Study on the Releasing Characteristics of Sulfur-Containing Gases in High-Sulfur Coal under Different Atmospheres during Mild Thermal Upgrading

Mild thermal upgrading before coal utilization was an efficient method for sulfur removal as well as the quality upgrading. Two coal samples with high sulfur content from Guizhou province were selected in this study to investigate the releasing mechanism of different forms of sulfur under different atmospheres during mild thermal upgrading. The study showed that sulfur in coal can be divided into three types: table organic sulfur, pyrlte sulfur and unstable organic sulfur. Small amount of oxygen in the carrier gas can significantly improve the release amount of SO₂ in coal especially for the pyrite sulfur. The breaking of C-C and C-S bonds during thermal upgrading were observed to have different selectivity for different oxygen contents. The study indicated that 4% O₂-N₂ low oxidizing atmosphere and 400 °C was the optimal working condition for mild thermal upgrading before combustion.