Valorization of the plastic residue from a WEEE treatment plant by pyrolysis.

The possibility of a pyrolysis process as a mean of recycling the residual plastic rich fraction (WEEE residue) derived from of a material recovery facility has been evaluated. The unknown product composition of WEEE residue has been supposed through coupled thermal - infrared analysis and ultimate analysis and resulted as PP 3 wt%, PBT 3 wt%, PVC 4 wt%, styrene-based polymers (principally ABS) 50 wt%, thermosetting resins (principally, epoxy/phenolic resins) 24 wt%, inorganic fraction (principally fiber glass) 16 wt%. DSC experiments showed that the overall energy, defined as the degradation heat, needed in order to completely degrade WEEE residue was about 4% of the exploitable energy of the input material. The effect of temperature and different zeolite catalysts were investigated, in particular in terms of yield and quality of the produced oils during the pyrolysis process. Produced oils were potentially exploitable as fuels and almost all catalysts improved their quality. The best performance was reached by NaUSY(5.7) with the second highest production of light oil and the greatest total monoaromatics yield, plus 12 wt% in comparison to thermal pyrolysis experiments. Furthermore, light oil produced by NaUSY(5.7) has one of the best LHV (36 MJ/kg) and no halogenated compounds were detected by GC-MS analysis. Char or pyrolytic gas combustion could supply the energy required for the thermal degradation of WEEE Residue.

Thermal and catalytic pyrolysis of a mixture of plastics from small waste electrical and electronic equipment (WEEE).

Pyrolysis seems a promising route for recycling of heterogeneous, contaminated and additives containing plastics from waste electrical and electronic equipment (WEEE). This study deals with the thermal and catalytic pyrolysis of a synthetic mixture containing real waste plastics, representative of polymers contained in small WEEE. Two zeolite-based catalysts were used at 400°C: HUSY and HZSM-5 with a high silica content, while three different temperatures were adopted for the thermal cracking: 400, 600 and 800°C. The mass balance showed that the oil produced by pyrolysis is always the main product regardless the process conditions selected, with yields ranging from 83% to 93%. A higher yield was obtained when pyrolysis was carried out with HZSM-5 at 400°C and without catalysts, but at 600 and 800°C. Formation of a significant amount of solid residue (about 13%) is observed using HUSY. The oily liquid product of pyrolysis, analysed by GC-MS and GC-FID, as well as by elemental analysis and for energy content, appeared lighter, less viscous and with a higher concentration of monoaromatics under catalytic condition, if compared to the liquid product derived from thermal degradation at the same temperature. HZSM-5 led to the production of a high yield of styrene (17.5%), while HUSY favoured the formation of ethylbenzene (15%). Energy released by combustion of the oil was around 39MJ/kg, thus suggesting the possibility to exploit it as a fuel, if the recovery of chemical compounds could not be realised. Elemental and proximate analysis of char and GC-TCD analysis of the gas were also performed. Finally, it was estimated to what extent these two products, showing a relevant ability to release energy, could fulfil the energy demand requested in pyrolysis.