Hydrothermal carbonization process (HTC) provides an attractive alternative for the treatment of high moisture waste and in particular digested sludge. HTC could reduce the costs and environ-mental risks associated with sludge handling and management. Although it is recognized that dewaterability of hydrochars produced from digested sludge, even at mild temperature (180-190 °C), is highly improved with respect to the starting material, filterability of HTC slurries for the recovery of the solid material (hydrochar) still represents a challenge. This study presents the re-sults of an investigation on the filterability of agro-industrial digested sludge HTC slurries pro-duced by C-700 CarboremTM HTC industrial scale plant. Filterability of HTC slurries, produced at 190 °C and 1 h, with the use of acid solutions of hydrochloric acid, sulfuric acid or citric acids was investigated by using a semi-industrial filter press. The use of sulfuric acid or citric acid solution, in particular, showed significant improvements in the filterability of HTC slurries reducing time of filtration and residual moisture content. The acid treatment promoted also the migration of heavy metals and phosphorus in the HTC filtrate solution. This study demonstrates that P can be recovered via precipitation of struvite in high yields, recovering up to 85 wt% by mass of its ini-tial P content.
Industrial-scale hydrothermal carbonization of agro-industrial digested sludge: filterability enhancement and phosphorus recovery
Antonio Messineo;Maurizio Volpe
Conceptualization
2021-01-01
Abstract
Hydrothermal carbonization process (HTC) provides an attractive alternative for the treatment of high moisture waste and in particular digested sludge. HTC could reduce the costs and environ-mental risks associated with sludge handling and management. Although it is recognized that dewaterability of hydrochars produced from digested sludge, even at mild temperature (180-190 °C), is highly improved with respect to the starting material, filterability of HTC slurries for the recovery of the solid material (hydrochar) still represents a challenge. This study presents the re-sults of an investigation on the filterability of agro-industrial digested sludge HTC slurries pro-duced by C-700 CarboremTM HTC industrial scale plant. Filterability of HTC slurries, produced at 190 °C and 1 h, with the use of acid solutions of hydrochloric acid, sulfuric acid or citric acids was investigated by using a semi-industrial filter press. The use of sulfuric acid or citric acid solution, in particular, showed significant improvements in the filterability of HTC slurries reducing time of filtration and residual moisture content. The acid treatment promoted also the migration of heavy metals and phosphorus in the HTC filtrate solution. This study demonstrates that P can be recovered via precipitation of struvite in high yields, recovering up to 85 wt% by mass of its ini-tial P content.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
