Integration of hydrothermal carbonization and aqueous phase reforming for energy recovery from sewage sludge

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 442; p. 136301
• Main Authors: Oliveira, Adriana S., Sarrión, Andrés, Baeza, José A., Diaz, Elena, Calvo, Luisa, Mohedano, Angel F., Gilarranz, Miguel A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.08.2022
• Subjects: Aqueous phase reforming; Energy recovery; Hydrothermal carbonization; Sewage sludge; Aqueous phase reforming; Energy recovery; Hydrothermal carbonization; Sewage sludge
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2022.136301

[Display omitted] •Sewage sludge was valorized through hydrochar and H2 production in integrated HTC-APR.•Hydrochar showed combustion properties suitable for use as a solid fuel.•Process water generated at low HTC temperature improved APR efficiency.•The highest H2 yield was obtained using a PtRh catalyst, low organic load and acidic pH.•Integrated HTC-APR maximize energy recovery. This study investigates the energy recovery from sewage sludge by combining hydrothermal carbonization and aqueous phase reforming of the generated process water. The hydrothermal treatment was carried out at 170 °C and 230 °C for 1 h, and produced a hydrochar with adequate physicochemical properties, such as a higher heating value (20–24 MJ kg−1) than sludge, improved fuel ratio (0.2–0.5) and a broad comprehensive combustion index (5.8 × 10−7 to 10.0 × 10−7 min−2 °C−3). Aqueous phase reforming of the process water was carried out at 220 °C and 25–29 bar for 4 h. A maximum H2 yield of 98.7 mmol H2 gTOC−1 was achieved using a bimetallic Pt/Rh catalyst supported on carbon black and for the process water obtained at the lowest carbonization temperature. The integration of hydrothermal carbonization and aqueous phase reforming processes is an interesting alternative for the management and energy recovery of sewage sludge, which allows reaching a potential energy recovery of 17.3 MJ per kg of dry sewage sludge, equivalent to 93.5 % gross energy recovery, under optimized conditions.