Cambridge Centre for Advanced Research and Education in Singapore, School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459, Singapore; Division of Environmental and Water Resources Engineering, School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Cambridge Centre for Advanced Research and Education in Singapore, School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459, Singapore.
Bioresour Technol. 2016 Jul;211:486-93. doi: 10.1016/j.biortech.2016.03.110. Epub 2016 Mar 22.
Dewatered sewage sludge was upgraded to hydrochar using hydrothermal conversion in sub- and near-critical water. Three characteristic temperature regimes responsible for the upgrading were identified. Drastic hydrolysis of carbohydrates, amide II or secondary amines occurred at 200°C while noticeable decarboxylation initiated above 260°C. Elevated temperature improved porosity but did not induce higher surface area. Aliphatic C was mainly transformed to aromatic hydrocarbon rather than aromatic C-O in subcritical water, whereas COO/N-CO and aromatic C-O were decomposed to carbohydrate C at 380°C. Below 300°C, carbon functionalities in hydrochars were thermally stable and faster decomposition of N than C-(C,H) resulted in dramatic decline of N/C. Above 300°C, C-H was gradually polymerized to aromatic C-(C,H) which was considerably transformed to C-(O,N) and C-H at 380°C. CaO favored intense destruction of aromatic C-C/C-H, anomeric O-C-O, C-H and C-(O,N) functionalities but introduced more aromatic C-O and OC-O.
脱水污水污泥通过亚临界和近临界水中的水热转化升级为水热炭。确定了三个负责升级的特征温度区。在 200°C 时发生碳水化合物、酰胺 II 或仲胺的剧烈水解，而在 260°C 以上时则开始明显脱羧。升高温度可以提高孔隙率，但不会导致更高的表面积。在亚临界水中，脂肪族 C 主要转化为芳烃而不是芳烃 C-O，而 COO/N-CO 和芳烃 C-O 在 380°C 时分解为碳水化合物 C。在 300°C 以下，水热炭中的碳官能团热稳定，N 的分解速度快于 C-(C,H)，导致 N/C 急剧下降。在 300°C 以上，C-H 逐渐聚合形成芳烃 C-(C,H)，其在 380°C 时被转化为 C-(O,N)和 C-H。CaO 有利于强烈破坏芳烃 C-C/C-H、糖苷 O-C-O、C-H 和 C-(O,N)官能团，但引入了更多的芳烃 C-O 和 OC-O。
