Conversion of sewage sludge from industrial wastewater treatment to solid fuel through hydrothermal carbonization process

Abstract

Sludge is the unwanted solid waste produced during the treatment of industrial wastewater. The hydrothermal carbonization process (HTC) can be used to convert sewage sludge into a coal-like solid fuel. The effects of solid-to-liquid ratio and feed water pH on the physicochemical properties of hydrochars were investigated. According to the results, hydrothermal treatment enhanced the fuel characteristics of hydrochar with a high HHV and fixed carbon. Adding 0.8 M acetic acid resulted in the highest rate of energy recovery at 96.98 %. The observed H/C and O/C atomic ratios of HTC-0.4AA have been lowered to levels comparable to lignite coal. ICP-OES confirmed the presence of the metal in the hydrochar product. Examining the thermogravity analysis of raw materials and hydrochars with a TGA analyzer was then used to determine the combustion kinetics. In addition, combustion characteristics indicate that HTC improves the S combustibility index.