Abstract
The vaporization of vanadium pentoxide from CaO-SiO2-VOx ternary slags using different gas treatment regimens and parallel vacuum gas extirpation to treat V-bearing slags at 1873 K has been developed in the present study. The novelty of the present study is to monitor the effect of parallel alumina dissolution on the vaporization phenomenon. Vanadium pentoxide has high vapor pressure at the temperatures over 1500 K. When CaO-SiO2-VOx ternary slags, kept in dense alumina crucibles, are injected with oxygen, V2O5 gas bubbles are formed which are forced out by using vacuum extirpation. The vanadium pentoxide could be then collected in the exhaust gases. The mechanism of the process phenomenon is described as the formation of V2O5 gas phase resulting from the oxidation of the lower-valent oxides present in the slag. This gas phase would form microbubbles in the molten slag bulk phase due to low surface tension between the gas phase and the slag, thereby increasing the contact surface. At the same time, the crucible material would dissolve in the slag causing an increase in the slag viscosity. Due to the high slag viscosity of the bulk slag, these microbubbles formed would have difficulty in coalescing and reaching the slag surface. The escaping of the bubbles into the gas phase is enabled by the vacuum extirpation.
Highlights
DURING the production of metals, especially iron and steel, considerable amounts of slags are generated every year all over the world
The present results indicate that vanadium could be extracted from the slag by evaporation using the combined oxygen injection and vacuum extirpation method
The vanadium extraction rate became significant with the application of vacuum extirpation and increased as a function of time
Summary
DURING the production of metals, especially iron and steel, considerable amounts of slags are generated every year all over the world. The annual amount of the slag produced in steelmaking industry exceeds 400 million tones.[1] Vanadium bearing steelmaking slags are classified as environmentally hazardous substances, which require special handling, storage, and restricted landfill, since vanadium higher oxide may be harmful for biological organisms.[2] At the same time, vanadium-containing silicate melts are valuable secondary sources for the recovery of vanadium in some cases containing up to 24 pct vanadium.[3] The concentration of vanadium in the fly ash collected in the furnace off-gas cleaning system after combustion process can be as high as to 40 pct in a form of V2O5.[4]. Manuscript submitted September 22, 2020; accepted February 8, 2021.
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