The effect of strengthening thermal fragmentation by rotary kiln on sulfur distribution of fragmentation char with low-rank coal

•Plastic layer hindered the effect of desulfurization by thermal fragmentation.•Destruction of conjoined structure reduced the sulfur content of the large-size char.•Thermo-mechanical action inhibited adhesion of the fine particles with high-sulfur.•Thermo-mechanical action promoted the fragmentation of sulfones into small-size char.