Hydrogen production in anaerobic thermophilic reactors

Author(s)

Adriana Ferreira Maluf Braga

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2014-04-29

Examining board members

Marcelo Zaiat; Magali Christe Cammarota; Luiz Olinto Monteggia; Paula Loureiro Paulo; José Alberto Domingues Rodrigues

• Advisor: Marcelo Zaiat

Abstract

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. (AU)

• FAPESP's process: 10/05495-0 - Hydrogen production assessment in thermofilic anaerobic reactors
• Grantee: Adriana Ferreira Maluf Braga
• Support Opportunities: Scholarships in Brazil - Doctorate