Distribution characteristics of trace elements (As/Cr/Mn/Cu/Pb) in the thermal fragmentation and strengthening fragmentation processes of low-rank coal with high sulfur content

Abstract

The thermal fragmentation of low-rank coal had been proven to be a new way of desulfurization for char with coarse-size. However, whether harmful trace elements (HTEs) could be effectively removed in coarse-size char by thermal fragmentation action demand for further study. Two high-sulfur low-rank coals were used to explore the distribution behavior of As, Cr, Cu, Mn, and Pb in thermal fragmentation char with different particle sizes obtained by the fixed-bed and rotary kiln pyrolysis. Combined with the occurrence forms of HTEs in raw coal and volatilization characteristics of HTEs obtained by thermodynamic simulation software, the distribution of HTEs in thermal fragmentation char was analyzed. The effectiveness of thermal fragmentation of HTEs components in fixed-bed pyrolysis was reliant on high temperatures, with poor distribution resulting in less than 20 % of As, Cu, and Pb components being allocated to pulverization char. The thermal fragmentation of Cu components in disulfide form, was severely hindered by the binding effect of metaplast. In contrast, rotary kiln pyrolysis facilitated a greater distribution proportion of HTEs components into pulverization char at lower temperatures. Under optimal conditions, the distribution of As, Pb, and Cr into pulverization char surpassed 70 %. The strengthening thermal fragmentation in the rotary kiln reduce the binding effects, effectively increasing the distribution of copper-rich components into pulverized char.