Effect of chromium on the spatial distribution of sulfur during pyrolysis of coal with high organic sulfur

Abstract

The selective removal of stable sulfur-configuration makes high-sulfur coking coal reserves available in coking process. However, stable organic sulfur is difficult to remove effectively and is easily immobilized by secondary reactions in the volatile phase migration pathway. In this work, Cr commonly found in steelmaking wastewater was used as additive for the desulfurization of high organic sulfur coking coal, and its effect on spatial distribution and conversion of sulfur forms during the high-temperature coking process was studied by sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy. The results show that the chromium additives effectively promote sulfur removal during pyrolysis. In the vertical direction, the addition of Cr2O3 captures sulfur radicals to form sulfide and promotes the breaking of sulfoxide OS bonds at the bottom of the coke. Furthermore, in the horizontal direction, the addition of CrCl3 by impregnation generates sulfide by combining with sulfur radicals after breaking down thiophenic CS bonds and promotes the breaking of sulfoxide O-S bonds. This results in a significant decrease of the desulfurization rate as the escape of volatiles from the bottom to top and from inside to outside of the coke. The results not only provide guidance for selective sulfur removal of coal during pyrolysis with high-sulfur coking coal but also for the conversion of polluting steelmaking wastewater into available resources.