Pyrolysis of mixed plastics in a fluidized bed of hard burnt lime

A mixture consisting of 45 wt % polyethylene, 20 wt % polypropylene, 20 wt % polystyrene, and 15 wt % poly(ethylene terephthalate) was pyrolyzed in the presence of steam as well as nitrogen, using a fluidized bed reactor with hard burnt lime (HBL) as bed material. The experiments were carried out at 600 and 700 °C. Unlike soft burnt lime, HBL exhibited good fluidizing properties, with negligible attrition. The impact of HBL on the product distribution and the ability of HBL to support the degradation of PET under certain conditions were investigated. Compared with experiments done in the presence of quartz sand, the gas yield increased, while the wax fraction was significantly reduced. In the presence of HBL, the benzene yield rose sharply due to the decarboxylation of PET. While terephthalic acid was present in the wax fraction derived from experiments with quartz sand, it was not detected as a part of the wax fraction when HBL was used.