Design and optimization of supercritical CO₂ atmosphere gasification system for syngas production from eucalyptus sawdust by thermodynamic analysis

With the depletion of fossil fuels and the advancement of carbon neutrality goals, biomass, as a renewable energy source, demonstrates significant potential in clean fuel production. To enhance the efficiency of gasification-reforming under different atmospheres while reducing energy consumption, the behavior and mechanisms of gasification-reforming were systematically investigated. The focus of this study was to produce H₂/CO of 2 and 3 from eucalyptus sawdust under N₂ and supercritical CO₂ (scCO₂) atmospheres for downstream synthesis of methanol and methane, respectively. The results indicated that during gasification at 500–700 °C, the scCO₂ atmosphere favored the formation of liquid-phase products and inhibited the secondary cracking of light compounds. During reforming, CO production increased markedly as the temperature rose from 550 to 850 °C, while H₂O addition notably promoted H₂ production. After gasification-reforming in the scCO₂ atmosphere, the total volume of H₂ and CO was 1.60 times higher than that in the N₂ atmosphere, indicating that the supercritical fluid environment effectively enhances syngas yield. Preliminary energy analysis under the screening conditions revealed that the production of methanol syngas and methane syngas feedstocks in scCO₂ atmosphere required additional energy inputs of 7160.36 kJ/kg and 9813.82 kJ/kg, respectively. It provides a basis for process optimization and offers theoretical support for the efficient and low-carbon conversion of biomass into gaseous fuels.