Hydrothermal carbonization of petrochemical sludge: The fate of hydrochar and oil components

Abstract

In this study, the physical and chemical properties, combustion behaviors, kinetics, and the distribution of C, O, N, and S during different hydrothermal carbonization (HTC) temperatures of petrochemical sludge (PS) were investigated. The increase in HTC temperature is favorable to obtain higher organic-dissolved oil (ODO) content and less water-soluble oil (WSO) content. The solid conversion rate of hydrochar reached a maximum of 83.90% and comprehensive combustion performance is the best at 270 °C. The higher heating values (HHVs) value of hydrochar is stable at 21.00 MJ/kg. While the HHVs value range of ODO and WSO are 32.03–38.65 MJ/kg and 13.90–19.83 MJ/kg, respectively. Except for hard to occur WSO combustion stageⅢ, the Coats-Redfern integral method is well suited for kinetic simulations of all stages of hydrochar, WSO, and ODO. The long-chain alkanes, aromatic hydrocarbons, and cycloalkanes attach to the surface of the solid particles to form ODO and further convert to hydrochar via carbonization process. Nitrogen heterocycles, amines, and ketones remain in the feedwater to form WSO. Therefore, Carbon was maximally preserved in hydrochar and ODO, while N and S were removed by migration into WSO.