Study of Hydrothermal Carbonization Treated Digested Sewage Sludge Pyrolysis through TGA And Py-GC/MS

摘要

In EU countries, more than 10 million tons of dry matter of digested sewage sludge is produced annually. The solid residue from AD of sewage sludge, digested sewage sludge (DSS), is currently mainly used as soil fertilizer because of its high nitrogen, phosphorous content and abundance of organic matters, which is mainly treated by incineration and landfill nowadays. Its high organic content makes it an interesting potential resource for value-added fuel and materials productions. Main challenges of utilization of DSS are water removal from its polymeric matrix, as well as disinfection. Hydrothermal carbonization (HTC) treatment has been proven as a promising technology that can overcome these difficulties to produce biocoal from sludge. Pyrolysis of biomass can provide widely applicable products such as liquid, syngas and coke. Thus, an integrated solution, starting with HTC then followed by pyrolysis to use DSS shall be of interesting, which lead to this work. Based on this solution, HTC treated digested sewage sludge (HDSS) was chosen in this study for pyrolysis experiment. The HDSS has been studied through thermogravimetric analysis to investigate its thermal decomposition properties. Thereafter, pyrolysis of HDSS has been studied in a Py-GC/MS setup, where a Pyrola2000 unit was employed to investigate the influence of pyrolysis temperature in a range of 450 -650 °C. Preliminary results show that the thermal decomposition of HTC biocoal from HDSS is a two-stage reaction, 25 % mass loss happened between 120 - 600 °C, while 14 % mass loss happened between 600 - 900 °C. The maximum peak area percentage of aromatic hydrocarbons was found as 13 % under 650 °C in pyrolytic vapor. Low peak area percentage of acids was found, which could be a result of the catalytic effect of ashes in the feedstock.