The desulphurization process by powder
injection and blowing in
RH refining of molten steel and its mechanism have been considered
and analyzed. Based on the two-resistance mass transfer theory and the mass balance of sulphur in the system, a kinetic model for the process has been developed. The ralated parameters of the model have been determined. Calculating and modelling for the process by injecting and blowing the lime based powder flux under the assumed operating modes in a RH degasser of 300 t capacity have been carried out using the model. The corresponding circulation rate and the powder
injection and blowing rate were taken as 100 t/min and 150 kg/min, respectively. The initial contents of sulphur and the amounts of powder injection and blowing were respectively assumed to be 70, 60, 50, 40, 30, 20×10-4% (massfraction) and 10, 8, 6, 5, 4, 3 kg/t-steel. The total treatment time for desulphurization under each mode was set up to be 24 min that is equivalent to eight circulation cycles of liquid steel to be treated. The results indicated that the prediction made by this model is in good agreement with some data of the industrial experiments and production practice, injecting and blowing the lime-based powder flux(85%CaO+15%CaF2)of 3-5 kg/t-steel with the total treatment time of 12-20 min, it is entirely possible to make the sulphur content in molten steel decrease to the ultra-low level below (5- 10)× 10-4% from (60-80)×10-4%; intensifying the powder injection and blowing operation and increasing the circulation rate of liquid steel may effectively raise the rate of the process in
RH refining.