The Effect of Residence Time during the Hydrothermal Carbonization Process of Sewage Sludge on the Properties of Hydrochar

Klaudia Czerwińska, Joanna Mikusińska, Aleksandra Błoniarz, Maciej Śliz and Małgorzata Wilk ()
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Klaudia Czerwińska: Department of Heat Engineering and Environment Protection, AGH University of Krakow, 30 Mickiewicza Avenue, 30-059 Krakow, Poland
Joanna Mikusińska: Department of Heat Engineering and Environment Protection, AGH University of Krakow, 30 Mickiewicza Avenue, 30-059 Krakow, Poland
Aleksandra Błoniarz: Department of Surface Engineering & Materials Characterisation, AGH University of Krakow, 30 Mickiewicza Avenue, 30-059 Krakow, Poland
Maciej Śliz: Department of Heat Engineering and Environment Protection, AGH University of Krakow, 30 Mickiewicza Avenue, 30-059 Krakow, Poland
Małgorzata Wilk: Department of Heat Engineering and Environment Protection, AGH University of Krakow, 30 Mickiewicza Avenue, 30-059 Krakow, Poland

Energies, 2024, vol. 17, issue 14, 1-13

Abstract: The optimal process conditions concerning the hydrothermal carbonization of digested sewage sludge are crucial to the economically effective technology needed to produce a solid product, hydrochar, for energy purposes. Accordingly, different residence times, 0.5 h, 1 h and 2 h, were investigated in order to understand the effect of residence time on the process. Furthermore, the physical and chemical properties of hydrochar were investigated and compared to the raw material. For these reasons, analyses describing fuel properties were performed, including ultimate and proximate analyses, HHV, and TGA analysis. The latter method was employed to study the combustion process of solid samples. In addition, the oxide content of different elements within the ash of solid samples was determined using the XRF method to calculate indices related to operational problems during the combustion process. The results confirmed that time did not matter significantly and the physical and chemical properties of hydrochar were very similar to each other. However, the contact angle for 2 h of residence time confirmed that a longer processing time resulted in a more hydrophobic character of hydrochar and enabled more effective dewaterability of hydrothermal slurry. It was also noted that the hydrothermal carbonization process affected the sewage sludge in a positive way. In brief, the results confirmed that the hydrochar was a brittle, moderately hydrophilic, solid carbon-containing product that provided a different combustion performance than the raw sewage sludge.

Keywords: hydrothermal carbonization; sewage sludge; residence time; hydrochar (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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