Research on the Jet Characteristics and Dephosphorization Efficiency of Converter Oxygen Lance Blowing CO2-O2 Mixed Gas

Utilization of CO2 in steelmaking process has attracted extensive attention in recent years, not only because of its social benefits, but also its better metallurgical performance. Mixing CO2 with O-2 blown by converter oxygen lance is gradually being adopted by steelmaking plants, due to its potential of reducing consumption and improving steel quality. In the present research, effect of mixing CO2 on the jet characteristics of a four-nozzle oxygen lance was studied in detail by numerical simulation, taking the combustion behavior between supersonic jets and ambient atmosphere into consideration innovatively. The simulated results showed that the combustion flame is mainly distributed in the region between multiple jets, and the high temperature flame has a noticeable influence on the low-velocity region of the jet. Due to the dilution effect of CO2, mixing CO2 into the oxygen jets will reduce the maximum temperature of the flame and slow down the combustion rate. With the increase of CO2 mixing ratio, the high-temperature zone of combustion flame moves away from the lance tip significantly. At the same distance from the nozzle, although mixing CO2 can hardly increase the velocity magnitude of the jet, but it can achieve higher dynamic pressure, indicating stronger impacting power. Then the industrial experiment of top blowing O-2-CO2 was carried out in a 120-ton converter. During the blowing time of 120 similar to 300 s, the mixing ratio of CO2 was 15 vol.% for better dephosphorization, and no CO2 was mixed in the rest time of blowing. Due to the stronger stirring and better thermodynamics, the average [P] content in the final molten steel was decreased from 0.0155 wt.% to 0.0129 wt.%, achieving higher dephosphorization efficiency.