Occurrence and emission characteristics of polycyclic aromatic hydrocarbons in CFB boiler

In order to understand the distribution and emission of polycyclic aromatic hydrocarbons (PAHs) in flue gas of circulating fluidized bed (CFB) boiler, the gaseous and granular PAHs in flue gas of a 200 MW CFB boiler were collected and analyzed, and the occurrence and distribution characteristics of PAHs in gas and solid of flue gas were studied. The content of PAHs in three solid samples ofcoal, fly ash and slag was analyzed. The results show that the final PAHs emission concentration of CFB boiler unit is 4.03 μg/m3, with the gas phase and solid phase PAHs concentration of 1.88 μg/m3 and 1.66 μg/m3, respectively. The gas phase PAHs in the flue gas are dominated by 2-5 rings, while the solid PAHs are dominated by 4 and 5 rings at the beginning of boiler emission. After a series of ultra-low emission control facilities treatment, the final emission of PAHs are mainly 2 and 3 rings. The total amount of PAHs in coal sample is 26.20 μg/g, with the content of 3-5 rings. The total amount of PAHs in slag and fly ash is 3.12 μg/g and 3.85 μg/g, respectively, mainly consisting of 3-4 rings . The overall collaborative removal efficiency of PAHs by all ultra-low emission control facilities can reach 97.46%. The results show that the synergistic removal effect of existing flue gas treatment facilities can meet the corresponding emission requirements.