This study explored the feasibility of char and tar formation inhibition during supercritical water gasification of sewage sludge (SS) by additive addition. Experiments were conducted in autoclave with 5 wt.% additives at 400 °C for 30 min. The non-additive gasification of SS resulted in a higher char yield (12.6%) and tar yield (16.4%). In contrast, the five additives reduced the char yield (3.4–11.2%), the inhibition of char yield by additives was in the order of NaOH > K₂CO₃ > H₂O₂ > acetic acid > NiCl₂. The inhibition of tar formation was limited, tar yield were 13.3–18.8% with additives. Fourier-transform infrared spectroscopy was used to determine the functional groups of char/tar, and it was observed that the spectra of char were more similar to those of hydrochar obtained in a low-temperature experiment. Model compounds of potential precursors was also tested to study the mechanism of action of additives, the results reveal that additives have different effects on char/tar formation from various components, the inhibitory effects of additives on the yield of char from humus and tar from lignin were limited. Finally, the effects of additives on gasification were also studied. The addition of additives will have an impact on the hydrogen yield and gasification efficiency, which also needs to be considered when use additive to reduce the by-products yield.

本研究探讨了通过添加添加剂抑制超临界水气化污泥（SS）时焦炭和焦油形成的可行性。在具有5重量％添加剂的高压釜中在400℃下进行实验30分钟。SS的非添加气化导致更高的焦炭收率（12.6％）和焦油收率（16.4％）。相反，这五种添加剂降低了焦炭收率（3.4-11.2％），添加剂对炭收率的抑制作用依次为NaOH> K ₂ CO ₃ > H ₂ O ₂ >乙酸> NiCl ₂。抑制焦油形成的作用是有限的，添加添加剂可使焦油收率达到13.3-18.8％。使用傅里叶变换红外光谱法确定炭/焦油的官能团，观察到炭的光谱与在低温实验中获得的水炭的光谱更相似。还测试了潜在前体的模型化合物以研究添加剂的作用机理，结果表明添加剂对各种组分对焦炭/焦油形成的影响不同，添加剂对腐殖质焦炭和木质素焦油产率的抑制作用是有限的。最后，还研究了添加剂对气化的影响。添加剂的添加将影响氢气的产率和气化效率，