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Abstract(s)
Atualmente, o biogás é uma fonte de energia que ainda se encontra em desenvolvimento em Portugal, sendo maioritariamente queimado para produção de energia através de cogeração. No entanto, o biogás pode ser purificado, de forma a aumentar a concentração de metano para que possa ser injetado na rede de gás natural. O presente trabalho teve como objetivo o estudo da viabilidade da produção de biometano, através da purificação do biogás, produzido na ETAR de Gaia Litoral. A unidade de purificação foi dimensionada com base na simulação, otimização e especificação de equipamento realizada usando o Aspen Plus®, tendo sido feita também uma análise económica do projeto. Para a concentração do biometano foi utilizada a tecnologia de lavagem de gases com água (Water Scrubbing), composto essencialmente por processos de absorção, destilação flash e desabsorção. Através deste processo foi possível a obtenção de um caudal de biometano igual a 7,12 kmol/h, com uma pureza de metano de 96,3%, correspondendo a uma recuperação na coluna de absorção de 96,7%. Em relação à análise económica, com base no preço da venda de metano à rede igual a de 0,059 €/kWhth, verificou-se que o projeto é rentável apresentando um valor atual líquido (VAL) de 125 908€, taxa interna de rentabilidade (TIR) de 14,8% e um período de recuperação do capital (PBP) de 5 anos, ainda durante o tempo de vida útil do projeto, que é de 6 anos. Adicionalmente, e com base na literatura disponível, foi ainda analisada a possibilidade de metanação do dióxido de carbono, tendo em vista o aumento do caudal e concentração da corrente de biometano. De uma forma geral e com carência de estudo posterior, verifica-se que caso seja realizada a recuperação e metanação do dióxido de carbono, a produção de biometano poderá sofrer um incremento em cerca de 57%.
Currently, biogas is an energy source that is still under development in Portugal, being predominantly burned for energy production through cogeneration. However, biogas can be purified in order to increase the methane concentration allowing it to be injected into the natural gas system. The goal of this research was to investigate the feasibility of producing biomethane at the Gaia Litoral WWTP via biogas purification. Aspen Plus® was used to simulate, optimize and support the design of the purification unit, and an economic analysis was also performed. The water scrubbing technology, which consists primarily of absorption, flash distillation, and disabsorption processes, was used for methane concentration. Using this process, it was possible to obtain a flow rate of biomethane of 7,12 kmol/h with a methane purity of 96,3%, which corresponds to a 96,7% recovery in the absorption column. In terms of economic analysis, based on the sale price of methane to the grid equal to 0,059 €/kWhth, the project appears to be profitable, with a net present value (NPV) of 125 908€, internal rate of return (IRR) of 14,8% and a capital recovery period (PBP) of 5 years, even during the project's lifetime, which is 6 years. In addition, based on the available literature, the possibility of carbon dioxyde methanation was investigated, considering the rise in the flow rate and concentration of the biomethane stream. In general, BM production may increase by 57% due to carbon dioxide recovery and methanation, although it requires further study.
Currently, biogas is an energy source that is still under development in Portugal, being predominantly burned for energy production through cogeneration. However, biogas can be purified in order to increase the methane concentration allowing it to be injected into the natural gas system. The goal of this research was to investigate the feasibility of producing biomethane at the Gaia Litoral WWTP via biogas purification. Aspen Plus® was used to simulate, optimize and support the design of the purification unit, and an economic analysis was also performed. The water scrubbing technology, which consists primarily of absorption, flash distillation, and disabsorption processes, was used for methane concentration. Using this process, it was possible to obtain a flow rate of biomethane of 7,12 kmol/h with a methane purity of 96,3%, which corresponds to a 96,7% recovery in the absorption column. In terms of economic analysis, based on the sale price of methane to the grid equal to 0,059 €/kWhth, the project appears to be profitable, with a net present value (NPV) of 125 908€, internal rate of return (IRR) of 14,8% and a capital recovery period (PBP) of 5 years, even during the project's lifetime, which is 6 years. In addition, based on the available literature, the possibility of carbon dioxyde methanation was investigated, considering the rise in the flow rate and concentration of the biomethane stream. In general, BM production may increase by 57% due to carbon dioxide recovery and methanation, although it requires further study.
Description
Keywords
Biogás Biometano Purificação do Biogás Water Scrubbing Biomethane Biogas Purification