Avaliação do perfil energético do carvão hidrotérmico de lodo de esgoto
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Data
2021-11-09
Autores
Avanzi, Guilherme Afonso de Campos
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
As estações de tratamento de esgoto (ETE) são responsáveis pela geração de grandes quantidades de lodo. A demanda pelo processo de tratamento é devido à preocupação recorrente com o meio ambiente e às condições de saneamento básico para a população. O município de São José do Rio Preto/SP registrou o montante de 14.832 toneladas de resíduo centrifugado em 2018, com gastos onerosos para seu tratamento e disposição. O lodo de esgoto é uma biomassa constituída por alto teor de matéria orgânica e outros compostos de acordo com a sua localidade. Esse material rico em carbono pode ser utilizado para reaproveitamento energético, desde que realizado seu tratamento adequado. Estudos têm demonstrado que a carbonização hidrotérmica (CHT) do lodo de esgoto produz um material denominado carvão hidrotérmico (do inglês, hydrochar) com poder calorífico superior (PCS) da ordem de 20 MJ/kg. Face ao exposto o objetivo deste trabalho é avaliar o potencial energético dos carvões hidrotérmicos (CH) produzidos a partir da CHT do lodo de esgoto doméstico da estação de tratamento de São José do Rio Preto/SP, bem como investigar essa possível via em prol de seu tratamento. Os parâmetros estudados foram temperatura (200, 240 e 280 oC) e tempo de reação (30, 75 e 120 min), com ou sem aditivo ácido sulfúrico. Temperatura e tempos maiores indicaram respostas mais efetivas. O lodo seco (LS) e os CH foram caracterizados por espectroscopia FTIR e análises elementar e termogravimétrica. O PCS foi calculado a partir da análise elementar e os valores aumentaram até 7% em relação à biomassa. Da água de processo (subproduto líquido) foi aferido o carbono orgânico total. Os resultados apontaram eficiência de rendimento energético próximo a 60% calculado a partir do rendimento e PCS do CH. A CHT causou o aparecimento de grupos alifáticos e aromáticos no produto final e alterou a natureza química dos grupos oxigenados. A adição de ácido na mistura promoveu o incremento de carbono elementar no produto e facilitou a separação de fases. Os dados tratados foram determinantes para avaliar os indicadores do balanço energético.
Sewage treatment plants (STP) are responsible for generating large amounts of sludge. The demand for the treatment process is due to the recurrent concern with the environment and the sanitation conditions for the population. The city of São José do Rio Preto/SP recorded the amount of 14,832 tons of centrifuged waste in 2018, with expensive costs for its treatment and disposal. Sewage sludge is a biomass consisting of a high content of organic matter and other compounds according to its location. This carbon-rich material can be used for energy reuse, as long as it is properly treated. Studies have shown that hydrothermal carbonization (HTC) of sewage sludge produces a material called hydrochar (HC) with higher heating value (HHV) of about 20 MJ/kg. In view of the above, the objective of this study is to evaluate the energy potential of HC produced from HTC of domestic sewage sludge from the treatment plant of São José do Rio Preto/SP, as well as to investigate this possible path in favor of your treatment. The parameters studied were temperature (200, 240 and 280 ºC) and reaction time (30, 75 and 120 minutes), with or without sulfuric acid additive. Higher temperature and time indicated more effective responses. Dry sludge (DS) and HC were characterized by FTIR spectroscopy and elemental and thermogravimetric analyses. The HHV was calculated from the elemental analysis and the values increased up to 7% compared to biomass. From the process water (liquid by product) the total organic carbon was measured. The results showed energy efficiency close to 60% calculated from the yield and HHV of HC. HTC caused the appearance of aliphatic and aromatic groups in the final product and changed the chemical character of the oxygen groups. The addition of acid to the mixture promoted the increment of elemental carbon and facilitated phase separation. The treated data were decisive for evaluating the energy balance indicators.
Sewage treatment plants (STP) are responsible for generating large amounts of sludge. The demand for the treatment process is due to the recurrent concern with the environment and the sanitation conditions for the population. The city of São José do Rio Preto/SP recorded the amount of 14,832 tons of centrifuged waste in 2018, with expensive costs for its treatment and disposal. Sewage sludge is a biomass consisting of a high content of organic matter and other compounds according to its location. This carbon-rich material can be used for energy reuse, as long as it is properly treated. Studies have shown that hydrothermal carbonization (HTC) of sewage sludge produces a material called hydrochar (HC) with higher heating value (HHV) of about 20 MJ/kg. In view of the above, the objective of this study is to evaluate the energy potential of HC produced from HTC of domestic sewage sludge from the treatment plant of São José do Rio Preto/SP, as well as to investigate this possible path in favor of your treatment. The parameters studied were temperature (200, 240 and 280 ºC) and reaction time (30, 75 and 120 minutes), with or without sulfuric acid additive. Higher temperature and time indicated more effective responses. Dry sludge (DS) and HC were characterized by FTIR spectroscopy and elemental and thermogravimetric analyses. The HHV was calculated from the elemental analysis and the values increased up to 7% compared to biomass. From the process water (liquid by product) the total organic carbon was measured. The results showed energy efficiency close to 60% calculated from the yield and HHV of HC. HTC caused the appearance of aliphatic and aromatic groups in the final product and changed the chemical character of the oxygen groups. The addition of acid to the mixture promoted the increment of elemental carbon and facilitated phase separation. The treated data were decisive for evaluating the energy balance indicators.
Descrição
Palavras-chave
Lodo de esgoto, Biomassa, Carbonização hidrotérmica, Poder calorífico superior, Sewage sludge, Biomass, Hydrothermal carbonization, Higher heating value