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Sequential hydrothermal processing of sewage sludge to produce low nitrogen biocrude

Zimmermann, Joscha; Raffelt, Klaus; Dahmen, Nicolaus

A hydrothermal pre-treatment has been developed to improve sewage sludge quality or to produce low nitrogen biocrude via hydrothermal liquefaction (HTL) in a subsequent step. The mild hydrothermal pre-treatment (150 °C) step was performed with deionized water, sulfuric acid (0.5 M), or citric acid (0.5 M) to solubilize nitrogen containing compounds in the aqueous supernatant. Downstream, the residual solid material was liquefied with the addition of sodium carbonate via hydrothermal liquefaction (350 °C). The pre-treatment with citric acid transferred up to 66.7 wt. % of nitrogen into the aqueous supernatant, while 62.0 wt. % of carbon was recovered in the solid. Due to the pre-treatment lipids retained in the sewage sludge solid, which increased the favored biocrude yield up to 42.9 wt. % and the quality evaluating value H/Ceff ratio significantly to 1.48. Multi-method characterization of the resulted biocrude samples showed a lower concentration of N-heterocycles, while long-chain aliphatics and free fatty acid are increased.

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Verlagsausgabe §
DOI: 10.5445/IR/1000131148
Veröffentlicht am 12.04.2021
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Katalyseforschung und -technologie (IKFT)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2021
Sprache Englisch
Identifikator ISSN: 2227-9717
KITopen-ID: 1000131148
Erschienen in Processes
Verlag MDPI
Band 9
Heft 3
Seiten Art.-Nr.: 491
Schlagwörter hydrothermal hydrolysis; nitrogen extraction; sequential hydrothermal liquefaction; sewage sludge; pre-treatment
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