Chemical, mineralogical and environmental characterization of combustion byproducts generated from mineral coal used for electricity production

Abstract

The coal combustion by-products, bottom ash (BA), fly ash from cyclone filter (CA) and fly ash from bag filter (FA), generated in a Brazilian thermoelectric power plant, were characterized by Xray fluorescence, X-ray diffractometry and leaching and solubilization tests. The material retention systems used in the Brazilian power plant from where these by-produtcts were sampled are showed in Figure 1. The three types of coal ashes presented similar chemical composition, with a total content of main oxides (SiO2, Al2O3 and Fe2O3) above 72% and were classified as class F (according to ASTM). The analysis of ash enrichment factor showed that arsenic, zinc and lead concentrate mainly on FA, whereas the elements that presented the greatest enrichment in the bottom ash (BA) and therefore present low volatility are K and Mg. All ashes presented quartz, mullite and magnetite as crystalline phases. In the leaching and solubilization study, the FA sample was considered hazardous and classified according to Brazilian regulation as Class I solid waste, whereas CA and BA samples were considered non-hazardous and not inert solid wastes and classified as Class II-A. Therefore, FA sample from this Brazilian power plant must be discarded only after treatment or stringent disposal criteria must be followed to avoid contamination on site.