Emission characteristics and source identification of polycyclic aromatic hydrocarbons (PAHs) from used mineral oil combustion

Abstract

Presently, the characteristic of hazardous polycyclic aromatic hydrocarbons (PAHs) emission from used mineral oil (UMO) combustion in the industrial scenario is poorly explored and elucidated. In this work, the emission characteristic and source identification of 16 PAHs emitted from atomization combustion of five kinds of UMO and two types of base oil were investigated. The influence of temperature (600–1000 °C) and excess air ratio (0.8–1.4) on PAHs emission were assessed. Regarding emission factor (EF) and distribution of specific PAHs, high similarities were observed for combustion of different UMOs. EFs of PAHs were within the range between 61.58 µg g−1 and 105.03 µg g−1 (800 °C, stoichiometric air). The 2- and 3-ring PAHs made up more than 70% of the total PAHs in the flue gas, with the naphthalene accounting for 30.7%–48.1%. Over 80% of the emitted PAHs was partitioned into gas phase. The EFs of PAHs showed a parabolic trend with temperature and peaked at 800 °C. Higher temperature can decrease the total PAHs emission but lead to the enrichment of high-ring PAHs. Adequate air supply can efficiently reduce PAHs formation, especially at high temperatures. More than 95% of the total PAHs was eliminated when the excess air ratio was increased from 0.8 to 1.4 at 900 °C. Temperature influence on PAHs emission can be greatly weakened in high excess air level. The PAHs emitted from UMO combustion were randomly irrelevant to the original PAHs in UMO.