In Russia and the nations of the CIS (Commonwealth of Independent States), the main natural sources of minerals are vanadium-bearing low-titanium titanomagnetites (Fe, V, Ti)304. Vanadium is usually extracted from these materials by a pyrometallurgical method that involves reducing concentrated titanomagnetite ore in a blast furnace, with the vanadium entering the pig iron that is formed in this operation. During subsequent conversion of the pig iron, the vanadium is concentrated in a vanadium slag containing 10-30% V205. Vanadium is extracted from the slag by subjecting the latter to a hydrometallurgical process in which vanadium is transferred to a solution. The compound V205 is precipitated from the solution by hydrolysis and, after drying and refining, is used as a commercial product and as a raw material for the production of ferrovanadium.As is known [1, 2], the reaction in which impurities are oxidized during conversion of the pig iron in a converter can be represented in general form as:With the establishment of equilibrium,where ~t(MexOy ) is the activity coefficient of MexOy in the slag phase; a(FeO ) is the activity of FeO; AZ(MexOy ) and AZ(FeO ) are the Gibbs free energies.The less of any element that remains in the metal and the more of any element that is transferred to the slag, the greater the amount by which the absolute value of the standard change in Gibbs free energy accompanying the formation of the oxide of the given element will exceed the isobaric-isothermal potential for the formation of ferrous oxide, the greater will be the activity of FeO, and the smaller will be the activity coefficient of the resulting oxide in the slag phase [3]. In the case of vanadium, the change in the isobaric potential is greater in the formation of V205 than in the formation of its lower oxides (at 1000 K, AZ(v205) = -1136.0; AZ(v204) = -1094.0; AZ(v2o3) = -981.8; AZFe O = -198.2 M/mole [4]). It seems that the conditions are more favorable for the oxidation of vanadium to V205 than for the oxidation of vanadium to V20 3. However, the degree of oxidation of the metal depends on the acid-base composition of the slag. In acid slags in the duplex process, vanadium is in the trivalent state in the form of spineUides. In basic slags in the monoprocess, vanadium is in the pentavalent state (in the form of anions of salt compounds). The distribution of oxygen among the elements in the slag depends appreciably on the activity coefficients of the oxides that are formed. For example, acid oxides (SiO2, P205) have lower activity coefficients in basic slags than in acid slags. Thus, the elements forming these oxides are more completely oxidized when the process is conducted with a predominantly basic slag.The activity coefficients of individual oxides in the slags formed in the duplex process (at the Chusovoi Metallurgical Plant -ChMZ) and in the monoprocess (at the Niznhiy Tagil Metallurgical Combine -NTMK) were calculated on the basis of the diagrams in [5]. It was established that the activity coefficients of oxygen an...
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