Physicochemical Analysis of Hydrothermal Upgraded Municipal Sewage Sludge with Low-Rank Lignite

Abstract

From the perspective of renewable energy and the waste utilization to produce high-grade fuel from municipal sewage sludge and low-rank lignite has a great significance, which not only can reduce the current dependence on fossil fuels, but also be able to solve the problem of sludge disposal. In this paper, the authors reported on the dehydrated and upgraded the municipal sewage sludge (MSS) and Inner Mongolia (IM) lignite according to certain proportions in autoclave, where the sludge coal ratio is 1:9, temperature range is 150–300 °C, and the residence time is 1 h. The original moisture content of the MSS is 82.27 %. The results show that with the increasing modification temperature, the solid yield of the upgraded solid product decreased, and when the reaction temperature is 300 °C, the solid yield is 83 %. The ultimate analysis and proximate analysis before and after modification of the solid product show that the moisture content of the upgraded solid product was significantly reduced with modified temperature increasing. While the fixed carbon content increased, the heat value is also greatly improved, and the solid product also becomes hydrophobic and hard to re-adsorb the lost moisture, which indicates coalification occurred during the process of upgrading. The changes of functional groups and carbon structures of the upgraded solid product were mainly determined by Fourier transform infrared spectroscopy (FTIR), ¹³C nuclear magnetic resonance spectrometer (¹³C-NMR).