Hydrothermal Carbonization of Sewage Sludge: Analysis of Process Severity and Solid Content

• Published in: Chemical engineering & technology Vol. 43; no. 12; pp. 2382 - 2392
• Main Authors: Tasca, Andrea Luca, Stefanelli, Eleonora, Raspolli Galletti, Anna Maria, Gori, Riccardo, Mannarino, Gemma, Vitolo, Sandra, Puccini, Monica
• Format: Journal Article
• Language: English
• Published: Frankfurt Wiley Subscription Services, Inc 01.12.2020
• Subjects: Cadmium; Carbonization; Copper; Dewaterability; Energy requirements; Hydrothermal carbonization; Lead; Nickel; Response surface methodology; Sewage sludge; Sludge; Specific resistance to filtration
• ISSN: 0930-7516; 1521-4125
• DOI: 10.1002/ceat.202000095

Hydrothermal carbonization of sewage sludge was carried out with the aim to evaluate the influence of process severity and initial solid content. Response surface methodology was applied to model yield and C yield responses. Enhanced dewaterability performance was recorded under mild processing conditions. The treatment promoted concentration and immobilization of Pb, Cd, Ni, Zn, and Cu. Variation of the solid content showed a stronger influence than severity on average yield and C yield. Higher heating values (HHVs) and energy retention efficiencies (EREs) of hydrochars obtained at the lowest solid content displayed the lowest values. Hence, the energy requirements of a first dewatering step should be compared with the related improvement in terms of HHV and ERE when sludge is used as feedstock. The influence of process severity and initial solid content was estimated in hydrothermal carbonization of sewage sludge. Response surface methodology was applied to model yield and C yield responses. Enhanced dewaterability performance was found for mild processing conditions. Higher heating values and energy retention efficiencies of hydrochars obtained at the lowest solid content had the lowest values.