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Advisor(s)
Abstract(s)
O presente trabalho teve como objetivo o estudo da aplicação de um novo combustível a uma das caldeiras aquatubulares da empresa Refinarias de Açúcar Reunidas (RAR). A empresa dispõe de três caldeiras deste tipo, sendo que este trabalho foi focado na caldeira nº 2. Para este estudo foi importante fazer uma comparação da eficiência da caldeira, através da análise dos gases de combustão e resíduos, tanto do combustível atual (nafta) como do alternativo, proveniente da lavagem dos tanques de armazenamento do fuelóleo transportado em barco. Hoje em dia é habitual usarem-se dois métodos para o cálculo da eficiência da caldeira, o direto e o indireto, sendo que ao longo deste documento se utilizou o método indireto baseado na norma ASME PTC 4-2013, por se admitir ser mais rigoroso. Mesmo assim, far-se-á a comparação com o método direto e com o método indireto sugerido pela ADENE (Agência para a Energia) que, embora não englobe todas as perdas mencionadas na norma referida, é o mais utilizado atualmente nas auditorias energéticas. Foram realizados alguns ensaios experimentais com caudal de nafta entre 220 e 550 kg/h, aproximadamente, para os quais se obtiveram rendimentos entre 68,8 e 82,2%, utilizando a norma ASME PTC 4-2013. Para os mesmos ensaios, os rendimentos calculados pelo método da ADENE são acompanhados de uma variação percentual de 5,0 e 6,9%. Analisando o rendimento a partir da variação do excesso de ar concluiu-se que a melhor gama de rendimentos foi obtida com a percentagem de excesso de ar a rondar os 36%. Quando estes valores subiram para 215%, o rendimento diminuiu cerca de 13%. Convém ainda referir que nestes ensaios os valores de CO, NOx e SO2, apesar de elevados, estiveram sempre abaixo do VLE (Valor Limite de Emissão). No teste de operação da caldeira com o novo combustível concluiu-se que os rendimentos se aproximam muito dos obtidos com a nafta, depois de alterada a relação ar-combustível. Verificou-se ainda que as percentagens obtidas dos poluentes NOx e SO2 nos gases de combustão foram inferiores, ou seja, para um caudal a rondar os 490 kg/h de combustível, estes valores foram de 394 e 452 ppm para a nafta, e 137 e 261 ppm para o novo combustível (fuelóleo nº3), respetivamente. Acrescente-se que a caldeira não apresentou alterações nem anomalias de funcionamento durante ou após o teste. Por fim, foi realizada uma simples análise económica que permitiu concluir que a substituição do combustível tem um payback de 5 meses e 19 dias, ou seja, sugere-se a sua implementação.
The present work had the purpose of studying the application of a new fuel in one of the water-tube boilers of the sugar refinery company. The company has three boilers of this type and this work was focused on boiler nº2. For this study it was important to make a comparison of the boiler efficiency through the analysis of the flue gases and residues from the current (naphtha) and the alternative (fuel oil nº3) fuel, which comes from the washing of the storage tanks from the carriage boat. Nowadays, it is usual to use two methods to calculate the efficiency of a boiler, the direct and the indirect. Throughout this document it was used the indirect method based on the ASME PTC 4-2013 standard because it is admitted being a stricter one. Even so, a comparison will be made with the direct method and the indirect method suggested by ADENE which, although not encompasses all the losses mentioned in the referred standard, is the most used in Portuguese energy audits. Some experiments were carried out with a naphtha flow between 220 and 550 kg/h, for which yields were obtained between 68.8 and 82.2% using the ASME PTC 4-2013 standard. For the same flows, the income calculated using the ADENE method were accompanied of a difference between 5.0 and 6.9%. By analyzing the yield from the excess air variation, it was concluded that the best range of yields were obtained with the percentage of the excess air surrounding 36%. When these values went up to 215%, the yields went down by 13%. It should also be noted that in these tests the values of CO, NOx e SO2 for the flue gases, although high, were below the VLE (Emission Limit Values). In the boiler operation test with the new fuel it was concluded that the incomes are very close to those obtained with the naphtha, after changing the air-fuel ratio. It was also found that the NOx and SO2 emissions decreased, which means that with a fuel flow rate of around 490 kg/h, these values were 394 and 452 ppm with naphtha, and 137 and 261 ppm with fuel oil nº3, respectively. At the end It should be noted that the boiler has not changed or malfunctioned during or after the test. Finally, a simple economic analysis was carried out, which allowed the conclusion that the fuel substitution has a payback of 5 months and 19 days, which means, its implementation can be done.
The present work had the purpose of studying the application of a new fuel in one of the water-tube boilers of the sugar refinery company. The company has three boilers of this type and this work was focused on boiler nº2. For this study it was important to make a comparison of the boiler efficiency through the analysis of the flue gases and residues from the current (naphtha) and the alternative (fuel oil nº3) fuel, which comes from the washing of the storage tanks from the carriage boat. Nowadays, it is usual to use two methods to calculate the efficiency of a boiler, the direct and the indirect. Throughout this document it was used the indirect method based on the ASME PTC 4-2013 standard because it is admitted being a stricter one. Even so, a comparison will be made with the direct method and the indirect method suggested by ADENE which, although not encompasses all the losses mentioned in the referred standard, is the most used in Portuguese energy audits. Some experiments were carried out with a naphtha flow between 220 and 550 kg/h, for which yields were obtained between 68.8 and 82.2% using the ASME PTC 4-2013 standard. For the same flows, the income calculated using the ADENE method were accompanied of a difference between 5.0 and 6.9%. By analyzing the yield from the excess air variation, it was concluded that the best range of yields were obtained with the percentage of the excess air surrounding 36%. When these values went up to 215%, the yields went down by 13%. It should also be noted that in these tests the values of CO, NOx e SO2 for the flue gases, although high, were below the VLE (Emission Limit Values). In the boiler operation test with the new fuel it was concluded that the incomes are very close to those obtained with the naphtha, after changing the air-fuel ratio. It was also found that the NOx and SO2 emissions decreased, which means that with a fuel flow rate of around 490 kg/h, these values were 394 and 452 ppm with naphtha, and 137 and 261 ppm with fuel oil nº3, respectively. At the end It should be noted that the boiler has not changed or malfunctioned during or after the test. Finally, a simple economic analysis was carried out, which allowed the conclusion that the fuel substitution has a payback of 5 months and 19 days, which means, its implementation can be done.
Description
Keywords
Caldeira Aquatubular Eficiência Fuelóleo ADENE ASME PTC 4- 2013 Water-Tube Boiler Efficiency Fuels