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Advisor(s)
Abstract(s)
O presente trabalho tem como objetivo o dimensionamento de uma unidade industrial produtora de bioetanol, valorizando um resíduo de baixo valor, a borra de café. A grande dependência do petróleo e a necessidade de reduzir as emissões de gases com efeito de estufa, levou à procura crescente de alternativas energéticas à utilização dos combustíveis fósseis. Uma dessas alternativas é a produção de biocombustíveis. Neste trabalho definiu-se que as etapas constituintes do processo de produção de bioetanol seriam: pré-tratamento químico com ácido diluído; sacarificação e fermentação simultâneas e destilação. Uma vez que não existe nenhuma unidade deste tipo em Portugal, a parte técnica baseou-se no estudo do processo utilizado pela Petrobras, no Brasil. Considerou-se uma base de cálculo de 4 toneladas de borra de café disponibilizadas por dia. Para a etapa de pré-tratamento químico, utilizou-se uma solução de ácido sulfúrico 5% (v/v). Nesta etapa, a matéria-prima permanece num reator durante 60 minutos, a uma temperatura de 85°C e a 50 rpm. A relação entre a quantidade de borra de café e o volume adicionado de H2SO4 5% (v/v) é de 20L de ácido por cada quilograma de borra de café. A hidrólise enzimática é realizada no mesmo reator onde ocorre a fermentação. Admitiu-se que o tempo de sacarificação e fermentação simultâneas seria de 50 horas (2h para que ocorra a hidrólise enzimática e 48h para a fermentação). Este reator encontra-se a uma temperatura de 35°C e a 30 rpm. A enzima escolhida para este processo é a Viscozyme L (complexo multienzimático que contém uma ampla gama de carboidrases) e a levedura utlizada na fermentação é a Saccharomyces cerevisiae. O processo de destilação é realizado numa coluna de destilação fraccionada. Depois de realizados todos os balanços de massa, obtém-se uma produção de cerca de 160 kg de etanol por cada 4 toneladas de biomassa, considerando que a unidade opera 335 dias por ano.
The present work has the objective of designing an industrial unit producing bioethanol, valuing a low value residue, the coffe grounds. The heavy dependance on oil and the need to reduce greenhouse gas emissions, has led to the growing demand for energy alternatives to the use of fossil fuels. One of these alternatives is the production of biofuels. In this work it was defined that the constituent stages of the bioethanol production process would be: chemical pretreatment with diluted acid; simultaneous saccharification and fermentation and distillation. Since there is no such unit in Portugal, the technical part was based on the study of the process used by Petrobras in Brazil. It was considered a basis of calculation of 4 tons of coffee grounds made available per day. For the chemical pretreatment step, a 5% (v/v) sulfuric acid solution was used. At this stage, the feedstock remains in a reactor for 60 minutes, at a temperature of 85°C and at 50 rpm. The ratio of the amount of coffee grounds to the added volume of 5% (v/v) H2SO4 is 20 L of acid per each kilogram of coffee grounds. The enzymatic hydrolysis is carried out in the same reactor where the fermentation takes place. It was assumed that the simultaneous saccharification and fermentation time would be 50 hours (2h for enzymatic hydrolysis and 48h for fermentation). This reactor is at a temperature of 35°C and 30 rpm. The enzyme chosen for this process is Viscozyme L (multienzymatic complex containing a wide range of carbohydrases) and the yeast used in the fermentation is Saccharomyces cerevisiae. The distillation process is carried out on a fractional distillation column. After all the mass balances have been carried out, a production of about 160 kg of ethanol is achieved for every 4 tons of biomass, considering that the unit operates 335 days a year.
The present work has the objective of designing an industrial unit producing bioethanol, valuing a low value residue, the coffe grounds. The heavy dependance on oil and the need to reduce greenhouse gas emissions, has led to the growing demand for energy alternatives to the use of fossil fuels. One of these alternatives is the production of biofuels. In this work it was defined that the constituent stages of the bioethanol production process would be: chemical pretreatment with diluted acid; simultaneous saccharification and fermentation and distillation. Since there is no such unit in Portugal, the technical part was based on the study of the process used by Petrobras in Brazil. It was considered a basis of calculation of 4 tons of coffee grounds made available per day. For the chemical pretreatment step, a 5% (v/v) sulfuric acid solution was used. At this stage, the feedstock remains in a reactor for 60 minutes, at a temperature of 85°C and at 50 rpm. The ratio of the amount of coffee grounds to the added volume of 5% (v/v) H2SO4 is 20 L of acid per each kilogram of coffee grounds. The enzymatic hydrolysis is carried out in the same reactor where the fermentation takes place. It was assumed that the simultaneous saccharification and fermentation time would be 50 hours (2h for enzymatic hydrolysis and 48h for fermentation). This reactor is at a temperature of 35°C and 30 rpm. The enzyme chosen for this process is Viscozyme L (multienzymatic complex containing a wide range of carbohydrases) and the yeast used in the fermentation is Saccharomyces cerevisiae. The distillation process is carried out on a fractional distillation column. After all the mass balances have been carried out, a production of about 160 kg of ethanol is achieved for every 4 tons of biomass, considering that the unit operates 335 days a year.
Description
Keywords
Bioetanol Borra de café Pré-tratamento químico Sacarificação e fermentação simultâneas Destilação Bioethanol Coffee grounds Chemical pre-treatment Simultaneous saccharification and fermentation Distillation