2007 Volume 47 Issue 3 Pages 408-417
The mass transfer characteristics between liquid steel and powder particles in RH-PB(IJ) refining process have been investigated on a water model of 1/4 linear scale for a 150 t multifunction RH degasser. Sodium chloride powder with analytical purity has been utilized as the flux for injection. The mass transfer coefficient (k) of solute (NaCl) in the liquid has been determined under the conditions of the RH-PB(IJ) process. The effects of the main technological and structural parameters on the characteristics have been examined. It may be concluded from the results that, under the conditions of the present work, the mass transfer coefficient in the liquid increases with increasing the lifting gas flow rate, with increasing the inner diameter of the upsnorkel, with increasing the circulation rate of the liquid, and with increasing the particle size of powdered flux, and decreases with an increase in the inner diameter of the downsnorkel. Its value is in the range of (3.392×10−5–2.661×10−4) m/s. The corresponding dimensionless relationships for the mass transfer coefficient in the range were obtained. Taking the relative velocity of the particles to the liquid into account, the mass transfer in the liquid may be characterized by
Sh=2+0.0285(Res)3/4Sc1/3
Considering the energy dissipation caused by the fluctuation in the velocity of the liquid in turbulent flow, the following dimensionless relationship has been reached:
Sh=2+0.0285(εsldp4/vl3)1/4Sc1/3
When the mass transfer is regarded as that between rigid bubbles and molten steel, it may be characterized by:
Sh=2+0.00731[Res0.48Sc0.339(g1/3dp/D2/3)0.072]1.455
In comparison with the mass transfers coefficient in the molten steel between the powder particles and the liquid in RH-PTB process, that in the conditions of RH-PB(IJ) refining is smaller, being about 1/4–1/3 of the former, but the both have a similar feature and pattern.
