop a dust flow separator type electrostatic precipitator (DFS-ESP) for the effective control of fine particulate matter emission from natural gas combustions. The characteristic of PM emitted from natural gas combustion is studied, and the performance of a DFS-ESP is evaluated by experiments and numerical predictions.</p><p>An experiment was conducted for natural gas combustion exhaust flow rates from 2.5 to 9 Nm^3/h, ESP applied voltages from 0 to 30kV, and gas temperature from 80 to 160°C. A series of particle measurements were conducted at upstream, downstream and middle of the DFS-ESP system by an optical particle counter for particle mass density, and by condensation nucleate particle counter for particle size distributions and particle number density. Particle sampled from the natural gas combustion system was also analyzed by an environmental scanning electron microscope (ESEM) technique. Flow velocity profile and pressure drop of the DFS-ESP were measured by a Pitot tube and diaphragm type pressure transducer, respectively.</p><p>The experimental results show that the particle size emitted from natural gas combustion ranges from 17 to 300nm in diameter, and the volume density is approximately from 5 x 10^8 #pt/m^3 to 5 x 10^9 #pt/m^3 depending on the combustion conditions. The dust flow separator can concentrate 90% of fine particles in 1 to 3% of the gas flow and divert it from the main flow to the ESP section where the particles can be removed. In terms of overall particle collection efficiency, the DFS-ESP system can remove up to 90% of the particles based on the number density. The pressure drop across the DFS-ESP is observed to be lower than lPa for the present range of flow rate, which is within acceptable limits for industrial applications.</p> / Thesis / Master of Applied Science (MASc)