Thermochemical Treatment of Sewage Sludge Waste: A Pyrolysis Study

Abstract

In this study, the thermal behavior of sewage sludge waste (SSW) samples was examined at three different heating rates 5, 10 and 15 °C/min in inert atmosphere using the technique of thermogravimetric analysis and pyrolysis in a stainless steel tubular reactor. As the increment of pyrolysis temperature and heating rate, the variations of characteristic parameters from TG-DTG curves and the yield of bio-oil, bio-char and gaseous products were determined. Three methods were used for the determination of activation energy: Friedman (FR), Ozawa-Flynn-Wall (OFW) and Vyazovkin (VYA) methods. The results showed that the mean values of apparent activation energy for sewage sludge waste were 162.40 KJ/mol, 141.08 KJ/mol and 150.91 KJ/mol for FR, VYA and OFW methods respectively. The results of our work showed that the amount of liquid product (bio-oil) from pyrolysis in a stainless steel tubular reactor of SSW samples increases with increasing the final temperature and decreases with increasing the heating rate. The highest yield of liquid product is obtained from the samples at 500 °C and at heating rate of 5 °C/min, the maximal average yield achieved almost 30.6 wt%. The yield of char generally decreases with increasing the temperature, the char yield passes from 35.21 wt% to 20 wt% at the heating rate of 5 °C/min and from 31.2 wt% to 17.5 wt% at the heating rate of 15 °C/min at the same range of temperature (200-700 °C). Concerning the yield of gaseous product and conversion degree (x), we notice that the efficiency increase with increasing the final temperature. The results show that final temperature and heating rate have a remarkable effect on the yields products.