Sulfur conversion and distribution during supercritical water gasification of sewage sludge

In order to study the transformation and distribution of sulfur element during supercritical water gasification (SCWG) of sewage sludge, sulfur contained products in different phase were detected in batch reactor. The XPS analysis showed that organic sulfur was the main part of sulfur compounds in sewage sludge. On the other hand, inorganic sulfur was dominated by SiS2, and SiS2 was subsequently converted into SiO2 and H2S during SCWG. The increase of temperature promoted H2S and SO2 yield but reduced their concentration. The addition of KOH could reduce the yield and concentration of H2S and SO2. The minimum concentration of H2S and SO2 was observed at 450 °C with KOH addition, which was 1313.94 ppm and 698.03 ppm, respectively. Sulfur compound in liquid was mainly found in the form of sulfate and its concentration decreased with increasing temperature.