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Advisor(s)
Abstract(s)
A dependência dos combustíveis fósseis tem sido uma constante ao longo dos anos, o que levou à procura de outras alternativas para a obtenção de grandes quantidades de energia que possibilitem satisfazer as necessidades do quotidiano do ser humano. A utilização de alternativas mais sustentáveis, ecológicas e que consigam substituir em termos energéticos o que os combustíveis fósseis oferecem em grandes quantias tem sido um desafio até aos dias de hoje.
Assim sendo, apareceu a biomassa como alternativa para reduzir a dependência do petróleo, carvão e do gás natural, em sistemas de aquecimento como é o caso das caldeiras.
O objetivo principal da presente tese, que decorreu na empresa Silvino Lindo Ibérica – S.A, passa pela seleção de dois ventiladores de tiragem forçada, para ar primário e ar secundário, a alimentar a uma caldeira de tubos de fumos com potência igual a 4,0 MW e rendimento de 80% alimentada a biomassa e pela comparação entre os ventiladores selecionados e os ventiladores que a empresa efetivamente colocou na caldeira.
Numa primeira fase é feita a caraterização da biomassa (serrim de madeira) bem como o caudal de combustível para alimentar a caldeira. Para determinar a quantidade de combustível foi necessário a determinação do seu poder calorífico inferior. A caraterização foi realizada com base na análise última e próxima e com estes resultados calculou-se por dois métodos a quantidade de ar que os ventiladores devem fornecer para a reação de combustão. Pelo método 1 calcula-se o caudal de ar estequiométrico usando a informação da análise elementar do serrim e pelo método 2, utilizado pela empresa, usa-se uma expressão empírica desenvolvida para madeira com uma composição típica. Para caldeiras alimentadas a biomassa como a lenha são utilizados fatores de excesso de ar entre 1,8 a 2. Estes valores foram considerados no decorrer de todo o trabalho.
Após a determinação do caudal de ar primário e secundário, são ainda determinadas, as perdas de carga totais que o ar sofre desde a saída dos ventiladores até à entrada da fornalha. A obtenção destes dois parâmetros, caudal de ar e perda de carga, permite selecionar o melhor ventilador. Os caudais de ar primário e secundário obtidos são, respetivamente, 6795 m3/h e 3883 m3/h e os valores para as perdas de carga totais no percurso de ar primário e secundário correspondem aos valores de 504 e 190 mm c.a.
Usando as curvas características dos ventiladores de ar primário e secundário que a empresa SML instalou na caldeira, obtiveram-se os valores de eficiência, de velocidade de rotação e de potência de 86 %, 2935 rpm e 7,5 KW, para o ventilador de ar primário, e de 82%, 2000 rpm e 2,2 KW para o ventilador de ar secundário.
Os ventiladores selecionados pela empresa SML foram da Marca MZ, o modelo GR 560/2 para o ventilador primário e o modelo GR 500/2 para o ventilador secundário. O ventilador de ar primário (GR 560/2) é adequado aos requisitos determinados neste trabalho mas o ventilador de ar secundário (GR 500/2) não é o mais adequado pois funcionaria a um valor de rotação próximo do valor mínimo.
The dependence of fossil fuels has been a constant over the years, which has led to the search for other alternatives to obtain large amounts of energy that make it possible to meet the daily needs of the human being. The use of more sustainable, environmentally friendly and energy-efficient alternatives to fossil fuels has been a challenge to the present day. Thus, biomass appeared as an alternative to reduce dependence on oil, coal and natural gas, in heating systems such as boilers. The main objective of this thesis, that took place at Silvino Lindo Ibérica- S.A, it’s the selection of two forced-draft fans for primary air and secondary air, to a biomass boiler of smoke pipes with a power of 4,0 MW and an 80% efficiency. Finally, one of the objectives is to compare the selected fans with the fans that the company actually use in the boiler. In a first phase the characterization of the selected biomass (wood sawmill) as well as the flow rate of fuel to feed the boiler. is determinated. In order to quantity the rate of fuel, it was necessary to experimentally determine the lower heating value. The characterization was carried out based on ultimate and proximate analysis and with this results, the amount of air that the fans provided for the combustion reaction was calculated by two methods. By method 1 the stoichiometric air flow rate is calculated using the information from the elemental analysis of the sawmill and method 2, used by the company, uses an empirical expression developed for wood with a typical composition. For biomass-fired boilers such as firewood, excess air factors are used between 1,8 and 2. These values were considered throughout the work. After the determination of the primary and secondary air flow rates that the fans provide to the boiler, the total air pressure losses from the exit of the fan to the entrance of the furnace are also determined. With these two parameters, air flow and pressure rop, selection of the best fan can be performed. The obtained primary and secondary air flow rates are respectively 6795 m3/h and 3883 m3/ h and the values obtained for the total head losses in the primary and secondary air path correspond to the values of 504 and 190 mm c.a. Using the characteristic curves of the primary and secondary air fans that the company SML installed in the boiler, the values of efficiency, of speed and power are 86%, 2935 rpm and 7,5 KW for the primary air fan and 82%, 2000 rpm and 2,2 KW for the secondary air fan. The fans selected by the company SML were the MZ brand, the GR 560/2 model for the primary fan and the GR 500/2 model for the secondary fan. The primary air fan (GR 560/2) is suitable for the requirements determined in the present work, but the secondary air fan (GR 500/2) is not the most suitable because it will operate at the minimum speed value.
The dependence of fossil fuels has been a constant over the years, which has led to the search for other alternatives to obtain large amounts of energy that make it possible to meet the daily needs of the human being. The use of more sustainable, environmentally friendly and energy-efficient alternatives to fossil fuels has been a challenge to the present day. Thus, biomass appeared as an alternative to reduce dependence on oil, coal and natural gas, in heating systems such as boilers. The main objective of this thesis, that took place at Silvino Lindo Ibérica- S.A, it’s the selection of two forced-draft fans for primary air and secondary air, to a biomass boiler of smoke pipes with a power of 4,0 MW and an 80% efficiency. Finally, one of the objectives is to compare the selected fans with the fans that the company actually use in the boiler. In a first phase the characterization of the selected biomass (wood sawmill) as well as the flow rate of fuel to feed the boiler. is determinated. In order to quantity the rate of fuel, it was necessary to experimentally determine the lower heating value. The characterization was carried out based on ultimate and proximate analysis and with this results, the amount of air that the fans provided for the combustion reaction was calculated by two methods. By method 1 the stoichiometric air flow rate is calculated using the information from the elemental analysis of the sawmill and method 2, used by the company, uses an empirical expression developed for wood with a typical composition. For biomass-fired boilers such as firewood, excess air factors are used between 1,8 and 2. These values were considered throughout the work. After the determination of the primary and secondary air flow rates that the fans provide to the boiler, the total air pressure losses from the exit of the fan to the entrance of the furnace are also determined. With these two parameters, air flow and pressure rop, selection of the best fan can be performed. The obtained primary and secondary air flow rates are respectively 6795 m3/h and 3883 m3/ h and the values obtained for the total head losses in the primary and secondary air path correspond to the values of 504 and 190 mm c.a. Using the characteristic curves of the primary and secondary air fans that the company SML installed in the boiler, the values of efficiency, of speed and power are 86%, 2935 rpm and 7,5 KW for the primary air fan and 82%, 2000 rpm and 2,2 KW for the secondary air fan. The fans selected by the company SML were the MZ brand, the GR 560/2 model for the primary fan and the GR 500/2 model for the secondary fan. The primary air fan (GR 560/2) is suitable for the requirements determined in the present work, but the secondary air fan (GR 500/2) is not the most suitable because it will operate at the minimum speed value.
Description
Keywords
Fan Primary and secondary air Pressure drop Boiler Biomass