Reforming sewage sludge pyrolysis volatile with Fe-embedded char: Minimization of liquid product yield

Obtaining high quality syngas from sewage sludge (SS) means transferring a low-grade SS into a high-grade fuel or raw materials for chemical products. In this study, Fe is added to SS in form of Fe₂(SO₄)₃ to produce an effective and self-sufficient catalyst in order to obtain more syngas and minimize liquid products from SS pyrolysis. The Fe-embedded sewage sludge chars (SSCs) were used as catalysts for volatile reforming at 600°C. It has been found that the gas yield increases from 15.9 to 35.8wt% of the SS and that of liquids decreases from 31.9 to 10.2wt% after volatile reforming with Fe-embedded SSC when Fe was added equal to 7 % in the dried SS. In addition, the content of nitrogen-containing compounds in the oily products decreased. After reforming with Fe-embedded SSC, the molar fractions of syngas combustible components, including H₂, CH₄ and CO, increase, and the higher heating value of the syngas increased to 17.0MJ/Nm³ from the original 12.5MJ/Nm³ obtained from SS pyrolysis at 550°C. Moreover, the volatile reforming seems to reduce the level of some important syngas pollutants, like H₂S, HCl and HCN, even though it was also observed an increase of the contents of SO₂, NH₃, NO_2, HCNO and N₂O.