Fly ash from coal combustion – An environmental source of organic compounds

Abstract

The fly ash resulting from coal combustion (anthracite A coal type) for power generation was investigated. The fly ash produced during the coal combustion was emplaced in surface landfills near the thermal power plant facilities. A total of six samples were collected in the fly ash landfills which were therefore analyzed for their geochemical characterization. The analysis comprised the determination of total organic carbon and total sulfur, the identification of aliphatic hydrocarbons, and the identification and quantification of the sixteen priority polycyclic aromatic hydrocarbons (PAHs). This study provides information about the potential environmental impacts associated with the disposal of fly ash and, in addition, it also provides scientific knowledge about the effects of combustion process in the soluble fraction of coal organic matter and about the behavior of these compounds during combustion. The results about the aliphatic compounds demonstrated that the long-chain n-alkanes, the pentacyclic terpanes, and the regular steranes (C-27, C-28, C-29) increase in fly ash samples comparatively to coal. The PAHs with two and three aromatic rings (low molecular weight PAHs – LMW PAHs) were not detected in fly ash while fluoranthene (four rings) was detected in all samples, and benzo[a]anthracene (four rings), benzo[b]fluoranthene (four rings), indeno[123-cd]pyrene (five rings), benzo[ghi]perylene (five rings), and dibenzo[ah]anthracene (six rings) were detected in some of the samples. The absence of LMW PAHs and the presence of some high molecular weight (HMW) PAHs, with four to six rings, are attributed to the combustion process. The low sum of the priority PAHs in fly ash samples can be related with both, the high rank of the coal burned in the thermal power plant (anthracite A), with the technical combustion conditions and/or leaching process in the fly ash landfills. The organic compounds adsorbed in fly ash particles may be released into the environment and therefore can represent a potential source of contamination of soils and waters and human health problems.