Effectiveness of gasification temperature and alkali catalyst action on hydrogen extraction from agricultural wastes via supercritical water gasification
摘要
Presently, agricultural wastes (rice straw and sugarcane bagasse) are the source for extracting hydrogen gas via supercritical water gasification (SCWG). During the SCWG process, gasification temperature has been varied from 400 °C to 700 °C with a span of 100 °C, and an optimum pressure of 25 MPa at 30 min residence time under both non-catalytic and catalytic conditions. The effect of gasification temperature on syngas production and SCWG performance was investigated with and without an alkali catalyst. The results showed that the SCWG process operated at 700 °C/25 MPa /30 min with alkali catalyst (1:0.5 ratio of Ni: NaOH) was found to have a high hydrogen yield of 29.5 mol/kg, enhanced carbon conversion efficiency of 84.6%, higher hydrogen selectivity of 79.2%, and superior gasification efficiency of 74.1%. With the significance of SCWG with catalyst action, the char formation is limited to 8.8 wt%, which is better than the non-catalyst SCWG system. Overall, the study identifies around 700 °C as the optimum gasification temperature for agricultural waste under the investigated conditions and demonstrates that Ni-NaOH catalysis significantly enhances hydrogen yield, carbon utilization, and energy recovery, providing valuable experimental insight for efficient hydrogen-rich syngas production via SCWG.