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The integration of low temperature supercritical water gasification with continuous in situ nano-catalyst synthesis for hydrogen generation from biomass wastewater

Siah Lee, Chai; Conradie, Alex V.; Lester, Edward

The integration of low temperature supercritical water gasification with continuous in situ nano-catalyst synthesis for hydrogen generation from biomass wastewater Thumbnail


Authors

Alex V. Conradie



Abstract

A continuous hydrothermal process is demonstrated, for the first time, that can operate at low gasification temperature (430 °C) and residence time (20 s) by combining supercritical water gasification (SCWG) and partial oxidation with in situ synthesis of virgin metal oxide nano-catalyst. Using olive wastewater as the feedstock, this gasification study experimentally investigated the impact of multiple variables: (1) COD feed concentration, (2) the in situ synthesis of different metal oxide nano-catalysts, (3) the partial oxidation coefficient (ɳ) and (4) the nano-catalyst precursor solution concentration. The optimum conditions for the generation of hydrogen and methane from olive wastewater were a feed COD of 38.6 g/L, ɳ = 0.8, and 60 mM precursor concentration for the in situ synthesis of Fe2O3 nano-catalyst. These optimised conditions were further investigated using spent lees and stillage. The efficiency of hydrogen and methane yields and COD reduction were in the order of stillage > spent lees > olive wastewater. The highest hydrogen molar selectivity, hydrogen and methane yields at 18.8 %, 17 and 11.4 mol/(kg biomass) respectively were obtained with stillage feedstock. Gasification, COD and TOC reduction efficiencies were 68.8–71.7 %, 72.6–76.5 % and 53.9–55.7 % respectively, with this process. Importantly, this novel gasification approach prevents any performance drop or catalyst deactivation during continuous operation. This study exemplifies that the co-generation of catalyst during SCWG is a promising and economically feasible direction for large-scale continuous generation of hydrogen and methane from different types of biomass wastewater at < 450 °C, whilst lowering its COD and TOC. (249 words)

Journal Article Type Article
Acceptance Date Dec 5, 2022
Online Publication Date Dec 9, 2022
Publication Date Jan 1, 2023
Deposit Date Dec 14, 2022
Publicly Available Date Dec 10, 2023
Journal Chemical Engineering Journal
Print ISSN 1385-8947
Publisher Elsevier BV
Peer Reviewed Peer Reviewed
Volume 455
DOI https://doi.org/10.1016/j.cej.2022.140845
Public URL https://nottingham-repository.worktribe.com/output/14888238
Publisher URL https://www.sciencedirect.com/science/article/pii/S1385894722063252

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