Reaction Mechanism of Bottom Blowing CO<sub>2</sub> with Molten Steel in Converter

Abstract

In the current study, the reaction behavior between bottom blowing CO2 and the molten steel at different converter stages was studied by the thermodynamic calculation. At the initial stage, CO2 reacts with [C] before the turning point and then reacts with [C] and [Si] simultaneously after that. CO2 completely reacts with [C] and twice volume of CO generates at the middle stage. The reaction ratio of CO2 and [C] gradually decreases at the final stage due to the ratio of CO2 reacting with [Fe] and the residual unreacted CO2 increases. Then the effect of the bottom blowing gas type and intensity on the [C]·[O] value and T.Fe content in the slag were studied by industrial trials in a 300 t converter. When Ar is blown at the final stage, the CO partial pressure decreases with the increasing of the bottom blowing intensity, while the opposite result is obtained when blowing with CO2. The CO2 bottom blowing into the converter should be switched with Ar, and the blowing time of CO2 should be controlled in the early 12 minutes to avoid increasing the [C]·[O] value and the T.Fe content in the slag. In order to improve the reaction rate of CO2 and [C], it is necessary for the CO2 to be blown during the high-speed decarburization period when the [C] content is between 0.7 mass% and 3.3 mass% and the bottom blowing time is between 5 and 12 minutes.