Release of nitrogen, sulfur and chlorine species from coal in carbon dioxide atmosphere

Abstract

In oxyfuel combustion, the release of minority species, such as sulfur, nitrogen and chlorine compounds from the fuel plays an essential role, since significant corrosion and emission issues arise from these species. In the present study, the release of nitrogen, sulfur and chlorine species from a US-American bituminous coal with high sulfur content was studied in CO2 atmosphere in an entrained flow reactor. With the entrained flow reactor, particle heating rates comparable to those observed in a full-scale furnace can be achieved. The experiments were performed at different reactor temperatures in CO2 atmosphere. Gas samples were extracted from the reactor, and the concentration of various gas species, including NO, N2O, NH3, HCN, H2S, SO2, COS and HCl, was determined. It was found that the formation and release of the considered minority species changes with temperature and fuel residence time. A rapid decrease of the N2O concentration and an increase of the NO concentration was observed with increasing temperature. The release of NH3 from the fuel increased with increasing temperature, whereas the release of HCN decreased. Furthermore, compared to pyrolysis in nitrogen atmosphere, the release of sulfur and chlorine species increased significantly. Finally, COS was detected in significant amounts in CO2 atmosphere, but not in inert N2 atmosphere.