Hydrothermal Carbonization Process of Digestate from Sewage Sludge: Chemical and Physical Properties of Hydrochar in Terms of Energy Application

Małgorzata Wilk, Marcin Gajek, Maciej Śliz, Klaudia Czerwińska and Lidia Lombardi
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Małgorzata Wilk: Department of Heat Engineering and Environment Protection, AGH University of Science and Technology, Mickiewicza 30 Av., 30-059 Kraków, Poland
Marcin Gajek: Faculty of Materials Science and Ceramics, AGH University of Science and Technology, Mickiewicza 30 Av., 30-059 Kraków, Poland
Maciej Śliz: Department of Heat Engineering and Environment Protection, AGH University of Science and Technology, Mickiewicza 30 Av., 30-059 Kraków, Poland
Klaudia Czerwińska: Department of Heat Engineering and Environment Protection, AGH University of Science and Technology, Mickiewicza 30 Av., 30-059 Kraków, Poland
Lidia Lombardi: Niccolò Cusano University, Via don Carlo Gnocchi 3, 00166 Rome, Italy

Energies, 2022, vol. 15, issue 18, 1-17

Abstract: Hydrochars (HTCD) derived from digestates, namely D1 and D2 (from two plants) of sewage sludge, were examined with respect to their fuel properties. The hydrothermal carbonization (HTC) tests were performed at temperatures of 200 and 220 °C, for 2 and 4 h of residence times, and with 1:10 and 1:8 digestate to water ratios (D/W), causing an increase of ash content (max. 55.8%), and a decrease c.a. 20% of the higher heating value except for a slight increase to 15 kJ/kg at 200 °C and 4 h in hydrochars. Conversely, the combustion profiles of hydrochars moved towards higher temperatures (225–257 °C) and finished earlier at lower temperatures (423–438 °C). The HTCD from D1 and D2 showed very similar properties under the same conditions (200 °C, 4 h, 1:8 D/W) for combustion characteristic temperatures, indices and profiles. The best efficiency was found for HTCD2. In addition, the polluted post-processing liquid phase was treated by a distillation process providing 30% higher pH, 50% lower BOD values, up to 15 times lower COD values, and c.a. three times lower conductivity.

Keywords: hydrothermal carbonization; sewage sludge; hydrochar; digestate; thermal analysis; post-processing water (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: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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