In modern EAF steelmaking process, control of the nitrogen content of molten steel has become more and more important and bottom-blowing technique has been widely applied to promote the molten bath fluid flow, accelerate the metallurgical reaction and improve the quality of molten steel. In this study, the influence of bottom-blowing gas species on the nitrogen content in molten steel during EAF steelmaking was systematically investigated and analysed. Combining the induction furnace experiments and theoretical analysis, the kinetic models of nitrogen change in molten steel with bottom blowing N₂, Ar and CO₂ were established theoretically and validated experimentally. Meanwhile, the thermodynamic laws and agitation capacity of different bottom-blowing gases were also clarified. Then, based on the industrial application research, the metallurgical effects, especially nitrogen removal, with different bottom-blowing gases were also studied and finally, a new concept was proposed for cyclic utilisation of CO₂ in the EAF steelmaking process.

Serious efforts have been carried out in China towards the utilization of CO₂ in different metallurgical processes. The research was initiated from feasibility study of CO₂ used in steel making process, followed by the use of CO₂ in decreasing the dust generation and further towards improving the dephosphorization efficiency in converter process. Industrial experiments on bottom blowing of CO₂ in BOF and electric arc furnace have been carried out in the plant with positive results. CO₂ is further applied in LF process for inclusions removal and in continuous casting process as shielding gas. CO₂ is also used in stainless steel refining process for decarburization, and results show a significant retention of chromium because of CO₂ introduction. CO₂ has also been tried in the ferroalloy industry to produce medium and low carbon ferrochrome/ferromanganese in the converter. Experimental results show that the Cr yield has been increased when CO₂ was introduced for M-LCFeCr production. The present paper aims to provide an overview of the progress of CO₂ application as resources/reactants in ferrous metallurgy processes.

Submerged CO₂–O₂ injection is a new method for electric arc furnace (EAF) steelmaking. And it’s necessary to optimize the arrangement of submerged nozzles and oven wall oxygen lances used in an EAF. In this study, the characteristics of metallurgical reaction in EAF metal bath during submerged injection and oven wall oxygen supply were analysed. The submerged nozzles’ agitation action was focused on the bath’s middle and lower part, while that of oven wall oxygen lances was focused on the upper part. The EAF combined blowing arrangement comprising two oven wall oxygen lances in Mode F and two submerged nozzles in Mode B contributes to the bath stirring significantly by forming a circulating flow. In the industrial experiments performed with submerged injection, the final phosphorus content, the endpoint carbon and oxygen equilibrium and the FeO content in molten slag were reduced by 5.28%, 0.00 066 and 0.0038%, respectively.