Pollutant emission during pyrolysis of waste wind turbine blades: Nitrogen-containing components and polycyclic aromatic hydrocarbons

Serious attention was lacked for various pollutants formed in both gas and tar phase during pyrolysis recycling of waste wind turbine blades (WWTB), especially for components of carcinogenic bisphenol A (BPA) and potentially toxic polycyclic aromatic hydrocarbons (PAHs) in tar. Pyrolysis temperature within 400-600 degrees C would significantly impact pollutant formations. Additionally, CO2 had a potential to mitigate pollutants emission as an economic alternative for N2. This article investigated the influence of these factors on nitrogenous and PAHs components during WWTB pyrolysis through fixed bed and thermogravimetric experiments. The results showed that NO2 was dominated in nitrogen containing pollutants and was related to the evolution of pyrrole nitrogen oxides. It was found 550 degrees C as a turning temperature, at which the polycondensation reaction appeared significantly. This resulted in a markedly increase for toxic N-PAHs in tar. At this temperature, CO2 could be used to mitigate nitrogen pollutants. 25% CO2 reduced NOX emission about 26% and selectively promoted NH3 releasing to over 4.3 times and depressed HCN generating to 0.6 times. Moreover, the primary depolymerization product of organic pact in WWTB was BPA. Increasing residence time, temperature and CO2 concentration were beneficial for converting hazardous BPA to high valued P-Isopropenylphenol (IPP). The value of IPP:BPA could increase to over 2 in this experiment. It was aimed to provide not only an evaluation for the yield and migration of pollutants, but also an cleaner recycling solution through graded pyrolysis WWTB to mitigate pollution and maximize the value of by-products.