An Experimental Study of the Decomposition of Pyrite in a Lignite during Pyrolysis
Thermal decomposition of pure pyrite, pyrite-free lignite, and samples of lignite blended with pyrite has been studied using a thermogravimetric analyser (TGA). Under nitrogen atmosphere pyrite decomposes to pyrrhotite (FeSx) before being further reduced to troilite (FeS). The troilite may further decompose to form elemental iron (Fe). The decomposition of pure pyrite occurs at a higher temperature than when it is blended in the lignite. Kinetic parameters of pyrolysis of lignite and lignite samples blended with pyrite were obtained in three temperature regions using the Coats and Redfern equation for the first order reaction. The activation energy (E) increases with increasing temperature for all samples. The concentration of pyrite in the blended samples does not affect the activation energy in the temperature regions of 573-673K and 683-783K, respectively. However the E value in the temperature region of 793-923 K increases with increasing pyrite concentration.
Keywords: activation energy, lignite, pyrite, pyrolysis