Sulfur release during combustion of Serbian coals

The sulfur release during combustion of six Serbian coals of different rank (from lignite to semi-anthracite) and sulfur content (0.28 - 6.04 %) was determined by analyzing the content of various sulfur forms in coal, char and ash samples. Based on theoretical considerations and behaviour of sulfur compounds during the processes of devolatilization and char combustion, correlations are proposed for estimation of the amount of sulfur released during devolatilization as well as during the overall process of coal combustion. Both correlations take into account the results of the proximate analysis of coal and that of the sulfur forms in the coal, while for the second one the sulfur retention efficiency during char combustion (eta) is needed. The correlations were successfully verified by using the obtained experimental data, as well as the data found in literature. For most of the coals the same value of eta = 0.7 may be used, unless if the molar Ca/S ratio is significantly smaller than 1.