Thermodynamic Calculation of the Decomposition of Inorganic Sulphur in Coal in Oxy-Fuel Atmosphere

In this paper, the effect of oxygen and steam on the decomposition of inorganic sulphur in coal in the oxy-fuel atmosphere is investigated using the thermodynamic equilibrium calculation method. To evaluate sulphur distribution in different gas environments, the authors apply the HSC Chemistry software for calculations of various sulphur-related chemical reactions and equilibria parameters, based on the principle of minimizing the Gibbs free energy. The influence of temperature and gas atmospheres on the equilibrium composition is also evaluated. In the thermodynamic calculation, the FeS 2 and FeSO 4 substances are used to simulate the pyrite and sulphate impurities in coal, respectively. The relationships are established between the CO 2 atmosphere and the inorganic sulphur content. It is shown, that the CO 2 presence in the atmosphere enhances the formation of FeO and the decomposition of FeS, resulting in a few intermediate products, including Fe 2 O 3 , Fe 3 O 4 , Fe 2 S 3 , FeCO 3 , and COS. The results show that oxygen has a significant effect on the sulpher distribution. Thе SO, FeO, and Fe 3 O 4 products are formed in the oxygen-deficient environment, while the SO 2 and Fe 2 O 3 substances are formed when oxygen is in excess. In the O 2 /CO 2 /H 2 O mixture atmosphere, the oxidation reaction of the sulphur-containing compounds becomes more complicated. A competitive relationship between the reactions of S-CO 2 and S-H 2 O is observed.