Gasification of landfill leachate in supercritical water: Effects on hydrogen yield and tar formation

Abstract Landfill leachate was gasified in supercritical water (SCW) in a batch reactor made of 316 SS. The effects of temperature, pressure, reaction time and oxidation coefficient (OC) on the pollutant removal efficiencies and gasification characteristics were investigated. To observe the formation of tar and char visually, a capillary quartz reactor was also used. Results indicated that CO 2 , H 2 and CH 4 were the most abundant gaseous products. Temperature has an appreciable effect on the gasification process. Increasing temperature enhanced the H 2 yield (GY H2 ) and TOC removal efficiency (TRE) significantly. Although the influence of reaction time on the fractions of gaseous products was negligible at time above 300 s, the yields of H 2 , CH 4 , and CO 2 increased with reaction time whereas the CO, C 2 H 4 and C 2 H 6 yields decreased. Tar and char formation was evident on the interior surface of capillary quartz reactor. Adding a little oxidant could increase H 2 and CH 4 yields and decrease tar and char formation. GY H2 reached up to the maximum of 231.3 mmol L −1 leachate at 500 °C, 25 MPa, 600 s and 0.2 OC, which was 2.4 times of that without oxidant.