The experimental study on supercritical CO₂ thermochemical reduction of eucalyptus sawdust

To mitigate the effects of the greenhouse effect, the capture, utilization and sequestration of carbon have become a focus of attention to reduce CO₂ in the atmosphere. Supercritical CO₂ (scCO₂: T≥31.26 °C, P≥7.38 MPa) was employed to enhance the gasification process because of the advantages of near-liquid density and high solubility. In this work, a novel method of carbon utilization was proposed, in which waste biomass was gasified under the scCO₂ atmosphere. This work aimed to investigate the effects of concentrations (5–––20 wt%), temperatures (400–––700 °C), residence times (10–––40 min) and initial pressures on the gas–liquid-solid products. When reacting at 700 °C for 40 min (Initial pressure: 6.4 MPa), CO was produced to a maximum of 32.92 ± 0.13 mol/kg, at which CE and HE were 96.10 % and 41.44 % respectively. As the temperature increased, the variety and quantity of liquid-phase products declined substantially. Based on the experimental results, two reaction paths were predicted. The method is of great significance for the thermochemical reduction of CO₂ to high-calorific gases and liquids and is expected to provide technical support for the accelerated realization of the low-carbon economy.