Novel Sessile Drop Software for Quantitative Estimation of Slag Foaming in Carbon/Slag Interactions
- PDF / 351,891 Bytes
- 5 Pages / 593.972 x 792 pts Page_size
- 78 Downloads / 286 Views
In electric arc furnace (EAF) steelmaking, slag foaming is the result of CO gas generated in the slag layer due to carbon interactions with slag, metal, and gas phases and has a significant influence on the operating efficiency of the furnace.[1,2] Foamy slag envelops the hot electrodes and arcs and protects the furnace roof and sidewalls from excessive heating and radiation; it provides an insulating layer to the melt, thereby reducing the loss of energy.[3] Maintaining a predictable and foamy slag for every level of heat has eluded steelmakers. Mostly, adequate slag foaming occurs at the beginning of refining but then decreases toward the end of the heat. This variability in the foaming behavior has forced many steelmakers to melt to a ‘‘generic’’ low C heat for every grade of steel, regardless of final carbon specifications. The loss in the iron yield that results from this practice is somewhat offset by a more predictable arc furnace foaming practice and meltdown time. The slag foaming phenomenon is rather complex depending on a number of factors/processes such as the kinetics of gas generation, chemical reactions, slag/metal and slag/ carbon interactions, appropriate slag characteristics for holding and sustaining gas bubbles in the slag layer, etc. RITA KHANNA, Research Fellow, MAHFUZUR RAHMAN, Graduate Student, and VEENA SAHAJWALLA, Professor, are with the School of Materials Science and Engineering, The University of New South Wales, Sydney NSW 2052, Australia. Contact e-mail: [email protected] RICHARD LEOW, Computer Programmer, is with the High Performance Computing Support Unit, The University of New South Wales, Sydney NSW 2052, Australia. Manuscript submitted December 17, 2006. Article published online August 7, 2007. METALLURGICAL AND MATERIALS TRANSACTIONS B
Previous research[4,5] on the steady-state slag foaming where the foam was generated through argon gas injection in the temperature range of 1250 C to 1400 C showed that foaming improved with decreasing surface tension, increasing viscosity of slag and suspension of second-phase particles. It has been shown that at low superficial gas velocities, the steady-state foam height increased nonlinearly with the gas flow rate.[6] At higher superficial velocities, the foam height was found to be a linear function of the gas velocity. Ito and Fruehan[6,7] developed a foam index in terms of the average traveling time of gas through the foam. Foam can also be characterized by its stability and decay time. Injection of oxygen and carbonaceous materials into EAF steelmaking furnaces create dynamic and nonsteady-state conditions. The rate of generation of CO gas and associated slag foaming can change significantly as a function of time depending on slag chemistry and operating conditions. Hong et al.[8,9] have reported on slag foaming originating from CO gas generated during the chemical reaction between iron oxide in slag with graphite. They observed that the slag did not foam when the gas evolution was below a critical value. Addition of sulfur suppressed slag
Data Loading...
