Thermal pyrolysis of a real plastic sample from small WEEE and characterization of the produced oil in view of fuel or feedstock uses

Abstract

The possibilities of valorizing by pyrolysis a plastic fraction from small waste from electrical and electronic equipment (WEEE-R4) rejected by a material recovery facility have been assessed. The characterization revealed that WEEE-R4 was mainly composed of acrylonitrile–butadiene–styrene (ABS) and blends of polycarbonate (PC)-ABS (75 and 25 wt%, respectively) and had good physicochemical properties as feed for pyrolysis processes: high values for volatile matter (95 wt%) and low heating value (LHV, 35 MJ/kg) and low ash and moisture content (2.5 and 0.33 wt%, respectively). On the contrary, the high content of heteroatoms, in particular Br from brominated flame retardants, arose as source of concern. Thermal analysis coupled with evolved gas Fourier transform Infrared (FTIR) spectroscopy showed that WEEE-R4 degraded in two steps in the range 310–460 °C and mainly to the monoaromatic compounds phenol and styrene. Thermal pyrolysis at 400 °C was carried out in a bench-scale reactor and the yields of the products were 18 wt% solids, 58 wt% light oil, 16 wt% tar and 8 wt% gas. The gaseous fraction was composed mainly of CO2 (60 wt%), originating from the thermal degradation of PC. After removing CO2, the gas had a good LHV (32.5 MJ/kg) such to contribute for the 66 % to the energy required for the pyrolysis process of WEEE-R4. The properties of the light oil were evaluated by means of the same standard tests used for commercial fuels or crude oils. The results were interesting but far from the more refined gasoline and diesel oil, with the concentration of nitrogen and bromine even higher than the typical composition of petroleum. Nevertheless, this study shows that pyrolysis followed by a refining treatment such as, distillation is capable of producing monoaromatic hydrocarbon in significant amount (>30 wt%).