Simulation of Gas-Liquid Two-Phase Flow and Mixing Phenomena During RH Refining Process

doi:10.11900/0412.1961.2017.00429

Acta Metall Sin

2018, Vol. 54

Issue (2): 347-356 DOI: 10.11900/0412.1961.2017.00429

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Simulation of Gas-Liquid Two-Phase Flow and Mixing Phenomena During RH Refining Process

Chang LIU, Shusen LI, Lifeng ZHANG(

)

School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China

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Chang LIU, Shusen LI, Lifeng ZHANG. Simulation of Gas-Liquid Two-Phase Flow and Mixing Phenomena During RH Refining Process. Acta Metall Sin, 2018, 54(2): 347-356.

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Abstract

The Ruhrstahl-Heraeus (RH) vacuum system is vitally important in the secondary refining process since it is highly effective on decarburization and degassing, which involves complex multiphase flow and transport phenomena. Many investigations on the flow field in the RH refining process have been reported. However, only several investigations are focused on the bubble expansion in the up-leg snorkel. In this work, the combined mathematical model and physical model were employed to simulate the fluid flow and mixing phenomena in the RH reactor. A water model for a practical 210 t RH reactor was established according to similitude principle, and the flow field on the center section of the physical model was captured by PIV (particle image velocimetry) system. The coupled VOF (volume of fluid) model and DPM (discrete phase model) were used to simulate the multiphase fluid flow in the RH reactor. Both the k-ε model and LES (large eddy simulation) model were performed to describe the turbulent characteristics during the RH refining process. The mathematical model was validated by the water model with the same experimental conditions. It suggests that the calculated results show a good agreement with the measured one. Based on the LES model, the instantaneous velocity distribution and the generate and the dissipate of vortex were computed. Also, the mixing time of different position in the ladle was measured and calculated. The results show that the mixing time near the up-leg snorkel is larger than that near the down-leg snorkel. A model for bubble expansion was developed and used to simulate the bubble behavior in the steel-argon system. The results show that the bubble expansion has a strong impact on the flow field in the RH reactor.

Key words: RH refining large eddy simulation mixing time bubble expansion

Received: 16 October 2017

Fund: Supported by National Natural Science Foundation of China (Nos.51725402, 51504020 and 51704018) and National Key R&D Program of China (Nos.2017YFB0304000, 2017YFB0304001 and 2016YFB0300102)

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	Chang LIU
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https://www.ams.org.cn/EN/10.11900/0412.1961.2017.00429 OR https://www.ams.org.cn/EN/Y2018/V54/I2/347

Fig.1 Geometric model and mesh configuration

Fig.2 Geometrical dimensions of experimental water model and monitors distribution in it (unit: mm)

Table 1 Physial parameters of materials for water model and prototype

Fig.3 Comparison of velocity distributions measured (a) and calculated by using k-ε model (b) and LES model (c) in vacuum chamber

Fig.4 Comparison of velocity distributions measured (a) and calculated by using k-ε model (b) and LES model (c) in ladle

Fig.5 Comparison of measured and calculated velocity magnitudes(a) along the horizontal line 500 mm from ladle bottom(b) along the center line of down-leg snorkel

Fig.6 Fluctuating velocities for different positions in physical model (U’—X component of fluctuating velocity, V’—Y component of fluctuating velocity)

Fig.7 Iso-surfaces of v=0.1 m/s for k-ε model (a) and LES model (b)

Fig.8 Instantaneous velocity distributions for LES model(a) Y=0, velocity vector(b) Y=0, volume fraciton of gas α_g=0.5, velocity contour

Fig.9 Averaged velocity distribution and bubble distribution calculated by using k-ε model (a) and LES model (b)

Fig.10 Initial distribution of tracer in vacuum chamber (C₀—initial concentration of tracer)

Fig.11 Variation of conductivities or tracer concentrations (C) of monitors measured (a) and calculated by k-ε model (b) and LES model (c) (C_∞—final trace concentration)

Fig.12 Comparison of mixing time distributions measured (a) and calculated by using k-ε model (b) and LES model (c)

Fig.13 Bubble diameter distributions without (a) and with (b) bubble expansion in up-leg snorkel (d_b—bubble diameter)

Fig.14 Velocity distributions on the section Y=0 without (a) and with (b) bubble expansion in up-leg snorkel

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