Kinetic study on the slow pyrolysis of nonmetal fraction of waste printed circuit boards (NMF-WPCBs)
Zhitong Yao, Jingjing Xiong, Shaoqi Yu, Weiping Su, Weihong Wu, Junhong Tang, Daidai Wu
Abstract
In this study, the pyrolysis behaviour of nonmetal fraction of waste printed circuit boards (NMF-WPCBs) was studied based on five model-free methods and distributed activation energy model (DAEM). The possible decomposition mechanism was further probed using the Criado method. Thermogravimetric analysis indicated that the NMF-WPCBs pyrolysis process could be divided into three stages with temperatures of 37–330°C, 330–380°C and 380–1000°C. The mass loss at different heating rate was determined as 26.85–29.98%, 13.47–24.21% and 20.43–23.36% for these stages, respectively. The activation energy ( E α ) from various model-free methods first increased with degree of conversion ( α) increasing from 0.05 to 0.275, and then decreased beyond this range. The coefficient ( R) from the Flynn–Wall–Ozawa (FWO) method was higher, and the resulting E α fell into the range of 214.947–565.660 kJ mol −1 . For the DAEM method, the average E α value was determined as 337.044 kJ mol −1 , comparable with 329.664 kJ mol −1 from the FWO method. The thermal decomposition kinetics of NMF-WPCBs could be better described by the second-order reaction.