Evolution and distribution characteristics of fluorine during the incineration of fluorine-containing waste in a hazardous waste incinerator

In this study, the evolution and distribution of fluorine during the incineration of fluorine-containing waste in a hazardous waste incinerator were investigated. The evolution characteristics of fluorine during the pyrolysis of the waste were investigated using thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TG-FTIR) analysis. The distribution of fluorine in the incineration systems and its form in the incineration residues were studied under two operating conditions. The results showed that fluorine in the waste had strong volatility and hydrogen fluoride (HF) and silicon fluoride (SiF4) were detected as the first fluorine compounds to be released during pyrolysis. The release of HF could be divided into three temperature ranges: 123.5-757.5 degrees C, 757.5-959.6 degrees C, and >959.6 degrees C. The emission of HF between 123.5 degrees C and 757.5 degrees C involved loosely bonded organic fluorine and ionic inorganic fluorine, while the HF released between 757.5 degrees C and 959.6 degrees C was caused by the crack of fixed carbon and further dehydroxylation, and the HF released above 959.6 degrees C was due to the decomposition of inorganic minerals. The emission of SiF4 was mainly concentrated between 132.6 degrees C and 684.0 degrees C, and almost no SiF4 was emitted from the waste above 684.0 degrees C. Less than 20.73% of the fluorine was retained in the incineration residues and over 79.17% of fluorine was absorbed in the absorbent solution of a wet flue gas desulfurization (WFGD) system. The amount of fluorine discharged into the atmosphere was below 0.12%. The fluorine in the bottom slag and burn-out chamber ash mainly existed in residual form. The proportions of water-soluble, exchangeable, and acid-soluble fluorine in the boiler ash and bag filter ash were both over 80%.