Experimental investigation on gasification of food waste in supercritical water: Effects of NaCl on syngas production and corrosion of reactor

Supercritical water gasification (SCWG) can efficiently convert food waste to hydrogen-rich syngas without pre-dewatering. NaCl salt is the most common food additive and therefore inevitably accumulated in food waste. Though, the role of NaCl in SCWG of food waste is still unexplored. In this study, the influences of NaCl salt in food waste during SCWG on syngas production and corrosion of reactor material were investigated. The model food waste, representing food waste in China, with different NaCl contents (0–6 wt% dry basis) was gasified in supercritical water at 500 °C and autogenous pressure of ca. 28 MPa. The highest total gas yield of 21.70 mol/kg and H₂ yield of 6.89 mol/kg were obtained in the case of 3 wt% NaCl. The corrosion test on Hastelloy C276 and stainless steel SS316L materials was conducted in supercritical water for 24 h with different NaCl concentrations. Hastelloy C276 showed better resistance to corrosion in supercritical water than stainless steel 316L. However, when NaCl was involved in the reaction, large oxides grains of NiFe₂O₄, FeCr₂O₄, NiO, and Fe₃O₄ were observed on the surface of both materials.