Chapter 18 – Mineralogy and Magnetic Parameters of Materials Resulting from the Mining and Consumption of Coal from the Douro Coalfield, Northwest Portugal

The mineralogy and magnetic parameters of materials resulting from coal mining in the Douro Coalfield and its consumption in a thermal power plant were investigated. The coal waste, fly ash disposal, and coal combustion represent a potential source of particulate matter that can be released into the atmosphere and, adversely, affect the environment and human health. The methodologies applied in this work included X-ray powder diffraction for mineralogical characterization, and magnetic susceptibility and isothermal remanent magnetization (IRM) determination for evaluation of magnetic parameters. The results demonstrate that the unburned coal waste material has quartz, illite, mica (mainly muscovite), and in many cases pyrophyllite as the main mineral. Some of the burning/burnt coal waste samples have similar mineralogy to the unburned materials, but some of them also contain mullite, cristobalite, and amorphous material, suggesting that higher temperatures were involved in the in situ combustion process. The fly ash contains amorphous material, mullite, cristobalite, and maghemite, similar to the burnt waste samples. The magnetic parameters show an increase in magnetic susceptibility and IRM in some of the burning/burnt zones, indicating a magnetic enhancement due to the burning process. The fly ash samples exhibit even higher magnetic susceptibility and IRM values, attributed to the industrial combustion in the thermal power plant.