Abstract: Through the thermodynamic analysis of top blowing CO2+O2 mixture gas in BOF, combined with laboratory thermal simulation result, the feasibility applying CO2+O2 in top blowing converter for decarburizingrestraining oxygen and decarbonizationpreservation of chromium were discussed. It was concluded that carbon could be reduced by blowing pure CO2, but the loss of temperature was relative large. When the intensity of supplying CO2 was 3.0 m3/(t·min), the velocity of temperature dropping could reach 15.1 ℃/min; to achieve temperature balance, the mode of top blowing mixture gas CO2+O2 was taken. The heat from exothermal reaction O2-Fe could make up for the loss from endothermic reaction CO2-C, and the whole heating effest was zero when decarburized by O2 and CO2, the maximum theoretical volume fraction of CO2 in mixture gas CO2+O2 could be increased to 79.1 %. When the mixture gas was φ(CO2)︰φ(O2)=1︰1, the \[%C\]·\[%O\] could be controlled between 0.0025－0.0032 in top blowing converter, almost equalled to the effect in combined converter. When the mixture gas was φ(CO2)︰φ(O2)=2︰1, the effect of decarbonization and preservation of chromium by top blowing CO2+O2 occurred.

Key words: BOF, CO2, mixture blowing, product of carbon and oxygen, decarbonization and restraining oxygen, decarbonization and preservation of chromium