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Advisor(s)
Abstract(s)
A indústria baseada na biomassa está a iniciar uma nova revolução que, se planeada apropriadamente, pode levar a uma nova era de desenvolvimento global sustentável. A conversão termoquímica de biomassa, através do processo de gasificação, pode ser vista como uma oportunidade de produzir gás de síntese limpo com baixo impacto ambiental.
Deste modo a gasificação de biomassa é uma das tecnologias que tem sido apontada como possibilidade para o aproveitamento energético de resíduos orgânicos de diferentes origens.
Neste sentido, esta dissertação busca divulgar o conceito de energia renovável a partir do processo de gasificação de biomassa, caracterizando os resíduos da cortiça, e determinado o potencial energético do gás produzido durante gasificação deste resíduo.
O trabalho consistiu no estudo da gasificação da cortiça, usando ar como agente gasificante. Foi avaliada a influência de certos parâmetros na qualidade de gás produzido, como: caudal de ar alimentado ao reator, temperatura do leito do reator e massa de amostra a tratar. A influência da carga de cortiça (2 a 7 gramas) e do caudal de ar (0,25 e 0,33 kg/h), foi avaliada a uma temperatura do leito de 850ºC. Para o caudal de 0,33 kg/h de ar e uma carga de 2 gramas de cortiça, estudou-se a influência da temperatura do leito, entre 782 – 900ºC.
Este estudo foi importante e teve como principais objetivos: avaliar a composição do gás de produção obtido e os parâmetros de gasificação, como a percentagem de conversão de carbono, o rendimento de gás seco, a eficiência de gás frio e o poder calorífico superior do gás produzido.
Os ensaios foram realizados num reator de leito fluidizado com ar, usando areia como enchimento, em regime semi-batch e aquecido por uma resistência elétrica de potência de 3 kW. As amostras de gás de produção recolhidas foram analisadas por cromatografia gasosa com detetor de condutividade térmica. Os compostos analisados e quantificados no gás foram: H2, N2, CO, CH4 e CO2.
O aumento da carga de cortiça e do caudal de ar resultam numa diminuição dos parâmetros que caracterizam a gasificação, à exceção do poder calorífico superior do gás.
Os valores mais elevados obtidos foram a um caudal de 0,33 kg/h, à exceção do poder calorífico que foi favorecido pelo caudal de 0,25 kg/h, na gama de massas estudadas.
Obteve-se valores elevados de eficiência de conversão do carbono, para o caudal de 0,33 kg/h de ar, na casa dos 86% e para o rendimento de gás seco os valores obtidos foram de cerca de 2,39 Nm3 /kg. No parâmetro da eficiência de gás frio, obteve-se valores na casa dos 63%, para o mesmo caudal que os anteriores. Por fim, os valores obtidos do poder calorífico superior do gás de produção foram cerca de 5,96 Nm3 /kg, para o caudal de ar menor.
Relativamente à influência da temperatura, pode-se concluir que esta variável tem um papel predominante no processo de gasificação. Todos os parâmetros revelaram um aumento com o aumento da temperatura. A partir da temperatura de 850ºC, todos os parâmetros apresentam uma ligeira diminuição, à exceção do rendimento de gás seco que se manteve praticamente constante.
Os resultados obtidos deste trabalho permitiram concluir que a cortiça é uma fonte energética de biomassa viável em processos de gasificação.
Biomass industry is beginning a new revolution step and, if properly planned, it can lead to a new sustainable era of global development. The thermochemical conversion of iomass via gasification processes can be seen as an opportunity to produce clean syngas with a low environmental impact. Thus, biomass gasification is a technology that has been identified as an option for energetic valorisation of organic residues from different processes. This work aims to disseminate the concept of renewable energy from biomass gasification processes. Cork particles were characterized and the high heating value of producer gas was also determined. Cork particles gasification was studied using air as oxidizing agent and it was also determined the influence of some parameters in producer gas quality such as: air flow rate, bed temperature and biomass load. The effect of cork particles load (2 – 7 g) and the effect of air flow rate (0.25 and 0.33 kg/h) on gasification performance were performed at a bed temperature of 850ºC. It was also studied the effect of bed temperature on cork gasification process, between 782 – 900ºC, using a fixed air flow rate of 0.33 kg/h and a biomass load of 2 g. This was an important study and the main goals were: to evaluate producer gas composition and to assess gasification parameters such as carbon conversion efficiency, dry gas yield, cold gas efficiency and the high heating value of producer gas. The assays were performed in a semi-batch fluidised bed reactor using air as oxidizing agent and sand particles as bed material. The heating was performed with an electrical resistance of 3 kW. The producer gas samples were analysed by a gas chromatograph fitted with a thermal conductivity detector. The gases detected and quantified in the gasification process were H2, N2, CO, CH4 and CO2. It was found that increasing biomass load and air flow rate lead to a decrease of all parameters which assess the gasification performance, with the exception of producer gas high heating value. The highest values were obtained at an air flow rate of 0.33 kg/h except, once again, for high heating value that was favoured by 0.25 kg/h of air, in the range of studied biomass loads. Regarding to carbon conversion efficiency, it was obtained values of 86 % using 0.33 kg/h of air flow rate and values of 2.39 Nm3 /kg for dry gas yield. Besides, using the same mentioned air flow rate, in cold gas efficiency it was obtained values of 63%. Contrarily, it was found the highest value for HHV of producer gas, about 5.96 Nm 3 /kg, at an air flow rate of 0.25 kg/h. Concerning to the effect of bed temperature on gasification performance, it was found that this variable had a predominant role in gasification process. All parameters showed an increase with the temperature rise. However, from 850ºC all parameters showed a slight decrease, except for dry gas yield which values had remained constant. The results showed that cork residues are a viable energy source for gasification processes.
Biomass industry is beginning a new revolution step and, if properly planned, it can lead to a new sustainable era of global development. The thermochemical conversion of iomass via gasification processes can be seen as an opportunity to produce clean syngas with a low environmental impact. Thus, biomass gasification is a technology that has been identified as an option for energetic valorisation of organic residues from different processes. This work aims to disseminate the concept of renewable energy from biomass gasification processes. Cork particles were characterized and the high heating value of producer gas was also determined. Cork particles gasification was studied using air as oxidizing agent and it was also determined the influence of some parameters in producer gas quality such as: air flow rate, bed temperature and biomass load. The effect of cork particles load (2 – 7 g) and the effect of air flow rate (0.25 and 0.33 kg/h) on gasification performance were performed at a bed temperature of 850ºC. It was also studied the effect of bed temperature on cork gasification process, between 782 – 900ºC, using a fixed air flow rate of 0.33 kg/h and a biomass load of 2 g. This was an important study and the main goals were: to evaluate producer gas composition and to assess gasification parameters such as carbon conversion efficiency, dry gas yield, cold gas efficiency and the high heating value of producer gas. The assays were performed in a semi-batch fluidised bed reactor using air as oxidizing agent and sand particles as bed material. The heating was performed with an electrical resistance of 3 kW. The producer gas samples were analysed by a gas chromatograph fitted with a thermal conductivity detector. The gases detected and quantified in the gasification process were H2, N2, CO, CH4 and CO2. It was found that increasing biomass load and air flow rate lead to a decrease of all parameters which assess the gasification performance, with the exception of producer gas high heating value. The highest values were obtained at an air flow rate of 0.33 kg/h except, once again, for high heating value that was favoured by 0.25 kg/h of air, in the range of studied biomass loads. Regarding to carbon conversion efficiency, it was obtained values of 86 % using 0.33 kg/h of air flow rate and values of 2.39 Nm3 /kg for dry gas yield. Besides, using the same mentioned air flow rate, in cold gas efficiency it was obtained values of 63%. Contrarily, it was found the highest value for HHV of producer gas, about 5.96 Nm 3 /kg, at an air flow rate of 0.25 kg/h. Concerning to the effect of bed temperature on gasification performance, it was found that this variable had a predominant role in gasification process. All parameters showed an increase with the temperature rise. However, from 850ºC all parameters showed a slight decrease, except for dry gas yield which values had remained constant. The results showed that cork residues are a viable energy source for gasification processes.
Description
Keywords
Biomassa Gasificação Leito fluidizado Gás de síntese Biomass Gasification Fluidised bed Syngas