Pyrolysis of e-waste: Kinetics and modeling
The global production of electric and electronic waste (e-waste) is increasing at an alarming rate in the recent years. The worldwide annual disposal of e-waste is estimated to be around 20-50 million metric tons. Pyrolysis is a viable option and a possible substitute to incineration and landfill of e-waste for resource and energy recovery. This study provides a comprehensive kinetic analysis of the pyrolysis of e-waste for the successful design of thermochemical processes for its effective treatment. In this study, non-isothermal experiments were conducted using thermogravimetric analysis (TGA) for two different samples viz. Printed Circuit Board (PCB) and Keyboard Keys (KB), in three different ratios of PCB : KB – 1 : 0, 0 : 1 and 1 : 1 respectively. The experiments were conducted in N2 atmosphere at four different heating rates viz. 10, 20, 30 and 40 °C min-1. The kinetic study was carried out using isoconversional methods such as Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO), model free method such as Kissinger, model fitting method such as Coats and Redfern equation. The average activation energy (Ea) obtained by KAS and FWO methods was in the range of 164-180 kJ mol-1, which is in good agreement with the value obtained by Kissinger method. The major pyrolysates at 500°C from PCB pyrolysis were identified as phenolic derivatives, oxygenated and aliphatic hydrocarbons with of 34%, 19%, and 13% selectivites respectively, while KB pyrolysis yielded styrene and nitrogen containing compounds with selectivites of 52% and 32% respectively.
Keywords: Pyrolysis, PCB, KB, Isoconversional method, model-fitting, activation energy.