The pyrolysis of automobile shredder residue (ASR) has been studied using a laboratory scale screw kiln reactor with a feed rate of about 100 g h − 1. Pyrolysis at temperatures between 500 and 750°C resulted in the production of gas, liquid and solid fractions with hydrocarbon yields of the organic fraction present in the feed increasing from 60 -85% with increasing pyrolysis temperature. While the hydrocarbon pyrolysis product yield increased with pyrolysis temperature, the yield of the oil fraction was higher at the lower pyrolysis temperatures. The composition of the pyrolysis oil also changed with pyrolysis temperature, containing larger quantities of aliphatic compounds at the lower temperatures than at higher temperatures where aromatics were the major compounds. Many of the liquid pyrolysis products have been identified including polycyclic aromatic hydrocarbons as well as organo nitrogen, sulphur and chlorine compounds. The data obtained have been compared with that obtained from a process using short pyrolysis residence times.

SynopsisThe high temperature engineering thermoplastic poly(ary1-ether-ether-ketone) (PEEK) has been subjected to dynamic and isothermal thermogravimetry in both nitrogen and air. The dynamic data have been analyzed using both the Kissinger peak maximum technique and an isoconversional procedure developed by Flynn. These techniques gave apparent global activation energies of 223.5 and 235.7 kJ/mol, respectively, for the degradation of PEEK in nitrogen, in good agreement with the value of 219.7 determined from the isothermal experiments. The thermal stability of PEEK in air is substantially less than in nitrogen, and the decomposition mechanism is more complex. The global apparent activation energies for the weight loss in air were found to be 116.9 and 159.5 kJ/mol from dynamic slow heat rate data and isothermal data, respectively. The data obtained from fast heating rate experiments in air were found to be misleading, suggesting caution in the use of "commercial" software packages for lifetime estimates under these conditions, especially where oxidative processes may be occurring.

The thermal decomposition of poly(ethylene terephthalate) has been studied using a conventional dynamic thermogravimetric technique in a flowing air atmosphere at several heating rates between 0.1°C and 100°C/min. The dynamic thermogravimetric analysis curve and its derivative have been analyzed using a variety of analytical methods reported in the literature to obtain information on the kinetic parameters. The degradation was found to be a complex process composed of at least three overlapping stages for which kinetic values can be calculated. The best approaches to solving the kinetics of the decomposition were found to be the multiple heating rate techniques of Friedman and Ozawa. The Friedman technique gave apparent activation energies (kJ/mol) for the three main decomposition stages of 122.2 ± 12.9, 201.0 ± 8.5, and 141.9 ± 12.7, with a value of 85.5 ± 10.2 for the prestage at low conversion. The Ozawa method, meanwhile, gave values of 101.6 ± 2.6, 182.6 ± 7.4, 142.5 ± 3.8, and 158.4 ± 26.1 for the prestage.

Degradation of contaminated plastics : A kinetic study

The pyrolysis of three plastics used by the electronics industry has been studied using pyrolysis/gas chromatography/mass spectrometry (Py/GC/MS). The materials selected for this study were acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC) and polyoxymethylene (POM). The selection was based upon the analysis of several pieces of electronic equipment, which had been the subject of laboratory studies. Each polymer was pyrolyzed at two pyrolysis temperatures (700 and 900°C) alone, together (side by side) with polyvinyl chloride (PVC) in a 50/50 co-pyrolysis experiment, and as an intimate chemical blend with PVC (50/50). In addition the three polymers were also pyrolyzed in the presence of copper powder to determine the role of copper contamination on the pyrolysis of each polymer. The results of the study suggest that both the presence of PVC and copper can influence the extent of degradation and the pyrolysis product distribution obtained when these polymers are pyrolyzed. However, no significant changes were noted that could drastically influence the value of the pyrolysis products.