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

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)

Citation

Siah Lee, C., Conradie, A. V., & Lester, E. (2023). The integration of low temperature supercritical water gasification with continuous in situ nano-catalyst synthesis for hydrogen generation from biomass wastewater. Chemical Engineering Journal, 455, https://doi.org/10.1016/j.cej.2022.140845

• 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
• 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