Tunable H2/CO syngas production from co-gasification integrated with steam reforming of sewage sludge and agricultural biomass: A experimental study

Biowastes to tunable H2/CO syngas is a promising way to produce clean energy carrier. This study proposed a new concept of improving the production of tunable H2/CO syngas and tar abatement via co-gasification integrated with inline steam reforming (co-GSR) of wheat straw (WS) and sewage sludge (SS) over self-derived gasification/co-gasification carbon materials (G/CGCMs). Binary mixtures with varying WS/SS mass ratios were initially subjected to steam co-gasification, achieving H2-enriched syngas with the tunable H2/CO molar ratio of 1.77 – 3.35. By introducing C[WS] in co-GSR process, the synergistic interactions between binary mixture and C[WS] on the cumulative gas yield, H2 yield, and syngas yield were more predominant by using WS/SS-9/1 as the feedstock, reaching 94.74, 51.53, and 77.99 mmol/g. Moreover, co-GSR of WS/SS-9/1 presented the highest CCE (98.77C%) and CGE (121.63%), suggesting the C content in the binary mixture and C[WS] was almost entirely converted and reformed into gaseous product. Correspondingly, WS/SS-9/1 subjected to co-GSR was also found to gain the lowest tar yield (5.99 g/Nm3). These observations were possibly because the addition of 10% of SS in the blend could not only assure the sufficient C and volatile contents in the blend, but also ensure the sufficient supply of alkali metals and alkaline earth metals (AAEMs) from SS as a catalyst to facilitate catalytic cracking and reforming of intermediate tar from decomposition of 90% of WS. When G/CGCMs were applied in both GSR and co-GSR processes, co-biocarbon C[WS + SS] used in the GSR of SS could garner a higher H2 concentration (57.79vol%) and H2/CO ratio (2.89). In addition, plausible reaction pathways and mechanisms regarding co-GSR of binary WS/SS mixture in the presence of G/CGCMs were discussed and elucidated. Simply put, this study provides a newly sustainable route to produce tunable H2/CO syngas towards a clean and sustainable waste management way.