Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET), Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China; College of Environment, Hohai University, Nanjing, Jiangsu 210024, China.
College of Environment, Hohai University, Nanjing, Jiangsu 210024, China.
Waste Manag. 2021 Mar 15;123:88-96. doi: 10.1016/j.wasman.2021.01.027. Epub 2021 Feb 8.
Supercritical water gasification (SCWG) is considered a promising technology for sewage sludge (SS) treatment and utilization; however, char produced by a side reaction has become a bottleneck in SCWG. In this study, SS and its model compound (10% humic acid) were treated in an autoclave by SCWG at 400 °C for 30 min and by hydrothermal carbonization (HTC) at 250 °C for 300 min. The char yield was 15.4% in SCWG and 41.3% in HTC. The chars were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, Brunauer-Emmett-Teller (BET) analysis, and elemental analysis. By comparing the properties the char produced by SCWG and the hydrochar produced by HTC, which has been considered a valuable product, the feasibility of using char as an additional product in SCWG was explored. Compared with the char produced by HTC, the char generated in SCWG exhibits a lower BET specific surface area (8.257 and 15.782 m/g) and combustion activity, a higher proportion of small pores (with pore sizes of 1-2 nm), and greater thermal stability. The formation pathway of the two types of chars is related to both dehydration and aromatization; decarboxylation also occurs in char formation during SCWG. Humus was proved to be related to char formation during the SCWG of SS based on experimental results obtained with the model compound. This work provides insights needed to guide follow-up treatments or utilization of the char produced during the SCWG of SS.
超临界水气化（SCWG）被认为是一种有前途的污水污泥（SS）处理和利用技术；然而，副反应产生的炭成为 SCWG 的瓶颈。在这项研究中，SS 及其模型化合物（10%腐殖酸）在高压釜中分别通过 SCWG（400°C，30min）和水热碳化（HTC）（250°C，300min）进行处理。SCWG 中的炭产率为 15.4%，HTC 中的炭产率为 41.3%。通过扫描电子显微镜、傅里叶变换红外光谱、热重分析、BET 分析和元素分析对炭进行了表征。通过比较 SCWG 产生的炭和 HTC 产生的水炭（被认为是有价值的产品）的性质，探讨了在 SCWG 中使用炭作为附加产品的可行性。与 HTC 产生的炭相比，SCWG 产生的炭具有较低的 BET 比表面积（8.257 和 15.782 m/g）和燃烧活性、较高比例的小孔（孔径为 1-2nm）和更好的热稳定性。两种类型的炭的形成途径都与脱水和芳构化有关；SCWG 中也发生脱羧反应。基于模型化合物的实验结果，证明腐殖质与 SS 的 SCWG 过程中的炭形成有关。这项工作为指导 SS 的 SCWG 过程中产生的炭的后续处理或利用提供了必要的见解。
