Kinetic Study of the Pyrolysis of Waste Printed Circuit Boards Subject to Conventional and Microwave Heating

• Published in: Energies (Basel) Vol. 5; no. 9; pp. 3295 - 3306
• Main Authors: Sun, Jing, Wang, Wenlong, Liu, Zhen, Ma, Qingluan, Zhao, Chao, Ma, Chunyuan
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.09.2012
• Subjects: activation energy; Decomposition; Energy; kinetic study; Kinetics; Metals; Microwave heating; microwave-induced pyrolysis; Printed circuit boards; Temperature; waste printed circuit boards (WPCB); China
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en5093295

This paper describes a kinetic study of the decomposition of waste printed circuit boards (WPCB) under conventional and microwave-induced pyrolysis conditions. We discuss the heating rates and the influence of the pyrolysis on the thermal decomposition kinetics of WPCB. We find that the thermal degradation of WPCB in a controlled conventional thermogravimetric analyzer (TGA) occurred in the temperature range of 300 °C–600 °C, where the main pyrolysis of organic matter takes place along with an expulsion of volumetric volatiles. The corresponding activation energy is decreased from 267 kJ/mol to 168 kJ/mol with increased heating rates from 20 °C/min to 50 °C/min. Similarly, the process of microwave-induced pyrolysis of WPCB material manifests in only one stage, judging by experiments with a microwave power of 700 W. Here, the activation energy is determined to be only 49 kJ/mol, much lower than that found in a conventional TGA subject to a similar heating rate. The low activation energy found in microwave-induced pyrolysis suggests that the adoption of microwave technology for the disposal of WPCB material and even for waste electronic and electrical equipment (WEEE) could be an attractive option.