Kinetic investigation on the catalytic pyrolysis of plastic fractions of waste electrical and electronic equipment (WEEE): A mathematical deconvolution approach.

Waste electrical and electronic equipment (WEEE) has become a critical environmental problem. Catalytic pyrolysis is an ideal technique to treat and convert the plastic fraction of WEEE into chemicals and fuels. Unfortunately, research using real WEEE remains relatively limited. Furthermore, the complexity of WEEE complicates the analysis of its pyrolytic kinetics. This study applied the Fraser-Suzuki mathematical deconvolution method to obtain the pseudo reactions of the thermal degradation of two types of WEEE, using four different catalysts (Al2O3, HBeta, HZSM-5, and TiO2) or without a catalyst. The main contributor(s) to each pseudo reaction were identified by comparing them with the pyrolysis results of the pure plastics in WEEE. The nth order model was then applied to estimate the kinetic parameters of the obtained pseudo reactions. In the low-grade electronics pyrolysis, the pseudo-1 reaction using TiO2 as a catalyst achieved the lowest activation energy of 92.10 kJ/mol, while the pseudo-2 reaction using HZSM-5 resulted in the lowest activation energy of 101.35 kJ/mol among the four catalytic cases. For medium-grade electronics, pseudo-3 and pseudo-4 were the main reactions for thermal degradation, with HZSM-5 and TiO2 yielding the lowest pyrolytic activation energies of 75.24 and 226.39 kJ/mol, respectively. This effort will play a crucial role in comprehending the pyrolysis kinetic mechanism of WEEE and propelling this technology toward a brighter future.

Reduction of brominated flame retardants (BFRs) in plastics from waste electrical and electronic equipment (WEEE) by solvent extraction and the influence on their thermal decomposition.

Consumption of electronics increases due to modern society's growing needs, which leads to increasing generation of waste electrical and electronic equipment (WEEE). Recycling of WEEE has been a global concern during the last few decades because of the toxic compounds that are produced during recycling. Different recycling techniques have been adapted on a commercial scale in order to overcome this issue, but the recycling of WEEE still lacks the technology to treat different kinds of feedstocks and to maximise the recycling rates. Pyrolysis is an alternative that has not been commercialised yet. One of the challenges for the implementation of this technology is the toxic brominated organic compounds that can be found in the pyrolysis oils. In this study, tetrabromobisphenol A (TBBPA), one of the major flame retardants, is reduced in three different WEEE fractions through solvent extraction as a treatment prior to pyrolysis. Two solvents have been experimentally investigated: isopropanol and toluene, the latter of which can be derived from pyrolysis oil. The results indicate that TBBPA was extracted during pre-treatment. Moreover, the total bromine content of WEEE material was reduced after the treatment with a maximum reduction of 36.5%. The pyrolysis experiments indicate that reduction of several brominated organic compounds was achieved in almost all the tested cases, and two brominated compounds (2,4,6-tribromophenol and 2,5-Dibromobenzo(b)thiophene) reached complete removal. Also, the thermal decomposition behaviour of the raw samples and the treated was investigated, showing that the reduction of TBBPA influences the decomposition by shifting the starting decomposition temperature.

Investigation on the low-temperature pyrolysis of automotive shredder residue (ASR) for energy recovery and metal recycling.

The automotive shredder residue (ASR) or shredder light fraction (SLF) is the remaining fraction from the metal recovery of end-of-life vehicles (ELVs). While processes for metal recovery from ELVs are well developed, the similar process for ASR remains a challenge. In this work, low-temperature pyrolysis of the ASR fraction was investigated under the assumption that a low temperature and inert environment would enhance the metal recovery, i.e. the metals would not be further oxidised from their original state and the organic material could be separated from the metals in the form of volatiles and char. Pyrolysis experiments were performed in a tube reactor operating at 300, 400 and 500 °C. The gas and oil obtained by pyrolysis were analysed by micro-GC (micro-Gas Chromatography) and GC/MS (Gas Chromatography/Mass Spectrometry), respectively. It was found that the gas produced contained a high amount of CO2, limiting the energy recovery from this fraction. The oil consisted of a high concentration of phenolic and aromatic compounds. The solid residue was crushed and fractionated into different particle sizes for further characterization. The pyrolysis temperature of 300 °C was found to be insufficient for metal liberation, while the char was easier to crush at tested temperature of 400 and 500 °C. The intermediate temperature of 400 °C is then suggested for the process to keep the energy consumption low.