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Abstract(s)
O crescimento populacional está a provocar o aumento do consumo de energia, que é maioritariamente obtida a partir do petróleo. Este pode ser utilizado na produção de combustíveis ou diretamente na indústria. Este crescimento populacional conduz à produção excessiva de resíduos e à escassez do petróleo, o que faz com que seja necessário explorar novas fontes alternativas para a obtenção de combustível e energia, e que contribuam para a gestão dos resíduos. Essas fontes podem ser energia eólica, solar, geotérmica, hidráulica, das marés e motriz; energia do hidrogénio e biomassa. A biomassa tem um papel fundamental na produção de biocombustíveis, levando também, quando de origem residual, à valorização dos resíduos gerados pela população e à minimização da deposição de resíduos em aterro. A borra de café, sendo um subproduto proveniente das bebidas mais consumidas mundialmente, o café, constitui um objeto de enorme interesse de estudo. A sua utilização e valorização como biomassa residual é, portanto, potencialmente interessante. O presente trabalho tem como objetivo estudar a valorização da borra de café através da produção de Biochar, com vista à sua utilização em solos, e de Bio-oil para a produção de energia, a partir do processo de pirólise. Iniciou-se o trabalho com a caracterização da borra de café; os parâmetros usados para a sua caracterização foram: distribuição granulométrica; percentagem de humidade (37,43 %); teor de cinzas (1,81%); teor de azoto Kjeldahl (1,97 g N/100 g borra de café); teor de proteínas (12,33 g proteína/100 g borra de café) poder calorífico superior (5121,81 cal/g borra de café); teor de carbono orgânico total (88,97 %); teor de lenhina total (32,81 %); teor de lenhina insolúvel (30,98 %); teor de lenhina solúvel (1,76 %). Sumariamente contatou-se que os valores obtidos para a caracterização da borra de café não diferem muito dos encontrados na literatura. O único valor que apresenta maior discrepância relativamente aos valores da literatura é o teor de humidade, o que é justificável pela possibilidade de secagem entre os momentos de produção e de análise da amostra. No processo de pirólise, estudou-se a influência de três parâmetros: temperatura de patamar (T) (400 a 600 °C), tempo de patamar (t) (5 a 15 min) e teor de humidade da borra (H) (9 a 44,4 %). Foi usado o software JMP Statistical Discovery v13 para realizar o planeamento experimental 23 , e para fazer a modelação dos efeitos dos parâmetros na função objetivo. Assim, para cada um dos objetivos (maximizar razão carvão/borra seca e maximizar a razão quantidade de energia do Bio-oil/borra seca) o tratamento dos resultados dos ensaios planeados, permitirá obter uma expressão distinta. O rendimento máximo obtido para o Biochar e para o Bio-oil foi de 29% e 64%, respetivamente, correspondentes aos ensaios 9 (t=5 min; T=400 °C; H=44 %) e 16 (t=5 min; T=400 °C; H=9 %) para o Biochar e o ensaio 24 (t=10 min; T= 500 °C; H=31 %) para o Biooil, as velocidades de aquecimento para os ensaios 9, 16 e 24 são respetivamente 120, 120 e 30 °C/min. Concluiu-se que o ensaio que promoveu a maximização da quantidade de energia associada ao Biochar foi o ensaio 16 (t=5; T=400; H=9%), 1993,794 cal/g e para o Bio-oil foi o ensaio 24 (t=10; T=500; H=31%), 3503,33 cal/g individualmente, para o total da quantidade de energia associada aos dois produtos, o ensaio com maior rendimento energético foi o 11 (t=5; T=400; H=9%), 5205,79 cal/g. Foram realizados ensaios que foram divididos em dois grupos, A e B, que correspondem a ensaios com velocidade de aquecimento baixa (30 °C/min), e ensaios com velocidade de aquecimento elevada (120 °C/min), respetivamente. Fez-se variar esses parâmetros (gama de valores) de forma a obter o máximo de quantidade de Biochar e o máximo de quantidade de energia de Bio-oil por massa de borra de café. Para o conjunto de ensaios A, obteve-se uma percentagem máxima de Biochar de 28% e o esperado usando o modelo otimizado seria 34%. Para maximizar a quantidade de energia em Bio-oil por massa de borra de café, o resultado obtido experimentalmente foi de 3894,45 cal/g borra seca e o esperado era de 3126,02 cal/g borra seca. Para o conjunto de ensaios B, obteve-se uma percentagem de Biochar de 29% e o esperado seria 30%; para a quantidade de energia do Bio-oil por massa de borra de café o resultado obtido experimentalmente foi de 956,89 cal/g borra seca e o esperado de 3576,94 cal/g borra seca. A discrepância nos valores relativos à energia do Bio-oil pode ficar a dever-se à dificuldade na recuperação de todo o óleo obtido no processo de pirólise, uma vez que, dada a configuração do forno e do sistema de arrefecimento de gás e condensação de líquido, era frequente a acumulação de óleo na tubagem de saída, o que falseava negativamente os resultados. Verificou-se que, comparando com os valores da literatura, o valor da quantidade de energia do Bio-oil (quando medido como amostra composta) é mais próximo (5481,64 cal/g) do que os melhores ensaios analisados isoladamente (3894,45 e 956,89 cal/g). Calculou-se também a quantidade de Bio-oil necessário para substituir o consumo anual (ano de referência 2016) de diesel, gasolina e carvão, que corresponde a, respetivamente, 1 218 460 t/ano, 2 029 074 t/ano; 4 885 295 t/ano.
The population growth is causing the increase in energy consumption, which is mostly obtained from petroleum. This can be used in the production of fuels or directly in the industry. This population growth leads to excessive production of waste and the scarcity of oil, which makes it necessary to explore new alternative sources for obtaining fuel and energy and contributes to waste management. These sources can be wind, solar, geothermal, hydraulic, tidal; hydrogen and biomass energy. Biomass has a key role in the production of biofuels, and when from residual source, can contribute to the valorization of waste generated by the population and the minimization of waste disposal in landfills. The spent coffee grounds, being a by-product from the world’s most consumed beverage, coffee, is an object of great interest as case study. Their use and valorization as biomass is therefore potentially interesting. The present work has the objective of studying the valorization of spent coffee grounds through the production of Biochar for use in soil, and Bio-oil as source of energy, from the pyrolysis process. The work started with the characterization of spent coffee grounds; the parameters used for its characterization were: particle size distribution; moisture content (37.43%); ash content (1.81%); Kjeldahl nitrogen content (12.33 g N / 100 g coffee); protein content (12.33 g protein / 100 g coffee), higher heating value (5121.81 cal / g); total organic carbon content (88.97%); total lignin content (32.81%); insoluble lignin content (30.98%); soluble lignin content (1.76%). Briefly, it was concluded that the values obtained for the characterization of the spent coffee grounds do not significantly differ from those found in literature. The only value that presents greater discrepancy comparing to the values from literature is the moisture content, what can be due to drying between the moments of production and analysis of the sample. In this work it was studied the influence of three parameters on the pyrolysis process: hold temperature (T) (400 to 600 °C), hold time (t) (5 to 15 min) and moisture content of the spent coffee grounds (H) (9 to 44.4 %). It was used the JMP Statistical Discovery v13 software to perform the 23 experimental planning, and to do the modelling of the effects of the parameters in the objective function. Therefore, for each specific goal (to maximize the ratio Biochar/spent coffee ground and to maximize the ratio amount of energy of the Bio-oil / dry spent coffee grounds) a different expression can be obtained. The maximum yield obtained for the Biochar and the Bio-oil was 29% and 64%, respectively, corresponding to tests 9 (t=5 min, T=400 °C, H=44 %) and 16 (t=5 min, T=400 °C, H=9 %) for Biochar and to test 24 (t=10 min, T=500 °C, H=31 %) for Bio-oil, the heating speed for the test 9, 16 and 24 was 120, 120 and 30 30 °C/min respectively. It was concluded that the assay that promoted the maximization of the amount of energy in Biochar was assay 16 (t=5, T=400, H=9%), 1993.794 cal/g (T=10, T=500, H=31%), 3503.33 cal/g for the total amount of energy, the highest value was 11 (t=5, T=400, H=9%), 5205.79 cal/g. It was also realized a set of assays that were divided into two groups of tests, A and B, that correspond to low heating speed tests (30 °C / min), and high heating speed tests (120 °C / min), respectively. These parameters (range of values) were varied in order to obtain the maximum amount of Biochar and the maximum amount of Bio-oil energy per mass of spent coffee grounds. For the set of tests, A, it was obtained a maximum Biochar yield of 28% while the expected using the optimized model would be 34%. To maximize the amount of energy in Bio-oil per mass of spent coffee grounds, the result obtained experimentally was 3894.45 cal/g dry spent coffee grounds and the expected was 3126.02 cal / g dry spent coffee grounds. For the set of tests, B, it was obtained a maximum Biochar yield of 29% while the expected using the optimized model would be 30%. To maximize the amount of energy in Bio-oil per mass of spent coffee grounds, the result obtained experimentally was 956.89 cal/g dry spent coffee grounds and the expected was 3576.94 cal / g dry spent coffee grounds. The difference between experimental and predicted values concerning the energy from Bio-oil can be due to the difficulty in the recovery of the oil obtained from the pyrolysis process, particularly to the configuration of the oven, gas exhaust and liquid condensation system, as often it was observed the accumulation of oil in the output tubing, what negatively affected the results. It has been found that comparing with the values from literature, the amount of energy of Biooil when measured as a composite sample is closer (5481.64 cal/g) than the best assays analyzed alone (3894.45 and 956.89 cal/g). The amount of Bio-oil required to replace the annual consumption (based in the year 2016) of diesel, gasoline and coal was also calculated as 1 218 460 t/year, 2 029 074 t/year; 4 885 295 t/year.
The population growth is causing the increase in energy consumption, which is mostly obtained from petroleum. This can be used in the production of fuels or directly in the industry. This population growth leads to excessive production of waste and the scarcity of oil, which makes it necessary to explore new alternative sources for obtaining fuel and energy and contributes to waste management. These sources can be wind, solar, geothermal, hydraulic, tidal; hydrogen and biomass energy. Biomass has a key role in the production of biofuels, and when from residual source, can contribute to the valorization of waste generated by the population and the minimization of waste disposal in landfills. The spent coffee grounds, being a by-product from the world’s most consumed beverage, coffee, is an object of great interest as case study. Their use and valorization as biomass is therefore potentially interesting. The present work has the objective of studying the valorization of spent coffee grounds through the production of Biochar for use in soil, and Bio-oil as source of energy, from the pyrolysis process. The work started with the characterization of spent coffee grounds; the parameters used for its characterization were: particle size distribution; moisture content (37.43%); ash content (1.81%); Kjeldahl nitrogen content (12.33 g N / 100 g coffee); protein content (12.33 g protein / 100 g coffee), higher heating value (5121.81 cal / g); total organic carbon content (88.97%); total lignin content (32.81%); insoluble lignin content (30.98%); soluble lignin content (1.76%). Briefly, it was concluded that the values obtained for the characterization of the spent coffee grounds do not significantly differ from those found in literature. The only value that presents greater discrepancy comparing to the values from literature is the moisture content, what can be due to drying between the moments of production and analysis of the sample. In this work it was studied the influence of three parameters on the pyrolysis process: hold temperature (T) (400 to 600 °C), hold time (t) (5 to 15 min) and moisture content of the spent coffee grounds (H) (9 to 44.4 %). It was used the JMP Statistical Discovery v13 software to perform the 23 experimental planning, and to do the modelling of the effects of the parameters in the objective function. Therefore, for each specific goal (to maximize the ratio Biochar/spent coffee ground and to maximize the ratio amount of energy of the Bio-oil / dry spent coffee grounds) a different expression can be obtained. The maximum yield obtained for the Biochar and the Bio-oil was 29% and 64%, respectively, corresponding to tests 9 (t=5 min, T=400 °C, H=44 %) and 16 (t=5 min, T=400 °C, H=9 %) for Biochar and to test 24 (t=10 min, T=500 °C, H=31 %) for Bio-oil, the heating speed for the test 9, 16 and 24 was 120, 120 and 30 30 °C/min respectively. It was concluded that the assay that promoted the maximization of the amount of energy in Biochar was assay 16 (t=5, T=400, H=9%), 1993.794 cal/g (T=10, T=500, H=31%), 3503.33 cal/g for the total amount of energy, the highest value was 11 (t=5, T=400, H=9%), 5205.79 cal/g. It was also realized a set of assays that were divided into two groups of tests, A and B, that correspond to low heating speed tests (30 °C / min), and high heating speed tests (120 °C / min), respectively. These parameters (range of values) were varied in order to obtain the maximum amount of Biochar and the maximum amount of Bio-oil energy per mass of spent coffee grounds. For the set of tests, A, it was obtained a maximum Biochar yield of 28% while the expected using the optimized model would be 34%. To maximize the amount of energy in Bio-oil per mass of spent coffee grounds, the result obtained experimentally was 3894.45 cal/g dry spent coffee grounds and the expected was 3126.02 cal / g dry spent coffee grounds. For the set of tests, B, it was obtained a maximum Biochar yield of 29% while the expected using the optimized model would be 30%. To maximize the amount of energy in Bio-oil per mass of spent coffee grounds, the result obtained experimentally was 956.89 cal/g dry spent coffee grounds and the expected was 3576.94 cal / g dry spent coffee grounds. The difference between experimental and predicted values concerning the energy from Bio-oil can be due to the difficulty in the recovery of the oil obtained from the pyrolysis process, particularly to the configuration of the oven, gas exhaust and liquid condensation system, as often it was observed the accumulation of oil in the output tubing, what negatively affected the results. It has been found that comparing with the values from literature, the amount of energy of Biooil when measured as a composite sample is closer (5481.64 cal/g) than the best assays analyzed alone (3894.45 and 956.89 cal/g). The amount of Bio-oil required to replace the annual consumption (based in the year 2016) of diesel, gasoline and coal was also calculated as 1 218 460 t/year, 2 029 074 t/year; 4 885 295 t/year.
Description
Keywords
Biochar Bio-oil Borra de café Pirólise Valorização energética de resíduos Pyrolysis Spent coffee grounds Waste to energy