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Valorização energética de resíduos de lamas e de combustíveis sólidos recuperados através de cogaseificação
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Resumo(s)
Os resíduos sólidos urbanos (RSU's), de construção e demolição (RCD's) e as lamas do tratamento
de águas residuais assumem níveis de produção significativos, sendo caraterizados pela grande
heterogeneidade, baixa friabilidade e teores significativos de humidade, cloro e azoto. Os problemas
ambientais causados por tratamentos como o aterro, incineração e valorização agrícola e as propriedades
peculiares desses resíduos difíceis de tratar suscitaram o interesse noutros processos de valorização
energética inovadores.
Neste trabalho testou-se a cogaseificação de misturas com lamas e combustíveis sólidos
recuperados (CSR's) derivados de frações orgânicas de RSU's e RCD's, com variação das respetivas
proporções. Executaram-se ensaios de torrefação/carbonização seca e hidrotérmica às misturas como
solução de pré-tratamento. Por último, testou-se a aplicação de carvões da gaseificação de resíduos
biomássicos na remediação de efluentes.
Os resultados mostraram que a torrefação/carbonização melhorou as propriedades combustíveis
das misturas, obtendo-se carvões mais homogéneos, friáveis e hidrofóbicos, e com um poder calorífico
superior melhorado, especialmente na carbonização hidrotérmica que também baixou a concentração de
cinzas. Nos testes de cogaseificação, a adição de lamas e a pré-carbonização das misturas com CSR's
aumentou o poder calorífico inferior do gás, a eficiência de gás frio e baixou a produção de alcatrões,
mas aumentou a de carvões. A mistura ótima possuiu 50 % m/m de CSR + lama carbonizado, e 50 %
de resíduo de madeira. Os testes de remediação de efluentes revelaram que o carvão da gaseificação de
acácia recolhido no reator foi mais eficaz na descontaminação de efluentes corados, enquanto o de
bagaço de azeitona permitiu a maior redução de carência química de oxigénio no lixiviado de aterro.
Finalmente, o estudo tecno-económico para uma unidade de gaseificação de CSR's e lamas mostrou viabilidade para os cenários de produção de energia elétrica e de hidrogénio, sendo o primeiro o mais favorável.
Municipal solid wastes (MSW), construction and demolition wastes (C&DW) and sewage sludge (SS) have been generated in large amounts and are characterised by a high heterogeneity, low grindability and high concentrations of moisture, chlorine and nitrogen. The specific properties of these wastes and the environmental problems induced by conventional treatments (e.g. landfilling, incineration and agricultural valorisation) have raised the interest in other innovative waste valorisation pathways for energy production. This work aimed to perform co-gasification tests with mixtures composed of SS's and solid recovered fuels (SRF) derived from MSW's and C&DW's, both incorporated with different proportions. Tests of dry torrefaction/carbonisation and hydrothermal carbonisation were conducted to evaluate their feasibility as a pre-treatment for such wastes. Lastly, chars from biomass waste gasification were studied as potential adsorbents in effluent remediation tests. Main results showed that torrefaction/carbonisation improved fuel properties of waste mixtures and generated chars with more homogeneous, grindable and hydrophobic properties, and presented an enhanced higher heating value and reduced ash contents particularly when using the hydrothermal treatment. Co-gasification experiments with mixtures incorporating SS and a pre-carbonisation of mixtures containing SRF's enhanced the lower heating value of product gas and the cold-gas efficiency, and reduced tar production; however, char generation increased. The optimal mixture presented a composition of 50 wt% carbonised SRF + SS, and 50 wt% waste wood. Effluent remediation tests confirmed that the gasification char obtained from acacia was more effective in the decontamination of dye effluents, while that from olive bagasse allowed the best reduction in chemical oxygen demand of a landfill leachate. Finally, a techno-economic assessment conducted for a gasification facility processing SRF's and SS revealed feasibility for implementation, considering both scenarios of electricity production and hydrogen production; however, the former was more favourable.
Municipal solid wastes (MSW), construction and demolition wastes (C&DW) and sewage sludge (SS) have been generated in large amounts and are characterised by a high heterogeneity, low grindability and high concentrations of moisture, chlorine and nitrogen. The specific properties of these wastes and the environmental problems induced by conventional treatments (e.g. landfilling, incineration and agricultural valorisation) have raised the interest in other innovative waste valorisation pathways for energy production. This work aimed to perform co-gasification tests with mixtures composed of SS's and solid recovered fuels (SRF) derived from MSW's and C&DW's, both incorporated with different proportions. Tests of dry torrefaction/carbonisation and hydrothermal carbonisation were conducted to evaluate their feasibility as a pre-treatment for such wastes. Lastly, chars from biomass waste gasification were studied as potential adsorbents in effluent remediation tests. Main results showed that torrefaction/carbonisation improved fuel properties of waste mixtures and generated chars with more homogeneous, grindable and hydrophobic properties, and presented an enhanced higher heating value and reduced ash contents particularly when using the hydrothermal treatment. Co-gasification experiments with mixtures incorporating SS and a pre-carbonisation of mixtures containing SRF's enhanced the lower heating value of product gas and the cold-gas efficiency, and reduced tar production; however, char generation increased. The optimal mixture presented a composition of 50 wt% carbonised SRF + SS, and 50 wt% waste wood. Effluent remediation tests confirmed that the gasification char obtained from acacia was more effective in the decontamination of dye effluents, while that from olive bagasse allowed the best reduction in chemical oxygen demand of a landfill leachate. Finally, a techno-economic assessment conducted for a gasification facility processing SRF's and SS revealed feasibility for implementation, considering both scenarios of electricity production and hydrogen production; however, the former was more favourable.
Descrição
Palavras-chave
combustível sólido recuperado lama carbonização gaseificação análise tecnoeconómica remediação de efluentes