Numerical Simulation of Recirculating Flow and Physical Model of Slag–Metal Behavior in an RH Reactor: Application to Desulfurization JOHNE JESUS MOL PEIXOTO, WESLEI VIANA GABRIEL, THIAGO ARAU ´ JO SANTOS DE OLIVEIRA, CARLOS ANTONIO DA SILVA, ITAVAHN ALVES DA SILVA, and VARADARAJAN SESHADRI Computational fluid dynamics (CFD) techniques and a 1:7.5 physical model of an RH degasser have been used to evaluate the flow of gas and metal inside an RH reactor for vacuum degassing of liquid steel. The effect of gas injection on the gas spatial distribution, steel circulation rate and flow field inside the ladle, snorkels and vacuum chamber have been assessed. N-pentane oil was employed to evaluate the average residence time as well as the slag droplet size distribution. The predicted radial gas distribution and liquid circulation rate have been validated against experimental data from a physical model. The results with incorporation of the virtual mass force coefficient of 0.25 and the turbulence dispersion force showed better predictions of gas distribution in the up-snorkel as well as circulation rate. Full-scale simulations were performed, and the predicted circulation rate was significantly affected by the argon bubble expansion. Data from these simulations were used to analyze the degree of desulfurization performed by the addition of desulfurizing agents inside the vacuum chamber. A model of the kinetics of desulfurization based on the results from the physical model and CFD simulation and on slag dispersion inside liquid steel yields degrees of desulfurization similar to the industrial trials reported in the literature. https://doi.org/10.1007/s11663-018-1355-z Ó The Minerals, Metals & Materials Society and ASM International 2018 I. INTRODUCTION THE Ruhrstahl–Heraeus (RH) process was originally developed for hydrogen removal from liquid steel, and now it is widely used to achieve high levels of decar- burization for the manufacture of ultra-low carbon steels. [1,2] Deoxidation and good composition control are also possible in this reactor. [1,3] The kinetics of these reactions is affected by the circulation rate. [1–3] The circulation rate is influenced by the geometry (ladle, vacuum chamber and snorkel dimensions), gas distri- bution, flow rate as well as vacuum level inside the vacuum chamber. [1–5] Various correlations by different authors can be found in the literature relating the circulation rate with other parameters as given below: Kuwabara: [4] Q t ton=min ð Þ¼ 114G 1=3 D 4=3 ln P 1 P 0   1=3 ; ½1 Q t circulation rate (ton/min); D snorkel diameter (m), G gas flow rate (STP m 3 /min); P 1 pressure inside vac- uum chamber, P 0 pressure at the injection nozzle. Seshadri and Costa: [3] Q t ¼ 5:89G 0:33 L ; ½2 G L gas flow rate (STP L/min). Silva et al.: [5] Q c ¼ 0:185 H 0:607 im Dc 0:665 n 0:389 H 0:102 l ; ½3 Q c circulation rate (kg/s), H im depth of snorkel immer- sion (m), D c snorkel diameter (cm), n gas specific power agitation (W/kg), H l static liquid level inside the vacuum chamber (cm). Mathematical modeling based on CFD has been used in different investigations of the flow field inside the RH, JOHNE JESUS MOL PEIXOTO, WESLEI VIANA GABRIEL, THIAGO ARAU ´ JO SANTOS DE OLIVEIRA, CARLOS ANTONIO DA SILVA, and ITAVAHN ALVES DA SILVA are with the Department of Metallurgical Engineering and Materials, Federal University of Ouro Preto, Morro do Cruzeiro, Ouro Preto, MG 35400-000, Brazil. Contact e-mail: johnepeix@yahoo.com.br VARADARAJAN SESHADRI is with the Department of Metallurgical Engineering and Materials, Federal University of Minas Gerais, 6627, Av. Antonio Carlos, Belo Horizonte 31270-901, Brazil. Manuscript submitted December 23, 2017. METALLURGICAL AND MATERIALS TRANSACTIONS B