Soluble polycyclic aromatic hydrocarbons in raw coals

Polycyclic aromatic hydrocarbons (PAHs) are considered to be a group of com pounds that pose potential health hazards since some PAHs are known carcino gens. During coal utilization processes, such as coal combustion and pyroly sis, PAHs released may be divided into two categories according to their fo rmation pathways. One category is derived from complex chemical reactions a nd the other is from free PAHs transferred from the original coals. PAHs re leased from complex chemical reactions during combustion and pyrolysis have received considerable attention in recent years. However, free PAHs contai ned in raw coals have not been seriously considered as a source of these ma terials to be released during the utilization of coal. The goal of this stu dy was to observe the relation between the content of PAHs in different coa ls and the elemental composition of the coals. In this study, eight bitumin ous coals with dry, ash-free carbon values varying from 65% to 90% were sel ected. Each coal was extracted with dichloromethane in a Soxhlet extractor for 6 h, The extracts were quantitatively analyzed with a gas chromatograph /mass spectrometer (GC-MS). More than 20 kinds of PAHs were identified. The total amount of PAHs determined varied from 1.2 to 28.3 mg/kg from the var ious coal types. The maximum total PAHs extracted was reached when the carb on content exceeded 84% by weight. (C) 2000 Elsevier Science B.V. All right s reserved.