Form and distribution of sulfur in pulverized Jincheng coal and their influence on its ash fusibility

Forms and distribution of sulfur in pulverzied Jincheng coal were analyzed, and their influence on ash fusion temperature (AFT) was studied. With the float-sink method, the whole coal was separated into four density fractions, i.e. < 1.6, 1.6-1.7, 1.7-2.0 and >2.0 g/cm³. The distribution of sulfur content and their forms were analyzed. SO₃ content and AFT of the coal samples ashed at 450, 815, 1000, and 1300℃ were determined. XRF and XRD were used to reveal the mechanism. The results show that sulfur in pulverized Jincheng coal is not evenly distributed in different density fractions, mainly concentrated in >2.0 g/cm³. With increase of the density, content of organic sulfur decreases rapidly, while those of sulphate sulfur and pyrite increase significantly. With increasing ashing temperature, sulfur contents in the whole coal and density fractions decrease. At 450℃, 87% sulfur is vaporized and at 1300℃ almost all sulfur is vaporized. Different density fraction shows different AFT, with >2.0 g/cm³ having the lowest AFT. Besides, AFT of >2.0 g/cm³ increases with rising ashing temperature. Mechanism study shows that the differentiation of AFT in different density fraction can be attributed to their chemical composition. The increase of AFT of >2.0 g/cm³ with ashing temperature is mainly due to sulfur SO₃ content in the ash residual.