Effect of Iron Redox Equilibrium on the Foaming Behavior of MgO-Saturated Slags
- PDF / 2,170,524 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 34 Downloads / 249 Views
RODUCTION
SLAG foaming phenomena in the steelmaking process result in various advantages related to process efficiency,[1,2] and hence, the fundamentals of these phenomena should be clearly understood to optimize foaming behavior. Bikerman[3,4] first suggested a ‘‘foaming index’’ to quantitatively interpret the foaming behavior of an aqueous solution and verified that it is only determined by the liquid’s property. The foaming index (R) is expressed in Eq. [1] as follows: R¼
Dh ; Vsg
½1
where Dh denotes the height of the foam layer (cm), and Vsg denotes the superficial gas velocity (cm s1) that flows through the melt in a crucible. Thus, the foaming index is recognized as the potential to foam when a given gas evolution condition is applied to the melt. A previous study on the pneumatic foam lifetime of CaO-SiO2-P2O5 melts was conducted by Cooper and Kitchener,[5] and the results indicated that the foam stability increased with increases in the P2O5 content, reduced CaO/SiO2 ratio, and decreases in the temperature. In a manner analogous to P2O5 in the study by
YOUNGJOO PARK and DONG JOON MIN are with the Department of Materials Science and Engineering, Yonsei University, 03722 Seoul, Korea. Contact e-mail: chemical@ yonsei.ac.kr Manuscript submitted December 26, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
Cooper and Kitchener, Cr2O3 is also reported as a foam-stabilizing element by Swisher and McCabe.[6] However, the concept of ‘‘foam lifetime’’ includes the limitation of comparisons between various experimental conditions and slag systems, since it is an arbitrary index that depends on individual experimental setups. Ito and Fruehan[1] introduced the abovementioned foaming index to a molten slag system, and several studies related to slag foaming were conducted based on the foaming index.[2,7–10] Furthermore, it is widely accepted that the foaming index suitably expresses the foaming behavior of molten slag for a stable and steady condition within the range of interest in the steelmaking process. Fundamentally, the foaming of liquid is related to both rheological and interfacial properties. Recently, the physico-chemical properties of foaming slags are well reviewed, specifically in perspective of liquid film drainage of molten slag.[11] Hence, the viscosity and surface tension are considered as crucial aspects in determining the foaming behavior of the liquid. However, in molten slag systems, the viscosity is a major factor in determining the foaming index in most cases, although each property simultaneously affects foaming.[1,2,7,12,13] The viscosity of the molten slag significantly exceeds that of the aqueous solution and also varies over a considerably wider range with the slag chemical composition than the surface tension. Consequently, the effect of surface tension is underestimated by that of the viscosity in several cases, and the foaming index is significantly affected by the viscosity of the molten slag. The effect of surface tension is also observed in specific case in which a strong surface-active compone
Data Loading...
