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Doctoral Thesis
DOI
10.11606/T.18.2014.tde-26052015-144012
Document
Author
Full name
Adriana Ferreira Maluf Braga
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2014
Supervisor
Committee
Zaiat, Marcelo (President)
Cammarota, Magali Christe
Monteggia, Luiz Olinto
Paulo, Paula Loureiro
Rodrigues, José Alberto Domingues
Title in Portuguese
Produção de hidrogênio em reatores anaeróbios termofílicos
Keywords in Portuguese
Acidogênese
Biohidrogênio
Reator tubular
Solventogênese
UASB
Abstract in Portuguese
A digestão anaeróbia termofílica é uma opção vantajosa para efluentes descartados a altas temperaturas, além de estimular rotas mais eficientes de produção de H2. No entanto, os resultados da literatura divergem bastante, os rendimentos de H2 são inferiores ao valor teórico possível e poucos estudos avaliaram diferentes configurações para indicar a mais eficiente. Assim, este estudo avaliou a produção de H2 a partir da sacarose em três tipos de reator: reator anaeróbio de fluxo ascendente e manta de lodo (UASB), reator tubular de fluxo ascendente com leito empacotado (TCS) e sem material suporte (TSS), operados a 55°C. Os tempos de detenção hidráulica (TDH) aplicados ao reator UASB foram 12, 6 e 2 h e aos reatores TCS e TSS foram 2 e 0,5 h. Pré-tratamento térmico (100°C por 15 min) foi aplicado ao inóculo metanogênico do UASB e TCS e TSS foram auto inoculados. O efeito de nutrientes e a concentração nutricional ótima para a produção de H2 foram investigados através de ensaios em batelada. Com TDH de 2 h, o material suporte afetou a transferência de massa, resultando em menor teor de H2 no biogás quando presente, porém, maior conversão de sacarose e produção de H2. O pré-tratamento térmico não inibiu a metanogênese, sendo as condições operacionais mais importantes para a seleção dos microrganismos. TCS e TSS com TDH de 0,5 h apresentaram produção de H2 similar e o material suporte afetou apenas as rotas metabólicas. Entre todas as operações, TCS e UASB com TDH de 2 h alcançaram os maiores valores de rendimento de H2 (YH2), respectivamente, 1,99 ± 0,36 e 2,56 ± 0,84 molH2.mol-sac-1, através da via metabólica do etanol. TCS2 também demonstrou estabilidade e, apesar de o U2 ter gerado maiores porcentagens de H2 no biogás, pode ser apontado como o mais eficiente para a produção de H2. A relação C:N:P, Fe+2 e Ni+2 tiveram efeito significativo sobre a produção de H2, e YH2 ótimo foi estimado para concentrações de 4,53 mgFe+2.L-1 e 0,045 mgNi+2.L-1.
Title in English
Hydrogen production in anaerobic thermophilic reactors
Keywords in English
Acidogenesis
Biohydrogen
Solventogenesis
Tubular reactor
UASB
Abstract in English
The thermophilic anaerobic digestion is a suitable option for wastewater discharged at high temperatures; in addition, it is suitable for more efficient pathways for H2 production. However, the results found in literature have divergences; the H2 yields are lower than the theoretical possible value and only few studies evaluated different types of reactors and defined the more advantageous one. Therefore, this study evaluated H2 production from sucrose in three types of reactor: upflow anaerobic sludge blanket (UASB), upflow tubular reactor with packed-bed (TCS) and without support materials (TSS), operated at 55°C. The hydraulic retention time (HRT) applied to UASB reactor was 12, 6 and 2h and to TCS and TSS was 2 and 0.5h.Thermal pretreatment (at 100°C, for 15 min) was applied to the methanogenic inoculum of UASB and TCS and TSS was inoculated through natural fermentation process. The effect of nutrients and the optimal concentration of t nutrients for H2 production were evaluated through batch assays. At HRT of 2h, the support material affected the mass transferring, leading to lower content of H2 in the biogas when it is used; however, in this condition it was found higher sucrose conversion and H2 production. The operational conditions showed to be more efficient for methanogenesis than pretreatment. TCS and TSS at HRT of 0.5h presented similar H2 production and the support material affected only the metabolic pathways. Among all the conditions assessed, TCS and UASB at HRT of 2h reached the highest values of H2 yield highest YH2, respectively, 1.99 ± 0.36 and 2.56 ± 0.84 molH2.mol-sac-1, through ethanol pathway. TCS2 demonstrated stability production also and, despite the U2 have achieved higher percentage of H2 in biogas, it can be pointed out as more efficient for H2 production. The ratio C:N:P, Fe+2 and Ni+2 showed significant effect on H2 production, and the optimal YH2 was estimated for 4.53 mgFe+2.L-1 e 0.045 mgNi+2.L-1.
 
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