Multiscale characteristics dynamics of hydrochar from hydrothermal conversion of sewage sludge under sub- and near-critical water

Chao He, Jun Zhao, Yanhui Yang*, Jing Yuan Wang

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

92 Citations (Scopus)

Abstract

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-C. O 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 O=C-O.

Original languageEnglish
Pages (from-to)486-493
Number of pages8
JournalBioresource Technology
Volume211
DOIs
Publication statusPublished - Jul 2016
Externally publishedYes

Scopus Subject Areas

  • Bioengineering
  • Environmental Engineering
  • Renewable Energy, Sustainability and the Environment
  • Waste Management and Disposal

User-Defined Keywords

  • Atomic ratio
  • Carbon functionality
  • Near-critical water
  • Subcritical water
  • Surface morphology

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