Effects of core materials on the evolution of products during the pyrolysis of end-of-life wind turbine blades

A wind turbine blade consists of pure glass fiber-reinforced polymer composites (GFRPs) and the sandwich part with core materials. Pyrolysis is a prospective technology to recycle end-of-life blades, but the pyrolysis performance of blades with core materials is still unclear. In this study, three retired blade parts were pyrolyzed, i.e., pure GFRPs, GFRPs filled with polyethylene terephthalate (PET) foam, and GFRPs filled with balsa wood. The results showed that CH4, CO, and CO2 were the majority of the pyrolysis gas when the pure GFRPs part was pyrolyzed at 400 degrees C, with five typical phenolic products in the pyrolysis oil, containing bisphenol A, phenol, 4-isopropenyl phenol, 4-isopropyl phenol, and o-cresol. As the temperature increased to 550 degrees C, the content of CH4 reached 48.0 vol% while that of CO2 reduced, raising the calorific value of the pyrolysis gas to 27.2 MJ/ Nm3. Meanwhile, the content of bisphenol A in the pyrolysis oil rapidly increased, owing to the enhanced breakage of oligomers. As PET foam was filled, CO2 was dominant in the pyrolysis gas, and the content of benzoic acid became comparable with those of phenols in the pyrolysis oil. Whilst several hydrocarbon substances were detected when balsa wood was filled, making the oil product more complex. In terms of solid products, char residues over the black fibers were formed mainly due to the decomposition of epoxy resin rather than core materials, and the oxidation duration should be extended when recovering the blade parts with sandwich structures. Moreover, elevating the pyrolysis temperature reduced the pyrolytic residues but degraded the recovered fibers' tensile strengths. The conclusions suggested that the blade parts with sandwich structures should be pyrolyzed separately, considering the core materials and their components.