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Article Dans Une Revue Chemical Engineering Journal Année : 2023

Phosphorus extracted municipal sludge-derived hydrochar as a potential solid fuel: Effects of acidic leaching and combustion mechanism

Résumé

Hydrochar from hydrothermal liquefaction (HTL) of municipal sludge is often seen as waste. Initially, acidic leaching has been performed on hydrochar to recover phosphorus. This study evaluated the resulting hydrochar as solid fuel, thus achieving zero waste for integrating HTL into wastewater treatment plants. The effects of various leaching conditions on acid-modified hydrochar properties were examined. Compared to raw hydrochar, acid-modified hydrochar had a significant ash reduction (up to 44%). The leaching conditions (10 mL of 0.6 N HNO3/g for 2 h) for near-complete phosphorus extraction also achieved the following most desirable properties of acid-modified hydrochar: Maximized fuel ratio (1.3), higher heating value (20.5 MJ/kg), carbon content (48%), and minimized ash content (34%) on a dry basis. By removing most alkali and alkaline earth metals, acid-modified hydrochar could carry a low slagging and fouling risk compared to a high/severe risk for raw hydrochar. Acidic leaching also enhanced ignition temperature from 317 to 351 °C for safer storage and transportation of hydrochar, with a higher comprehensive combustion index (up to 9.9 × 10−8 min−2 °C−3). Overall, hydrochar fuel property was improved by acid modification, comparable to bituminous coal. For the first time, it was identified that hydrochar combustion was controlled by a two-step nth-order reaction mechanism f(α) = (1 − α)n with the reaction order changing from 3 to 1 as progressed. The acid modification did not affect combustion mechanisms but reduced activation energy in the first stage. The results demonstrated a sustainable approach for closing the waste loop and provided a pathway for transforming hydrochar into biofuel.
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Dates et versions

hal-04203217 , version 1 (13-09-2023)

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Huan Liu, Nathalie Lyczko, Ange Nzihou, Cigdem Eskicioglu. Phosphorus extracted municipal sludge-derived hydrochar as a potential solid fuel: Effects of acidic leaching and combustion mechanism. Chemical Engineering Journal, 2023, 473, pp.145191. ⟨10.1016/j.cej.2023.145191⟩. ⟨hal-04203217⟩
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