During the magnesium-lime co-injection process for hot metal desulphurisation, graphite can precipitate as a result of carbon oversaturation. The formed graphite is known to form a layer between the slag and the hot metal. This potentially blocks the sulphides, that are formed during the desulphurisation process, to reach the slag phase thus hampering the desulphurisation efficiency.
In this research it was aimed to obtain experimental evidence for the postulated hampering effect of graphite on the hot metal desulphurisation efficiency at an industrial process. In 2018 at Tata Steel in IJmuiden, the Netherlands, the carbon concentration in the hot metal was measured after the reagent injection, instead of being calculated assuming carbon saturation of the hot metal. This provides the opportunity to predict graphite formation during the process. Although a correlation is found between graphite formation and specific magnesium consumption, which is a measure for desulphurisation efficiency, the effect could not be directly proven, as too many other parameters could have influenced the desulphurisation process. Data analysis does show that the observed correlation could not be attributed to temperature and initial sulphur concentration of the hot metal, which are the two most important factors for the desulphurisation efficiency. The observed correlation between graphite formation and desulphurisation efficiency is significant at low initial sulphur concentrations (<225 ppm) and insignificant at high initial sulphur concentrations (>225 ppm).
Key Words Hot metal desulphurisation, magnesium consumption, graphite precipitation, kish
- Hot Metal Desulphurisation
- magnesium consumption
- graphite precipitation