Feedstock recycling from plastic and thermoset fractions of used computers (I): pyrolysis

Abstract

The increasing production of computers, the progress in their performance, and the shorter time between innovation and production has led to increasing numbers of obsolete products. It has thus become necessary to recover some materials from old computers and to protect the environment from a new type of pollution. Such recycling is difficult because of the diversity of polymeric materials used, e.g., thermoplastics (polystyrene or acrylonitrile-butadienestyrene) and thermosets (epoxy resins), and the relatively high levels of flame retardants (halogen-and nitrogencontaining compounds) added during production. Pyrolysis seems to be a suitable way to recover materials and energy from such waste without component separation if an efficient method for reducing toxic compounds can be applied. In this study, the pyrolysis of plastic and thermoset fractions (keyboards, casings, printed circuit boards, and mixtures thereof) of used computers was studied by thermogravimetry and batch reactor pyrolysis. The degradation products were separated into three fractions, solid, liquid, and gaseous, each of them being characterized by suitable methods such as gas chromatography (GC-MSD, gas chromatography-mass spectrometry detection; GC-AED, gas chromatography-atomic emission detection), infrared (FT-IR) and 1H-NMR (nuclear magnetic resonanace) spectroscopy, and elemental analysis. It has been established that most of the halogens, nitrogen, and sulfur is concentrated in the residue. However, the elimination of hazardous toxic compounds, mainly those containing bromine, is necessary before being able to safely use the pyrolysis oils as fuels or in refinery or petrochemical industry flows.

Alternative Reducing Agents in Metallurgical Processes: Devolatilization of Shredder Residue Materials

“…The observation of two stages during devolatilization of plastics derived from electrical and electronic equipment is in agreement with the findings of other researchers [24,25]. Vasile et al [24] studied devolatilization of keyboards and computer case, and reported that devolatilization starts at about 250°C, with release of halogenated compounds mainly due to presence of PVC.…”

“…Vasile et al [24] studied devolatilization of keyboards and computer case, and reported that devolatilization starts at about 250°C, with release of halogenated compounds mainly due to presence of PVC. At temperatures higher than 370°C, releases of phenol and alkyl aromatic compounds were observed.…”

Pollution profiles and health risk assessment of VOCs emitted during e-waste dismantling processes associated with different dismantling methods

“…For instance, styrene was the most significant constituent during the pyrolysis and combustion of mobile phones (PCBAs and casing) and PCBAs alone (Moltó et al, 2009). Similarly, both the casings and keyboards of computers provide mainly aromatic derivatives, especially styrene and ethylbenzene and then toluene during pyrolysis (Vasile et al, 2006). In contrast, the predominant constituent of AHs was toluene (86.3%) in RI-HD, and the others are trivial (0-1.2%) except benzene (4.9%) and styrene (4.6%), which is different from the reported results of (Vasile et al, 2006) suggesting that phenol and its derivatives were the most abundant compositions during the pyrolysis of computer PCBAs.…”

“…Similarly, both the casings and keyboards of computers provide mainly aromatic derivatives, especially styrene and ethylbenzene and then toluene during pyrolysis (Vasile et al, 2006). In contrast, the predominant constituent of AHs was toluene (86.3%) in RI-HD, and the others are trivial (0-1.2%) except benzene (4.9%) and styrene (4.6%), which is different from the reported results of (Vasile et al, 2006) suggesting that phenol and its derivatives were the most abundant compositions during the pyrolysis of computer PCBAs. This difference is due to the poor volatility of phenol leading low detected concentration in gas phase.…”

Effect of the Bromine-Based Flame Retardant Plastic Pyrolysis of Hydrotalcite

“…For example, the yield of the product oil can be increased using ZSM-5 zeolite red mud mesoporous molecular sieve in the pyrolysis of plastics [18,19]. However, the toxic brominated flame retardant is a problem for plastic recycling of household electrical appliances [20][21][22][23][24]. The generation of harmful byproducts has been studied to prevent the release of halogen gas, and additives have been used to promote recycling [22].…”