Influence of traces of gaseous sulphur on carburisation rate of iron in CO-H2 mixtures

The influence of traces of gaseous sulphur on the carburisation rate of a pure iron plate in CO-H-2-H2S gas mixtures was examined at 920-1200 degrees C to clarify the carburisation behaviour in the blast furnace utilising hydrogen or the direct reduction processes. The initial rates were analysed based on two chemical reactions for gas carburisation and the chemisorption equilibrium of sulphur atoms on the surface of iron. Traces of sulphur in gas mixtures significantly decreased the carburisation rate as the sulphur content increased. The carburisation was found to proceed to a small extent dependent on temperature and gas composition even under sulphur saturated chemisorption. The higher sulphur gas mixtures caused simultaneous reactions of carburisation and sulphurisation. When 50% of the CO was substituted by hydrogen, the rates were roughly twice as large as the condition without hydrogen, and approximately independent of the existence of sulphur. With rising temperature, the carburisation rates without sulphur tended to increase until around 1000 degrees C and decrease beyond 1100 degrees C, while the rates under sulphur saturated chemisorption increased gradually with rising temperature. The results are discussed relating to the carburisation behaviour inside the blast furnace utilising hydrogen or the direct reduction processes.