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Baokuan Li (Speaker) Fengsheng Qi Northeastern University, China

z. y. x. o. Improving of Refining Efficiency Using Electromagnetic Force Driven Swirling Flow in Metallurgical Reactor. Baokuan Li (Speaker) Fengsheng Qi Northeastern University, China. Fumitaka Tsukihashi The University of Tokyo, Japan. θ. r. z. y. x. o. Research background.

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Baokuan Li (Speaker) Fengsheng Qi Northeastern University, China

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  1. z y x o Improving of Refining Efficiency Using Electromagnetic Force Driven Swirling Flow in Metallurgical Reactor Baokuan Li (Speaker) Fengsheng Qi Northeastern University, China Fumitaka Tsukihashi The University of Tokyo, Japan

  2. θ r z y x o Research background Inclusions are mainly removed by attachment of argon gas bubbles in molten steel. Removal rate of inclusions depend on the number, size, shape, self- motion and distribution of gas bubbles in melt. A optimum behavior of argon gas bubbles for refining efficiency is very important. life of RH equipment is also affected by attachment and action of gas bubbles near wall. Vacuum Pump Argon gas bubbles Air Molten steel +inclusions

  3. θ r z y x o Innovative Steelmaking -Application of Swirling Flow • Swirling flow is produced bythe application of rotating magnetic field, and effect of swirling flow included: • Efficient mixing and • Efficient separation of inclusions by improving probability of attachment, collisions and coalescence with dispersed gas bubbles in Refining processes. Vacuum Pump Argon gas bubbles Air Molten steel + inclusions

  4. Water model experiments examine the research ideas Impeller Gas distributor Manometer Rotameter Nozzle distribution RH degassing vessel Ultrasonic flowmeter

  5. ( a) ( b) ( c) ( d) Effect of impeller input power on gas bubbles distribution, shutter speed is 1/125 second. Q=0.25 m3/h. (a) 0, (b) 20 W, (c) 25 W and (d) 35 W

  6. 10 9 8 Circulation flow rate, 10-5 m3/s 7 6.944×10-5m3/s 6 11.111×10-5m3/s 16.667×10-5m3/s 5 10 15 20 25 30 35 40 0 Input power, W Effect of plane blade impeller on circulation flow rate of RH vessel

  7. (Yokoya et al )

  8. Nozzle diameter is 2 mm, gas flow rate is 0.25 m3/h, strobe light speed is 1/2000s. swirl number is 0, 0.23, 0.53, 0.68, respectively.

  9. Effect of swirl number on the gas bubble diameter at outlet of nozzle 6 5 4 3 Averaged gas bubble diameter at outlet of nozzle, mm 2 Nozzle diameter is 2 mm Gas flow rate 0.25 l/h 1 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Swirl number

  10. θ r z y x o Mathematical model Vacuum Pump • A homogeneous model for the two-phase turbulent flow in the RH vessel with the rotating magnetic field in the up-leg. • The momentum equation for gas phase is ignored. • The previous model is only valid for bottom blown reactors. Argon gas bubbles Air Molten steel + inclusions

  11. Spitzer et al. [1] Formulation

  12. Up - leg Nozzle z Gas jet zone 1 2 y x Penetrating velocity and slip velocity Horizontal penetrating velocity: Qg : total argon gas flow rate, n :nozzle number A : cross nozzle inlet area α : gas volume fraction (at inlet α0) Centripetal force and horizontal slip velocity caused by rotating magnetic field Vertical slip velocity

  13. Boundary conditions and solution method Flow field Gas volume fraction Self-developed computer code in Fortran language

  14. Vacuum Pump Air θ r z water y x o B0 = 0.1 mT Frequency = 50 Hz

  15. B0 = 0.1 mT Frequency = 50 Hz (d) (c) (b) (a) (a) (b) (c) (d) Calculated flow velocities at horizontal sections of RH degassing vessels, (a) up-leg, (b) bottom of vacuum chamber, (c) middle of vacuum chamber, and (d) surface of vacuum chamber.

  16. 0.7 0.7 0.6 0.6 0.6 0.5 0.5 0.5 0.4 0.4 0.4 0.3 0.3 0.3 0.2 0.2 0.2 0.1 0.1 0.1 0 0 0.3 0.4 0.5 0.1 0.2 0.1 0.2 0.3 0.4 0.5 0 0 0 B0 = 0.1 mT Frequency = 50 Hz (b) (a) Computed gas volume fraction at main sections of RH degassing vessels, (a) no swirling flow (b) with swirling flow.

  17. 0.8 0.5 0.7 0.4 0.6 0.5 0.3 Gas volume fraction Vertical velocity, m/s 0.4 0.2 0.3 0.2 0.1 0.1 0.04 -0.04 0 -0.04 0.04 0 Diameter of up-leg, m Diameter of up-leg, m No swirling flow With swirling flow No swirling flow With swirling flow Velocity distribution of RH degassing vessel Gas volume distribution of RH degassing vessel

  18. CONCLUSIONS Water model experiments showed that the gas bubbles may be moved toward the central zone in up-leg in RH vessel under the swirling flow. the size of gas bubbles produced from nozzle become small and number of gas bubbles increases. the gas bubbles are dispersed in the whole up-leg. Residence time and journey of gas bubbles in up-leg is prolonged. The numerical results showed that a swirling flow may be produced and extended into the vacuum chamber in case that rotating magnetic field is applied in up-leg. The maximum of gas volume fraction moves toward the center zone of the up-leg.The upward velocity distribution in up-leg changes from M type to parabolic type.

  19. θ r z y x o The future works --- application of swirling flow Vacuum Control of size, shape and distribution of argon gas bubbles Change of collisions, coalescence and attachment of the inclusions Pump Argon gas bubbles Air Molten steel + inclusions

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