Transformation of Mineral Matter to Ash

The mineral matter in coal loses weight during thermal conversion to ash because of the loss of water from clays, the loss of carbon dioxide from carbonate minerals such as CaCOs, and the oxidation of Fe 2 to ferric oxide (Fe20s). In addition, any chlorine in the coal is converted to hydrogen chloride, but the 

Al203-2Si02-2H20 AhOs SiOj + 2H2O +145.6 400 and 580 

The enthalpy and temperature data in Table 3.13 is intended to identify the main groups of minerals from an available TGA or DTA diagram from coal pyrolysis or low-temperature ash (ashing below 380 °C). If, for example, in a pyrolysis curve from TGA, the mass change per time peaks at 670 °C, it can be concluded that MgCOs is part of the coal and a part of the measured ultimate carbon content will require heat to be gasified. To quantify the effect, the carbonate CO2 should be determined for that sample. 

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