Coal Fly Ash from Brazilian Power Plants: Chemical and Physical Properties and Leaching Characteristics

Abstract

In this work, coal fly ash samples were collected from baghouse filter, electrostatic precipitators and cyclone filter of five different Brazilian thermal power plants: Figueira, Jorge Lacerda, President Médici, São Jerônimo and Charqueadas. The materials were characterized in terms of pH, conductivity, real density, specific surface area (BET method), morphological analysis (SEM), chemical composition (XRF), mineralogical composition (XRD), cation exchange capacity, humidity, loss-on-ignition among other parameters. Leaching and solubilization tests were carried out following the Brazilian NBR 10004 code. Analyses of major elements indicate a high SiO2, Al2O3 and Fe2O3 content. The mineralogical composition of fly ashes includes mainly mullite and quartz, some amounts of magnetite and hematite and an amorphous phase. Most element concentrations were of the same magnitude, independent of the power plant, with the exception of Figueira. The fly ash from São Jerônimo power plant presents a higher content of unburned carbon and specific surface area. According to its mineralogical and chemical composition, Brazilian fly ashes can be used as raw material for synthesis of zeolites using hydrothermal method.