ARTICLE pubs.acs.org/est
Environmental Impact of Pyrolysis of Mixed WEEE Plastics Part 1: Experimental Pyrolysis Data Sue M. Alston,*,† Allan D. Clark,‡ J. Cris Arnold,† and Bridget K. Stein§ †
Materials Research Centre, Swansea University, Singleton Park, Swansea SA2 8PP, U.K. ITEM Wales Ltd, 11 Heol Morlais, Llannon, Carmarthenshire SA14 6BD, U.K. § EPSRC National Mass Spectrometry Service Centre, Swansea SA2 8PP, U.K. ‡
bS Supporting Information ABSTRACT: Growth in waste electrical and electronic equipment (WEEE) is posing increasing problems of waste management, partly resulting from its plastic content. WEEE plastics include a range of polymers, some of which can be sorted and extracted for recycling. However a nonrecyclable fraction remains containing a mixture of polymers contaminated with other materials, and pyrolysis is a potential means of recovering the energy content of this. In preparation for a life cycle assessment of this option, described in part 2 of this paper set, data were collected from trials using experimental pyrolysis equipment representative of a continuous commercial process operated at 800 °C. The feedstock contained acrylonitrile-butadiene-styrene and high impact polystyrene with high levels of additives, and dense polymers including polyvinylchloride, polycarbonate, polyphenylene oxide, and polymethyl methacrylate. On average 39% was converted to gases, 36% to oils, and 25% remained as residue. About 35% of the gas was methane and 42% carbon monoxide, plus other hydrocarbons, oxygen and carbon dioxide. The oils were almost all aromatic, forming a similar mixture to fuel oil. The residue was mainly carbon with inorganic compounds from the plastic additives and most of the chlorine from the feedstock. The results showed that the process produced around 70% of the original plastic weight as potential fuel.
’ INTRODUCTION The growth in waste electrical and electronic equipment (WEEE) is posing an increasing problem of waste management. The EU was estimated to dispose of 9.5 million tonnes of WEEE in 2008, and this was forecast to rise to 12.3 million tonnes by 2020.1,2 Historically the only WEEE recycled on a large scale in the UK has been large household appliances (e.g., washing machines, refrigerators), either because they contain ozone depleting substances or for their scrap metal value. The remainder has been untreated and mostly sent to landfill.3 However landfill space is becoming scarcer, and there is a need to make use of products’ embodied energy both to decrease dependency on natural sources of fuel, and to reduce the climate change implications of further energy use. Typically WEEE contains 20 25% plastics.4 A range of different polymers are in use; an example of the breakdown from actually collected WEEE is acrylonitrile-butadiene-styrene (ABS) 30%, high impact polystyrene (HIPS) 25%, polycarbonate (PC) 10%, PC/ABS 9%, polypropylene (PP) 8%, polyphenylene ether(PPE)/HIPS 7%, polyvinyl chloride (PVC) 3%, polystyrene (PS) 3%, polyamide (PA) 3%, polybutylene terephthalate (PBT) 2%.5 Recent improvements in sorting methods are enabling an increasing proportion of these to be extracted for mechanical recycling. Density sorting is most commonly used r 2011 American Chemical Society
and can separate light polymers (e.g., PP, polyethylene (PE)) and medium ones (e.g., ABS, HIPS without significant additives). However, this leaves a mixed “heavy fraction” containing less common denser polymers, those with high additive content (including brominated flame retardants (BFRs)) and contaminants. The complexity of the mix and small quantity of individual polymers mean that this is not currently recycled. A possible alternative to landfill for treatment of this heavy fraction is pyrolysis, giving breakdown products which can be used as fuels in place of gas, diesel or fuel oils. Many studies of pyrolysis of relevant polymers have been published, showing a wide range of gas and liquid yields. Pyrolysis of styrenic polymers such as ABS, HIPS, and styrene-acrylonitrile (SAN) has been reported to produce benzene, toluene, styrene, ethylbenzene, 2-propenenitrile, naphthalene, and a range of other aromatic compounds; in the case of acrylonitriles the aromatics may have attached nitrile functional groups and quinoline may be produced.6 9 The gas yields found varied considerably, from negligible8 to 26%6 at 400 500 °C, and increasing to over 40% Received: May 16, 2011 Accepted: September 22, 2011 Revised: September 21, 2011 Published: September 22, 2011 9380
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Figure 1. Schematic of experimental rig.
at 875 °C.7 Results for polycarbonate at a slower temperature ramp showed that the oxygen content in the polymer led to phenol compounds in the oils and carbon dioxide in the gas.10,11 The presence of brominated flame retardants in the feedstock could lead to brominated organic compounds in the oils and antimony tribromide in both the oils and residue.12,8,9 PVC undergoes two stages of decomposition during slow heating, with the formation of hydrogen chloride at around 300 °C followed by the production of aromatics from the remaining polyene backbone at about 450 °C. If PVC is mixed with other polymers then the hydrogen chloride can react with other breakdown products to form chlorinated organic compounds.13 Polyolefins have been found to produce higher proportions of gas, ranging from 34 to 57%, with oils containing linear hydrocarbons as well as some benzene, toluene and naphthalene.14 16 The addition of 20% PE or PP to HIPS was found to increase the gas proportion from less than 1% to around 8%.17,18 The products from WEEE plastics of specific types (e.g., wire cladding, table phones, mobile phones) reflected the polymers involved in each case,19 with the trials being carried out at a slow ramp rate and resulting in relatively low gas levels. The environmental effect of using pyrolysis to deal with WEEE plastics can only be assessed if data is available for the specific process being considered, since published research clearly indicates a significant dependence of pyrolysis products on the plastic mix, temperature and ramp rate. A commercial process is likely to be continuous, in order to maximize productivity, meaning that feedstock would be introduced to a preheated chamber and undergo very rapid heating. It would also operate at a temperature sufficiently high to avoid dioxin formation, probably above 600 °C. In preparation for carrying out a life cycle assessment (LCA) to establish the environmental impact, experimental work was undertaken to identify the pyrolysis products from such a process. The equipment design was based on a pilot plant developed and patented by ITEM Technology Solutions Ltd.20 which had been used for plastics from agricultural and municipal waste. This study looked specifically at the
potential for use of this process for WEEE plastics remaining after density sorting. This paper forms the first part of a two part paper set, with part 2 describing the LCA study based on the data.
’ MATERIALS AND METHODS Materials. The trial feedstock was obtained from Axion Polymers (Salford, UK) and consisted of the “heavy fraction” of mixed WEEE plastics after shredding and density sorting. This fraction was expected to contain all polymers heavier than ABS and HIPS, together with those containing significant amounts of higher density additives, including BFRs. Two batches of shredded material were provided, in the form of granules from 1 mm to 10 mm in size. Pyrolysis Process. The experimental equipment was designed to be as representative as possible of the ITEM Technology Solutions Ltd. process. The design is shown in the schematic in Figure 1. Feed material was ground in a ball mill to produce granules less than 4 mm in size, then introduced to the rig through two gate valves, between which an argon purge was fed. When released from the second valve, the material fell into a “boat”, which was then pushed into the pyrolysis cylinder, rotated to deposit the material, then retracted. The pyrolysis cylinder itself was rotated during operation to allow the feed material to reach temperature as quickly as possible. The pyrolysis products then passed through a filter, maintained at 400 °C, to remove dust and soot. Two flasks containing glass balls, kept cool with ice, were used to condense out volatiles, and then the gases passed through distilled water to dissolve any soluble gases such as hydrogen chloride, hydrogen bromide, hydrogen cyanide, or ammonia. Gas sampling was carried out via a T-piece and valve after the last flask. A pressure gauge at the entry to the filter and a valve at the system outlet were used to control to around 20 mbar above atmospheric pressure to reduce risk of air ingress. Repeated “boatfuls” of feed material were processed until a steady flow of 9381
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Figure 2. Comparison of residues with ground polymers and ash for (a) Batch 1 and (b) Batch 2 (note different scales).
pyrolysis gases reached the final outlet, at which point samples were taken. The residence time was estimated as around 6 min. Analytical Methods. In order to get an indication of the difference between the two batches of plastic supplied, a basic density sorting exercise was carried out by dropping a random sample of granules from each batch into salt solution at a specific gravity of 1.1, determined using a hydrometer. The density level was selected so that polyolefins and ABS and HIPS granules without significant additives would float, but those with BFRs, plus heavier polymers such as PVC, would sink. It was found that 60% of the second batch sank, compared to only 16% of the first batch. This indicated that the sorting method had been tuned between the batches so as to retain more of the higher quality, lighter material for mechanical recycling. Polymer type analysis of individual granules was carried out using Fourier transform infrared spectroscopy (FTIR), after compression molding to provide a suitable surface. This used a Perkin-Elmer Spectrum One FT-IR spectrometer in reflectance mode. A random sample of 211 granules from Batch 1 contained 46.3% ABS/SAN, 40.9% HIPS, 1.5% PVC, 1.2% PP, and 10.1% other; a more limited but visually representative sample of 25 granules from Batch 2 contained 12% ABS/SAN, 20% HIPS, 40% PVC and other chlorinated polymers, and 28% other. The increased percentage of chlorinated and “other” polymers in Batch 2 correlated with the higher proportion of denser granules in this batch. The elemental content of the plastics was identified using energy dispersive X-ray analysis (EDX) with a Jeol JSM-35C scanning electron microscope linked to Oxford Instruments Link ISIS software. Samples were prepared from a random selection of granules by two methods, chosen so as to obtain results representative of the bulk of the plastics not just the surface. These were, first, to grind the granules to a powder, and second, to heat them in air at 700 °C until all organic content had been removed to produce an ash. In each case the resulting powder was scattered on to an adhesive disk 1 cm in diameter and an average taken from five scans, each covering a different area of around 1 mm2. In the case of the ground polymer each scan covered about 100 different particle surfaces, mostly from the inside of original granules. The ashing process entirely removed the original granule structure to give a much finer powder. There is the possibility of some additional oxygen being incorporated onto these newly created surfaces during their preparation, but
the oxygen content from EDX was not a significant factor in the LCA. The results are shown as part of Figure 2. Batch 2 showed a significantly higher percentage of chlorine, corresponding to the higher proportion of PVC, and also of calcium; calcium carbonate is commonly used as filler for PVC, sometimes with a calcium stearate coating. Generally the ground polymer and ash results showed a similar pattern. Where differences did occur the reasons for these were not entirely clear, although some elements other than carbon might have been lost during the ashing process. Bromine was not found in the ground polymer but EDX analysis of individual granules confirmed its presence as found in the ash, suggesting that the concentration in the overall mix was too low to be detected. The amount found in the ash was taken to be a reasonable indication of the amount in the polymer; the results from individual granules were for a smaller sample and for the surface only so could not be treated as quantitative. The pyrolysis results were based on four trials. One was carried out on the first batch of material and three on the second batch of material. All used a pyrolyser temperature of 800 °C. The gases from each trial were collected in a gas collection bottle and subsequently extracted through a septum seal for analysis. A range of compounds was expected, including light hydrocarbon gases, vapor from heavier hydrocarbons, and oxygen- and nitrogen-containing gases. No single analysis method was suitable for the whole of this range and so a range of methods was used. Immediate analysis for C1 C5 compounds was carried out using a Philips PU 4400-19 chromatograph with a flame ionization detector (GC/FID), using a wide bore (0.53 mm inside diameter) 50 m Restek RT-Alumina PLOT (porous layer open tubular) column with a 6 μm film thickness. This was calibrated by running a known mixture of C1 C4 gases before each analysis. A temperature program of 40 °C for 6 min, then a ramp at 5 °C/min to 200 °C and hold for 30 min, was used. At the same time samples of 20 30 μL were extracted from the gas collection bottle and passed through a thermal desorption tube for later analysis (TD/GC/MS). Tenax was used as an adsorbent, with an approximate volatility range from C6 to C26. Analysis was carried out using a Markes International Ultra TD/ Unity desorption unit, connected to an Agilent 6890N GC and Agilent 5973 MS with electron impact ionization. A 30 m 0.25 mm 0.25 μm HP5-MS GC column was used, with a temperature program ramping from 40 to 200 °C at 5 °C/minute then holding for 8 min. Direct injection of 2 μL samples of collected 9382
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Table 1. Overall Percentage Weight Breakdown of Pyrolysis Products Batch 1 permanent gases methane
30.4
Batch 2
Batch 2
average
std dev
45.5
4.8
9.6
17.1
2.0
11.7
21.0
2.4
ethane
1.2
1.2
0.1
ethene
4.6
4.6
0.7
propene
0.1
0.2
0.04
C4 hydrocarbons
0.1
0.1
0.1
oxygen
1.1
0.6
0.2
carbon dioxide sulfur dioxide
1.4 0.5
0.7 0.02
0.3 0.02
carbon monoxide
propenenitrile oils + tars
0.1 46.1
0.02 27.8
0.03 4.7
benzene
23.7
13.3
4.3
toluene
5.3
2.6
1.5
styrene
1.0
0.7
0.6
chlorobenzenes
0.2
0.01
0.02
other < c8 naphthalene
0.2 3.8
0 4.9
0 2.3
benzo- and naphthalene carbonitrile
0.6
0.2
0.1
other 2 ring aromatic
1.4
1.4
1.0
3 ring aromatic
5.2
2.1
1.4
4 ring aromatic
3.2
1.9
1.2
5 ring aromatic
0.3
0.2
0.1
alcohols, aldehydes, esters
0.9
0.4
0.3
other c8+ residues
0.3
0.1
0.1
23.5
26.7
total potential fuel
73.4
72.0
1.0
gases into a GC/MS was used to give an indication of the levels of carbon dioxide, oxygen and nitrogen oxides. This used an Agilent 7890A GC with a 30 m 250 μm 0.25 μm HP5-MS column, connected to an Agilent 5975C MS system using electron impact ionization. Finally a Finnigan MAT 95 XP double-focusing mass spectrometer with electron impact ionization was used to quantify the amount of carbon monoxide and check for the presence of ammonia. A direct injection of a 10 μL sample from the gas collection bottle was made. The above two instruments were also used to analyze the oils, using both electron impact (EI) and chemical ionization (CI). In this case the GC temperature program comprised a hold at 30 °C for 1 min, then a ramp at 30 °C/min to 300 °C and a final hold for 5 min. The contents of the water flask were investigated in two ways. FTIR in reflectance mode as described above was used to look for the presence of CtN triple bonds indicating the presence of HCN. Samples dissolved in methanol were analyzed using a Waters ZQ4000 low resolution single quadrupole mass spectrometer with electrospray ionization, and spectra collected for both negative and positive ions. Neither of these methods indicated any significant dissolved compounds. The elemental breakdown of the residues collected from the pyrolyser and filter was obtained using EDX analysis, after the residues had been ground to a fine powder. As above, five scans were carried out for each sample from different areas of powder.
’ RESULTS AND DISCUSSION Gas and Oil Analysis. Analysis of the gases and oils was strongly interdependent since, as well as permanent gases, the collected gases contained vapor from the oils, the proportions depending on the volatility of individual components in the oils and the effectiveness of the condensing flasks. The composition of the oils was therefore obtained by adding the amounts of volatile compounds from the gas analysis to the results from the oil analysis. Quantification of oils and gases is given in Table 1. GC/FID analysis of the gases showed 99.5 molar % of the detectable gases to be methane, ethane, ethene, propene, benzene, toluene and styrene. Around 93 molar % of the compounds detected by TD/GC/MS analysis were benzene and toluene (percentages based on peak area). The remainder included linear, cyclic and aromatic hydrocarbons, alcohols, acids, aldehydes and nitriles, with little difference between the two batches. Both also indicated the presence of carbon dioxide and sulfur dioxide. Halogenated compounds found were small percentages of chloro- and dichloro-benzene. Direct injection GC/MS analysis of the gases showed approximately equal molar concentrations of oxygen and carbon dioxide but no nitrogen oxides. High resolution mass spectrometry showed the molar percentage of carbon monoxide to be 70% of that of methane. A check was also made for ammonia but none was found. The four sets of gas analysis data each provided relative percentages of the compounds identified by the corresponding method. In order to combine them to cover all the gases found, some common compounds were required. Benzene, toluene, and styrene were identified from the GC/FID, TD/GC/MS, and GC/MS results and were used to match these, whereas methane enabled the accurate mass data to be matched to the GC/FID results. The data were then converted to weight percentages to give an overall breakdown. The condensed “oils” produced by the pyrolysis process were yellow/brown in color and included both a fairly low viscosity liquid and sticky tar. Since the GC/FID and TD/GC/MS results had shown the presence of benzene and toluene, a solvent which would allow these to be identified was required for GC/MS analysis. Ethanol together with EI was used and approximate quantification carried out taking account of the lower solubility of some of the compounds in ethanol. Samples were also dissolved in toluene to provide further information on higher molecular weight compounds and analysis was carried out using both EI and CI. The range of compounds found was the same for both batches of material. Almost all were aromatic or polyaromatic hydrocarbons (PAHs), some with attached functional groups. The separate analyses using EI, positive ion CI and negative ion CI indicated the presence of different isomers and functional groups.21,22 High resolution MS was used to identify the nitrogen-containing functional groups as nitrile groups, which would be expected given the acrylonitrile component of the feedstock. No indication of nitro compounds was found. The composition of the oils was similar to coal tar or fuel oil. Residue Analysis. The pyrolyser and filter residues from each trial were analyzed separately using EDX. The levels of iron found in the residues were higher than could be explained by the content in the original polymers, which was thought to be due to some corrosion of the stainless steel pyrolyser and filter casing by the chlorine content of the pyrolysis gases. It was therefore 9383
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Environmental Science & Technology assumed that the level of iron equaled that found in the ash from the relevant plastic batch. For each of the trials, the percentage of each element found in the combined residues was converted into a percentage of the original plastic feedstock weight. These figures are given in Figure 2 (note the different scales for Batch 1 and Batch 2) and compared with those from the ground polymers and ash for the main elements. The agreement was found to be quite good, with the closeness of the chlorine content from polymer to residues supporting the lack of chlorinated compounds in the oils and gases. The error bars show the standard errors for the results. The higher variability of the ground polymer results compared to the ash suggests that this was a less successful method of homogenization than the ashing. Some difference between the ground polymer and ash figures might also be expected as a result of the smaller sample of the ground polymer giving a less representative mix. Bromine was not detected in the residue and this is discussed below. Figure 2 shows that the higher level of chlorine in Batch 2 corresponded to a higher level of calcium. A sample of pyrolyser residue from Batch 2 was dissolved in water and the EDX analysis was then repeated. The original percentages (by weight of residue) of 11.4% chlorine and 6.7% calcium were reduced to 1.4% and 3.3% respectively, indicating that the chlorine in the residue was largely in the form of water-soluble calcium chloride. Overall Analysis. The weights of gases, oils and residue, and the composition of gases and oils, are summarized in Table 1. A small amount of heavy oils condensed in the system pipework before they reached the condensing flasks, estimated as 2% of the feedstock weight. The weight of gases (including volatiles) was calculated as the difference between the feedstock weight and the total weight of residues and condensed tars and oils. These weights were then converted to percentages of the original feedstock. The figure for potential fuel, at more than 70% of the original feedstock weight, is made up of the oils and tars, and the permanent gases other than oxygen, carbon dioxide, sulfur dioxide and nitriles. The residues are not included as fuel since these include a variety of metals and halogens which would require additional treatment. Batch 2 produced considerably more gas than Batch 1, a result which would correspond to the difference in plastic types. The aromatic rings in the structure of styrenic polymers are unlikely to break down at the temperatures considered, so contributing to the production of oils. The linear compounds within these polymers (the acrylonitrile backbone or butadiene), and similarly the linear backbone of PVC, may either form aromatic rings or break up into gases, depending on processing conditions. The increased amount of PVC in Batch 2 would have provided a greater chance of producing gases. The results for the three trials on Batch 2 were reasonably consistent. An approximate calculation of the amount of oxygen in the gases from Batch 1 indicated that there was around 6% (by weight of original feedstock) more than could be explained by the estimated amount in the polymers. This was most likely to have come from air ingress to, or residual air in, the experimental rig, despite the attempts to make the rig airtight and maintain positive pressure during the trials. The presence of oxygen might be expected to have led to water in the pyrolysis products. Identification or quantification of this was problematic due to the presence of water in the condensation system; however a proportion would be expected to condense along with the oils, which was not detected. The presence of oxygen but absence of
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water could have been a result of oxygen ingress occurring after the pyrolysis chamber. However, the possible presence of a small amount of water was allowed for in the LCA within the uncertainty ranges for quantity and calorific value of oils. In a fully sealed production process this possibility should be reduced and a lower proportion of carbon monoxide and other oxygencontaining compounds could be achieved. The proportion of gases from both feedstocks was significantly higher than had been found in most other work using comparable plastics. The closest was for fast pyrolysis of HIPS at temperatures above 800 °C,7 whereas WEEE-type mixtures at temperatures from 500 to 600 °C and slow temperature increases gave at most 12% gas. It therefore seems likely that the combination of fast pyrolysis and a higher temperature were the reason for the high gas proportion. The oils found in these trials showed some difference from other reported work, as might be expected given both the variety of mixed WEEE plastics and differences in process conditions. Although all trials with similar plastic mixes reported mostly aromatics, with some substituted nitrile and halogen groups, most of these were single ring and some also reported quite high levels of phenols. The trials described here showed PAHs with two or more rings to constitute 30 40% of the oils. Since these were not part of the structure of any of the original polymers, they must have been formed during the pyrolysis process as a result of the combination of temperature and residence time. Similarly it seems likely that the absence of phenols but significant level of carbon monoxide also reflected the process conditions. One of the key concerns in any thermal treatment of plastics containing chlorine or bromine is the creation of halogenated organic compounds and the potential for polyhalogenated dibenzodioxin creation, as well as the problem of corrosion caused by hydrogen chloride or hydrogen bromide in the system. In these trials the bulk of the chlorine measured in the feed material (mostly in the form of PVC plus a small amount included in flame retardants) remained in the pyrolysis residue, largely as calcium chloride. This appears to be a serendipitous result of calcium compounds being a common filler in PVC, and fits with results from other research.23,24 Some chlorine was also “trapped” by the steel of the filter housing even when stainless steel was used. Chlorinated aromatic compounds were found at a very low level in the gases from some trials, which would be expected since it was unlikely that the mechanisms just described would remove all of the chlorine. Only a very small amount of chlorine and no bromine were found in the water from the trials, suggesting that any HCl or HBr that was formed reacted with other elements or compounds in the pyrolyser or filter. The fate of the bromine detected in the original samples was not established as it could not be detected in any of the pyrolysis products, possibly because it was at too low a level (as was found for the ground polymer). Since the control of halogens is a significant factor in the use of WEEE plastics for pyrolysis, for commercial use a method would be required to ensure that halogens were removed from the gases and oils. Therefore for the LCA, the amount of bromine found in the polymer analysis was assumed to be present in the residue, while up to legal limits of polyhalogenated dibenzodioxins were allowed for in the gases and oils. Removal of halogens could involve the addition of an excess of a calcium containing substance such as lime to the feed, or the use of a catalyst after the pyrolysis chamber to remove halogens from organic compounds. 9384
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Environmental Science & Technology These trials provided the bulk of data required for an LCA of the pyrolysis process. Results which were not established, such as the exact breakdown of the oils and the fate of bromine, were taken account of by uncertainty analysis in the LCA allowing for a realistic range of possible values.
’ ASSOCIATED CONTENT
bS
Supporting Information. Detailed breakdown of gas and oil analysis. This material is available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION Corresponding Author
*Phone: (44) 1792 602009; e-mail:
[email protected].
’ ACKNOWLEDGMENT We thank ITEM Recycling Ltd for the design and building of the experimental rig, Axion Polymers for the supply of WEEE plastics, and the European Social Fund for financial assistance for this work. ’ REFERENCES (1) Waste Electrical and Electronical Equipment, Data 2008 (Tonnes, Updated 17 June 2011), WEEE Key Statistics and Data; Eurostat; European Commission: Brussels, 2011; http://epp.eurostat.ec.europa. eu/portal/page/portal/waste/data/wastestreams/weee. (2) Summary of the Impact Assessment on WEEE, SEC(2008) 2934; European Commission: Brussels, 2008; http://eur-lex.europa. eu/LexUriServ/LexUriServ.do?uri=SEC:2008:2934:FIN:EN:PDF. (3) Electronic Waste, Postnote number 291; UK Parliamentary Office of Science and Technology: London, UK, 2007; http://www.parliament.uk/documents/post/postpn291.pdf. (4) Dalrymple, I.; Wright N.; Kellner R.; Bains N.; Geraghty K.; Goosey M.; Lightfoot L. An integrated approach to electronic waste (WEEE) recycling. Circuit World. 2007, 33(2), 52; DOI: 10.1108/ 03056120710750256. (5) Develop a Process to Separate Brominated Flame Retardants from WEEE Polymers Final Report; PLA-037(2006); UK Waste & Resources Action Programme: Banbury, UK, 2007; http://www.wrap.org.uk/ recycling_industry/publications/develop_a_process__1.html. (6) Shun, D.; Dal-Hee, B.; Sung-Ho, C.; Keun-Hee, H. Bench-Scale Fluidized Bed Pyrolysis of Waste ABS Resin. In Proceedings of ISES 1997 Solar World Congress: Taejon, Korea, August 24 30, 1997. (7) Karaduman A.; S-ims-ek E. H.; C-ic-ek B.; Bilgesu A. Y. Flash pyrolysis of polystyrene wastes in a free-fall reactor under vacuum. J. Anal. Appl. Pyrol. 2001, 60, 179; DOI: 10.1016/S0165-2370(00) 00169-8. (8) Hall W. J.; Williams P. T. Pyrolysis of brominated feedstock plastic in a fluidised bed reactor. J. Anal. Appl. Pyrol. 2006, 77, 75; DOI: 10.1016/j.jaap.2006.01.006. (9) Hall W. J.; Williams P. T. Fast pyrolysis of halogenated plastics recovered from waste computers. Energ. Fuel. 2006, 20, 1536; DOI: 10.1021/ef060088n. (10) Day M.; Cooney J. D.; Touchette-Barrette C.; Sheehan S. E. Pyrolysis of mixed plastics used in the electronics industry. J. Anal. Appl. Pyrol. 1999, 52, 199 ;DOI: 10.1016/S0165-2370(99)00045-5. (11) Chiu S.; Chen S.; Tsai C. Effect of metal chlorides on thermal degradation of (waste) polycarbonate. Waste Manage. 2006, 26, 252; DOI: 10.1016/j.wasman.2005.03.003. (12) Bhaskar T.; Hall W. J.; Mitan N. M. M.; Muto A.; Williams P. T.; Sakata Y. Controlled pyrolysis of polyethylene/polypropylene/ polystyrene mixed plastics with high impact polystyrene containing
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