Thermodynamic research on the effect of H2O on transformation of organic sulphur during coal pyrolysis under CO2 atmosphere

Abstract

This study investigates the effect of H2O on transformation of organic sulphur in coal during CO2 atmospheres by thermodynamic equilibrium calculation by HSC Chemistry. The effect of water vapour on the release of sulphur containing compounds was studied. Detailed S distribution between 200-1400°C was explored. The results show that CO2 not only promotes the formation of inorganic compounds, but also moves the peak of released less complicated organic compounds such as Thiophene, Methylthiophene, Dimethylthiophene, etc. to a much lower temperature. The ranking of the sulphur release in CO2 atmosphere by HSC is: SO2 > Methyl thiophene > Dimethyl thiophene > Ethyl thiophene > dimethyl sulfone. Temperature affects the transformation of sulphur greatly during pyrolysis in CO2 atmosphere. Below 700 °C, COS and H2S are two major sulphur containing compounds formed during pyrolysis in CO2. Above 700 °C, SO2 plays the main role. H2O at different temperature range during heating also reacts with organic sulphur compounds, leading to a further decomposition. Since more organic S stays in inert gas, water promotes the decomposition of organic S compounds more intense than that in CO2 atmosphere. Besides, the effect of water vapour on S distribution depends on the amount of H2O in the reaction.