Washability of sulfur in Late Permian coal from Zhenxiong coalfield, northeastern Yunnan

The screening and sink-and-float tests of raw coal have been carried out on the No.C₅ coal in the Zhenxiong coalfield,northeastern Yunnan,with the samples from the Rongxing coal mine at the Gangou Town of the Zhaotong City.Distribution of sulfur in different density grading and size grading of coal is studied.The results show that the levels of the total sulfur and pyritic sulfur vary little in different size grades of coal,but in a same size grade the sulfur content increases with the density grades.In addition,the proportion of pyritic sulfur in the total sulfur is increasing with the sizes.The properties of crushing and separation of this coal are poor as the sulfur con-tents are relatively constant during the whole crushing process.However,the float coal with 2.35% total sulfur can account for 88% when size less than 3.0 mm.Generally pyritic sulfur is the most important form of sulfur in the high density grades,accounting for 95% in total sulfur,and this figure drops down to less than 65% in the light density grades in which the organic sulfur can take up to 30% although the total sulfur is low.In conclusion,physical methods can be used to reduce the sulfur in float coal.