(117k) Plastic Pyrolysis Oil in Fluidized Bed and Fixed Bed Reactors

In response to the increasingly prominent double crisis of the environment (especially the white pollution of plastic waste) and energy, in this study a sustainable development strategy for converting plastic waste into energy through pyrolysis technology has been proposed. Furthermore, in order to improve the working efficiency as well as the yield and quality of liquid oil, in the present work, a fluidized bed was designed for the pyrolysis of three plastic wastes (PP, LDPE, and ABS) for the first time. A traditional fixed bed was used as comparison. Although reactor type does not significantly affect the yield of liquid oil (PP: 61~62%, LDPE: 82~87%, ABS: 82~85%), it can greatly affect its quality. Compared with fixed reactor, fluidized reactor can transfer more middle oil (C₁₁-C₂₂) (and heavy oil (> C₂₃)) to light oil (C₅-C₁₀) for ABS (LO: ~61%) and PP (LO: ~26%), due to its better heat transfer efficiency. However, for LDPE, due to its unsuitable pyrolysis temperature (520 ℃ used in this work), heavy oil was the main fraction (47~67%) regardless of the reactor type. Plastic oils over fluidized reactor showed a high similarity with diesel, especially ABS (ABS: 92% and PP: 69%), with several important properties such as HHV: 45~46 MJ/kg, viscosity: 1.12~2.65 cSt@40 ℃ and TAN: 0.0~1.5 mg_KOH/g_oi. In addition, according to the naphtha standard (BP < 200°C), the contents of ABS and PP oil are 62% and 33% respectively. Furthermore, GC-MS analysis showed that ABS fluidized bed oil mainly contained aromatics (~71%), aromatic-N (~13%) and olefins (~8%), and LDPE fluidized bed oil mainly contained olefins (~66%) and paraffins (~30%), PP fluidized bed oil mainly contains olefins (~41%), paraffins (~21%) and a large amount of oxygenated compounds (e.g. esters, alcohols and ketones). Another thing worth noting is that although oxygen content of 0~2.5% exists in plastic waste, it converted into other oxygenated compounds instead of acids (eg. esters, alcohols and ketones) with a help of fluidized reactor, resulting in very low TAN value. Finally, the current study suggested that the fluidized bed has great potential for the pyrolysis application of plastic waste.