Effect of gas type and pressure on slag foaming
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1.78 • 10 -5 exp
I_~T~_I
[4]
Equation [4] is valid for the slag and experimental conditions used in this investigation. From Eq. [4], the apparent activation energy for the decay of the foam is obtained to be 139.6 kJ/mole. From the slope of the line for the viscosity, the activation energy for the viscous flow is 144.7 kJ/mole, which is slightly higher than that for the foam decay but within the experimental uncertainty of the two properties. Experiments were carried out to investigate the effect of slag volume on the foaming index. In these experiments, only the amount of slag used was changed but all the variables were kept constant. A slag containing 40 pet SiO2, 40 pct CaO, 10 pet AI20~, and 10 pct FeO was used. Due to the limitations of the experimental apparatus, the maximum amount of slag used was 205 g. It was found that the foam index was 2.1, 2.23, and 2.36 s at 1723 K for 80, 140, and 205 g of slag, respectively. The experimental results indicate that the foaming index is almost independent of the amount of slag. The small increase in the foaming index might be due to the gas holdup in the slag. The relation, Eq. [3], developed by Zhangl"l indicates that the foaming index is independent of the amount of slag used. Using their correlations, the foaming for the same slag is calculated to be 2.07 s at 1723 K, which is in agreement with the present results. It must be noted that more substantial experiments are required to demonstrate the effect of slag height on foaming index.
Support of this work by the National Science Foundation under Grant No. DMI-9t21002 and the member companies of the Center for Iron and Steelmaking Research is gratefully acknowledged. REFERENCES 1. C.F. Cooper and J.A. Kitchener: d. Iron Steel Inst., 1959, vol. 193, pp. 48-55. 2. J.H. Swisher and C.L. McCabe: Trans. AIME, 1964, vol. 230, pp. 166975. 3. S. Hara and K. Ogino: The Reinhardt Schuhmann lnt. Symp. on Innovative Technology and Reactor Design in Extractive Metallurgy, TMS-AIME, Warrendale, PA, 1986, p. 639. 4. K. Ito and RJ. Fruehan: Metall. Trans. B, 1989, vol. 20B, pp. 509-14. 5. K. Ito and R.J. Fruehan: Metall. Trans. B, 1989, vol. 20B, pp. 515-21. 6. Y. Zhang: Ph.D. Thesis, Carnegie Mellon University, Pittsburgh, PA, 1992. 7. R. Jiang and R.J. Fruehan: Metall. Trans. B, 1991, vol. 22B, pp. 48189. 8. G. Urbain: SteelRes., 1987, vol. 58, pp. 111-116.
Effect of Gas Type and Pressure on Slag Foaming Y. ZHANG and R.J. FRUEHAN In previous publications,t1,2] experimental results on the effect of the bubble size and the effect of the carbonaceous particles on slag foaming have been reported. It was found that the foam index is inversely proportional to the average bubble diameter. The foam index (E) is defined as
Z=
v,
[1]
where H I is the foam height and v~ is the superficial gas velocity, which is the ratio of the volumetric gas flow rate to the cross-sectional area of the container. A general correlation obtained by dimensional analysis can be used to predict the foam index for the liquid slag as a function of its p
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