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dium is an important alloying element to steel. During the production of vanadium-containing steel, the by-product slag can contain up to ca 5 mass pct vanadium as V2O5. While the presence of vanadium can be a potential environmental hazard when the slag is used for landfills, it should be noted that these slags form a valuable secondary source of vanadium, if a process could be designed for the economic recovery of vanadium. Such a process can even be applied to Swedish magnetite iron ores containing about 1.5 mass pct vanadium and also pet coke ash in which the vanadium content is higher. The oxide of vanadium at the pentavalent state (V2O5) is a low melting oxide with a melting point of 963 K (690 °C). According to standard thermochemical tables,[1] the vapor pressure of V2O5 is given by the Eq. [1]: log10 P ¼

7100 þ 5:05ðmmHgÞ T

½1

SESHADRI SEETHARAMAN, formerly Mercator Visiting Professor with Institute of Iron and Steel Technology, TU-Bergakademie (TUBAF), 09596 Freiberg Germany, is now Professor Emeritus with Royal Institute of Technology, 10044, Stockhlm, Sweden. Contact email: [email protected] TETIANA SHYROKYKH, Ph.D. Student, National Metallurgical Academy of Ukraine, NMAU, Dnipropetrovsk 49600, Ukraine, is also Visiting Researcher at TU-Bergakademie (TUBAF). CHRISTINA SCHRO¨DER, Senior Researcher, and PIOTR R. SCHELLER, Professor, are with TU-Bergakademie (TUBAF). Manuscript submitted January 19, 2013. Article published online May 14, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B

The vapor pressure of vanadium pentoxide at steelmaking temperatures is presented in Figure 1. It is seen in Figure 1 that the vapor pressure is significant at these temperatures. Recently, Yang et al.[2] studied the evaporation kinetics of pure V2O5 at these temperatures with pure oxygen, air, and pure CO2 as oxidizing atmospheres. These authors reported that the evaporation loss of V2O5 was 100 pct in about 17,000 seconds at 1873 K (1600 °C) in pure oxygen, while the evaporation rate is slightly lower in air at the same temperature. It would be interesting to examine the evaporation of vanadium as V2O5 from steelmaking slags. The loss of vanadium from slag surfaces can be difficult to study experimentally due to the slow rate of evaporation since vanadium is bound in the silicate matrix of the slag. Preliminary experiments at the Royal Institute of Technology, Stockholm, with oxygen blowing through molten slags conducted in an induction furnace by Yang et al. indicate a loss of 36 mass pct in about 6 hours. On the other hand, if the evaporation studies are conducted on thin slag films in an oxidizing atmosphere, it should be possible to monitor the surface evaporation of V2O5, minimizing the effect of the diffusion of vanadium ions from the bulk. Estimation of the Rayleigh and Reynolds number in such a thin film system by the present authors indicates that natural or forced convection may not have any influence on the surface evaporation. In thin film experiments, both surfaces of the slag film would be available for evaporation and t