Evaluation of the Effects of Gas Injection in the Vaccum Chamber of a RH Degasser on Melt Circulation and Decarburization Rates

• Published in: ISIJ International Vol. 49; no. 8; pp. 1141 - 1149
• Main Authors: Neves, Leonardo, Hugo Passos Ornelas de Oliveira, Tavares, Roberto Parreiras
• Format: Journal Article
• Language: English
• Published: Tokyo The Iron and Steel Institute of Japan 01-01-2009; Iron and Steel Institute of Japan
• Subjects: Applied sciences; decarburization rate; Exact sciences and technology; melt circulation and secondary refining; Metals. Metallurgy; RH degasser; melt circulation and secondary refining; RH degasser; Gas injection; Refining; decarburization rate
• ISSN: 0915-1559; 1347-5460
• DOI: 10.2355/isijinternational.49.1141

Steels with low concentrations of nitrogen, hydrogen and carbon have in large demand lately. The RH process is a secondary refining process that can simultaneously attain significant levels of removal of these interstitial elements from liquid steel. In the RH process, the melt circulation rate plays a very important role in determining productivity of the equipment, since it affects the decarburization rate. In the present work, a physical model of a RH degasser in a 1 : 5 scale of an industrial reactor from USIMINAS (Minas Gerais, Brazil). This model has been built and used in the study of the circulation rate and of the kinetics of decarburization. The effects of the gas flow rate and of the configurations of the nozzles used in the injection of the gas have been analyzed. The effect of gas injection in the vacuum chamber was also investigated. The decarburization reaction of liquid steel was simulated using a reaction involving CO2 and caustic solutions. The concentration of CO2 in the solution was evaluated using pH measurements. The experimental results indicated that the kinetic of decarburization is controlled by mass transfer in the liquid phase. It was also observed that, in certain configurations, the injection of gas in the vacuum chamber can increase the decarburization rate.