Mathematical Model for Nitrogen Desorption and Decarburization Reaction in Vacuum Degasser

• Published in: ISIJ International Vol. 36; no. 4; pp. 395 - 401
• Main Authors: Kitamura, Toshihiro, Miyamoto, Kenichiro, Tsujino, Ryouji, Mizoguchi, Shozo, Kato, Katsuhiko
• Format: Journal Article
• Language: English
• Published: Tokyo The Iron and Steel Institute of Japan 01.01.1996; Iron and Steel Institute of Japan
• Subjects: Applied sciences; decarburization; Exact sciences and technology; Iron and steel making; mathematical model; Metals. Metallurgy; nitrogen desorption; Production of metals; secondary steelmaking; Treatment before gravity die casting and continuous casting; vacuum degasser; VOD; Decarburization; Steelmaking; Vacuum degassing; Desorption; Nitrogen; Mathematical model
• ISSN: 0915-1559; 1347-5460
• DOI: 10.2355/isijinternational.36.395

A mathematical model for nitrogen desorption and decarburization reactions in vacuum degasser was developed. The rate controlling step is assumed to be the mass transfer of nitrogen, carbon and oxygen in molten steel and the chemical reaction of N+N=N2 and C+O=CO. The bath surface and the surface both of the injected Ar gas bubble and CO gas bubble formed inside the bath are considered as the reaction sites. This model was verified by the agreement of the calculated results with the results of small scale experiments for nitrogen desorption and absorption reaction. The following results were obtained by the analysis of a VOD process of commercial scale for degassing of stainless steel by this model. The ratio of reaction rate for nitrogen desorption and decarburization at each reaction site during operation was evaluated. The nitrogen desorption reaction occurs at the CO gas bubble formed inside steel (51%), at bath surface (36%) and injected Ar gas bubble (13%). The decarburization reaction proceeds at bath surface (90%), at CO gas bubble (8%) and at injected gas bubble in (2%).