Thermodynamic Discussion of CO2 Injection in Molten Steel

CO2 utilization in the steel industry is indispensable to energy saving and emission reduction. Blowing CO2 into a basic oxygen furnace assists decarburization. Thermodynamics of the decarburization reaction while injecting CO2 into molten steel and the effects of the mixed-gas ratio, initial carbon content of the molten steel, and system pressure on decarburization and temperature change are discussed. The final carbon content of the molten steel increases and its temperature decreases with the increased volume fraction of CO2. Under normal atmospheric pressure, the decarburization reaction gradually stagnates. As the system pressure decreases, decarburization is more efficient and a lower gas mass is required. Compared with O-2 blowing, CO2 mixed-gas blowing under a pressure of 10.1325 kPa results in a lower oxygen content in the molten steel of 0.028% and decarburization of 0.0065% is also achieved. An excessively high volume fraction of CO2, however, greatly reduces the bath temperature.