Formation and distribution of polycyclic aromatic hydrocarbons (PAHs) derived from coal seam combustion: A case study of the Ulanqab lignite from Inner Mongolia, northern China

Abstract

Abstract Coalfield fires are hazardous to the environment and human health as a result of the release of polycyclic aromatic hydrocarbons (PAHs). The incomplete combustion processes of the Ulanqab lignite from Inner Mongolia of northern China during coalfield fires were simulated in a tubular furnace, and 16 US Environmental Protection Agency priority pollutant PAHs in the flue gas were absorbed and analyzed. The results indicate that incomplete combustion results in a clear increase in PAH emission compared with other combustion methods; this is attributed to the formation of species with two and three benzene rings, such as naphthalene, acenaphthylene, and acenaphthene. Benzo[ a ]pyrene, dibenz[ a , h ]anthracene, and benz[ a ]anthracene make a large contribution to the toxicity equivalent value (TEQ), although they make up a small proportion of the PAHs. With temperature increasing, the total PAH yield peak occurs at 800 °C with a yield of 923.41 mg/kg at an air/coal ratio of 1 m 3 /kg. As the air/coal ratio increases, the amount of PAHs varies with the addition of oxygen. At a ratio of 2 m 3 /kg, the minimum PAH yield of 486.07 mg/kg occurs at 800 °C and the maximum concentrations of the most toxic species, benzo[ a ]pyrene, and dibenz[ a , h ]anthracene, are found. Increasing the coal particle size from 0.25 to 20 mm results in a significant growth of both the yields and TEQs of the PAH species.