The evolution characteristic of sulfur-containing gases during coal thermal conversion

Abstract

In this study, the evolution characteristics of sulfur-containing gases during thermal conversion of two coals under different atmospheres were studied through temperature-program decomposition (TPD) and rapid-heating decomposition (RHD) coupled with online mass spectrum (MS). The releasing profiles of H2, CH4 and CO were also measured. Results showed that the effect of atmosphere and heating rate on evolution of sulfur-containing gases was very significant. It was found that Ar atmosphere was more favorable to the formation of sulfur-containing gases than CO2 atmosphere by using TPD-MS. In CO2, the formation of H2S and SO2 was restrained in 260–650 °C, but was promoted in 880–980 °C; the formation of COS was promoted during the whole process. In Ar, high releasing intensity of H2 and CH4 could stabilize sulfur-containing radicals which led to high amount of H2S and SO2; while high releasing intensity of CO in CO2 resulted in high amount of COS. By using RHD-MS, it was found that the steam atmosphere was highly favorable for the transformation of H2S, SO2 and COS during the entire reaction period. However, the CO2 atmosphere was disadvantageous to the transformation of H2S, SO2 and COS at the initial stage, but slight favorable for the transformation of H2S, SO2 and COS during the later stage. These was resulted from the gasification reaction of steam/CO2 with coal. The key factor was the releasing amount of H2 and CO, which promoted the formation and transformation of H2S, SO2 and COS.